text: // Copyright 2012 the V8 project authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #include <stdlib.h>
  #include <limits>
  
  #include "src/v8.h"
  
  #include "src/accessors.h"
  #include "src/allocation-site-scopes.h"
  #include "src/api.h"
  #include "src/arguments.h"
  #include "src/base/cpu.h"
  #include "src/base/platform/platform.h"
  #include "src/bootstrapper.h"
  #include "src/codegen.h"
  #include "src/compilation-cache.h"
  #include "src/compiler.h"
  #include "src/conversions.h"
  #include "src/cpu-profiler.h"
  #include "src/date.h"
  #include "src/dateparser-inl.h"
  #include "src/debug.h"
  #include "src/deoptimizer.h"
  #include "src/execution.h"
  #include "src/full-codegen.h"
  #include "src/global-handles.h"
  #include "src/isolate-inl.h"
  #include "src/json-parser.h"
  #include "src/json-stringifier.h"
  #include "src/jsregexp-inl.h"
  #include "src/jsregexp.h"
  #include "src/liveedit.h"
  #include "src/misc-intrinsics.h"
  #include "src/parser.h"
  #include "src/prototype.h"
  #include "src/runtime.h"
  #include "src/runtime-profiler.h"
  #include "src/scopeinfo.h"
  #include "src/smart-pointers.h"
  #include "src/string-search.h"
  #include "src/stub-cache.h"
  #include "src/uri.h"
  #include "src/utils.h"
  #include "src/v8threads.h"
  #include "src/vm-state-inl.h"
  #include "third_party/fdlibm/fdlibm.h"
  
  #ifdef V8_I18N_SUPPORT
  #include "src/i18n.h"
  #include "unicode/brkiter.h"
  #include "unicode/calendar.h"
  #include "unicode/coll.h"
  #include "unicode/curramt.h"
  #include "unicode/datefmt.h"
  #include "unicode/dcfmtsym.h"
  #include "unicode/decimfmt.h"
  #include "unicode/dtfmtsym.h"
  #include "unicode/dtptngen.h"
  #include "unicode/locid.h"
  #include "unicode/numfmt.h"
  #include "unicode/numsys.h"
  #include "unicode/rbbi.h"
  #include "unicode/smpdtfmt.h"
  #include "unicode/timezone.h"
  #include "unicode/uchar.h"
  #include "unicode/ucol.h"
  #include "unicode/ucurr.h"
  #include "unicode/uloc.h"
  #include "unicode/unum.h"
  #include "unicode/uversion.h"
  #endif
  
  #ifndef _STLP_VENDOR_CSTD
  // STLPort doesn't import fpclassify and isless into the std namespace.
  using std::fpclassify;
  using std::isless;
  #endif
  
  namespace v8 {
  namespace internal {
  
  
  #define RUNTIME_ASSERT(value) \
    if (!(value)) return isolate->ThrowIllegalOperation();
  
  #define RUNTIME_ASSERT_HANDLIFIED(value, T)                          \
    if (!(value)) {                                                    \
      isolate->ThrowIllegalOperation();                                \
      return MaybeHandle<T>();                                         \
    }
  
  // Cast the given object to a value of the specified type and store
  // it in a variable with the given name.  If the object is not of the
  // expected type call IllegalOperation and return.
  #define CONVERT_ARG_CHECKED(Type, name, index)                       \
    RUNTIME_ASSERT(args[index]->Is##Type());                           \
    Type* name = Type::cast(args[index]);
  
  #define CONVERT_ARG_HANDLE_CHECKED(Type, name, index)                \
    RUNTIME_ASSERT(args[index]->Is##Type());                           \
    Handle<Type> name = args.at<Type>(index);
  
  #define CONVERT_NUMBER_ARG_HANDLE_CHECKED(name, index)               \
    RUNTIME_ASSERT(args[index]->IsNumber());                           \
    Handle<Object> name = args.at<Object>(index);
  
  // Cast the given object to a boolean and store it in a variable with
  // the given name.  If the object is not a boolean call IllegalOperation
  // and return.
  #define CONVERT_BOOLEAN_ARG_CHECKED(name, index)                     \
    RUNTIME_ASSERT(args[index]->IsBoolean());                          \
    bool name = args[index]->IsTrue();
  
  // Cast the given argument to a Smi and store its value in an int variable
  // with the given name.  If the argument is not a Smi call IllegalOperation
  // and return.
  #define CONVERT_SMI_ARG_CHECKED(name, index)                         \
    RUNTIME_ASSERT(args[index]->IsSmi());                              \
    int name = args.smi_at(index);
  
  // Cast the given argument to a double and store it in a variable with
  // the given name.  If the argument is not a number (as opposed to
  // the number not-a-number) call IllegalOperation and return.
  #define CONVERT_DOUBLE_ARG_CHECKED(name, index)                      \
    RUNTIME_ASSERT(args[index]->IsNumber());                           \
    double name = args.number_at(index);
  
  // Call the specified converter on the object *comand store the result in
  // a variable of the specified type with the given name.  If the
  // object is not a Number call IllegalOperation and return.
  #define CONVERT_NUMBER_CHECKED(type, name, Type, obj)                \
    RUNTIME_ASSERT(obj->IsNumber());                                   \
    type name = NumberTo##Type(obj);
  
  
  // Cast the given argument to PropertyDetails and store its value in a
  // variable with the given name.  If the argument is not a Smi call
  // IllegalOperation and return.
  #define CONVERT_PROPERTY_DETAILS_CHECKED(name, index)                \
    RUNTIME_ASSERT(args[index]->IsSmi());                              \
    PropertyDetails name = PropertyDetails(Smi::cast(args[index]));
  
  
  // Assert that the given argument has a valid value for a StrictMode
  // and store it in a StrictMode variable with the given name.
  #define CONVERT_STRICT_MODE_ARG_CHECKED(name, index)                 \
    RUNTIME_ASSERT(args[index]->IsSmi());                              \
    RUNTIME_ASSERT(args.smi_at(index) == STRICT ||                     \
                   args.smi_at(index) == SLOPPY);                      \
    StrictMode name = static_cast<StrictMode>(args.smi_at(index));
  
  
  static Handle<Map> ComputeObjectLiteralMap(
      Handle<Context> context,
      Handle<FixedArray> constant_properties,
      bool* is_result_from_cache) {
    Isolate* isolate = context->GetIsolate();
    int properties_length = constant_properties->length();
    int number_of_properties = properties_length / 2;
    // Check that there are only internal strings and array indices among keys.
    int number_of_string_keys = 0;
    for (int p = 0; p != properties_length; p += 2) {
      Object* key = constant_properties->get(p);
      uint32_t element_index = 0;
      if (key->IsInternalizedString()) {
        number_of_string_keys++;
      } else if (key->ToArrayIndex(&element_index)) {
        // An index key does not require space in the property backing store.
        number_of_properties--;
      } else {
        // Bail out as a non-internalized-string non-index key makes caching
        // impossible.
        // DCHECK to make sure that the if condition after the loop is false.
        DCHECK(number_of_string_keys != number_of_properties);
        break;
      }
    }
    // If we only have internalized strings and array indices among keys then we
    // can use the map cache in the native context.
    const int kMaxKeys = 10;
    if ((number_of_string_keys == number_of_properties) &&
        (number_of_string_keys < kMaxKeys)) {
      // Create the fixed array with the key.
      Handle<FixedArray> keys =
          isolate->factory()->NewFixedArray(number_of_string_keys);
      if (number_of_string_keys > 0) {
        int index = 0;
        for (int p = 0; p < properties_length; p += 2) {
          Object* key = constant_properties->get(p);
          if (key->IsInternalizedString()) {
            keys->set(index++, key);
          }
        }
        DCHECK(index == number_of_string_keys);
      }
      *is_result_from_cache = true;
      return isolate->factory()->ObjectLiteralMapFromCache(context, keys);
    }
    *is_result_from_cache = false;
    return Map::Create(handle(context->object_function()), number_of_properties);
  }
  
  
  MUST_USE_RESULT static MaybeHandle<Object> CreateLiteralBoilerplate(
      Isolate* isolate,
      Handle<FixedArray> literals,
      Handle<FixedArray> constant_properties);
  
  
  MUST_USE_RESULT static MaybeHandle<Object> CreateObjectLiteralBoilerplate(
      Isolate* isolate,
      Handle<FixedArray> literals,
      Handle<FixedArray> constant_properties,
      bool should_have_fast_elements,
      bool has_function_literal) {
    // Get the native context from the literals array.  This is the
    // context in which the function was created and we use the object
    // function from this context to create the object literal.  We do
    // not use the object function from the current native context
    // because this might be the object function from another context
    // which we should not have access to.
    Handle<Context> context =
        Handle<Context>(JSFunction::NativeContextFromLiterals(*literals));
  
    // In case we have function literals, we want the object to be in
    // slow properties mode for now. We don't go in the map cache because
    // maps with constant functions can't be shared if the functions are
    // not the same (which is the common case).
    bool is_result_from_cache = false;
    Handle<Map> map = has_function_literal
        ? Handle<Map>(context->object_function()->initial_map())
        : ComputeObjectLiteralMap(context,
                                  constant_properties,
                                  &is_result_from_cache);
  
    PretenureFlag pretenure_flag =
        isolate->heap()->InNewSpace(*literals) ? NOT_TENURED : TENURED;
  
    Handle<JSObject> boilerplate =
        isolate->factory()->NewJSObjectFromMap(map, pretenure_flag);
  
    // Normalize the elements of the boilerplate to save space if needed.
    if (!should_have_fast_elements) JSObject::NormalizeElements(boilerplate);
  
    // Add the constant properties to the boilerplate.
    int length = constant_properties->length();
    bool should_transform =
        !is_result_from_cache && boilerplate->HasFastProperties();
    bool should_normalize = should_transform || has_function_literal;
    if (should_normalize) {
      // TODO(verwaest): We might not want to ever normalize here.
      JSObject::NormalizeProperties(
          boilerplate, KEEP_INOBJECT_PROPERTIES, length / 2);
    }
    // TODO(verwaest): Support tracking representations in the boilerplate.
    for (int index = 0; index < length; index +=2) {
      Handle<Object> key(constant_properties->get(index+0), isolate);
      Handle<Object> value(constant_properties->get(index+1), isolate);
      if (value->IsFixedArray()) {
        // The value contains the constant_properties of a
        // simple object or array literal.
        Handle<FixedArray> array = Handle<FixedArray>::cast(value);
        ASSIGN_RETURN_ON_EXCEPTION(
            isolate, value,
            CreateLiteralBoilerplate(isolate, literals, array),
            Object);
      }
      MaybeHandle<Object> maybe_result;
      uint32_t element_index = 0;
      if (key->IsInternalizedString()) {
        if (Handle<String>::cast(key)->AsArrayIndex(&element_index)) {
          // Array index as string (uint32).
          if (value->IsUninitialized()) value = handle(Smi::FromInt(0), isolate);
          maybe_result =
              JSObject::SetOwnElement(boilerplate, element_index, value, SLOPPY);
        } else {
          Handle<String> name(String::cast(*key));
          DCHECK(!name->AsArrayIndex(&element_index));
          maybe_result = JSObject::SetOwnPropertyIgnoreAttributes(
              boilerplate, name, value, NONE);
        }
      } else if (key->ToArrayIndex(&element_index)) {
        // Array index (uint32).
        if (value->IsUninitialized()) value = handle(Smi::FromInt(0), isolate);
        maybe_result =
            JSObject::SetOwnElement(boilerplate, element_index, value, SLOPPY);
      } else {
        // Non-uint32 number.
        DCHECK(key->IsNumber());
        double num = key->Number();
        char arr[100];
        Vector<char> buffer(arr, ARRAY_SIZE(arr));
        const char* str = DoubleToCString(num, buffer);
        Handle<String> name = isolate->factory()->NewStringFromAsciiChecked(str);
        maybe_result = JSObject::SetOwnPropertyIgnoreAttributes(boilerplate, name,
                                                                value, NONE);
      }
      // If setting the property on the boilerplate throws an
      // exception, the exception is converted to an empty handle in
      // the handle based operations.  In that case, we need to
      // convert back to an exception.
      RETURN_ON_EXCEPTION(isolate, maybe_result, Object);
    }
  
    // Transform to fast properties if necessary. For object literals with
    // containing function literals we defer this operation until after all
    // computed properties have been assigned so that we can generate
    // constant function properties.
    if (should_transform && !has_function_literal) {
      JSObject::MigrateSlowToFast(
          boilerplate, boilerplate->map()->unused_property_fields());
    }
  
    return boilerplate;
  }
  
  
  MUST_USE_RESULT static MaybeHandle<Object> TransitionElements(
      Handle<Object> object,
      ElementsKind to_kind,
      Isolate* isolate) {
    HandleScope scope(isolate);
    if (!object->IsJSObject()) {
      isolate->ThrowIllegalOperation();
      return MaybeHandle<Object>();
    }
    ElementsKind from_kind =
        Handle<JSObject>::cast(object)->map()->elements_kind();
    if (Map::IsValidElementsTransition(from_kind, to_kind)) {
      JSObject::TransitionElementsKind(Handle<JSObject>::cast(object), to_kind);
      return object;
    }
    isolate->ThrowIllegalOperation();
    return MaybeHandle<Object>();
  }
  
  
  MaybeHandle<Object> Runtime::CreateArrayLiteralBoilerplate(
      Isolate* isolate,
      Handle<FixedArray> literals,
      Handle<FixedArray> elements) {
    // Create the JSArray.
    Handle<JSFunction> constructor(
        JSFunction::NativeContextFromLiterals(*literals)->array_function());
  
    PretenureFlag pretenure_flag =
        isolate->heap()->InNewSpace(*literals) ? NOT_TENURED : TENURED;
  
    Handle<JSArray> object = Handle<JSArray>::cast(
        isolate->factory()->NewJSObject(constructor, pretenure_flag));
  
    ElementsKind constant_elements_kind =
        static_cast<ElementsKind>(Smi::cast(elements->get(0))->value());
    Handle<FixedArrayBase> constant_elements_values(
        FixedArrayBase::cast(elements->get(1)));
  
    { DisallowHeapAllocation no_gc;
      DCHECK(IsFastElementsKind(constant_elements_kind));
      Context* native_context = isolate->context()->native_context();
      Object* maps_array = native_context->js_array_maps();
      DCHECK(!maps_array->IsUndefined());
      Object* map = FixedArray::cast(maps_array)->get(constant_elements_kind);
      object->set_map(Map::cast(map));
    }
  
    Handle<FixedArrayBase> copied_elements_values;
    if (IsFastDoubleElementsKind(constant_elements_kind)) {
      copied_elements_values = isolate->factory()->CopyFixedDoubleArray(
          Handle<FixedDoubleArray>::cast(constant_elements_values));
    } else {
      DCHECK(IsFastSmiOrObjectElementsKind(constant_elements_kind));
      const bool is_cow =
          (constant_elements_values->map() ==
           isolate->heap()->fixed_cow_array_map());
      if (is_cow) {
        copied_elements_values = constant_elements_values;
  #if DEBUG
        Handle<FixedArray> fixed_array_values =
            Handle<FixedArray>::cast(copied_elements_values);
        for (int i = 0; i < fixed_array_values->length(); i++) {
          DCHECK(!fixed_array_values->get(i)->IsFixedArray());
        }
  #endif
      } else {
        Handle<FixedArray> fixed_array_values =
            Handle<FixedArray>::cast(constant_elements_values);
        Handle<FixedArray> fixed_array_values_copy =
            isolate->factory()->CopyFixedArray(fixed_array_values);
        copied_elements_values = fixed_array_values_copy;
        for (int i = 0; i < fixed_array_values->length(); i++) {
          if (fixed_array_values->get(i)->IsFixedArray()) {
            // The value contains the constant_properties of a
            // simple object or array literal.
            Handle<FixedArray> fa(FixedArray::cast(fixed_array_values->get(i)));
            Handle<Object> result;
            ASSIGN_RETURN_ON_EXCEPTION(
                isolate, result,
                CreateLiteralBoilerplate(isolate, literals, fa),
                Object);
            fixed_array_values_copy->set(i, *result);
          }
        }
      }
    }
    object->set_elements(*copied_elements_values);
    object->set_length(Smi::FromInt(copied_elements_values->length()));
  
    JSObject::ValidateElements(object);
    return object;
  }
  
  
  MUST_USE_RESULT static MaybeHandle<Object> CreateLiteralBoilerplate(
      Isolate* isolate,
      Handle<FixedArray> literals,
      Handle<FixedArray> array) {
    Handle<FixedArray> elements = CompileTimeValue::GetElements(array);
    const bool kHasNoFunctionLiteral = false;
    switch (CompileTimeValue::GetLiteralType(array)) {
      case CompileTimeValue::OBJECT_LITERAL_FAST_ELEMENTS:
        return CreateObjectLiteralBoilerplate(isolate,
                                              literals,
                                              elements,
                                              true,
                                              kHasNoFunctionLiteral);
      case CompileTimeValue::OBJECT_LITERAL_SLOW_ELEMENTS:
        return CreateObjectLiteralBoilerplate(isolate,
                                              literals,
                                              elements,
                                              false,
                                              kHasNoFunctionLiteral);
      case CompileTimeValue::ARRAY_LITERAL:
        return Runtime::CreateArrayLiteralBoilerplate(
            isolate, literals, elements);
      default:
        UNREACHABLE();
        return MaybeHandle<Object>();
    }
  }
  
  
  RUNTIME_FUNCTION(Runtime_CreateObjectLiteral) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 4);
    CONVERT_ARG_HANDLE_CHECKED(FixedArray, literals, 0);
    CONVERT_SMI_ARG_CHECKED(literals_index, 1);
    CONVERT_ARG_HANDLE_CHECKED(FixedArray, constant_properties, 2);
    CONVERT_SMI_ARG_CHECKED(flags, 3);
    bool should_have_fast_elements = (flags & ObjectLiteral::kFastElements) != 0;
    bool has_function_literal = (flags & ObjectLiteral::kHasFunction) != 0;
  
    RUNTIME_ASSERT(literals_index >= 0 && literals_index < literals->length());
  
    // Check if boilerplate exists. If not, create it first.
    Handle<Object> literal_site(literals->get(literals_index), isolate);
    Handle<AllocationSite> site;
    Handle<JSObject> boilerplate;
    if (*literal_site == isolate->heap()->undefined_value()) {
      Handle<Object> raw_boilerplate;
      ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
          isolate, raw_boilerplate,
          CreateObjectLiteralBoilerplate(
              isolate,
              literals,
              constant_properties,
              should_have_fast_elements,
              has_function_literal));
      boilerplate = Handle<JSObject>::cast(raw_boilerplate);
  
      AllocationSiteCreationContext creation_context(isolate);
      site = creation_context.EnterNewScope();
      RETURN_FAILURE_ON_EXCEPTION(
          isolate,
          JSObject::DeepWalk(boilerplate, &creation_context));
      creation_context.ExitScope(site, boilerplate);
  
      // Update the functions literal and return the boilerplate.
      literals->set(literals_index, *site);
    } else {
      site = Handle<AllocationSite>::cast(literal_site);
      boilerplate = Handle<JSObject>(JSObject::cast(site->transition_info()),
                                     isolate);
    }
  
    AllocationSiteUsageContext usage_context(isolate, site, true);
    usage_context.EnterNewScope();
    MaybeHandle<Object> maybe_copy = JSObject::DeepCopy(
        boilerplate, &usage_context);
    usage_context.ExitScope(site, boilerplate);
    Handle<Object> copy;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, copy, maybe_copy);
    return *copy;
  }
  
  
  MUST_USE_RESULT static MaybeHandle<AllocationSite> GetLiteralAllocationSite(
      Isolate* isolate,
      Handle<FixedArray> literals,
      int literals_index,
      Handle<FixedArray> elements) {
    // Check if boilerplate exists. If not, create it first.
    Handle<Object> literal_site(literals->get(literals_index), isolate);
    Handle<AllocationSite> site;
    if (*literal_site == isolate->heap()->undefined_value()) {
      DCHECK(*elements != isolate->heap()->empty_fixed_array());
      Handle<Object> boilerplate;
      ASSIGN_RETURN_ON_EXCEPTION(
          isolate, boilerplate,
          Runtime::CreateArrayLiteralBoilerplate(isolate, literals, elements),
          AllocationSite);
  
      AllocationSiteCreationContext creation_context(isolate);
      site = creation_context.EnterNewScope();
      if (JSObject::DeepWalk(Handle<JSObject>::cast(boilerplate),
                             &creation_context).is_null()) {
        return Handle<AllocationSite>::null();
      }
      creation_context.ExitScope(site, Handle<JSObject>::cast(boilerplate));
  
      literals->set(literals_index, *site);
    } else {
      site = Handle<AllocationSite>::cast(literal_site);
    }
  
    return site;
  }
  
  
  static MaybeHandle<JSObject> CreateArrayLiteralImpl(Isolate* isolate,
                                             Handle<FixedArray> literals,
                                             int literals_index,
                                             Handle<FixedArray> elements,
                                             int flags) {
    RUNTIME_ASSERT_HANDLIFIED(literals_index >= 0 &&
                              literals_index < literals->length(), JSObject);
    Handle<AllocationSite> site;
    ASSIGN_RETURN_ON_EXCEPTION(
        isolate, site,
        GetLiteralAllocationSite(isolate, literals, literals_index, elements),
        JSObject);
  
    bool enable_mementos = (flags & ArrayLiteral::kDisableMementos) == 0;
    Handle<JSObject> boilerplate(JSObject::cast(site->transition_info()));
    AllocationSiteUsageContext usage_context(isolate, site, enable_mementos);
    usage_context.EnterNewScope();
    JSObject::DeepCopyHints hints = (flags & ArrayLiteral::kShallowElements) == 0
                                        ? JSObject::kNoHints
                                        : JSObject::kObjectIsShallow;
    MaybeHandle<JSObject> copy = JSObject::DeepCopy(boilerplate, &usage_context,
                                                    hints);
    usage_context.ExitScope(site, boilerplate);
    return copy;
  }
  
  
  RUNTIME_FUNCTION(Runtime_CreateArrayLiteral) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 4);
    CONVERT_ARG_HANDLE_CHECKED(FixedArray, literals, 0);
    CONVERT_SMI_ARG_CHECKED(literals_index, 1);
    CONVERT_ARG_HANDLE_CHECKED(FixedArray, elements, 2);
    CONVERT_SMI_ARG_CHECKED(flags, 3);
  
    Handle<JSObject> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, result,
        CreateArrayLiteralImpl(isolate, literals, literals_index, elements,
                               flags));
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_CreateArrayLiteralStubBailout) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
    CONVERT_ARG_HANDLE_CHECKED(FixedArray, literals, 0);
    CONVERT_SMI_ARG_CHECKED(literals_index, 1);
    CONVERT_ARG_HANDLE_CHECKED(FixedArray, elements, 2);
  
    Handle<JSObject> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, result,
       CreateArrayLiteralImpl(isolate, literals, literals_index, elements,
                              ArrayLiteral::kShallowElements));
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_CreateSymbol) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, name, 0);
    RUNTIME_ASSERT(name->IsString() || name->IsUndefined());
    Handle<Symbol> symbol = isolate->factory()->NewSymbol();
    if (name->IsString()) symbol->set_name(*name);
    return *symbol;
  }
  
  
  RUNTIME_FUNCTION(Runtime_CreatePrivateSymbol) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, name, 0);
    RUNTIME_ASSERT(name->IsString() || name->IsUndefined());
    Handle<Symbol> symbol = isolate->factory()->NewPrivateSymbol();
    if (name->IsString()) symbol->set_name(*name);
    return *symbol;
  }
  
  
  RUNTIME_FUNCTION(Runtime_CreateGlobalPrivateSymbol) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(String, name, 0);
    Handle<JSObject> registry = isolate->GetSymbolRegistry();
    Handle<String> part = isolate->factory()->private_intern_string();
    Handle<Object> privates;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, privates, Object::GetPropertyOrElement(registry, part));
    Handle<Object> symbol;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, symbol, Object::GetPropertyOrElement(privates, name));
    if (!symbol->IsSymbol()) {
      DCHECK(symbol->IsUndefined());
      symbol = isolate->factory()->NewPrivateSymbol();
      Handle<Symbol>::cast(symbol)->set_name(*name);
      JSObject::SetProperty(Handle<JSObject>::cast(privates), name, symbol,
                            STRICT).Assert();
    }
    return *symbol;
  }
  
  
  RUNTIME_FUNCTION(Runtime_NewSymbolWrapper) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(Symbol, symbol, 0);
    return *Object::ToObject(isolate, symbol).ToHandleChecked();
  }
  
  
  RUNTIME_FUNCTION(Runtime_SymbolDescription) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(Symbol, symbol, 0);
    return symbol->name();
  }
  
  
  RUNTIME_FUNCTION(Runtime_SymbolRegistry) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 0);
    return *isolate->GetSymbolRegistry();
  }
  
  
  RUNTIME_FUNCTION(Runtime_SymbolIsPrivate) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(Symbol, symbol, 0);
    return isolate->heap()->ToBoolean(symbol->is_private());
  }
  
  
  RUNTIME_FUNCTION(Runtime_CreateJSProxy) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSReceiver, handler, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, prototype, 1);
    if (!prototype->IsJSReceiver()) prototype = isolate->factory()->null_value();
    return *isolate->factory()->NewJSProxy(handler, prototype);
  }
  
  
  RUNTIME_FUNCTION(Runtime_CreateJSFunctionProxy) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 4);
    CONVERT_ARG_HANDLE_CHECKED(JSReceiver, handler, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, call_trap, 1);
    RUNTIME_ASSERT(call_trap->IsJSFunction() || call_trap->IsJSFunctionProxy());
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, construct_trap, 2);
    CONVERT_ARG_HANDLE_CHECKED(Object, prototype, 3);
    if (!prototype->IsJSReceiver()) prototype = isolate->factory()->null_value();
    return *isolate->factory()->NewJSFunctionProxy(
        handler, call_trap, construct_trap, prototype);
  }
  
  
  RUNTIME_FUNCTION(Runtime_IsJSProxy) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, obj, 0);
    return isolate->heap()->ToBoolean(obj->IsJSProxy());
  }
  
  
  RUNTIME_FUNCTION(Runtime_IsJSFunctionProxy) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, obj, 0);
    return isolate->heap()->ToBoolean(obj->IsJSFunctionProxy());
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetHandler) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(JSProxy, proxy, 0);
    return proxy->handler();
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetCallTrap) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(JSFunctionProxy, proxy, 0);
    return proxy->call_trap();
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetConstructTrap) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(JSFunctionProxy, proxy, 0);
    return proxy->construct_trap();
  }
  
  
  RUNTIME_FUNCTION(Runtime_Fix) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSProxy, proxy, 0);
    JSProxy::Fix(proxy);
    return isolate->heap()->undefined_value();
  }
  
  
  void Runtime::FreeArrayBuffer(Isolate* isolate,
                                JSArrayBuffer* phantom_array_buffer) {
    if (phantom_array_buffer->should_be_freed()) {
      DCHECK(phantom_array_buffer->is_external());
      free(phantom_array_buffer->backing_store());
    }
    if (phantom_array_buffer->is_external()) return;
  
    size_t allocated_length = NumberToSize(
        isolate, phantom_array_buffer->byte_length());
  
    reinterpret_cast<v8::Isolate*>(isolate)
        ->AdjustAmountOfExternalAllocatedMemory(
            -static_cast<int64_t>(allocated_length));
    CHECK(V8::ArrayBufferAllocator() != NULL);
    V8::ArrayBufferAllocator()->Free(
        phantom_array_buffer->backing_store(),
        allocated_length);
  }
  
  
  void Runtime::SetupArrayBuffer(Isolate* isolate,
                                 Handle<JSArrayBuffer> array_buffer,
                                 bool is_external,
                                 void* data,
                                 size_t allocated_length) {
    DCHECK(array_buffer->GetInternalFieldCount() ==
        v8::ArrayBuffer::kInternalFieldCount);
    for (int i = 0; i < v8::ArrayBuffer::kInternalFieldCount; i++) {
      array_buffer->SetInternalField(i, Smi::FromInt(0));
    }
    array_buffer->set_backing_store(data);
    array_buffer->set_flag(Smi::FromInt(0));
    array_buffer->set_is_external(is_external);
  
    Handle<Object> byte_length =
        isolate->factory()->NewNumberFromSize(allocated_length);
    CHECK(byte_length->IsSmi() || byte_length->IsHeapNumber());
    array_buffer->set_byte_length(*byte_length);
  
    array_buffer->set_weak_next(isolate->heap()->array_buffers_list());
    isolate->heap()->set_array_buffers_list(*array_buffer);
    array_buffer->set_weak_first_view(isolate->heap()->undefined_value());
  }
  
  
  bool Runtime::SetupArrayBufferAllocatingData(
      Isolate* isolate,
      Handle<JSArrayBuffer> array_buffer,
      size_t allocated_length,
      bool initialize) {
    void* data;
    CHECK(V8::ArrayBufferAllocator() != NULL);
    if (allocated_length != 0) {
      if (initialize) {
        data = V8::ArrayBufferAllocator()->Allocate(allocated_length);
      } else {
        data =
            V8::ArrayBufferAllocator()->AllocateUninitialized(allocated_length);
      }
      if (data == NULL) return false;
    } else {
      data = NULL;
    }
  
    SetupArrayBuffer(isolate, array_buffer, false, data, allocated_length);
  
    reinterpret_cast<v8::Isolate*>(isolate)
        ->AdjustAmountOfExternalAllocatedMemory(allocated_length);
  
    return true;
  }
  
  
  void Runtime::NeuterArrayBuffer(Handle<JSArrayBuffer> array_buffer) {
    Isolate* isolate = array_buffer->GetIsolate();
    for (Handle<Object> view_obj(array_buffer->weak_first_view(), isolate);
         !view_obj->IsUndefined();) {
      Handle<JSArrayBufferView> view(JSArrayBufferView::cast(*view_obj));
      if (view->IsJSTypedArray()) {
        JSTypedArray::cast(*view)->Neuter();
      } else if (view->IsJSDataView()) {
        JSDataView::cast(*view)->Neuter();
      } else {
        UNREACHABLE();
      }
      view_obj = handle(view->weak_next(), isolate);
    }
    array_buffer->Neuter();
  }
  
  
  RUNTIME_FUNCTION(Runtime_ArrayBufferInitialize) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSArrayBuffer, holder, 0);
    CONVERT_NUMBER_ARG_HANDLE_CHECKED(byteLength, 1);
    if (!holder->byte_length()->IsUndefined()) {
      // ArrayBuffer is already initialized; probably a fuzz test.
      return *holder;
    }
    size_t allocated_length = 0;
    if (!TryNumberToSize(isolate, *byteLength, &allocated_length)) {
      return isolate->Throw(
          *isolate->factory()->NewRangeError("invalid_array_buffer_length",
                                             HandleVector<Object>(NULL, 0)));
    }
    if (!Runtime::SetupArrayBufferAllocatingData(isolate,
                                                 holder, allocated_length)) {
      return isolate->Throw(
          *isolate->factory()->NewRangeError("invalid_array_buffer_length",
                                             HandleVector<Object>(NULL, 0)));
    }
    return *holder;
  }
  
  
  RUNTIME_FUNCTION(Runtime_ArrayBufferGetByteLength) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(JSArrayBuffer, holder, 0);
    return holder->byte_length();
  }
  
  
  RUNTIME_FUNCTION(Runtime_ArrayBufferSliceImpl) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
    CONVERT_ARG_HANDLE_CHECKED(JSArrayBuffer, source, 0);
    CONVERT_ARG_HANDLE_CHECKED(JSArrayBuffer, target, 1);
    CONVERT_NUMBER_ARG_HANDLE_CHECKED(first, 2);
    RUNTIME_ASSERT(!source.is_identical_to(target));
    size_t start = 0;
    RUNTIME_ASSERT(TryNumberToSize(isolate, *first, &start));
    size_t target_length = NumberToSize(isolate, target->byte_length());
  
    if (target_length == 0) return isolate->heap()->undefined_value();
  
    size_t source_byte_length = NumberToSize(isolate, source->byte_length());
    RUNTIME_ASSERT(start <= source_byte_length);
    RUNTIME_ASSERT(source_byte_length - start >= target_length);
    uint8_t* source_data = reinterpret_cast<uint8_t*>(source->backing_store());
    uint8_t* target_data = reinterpret_cast<uint8_t*>(target->backing_store());
    CopyBytes(target_data, source_data + start, target_length);
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_ArrayBufferIsView) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(Object, object, 0);
    return isolate->heap()->ToBoolean(object->IsJSArrayBufferView());
  }
  
  
  RUNTIME_FUNCTION(Runtime_ArrayBufferNeuter) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSArrayBuffer, array_buffer, 0);
    if (array_buffer->backing_store() == NULL) {
      CHECK(Smi::FromInt(0) == array_buffer->byte_length());
      return isolate->heap()->undefined_value();
    }
    DCHECK(!array_buffer->is_external());
    void* backing_store = array_buffer->backing_store();
    size_t byte_length = NumberToSize(isolate, array_buffer->byte_length());
    array_buffer->set_is_external(true);
    Runtime::NeuterArrayBuffer(array_buffer);
    V8::ArrayBufferAllocator()->Free(backing_store, byte_length);
    return isolate->heap()->undefined_value();
  }
  
  
  void Runtime::ArrayIdToTypeAndSize(
      int arrayId,
      ExternalArrayType* array_type,
      ElementsKind* external_elements_kind,
      ElementsKind* fixed_elements_kind,
      size_t* element_size) {
    switch (arrayId) {
  #define ARRAY_ID_CASE(Type, type, TYPE, ctype, size)                           \
      case ARRAY_ID_##TYPE:                                                      \
        *array_type = kExternal##Type##Array;                                    \
        *external_elements_kind = EXTERNAL_##TYPE##_ELEMENTS;                    \
        *fixed_elements_kind = TYPE##_ELEMENTS;                                  \
        *element_size = size;                                                    \
        break;
  
      TYPED_ARRAYS(ARRAY_ID_CASE)
  #undef ARRAY_ID_CASE
  
      default:
        UNREACHABLE();
    }
  }
  
  
  RUNTIME_FUNCTION(Runtime_TypedArrayInitialize) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 5);
    CONVERT_ARG_HANDLE_CHECKED(JSTypedArray, holder, 0);
    CONVERT_SMI_ARG_CHECKED(arrayId, 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, maybe_buffer, 2);
    CONVERT_NUMBER_ARG_HANDLE_CHECKED(byte_offset_object, 3);
    CONVERT_NUMBER_ARG_HANDLE_CHECKED(byte_length_object, 4);
  
    RUNTIME_ASSERT(arrayId >= Runtime::ARRAY_ID_FIRST &&
                   arrayId <= Runtime::ARRAY_ID_LAST);
  
    ExternalArrayType array_type = kExternalInt8Array;  // Bogus initialization.
    size_t element_size = 1;  // Bogus initialization.
    ElementsKind external_elements_kind =
        EXTERNAL_INT8_ELEMENTS;  // Bogus initialization.
    ElementsKind fixed_elements_kind = INT8_ELEMENTS;  // Bogus initialization.
    Runtime::ArrayIdToTypeAndSize(arrayId,
        &array_type,
        &external_elements_kind,
        &fixed_elements_kind,
        &element_size);
    RUNTIME_ASSERT(holder->map()->elements_kind() == fixed_elements_kind);
  
    size_t byte_offset = 0;
    size_t byte_length = 0;
    RUNTIME_ASSERT(TryNumberToSize(isolate, *byte_offset_object, &byte_offset));
    RUNTIME_ASSERT(TryNumberToSize(isolate, *byte_length_object, &byte_length));
  
    if (maybe_buffer->IsJSArrayBuffer()) {
      Handle<JSArrayBuffer> buffer = Handle<JSArrayBuffer>::cast(maybe_buffer);
      size_t array_buffer_byte_length =
          NumberToSize(isolate, buffer->byte_length());
      RUNTIME_ASSERT(byte_offset <= array_buffer_byte_length);
      RUNTIME_ASSERT(array_buffer_byte_length - byte_offset >= byte_length);
    } else {
      RUNTIME_ASSERT(maybe_buffer->IsNull());
    }
  
    RUNTIME_ASSERT(byte_length % element_size == 0);
    size_t length = byte_length / element_size;
  
    if (length > static_cast<unsigned>(Smi::kMaxValue)) {
      return isolate->Throw(
          *isolate->factory()->NewRangeError("invalid_typed_array_length",
                                             HandleVector<Object>(NULL, 0)));
    }
  
    // All checks are done, now we can modify objects.
  
    DCHECK(holder->GetInternalFieldCount() ==
        v8::ArrayBufferView::kInternalFieldCount);
    for (int i = 0; i < v8::ArrayBufferView::kInternalFieldCount; i++) {
      holder->SetInternalField(i, Smi::FromInt(0));
    }
    Handle<Object> length_obj = isolate->factory()->NewNumberFromSize(length);
    holder->set_length(*length_obj);
    holder->set_byte_offset(*byte_offset_object);
    holder->set_byte_length(*byte_length_object);
  
    if (!maybe_buffer->IsNull()) {
      Handle<JSArrayBuffer> buffer = Handle<JSArrayBuffer>::cast(maybe_buffer);
      holder->set_buffer(*buffer);
      holder->set_weak_next(buffer->weak_first_view());
      buffer->set_weak_first_view(*holder);
  
      Handle<ExternalArray> elements =
          isolate->factory()->NewExternalArray(
              static_cast<int>(length), array_type,
              static_cast<uint8_t*>(buffer->backing_store()) + byte_offset);
      Handle<Map> map =
          JSObject::GetElementsTransitionMap(holder, external_elements_kind);
      JSObject::SetMapAndElements(holder, map, elements);
      DCHECK(IsExternalArrayElementsKind(holder->map()->elements_kind()));
    } else {
      holder->set_buffer(Smi::FromInt(0));
      holder->set_weak_next(isolate->heap()->undefined_value());
      Handle<FixedTypedArrayBase> elements =
          isolate->factory()->NewFixedTypedArray(
              static_cast<int>(length), array_type);
      holder->set_elements(*elements);
    }
    return isolate->heap()->undefined_value();
  }
  
  
  // Initializes a typed array from an array-like object.
  // If an array-like object happens to be a typed array of the same type,
  // initializes backing store using memove.
  //
  // Returns true if backing store was initialized or false otherwise.
  RUNTIME_FUNCTION(Runtime_TypedArrayInitializeFromArrayLike) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 4);
    CONVERT_ARG_HANDLE_CHECKED(JSTypedArray, holder, 0);
    CONVERT_SMI_ARG_CHECKED(arrayId, 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, source, 2);
    CONVERT_NUMBER_ARG_HANDLE_CHECKED(length_obj, 3);
  
    RUNTIME_ASSERT(arrayId >= Runtime::ARRAY_ID_FIRST &&
                   arrayId <= Runtime::ARRAY_ID_LAST);
  
    ExternalArrayType array_type = kExternalInt8Array;  // Bogus initialization.
    size_t element_size = 1;  // Bogus initialization.
    ElementsKind external_elements_kind =
        EXTERNAL_INT8_ELEMENTS;  // Bogus intialization.
    ElementsKind fixed_elements_kind = INT8_ELEMENTS;  // Bogus initialization.
    Runtime::ArrayIdToTypeAndSize(arrayId,
        &array_type,
        &external_elements_kind,
        &fixed_elements_kind,
        &element_size);
  
    RUNTIME_ASSERT(holder->map()->elements_kind() == fixed_elements_kind);
  
    Handle<JSArrayBuffer> buffer = isolate->factory()->NewJSArrayBuffer();
    if (source->IsJSTypedArray() &&
        JSTypedArray::cast(*source)->type() == array_type) {
      length_obj = Handle<Object>(JSTypedArray::cast(*source)->length(), isolate);
    }
    size_t length = 0;
    RUNTIME_ASSERT(TryNumberToSize(isolate, *length_obj, &length));
  
    if ((length > static_cast<unsigned>(Smi::kMaxValue)) ||
        (length > (kMaxInt / element_size))) {
      return isolate->Throw(*isolate->factory()->
            NewRangeError("invalid_typed_array_length",
              HandleVector<Object>(NULL, 0)));
    }
    size_t byte_length = length * element_size;
  
    DCHECK(holder->GetInternalFieldCount() ==
        v8::ArrayBufferView::kInternalFieldCount);
    for (int i = 0; i < v8::ArrayBufferView::kInternalFieldCount; i++) {
      holder->SetInternalField(i, Smi::FromInt(0));
    }
  
    // NOTE: not initializing backing store.
    // We assume that the caller of this function will initialize holder
    // with the loop
    //      for(i = 0; i < length; i++) { holder[i] = source[i]; }
    // We assume that the caller of this function is always a typed array
    // constructor.
    // If source is a typed array, this loop will always run to completion,
    // so we are sure that the backing store will be initialized.
    // Otherwise, the indexing operation might throw, so the loop will not
    // run to completion and the typed array might remain partly initialized.
    // However we further assume that the caller of this function is a typed array
    // constructor, and the exception will propagate out of the constructor,
    // therefore uninitialized memory will not be accessible by a user program.
    //
    // TODO(dslomov): revise this once we support subclassing.
  
    if (!Runtime::SetupArrayBufferAllocatingData(
          isolate, buffer, byte_length, false)) {
      return isolate->Throw(*isolate->factory()->
            NewRangeError("invalid_array_buffer_length",
              HandleVector<Object>(NULL, 0)));
    }
  
    holder->set_buffer(*buffer);
    holder->set_byte_offset(Smi::FromInt(0));
    Handle<Object> byte_length_obj(
        isolate->factory()->NewNumberFromSize(byte_length));
    holder->set_byte_length(*byte_length_obj);
    holder->set_length(*length_obj);
    holder->set_weak_next(buffer->weak_first_view());
    buffer->set_weak_first_view(*holder);
  
    Handle<ExternalArray> elements =
        isolate->factory()->NewExternalArray(
            static_cast<int>(length), array_type,
            static_cast<uint8_t*>(buffer->backing_store()));
    Handle<Map> map = JSObject::GetElementsTransitionMap(
        holder, external_elements_kind);
    JSObject::SetMapAndElements(holder, map, elements);
  
    if (source->IsJSTypedArray()) {
      Handle<JSTypedArray> typed_array(JSTypedArray::cast(*source));
  
      if (typed_array->type() == holder->type()) {
        uint8_t* backing_store =
          static_cast<uint8_t*>(
            typed_array->GetBuffer()->backing_store());
        size_t source_byte_offset =
            NumberToSize(isolate, typed_array->byte_offset());
        memcpy(
            buffer->backing_store(),
            backing_store + source_byte_offset,
            byte_length);
        return isolate->heap()->true_value();
      }
    }
  
    return isolate->heap()->false_value();
  }
  
  
  #define BUFFER_VIEW_GETTER(Type, getter, accessor) \
    RUNTIME_FUNCTION(Runtime_##Type##Get##getter) {                    \
      HandleScope scope(isolate);                                               \
      DCHECK(args.length() == 1);                                               \
      CONVERT_ARG_HANDLE_CHECKED(JS##Type, holder, 0);                          \
      return holder->accessor();                                                \
    }
  
  BUFFER_VIEW_GETTER(ArrayBufferView, ByteLength, byte_length)
  BUFFER_VIEW_GETTER(ArrayBufferView, ByteOffset, byte_offset)
  BUFFER_VIEW_GETTER(TypedArray, Length, length)
  BUFFER_VIEW_GETTER(DataView, Buffer, buffer)
  
  #undef BUFFER_VIEW_GETTER
  
  RUNTIME_FUNCTION(Runtime_TypedArrayGetBuffer) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSTypedArray, holder, 0);
    return *holder->GetBuffer();
  }
  
  
  // Return codes for Runtime_TypedArraySetFastCases.
  // Should be synchronized with typedarray.js natives.
  enum TypedArraySetResultCodes {
    // Set from typed array of the same type.
    // This is processed by TypedArraySetFastCases
    TYPED_ARRAY_SET_TYPED_ARRAY_SAME_TYPE = 0,
    // Set from typed array of the different type, overlapping in memory.
    TYPED_ARRAY_SET_TYPED_ARRAY_OVERLAPPING = 1,
    // Set from typed array of the different type, non-overlapping.
    TYPED_ARRAY_SET_TYPED_ARRAY_NONOVERLAPPING = 2,
    // Set from non-typed array.
    TYPED_ARRAY_SET_NON_TYPED_ARRAY = 3
  };
  
  
  RUNTIME_FUNCTION(Runtime_TypedArraySetFastCases) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
    if (!args[0]->IsJSTypedArray())
      return isolate->Throw(*isolate->factory()->NewTypeError(
          "not_typed_array", HandleVector<Object>(NULL, 0)));
  
    if (!args[1]->IsJSTypedArray())
      return Smi::FromInt(TYPED_ARRAY_SET_NON_TYPED_ARRAY);
  
    CONVERT_ARG_HANDLE_CHECKED(JSTypedArray, target_obj, 0);
    CONVERT_ARG_HANDLE_CHECKED(JSTypedArray, source_obj, 1);
    CONVERT_NUMBER_ARG_HANDLE_CHECKED(offset_obj, 2);
  
    Handle<JSTypedArray> target(JSTypedArray::cast(*target_obj));
    Handle<JSTypedArray> source(JSTypedArray::cast(*source_obj));
    size_t offset = 0;
    RUNTIME_ASSERT(TryNumberToSize(isolate, *offset_obj, &offset));
    size_t target_length = NumberToSize(isolate, target->length());
    size_t source_length = NumberToSize(isolate, source->length());
    size_t target_byte_length = NumberToSize(isolate, target->byte_length());
    size_t source_byte_length = NumberToSize(isolate, source->byte_length());
    if (offset > target_length ||
        offset + source_length > target_length ||
        offset + source_length < offset)  // overflow
      return isolate->Throw(*isolate->factory()->NewRangeError(
            "typed_array_set_source_too_large", HandleVector<Object>(NULL, 0)));
  
    size_t target_offset = NumberToSize(isolate, target->byte_offset());
    size_t source_offset = NumberToSize(isolate, source->byte_offset());
    uint8_t* target_base =
        static_cast<uint8_t*>(
          target->GetBuffer()->backing_store()) + target_offset;
    uint8_t* source_base =
        static_cast<uint8_t*>(
          source->GetBuffer()->backing_store()) + source_offset;
  
    // Typed arrays of the same type: use memmove.
    if (target->type() == source->type()) {
      memmove(target_base + offset * target->element_size(),
          source_base, source_byte_length);
      return Smi::FromInt(TYPED_ARRAY_SET_TYPED_ARRAY_SAME_TYPE);
    }
  
    // Typed arrays of different types over the same backing store
    if ((source_base <= target_base &&
          source_base + source_byte_length > target_base) ||
        (target_base <= source_base &&
          target_base + target_byte_length > source_base)) {
      // We do not support overlapping ArrayBuffers
      DCHECK(
        target->GetBuffer()->backing_store() ==
        source->GetBuffer()->backing_store());
      return Smi::FromInt(TYPED_ARRAY_SET_TYPED_ARRAY_OVERLAPPING);
    } else {  // Non-overlapping typed arrays
      return Smi::FromInt(TYPED_ARRAY_SET_TYPED_ARRAY_NONOVERLAPPING);
    }
  }
  
  
  RUNTIME_FUNCTION(Runtime_TypedArrayMaxSizeInHeap) {
    DCHECK(args.length() == 0);
    DCHECK_OBJECT_SIZE(
        FLAG_typed_array_max_size_in_heap + FixedTypedArrayBase::kDataOffset);
    return Smi::FromInt(FLAG_typed_array_max_size_in_heap);
  }
  
  
  RUNTIME_FUNCTION(Runtime_DataViewInitialize) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 4);
    CONVERT_ARG_HANDLE_CHECKED(JSDataView, holder, 0);
    CONVERT_ARG_HANDLE_CHECKED(JSArrayBuffer, buffer, 1);
    CONVERT_NUMBER_ARG_HANDLE_CHECKED(byte_offset, 2);
    CONVERT_NUMBER_ARG_HANDLE_CHECKED(byte_length, 3);
  
    DCHECK(holder->GetInternalFieldCount() ==
        v8::ArrayBufferView::kInternalFieldCount);
    for (int i = 0; i < v8::ArrayBufferView::kInternalFieldCount; i++) {
      holder->SetInternalField(i, Smi::FromInt(0));
    }
    size_t buffer_length = 0;
    size_t offset = 0;
    size_t length = 0;
    RUNTIME_ASSERT(
        TryNumberToSize(isolate, buffer->byte_length(), &buffer_length));
    RUNTIME_ASSERT(TryNumberToSize(isolate, *byte_offset, &offset));
    RUNTIME_ASSERT(TryNumberToSize(isolate, *byte_length, &length));
  
    // TODO(jkummerow): When we have a "safe numerics" helper class, use it here.
    // Entire range [offset, offset + length] must be in bounds.
    RUNTIME_ASSERT(offset <= buffer_length);
    RUNTIME_ASSERT(offset + length <= buffer_length);
    // No overflow.
    RUNTIME_ASSERT(offset + length >= offset);
  
    holder->set_buffer(*buffer);
    holder->set_byte_offset(*byte_offset);
    holder->set_byte_length(*byte_length);
  
    holder->set_weak_next(buffer->weak_first_view());
    buffer->set_weak_first_view(*holder);
  
    return isolate->heap()->undefined_value();
  }
  
  
  inline static bool NeedToFlipBytes(bool is_little_endian) {
  #ifdef V8_TARGET_LITTLE_ENDIAN
    return !is_little_endian;
  #else
    return is_little_endian;
  #endif
  }
  
  
  template<int n>
  inline void CopyBytes(uint8_t* target, uint8_t* source) {
    for (int i = 0; i < n; i++) {
      *(target++) = *(source++);
    }
  }
  
  
  template<int n>
  inline void FlipBytes(uint8_t* target, uint8_t* source) {
    source = source + (n-1);
    for (int i = 0; i < n; i++) {
      *(target++) = *(source--);
    }
  }
  
  
  template<typename T>
  inline static bool DataViewGetValue(
      Isolate* isolate,
      Handle<JSDataView> data_view,
      Handle<Object> byte_offset_obj,
      bool is_little_endian,
      T* result) {
    size_t byte_offset = 0;
    if (!TryNumberToSize(isolate, *byte_offset_obj, &byte_offset)) {
      return false;
    }
    Handle<JSArrayBuffer> buffer(JSArrayBuffer::cast(data_view->buffer()));
  
    size_t data_view_byte_offset =
        NumberToSize(isolate, data_view->byte_offset());
    size_t data_view_byte_length =
        NumberToSize(isolate, data_view->byte_length());
    if (byte_offset + sizeof(T) > data_view_byte_length ||
        byte_offset + sizeof(T) < byte_offset)  {  // overflow
      return false;
    }
  
    union Value {
      T data;
      uint8_t bytes[sizeof(T)];
    };
  
    Value value;
    size_t buffer_offset = data_view_byte_offset + byte_offset;
    DCHECK(
        NumberToSize(isolate, buffer->byte_length())
        >= buffer_offset + sizeof(T));
    uint8_t* source =
          static_cast<uint8_t*>(buffer->backing_store()) + buffer_offset;
    if (NeedToFlipBytes(is_little_endian)) {
      FlipBytes<sizeof(T)>(value.bytes, source);
    } else {
      CopyBytes<sizeof(T)>(value.bytes, source);
    }
    *result = value.data;
    return true;
  }
  
  
  template<typename T>
  static bool DataViewSetValue(
      Isolate* isolate,
      Handle<JSDataView> data_view,
      Handle<Object> byte_offset_obj,
      bool is_little_endian,
      T data) {
    size_t byte_offset = 0;
    if (!TryNumberToSize(isolate, *byte_offset_obj, &byte_offset)) {
      return false;
    }
    Handle<JSArrayBuffer> buffer(JSArrayBuffer::cast(data_view->buffer()));
  
    size_t data_view_byte_offset =
        NumberToSize(isolate, data_view->byte_offset());
    size_t data_view_byte_length =
        NumberToSize(isolate, data_view->byte_length());
    if (byte_offset + sizeof(T) > data_view_byte_length ||
        byte_offset + sizeof(T) < byte_offset)  {  // overflow
      return false;
    }
  
    union Value {
      T data;
      uint8_t bytes[sizeof(T)];
    };
  
    Value value;
    value.data = data;
    size_t buffer_offset = data_view_byte_offset + byte_offset;
    DCHECK(
        NumberToSize(isolate, buffer->byte_length())
        >= buffer_offset + sizeof(T));
    uint8_t* target =
          static_cast<uint8_t*>(buffer->backing_store()) + buffer_offset;
    if (NeedToFlipBytes(is_little_endian)) {
      FlipBytes<sizeof(T)>(target, value.bytes);
    } else {
      CopyBytes<sizeof(T)>(target, value.bytes);
    }
    return true;
  }
  
  
  #define DATA_VIEW_GETTER(TypeName, Type, Converter)                           \
    RUNTIME_FUNCTION(Runtime_DataViewGet##TypeName) {                           \
      HandleScope scope(isolate);                                               \
      DCHECK(args.length() == 3);                                               \
      CONVERT_ARG_HANDLE_CHECKED(JSDataView, holder, 0);                        \
      CONVERT_NUMBER_ARG_HANDLE_CHECKED(offset, 1);                             \
      CONVERT_BOOLEAN_ARG_CHECKED(is_little_endian, 2);                         \
      Type result;                                                              \
      if (DataViewGetValue(                                                     \
            isolate, holder, offset, is_little_endian, &result)) {              \
        return *isolate->factory()->Converter(result);                          \
      } else {                                                                  \
        return isolate->Throw(*isolate->factory()->NewRangeError(               \
            "invalid_data_view_accessor_offset",                                \
            HandleVector<Object>(NULL, 0)));                                    \
      }                                                                         \
    }
  
  DATA_VIEW_GETTER(Uint8, uint8_t, NewNumberFromUint)
  DATA_VIEW_GETTER(Int8, int8_t, NewNumberFromInt)
  DATA_VIEW_GETTER(Uint16, uint16_t, NewNumberFromUint)
  DATA_VIEW_GETTER(Int16, int16_t, NewNumberFromInt)
  DATA_VIEW_GETTER(Uint32, uint32_t, NewNumberFromUint)
  DATA_VIEW_GETTER(Int32, int32_t, NewNumberFromInt)
  DATA_VIEW_GETTER(Float32, float, NewNumber)
  DATA_VIEW_GETTER(Float64, double, NewNumber)
  
  #undef DATA_VIEW_GETTER
  
  
  template <typename T>
  static T DataViewConvertValue(double value);
  
  
  template <>
  int8_t DataViewConvertValue<int8_t>(double value) {
    return static_cast<int8_t>(DoubleToInt32(value));
  }
  
  
  template <>
  int16_t DataViewConvertValue<int16_t>(double value) {
    return static_cast<int16_t>(DoubleToInt32(value));
  }
  
  
  template <>
  int32_t DataViewConvertValue<int32_t>(double value) {
    return DoubleToInt32(value);
  }
  
  
  template <>
  uint8_t DataViewConvertValue<uint8_t>(double value) {
    return static_cast<uint8_t>(DoubleToUint32(value));
  }
  
  
  template <>
  uint16_t DataViewConvertValue<uint16_t>(double value) {
    return static_cast<uint16_t>(DoubleToUint32(value));
  }
  
  
  template <>
  uint32_t DataViewConvertValue<uint32_t>(double value) {
    return DoubleToUint32(value);
  }
  
  
  template <>
  float DataViewConvertValue<float>(double value) {
    return static_cast<float>(value);
  }
  
  
  template <>
  double DataViewConvertValue<double>(double value) {
    return value;
  }
  
  
  #define DATA_VIEW_SETTER(TypeName, Type)                                      \
    RUNTIME_FUNCTION(Runtime_DataViewSet##TypeName) {                           \
      HandleScope scope(isolate);                                               \
      DCHECK(args.length() == 4);                                               \
      CONVERT_ARG_HANDLE_CHECKED(JSDataView, holder, 0);                        \
      CONVERT_NUMBER_ARG_HANDLE_CHECKED(offset, 1);                             \
      CONVERT_NUMBER_ARG_HANDLE_CHECKED(value, 2);                              \
      CONVERT_BOOLEAN_ARG_CHECKED(is_little_endian, 3);                         \
      Type v = DataViewConvertValue<Type>(value->Number());                     \
      if (DataViewSetValue(                                                     \
            isolate, holder, offset, is_little_endian, v)) {                    \
        return isolate->heap()->undefined_value();                              \
      } else {                                                                  \
        return isolate->Throw(*isolate->factory()->NewRangeError(               \
            "invalid_data_view_accessor_offset",                                \
            HandleVector<Object>(NULL, 0)));                                    \
      }                                                                         \
    }
  
  DATA_VIEW_SETTER(Uint8, uint8_t)
  DATA_VIEW_SETTER(Int8, int8_t)
  DATA_VIEW_SETTER(Uint16, uint16_t)
  DATA_VIEW_SETTER(Int16, int16_t)
  DATA_VIEW_SETTER(Uint32, uint32_t)
  DATA_VIEW_SETTER(Int32, int32_t)
  DATA_VIEW_SETTER(Float32, float)
  DATA_VIEW_SETTER(Float64, double)
  
  #undef DATA_VIEW_SETTER
  
  
  RUNTIME_FUNCTION(Runtime_SetInitialize) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSSet, holder, 0);
    Handle<OrderedHashSet> table = isolate->factory()->NewOrderedHashSet();
    holder->set_table(*table);
    return *holder;
  }
  
  
  RUNTIME_FUNCTION(Runtime_SetAdd) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSSet, holder, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, key, 1);
    Handle<OrderedHashSet> table(OrderedHashSet::cast(holder->table()));
    table = OrderedHashSet::Add(table, key);
    holder->set_table(*table);
    return *holder;
  }
  
  
  RUNTIME_FUNCTION(Runtime_SetHas) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSSet, holder, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, key, 1);
    Handle<OrderedHashSet> table(OrderedHashSet::cast(holder->table()));
    return isolate->heap()->ToBoolean(table->Contains(key));
  }
  
  
  RUNTIME_FUNCTION(Runtime_SetDelete) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSSet, holder, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, key, 1);
    Handle<OrderedHashSet> table(OrderedHashSet::cast(holder->table()));
    bool was_present = false;
    table = OrderedHashSet::Remove(table, key, &was_present);
    holder->set_table(*table);
    return isolate->heap()->ToBoolean(was_present);
  }
  
  
  RUNTIME_FUNCTION(Runtime_SetClear) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSSet, holder, 0);
    Handle<OrderedHashSet> table(OrderedHashSet::cast(holder->table()));
    table = OrderedHashSet::Clear(table);
    holder->set_table(*table);
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_SetGetSize) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSSet, holder, 0);
    Handle<OrderedHashSet> table(OrderedHashSet::cast(holder->table()));
    return Smi::FromInt(table->NumberOfElements());
  }
  
  
  RUNTIME_FUNCTION(Runtime_SetIteratorInitialize) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
    CONVERT_ARG_HANDLE_CHECKED(JSSetIterator, holder, 0);
    CONVERT_ARG_HANDLE_CHECKED(JSSet, set, 1);
    CONVERT_SMI_ARG_CHECKED(kind, 2)
    RUNTIME_ASSERT(kind == JSSetIterator::kKindValues ||
                   kind == JSSetIterator::kKindEntries);
    Handle<OrderedHashSet> table(OrderedHashSet::cast(set->table()));
    holder->set_table(*table);
    holder->set_index(Smi::FromInt(0));
    holder->set_kind(Smi::FromInt(kind));
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_SetIteratorNext) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_CHECKED(JSSetIterator, holder, 0);
    CONVERT_ARG_CHECKED(JSArray, value_array, 1);
    return holder->Next(value_array);
  }
  
  
  RUNTIME_FUNCTION(Runtime_MapInitialize) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSMap, holder, 0);
    Handle<OrderedHashMap> table = isolate->factory()->NewOrderedHashMap();
    holder->set_table(*table);
    return *holder;
  }
  
  
  RUNTIME_FUNCTION(Runtime_MapGet) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSMap, holder, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, key, 1);
    Handle<OrderedHashMap> table(OrderedHashMap::cast(holder->table()));
    Handle<Object> lookup(table->Lookup(key), isolate);
    return lookup->IsTheHole() ? isolate->heap()->undefined_value() : *lookup;
  }
  
  
  RUNTIME_FUNCTION(Runtime_MapHas) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSMap, holder, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, key, 1);
    Handle<OrderedHashMap> table(OrderedHashMap::cast(holder->table()));
    Handle<Object> lookup(table->Lookup(key), isolate);
    return isolate->heap()->ToBoolean(!lookup->IsTheHole());
  }
  
  
  RUNTIME_FUNCTION(Runtime_MapDelete) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSMap, holder, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, key, 1);
    Handle<OrderedHashMap> table(OrderedHashMap::cast(holder->table()));
    bool was_present = false;
    Handle<OrderedHashMap> new_table =
        OrderedHashMap::Remove(table, key, &was_present);
    holder->set_table(*new_table);
    return isolate->heap()->ToBoolean(was_present);
  }
  
  
  RUNTIME_FUNCTION(Runtime_MapClear) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSMap, holder, 0);
    Handle<OrderedHashMap> table(OrderedHashMap::cast(holder->table()));
    table = OrderedHashMap::Clear(table);
    holder->set_table(*table);
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_MapSet) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
    CONVERT_ARG_HANDLE_CHECKED(JSMap, holder, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, key, 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, value, 2);
    Handle<OrderedHashMap> table(OrderedHashMap::cast(holder->table()));
    Handle<OrderedHashMap> new_table = OrderedHashMap::Put(table, key, value);
    holder->set_table(*new_table);
    return *holder;
  }
  
  
  RUNTIME_FUNCTION(Runtime_MapGetSize) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSMap, holder, 0);
    Handle<OrderedHashMap> table(OrderedHashMap::cast(holder->table()));
    return Smi::FromInt(table->NumberOfElements());
  }
  
  
  RUNTIME_FUNCTION(Runtime_MapIteratorInitialize) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
    CONVERT_ARG_HANDLE_CHECKED(JSMapIterator, holder, 0);
    CONVERT_ARG_HANDLE_CHECKED(JSMap, map, 1);
    CONVERT_SMI_ARG_CHECKED(kind, 2)
    RUNTIME_ASSERT(kind == JSMapIterator::kKindKeys
        || kind == JSMapIterator::kKindValues
        || kind == JSMapIterator::kKindEntries);
    Handle<OrderedHashMap> table(OrderedHashMap::cast(map->table()));
    holder->set_table(*table);
    holder->set_index(Smi::FromInt(0));
    holder->set_kind(Smi::FromInt(kind));
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetWeakMapEntries) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSWeakCollection, holder, 0);
    Handle<ObjectHashTable> table(ObjectHashTable::cast(holder->table()));
    Handle<FixedArray> entries =
        isolate->factory()->NewFixedArray(table->NumberOfElements() * 2);
    {
      DisallowHeapAllocation no_gc;
      int number_of_non_hole_elements = 0;
      for (int i = 0; i < table->Capacity(); i++) {
        Handle<Object> key(table->KeyAt(i), isolate);
        if (table->IsKey(*key)) {
          entries->set(number_of_non_hole_elements++, *key);
          entries->set(number_of_non_hole_elements++, table->Lookup(key));
        }
      }
      DCHECK_EQ(table->NumberOfElements() * 2, number_of_non_hole_elements);
    }
    return *isolate->factory()->NewJSArrayWithElements(entries);
  }
  
  
  RUNTIME_FUNCTION(Runtime_MapIteratorNext) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_CHECKED(JSMapIterator, holder, 0);
    CONVERT_ARG_CHECKED(JSArray, value_array, 1);
    return holder->Next(value_array);
  }
  
  
  static Handle<JSWeakCollection> WeakCollectionInitialize(
      Isolate* isolate,
      Handle<JSWeakCollection> weak_collection) {
    DCHECK(weak_collection->map()->inobject_properties() == 0);
    Handle<ObjectHashTable> table = ObjectHashTable::New(isolate, 0);
    weak_collection->set_table(*table);
    return weak_collection;
  }
  
  
  RUNTIME_FUNCTION(Runtime_WeakCollectionInitialize) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSWeakCollection, weak_collection, 0);
    return *WeakCollectionInitialize(isolate, weak_collection);
  }
  
  
  RUNTIME_FUNCTION(Runtime_WeakCollectionGet) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSWeakCollection, weak_collection, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, key, 1);
    RUNTIME_ASSERT(key->IsJSReceiver() || key->IsSymbol());
    Handle<ObjectHashTable> table(
        ObjectHashTable::cast(weak_collection->table()));
    RUNTIME_ASSERT(table->IsKey(*key));
    Handle<Object> lookup(table->Lookup(key), isolate);
    return lookup->IsTheHole() ? isolate->heap()->undefined_value() : *lookup;
  }
  
  
  RUNTIME_FUNCTION(Runtime_WeakCollectionHas) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSWeakCollection, weak_collection, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, key, 1);
    RUNTIME_ASSERT(key->IsJSReceiver() || key->IsSymbol());
    Handle<ObjectHashTable> table(
        ObjectHashTable::cast(weak_collection->table()));
    RUNTIME_ASSERT(table->IsKey(*key));
    Handle<Object> lookup(table->Lookup(key), isolate);
    return isolate->heap()->ToBoolean(!lookup->IsTheHole());
  }
  
  
  RUNTIME_FUNCTION(Runtime_WeakCollectionDelete) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSWeakCollection, weak_collection, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, key, 1);
    RUNTIME_ASSERT(key->IsJSReceiver() || key->IsSymbol());
    Handle<ObjectHashTable> table(ObjectHashTable::cast(
        weak_collection->table()));
    RUNTIME_ASSERT(table->IsKey(*key));
    bool was_present = false;
    Handle<ObjectHashTable> new_table =
        ObjectHashTable::Remove(table, key, &was_present);
    weak_collection->set_table(*new_table);
    return isolate->heap()->ToBoolean(was_present);
  }
  
  
  RUNTIME_FUNCTION(Runtime_WeakCollectionSet) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
    CONVERT_ARG_HANDLE_CHECKED(JSWeakCollection, weak_collection, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, key, 1);
    RUNTIME_ASSERT(key->IsJSReceiver() || key->IsSymbol());
    CONVERT_ARG_HANDLE_CHECKED(Object, value, 2);
    Handle<ObjectHashTable> table(
        ObjectHashTable::cast(weak_collection->table()));
    RUNTIME_ASSERT(table->IsKey(*key));
    Handle<ObjectHashTable> new_table = ObjectHashTable::Put(table, key, value);
    weak_collection->set_table(*new_table);
    return *weak_collection;
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetWeakSetValues) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSWeakCollection, holder, 0);
    Handle<ObjectHashTable> table(ObjectHashTable::cast(holder->table()));
    Handle<FixedArray> values =
        isolate->factory()->NewFixedArray(table->NumberOfElements());
    {
      DisallowHeapAllocation no_gc;
      int number_of_non_hole_elements = 0;
      for (int i = 0; i < table->Capacity(); i++) {
        Handle<Object> key(table->KeyAt(i), isolate);
        if (table->IsKey(*key)) {
          values->set(number_of_non_hole_elements++, *key);
        }
      }
      DCHECK_EQ(table->NumberOfElements(), number_of_non_hole_elements);
    }
    return *isolate->factory()->NewJSArrayWithElements(values);
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetPrototype) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, obj, 0);
    // We don't expect access checks to be needed on JSProxy objects.
    DCHECK(!obj->IsAccessCheckNeeded() || obj->IsJSObject());
    PrototypeIterator iter(isolate, obj, PrototypeIterator::START_AT_RECEIVER);
    do {
      if (PrototypeIterator::GetCurrent(iter)->IsAccessCheckNeeded() &&
          !isolate->MayNamedAccess(
              Handle<JSObject>::cast(PrototypeIterator::GetCurrent(iter)),
              isolate->factory()->proto_string(), v8::ACCESS_GET)) {
        isolate->ReportFailedAccessCheck(
            Handle<JSObject>::cast(PrototypeIterator::GetCurrent(iter)),
            v8::ACCESS_GET);
        RETURN_FAILURE_IF_SCHEDULED_EXCEPTION(isolate);
        return isolate->heap()->undefined_value();
      }
      iter.AdvanceIgnoringProxies();
      if (PrototypeIterator::GetCurrent(iter)->IsJSProxy()) {
        return *PrototypeIterator::GetCurrent(iter);
      }
    } while (!iter.IsAtEnd(PrototypeIterator::END_AT_NON_HIDDEN));
    return *PrototypeIterator::GetCurrent(iter);
  }
  
  
  static inline Handle<Object> GetPrototypeSkipHiddenPrototypes(
      Isolate* isolate, Handle<Object> receiver) {
    PrototypeIterator iter(isolate, receiver);
    while (!iter.IsAtEnd(PrototypeIterator::END_AT_NON_HIDDEN)) {
      if (PrototypeIterator::GetCurrent(iter)->IsJSProxy()) {
        return PrototypeIterator::GetCurrent(iter);
      }
      iter.Advance();
    }
    return PrototypeIterator::GetCurrent(iter);
  }
  
  
  RUNTIME_FUNCTION(Runtime_InternalSetPrototype) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, obj, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, prototype, 1);
    DCHECK(!obj->IsAccessCheckNeeded());
    DCHECK(!obj->map()->is_observed());
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result, JSObject::SetPrototype(obj, prototype, false));
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_SetPrototype) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, obj, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, prototype, 1);
    if (obj->IsAccessCheckNeeded() &&
        !isolate->MayNamedAccess(
            obj, isolate->factory()->proto_string(), v8::ACCESS_SET)) {
      isolate->ReportFailedAccessCheck(obj, v8::ACCESS_SET);
      RETURN_FAILURE_IF_SCHEDULED_EXCEPTION(isolate);
      return isolate->heap()->undefined_value();
    }
    if (obj->map()->is_observed()) {
      Handle<Object> old_value = GetPrototypeSkipHiddenPrototypes(isolate, obj);
      Handle<Object> result;
      ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
          isolate, result,
          JSObject::SetPrototype(obj, prototype, true));
  
      Handle<Object> new_value = GetPrototypeSkipHiddenPrototypes(isolate, obj);
      if (!new_value->SameValue(*old_value)) {
        JSObject::EnqueueChangeRecord(obj, "setPrototype",
                                      isolate->factory()->proto_string(),
                                      old_value);
      }
      return *result;
    }
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result,
        JSObject::SetPrototype(obj, prototype, true));
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_IsInPrototypeChain) {
    HandleScope shs(isolate);
    DCHECK(args.length() == 2);
    // See ECMA-262, section 15.3.5.3, page 88 (steps 5 - 8).
    CONVERT_ARG_HANDLE_CHECKED(Object, O, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, V, 1);
    PrototypeIterator iter(isolate, V, PrototypeIterator::START_AT_RECEIVER);
    while (true) {
      iter.AdvanceIgnoringProxies();
      if (iter.IsAtEnd()) return isolate->heap()->false_value();
      if (iter.IsAtEnd(O)) return isolate->heap()->true_value();
    }
  }
  
  
  // Enumerator used as indices into the array returned from GetOwnProperty
  enum PropertyDescriptorIndices {
    IS_ACCESSOR_INDEX,
    VALUE_INDEX,
    GETTER_INDEX,
    SETTER_INDEX,
    WRITABLE_INDEX,
    ENUMERABLE_INDEX,
    CONFIGURABLE_INDEX,
    DESCRIPTOR_SIZE
  };
  
  
  MUST_USE_RESULT static MaybeHandle<Object> GetOwnProperty(Isolate* isolate,
                                                            Handle<JSObject> obj,
                                                            Handle<Name> name) {
    Heap* heap = isolate->heap();
    Factory* factory = isolate->factory();
  
    PropertyAttributes attrs;
    uint32_t index = 0;
    Handle<Object> value;
    MaybeHandle<AccessorPair> maybe_accessors;
    // TODO(verwaest): Unify once indexed properties can be handled by the
    // LookupIterator.
    if (name->AsArrayIndex(&index)) {
      // Get attributes.
      Maybe<PropertyAttributes> maybe =
          JSReceiver::GetOwnElementAttribute(obj, index);
      if (!maybe.has_value) return MaybeHandle<Object>();
      attrs = maybe.value;
      if (attrs == ABSENT) return factory->undefined_value();
  
      // Get AccessorPair if present.
      maybe_accessors = JSObject::GetOwnElementAccessorPair(obj, index);
  
      // Get value if not an AccessorPair.
      if (maybe_accessors.is_null()) {
        ASSIGN_RETURN_ON_EXCEPTION(isolate, value,
            Runtime::GetElementOrCharAt(isolate, obj, index), Object);
      }
    } else {
      // Get attributes.
      LookupIterator it(obj, name, LookupIterator::CHECK_OWN);
      Maybe<PropertyAttributes> maybe = JSObject::GetPropertyAttributes(&it);
      if (!maybe.has_value) return MaybeHandle<Object>();
      attrs = maybe.value;
      if (attrs == ABSENT) return factory->undefined_value();
  
      // Get AccessorPair if present.
      if (it.state() == LookupIterator::PROPERTY &&
          it.property_kind() == LookupIterator::ACCESSOR &&
          it.GetAccessors()->IsAccessorPair()) {
        maybe_accessors = Handle<AccessorPair>::cast(it.GetAccessors());
      }
  
      // Get value if not an AccessorPair.
      if (maybe_accessors.is_null()) {
        ASSIGN_RETURN_ON_EXCEPTION(
            isolate, value, Object::GetProperty(&it), Object);
      }
    }
    DCHECK(!isolate->has_pending_exception());
    Handle<FixedArray> elms = factory->NewFixedArray(DESCRIPTOR_SIZE);
    elms->set(ENUMERABLE_INDEX, heap->ToBoolean((attrs & DONT_ENUM) == 0));
    elms->set(CONFIGURABLE_INDEX, heap->ToBoolean((attrs & DONT_DELETE) == 0));
    elms->set(IS_ACCESSOR_INDEX, heap->ToBoolean(!maybe_accessors.is_null()));
  
    Handle<AccessorPair> accessors;
    if (maybe_accessors.ToHandle(&accessors)) {
      Handle<Object> getter(accessors->GetComponent(ACCESSOR_GETTER), isolate);
      Handle<Object> setter(accessors->GetComponent(ACCESSOR_SETTER), isolate);
      elms->set(GETTER_INDEX, *getter);
      elms->set(SETTER_INDEX, *setter);
    } else {
      elms->set(WRITABLE_INDEX, heap->ToBoolean((attrs & READ_ONLY) == 0));
      elms->set(VALUE_INDEX, *value);
    }
  
    return factory->NewJSArrayWithElements(elms);
  }
  
  
  // Returns an array with the property description:
  //  if args[1] is not a property on args[0]
  //          returns undefined
  //  if args[1] is a data property on args[0]
  //         [false, value, Writeable, Enumerable, Configurable]
  //  if args[1] is an accessor on args[0]
  //         [true, GetFunction, SetFunction, Enumerable, Configurable]
  RUNTIME_FUNCTION(Runtime_GetOwnProperty) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, obj, 0);
    CONVERT_ARG_HANDLE_CHECKED(Name, name, 1);
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result, GetOwnProperty(isolate, obj, name));
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_PreventExtensions) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, obj, 0);
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result, JSObject::PreventExtensions(obj));
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_IsExtensible) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(JSObject, obj, 0);
    if (obj->IsJSGlobalProxy()) {
      PrototypeIterator iter(isolate, obj);
      if (iter.IsAtEnd()) return isolate->heap()->false_value();
      DCHECK(iter.GetCurrent()->IsJSGlobalObject());
      obj = JSObject::cast(iter.GetCurrent());
    }
    return isolate->heap()->ToBoolean(obj->map()->is_extensible());
  }
  
  
  RUNTIME_FUNCTION(Runtime_RegExpCompile) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
    CONVERT_ARG_HANDLE_CHECKED(JSRegExp, re, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, pattern, 1);
    CONVERT_ARG_HANDLE_CHECKED(String, flags, 2);
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result, RegExpImpl::Compile(re, pattern, flags));
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_CreateApiFunction) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(FunctionTemplateInfo, data, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, prototype, 1);
    return *isolate->factory()->CreateApiFunction(data, prototype);
  }
  
  
  RUNTIME_FUNCTION(Runtime_IsTemplate) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, arg, 0);
    bool result = arg->IsObjectTemplateInfo() || arg->IsFunctionTemplateInfo();
    return isolate->heap()->ToBoolean(result);
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetTemplateField) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_CHECKED(HeapObject, templ, 0);
    CONVERT_SMI_ARG_CHECKED(index, 1);
    int offset = index * kPointerSize + HeapObject::kHeaderSize;
    InstanceType type = templ->map()->instance_type();
    RUNTIME_ASSERT(type == FUNCTION_TEMPLATE_INFO_TYPE ||
                   type == OBJECT_TEMPLATE_INFO_TYPE);
    RUNTIME_ASSERT(offset > 0);
    if (type == FUNCTION_TEMPLATE_INFO_TYPE) {
      RUNTIME_ASSERT(offset < FunctionTemplateInfo::kSize);
    } else {
      RUNTIME_ASSERT(offset < ObjectTemplateInfo::kSize);
    }
    return *HeapObject::RawField(templ, offset);
  }
  
  
  RUNTIME_FUNCTION(Runtime_DisableAccessChecks) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(HeapObject, object, 0);
    Handle<Map> old_map(object->map());
    bool needs_access_checks = old_map->is_access_check_needed();
    if (needs_access_checks) {
      // Copy map so it won't interfere constructor's initial map.
      Handle<Map> new_map = Map::Copy(old_map);
      new_map->set_is_access_check_needed(false);
      JSObject::MigrateToMap(Handle<JSObject>::cast(object), new_map);
    }
    return isolate->heap()->ToBoolean(needs_access_checks);
  }
  
  
  RUNTIME_FUNCTION(Runtime_EnableAccessChecks) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
    Handle<Map> old_map(object->map());
    RUNTIME_ASSERT(!old_map->is_access_check_needed());
    // Copy map so it won't interfere constructor's initial map.
    Handle<Map> new_map = Map::Copy(old_map);
    new_map->set_is_access_check_needed(true);
    JSObject::MigrateToMap(object, new_map);
    return isolate->heap()->undefined_value();
  }
  
  
  static Object* ThrowRedeclarationError(Isolate* isolate, Handle<String> name) {
    HandleScope scope(isolate);
    Handle<Object> args[1] = { name };
    Handle<Object> error = isolate->factory()->NewTypeError(
        "var_redeclaration", HandleVector(args, 1));
    return isolate->Throw(*error);
  }
  
  
  // May throw a RedeclarationError.
  static Object* DeclareGlobals(Isolate* isolate, Handle<GlobalObject> global,
                                Handle<String> name, Handle<Object> value,
                                PropertyAttributes attr, bool is_var,
                                bool is_const, bool is_function) {
    // Do the lookup own properties only, see ES5 erratum.
    LookupIterator it(global, name, LookupIterator::CHECK_HIDDEN);
    Maybe<PropertyAttributes> maybe = JSReceiver::GetPropertyAttributes(&it);
    DCHECK(maybe.has_value);
    PropertyAttributes old_attributes = maybe.value;
  
    if (old_attributes != ABSENT) {
      // The name was declared before; check for conflicting re-declarations.
      if (is_const) return ThrowRedeclarationError(isolate, name);
  
      // Skip var re-declarations.
      if (is_var) return isolate->heap()->undefined_value();
  
      DCHECK(is_function);
      if ((old_attributes & DONT_DELETE) != 0) {
        // Only allow reconfiguring globals to functions in user code (no
        // natives, which are marked as read-only).
        DCHECK((attr & READ_ONLY) == 0);
  
        // Check whether we can reconfigure the existing property into a
        // function.
        PropertyDetails old_details = it.property_details();
        // TODO(verwaest): CALLBACKS invalidly includes ExecutableAccessInfo,
        // which are actually data properties, not accessor properties.
        if (old_details.IsReadOnly() || old_details.IsDontEnum() ||
            old_details.type() == CALLBACKS) {
          return ThrowRedeclarationError(isolate, name);
        }
        // If the existing property is not configurable, keep its attributes. Do
        attr = old_attributes;
      }
    }
  
    // Define or redefine own property.
    RETURN_FAILURE_ON_EXCEPTION(isolate, JSObject::SetOwnPropertyIgnoreAttributes(
                                             global, name, value, attr));
  
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_DeclareGlobals) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
    Handle<GlobalObject> global(isolate->global_object());
  
    CONVERT_ARG_HANDLE_CHECKED(Context, context, 0);
    CONVERT_ARG_HANDLE_CHECKED(FixedArray, pairs, 1);
    CONVERT_SMI_ARG_CHECKED(flags, 2);
  
    // Traverse the name/value pairs and set the properties.
    int length = pairs->length();
    for (int i = 0; i < length; i += 2) {
      HandleScope scope(isolate);
      Handle<String> name(String::cast(pairs->get(i)));
      Handle<Object> initial_value(pairs->get(i + 1), isolate);
  
      // We have to declare a global const property. To capture we only
      // assign to it when evaluating the assignment for "const x =
      // <expr>" the initial value is the hole.
      bool is_var = initial_value->IsUndefined();
      bool is_const = initial_value->IsTheHole();
      bool is_function = initial_value->IsSharedFunctionInfo();
      DCHECK(is_var + is_const + is_function == 1);
  
      Handle<Object> value;
      if (is_function) {
        // Copy the function and update its context. Use it as value.
        Handle<SharedFunctionInfo> shared =
            Handle<SharedFunctionInfo>::cast(initial_value);
        Handle<JSFunction> function =
            isolate->factory()->NewFunctionFromSharedFunctionInfo(shared, context,
                                                                  TENURED);
        value = function;
      } else {
        value = isolate->factory()->undefined_value();
      }
  
      // Compute the property attributes. According to ECMA-262,
      // the property must be non-configurable except in eval.
      bool is_native = DeclareGlobalsNativeFlag::decode(flags);
      bool is_eval = DeclareGlobalsEvalFlag::decode(flags);
      int attr = NONE;
      if (is_const) attr |= READ_ONLY;
      if (is_function && is_native) attr |= READ_ONLY;
      if (!is_const && !is_eval) attr |= DONT_DELETE;
  
      Object* result = DeclareGlobals(isolate, global, name, value,
                                      static_cast<PropertyAttributes>(attr),
                                      is_var, is_const, is_function);
      if (isolate->has_pending_exception()) return result;
    }
  
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_InitializeVarGlobal) {
    HandleScope scope(isolate);
    // args[0] == name
    // args[1] == language_mode
    // args[2] == value (optional)
  
    // Determine if we need to assign to the variable if it already
    // exists (based on the number of arguments).
    RUNTIME_ASSERT(args.length() == 3);
  
    CONVERT_ARG_HANDLE_CHECKED(String, name, 0);
    CONVERT_STRICT_MODE_ARG_CHECKED(strict_mode, 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, value, 2);
  
    Handle<GlobalObject> global(isolate->context()->global_object());
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result, Object::SetProperty(global, name, value, strict_mode));
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_InitializeConstGlobal) {
    HandleScope handle_scope(isolate);
    // All constants are declared with an initial value. The name
    // of the constant is the first argument and the initial value
    // is the second.
    RUNTIME_ASSERT(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(String, name, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, value, 1);
  
    Handle<GlobalObject> global = isolate->global_object();
  
    // Lookup the property as own on the global object.
    LookupIterator it(global, name, LookupIterator::CHECK_HIDDEN);
    Maybe<PropertyAttributes> maybe = JSReceiver::GetPropertyAttributes(&it);
    DCHECK(maybe.has_value);
    PropertyAttributes old_attributes = maybe.value;
  
    PropertyAttributes attr =
        static_cast<PropertyAttributes>(DONT_DELETE | READ_ONLY);
    // Set the value if the property is either missing, or the property attributes
    // allow setting the value without invoking an accessor.
    if (it.IsFound()) {
      // Ignore if we can't reconfigure the value.
      if ((old_attributes & DONT_DELETE) != 0) {
        if ((old_attributes & READ_ONLY) != 0 ||
            it.property_kind() == LookupIterator::ACCESSOR) {
          return *value;
        }
        attr = static_cast<PropertyAttributes>(old_attributes | READ_ONLY);
      }
    }
  
    RETURN_FAILURE_ON_EXCEPTION(isolate, JSObject::SetOwnPropertyIgnoreAttributes(
                                             global, name, value, attr));
  
    return *value;
  }
  
  
  RUNTIME_FUNCTION(Runtime_DeclareLookupSlot) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 4);
  
    // Declarations are always made in a function, native, or global context. In
    // the case of eval code, the context passed is the context of the caller,
    // which may be some nested context and not the declaration context.
    CONVERT_ARG_HANDLE_CHECKED(Context, context_arg, 0);
    Handle<Context> context(context_arg->declaration_context());
    CONVERT_ARG_HANDLE_CHECKED(String, name, 1);
    CONVERT_SMI_ARG_CHECKED(attr_arg, 2);
    PropertyAttributes attr = static_cast<PropertyAttributes>(attr_arg);
    RUNTIME_ASSERT(attr == READ_ONLY || attr == NONE);
    CONVERT_ARG_HANDLE_CHECKED(Object, initial_value, 3);
  
    // TODO(verwaest): Unify the encoding indicating "var" with DeclareGlobals.
    bool is_var = *initial_value == NULL;
    bool is_const = initial_value->IsTheHole();
    bool is_function = initial_value->IsJSFunction();
    DCHECK(is_var + is_const + is_function == 1);
  
    int index;
    PropertyAttributes attributes;
    ContextLookupFlags flags = DONT_FOLLOW_CHAINS;
    BindingFlags binding_flags;
    Handle<Object> holder =
        context->Lookup(name, flags, &index, &attributes, &binding_flags);
  
    Handle<JSObject> object;
    Handle<Object> value =
        is_function ? initial_value
                    : Handle<Object>::cast(isolate->factory()->undefined_value());
  
    // TODO(verwaest): This case should probably not be covered by this function,
    // but by DeclareGlobals instead.
    if ((attributes != ABSENT && holder->IsJSGlobalObject()) ||
        (context_arg->has_extension() &&
         context_arg->extension()->IsJSGlobalObject())) {
      return DeclareGlobals(isolate, Handle<JSGlobalObject>::cast(holder), name,
                            value, attr, is_var, is_const, is_function);
    }
  
    if (attributes != ABSENT) {
      // The name was declared before; check for conflicting re-declarations.
      if (is_const || (attributes & READ_ONLY) != 0) {
        return ThrowRedeclarationError(isolate, name);
      }
  
      // Skip var re-declarations.
      if (is_var) return isolate->heap()->undefined_value();
  
      DCHECK(is_function);
      if (index >= 0) {
        DCHECK(holder.is_identical_to(context));
        context->set(index, *initial_value);
        return isolate->heap()->undefined_value();
      }
  
      object = Handle<JSObject>::cast(holder);
  
    } else if (context->has_extension()) {
      object = handle(JSObject::cast(context->extension()));
      DCHECK(object->IsJSContextExtensionObject() || object->IsJSGlobalObject());
    } else {
      DCHECK(context->IsFunctionContext());
      object =
          isolate->factory()->NewJSObject(isolate->context_extension_function());
      context->set_extension(*object);
    }
  
    RETURN_FAILURE_ON_EXCEPTION(isolate, JSObject::SetOwnPropertyIgnoreAttributes(
                                             object, name, value, attr));
  
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_InitializeLegacyConstLookupSlot) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
  
    CONVERT_ARG_HANDLE_CHECKED(Object, value, 0);
    DCHECK(!value->IsTheHole());
    // Initializations are always done in a function or native context.
    CONVERT_ARG_HANDLE_CHECKED(Context, context_arg, 1);
    Handle<Context> context(context_arg->declaration_context());
    CONVERT_ARG_HANDLE_CHECKED(String, name, 2);
  
    int index;
    PropertyAttributes attributes;
    ContextLookupFlags flags = DONT_FOLLOW_CHAINS;
    BindingFlags binding_flags;
    Handle<Object> holder =
        context->Lookup(name, flags, &index, &attributes, &binding_flags);
  
    if (index >= 0) {
      DCHECK(holder->IsContext());
      // Property was found in a context.  Perform the assignment if the constant
      // was uninitialized.
      Handle<Context> context = Handle<Context>::cast(holder);
      DCHECK((attributes & READ_ONLY) != 0);
      if (context->get(index)->IsTheHole()) context->set(index, *value);
      return *value;
    }
  
    PropertyAttributes attr =
        static_cast<PropertyAttributes>(DONT_DELETE | READ_ONLY);
  
    // Strict mode handling not needed (legacy const is disallowed in strict
    // mode).
  
    // The declared const was configurable, and may have been deleted in the
    // meanwhile. If so, re-introduce the variable in the context extension.
    DCHECK(context_arg->has_extension());
    if (attributes == ABSENT) {
      holder = handle(context_arg->extension(), isolate);
    } else {
      // For JSContextExtensionObjects, the initializer can be run multiple times
      // if in a for loop: for (var i = 0; i < 2; i++) { const x = i; }. Only the
      // first assignment should go through. For JSGlobalObjects, additionally any
      // code can run in between that modifies the declared property.
      DCHECK(holder->IsJSGlobalObject() || holder->IsJSContextExtensionObject());
  
      LookupIterator it(holder, name, LookupIterator::CHECK_HIDDEN);
      Maybe<PropertyAttributes> maybe = JSReceiver::GetPropertyAttributes(&it);
      if (!maybe.has_value) return isolate->heap()->exception();
      PropertyAttributes old_attributes = maybe.value;
  
      // Ignore if we can't reconfigure the value.
      if ((old_attributes & DONT_DELETE) != 0) {
        if ((old_attributes & READ_ONLY) != 0 ||
            it.property_kind() == LookupIterator::ACCESSOR) {
          return *value;
        }
        attr = static_cast<PropertyAttributes>(old_attributes | READ_ONLY);
      }
    }
  
    RETURN_FAILURE_ON_EXCEPTION(
        isolate, JSObject::SetOwnPropertyIgnoreAttributes(
                     Handle<JSObject>::cast(holder), name, value, attr));
  
    return *value;
  }
  
  
  RUNTIME_FUNCTION(Runtime_OptimizeObjectForAddingMultipleProperties) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
    CONVERT_SMI_ARG_CHECKED(properties, 1);
    // Conservative upper limit to prevent fuzz tests from going OOM.
    RUNTIME_ASSERT(properties <= 100000);
    if (object->HasFastProperties() && !object->IsJSGlobalProxy()) {
      JSObject::NormalizeProperties(object, KEEP_INOBJECT_PROPERTIES, properties);
    }
    return *object;
  }
  
  
  RUNTIME_FUNCTION(Runtime_RegExpExecRT) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 4);
    CONVERT_ARG_HANDLE_CHECKED(JSRegExp, regexp, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, subject, 1);
    // Due to the way the JS calls are constructed this must be less than the
    // length of a string, i.e. it is always a Smi.  We check anyway for security.
    CONVERT_SMI_ARG_CHECKED(index, 2);
    CONVERT_ARG_HANDLE_CHECKED(JSArray, last_match_info, 3);
    RUNTIME_ASSERT(index >= 0);
    RUNTIME_ASSERT(index <= subject->length());
    isolate->counters()->regexp_entry_runtime()->Increment();
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result,
        RegExpImpl::Exec(regexp, subject, index, last_match_info));
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_RegExpConstructResult) {
    HandleScope handle_scope(isolate);
    DCHECK(args.length() == 3);
    CONVERT_SMI_ARG_CHECKED(size, 0);
    RUNTIME_ASSERT(size >= 0 && size <= FixedArray::kMaxLength);
    CONVERT_ARG_HANDLE_CHECKED(Object, index, 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, input, 2);
    Handle<FixedArray> elements =  isolate->factory()->NewFixedArray(size);
    Handle<Map> regexp_map(isolate->native_context()->regexp_result_map());
    Handle<JSObject> object =
        isolate->factory()->NewJSObjectFromMap(regexp_map, NOT_TENURED, false);
    Handle<JSArray> array = Handle<JSArray>::cast(object);
    array->set_elements(*elements);
    array->set_length(Smi::FromInt(size));
    // Write in-object properties after the length of the array.
    array->InObjectPropertyAtPut(JSRegExpResult::kIndexIndex, *index);
    array->InObjectPropertyAtPut(JSRegExpResult::kInputIndex, *input);
    return *array;
  }
  
  
  RUNTIME_FUNCTION(Runtime_RegExpInitializeObject) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 5);
    CONVERT_ARG_HANDLE_CHECKED(JSRegExp, regexp, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, source, 1);
    // If source is the empty string we set it to "(?:)" instead as
    // suggested by ECMA-262, 5th, section 15.10.4.1.
    if (source->length() == 0) source = isolate->factory()->query_colon_string();
  
    CONVERT_ARG_HANDLE_CHECKED(Object, global, 2);
    if (!global->IsTrue()) global = isolate->factory()->false_value();
  
    CONVERT_ARG_HANDLE_CHECKED(Object, ignoreCase, 3);
    if (!ignoreCase->IsTrue()) ignoreCase = isolate->factory()->false_value();
  
    CONVERT_ARG_HANDLE_CHECKED(Object, multiline, 4);
    if (!multiline->IsTrue()) multiline = isolate->factory()->false_value();
  
    Map* map = regexp->map();
    Object* constructor = map->constructor();
    if (constructor->IsJSFunction() &&
        JSFunction::cast(constructor)->initial_map() == map) {
      // If we still have the original map, set in-object properties directly.
      regexp->InObjectPropertyAtPut(JSRegExp::kSourceFieldIndex, *source);
      // Both true and false are immovable immortal objects so no need for write
      // barrier.
      regexp->InObjectPropertyAtPut(
          JSRegExp::kGlobalFieldIndex, *global, SKIP_WRITE_BARRIER);
      regexp->InObjectPropertyAtPut(
          JSRegExp::kIgnoreCaseFieldIndex, *ignoreCase, SKIP_WRITE_BARRIER);
      regexp->InObjectPropertyAtPut(
          JSRegExp::kMultilineFieldIndex, *multiline, SKIP_WRITE_BARRIER);
      regexp->InObjectPropertyAtPut(
          JSRegExp::kLastIndexFieldIndex, Smi::FromInt(0), SKIP_WRITE_BARRIER);
      return *regexp;
    }
  
    // Map has changed, so use generic, but slower, method.
    PropertyAttributes final =
        static_cast<PropertyAttributes>(READ_ONLY | DONT_ENUM | DONT_DELETE);
    PropertyAttributes writable =
        static_cast<PropertyAttributes>(DONT_ENUM | DONT_DELETE);
    Handle<Object> zero(Smi::FromInt(0), isolate);
    Factory* factory = isolate->factory();
    JSObject::SetOwnPropertyIgnoreAttributes(
        regexp, factory->source_string(), source, final).Check();
    JSObject::SetOwnPropertyIgnoreAttributes(
        regexp, factory->global_string(), global, final).Check();
    JSObject::SetOwnPropertyIgnoreAttributes(
        regexp, factory->ignore_case_string(), ignoreCase, final).Check();
    JSObject::SetOwnPropertyIgnoreAttributes(
        regexp, factory->multiline_string(), multiline, final).Check();
    JSObject::SetOwnPropertyIgnoreAttributes(
        regexp, factory->last_index_string(), zero, writable).Check();
    return *regexp;
  }
  
  
  RUNTIME_FUNCTION(Runtime_FinishArrayPrototypeSetup) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSArray, prototype, 0);
    Object* length = prototype->length();
    RUNTIME_ASSERT(length->IsSmi() && Smi::cast(length)->value() == 0);
    RUNTIME_ASSERT(prototype->HasFastSmiOrObjectElements());
    // This is necessary to enable fast checks for absence of elements
    // on Array.prototype and below.
    prototype->set_elements(isolate->heap()->empty_fixed_array());
    return Smi::FromInt(0);
  }
  
  
  static void InstallBuiltin(Isolate* isolate,
                             Handle<JSObject> holder,
                             const char* name,
                             Builtins::Name builtin_name) {
    Handle<String> key = isolate->factory()->InternalizeUtf8String(name);
    Handle<Code> code(isolate->builtins()->builtin(builtin_name));
    Handle<JSFunction> optimized =
        isolate->factory()->NewFunctionWithoutPrototype(key, code);
    optimized->shared()->DontAdaptArguments();
    JSObject::AddProperty(holder, key, optimized, NONE);
  }
  
  
  RUNTIME_FUNCTION(Runtime_SpecialArrayFunctions) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 0);
    Handle<JSObject> holder =
        isolate->factory()->NewJSObject(isolate->object_function());
  
    InstallBuiltin(isolate, holder, "pop", Builtins::kArrayPop);
    InstallBuiltin(isolate, holder, "push", Builtins::kArrayPush);
    InstallBuiltin(isolate, holder, "shift", Builtins::kArrayShift);
    InstallBuiltin(isolate, holder, "unshift", Builtins::kArrayUnshift);
    InstallBuiltin(isolate, holder, "slice", Builtins::kArraySlice);
    InstallBuiltin(isolate, holder, "splice", Builtins::kArraySplice);
    InstallBuiltin(isolate, holder, "concat", Builtins::kArrayConcat);
  
    return *holder;
  }
  
  
  RUNTIME_FUNCTION(Runtime_IsSloppyModeFunction) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(JSReceiver, callable, 0);
    if (!callable->IsJSFunction()) {
      HandleScope scope(isolate);
      Handle<Object> delegate;
      ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
          isolate, delegate,
          Execution::TryGetFunctionDelegate(
              isolate, Handle<JSReceiver>(callable)));
      callable = JSFunction::cast(*delegate);
    }
    JSFunction* function = JSFunction::cast(callable);
    SharedFunctionInfo* shared = function->shared();
    return isolate->heap()->ToBoolean(shared->strict_mode() == SLOPPY);
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetDefaultReceiver) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(JSReceiver, callable, 0);
  
    if (!callable->IsJSFunction()) {
      HandleScope scope(isolate);
      Handle<Object> delegate;
      ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
          isolate, delegate,
          Execution::TryGetFunctionDelegate(
              isolate, Handle<JSReceiver>(callable)));
      callable = JSFunction::cast(*delegate);
    }
    JSFunction* function = JSFunction::cast(callable);
  
    SharedFunctionInfo* shared = function->shared();
    if (shared->native() || shared->strict_mode() == STRICT) {
      return isolate->heap()->undefined_value();
    }
    // Returns undefined for strict or native functions, or
    // the associated global receiver for "normal" functions.
  
    return function->global_proxy();
  }
  
  
  RUNTIME_FUNCTION(Runtime_MaterializeRegExpLiteral) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 4);
    CONVERT_ARG_HANDLE_CHECKED(FixedArray, literals, 0);
    CONVERT_SMI_ARG_CHECKED(index, 1);
    CONVERT_ARG_HANDLE_CHECKED(String, pattern, 2);
    CONVERT_ARG_HANDLE_CHECKED(String, flags, 3);
  
    // Get the RegExp function from the context in the literals array.
    // This is the RegExp function from the context in which the
    // function was created.  We do not use the RegExp function from the
    // current native context because this might be the RegExp function
    // from another context which we should not have access to.
    Handle<JSFunction> constructor =
        Handle<JSFunction>(
            JSFunction::NativeContextFromLiterals(*literals)->regexp_function());
    // Compute the regular expression literal.
    Handle<Object> regexp;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, regexp,
        RegExpImpl::CreateRegExpLiteral(constructor, pattern, flags));
    literals->set(index, *regexp);
    return *regexp;
  }
  
  
  RUNTIME_FUNCTION(Runtime_FunctionGetName) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
  
    CONVERT_ARG_CHECKED(JSFunction, f, 0);
    return f->shared()->name();
  }
  
  
  RUNTIME_FUNCTION(Runtime_FunctionSetName) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_CHECKED(JSFunction, f, 0);
    CONVERT_ARG_CHECKED(String, name, 1);
    f->shared()->set_name(name);
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_FunctionNameShouldPrintAsAnonymous) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(JSFunction, f, 0);
    return isolate->heap()->ToBoolean(
        f->shared()->name_should_print_as_anonymous());
  }
  
  
  RUNTIME_FUNCTION(Runtime_FunctionMarkNameShouldPrintAsAnonymous) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(JSFunction, f, 0);
    f->shared()->set_name_should_print_as_anonymous(true);
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_FunctionIsGenerator) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(JSFunction, f, 0);
    return isolate->heap()->ToBoolean(f->shared()->is_generator());
  }
  
  
  RUNTIME_FUNCTION(Runtime_FunctionIsArrow) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(JSFunction, f, 0);
    return isolate->heap()->ToBoolean(f->shared()->is_arrow());
  }
  
  
  RUNTIME_FUNCTION(Runtime_FunctionRemovePrototype) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
  
    CONVERT_ARG_CHECKED(JSFunction, f, 0);
    RUNTIME_ASSERT(f->RemovePrototype());
  
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_FunctionGetScript) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
  
    CONVERT_ARG_CHECKED(JSFunction, fun, 0);
    Handle<Object> script = Handle<Object>(fun->shared()->script(), isolate);
    if (!script->IsScript()) return isolate->heap()->undefined_value();
  
    return *Script::GetWrapper(Handle<Script>::cast(script));
  }
  
  
  RUNTIME_FUNCTION(Runtime_FunctionGetSourceCode) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
  
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, f, 0);
    Handle<SharedFunctionInfo> shared(f->shared());
    return *shared->GetSourceCode();
  }
  
  
  RUNTIME_FUNCTION(Runtime_FunctionGetScriptSourcePosition) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
  
    CONVERT_ARG_CHECKED(JSFunction, fun, 0);
    int pos = fun->shared()->start_position();
    return Smi::FromInt(pos);
  }
  
  
  RUNTIME_FUNCTION(Runtime_FunctionGetPositionForOffset) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_CHECKED(Code, code, 0);
    CONVERT_NUMBER_CHECKED(int, offset, Int32, args[1]);
  
    RUNTIME_ASSERT(0 <= offset && offset < code->Size());
  
    Address pc = code->address() + offset;
    return Smi::FromInt(code->SourcePosition(pc));
  }
  
  
  RUNTIME_FUNCTION(Runtime_FunctionSetInstanceClassName) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_CHECKED(JSFunction, fun, 0);
    CONVERT_ARG_CHECKED(String, name, 1);
    fun->SetInstanceClassName(name);
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_FunctionSetLength) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_CHECKED(JSFunction, fun, 0);
    CONVERT_SMI_ARG_CHECKED(length, 1);
    RUNTIME_ASSERT((length & 0xC0000000) == 0xC0000000 ||
                   (length & 0xC0000000) == 0x0);
    fun->shared()->set_length(length);
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_FunctionSetPrototype) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, fun, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, value, 1);
    RUNTIME_ASSERT(fun->should_have_prototype());
    Accessors::FunctionSetPrototype(fun, value);
    return args[0];  // return TOS
  }
  
  
  RUNTIME_FUNCTION(Runtime_FunctionIsAPIFunction) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
  
    CONVERT_ARG_CHECKED(JSFunction, f, 0);
    return isolate->heap()->ToBoolean(f->shared()->IsApiFunction());
  }
  
  
  RUNTIME_FUNCTION(Runtime_FunctionIsBuiltin) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
  
    CONVERT_ARG_CHECKED(JSFunction, f, 0);
    return isolate->heap()->ToBoolean(f->IsBuiltin());
  }
  
  
  RUNTIME_FUNCTION(Runtime_SetCode) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, target, 0);
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, source, 1);
  
    Handle<SharedFunctionInfo> target_shared(target->shared());
    Handle<SharedFunctionInfo> source_shared(source->shared());
    RUNTIME_ASSERT(!source_shared->bound());
  
    if (!Compiler::EnsureCompiled(source, KEEP_EXCEPTION)) {
      return isolate->heap()->exception();
    }
  
    // Mark both, the source and the target, as un-flushable because the
    // shared unoptimized code makes them impossible to enqueue in a list.
    DCHECK(target_shared->code()->gc_metadata() == NULL);
    DCHECK(source_shared->code()->gc_metadata() == NULL);
    target_shared->set_dont_flush(true);
    source_shared->set_dont_flush(true);
  
    // Set the code, scope info, formal parameter count, and the length
    // of the target shared function info.
    target_shared->ReplaceCode(source_shared->code());
    target_shared->set_scope_info(source_shared->scope_info());
    target_shared->set_length(source_shared->length());
    target_shared->set_feedback_vector(source_shared->feedback_vector());
    target_shared->set_formal_parameter_count(
        source_shared->formal_parameter_count());
    target_shared->set_script(source_shared->script());
    target_shared->set_start_position_and_type(
        source_shared->start_position_and_type());
    target_shared->set_end_position(source_shared->end_position());
    bool was_native = target_shared->native();
    target_shared->set_compiler_hints(source_shared->compiler_hints());
    target_shared->set_native(was_native);
    target_shared->set_profiler_ticks(source_shared->profiler_ticks());
  
    // Set the code of the target function.
    target->ReplaceCode(source_shared->code());
    DCHECK(target->next_function_link()->IsUndefined());
  
    // Make sure we get a fresh copy of the literal vector to avoid cross
    // context contamination.
    Handle<Context> context(source->context());
    int number_of_literals = source->NumberOfLiterals();
    Handle<FixedArray> literals =
        isolate->factory()->NewFixedArray(number_of_literals, TENURED);
    if (number_of_literals > 0) {
      literals->set(JSFunction::kLiteralNativeContextIndex,
                    context->native_context());
    }
    target->set_context(*context);
    target->set_literals(*literals);
  
    if (isolate->logger()->is_logging_code_events() ||
        isolate->cpu_profiler()->is_profiling()) {
      isolate->logger()->LogExistingFunction(
          source_shared, Handle<Code>(source_shared->code()));
    }
  
    return *target;
  }
  
  
  RUNTIME_FUNCTION(Runtime_CreateJSGeneratorObject) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 0);
  
    JavaScriptFrameIterator it(isolate);
    JavaScriptFrame* frame = it.frame();
    Handle<JSFunction> function(frame->function());
    RUNTIME_ASSERT(function->shared()->is_generator());
  
    Handle<JSGeneratorObject> generator;
    if (frame->IsConstructor()) {
      generator = handle(JSGeneratorObject::cast(frame->receiver()));
    } else {
      generator = isolate->factory()->NewJSGeneratorObject(function);
    }
    generator->set_function(*function);
    generator->set_context(Context::cast(frame->context()));
    generator->set_receiver(frame->receiver());
    generator->set_continuation(0);
    generator->set_operand_stack(isolate->heap()->empty_fixed_array());
    generator->set_stack_handler_index(-1);
  
    return *generator;
  }
  
  
  RUNTIME_FUNCTION(Runtime_SuspendJSGeneratorObject) {
    HandleScope handle_scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSGeneratorObject, generator_object, 0);
  
    JavaScriptFrameIterator stack_iterator(isolate);
    JavaScriptFrame* frame = stack_iterator.frame();
    RUNTIME_ASSERT(frame->function()->shared()->is_generator());
    DCHECK_EQ(frame->function(), generator_object->function());
  
    // The caller should have saved the context and continuation already.
    DCHECK_EQ(generator_object->context(), Context::cast(frame->context()));
    DCHECK_LT(0, generator_object->continuation());
  
    // We expect there to be at least two values on the operand stack: the return
    // value of the yield expression, and the argument to this runtime call.
    // Neither of those should be saved.
    int operands_count = frame->ComputeOperandsCount();
    DCHECK_GE(operands_count, 2);
    operands_count -= 2;
  
    if (operands_count == 0) {
      // Although it's semantically harmless to call this function with an
      // operands_count of zero, it is also unnecessary.
      DCHECK_EQ(generator_object->operand_stack(),
                isolate->heap()->empty_fixed_array());
      DCHECK_EQ(generator_object->stack_handler_index(), -1);
      // If there are no operands on the stack, there shouldn't be a handler
      // active either.
      DCHECK(!frame->HasHandler());
    } else {
      int stack_handler_index = -1;
      Handle<FixedArray> operand_stack =
          isolate->factory()->NewFixedArray(operands_count);
      frame->SaveOperandStack(*operand_stack, &stack_handler_index);
      generator_object->set_operand_stack(*operand_stack);
      generator_object->set_stack_handler_index(stack_handler_index);
    }
  
    return isolate->heap()->undefined_value();
  }
  
  
  // Note that this function is the slow path for resuming generators.  It is only
  // called if the suspended activation had operands on the stack, stack handlers
  // needing rewinding, or if the resume should throw an exception.  The fast path
  // is handled directly in FullCodeGenerator::EmitGeneratorResume(), which is
  // inlined into GeneratorNext and GeneratorThrow.  EmitGeneratorResumeResume is
  // called in any case, as it needs to reconstruct the stack frame and make space
  // for arguments and operands.
  RUNTIME_FUNCTION(Runtime_ResumeJSGeneratorObject) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 3);
    CONVERT_ARG_CHECKED(JSGeneratorObject, generator_object, 0);
    CONVERT_ARG_CHECKED(Object, value, 1);
    CONVERT_SMI_ARG_CHECKED(resume_mode_int, 2);
    JavaScriptFrameIterator stack_iterator(isolate);
    JavaScriptFrame* frame = stack_iterator.frame();
  
    DCHECK_EQ(frame->function(), generator_object->function());
    DCHECK(frame->function()->is_compiled());
  
    STATIC_ASSERT(JSGeneratorObject::kGeneratorExecuting < 0);
    STATIC_ASSERT(JSGeneratorObject::kGeneratorClosed == 0);
  
    Address pc = generator_object->function()->code()->instruction_start();
    int offset = generator_object->continuation();
    DCHECK(offset > 0);
    frame->set_pc(pc + offset);
    if (FLAG_enable_ool_constant_pool) {
      frame->set_constant_pool(
          generator_object->function()->code()->constant_pool());
    }
    generator_object->set_continuation(JSGeneratorObject::kGeneratorExecuting);
  
    FixedArray* operand_stack = generator_object->operand_stack();
    int operands_count = operand_stack->length();
    if (operands_count != 0) {
      frame->RestoreOperandStack(operand_stack,
                                 generator_object->stack_handler_index());
      generator_object->set_operand_stack(isolate->heap()->empty_fixed_array());
      generator_object->set_stack_handler_index(-1);
    }
  
    JSGeneratorObject::ResumeMode resume_mode =
        static_cast<JSGeneratorObject::ResumeMode>(resume_mode_int);
    switch (resume_mode) {
      case JSGeneratorObject::NEXT:
        return value;
      case JSGeneratorObject::THROW:
        return isolate->Throw(value);
    }
  
    UNREACHABLE();
    return isolate->ThrowIllegalOperation();
  }
  
  
  RUNTIME_FUNCTION(Runtime_ThrowGeneratorStateError) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSGeneratorObject, generator, 0);
    int continuation = generator->continuation();
    const char* message = continuation == JSGeneratorObject::kGeneratorClosed ?
        "generator_finished" : "generator_running";
    Vector< Handle<Object> > argv = HandleVector<Object>(NULL, 0);
    Handle<Object> error = isolate->factory()->NewError(message, argv);
    return isolate->Throw(*error);
  }
  
  
  RUNTIME_FUNCTION(Runtime_ObjectFreeze) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
  
    // %ObjectFreeze is a fast path and these cases are handled elsewhere.
    RUNTIME_ASSERT(!object->HasSloppyArgumentsElements() &&
                   !object->map()->is_observed() &&
                   !object->IsJSProxy());
  
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, result, JSObject::Freeze(object));
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_StringCharCodeAtRT) {
    HandleScope handle_scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_HANDLE_CHECKED(String, subject, 0);
    CONVERT_NUMBER_CHECKED(uint32_t, i, Uint32, args[1]);
  
    // Flatten the string.  If someone wants to get a char at an index
    // in a cons string, it is likely that more indices will be
    // accessed.
    subject = String::Flatten(subject);
  
    if (i >= static_cast<uint32_t>(subject->length())) {
      return isolate->heap()->nan_value();
    }
  
    return Smi::FromInt(subject->Get(i));
  }
  
  
  RUNTIME_FUNCTION(Runtime_CharFromCode) {
    HandleScope handlescope(isolate);
    DCHECK(args.length() == 1);
    if (args[0]->IsNumber()) {
      CONVERT_NUMBER_CHECKED(uint32_t, code, Uint32, args[0]);
      code &= 0xffff;
      return *isolate->factory()->LookupSingleCharacterStringFromCode(code);
    }
    return isolate->heap()->empty_string();
  }
  
  
  class FixedArrayBuilder {
   public:
    explicit FixedArrayBuilder(Isolate* isolate, int initial_capacity)
        : array_(isolate->factory()->NewFixedArrayWithHoles(initial_capacity)),
          length_(0),
          has_non_smi_elements_(false) {
      // Require a non-zero initial size. Ensures that doubling the size to
      // extend the array will work.
      DCHECK(initial_capacity > 0);
    }
  
    explicit FixedArrayBuilder(Handle<FixedArray> backing_store)
        : array_(backing_store),
          length_(0),
          has_non_smi_elements_(false) {
      // Require a non-zero initial size. Ensures that doubling the size to
      // extend the array will work.
      DCHECK(backing_store->length() > 0);
    }
  
    bool HasCapacity(int elements) {
      int length = array_->length();
      int required_length = length_ + elements;
      return (length >= required_length);
    }
  
    void EnsureCapacity(int elements) {
      int length = array_->length();
      int required_length = length_ + elements;
      if (length < required_length) {
        int new_length = length;
        do {
          new_length *= 2;
        } while (new_length < required_length);
        Handle<FixedArray> extended_array =
            array_->GetIsolate()->factory()->NewFixedArrayWithHoles(new_length);
        array_->CopyTo(0, *extended_array, 0, length_);
        array_ = extended_array;
      }
    }
  
    void Add(Object* value) {
      DCHECK(!value->IsSmi());
      DCHECK(length_ < capacity());
      array_->set(length_, value);
      length_++;
      has_non_smi_elements_ = true;
    }
  
    void Add(Smi* value) {
      DCHECK(value->IsSmi());
      DCHECK(length_ < capacity());
      array_->set(length_, value);
      length_++;
    }
  
    Handle<FixedArray> array() {
      return array_;
    }
  
    int length() {
      return length_;
    }
  
    int capacity() {
      return array_->length();
    }
  
    Handle<JSArray> ToJSArray(Handle<JSArray> target_array) {
      JSArray::SetContent(target_array, array_);
      target_array->set_length(Smi::FromInt(length_));
      return target_array;
    }
  
  
   private:
    Handle<FixedArray> array_;
    int length_;
    bool has_non_smi_elements_;
  };
  
  
  // Forward declarations.
  const int kStringBuilderConcatHelperLengthBits = 11;
  const int kStringBuilderConcatHelperPositionBits = 19;
  
  template <typename schar>
  static inline void StringBuilderConcatHelper(String*,
                                               schar*,
                                               FixedArray*,
                                               int);
  
  typedef BitField<int, 0, kStringBuilderConcatHelperLengthBits>
      StringBuilderSubstringLength;
  typedef BitField<int,
                   kStringBuilderConcatHelperLengthBits,
                   kStringBuilderConcatHelperPositionBits>
      StringBuilderSubstringPosition;
  
  
  class ReplacementStringBuilder {
   public:
    ReplacementStringBuilder(Heap* heap,
                             Handle<String> subject,
                             int estimated_part_count)
        : heap_(heap),
          array_builder_(heap->isolate(), estimated_part_count),
          subject_(subject),
          character_count_(0),
          is_ascii_(subject->IsOneByteRepresentation()) {
      // Require a non-zero initial size. Ensures that doubling the size to
      // extend the array will work.
      DCHECK(estimated_part_count > 0);
    }
  
    static inline void AddSubjectSlice(FixedArrayBuilder* builder,
                                       int from,
                                       int to) {
      DCHECK(from >= 0);
      int length = to - from;
      DCHECK(length > 0);
      if (StringBuilderSubstringLength::is_valid(length) &&
          StringBuilderSubstringPosition::is_valid(from)) {
        int encoded_slice = StringBuilderSubstringLength::encode(length) |
            StringBuilderSubstringPosition::encode(from);
        builder->Add(Smi::FromInt(encoded_slice));
      } else {
        // Otherwise encode as two smis.
        builder->Add(Smi::FromInt(-length));
        builder->Add(Smi::FromInt(from));
      }
    }
  
  
    void EnsureCapacity(int elements) {
      array_builder_.EnsureCapacity(elements);
    }
  
  
    void AddSubjectSlice(int from, int to) {
      AddSubjectSlice(&array_builder_, from, to);
      IncrementCharacterCount(to - from);
    }
  
  
    void AddString(Handle<String> string) {
      int length = string->length();
      DCHECK(length > 0);
      AddElement(*string);
      if (!string->IsOneByteRepresentation()) {
        is_ascii_ = false;
      }
      IncrementCharacterCount(length);
    }
  
  
    MaybeHandle<String> ToString() {
      Isolate* isolate = heap_->isolate();
      if (array_builder_.length() == 0) {
        return isolate->factory()->empty_string();
      }
  
      Handle<String> joined_string;
      if (is_ascii_) {
        Handle<SeqOneByteString> seq;
        ASSIGN_RETURN_ON_EXCEPTION(
            isolate, seq,
            isolate->factory()->NewRawOneByteString(character_count_),
            String);
  
        DisallowHeapAllocation no_gc;
        uint8_t* char_buffer = seq->GetChars();
        StringBuilderConcatHelper(*subject_,
                                  char_buffer,
                                  *array_builder_.array(),
                                  array_builder_.length());
        joined_string = Handle<String>::cast(seq);
      } else {
        // Non-ASCII.
        Handle<SeqTwoByteString> seq;
        ASSIGN_RETURN_ON_EXCEPTION(
            isolate, seq,
            isolate->factory()->NewRawTwoByteString(character_count_),
            String);
  
        DisallowHeapAllocation no_gc;
        uc16* char_buffer = seq->GetChars();
        StringBuilderConcatHelper(*subject_,
                                  char_buffer,
                                  *array_builder_.array(),
                                  array_builder_.length());
        joined_string = Handle<String>::cast(seq);
      }
      return joined_string;
    }
  
  
    void IncrementCharacterCount(int by) {
      if (character_count_ > String::kMaxLength - by) {
        STATIC_ASSERT(String::kMaxLength < kMaxInt);
        character_count_ = kMaxInt;
      } else {
        character_count_ += by;
      }
    }
  
   private:
    void AddElement(Object* element) {
      DCHECK(element->IsSmi() || element->IsString());
      DCHECK(array_builder_.capacity() > array_builder_.length());
      array_builder_.Add(element);
    }
  
    Heap* heap_;
    FixedArrayBuilder array_builder_;
    Handle<String> subject_;
    int character_count_;
    bool is_ascii_;
  };
  
  
  class CompiledReplacement {
   public:
    explicit CompiledReplacement(Zone* zone)
        : parts_(1, zone), replacement_substrings_(0, zone), zone_(zone) {}
  
    // Return whether the replacement is simple.
    bool Compile(Handle<String> replacement,
                 int capture_count,
                 int subject_length);
  
    // Use Apply only if Compile returned false.
    void Apply(ReplacementStringBuilder* builder,
               int match_from,
               int match_to,
               int32_t* match);
  
    // Number of distinct parts of the replacement pattern.
    int parts() {
      return parts_.length();
    }
  
    Zone* zone() const { return zone_; }
  
   private:
    enum PartType {
      SUBJECT_PREFIX = 1,
      SUBJECT_SUFFIX,
      SUBJECT_CAPTURE,
      REPLACEMENT_SUBSTRING,
      REPLACEMENT_STRING,
  
      NUMBER_OF_PART_TYPES
    };
  
    struct ReplacementPart {
      static inline ReplacementPart SubjectMatch() {
        return ReplacementPart(SUBJECT_CAPTURE, 0);
      }
      static inline ReplacementPart SubjectCapture(int capture_index) {
        return ReplacementPart(SUBJECT_CAPTURE, capture_index);
      }
      static inline ReplacementPart SubjectPrefix() {
        return ReplacementPart(SUBJECT_PREFIX, 0);
      }
      static inline ReplacementPart SubjectSuffix(int subject_length) {
        return ReplacementPart(SUBJECT_SUFFIX, subject_length);
      }
      static inline ReplacementPart ReplacementString() {
        return ReplacementPart(REPLACEMENT_STRING, 0);
      }
      static inline ReplacementPart ReplacementSubString(int from, int to) {
        DCHECK(from >= 0);
        DCHECK(to > from);
        return ReplacementPart(-from, to);
      }
  
      // If tag <= 0 then it is the negation of a start index of a substring of
      // the replacement pattern, otherwise it's a value from PartType.
      ReplacementPart(int tag, int data)
          : tag(tag), data(data) {
        // Must be non-positive or a PartType value.
        DCHECK(tag < NUMBER_OF_PART_TYPES);
      }
      // Either a value of PartType or a non-positive number that is
      // the negation of an index into the replacement string.
      int tag;
      // The data value's interpretation depends on the value of tag:
      // tag == SUBJECT_PREFIX ||
      // tag == SUBJECT_SUFFIX:  data is unused.
      // tag == SUBJECT_CAPTURE: data is the number of the capture.
      // tag == REPLACEMENT_SUBSTRING ||
      // tag == REPLACEMENT_STRING:    data is index into array of substrings
      //                               of the replacement string.
      // tag <= 0: Temporary representation of the substring of the replacement
      //           string ranging over -tag .. data.
      //           Is replaced by REPLACEMENT_{SUB,}STRING when we create the
      //           substring objects.
      int data;
    };
  
    template<typename Char>
    bool ParseReplacementPattern(ZoneList<ReplacementPart>* parts,
                                 Vector<Char> characters,
                                 int capture_count,
                                 int subject_length,
                                 Zone* zone) {
      int length = characters.length();
      int last = 0;
      for (int i = 0; i < length; i++) {
        Char c = characters[i];
        if (c == '$') {
          int next_index = i + 1;
          if (next_index == length) {  // No next character!
            break;
          }
          Char c2 = characters[next_index];
          switch (c2) {
          case '$':
            if (i > last) {
              // There is a substring before. Include the first "$".
              parts->Add(ReplacementPart::ReplacementSubString(last, next_index),
                         zone);
              last = next_index + 1;  // Continue after the second "$".
            } else {
              // Let the next substring start with the second "$".
              last = next_index;
            }
            i = next_index;
            break;
          case '`':
            if (i > last) {
              parts->Add(ReplacementPart::ReplacementSubString(last, i), zone);
            }
            parts->Add(ReplacementPart::SubjectPrefix(), zone);
            i = next_index;
            last = i + 1;
            break;
          case '\'':
            if (i > last) {
              parts->Add(ReplacementPart::ReplacementSubString(last, i), zone);
            }
            parts->Add(ReplacementPart::SubjectSuffix(subject_length), zone);
            i = next_index;
            last = i + 1;
            break;
          case '&':
            if (i > last) {
              parts->Add(ReplacementPart::ReplacementSubString(last, i), zone);
            }
            parts->Add(ReplacementPart::SubjectMatch(), zone);
            i = next_index;
            last = i + 1;
            break;
          case '0':
          case '1':
          case '2':
          case '3':
          case '4':
          case '5':
          case '6':
          case '7':
          case '8':
          case '9': {
            int capture_ref = c2 - '0';
            if (capture_ref > capture_count) {
              i = next_index;
              continue;
            }
            int second_digit_index = next_index + 1;
            if (second_digit_index < length) {
              // Peek ahead to see if we have two digits.
              Char c3 = characters[second_digit_index];
              if ('0' <= c3 && c3 <= '9') {  // Double digits.
                int double_digit_ref = capture_ref * 10 + c3 - '0';
                if (double_digit_ref <= capture_count) {
                  next_index = second_digit_index;
                  capture_ref = double_digit_ref;
                }
              }
            }
            if (capture_ref > 0) {
              if (i > last) {
                parts->Add(ReplacementPart::ReplacementSubString(last, i), zone);
              }
              DCHECK(capture_ref <= capture_count);
              parts->Add(ReplacementPart::SubjectCapture(capture_ref), zone);
              last = next_index + 1;
            }
            i = next_index;
            break;
          }
          default:
            i = next_index;
            break;
          }
        }
      }
      if (length > last) {
        if (last == 0) {
          // Replacement is simple.  Do not use Apply to do the replacement.
          return true;
        } else {
          parts->Add(ReplacementPart::ReplacementSubString(last, length), zone);
        }
      }
      return false;
    }
  
    ZoneList<ReplacementPart> parts_;
    ZoneList<Handle<String> > replacement_substrings_;
    Zone* zone_;
  };
  
  
  bool CompiledReplacement::Compile(Handle<String> replacement,
                                    int capture_count,
                                    int subject_length) {
    {
      DisallowHeapAllocation no_gc;
      String::FlatContent content = replacement->GetFlatContent();
      DCHECK(content.IsFlat());
      bool simple = false;
      if (content.IsAscii()) {
        simple = ParseReplacementPattern(&parts_,
                                         content.ToOneByteVector(),
                                         capture_count,
                                         subject_length,
                                         zone());
      } else {
        DCHECK(content.IsTwoByte());
        simple = ParseReplacementPattern(&parts_,
                                         content.ToUC16Vector(),
                                         capture_count,
                                         subject_length,
                                         zone());
      }
      if (simple) return true;
    }
  
    Isolate* isolate = replacement->GetIsolate();
    // Find substrings of replacement string and create them as String objects.
    int substring_index = 0;
    for (int i = 0, n = parts_.length(); i < n; i++) {
      int tag = parts_[i].tag;
      if (tag <= 0) {  // A replacement string slice.
        int from = -tag;
        int to = parts_[i].data;
        replacement_substrings_.Add(
            isolate->factory()->NewSubString(replacement, from, to), zone());
        parts_[i].tag = REPLACEMENT_SUBSTRING;
        parts_[i].data = substring_index;
        substring_index++;
      } else if (tag == REPLACEMENT_STRING) {
        replacement_substrings_.Add(replacement, zone());
        parts_[i].data = substring_index;
        substring_index++;
      }
    }
    return false;
  }
  
  
  void CompiledReplacement::Apply(ReplacementStringBuilder* builder,
                                  int match_from,
                                  int match_to,
                                  int32_t* match) {
    DCHECK_LT(0, parts_.length());
    for (int i = 0, n = parts_.length(); i < n; i++) {
      ReplacementPart part = parts_[i];
      switch (part.tag) {
        case SUBJECT_PREFIX:
          if (match_from > 0) builder->AddSubjectSlice(0, match_from);
          break;
        case SUBJECT_SUFFIX: {
          int subject_length = part.data;
          if (match_to < subject_length) {
            builder->AddSubjectSlice(match_to, subject_length);
          }
          break;
        }
        case SUBJECT_CAPTURE: {
          int capture = part.data;
          int from = match[capture * 2];
          int to = match[capture * 2 + 1];
          if (from >= 0 && to > from) {
            builder->AddSubjectSlice(from, to);
          }
          break;
        }
        case REPLACEMENT_SUBSTRING:
        case REPLACEMENT_STRING:
          builder->AddString(replacement_substrings_[part.data]);
          break;
        default:
          UNREACHABLE();
      }
    }
  }
  
  
  void FindAsciiStringIndices(Vector<const uint8_t> subject,
                              char pattern,
                              ZoneList<int>* indices,
                              unsigned int limit,
                              Zone* zone) {
    DCHECK(limit > 0);
    // Collect indices of pattern in subject using memchr.
    // Stop after finding at most limit values.
    const uint8_t* subject_start = subject.start();
    const uint8_t* subject_end = subject_start + subject.length();
    const uint8_t* pos = subject_start;
    while (limit > 0) {
      pos = reinterpret_cast<const uint8_t*>(
          memchr(pos, pattern, subject_end - pos));
      if (pos == NULL) return;
      indices->Add(static_cast<int>(pos - subject_start), zone);
      pos++;
      limit--;
    }
  }
  
  
  void FindTwoByteStringIndices(const Vector<const uc16> subject,
                                uc16 pattern,
                                ZoneList<int>* indices,
                                unsigned int limit,
                                Zone* zone) {
    DCHECK(limit > 0);
    const uc16* subject_start = subject.start();
    const uc16* subject_end = subject_start + subject.length();
    for (const uc16* pos = subject_start; pos < subject_end && limit > 0; pos++) {
      if (*pos == pattern) {
        indices->Add(static_cast<int>(pos - subject_start), zone);
        limit--;
      }
    }
  }
  
  
  template <typename SubjectChar, typename PatternChar>
  void FindStringIndices(Isolate* isolate,
                         Vector<const SubjectChar> subject,
                         Vector<const PatternChar> pattern,
                         ZoneList<int>* indices,
                         unsigned int limit,
                         Zone* zone) {
    DCHECK(limit > 0);
    // Collect indices of pattern in subject.
    // Stop after finding at most limit values.
    int pattern_length = pattern.length();
    int index = 0;
    StringSearch<PatternChar, SubjectChar> search(isolate, pattern);
    while (limit > 0) {
      index = search.Search(subject, index);
      if (index < 0) return;
      indices->Add(index, zone);
      index += pattern_length;
      limit--;
    }
  }
  
  
  void FindStringIndicesDispatch(Isolate* isolate,
                                 String* subject,
                                 String* pattern,
                                 ZoneList<int>* indices,
                                 unsigned int limit,
                                 Zone* zone) {
    {
      DisallowHeapAllocation no_gc;
      String::FlatContent subject_content = subject->GetFlatContent();
      String::FlatContent pattern_content = pattern->GetFlatContent();
      DCHECK(subject_content.IsFlat());
      DCHECK(pattern_content.IsFlat());
      if (subject_content.IsAscii()) {
        Vector<const uint8_t> subject_vector = subject_content.ToOneByteVector();
        if (pattern_content.IsAscii()) {
          Vector<const uint8_t> pattern_vector =
              pattern_content.ToOneByteVector();
          if (pattern_vector.length() == 1) {
            FindAsciiStringIndices(subject_vector,
                                   pattern_vector[0],
                                   indices,
                                   limit,
                                   zone);
          } else {
            FindStringIndices(isolate,
                              subject_vector,
                              pattern_vector,
                              indices,
                              limit,
                              zone);
          }
        } else {
          FindStringIndices(isolate,
                            subject_vector,
                            pattern_content.ToUC16Vector(),
                            indices,
                            limit,
                            zone);
        }
      } else {
        Vector<const uc16> subject_vector = subject_content.ToUC16Vector();
        if (pattern_content.IsAscii()) {
          Vector<const uint8_t> pattern_vector =
              pattern_content.ToOneByteVector();
          if (pattern_vector.length() == 1) {
            FindTwoByteStringIndices(subject_vector,
                                     pattern_vector[0],
                                     indices,
                                     limit,
                                     zone);
          } else {
            FindStringIndices(isolate,
                              subject_vector,
                              pattern_vector,
                              indices,
                              limit,
                              zone);
          }
        } else {
          Vector<const uc16> pattern_vector = pattern_content.ToUC16Vector();
          if (pattern_vector.length() == 1) {
            FindTwoByteStringIndices(subject_vector,
                                     pattern_vector[0],
                                     indices,
                                     limit,
                                     zone);
          } else {
            FindStringIndices(isolate,
                              subject_vector,
                              pattern_vector,
                              indices,
                              limit,
                              zone);
          }
        }
      }
    }
  }
  
  
  template<typename ResultSeqString>
  MUST_USE_RESULT static Object* StringReplaceGlobalAtomRegExpWithString(
      Isolate* isolate,
      Handle<String> subject,
      Handle<JSRegExp> pattern_regexp,
      Handle<String> replacement,
      Handle<JSArray> last_match_info) {
    DCHECK(subject->IsFlat());
    DCHECK(replacement->IsFlat());
  
    ZoneScope zone_scope(isolate->runtime_zone());
    ZoneList<int> indices(8, zone_scope.zone());
    DCHECK_EQ(JSRegExp::ATOM, pattern_regexp->TypeTag());
    String* pattern =
        String::cast(pattern_regexp->DataAt(JSRegExp::kAtomPatternIndex));
    int subject_len = subject->length();
    int pattern_len = pattern->length();
    int replacement_len = replacement->length();
  
    FindStringIndicesDispatch(
        isolate, *subject, pattern, &indices, 0xffffffff, zone_scope.zone());
  
    int matches = indices.length();
    if (matches == 0) return *subject;
  
    // Detect integer overflow.
    int64_t result_len_64 =
        (static_cast<int64_t>(replacement_len) -
         static_cast<int64_t>(pattern_len)) *
        static_cast<int64_t>(matches) +
        static_cast<int64_t>(subject_len);
    int result_len;
    if (result_len_64 > static_cast<int64_t>(String::kMaxLength)) {
      STATIC_ASSERT(String::kMaxLength < kMaxInt);
      result_len = kMaxInt;  // Provoke exception.
    } else {
      result_len = static_cast<int>(result_len_64);
    }
  
    int subject_pos = 0;
    int result_pos = 0;
  
    MaybeHandle<SeqString> maybe_res;
    if (ResultSeqString::kHasAsciiEncoding) {
      maybe_res = isolate->factory()->NewRawOneByteString(result_len);
    } else {
      maybe_res = isolate->factory()->NewRawTwoByteString(result_len);
    }
    Handle<SeqString> untyped_res;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, untyped_res, maybe_res);
    Handle<ResultSeqString> result = Handle<ResultSeqString>::cast(untyped_res);
  
    for (int i = 0; i < matches; i++) {
      // Copy non-matched subject content.
      if (subject_pos < indices.at(i)) {
        String::WriteToFlat(*subject,
                            result->GetChars() + result_pos,
                            subject_pos,
                            indices.at(i));
        result_pos += indices.at(i) - subject_pos;
      }
  
      // Replace match.
      if (replacement_len > 0) {
        String::WriteToFlat(*replacement,
                            result->GetChars() + result_pos,
                            0,
                            replacement_len);
        result_pos += replacement_len;
      }
  
      subject_pos = indices.at(i) + pattern_len;
    }
    // Add remaining subject content at the end.
    if (subject_pos < subject_len) {
      String::WriteToFlat(*subject,
                          result->GetChars() + result_pos,
                          subject_pos,
                          subject_len);
    }
  
    int32_t match_indices[] = { indices.at(matches - 1),
                                indices.at(matches - 1) + pattern_len };
    RegExpImpl::SetLastMatchInfo(last_match_info, subject, 0, match_indices);
  
    return *result;
  }
  
  
  MUST_USE_RESULT static Object* StringReplaceGlobalRegExpWithString(
      Isolate* isolate,
      Handle<String> subject,
      Handle<JSRegExp> regexp,
      Handle<String> replacement,
      Handle<JSArray> last_match_info) {
    DCHECK(subject->IsFlat());
    DCHECK(replacement->IsFlat());
  
    int capture_count = regexp->CaptureCount();
    int subject_length = subject->length();
  
    // CompiledReplacement uses zone allocation.
    ZoneScope zone_scope(isolate->runtime_zone());
    CompiledReplacement compiled_replacement(zone_scope.zone());
    bool simple_replace = compiled_replacement.Compile(replacement,
                                                       capture_count,
                                                       subject_length);
  
    // Shortcut for simple non-regexp global replacements
    if (regexp->TypeTag() == JSRegExp::ATOM && simple_replace) {
      if (subject->HasOnlyOneByteChars() &&
          replacement->HasOnlyOneByteChars()) {
        return StringReplaceGlobalAtomRegExpWithString<SeqOneByteString>(
            isolate, subject, regexp, replacement, last_match_info);
      } else {
        return StringReplaceGlobalAtomRegExpWithString<SeqTwoByteString>(
            isolate, subject, regexp, replacement, last_match_info);
      }
    }
  
    RegExpImpl::GlobalCache global_cache(regexp, subject, true, isolate);
    if (global_cache.HasException()) return isolate->heap()->exception();
  
    int32_t* current_match = global_cache.FetchNext();
    if (current_match == NULL) {
      if (global_cache.HasException()) return isolate->heap()->exception();
      return *subject;
    }
  
    // Guessing the number of parts that the final result string is built
    // from. Global regexps can match any number of times, so we guess
    // conservatively.
    int expected_parts = (compiled_replacement.parts() + 1) * 4 + 1;
    ReplacementStringBuilder builder(isolate->heap(),
                                     subject,
                                     expected_parts);
  
    // Number of parts added by compiled replacement plus preceeding
    // string and possibly suffix after last match.  It is possible for
    // all components to use two elements when encoded as two smis.
    const int parts_added_per_loop = 2 * (compiled_replacement.parts() + 2);
  
    int prev = 0;
  
    do {
      builder.EnsureCapacity(parts_added_per_loop);
  
      int start = current_match[0];
      int end = current_match[1];
  
      if (prev < start) {
        builder.AddSubjectSlice(prev, start);
      }
  
      if (simple_replace) {
        builder.AddString(replacement);
      } else {
        compiled_replacement.Apply(&builder,
                                   start,
                                   end,
                                   current_match);
      }
      prev = end;
  
      current_match = global_cache.FetchNext();
    } while (current_match != NULL);
  
    if (global_cache.HasException()) return isolate->heap()->exception();
  
    if (prev < subject_length) {
      builder.EnsureCapacity(2);
      builder.AddSubjectSlice(prev, subject_length);
    }
  
    RegExpImpl::SetLastMatchInfo(last_match_info,
                                 subject,
                                 capture_count,
                                 global_cache.LastSuccessfulMatch());
  
    Handle<String> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, result, builder.ToString());
    return *result;
  }
  
  
  template <typename ResultSeqString>
  MUST_USE_RESULT static Object* StringReplaceGlobalRegExpWithEmptyString(
      Isolate* isolate,
      Handle<String> subject,
      Handle<JSRegExp> regexp,
      Handle<JSArray> last_match_info) {
    DCHECK(subject->IsFlat());
  
    // Shortcut for simple non-regexp global replacements
    if (regexp->TypeTag() == JSRegExp::ATOM) {
      Handle<String> empty_string = isolate->factory()->empty_string();
      if (subject->IsOneByteRepresentation()) {
        return StringReplaceGlobalAtomRegExpWithString<SeqOneByteString>(
            isolate, subject, regexp, empty_string, last_match_info);
      } else {
        return StringReplaceGlobalAtomRegExpWithString<SeqTwoByteString>(
            isolate, subject, regexp, empty_string, last_match_info);
      }
    }
  
    RegExpImpl::GlobalCache global_cache(regexp, subject, true, isolate);
    if (global_cache.HasException()) return isolate->heap()->exception();
  
    int32_t* current_match = global_cache.FetchNext();
    if (current_match == NULL) {
      if (global_cache.HasException()) return isolate->heap()->exception();
      return *subject;
    }
  
    int start = current_match[0];
    int end = current_match[1];
    int capture_count = regexp->CaptureCount();
    int subject_length = subject->length();
  
    int new_length = subject_length - (end - start);
    if (new_length == 0) return isolate->heap()->empty_string();
  
    Handle<ResultSeqString> answer;
    if (ResultSeqString::kHasAsciiEncoding) {
      answer = Handle<ResultSeqString>::cast(
          isolate->factory()->NewRawOneByteString(new_length).ToHandleChecked());
    } else {
      answer = Handle<ResultSeqString>::cast(
          isolate->factory()->NewRawTwoByteString(new_length).ToHandleChecked());
    }
  
    int prev = 0;
    int position = 0;
  
    do {
      start = current_match[0];
      end = current_match[1];
      if (prev < start) {
        // Add substring subject[prev;start] to answer string.
        String::WriteToFlat(*subject, answer->GetChars() + position, prev, start);
        position += start - prev;
      }
      prev = end;
  
      current_match = global_cache.FetchNext();
    } while (current_match != NULL);
  
    if (global_cache.HasException()) return isolate->heap()->exception();
  
    RegExpImpl::SetLastMatchInfo(last_match_info,
                                 subject,
                                 capture_count,
                                 global_cache.LastSuccessfulMatch());
  
    if (prev < subject_length) {
      // Add substring subject[prev;length] to answer string.
      String::WriteToFlat(
          *subject, answer->GetChars() + position, prev, subject_length);
      position += subject_length - prev;
    }
  
    if (position == 0) return isolate->heap()->empty_string();
  
    // Shorten string and fill
    int string_size = ResultSeqString::SizeFor(position);
    int allocated_string_size = ResultSeqString::SizeFor(new_length);
    int delta = allocated_string_size - string_size;
  
    answer->set_length(position);
    if (delta == 0) return *answer;
  
    Address end_of_string = answer->address() + string_size;
    Heap* heap = isolate->heap();
  
    // The trimming is performed on a newly allocated object, which is on a
    // fresly allocated page or on an already swept page. Hence, the sweeper
    // thread can not get confused with the filler creation. No synchronization
    // needed.
    heap->CreateFillerObjectAt(end_of_string, delta);
    heap->AdjustLiveBytes(answer->address(), -delta, Heap::FROM_MUTATOR);
    return *answer;
  }
  
  
  RUNTIME_FUNCTION(Runtime_StringReplaceGlobalRegExpWithString) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 4);
  
    CONVERT_ARG_HANDLE_CHECKED(String, subject, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, replacement, 2);
    CONVERT_ARG_HANDLE_CHECKED(JSRegExp, regexp, 1);
    CONVERT_ARG_HANDLE_CHECKED(JSArray, last_match_info, 3);
  
    RUNTIME_ASSERT(regexp->GetFlags().is_global());
    RUNTIME_ASSERT(last_match_info->HasFastObjectElements());
  
    subject = String::Flatten(subject);
  
    if (replacement->length() == 0) {
      if (subject->HasOnlyOneByteChars()) {
        return StringReplaceGlobalRegExpWithEmptyString<SeqOneByteString>(
            isolate, subject, regexp, last_match_info);
      } else {
        return StringReplaceGlobalRegExpWithEmptyString<SeqTwoByteString>(
            isolate, subject, regexp, last_match_info);
      }
    }
  
    replacement = String::Flatten(replacement);
  
    return StringReplaceGlobalRegExpWithString(
        isolate, subject, regexp, replacement, last_match_info);
  }
  
  
  // This may return an empty MaybeHandle if an exception is thrown or
  // we abort due to reaching the recursion limit.
  MaybeHandle<String> StringReplaceOneCharWithString(Isolate* isolate,
                                                     Handle<String> subject,
                                                     Handle<String> search,
                                                     Handle<String> replace,
                                                     bool* found,
                                                     int recursion_limit) {
    StackLimitCheck stackLimitCheck(isolate);
    if (stackLimitCheck.HasOverflowed() || (recursion_limit == 0)) {
      return MaybeHandle<String>();
    }
    recursion_limit--;
    if (subject->IsConsString()) {
      ConsString* cons = ConsString::cast(*subject);
      Handle<String> first = Handle<String>(cons->first());
      Handle<String> second = Handle<String>(cons->second());
      Handle<String> new_first;
      if (!StringReplaceOneCharWithString(
              isolate, first, search, replace, found, recursion_limit)
              .ToHandle(&new_first)) {
        return MaybeHandle<String>();
      }
      if (*found) return isolate->factory()->NewConsString(new_first, second);
  
      Handle<String> new_second;
      if (!StringReplaceOneCharWithString(
              isolate, second, search, replace, found, recursion_limit)
              .ToHandle(&new_second)) {
        return MaybeHandle<String>();
      }
      if (*found) return isolate->factory()->NewConsString(first, new_second);
  
      return subject;
    } else {
      int index = Runtime::StringMatch(isolate, subject, search, 0);
      if (index == -1) return subject;
      *found = true;
      Handle<String> first = isolate->factory()->NewSubString(subject, 0, index);
      Handle<String> cons1;
      ASSIGN_RETURN_ON_EXCEPTION(
          isolate, cons1,
          isolate->factory()->NewConsString(first, replace),
          String);
      Handle<String> second =
          isolate->factory()->NewSubString(subject, index + 1, subject->length());
      return isolate->factory()->NewConsString(cons1, second);
    }
  }
  
  
  RUNTIME_FUNCTION(Runtime_StringReplaceOneCharWithString) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
    CONVERT_ARG_HANDLE_CHECKED(String, subject, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, search, 1);
    CONVERT_ARG_HANDLE_CHECKED(String, replace, 2);
  
    // If the cons string tree is too deep, we simply abort the recursion and
    // retry with a flattened subject string.
    const int kRecursionLimit = 0x1000;
    bool found = false;
    Handle<String> result;
    if (StringReplaceOneCharWithString(
            isolate, subject, search, replace, &found, kRecursionLimit)
            .ToHandle(&result)) {
      return *result;
    }
    if (isolate->has_pending_exception()) return isolate->heap()->exception();
  
    subject = String::Flatten(subject);
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result,
        StringReplaceOneCharWithString(
            isolate, subject, search, replace, &found, kRecursionLimit));
    return *result;
  }
  
  
  // Perform string match of pattern on subject, starting at start index.
  // Caller must ensure that 0 <= start_index <= sub->length(),
  // and should check that pat->length() + start_index <= sub->length().
  int Runtime::StringMatch(Isolate* isolate,
                           Handle<String> sub,
                           Handle<String> pat,
                           int start_index) {
    DCHECK(0 <= start_index);
    DCHECK(start_index <= sub->length());
  
    int pattern_length = pat->length();
    if (pattern_length == 0) return start_index;
  
    int subject_length = sub->length();
    if (start_index + pattern_length > subject_length) return -1;
  
    sub = String::Flatten(sub);
    pat = String::Flatten(pat);
  
    DisallowHeapAllocation no_gc;  // ensure vectors stay valid
    // Extract flattened substrings of cons strings before determining asciiness.
    String::FlatContent seq_sub = sub->GetFlatContent();
    String::FlatContent seq_pat = pat->GetFlatContent();
  
    // dispatch on type of strings
    if (seq_pat.IsAscii()) {
      Vector<const uint8_t> pat_vector = seq_pat.ToOneByteVector();
      if (seq_sub.IsAscii()) {
        return SearchString(isolate,
                            seq_sub.ToOneByteVector(),
                            pat_vector,
                            start_index);
      }
      return SearchString(isolate,
                          seq_sub.ToUC16Vector(),
                          pat_vector,
                          start_index);
    }
    Vector<const uc16> pat_vector = seq_pat.ToUC16Vector();
    if (seq_sub.IsAscii()) {
      return SearchString(isolate,
                          seq_sub.ToOneByteVector(),
                          pat_vector,
                          start_index);
    }
    return SearchString(isolate,
                        seq_sub.ToUC16Vector(),
                        pat_vector,
                        start_index);
  }
  
  
  RUNTIME_FUNCTION(Runtime_StringIndexOf) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
  
    CONVERT_ARG_HANDLE_CHECKED(String, sub, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, pat, 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, index, 2);
  
    uint32_t start_index;
    if (!index->ToArrayIndex(&start_index)) return Smi::FromInt(-1);
  
    RUNTIME_ASSERT(start_index <= static_cast<uint32_t>(sub->length()));
    int position = Runtime::StringMatch(isolate, sub, pat, start_index);
    return Smi::FromInt(position);
  }
  
  
  template <typename schar, typename pchar>
  static int StringMatchBackwards(Vector<const schar> subject,
                                  Vector<const pchar> pattern,
                                  int idx) {
    int pattern_length = pattern.length();
    DCHECK(pattern_length >= 1);
    DCHECK(idx + pattern_length <= subject.length());
  
    if (sizeof(schar) == 1 && sizeof(pchar) > 1) {
      for (int i = 0; i < pattern_length; i++) {
        uc16 c = pattern[i];
        if (c > String::kMaxOneByteCharCode) {
          return -1;
        }
      }
    }
  
    pchar pattern_first_char = pattern[0];
    for (int i = idx; i >= 0; i--) {
      if (subject[i] != pattern_first_char) continue;
      int j = 1;
      while (j < pattern_length) {
        if (pattern[j] != subject[i+j]) {
          break;
        }
        j++;
      }
      if (j == pattern_length) {
        return i;
      }
    }
    return -1;
  }
  
  
  RUNTIME_FUNCTION(Runtime_StringLastIndexOf) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
  
    CONVERT_ARG_HANDLE_CHECKED(String, sub, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, pat, 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, index, 2);
  
    uint32_t start_index;
    if (!index->ToArrayIndex(&start_index)) return Smi::FromInt(-1);
  
    uint32_t pat_length = pat->length();
    uint32_t sub_length = sub->length();
  
    if (start_index + pat_length > sub_length) {
      start_index = sub_length - pat_length;
    }
  
    if (pat_length == 0) {
      return Smi::FromInt(start_index);
    }
  
    sub = String::Flatten(sub);
    pat = String::Flatten(pat);
  
    int position = -1;
    DisallowHeapAllocation no_gc;  // ensure vectors stay valid
  
    String::FlatContent sub_content = sub->GetFlatContent();
    String::FlatContent pat_content = pat->GetFlatContent();
  
    if (pat_content.IsAscii()) {
      Vector<const uint8_t> pat_vector = pat_content.ToOneByteVector();
      if (sub_content.IsAscii()) {
        position = StringMatchBackwards(sub_content.ToOneByteVector(),
                                        pat_vector,
                                        start_index);
      } else {
        position = StringMatchBackwards(sub_content.ToUC16Vector(),
                                        pat_vector,
                                        start_index);
      }
    } else {
      Vector<const uc16> pat_vector = pat_content.ToUC16Vector();
      if (sub_content.IsAscii()) {
        position = StringMatchBackwards(sub_content.ToOneByteVector(),
                                        pat_vector,
                                        start_index);
      } else {
        position = StringMatchBackwards(sub_content.ToUC16Vector(),
                                        pat_vector,
                                        start_index);
      }
    }
  
    return Smi::FromInt(position);
  }
  
  
  RUNTIME_FUNCTION(Runtime_StringLocaleCompare) {
    HandleScope handle_scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_HANDLE_CHECKED(String, str1, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, str2, 1);
  
    if (str1.is_identical_to(str2)) return Smi::FromInt(0);  // Equal.
    int str1_length = str1->length();
    int str2_length = str2->length();
  
    // Decide trivial cases without flattening.
    if (str1_length == 0) {
      if (str2_length == 0) return Smi::FromInt(0);  // Equal.
      return Smi::FromInt(-str2_length);
    } else {
      if (str2_length == 0) return Smi::FromInt(str1_length);
    }
  
    int end = str1_length < str2_length ? str1_length : str2_length;
  
    // No need to flatten if we are going to find the answer on the first
    // character.  At this point we know there is at least one character
    // in each string, due to the trivial case handling above.
    int d = str1->Get(0) - str2->Get(0);
    if (d != 0) return Smi::FromInt(d);
  
    str1 = String::Flatten(str1);
    str2 = String::Flatten(str2);
  
    DisallowHeapAllocation no_gc;
    String::FlatContent flat1 = str1->GetFlatContent();
    String::FlatContent flat2 = str2->GetFlatContent();
  
    for (int i = 0; i < end; i++) {
      if (flat1.Get(i) != flat2.Get(i)) {
        return Smi::FromInt(flat1.Get(i) - flat2.Get(i));
      }
    }
  
    return Smi::FromInt(str1_length - str2_length);
  }
  
  
  RUNTIME_FUNCTION(Runtime_SubString) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
  
    CONVERT_ARG_HANDLE_CHECKED(String, string, 0);
    int start, end;
    // We have a fast integer-only case here to avoid a conversion to double in
    // the common case where from and to are Smis.
    if (args[1]->IsSmi() && args[2]->IsSmi()) {
      CONVERT_SMI_ARG_CHECKED(from_number, 1);
      CONVERT_SMI_ARG_CHECKED(to_number, 2);
      start = from_number;
      end = to_number;
    } else {
      CONVERT_DOUBLE_ARG_CHECKED(from_number, 1);
      CONVERT_DOUBLE_ARG_CHECKED(to_number, 2);
      start = FastD2IChecked(from_number);
      end = FastD2IChecked(to_number);
    }
    RUNTIME_ASSERT(end >= start);
    RUNTIME_ASSERT(start >= 0);
    RUNTIME_ASSERT(end <= string->length());
    isolate->counters()->sub_string_runtime()->Increment();
  
    return *isolate->factory()->NewSubString(string, start, end);
  }
  
  
  RUNTIME_FUNCTION(Runtime_InternalizeString) {
    HandleScope handles(isolate);
    RUNTIME_ASSERT(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(String, string, 0);
    return *isolate->factory()->InternalizeString(string);
  }
  
  
  RUNTIME_FUNCTION(Runtime_StringMatch) {
    HandleScope handles(isolate);
    DCHECK(args.length() == 3);
  
    CONVERT_ARG_HANDLE_CHECKED(String, subject, 0);
    CONVERT_ARG_HANDLE_CHECKED(JSRegExp, regexp, 1);
    CONVERT_ARG_HANDLE_CHECKED(JSArray, regexp_info, 2);
  
    RUNTIME_ASSERT(regexp_info->HasFastObjectElements());
  
    RegExpImpl::GlobalCache global_cache(regexp, subject, true, isolate);
    if (global_cache.HasException()) return isolate->heap()->exception();
  
    int capture_count = regexp->CaptureCount();
  
    ZoneScope zone_scope(isolate->runtime_zone());
    ZoneList<int> offsets(8, zone_scope.zone());
  
    while (true) {
      int32_t* match = global_cache.FetchNext();
      if (match == NULL) break;
      offsets.Add(match[0], zone_scope.zone());  // start
      offsets.Add(match[1], zone_scope.zone());  // end
    }
  
    if (global_cache.HasException()) return isolate->heap()->exception();
  
    if (offsets.length() == 0) {
      // Not a single match.
      return isolate->heap()->null_value();
    }
  
    RegExpImpl::SetLastMatchInfo(regexp_info,
                                 subject,
                                 capture_count,
                                 global_cache.LastSuccessfulMatch());
  
    int matches = offsets.length() / 2;
    Handle<FixedArray> elements = isolate->factory()->NewFixedArray(matches);
    Handle<String> substring =
        isolate->factory()->NewSubString(subject, offsets.at(0), offsets.at(1));
    elements->set(0, *substring);
    for (int i = 1; i < matches; i++) {
      HandleScope temp_scope(isolate);
      int from = offsets.at(i * 2);
      int to = offsets.at(i * 2 + 1);
      Handle<String> substring =
          isolate->factory()->NewProperSubString(subject, from, to);
      elements->set(i, *substring);
    }
    Handle<JSArray> result = isolate->factory()->NewJSArrayWithElements(elements);
    result->set_length(Smi::FromInt(matches));
    return *result;
  }
  
  
  // Only called from Runtime_RegExpExecMultiple so it doesn't need to maintain
  // separate last match info.  See comment on that function.
  template<bool has_capture>
  static Object* SearchRegExpMultiple(
      Isolate* isolate,
      Handle<String> subject,
      Handle<JSRegExp> regexp,
      Handle<JSArray> last_match_array,
      Handle<JSArray> result_array) {
    DCHECK(subject->IsFlat());
    DCHECK_NE(has_capture, regexp->CaptureCount() == 0);
  
    int capture_count = regexp->CaptureCount();
    int subject_length = subject->length();
  
    static const int kMinLengthToCache = 0x1000;
  
    if (subject_length > kMinLengthToCache) {
      Handle<Object> cached_answer(RegExpResultsCache::Lookup(
          isolate->heap(),
          *subject,
          regexp->data(),
          RegExpResultsCache::REGEXP_MULTIPLE_INDICES), isolate);
      if (*cached_answer != Smi::FromInt(0)) {
        Handle<FixedArray> cached_fixed_array =
            Handle<FixedArray>(FixedArray::cast(*cached_answer));
        // The cache FixedArray is a COW-array and can therefore be reused.
        JSArray::SetContent(result_array, cached_fixed_array);
        // The actual length of the result array is stored in the last element of
        // the backing store (the backing FixedArray may have a larger capacity).
        Object* cached_fixed_array_last_element =
            cached_fixed_array->get(cached_fixed_array->length() - 1);
        Smi* js_array_length = Smi::cast(cached_fixed_array_last_element);
        result_array->set_length(js_array_length);
        RegExpImpl::SetLastMatchInfo(
            last_match_array, subject, capture_count, NULL);
        return *result_array;
      }
    }
  
    RegExpImpl::GlobalCache global_cache(regexp, subject, true, isolate);
    if (global_cache.HasException()) return isolate->heap()->exception();
  
    // Ensured in Runtime_RegExpExecMultiple.
    DCHECK(result_array->HasFastObjectElements());
    Handle<FixedArray> result_elements(
        FixedArray::cast(result_array->elements()));
    if (result_elements->length() < 16) {
      result_elements = isolate->factory()->NewFixedArrayWithHoles(16);
    }
  
    FixedArrayBuilder builder(result_elements);
  
    // Position to search from.
    int match_start = -1;
    int match_end = 0;
    bool first = true;
  
    // Two smis before and after the match, for very long strings.
    static const int kMaxBuilderEntriesPerRegExpMatch = 5;
  
    while (true) {
      int32_t* current_match = global_cache.FetchNext();
      if (current_match == NULL) break;
      match_start = current_match[0];
      builder.EnsureCapacity(kMaxBuilderEntriesPerRegExpMatch);
      if (match_end < match_start) {
        ReplacementStringBuilder::AddSubjectSlice(&builder,
                                                  match_end,
                                                  match_start);
      }
      match_end = current_match[1];
      {
        // Avoid accumulating new handles inside loop.
        HandleScope temp_scope(isolate);
        Handle<String> match;
        if (!first) {
          match = isolate->factory()->NewProperSubString(subject,
                                                         match_start,
                                                         match_end);
        } else {
          match = isolate->factory()->NewSubString(subject,
                                                   match_start,
                                                   match_end);
          first = false;
        }
  
        if (has_capture) {
          // Arguments array to replace function is match, captures, index and
          // subject, i.e., 3 + capture count in total.
          Handle<FixedArray> elements =
              isolate->factory()->NewFixedArray(3 + capture_count);
  
          elements->set(0, *match);
          for (int i = 1; i <= capture_count; i++) {
            int start = current_match[i * 2];
            if (start >= 0) {
              int end = current_match[i * 2 + 1];
              DCHECK(start <= end);
              Handle<String> substring =
                  isolate->factory()->NewSubString(subject, start, end);
              elements->set(i, *substring);
            } else {
              DCHECK(current_match[i * 2 + 1] < 0);
              elements->set(i, isolate->heap()->undefined_value());
            }
          }
          elements->set(capture_count + 1, Smi::FromInt(match_start));
          elements->set(capture_count + 2, *subject);
          builder.Add(*isolate->factory()->NewJSArrayWithElements(elements));
        } else {
          builder.Add(*match);
        }
      }
    }
  
    if (global_cache.HasException()) return isolate->heap()->exception();
  
    if (match_start >= 0) {
      // Finished matching, with at least one match.
      if (match_end < subject_length) {
        ReplacementStringBuilder::AddSubjectSlice(&builder,
                                                  match_end,
                                                  subject_length);
      }
  
      RegExpImpl::SetLastMatchInfo(
          last_match_array, subject, capture_count, NULL);
  
      if (subject_length > kMinLengthToCache) {
        // Store the length of the result array into the last element of the
        // backing FixedArray.
        builder.EnsureCapacity(1);
        Handle<FixedArray> fixed_array = builder.array();
        fixed_array->set(fixed_array->length() - 1,
                         Smi::FromInt(builder.length()));
        // Cache the result and turn the FixedArray into a COW array.
        RegExpResultsCache::Enter(isolate,
                                  subject,
                                  handle(regexp->data(), isolate),
                                  fixed_array,
                                  RegExpResultsCache::REGEXP_MULTIPLE_INDICES);
      }
      return *builder.ToJSArray(result_array);
    } else {
      return isolate->heap()->null_value();  // No matches at all.
    }
  }
  
  
  // This is only called for StringReplaceGlobalRegExpWithFunction.  This sets
  // lastMatchInfoOverride to maintain the last match info, so we don't need to
  // set any other last match array info.
  RUNTIME_FUNCTION(Runtime_RegExpExecMultiple) {
    HandleScope handles(isolate);
    DCHECK(args.length() == 4);
  
    CONVERT_ARG_HANDLE_CHECKED(String, subject, 1);
    CONVERT_ARG_HANDLE_CHECKED(JSRegExp, regexp, 0);
    CONVERT_ARG_HANDLE_CHECKED(JSArray, last_match_info, 2);
    CONVERT_ARG_HANDLE_CHECKED(JSArray, result_array, 3);
    RUNTIME_ASSERT(last_match_info->HasFastObjectElements());
    RUNTIME_ASSERT(result_array->HasFastObjectElements());
  
    subject = String::Flatten(subject);
    RUNTIME_ASSERT(regexp->GetFlags().is_global());
  
    if (regexp->CaptureCount() == 0) {
      return SearchRegExpMultiple<false>(
          isolate, subject, regexp, last_match_info, result_array);
    } else {
      return SearchRegExpMultiple<true>(
          isolate, subject, regexp, last_match_info, result_array);
    }
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberToRadixString) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_SMI_ARG_CHECKED(radix, 1);
    RUNTIME_ASSERT(2 <= radix && radix <= 36);
  
    // Fast case where the result is a one character string.
    if (args[0]->IsSmi()) {
      int value = args.smi_at(0);
      if (value >= 0 && value < radix) {
        // Character array used for conversion.
        static const char kCharTable[] = "0123456789abcdefghijklmnopqrstuvwxyz";
        return *isolate->factory()->
            LookupSingleCharacterStringFromCode(kCharTable[value]);
      }
    }
  
    // Slow case.
    CONVERT_DOUBLE_ARG_CHECKED(value, 0);
    if (std::isnan(value)) {
      return isolate->heap()->nan_string();
    }
    if (std::isinf(value)) {
      if (value < 0) {
        return isolate->heap()->minus_infinity_string();
      }
      return isolate->heap()->infinity_string();
    }
    char* str = DoubleToRadixCString(value, radix);
    Handle<String> result = isolate->factory()->NewStringFromAsciiChecked(str);
    DeleteArray(str);
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberToFixed) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_DOUBLE_ARG_CHECKED(value, 0);
    CONVERT_DOUBLE_ARG_CHECKED(f_number, 1);
    int f = FastD2IChecked(f_number);
    // See DoubleToFixedCString for these constants:
    RUNTIME_ASSERT(f >= 0 && f <= 20);
    RUNTIME_ASSERT(!Double(value).IsSpecial());
    char* str = DoubleToFixedCString(value, f);
    Handle<String> result = isolate->factory()->NewStringFromAsciiChecked(str);
    DeleteArray(str);
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberToExponential) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_DOUBLE_ARG_CHECKED(value, 0);
    CONVERT_DOUBLE_ARG_CHECKED(f_number, 1);
    int f = FastD2IChecked(f_number);
    RUNTIME_ASSERT(f >= -1 && f <= 20);
    RUNTIME_ASSERT(!Double(value).IsSpecial());
    char* str = DoubleToExponentialCString(value, f);
    Handle<String> result = isolate->factory()->NewStringFromAsciiChecked(str);
    DeleteArray(str);
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberToPrecision) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_DOUBLE_ARG_CHECKED(value, 0);
    CONVERT_DOUBLE_ARG_CHECKED(f_number, 1);
    int f = FastD2IChecked(f_number);
    RUNTIME_ASSERT(f >= 1 && f <= 21);
    RUNTIME_ASSERT(!Double(value).IsSpecial());
    char* str = DoubleToPrecisionCString(value, f);
    Handle<String> result = isolate->factory()->NewStringFromAsciiChecked(str);
    DeleteArray(str);
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_IsValidSmi) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
  
    CONVERT_NUMBER_CHECKED(int32_t, number, Int32, args[0]);
    return isolate->heap()->ToBoolean(Smi::IsValid(number));
  }
  
  
  // Returns a single character string where first character equals
  // string->Get(index).
  static Handle<Object> GetCharAt(Handle<String> string, uint32_t index) {
    if (index < static_cast<uint32_t>(string->length())) {
      Factory* factory = string->GetIsolate()->factory();
      return factory->LookupSingleCharacterStringFromCode(
          String::Flatten(string)->Get(index));
    }
    return Execution::CharAt(string, index);
  }
  
  
  MaybeHandle<Object> Runtime::GetElementOrCharAt(Isolate* isolate,
                                                  Handle<Object> object,
                                                  uint32_t index) {
    // Handle [] indexing on Strings
    if (object->IsString()) {
      Handle<Object> result = GetCharAt(Handle<String>::cast(object), index);
      if (!result->IsUndefined()) return result;
    }
  
    // Handle [] indexing on String objects
    if (object->IsStringObjectWithCharacterAt(index)) {
      Handle<JSValue> js_value = Handle<JSValue>::cast(object);
      Handle<Object> result =
          GetCharAt(Handle<String>(String::cast(js_value->value())), index);
      if (!result->IsUndefined()) return result;
    }
  
    Handle<Object> result;
    if (object->IsString() || object->IsNumber() || object->IsBoolean()) {
      PrototypeIterator iter(isolate, object);
      return Object::GetElement(isolate, PrototypeIterator::GetCurrent(iter),
                                index);
    } else {
      return Object::GetElement(isolate, object, index);
    }
  }
  
  
  MUST_USE_RESULT
  static MaybeHandle<Name> ToName(Isolate* isolate, Handle<Object> key) {
    if (key->IsName()) {
      return Handle<Name>::cast(key);
    } else {
      Handle<Object> converted;
      ASSIGN_RETURN_ON_EXCEPTION(
          isolate, converted, Execution::ToString(isolate, key), Name);
      return Handle<Name>::cast(converted);
    }
  }
  
  
  MaybeHandle<Object> Runtime::HasObjectProperty(Isolate* isolate,
                                                 Handle<JSReceiver> object,
                                                 Handle<Object> key) {
    Maybe<bool> maybe;
    // Check if the given key is an array index.
    uint32_t index;
    if (key->ToArrayIndex(&index)) {
      maybe = JSReceiver::HasElement(object, index);
    } else {
      // Convert the key to a name - possibly by calling back into JavaScript.
      Handle<Name> name;
      ASSIGN_RETURN_ON_EXCEPTION(isolate, name, ToName(isolate, key), Object);
  
      maybe = JSReceiver::HasProperty(object, name);
    }
  
    if (!maybe.has_value) return MaybeHandle<Object>();
    return isolate->factory()->ToBoolean(maybe.value);
  }
  
  
  MaybeHandle<Object> Runtime::GetObjectProperty(Isolate* isolate,
                                                 Handle<Object> object,
                                                 Handle<Object> key) {
    if (object->IsUndefined() || object->IsNull()) {
      Handle<Object> args[2] = { key, object };
      return isolate->Throw<Object>(
          isolate->factory()->NewTypeError("non_object_property_load",
                                           HandleVector(args, 2)));
    }
  
    // Check if the given key is an array index.
    uint32_t index;
    if (key->ToArrayIndex(&index)) {
      return GetElementOrCharAt(isolate, object, index);
    }
  
    // Convert the key to a name - possibly by calling back into JavaScript.
    Handle<Name> name;
    ASSIGN_RETURN_ON_EXCEPTION(isolate, name, ToName(isolate, key), Object);
  
    // Check if the name is trivially convertible to an index and get
    // the element if so.
    if (name->AsArrayIndex(&index)) {
      return GetElementOrCharAt(isolate, object, index);
    } else {
      return Object::GetProperty(object, name);
    }
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetProperty) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, key, 1);
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result,
        Runtime::GetObjectProperty(isolate, object, key));
    return *result;
  }
  
  
  // KeyedGetProperty is called from KeyedLoadIC::GenerateGeneric.
  RUNTIME_FUNCTION(Runtime_KeyedGetProperty) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_HANDLE_CHECKED(Object, receiver_obj, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, key_obj, 1);
  
    // Fast cases for getting named properties of the receiver JSObject
    // itself.
    //
    // The global proxy objects has to be excluded since LookupOwn on
    // the global proxy object can return a valid result even though the
    // global proxy object never has properties.  This is the case
    // because the global proxy object forwards everything to its hidden
    // prototype including own lookups.
    //
    // Additionally, we need to make sure that we do not cache results
    // for objects that require access checks.
    if (receiver_obj->IsJSObject()) {
      if (!receiver_obj->IsJSGlobalProxy() &&
          !receiver_obj->IsAccessCheckNeeded() &&
          key_obj->IsName()) {
        DisallowHeapAllocation no_allocation;
        Handle<JSObject> receiver = Handle<JSObject>::cast(receiver_obj);
        Handle<Name> key = Handle<Name>::cast(key_obj);
        if (receiver->HasFastProperties()) {
          // Attempt to use lookup cache.
          Handle<Map> receiver_map(receiver->map(), isolate);
          KeyedLookupCache* keyed_lookup_cache = isolate->keyed_lookup_cache();
          int index = keyed_lookup_cache->Lookup(receiver_map, key);
          if (index != -1) {
            // Doubles are not cached, so raw read the value.
            return receiver->RawFastPropertyAt(
                FieldIndex::ForKeyedLookupCacheIndex(*receiver_map, index));
          }
          // Lookup cache miss.  Perform lookup and update the cache if
          // appropriate.
          LookupResult result(isolate);
          receiver->LookupOwn(key, &result);
          if (result.IsField()) {
            FieldIndex field_index = result.GetFieldIndex();
            // Do not track double fields in the keyed lookup cache. Reading
            // double values requires boxing.
            if (!result.representation().IsDouble()) {
              keyed_lookup_cache->Update(receiver_map, key,
                  field_index.GetKeyedLookupCacheIndex());
            }
            AllowHeapAllocation allow_allocation;
            return *JSObject::FastPropertyAt(receiver, result.representation(),
                                             field_index);
          }
        } else {
          // Attempt dictionary lookup.
          NameDictionary* dictionary = receiver->property_dictionary();
          int entry = dictionary->FindEntry(key);
          if ((entry != NameDictionary::kNotFound) &&
              (dictionary->DetailsAt(entry).type() == NORMAL)) {
            Object* value = dictionary->ValueAt(entry);
            if (!receiver->IsGlobalObject()) return value;
            value = PropertyCell::cast(value)->value();
            if (!value->IsTheHole()) return value;
            // If value is the hole (meaning, absent) do the general lookup.
          }
        }
      } else if (key_obj->IsSmi()) {
        // JSObject without a name key. If the key is a Smi, check for a
        // definite out-of-bounds access to elements, which is a strong indicator
        // that subsequent accesses will also call the runtime. Proactively
        // transition elements to FAST_*_ELEMENTS to avoid excessive boxing of
        // doubles for those future calls in the case that the elements would
        // become FAST_DOUBLE_ELEMENTS.
        Handle<JSObject> js_object = Handle<JSObject>::cast(receiver_obj);
        ElementsKind elements_kind = js_object->GetElementsKind();
        if (IsFastDoubleElementsKind(elements_kind)) {
          Handle<Smi> key = Handle<Smi>::cast(key_obj);
          if (key->value() >= js_object->elements()->length()) {
            if (IsFastHoleyElementsKind(elements_kind)) {
              elements_kind = FAST_HOLEY_ELEMENTS;
            } else {
              elements_kind = FAST_ELEMENTS;
            }
            RETURN_FAILURE_ON_EXCEPTION(
                isolate, TransitionElements(js_object, elements_kind, isolate));
          }
        } else {
          DCHECK(IsFastSmiOrObjectElementsKind(elements_kind) ||
                 !IsFastElementsKind(elements_kind));
        }
      }
    } else if (receiver_obj->IsString() && key_obj->IsSmi()) {
      // Fast case for string indexing using [] with a smi index.
      Handle<String> str = Handle<String>::cast(receiver_obj);
      int index = args.smi_at(1);
      if (index >= 0 && index < str->length()) {
        return *GetCharAt(str, index);
      }
    }
  
    // Fall back to GetObjectProperty.
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result,
        Runtime::GetObjectProperty(isolate, receiver_obj, key_obj));
    return *result;
  }
  
  
  static bool IsValidAccessor(Handle<Object> obj) {
    return obj->IsUndefined() || obj->IsSpecFunction() || obj->IsNull();
  }
  
  
  // Transform getter or setter into something DefineAccessor can handle.
  static Handle<Object> InstantiateAccessorComponent(Isolate* isolate,
                                                     Handle<Object> component) {
    if (component->IsUndefined()) return isolate->factory()->null_value();
    Handle<FunctionTemplateInfo> info =
        Handle<FunctionTemplateInfo>::cast(component);
    return Utils::OpenHandle(*Utils::ToLocal(info)->GetFunction());
  }
  
  
  RUNTIME_FUNCTION(Runtime_DefineApiAccessorProperty) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 5);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
    CONVERT_ARG_HANDLE_CHECKED(Name, name, 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, getter, 2);
    CONVERT_ARG_HANDLE_CHECKED(Object, setter, 3);
    CONVERT_SMI_ARG_CHECKED(attribute, 4);
    RUNTIME_ASSERT(getter->IsUndefined() || getter->IsFunctionTemplateInfo());
    RUNTIME_ASSERT(setter->IsUndefined() || setter->IsFunctionTemplateInfo());
    RUNTIME_ASSERT(PropertyDetails::AttributesField::is_valid(
        static_cast<PropertyAttributes>(attribute)));
    RETURN_FAILURE_ON_EXCEPTION(
        isolate, JSObject::DefineAccessor(
                     object, name, InstantiateAccessorComponent(isolate, getter),
                     InstantiateAccessorComponent(isolate, setter),
                     static_cast<PropertyAttributes>(attribute)));
    return isolate->heap()->undefined_value();
  }
  
  
  // Implements part of 8.12.9 DefineOwnProperty.
  // There are 3 cases that lead here:
  // Step 4b - define a new accessor property.
  // Steps 9c & 12 - replace an existing data property with an accessor property.
  // Step 12 - update an existing accessor property with an accessor or generic
  //           descriptor.
  RUNTIME_FUNCTION(Runtime_DefineAccessorPropertyUnchecked) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 5);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, obj, 0);
    RUNTIME_ASSERT(!obj->IsNull());
    CONVERT_ARG_HANDLE_CHECKED(Name, name, 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, getter, 2);
    RUNTIME_ASSERT(IsValidAccessor(getter));
    CONVERT_ARG_HANDLE_CHECKED(Object, setter, 3);
    RUNTIME_ASSERT(IsValidAccessor(setter));
    CONVERT_SMI_ARG_CHECKED(unchecked, 4);
    RUNTIME_ASSERT((unchecked & ~(READ_ONLY | DONT_ENUM | DONT_DELETE)) == 0);
    PropertyAttributes attr = static_cast<PropertyAttributes>(unchecked);
  
    bool fast = obj->HasFastProperties();
    RETURN_FAILURE_ON_EXCEPTION(
        isolate, JSObject::DefineAccessor(obj, name, getter, setter, attr));
    if (fast) JSObject::MigrateSlowToFast(obj, 0);
    return isolate->heap()->undefined_value();
  }
  
  
  // Implements part of 8.12.9 DefineOwnProperty.
  // There are 3 cases that lead here:
  // Step 4a - define a new data property.
  // Steps 9b & 12 - replace an existing accessor property with a data property.
  // Step 12 - update an existing data property with a data or generic
  //           descriptor.
  RUNTIME_FUNCTION(Runtime_DefineDataPropertyUnchecked) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 4);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, js_object, 0);
    CONVERT_ARG_HANDLE_CHECKED(Name, name, 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, obj_value, 2);
    CONVERT_SMI_ARG_CHECKED(unchecked, 3);
    RUNTIME_ASSERT((unchecked & ~(READ_ONLY | DONT_ENUM | DONT_DELETE)) == 0);
    PropertyAttributes attr = static_cast<PropertyAttributes>(unchecked);
  
    // Check access rights if needed.
    if (js_object->IsAccessCheckNeeded() &&
        !isolate->MayNamedAccess(js_object, name, v8::ACCESS_SET)) {
      return isolate->heap()->undefined_value();
    }
  
    LookupResult lookup(isolate);
    js_object->LookupOwnRealNamedProperty(name, &lookup);
  
    // Take special care when attributes are different and there is already
    // a property. For simplicity we normalize the property which enables us
    // to not worry about changing the instance_descriptor and creating a new
    // map.
    if (lookup.IsFound() &&
        (attr != lookup.GetAttributes() || lookup.IsPropertyCallbacks())) {
      // Use IgnoreAttributes version since a readonly property may be
      // overridden and SetProperty does not allow this.
      Handle<Object> result;
      ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
          isolate, result,
          JSObject::SetOwnPropertyIgnoreAttributes(
              js_object, name, obj_value, attr,
              JSReceiver::PERFORM_EXTENSIBILITY_CHECK,
              JSReceiver::MAY_BE_STORE_FROM_KEYED,
              JSObject::DONT_FORCE_FIELD));
      return *result;
    }
  
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result,
        Runtime::DefineObjectProperty(
            js_object, name, obj_value, attr,
            JSReceiver::CERTAINLY_NOT_STORE_FROM_KEYED));
    return *result;
  }
  
  
  // Return property without being observable by accessors or interceptors.
  RUNTIME_FUNCTION(Runtime_GetDataProperty) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
    CONVERT_ARG_HANDLE_CHECKED(Name, key, 1);
    return *JSObject::GetDataProperty(object, key);
  }
  
  
  MaybeHandle<Object> Runtime::SetObjectProperty(Isolate* isolate,
                                                 Handle<Object> object,
                                                 Handle<Object> key,
                                                 Handle<Object> value,
                                                 StrictMode strict_mode) {
    if (object->IsUndefined() || object->IsNull()) {
      Handle<Object> args[2] = { key, object };
      Handle<Object> error =
          isolate->factory()->NewTypeError("non_object_property_store",
                                           HandleVector(args, 2));
      return isolate->Throw<Object>(error);
    }
  
    if (object->IsJSProxy()) {
      Handle<Object> name_object;
      if (key->IsSymbol()) {
        name_object = key;
      } else {
        ASSIGN_RETURN_ON_EXCEPTION(
            isolate, name_object, Execution::ToString(isolate, key), Object);
      }
      Handle<Name> name = Handle<Name>::cast(name_object);
      return Object::SetProperty(Handle<JSProxy>::cast(object), name, value,
                                 strict_mode);
    }
  
    // Check if the given key is an array index.
    uint32_t index;
    if (key->ToArrayIndex(&index)) {
      // TODO(verwaest): Support non-JSObject receivers.
      if (!object->IsJSObject()) return value;
      Handle<JSObject> js_object = Handle<JSObject>::cast(object);
  
      // In Firefox/SpiderMonkey, Safari and Opera you can access the characters
      // of a string using [] notation.  We need to support this too in
      // JavaScript.
      // In the case of a String object we just need to redirect the assignment to
      // the underlying string if the index is in range.  Since the underlying
      // string does nothing with the assignment then we can ignore such
      // assignments.
      if (js_object->IsStringObjectWithCharacterAt(index)) {
        return value;
      }
  
      JSObject::ValidateElements(js_object);
      if (js_object->HasExternalArrayElements() ||
          js_object->HasFixedTypedArrayElements()) {
        if (!value->IsNumber() && !value->IsUndefined()) {
          ASSIGN_RETURN_ON_EXCEPTION(
              isolate, value, Execution::ToNumber(isolate, value), Object);
        }
      }
  
      MaybeHandle<Object> result = JSObject::SetElement(
          js_object, index, value, NONE, strict_mode, true, SET_PROPERTY);
      JSObject::ValidateElements(js_object);
  
      return result.is_null() ? result : value;
    }
  
    if (key->IsName()) {
      Handle<Name> name = Handle<Name>::cast(key);
      if (name->AsArrayIndex(&index)) {
        // TODO(verwaest): Support non-JSObject receivers.
        if (!object->IsJSObject()) return value;
        Handle<JSObject> js_object = Handle<JSObject>::cast(object);
        if (js_object->HasExternalArrayElements()) {
          if (!value->IsNumber() && !value->IsUndefined()) {
            ASSIGN_RETURN_ON_EXCEPTION(
                isolate, value, Execution::ToNumber(isolate, value), Object);
          }
        }
        return JSObject::SetElement(js_object, index, value, NONE, strict_mode,
                                    true, SET_PROPERTY);
      } else {
        if (name->IsString()) name = String::Flatten(Handle<String>::cast(name));
        return Object::SetProperty(object, name, value, strict_mode);
      }
    }
  
    // Call-back into JavaScript to convert the key to a string.
    Handle<Object> converted;
    ASSIGN_RETURN_ON_EXCEPTION(
        isolate, converted, Execution::ToString(isolate, key), Object);
    Handle<String> name = Handle<String>::cast(converted);
  
    if (name->AsArrayIndex(&index)) {
      // TODO(verwaest): Support non-JSObject receivers.
      if (!object->IsJSObject()) return value;
      Handle<JSObject> js_object = Handle<JSObject>::cast(object);
      return JSObject::SetElement(js_object, index, value, NONE, strict_mode,
                                  true, SET_PROPERTY);
    }
    return Object::SetProperty(object, name, value, strict_mode);
  }
  
  
  MaybeHandle<Object> Runtime::DefineObjectProperty(
      Handle<JSObject> js_object,
      Handle<Object> key,
      Handle<Object> value,
      PropertyAttributes attr,
      JSReceiver::StoreFromKeyed store_from_keyed) {
    Isolate* isolate = js_object->GetIsolate();
    // Check if the given key is an array index.
    uint32_t index;
    if (key->ToArrayIndex(&index)) {
      // In Firefox/SpiderMonkey, Safari and Opera you can access the characters
      // of a string using [] notation.  We need to support this too in
      // JavaScript.
      // In the case of a String object we just need to redirect the assignment to
      // the underlying string if the index is in range.  Since the underlying
      // string does nothing with the assignment then we can ignore such
      // assignments.
      if (js_object->IsStringObjectWithCharacterAt(index)) {
        return value;
      }
  
      return JSObject::SetElement(js_object, index, value, attr,
                                  SLOPPY, false, DEFINE_PROPERTY);
    }
  
    if (key->IsName()) {
      Handle<Name> name = Handle<Name>::cast(key);
      if (name->AsArrayIndex(&index)) {
        return JSObject::SetElement(js_object, index, value, attr,
                                    SLOPPY, false, DEFINE_PROPERTY);
      } else {
        if (name->IsString()) name = String::Flatten(Handle<String>::cast(name));
        return JSObject::SetOwnPropertyIgnoreAttributes(
            js_object, name, value, attr, JSReceiver::PERFORM_EXTENSIBILITY_CHECK,
            store_from_keyed);
      }
    }
  
    // Call-back into JavaScript to convert the key to a string.
    Handle<Object> converted;
    ASSIGN_RETURN_ON_EXCEPTION(
        isolate, converted, Execution::ToString(isolate, key), Object);
    Handle<String> name = Handle<String>::cast(converted);
  
    if (name->AsArrayIndex(&index)) {
      return JSObject::SetElement(js_object, index, value, attr,
                                  SLOPPY, false, DEFINE_PROPERTY);
    } else {
      return JSObject::SetOwnPropertyIgnoreAttributes(
          js_object, name, value, attr, JSReceiver::PERFORM_EXTENSIBILITY_CHECK,
          store_from_keyed);
    }
  }
  
  
  MaybeHandle<Object> Runtime::DeleteObjectProperty(Isolate* isolate,
                                                    Handle<JSReceiver> receiver,
                                                    Handle<Object> key,
                                                    JSReceiver::DeleteMode mode) {
    // Check if the given key is an array index.
    uint32_t index;
    if (key->ToArrayIndex(&index)) {
      // In Firefox/SpiderMonkey, Safari and Opera you can access the
      // characters of a string using [] notation.  In the case of a
      // String object we just need to redirect the deletion to the
      // underlying string if the index is in range.  Since the
      // underlying string does nothing with the deletion, we can ignore
      // such deletions.
      if (receiver->IsStringObjectWithCharacterAt(index)) {
        return isolate->factory()->true_value();
      }
  
      return JSReceiver::DeleteElement(receiver, index, mode);
    }
  
    Handle<Name> name;
    if (key->IsName()) {
      name = Handle<Name>::cast(key);
    } else {
      // Call-back into JavaScript to convert the key to a string.
      Handle<Object> converted;
      ASSIGN_RETURN_ON_EXCEPTION(
          isolate, converted, Execution::ToString(isolate, key), Object);
      name = Handle<String>::cast(converted);
    }
  
    if (name->IsString()) name = String::Flatten(Handle<String>::cast(name));
    return JSReceiver::DeleteProperty(receiver, name, mode);
  }
  
  
  RUNTIME_FUNCTION(Runtime_SetHiddenProperty) {
    HandleScope scope(isolate);
    RUNTIME_ASSERT(args.length() == 3);
  
    CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, key, 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, value, 2);
    RUNTIME_ASSERT(key->IsUniqueName());
    return *JSObject::SetHiddenProperty(object, key, value);
  }
  
  
  RUNTIME_FUNCTION(Runtime_AddNamedProperty) {
    HandleScope scope(isolate);
    RUNTIME_ASSERT(args.length() == 4);
  
    CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
    CONVERT_ARG_HANDLE_CHECKED(Name, key, 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, value, 2);
    CONVERT_SMI_ARG_CHECKED(unchecked_attributes, 3);
    RUNTIME_ASSERT(
        (unchecked_attributes & ~(READ_ONLY | DONT_ENUM | DONT_DELETE)) == 0);
    // Compute attributes.
    PropertyAttributes attributes =
        static_cast<PropertyAttributes>(unchecked_attributes);
  
  #ifdef DEBUG
    uint32_t index = 0;
    DCHECK(!key->ToArrayIndex(&index));
    LookupIterator it(object, key, LookupIterator::CHECK_OWN_REAL);
    Maybe<PropertyAttributes> maybe = JSReceiver::GetPropertyAttributes(&it);
    DCHECK(maybe.has_value);
    RUNTIME_ASSERT(!it.IsFound());
  #endif
  
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result,
        JSObject::SetOwnPropertyIgnoreAttributes(object, key, value, attributes));
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_AddPropertyForTemplate) {
    HandleScope scope(isolate);
    RUNTIME_ASSERT(args.length() == 4);
  
    CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, key, 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, value, 2);
    CONVERT_SMI_ARG_CHECKED(unchecked_attributes, 3);
    RUNTIME_ASSERT(
        (unchecked_attributes & ~(READ_ONLY | DONT_ENUM | DONT_DELETE)) == 0);
    // Compute attributes.
    PropertyAttributes attributes =
        static_cast<PropertyAttributes>(unchecked_attributes);
  
  #ifdef DEBUG
    bool duplicate;
    if (key->IsName()) {
      LookupIterator it(object, Handle<Name>::cast(key),
                        LookupIterator::CHECK_OWN_REAL);
      Maybe<PropertyAttributes> maybe = JSReceiver::GetPropertyAttributes(&it);
      DCHECK(maybe.has_value);
      duplicate = it.IsFound();
    } else {
      uint32_t index = 0;
      RUNTIME_ASSERT(key->ToArrayIndex(&index));
      Maybe<bool> maybe = JSReceiver::HasOwnElement(object, index);
      if (!maybe.has_value) return isolate->heap()->exception();
      duplicate = maybe.value;
    }
    if (duplicate) {
      Handle<Object> args[1] = { key };
      Handle<Object> error = isolate->factory()->NewTypeError(
          "duplicate_template_property", HandleVector(args, 1));
      return isolate->Throw(*error);
    }
  #endif
  
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result,
        Runtime::DefineObjectProperty(object, key, value, attributes));
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_SetProperty) {
    HandleScope scope(isolate);
    RUNTIME_ASSERT(args.length() == 4);
  
    CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, key, 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, value, 2);
    CONVERT_STRICT_MODE_ARG_CHECKED(strict_mode_arg, 3);
    StrictMode strict_mode = strict_mode_arg;
  
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result,
        Runtime::SetObjectProperty(isolate, object, key, value, strict_mode));
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_TransitionElementsKind) {
    HandleScope scope(isolate);
    RUNTIME_ASSERT(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSArray, array, 0);
    CONVERT_ARG_HANDLE_CHECKED(Map, map, 1);
    JSObject::TransitionElementsKind(array, map->elements_kind());
    return *array;
  }
  
  
  // Set the native flag on the function.
  // This is used to decide if we should transform null and undefined
  // into the global object when doing call and apply.
  RUNTIME_FUNCTION(Runtime_SetNativeFlag) {
    SealHandleScope shs(isolate);
    RUNTIME_ASSERT(args.length() == 1);
  
    CONVERT_ARG_CHECKED(Object, object, 0);
  
    if (object->IsJSFunction()) {
      JSFunction* func = JSFunction::cast(object);
      func->shared()->set_native(true);
    }
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_SetInlineBuiltinFlag) {
    SealHandleScope shs(isolate);
    RUNTIME_ASSERT(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
  
    if (object->IsJSFunction()) {
      JSFunction* func = JSFunction::cast(*object);
      func->shared()->set_inline_builtin(true);
    }
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_StoreArrayLiteralElement) {
    HandleScope scope(isolate);
    RUNTIME_ASSERT(args.length() == 5);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
    CONVERT_SMI_ARG_CHECKED(store_index, 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, value, 2);
    CONVERT_ARG_HANDLE_CHECKED(FixedArray, literals, 3);
    CONVERT_SMI_ARG_CHECKED(literal_index, 4);
  
    Object* raw_literal_cell = literals->get(literal_index);
    JSArray* boilerplate = NULL;
    if (raw_literal_cell->IsAllocationSite()) {
      AllocationSite* site = AllocationSite::cast(raw_literal_cell);
      boilerplate = JSArray::cast(site->transition_info());
    } else {
      boilerplate = JSArray::cast(raw_literal_cell);
    }
    Handle<JSArray> boilerplate_object(boilerplate);
    ElementsKind elements_kind = object->GetElementsKind();
    DCHECK(IsFastElementsKind(elements_kind));
    // Smis should never trigger transitions.
    DCHECK(!value->IsSmi());
  
    if (value->IsNumber()) {
      DCHECK(IsFastSmiElementsKind(elements_kind));
      ElementsKind transitioned_kind = IsFastHoleyElementsKind(elements_kind)
          ? FAST_HOLEY_DOUBLE_ELEMENTS
          : FAST_DOUBLE_ELEMENTS;
      if (IsMoreGeneralElementsKindTransition(
              boilerplate_object->GetElementsKind(),
              transitioned_kind)) {
        JSObject::TransitionElementsKind(boilerplate_object, transitioned_kind);
      }
      JSObject::TransitionElementsKind(object, transitioned_kind);
      DCHECK(IsFastDoubleElementsKind(object->GetElementsKind()));
      FixedDoubleArray* double_array = FixedDoubleArray::cast(object->elements());
      HeapNumber* number = HeapNumber::cast(*value);
      double_array->set(store_index, number->Number());
    } else {
      if (!IsFastObjectElementsKind(elements_kind)) {
        ElementsKind transitioned_kind = IsFastHoleyElementsKind(elements_kind)
            ? FAST_HOLEY_ELEMENTS
            : FAST_ELEMENTS;
        JSObject::TransitionElementsKind(object, transitioned_kind);
        ElementsKind boilerplate_elements_kind =
            boilerplate_object->GetElementsKind();
        if (IsMoreGeneralElementsKindTransition(boilerplate_elements_kind,
                                                transitioned_kind)) {
          JSObject::TransitionElementsKind(boilerplate_object, transitioned_kind);
        }
      }
      FixedArray* object_array = FixedArray::cast(object->elements());
      object_array->set(store_index, *value);
    }
    return *object;
  }
  
  
  // Check whether debugger and is about to step into the callback that is passed
  // to a built-in function such as Array.forEach.
  RUNTIME_FUNCTION(Runtime_DebugCallbackSupportsStepping) {
    DCHECK(args.length() == 1);
    if (!isolate->debug()->is_active() || !isolate->debug()->StepInActive()) {
      return isolate->heap()->false_value();
    }
    CONVERT_ARG_CHECKED(Object, callback, 0);
    // We do not step into the callback if it's a builtin or not even a function.
    return isolate->heap()->ToBoolean(
        callback->IsJSFunction() && !JSFunction::cast(callback)->IsBuiltin());
  }
  
  
  // Set one shot breakpoints for the callback function that is passed to a
  // built-in function such as Array.forEach to enable stepping into the callback.
  RUNTIME_FUNCTION(Runtime_DebugPrepareStepInIfStepping) {
    DCHECK(args.length() == 1);
    Debug* debug = isolate->debug();
    if (!debug->IsStepping()) return isolate->heap()->undefined_value();
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, callback, 0);
    HandleScope scope(isolate);
    // When leaving the callback, step out has been activated, but not performed
    // if we do not leave the builtin.  To be able to step into the callback
    // again, we need to clear the step out at this point.
    debug->ClearStepOut();
    debug->FloodWithOneShot(callback);
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_DebugPushPromise) {
    DCHECK(args.length() == 1);
    HandleScope scope(isolate);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, promise, 0);
    isolate->debug()->PushPromise(promise);
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_DebugPopPromise) {
    DCHECK(args.length() == 0);
    SealHandleScope shs(isolate);
    isolate->debug()->PopPromise();
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_DebugPromiseEvent) {
    DCHECK(args.length() == 1);
    HandleScope scope(isolate);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, data, 0);
    isolate->debug()->OnPromiseEvent(data);
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_DebugPromiseRejectEvent) {
    DCHECK(args.length() == 2);
    HandleScope scope(isolate);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, promise, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, value, 1);
    isolate->debug()->OnPromiseReject(promise, value);
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_DebugAsyncTaskEvent) {
    DCHECK(args.length() == 1);
    HandleScope scope(isolate);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, data, 0);
    isolate->debug()->OnAsyncTaskEvent(data);
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_DeleteProperty) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
    CONVERT_ARG_HANDLE_CHECKED(JSReceiver, object, 0);
    CONVERT_ARG_HANDLE_CHECKED(Name, key, 1);
    CONVERT_STRICT_MODE_ARG_CHECKED(strict_mode, 2);
    JSReceiver::DeleteMode delete_mode = strict_mode == STRICT
        ? JSReceiver::STRICT_DELETION : JSReceiver::NORMAL_DELETION;
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result,
        JSReceiver::DeleteProperty(object, key, delete_mode));
    return *result;
  }
  
  
  static Object* HasOwnPropertyImplementation(Isolate* isolate,
                                              Handle<JSObject> object,
                                              Handle<Name> key) {
    Maybe<bool> maybe = JSReceiver::HasOwnProperty(object, key);
    if (!maybe.has_value) return isolate->heap()->exception();
    if (maybe.value) return isolate->heap()->true_value();
    // Handle hidden prototypes.  If there's a hidden prototype above this thing
    // then we have to check it for properties, because they are supposed to
    // look like they are on this object.
    PrototypeIterator iter(isolate, object);
    if (!iter.IsAtEnd() &&
        Handle<JSObject>::cast(PrototypeIterator::GetCurrent(iter))
            ->map()
            ->is_hidden_prototype()) {
      // TODO(verwaest): The recursion is not necessary for keys that are array
      // indices. Removing this.
      return HasOwnPropertyImplementation(
          isolate, Handle<JSObject>::cast(PrototypeIterator::GetCurrent(iter)),
          key);
    }
    RETURN_FAILURE_IF_SCHEDULED_EXCEPTION(isolate);
    return isolate->heap()->false_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_HasOwnProperty) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(Object, object, 0)
    CONVERT_ARG_HANDLE_CHECKED(Name, key, 1);
  
    uint32_t index;
    const bool key_is_array_index = key->AsArrayIndex(&index);
  
    // Only JS objects can have properties.
    if (object->IsJSObject()) {
      Handle<JSObject> js_obj = Handle<JSObject>::cast(object);
      // Fast case: either the key is a real named property or it is not
      // an array index and there are no interceptors or hidden
      // prototypes.
      Maybe<bool> maybe = JSObject::HasRealNamedProperty(js_obj, key);
      if (!maybe.has_value) return isolate->heap()->exception();
      DCHECK(!isolate->has_pending_exception());
      if (maybe.value) {
        return isolate->heap()->true_value();
      }
      Map* map = js_obj->map();
      if (!key_is_array_index &&
          !map->has_named_interceptor() &&
          !HeapObject::cast(map->prototype())->map()->is_hidden_prototype()) {
        return isolate->heap()->false_value();
      }
      // Slow case.
      return HasOwnPropertyImplementation(isolate,
                                          Handle<JSObject>(js_obj),
                                          Handle<Name>(key));
    } else if (object->IsString() && key_is_array_index) {
      // Well, there is one exception:  Handle [] on strings.
      Handle<String> string = Handle<String>::cast(object);
      if (index < static_cast<uint32_t>(string->length())) {
        return isolate->heap()->true_value();
      }
    }
    return isolate->heap()->false_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_HasProperty) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSReceiver, receiver, 0);
    CONVERT_ARG_HANDLE_CHECKED(Name, key, 1);
  
    Maybe<bool> maybe = JSReceiver::HasProperty(receiver, key);
    if (!maybe.has_value) return isolate->heap()->exception();
    return isolate->heap()->ToBoolean(maybe.value);
  }
  
  
  RUNTIME_FUNCTION(Runtime_HasElement) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSReceiver, receiver, 0);
    CONVERT_SMI_ARG_CHECKED(index, 1);
  
    Maybe<bool> maybe = JSReceiver::HasElement(receiver, index);
    if (!maybe.has_value) return isolate->heap()->exception();
    return isolate->heap()->ToBoolean(maybe.value);
  }
  
  
  RUNTIME_FUNCTION(Runtime_IsPropertyEnumerable) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
    CONVERT_ARG_HANDLE_CHECKED(Name, key, 1);
  
    Maybe<PropertyAttributes> maybe =
        JSReceiver::GetOwnPropertyAttributes(object, key);
    if (!maybe.has_value) return isolate->heap()->exception();
    if (maybe.value == ABSENT) maybe.value = DONT_ENUM;
    return isolate->heap()->ToBoolean((maybe.value & DONT_ENUM) == 0);
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetPropertyNames) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSReceiver, object, 0);
    Handle<JSArray> result;
  
    isolate->counters()->for_in()->Increment();
    Handle<FixedArray> elements;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, elements,
        JSReceiver::GetKeys(object, JSReceiver::INCLUDE_PROTOS));
    return *isolate->factory()->NewJSArrayWithElements(elements);
  }
  
  
  // Returns either a FixedArray as Runtime_GetPropertyNames,
  // or, if the given object has an enum cache that contains
  // all enumerable properties of the object and its prototypes
  // have none, the map of the object. This is used to speed up
  // the check for deletions during a for-in.
  RUNTIME_FUNCTION(Runtime_GetPropertyNamesFast) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
  
    CONVERT_ARG_CHECKED(JSReceiver, raw_object, 0);
  
    if (raw_object->IsSimpleEnum()) return raw_object->map();
  
    HandleScope scope(isolate);
    Handle<JSReceiver> object(raw_object);
    Handle<FixedArray> content;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, content,
        JSReceiver::GetKeys(object, JSReceiver::INCLUDE_PROTOS));
  
    // Test again, since cache may have been built by preceding call.
    if (object->IsSimpleEnum()) return object->map();
  
    return *content;
  }
  
  
  // Find the length of the prototype chain that is to be handled as one. If a
  // prototype object is hidden it is to be viewed as part of the the object it
  // is prototype for.
  static int OwnPrototypeChainLength(JSObject* obj) {
    int count = 1;
    for (PrototypeIterator iter(obj->GetIsolate(), obj);
         !iter.IsAtEnd(PrototypeIterator::END_AT_NON_HIDDEN); iter.Advance()) {
      count++;
    }
    return count;
  }
  
  
  // Return the names of the own named properties.
  // args[0]: object
  // args[1]: PropertyAttributes as int
  RUNTIME_FUNCTION(Runtime_GetOwnPropertyNames) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    if (!args[0]->IsJSObject()) {
      return isolate->heap()->undefined_value();
    }
    CONVERT_ARG_HANDLE_CHECKED(JSObject, obj, 0);
    CONVERT_SMI_ARG_CHECKED(filter_value, 1);
    PropertyAttributes filter = static_cast<PropertyAttributes>(filter_value);
  
    // Skip the global proxy as it has no properties and always delegates to the
    // real global object.
    if (obj->IsJSGlobalProxy()) {
      // Only collect names if access is permitted.
      if (obj->IsAccessCheckNeeded() &&
          !isolate->MayNamedAccess(
              obj, isolate->factory()->undefined_value(), v8::ACCESS_KEYS)) {
        isolate->ReportFailedAccessCheck(obj, v8::ACCESS_KEYS);
        RETURN_FAILURE_IF_SCHEDULED_EXCEPTION(isolate);
        return *isolate->factory()->NewJSArray(0);
      }
      PrototypeIterator iter(isolate, obj);
      obj = Handle<JSObject>::cast(PrototypeIterator::GetCurrent(iter));
    }
  
    // Find the number of objects making up this.
    int length = OwnPrototypeChainLength(*obj);
  
    // Find the number of own properties for each of the objects.
    ScopedVector<int> own_property_count(length);
    int total_property_count = 0;
    {
      PrototypeIterator iter(isolate, obj, PrototypeIterator::START_AT_RECEIVER);
      for (int i = 0; i < length; i++) {
        DCHECK(!iter.IsAtEnd());
        Handle<JSObject> jsproto =
            Handle<JSObject>::cast(PrototypeIterator::GetCurrent(iter));
        // Only collect names if access is permitted.
        if (jsproto->IsAccessCheckNeeded() &&
            !isolate->MayNamedAccess(jsproto,
                                     isolate->factory()->undefined_value(),
                                     v8::ACCESS_KEYS)) {
          isolate->ReportFailedAccessCheck(jsproto, v8::ACCESS_KEYS);
          RETURN_FAILURE_IF_SCHEDULED_EXCEPTION(isolate);
          return *isolate->factory()->NewJSArray(0);
        }
        int n;
        n = jsproto->NumberOfOwnProperties(filter);
        own_property_count[i] = n;
        total_property_count += n;
        iter.Advance();
      }
    }
  
    // Allocate an array with storage for all the property names.
    Handle<FixedArray> names =
        isolate->factory()->NewFixedArray(total_property_count);
  
    // Get the property names.
    int next_copy_index = 0;
    int hidden_strings = 0;
    {
      PrototypeIterator iter(isolate, obj, PrototypeIterator::START_AT_RECEIVER);
      for (int i = 0; i < length; i++) {
        DCHECK(!iter.IsAtEnd());
        Handle<JSObject> jsproto =
            Handle<JSObject>::cast(PrototypeIterator::GetCurrent(iter));
        jsproto->GetOwnPropertyNames(*names, next_copy_index, filter);
        if (i > 0) {
          // Names from hidden prototypes may already have been added
          // for inherited function template instances. Count the duplicates
          // and stub them out; the final copy pass at the end ignores holes.
          for (int j = next_copy_index;
               j < next_copy_index + own_property_count[i]; j++) {
            Object* name_from_hidden_proto = names->get(j);
            for (int k = 0; k < next_copy_index; k++) {
              if (names->get(k) != isolate->heap()->hidden_string()) {
                Object* name = names->get(k);
                if (name_from_hidden_proto == name) {
                  names->set(j, isolate->heap()->hidden_string());
                  hidden_strings++;
                  break;
                }
              }
            }
          }
        }
        next_copy_index += own_property_count[i];
  
        // Hidden properties only show up if the filter does not skip strings.
        if ((filter & STRING) == 0 && JSObject::HasHiddenProperties(jsproto)) {
          hidden_strings++;
        }
        iter.Advance();
      }
    }
  
    // Filter out name of hidden properties object and
    // hidden prototype duplicates.
    if (hidden_strings > 0) {
      Handle<FixedArray> old_names = names;
      names = isolate->factory()->NewFixedArray(
          names->length() - hidden_strings);
      int dest_pos = 0;
      for (int i = 0; i < total_property_count; i++) {
        Object* name = old_names->get(i);
        if (name == isolate->heap()->hidden_string()) {
          hidden_strings--;
          continue;
        }
        names->set(dest_pos++, name);
      }
      DCHECK_EQ(0, hidden_strings);
    }
  
    return *isolate->factory()->NewJSArrayWithElements(names);
  }
  
  
  // Return the names of the own indexed properties.
  // args[0]: object
  RUNTIME_FUNCTION(Runtime_GetOwnElementNames) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    if (!args[0]->IsJSObject()) {
      return isolate->heap()->undefined_value();
    }
    CONVERT_ARG_HANDLE_CHECKED(JSObject, obj, 0);
  
    int n = obj->NumberOfOwnElements(static_cast<PropertyAttributes>(NONE));
    Handle<FixedArray> names = isolate->factory()->NewFixedArray(n);
    obj->GetOwnElementKeys(*names, static_cast<PropertyAttributes>(NONE));
    return *isolate->factory()->NewJSArrayWithElements(names);
  }
  
  
  // Return information on whether an object has a named or indexed interceptor.
  // args[0]: object
  RUNTIME_FUNCTION(Runtime_GetInterceptorInfo) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    if (!args[0]->IsJSObject()) {
      return Smi::FromInt(0);
    }
    CONVERT_ARG_HANDLE_CHECKED(JSObject, obj, 0);
  
    int result = 0;
    if (obj->HasNamedInterceptor()) result |= 2;
    if (obj->HasIndexedInterceptor()) result |= 1;
  
    return Smi::FromInt(result);
  }
  
  
  // Return property names from named interceptor.
  // args[0]: object
  RUNTIME_FUNCTION(Runtime_GetNamedInterceptorPropertyNames) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, obj, 0);
  
    if (obj->HasNamedInterceptor()) {
      Handle<JSObject> result;
      if (JSObject::GetKeysForNamedInterceptor(obj, obj).ToHandle(&result)) {
        return *result;
      }
    }
    return isolate->heap()->undefined_value();
  }
  
  
  // Return element names from indexed interceptor.
  // args[0]: object
  RUNTIME_FUNCTION(Runtime_GetIndexedInterceptorElementNames) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, obj, 0);
  
    if (obj->HasIndexedInterceptor()) {
      Handle<JSObject> result;
      if (JSObject::GetKeysForIndexedInterceptor(obj, obj).ToHandle(&result)) {
        return *result;
      }
    }
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_OwnKeys) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(JSObject, raw_object, 0);
    Handle<JSObject> object(raw_object);
  
    if (object->IsJSGlobalProxy()) {
      // Do access checks before going to the global object.
      if (object->IsAccessCheckNeeded() &&
          !isolate->MayNamedAccess(
              object, isolate->factory()->undefined_value(), v8::ACCESS_KEYS)) {
        isolate->ReportFailedAccessCheck(object, v8::ACCESS_KEYS);
        RETURN_FAILURE_IF_SCHEDULED_EXCEPTION(isolate);
        return *isolate->factory()->NewJSArray(0);
      }
  
      PrototypeIterator iter(isolate, object);
      // If proxy is detached we simply return an empty array.
      if (iter.IsAtEnd()) return *isolate->factory()->NewJSArray(0);
      object = Handle<JSObject>::cast(PrototypeIterator::GetCurrent(iter));
    }
  
    Handle<FixedArray> contents;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, contents,
        JSReceiver::GetKeys(object, JSReceiver::OWN_ONLY));
  
    // Some fast paths through GetKeysInFixedArrayFor reuse a cached
    // property array and since the result is mutable we have to create
    // a fresh clone on each invocation.
    int length = contents->length();
    Handle<FixedArray> copy = isolate->factory()->NewFixedArray(length);
    for (int i = 0; i < length; i++) {
      Object* entry = contents->get(i);
      if (entry->IsString()) {
        copy->set(i, entry);
      } else {
        DCHECK(entry->IsNumber());
        HandleScope scope(isolate);
        Handle<Object> entry_handle(entry, isolate);
        Handle<Object> entry_str =
            isolate->factory()->NumberToString(entry_handle);
        copy->set(i, *entry_str);
      }
    }
    return *isolate->factory()->NewJSArrayWithElements(copy);
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetArgumentsProperty) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, raw_key, 0);
  
    // Compute the frame holding the arguments.
    JavaScriptFrameIterator it(isolate);
    it.AdvanceToArgumentsFrame();
    JavaScriptFrame* frame = it.frame();
  
    // Get the actual number of provided arguments.
    const uint32_t n = frame->ComputeParametersCount();
  
    // Try to convert the key to an index. If successful and within
    // index return the the argument from the frame.
    uint32_t index;
    if (raw_key->ToArrayIndex(&index) && index < n) {
      return frame->GetParameter(index);
    }
  
    HandleScope scope(isolate);
    if (raw_key->IsSymbol()) {
      // Lookup in the initial Object.prototype object.
      Handle<Object> result;
      ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
          isolate, result,
          Object::GetProperty(isolate->initial_object_prototype(),
                              Handle<Symbol>::cast(raw_key)));
      return *result;
    }
  
    // Convert the key to a string.
    Handle<Object> converted;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, converted, Execution::ToString(isolate, raw_key));
    Handle<String> key = Handle<String>::cast(converted);
  
    // Try to convert the string key into an array index.
    if (key->AsArrayIndex(&index)) {
      if (index < n) {
        return frame->GetParameter(index);
      } else {
        Handle<Object> initial_prototype(isolate->initial_object_prototype());
        Handle<Object> result;
        ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
            isolate, result,
            Object::GetElement(isolate, initial_prototype, index));
        return *result;
      }
    }
  
    // Handle special arguments properties.
    if (String::Equals(isolate->factory()->length_string(), key)) {
      return Smi::FromInt(n);
    }
    if (String::Equals(isolate->factory()->callee_string(), key)) {
      JSFunction* function = frame->function();
      if (function->shared()->strict_mode() == STRICT) {
        return isolate->Throw(*isolate->factory()->NewTypeError(
            "strict_arguments_callee", HandleVector<Object>(NULL, 0)));
      }
      return function;
    }
  
    // Lookup in the initial Object.prototype object.
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result,
        Object::GetProperty(isolate->initial_object_prototype(), key));
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_ToFastProperties) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
    if (object->IsJSObject() && !object->IsGlobalObject()) {
      JSObject::MigrateSlowToFast(Handle<JSObject>::cast(object), 0);
    }
    return *object;
  }
  
  
  RUNTIME_FUNCTION(Runtime_ToBool) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(Object, object, 0);
  
    return isolate->heap()->ToBoolean(object->BooleanValue());
  }
  
  
  // Returns the type string of a value; see ECMA-262, 11.4.3 (p 47).
  // Possible optimizations: put the type string into the oddballs.
  RUNTIME_FUNCTION(Runtime_Typeof) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(Object, obj, 0);
    if (obj->IsNumber()) return isolate->heap()->number_string();
    HeapObject* heap_obj = HeapObject::cast(obj);
  
    // typeof an undetectable object is 'undefined'
    if (heap_obj->map()->is_undetectable()) {
      return isolate->heap()->undefined_string();
    }
  
    InstanceType instance_type = heap_obj->map()->instance_type();
    if (instance_type < FIRST_NONSTRING_TYPE) {
      return isolate->heap()->string_string();
    }
  
    switch (instance_type) {
      case ODDBALL_TYPE:
        if (heap_obj->IsTrue() || heap_obj->IsFalse()) {
          return isolate->heap()->boolean_string();
        }
        if (heap_obj->IsNull()) {
          return isolate->heap()->object_string();
        }
        DCHECK(heap_obj->IsUndefined());
        return isolate->heap()->undefined_string();
      case SYMBOL_TYPE:
        return isolate->heap()->symbol_string();
      case JS_FUNCTION_TYPE:
      case JS_FUNCTION_PROXY_TYPE:
        return isolate->heap()->function_string();
      default:
        // For any kind of object not handled above, the spec rule for
        // host objects gives that it is okay to return "object"
        return isolate->heap()->object_string();
    }
  }
  
  
  RUNTIME_FUNCTION(Runtime_Booleanize) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_CHECKED(Object, value_raw, 0);
    CONVERT_SMI_ARG_CHECKED(token_raw, 1);
    intptr_t value = reinterpret_cast<intptr_t>(value_raw);
    Token::Value token = static_cast<Token::Value>(token_raw);
    switch (token) {
      case Token::EQ:
      case Token::EQ_STRICT:
        return isolate->heap()->ToBoolean(value == 0);
      case Token::NE:
      case Token::NE_STRICT:
        return isolate->heap()->ToBoolean(value != 0);
      case Token::LT:
        return isolate->heap()->ToBoolean(value < 0);
      case Token::GT:
        return isolate->heap()->ToBoolean(value > 0);
      case Token::LTE:
        return isolate->heap()->ToBoolean(value <= 0);
      case Token::GTE:
        return isolate->heap()->ToBoolean(value >= 0);
      default:
        // This should only happen during natives fuzzing.
        return isolate->heap()->undefined_value();
    }
  }
  
  
  static bool AreDigits(const uint8_t*s, int from, int to) {
    for (int i = from; i < to; i++) {
      if (s[i] < '0' || s[i] > '9') return false;
    }
  
    return true;
  }
  
  
  static int ParseDecimalInteger(const uint8_t*s, int from, int to) {
    DCHECK(to - from < 10);  // Overflow is not possible.
    DCHECK(from < to);
    int d = s[from] - '0';
  
    for (int i = from + 1; i < to; i++) {
      d = 10 * d + (s[i] - '0');
    }
  
    return d;
  }
  
  
  RUNTIME_FUNCTION(Runtime_StringToNumber) {
    HandleScope handle_scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(String, subject, 0);
    subject = String::Flatten(subject);
  
    // Fast case: short integer or some sorts of junk values.
    if (subject->IsSeqOneByteString()) {
      int len = subject->length();
      if (len == 0) return Smi::FromInt(0);
  
      DisallowHeapAllocation no_gc;
      uint8_t const* data = Handle<SeqOneByteString>::cast(subject)->GetChars();
      bool minus = (data[0] == '-');
      int start_pos = (minus ? 1 : 0);
  
      if (start_pos == len) {
        return isolate->heap()->nan_value();
      } else if (data[start_pos] > '9') {
        // Fast check for a junk value. A valid string may start from a
        // whitespace, a sign ('+' or '-'), the decimal point, a decimal digit
        // or the 'I' character ('Infinity'). All of that have codes not greater
        // than '9' except 'I' and &nbsp;.
        if (data[start_pos] != 'I' && data[start_pos] != 0xa0) {
          return isolate->heap()->nan_value();
        }
      } else if (len - start_pos < 10 && AreDigits(data, start_pos, len)) {
        // The maximal/minimal smi has 10 digits. If the string has less digits
        // we know it will fit into the smi-data type.
        int d = ParseDecimalInteger(data, start_pos, len);
        if (minus) {
          if (d == 0) return isolate->heap()->minus_zero_value();
          d = -d;
        } else if (!subject->HasHashCode() &&
                   len <= String::kMaxArrayIndexSize &&
                   (len == 1 || data[0] != '0')) {
          // String hash is not calculated yet but all the data are present.
          // Update the hash field to speed up sequential convertions.
          uint32_t hash = StringHasher::MakeArrayIndexHash(d, len);
  #ifdef DEBUG
          subject->Hash();  // Force hash calculation.
          DCHECK_EQ(static_cast<int>(subject->hash_field()),
                    static_cast<int>(hash));
  #endif
          subject->set_hash_field(hash);
        }
        return Smi::FromInt(d);
      }
    }
  
    // Slower case.
    int flags = ALLOW_HEX;
    if (FLAG_harmony_numeric_literals) {
      // The current spec draft has not updated "ToNumber Applied to the String
      // Type", https://bugs.ecmascript.org/show_bug.cgi?id=1584
      flags |= ALLOW_OCTAL | ALLOW_BINARY;
    }
  
    return *isolate->factory()->NewNumber(StringToDouble(
        isolate->unicode_cache(), *subject, flags));
  }
  
  
  RUNTIME_FUNCTION(Runtime_NewString) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_SMI_ARG_CHECKED(length, 0);
    CONVERT_BOOLEAN_ARG_CHECKED(is_one_byte, 1);
    if (length == 0) return isolate->heap()->empty_string();
    Handle<String> result;
    if (is_one_byte) {
      ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
          isolate, result, isolate->factory()->NewRawOneByteString(length));
    } else {
      ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
          isolate, result, isolate->factory()->NewRawTwoByteString(length));
    }
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_TruncateString) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(SeqString, string, 0);
    CONVERT_SMI_ARG_CHECKED(new_length, 1);
    RUNTIME_ASSERT(new_length >= 0);
    return *SeqString::Truncate(string, new_length);
  }
  
  
  RUNTIME_FUNCTION(Runtime_URIEscape) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(String, source, 0);
    Handle<String> string = String::Flatten(source);
    DCHECK(string->IsFlat());
    Handle<String> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result,
        string->IsOneByteRepresentationUnderneath()
              ? URIEscape::Escape<uint8_t>(isolate, source)
              : URIEscape::Escape<uc16>(isolate, source));
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_URIUnescape) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(String, source, 0);
    Handle<String> string = String::Flatten(source);
    DCHECK(string->IsFlat());
    Handle<String> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result,
        string->IsOneByteRepresentationUnderneath()
              ? URIUnescape::Unescape<uint8_t>(isolate, source)
              : URIUnescape::Unescape<uc16>(isolate, source));
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_QuoteJSONString) {
    HandleScope scope(isolate);
    CONVERT_ARG_HANDLE_CHECKED(String, string, 0);
    DCHECK(args.length() == 1);
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result, BasicJsonStringifier::StringifyString(isolate, string));
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_BasicJSONStringify) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
    BasicJsonStringifier stringifier(isolate);
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result, stringifier.Stringify(object));
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_StringParseInt) {
    HandleScope handle_scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(String, subject, 0);
    CONVERT_NUMBER_CHECKED(int, radix, Int32, args[1]);
    RUNTIME_ASSERT(radix == 0 || (2 <= radix && radix <= 36));
  
    subject = String::Flatten(subject);
    double value;
  
    { DisallowHeapAllocation no_gc;
      String::FlatContent flat = subject->GetFlatContent();
  
      // ECMA-262 section 15.1.2.3, empty string is NaN
      if (flat.IsAscii()) {
        value = StringToInt(
            isolate->unicode_cache(), flat.ToOneByteVector(), radix);
      } else {
        value = StringToInt(
            isolate->unicode_cache(), flat.ToUC16Vector(), radix);
      }
    }
  
    return *isolate->factory()->NewNumber(value);
  }
  
  
  RUNTIME_FUNCTION(Runtime_StringParseFloat) {
    HandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(String, subject, 0);
  
    subject = String::Flatten(subject);
    double value = StringToDouble(isolate->unicode_cache(), *subject,
                                  ALLOW_TRAILING_JUNK, base::OS::nan_value());
  
    return *isolate->factory()->NewNumber(value);
  }
  
  
  static inline bool ToUpperOverflows(uc32 character) {
    // y with umlauts and the micro sign are the only characters that stop
    // fitting into one-byte when converting to uppercase.
    static const uc32 yuml_code = 0xff;
    static const uc32 micro_code = 0xb5;
    return (character == yuml_code || character == micro_code);
  }
  
  
  template <class Converter>
  MUST_USE_RESULT static Object* ConvertCaseHelper(
      Isolate* isolate,
      String* string,
      SeqString* result,
      int result_length,
      unibrow::Mapping<Converter, 128>* mapping) {
    DisallowHeapAllocation no_gc;
    // We try this twice, once with the assumption that the result is no longer
    // than the input and, if that assumption breaks, again with the exact
    // length.  This may not be pretty, but it is nicer than what was here before
    // and I hereby claim my vaffel-is.
    //
    // NOTE: This assumes that the upper/lower case of an ASCII
    // character is also ASCII.  This is currently the case, but it
    // might break in the future if we implement more context and locale
    // dependent upper/lower conversions.
    bool has_changed_character = false;
  
    // Convert all characters to upper case, assuming that they will fit
    // in the buffer
    Access<ConsStringIteratorOp> op(
        isolate->runtime_state()->string_iterator());
    StringCharacterStream stream(string, op.value());
    unibrow::uchar chars[Converter::kMaxWidth];
    // We can assume that the string is not empty
    uc32 current = stream.GetNext();
    bool ignore_overflow = Converter::kIsToLower || result->IsSeqTwoByteString();
    for (int i = 0; i < result_length;) {
      bool has_next = stream.HasMore();
      uc32 next = has_next ? stream.GetNext() : 0;
      int char_length = mapping->get(current, next, chars);
      if (char_length == 0) {
        // The case conversion of this character is the character itself.
        result->Set(i, current);
        i++;
      } else if (char_length == 1 &&
                 (ignore_overflow || !ToUpperOverflows(current))) {
        // Common case: converting the letter resulted in one character.
        DCHECK(static_cast<uc32>(chars[0]) != current);
        result->Set(i, chars[0]);
        has_changed_character = true;
        i++;
      } else if (result_length == string->length()) {
        bool overflows = ToUpperOverflows(current);
        // We've assumed that the result would be as long as the
        // input but here is a character that converts to several
        // characters.  No matter, we calculate the exact length
        // of the result and try the whole thing again.
        //
        // Note that this leaves room for optimization.  We could just
        // memcpy what we already have to the result string.  Also,
        // the result string is the last object allocated we could
        // "realloc" it and probably, in the vast majority of cases,
        // extend the existing string to be able to hold the full
        // result.
        int next_length = 0;
        if (has_next) {
          next_length = mapping->get(next, 0, chars);
          if (next_length == 0) next_length = 1;
        }
        int current_length = i + char_length + next_length;
        while (stream.HasMore()) {
          current = stream.GetNext();
          overflows |= ToUpperOverflows(current);
          // NOTE: we use 0 as the next character here because, while
          // the next character may affect what a character converts to,
          // it does not in any case affect the length of what it convert
          // to.
          int char_length = mapping->get(current, 0, chars);
          if (char_length == 0) char_length = 1;
          current_length += char_length;
          if (current_length > String::kMaxLength) {
            AllowHeapAllocation allocate_error_and_return;
            return isolate->ThrowInvalidStringLength();
          }
        }
        // Try again with the real length.  Return signed if we need
        // to allocate a two-byte string for to uppercase.
        return (overflows && !ignore_overflow) ? Smi::FromInt(-current_length)
                                               : Smi::FromInt(current_length);
      } else {
        for (int j = 0; j < char_length; j++) {
          result->Set(i, chars[j]);
          i++;
        }
        has_changed_character = true;
      }
      current = next;
    }
    if (has_changed_character) {
      return result;
    } else {
      // If we didn't actually change anything in doing the conversion
      // we simple return the result and let the converted string
      // become garbage; there is no reason to keep two identical strings
      // alive.
      return string;
    }
  }
  
  
  namespace {
  
  static const uintptr_t kOneInEveryByte = kUintptrAllBitsSet / 0xFF;
  static const uintptr_t kAsciiMask = kOneInEveryByte << 7;
  
  // Given a word and two range boundaries returns a word with high bit
  // set in every byte iff the corresponding input byte was strictly in
  // the range (m, n). All the other bits in the result are cleared.
  // This function is only useful when it can be inlined and the
  // boundaries are statically known.
  // Requires: all bytes in the input word and the boundaries must be
  // ASCII (less than 0x7F).
  static inline uintptr_t AsciiRangeMask(uintptr_t w, char m, char n) {
    // Use strict inequalities since in edge cases the function could be
    // further simplified.
    DCHECK(0 < m && m < n);
    // Has high bit set in every w byte less than n.
    uintptr_t tmp1 = kOneInEveryByte * (0x7F + n) - w;
    // Has high bit set in every w byte greater than m.
    uintptr_t tmp2 = w + kOneInEveryByte * (0x7F - m);
    return (tmp1 & tmp2 & (kOneInEveryByte * 0x80));
  }
  
  
  #ifdef DEBUG
  static bool CheckFastAsciiConvert(char* dst,
                                    const char* src,
                                    int length,
                                    bool changed,
                                    bool is_to_lower) {
    bool expected_changed = false;
    for (int i = 0; i < length; i++) {
      if (dst[i] == src[i]) continue;
      expected_changed = true;
      if (is_to_lower) {
        DCHECK('A' <= src[i] && src[i] <= 'Z');
        DCHECK(dst[i] == src[i] + ('a' - 'A'));
      } else {
        DCHECK('a' <= src[i] && src[i] <= 'z');
        DCHECK(dst[i] == src[i] - ('a' - 'A'));
      }
    }
    return (expected_changed == changed);
  }
  #endif
  
  
  template<class Converter>
  static bool FastAsciiConvert(char* dst,
                               const char* src,
                               int length,
                               bool* changed_out) {
  #ifdef DEBUG
      char* saved_dst = dst;
      const char* saved_src = src;
  #endif
    DisallowHeapAllocation no_gc;
    // We rely on the distance between upper and lower case letters
    // being a known power of 2.
    DCHECK('a' - 'A' == (1 << 5));
    // Boundaries for the range of input characters than require conversion.
    static const char lo = Converter::kIsToLower ? 'A' - 1 : 'a' - 1;
    static const char hi = Converter::kIsToLower ? 'Z' + 1 : 'z' + 1;
    bool changed = false;
    uintptr_t or_acc = 0;
    const char* const limit = src + length;
  #ifdef V8_HOST_CAN_READ_UNALIGNED
    // Process the prefix of the input that requires no conversion one
    // (machine) word at a time.
    while (src <= limit - sizeof(uintptr_t)) {
      const uintptr_t w = *reinterpret_cast<const uintptr_t*>(src);
      or_acc |= w;
      if (AsciiRangeMask(w, lo, hi) != 0) {
        changed = true;
        break;
      }
      *reinterpret_cast<uintptr_t*>(dst) = w;
      src += sizeof(uintptr_t);
      dst += sizeof(uintptr_t);
    }
    // Process the remainder of the input performing conversion when
    // required one word at a time.
    while (src <= limit - sizeof(uintptr_t)) {
      const uintptr_t w = *reinterpret_cast<const uintptr_t*>(src);
      or_acc |= w;
      uintptr_t m = AsciiRangeMask(w, lo, hi);
      // The mask has high (7th) bit set in every byte that needs
      // conversion and we know that the distance between cases is
      // 1 << 5.
      *reinterpret_cast<uintptr_t*>(dst) = w ^ (m >> 2);
      src += sizeof(uintptr_t);
      dst += sizeof(uintptr_t);
    }
  #endif
    // Process the last few bytes of the input (or the whole input if
    // unaligned access is not supported).
    while (src < limit) {
      char c = *src;
      or_acc |= c;
      if (lo < c && c < hi) {
        c ^= (1 << 5);
        changed = true;
      }
      *dst = c;
      ++src;
      ++dst;
    }
    if ((or_acc & kAsciiMask) != 0) {
      return false;
    }
  
    DCHECK(CheckFastAsciiConvert(
               saved_dst, saved_src, length, changed, Converter::kIsToLower));
  
    *changed_out = changed;
    return true;
  }
  
  }  // namespace
  
  
  template <class Converter>
  MUST_USE_RESULT static Object* ConvertCase(
      Handle<String> s,
      Isolate* isolate,
      unibrow::Mapping<Converter, 128>* mapping) {
    s = String::Flatten(s);
    int length = s->length();
    // Assume that the string is not empty; we need this assumption later
    if (length == 0) return *s;
  
    // Simpler handling of ASCII strings.
    //
    // NOTE: This assumes that the upper/lower case of an ASCII
    // character is also ASCII.  This is currently the case, but it
    // might break in the future if we implement more context and locale
    // dependent upper/lower conversions.
    if (s->IsOneByteRepresentationUnderneath()) {
      // Same length as input.
      Handle<SeqOneByteString> result =
          isolate->factory()->NewRawOneByteString(length).ToHandleChecked();
      DisallowHeapAllocation no_gc;
      String::FlatContent flat_content = s->GetFlatContent();
      DCHECK(flat_content.IsFlat());
      bool has_changed_character = false;
      bool is_ascii = FastAsciiConvert<Converter>(
          reinterpret_cast<char*>(result->GetChars()),
          reinterpret_cast<const char*>(flat_content.ToOneByteVector().start()),
          length,
          &has_changed_character);
      // If not ASCII, we discard the result and take the 2 byte path.
      if (is_ascii) return has_changed_character ? *result : *s;
    }
  
    Handle<SeqString> result;  // Same length as input.
    if (s->IsOneByteRepresentation()) {
      result = isolate->factory()->NewRawOneByteString(length).ToHandleChecked();
    } else {
      result = isolate->factory()->NewRawTwoByteString(length).ToHandleChecked();
    }
  
    Object* answer = ConvertCaseHelper(isolate, *s, *result, length, mapping);
    if (answer->IsException() || answer->IsString()) return answer;
  
    DCHECK(answer->IsSmi());
    length = Smi::cast(answer)->value();
    if (s->IsOneByteRepresentation() && length > 0) {
      ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
          isolate, result, isolate->factory()->NewRawOneByteString(length));
    } else {
      if (length < 0) length = -length;
      ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
          isolate, result, isolate->factory()->NewRawTwoByteString(length));
    }
    return ConvertCaseHelper(isolate, *s, *result, length, mapping);
  }
  
  
  RUNTIME_FUNCTION(Runtime_StringToLowerCase) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(String, s, 0);
    return ConvertCase(
        s, isolate, isolate->runtime_state()->to_lower_mapping());
  }
  
  
  RUNTIME_FUNCTION(Runtime_StringToUpperCase) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(String, s, 0);
    return ConvertCase(
        s, isolate, isolate->runtime_state()->to_upper_mapping());
  }
  
  
  RUNTIME_FUNCTION(Runtime_StringTrim) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
  
    CONVERT_ARG_HANDLE_CHECKED(String, string, 0);
    CONVERT_BOOLEAN_ARG_CHECKED(trimLeft, 1);
    CONVERT_BOOLEAN_ARG_CHECKED(trimRight, 2);
  
    string = String::Flatten(string);
    int length = string->length();
  
    int left = 0;
    UnicodeCache* unicode_cache = isolate->unicode_cache();
    if (trimLeft) {
      while (left < length &&
             unicode_cache->IsWhiteSpaceOrLineTerminator(string->Get(left))) {
        left++;
      }
    }
  
    int right = length;
    if (trimRight) {
      while (right > left &&
             unicode_cache->IsWhiteSpaceOrLineTerminator(
                 string->Get(right - 1))) {
        right--;
      }
    }
  
    return *isolate->factory()->NewSubString(string, left, right);
  }
  
  
  RUNTIME_FUNCTION(Runtime_StringSplit) {
    HandleScope handle_scope(isolate);
    DCHECK(args.length() == 3);
    CONVERT_ARG_HANDLE_CHECKED(String, subject, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, pattern, 1);
    CONVERT_NUMBER_CHECKED(uint32_t, limit, Uint32, args[2]);
    RUNTIME_ASSERT(limit > 0);
  
    int subject_length = subject->length();
    int pattern_length = pattern->length();
    RUNTIME_ASSERT(pattern_length > 0);
  
    if (limit == 0xffffffffu) {
      Handle<Object> cached_answer(
          RegExpResultsCache::Lookup(isolate->heap(),
                                     *subject,
                                     *pattern,
                                     RegExpResultsCache::STRING_SPLIT_SUBSTRINGS),
          isolate);
      if (*cached_answer != Smi::FromInt(0)) {
        // The cache FixedArray is a COW-array and can therefore be reused.
        Handle<JSArray> result =
            isolate->factory()->NewJSArrayWithElements(
                Handle<FixedArray>::cast(cached_answer));
        return *result;
      }
    }
  
    // The limit can be very large (0xffffffffu), but since the pattern
    // isn't empty, we can never create more parts than ~half the length
    // of the subject.
  
    subject = String::Flatten(subject);
    pattern = String::Flatten(pattern);
  
    static const int kMaxInitialListCapacity = 16;
  
    ZoneScope zone_scope(isolate->runtime_zone());
  
    // Find (up to limit) indices of separator and end-of-string in subject
    int initial_capacity = Min<uint32_t>(kMaxInitialListCapacity, limit);
    ZoneList<int> indices(initial_capacity, zone_scope.zone());
  
    FindStringIndicesDispatch(isolate, *subject, *pattern,
                              &indices, limit, zone_scope.zone());
  
    if (static_cast<uint32_t>(indices.length()) < limit) {
      indices.Add(subject_length, zone_scope.zone());
    }
  
    // The list indices now contains the end of each part to create.
  
    // Create JSArray of substrings separated by separator.
    int part_count = indices.length();
  
    Handle<JSArray> result = isolate->factory()->NewJSArray(part_count);
    JSObject::EnsureCanContainHeapObjectElements(result);
    result->set_length(Smi::FromInt(part_count));
  
    DCHECK(result->HasFastObjectElements());
  
    if (part_count == 1 && indices.at(0) == subject_length) {
      FixedArray::cast(result->elements())->set(0, *subject);
      return *result;
    }
  
    Handle<FixedArray> elements(FixedArray::cast(result->elements()));
    int part_start = 0;
    for (int i = 0; i < part_count; i++) {
      HandleScope local_loop_handle(isolate);
      int part_end = indices.at(i);
      Handle<String> substring =
          isolate->factory()->NewProperSubString(subject, part_start, part_end);
      elements->set(i, *substring);
      part_start = part_end + pattern_length;
    }
  
    if (limit == 0xffffffffu) {
      if (result->HasFastObjectElements()) {
        RegExpResultsCache::Enter(isolate,
                                  subject,
                                  pattern,
                                  elements,
                                  RegExpResultsCache::STRING_SPLIT_SUBSTRINGS);
      }
    }
  
    return *result;
  }
  
  
  // Copies ASCII characters to the given fixed array looking up
  // one-char strings in the cache. Gives up on the first char that is
  // not in the cache and fills the remainder with smi zeros. Returns
  // the length of the successfully copied prefix.
  static int CopyCachedAsciiCharsToArray(Heap* heap,
                                         const uint8_t* chars,
                                         FixedArray* elements,
                                         int length) {
    DisallowHeapAllocation no_gc;
    FixedArray* ascii_cache = heap->single_character_string_cache();
    Object* undefined = heap->undefined_value();
    int i;
    WriteBarrierMode mode = elements->GetWriteBarrierMode(no_gc);
    for (i = 0; i < length; ++i) {
      Object* value = ascii_cache->get(chars[i]);
      if (value == undefined) break;
      elements->set(i, value, mode);
    }
    if (i < length) {
      DCHECK(Smi::FromInt(0) == 0);
      memset(elements->data_start() + i, 0, kPointerSize * (length - i));
    }
  #ifdef DEBUG
    for (int j = 0; j < length; ++j) {
      Object* element = elements->get(j);
      DCHECK(element == Smi::FromInt(0) ||
             (element->IsString() && String::cast(element)->LooksValid()));
    }
  #endif
    return i;
  }
  
  
  // Converts a String to JSArray.
  // For example, "foo" => ["f", "o", "o"].
  RUNTIME_FUNCTION(Runtime_StringToArray) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(String, s, 0);
    CONVERT_NUMBER_CHECKED(uint32_t, limit, Uint32, args[1]);
  
    s = String::Flatten(s);
    const int length = static_cast<int>(Min<uint32_t>(s->length(), limit));
  
    Handle<FixedArray> elements;
    int position = 0;
    if (s->IsFlat() && s->IsOneByteRepresentation()) {
      // Try using cached chars where possible.
      elements = isolate->factory()->NewUninitializedFixedArray(length);
  
      DisallowHeapAllocation no_gc;
      String::FlatContent content = s->GetFlatContent();
      if (content.IsAscii()) {
        Vector<const uint8_t> chars = content.ToOneByteVector();
        // Note, this will initialize all elements (not only the prefix)
        // to prevent GC from seeing partially initialized array.
        position = CopyCachedAsciiCharsToArray(isolate->heap(),
                                               chars.start(),
                                               *elements,
                                               length);
      } else {
        MemsetPointer(elements->data_start(),
                      isolate->heap()->undefined_value(),
                      length);
      }
    } else {
      elements = isolate->factory()->NewFixedArray(length);
    }
    for (int i = position; i < length; ++i) {
      Handle<Object> str =
          isolate->factory()->LookupSingleCharacterStringFromCode(s->Get(i));
      elements->set(i, *str);
    }
  
  #ifdef DEBUG
    for (int i = 0; i < length; ++i) {
      DCHECK(String::cast(elements->get(i))->length() == 1);
    }
  #endif
  
    return *isolate->factory()->NewJSArrayWithElements(elements);
  }
  
  
  RUNTIME_FUNCTION(Runtime_NewStringWrapper) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(String, value, 0);
    return *Object::ToObject(isolate, value).ToHandleChecked();
  }
  
  
  bool Runtime::IsUpperCaseChar(RuntimeState* runtime_state, uint16_t ch) {
    unibrow::uchar chars[unibrow::ToUppercase::kMaxWidth];
    int char_length = runtime_state->to_upper_mapping()->get(ch, 0, chars);
    return char_length == 0;
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberToStringRT) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_NUMBER_ARG_HANDLE_CHECKED(number, 0);
  
    return *isolate->factory()->NumberToString(number);
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberToStringSkipCache) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_NUMBER_ARG_HANDLE_CHECKED(number, 0);
  
    return *isolate->factory()->NumberToString(number, false);
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberToInteger) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
  
    CONVERT_DOUBLE_ARG_CHECKED(number, 0);
    return *isolate->factory()->NewNumber(DoubleToInteger(number));
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberToIntegerMapMinusZero) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
  
    CONVERT_DOUBLE_ARG_CHECKED(number, 0);
    double double_value = DoubleToInteger(number);
    // Map both -0 and +0 to +0.
    if (double_value == 0) double_value = 0;
  
    return *isolate->factory()->NewNumber(double_value);
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberToJSUint32) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
  
    CONVERT_NUMBER_CHECKED(int32_t, number, Uint32, args[0]);
    return *isolate->factory()->NewNumberFromUint(number);
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberToJSInt32) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
  
    CONVERT_DOUBLE_ARG_CHECKED(number, 0);
    return *isolate->factory()->NewNumberFromInt(DoubleToInt32(number));
  }
  
  
  // Converts a Number to a Smi, if possible. Returns NaN if the number is not
  // a small integer.
  RUNTIME_FUNCTION(Runtime_NumberToSmi) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(Object, obj, 0);
    if (obj->IsSmi()) {
      return obj;
    }
    if (obj->IsHeapNumber()) {
      double value = HeapNumber::cast(obj)->value();
      int int_value = FastD2I(value);
      if (value == FastI2D(int_value) && Smi::IsValid(int_value)) {
        return Smi::FromInt(int_value);
      }
    }
    return isolate->heap()->nan_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_AllocateHeapNumber) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 0);
    return *isolate->factory()->NewHeapNumber(0);
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberAdd) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_DOUBLE_ARG_CHECKED(x, 0);
    CONVERT_DOUBLE_ARG_CHECKED(y, 1);
    return *isolate->factory()->NewNumber(x + y);
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberSub) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_DOUBLE_ARG_CHECKED(x, 0);
    CONVERT_DOUBLE_ARG_CHECKED(y, 1);
    return *isolate->factory()->NewNumber(x - y);
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberMul) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_DOUBLE_ARG_CHECKED(x, 0);
    CONVERT_DOUBLE_ARG_CHECKED(y, 1);
    return *isolate->factory()->NewNumber(x * y);
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberUnaryMinus) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
  
    CONVERT_DOUBLE_ARG_CHECKED(x, 0);
    return *isolate->factory()->NewNumber(-x);
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberDiv) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_DOUBLE_ARG_CHECKED(x, 0);
    CONVERT_DOUBLE_ARG_CHECKED(y, 1);
    return *isolate->factory()->NewNumber(x / y);
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberMod) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_DOUBLE_ARG_CHECKED(x, 0);
    CONVERT_DOUBLE_ARG_CHECKED(y, 1);
    return *isolate->factory()->NewNumber(modulo(x, y));
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberImul) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    // We rely on implementation-defined behavior below, but at least not on
    // undefined behavior.
    CONVERT_NUMBER_CHECKED(uint32_t, x, Int32, args[0]);
    CONVERT_NUMBER_CHECKED(uint32_t, y, Int32, args[1]);
    int32_t product = static_cast<int32_t>(x * y);
    return *isolate->factory()->NewNumberFromInt(product);
  }
  
  
  RUNTIME_FUNCTION(Runtime_StringAdd) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(String, str1, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, str2, 1);
    isolate->counters()->string_add_runtime()->Increment();
    Handle<String> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result, isolate->factory()->NewConsString(str1, str2));
    return *result;
  }
  
  
  template <typename sinkchar>
  static inline void StringBuilderConcatHelper(String* special,
                                               sinkchar* sink,
                                               FixedArray* fixed_array,
                                               int array_length) {
    DisallowHeapAllocation no_gc;
    int position = 0;
    for (int i = 0; i < array_length; i++) {
      Object* element = fixed_array->get(i);
      if (element->IsSmi()) {
        // Smi encoding of position and length.
        int encoded_slice = Smi::cast(element)->value();
        int pos;
        int len;
        if (encoded_slice > 0) {
          // Position and length encoded in one smi.
          pos = StringBuilderSubstringPosition::decode(encoded_slice);
          len = StringBuilderSubstringLength::decode(encoded_slice);
        } else {
          // Position and length encoded in two smis.
          Object* obj = fixed_array->get(++i);
          DCHECK(obj->IsSmi());
          pos = Smi::cast(obj)->value();
          len = -encoded_slice;
        }
        String::WriteToFlat(special,
                            sink + position,
                            pos,
                            pos + len);
        position += len;
      } else {
        String* string = String::cast(element);
        int element_length = string->length();
        String::WriteToFlat(string, sink + position, 0, element_length);
        position += element_length;
      }
    }
  }
  
  
  // Returns the result length of the concatenation.
  // On illegal argument, -1 is returned.
  static inline int StringBuilderConcatLength(int special_length,
                                              FixedArray* fixed_array,
                                              int array_length,
                                              bool* one_byte) {
    DisallowHeapAllocation no_gc;
    int position = 0;
    for (int i = 0; i < array_length; i++) {
      int increment = 0;
      Object* elt = fixed_array->get(i);
      if (elt->IsSmi()) {
        // Smi encoding of position and length.
        int smi_value = Smi::cast(elt)->value();
        int pos;
        int len;
        if (smi_value > 0) {
          // Position and length encoded in one smi.
          pos = StringBuilderSubstringPosition::decode(smi_value);
          len = StringBuilderSubstringLength::decode(smi_value);
        } else {
          // Position and length encoded in two smis.
          len = -smi_value;
          // Get the position and check that it is a positive smi.
          i++;
          if (i >= array_length) return -1;
          Object* next_smi = fixed_array->get(i);
          if (!next_smi->IsSmi()) return -1;
          pos = Smi::cast(next_smi)->value();
          if (pos < 0) return -1;
        }
        DCHECK(pos >= 0);
        DCHECK(len >= 0);
        if (pos > special_length || len > special_length - pos) return -1;
        increment = len;
      } else if (elt->IsString()) {
        String* element = String::cast(elt);
        int element_length = element->length();
        increment = element_length;
        if (*one_byte && !element->HasOnlyOneByteChars()) {
          *one_byte = false;
        }
      } else {
        return -1;
      }
      if (increment > String::kMaxLength - position) {
        return kMaxInt;  // Provoke throw on allocation.
      }
      position += increment;
    }
    return position;
  }
  
  
  RUNTIME_FUNCTION(Runtime_StringBuilderConcat) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
    CONVERT_ARG_HANDLE_CHECKED(JSArray, array, 0);
    if (!args[1]->IsSmi()) return isolate->ThrowInvalidStringLength();
    CONVERT_SMI_ARG_CHECKED(array_length, 1);
    CONVERT_ARG_HANDLE_CHECKED(String, special, 2);
  
    size_t actual_array_length = 0;
    RUNTIME_ASSERT(
        TryNumberToSize(isolate, array->length(), &actual_array_length));
    RUNTIME_ASSERT(array_length >= 0);
    RUNTIME_ASSERT(static_cast<size_t>(array_length) <= actual_array_length);
  
    // This assumption is used by the slice encoding in one or two smis.
    DCHECK(Smi::kMaxValue >= String::kMaxLength);
  
    RUNTIME_ASSERT(array->HasFastElements());
    JSObject::EnsureCanContainHeapObjectElements(array);
  
    int special_length = special->length();
    if (!array->HasFastObjectElements()) {
      return isolate->Throw(isolate->heap()->illegal_argument_string());
    }
  
    int length;
    bool one_byte = special->HasOnlyOneByteChars();
  
    { DisallowHeapAllocation no_gc;
      FixedArray* fixed_array = FixedArray::cast(array->elements());
      if (fixed_array->length() < array_length) {
        array_length = fixed_array->length();
      }
  
      if (array_length == 0) {
        return isolate->heap()->empty_string();
      } else if (array_length == 1) {
        Object* first = fixed_array->get(0);
        if (first->IsString()) return first;
      }
      length = StringBuilderConcatLength(
          special_length, fixed_array, array_length, &one_byte);
    }
  
    if (length == -1) {
      return isolate->Throw(isolate->heap()->illegal_argument_string());
    }
  
    if (one_byte) {
      Handle<SeqOneByteString> answer;
      ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
          isolate, answer,
          isolate->factory()->NewRawOneByteString(length));
      StringBuilderConcatHelper(*special,
                                answer->GetChars(),
                                FixedArray::cast(array->elements()),
                                array_length);
      return *answer;
    } else {
      Handle<SeqTwoByteString> answer;
      ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
          isolate, answer,
          isolate->factory()->NewRawTwoByteString(length));
      StringBuilderConcatHelper(*special,
                                answer->GetChars(),
                                FixedArray::cast(array->elements()),
                                array_length);
      return *answer;
    }
  }
  
  
  RUNTIME_FUNCTION(Runtime_StringBuilderJoin) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
    CONVERT_ARG_HANDLE_CHECKED(JSArray, array, 0);
    if (!args[1]->IsSmi()) return isolate->ThrowInvalidStringLength();
    CONVERT_SMI_ARG_CHECKED(array_length, 1);
    CONVERT_ARG_HANDLE_CHECKED(String, separator, 2);
    RUNTIME_ASSERT(array->HasFastObjectElements());
    RUNTIME_ASSERT(array_length >= 0);
  
    Handle<FixedArray> fixed_array(FixedArray::cast(array->elements()));
    if (fixed_array->length() < array_length) {
      array_length = fixed_array->length();
    }
  
    if (array_length == 0) {
      return isolate->heap()->empty_string();
    } else if (array_length == 1) {
      Object* first = fixed_array->get(0);
      RUNTIME_ASSERT(first->IsString());
      return first;
    }
  
    int separator_length = separator->length();
    RUNTIME_ASSERT(separator_length > 0);
    int max_nof_separators =
        (String::kMaxLength + separator_length - 1) / separator_length;
    if (max_nof_separators < (array_length - 1)) {
      return isolate->ThrowInvalidStringLength();
    }
    int length = (array_length - 1) * separator_length;
    for (int i = 0; i < array_length; i++) {
      Object* element_obj = fixed_array->get(i);
      RUNTIME_ASSERT(element_obj->IsString());
      String* element = String::cast(element_obj);
      int increment = element->length();
      if (increment > String::kMaxLength - length) {
        STATIC_ASSERT(String::kMaxLength < kMaxInt);
        length = kMaxInt;  // Provoke exception;
        break;
      }
      length += increment;
    }
  
    Handle<SeqTwoByteString> answer;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, answer,
        isolate->factory()->NewRawTwoByteString(length));
  
    DisallowHeapAllocation no_gc;
  
    uc16* sink = answer->GetChars();
  #ifdef DEBUG
    uc16* end = sink + length;
  #endif
  
    RUNTIME_ASSERT(fixed_array->get(0)->IsString());
    String* first = String::cast(fixed_array->get(0));
    String* separator_raw = *separator;
    int first_length = first->length();
    String::WriteToFlat(first, sink, 0, first_length);
    sink += first_length;
  
    for (int i = 1; i < array_length; i++) {
      DCHECK(sink + separator_length <= end);
      String::WriteToFlat(separator_raw, sink, 0, separator_length);
      sink += separator_length;
  
      RUNTIME_ASSERT(fixed_array->get(i)->IsString());
      String* element = String::cast(fixed_array->get(i));
      int element_length = element->length();
      DCHECK(sink + element_length <= end);
      String::WriteToFlat(element, sink, 0, element_length);
      sink += element_length;
    }
    DCHECK(sink == end);
  
    // Use %_FastAsciiArrayJoin instead.
    DCHECK(!answer->IsOneByteRepresentation());
    return *answer;
  }
  
  template <typename Char>
  static void JoinSparseArrayWithSeparator(FixedArray* elements,
                                           int elements_length,
                                           uint32_t array_length,
                                           String* separator,
                                           Vector<Char> buffer) {
    DisallowHeapAllocation no_gc;
    int previous_separator_position = 0;
    int separator_length = separator->length();
    int cursor = 0;
    for (int i = 0; i < elements_length; i += 2) {
      int position = NumberToInt32(elements->get(i));
      String* string = String::cast(elements->get(i + 1));
      int string_length = string->length();
      if (string->length() > 0) {
        while (previous_separator_position < position) {
          String::WriteToFlat<Char>(separator, &buffer[cursor],
                                    0, separator_length);
          cursor += separator_length;
          previous_separator_position++;
        }
        String::WriteToFlat<Char>(string, &buffer[cursor],
                                  0, string_length);
        cursor += string->length();
      }
    }
    if (separator_length > 0) {
      // Array length must be representable as a signed 32-bit number,
      // otherwise the total string length would have been too large.
      DCHECK(array_length <= 0x7fffffff);  // Is int32_t.
      int last_array_index = static_cast<int>(array_length - 1);
      while (previous_separator_position < last_array_index) {
        String::WriteToFlat<Char>(separator, &buffer[cursor],
                                  0, separator_length);
        cursor += separator_length;
        previous_separator_position++;
      }
    }
    DCHECK(cursor <= buffer.length());
  }
  
  
  RUNTIME_FUNCTION(Runtime_SparseJoinWithSeparator) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
    CONVERT_ARG_HANDLE_CHECKED(JSArray, elements_array, 0);
    CONVERT_NUMBER_CHECKED(uint32_t, array_length, Uint32, args[1]);
    CONVERT_ARG_HANDLE_CHECKED(String, separator, 2);
    // elements_array is fast-mode JSarray of alternating positions
    // (increasing order) and strings.
    RUNTIME_ASSERT(elements_array->HasFastSmiOrObjectElements());
    // array_length is length of original array (used to add separators);
    // separator is string to put between elements. Assumed to be non-empty.
    RUNTIME_ASSERT(array_length > 0);
  
    // Find total length of join result.
    int string_length = 0;
    bool is_ascii = separator->IsOneByteRepresentation();
    bool overflow = false;
    CONVERT_NUMBER_CHECKED(int, elements_length, Int32, elements_array->length());
    RUNTIME_ASSERT(elements_length <= elements_array->elements()->length());
    RUNTIME_ASSERT((elements_length & 1) == 0);  // Even length.
    FixedArray* elements = FixedArray::cast(elements_array->elements());
    for (int i = 0; i < elements_length; i += 2) {
      RUNTIME_ASSERT(elements->get(i)->IsNumber());
      CONVERT_NUMBER_CHECKED(uint32_t, position, Uint32, elements->get(i));
      RUNTIME_ASSERT(position < array_length);
      RUNTIME_ASSERT(elements->get(i + 1)->IsString());
    }
  
    { DisallowHeapAllocation no_gc;
      for (int i = 0; i < elements_length; i += 2) {
        String* string = String::cast(elements->get(i + 1));
        int length = string->length();
        if (is_ascii && !string->IsOneByteRepresentation()) {
          is_ascii = false;
        }
        if (length > String::kMaxLength ||
            String::kMaxLength - length < string_length) {
          overflow = true;
          break;
        }
        string_length += length;
      }
    }
  
    int separator_length = separator->length();
    if (!overflow && separator_length > 0) {
      if (array_length <= 0x7fffffffu) {
        int separator_count = static_cast<int>(array_length) - 1;
        int remaining_length = String::kMaxLength - string_length;
        if ((remaining_length / separator_length) >= separator_count) {
          string_length += separator_length * (array_length - 1);
        } else {
          // Not room for the separators within the maximal string length.
          overflow = true;
        }
      } else {
        // Nonempty separator and at least 2^31-1 separators necessary
        // means that the string is too large to create.
        STATIC_ASSERT(String::kMaxLength < 0x7fffffff);
        overflow = true;
      }
    }
    if (overflow) {
      // Throw an exception if the resulting string is too large. See
      // https://code.google.com/p/chromium/issues/detail?id=336820
      // for details.
      return isolate->ThrowInvalidStringLength();
    }
  
    if (is_ascii) {
      Handle<SeqOneByteString> result = isolate->factory()->NewRawOneByteString(
          string_length).ToHandleChecked();
      JoinSparseArrayWithSeparator<uint8_t>(
          FixedArray::cast(elements_array->elements()),
          elements_length,
          array_length,
          *separator,
          Vector<uint8_t>(result->GetChars(), string_length));
      return *result;
    } else {
      Handle<SeqTwoByteString> result = isolate->factory()->NewRawTwoByteString(
          string_length).ToHandleChecked();
      JoinSparseArrayWithSeparator<uc16>(
          FixedArray::cast(elements_array->elements()),
          elements_length,
          array_length,
          *separator,
          Vector<uc16>(result->GetChars(), string_length));
      return *result;
    }
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberOr) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_NUMBER_CHECKED(int32_t, x, Int32, args[0]);
    CONVERT_NUMBER_CHECKED(int32_t, y, Int32, args[1]);
    return *isolate->factory()->NewNumberFromInt(x | y);
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberAnd) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_NUMBER_CHECKED(int32_t, x, Int32, args[0]);
    CONVERT_NUMBER_CHECKED(int32_t, y, Int32, args[1]);
    return *isolate->factory()->NewNumberFromInt(x & y);
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberXor) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_NUMBER_CHECKED(int32_t, x, Int32, args[0]);
    CONVERT_NUMBER_CHECKED(int32_t, y, Int32, args[1]);
    return *isolate->factory()->NewNumberFromInt(x ^ y);
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberShl) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_NUMBER_CHECKED(int32_t, x, Int32, args[0]);
    CONVERT_NUMBER_CHECKED(int32_t, y, Int32, args[1]);
    return *isolate->factory()->NewNumberFromInt(x << (y & 0x1f));
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberShr) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_NUMBER_CHECKED(uint32_t, x, Uint32, args[0]);
    CONVERT_NUMBER_CHECKED(int32_t, y, Int32, args[1]);
    return *isolate->factory()->NewNumberFromUint(x >> (y & 0x1f));
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberSar) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_NUMBER_CHECKED(int32_t, x, Int32, args[0]);
    CONVERT_NUMBER_CHECKED(int32_t, y, Int32, args[1]);
    return *isolate->factory()->NewNumberFromInt(
        ArithmeticShiftRight(x, y & 0x1f));
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberEquals) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_DOUBLE_ARG_CHECKED(x, 0);
    CONVERT_DOUBLE_ARG_CHECKED(y, 1);
    if (std::isnan(x)) return Smi::FromInt(NOT_EQUAL);
    if (std::isnan(y)) return Smi::FromInt(NOT_EQUAL);
    if (x == y) return Smi::FromInt(EQUAL);
    Object* result;
    if ((fpclassify(x) == FP_ZERO) && (fpclassify(y) == FP_ZERO)) {
      result = Smi::FromInt(EQUAL);
    } else {
      result = Smi::FromInt(NOT_EQUAL);
    }
    return result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_StringEquals) {
    HandleScope handle_scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_HANDLE_CHECKED(String, x, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, y, 1);
  
    bool not_equal = !String::Equals(x, y);
    // This is slightly convoluted because the value that signifies
    // equality is 0 and inequality is 1 so we have to negate the result
    // from String::Equals.
    DCHECK(not_equal == 0 || not_equal == 1);
    STATIC_ASSERT(EQUAL == 0);
    STATIC_ASSERT(NOT_EQUAL == 1);
    return Smi::FromInt(not_equal);
  }
  
  
  RUNTIME_FUNCTION(Runtime_NumberCompare) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 3);
  
    CONVERT_DOUBLE_ARG_CHECKED(x, 0);
    CONVERT_DOUBLE_ARG_CHECKED(y, 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, uncomparable_result, 2)
    if (std::isnan(x) || std::isnan(y)) return *uncomparable_result;
    if (x == y) return Smi::FromInt(EQUAL);
    if (isless(x, y)) return Smi::FromInt(LESS);
    return Smi::FromInt(GREATER);
  }
  
  
  // Compare two Smis as if they were converted to strings and then
  // compared lexicographically.
  RUNTIME_FUNCTION(Runtime_SmiLexicographicCompare) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 2);
    CONVERT_SMI_ARG_CHECKED(x_value, 0);
    CONVERT_SMI_ARG_CHECKED(y_value, 1);
  
    // If the integers are equal so are the string representations.
    if (x_value == y_value) return Smi::FromInt(EQUAL);
  
    // If one of the integers is zero the normal integer order is the
    // same as the lexicographic order of the string representations.
    if (x_value == 0 || y_value == 0)
      return Smi::FromInt(x_value < y_value ? LESS : GREATER);
  
    // If only one of the integers is negative the negative number is
    // smallest because the char code of '-' is less than the char code
    // of any digit.  Otherwise, we make both values positive.
  
    // Use unsigned values otherwise the logic is incorrect for -MIN_INT on
    // architectures using 32-bit Smis.
    uint32_t x_scaled = x_value;
    uint32_t y_scaled = y_value;
    if (x_value < 0 || y_value < 0) {
      if (y_value >= 0) return Smi::FromInt(LESS);
      if (x_value >= 0) return Smi::FromInt(GREATER);
      x_scaled = -x_value;
      y_scaled = -y_value;
    }
  
    static const uint32_t kPowersOf10[] = {
      1, 10, 100, 1000, 10*1000, 100*1000,
      1000*1000, 10*1000*1000, 100*1000*1000,
      1000*1000*1000
    };
  
    // If the integers have the same number of decimal digits they can be
    // compared directly as the numeric order is the same as the
    // lexicographic order.  If one integer has fewer digits, it is scaled
    // by some power of 10 to have the same number of digits as the longer
    // integer.  If the scaled integers are equal it means the shorter
    // integer comes first in the lexicographic order.
  
    // From http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog10
    int x_log2 = IntegerLog2(x_scaled);
    int x_log10 = ((x_log2 + 1) * 1233) >> 12;
    x_log10 -= x_scaled < kPowersOf10[x_log10];
  
    int y_log2 = IntegerLog2(y_scaled);
    int y_log10 = ((y_log2 + 1) * 1233) >> 12;
    y_log10 -= y_scaled < kPowersOf10[y_log10];
  
    int tie = EQUAL;
  
    if (x_log10 < y_log10) {
      // X has fewer digits.  We would like to simply scale up X but that
      // might overflow, e.g when comparing 9 with 1_000_000_000, 9 would
      // be scaled up to 9_000_000_000. So we scale up by the next
      // smallest power and scale down Y to drop one digit. It is OK to
      // drop one digit from the longer integer since the final digit is
      // past the length of the shorter integer.
      x_scaled *= kPowersOf10[y_log10 - x_log10 - 1];
      y_scaled /= 10;
      tie = LESS;
    } else if (y_log10 < x_log10) {
      y_scaled *= kPowersOf10[x_log10 - y_log10 - 1];
      x_scaled /= 10;
      tie = GREATER;
    }
  
    if (x_scaled < y_scaled) return Smi::FromInt(LESS);
    if (x_scaled > y_scaled) return Smi::FromInt(GREATER);
    return Smi::FromInt(tie);
  }
  
  
  RUNTIME_FUNCTION(Runtime_StringCompare) {
    HandleScope handle_scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_HANDLE_CHECKED(String, x, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, y, 1);
  
    isolate->counters()->string_compare_runtime()->Increment();
  
    // A few fast case tests before we flatten.
    if (x.is_identical_to(y)) return Smi::FromInt(EQUAL);
    if (y->length() == 0) {
      if (x->length() == 0) return Smi::FromInt(EQUAL);
      return Smi::FromInt(GREATER);
    } else if (x->length() == 0) {
      return Smi::FromInt(LESS);
    }
  
    int d = x->Get(0) - y->Get(0);
    if (d < 0) return Smi::FromInt(LESS);
    else if (d > 0) return Smi::FromInt(GREATER);
  
    // Slow case.
    x = String::Flatten(x);
    y = String::Flatten(y);
  
    DisallowHeapAllocation no_gc;
    Object* equal_prefix_result = Smi::FromInt(EQUAL);
    int prefix_length = x->length();
    if (y->length() < prefix_length) {
      prefix_length = y->length();
      equal_prefix_result = Smi::FromInt(GREATER);
    } else if (y->length() > prefix_length) {
      equal_prefix_result = Smi::FromInt(LESS);
    }
    int r;
    String::FlatContent x_content = x->GetFlatContent();
    String::FlatContent y_content = y->GetFlatContent();
    if (x_content.IsAscii()) {
      Vector<const uint8_t> x_chars = x_content.ToOneByteVector();
      if (y_content.IsAscii()) {
        Vector<const uint8_t> y_chars = y_content.ToOneByteVector();
        r = CompareChars(x_chars.start(), y_chars.start(), prefix_length);
      } else {
        Vector<const uc16> y_chars = y_content.ToUC16Vector();
        r = CompareChars(x_chars.start(), y_chars.start(), prefix_length);
      }
    } else {
      Vector<const uc16> x_chars = x_content.ToUC16Vector();
      if (y_content.IsAscii()) {
        Vector<const uint8_t> y_chars = y_content.ToOneByteVector();
        r = CompareChars(x_chars.start(), y_chars.start(), prefix_length);
      } else {
        Vector<const uc16> y_chars = y_content.ToUC16Vector();
        r = CompareChars(x_chars.start(), y_chars.start(), prefix_length);
      }
    }
    Object* result;
    if (r == 0) {
      result = equal_prefix_result;
    } else {
      result = (r < 0) ? Smi::FromInt(LESS) : Smi::FromInt(GREATER);
    }
    return result;
  }
  
  
  #define RUNTIME_UNARY_MATH(Name, name)                                         \
  RUNTIME_FUNCTION(Runtime_Math##Name) {                           \
    HandleScope scope(isolate);                                                  \
    DCHECK(args.length() == 1);                                                  \
    isolate->counters()->math_##name()->Increment();                             \
    CONVERT_DOUBLE_ARG_CHECKED(x, 0);                                            \
    return *isolate->factory()->NewHeapNumber(std::name(x));                     \
  }
  
  RUNTIME_UNARY_MATH(Acos, acos)
  RUNTIME_UNARY_MATH(Asin, asin)
  RUNTIME_UNARY_MATH(Atan, atan)
  RUNTIME_UNARY_MATH(LogRT, log)
  #undef RUNTIME_UNARY_MATH
  
  
  RUNTIME_FUNCTION(Runtime_DoubleHi) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_DOUBLE_ARG_CHECKED(x, 0);
    uint64_t integer = double_to_uint64(x);
    integer = (integer >> 32) & 0xFFFFFFFFu;
    return *isolate->factory()->NewNumber(static_cast<int32_t>(integer));
  }
  
  
  RUNTIME_FUNCTION(Runtime_DoubleLo) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_DOUBLE_ARG_CHECKED(x, 0);
    return *isolate->factory()->NewNumber(
        static_cast<int32_t>(double_to_uint64(x) & 0xFFFFFFFFu));
  }
  
  
  RUNTIME_FUNCTION(Runtime_ConstructDouble) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_NUMBER_CHECKED(uint32_t, hi, Uint32, args[0]);
    CONVERT_NUMBER_CHECKED(uint32_t, lo, Uint32, args[1]);
    uint64_t result = (static_cast<uint64_t>(hi) << 32) | lo;
    return *isolate->factory()->NewNumber(uint64_to_double(result));
  }
  
  
  RUNTIME_FUNCTION(Runtime_RemPiO2) {
    HandleScope handle_scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_DOUBLE_ARG_CHECKED(x, 0);
    Factory* factory = isolate->factory();
    double y[2];
    int n = fdlibm::rempio2(x, y);
    Handle<FixedArray> array = factory->NewFixedArray(3);
    Handle<HeapNumber> y0 = factory->NewHeapNumber(y[0]);
    Handle<HeapNumber> y1 = factory->NewHeapNumber(y[1]);
    array->set(0, Smi::FromInt(n));
    array->set(1, *y0);
    array->set(2, *y1);
    return *factory->NewJSArrayWithElements(array);
  }
  
  
  static const double kPiDividedBy4 = 0.78539816339744830962;
  
  
  RUNTIME_FUNCTION(Runtime_MathAtan2) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    isolate->counters()->math_atan2()->Increment();
  
    CONVERT_DOUBLE_ARG_CHECKED(x, 0);
    CONVERT_DOUBLE_ARG_CHECKED(y, 1);
    double result;
    if (std::isinf(x) && std::isinf(y)) {
      // Make sure that the result in case of two infinite arguments
      // is a multiple of Pi / 4. The sign of the result is determined
      // by the first argument (x) and the sign of the second argument
      // determines the multiplier: one or three.
      int multiplier = (x < 0) ? -1 : 1;
      if (y < 0) multiplier *= 3;
      result = multiplier * kPiDividedBy4;
    } else {
      result = std::atan2(x, y);
    }
    return *isolate->factory()->NewNumber(result);
  }
  
  
  RUNTIME_FUNCTION(Runtime_MathExpRT) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    isolate->counters()->math_exp()->Increment();
  
    CONVERT_DOUBLE_ARG_CHECKED(x, 0);
    lazily_initialize_fast_exp();
    return *isolate->factory()->NewNumber(fast_exp(x));
  }
  
  
  RUNTIME_FUNCTION(Runtime_MathFloorRT) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    isolate->counters()->math_floor()->Increment();
  
    CONVERT_DOUBLE_ARG_CHECKED(x, 0);
    return *isolate->factory()->NewNumber(Floor(x));
  }
  
  
  // Slow version of Math.pow.  We check for fast paths for special cases.
  // Used if VFP3 is not available.
  RUNTIME_FUNCTION(Runtime_MathPowSlow) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    isolate->counters()->math_pow()->Increment();
  
    CONVERT_DOUBLE_ARG_CHECKED(x, 0);
  
    // If the second argument is a smi, it is much faster to call the
    // custom powi() function than the generic pow().
    if (args[1]->IsSmi()) {
      int y = args.smi_at(1);
      return *isolate->factory()->NewNumber(power_double_int(x, y));
    }
  
    CONVERT_DOUBLE_ARG_CHECKED(y, 1);
    double result = power_helper(x, y);
    if (std::isnan(result)) return isolate->heap()->nan_value();
    return *isolate->factory()->NewNumber(result);
  }
  
  
  // Fast version of Math.pow if we know that y is not an integer and y is not
  // -0.5 or 0.5.  Used as slow case from full codegen.
  RUNTIME_FUNCTION(Runtime_MathPowRT) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    isolate->counters()->math_pow()->Increment();
  
    CONVERT_DOUBLE_ARG_CHECKED(x, 0);
    CONVERT_DOUBLE_ARG_CHECKED(y, 1);
    if (y == 0) {
      return Smi::FromInt(1);
    } else {
      double result = power_double_double(x, y);
      if (std::isnan(result)) return isolate->heap()->nan_value();
      return *isolate->factory()->NewNumber(result);
    }
  }
  
  
  RUNTIME_FUNCTION(Runtime_RoundNumber) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_NUMBER_ARG_HANDLE_CHECKED(input, 0);
    isolate->counters()->math_round()->Increment();
  
    if (!input->IsHeapNumber()) {
      DCHECK(input->IsSmi());
      return *input;
    }
  
    Handle<HeapNumber> number = Handle<HeapNumber>::cast(input);
  
    double value = number->value();
    int exponent = number->get_exponent();
    int sign = number->get_sign();
  
    if (exponent < -1) {
      // Number in range ]-0.5..0.5[. These always round to +/-zero.
      if (sign) return isolate->heap()->minus_zero_value();
      return Smi::FromInt(0);
    }
  
    // We compare with kSmiValueSize - 2 because (2^30 - 0.1) has exponent 29 and
    // should be rounded to 2^30, which is not smi (for 31-bit smis, similar
    // argument holds for 32-bit smis).
    if (!sign && exponent < kSmiValueSize - 2) {
      return Smi::FromInt(static_cast<int>(value + 0.5));
    }
  
    // If the magnitude is big enough, there's no place for fraction part. If we
    // try to add 0.5 to this number, 1.0 will be added instead.
    if (exponent >= 52) {
      return *number;
    }
  
    if (sign && value >= -0.5) return isolate->heap()->minus_zero_value();
  
    // Do not call NumberFromDouble() to avoid extra checks.
    return *isolate->factory()->NewNumber(Floor(value + 0.5));
  }
  
  
  RUNTIME_FUNCTION(Runtime_MathSqrtRT) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    isolate->counters()->math_sqrt()->Increment();
  
    CONVERT_DOUBLE_ARG_CHECKED(x, 0);
    return *isolate->factory()->NewNumber(fast_sqrt(x));
  }
  
  
  RUNTIME_FUNCTION(Runtime_MathFround) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
  
    CONVERT_DOUBLE_ARG_CHECKED(x, 0);
    float xf = static_cast<float>(x);
    return *isolate->factory()->NewNumber(xf);
  }
  
  
  RUNTIME_FUNCTION(Runtime_DateMakeDay) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_SMI_ARG_CHECKED(year, 0);
    CONVERT_SMI_ARG_CHECKED(month, 1);
  
    int days = isolate->date_cache()->DaysFromYearMonth(year, month);
    RUNTIME_ASSERT(Smi::IsValid(days));
    return Smi::FromInt(days);
  }
  
  
  RUNTIME_FUNCTION(Runtime_DateSetValue) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
  
    CONVERT_ARG_HANDLE_CHECKED(JSDate, date, 0);
    CONVERT_DOUBLE_ARG_CHECKED(time, 1);
    CONVERT_SMI_ARG_CHECKED(is_utc, 2);
  
    DateCache* date_cache = isolate->date_cache();
  
    Handle<Object> value;;
    bool is_value_nan = false;
    if (std::isnan(time)) {
      value = isolate->factory()->nan_value();
      is_value_nan = true;
    } else if (!is_utc &&
               (time < -DateCache::kMaxTimeBeforeUTCInMs ||
                time > DateCache::kMaxTimeBeforeUTCInMs)) {
      value = isolate->factory()->nan_value();
      is_value_nan = true;
    } else {
      time = is_utc ? time : date_cache->ToUTC(static_cast<int64_t>(time));
      if (time < -DateCache::kMaxTimeInMs ||
          time > DateCache::kMaxTimeInMs) {
        value = isolate->factory()->nan_value();
        is_value_nan = true;
      } else  {
        value = isolate->factory()->NewNumber(DoubleToInteger(time));
      }
    }
    date->SetValue(*value, is_value_nan);
    return *value;
  }
  
  
  static Handle<JSObject> NewSloppyArguments(Isolate* isolate,
                                             Handle<JSFunction> callee,
                                             Object** parameters,
                                             int argument_count) {
    Handle<JSObject> result =
        isolate->factory()->NewArgumentsObject(callee, argument_count);
  
    // Allocate the elements if needed.
    int parameter_count = callee->shared()->formal_parameter_count();
    if (argument_count > 0) {
      if (parameter_count > 0) {
        int mapped_count = Min(argument_count, parameter_count);
        Handle<FixedArray> parameter_map =
            isolate->factory()->NewFixedArray(mapped_count + 2, NOT_TENURED);
        parameter_map->set_map(
            isolate->heap()->sloppy_arguments_elements_map());
  
        Handle<Map> map = Map::Copy(handle(result->map()));
        map->set_elements_kind(SLOPPY_ARGUMENTS_ELEMENTS);
  
        result->set_map(*map);
        result->set_elements(*parameter_map);
  
        // Store the context and the arguments array at the beginning of the
        // parameter map.
        Handle<Context> context(isolate->context());
        Handle<FixedArray> arguments =
            isolate->factory()->NewFixedArray(argument_count, NOT_TENURED);
        parameter_map->set(0, *context);
        parameter_map->set(1, *arguments);
  
        // Loop over the actual parameters backwards.
        int index = argument_count - 1;
        while (index >= mapped_count) {
          // These go directly in the arguments array and have no
          // corresponding slot in the parameter map.
          arguments->set(index, *(parameters - index - 1));
          --index;
        }
  
        Handle<ScopeInfo> scope_info(callee->shared()->scope_info());
        while (index >= 0) {
          // Detect duplicate names to the right in the parameter list.
          Handle<String> name(scope_info->ParameterName(index));
          int context_local_count = scope_info->ContextLocalCount();
          bool duplicate = false;
          for (int j = index + 1; j < parameter_count; ++j) {
            if (scope_info->ParameterName(j) == *name) {
              duplicate = true;
              break;
            }
          }
  
          if (duplicate) {
            // This goes directly in the arguments array with a hole in the
            // parameter map.
            arguments->set(index, *(parameters - index - 1));
            parameter_map->set_the_hole(index + 2);
          } else {
            // The context index goes in the parameter map with a hole in the
            // arguments array.
            int context_index = -1;
            for (int j = 0; j < context_local_count; ++j) {
              if (scope_info->ContextLocalName(j) == *name) {
                context_index = j;
                break;
              }
            }
            DCHECK(context_index >= 0);
            arguments->set_the_hole(index);
            parameter_map->set(index + 2, Smi::FromInt(
                Context::MIN_CONTEXT_SLOTS + context_index));
          }
  
          --index;
        }
      } else {
        // If there is no aliasing, the arguments object elements are not
        // special in any way.
        Handle<FixedArray> elements =
            isolate->factory()->NewFixedArray(argument_count, NOT_TENURED);
        result->set_elements(*elements);
        for (int i = 0; i < argument_count; ++i) {
          elements->set(i, *(parameters - i - 1));
        }
      }
    }
    return result;
  }
  
  
  static Handle<JSObject> NewStrictArguments(Isolate* isolate,
                                             Handle<JSFunction> callee,
                                             Object** parameters,
                                             int argument_count) {
    Handle<JSObject> result =
        isolate->factory()->NewArgumentsObject(callee, argument_count);
  
    if (argument_count > 0) {
      Handle<FixedArray> array =
          isolate->factory()->NewUninitializedFixedArray(argument_count);
      DisallowHeapAllocation no_gc;
      WriteBarrierMode mode = array->GetWriteBarrierMode(no_gc);
      for (int i = 0; i < argument_count; i++) {
        array->set(i, *--parameters, mode);
      }
      result->set_elements(*array);
    }
    return result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_NewArguments) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, callee, 0);
    JavaScriptFrameIterator it(isolate);
  
    // Find the frame that holds the actual arguments passed to the function.
    it.AdvanceToArgumentsFrame();
    JavaScriptFrame* frame = it.frame();
  
    // Determine parameter location on the stack and dispatch on language mode.
    int argument_count = frame->GetArgumentsLength();
    Object** parameters = reinterpret_cast<Object**>(frame->GetParameterSlot(-1));
    return callee->shared()->strict_mode() == STRICT
               ? *NewStrictArguments(isolate, callee, parameters, argument_count)
               : *NewSloppyArguments(isolate, callee, parameters, argument_count);
  }
  
  
  RUNTIME_FUNCTION(Runtime_NewSloppyArguments) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, callee, 0);
    Object** parameters = reinterpret_cast<Object**>(args[1]);
    CONVERT_SMI_ARG_CHECKED(argument_count, 2);
    return *NewSloppyArguments(isolate, callee, parameters, argument_count);
  }
  
  
  RUNTIME_FUNCTION(Runtime_NewStrictArguments) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, callee, 0)
    Object** parameters = reinterpret_cast<Object**>(args[1]);
    CONVERT_SMI_ARG_CHECKED(argument_count, 2);
    return *NewStrictArguments(isolate, callee, parameters, argument_count);
  }
  
  
  RUNTIME_FUNCTION(Runtime_NewClosureFromStubFailure) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(SharedFunctionInfo, shared, 0);
    Handle<Context> context(isolate->context());
    PretenureFlag pretenure_flag = NOT_TENURED;
    return *isolate->factory()->NewFunctionFromSharedFunctionInfo(
        shared,  context, pretenure_flag);
  }
  
  
  RUNTIME_FUNCTION(Runtime_NewClosure) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
    CONVERT_ARG_HANDLE_CHECKED(Context, context, 0);
    CONVERT_ARG_HANDLE_CHECKED(SharedFunctionInfo, shared, 1);
    CONVERT_BOOLEAN_ARG_CHECKED(pretenure, 2);
  
    // The caller ensures that we pretenure closures that are assigned
    // directly to properties.
    PretenureFlag pretenure_flag = pretenure ? TENURED : NOT_TENURED;
    return *isolate->factory()->NewFunctionFromSharedFunctionInfo(
        shared, context, pretenure_flag);
  }
  
  
  // Find the arguments of the JavaScript function invocation that called
  // into C++ code. Collect these in a newly allocated array of handles (possibly
  // prefixed by a number of empty handles).
  static SmartArrayPointer<Handle<Object> > GetCallerArguments(
      Isolate* isolate,
      int prefix_argc,
      int* total_argc) {
    // Find frame containing arguments passed to the caller.
    JavaScriptFrameIterator it(isolate);
    JavaScriptFrame* frame = it.frame();
    List<JSFunction*> functions(2);
    frame->GetFunctions(&functions);
    if (functions.length() > 1) {
      int inlined_jsframe_index = functions.length() - 1;
      JSFunction* inlined_function = functions[inlined_jsframe_index];
      SlotRefValueBuilder slot_refs(
          frame,
          inlined_jsframe_index,
          inlined_function->shared()->formal_parameter_count());
  
      int args_count = slot_refs.args_length();
  
      *total_argc = prefix_argc + args_count;
      SmartArrayPointer<Handle<Object> > param_data(
          NewArray<Handle<Object> >(*total_argc));
      slot_refs.Prepare(isolate);
      for (int i = 0; i < args_count; i++) {
        Handle<Object> val = slot_refs.GetNext(isolate, 0);
        param_data[prefix_argc + i] = val;
      }
      slot_refs.Finish(isolate);
  
      return param_data;
    } else {
      it.AdvanceToArgumentsFrame();
      frame = it.frame();
      int args_count = frame->ComputeParametersCount();
  
      *total_argc = prefix_argc + args_count;
      SmartArrayPointer<Handle<Object> > param_data(
          NewArray<Handle<Object> >(*total_argc));
      for (int i = 0; i < args_count; i++) {
        Handle<Object> val = Handle<Object>(frame->GetParameter(i), isolate);
        param_data[prefix_argc + i] = val;
      }
      return param_data;
    }
  }
  
  
  RUNTIME_FUNCTION(Runtime_FunctionBindArguments) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 4);
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, bound_function, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, bindee, 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, this_object, 2);
    CONVERT_NUMBER_ARG_HANDLE_CHECKED(new_length, 3);
  
    // TODO(lrn): Create bound function in C++ code from premade shared info.
    bound_function->shared()->set_bound(true);
    // Get all arguments of calling function (Function.prototype.bind).
    int argc = 0;
    SmartArrayPointer<Handle<Object> > arguments =
        GetCallerArguments(isolate, 0, &argc);
    // Don't count the this-arg.
    if (argc > 0) {
      RUNTIME_ASSERT(arguments[0].is_identical_to(this_object));
      argc--;
    } else {
      RUNTIME_ASSERT(this_object->IsUndefined());
    }
    // Initialize array of bindings (function, this, and any existing arguments
    // if the function was already bound).
    Handle<FixedArray> new_bindings;
    int i;
    if (bindee->IsJSFunction() && JSFunction::cast(*bindee)->shared()->bound()) {
      Handle<FixedArray> old_bindings(
          JSFunction::cast(*bindee)->function_bindings());
      RUNTIME_ASSERT(old_bindings->length() > JSFunction::kBoundFunctionIndex);
      new_bindings =
          isolate->factory()->NewFixedArray(old_bindings->length() + argc);
      bindee = Handle<Object>(old_bindings->get(JSFunction::kBoundFunctionIndex),
                              isolate);
      i = 0;
      for (int n = old_bindings->length(); i < n; i++) {
        new_bindings->set(i, old_bindings->get(i));
      }
    } else {
      int array_size = JSFunction::kBoundArgumentsStartIndex + argc;
      new_bindings = isolate->factory()->NewFixedArray(array_size);
      new_bindings->set(JSFunction::kBoundFunctionIndex, *bindee);
      new_bindings->set(JSFunction::kBoundThisIndex, *this_object);
      i = 2;
    }
    // Copy arguments, skipping the first which is "this_arg".
    for (int j = 0; j < argc; j++, i++) {
      new_bindings->set(i, *arguments[j + 1]);
    }
    new_bindings->set_map_no_write_barrier(
        isolate->heap()->fixed_cow_array_map());
    bound_function->set_function_bindings(*new_bindings);
  
    // Update length. Have to remove the prototype first so that map migration
    // is happy about the number of fields.
    RUNTIME_ASSERT(bound_function->RemovePrototype());
    Handle<Map> bound_function_map(
        isolate->native_context()->bound_function_map());
    JSObject::MigrateToMap(bound_function, bound_function_map);
    Handle<String> length_string = isolate->factory()->length_string();
    PropertyAttributes attr =
        static_cast<PropertyAttributes>(DONT_DELETE | DONT_ENUM | READ_ONLY);
    RETURN_FAILURE_ON_EXCEPTION(
        isolate,
        JSObject::SetOwnPropertyIgnoreAttributes(
            bound_function, length_string, new_length, attr));
    return *bound_function;
  }
  
  
  RUNTIME_FUNCTION(Runtime_BoundFunctionGetBindings) {
    HandleScope handles(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSReceiver, callable, 0);
    if (callable->IsJSFunction()) {
      Handle<JSFunction> function = Handle<JSFunction>::cast(callable);
      if (function->shared()->bound()) {
        Handle<FixedArray> bindings(function->function_bindings());
        RUNTIME_ASSERT(bindings->map() == isolate->heap()->fixed_cow_array_map());
        return *isolate->factory()->NewJSArrayWithElements(bindings);
      }
    }
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_NewObjectFromBound) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    // First argument is a function to use as a constructor.
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 0);
    RUNTIME_ASSERT(function->shared()->bound());
  
    // The argument is a bound function. Extract its bound arguments
    // and callable.
    Handle<FixedArray> bound_args =
        Handle<FixedArray>(FixedArray::cast(function->function_bindings()));
    int bound_argc = bound_args->length() - JSFunction::kBoundArgumentsStartIndex;
    Handle<Object> bound_function(
        JSReceiver::cast(bound_args->get(JSFunction::kBoundFunctionIndex)),
        isolate);
    DCHECK(!bound_function->IsJSFunction() ||
           !Handle<JSFunction>::cast(bound_function)->shared()->bound());
  
    int total_argc = 0;
    SmartArrayPointer<Handle<Object> > param_data =
        GetCallerArguments(isolate, bound_argc, &total_argc);
    for (int i = 0; i < bound_argc; i++) {
      param_data[i] = Handle<Object>(bound_args->get(
          JSFunction::kBoundArgumentsStartIndex + i), isolate);
    }
  
    if (!bound_function->IsJSFunction()) {
      ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
          isolate, bound_function,
          Execution::TryGetConstructorDelegate(isolate, bound_function));
    }
    DCHECK(bound_function->IsJSFunction());
  
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result,
        Execution::New(Handle<JSFunction>::cast(bound_function),
                       total_argc, param_data.get()));
    return *result;
  }
  
  
  static Object* Runtime_NewObjectHelper(Isolate* isolate,
                                              Handle<Object> constructor,
                                              Handle<AllocationSite> site) {
    // If the constructor isn't a proper function we throw a type error.
    if (!constructor->IsJSFunction()) {
      Vector< Handle<Object> > arguments = HandleVector(&constructor, 1);
      Handle<Object> type_error =
          isolate->factory()->NewTypeError("not_constructor", arguments);
      return isolate->Throw(*type_error);
    }
  
    Handle<JSFunction> function = Handle<JSFunction>::cast(constructor);
  
    // If function should not have prototype, construction is not allowed. In this
    // case generated code bailouts here, since function has no initial_map.
    if (!function->should_have_prototype() && !function->shared()->bound()) {
      Vector< Handle<Object> > arguments = HandleVector(&constructor, 1);
      Handle<Object> type_error =
          isolate->factory()->NewTypeError("not_constructor", arguments);
      return isolate->Throw(*type_error);
    }
  
    Debug* debug = isolate->debug();
    // Handle stepping into constructors if step into is active.
    if (debug->StepInActive()) {
      debug->HandleStepIn(function, Handle<Object>::null(), 0, true);
    }
  
    if (function->has_initial_map()) {
      if (function->initial_map()->instance_type() == JS_FUNCTION_TYPE) {
        // The 'Function' function ignores the receiver object when
        // called using 'new' and creates a new JSFunction object that
        // is returned.  The receiver object is only used for error
        // reporting if an error occurs when constructing the new
        // JSFunction. Factory::NewJSObject() should not be used to
        // allocate JSFunctions since it does not properly initialize
        // the shared part of the function. Since the receiver is
        // ignored anyway, we use the global object as the receiver
        // instead of a new JSFunction object. This way, errors are
        // reported the same way whether or not 'Function' is called
        // using 'new'.
        return isolate->global_proxy();
      }
    }
  
    // The function should be compiled for the optimization hints to be
    // available.
    Compiler::EnsureCompiled(function, CLEAR_EXCEPTION);
  
    Handle<JSObject> result;
    if (site.is_null()) {
      result = isolate->factory()->NewJSObject(function);
    } else {
      result = isolate->factory()->NewJSObjectWithMemento(function, site);
    }
  
    isolate->counters()->constructed_objects()->Increment();
    isolate->counters()->constructed_objects_runtime()->Increment();
  
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_NewObject) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, constructor, 0);
    return Runtime_NewObjectHelper(isolate,
                                   constructor,
                                   Handle<AllocationSite>::null());
  }
  
  
  RUNTIME_FUNCTION(Runtime_NewObjectWithAllocationSite) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(Object, constructor, 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, feedback, 0);
    Handle<AllocationSite> site;
    if (feedback->IsAllocationSite()) {
      // The feedback can be an AllocationSite or undefined.
      site = Handle<AllocationSite>::cast(feedback);
    }
    return Runtime_NewObjectHelper(isolate, constructor, site);
  }
  
  
  RUNTIME_FUNCTION(Runtime_FinalizeInstanceSize) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
  
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 0);
    function->CompleteInobjectSlackTracking();
  
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_CompileUnoptimized) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 0);
  #ifdef DEBUG
    if (FLAG_trace_lazy && !function->shared()->is_compiled()) {
      PrintF("[unoptimized: ");
      function->PrintName();
      PrintF("]\n");
    }
  #endif
  
    // Compile the target function.
    DCHECK(function->shared()->allows_lazy_compilation());
  
    Handle<Code> code;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, code,
                                       Compiler::GetUnoptimizedCode(function));
    function->ReplaceCode(*code);
  
    // All done. Return the compiled code.
    DCHECK(function->is_compiled());
    DCHECK(function->code()->kind() == Code::FUNCTION ||
           (FLAG_always_opt &&
            function->code()->kind() == Code::OPTIMIZED_FUNCTION));
    return *code;
  }
  
  
  RUNTIME_FUNCTION(Runtime_CompileOptimized) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 0);
    CONVERT_BOOLEAN_ARG_CHECKED(concurrent, 1);
  
    Handle<Code> unoptimized(function->shared()->code());
    if (!function->shared()->is_compiled()) {
      // If the function is not compiled, do not optimize.
      // This can happen if the debugger is activated and
      // the function is returned to the not compiled state.
      // TODO(yangguo): reconsider this.
      function->ReplaceCode(function->shared()->code());
    } else if (!isolate->use_crankshaft() ||
               function->shared()->optimization_disabled() ||
               isolate->DebuggerHasBreakPoints()) {
      // If the function is not optimizable or debugger is active continue
      // using the code from the full compiler.
      if (FLAG_trace_opt) {
        PrintF("[failed to optimize ");
        function->PrintName();
        PrintF(": is code optimizable: %s, is debugger enabled: %s]\n",
            function->shared()->optimization_disabled() ? "F" : "T",
            isolate->DebuggerHasBreakPoints() ? "T" : "F");
      }
      function->ReplaceCode(*unoptimized);
    } else {
      Compiler::ConcurrencyMode mode = concurrent ? Compiler::CONCURRENT
                                                  : Compiler::NOT_CONCURRENT;
      Handle<Code> code;
      if (Compiler::GetOptimizedCode(
              function, unoptimized, mode).ToHandle(&code)) {
        function->ReplaceCode(*code);
      } else {
        function->ReplaceCode(*unoptimized);
      }
    }
  
    DCHECK(function->code()->kind() == Code::FUNCTION ||
           function->code()->kind() == Code::OPTIMIZED_FUNCTION ||
           function->IsInOptimizationQueue());
    return function->code();
  }
  
  
  class ActivationsFinder : public ThreadVisitor {
   public:
    Code* code_;
    bool has_code_activations_;
  
    explicit ActivationsFinder(Code* code)
      : code_(code),
        has_code_activations_(false) { }
  
    void VisitThread(Isolate* isolate, ThreadLocalTop* top) {
      JavaScriptFrameIterator it(isolate, top);
      VisitFrames(&it);
    }
  
    void VisitFrames(JavaScriptFrameIterator* it) {
      for (; !it->done(); it->Advance()) {
        JavaScriptFrame* frame = it->frame();
        if (code_->contains(frame->pc())) has_code_activations_ = true;
      }
    }
  };
  
  
  RUNTIME_FUNCTION(Runtime_NotifyStubFailure) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 0);
    Deoptimizer* deoptimizer = Deoptimizer::Grab(isolate);
    DCHECK(AllowHeapAllocation::IsAllowed());
    delete deoptimizer;
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_NotifyDeoptimized) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_SMI_ARG_CHECKED(type_arg, 0);
    Deoptimizer::BailoutType type =
        static_cast<Deoptimizer::BailoutType>(type_arg);
    Deoptimizer* deoptimizer = Deoptimizer::Grab(isolate);
    DCHECK(AllowHeapAllocation::IsAllowed());
  
    Handle<JSFunction> function = deoptimizer->function();
    Handle<Code> optimized_code = deoptimizer->compiled_code();
  
    DCHECK(optimized_code->kind() == Code::OPTIMIZED_FUNCTION);
    DCHECK(type == deoptimizer->bailout_type());
  
    // Make sure to materialize objects before causing any allocation.
    JavaScriptFrameIterator it(isolate);
    deoptimizer->MaterializeHeapObjects(&it);
    delete deoptimizer;
  
    JavaScriptFrame* frame = it.frame();
    RUNTIME_ASSERT(frame->function()->IsJSFunction());
    DCHECK(frame->function() == *function);
  
    // Avoid doing too much work when running with --always-opt and keep
    // the optimized code around.
    if (FLAG_always_opt || type == Deoptimizer::LAZY) {
      return isolate->heap()->undefined_value();
    }
  
    // Search for other activations of the same function and code.
    ActivationsFinder activations_finder(*optimized_code);
    activations_finder.VisitFrames(&it);
    isolate->thread_manager()->IterateArchivedThreads(&activations_finder);
  
    if (!activations_finder.has_code_activations_) {
      if (function->code() == *optimized_code) {
        if (FLAG_trace_deopt) {
          PrintF("[removing optimized code for: ");
          function->PrintName();
          PrintF("]\n");
        }
        function->ReplaceCode(function->shared()->code());
        // Evict optimized code for this function from the cache so that it
        // doesn't get used for new closures.
        function->shared()->EvictFromOptimizedCodeMap(*optimized_code,
                                                      "notify deoptimized");
      }
    } else {
      // TODO(titzer): we should probably do DeoptimizeCodeList(code)
      // unconditionally if the code is not already marked for deoptimization.
      // If there is an index by shared function info, all the better.
      Deoptimizer::DeoptimizeFunction(*function);
    }
  
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_DeoptimizeFunction) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 0);
    if (!function->IsOptimized()) return isolate->heap()->undefined_value();
  
    // TODO(turbofan): Deoptimization is not supported yet.
    if (function->code()->is_turbofanned() && !FLAG_turbo_deoptimization) {
      return isolate->heap()->undefined_value();
    }
  
    Deoptimizer::DeoptimizeFunction(*function);
  
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_ClearFunctionTypeFeedback) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 0);
    function->shared()->ClearTypeFeedbackInfo();
    Code* unoptimized = function->shared()->code();
    if (unoptimized->kind() == Code::FUNCTION) {
      unoptimized->ClearInlineCaches();
    }
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_RunningInSimulator) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 0);
  #if defined(USE_SIMULATOR)
    return isolate->heap()->true_value();
  #else
    return isolate->heap()->false_value();
  #endif
  }
  
  
  RUNTIME_FUNCTION(Runtime_IsConcurrentRecompilationSupported) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 0);
    return isolate->heap()->ToBoolean(
        isolate->concurrent_recompilation_enabled());
  }
  
  
  RUNTIME_FUNCTION(Runtime_OptimizeFunctionOnNextCall) {
    HandleScope scope(isolate);
    RUNTIME_ASSERT(args.length() == 1 || args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 0);
  
    if (!function->IsOptimizable() &&
        !function->IsMarkedForConcurrentOptimization() &&
        !function->IsInOptimizationQueue()) {
      return isolate->heap()->undefined_value();
    }
  
    function->MarkForOptimization();
  
    Code* unoptimized = function->shared()->code();
    if (args.length() == 2 &&
        unoptimized->kind() == Code::FUNCTION) {
      CONVERT_ARG_HANDLE_CHECKED(String, type, 1);
      if (type->IsOneByteEqualTo(STATIC_ASCII_VECTOR("osr")) && FLAG_use_osr) {
        // Start patching from the currently patched loop nesting level.
        DCHECK(BackEdgeTable::Verify(isolate, unoptimized));
        isolate->runtime_profiler()->AttemptOnStackReplacement(
            *function, Code::kMaxLoopNestingMarker);
      } else if (type->IsOneByteEqualTo(STATIC_ASCII_VECTOR("concurrent")) &&
                 isolate->concurrent_recompilation_enabled()) {
        function->MarkForConcurrentOptimization();
      }
    }
  
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_NeverOptimizeFunction) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(JSFunction, function, 0);
    function->shared()->set_optimization_disabled(true);
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetOptimizationStatus) {
    HandleScope scope(isolate);
    RUNTIME_ASSERT(args.length() == 1 || args.length() == 2);
    if (!isolate->use_crankshaft()) {
      return Smi::FromInt(4);  // 4 == "never".
    }
    bool sync_with_compiler_thread = true;
    if (args.length() == 2) {
      CONVERT_ARG_HANDLE_CHECKED(String, sync, 1);
      if (sync->IsOneByteEqualTo(STATIC_ASCII_VECTOR("no sync"))) {
        sync_with_compiler_thread = false;
      }
    }
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 0);
    if (isolate->concurrent_recompilation_enabled() &&
        sync_with_compiler_thread) {
      while (function->IsInOptimizationQueue()) {
        isolate->optimizing_compiler_thread()->InstallOptimizedFunctions();
        base::OS::Sleep(50);
      }
    }
    if (FLAG_always_opt) {
      // We may have always opt, but that is more best-effort than a real
      // promise, so we still say "no" if it is not optimized.
      return function->IsOptimized() ? Smi::FromInt(3)   // 3 == "always".
                                     : Smi::FromInt(2);  // 2 == "no".
    }
    if (FLAG_deopt_every_n_times) {
      return Smi::FromInt(6);  // 6 == "maybe deopted".
    }
    if (function->IsOptimized() && function->code()->is_turbofanned()) {
      return Smi::FromInt(7);  // 7 == "TurboFan compiler".
    }
    return function->IsOptimized() ? Smi::FromInt(1)   // 1 == "yes".
                                   : Smi::FromInt(2);  // 2 == "no".
  }
  
  
  RUNTIME_FUNCTION(Runtime_UnblockConcurrentRecompilation) {
    DCHECK(args.length() == 0);
    RUNTIME_ASSERT(FLAG_block_concurrent_recompilation);
    RUNTIME_ASSERT(isolate->concurrent_recompilation_enabled());
    isolate->optimizing_compiler_thread()->Unblock();
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetOptimizationCount) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 0);
    return Smi::FromInt(function->shared()->opt_count());
  }
  
  
  static bool IsSuitableForOnStackReplacement(Isolate* isolate,
                                              Handle<JSFunction> function,
                                              Handle<Code> current_code) {
    // Keep track of whether we've succeeded in optimizing.
    if (!isolate->use_crankshaft() || !current_code->optimizable()) return false;
    // If we are trying to do OSR when there are already optimized
    // activations of the function, it means (a) the function is directly or
    // indirectly recursive and (b) an optimized invocation has been
    // deoptimized so that we are currently in an unoptimized activation.
    // Check for optimized activations of this function.
    for (JavaScriptFrameIterator it(isolate); !it.done(); it.Advance()) {
      JavaScriptFrame* frame = it.frame();
      if (frame->is_optimized() && frame->function() == *function) return false;
    }
  
    return true;
  }
  
  
  RUNTIME_FUNCTION(Runtime_CompileForOnStackReplacement) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 0);
    Handle<Code> caller_code(function->shared()->code());
  
    // We're not prepared to handle a function with arguments object.
    DCHECK(!function->shared()->uses_arguments());
  
    RUNTIME_ASSERT(FLAG_use_osr);
  
    // Passing the PC in the javascript frame from the caller directly is
    // not GC safe, so we walk the stack to get it.
    JavaScriptFrameIterator it(isolate);
    JavaScriptFrame* frame = it.frame();
    if (!caller_code->contains(frame->pc())) {
      // Code on the stack may not be the code object referenced by the shared
      // function info.  It may have been replaced to include deoptimization data.
      caller_code = Handle<Code>(frame->LookupCode());
    }
  
    uint32_t pc_offset = static_cast<uint32_t>(
        frame->pc() - caller_code->instruction_start());
  
  #ifdef DEBUG
    DCHECK_EQ(frame->function(), *function);
    DCHECK_EQ(frame->LookupCode(), *caller_code);
    DCHECK(caller_code->contains(frame->pc()));
  #endif  // DEBUG
  
  
    BailoutId ast_id = caller_code->TranslatePcOffsetToAstId(pc_offset);
    DCHECK(!ast_id.IsNone());
  
    Compiler::ConcurrencyMode mode =
        isolate->concurrent_osr_enabled() &&
        (function->shared()->ast_node_count() > 512) ? Compiler::CONCURRENT
                                                     : Compiler::NOT_CONCURRENT;
    Handle<Code> result = Handle<Code>::null();
  
    OptimizedCompileJob* job = NULL;
    if (mode == Compiler::CONCURRENT) {
      // Gate the OSR entry with a stack check.
      BackEdgeTable::AddStackCheck(caller_code, pc_offset);
      // Poll already queued compilation jobs.
      OptimizingCompilerThread* thread = isolate->optimizing_compiler_thread();
      if (thread->IsQueuedForOSR(function, ast_id)) {
        if (FLAG_trace_osr) {
          PrintF("[OSR - Still waiting for queued: ");
          function->PrintName();
          PrintF(" at AST id %d]\n", ast_id.ToInt());
        }
        return NULL;
      }
  
      job = thread->FindReadyOSRCandidate(function, ast_id);
    }
  
    if (job != NULL) {
      if (FLAG_trace_osr) {
        PrintF("[OSR - Found ready: ");
        function->PrintName();
        PrintF(" at AST id %d]\n", ast_id.ToInt());
      }
      result = Compiler::GetConcurrentlyOptimizedCode(job);
    } else if (IsSuitableForOnStackReplacement(isolate, function, caller_code)) {
      if (FLAG_trace_osr) {
        PrintF("[OSR - Compiling: ");
        function->PrintName();
        PrintF(" at AST id %d]\n", ast_id.ToInt());
      }
      MaybeHandle<Code> maybe_result = Compiler::GetOptimizedCode(
          function, caller_code, mode, ast_id);
      if (maybe_result.ToHandle(&result) &&
          result.is_identical_to(isolate->builtins()->InOptimizationQueue())) {
        // Optimization is queued.  Return to check later.
        return NULL;
      }
    }
  
    // Revert the patched back edge table, regardless of whether OSR succeeds.
    BackEdgeTable::Revert(isolate, *caller_code);
  
    // Check whether we ended up with usable optimized code.
    if (!result.is_null() && result->kind() == Code::OPTIMIZED_FUNCTION) {
      DeoptimizationInputData* data =
          DeoptimizationInputData::cast(result->deoptimization_data());
  
      if (data->OsrPcOffset()->value() >= 0) {
        DCHECK(BailoutId(data->OsrAstId()->value()) == ast_id);
        if (FLAG_trace_osr) {
          PrintF("[OSR - Entry at AST id %d, offset %d in optimized code]\n",
                 ast_id.ToInt(), data->OsrPcOffset()->value());
        }
        // TODO(titzer): this is a massive hack to make the deopt counts
        // match. Fix heuristics for reenabling optimizations!
        function->shared()->increment_deopt_count();
  
        // TODO(titzer): Do not install code into the function.
        function->ReplaceCode(*result);
        return *result;
      }
    }
  
    // Failed.
    if (FLAG_trace_osr) {
      PrintF("[OSR - Failed: ");
      function->PrintName();
      PrintF(" at AST id %d]\n", ast_id.ToInt());
    }
  
    if (!function->IsOptimized()) {
      function->ReplaceCode(function->shared()->code());
    }
    return NULL;
  }
  
  
  RUNTIME_FUNCTION(Runtime_SetAllocationTimeout) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 2 || args.length() == 3);
  #ifdef DEBUG
    CONVERT_SMI_ARG_CHECKED(interval, 0);
    CONVERT_SMI_ARG_CHECKED(timeout, 1);
    isolate->heap()->set_allocation_timeout(timeout);
    FLAG_gc_interval = interval;
    if (args.length() == 3) {
      // Enable/disable inline allocation if requested.
      CONVERT_BOOLEAN_ARG_CHECKED(inline_allocation, 2);
      if (inline_allocation) {
        isolate->heap()->EnableInlineAllocation();
      } else {
        isolate->heap()->DisableInlineAllocation();
      }
    }
  #endif
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_CheckIsBootstrapping) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 0);
    RUNTIME_ASSERT(isolate->bootstrapper()->IsActive());
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetRootNaN) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 0);
    RUNTIME_ASSERT(isolate->bootstrapper()->IsActive());
    return isolate->heap()->nan_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_Call) {
    HandleScope scope(isolate);
    DCHECK(args.length() >= 2);
    int argc = args.length() - 2;
    CONVERT_ARG_CHECKED(JSReceiver, fun, argc + 1);
    Object* receiver = args[0];
  
    // If there are too many arguments, allocate argv via malloc.
    const int argv_small_size = 10;
    Handle<Object> argv_small_buffer[argv_small_size];
    SmartArrayPointer<Handle<Object> > argv_large_buffer;
    Handle<Object>* argv = argv_small_buffer;
    if (argc > argv_small_size) {
      argv = new Handle<Object>[argc];
      if (argv == NULL) return isolate->StackOverflow();
      argv_large_buffer = SmartArrayPointer<Handle<Object> >(argv);
    }
  
    for (int i = 0; i < argc; ++i) {
       argv[i] = Handle<Object>(args[1 + i], isolate);
    }
  
    Handle<JSReceiver> hfun(fun);
    Handle<Object> hreceiver(receiver, isolate);
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result,
        Execution::Call(isolate, hfun, hreceiver, argc, argv, true));
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_Apply) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 5);
    CONVERT_ARG_HANDLE_CHECKED(JSReceiver, fun, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, receiver, 1);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, arguments, 2);
    CONVERT_SMI_ARG_CHECKED(offset, 3);
    CONVERT_SMI_ARG_CHECKED(argc, 4);
    RUNTIME_ASSERT(offset >= 0);
    // Loose upper bound to allow fuzzing. We'll most likely run out of
    // stack space before hitting this limit.
    static int kMaxArgc = 1000000;
    RUNTIME_ASSERT(argc >= 0 && argc <= kMaxArgc);
  
    // If there are too many arguments, allocate argv via malloc.
    const int argv_small_size = 10;
    Handle<Object> argv_small_buffer[argv_small_size];
    SmartArrayPointer<Handle<Object> > argv_large_buffer;
    Handle<Object>* argv = argv_small_buffer;
    if (argc > argv_small_size) {
      argv = new Handle<Object>[argc];
      if (argv == NULL) return isolate->StackOverflow();
      argv_large_buffer = SmartArrayPointer<Handle<Object> >(argv);
    }
  
    for (int i = 0; i < argc; ++i) {
      ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
          isolate, argv[i],
          Object::GetElement(isolate, arguments, offset + i));
    }
  
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result,
        Execution::Call(isolate, fun, receiver, argc, argv, true));
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetFunctionDelegate) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
    RUNTIME_ASSERT(!object->IsJSFunction());
    return *Execution::GetFunctionDelegate(isolate, object);
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetConstructorDelegate) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
    RUNTIME_ASSERT(!object->IsJSFunction());
    return *Execution::GetConstructorDelegate(isolate, object);
  }
  
  
  RUNTIME_FUNCTION(Runtime_NewGlobalContext) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 0);
    CONVERT_ARG_HANDLE_CHECKED(ScopeInfo, scope_info, 1);
    Handle<Context> result =
        isolate->factory()->NewGlobalContext(function, scope_info);
  
    DCHECK(function->context() == isolate->context());
    DCHECK(function->context()->global_object() == result->global_object());
    result->global_object()->set_global_context(*result);
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_NewFunctionContext) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
  
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 0);
  
    DCHECK(function->context() == isolate->context());
    int length = function->shared()->scope_info()->ContextLength();
    return *isolate->factory()->NewFunctionContext(length, function);
  }
  
  
  RUNTIME_FUNCTION(Runtime_PushWithContext) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    Handle<JSReceiver> extension_object;
    if (args[0]->IsJSReceiver()) {
      extension_object = args.at<JSReceiver>(0);
    } else {
      // Try to convert the object to a proper JavaScript object.
      MaybeHandle<JSReceiver> maybe_object =
          Object::ToObject(isolate, args.at<Object>(0));
      if (!maybe_object.ToHandle(&extension_object)) {
        Handle<Object> handle = args.at<Object>(0);
        Handle<Object> result =
            isolate->factory()->NewTypeError("with_expression",
                                             HandleVector(&handle, 1));
        return isolate->Throw(*result);
      }
    }
  
    Handle<JSFunction> function;
    if (args[1]->IsSmi()) {
      // A smi sentinel indicates a context nested inside global code rather
      // than some function.  There is a canonical empty function that can be
      // gotten from the native context.
      function = handle(isolate->native_context()->closure());
    } else {
      function = args.at<JSFunction>(1);
    }
  
    Handle<Context> current(isolate->context());
    Handle<Context> context = isolate->factory()->NewWithContext(
        function, current, extension_object);
    isolate->set_context(*context);
    return *context;
  }
  
  
  RUNTIME_FUNCTION(Runtime_PushCatchContext) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
    CONVERT_ARG_HANDLE_CHECKED(String, name, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, thrown_object, 1);
    Handle<JSFunction> function;
    if (args[2]->IsSmi()) {
      // A smi sentinel indicates a context nested inside global code rather
      // than some function.  There is a canonical empty function that can be
      // gotten from the native context.
      function = handle(isolate->native_context()->closure());
    } else {
      function = args.at<JSFunction>(2);
    }
    Handle<Context> current(isolate->context());
    Handle<Context> context = isolate->factory()->NewCatchContext(
        function, current, name, thrown_object);
    isolate->set_context(*context);
    return *context;
  }
  
  
  RUNTIME_FUNCTION(Runtime_PushBlockContext) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(ScopeInfo, scope_info, 0);
    Handle<JSFunction> function;
    if (args[1]->IsSmi()) {
      // A smi sentinel indicates a context nested inside global code rather
      // than some function.  There is a canonical empty function that can be
      // gotten from the native context.
      function = handle(isolate->native_context()->closure());
    } else {
      function = args.at<JSFunction>(1);
    }
    Handle<Context> current(isolate->context());
    Handle<Context> context = isolate->factory()->NewBlockContext(
        function, current, scope_info);
    isolate->set_context(*context);
    return *context;
  }
  
  
  RUNTIME_FUNCTION(Runtime_IsJSModule) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(Object, obj, 0);
    return isolate->heap()->ToBoolean(obj->IsJSModule());
  }
  
  
  RUNTIME_FUNCTION(Runtime_PushModuleContext) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 2);
    CONVERT_SMI_ARG_CHECKED(index, 0);
  
    if (!args[1]->IsScopeInfo()) {
      // Module already initialized. Find hosting context and retrieve context.
      Context* host = Context::cast(isolate->context())->global_context();
      Context* context = Context::cast(host->get(index));
      DCHECK(context->previous() == isolate->context());
      isolate->set_context(context);
      return context;
    }
  
    CONVERT_ARG_HANDLE_CHECKED(ScopeInfo, scope_info, 1);
  
    // Allocate module context.
    HandleScope scope(isolate);
    Factory* factory = isolate->factory();
    Handle<Context> context = factory->NewModuleContext(scope_info);
    Handle<JSModule> module = factory->NewJSModule(context, scope_info);
    context->set_module(*module);
    Context* previous = isolate->context();
    context->set_previous(previous);
    context->set_closure(previous->closure());
    context->set_global_object(previous->global_object());
    isolate->set_context(*context);
  
    // Find hosting scope and initialize internal variable holding module there.
    previous->global_context()->set(index, *context);
  
    return *context;
  }
  
  
  RUNTIME_FUNCTION(Runtime_DeclareModules) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(FixedArray, descriptions, 0);
    Context* host_context = isolate->context();
  
    for (int i = 0; i < descriptions->length(); ++i) {
      Handle<ModuleInfo> description(ModuleInfo::cast(descriptions->get(i)));
      int host_index = description->host_index();
      Handle<Context> context(Context::cast(host_context->get(host_index)));
      Handle<JSModule> module(context->module());
  
      for (int j = 0; j < description->length(); ++j) {
        Handle<String> name(description->name(j));
        VariableMode mode = description->mode(j);
        int index = description->index(j);
        switch (mode) {
          case VAR:
          case LET:
          case CONST:
          case CONST_LEGACY: {
            PropertyAttributes attr =
                IsImmutableVariableMode(mode) ? FROZEN : SEALED;
            Handle<AccessorInfo> info =
                Accessors::MakeModuleExport(name, index, attr);
            Handle<Object> result =
                JSObject::SetAccessor(module, info).ToHandleChecked();
            DCHECK(!result->IsUndefined());
            USE(result);
            break;
          }
          case MODULE: {
            Object* referenced_context = Context::cast(host_context)->get(index);
            Handle<JSModule> value(Context::cast(referenced_context)->module());
            JSObject::SetOwnPropertyIgnoreAttributes(module, name, value, FROZEN)
                .Assert();
            break;
          }
          case INTERNAL:
          case TEMPORARY:
          case DYNAMIC:
          case DYNAMIC_GLOBAL:
          case DYNAMIC_LOCAL:
            UNREACHABLE();
        }
      }
  
      JSObject::PreventExtensions(module).Assert();
    }
  
    DCHECK(!isolate->has_pending_exception());
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_DeleteLookupSlot) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_HANDLE_CHECKED(Context, context, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, name, 1);
  
    int index;
    PropertyAttributes attributes;
    ContextLookupFlags flags = FOLLOW_CHAINS;
    BindingFlags binding_flags;
    Handle<Object> holder = context->Lookup(name,
                                            flags,
                                            &index,
                                            &attributes,
                                            &binding_flags);
  
    // If the slot was not found the result is true.
    if (holder.is_null()) {
      return isolate->heap()->true_value();
    }
  
    // If the slot was found in a context, it should be DONT_DELETE.
    if (holder->IsContext()) {
      return isolate->heap()->false_value();
    }
  
    // The slot was found in a JSObject, either a context extension object,
    // the global object, or the subject of a with.  Try to delete it
    // (respecting DONT_DELETE).
    Handle<JSObject> object = Handle<JSObject>::cast(holder);
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result,
        JSReceiver::DeleteProperty(object, name));
    return *result;
  }
  
  
  // A mechanism to return a pair of Object pointers in registers (if possible).
  // How this is achieved is calling convention-dependent.
  // All currently supported x86 compiles uses calling conventions that are cdecl
  // variants where a 64-bit value is returned in two 32-bit registers
  // (edx:eax on ia32, r1:r0 on ARM).
  // In AMD-64 calling convention a struct of two pointers is returned in rdx:rax.
  // In Win64 calling convention, a struct of two pointers is returned in memory,
  // allocated by the caller, and passed as a pointer in a hidden first parameter.
  #ifdef V8_HOST_ARCH_64_BIT
  struct ObjectPair {
    Object* x;
    Object* y;
  };
  
  
  static inline ObjectPair MakePair(Object* x, Object* y) {
    ObjectPair result = {x, y};
    // Pointers x and y returned in rax and rdx, in AMD-x64-abi.
    // In Win64 they are assigned to a hidden first argument.
    return result;
  }
  #elif V8_TARGET_ARCH_X64 && V8_TARGET_ARCH_32_BIT
  // For x32 a 128-bit struct return is done as rax and rdx from the ObjectPair
  // are used in the full codegen and Crankshaft compiler. An alternative is
  // using uint64_t and modifying full codegen and Crankshaft compiler.
  struct ObjectPair {
    Object* x;
    uint32_t x_upper;
    Object* y;
    uint32_t y_upper;
  };
  
  
  static inline ObjectPair MakePair(Object* x, Object* y) {
    ObjectPair result = {x, 0, y, 0};
    // Pointers x and y returned in rax and rdx, in x32-abi.
    return result;
  }
  #else
  typedef uint64_t ObjectPair;
  static inline ObjectPair MakePair(Object* x, Object* y) {
  #if defined(V8_TARGET_LITTLE_ENDIAN)
    return reinterpret_cast<uint32_t>(x) |
        (reinterpret_cast<ObjectPair>(y) << 32);
  #elif defined(V8_TARGET_BIG_ENDIAN)
      return reinterpret_cast<uint32_t>(y) |
          (reinterpret_cast<ObjectPair>(x) << 32);
  #else
  #error Unknown endianness
  #endif
  }
  #endif
  
  
  static Object* ComputeReceiverForNonGlobal(Isolate* isolate,
                                             JSObject* holder) {
    DCHECK(!holder->IsGlobalObject());
    Context* top = isolate->context();
    // Get the context extension function.
    JSFunction* context_extension_function =
        top->native_context()->context_extension_function();
    // If the holder isn't a context extension object, we just return it
    // as the receiver. This allows arguments objects to be used as
    // receivers, but only if they are put in the context scope chain
    // explicitly via a with-statement.
    Object* constructor = holder->map()->constructor();
    if (constructor != context_extension_function) return holder;
    // Fall back to using the global object as the implicit receiver if
    // the property turns out to be a local variable allocated in a
    // context extension object - introduced via eval.
    return isolate->heap()->undefined_value();
  }
  
  
  static ObjectPair LoadLookupSlotHelper(Arguments args, Isolate* isolate,
                                         bool throw_error) {
    HandleScope scope(isolate);
    DCHECK_EQ(2, args.length());
  
    if (!args[0]->IsContext() || !args[1]->IsString()) {
      return MakePair(isolate->ThrowIllegalOperation(), NULL);
    }
    Handle<Context> context = args.at<Context>(0);
    Handle<String> name = args.at<String>(1);
  
    int index;
    PropertyAttributes attributes;
    ContextLookupFlags flags = FOLLOW_CHAINS;
    BindingFlags binding_flags;
    Handle<Object> holder = context->Lookup(name,
                                            flags,
                                            &index,
                                            &attributes,
                                            &binding_flags);
    if (isolate->has_pending_exception()) {
      return MakePair(isolate->heap()->exception(), NULL);
    }
  
    // If the index is non-negative, the slot has been found in a context.
    if (index >= 0) {
      DCHECK(holder->IsContext());
      // If the "property" we were looking for is a local variable, the
      // receiver is the global object; see ECMA-262, 3rd., 10.1.6 and 10.2.3.
      Handle<Object> receiver = isolate->factory()->undefined_value();
      Object* value = Context::cast(*holder)->get(index);
      // Check for uninitialized bindings.
      switch (binding_flags) {
        case MUTABLE_CHECK_INITIALIZED:
        case IMMUTABLE_CHECK_INITIALIZED_HARMONY:
          if (value->IsTheHole()) {
            Handle<Object> reference_error =
                isolate->factory()->NewReferenceError("not_defined",
                                                      HandleVector(&name, 1));
            return MakePair(isolate->Throw(*reference_error), NULL);
          }
          // FALLTHROUGH
        case MUTABLE_IS_INITIALIZED:
        case IMMUTABLE_IS_INITIALIZED:
        case IMMUTABLE_IS_INITIALIZED_HARMONY:
          DCHECK(!value->IsTheHole());
          return MakePair(value, *receiver);
        case IMMUTABLE_CHECK_INITIALIZED:
          if (value->IsTheHole()) {
            DCHECK((attributes & READ_ONLY) != 0);
            value = isolate->heap()->undefined_value();
          }
          return MakePair(value, *receiver);
        case MISSING_BINDING:
          UNREACHABLE();
          return MakePair(NULL, NULL);
      }
    }
  
    // Otherwise, if the slot was found the holder is a context extension
    // object, subject of a with, or a global object.  We read the named
    // property from it.
    if (!holder.is_null()) {
      Handle<JSReceiver> object = Handle<JSReceiver>::cast(holder);
  #ifdef DEBUG
      if (!object->IsJSProxy()) {
        Maybe<bool> maybe = JSReceiver::HasProperty(object, name);
        DCHECK(maybe.has_value);
        DCHECK(maybe.value);
      }
  #endif
      // GetProperty below can cause GC.
      Handle<Object> receiver_handle(
          object->IsGlobalObject()
              ? Object::cast(isolate->heap()->undefined_value())
              : object->IsJSProxy() ? static_cast<Object*>(*object)
                  : ComputeReceiverForNonGlobal(isolate, JSObject::cast(*object)),
          isolate);
  
      // No need to unhole the value here.  This is taken care of by the
      // GetProperty function.
      Handle<Object> value;
      ASSIGN_RETURN_ON_EXCEPTION_VALUE(
          isolate, value,
          Object::GetProperty(object, name),
          MakePair(isolate->heap()->exception(), NULL));
      return MakePair(*value, *receiver_handle);
    }
  
    if (throw_error) {
      // The property doesn't exist - throw exception.
      Handle<Object> reference_error =
          isolate->factory()->NewReferenceError("not_defined",
                                                HandleVector(&name, 1));
      return MakePair(isolate->Throw(*reference_error), NULL);
    } else {
      // The property doesn't exist - return undefined.
      return MakePair(isolate->heap()->undefined_value(),
                      isolate->heap()->undefined_value());
    }
  }
  
  
  RUNTIME_FUNCTION_RETURN_PAIR(Runtime_LoadLookupSlot) {
    return LoadLookupSlotHelper(args, isolate, true);
  }
  
  
  RUNTIME_FUNCTION_RETURN_PAIR(Runtime_LoadLookupSlotNoReferenceError) {
    return LoadLookupSlotHelper(args, isolate, false);
  }
  
  
  RUNTIME_FUNCTION(Runtime_StoreLookupSlot) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 4);
  
    CONVERT_ARG_HANDLE_CHECKED(Object, value, 0);
    CONVERT_ARG_HANDLE_CHECKED(Context, context, 1);
    CONVERT_ARG_HANDLE_CHECKED(String, name, 2);
    CONVERT_STRICT_MODE_ARG_CHECKED(strict_mode, 3);
  
    int index;
    PropertyAttributes attributes;
    ContextLookupFlags flags = FOLLOW_CHAINS;
    BindingFlags binding_flags;
    Handle<Object> holder = context->Lookup(name,
                                            flags,
                                            &index,
                                            &attributes,
                                            &binding_flags);
    // In case of JSProxy, an exception might have been thrown.
    if (isolate->has_pending_exception()) return isolate->heap()->exception();
  
    // The property was found in a context slot.
    if (index >= 0) {
      if ((attributes & READ_ONLY) == 0) {
        Handle<Context>::cast(holder)->set(index, *value);
      } else if (strict_mode == STRICT) {
        // Setting read only property in strict mode.
        Handle<Object> error =
            isolate->factory()->NewTypeError("strict_cannot_assign",
                                             HandleVector(&name, 1));
        return isolate->Throw(*error);
      }
      return *value;
    }
  
    // Slow case: The property is not in a context slot.  It is either in a
    // context extension object, a property of the subject of a with, or a
    // property of the global object.
    Handle<JSReceiver> object;
    if (attributes != ABSENT) {
      // The property exists on the holder.
      object = Handle<JSReceiver>::cast(holder);
    } else if (strict_mode == STRICT) {
      // If absent in strict mode: throw.
      Handle<Object> error = isolate->factory()->NewReferenceError(
          "not_defined", HandleVector(&name, 1));
      return isolate->Throw(*error);
    } else {
      // If absent in sloppy mode: add the property to the global object.
      object = Handle<JSReceiver>(context->global_object());
    }
  
    RETURN_FAILURE_ON_EXCEPTION(
        isolate, Object::SetProperty(object, name, value, strict_mode));
  
    return *value;
  }
  
  
  RUNTIME_FUNCTION(Runtime_Throw) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
  
    return isolate->Throw(args[0]);
  }
  
  
  RUNTIME_FUNCTION(Runtime_ReThrow) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
  
    return isolate->ReThrow(args[0]);
  }
  
  
  RUNTIME_FUNCTION(Runtime_PromoteScheduledException) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 0);
    return isolate->PromoteScheduledException();
  }
  
  
  RUNTIME_FUNCTION(Runtime_ThrowReferenceError) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, name, 0);
    Handle<Object> reference_error =
      isolate->factory()->NewReferenceError("not_defined",
                                            HandleVector(&name, 1));
    return isolate->Throw(*reference_error);
  }
  
  
  RUNTIME_FUNCTION(Runtime_ThrowNotDateError) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 0);
    return isolate->Throw(*isolate->factory()->NewTypeError(
        "not_date_object", HandleVector<Object>(NULL, 0)));
  }
  
  
  RUNTIME_FUNCTION(Runtime_StackGuard) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 0);
  
    // First check if this is a real stack overflow.
    StackLimitCheck check(isolate);
    if (check.JsHasOverflowed()) {
      return isolate->StackOverflow();
    }
  
    return isolate->stack_guard()->HandleInterrupts();
  }
  
  
  RUNTIME_FUNCTION(Runtime_TryInstallOptimizedCode) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 0);
  
    // First check if this is a real stack overflow.
    StackLimitCheck check(isolate);
    if (check.JsHasOverflowed()) {
      SealHandleScope shs(isolate);
      return isolate->StackOverflow();
    }
  
    isolate->optimizing_compiler_thread()->InstallOptimizedFunctions();
    return (function->IsOptimized()) ? function->code()
                                     : function->shared()->code();
  }
  
  
  RUNTIME_FUNCTION(Runtime_Interrupt) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 0);
    return isolate->stack_guard()->HandleInterrupts();
  }
  
  
  static int StackSize(Isolate* isolate) {
    int n = 0;
    for (JavaScriptFrameIterator it(isolate); !it.done(); it.Advance()) n++;
    return n;
  }
  
  
  static void PrintTransition(Isolate* isolate, Object* result) {
    // indentation
    { const int nmax = 80;
      int n = StackSize(isolate);
      if (n <= nmax)
        PrintF("%4d:%*s", n, n, "");
      else
        PrintF("%4d:%*s", n, nmax, "...");
    }
  
    if (result == NULL) {
      JavaScriptFrame::PrintTop(isolate, stdout, true, false);
      PrintF(" {\n");
    } else {
      // function result
      PrintF("} -> ");
      result->ShortPrint();
      PrintF("\n");
    }
  }
  
  
  RUNTIME_FUNCTION(Runtime_TraceEnter) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 0);
    PrintTransition(isolate, NULL);
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_TraceExit) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(Object, obj, 0);
    PrintTransition(isolate, obj);
    return obj;  // return TOS
  }
  
  
  RUNTIME_FUNCTION(Runtime_DebugPrint) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
  
    OFStream os(stdout);
  #ifdef DEBUG
    if (args[0]->IsString()) {
      // If we have a string, assume it's a code "marker"
      // and print some interesting cpu debugging info.
      JavaScriptFrameIterator it(isolate);
      JavaScriptFrame* frame = it.frame();
      os << "fp = " << frame->fp() << ", sp = " << frame->sp()
         << ", caller_sp = " << frame->caller_sp() << ": ";
    } else {
      os << "DebugPrint: ";
    }
    args[0]->Print(os);
    if (args[0]->IsHeapObject()) {
      os << "\n";
      HeapObject::cast(args[0])->map()->Print(os);
    }
  #else
    // ShortPrint is available in release mode. Print is not.
    os << Brief(args[0]);
  #endif
    os << endl;
  
    return args[0];  // return TOS
  }
  
  
  RUNTIME_FUNCTION(Runtime_DebugTrace) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 0);
    isolate->PrintStack(stdout);
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_DateCurrentTime) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 0);
    if (FLAG_log_timer_events) LOG(isolate, CurrentTimeEvent());
  
    // According to ECMA-262, section 15.9.1, page 117, the precision of
    // the number in a Date object representing a particular instant in
    // time is milliseconds. Therefore, we floor the result of getting
    // the OS time.
    double millis;
    if (FLAG_verify_predictable) {
      millis = 1388534400000.0;  // Jan 1 2014 00:00:00 GMT+0000
      millis += Floor(isolate->heap()->synthetic_time());
    } else {
      millis = Floor(base::OS::TimeCurrentMillis());
    }
    return *isolate->factory()->NewNumber(millis);
  }
  
  
  RUNTIME_FUNCTION(Runtime_DateParseString) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(String, str, 0);
    CONVERT_ARG_HANDLE_CHECKED(JSArray, output, 1);
  
    RUNTIME_ASSERT(output->HasFastElements());
    JSObject::EnsureCanContainHeapObjectElements(output);
    RUNTIME_ASSERT(output->HasFastObjectElements());
    Handle<FixedArray> output_array(FixedArray::cast(output->elements()));
    RUNTIME_ASSERT(output_array->length() >= DateParser::OUTPUT_SIZE);
  
    str = String::Flatten(str);
    DisallowHeapAllocation no_gc;
  
    bool result;
    String::FlatContent str_content = str->GetFlatContent();
    if (str_content.IsAscii()) {
      result = DateParser::Parse(str_content.ToOneByteVector(),
                                 *output_array,
                                 isolate->unicode_cache());
    } else {
      DCHECK(str_content.IsTwoByte());
      result = DateParser::Parse(str_content.ToUC16Vector(),
                                 *output_array,
                                 isolate->unicode_cache());
    }
  
    if (result) {
      return *output;
    } else {
      return isolate->heap()->null_value();
    }
  }
  
  
  RUNTIME_FUNCTION(Runtime_DateLocalTimezone) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
  
    CONVERT_DOUBLE_ARG_CHECKED(x, 0);
    RUNTIME_ASSERT(x >= -DateCache::kMaxTimeBeforeUTCInMs &&
                   x <= DateCache::kMaxTimeBeforeUTCInMs);
    const char* zone =
        isolate->date_cache()->LocalTimezone(static_cast<int64_t>(x));
    Handle<String> result = isolate->factory()->NewStringFromUtf8(
        CStrVector(zone)).ToHandleChecked();
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_DateToUTC) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
  
    CONVERT_DOUBLE_ARG_CHECKED(x, 0);
    RUNTIME_ASSERT(x >= -DateCache::kMaxTimeBeforeUTCInMs &&
                   x <= DateCache::kMaxTimeBeforeUTCInMs);
    int64_t time = isolate->date_cache()->ToUTC(static_cast<int64_t>(x));
  
    return *isolate->factory()->NewNumber(static_cast<double>(time));
  }
  
  
  RUNTIME_FUNCTION(Runtime_DateCacheVersion) {
    HandleScope hs(isolate);
    DCHECK(args.length() == 0);
    if (!isolate->eternal_handles()->Exists(EternalHandles::DATE_CACHE_VERSION)) {
      Handle<FixedArray> date_cache_version =
          isolate->factory()->NewFixedArray(1, TENURED);
      date_cache_version->set(0, Smi::FromInt(0));
      isolate->eternal_handles()->CreateSingleton(
          isolate, *date_cache_version, EternalHandles::DATE_CACHE_VERSION);
    }
    Handle<FixedArray> date_cache_version =
        Handle<FixedArray>::cast(isolate->eternal_handles()->GetSingleton(
            EternalHandles::DATE_CACHE_VERSION));
    // Return result as a JS array.
    Handle<JSObject> result =
        isolate->factory()->NewJSObject(isolate->array_function());
    JSArray::SetContent(Handle<JSArray>::cast(result), date_cache_version);
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_GlobalProxy) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(Object, global, 0);
    if (!global->IsJSGlobalObject()) return isolate->heap()->null_value();
    return JSGlobalObject::cast(global)->global_proxy();
  }
  
  
  RUNTIME_FUNCTION(Runtime_IsAttachedGlobal) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(Object, global, 0);
    if (!global->IsJSGlobalObject()) return isolate->heap()->false_value();
    return isolate->heap()->ToBoolean(
        !JSGlobalObject::cast(global)->IsDetached());
  }
  
  
  RUNTIME_FUNCTION(Runtime_ParseJson) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(String, source, 0);
  
    source = String::Flatten(source);
    // Optimized fast case where we only have ASCII characters.
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result,
        source->IsSeqOneByteString() ? JsonParser<true>::Parse(source)
                                     : JsonParser<false>::Parse(source));
    return *result;
  }
  
  
  bool CodeGenerationFromStringsAllowed(Isolate* isolate,
                                        Handle<Context> context) {
    DCHECK(context->allow_code_gen_from_strings()->IsFalse());
    // Check with callback if set.
    AllowCodeGenerationFromStringsCallback callback =
        isolate->allow_code_gen_callback();
    if (callback == NULL) {
      // No callback set and code generation disallowed.
      return false;
    } else {
      // Callback set. Let it decide if code generation is allowed.
      VMState<EXTERNAL> state(isolate);
      return callback(v8::Utils::ToLocal(context));
    }
  }
  
  
  RUNTIME_FUNCTION(Runtime_CompileString) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(String, source, 0);
    CONVERT_BOOLEAN_ARG_CHECKED(function_literal_only, 1);
  
    // Extract native context.
    Handle<Context> context(isolate->native_context());
  
    // Check if native context allows code generation from
    // strings. Throw an exception if it doesn't.
    if (context->allow_code_gen_from_strings()->IsFalse() &&
        !CodeGenerationFromStringsAllowed(isolate, context)) {
      Handle<Object> error_message =
          context->ErrorMessageForCodeGenerationFromStrings();
      return isolate->Throw(*isolate->factory()->NewEvalError(
          "code_gen_from_strings", HandleVector<Object>(&error_message, 1)));
    }
  
    // Compile source string in the native context.
    ParseRestriction restriction = function_literal_only
        ? ONLY_SINGLE_FUNCTION_LITERAL : NO_PARSE_RESTRICTION;
    Handle<JSFunction> fun;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, fun,
        Compiler::GetFunctionFromEval(
            source, context, SLOPPY, restriction, RelocInfo::kNoPosition));
    return *fun;
  }
  
  
  static ObjectPair CompileGlobalEval(Isolate* isolate,
                                      Handle<String> source,
                                      Handle<Object> receiver,
                                      StrictMode strict_mode,
                                      int scope_position) {
    Handle<Context> context = Handle<Context>(isolate->context());
    Handle<Context> native_context = Handle<Context>(context->native_context());
  
    // Check if native context allows code generation from
    // strings. Throw an exception if it doesn't.
    if (native_context->allow_code_gen_from_strings()->IsFalse() &&
        !CodeGenerationFromStringsAllowed(isolate, native_context)) {
      Handle<Object> error_message =
          native_context->ErrorMessageForCodeGenerationFromStrings();
      isolate->Throw(*isolate->factory()->NewEvalError(
          "code_gen_from_strings", HandleVector<Object>(&error_message, 1)));
      return MakePair(isolate->heap()->exception(), NULL);
    }
  
    // Deal with a normal eval call with a string argument. Compile it
    // and return the compiled function bound in the local context.
    static const ParseRestriction restriction = NO_PARSE_RESTRICTION;
    Handle<JSFunction> compiled;
    ASSIGN_RETURN_ON_EXCEPTION_VALUE(
        isolate, compiled,
        Compiler::GetFunctionFromEval(
            source, context, strict_mode, restriction, scope_position),
        MakePair(isolate->heap()->exception(), NULL));
    return MakePair(*compiled, *receiver);
  }
  
  
  RUNTIME_FUNCTION_RETURN_PAIR(Runtime_ResolvePossiblyDirectEval) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 5);
  
    Handle<Object> callee = args.at<Object>(0);
  
    // If "eval" didn't refer to the original GlobalEval, it's not a
    // direct call to eval.
    // (And even if it is, but the first argument isn't a string, just let
    // execution default to an indirect call to eval, which will also return
    // the first argument without doing anything).
    if (*callee != isolate->native_context()->global_eval_fun() ||
        !args[1]->IsString()) {
      return MakePair(*callee, isolate->heap()->undefined_value());
    }
  
    DCHECK(args[3]->IsSmi());
    DCHECK(args.smi_at(3) == SLOPPY || args.smi_at(3) == STRICT);
    StrictMode strict_mode = static_cast<StrictMode>(args.smi_at(3));
    DCHECK(args[4]->IsSmi());
    return CompileGlobalEval(isolate,
                             args.at<String>(1),
                             args.at<Object>(2),
                             strict_mode,
                             args.smi_at(4));
  }
  
  
  RUNTIME_FUNCTION(Runtime_AllocateInNewSpace) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_SMI_ARG_CHECKED(size, 0);
    RUNTIME_ASSERT(IsAligned(size, kPointerSize));
    RUNTIME_ASSERT(size > 0);
    RUNTIME_ASSERT(size <= Page::kMaxRegularHeapObjectSize);
    return *isolate->factory()->NewFillerObject(size, false, NEW_SPACE);
  }
  
  
  RUNTIME_FUNCTION(Runtime_AllocateInTargetSpace) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_SMI_ARG_CHECKED(size, 0);
    CONVERT_SMI_ARG_CHECKED(flags, 1);
    RUNTIME_ASSERT(IsAligned(size, kPointerSize));
    RUNTIME_ASSERT(size > 0);
    RUNTIME_ASSERT(size <= Page::kMaxRegularHeapObjectSize);
    bool double_align = AllocateDoubleAlignFlag::decode(flags);
    AllocationSpace space = AllocateTargetSpace::decode(flags);
    return *isolate->factory()->NewFillerObject(size, double_align, space);
  }
  
  
  // Push an object unto an array of objects if it is not already in the
  // array.  Returns true if the element was pushed on the stack and
  // false otherwise.
  RUNTIME_FUNCTION(Runtime_PushIfAbsent) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSArray, array, 0);
    CONVERT_ARG_HANDLE_CHECKED(JSReceiver, element, 1);
    RUNTIME_ASSERT(array->HasFastSmiOrObjectElements());
    int length = Smi::cast(array->length())->value();
    FixedArray* elements = FixedArray::cast(array->elements());
    for (int i = 0; i < length; i++) {
      if (elements->get(i) == *element) return isolate->heap()->false_value();
    }
  
    // Strict not needed. Used for cycle detection in Array join implementation.
    RETURN_FAILURE_ON_EXCEPTION(
        isolate,
        JSObject::SetFastElement(array, length, element, SLOPPY, true));
    return isolate->heap()->true_value();
  }
  
  
  /**
   * A simple visitor visits every element of Array's.
   * The backend storage can be a fixed array for fast elements case,
   * or a dictionary for sparse array. Since Dictionary is a subtype
   * of FixedArray, the class can be used by both fast and slow cases.
   * The second parameter of the constructor, fast_elements, specifies
   * whether the storage is a FixedArray or Dictionary.
   *
   * An index limit is used to deal with the situation that a result array
   * length overflows 32-bit non-negative integer.
   */
  class ArrayConcatVisitor {
   public:
    ArrayConcatVisitor(Isolate* isolate,
                       Handle<FixedArray> storage,
                       bool fast_elements) :
        isolate_(isolate),
        storage_(Handle<FixedArray>::cast(
            isolate->global_handles()->Create(*storage))),
        index_offset_(0u),
        fast_elements_(fast_elements),
        exceeds_array_limit_(false) { }
  
    ~ArrayConcatVisitor() {
      clear_storage();
    }
  
    void visit(uint32_t i, Handle<Object> elm) {
      if (i > JSObject::kMaxElementCount - index_offset_) {
        exceeds_array_limit_ = true;
        return;
      }
      uint32_t index = index_offset_ + i;
  
      if (fast_elements_) {
        if (index < static_cast<uint32_t>(storage_->length())) {
          storage_->set(index, *elm);
          return;
        }
        // Our initial estimate of length was foiled, possibly by
        // getters on the arrays increasing the length of later arrays
        // during iteration.
        // This shouldn't happen in anything but pathological cases.
        SetDictionaryMode();
        // Fall-through to dictionary mode.
      }
      DCHECK(!fast_elements_);
      Handle<SeededNumberDictionary> dict(
          SeededNumberDictionary::cast(*storage_));
      Handle<SeededNumberDictionary> result =
          SeededNumberDictionary::AtNumberPut(dict, index, elm);
      if (!result.is_identical_to(dict)) {
        // Dictionary needed to grow.
        clear_storage();
        set_storage(*result);
      }
    }
  
    void increase_index_offset(uint32_t delta) {
      if (JSObject::kMaxElementCount - index_offset_ < delta) {
        index_offset_ = JSObject::kMaxElementCount;
      } else {
        index_offset_ += delta;
      }
      // If the initial length estimate was off (see special case in visit()),
      // but the array blowing the limit didn't contain elements beyond the
      // provided-for index range, go to dictionary mode now.
      if (fast_elements_ &&
          index_offset_ >
              static_cast<uint32_t>(FixedArrayBase::cast(*storage_)->length())) {
        SetDictionaryMode();
      }
    }
  
    bool exceeds_array_limit() {
      return exceeds_array_limit_;
    }
  
    Handle<JSArray> ToArray() {
      Handle<JSArray> array = isolate_->factory()->NewJSArray(0);
      Handle<Object> length =
          isolate_->factory()->NewNumber(static_cast<double>(index_offset_));
      Handle<Map> map = JSObject::GetElementsTransitionMap(
          array,
          fast_elements_ ? FAST_HOLEY_ELEMENTS : DICTIONARY_ELEMENTS);
      array->set_map(*map);
      array->set_length(*length);
      array->set_elements(*storage_);
      return array;
    }
  
   private:
    // Convert storage to dictionary mode.
    void SetDictionaryMode() {
      DCHECK(fast_elements_);
      Handle<FixedArray> current_storage(*storage_);
      Handle<SeededNumberDictionary> slow_storage(
          SeededNumberDictionary::New(isolate_, current_storage->length()));
      uint32_t current_length = static_cast<uint32_t>(current_storage->length());
      for (uint32_t i = 0; i < current_length; i++) {
        HandleScope loop_scope(isolate_);
        Handle<Object> element(current_storage->get(i), isolate_);
        if (!element->IsTheHole()) {
          Handle<SeededNumberDictionary> new_storage =
              SeededNumberDictionary::AtNumberPut(slow_storage, i, element);
          if (!new_storage.is_identical_to(slow_storage)) {
            slow_storage = loop_scope.CloseAndEscape(new_storage);
          }
        }
      }
      clear_storage();
      set_storage(*slow_storage);
      fast_elements_ = false;
    }
  
    inline void clear_storage() {
      GlobalHandles::Destroy(Handle<Object>::cast(storage_).location());
    }
  
    inline void set_storage(FixedArray* storage) {
      storage_ = Handle<FixedArray>::cast(
          isolate_->global_handles()->Create(storage));
    }
  
    Isolate* isolate_;
    Handle<FixedArray> storage_;  // Always a global handle.
    // Index after last seen index. Always less than or equal to
    // JSObject::kMaxElementCount.
    uint32_t index_offset_;
    bool fast_elements_ : 1;
    bool exceeds_array_limit_ : 1;
  };
  
  
  static uint32_t EstimateElementCount(Handle<JSArray> array) {
    uint32_t length = static_cast<uint32_t>(array->length()->Number());
    int element_count = 0;
    switch (array->GetElementsKind()) {
      case FAST_SMI_ELEMENTS:
      case FAST_HOLEY_SMI_ELEMENTS:
      case FAST_ELEMENTS:
      case FAST_HOLEY_ELEMENTS: {
        // Fast elements can't have lengths that are not representable by
        // a 32-bit signed integer.
        DCHECK(static_cast<int32_t>(FixedArray::kMaxLength) >= 0);
        int fast_length = static_cast<int>(length);
        Handle<FixedArray> elements(FixedArray::cast(array->elements()));
        for (int i = 0; i < fast_length; i++) {
          if (!elements->get(i)->IsTheHole()) element_count++;
        }
        break;
      }
      case FAST_DOUBLE_ELEMENTS:
      case FAST_HOLEY_DOUBLE_ELEMENTS: {
        // Fast elements can't have lengths that are not representable by
        // a 32-bit signed integer.
        DCHECK(static_cast<int32_t>(FixedDoubleArray::kMaxLength) >= 0);
        int fast_length = static_cast<int>(length);
        if (array->elements()->IsFixedArray()) {
          DCHECK(FixedArray::cast(array->elements())->length() == 0);
          break;
        }
        Handle<FixedDoubleArray> elements(
            FixedDoubleArray::cast(array->elements()));
        for (int i = 0; i < fast_length; i++) {
          if (!elements->is_the_hole(i)) element_count++;
        }
        break;
      }
      case DICTIONARY_ELEMENTS: {
        Handle<SeededNumberDictionary> dictionary(
            SeededNumberDictionary::cast(array->elements()));
        int capacity = dictionary->Capacity();
        for (int i = 0; i < capacity; i++) {
          Handle<Object> key(dictionary->KeyAt(i), array->GetIsolate());
          if (dictionary->IsKey(*key)) {
            element_count++;
          }
        }
        break;
      }
      case SLOPPY_ARGUMENTS_ELEMENTS:
  #define TYPED_ARRAY_CASE(Type, type, TYPE, ctype, size)                      \
      case EXTERNAL_##TYPE##_ELEMENTS:                                         \
      case TYPE##_ELEMENTS:                                                    \
  
      TYPED_ARRAYS(TYPED_ARRAY_CASE)
  #undef TYPED_ARRAY_CASE
        // External arrays are always dense.
        return length;
    }
    // As an estimate, we assume that the prototype doesn't contain any
    // inherited elements.
    return element_count;
  }
  
  
  
  template<class ExternalArrayClass, class ElementType>
  static void IterateExternalArrayElements(Isolate* isolate,
                                           Handle<JSObject> receiver,
                                           bool elements_are_ints,
                                           bool elements_are_guaranteed_smis,
                                           ArrayConcatVisitor* visitor) {
    Handle<ExternalArrayClass> array(
        ExternalArrayClass::cast(receiver->elements()));
    uint32_t len = static_cast<uint32_t>(array->length());
  
    DCHECK(visitor != NULL);
    if (elements_are_ints) {
      if (elements_are_guaranteed_smis) {
        for (uint32_t j = 0; j < len; j++) {
          HandleScope loop_scope(isolate);
          Handle<Smi> e(Smi::FromInt(static_cast<int>(array->get_scalar(j))),
                        isolate);
          visitor->visit(j, e);
        }
      } else {
        for (uint32_t j = 0; j < len; j++) {
          HandleScope loop_scope(isolate);
          int64_t val = static_cast<int64_t>(array->get_scalar(j));
          if (Smi::IsValid(static_cast<intptr_t>(val))) {
            Handle<Smi> e(Smi::FromInt(static_cast<int>(val)), isolate);
            visitor->visit(j, e);
          } else {
            Handle<Object> e =
                isolate->factory()->NewNumber(static_cast<ElementType>(val));
            visitor->visit(j, e);
          }
        }
      }
    } else {
      for (uint32_t j = 0; j < len; j++) {
        HandleScope loop_scope(isolate);
        Handle<Object> e = isolate->factory()->NewNumber(array->get_scalar(j));
        visitor->visit(j, e);
      }
    }
  }
  
  
  // Used for sorting indices in a List<uint32_t>.
  static int compareUInt32(const uint32_t* ap, const uint32_t* bp) {
    uint32_t a = *ap;
    uint32_t b = *bp;
    return (a == b) ? 0 : (a < b) ? -1 : 1;
  }
  
  
  static void CollectElementIndices(Handle<JSObject> object,
                                    uint32_t range,
                                    List<uint32_t>* indices) {
    Isolate* isolate = object->GetIsolate();
    ElementsKind kind = object->GetElementsKind();
    switch (kind) {
      case FAST_SMI_ELEMENTS:
      case FAST_ELEMENTS:
      case FAST_HOLEY_SMI_ELEMENTS:
      case FAST_HOLEY_ELEMENTS: {
        Handle<FixedArray> elements(FixedArray::cast(object->elements()));
        uint32_t length = static_cast<uint32_t>(elements->length());
        if (range < length) length = range;
        for (uint32_t i = 0; i < length; i++) {
          if (!elements->get(i)->IsTheHole()) {
            indices->Add(i);
          }
        }
        break;
      }
      case FAST_HOLEY_DOUBLE_ELEMENTS:
      case FAST_DOUBLE_ELEMENTS: {
        // TODO(1810): Decide if it's worthwhile to implement this.
        UNREACHABLE();
        break;
      }
      case DICTIONARY_ELEMENTS: {
        Handle<SeededNumberDictionary> dict(
            SeededNumberDictionary::cast(object->elements()));
        uint32_t capacity = dict->Capacity();
        for (uint32_t j = 0; j < capacity; j++) {
          HandleScope loop_scope(isolate);
          Handle<Object> k(dict->KeyAt(j), isolate);
          if (dict->IsKey(*k)) {
            DCHECK(k->IsNumber());
            uint32_t index = static_cast<uint32_t>(k->Number());
            if (index < range) {
              indices->Add(index);
            }
          }
        }
        break;
      }
      default: {
        int dense_elements_length;
        switch (kind) {
  #define TYPED_ARRAY_CASE(Type, type, TYPE, ctype, size)                        \
          case EXTERNAL_##TYPE##_ELEMENTS: {                                     \
            dense_elements_length =                                              \
                External##Type##Array::cast(object->elements())->length();       \
            break;                                                               \
          }
  
          TYPED_ARRAYS(TYPED_ARRAY_CASE)
  #undef TYPED_ARRAY_CASE
  
          default:
            UNREACHABLE();
            dense_elements_length = 0;
            break;
        }
        uint32_t length = static_cast<uint32_t>(dense_elements_length);
        if (range <= length) {
          length = range;
          // We will add all indices, so we might as well clear it first
          // and avoid duplicates.
          indices->Clear();
        }
        for (uint32_t i = 0; i < length; i++) {
          indices->Add(i);
        }
        if (length == range) return;  // All indices accounted for already.
        break;
      }
    }
  
    PrototypeIterator iter(isolate, object);
    if (!iter.IsAtEnd()) {
      // The prototype will usually have no inherited element indices,
      // but we have to check.
      CollectElementIndices(
          Handle<JSObject>::cast(PrototypeIterator::GetCurrent(iter)), range,
          indices);
    }
  }
  
  
  /**
   * A helper function that visits elements of a JSArray in numerical
   * order.
   *
   * The visitor argument called for each existing element in the array
   * with the element index and the element's value.
   * Afterwards it increments the base-index of the visitor by the array
   * length.
   * Returns false if any access threw an exception, otherwise true.
   */
  static bool IterateElements(Isolate* isolate,
                              Handle<JSArray> receiver,
                              ArrayConcatVisitor* visitor) {
    uint32_t length = static_cast<uint32_t>(receiver->length()->Number());
    switch (receiver->GetElementsKind()) {
      case FAST_SMI_ELEMENTS:
      case FAST_ELEMENTS:
      case FAST_HOLEY_SMI_ELEMENTS:
      case FAST_HOLEY_ELEMENTS: {
        // Run through the elements FixedArray and use HasElement and GetElement
        // to check the prototype for missing elements.
        Handle<FixedArray> elements(FixedArray::cast(receiver->elements()));
        int fast_length = static_cast<int>(length);
        DCHECK(fast_length <= elements->length());
        for (int j = 0; j < fast_length; j++) {
          HandleScope loop_scope(isolate);
          Handle<Object> element_value(elements->get(j), isolate);
          if (!element_value->IsTheHole()) {
            visitor->visit(j, element_value);
          } else {
            Maybe<bool> maybe = JSReceiver::HasElement(receiver, j);
            if (!maybe.has_value) return false;
            if (maybe.value) {
              // Call GetElement on receiver, not its prototype, or getters won't
              // have the correct receiver.
              ASSIGN_RETURN_ON_EXCEPTION_VALUE(
                  isolate, element_value,
                  Object::GetElement(isolate, receiver, j), false);
              visitor->visit(j, element_value);
            }
          }
        }
        break;
      }
      case FAST_HOLEY_DOUBLE_ELEMENTS:
      case FAST_DOUBLE_ELEMENTS: {
        // Empty array is FixedArray but not FixedDoubleArray.
        if (length == 0) break;
        // Run through the elements FixedArray and use HasElement and GetElement
        // to check the prototype for missing elements.
        if (receiver->elements()->IsFixedArray()) {
          DCHECK(receiver->elements()->length() == 0);
          break;
        }
        Handle<FixedDoubleArray> elements(
            FixedDoubleArray::cast(receiver->elements()));
        int fast_length = static_cast<int>(length);
        DCHECK(fast_length <= elements->length());
        for (int j = 0; j < fast_length; j++) {
          HandleScope loop_scope(isolate);
          if (!elements->is_the_hole(j)) {
            double double_value = elements->get_scalar(j);
            Handle<Object> element_value =
                isolate->factory()->NewNumber(double_value);
            visitor->visit(j, element_value);
          } else {
            Maybe<bool> maybe = JSReceiver::HasElement(receiver, j);
            if (!maybe.has_value) return false;
            if (maybe.value) {
              // Call GetElement on receiver, not its prototype, or getters won't
              // have the correct receiver.
              Handle<Object> element_value;
              ASSIGN_RETURN_ON_EXCEPTION_VALUE(
                  isolate, element_value,
                  Object::GetElement(isolate, receiver, j), false);
              visitor->visit(j, element_value);
            }
          }
        }
        break;
      }
      case DICTIONARY_ELEMENTS: {
        Handle<SeededNumberDictionary> dict(receiver->element_dictionary());
        List<uint32_t> indices(dict->Capacity() / 2);
        // Collect all indices in the object and the prototypes less
        // than length. This might introduce duplicates in the indices list.
        CollectElementIndices(receiver, length, &indices);
        indices.Sort(&compareUInt32);
        int j = 0;
        int n = indices.length();
        while (j < n) {
          HandleScope loop_scope(isolate);
          uint32_t index = indices[j];
          Handle<Object> element;
          ASSIGN_RETURN_ON_EXCEPTION_VALUE(
              isolate, element,
              Object::GetElement(isolate, receiver, index),
              false);
          visitor->visit(index, element);
          // Skip to next different index (i.e., omit duplicates).
          do {
            j++;
          } while (j < n && indices[j] == index);
        }
        break;
      }
      case EXTERNAL_UINT8_CLAMPED_ELEMENTS: {
        Handle<ExternalUint8ClampedArray> pixels(ExternalUint8ClampedArray::cast(
            receiver->elements()));
        for (uint32_t j = 0; j < length; j++) {
          Handle<Smi> e(Smi::FromInt(pixels->get_scalar(j)), isolate);
          visitor->visit(j, e);
        }
        break;
      }
      case EXTERNAL_INT8_ELEMENTS: {
        IterateExternalArrayElements<ExternalInt8Array, int8_t>(
            isolate, receiver, true, true, visitor);
        break;
      }
      case EXTERNAL_UINT8_ELEMENTS: {
        IterateExternalArrayElements<ExternalUint8Array, uint8_t>(
            isolate, receiver, true, true, visitor);
        break;
      }
      case EXTERNAL_INT16_ELEMENTS: {
        IterateExternalArrayElements<ExternalInt16Array, int16_t>(
            isolate, receiver, true, true, visitor);
        break;
      }
      case EXTERNAL_UINT16_ELEMENTS: {
        IterateExternalArrayElements<ExternalUint16Array, uint16_t>(
            isolate, receiver, true, true, visitor);
        break;
      }
      case EXTERNAL_INT32_ELEMENTS: {
        IterateExternalArrayElements<ExternalInt32Array, int32_t>(
            isolate, receiver, true, false, visitor);
        break;
      }
      case EXTERNAL_UINT32_ELEMENTS: {
        IterateExternalArrayElements<ExternalUint32Array, uint32_t>(
            isolate, receiver, true, false, visitor);
        break;
      }
      case EXTERNAL_FLOAT32_ELEMENTS: {
        IterateExternalArrayElements<ExternalFloat32Array, float>(
            isolate, receiver, false, false, visitor);
        break;
      }
      case EXTERNAL_FLOAT64_ELEMENTS: {
        IterateExternalArrayElements<ExternalFloat64Array, double>(
            isolate, receiver, false, false, visitor);
        break;
      }
      default:
        UNREACHABLE();
        break;
    }
    visitor->increase_index_offset(length);
    return true;
  }
  
  
  /**
   * Array::concat implementation.
   * See ECMAScript 262, 15.4.4.4.
   * TODO(581): Fix non-compliance for very large concatenations and update to
   * following the ECMAScript 5 specification.
   */
  RUNTIME_FUNCTION(Runtime_ArrayConcat) {
    HandleScope handle_scope(isolate);
    DCHECK(args.length() == 1);
  
    CONVERT_ARG_HANDLE_CHECKED(JSArray, arguments, 0);
    int argument_count = static_cast<int>(arguments->length()->Number());
    RUNTIME_ASSERT(arguments->HasFastObjectElements());
    Handle<FixedArray> elements(FixedArray::cast(arguments->elements()));
  
    // Pass 1: estimate the length and number of elements of the result.
    // The actual length can be larger if any of the arguments have getters
    // that mutate other arguments (but will otherwise be precise).
    // The number of elements is precise if there are no inherited elements.
  
    ElementsKind kind = FAST_SMI_ELEMENTS;
  
    uint32_t estimate_result_length = 0;
    uint32_t estimate_nof_elements = 0;
    for (int i = 0; i < argument_count; i++) {
      HandleScope loop_scope(isolate);
      Handle<Object> obj(elements->get(i), isolate);
      uint32_t length_estimate;
      uint32_t element_estimate;
      if (obj->IsJSArray()) {
        Handle<JSArray> array(Handle<JSArray>::cast(obj));
        length_estimate = static_cast<uint32_t>(array->length()->Number());
        if (length_estimate != 0) {
          ElementsKind array_kind =
              GetPackedElementsKind(array->map()->elements_kind());
          if (IsMoreGeneralElementsKindTransition(kind, array_kind)) {
            kind = array_kind;
          }
        }
        element_estimate = EstimateElementCount(array);
      } else {
        if (obj->IsHeapObject()) {
          if (obj->IsNumber()) {
            if (IsMoreGeneralElementsKindTransition(kind, FAST_DOUBLE_ELEMENTS)) {
              kind = FAST_DOUBLE_ELEMENTS;
            }
          } else if (IsMoreGeneralElementsKindTransition(kind, FAST_ELEMENTS)) {
            kind = FAST_ELEMENTS;
          }
        }
        length_estimate = 1;
        element_estimate = 1;
      }
      // Avoid overflows by capping at kMaxElementCount.
      if (JSObject::kMaxElementCount - estimate_result_length <
          length_estimate) {
        estimate_result_length = JSObject::kMaxElementCount;
      } else {
        estimate_result_length += length_estimate;
      }
      if (JSObject::kMaxElementCount - estimate_nof_elements <
          element_estimate) {
        estimate_nof_elements = JSObject::kMaxElementCount;
      } else {
        estimate_nof_elements += element_estimate;
      }
    }
  
    // If estimated number of elements is more than half of length, a
    // fixed array (fast case) is more time and space-efficient than a
    // dictionary.
    bool fast_case = (estimate_nof_elements * 2) >= estimate_result_length;
  
    if (fast_case && kind == FAST_DOUBLE_ELEMENTS) {
      Handle<FixedArrayBase> storage =
          isolate->factory()->NewFixedDoubleArray(estimate_result_length);
      int j = 0;
      bool failure = false;
      if (estimate_result_length > 0) {
        Handle<FixedDoubleArray> double_storage =
            Handle<FixedDoubleArray>::cast(storage);
        for (int i = 0; i < argument_count; i++) {
          Handle<Object> obj(elements->get(i), isolate);
          if (obj->IsSmi()) {
            double_storage->set(j, Smi::cast(*obj)->value());
            j++;
          } else if (obj->IsNumber()) {
            double_storage->set(j, obj->Number());
            j++;
          } else {
            JSArray* array = JSArray::cast(*obj);
            uint32_t length = static_cast<uint32_t>(array->length()->Number());
            switch (array->map()->elements_kind()) {
              case FAST_HOLEY_DOUBLE_ELEMENTS:
              case FAST_DOUBLE_ELEMENTS: {
                // Empty array is FixedArray but not FixedDoubleArray.
                if (length == 0) break;
                FixedDoubleArray* elements =
                    FixedDoubleArray::cast(array->elements());
                for (uint32_t i = 0; i < length; i++) {
                  if (elements->is_the_hole(i)) {
                    // TODO(jkummerow/verwaest): We could be a bit more clever
                    // here: Check if there are no elements/getters on the
                    // prototype chain, and if so, allow creation of a holey
                    // result array.
                    // Same thing below (holey smi case).
                    failure = true;
                    break;
                  }
                  double double_value = elements->get_scalar(i);
                  double_storage->set(j, double_value);
                  j++;
                }
                break;
              }
              case FAST_HOLEY_SMI_ELEMENTS:
              case FAST_SMI_ELEMENTS: {
                FixedArray* elements(
                    FixedArray::cast(array->elements()));
                for (uint32_t i = 0; i < length; i++) {
                  Object* element = elements->get(i);
                  if (element->IsTheHole()) {
                    failure = true;
                    break;
                  }
                  int32_t int_value = Smi::cast(element)->value();
                  double_storage->set(j, int_value);
                  j++;
                }
                break;
              }
              case FAST_HOLEY_ELEMENTS:
              case FAST_ELEMENTS:
                DCHECK_EQ(0, length);
                break;
              default:
                UNREACHABLE();
            }
          }
          if (failure) break;
        }
      }
      if (!failure) {
        Handle<JSArray> array = isolate->factory()->NewJSArray(0);
        Smi* length = Smi::FromInt(j);
        Handle<Map> map;
        map = JSObject::GetElementsTransitionMap(array, kind);
        array->set_map(*map);
        array->set_length(length);
        array->set_elements(*storage);
        return *array;
      }
      // In case of failure, fall through.
    }
  
    Handle<FixedArray> storage;
    if (fast_case) {
      // The backing storage array must have non-existing elements to preserve
      // holes across concat operations.
      storage = isolate->factory()->NewFixedArrayWithHoles(
          estimate_result_length);
    } else {
      // TODO(126): move 25% pre-allocation logic into Dictionary::Allocate
      uint32_t at_least_space_for = estimate_nof_elements +
                                    (estimate_nof_elements >> 2);
      storage = Handle<FixedArray>::cast(
          SeededNumberDictionary::New(isolate, at_least_space_for));
    }
  
    ArrayConcatVisitor visitor(isolate, storage, fast_case);
  
    for (int i = 0; i < argument_count; i++) {
      Handle<Object> obj(elements->get(i), isolate);
      if (obj->IsJSArray()) {
        Handle<JSArray> array = Handle<JSArray>::cast(obj);
        if (!IterateElements(isolate, array, &visitor)) {
          return isolate->heap()->exception();
        }
      } else {
        visitor.visit(0, obj);
        visitor.increase_index_offset(1);
      }
    }
  
    if (visitor.exceeds_array_limit()) {
      return isolate->Throw(
          *isolate->factory()->NewRangeError("invalid_array_length",
                                             HandleVector<Object>(NULL, 0)));
    }
    return *visitor.ToArray();
  }
  
  
  // This will not allocate (flatten the string), but it may run
  // very slowly for very deeply nested ConsStrings.  For debugging use only.
  RUNTIME_FUNCTION(Runtime_GlobalPrint) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
  
    CONVERT_ARG_CHECKED(String, string, 0);
    ConsStringIteratorOp op;
    StringCharacterStream stream(string, &op);
    while (stream.HasMore()) {
      uint16_t character = stream.GetNext();
      PrintF("%c", character);
    }
    return string;
  }
  
  
  // Moves all own elements of an object, that are below a limit, to positions
  // starting at zero. All undefined values are placed after non-undefined values,
  // and are followed by non-existing element. Does not change the length
  // property.
  // Returns the number of non-undefined elements collected.
  // Returns -1 if hole removal is not supported by this method.
  RUNTIME_FUNCTION(Runtime_RemoveArrayHoles) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
    CONVERT_NUMBER_CHECKED(uint32_t, limit, Uint32, args[1]);
    return *JSObject::PrepareElementsForSort(object, limit);
  }
  
  
  // Move contents of argument 0 (an array) to argument 1 (an array)
  RUNTIME_FUNCTION(Runtime_MoveArrayContents) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSArray, from, 0);
    CONVERT_ARG_HANDLE_CHECKED(JSArray, to, 1);
    JSObject::ValidateElements(from);
    JSObject::ValidateElements(to);
  
    Handle<FixedArrayBase> new_elements(from->elements());
    ElementsKind from_kind = from->GetElementsKind();
    Handle<Map> new_map = JSObject::GetElementsTransitionMap(to, from_kind);
    JSObject::SetMapAndElements(to, new_map, new_elements);
    to->set_length(from->length());
  
    JSObject::ResetElements(from);
    from->set_length(Smi::FromInt(0));
  
    JSObject::ValidateElements(to);
    return *to;
  }
  
  
  // How many elements does this object/array have?
  RUNTIME_FUNCTION(Runtime_EstimateNumberOfElements) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSArray, array, 0);
    Handle<FixedArrayBase> elements(array->elements(), isolate);
    SealHandleScope shs(isolate);
    if (elements->IsDictionary()) {
      int result =
          Handle<SeededNumberDictionary>::cast(elements)->NumberOfElements();
      return Smi::FromInt(result);
    } else {
      DCHECK(array->length()->IsSmi());
      // For packed elements, we know the exact number of elements
      int length = elements->length();
      ElementsKind kind = array->GetElementsKind();
      if (IsFastPackedElementsKind(kind)) {
        return Smi::FromInt(length);
      }
      // For holey elements, take samples from the buffer checking for holes
      // to generate the estimate.
      const int kNumberOfHoleCheckSamples = 97;
      int increment = (length < kNumberOfHoleCheckSamples)
                          ? 1
                          : static_cast<int>(length / kNumberOfHoleCheckSamples);
      ElementsAccessor* accessor = array->GetElementsAccessor();
      int holes = 0;
      for (int i = 0; i < length; i += increment) {
        if (!accessor->HasElement(array, array, i, elements)) {
          ++holes;
        }
      }
      int estimate = static_cast<int>((kNumberOfHoleCheckSamples - holes) /
                                      kNumberOfHoleCheckSamples * length);
      return Smi::FromInt(estimate);
    }
  }
  
  
  // Returns an array that tells you where in the [0, length) interval an array
  // might have elements.  Can either return an array of keys (positive integers
  // or undefined) or a number representing the positive length of an interval
  // starting at index 0.
  // Intervals can span over some keys that are not in the object.
  RUNTIME_FUNCTION(Runtime_GetArrayKeys) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, array, 0);
    CONVERT_NUMBER_CHECKED(uint32_t, length, Uint32, args[1]);
    if (array->elements()->IsDictionary()) {
      Handle<FixedArray> keys = isolate->factory()->empty_fixed_array();
      for (PrototypeIterator iter(isolate, array,
                                  PrototypeIterator::START_AT_RECEIVER);
           !iter.IsAtEnd(); iter.Advance()) {
        if (PrototypeIterator::GetCurrent(iter)->IsJSProxy() ||
            JSObject::cast(*PrototypeIterator::GetCurrent(iter))
                ->HasIndexedInterceptor()) {
          // Bail out if we find a proxy or interceptor, likely not worth
          // collecting keys in that case.
          return *isolate->factory()->NewNumberFromUint(length);
        }
        Handle<JSObject> current =
            Handle<JSObject>::cast(PrototypeIterator::GetCurrent(iter));
        Handle<FixedArray> current_keys =
            isolate->factory()->NewFixedArray(current->NumberOfOwnElements(NONE));
        current->GetOwnElementKeys(*current_keys, NONE);
        ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
            isolate, keys, FixedArray::UnionOfKeys(keys, current_keys));
      }
      // Erase any keys >= length.
      // TODO(adamk): Remove this step when the contract of %GetArrayKeys
      // is changed to let this happen on the JS side.
      for (int i = 0; i < keys->length(); i++) {
        if (NumberToUint32(keys->get(i)) >= length) keys->set_undefined(i);
      }
      return *isolate->factory()->NewJSArrayWithElements(keys);
    } else {
      RUNTIME_ASSERT(array->HasFastSmiOrObjectElements() ||
                     array->HasFastDoubleElements());
      uint32_t actual_length = static_cast<uint32_t>(array->elements()->length());
      return *isolate->factory()->NewNumberFromUint(Min(actual_length, length));
    }
  }
  
  
  RUNTIME_FUNCTION(Runtime_LookupAccessor) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
    CONVERT_ARG_HANDLE_CHECKED(JSReceiver, receiver, 0);
    CONVERT_ARG_HANDLE_CHECKED(Name, name, 1);
    CONVERT_SMI_ARG_CHECKED(flag, 2);
    AccessorComponent component = flag == 0 ? ACCESSOR_GETTER : ACCESSOR_SETTER;
    if (!receiver->IsJSObject()) return isolate->heap()->undefined_value();
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result,
        JSObject::GetAccessor(Handle<JSObject>::cast(receiver), name, component));
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_DebugBreak) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 0);
    isolate->debug()->HandleDebugBreak();
    return isolate->heap()->undefined_value();
  }
  
  
  // Helper functions for wrapping and unwrapping stack frame ids.
  static Smi* WrapFrameId(StackFrame::Id id) {
    DCHECK(IsAligned(OffsetFrom(id), static_cast<intptr_t>(4)));
    return Smi::FromInt(id >> 2);
  }
  
  
  static StackFrame::Id UnwrapFrameId(int wrapped) {
    return static_cast<StackFrame::Id>(wrapped << 2);
  }
  
  
  // Adds a JavaScript function as a debug event listener.
  // args[0]: debug event listener function to set or null or undefined for
  //          clearing the event listener function
  // args[1]: object supplied during callback
  RUNTIME_FUNCTION(Runtime_SetDebugEventListener) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 2);
    RUNTIME_ASSERT(args[0]->IsJSFunction() ||
                   args[0]->IsUndefined() ||
                   args[0]->IsNull());
    CONVERT_ARG_HANDLE_CHECKED(Object, callback, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, data, 1);
    isolate->debug()->SetEventListener(callback, data);
  
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_Break) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 0);
    isolate->stack_guard()->RequestDebugBreak();
    return isolate->heap()->undefined_value();
  }
  
  
  static Handle<Object> DebugLookupResultValue(Isolate* isolate,
                                               Handle<Object> receiver,
                                               Handle<Name> name,
                                               LookupResult* result,
                                               bool* has_caught = NULL) {
    Handle<Object> value = isolate->factory()->undefined_value();
    if  (!result->IsFound()) return value;
    switch (result->type()) {
      case NORMAL:
        return JSObject::GetNormalizedProperty(handle(result->holder(), isolate),
                                               result);
      case FIELD:
        return JSObject::FastPropertyAt(handle(result->holder(), isolate),
                                        result->representation(),
                                        result->GetFieldIndex());
      case CONSTANT:
        return handle(result->GetConstant(), isolate);
      case CALLBACKS: {
        Handle<Object> structure(result->GetCallbackObject(), isolate);
        DCHECK(!structure->IsForeign());
        if (structure->IsAccessorInfo()) {
          MaybeHandle<Object> obj = JSObject::GetPropertyWithAccessor(
              receiver, name, handle(result->holder(), isolate), structure);
          if (!obj.ToHandle(&value)) {
            value = handle(isolate->pending_exception(), isolate);
            isolate->clear_pending_exception();
            if (has_caught != NULL) *has_caught = true;
            return value;
          }
        }
        break;
      }
      case INTERCEPTOR:
      case HANDLER:
        break;
      case NONEXISTENT:
        UNREACHABLE();
        break;
    }
    return value;
  }
  
  
  // Get debugger related details for an object property.
  // args[0]: object holding property
  // args[1]: name of the property
  //
  // The array returned contains the following information:
  // 0: Property value
  // 1: Property details
  // 2: Property value is exception
  // 3: Getter function if defined
  // 4: Setter function if defined
  // Items 2-4 are only filled if the property has either a getter or a setter
  // defined through __defineGetter__ and/or __defineSetter__.
  RUNTIME_FUNCTION(Runtime_DebugGetPropertyDetails) {
    HandleScope scope(isolate);
  
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_HANDLE_CHECKED(JSObject, obj, 0);
    CONVERT_ARG_HANDLE_CHECKED(Name, name, 1);
  
    // Make sure to set the current context to the context before the debugger was
    // entered (if the debugger is entered). The reason for switching context here
    // is that for some property lookups (accessors and interceptors) callbacks
    // into the embedding application can occour, and the embedding application
    // could have the assumption that its own native context is the current
    // context and not some internal debugger context.
    SaveContext save(isolate);
    if (isolate->debug()->in_debug_scope()) {
      isolate->set_context(*isolate->debug()->debugger_entry()->GetContext());
    }
  
    // Check if the name is trivially convertible to an index and get the element
    // if so.
    uint32_t index;
    if (name->AsArrayIndex(&index)) {
      Handle<FixedArray> details = isolate->factory()->NewFixedArray(2);
      Handle<Object> element_or_char;
      ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
          isolate, element_or_char,
          Runtime::GetElementOrCharAt(isolate, obj, index));
      details->set(0, *element_or_char);
      details->set(
          1, PropertyDetails(NONE, NORMAL, Representation::None()).AsSmi());
      return *isolate->factory()->NewJSArrayWithElements(details);
    }
  
    // Find the number of objects making up this.
    int length = OwnPrototypeChainLength(*obj);
  
    // Try own lookup on each of the objects.
    PrototypeIterator iter(isolate, obj, PrototypeIterator::START_AT_RECEIVER);
    for (int i = 0; i < length; i++) {
      DCHECK(!iter.IsAtEnd());
      Handle<JSObject> jsproto =
          Handle<JSObject>::cast(PrototypeIterator::GetCurrent(iter));
      LookupResult result(isolate);
      jsproto->LookupOwn(name, &result);
      if (result.IsFound()) {
        // LookupResult is not GC safe as it holds raw object pointers.
        // GC can happen later in this code so put the required fields into
        // local variables using handles when required for later use.
        Handle<Object> result_callback_obj;
        if (result.IsPropertyCallbacks()) {
          result_callback_obj = Handle<Object>(result.GetCallbackObject(),
                                               isolate);
        }
  
  
        bool has_caught = false;
        Handle<Object> value = DebugLookupResultValue(
            isolate, obj, name, &result, &has_caught);
  
        // If the callback object is a fixed array then it contains JavaScript
        // getter and/or setter.
        bool has_js_accessors = result.IsPropertyCallbacks() &&
                                result_callback_obj->IsAccessorPair();
        Handle<FixedArray> details =
            isolate->factory()->NewFixedArray(has_js_accessors ? 5 : 2);
        details->set(0, *value);
        details->set(1, result.GetPropertyDetails().AsSmi());
        if (has_js_accessors) {
          AccessorPair* accessors = AccessorPair::cast(*result_callback_obj);
          details->set(2, isolate->heap()->ToBoolean(has_caught));
          details->set(3, accessors->GetComponent(ACCESSOR_GETTER));
          details->set(4, accessors->GetComponent(ACCESSOR_SETTER));
        }
  
        return *isolate->factory()->NewJSArrayWithElements(details);
      }
      iter.Advance();
    }
  
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_DebugGetProperty) {
    HandleScope scope(isolate);
  
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_HANDLE_CHECKED(JSObject, obj, 0);
    CONVERT_ARG_HANDLE_CHECKED(Name, name, 1);
  
    LookupResult result(isolate);
    obj->Lookup(name, &result);
    return *DebugLookupResultValue(isolate, obj, name, &result);
  }
  
  
  // Return the property type calculated from the property details.
  // args[0]: smi with property details.
  RUNTIME_FUNCTION(Runtime_DebugPropertyTypeFromDetails) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_PROPERTY_DETAILS_CHECKED(details, 0);
    return Smi::FromInt(static_cast<int>(details.type()));
  }
  
  
  // Return the property attribute calculated from the property details.
  // args[0]: smi with property details.
  RUNTIME_FUNCTION(Runtime_DebugPropertyAttributesFromDetails) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_PROPERTY_DETAILS_CHECKED(details, 0);
    return Smi::FromInt(static_cast<int>(details.attributes()));
  }
  
  
  // Return the property insertion index calculated from the property details.
  // args[0]: smi with property details.
  RUNTIME_FUNCTION(Runtime_DebugPropertyIndexFromDetails) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_PROPERTY_DETAILS_CHECKED(details, 0);
    // TODO(verwaest): Depends on the type of details.
    return Smi::FromInt(details.dictionary_index());
  }
  
  
  // Return property value from named interceptor.
  // args[0]: object
  // args[1]: property name
  RUNTIME_FUNCTION(Runtime_DebugNamedInterceptorPropertyValue) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, obj, 0);
    RUNTIME_ASSERT(obj->HasNamedInterceptor());
    CONVERT_ARG_HANDLE_CHECKED(Name, name, 1);
  
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result, JSObject::GetProperty(obj, name));
    return *result;
  }
  
  
  // Return element value from indexed interceptor.
  // args[0]: object
  // args[1]: index
  RUNTIME_FUNCTION(Runtime_DebugIndexedInterceptorElementValue) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, obj, 0);
    RUNTIME_ASSERT(obj->HasIndexedInterceptor());
    CONVERT_NUMBER_CHECKED(uint32_t, index, Uint32, args[1]);
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result, JSObject::GetElementWithInterceptor(obj, obj, index));
    return *result;
  }
  
  
  static bool CheckExecutionState(Isolate* isolate, int break_id) {
    return !isolate->debug()->debug_context().is_null() &&
           isolate->debug()->break_id() != 0 &&
           isolate->debug()->break_id() == break_id;
  }
  
  
  RUNTIME_FUNCTION(Runtime_CheckExecutionState) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_NUMBER_CHECKED(int, break_id, Int32, args[0]);
    RUNTIME_ASSERT(CheckExecutionState(isolate, break_id));
    return isolate->heap()->true_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetFrameCount) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_NUMBER_CHECKED(int, break_id, Int32, args[0]);
    RUNTIME_ASSERT(CheckExecutionState(isolate, break_id));
  
    // Count all frames which are relevant to debugging stack trace.
    int n = 0;
    StackFrame::Id id = isolate->debug()->break_frame_id();
    if (id == StackFrame::NO_ID) {
      // If there is no JavaScript stack frame count is 0.
      return Smi::FromInt(0);
    }
  
    for (JavaScriptFrameIterator it(isolate, id); !it.done(); it.Advance()) {
      List<FrameSummary> frames(FLAG_max_inlining_levels + 1);
      it.frame()->Summarize(&frames);
      for (int i = frames.length() - 1; i >= 0; i--) {
        // Omit functions from native scripts.
        if (!frames[i].function()->IsFromNativeScript()) n++;
      }
    }
    return Smi::FromInt(n);
  }
  
  
  class FrameInspector {
   public:
    FrameInspector(JavaScriptFrame* frame,
                   int inlined_jsframe_index,
                   Isolate* isolate)
        : frame_(frame), deoptimized_frame_(NULL), isolate_(isolate) {
      // Calculate the deoptimized frame.
      if (frame->is_optimized()) {
        deoptimized_frame_ = Deoptimizer::DebuggerInspectableFrame(
            frame, inlined_jsframe_index, isolate);
      }
      has_adapted_arguments_ = frame_->has_adapted_arguments();
      is_bottommost_ = inlined_jsframe_index == 0;
      is_optimized_ = frame_->is_optimized();
    }
  
    ~FrameInspector() {
      // Get rid of the calculated deoptimized frame if any.
      if (deoptimized_frame_ != NULL) {
        Deoptimizer::DeleteDebuggerInspectableFrame(deoptimized_frame_,
                                                    isolate_);
      }
    }
  
    int GetParametersCount() {
      return is_optimized_
          ? deoptimized_frame_->parameters_count()
          : frame_->ComputeParametersCount();
    }
    int expression_count() { return deoptimized_frame_->expression_count(); }
    Object* GetFunction() {
      return is_optimized_
          ? deoptimized_frame_->GetFunction()
          : frame_->function();
    }
    Object* GetParameter(int index) {
      return is_optimized_
          ? deoptimized_frame_->GetParameter(index)
          : frame_->GetParameter(index);
    }
    Object* GetExpression(int index) {
      return is_optimized_
          ? deoptimized_frame_->GetExpression(index)
          : frame_->GetExpression(index);
    }
    int GetSourcePosition() {
      return is_optimized_
          ? deoptimized_frame_->GetSourcePosition()
          : frame_->LookupCode()->SourcePosition(frame_->pc());
    }
    bool IsConstructor() {
      return is_optimized_ && !is_bottommost_
          ? deoptimized_frame_->HasConstructStub()
          : frame_->IsConstructor();
    }
  
    // To inspect all the provided arguments the frame might need to be
    // replaced with the arguments frame.
    void SetArgumentsFrame(JavaScriptFrame* frame) {
      DCHECK(has_adapted_arguments_);
      frame_ = frame;
      is_optimized_ = frame_->is_optimized();
      DCHECK(!is_optimized_);
    }
  
   private:
    JavaScriptFrame* frame_;
    DeoptimizedFrameInfo* deoptimized_frame_;
    Isolate* isolate_;
    bool is_optimized_;
    bool is_bottommost_;
    bool has_adapted_arguments_;
  
    DISALLOW_COPY_AND_ASSIGN(FrameInspector);
  };
  
  
  static const int kFrameDetailsFrameIdIndex = 0;
  static const int kFrameDetailsReceiverIndex = 1;
  static const int kFrameDetailsFunctionIndex = 2;
  static const int kFrameDetailsArgumentCountIndex = 3;
  static const int kFrameDetailsLocalCountIndex = 4;
  static const int kFrameDetailsSourcePositionIndex = 5;
  static const int kFrameDetailsConstructCallIndex = 6;
  static const int kFrameDetailsAtReturnIndex = 7;
  static const int kFrameDetailsFlagsIndex = 8;
  static const int kFrameDetailsFirstDynamicIndex = 9;
  
  
  static SaveContext* FindSavedContextForFrame(Isolate* isolate,
                                               JavaScriptFrame* frame) {
    SaveContext* save = isolate->save_context();
    while (save != NULL && !save->IsBelowFrame(frame)) {
      save = save->prev();
    }
    DCHECK(save != NULL);
    return save;
  }
  
  
  RUNTIME_FUNCTION(Runtime_IsOptimized) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 0);
    JavaScriptFrameIterator it(isolate);
    JavaScriptFrame* frame = it.frame();
    return isolate->heap()->ToBoolean(frame->is_optimized());
  }
  
  
  // Advances the iterator to the frame that matches the index and returns the
  // inlined frame index, or -1 if not found.  Skips native JS functions.
  static int FindIndexedNonNativeFrame(JavaScriptFrameIterator* it, int index) {
    int count = -1;
    for (; !it->done(); it->Advance()) {
      List<FrameSummary> frames(FLAG_max_inlining_levels + 1);
      it->frame()->Summarize(&frames);
      for (int i = frames.length() - 1; i >= 0; i--) {
        // Omit functions from native scripts.
        if (frames[i].function()->IsFromNativeScript()) continue;
        if (++count == index) return i;
      }
    }
    return -1;
  }
  
  
  // Return an array with frame details
  // args[0]: number: break id
  // args[1]: number: frame index
  //
  // The array returned contains the following information:
  // 0: Frame id
  // 1: Receiver
  // 2: Function
  // 3: Argument count
  // 4: Local count
  // 5: Source position
  // 6: Constructor call
  // 7: Is at return
  // 8: Flags
  // Arguments name, value
  // Locals name, value
  // Return value if any
  RUNTIME_FUNCTION(Runtime_GetFrameDetails) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_NUMBER_CHECKED(int, break_id, Int32, args[0]);
    RUNTIME_ASSERT(CheckExecutionState(isolate, break_id));
  
    CONVERT_NUMBER_CHECKED(int, index, Int32, args[1]);
    Heap* heap = isolate->heap();
  
    // Find the relevant frame with the requested index.
    StackFrame::Id id = isolate->debug()->break_frame_id();
    if (id == StackFrame::NO_ID) {
      // If there are no JavaScript stack frames return undefined.
      return heap->undefined_value();
    }
  
    JavaScriptFrameIterator it(isolate, id);
    // Inlined frame index in optimized frame, starting from outer function.
    int inlined_jsframe_index = FindIndexedNonNativeFrame(&it, index);
    if (inlined_jsframe_index == -1) return heap->undefined_value();
  
    FrameInspector frame_inspector(it.frame(), inlined_jsframe_index, isolate);
    bool is_optimized = it.frame()->is_optimized();
  
    // Traverse the saved contexts chain to find the active context for the
    // selected frame.
    SaveContext* save = FindSavedContextForFrame(isolate, it.frame());
  
    // Get the frame id.
    Handle<Object> frame_id(WrapFrameId(it.frame()->id()), isolate);
  
    // Find source position in unoptimized code.
    int position = frame_inspector.GetSourcePosition();
  
    // Check for constructor frame.
    bool constructor = frame_inspector.IsConstructor();
  
    // Get scope info and read from it for local variable information.
    Handle<JSFunction> function(JSFunction::cast(frame_inspector.GetFunction()));
    Handle<SharedFunctionInfo> shared(function->shared());
    Handle<ScopeInfo> scope_info(shared->scope_info());
    DCHECK(*scope_info != ScopeInfo::Empty(isolate));
  
    // Get the locals names and values into a temporary array.
    int local_count = scope_info->LocalCount();
    for (int slot = 0; slot < scope_info->LocalCount(); ++slot) {
      // Hide compiler-introduced temporary variables, whether on the stack or on
      // the context.
      if (scope_info->LocalIsSynthetic(slot))
        local_count--;
    }
  
    Handle<FixedArray> locals =
        isolate->factory()->NewFixedArray(local_count * 2);
  
    // Fill in the values of the locals.
    int local = 0;
    int i = 0;
    for (; i < scope_info->StackLocalCount(); ++i) {
      // Use the value from the stack.
      if (scope_info->LocalIsSynthetic(i))
        continue;
      locals->set(local * 2, scope_info->LocalName(i));
      locals->set(local * 2 + 1, frame_inspector.GetExpression(i));
      local++;
    }
    if (local < local_count) {
      // Get the context containing declarations.
      Handle<Context> context(
          Context::cast(it.frame()->context())->declaration_context());
      for (; i < scope_info->LocalCount(); ++i) {
        if (scope_info->LocalIsSynthetic(i))
          continue;
        Handle<String> name(scope_info->LocalName(i));
        VariableMode mode;
        InitializationFlag init_flag;
        MaybeAssignedFlag maybe_assigned_flag;
        locals->set(local * 2, *name);
        int context_slot_index = ScopeInfo::ContextSlotIndex(
            scope_info, name, &mode, &init_flag, &maybe_assigned_flag);
        Object* value = context->get(context_slot_index);
        locals->set(local * 2 + 1, value);
        local++;
      }
    }
  
    // Check whether this frame is positioned at return. If not top
    // frame or if the frame is optimized it cannot be at a return.
    bool at_return = false;
    if (!is_optimized && index == 0) {
      at_return = isolate->debug()->IsBreakAtReturn(it.frame());
    }
  
    // If positioned just before return find the value to be returned and add it
    // to the frame information.
    Handle<Object> return_value = isolate->factory()->undefined_value();
    if (at_return) {
      StackFrameIterator it2(isolate);
      Address internal_frame_sp = NULL;
      while (!it2.done()) {
        if (it2.frame()->is_internal()) {
          internal_frame_sp = it2.frame()->sp();
        } else {
          if (it2.frame()->is_java_script()) {
            if (it2.frame()->id() == it.frame()->id()) {
              // The internal frame just before the JavaScript frame contains the
              // value to return on top. A debug break at return will create an
              // internal frame to store the return value (eax/rax/r0) before
              // entering the debug break exit frame.
              if (internal_frame_sp != NULL) {
                return_value =
                    Handle<Object>(Memory::Object_at(internal_frame_sp),
                                   isolate);
                break;
              }
            }
          }
  
          // Indicate that the previous frame was not an internal frame.
          internal_frame_sp = NULL;
        }
        it2.Advance();
      }
    }
  
    // Now advance to the arguments adapter frame (if any). It contains all
    // the provided parameters whereas the function frame always have the number
    // of arguments matching the functions parameters. The rest of the
    // information (except for what is collected above) is the same.
    if ((inlined_jsframe_index == 0) && it.frame()->has_adapted_arguments()) {
      it.AdvanceToArgumentsFrame();
      frame_inspector.SetArgumentsFrame(it.frame());
    }
  
    // Find the number of arguments to fill. At least fill the number of
    // parameters for the function and fill more if more parameters are provided.
    int argument_count = scope_info->ParameterCount();
    if (argument_count < frame_inspector.GetParametersCount()) {
      argument_count = frame_inspector.GetParametersCount();
    }
  
    // Calculate the size of the result.
    int details_size = kFrameDetailsFirstDynamicIndex +
                       2 * (argument_count + local_count) +
                       (at_return ? 1 : 0);
    Handle<FixedArray> details = isolate->factory()->NewFixedArray(details_size);
  
    // Add the frame id.
    details->set(kFrameDetailsFrameIdIndex, *frame_id);
  
    // Add the function (same as in function frame).
    details->set(kFrameDetailsFunctionIndex, frame_inspector.GetFunction());
  
    // Add the arguments count.
    details->set(kFrameDetailsArgumentCountIndex, Smi::FromInt(argument_count));
  
    // Add the locals count
    details->set(kFrameDetailsLocalCountIndex,
                 Smi::FromInt(local_count));
  
    // Add the source position.
    if (position != RelocInfo::kNoPosition) {
      details->set(kFrameDetailsSourcePositionIndex, Smi::FromInt(position));
    } else {
      details->set(kFrameDetailsSourcePositionIndex, heap->undefined_value());
    }
  
    // Add the constructor information.
    details->set(kFrameDetailsConstructCallIndex, heap->ToBoolean(constructor));
  
    // Add the at return information.
    details->set(kFrameDetailsAtReturnIndex, heap->ToBoolean(at_return));
  
    // Add flags to indicate information on whether this frame is
    //   bit 0: invoked in the debugger context.
    //   bit 1: optimized frame.
    //   bit 2: inlined in optimized frame
    int flags = 0;
    if (*save->context() == *isolate->debug()->debug_context()) {
      flags |= 1 << 0;
    }
    if (is_optimized) {
      flags |= 1 << 1;
      flags |= inlined_jsframe_index << 2;
    }
    details->set(kFrameDetailsFlagsIndex, Smi::FromInt(flags));
  
    // Fill the dynamic part.
    int details_index = kFrameDetailsFirstDynamicIndex;
  
    // Add arguments name and value.
    for (int i = 0; i < argument_count; i++) {
      // Name of the argument.
      if (i < scope_info->ParameterCount()) {
        details->set(details_index++, scope_info->ParameterName(i));
      } else {
        details->set(details_index++, heap->undefined_value());
      }
  
      // Parameter value.
      if (i < frame_inspector.GetParametersCount()) {
        // Get the value from the stack.
        details->set(details_index++, frame_inspector.GetParameter(i));
      } else {
        details->set(details_index++, heap->undefined_value());
      }
    }
  
    // Add locals name and value from the temporary copy from the function frame.
    for (int i = 0; i < local_count * 2; i++) {
      details->set(details_index++, locals->get(i));
    }
  
    // Add the value being returned.
    if (at_return) {
      details->set(details_index++, *return_value);
    }
  
    // Add the receiver (same as in function frame).
    // THIS MUST BE DONE LAST SINCE WE MIGHT ADVANCE
    // THE FRAME ITERATOR TO WRAP THE RECEIVER.
    Handle<Object> receiver(it.frame()->receiver(), isolate);
    if (!receiver->IsJSObject() &&
        shared->strict_mode() == SLOPPY &&
        !function->IsBuiltin()) {
      // If the receiver is not a JSObject and the function is not a
      // builtin or strict-mode we have hit an optimization where a
      // value object is not converted into a wrapped JS objects. To
      // hide this optimization from the debugger, we wrap the receiver
      // by creating correct wrapper object based on the calling frame's
      // native context.
      it.Advance();
      if (receiver->IsUndefined()) {
        receiver = handle(function->global_proxy());
      } else {
        DCHECK(!receiver->IsNull());
        Context* context = Context::cast(it.frame()->context());
        Handle<Context> native_context(Context::cast(context->native_context()));
        receiver = Object::ToObject(
            isolate, receiver, native_context).ToHandleChecked();
      }
    }
    details->set(kFrameDetailsReceiverIndex, *receiver);
  
    DCHECK_EQ(details_size, details_index);
    return *isolate->factory()->NewJSArrayWithElements(details);
  }
  
  
  static bool ParameterIsShadowedByContextLocal(Handle<ScopeInfo> info,
                                                Handle<String> parameter_name) {
    VariableMode mode;
    InitializationFlag init_flag;
    MaybeAssignedFlag maybe_assigned_flag;
    return ScopeInfo::ContextSlotIndex(info, parameter_name, &mode, &init_flag,
                                       &maybe_assigned_flag) != -1;
  }
  
  
  // Create a plain JSObject which materializes the local scope for the specified
  // frame.
  MUST_USE_RESULT
  static MaybeHandle<JSObject> MaterializeStackLocalsWithFrameInspector(
      Isolate* isolate,
      Handle<JSObject> target,
      Handle<JSFunction> function,
      FrameInspector* frame_inspector) {
    Handle<SharedFunctionInfo> shared(function->shared());
    Handle<ScopeInfo> scope_info(shared->scope_info());
  
    // First fill all parameters.
    for (int i = 0; i < scope_info->ParameterCount(); ++i) {
      // Do not materialize the parameter if it is shadowed by a context local.
      Handle<String> name(scope_info->ParameterName(i));
      if (ParameterIsShadowedByContextLocal(scope_info, name)) continue;
  
      HandleScope scope(isolate);
      Handle<Object> value(i < frame_inspector->GetParametersCount()
                               ? frame_inspector->GetParameter(i)
                               : isolate->heap()->undefined_value(),
                           isolate);
      DCHECK(!value->IsTheHole());
  
      RETURN_ON_EXCEPTION(
          isolate,
          Runtime::SetObjectProperty(isolate, target, name, value, SLOPPY),
          JSObject);
    }
  
    // Second fill all stack locals.
    for (int i = 0; i < scope_info->StackLocalCount(); ++i) {
      if (scope_info->LocalIsSynthetic(i)) continue;
      Handle<String> name(scope_info->StackLocalName(i));
      Handle<Object> value(frame_inspector->GetExpression(i), isolate);
      if (value->IsTheHole()) continue;
  
      RETURN_ON_EXCEPTION(
          isolate,
          Runtime::SetObjectProperty(isolate, target, name, value, SLOPPY),
          JSObject);
    }
  
    return target;
  }
  
  
  static void UpdateStackLocalsFromMaterializedObject(Isolate* isolate,
                                                      Handle<JSObject> target,
                                                      Handle<JSFunction> function,
                                                      JavaScriptFrame* frame,
                                                      int inlined_jsframe_index) {
    if (inlined_jsframe_index != 0 || frame->is_optimized()) {
      // Optimized frames are not supported.
      // TODO(yangguo): make sure all code deoptimized when debugger is active
      //                and assert that this cannot happen.
      return;
    }
  
    Handle<SharedFunctionInfo> shared(function->shared());
    Handle<ScopeInfo> scope_info(shared->scope_info());
  
    // Parameters.
    for (int i = 0; i < scope_info->ParameterCount(); ++i) {
      // Shadowed parameters were not materialized.
      Handle<String> name(scope_info->ParameterName(i));
      if (ParameterIsShadowedByContextLocal(scope_info, name)) continue;
  
      DCHECK(!frame->GetParameter(i)->IsTheHole());
      HandleScope scope(isolate);
      Handle<Object> value =
          Object::GetPropertyOrElement(target, name).ToHandleChecked();
      frame->SetParameterValue(i, *value);
    }
  
    // Stack locals.
    for (int i = 0; i < scope_info->StackLocalCount(); ++i) {
      if (scope_info->LocalIsSynthetic(i)) continue;
      if (frame->GetExpression(i)->IsTheHole()) continue;
      HandleScope scope(isolate);
      Handle<Object> value = Object::GetPropertyOrElement(
          target,
          handle(scope_info->StackLocalName(i), isolate)).ToHandleChecked();
      frame->SetExpression(i, *value);
    }
  }
  
  
  MUST_USE_RESULT static MaybeHandle<JSObject> MaterializeLocalContext(
      Isolate* isolate,
      Handle<JSObject> target,
      Handle<JSFunction> function,
      JavaScriptFrame* frame) {
    HandleScope scope(isolate);
    Handle<SharedFunctionInfo> shared(function->shared());
    Handle<ScopeInfo> scope_info(shared->scope_info());
  
    if (!scope_info->HasContext()) return target;
  
    // Third fill all context locals.
    Handle<Context> frame_context(Context::cast(frame->context()));
    Handle<Context> function_context(frame_context->declaration_context());
    if (!ScopeInfo::CopyContextLocalsToScopeObject(
            scope_info, function_context, target)) {
      return MaybeHandle<JSObject>();
    }
  
    // Finally copy any properties from the function context extension.
    // These will be variables introduced by eval.
    if (function_context->closure() == *function) {
      if (function_context->has_extension() &&
          !function_context->IsNativeContext()) {
        Handle<JSObject> ext(JSObject::cast(function_context->extension()));
        Handle<FixedArray> keys;
        ASSIGN_RETURN_ON_EXCEPTION(
            isolate, keys,
            JSReceiver::GetKeys(ext, JSReceiver::INCLUDE_PROTOS),
            JSObject);
  
        for (int i = 0; i < keys->length(); i++) {
          // Names of variables introduced by eval are strings.
          DCHECK(keys->get(i)->IsString());
          Handle<String> key(String::cast(keys->get(i)));
          Handle<Object> value;
          ASSIGN_RETURN_ON_EXCEPTION(
              isolate, value, Object::GetPropertyOrElement(ext, key), JSObject);
          RETURN_ON_EXCEPTION(
              isolate,
              Runtime::SetObjectProperty(isolate, target, key, value, SLOPPY),
              JSObject);
        }
      }
    }
  
    return target;
  }
  
  
  MUST_USE_RESULT static MaybeHandle<JSObject> MaterializeLocalScope(
      Isolate* isolate,
      JavaScriptFrame* frame,
      int inlined_jsframe_index) {
    FrameInspector frame_inspector(frame, inlined_jsframe_index, isolate);
    Handle<JSFunction> function(JSFunction::cast(frame_inspector.GetFunction()));
  
    Handle<JSObject> local_scope =
        isolate->factory()->NewJSObject(isolate->object_function());
    ASSIGN_RETURN_ON_EXCEPTION(
        isolate, local_scope,
        MaterializeStackLocalsWithFrameInspector(
            isolate, local_scope, function, &frame_inspector),
        JSObject);
  
    return MaterializeLocalContext(isolate, local_scope, function, frame);
  }
  
  
  // Set the context local variable value.
  static bool SetContextLocalValue(Isolate* isolate,
                                   Handle<ScopeInfo> scope_info,
                                   Handle<Context> context,
                                   Handle<String> variable_name,
                                   Handle<Object> new_value) {
    for (int i = 0; i < scope_info->ContextLocalCount(); i++) {
      Handle<String> next_name(scope_info->ContextLocalName(i));
      if (String::Equals(variable_name, next_name)) {
        VariableMode mode;
        InitializationFlag init_flag;
        MaybeAssignedFlag maybe_assigned_flag;
        int context_index = ScopeInfo::ContextSlotIndex(
            scope_info, next_name, &mode, &init_flag, &maybe_assigned_flag);
        context->set(context_index, *new_value);
        return true;
      }
    }
  
    return false;
  }
  
  
  static bool SetLocalVariableValue(Isolate* isolate,
                                    JavaScriptFrame* frame,
                                    int inlined_jsframe_index,
                                    Handle<String> variable_name,
                                    Handle<Object> new_value) {
    if (inlined_jsframe_index != 0 || frame->is_optimized()) {
      // Optimized frames are not supported.
      return false;
    }
  
    Handle<JSFunction> function(frame->function());
    Handle<SharedFunctionInfo> shared(function->shared());
    Handle<ScopeInfo> scope_info(shared->scope_info());
  
    bool default_result = false;
  
    // Parameters.
    for (int i = 0; i < scope_info->ParameterCount(); ++i) {
      HandleScope scope(isolate);
      if (String::Equals(handle(scope_info->ParameterName(i)), variable_name)) {
        frame->SetParameterValue(i, *new_value);
        // Argument might be shadowed in heap context, don't stop here.
        default_result = true;
      }
    }
  
    // Stack locals.
    for (int i = 0; i < scope_info->StackLocalCount(); ++i) {
      HandleScope scope(isolate);
      if (String::Equals(handle(scope_info->StackLocalName(i)), variable_name)) {
        frame->SetExpression(i, *new_value);
        return true;
      }
    }
  
    if (scope_info->HasContext()) {
      // Context locals.
      Handle<Context> frame_context(Context::cast(frame->context()));
      Handle<Context> function_context(frame_context->declaration_context());
      if (SetContextLocalValue(
          isolate, scope_info, function_context, variable_name, new_value)) {
        return true;
      }
  
      // Function context extension. These are variables introduced by eval.
      if (function_context->closure() == *function) {
        if (function_context->has_extension() &&
            !function_context->IsNativeContext()) {
          Handle<JSObject> ext(JSObject::cast(function_context->extension()));
  
          Maybe<bool> maybe = JSReceiver::HasProperty(ext, variable_name);
          DCHECK(maybe.has_value);
          if (maybe.value) {
            // We don't expect this to do anything except replacing
            // property value.
            Runtime::SetObjectProperty(isolate, ext, variable_name, new_value,
                                       SLOPPY).Assert();
            return true;
          }
        }
      }
    }
  
    return default_result;
  }
  
  
  // Create a plain JSObject which materializes the closure content for the
  // context.
  MUST_USE_RESULT static MaybeHandle<JSObject> MaterializeClosure(
      Isolate* isolate,
      Handle<Context> context) {
    DCHECK(context->IsFunctionContext());
  
    Handle<SharedFunctionInfo> shared(context->closure()->shared());
    Handle<ScopeInfo> scope_info(shared->scope_info());
  
    // Allocate and initialize a JSObject with all the content of this function
    // closure.
    Handle<JSObject> closure_scope =
        isolate->factory()->NewJSObject(isolate->object_function());
  
    // Fill all context locals to the context extension.
    if (!ScopeInfo::CopyContextLocalsToScopeObject(
            scope_info, context, closure_scope)) {
      return MaybeHandle<JSObject>();
    }
  
    // Finally copy any properties from the function context extension. This will
    // be variables introduced by eval.
    if (context->has_extension()) {
      Handle<JSObject> ext(JSObject::cast(context->extension()));
      Handle<FixedArray> keys;
      ASSIGN_RETURN_ON_EXCEPTION(
          isolate, keys,
          JSReceiver::GetKeys(ext, JSReceiver::INCLUDE_PROTOS), JSObject);
  
      for (int i = 0; i < keys->length(); i++) {
        HandleScope scope(isolate);
        // Names of variables introduced by eval are strings.
        DCHECK(keys->get(i)->IsString());
        Handle<String> key(String::cast(keys->get(i)));
        Handle<Object> value;
        ASSIGN_RETURN_ON_EXCEPTION(
            isolate, value, Object::GetPropertyOrElement(ext, key), JSObject);
        RETURN_ON_EXCEPTION(
            isolate,
            Runtime::DefineObjectProperty(closure_scope, key, value, NONE),
            JSObject);
      }
    }
  
    return closure_scope;
  }
  
  
  // This method copies structure of MaterializeClosure method above.
  static bool SetClosureVariableValue(Isolate* isolate,
                                      Handle<Context> context,
                                      Handle<String> variable_name,
                                      Handle<Object> new_value) {
    DCHECK(context->IsFunctionContext());
  
    Handle<SharedFunctionInfo> shared(context->closure()->shared());
    Handle<ScopeInfo> scope_info(shared->scope_info());
  
    // Context locals to the context extension.
    if (SetContextLocalValue(
            isolate, scope_info, context, variable_name, new_value)) {
      return true;
    }
  
    // Properties from the function context extension. This will
    // be variables introduced by eval.
    if (context->has_extension()) {
      Handle<JSObject> ext(JSObject::cast(context->extension()));
      Maybe<bool> maybe = JSReceiver::HasProperty(ext, variable_name);
      DCHECK(maybe.has_value);
      if (maybe.value) {
        // We don't expect this to do anything except replacing property value.
        Runtime::DefineObjectProperty(
            ext, variable_name, new_value, NONE).Assert();
        return true;
      }
    }
  
    return false;
  }
  
  
  // Create a plain JSObject which materializes the scope for the specified
  // catch context.
  MUST_USE_RESULT static MaybeHandle<JSObject> MaterializeCatchScope(
      Isolate* isolate,
      Handle<Context> context) {
    DCHECK(context->IsCatchContext());
    Handle<String> name(String::cast(context->extension()));
    Handle<Object> thrown_object(context->get(Context::THROWN_OBJECT_INDEX),
                                 isolate);
    Handle<JSObject> catch_scope =
        isolate->factory()->NewJSObject(isolate->object_function());
    RETURN_ON_EXCEPTION(
        isolate,
        Runtime::DefineObjectProperty(catch_scope, name, thrown_object, NONE),
        JSObject);
    return catch_scope;
  }
  
  
  static bool SetCatchVariableValue(Isolate* isolate,
                                    Handle<Context> context,
                                    Handle<String> variable_name,
                                    Handle<Object> new_value) {
    DCHECK(context->IsCatchContext());
    Handle<String> name(String::cast(context->extension()));
    if (!String::Equals(name, variable_name)) {
      return false;
    }
    context->set(Context::THROWN_OBJECT_INDEX, *new_value);
    return true;
  }
  
  
  // Create a plain JSObject which materializes the block scope for the specified
  // block context.
  MUST_USE_RESULT static MaybeHandle<JSObject> MaterializeBlockScope(
      Isolate* isolate,
      Handle<Context> context) {
    DCHECK(context->IsBlockContext());
    Handle<ScopeInfo> scope_info(ScopeInfo::cast(context->extension()));
  
    // Allocate and initialize a JSObject with all the arguments, stack locals
    // heap locals and extension properties of the debugged function.
    Handle<JSObject> block_scope =
        isolate->factory()->NewJSObject(isolate->object_function());
  
    // Fill all context locals.
    if (!ScopeInfo::CopyContextLocalsToScopeObject(
            scope_info, context, block_scope)) {
      return MaybeHandle<JSObject>();
    }
  
    return block_scope;
  }
  
  
  // Create a plain JSObject which materializes the module scope for the specified
  // module context.
  MUST_USE_RESULT static MaybeHandle<JSObject> MaterializeModuleScope(
      Isolate* isolate,
      Handle<Context> context) {
    DCHECK(context->IsModuleContext());
    Handle<ScopeInfo> scope_info(ScopeInfo::cast(context->extension()));
  
    // Allocate and initialize a JSObject with all the members of the debugged
    // module.
    Handle<JSObject> module_scope =
        isolate->factory()->NewJSObject(isolate->object_function());
  
    // Fill all context locals.
    if (!ScopeInfo::CopyContextLocalsToScopeObject(
            scope_info, context, module_scope)) {
      return MaybeHandle<JSObject>();
    }
  
    return module_scope;
  }
  
  
  // Iterate over the actual scopes visible from a stack frame or from a closure.
  // The iteration proceeds from the innermost visible nested scope outwards.
  // All scopes are backed by an actual context except the local scope,
  // which is inserted "artificially" in the context chain.
  class ScopeIterator {
   public:
    enum ScopeType {
      ScopeTypeGlobal = 0,
      ScopeTypeLocal,
      ScopeTypeWith,
      ScopeTypeClosure,
      ScopeTypeCatch,
      ScopeTypeBlock,
      ScopeTypeModule
    };
  
    ScopeIterator(Isolate* isolate,
                  JavaScriptFrame* frame,
                  int inlined_jsframe_index,
                  bool ignore_nested_scopes = false)
      : isolate_(isolate),
        frame_(frame),
        inlined_jsframe_index_(inlined_jsframe_index),
        function_(frame->function()),
        context_(Context::cast(frame->context())),
        nested_scope_chain_(4),
        failed_(false) {
  
      // Catch the case when the debugger stops in an internal function.
      Handle<SharedFunctionInfo> shared_info(function_->shared());
      Handle<ScopeInfo> scope_info(shared_info->scope_info());
      if (shared_info->script() == isolate->heap()->undefined_value()) {
        while (context_->closure() == *function_) {
          context_ = Handle<Context>(context_->previous(), isolate_);
        }
        return;
      }
  
      // Get the debug info (create it if it does not exist).
      if (!isolate->debug()->EnsureDebugInfo(shared_info, function_)) {
        // Return if ensuring debug info failed.
        return;
      }
  
      // Currently it takes too much time to find nested scopes due to script
      // parsing. Sometimes we want to run the ScopeIterator as fast as possible
      // (for example, while collecting async call stacks on every
      // addEventListener call), even if we drop some nested scopes.
      // Later we may optimize getting the nested scopes (cache the result?)
      // and include nested scopes into the "fast" iteration case as well.
      if (!ignore_nested_scopes) {
        Handle<DebugInfo> debug_info = Debug::GetDebugInfo(shared_info);
  
        // Find the break point where execution has stopped.
        BreakLocationIterator break_location_iterator(debug_info,
                                                      ALL_BREAK_LOCATIONS);
        // pc points to the instruction after the current one, possibly a break
        // location as well. So the "- 1" to exclude it from the search.
        break_location_iterator.FindBreakLocationFromAddress(frame->pc() - 1);
  
        // Within the return sequence at the moment it is not possible to
        // get a source position which is consistent with the current scope chain.
        // Thus all nested with, catch and block contexts are skipped and we only
        // provide the function scope.
        ignore_nested_scopes = break_location_iterator.IsExit();
      }
  
      if (ignore_nested_scopes) {
        if (scope_info->HasContext()) {
          context_ = Handle<Context>(context_->declaration_context(), isolate_);
        } else {
          while (context_->closure() == *function_) {
            context_ = Handle<Context>(context_->previous(), isolate_);
          }
        }
        if (scope_info->scope_type() == FUNCTION_SCOPE) {
          nested_scope_chain_.Add(scope_info);
        }
      } else {
        // Reparse the code and analyze the scopes.
        Handle<Script> script(Script::cast(shared_info->script()));
        Scope* scope = NULL;
  
        // Check whether we are in global, eval or function code.
        Handle<ScopeInfo> scope_info(shared_info->scope_info());
        if (scope_info->scope_type() != FUNCTION_SCOPE) {
          // Global or eval code.
          CompilationInfoWithZone info(script);
          if (scope_info->scope_type() == GLOBAL_SCOPE) {
            info.MarkAsGlobal();
          } else {
            DCHECK(scope_info->scope_type() == EVAL_SCOPE);
            info.MarkAsEval();
            info.SetContext(Handle<Context>(function_->context()));
          }
          if (Parser::Parse(&info) && Scope::Analyze(&info)) {
            scope = info.function()->scope();
          }
          RetrieveScopeChain(scope, shared_info);
        } else {
          // Function code
          CompilationInfoWithZone info(shared_info);
          if (Parser::Parse(&info) && Scope::Analyze(&info)) {
            scope = info.function()->scope();
          }
          RetrieveScopeChain(scope, shared_info);
        }
      }
    }
  
    ScopeIterator(Isolate* isolate,
                  Handle<JSFunction> function)
      : isolate_(isolate),
        frame_(NULL),
        inlined_jsframe_index_(0),
        function_(function),
        context_(function->context()),
        failed_(false) {
      if (function->IsBuiltin()) {
        context_ = Handle<Context>();
      }
    }
  
    // More scopes?
    bool Done() {
      DCHECK(!failed_);
      return context_.is_null();
    }
  
    bool Failed() { return failed_; }
  
    // Move to the next scope.
    void Next() {
      DCHECK(!failed_);
      ScopeType scope_type = Type();
      if (scope_type == ScopeTypeGlobal) {
        // The global scope is always the last in the chain.
        DCHECK(context_->IsNativeContext());
        context_ = Handle<Context>();
        return;
      }
      if (nested_scope_chain_.is_empty()) {
        context_ = Handle<Context>(context_->previous(), isolate_);
      } else {
        if (nested_scope_chain_.last()->HasContext()) {
          DCHECK(context_->previous() != NULL);
          context_ = Handle<Context>(context_->previous(), isolate_);
        }
        nested_scope_chain_.RemoveLast();
      }
    }
  
    // Return the type of the current scope.
    ScopeType Type() {
      DCHECK(!failed_);
      if (!nested_scope_chain_.is_empty()) {
        Handle<ScopeInfo> scope_info = nested_scope_chain_.last();
        switch (scope_info->scope_type()) {
          case FUNCTION_SCOPE:
            DCHECK(context_->IsFunctionContext() ||
                   !scope_info->HasContext());
            return ScopeTypeLocal;
          case MODULE_SCOPE:
            DCHECK(context_->IsModuleContext());
            return ScopeTypeModule;
          case GLOBAL_SCOPE:
            DCHECK(context_->IsNativeContext());
            return ScopeTypeGlobal;
          case WITH_SCOPE:
            DCHECK(context_->IsWithContext());
            return ScopeTypeWith;
          case CATCH_SCOPE:
            DCHECK(context_->IsCatchContext());
            return ScopeTypeCatch;
          case BLOCK_SCOPE:
            DCHECK(!scope_info->HasContext() ||
                   context_->IsBlockContext());
            return ScopeTypeBlock;
          case EVAL_SCOPE:
            UNREACHABLE();
        }
      }
      if (context_->IsNativeContext()) {
        DCHECK(context_->global_object()->IsGlobalObject());
        return ScopeTypeGlobal;
      }
      if (context_->IsFunctionContext()) {
        return ScopeTypeClosure;
      }
      if (context_->IsCatchContext()) {
        return ScopeTypeCatch;
      }
      if (context_->IsBlockContext()) {
        return ScopeTypeBlock;
      }
      if (context_->IsModuleContext()) {
        return ScopeTypeModule;
      }
      DCHECK(context_->IsWithContext());
      return ScopeTypeWith;
    }
  
    // Return the JavaScript object with the content of the current scope.
    MaybeHandle<JSObject> ScopeObject() {
      DCHECK(!failed_);
      switch (Type()) {
        case ScopeIterator::ScopeTypeGlobal:
          return Handle<JSObject>(CurrentContext()->global_object());
        case ScopeIterator::ScopeTypeLocal:
          // Materialize the content of the local scope into a JSObject.
          DCHECK(nested_scope_chain_.length() == 1);
          return MaterializeLocalScope(isolate_, frame_, inlined_jsframe_index_);
        case ScopeIterator::ScopeTypeWith:
          // Return the with object.
          return Handle<JSObject>(JSObject::cast(CurrentContext()->extension()));
        case ScopeIterator::ScopeTypeCatch:
          return MaterializeCatchScope(isolate_, CurrentContext());
        case ScopeIterator::ScopeTypeClosure:
          // Materialize the content of the closure scope into a JSObject.
          return MaterializeClosure(isolate_, CurrentContext());
        case ScopeIterator::ScopeTypeBlock:
          return MaterializeBlockScope(isolate_, CurrentContext());
        case ScopeIterator::ScopeTypeModule:
          return MaterializeModuleScope(isolate_, CurrentContext());
      }
      UNREACHABLE();
      return Handle<JSObject>();
    }
  
    bool SetVariableValue(Handle<String> variable_name,
                          Handle<Object> new_value) {
      DCHECK(!failed_);
      switch (Type()) {
        case ScopeIterator::ScopeTypeGlobal:
          break;
        case ScopeIterator::ScopeTypeLocal:
          return SetLocalVariableValue(isolate_, frame_, inlined_jsframe_index_,
              variable_name, new_value);
        case ScopeIterator::ScopeTypeWith:
          break;
        case ScopeIterator::ScopeTypeCatch:
          return SetCatchVariableValue(isolate_, CurrentContext(),
              variable_name, new_value);
        case ScopeIterator::ScopeTypeClosure:
          return SetClosureVariableValue(isolate_, CurrentContext(),
              variable_name, new_value);
        case ScopeIterator::ScopeTypeBlock:
          // TODO(2399): should we implement it?
          break;
        case ScopeIterator::ScopeTypeModule:
          // TODO(2399): should we implement it?
          break;
      }
      return false;
    }
  
    Handle<ScopeInfo> CurrentScopeInfo() {
      DCHECK(!failed_);
      if (!nested_scope_chain_.is_empty()) {
        return nested_scope_chain_.last();
      } else if (context_->IsBlockContext()) {
        return Handle<ScopeInfo>(ScopeInfo::cast(context_->extension()));
      } else if (context_->IsFunctionContext()) {
        return Handle<ScopeInfo>(context_->closure()->shared()->scope_info());
      }
      return Handle<ScopeInfo>::null();
    }
  
    // Return the context for this scope. For the local context there might not
    // be an actual context.
    Handle<Context> CurrentContext() {
      DCHECK(!failed_);
      if (Type() == ScopeTypeGlobal ||
          nested_scope_chain_.is_empty()) {
        return context_;
      } else if (nested_scope_chain_.last()->HasContext()) {
        return context_;
      } else {
        return Handle<Context>();
      }
    }
  
  #ifdef DEBUG
    // Debug print of the content of the current scope.
    void DebugPrint() {
      OFStream os(stdout);
      DCHECK(!failed_);
      switch (Type()) {
        case ScopeIterator::ScopeTypeGlobal:
          os << "Global:\n";
          CurrentContext()->Print(os);
          break;
  
        case ScopeIterator::ScopeTypeLocal: {
          os << "Local:\n";
          function_->shared()->scope_info()->Print();
          if (!CurrentContext().is_null()) {
            CurrentContext()->Print(os);
            if (CurrentContext()->has_extension()) {
              Handle<Object> extension(CurrentContext()->extension(), isolate_);
              if (extension->IsJSContextExtensionObject()) {
                extension->Print(os);
              }
            }
          }
          break;
        }
  
        case ScopeIterator::ScopeTypeWith:
          os << "With:\n";
          CurrentContext()->extension()->Print(os);
          break;
  
        case ScopeIterator::ScopeTypeCatch:
          os << "Catch:\n";
          CurrentContext()->extension()->Print(os);
          CurrentContext()->get(Context::THROWN_OBJECT_INDEX)->Print(os);
          break;
  
        case ScopeIterator::ScopeTypeClosure:
          os << "Closure:\n";
          CurrentContext()->Print(os);
          if (CurrentContext()->has_extension()) {
            Handle<Object> extension(CurrentContext()->extension(), isolate_);
            if (extension->IsJSContextExtensionObject()) {
              extension->Print(os);
            }
          }
          break;
  
        default:
          UNREACHABLE();
      }
      PrintF("\n");
    }
  #endif
  
   private:
    Isolate* isolate_;
    JavaScriptFrame* frame_;
    int inlined_jsframe_index_;
    Handle<JSFunction> function_;
    Handle<Context> context_;
    List<Handle<ScopeInfo> > nested_scope_chain_;
    bool failed_;
  
    void RetrieveScopeChain(Scope* scope,
                            Handle<SharedFunctionInfo> shared_info) {
      if (scope != NULL) {
        int source_position = shared_info->code()->SourcePosition(frame_->pc());
        scope->GetNestedScopeChain(&nested_scope_chain_, source_position);
      } else {
        // A failed reparse indicates that the preparser has diverged from the
        // parser or that the preparse data given to the initial parse has been
        // faulty. We fail in debug mode but in release mode we only provide the
        // information we get from the context chain but nothing about
        // completely stack allocated scopes or stack allocated locals.
        // Or it could be due to stack overflow.
        DCHECK(isolate_->has_pending_exception());
        failed_ = true;
      }
    }
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(ScopeIterator);
  };
  
  
  RUNTIME_FUNCTION(Runtime_GetScopeCount) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_NUMBER_CHECKED(int, break_id, Int32, args[0]);
    RUNTIME_ASSERT(CheckExecutionState(isolate, break_id));
  
    CONVERT_SMI_ARG_CHECKED(wrapped_id, 1);
  
    // Get the frame where the debugging is performed.
    StackFrame::Id id = UnwrapFrameId(wrapped_id);
    JavaScriptFrameIterator it(isolate, id);
    JavaScriptFrame* frame = it.frame();
  
    // Count the visible scopes.
    int n = 0;
    for (ScopeIterator it(isolate, frame, 0);
         !it.Done();
         it.Next()) {
      n++;
    }
  
    return Smi::FromInt(n);
  }
  
  
  // Returns the list of step-in positions (text offset) in a function of the
  // stack frame in a range from the current debug break position to the end
  // of the corresponding statement.
  RUNTIME_FUNCTION(Runtime_GetStepInPositions) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_NUMBER_CHECKED(int, break_id, Int32, args[0]);
    RUNTIME_ASSERT(CheckExecutionState(isolate, break_id));
  
    CONVERT_SMI_ARG_CHECKED(wrapped_id, 1);
  
    // Get the frame where the debugging is performed.
    StackFrame::Id id = UnwrapFrameId(wrapped_id);
    JavaScriptFrameIterator frame_it(isolate, id);
    RUNTIME_ASSERT(!frame_it.done());
  
    JavaScriptFrame* frame = frame_it.frame();
  
    Handle<JSFunction> fun =
        Handle<JSFunction>(frame->function());
    Handle<SharedFunctionInfo> shared =
        Handle<SharedFunctionInfo>(fun->shared());
  
    if (!isolate->debug()->EnsureDebugInfo(shared, fun)) {
      return isolate->heap()->undefined_value();
    }
  
    Handle<DebugInfo> debug_info = Debug::GetDebugInfo(shared);
  
    int len = 0;
    Handle<JSArray> array(isolate->factory()->NewJSArray(10));
    // Find the break point where execution has stopped.
    BreakLocationIterator break_location_iterator(debug_info,
                                                  ALL_BREAK_LOCATIONS);
  
    break_location_iterator.FindBreakLocationFromAddress(frame->pc() - 1);
    int current_statement_pos = break_location_iterator.statement_position();
  
    while (!break_location_iterator.Done()) {
      bool accept;
      if (break_location_iterator.pc() > frame->pc()) {
        accept = true;
      } else {
        StackFrame::Id break_frame_id = isolate->debug()->break_frame_id();
        // The break point is near our pc. Could be a step-in possibility,
        // that is currently taken by active debugger call.
        if (break_frame_id == StackFrame::NO_ID) {
          // We are not stepping.
          accept = false;
        } else {
          JavaScriptFrameIterator additional_frame_it(isolate, break_frame_id);
          // If our frame is a top frame and we are stepping, we can do step-in
          // at this place.
          accept = additional_frame_it.frame()->id() == id;
        }
      }
      if (accept) {
        if (break_location_iterator.IsStepInLocation(isolate)) {
          Smi* position_value = Smi::FromInt(break_location_iterator.position());
          RETURN_FAILURE_ON_EXCEPTION(
              isolate,
              JSObject::SetElement(array, len,
                                   Handle<Object>(position_value, isolate),
                                   NONE, SLOPPY));
          len++;
        }
      }
      // Advance iterator.
      break_location_iterator.Next();
      if (current_statement_pos !=
          break_location_iterator.statement_position()) {
        break;
      }
    }
    return *array;
  }
  
  
  static const int kScopeDetailsTypeIndex = 0;
  static const int kScopeDetailsObjectIndex = 1;
  static const int kScopeDetailsSize = 2;
  
  
  MUST_USE_RESULT static MaybeHandle<JSObject> MaterializeScopeDetails(
      Isolate* isolate,
      ScopeIterator* it) {
    // Calculate the size of the result.
    int details_size = kScopeDetailsSize;
    Handle<FixedArray> details = isolate->factory()->NewFixedArray(details_size);
  
    // Fill in scope details.
    details->set(kScopeDetailsTypeIndex, Smi::FromInt(it->Type()));
    Handle<JSObject> scope_object;
    ASSIGN_RETURN_ON_EXCEPTION(
        isolate, scope_object, it->ScopeObject(), JSObject);
    details->set(kScopeDetailsObjectIndex, *scope_object);
  
    return isolate->factory()->NewJSArrayWithElements(details);
  }
  
  
  // Return an array with scope details
  // args[0]: number: break id
  // args[1]: number: frame index
  // args[2]: number: inlined frame index
  // args[3]: number: scope index
  //
  // The array returned contains the following information:
  // 0: Scope type
  // 1: Scope object
  RUNTIME_FUNCTION(Runtime_GetScopeDetails) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 4);
    CONVERT_NUMBER_CHECKED(int, break_id, Int32, args[0]);
    RUNTIME_ASSERT(CheckExecutionState(isolate, break_id));
  
    CONVERT_SMI_ARG_CHECKED(wrapped_id, 1);
    CONVERT_NUMBER_CHECKED(int, inlined_jsframe_index, Int32, args[2]);
    CONVERT_NUMBER_CHECKED(int, index, Int32, args[3]);
  
    // Get the frame where the debugging is performed.
    StackFrame::Id id = UnwrapFrameId(wrapped_id);
    JavaScriptFrameIterator frame_it(isolate, id);
    JavaScriptFrame* frame = frame_it.frame();
  
    // Find the requested scope.
    int n = 0;
    ScopeIterator it(isolate, frame, inlined_jsframe_index);
    for (; !it.Done() && n < index; it.Next()) {
      n++;
    }
    if (it.Done()) {
      return isolate->heap()->undefined_value();
    }
    Handle<JSObject> details;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, details, MaterializeScopeDetails(isolate, &it));
    return *details;
  }
  
  
  // Return an array of scope details
  // args[0]: number: break id
  // args[1]: number: frame index
  // args[2]: number: inlined frame index
  // args[3]: boolean: ignore nested scopes
  //
  // The array returned contains arrays with the following information:
  // 0: Scope type
  // 1: Scope object
  RUNTIME_FUNCTION(Runtime_GetAllScopesDetails) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3 || args.length() == 4);
    CONVERT_NUMBER_CHECKED(int, break_id, Int32, args[0]);
    RUNTIME_ASSERT(CheckExecutionState(isolate, break_id));
  
    CONVERT_SMI_ARG_CHECKED(wrapped_id, 1);
    CONVERT_NUMBER_CHECKED(int, inlined_jsframe_index, Int32, args[2]);
  
    bool ignore_nested_scopes = false;
    if (args.length() == 4) {
      CONVERT_BOOLEAN_ARG_CHECKED(flag, 3);
      ignore_nested_scopes = flag;
    }
  
    // Get the frame where the debugging is performed.
    StackFrame::Id id = UnwrapFrameId(wrapped_id);
    JavaScriptFrameIterator frame_it(isolate, id);
    JavaScriptFrame* frame = frame_it.frame();
  
    List<Handle<JSObject> > result(4);
    ScopeIterator it(isolate, frame, inlined_jsframe_index, ignore_nested_scopes);
    for (; !it.Done(); it.Next()) {
      Handle<JSObject> details;
      ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
          isolate, details, MaterializeScopeDetails(isolate, &it));
      result.Add(details);
    }
  
    Handle<FixedArray> array = isolate->factory()->NewFixedArray(result.length());
    for (int i = 0; i < result.length(); ++i) {
      array->set(i, *result[i]);
    }
    return *isolate->factory()->NewJSArrayWithElements(array);
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetFunctionScopeCount) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
  
    // Check arguments.
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, fun, 0);
  
    // Count the visible scopes.
    int n = 0;
    for (ScopeIterator it(isolate, fun); !it.Done(); it.Next()) {
      n++;
    }
  
    return Smi::FromInt(n);
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetFunctionScopeDetails) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    // Check arguments.
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, fun, 0);
    CONVERT_NUMBER_CHECKED(int, index, Int32, args[1]);
  
    // Find the requested scope.
    int n = 0;
    ScopeIterator it(isolate, fun);
    for (; !it.Done() && n < index; it.Next()) {
      n++;
    }
    if (it.Done()) {
      return isolate->heap()->undefined_value();
    }
  
    Handle<JSObject> details;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, details, MaterializeScopeDetails(isolate, &it));
    return *details;
  }
  
  
  static bool SetScopeVariableValue(ScopeIterator* it, int index,
                                    Handle<String> variable_name,
                                    Handle<Object> new_value) {
    for (int n = 0; !it->Done() && n < index; it->Next()) {
      n++;
    }
    if (it->Done()) {
      return false;
    }
    return it->SetVariableValue(variable_name, new_value);
  }
  
  
  // Change variable value in closure or local scope
  // args[0]: number or JsFunction: break id or function
  // args[1]: number: frame index (when arg[0] is break id)
  // args[2]: number: inlined frame index (when arg[0] is break id)
  // args[3]: number: scope index
  // args[4]: string: variable name
  // args[5]: object: new value
  //
  // Return true if success and false otherwise
  RUNTIME_FUNCTION(Runtime_SetScopeVariableValue) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 6);
  
    // Check arguments.
    CONVERT_NUMBER_CHECKED(int, index, Int32, args[3]);
    CONVERT_ARG_HANDLE_CHECKED(String, variable_name, 4);
    CONVERT_ARG_HANDLE_CHECKED(Object, new_value, 5);
  
    bool res;
    if (args[0]->IsNumber()) {
      CONVERT_NUMBER_CHECKED(int, break_id, Int32, args[0]);
      RUNTIME_ASSERT(CheckExecutionState(isolate, break_id));
  
      CONVERT_SMI_ARG_CHECKED(wrapped_id, 1);
      CONVERT_NUMBER_CHECKED(int, inlined_jsframe_index, Int32, args[2]);
  
      // Get the frame where the debugging is performed.
      StackFrame::Id id = UnwrapFrameId(wrapped_id);
      JavaScriptFrameIterator frame_it(isolate, id);
      JavaScriptFrame* frame = frame_it.frame();
  
      ScopeIterator it(isolate, frame, inlined_jsframe_index);
      res = SetScopeVariableValue(&it, index, variable_name, new_value);
    } else {
      CONVERT_ARG_HANDLE_CHECKED(JSFunction, fun, 0);
      ScopeIterator it(isolate, fun);
      res = SetScopeVariableValue(&it, index, variable_name, new_value);
    }
  
    return isolate->heap()->ToBoolean(res);
  }
  
  
  RUNTIME_FUNCTION(Runtime_DebugPrintScopes) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 0);
  
  #ifdef DEBUG
    // Print the scopes for the top frame.
    StackFrameLocator locator(isolate);
    JavaScriptFrame* frame = locator.FindJavaScriptFrame(0);
    for (ScopeIterator it(isolate, frame, 0);
         !it.Done();
         it.Next()) {
      it.DebugPrint();
    }
  #endif
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetThreadCount) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_NUMBER_CHECKED(int, break_id, Int32, args[0]);
    RUNTIME_ASSERT(CheckExecutionState(isolate, break_id));
  
    // Count all archived V8 threads.
    int n = 0;
    for (ThreadState* thread =
            isolate->thread_manager()->FirstThreadStateInUse();
         thread != NULL;
         thread = thread->Next()) {
      n++;
    }
  
    // Total number of threads is current thread and archived threads.
    return Smi::FromInt(n + 1);
  }
  
  
  static const int kThreadDetailsCurrentThreadIndex = 0;
  static const int kThreadDetailsThreadIdIndex = 1;
  static const int kThreadDetailsSize = 2;
  
  // Return an array with thread details
  // args[0]: number: break id
  // args[1]: number: thread index
  //
  // The array returned contains the following information:
  // 0: Is current thread?
  // 1: Thread id
  RUNTIME_FUNCTION(Runtime_GetThreadDetails) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_NUMBER_CHECKED(int, break_id, Int32, args[0]);
    RUNTIME_ASSERT(CheckExecutionState(isolate, break_id));
  
    CONVERT_NUMBER_CHECKED(int, index, Int32, args[1]);
  
    // Allocate array for result.
    Handle<FixedArray> details =
        isolate->factory()->NewFixedArray(kThreadDetailsSize);
  
    // Thread index 0 is current thread.
    if (index == 0) {
      // Fill the details.
      details->set(kThreadDetailsCurrentThreadIndex,
                   isolate->heap()->true_value());
      details->set(kThreadDetailsThreadIdIndex,
                   Smi::FromInt(ThreadId::Current().ToInteger()));
    } else {
      // Find the thread with the requested index.
      int n = 1;
      ThreadState* thread =
          isolate->thread_manager()->FirstThreadStateInUse();
      while (index != n && thread != NULL) {
        thread = thread->Next();
        n++;
      }
      if (thread == NULL) {
        return isolate->heap()->undefined_value();
      }
  
      // Fill the details.
      details->set(kThreadDetailsCurrentThreadIndex,
                   isolate->heap()->false_value());
      details->set(kThreadDetailsThreadIdIndex,
                   Smi::FromInt(thread->id().ToInteger()));
    }
  
    // Convert to JS array and return.
    return *isolate->factory()->NewJSArrayWithElements(details);
  }
  
  
  // Sets the disable break state
  // args[0]: disable break state
  RUNTIME_FUNCTION(Runtime_SetDisableBreak) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_BOOLEAN_ARG_CHECKED(disable_break, 0);
    isolate->debug()->set_disable_break(disable_break);
    return  isolate->heap()->undefined_value();
  }
  
  
  static bool IsPositionAlignmentCodeCorrect(int alignment) {
    return alignment == STATEMENT_ALIGNED || alignment == BREAK_POSITION_ALIGNED;
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetBreakLocations) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, fun, 0);
    CONVERT_NUMBER_CHECKED(int32_t, statement_aligned_code, Int32, args[1]);
  
    if (!IsPositionAlignmentCodeCorrect(statement_aligned_code)) {
      return isolate->ThrowIllegalOperation();
    }
    BreakPositionAlignment alignment =
        static_cast<BreakPositionAlignment>(statement_aligned_code);
  
    Handle<SharedFunctionInfo> shared(fun->shared());
    // Find the number of break points
    Handle<Object> break_locations =
        Debug::GetSourceBreakLocations(shared, alignment);
    if (break_locations->IsUndefined()) return isolate->heap()->undefined_value();
    // Return array as JS array
    return *isolate->factory()->NewJSArrayWithElements(
        Handle<FixedArray>::cast(break_locations));
  }
  
  
  // Set a break point in a function.
  // args[0]: function
  // args[1]: number: break source position (within the function source)
  // args[2]: number: break point object
  RUNTIME_FUNCTION(Runtime_SetFunctionBreakPoint) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 0);
    CONVERT_NUMBER_CHECKED(int32_t, source_position, Int32, args[1]);
    RUNTIME_ASSERT(source_position >= function->shared()->start_position() &&
                   source_position <= function->shared()->end_position());
    CONVERT_ARG_HANDLE_CHECKED(Object, break_point_object_arg, 2);
  
    // Set break point.
    RUNTIME_ASSERT(isolate->debug()->SetBreakPoint(
        function, break_point_object_arg, &source_position));
  
    return Smi::FromInt(source_position);
  }
  
  
  // Changes the state of a break point in a script and returns source position
  // where break point was set. NOTE: Regarding performance see the NOTE for
  // GetScriptFromScriptData.
  // args[0]: script to set break point in
  // args[1]: number: break source position (within the script source)
  // args[2]: number, breakpoint position alignment
  // args[3]: number: break point object
  RUNTIME_FUNCTION(Runtime_SetScriptBreakPoint) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 4);
    CONVERT_ARG_HANDLE_CHECKED(JSValue, wrapper, 0);
    CONVERT_NUMBER_CHECKED(int32_t, source_position, Int32, args[1]);
    RUNTIME_ASSERT(source_position >= 0);
    CONVERT_NUMBER_CHECKED(int32_t, statement_aligned_code, Int32, args[2]);
    CONVERT_ARG_HANDLE_CHECKED(Object, break_point_object_arg, 3);
  
    if (!IsPositionAlignmentCodeCorrect(statement_aligned_code)) {
      return isolate->ThrowIllegalOperation();
    }
    BreakPositionAlignment alignment =
        static_cast<BreakPositionAlignment>(statement_aligned_code);
  
    // Get the script from the script wrapper.
    RUNTIME_ASSERT(wrapper->value()->IsScript());
    Handle<Script> script(Script::cast(wrapper->value()));
  
    // Set break point.
    if (!isolate->debug()->SetBreakPointForScript(script, break_point_object_arg,
                                                  &source_position,
                                                  alignment)) {
      return isolate->heap()->undefined_value();
    }
  
    return Smi::FromInt(source_position);
  }
  
  
  // Clear a break point
  // args[0]: number: break point object
  RUNTIME_FUNCTION(Runtime_ClearBreakPoint) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, break_point_object_arg, 0);
  
    // Clear break point.
    isolate->debug()->ClearBreakPoint(break_point_object_arg);
  
    return isolate->heap()->undefined_value();
  }
  
  
  // Change the state of break on exceptions.
  // args[0]: Enum value indicating whether to affect caught/uncaught exceptions.
  // args[1]: Boolean indicating on/off.
  RUNTIME_FUNCTION(Runtime_ChangeBreakOnException) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_NUMBER_CHECKED(uint32_t, type_arg, Uint32, args[0]);
    CONVERT_BOOLEAN_ARG_CHECKED(enable, 1);
  
    // If the number doesn't match an enum value, the ChangeBreakOnException
    // function will default to affecting caught exceptions.
    ExceptionBreakType type = static_cast<ExceptionBreakType>(type_arg);
    // Update break point state.
    isolate->debug()->ChangeBreakOnException(type, enable);
    return isolate->heap()->undefined_value();
  }
  
  
  // Returns the state of break on exceptions
  // args[0]: boolean indicating uncaught exceptions
  RUNTIME_FUNCTION(Runtime_IsBreakOnException) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_NUMBER_CHECKED(uint32_t, type_arg, Uint32, args[0]);
  
    ExceptionBreakType type = static_cast<ExceptionBreakType>(type_arg);
    bool result = isolate->debug()->IsBreakOnException(type);
    return Smi::FromInt(result);
  }
  
  
  // Prepare for stepping
  // args[0]: break id for checking execution state
  // args[1]: step action from the enumeration StepAction
  // args[2]: number of times to perform the step, for step out it is the number
  //          of frames to step down.
  RUNTIME_FUNCTION(Runtime_PrepareStep) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 4);
    CONVERT_NUMBER_CHECKED(int, break_id, Int32, args[0]);
    RUNTIME_ASSERT(CheckExecutionState(isolate, break_id));
  
    if (!args[1]->IsNumber() || !args[2]->IsNumber()) {
      return isolate->Throw(isolate->heap()->illegal_argument_string());
    }
  
    CONVERT_NUMBER_CHECKED(int, wrapped_frame_id, Int32, args[3]);
  
    StackFrame::Id frame_id;
    if (wrapped_frame_id == 0) {
      frame_id = StackFrame::NO_ID;
    } else {
      frame_id = UnwrapFrameId(wrapped_frame_id);
    }
  
    // Get the step action and check validity.
    StepAction step_action = static_cast<StepAction>(NumberToInt32(args[1]));
    if (step_action != StepIn &&
        step_action != StepNext &&
        step_action != StepOut &&
        step_action != StepInMin &&
        step_action != StepMin) {
      return isolate->Throw(isolate->heap()->illegal_argument_string());
    }
  
    if (frame_id != StackFrame::NO_ID && step_action != StepNext &&
        step_action != StepMin && step_action != StepOut) {
      return isolate->ThrowIllegalOperation();
    }
  
    // Get the number of steps.
    int step_count = NumberToInt32(args[2]);
    if (step_count < 1) {
      return isolate->Throw(isolate->heap()->illegal_argument_string());
    }
  
    // Clear all current stepping setup.
    isolate->debug()->ClearStepping();
  
    // Prepare step.
    isolate->debug()->PrepareStep(static_cast<StepAction>(step_action),
                                  step_count,
                                  frame_id);
    return isolate->heap()->undefined_value();
  }
  
  
  // Clear all stepping set by PrepareStep.
  RUNTIME_FUNCTION(Runtime_ClearStepping) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 0);
    isolate->debug()->ClearStepping();
    return isolate->heap()->undefined_value();
  }
  
  
  // Helper function to find or create the arguments object for
  // Runtime_DebugEvaluate.
  MUST_USE_RESULT static MaybeHandle<JSObject> MaterializeArgumentsObject(
      Isolate* isolate,
      Handle<JSObject> target,
      Handle<JSFunction> function) {
    // Do not materialize the arguments object for eval or top-level code.
    // Skip if "arguments" is already taken.
    if (!function->shared()->is_function()) return target;
    Maybe<bool> maybe = JSReceiver::HasOwnProperty(
        target, isolate->factory()->arguments_string());
    if (!maybe.has_value) return MaybeHandle<JSObject>();
    if (maybe.value) return target;
  
    // FunctionGetArguments can't throw an exception.
    Handle<JSObject> arguments = Handle<JSObject>::cast(
        Accessors::FunctionGetArguments(function));
    Handle<String> arguments_str = isolate->factory()->arguments_string();
    RETURN_ON_EXCEPTION(
        isolate,
        Runtime::DefineObjectProperty(target, arguments_str, arguments, NONE),
        JSObject);
    return target;
  }
  
  
  // Compile and evaluate source for the given context.
  static MaybeHandle<Object> DebugEvaluate(Isolate* isolate,
                                           Handle<Context> context,
                                           Handle<Object> context_extension,
                                           Handle<Object> receiver,
                                           Handle<String> source) {
    if (context_extension->IsJSObject()) {
      Handle<JSObject> extension = Handle<JSObject>::cast(context_extension);
      Handle<JSFunction> closure(context->closure(), isolate);
      context = isolate->factory()->NewWithContext(closure, context, extension);
    }
  
    Handle<JSFunction> eval_fun;
    ASSIGN_RETURN_ON_EXCEPTION(
        isolate, eval_fun,
        Compiler::GetFunctionFromEval(source,
                                      context,
                                      SLOPPY,
                                      NO_PARSE_RESTRICTION,
                                      RelocInfo::kNoPosition),
        Object);
  
    Handle<Object> result;
    ASSIGN_RETURN_ON_EXCEPTION(
        isolate, result,
        Execution::Call(isolate, eval_fun, receiver, 0, NULL),
        Object);
  
    // Skip the global proxy as it has no properties and always delegates to the
    // real global object.
    if (result->IsJSGlobalProxy()) {
      PrototypeIterator iter(isolate, result);
      // TODO(verwaest): This will crash when the global proxy is detached.
      result = Handle<JSObject>::cast(PrototypeIterator::GetCurrent(iter));
    }
  
    // Clear the oneshot breakpoints so that the debugger does not step further.
    isolate->debug()->ClearStepping();
    return result;
  }
  
  
  // Evaluate a piece of JavaScript in the context of a stack frame for
  // debugging.  Things that need special attention are:
  // - Parameters and stack-allocated locals need to be materialized.  Altered
  //   values need to be written back to the stack afterwards.
  // - The arguments object needs to materialized.
  RUNTIME_FUNCTION(Runtime_DebugEvaluate) {
    HandleScope scope(isolate);
  
    // Check the execution state and decode arguments frame and source to be
    // evaluated.
    DCHECK(args.length() == 6);
    CONVERT_NUMBER_CHECKED(int, break_id, Int32, args[0]);
    RUNTIME_ASSERT(CheckExecutionState(isolate, break_id));
  
    CONVERT_SMI_ARG_CHECKED(wrapped_id, 1);
    CONVERT_NUMBER_CHECKED(int, inlined_jsframe_index, Int32, args[2]);
    CONVERT_ARG_HANDLE_CHECKED(String, source, 3);
    CONVERT_BOOLEAN_ARG_CHECKED(disable_break, 4);
    CONVERT_ARG_HANDLE_CHECKED(Object, context_extension, 5);
  
    // Handle the processing of break.
    DisableBreak disable_break_scope(isolate->debug(), disable_break);
  
    // Get the frame where the debugging is performed.
    StackFrame::Id id = UnwrapFrameId(wrapped_id);
    JavaScriptFrameIterator it(isolate, id);
    JavaScriptFrame* frame = it.frame();
    FrameInspector frame_inspector(frame, inlined_jsframe_index, isolate);
    Handle<JSFunction> function(JSFunction::cast(frame_inspector.GetFunction()));
  
    // Traverse the saved contexts chain to find the active context for the
    // selected frame.
    SaveContext* save = FindSavedContextForFrame(isolate, frame);
  
    SaveContext savex(isolate);
    isolate->set_context(*(save->context()));
  
    // Evaluate on the context of the frame.
    Handle<Context> context(Context::cast(frame->context()));
    DCHECK(!context.is_null());
  
    // Materialize stack locals and the arguments object.
    Handle<JSObject> materialized =
        isolate->factory()->NewJSObject(isolate->object_function());
  
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, materialized,
        MaterializeStackLocalsWithFrameInspector(
            isolate, materialized, function, &frame_inspector));
  
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, materialized,
        MaterializeArgumentsObject(isolate, materialized, function));
  
    // Add the materialized object in a with-scope to shadow the stack locals.
    context = isolate->factory()->NewWithContext(function, context, materialized);
  
    Handle<Object> receiver(frame->receiver(), isolate);
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result,
        DebugEvaluate(isolate, context, context_extension, receiver, source));
  
    // Write back potential changes to materialized stack locals to the stack.
    UpdateStackLocalsFromMaterializedObject(
        isolate, materialized, function, frame, inlined_jsframe_index);
  
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_DebugEvaluateGlobal) {
    HandleScope scope(isolate);
  
    // Check the execution state and decode arguments frame and source to be
    // evaluated.
    DCHECK(args.length() == 4);
    CONVERT_NUMBER_CHECKED(int, break_id, Int32, args[0]);
    RUNTIME_ASSERT(CheckExecutionState(isolate, break_id));
  
    CONVERT_ARG_HANDLE_CHECKED(String, source, 1);
    CONVERT_BOOLEAN_ARG_CHECKED(disable_break, 2);
    CONVERT_ARG_HANDLE_CHECKED(Object, context_extension, 3);
  
    // Handle the processing of break.
    DisableBreak disable_break_scope(isolate->debug(), disable_break);
  
    // Enter the top context from before the debugger was invoked.
    SaveContext save(isolate);
    SaveContext* top = &save;
    while (top != NULL && *top->context() == *isolate->debug()->debug_context()) {
      top = top->prev();
    }
    if (top != NULL) {
      isolate->set_context(*top->context());
    }
  
    // Get the native context now set to the top context from before the
    // debugger was invoked.
    Handle<Context> context = isolate->native_context();
    Handle<JSObject> receiver(context->global_proxy());
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result,
        DebugEvaluate(isolate, context, context_extension, receiver, source));
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_DebugGetLoadedScripts) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 0);
  
    // Fill the script objects.
    Handle<FixedArray> instances = isolate->debug()->GetLoadedScripts();
  
    // Convert the script objects to proper JS objects.
    for (int i = 0; i < instances->length(); i++) {
      Handle<Script> script = Handle<Script>(Script::cast(instances->get(i)));
      // Get the script wrapper in a local handle before calling GetScriptWrapper,
      // because using
      //   instances->set(i, *GetScriptWrapper(script))
      // is unsafe as GetScriptWrapper might call GC and the C++ compiler might
      // already have dereferenced the instances handle.
      Handle<JSObject> wrapper = Script::GetWrapper(script);
      instances->set(i, *wrapper);
    }
  
    // Return result as a JS array.
    Handle<JSObject> result =
        isolate->factory()->NewJSObject(isolate->array_function());
    JSArray::SetContent(Handle<JSArray>::cast(result), instances);
    return *result;
  }
  
  
  // Helper function used by Runtime_DebugReferencedBy below.
  static int DebugReferencedBy(HeapIterator* iterator,
                               JSObject* target,
                               Object* instance_filter, int max_references,
                               FixedArray* instances, int instances_size,
                               JSFunction* arguments_function) {
    Isolate* isolate = target->GetIsolate();
    SealHandleScope shs(isolate);
    DisallowHeapAllocation no_allocation;
  
    // Iterate the heap.
    int count = 0;
    JSObject* last = NULL;
    HeapObject* heap_obj = NULL;
    while (((heap_obj = iterator->next()) != NULL) &&
           (max_references == 0 || count < max_references)) {
      // Only look at all JSObjects.
      if (heap_obj->IsJSObject()) {
        // Skip context extension objects and argument arrays as these are
        // checked in the context of functions using them.
        JSObject* obj = JSObject::cast(heap_obj);
        if (obj->IsJSContextExtensionObject() ||
            obj->map()->constructor() == arguments_function) {
          continue;
        }
  
        // Check if the JS object has a reference to the object looked for.
        if (obj->ReferencesObject(target)) {
          // Check instance filter if supplied. This is normally used to avoid
          // references from mirror objects (see Runtime_IsInPrototypeChain).
          if (!instance_filter->IsUndefined()) {
            for (PrototypeIterator iter(isolate, obj); !iter.IsAtEnd();
                 iter.Advance()) {
              if (iter.GetCurrent() == instance_filter) {
                obj = NULL;  // Don't add this object.
                break;
              }
            }
          }
  
          if (obj != NULL) {
            // Valid reference found add to instance array if supplied an update
            // count.
            if (instances != NULL && count < instances_size) {
              instances->set(count, obj);
            }
            last = obj;
            count++;
          }
        }
      }
    }
  
    // Check for circular reference only. This can happen when the object is only
    // referenced from mirrors and has a circular reference in which case the
    // object is not really alive and would have been garbage collected if not
    // referenced from the mirror.
    if (count == 1 && last == target) {
      count = 0;
    }
  
    // Return the number of referencing objects found.
    return count;
  }
  
  
  // Scan the heap for objects with direct references to an object
  // args[0]: the object to find references to
  // args[1]: constructor function for instances to exclude (Mirror)
  // args[2]: the the maximum number of objects to return
  RUNTIME_FUNCTION(Runtime_DebugReferencedBy) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
  
    // Check parameters.
    CONVERT_ARG_HANDLE_CHECKED(JSObject, target, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, instance_filter, 1);
    RUNTIME_ASSERT(instance_filter->IsUndefined() ||
                   instance_filter->IsJSObject());
    CONVERT_NUMBER_CHECKED(int32_t, max_references, Int32, args[2]);
    RUNTIME_ASSERT(max_references >= 0);
  
  
    // Get the constructor function for context extension and arguments array.
    Handle<JSFunction> arguments_function(
        JSFunction::cast(isolate->sloppy_arguments_map()->constructor()));
  
    // Get the number of referencing objects.
    int count;
    // First perform a full GC in order to avoid dead objects and to make the heap
    // iterable.
    Heap* heap = isolate->heap();
    heap->CollectAllGarbage(Heap::kMakeHeapIterableMask, "%DebugConstructedBy");
    {
      HeapIterator heap_iterator(heap);
      count = DebugReferencedBy(&heap_iterator,
                                *target, *instance_filter, max_references,
                                NULL, 0, *arguments_function);
    }
  
    // Allocate an array to hold the result.
    Handle<FixedArray> instances = isolate->factory()->NewFixedArray(count);
  
    // Fill the referencing objects.
    {
      HeapIterator heap_iterator(heap);
      count = DebugReferencedBy(&heap_iterator,
                                *target, *instance_filter, max_references,
                                *instances, count, *arguments_function);
    }
  
    // Return result as JS array.
    Handle<JSFunction> constructor = isolate->array_function();
  
    Handle<JSObject> result = isolate->factory()->NewJSObject(constructor);
    JSArray::SetContent(Handle<JSArray>::cast(result), instances);
    return *result;
  }
  
  
  // Helper function used by Runtime_DebugConstructedBy below.
  static int DebugConstructedBy(HeapIterator* iterator,
                                JSFunction* constructor,
                                int max_references,
                                FixedArray* instances,
                                int instances_size) {
    DisallowHeapAllocation no_allocation;
  
    // Iterate the heap.
    int count = 0;
    HeapObject* heap_obj = NULL;
    while (((heap_obj = iterator->next()) != NULL) &&
           (max_references == 0 || count < max_references)) {
      // Only look at all JSObjects.
      if (heap_obj->IsJSObject()) {
        JSObject* obj = JSObject::cast(heap_obj);
        if (obj->map()->constructor() == constructor) {
          // Valid reference found add to instance array if supplied an update
          // count.
          if (instances != NULL && count < instances_size) {
            instances->set(count, obj);
          }
          count++;
        }
      }
    }
  
    // Return the number of referencing objects found.
    return count;
  }
  
  
  // Scan the heap for objects constructed by a specific function.
  // args[0]: the constructor to find instances of
  // args[1]: the the maximum number of objects to return
  RUNTIME_FUNCTION(Runtime_DebugConstructedBy) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
  
    // Check parameters.
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, constructor, 0);
    CONVERT_NUMBER_CHECKED(int32_t, max_references, Int32, args[1]);
    RUNTIME_ASSERT(max_references >= 0);
  
    // Get the number of referencing objects.
    int count;
    // First perform a full GC in order to avoid dead objects and to make the heap
    // iterable.
    Heap* heap = isolate->heap();
    heap->CollectAllGarbage(Heap::kMakeHeapIterableMask, "%DebugConstructedBy");
    {
      HeapIterator heap_iterator(heap);
      count = DebugConstructedBy(&heap_iterator,
                                 *constructor,
                                 max_references,
                                 NULL,
                                 0);
    }
  
    // Allocate an array to hold the result.
    Handle<FixedArray> instances = isolate->factory()->NewFixedArray(count);
  
    // Fill the referencing objects.
    {
      HeapIterator heap_iterator2(heap);
      count = DebugConstructedBy(&heap_iterator2,
                                 *constructor,
                                 max_references,
                                 *instances,
                                 count);
    }
  
    // Return result as JS array.
    Handle<JSFunction> array_function = isolate->array_function();
    Handle<JSObject> result = isolate->factory()->NewJSObject(array_function);
    JSArray::SetContent(Handle<JSArray>::cast(result), instances);
    return *result;
  }
  
  
  // Find the effective prototype object as returned by __proto__.
  // args[0]: the object to find the prototype for.
  RUNTIME_FUNCTION(Runtime_DebugGetPrototype) {
    HandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, obj, 0);
    return *GetPrototypeSkipHiddenPrototypes(isolate, obj);
  }
  
  
  // Patches script source (should be called upon BeforeCompile event).
  RUNTIME_FUNCTION(Runtime_DebugSetScriptSource) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_HANDLE_CHECKED(JSValue, script_wrapper, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, source, 1);
  
    RUNTIME_ASSERT(script_wrapper->value()->IsScript());
    Handle<Script> script(Script::cast(script_wrapper->value()));
  
    int compilation_state = script->compilation_state();
    RUNTIME_ASSERT(compilation_state == Script::COMPILATION_STATE_INITIAL);
    script->set_source(*source);
  
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_SystemBreak) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 0);
    base::OS::DebugBreak();
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_DebugDisassembleFunction) {
    HandleScope scope(isolate);
  #ifdef DEBUG
    DCHECK(args.length() == 1);
    // Get the function and make sure it is compiled.
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, func, 0);
    if (!Compiler::EnsureCompiled(func, KEEP_EXCEPTION)) {
      return isolate->heap()->exception();
    }
    OFStream os(stdout);
    func->code()->Print(os);
    os << endl;
  #endif  // DEBUG
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_DebugDisassembleConstructor) {
    HandleScope scope(isolate);
  #ifdef DEBUG
    DCHECK(args.length() == 1);
    // Get the function and make sure it is compiled.
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, func, 0);
    if (!Compiler::EnsureCompiled(func, KEEP_EXCEPTION)) {
      return isolate->heap()->exception();
    }
    OFStream os(stdout);
    func->shared()->construct_stub()->Print(os);
    os << endl;
  #endif  // DEBUG
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_FunctionGetInferredName) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
  
    CONVERT_ARG_CHECKED(JSFunction, f, 0);
    return f->shared()->inferred_name();
  }
  
  
  static int FindSharedFunctionInfosForScript(HeapIterator* iterator,
                                              Script* script,
                                              FixedArray* buffer) {
    DisallowHeapAllocation no_allocation;
    int counter = 0;
    int buffer_size = buffer->length();
    for (HeapObject* obj = iterator->next();
         obj != NULL;
         obj = iterator->next()) {
      DCHECK(obj != NULL);
      if (!obj->IsSharedFunctionInfo()) {
        continue;
      }
      SharedFunctionInfo* shared = SharedFunctionInfo::cast(obj);
      if (shared->script() != script) {
        continue;
      }
      if (counter < buffer_size) {
        buffer->set(counter, shared);
      }
      counter++;
    }
    return counter;
  }
  
  
  // For a script finds all SharedFunctionInfo's in the heap that points
  // to this script. Returns JSArray of SharedFunctionInfo wrapped
  // in OpaqueReferences.
  RUNTIME_FUNCTION(Runtime_LiveEditFindSharedFunctionInfosForScript) {
    HandleScope scope(isolate);
    CHECK(isolate->debug()->live_edit_enabled());
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(JSValue, script_value, 0);
  
    RUNTIME_ASSERT(script_value->value()->IsScript());
    Handle<Script> script = Handle<Script>(Script::cast(script_value->value()));
  
    const int kBufferSize = 32;
  
    Handle<FixedArray> array;
    array = isolate->factory()->NewFixedArray(kBufferSize);
    int number;
    Heap* heap = isolate->heap();
    {
      HeapIterator heap_iterator(heap);
      Script* scr = *script;
      FixedArray* arr = *array;
      number = FindSharedFunctionInfosForScript(&heap_iterator, scr, arr);
    }
    if (number > kBufferSize) {
      array = isolate->factory()->NewFixedArray(number);
      HeapIterator heap_iterator(heap);
      Script* scr = *script;
      FixedArray* arr = *array;
      FindSharedFunctionInfosForScript(&heap_iterator, scr, arr);
    }
  
    Handle<JSArray> result = isolate->factory()->NewJSArrayWithElements(array);
    result->set_length(Smi::FromInt(number));
  
    LiveEdit::WrapSharedFunctionInfos(result);
  
    return *result;
  }
  
  
  // For a script calculates compilation information about all its functions.
  // The script source is explicitly specified by the second argument.
  // The source of the actual script is not used, however it is important that
  // all generated code keeps references to this particular instance of script.
  // Returns a JSArray of compilation infos. The array is ordered so that
  // each function with all its descendant is always stored in a continues range
  // with the function itself going first. The root function is a script function.
  RUNTIME_FUNCTION(Runtime_LiveEditGatherCompileInfo) {
    HandleScope scope(isolate);
    CHECK(isolate->debug()->live_edit_enabled());
    DCHECK(args.length() == 2);
    CONVERT_ARG_CHECKED(JSValue, script, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, source, 1);
  
    RUNTIME_ASSERT(script->value()->IsScript());
    Handle<Script> script_handle = Handle<Script>(Script::cast(script->value()));
  
    Handle<JSArray> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result, LiveEdit::GatherCompileInfo(script_handle, source));
    return *result;
  }
  
  
  // Changes the source of the script to a new_source.
  // If old_script_name is provided (i.e. is a String), also creates a copy of
  // the script with its original source and sends notification to debugger.
  RUNTIME_FUNCTION(Runtime_LiveEditReplaceScript) {
    HandleScope scope(isolate);
    CHECK(isolate->debug()->live_edit_enabled());
    DCHECK(args.length() == 3);
    CONVERT_ARG_CHECKED(JSValue, original_script_value, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, new_source, 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, old_script_name, 2);
  
    RUNTIME_ASSERT(original_script_value->value()->IsScript());
    Handle<Script> original_script(Script::cast(original_script_value->value()));
  
    Handle<Object> old_script = LiveEdit::ChangeScriptSource(
        original_script,  new_source,  old_script_name);
  
    if (old_script->IsScript()) {
      Handle<Script> script_handle = Handle<Script>::cast(old_script);
      return *Script::GetWrapper(script_handle);
    } else {
      return isolate->heap()->null_value();
    }
  }
  
  
  RUNTIME_FUNCTION(Runtime_LiveEditFunctionSourceUpdated) {
    HandleScope scope(isolate);
    CHECK(isolate->debug()->live_edit_enabled());
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSArray, shared_info, 0);
    RUNTIME_ASSERT(SharedInfoWrapper::IsInstance(shared_info));
  
    LiveEdit::FunctionSourceUpdated(shared_info);
    return isolate->heap()->undefined_value();
  }
  
  
  // Replaces code of SharedFunctionInfo with a new one.
  RUNTIME_FUNCTION(Runtime_LiveEditReplaceFunctionCode) {
    HandleScope scope(isolate);
    CHECK(isolate->debug()->live_edit_enabled());
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSArray, new_compile_info, 0);
    CONVERT_ARG_HANDLE_CHECKED(JSArray, shared_info, 1);
    RUNTIME_ASSERT(SharedInfoWrapper::IsInstance(shared_info));
  
    LiveEdit::ReplaceFunctionCode(new_compile_info, shared_info);
    return isolate->heap()->undefined_value();
  }
  
  
  // Connects SharedFunctionInfo to another script.
  RUNTIME_FUNCTION(Runtime_LiveEditFunctionSetScript) {
    HandleScope scope(isolate);
    CHECK(isolate->debug()->live_edit_enabled());
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(Object, function_object, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, script_object, 1);
  
    if (function_object->IsJSValue()) {
      Handle<JSValue> function_wrapper = Handle<JSValue>::cast(function_object);
      if (script_object->IsJSValue()) {
        RUNTIME_ASSERT(JSValue::cast(*script_object)->value()->IsScript());
        Script* script = Script::cast(JSValue::cast(*script_object)->value());
        script_object = Handle<Object>(script, isolate);
      }
      RUNTIME_ASSERT(function_wrapper->value()->IsSharedFunctionInfo());
      LiveEdit::SetFunctionScript(function_wrapper, script_object);
    } else {
      // Just ignore this. We may not have a SharedFunctionInfo for some functions
      // and we check it in this function.
    }
  
    return isolate->heap()->undefined_value();
  }
  
  
  // In a code of a parent function replaces original function as embedded object
  // with a substitution one.
  RUNTIME_FUNCTION(Runtime_LiveEditReplaceRefToNestedFunction) {
    HandleScope scope(isolate);
    CHECK(isolate->debug()->live_edit_enabled());
    DCHECK(args.length() == 3);
  
    CONVERT_ARG_HANDLE_CHECKED(JSValue, parent_wrapper, 0);
    CONVERT_ARG_HANDLE_CHECKED(JSValue, orig_wrapper, 1);
    CONVERT_ARG_HANDLE_CHECKED(JSValue, subst_wrapper, 2);
    RUNTIME_ASSERT(parent_wrapper->value()->IsSharedFunctionInfo());
    RUNTIME_ASSERT(orig_wrapper->value()->IsSharedFunctionInfo());
    RUNTIME_ASSERT(subst_wrapper->value()->IsSharedFunctionInfo());
  
    LiveEdit::ReplaceRefToNestedFunction(
        parent_wrapper, orig_wrapper, subst_wrapper);
    return isolate->heap()->undefined_value();
  }
  
  
  // Updates positions of a shared function info (first parameter) according
  // to script source change. Text change is described in second parameter as
  // array of groups of 3 numbers:
  // (change_begin, change_end, change_end_new_position).
  // Each group describes a change in text; groups are sorted by change_begin.
  RUNTIME_FUNCTION(Runtime_LiveEditPatchFunctionPositions) {
    HandleScope scope(isolate);
    CHECK(isolate->debug()->live_edit_enabled());
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSArray, shared_array, 0);
    CONVERT_ARG_HANDLE_CHECKED(JSArray, position_change_array, 1);
    RUNTIME_ASSERT(SharedInfoWrapper::IsInstance(shared_array))
  
    LiveEdit::PatchFunctionPositions(shared_array, position_change_array);
    return isolate->heap()->undefined_value();
  }
  
  
  // For array of SharedFunctionInfo's (each wrapped in JSValue)
  // checks that none of them have activations on stacks (of any thread).
  // Returns array of the same length with corresponding results of
  // LiveEdit::FunctionPatchabilityStatus type.
  RUNTIME_FUNCTION(Runtime_LiveEditCheckAndDropActivations) {
    HandleScope scope(isolate);
    CHECK(isolate->debug()->live_edit_enabled());
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSArray, shared_array, 0);
    CONVERT_BOOLEAN_ARG_CHECKED(do_drop, 1);
    RUNTIME_ASSERT(shared_array->length()->IsSmi());
    RUNTIME_ASSERT(shared_array->HasFastElements())
    int array_length = Smi::cast(shared_array->length())->value();
    for (int i = 0; i < array_length; i++) {
      Handle<Object> element =
          Object::GetElement(isolate, shared_array, i).ToHandleChecked();
      RUNTIME_ASSERT(
          element->IsJSValue() &&
          Handle<JSValue>::cast(element)->value()->IsSharedFunctionInfo());
    }
  
    return *LiveEdit::CheckAndDropActivations(shared_array, do_drop);
  }
  
  
  // Compares 2 strings line-by-line, then token-wise and returns diff in form
  // of JSArray of triplets (pos1, pos1_end, pos2_end) describing list
  // of diff chunks.
  RUNTIME_FUNCTION(Runtime_LiveEditCompareStrings) {
    HandleScope scope(isolate);
    CHECK(isolate->debug()->live_edit_enabled());
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(String, s1, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, s2, 1);
  
    return *LiveEdit::CompareStrings(s1, s2);
  }
  
  
  // Restarts a call frame and completely drops all frames above.
  // Returns true if successful. Otherwise returns undefined or an error message.
  RUNTIME_FUNCTION(Runtime_LiveEditRestartFrame) {
    HandleScope scope(isolate);
    CHECK(isolate->debug()->live_edit_enabled());
    DCHECK(args.length() == 2);
    CONVERT_NUMBER_CHECKED(int, break_id, Int32, args[0]);
    RUNTIME_ASSERT(CheckExecutionState(isolate, break_id));
  
    CONVERT_NUMBER_CHECKED(int, index, Int32, args[1]);
    Heap* heap = isolate->heap();
  
    // Find the relevant frame with the requested index.
    StackFrame::Id id = isolate->debug()->break_frame_id();
    if (id == StackFrame::NO_ID) {
      // If there are no JavaScript stack frames return undefined.
      return heap->undefined_value();
    }
  
    JavaScriptFrameIterator it(isolate, id);
    int inlined_jsframe_index = FindIndexedNonNativeFrame(&it, index);
    if (inlined_jsframe_index == -1) return heap->undefined_value();
    // We don't really care what the inlined frame index is, since we are
    // throwing away the entire frame anyways.
    const char* error_message = LiveEdit::RestartFrame(it.frame());
    if (error_message) {
      return *(isolate->factory()->InternalizeUtf8String(error_message));
    }
    return heap->true_value();
  }
  
  
  // A testing entry. Returns statement position which is the closest to
  // source_position.
  RUNTIME_FUNCTION(Runtime_GetFunctionCodePositionFromSource) {
    HandleScope scope(isolate);
    CHECK(isolate->debug()->live_edit_enabled());
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 0);
    CONVERT_NUMBER_CHECKED(int32_t, source_position, Int32, args[1]);
  
    Handle<Code> code(function->code(), isolate);
  
    if (code->kind() != Code::FUNCTION &&
        code->kind() != Code::OPTIMIZED_FUNCTION) {
      return isolate->heap()->undefined_value();
    }
  
    RelocIterator it(*code, RelocInfo::ModeMask(RelocInfo::STATEMENT_POSITION));
    int closest_pc = 0;
    int distance = kMaxInt;
    while (!it.done()) {
      int statement_position = static_cast<int>(it.rinfo()->data());
      // Check if this break point is closer that what was previously found.
      if (source_position <= statement_position &&
          statement_position - source_position < distance) {
        closest_pc =
            static_cast<int>(it.rinfo()->pc() - code->instruction_start());
        distance = statement_position - source_position;
        // Check whether we can't get any closer.
        if (distance == 0) break;
      }
      it.next();
    }
  
    return Smi::FromInt(closest_pc);
  }
  
  
  // Calls specified function with or without entering the debugger.
  // This is used in unit tests to run code as if debugger is entered or simply
  // to have a stack with C++ frame in the middle.
  RUNTIME_FUNCTION(Runtime_ExecuteInDebugContext) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 0);
    CONVERT_BOOLEAN_ARG_CHECKED(without_debugger, 1);
  
    MaybeHandle<Object> maybe_result;
    if (without_debugger) {
      maybe_result = Execution::Call(isolate,
                                     function,
                                     handle(function->global_proxy()),
                                     0,
                                     NULL);
    } else {
      DebugScope debug_scope(isolate->debug());
      maybe_result = Execution::Call(isolate,
                                     function,
                                     handle(function->global_proxy()),
                                     0,
                                     NULL);
    }
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, result, maybe_result);
    return *result;
  }
  
  
  // Sets a v8 flag.
  RUNTIME_FUNCTION(Runtime_SetFlags) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(String, arg, 0);
    SmartArrayPointer<char> flags =
        arg->ToCString(DISALLOW_NULLS, ROBUST_STRING_TRAVERSAL);
    FlagList::SetFlagsFromString(flags.get(), StrLength(flags.get()));
    return isolate->heap()->undefined_value();
  }
  
  
  // Performs a GC.
  // Presently, it only does a full GC.
  RUNTIME_FUNCTION(Runtime_CollectGarbage) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags, "%CollectGarbage");
    return isolate->heap()->undefined_value();
  }
  
  
  // Gets the current heap usage.
  RUNTIME_FUNCTION(Runtime_GetHeapUsage) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 0);
    int usage = static_cast<int>(isolate->heap()->SizeOfObjects());
    if (!Smi::IsValid(usage)) {
      return *isolate->factory()->NewNumberFromInt(usage);
    }
    return Smi::FromInt(usage);
  }
  
  
  #ifdef V8_I18N_SUPPORT
  RUNTIME_FUNCTION(Runtime_CanonicalizeLanguageTag) {
    HandleScope scope(isolate);
    Factory* factory = isolate->factory();
  
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(String, locale_id_str, 0);
  
    v8::String::Utf8Value locale_id(v8::Utils::ToLocal(locale_id_str));
  
    // Return value which denotes invalid language tag.
    const char* const kInvalidTag = "invalid-tag";
  
    UErrorCode error = U_ZERO_ERROR;
    char icu_result[ULOC_FULLNAME_CAPACITY];
    int icu_length = 0;
  
    uloc_forLanguageTag(*locale_id, icu_result, ULOC_FULLNAME_CAPACITY,
                        &icu_length, &error);
    if (U_FAILURE(error) || icu_length == 0) {
      return *factory->NewStringFromAsciiChecked(kInvalidTag);
    }
  
    char result[ULOC_FULLNAME_CAPACITY];
  
    // Force strict BCP47 rules.
    uloc_toLanguageTag(icu_result, result, ULOC_FULLNAME_CAPACITY, TRUE, &error);
  
    if (U_FAILURE(error)) {
      return *factory->NewStringFromAsciiChecked(kInvalidTag);
    }
  
    return *factory->NewStringFromAsciiChecked(result);
  }
  
  
  RUNTIME_FUNCTION(Runtime_AvailableLocalesOf) {
    HandleScope scope(isolate);
    Factory* factory = isolate->factory();
  
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(String, service, 0);
  
    const icu::Locale* available_locales = NULL;
    int32_t count = 0;
  
    if (service->IsUtf8EqualTo(CStrVector("collator"))) {
      available_locales = icu::Collator::getAvailableLocales(count);
    } else if (service->IsUtf8EqualTo(CStrVector("numberformat"))) {
      available_locales = icu::NumberFormat::getAvailableLocales(count);
    } else if (service->IsUtf8EqualTo(CStrVector("dateformat"))) {
      available_locales = icu::DateFormat::getAvailableLocales(count);
    } else if (service->IsUtf8EqualTo(CStrVector("breakiterator"))) {
      available_locales = icu::BreakIterator::getAvailableLocales(count);
    }
  
    UErrorCode error = U_ZERO_ERROR;
    char result[ULOC_FULLNAME_CAPACITY];
    Handle<JSObject> locales =
        factory->NewJSObject(isolate->object_function());
  
    for (int32_t i = 0; i < count; ++i) {
      const char* icu_name = available_locales[i].getName();
  
      error = U_ZERO_ERROR;
      // No need to force strict BCP47 rules.
      uloc_toLanguageTag(icu_name, result, ULOC_FULLNAME_CAPACITY, FALSE, &error);
      if (U_FAILURE(error)) {
        // This shouldn't happen, but lets not break the user.
        continue;
      }
  
      RETURN_FAILURE_ON_EXCEPTION(isolate,
          JSObject::SetOwnPropertyIgnoreAttributes(
              locales,
              factory->NewStringFromAsciiChecked(result),
              factory->NewNumber(i),
              NONE));
    }
  
    return *locales;
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetDefaultICULocale) {
    HandleScope scope(isolate);
    Factory* factory = isolate->factory();
  
    DCHECK(args.length() == 0);
  
    icu::Locale default_locale;
  
    // Set the locale
    char result[ULOC_FULLNAME_CAPACITY];
    UErrorCode status = U_ZERO_ERROR;
    uloc_toLanguageTag(
        default_locale.getName(), result, ULOC_FULLNAME_CAPACITY, FALSE, &status);
    if (U_SUCCESS(status)) {
      return *factory->NewStringFromAsciiChecked(result);
    }
  
    return *factory->NewStringFromStaticAscii("und");
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetLanguageTagVariants) {
    HandleScope scope(isolate);
    Factory* factory = isolate->factory();
  
    DCHECK(args.length() == 1);
  
    CONVERT_ARG_HANDLE_CHECKED(JSArray, input, 0);
  
    uint32_t length = static_cast<uint32_t>(input->length()->Number());
    // Set some limit to prevent fuzz tests from going OOM.
    // Can be bumped when callers' requirements change.
    RUNTIME_ASSERT(length < 100);
    Handle<FixedArray> output = factory->NewFixedArray(length);
    Handle<Name> maximized = factory->NewStringFromStaticAscii("maximized");
    Handle<Name> base = factory->NewStringFromStaticAscii("base");
    for (unsigned int i = 0; i < length; ++i) {
      Handle<Object> locale_id;
      ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
          isolate, locale_id, Object::GetElement(isolate, input, i));
      if (!locale_id->IsString()) {
        return isolate->Throw(*factory->illegal_argument_string());
      }
  
      v8::String::Utf8Value utf8_locale_id(
          v8::Utils::ToLocal(Handle<String>::cast(locale_id)));
  
      UErrorCode error = U_ZERO_ERROR;
  
      // Convert from BCP47 to ICU format.
      // de-DE-u-co-phonebk -> de_DE@collation=phonebook
      char icu_locale[ULOC_FULLNAME_CAPACITY];
      int icu_locale_length = 0;
      uloc_forLanguageTag(*utf8_locale_id, icu_locale, ULOC_FULLNAME_CAPACITY,
                          &icu_locale_length, &error);
      if (U_FAILURE(error) || icu_locale_length == 0) {
        return isolate->Throw(*factory->illegal_argument_string());
      }
  
      // Maximize the locale.
      // de_DE@collation=phonebook -> de_Latn_DE@collation=phonebook
      char icu_max_locale[ULOC_FULLNAME_CAPACITY];
      uloc_addLikelySubtags(
          icu_locale, icu_max_locale, ULOC_FULLNAME_CAPACITY, &error);
  
      // Remove extensions from maximized locale.
      // de_Latn_DE@collation=phonebook -> de_Latn_DE
      char icu_base_max_locale[ULOC_FULLNAME_CAPACITY];
      uloc_getBaseName(
          icu_max_locale, icu_base_max_locale, ULOC_FULLNAME_CAPACITY, &error);
  
      // Get original name without extensions.
      // de_DE@collation=phonebook -> de_DE
      char icu_base_locale[ULOC_FULLNAME_CAPACITY];
      uloc_getBaseName(
          icu_locale, icu_base_locale, ULOC_FULLNAME_CAPACITY, &error);
  
      // Convert from ICU locale format to BCP47 format.
      // de_Latn_DE -> de-Latn-DE
      char base_max_locale[ULOC_FULLNAME_CAPACITY];
      uloc_toLanguageTag(icu_base_max_locale, base_max_locale,
                         ULOC_FULLNAME_CAPACITY, FALSE, &error);
  
      // de_DE -> de-DE
      char base_locale[ULOC_FULLNAME_CAPACITY];
      uloc_toLanguageTag(
          icu_base_locale, base_locale, ULOC_FULLNAME_CAPACITY, FALSE, &error);
  
      if (U_FAILURE(error)) {
        return isolate->Throw(*factory->illegal_argument_string());
      }
  
      Handle<JSObject> result = factory->NewJSObject(isolate->object_function());
      Handle<String> value = factory->NewStringFromAsciiChecked(base_max_locale);
      JSObject::AddProperty(result, maximized, value, NONE);
      value = factory->NewStringFromAsciiChecked(base_locale);
      JSObject::AddProperty(result, base, value, NONE);
      output->set(i, *result);
    }
  
    Handle<JSArray> result = factory->NewJSArrayWithElements(output);
    result->set_length(Smi::FromInt(length));
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_IsInitializedIntlObject) {
    HandleScope scope(isolate);
  
    DCHECK(args.length() == 1);
  
    CONVERT_ARG_HANDLE_CHECKED(Object, input, 0);
  
    if (!input->IsJSObject()) return isolate->heap()->false_value();
    Handle<JSObject> obj = Handle<JSObject>::cast(input);
  
    Handle<String> marker = isolate->factory()->intl_initialized_marker_string();
    Handle<Object> tag(obj->GetHiddenProperty(marker), isolate);
    return isolate->heap()->ToBoolean(!tag->IsTheHole());
  }
  
  
  RUNTIME_FUNCTION(Runtime_IsInitializedIntlObjectOfType) {
    HandleScope scope(isolate);
  
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_HANDLE_CHECKED(Object, input, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, expected_type, 1);
  
    if (!input->IsJSObject()) return isolate->heap()->false_value();
    Handle<JSObject> obj = Handle<JSObject>::cast(input);
  
    Handle<String> marker = isolate->factory()->intl_initialized_marker_string();
    Handle<Object> tag(obj->GetHiddenProperty(marker), isolate);
    return isolate->heap()->ToBoolean(
        tag->IsString() && String::cast(*tag)->Equals(*expected_type));
  }
  
  
  RUNTIME_FUNCTION(Runtime_MarkAsInitializedIntlObjectOfType) {
    HandleScope scope(isolate);
  
    DCHECK(args.length() == 3);
  
    CONVERT_ARG_HANDLE_CHECKED(JSObject, input, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, type, 1);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, impl, 2);
  
    Handle<String> marker = isolate->factory()->intl_initialized_marker_string();
    JSObject::SetHiddenProperty(input, marker, type);
  
    marker = isolate->factory()->intl_impl_object_string();
    JSObject::SetHiddenProperty(input, marker, impl);
  
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetImplFromInitializedIntlObject) {
    HandleScope scope(isolate);
  
    DCHECK(args.length() == 1);
  
    CONVERT_ARG_HANDLE_CHECKED(Object, input, 0);
  
    if (!input->IsJSObject()) {
      Vector< Handle<Object> > arguments = HandleVector(&input, 1);
      Handle<Object> type_error =
          isolate->factory()->NewTypeError("not_intl_object", arguments);
      return isolate->Throw(*type_error);
    }
  
    Handle<JSObject> obj = Handle<JSObject>::cast(input);
  
    Handle<String> marker = isolate->factory()->intl_impl_object_string();
    Handle<Object> impl(obj->GetHiddenProperty(marker), isolate);
    if (impl->IsTheHole()) {
      Vector< Handle<Object> > arguments = HandleVector(&obj, 1);
      Handle<Object> type_error =
          isolate->factory()->NewTypeError("not_intl_object", arguments);
      return isolate->Throw(*type_error);
    }
    return *impl;
  }
  
  
  RUNTIME_FUNCTION(Runtime_CreateDateTimeFormat) {
    HandleScope scope(isolate);
  
    DCHECK(args.length() == 3);
  
    CONVERT_ARG_HANDLE_CHECKED(String, locale, 0);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, options, 1);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, resolved, 2);
  
    Handle<ObjectTemplateInfo> date_format_template =
        I18N::GetTemplate(isolate);
  
    // Create an empty object wrapper.
    Handle<JSObject> local_object;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, local_object,
        Execution::InstantiateObject(date_format_template));
  
    // Set date time formatter as internal field of the resulting JS object.
    icu::SimpleDateFormat* date_format = DateFormat::InitializeDateTimeFormat(
        isolate, locale, options, resolved);
  
    if (!date_format) return isolate->ThrowIllegalOperation();
  
    local_object->SetInternalField(0, reinterpret_cast<Smi*>(date_format));
  
    Factory* factory = isolate->factory();
    Handle<String> key = factory->NewStringFromStaticAscii("dateFormat");
    Handle<String> value = factory->NewStringFromStaticAscii("valid");
    JSObject::AddProperty(local_object, key, value, NONE);
  
    // Make object handle weak so we can delete the data format once GC kicks in.
    Handle<Object> wrapper = isolate->global_handles()->Create(*local_object);
    GlobalHandles::MakeWeak(wrapper.location(),
                            reinterpret_cast<void*>(wrapper.location()),
                            DateFormat::DeleteDateFormat);
    return *local_object;
  }
  
  
  RUNTIME_FUNCTION(Runtime_InternalDateFormat) {
    HandleScope scope(isolate);
  
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_HANDLE_CHECKED(JSObject, date_format_holder, 0);
    CONVERT_ARG_HANDLE_CHECKED(JSDate, date, 1);
  
    Handle<Object> value;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, value, Execution::ToNumber(isolate, date));
  
    icu::SimpleDateFormat* date_format =
        DateFormat::UnpackDateFormat(isolate, date_format_holder);
    if (!date_format) return isolate->ThrowIllegalOperation();
  
    icu::UnicodeString result;
    date_format->format(value->Number(), result);
  
    Handle<String> result_str;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result_str,
        isolate->factory()->NewStringFromTwoByte(
            Vector<const uint16_t>(
                reinterpret_cast<const uint16_t*>(result.getBuffer()),
                result.length())));
    return *result_str;
  }
  
  
  RUNTIME_FUNCTION(Runtime_InternalDateParse) {
    HandleScope scope(isolate);
  
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_HANDLE_CHECKED(JSObject, date_format_holder, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, date_string, 1);
  
    v8::String::Utf8Value utf8_date(v8::Utils::ToLocal(date_string));
    icu::UnicodeString u_date(icu::UnicodeString::fromUTF8(*utf8_date));
    icu::SimpleDateFormat* date_format =
        DateFormat::UnpackDateFormat(isolate, date_format_holder);
    if (!date_format) return isolate->ThrowIllegalOperation();
  
    UErrorCode status = U_ZERO_ERROR;
    UDate date = date_format->parse(u_date, status);
    if (U_FAILURE(status)) return isolate->heap()->undefined_value();
  
    Handle<Object> result;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result,
        Execution::NewDate(isolate, static_cast<double>(date)));
    DCHECK(result->IsJSDate());
    return *result;
  }
  
  
  RUNTIME_FUNCTION(Runtime_CreateNumberFormat) {
    HandleScope scope(isolate);
  
    DCHECK(args.length() == 3);
  
    CONVERT_ARG_HANDLE_CHECKED(String, locale, 0);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, options, 1);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, resolved, 2);
  
    Handle<ObjectTemplateInfo> number_format_template =
        I18N::GetTemplate(isolate);
  
    // Create an empty object wrapper.
    Handle<JSObject> local_object;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, local_object,
        Execution::InstantiateObject(number_format_template));
  
    // Set number formatter as internal field of the resulting JS object.
    icu::DecimalFormat* number_format = NumberFormat::InitializeNumberFormat(
        isolate, locale, options, resolved);
  
    if (!number_format) return isolate->ThrowIllegalOperation();
  
    local_object->SetInternalField(0, reinterpret_cast<Smi*>(number_format));
  
    Factory* factory = isolate->factory();
    Handle<String> key = factory->NewStringFromStaticAscii("numberFormat");
    Handle<String> value = factory->NewStringFromStaticAscii("valid");
    JSObject::AddProperty(local_object, key, value, NONE);
  
    Handle<Object> wrapper = isolate->global_handles()->Create(*local_object);
    GlobalHandles::MakeWeak(wrapper.location(),
                            reinterpret_cast<void*>(wrapper.location()),
                            NumberFormat::DeleteNumberFormat);
    return *local_object;
  }
  
  
  RUNTIME_FUNCTION(Runtime_InternalNumberFormat) {
    HandleScope scope(isolate);
  
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_HANDLE_CHECKED(JSObject, number_format_holder, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, number, 1);
  
    Handle<Object> value;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, value, Execution::ToNumber(isolate, number));
  
    icu::DecimalFormat* number_format =
        NumberFormat::UnpackNumberFormat(isolate, number_format_holder);
    if (!number_format) return isolate->ThrowIllegalOperation();
  
    icu::UnicodeString result;
    number_format->format(value->Number(), result);
  
    Handle<String> result_str;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result_str,
        isolate->factory()->NewStringFromTwoByte(
            Vector<const uint16_t>(
                reinterpret_cast<const uint16_t*>(result.getBuffer()),
                result.length())));
    return *result_str;
  }
  
  
  RUNTIME_FUNCTION(Runtime_InternalNumberParse) {
    HandleScope scope(isolate);
  
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_HANDLE_CHECKED(JSObject, number_format_holder, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, number_string, 1);
  
    v8::String::Utf8Value utf8_number(v8::Utils::ToLocal(number_string));
    icu::UnicodeString u_number(icu::UnicodeString::fromUTF8(*utf8_number));
    icu::DecimalFormat* number_format =
        NumberFormat::UnpackNumberFormat(isolate, number_format_holder);
    if (!number_format) return isolate->ThrowIllegalOperation();
  
    UErrorCode status = U_ZERO_ERROR;
    icu::Formattable result;
    // ICU 4.6 doesn't support parseCurrency call. We need to wait for ICU49
    // to be part of Chrome.
    // TODO(cira): Include currency parsing code using parseCurrency call.
    // We need to check if the formatter parses all currencies or only the
    // one it was constructed with (it will impact the API - how to return ISO
    // code and the value).
    number_format->parse(u_number, result, status);
    if (U_FAILURE(status)) return isolate->heap()->undefined_value();
  
    switch (result.getType()) {
    case icu::Formattable::kDouble:
      return *isolate->factory()->NewNumber(result.getDouble());
    case icu::Formattable::kLong:
      return *isolate->factory()->NewNumberFromInt(result.getLong());
    case icu::Formattable::kInt64:
      return *isolate->factory()->NewNumber(
          static_cast<double>(result.getInt64()));
    default:
      return isolate->heap()->undefined_value();
    }
  }
  
  
  RUNTIME_FUNCTION(Runtime_CreateCollator) {
    HandleScope scope(isolate);
  
    DCHECK(args.length() == 3);
  
    CONVERT_ARG_HANDLE_CHECKED(String, locale, 0);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, options, 1);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, resolved, 2);
  
    Handle<ObjectTemplateInfo> collator_template = I18N::GetTemplate(isolate);
  
    // Create an empty object wrapper.
    Handle<JSObject> local_object;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, local_object, Execution::InstantiateObject(collator_template));
  
    // Set collator as internal field of the resulting JS object.
    icu::Collator* collator = Collator::InitializeCollator(
        isolate, locale, options, resolved);
  
    if (!collator) return isolate->ThrowIllegalOperation();
  
    local_object->SetInternalField(0, reinterpret_cast<Smi*>(collator));
  
    Factory* factory = isolate->factory();
    Handle<String> key = factory->NewStringFromStaticAscii("collator");
    Handle<String> value = factory->NewStringFromStaticAscii("valid");
    JSObject::AddProperty(local_object, key, value, NONE);
  
    Handle<Object> wrapper = isolate->global_handles()->Create(*local_object);
    GlobalHandles::MakeWeak(wrapper.location(),
                            reinterpret_cast<void*>(wrapper.location()),
                            Collator::DeleteCollator);
    return *local_object;
  }
  
  
  RUNTIME_FUNCTION(Runtime_InternalCompare) {
    HandleScope scope(isolate);
  
    DCHECK(args.length() == 3);
  
    CONVERT_ARG_HANDLE_CHECKED(JSObject, collator_holder, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, string1, 1);
    CONVERT_ARG_HANDLE_CHECKED(String, string2, 2);
  
    icu::Collator* collator = Collator::UnpackCollator(isolate, collator_holder);
    if (!collator) return isolate->ThrowIllegalOperation();
  
    v8::String::Value string_value1(v8::Utils::ToLocal(string1));
    v8::String::Value string_value2(v8::Utils::ToLocal(string2));
    const UChar* u_string1 = reinterpret_cast<const UChar*>(*string_value1);
    const UChar* u_string2 = reinterpret_cast<const UChar*>(*string_value2);
    UErrorCode status = U_ZERO_ERROR;
    UCollationResult result = collator->compare(u_string1,
                                                string_value1.length(),
                                                u_string2,
                                                string_value2.length(),
                                                status);
    if (U_FAILURE(status)) return isolate->ThrowIllegalOperation();
  
    return *isolate->factory()->NewNumberFromInt(result);
  }
  
  
  RUNTIME_FUNCTION(Runtime_StringNormalize) {
    HandleScope scope(isolate);
    static const UNormalizationMode normalizationForms[] =
        { UNORM_NFC, UNORM_NFD, UNORM_NFKC, UNORM_NFKD };
  
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_HANDLE_CHECKED(String, stringValue, 0);
    CONVERT_NUMBER_CHECKED(int, form_id, Int32, args[1]);
    RUNTIME_ASSERT(form_id >= 0 &&
                   static_cast<size_t>(form_id) < ARRAY_SIZE(normalizationForms));
  
    v8::String::Value string_value(v8::Utils::ToLocal(stringValue));
    const UChar* u_value = reinterpret_cast<const UChar*>(*string_value);
  
    // TODO(mnita): check Normalizer2 (not available in ICU 46)
    UErrorCode status = U_ZERO_ERROR;
    icu::UnicodeString result;
    icu::Normalizer::normalize(u_value, normalizationForms[form_id], 0,
        result, status);
    if (U_FAILURE(status)) {
      return isolate->heap()->undefined_value();
    }
  
    Handle<String> result_str;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, result_str,
        isolate->factory()->NewStringFromTwoByte(
            Vector<const uint16_t>(
                reinterpret_cast<const uint16_t*>(result.getBuffer()),
                result.length())));
    return *result_str;
  }
  
  
  RUNTIME_FUNCTION(Runtime_CreateBreakIterator) {
    HandleScope scope(isolate);
  
    DCHECK(args.length() == 3);
  
    CONVERT_ARG_HANDLE_CHECKED(String, locale, 0);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, options, 1);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, resolved, 2);
  
    Handle<ObjectTemplateInfo> break_iterator_template =
        I18N::GetTemplate2(isolate);
  
    // Create an empty object wrapper.
    Handle<JSObject> local_object;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
        isolate, local_object,
        Execution::InstantiateObject(break_iterator_template));
  
    // Set break iterator as internal field of the resulting JS object.
    icu::BreakIterator* break_iterator = BreakIterator::InitializeBreakIterator(
        isolate, locale, options, resolved);
  
    if (!break_iterator) return isolate->ThrowIllegalOperation();
  
    local_object->SetInternalField(0, reinterpret_cast<Smi*>(break_iterator));
    // Make sure that the pointer to adopted text is NULL.
    local_object->SetInternalField(1, reinterpret_cast<Smi*>(NULL));
  
    Factory* factory = isolate->factory();
    Handle<String> key = factory->NewStringFromStaticAscii("breakIterator");
    Handle<String> value = factory->NewStringFromStaticAscii("valid");
    JSObject::AddProperty(local_object, key, value, NONE);
  
    // Make object handle weak so we can delete the break iterator once GC kicks
    // in.
    Handle<Object> wrapper = isolate->global_handles()->Create(*local_object);
    GlobalHandles::MakeWeak(wrapper.location(),
                            reinterpret_cast<void*>(wrapper.location()),
                            BreakIterator::DeleteBreakIterator);
    return *local_object;
  }
  
  
  RUNTIME_FUNCTION(Runtime_BreakIteratorAdoptText) {
    HandleScope scope(isolate);
  
    DCHECK(args.length() == 2);
  
    CONVERT_ARG_HANDLE_CHECKED(JSObject, break_iterator_holder, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, text, 1);
  
    icu::BreakIterator* break_iterator =
        BreakIterator::UnpackBreakIterator(isolate, break_iterator_holder);
    if (!break_iterator) return isolate->ThrowIllegalOperation();
  
    icu::UnicodeString* u_text = reinterpret_cast<icu::UnicodeString*>(
        break_iterator_holder->GetInternalField(1));
    delete u_text;
  
    v8::String::Value text_value(v8::Utils::ToLocal(text));
    u_text = new icu::UnicodeString(
        reinterpret_cast<const UChar*>(*text_value), text_value.length());
    break_iterator_holder->SetInternalField(1, reinterpret_cast<Smi*>(u_text));
  
    break_iterator->setText(*u_text);
  
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_BreakIteratorFirst) {
    HandleScope scope(isolate);
  
    DCHECK(args.length() == 1);
  
    CONVERT_ARG_HANDLE_CHECKED(JSObject, break_iterator_holder, 0);
  
    icu::BreakIterator* break_iterator =
        BreakIterator::UnpackBreakIterator(isolate, break_iterator_holder);
    if (!break_iterator) return isolate->ThrowIllegalOperation();
  
    return *isolate->factory()->NewNumberFromInt(break_iterator->first());
  }
  
  
  RUNTIME_FUNCTION(Runtime_BreakIteratorNext) {
    HandleScope scope(isolate);
  
    DCHECK(args.length() == 1);
  
    CONVERT_ARG_HANDLE_CHECKED(JSObject, break_iterator_holder, 0);
  
    icu::BreakIterator* break_iterator =
        BreakIterator::UnpackBreakIterator(isolate, break_iterator_holder);
    if (!break_iterator) return isolate->ThrowIllegalOperation();
  
    return *isolate->factory()->NewNumberFromInt(break_iterator->next());
  }
  
  
  RUNTIME_FUNCTION(Runtime_BreakIteratorCurrent) {
    HandleScope scope(isolate);
  
    DCHECK(args.length() == 1);
  
    CONVERT_ARG_HANDLE_CHECKED(JSObject, break_iterator_holder, 0);
  
    icu::BreakIterator* break_iterator =
        BreakIterator::UnpackBreakIterator(isolate, break_iterator_holder);
    if (!break_iterator) return isolate->ThrowIllegalOperation();
  
    return *isolate->factory()->NewNumberFromInt(break_iterator->current());
  }
  
  
  RUNTIME_FUNCTION(Runtime_BreakIteratorBreakType) {
    HandleScope scope(isolate);
  
    DCHECK(args.length() == 1);
  
    CONVERT_ARG_HANDLE_CHECKED(JSObject, break_iterator_holder, 0);
  
    icu::BreakIterator* break_iterator =
        BreakIterator::UnpackBreakIterator(isolate, break_iterator_holder);
    if (!break_iterator) return isolate->ThrowIllegalOperation();
  
    // TODO(cira): Remove cast once ICU fixes base BreakIterator class.
    icu::RuleBasedBreakIterator* rule_based_iterator =
        static_cast<icu::RuleBasedBreakIterator*>(break_iterator);
    int32_t status = rule_based_iterator->getRuleStatus();
    // Keep return values in sync with JavaScript BreakType enum.
    if (status >= UBRK_WORD_NONE && status < UBRK_WORD_NONE_LIMIT) {
      return *isolate->factory()->NewStringFromStaticAscii("none");
    } else if (status >= UBRK_WORD_NUMBER && status < UBRK_WORD_NUMBER_LIMIT) {
      return *isolate->factory()->NewStringFromStaticAscii("number");
    } else if (status >= UBRK_WORD_LETTER && status < UBRK_WORD_LETTER_LIMIT) {
      return *isolate->factory()->NewStringFromStaticAscii("letter");
    } else if (status >= UBRK_WORD_KANA && status < UBRK_WORD_KANA_LIMIT) {
      return *isolate->factory()->NewStringFromStaticAscii("kana");
    } else if (status >= UBRK_WORD_IDEO && status < UBRK_WORD_IDEO_LIMIT) {
      return *isolate->factory()->NewStringFromStaticAscii("ideo");
    } else {
      return *isolate->factory()->NewStringFromStaticAscii("unknown");
    }
  }
  #endif  // V8_I18N_SUPPORT
  
  
  // Finds the script object from the script data. NOTE: This operation uses
  // heap traversal to find the function generated for the source position
  // for the requested break point. For lazily compiled functions several heap
  // traversals might be required rendering this operation as a rather slow
  // operation. However for setting break points which is normally done through
  // some kind of user interaction the performance is not crucial.
  static Handle<Object> Runtime_GetScriptFromScriptName(
      Handle<String> script_name) {
    // Scan the heap for Script objects to find the script with the requested
    // script data.
    Handle<Script> script;
    Factory* factory = script_name->GetIsolate()->factory();
    Heap* heap = script_name->GetHeap();
    HeapIterator iterator(heap);
    HeapObject* obj = NULL;
    while (script.is_null() && ((obj = iterator.next()) != NULL)) {
      // If a script is found check if it has the script data requested.
      if (obj->IsScript()) {
        if (Script::cast(obj)->name()->IsString()) {
          if (String::cast(Script::cast(obj)->name())->Equals(*script_name)) {
            script = Handle<Script>(Script::cast(obj));
          }
        }
      }
    }
  
    // If no script with the requested script data is found return undefined.
    if (script.is_null()) return factory->undefined_value();
  
    // Return the script found.
    return Script::GetWrapper(script);
  }
  
  
  // Get the script object from script data. NOTE: Regarding performance
  // see the NOTE for GetScriptFromScriptData.
  // args[0]: script data for the script to find the source for
  RUNTIME_FUNCTION(Runtime_GetScript) {
    HandleScope scope(isolate);
  
    DCHECK(args.length() == 1);
  
    CONVERT_ARG_CHECKED(String, script_name, 0);
  
    // Find the requested script.
    Handle<Object> result =
        Runtime_GetScriptFromScriptName(Handle<String>(script_name));
    return *result;
  }
  
  
  // Collect the raw data for a stack trace.  Returns an array of 4
  // element segments each containing a receiver, function, code and
  // native code offset.
  RUNTIME_FUNCTION(Runtime_CollectStackTrace) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, error_object, 0);
    CONVERT_ARG_HANDLE_CHECKED(Object, caller, 1);
  
    if (!isolate->bootstrapper()->IsActive()) {
      // Optionally capture a more detailed stack trace for the message.
      isolate->CaptureAndSetDetailedStackTrace(error_object);
      // Capture a simple stack trace for the stack property.
      isolate->CaptureAndSetSimpleStackTrace(error_object, caller);
    }
    return isolate->heap()->undefined_value();
  }
  
  
  // Returns V8 version as a string.
  RUNTIME_FUNCTION(Runtime_GetV8Version) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 0);
  
    const char* version_string = v8::V8::GetVersion();
  
    return *isolate->factory()->NewStringFromAsciiChecked(version_string);
  }
  
  
  RUNTIME_FUNCTION(Runtime_Abort) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_SMI_ARG_CHECKED(message_id, 0);
    const char* message = GetBailoutReason(
        static_cast<BailoutReason>(message_id));
    base::OS::PrintError("abort: %s\n", message);
    isolate->PrintStack(stderr);
    base::OS::Abort();
    UNREACHABLE();
    return NULL;
  }
  
  
  RUNTIME_FUNCTION(Runtime_AbortJS) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(String, message, 0);
    base::OS::PrintError("abort: %s\n", message->ToCString().get());
    isolate->PrintStack(stderr);
    base::OS::Abort();
    UNREACHABLE();
    return NULL;
  }
  
  
  RUNTIME_FUNCTION(Runtime_FlattenString) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(String, str, 0);
    return *String::Flatten(str);
  }
  
  
  RUNTIME_FUNCTION(Runtime_NotifyContextDisposed) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 0);
    isolate->heap()->NotifyContextDisposed();
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_LoadMutableDouble) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
    CONVERT_ARG_HANDLE_CHECKED(Smi, index, 1);
    RUNTIME_ASSERT((index->value() & 1) == 1);
    FieldIndex field_index =
        FieldIndex::ForLoadByFieldIndex(object->map(), index->value());
    if (field_index.is_inobject()) {
      RUNTIME_ASSERT(field_index.property_index() <
                     object->map()->inobject_properties());
    } else {
      RUNTIME_ASSERT(field_index.outobject_array_index() <
                     object->properties()->length());
    }
    Handle<Object> raw_value(object->RawFastPropertyAt(field_index), isolate);
    RUNTIME_ASSERT(raw_value->IsMutableHeapNumber());
    return *Object::WrapForRead(isolate, raw_value, Representation::Double());
  }
  
  
  RUNTIME_FUNCTION(Runtime_TryMigrateInstance) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
    if (!object->IsJSObject()) return Smi::FromInt(0);
    Handle<JSObject> js_object = Handle<JSObject>::cast(object);
    if (!js_object->map()->is_deprecated()) return Smi::FromInt(0);
    // This call must not cause lazy deopts, because it's called from deferred
    // code where we can't handle lazy deopts for lack of a suitable bailout
    // ID. So we just try migration and signal failure if necessary,
    // which will also trigger a deopt.
    if (!JSObject::TryMigrateInstance(js_object)) return Smi::FromInt(0);
    return *object;
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetFromCache) {
    SealHandleScope shs(isolate);
    // This is only called from codegen, so checks might be more lax.
    CONVERT_ARG_CHECKED(JSFunctionResultCache, cache, 0);
    CONVERT_ARG_CHECKED(Object, key, 1);
  
    {
      DisallowHeapAllocation no_alloc;
  
      int finger_index = cache->finger_index();
      Object* o = cache->get(finger_index);
      if (o == key) {
        // The fastest case: hit the same place again.
        return cache->get(finger_index + 1);
      }
  
      for (int i = finger_index - 2;
           i >= JSFunctionResultCache::kEntriesIndex;
           i -= 2) {
        o = cache->get(i);
        if (o == key) {
          cache->set_finger_index(i);
          return cache->get(i + 1);
        }
      }
  
      int size = cache->size();
      DCHECK(size <= cache->length());
  
      for (int i = size - 2; i > finger_index; i -= 2) {
        o = cache->get(i);
        if (o == key) {
          cache->set_finger_index(i);
          return cache->get(i + 1);
        }
      }
    }
  
    // There is no value in the cache.  Invoke the function and cache result.
    HandleScope scope(isolate);
  
    Handle<JSFunctionResultCache> cache_handle(cache);
    Handle<Object> key_handle(key, isolate);
    Handle<Object> value;
    {
      Handle<JSFunction> factory(JSFunction::cast(
            cache_handle->get(JSFunctionResultCache::kFactoryIndex)));
      // TODO(antonm): consider passing a receiver when constructing a cache.
      Handle<JSObject> receiver(isolate->global_proxy());
      // This handle is nor shared, nor used later, so it's safe.
      Handle<Object> argv[] = { key_handle };
      ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
          isolate, value,
          Execution::Call(isolate, factory, receiver, ARRAY_SIZE(argv), argv));
    }
  
  #ifdef VERIFY_HEAP
    if (FLAG_verify_heap) {
      cache_handle->JSFunctionResultCacheVerify();
    }
  #endif
  
    // Function invocation may have cleared the cache.  Reread all the data.
    int finger_index = cache_handle->finger_index();
    int size = cache_handle->size();
  
    // If we have spare room, put new data into it, otherwise evict post finger
    // entry which is likely to be the least recently used.
    int index = -1;
    if (size < cache_handle->length()) {
      cache_handle->set_size(size + JSFunctionResultCache::kEntrySize);
      index = size;
    } else {
      index = finger_index + JSFunctionResultCache::kEntrySize;
      if (index == cache_handle->length()) {
        index = JSFunctionResultCache::kEntriesIndex;
      }
    }
  
    DCHECK(index % 2 == 0);
    DCHECK(index >= JSFunctionResultCache::kEntriesIndex);
    DCHECK(index < cache_handle->length());
  
    cache_handle->set(index, *key_handle);
    cache_handle->set(index + 1, *value);
    cache_handle->set_finger_index(index);
  
  #ifdef VERIFY_HEAP
    if (FLAG_verify_heap) {
      cache_handle->JSFunctionResultCacheVerify();
    }
  #endif
  
    return *value;
  }
  
  
  RUNTIME_FUNCTION(Runtime_MessageGetStartPosition) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(JSMessageObject, message, 0);
    return Smi::FromInt(message->start_position());
  }
  
  
  RUNTIME_FUNCTION(Runtime_MessageGetScript) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(JSMessageObject, message, 0);
    return message->script();
  }
  
  
  #ifdef DEBUG
  // ListNatives is ONLY used by the fuzz-natives.js in debug mode
  // Exclude the code in release mode.
  RUNTIME_FUNCTION(Runtime_ListNatives) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 0);
  #define COUNT_ENTRY(Name, argc, ressize) + 1
    int entry_count = 0
        RUNTIME_FUNCTION_LIST(COUNT_ENTRY)
        INLINE_FUNCTION_LIST(COUNT_ENTRY)
        INLINE_OPTIMIZED_FUNCTION_LIST(COUNT_ENTRY);
  #undef COUNT_ENTRY
    Factory* factory = isolate->factory();
    Handle<FixedArray> elements = factory->NewFixedArray(entry_count);
    int index = 0;
    bool inline_runtime_functions = false;
  #define ADD_ENTRY(Name, argc, ressize)                                       \
    {                                                                          \
      HandleScope inner(isolate);                                              \
      Handle<String> name;                                                     \
      /* Inline runtime functions have an underscore in front of the name. */  \
      if (inline_runtime_functions) {                                          \
        name = factory->NewStringFromStaticAscii("_" #Name);                   \
      } else {                                                                 \
        name = factory->NewStringFromStaticAscii(#Name);                       \
      }                                                                        \
      Handle<FixedArray> pair_elements = factory->NewFixedArray(2);            \
      pair_elements->set(0, *name);                                            \
      pair_elements->set(1, Smi::FromInt(argc));                               \
      Handle<JSArray> pair = factory->NewJSArrayWithElements(pair_elements);   \
      elements->set(index++, *pair);                                           \
    }
    inline_runtime_functions = false;
    RUNTIME_FUNCTION_LIST(ADD_ENTRY)
    INLINE_OPTIMIZED_FUNCTION_LIST(ADD_ENTRY)
    inline_runtime_functions = true;
    INLINE_FUNCTION_LIST(ADD_ENTRY)
  #undef ADD_ENTRY
    DCHECK_EQ(index, entry_count);
    Handle<JSArray> result = factory->NewJSArrayWithElements(elements);
    return *result;
  }
  #endif
  
  
  RUNTIME_FUNCTION(Runtime_IS_VAR) {
    UNREACHABLE();  // implemented as macro in the parser
    return NULL;
  }
  
  
  #define ELEMENTS_KIND_CHECK_RUNTIME_FUNCTION(Name)        \
    RUNTIME_FUNCTION(Runtime_Has##Name) {          \
      CONVERT_ARG_CHECKED(JSObject, obj, 0);                \
      return isolate->heap()->ToBoolean(obj->Has##Name());  \
    }
  
  ELEMENTS_KIND_CHECK_RUNTIME_FUNCTION(FastSmiElements)
  ELEMENTS_KIND_CHECK_RUNTIME_FUNCTION(FastObjectElements)
  ELEMENTS_KIND_CHECK_RUNTIME_FUNCTION(FastSmiOrObjectElements)
  ELEMENTS_KIND_CHECK_RUNTIME_FUNCTION(FastDoubleElements)
  ELEMENTS_KIND_CHECK_RUNTIME_FUNCTION(FastHoleyElements)
  ELEMENTS_KIND_CHECK_RUNTIME_FUNCTION(DictionaryElements)
  ELEMENTS_KIND_CHECK_RUNTIME_FUNCTION(SloppyArgumentsElements)
  ELEMENTS_KIND_CHECK_RUNTIME_FUNCTION(ExternalArrayElements)
  // Properties test sitting with elements tests - not fooling anyone.
  ELEMENTS_KIND_CHECK_RUNTIME_FUNCTION(FastProperties)
  
  #undef ELEMENTS_KIND_CHECK_RUNTIME_FUNCTION
  
  
  #define TYPED_ARRAYS_CHECK_RUNTIME_FUNCTION(Type, type, TYPE, ctype, size)     \
    RUNTIME_FUNCTION(Runtime_HasExternal##Type##Elements) {             \
      CONVERT_ARG_CHECKED(JSObject, obj, 0);                                     \
      return isolate->heap()->ToBoolean(obj->HasExternal##Type##Elements());     \
    }
  
  TYPED_ARRAYS(TYPED_ARRAYS_CHECK_RUNTIME_FUNCTION)
  
  #undef TYPED_ARRAYS_CHECK_RUNTIME_FUNCTION
  
  
  #define FIXED_TYPED_ARRAYS_CHECK_RUNTIME_FUNCTION(Type, type, TYPE, ctype, s)  \
    RUNTIME_FUNCTION(Runtime_HasFixed##Type##Elements) {                \
      CONVERT_ARG_CHECKED(JSObject, obj, 0);                                     \
      return isolate->heap()->ToBoolean(obj->HasFixed##Type##Elements());        \
    }
  
  TYPED_ARRAYS(FIXED_TYPED_ARRAYS_CHECK_RUNTIME_FUNCTION)
  
  #undef FIXED_TYPED_ARRAYS_CHECK_RUNTIME_FUNCTION
  
  
  RUNTIME_FUNCTION(Runtime_HaveSameMap) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_CHECKED(JSObject, obj1, 0);
    CONVERT_ARG_CHECKED(JSObject, obj2, 1);
    return isolate->heap()->ToBoolean(obj1->map() == obj2->map());
  }
  
  
  RUNTIME_FUNCTION(Runtime_IsJSGlobalProxy) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(Object, obj, 0);
    return isolate->heap()->ToBoolean(obj->IsJSGlobalProxy());
  }
  
  
  RUNTIME_FUNCTION(Runtime_IsObserved) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
  
    if (!args[0]->IsJSReceiver()) return isolate->heap()->false_value();
    CONVERT_ARG_CHECKED(JSReceiver, obj, 0);
    DCHECK(!obj->IsJSGlobalProxy() || !obj->map()->is_observed());
    return isolate->heap()->ToBoolean(obj->map()->is_observed());
  }
  
  
  RUNTIME_FUNCTION(Runtime_SetIsObserved) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSReceiver, obj, 0);
    RUNTIME_ASSERT(!obj->IsJSGlobalProxy());
    if (obj->IsJSProxy()) return isolate->heap()->undefined_value();
    RUNTIME_ASSERT(!obj->map()->is_observed());
  
    DCHECK(obj->IsJSObject());
    JSObject::SetObserved(Handle<JSObject>::cast(obj));
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_EnqueueMicrotask) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, microtask, 0);
    isolate->EnqueueMicrotask(microtask);
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_RunMicrotasks) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 0);
    isolate->RunMicrotasks();
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetObservationState) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 0);
    return isolate->heap()->observation_state();
  }
  
  
  RUNTIME_FUNCTION(Runtime_ObservationWeakMapCreate) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 0);
    // TODO(adamk): Currently this runtime function is only called three times per
    // isolate. If it's called more often, the map should be moved into the
    // strong root list.
    Handle<Map> map =
        isolate->factory()->NewMap(JS_WEAK_MAP_TYPE, JSWeakMap::kSize);
    Handle<JSWeakMap> weakmap =
        Handle<JSWeakMap>::cast(isolate->factory()->NewJSObjectFromMap(map));
    return *WeakCollectionInitialize(isolate, weakmap);
  }
  
  
  static bool ContextsHaveSameOrigin(Handle<Context> context1,
                                     Handle<Context> context2) {
    return context1->security_token() == context2->security_token();
  }
  
  
  RUNTIME_FUNCTION(Runtime_ObserverObjectAndRecordHaveSameOrigin) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 3);
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, observer, 0);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 1);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, record, 2);
  
    Handle<Context> observer_context(observer->context()->native_context());
    Handle<Context> object_context(object->GetCreationContext());
    Handle<Context> record_context(record->GetCreationContext());
  
    return isolate->heap()->ToBoolean(
        ContextsHaveSameOrigin(object_context, observer_context) &&
        ContextsHaveSameOrigin(object_context, record_context));
  }
  
  
  RUNTIME_FUNCTION(Runtime_ObjectWasCreatedInCurrentOrigin) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
  
    Handle<Context> creation_context(object->GetCreationContext(), isolate);
    return isolate->heap()->ToBoolean(
        ContextsHaveSameOrigin(creation_context, isolate->native_context()));
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetObjectContextObjectObserve) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
  
    Handle<Context> context(object->GetCreationContext(), isolate);
    return context->native_object_observe();
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetObjectContextObjectGetNotifier) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
  
    Handle<Context> context(object->GetCreationContext(), isolate);
    return context->native_object_get_notifier();
  }
  
  
  RUNTIME_FUNCTION(Runtime_GetObjectContextNotifierPerformChange) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, object_info, 0);
  
    Handle<Context> context(object_info->GetCreationContext(), isolate);
    return context->native_object_notifier_perform_change();
  }
  
  
  static Object* ArrayConstructorCommon(Isolate* isolate,
                                             Handle<JSFunction> constructor,
                                             Handle<AllocationSite> site,
                                             Arguments* caller_args) {
    Factory* factory = isolate->factory();
  
    bool holey = false;
    bool can_use_type_feedback = true;
    if (caller_args->length() == 1) {
      Handle<Object> argument_one = caller_args->at<Object>(0);
      if (argument_one->IsSmi()) {
        int value = Handle<Smi>::cast(argument_one)->value();
        if (value < 0 || value >= JSObject::kInitialMaxFastElementArray) {
          // the array is a dictionary in this case.
          can_use_type_feedback = false;
        } else if (value != 0) {
          holey = true;
        }
      } else {
        // Non-smi length argument produces a dictionary
        can_use_type_feedback = false;
      }
    }
  
    Handle<JSArray> array;
    if (!site.is_null() && can_use_type_feedback) {
      ElementsKind to_kind = site->GetElementsKind();
      if (holey && !IsFastHoleyElementsKind(to_kind)) {
        to_kind = GetHoleyElementsKind(to_kind);
        // Update the allocation site info to reflect the advice alteration.
        site->SetElementsKind(to_kind);
      }
  
      // We should allocate with an initial map that reflects the allocation site
      // advice. Therefore we use AllocateJSObjectFromMap instead of passing
      // the constructor.
      Handle<Map> initial_map(constructor->initial_map(), isolate);
      if (to_kind != initial_map->elements_kind()) {
        initial_map = Map::AsElementsKind(initial_map, to_kind);
      }
  
      // If we don't care to track arrays of to_kind ElementsKind, then
      // don't emit a memento for them.
      Handle<AllocationSite> allocation_site;
      if (AllocationSite::GetMode(to_kind) == TRACK_ALLOCATION_SITE) {
        allocation_site = site;
      }
  
      array = Handle<JSArray>::cast(factory->NewJSObjectFromMap(
          initial_map, NOT_TENURED, true, allocation_site));
    } else {
      array = Handle<JSArray>::cast(factory->NewJSObject(constructor));
  
      // We might need to transition to holey
      ElementsKind kind = constructor->initial_map()->elements_kind();
      if (holey && !IsFastHoleyElementsKind(kind)) {
        kind = GetHoleyElementsKind(kind);
        JSObject::TransitionElementsKind(array, kind);
      }
    }
  
    factory->NewJSArrayStorage(array, 0, 0, DONT_INITIALIZE_ARRAY_ELEMENTS);
  
    ElementsKind old_kind = array->GetElementsKind();
    RETURN_FAILURE_ON_EXCEPTION(
        isolate, ArrayConstructInitializeElements(array, caller_args));
    if (!site.is_null() &&
        (old_kind != array->GetElementsKind() ||
         !can_use_type_feedback)) {
      // The arguments passed in caused a transition. This kind of complexity
      // can't be dealt with in the inlined hydrogen array constructor case.
      // We must mark the allocationsite as un-inlinable.
      site->SetDoNotInlineCall();
    }
    return *array;
  }
  
  
  RUNTIME_FUNCTION(Runtime_ArrayConstructor) {
    HandleScope scope(isolate);
    // If we get 2 arguments then they are the stub parameters (constructor, type
    // info).  If we get 4, then the first one is a pointer to the arguments
    // passed by the caller, and the last one is the length of the arguments
    // passed to the caller (redundant, but useful to check on the deoptimizer
    // with an assert).
    Arguments empty_args(0, NULL);
    bool no_caller_args = args.length() == 2;
    DCHECK(no_caller_args || args.length() == 4);
    int parameters_start = no_caller_args ? 0 : 1;
    Arguments* caller_args = no_caller_args
        ? &empty_args
        : reinterpret_cast<Arguments*>(args[0]);
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, constructor, parameters_start);
    CONVERT_ARG_HANDLE_CHECKED(Object, type_info, parameters_start + 1);
  #ifdef DEBUG
    if (!no_caller_args) {
      CONVERT_SMI_ARG_CHECKED(arg_count, parameters_start + 2);
      DCHECK(arg_count == caller_args->length());
    }
  #endif
  
    Handle<AllocationSite> site;
    if (!type_info.is_null() &&
        *type_info != isolate->heap()->undefined_value()) {
      site = Handle<AllocationSite>::cast(type_info);
      DCHECK(!site->SitePointsToLiteral());
    }
  
    return ArrayConstructorCommon(isolate,
                                  constructor,
                                  site,
                                  caller_args);
  }
  
  
  RUNTIME_FUNCTION(Runtime_InternalArrayConstructor) {
    HandleScope scope(isolate);
    Arguments empty_args(0, NULL);
    bool no_caller_args = args.length() == 1;
    DCHECK(no_caller_args || args.length() == 3);
    int parameters_start = no_caller_args ? 0 : 1;
    Arguments* caller_args = no_caller_args
        ? &empty_args
        : reinterpret_cast<Arguments*>(args[0]);
    CONVERT_ARG_HANDLE_CHECKED(JSFunction, constructor, parameters_start);
  #ifdef DEBUG
    if (!no_caller_args) {
      CONVERT_SMI_ARG_CHECKED(arg_count, parameters_start + 1);
      DCHECK(arg_count == caller_args->length());
    }
  #endif
    return ArrayConstructorCommon(isolate,
                                  constructor,
                                  Handle<AllocationSite>::null(),
                                  caller_args);
  }
  
  
  RUNTIME_FUNCTION(Runtime_NormalizeElements) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_HANDLE_CHECKED(JSObject, array, 0);
    RUNTIME_ASSERT(!array->HasExternalArrayElements() &&
                   !array->HasFixedTypedArrayElements());
    JSObject::NormalizeElements(array);
    return *array;
  }
  
  
  RUNTIME_FUNCTION(Runtime_MaxSmi) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 0);
    return Smi::FromInt(Smi::kMaxValue);
  }
  
  
  // TODO(dcarney): remove this function when TurboFan supports it.
  // Takes the object to be iterated over and the result of GetPropertyNamesFast
  // Returns pair (cache_array, cache_type).
  RUNTIME_FUNCTION_RETURN_PAIR(Runtime_ForInInit) {
    SealHandleScope scope(isolate);
    DCHECK(args.length() == 2);
    // This simulates CONVERT_ARG_HANDLE_CHECKED for calls returning pairs.
    // Not worth creating a macro atm as this function should be removed.
    if (!args[0]->IsJSReceiver() || !args[1]->IsObject()) {
      Object* error = isolate->ThrowIllegalOperation();
      return MakePair(error, isolate->heap()->undefined_value());
    }
    Handle<JSReceiver> object = args.at<JSReceiver>(0);
    Handle<Object> cache_type = args.at<Object>(1);
    if (cache_type->IsMap()) {
      // Enum cache case.
      if (Map::EnumLengthBits::decode(Map::cast(*cache_type)->bit_field3()) ==
          0) {
        // 0 length enum.
        // Can't handle this case in the graph builder,
        // so transform it into the empty fixed array case.
        return MakePair(isolate->heap()->empty_fixed_array(), Smi::FromInt(1));
      }
      return MakePair(object->map()->instance_descriptors()->GetEnumCache(),
                      *cache_type);
    } else {
      // FixedArray case.
      Smi* new_cache_type = Smi::FromInt(object->IsJSProxy() ? 0 : 1);
      return MakePair(*Handle<FixedArray>::cast(cache_type), new_cache_type);
    }
  }
  
  
  // TODO(dcarney): remove this function when TurboFan supports it.
  RUNTIME_FUNCTION(Runtime_ForInCacheArrayLength) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_HANDLE_CHECKED(Object, cache_type, 0);
    CONVERT_ARG_HANDLE_CHECKED(FixedArray, array, 1);
    int length = 0;
    if (cache_type->IsMap()) {
      length = Map::cast(*cache_type)->EnumLength();
    } else {
      DCHECK(cache_type->IsSmi());
      length = array->length();
    }
    return Smi::FromInt(length);
  }
  
  
  // TODO(dcarney): remove this function when TurboFan supports it.
  // Takes (the object to be iterated over,
  //        cache_array from ForInInit,
  //        cache_type from ForInInit,
  //        the current index)
  // Returns pair (array[index], needs_filtering).
  RUNTIME_FUNCTION_RETURN_PAIR(Runtime_ForInNext) {
    SealHandleScope scope(isolate);
    DCHECK(args.length() == 4);
    // This simulates CONVERT_ARG_HANDLE_CHECKED for calls returning pairs.
    // Not worth creating a macro atm as this function should be removed.
    if (!args[0]->IsJSReceiver() || !args[1]->IsFixedArray() ||
        !args[2]->IsObject() || !args[3]->IsSmi()) {
      Object* error = isolate->ThrowIllegalOperation();
      return MakePair(error, isolate->heap()->undefined_value());
    }
    Handle<JSReceiver> object = args.at<JSReceiver>(0);
    Handle<FixedArray> array = args.at<FixedArray>(1);
    Handle<Object> cache_type = args.at<Object>(2);
    int index = args.smi_at(3);
    // Figure out first if a slow check is needed for this object.
    bool slow_check_needed = false;
    if (cache_type->IsMap()) {
      if (object->map() != Map::cast(*cache_type)) {
        // Object transitioned.  Need slow check.
        slow_check_needed = true;
      }
    } else {
      // No slow check needed for proxies.
      slow_check_needed = Smi::cast(*cache_type)->value() == 1;
    }
    return MakePair(array->get(index),
                    isolate->heap()->ToBoolean(slow_check_needed));
  }
  
  
  // ----------------------------------------------------------------------------
  // Reference implementation for inlined runtime functions.  Only used when the
  // compiler does not support a certain intrinsic.  Don't optimize these, but
  // implement the intrinsic in the respective compiler instead.
  
  // TODO(mstarzinger): These are place-holder stubs for TurboFan and will
  // eventually all have a C++ implementation and this macro will be gone.
  #define U(name)                               \
    RUNTIME_FUNCTION(RuntimeReference_##name) { \
      UNIMPLEMENTED();                          \
      return NULL;                              \
    }
  
  U(IsStringWrapperSafeForDefaultValueOf)
  U(GeneratorNext)
  U(GeneratorThrow)
  U(DebugBreakInOptimizedCode)
  
  #undef U
  
  
  RUNTIME_FUNCTION(RuntimeReference_IsSmi) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(Object, obj, 0);
    return isolate->heap()->ToBoolean(obj->IsSmi());
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_IsNonNegativeSmi) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(Object, obj, 0);
    return isolate->heap()->ToBoolean(obj->IsSmi() &&
                                      Smi::cast(obj)->value() >= 0);
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_IsArray) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(Object, obj, 0);
    return isolate->heap()->ToBoolean(obj->IsJSArray());
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_IsRegExp) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(Object, obj, 0);
    return isolate->heap()->ToBoolean(obj->IsJSRegExp());
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_IsConstructCall) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 0);
    JavaScriptFrameIterator it(isolate);
    JavaScriptFrame* frame = it.frame();
    return isolate->heap()->ToBoolean(frame->IsConstructor());
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_CallFunction) {
    SealHandleScope shs(isolate);
    return __RT_impl_Runtime_Call(args, isolate);
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_ArgumentsLength) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 0);
    JavaScriptFrameIterator it(isolate);
    JavaScriptFrame* frame = it.frame();
    return Smi::FromInt(frame->GetArgumentsLength());
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_Arguments) {
    SealHandleScope shs(isolate);
    return __RT_impl_Runtime_GetArgumentsProperty(args, isolate);
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_ValueOf) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(Object, obj, 0);
    if (!obj->IsJSValue()) return obj;
    return JSValue::cast(obj)->value();
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_SetValueOf) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_CHECKED(Object, obj, 0);
    CONVERT_ARG_CHECKED(Object, value, 1);
    if (!obj->IsJSValue()) return value;
    JSValue::cast(obj)->set_value(value);
    return value;
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_DateField) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_CHECKED(Object, obj, 0);
    CONVERT_SMI_ARG_CHECKED(index, 1);
    if (!obj->IsJSDate()) {
      HandleScope scope(isolate);
      return isolate->Throw(*isolate->factory()->NewTypeError(
          "not_date_object", HandleVector<Object>(NULL, 0)));
    }
    JSDate* date = JSDate::cast(obj);
    if (index == 0) return date->value();
    return JSDate::GetField(date, Smi::FromInt(index));
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_StringCharFromCode) {
    SealHandleScope shs(isolate);
    return __RT_impl_Runtime_CharFromCode(args, isolate);
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_StringCharAt) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 2);
    if (!args[0]->IsString()) return Smi::FromInt(0);
    if (!args[1]->IsNumber()) return Smi::FromInt(0);
    if (std::isinf(args.number_at(1))) return isolate->heap()->empty_string();
    Object* code = __RT_impl_Runtime_StringCharCodeAtRT(args, isolate);
    if (code->IsNaN()) return isolate->heap()->empty_string();
    return __RT_impl_Runtime_CharFromCode(Arguments(1, &code), isolate);
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_OneByteSeqStringSetChar) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 3);
    CONVERT_ARG_CHECKED(SeqOneByteString, string, 0);
    CONVERT_SMI_ARG_CHECKED(index, 1);
    CONVERT_SMI_ARG_CHECKED(value, 2);
    string->SeqOneByteStringSet(index, value);
    return string;
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_TwoByteSeqStringSetChar) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 3);
    CONVERT_ARG_CHECKED(SeqTwoByteString, string, 0);
    CONVERT_SMI_ARG_CHECKED(index, 1);
    CONVERT_SMI_ARG_CHECKED(value, 2);
    string->SeqTwoByteStringSet(index, value);
    return string;
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_ObjectEquals) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 2);
    CONVERT_ARG_CHECKED(Object, obj1, 0);
    CONVERT_ARG_CHECKED(Object, obj2, 1);
    return isolate->heap()->ToBoolean(obj1 == obj2);
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_IsObject) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(Object, obj, 0);
    if (!obj->IsHeapObject()) return isolate->heap()->false_value();
    if (obj->IsNull()) return isolate->heap()->true_value();
    if (obj->IsUndetectableObject()) return isolate->heap()->false_value();
    Map* map = HeapObject::cast(obj)->map();
    bool is_non_callable_spec_object =
        map->instance_type() >= FIRST_NONCALLABLE_SPEC_OBJECT_TYPE &&
        map->instance_type() <= LAST_NONCALLABLE_SPEC_OBJECT_TYPE;
    return isolate->heap()->ToBoolean(is_non_callable_spec_object);
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_IsFunction) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(Object, obj, 0);
    return isolate->heap()->ToBoolean(obj->IsJSFunction());
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_IsUndetectableObject) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(Object, obj, 0);
    return isolate->heap()->ToBoolean(obj->IsUndetectableObject());
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_IsSpecObject) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(Object, obj, 0);
    return isolate->heap()->ToBoolean(obj->IsSpecObject());
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_MathPow) {
    SealHandleScope shs(isolate);
    return __RT_impl_Runtime_MathPowSlow(args, isolate);
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_IsMinusZero) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(Object, obj, 0);
    if (!obj->IsHeapNumber()) return isolate->heap()->false_value();
    HeapNumber* number = HeapNumber::cast(obj);
    return isolate->heap()->ToBoolean(IsMinusZero(number->value()));
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_HasCachedArrayIndex) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    return isolate->heap()->false_value();
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_GetCachedArrayIndex) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_FastAsciiArrayJoin) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 2);
    return isolate->heap()->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_ClassOf) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 1);
    CONVERT_ARG_CHECKED(Object, obj, 0);
    if (!obj->IsJSReceiver()) return isolate->heap()->null_value();
    return JSReceiver::cast(obj)->class_name();
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_StringCharCodeAt) {
    SealHandleScope shs(isolate);
    DCHECK(args.length() == 2);
    if (!args[0]->IsString()) return isolate->heap()->undefined_value();
    if (!args[1]->IsNumber()) return isolate->heap()->undefined_value();
    if (std::isinf(args.number_at(1))) return isolate->heap()->nan_value();
    return __RT_impl_Runtime_StringCharCodeAtRT(args, isolate);
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_StringAdd) {
    SealHandleScope shs(isolate);
    return __RT_impl_Runtime_StringAdd(args, isolate);
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_SubString) {
    SealHandleScope shs(isolate);
    return __RT_impl_Runtime_SubString(args, isolate);
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_StringCompare) {
    SealHandleScope shs(isolate);
    return __RT_impl_Runtime_StringCompare(args, isolate);
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_RegExpExec) {
    SealHandleScope shs(isolate);
    return __RT_impl_Runtime_RegExpExecRT(args, isolate);
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_RegExpConstructResult) {
    SealHandleScope shs(isolate);
    return __RT_impl_Runtime_RegExpConstructResult(args, isolate);
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_GetFromCache) {
    HandleScope scope(isolate);
    DCHECK(args.length() == 2);
    CONVERT_SMI_ARG_CHECKED(id, 0);
    args[0] = isolate->native_context()->jsfunction_result_caches()->get(id);
    return __RT_impl_Runtime_GetFromCache(args, isolate);
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_NumberToString) {
    SealHandleScope shs(isolate);
    return __RT_impl_Runtime_NumberToStringRT(args, isolate);
  }
  
  
  RUNTIME_FUNCTION(RuntimeReference_DebugIsActive) {
    SealHandleScope shs(isolate);
    return Smi::FromInt(isolate->debug()->is_active());
  }
  
  
  // ----------------------------------------------------------------------------
  // Implementation of Runtime
  
  #define F(name, number_of_args, result_size)                                  \
    {                                                                           \
      Runtime::k##name, Runtime::RUNTIME, #name, FUNCTION_ADDR(Runtime_##name), \
          number_of_args, result_size                                           \
    }                                                                           \
    ,
  
  
  #define I(name, number_of_args, result_size)                                \
    {                                                                         \
      Runtime::kInline##name, Runtime::INLINE, "_" #name,                     \
          FUNCTION_ADDR(RuntimeReference_##name), number_of_args, result_size \
    }                                                                         \
    ,
  
  
  #define IO(name, number_of_args, result_size)                              \
    {                                                                        \
      Runtime::kInlineOptimized##name, Runtime::INLINE_OPTIMIZED, "_" #name, \
          FUNCTION_ADDR(Runtime_##name), number_of_args, result_size         \
    }                                                                        \
    ,
  
  
  static const Runtime::Function kIntrinsicFunctions[] = {
    RUNTIME_FUNCTION_LIST(F)
    INLINE_OPTIMIZED_FUNCTION_LIST(F)
    INLINE_FUNCTION_LIST(I)
    INLINE_OPTIMIZED_FUNCTION_LIST(IO)
  };
  
  #undef IO
  #undef I
  #undef F
  
  
  void Runtime::InitializeIntrinsicFunctionNames(Isolate* isolate,
                                                 Handle<NameDictionary> dict) {
    DCHECK(dict->NumberOfElements() == 0);
    HandleScope scope(isolate);
    for (int i = 0; i < kNumFunctions; ++i) {
      const char* name = kIntrinsicFunctions[i].name;
      if (name == NULL) continue;
      Handle<NameDictionary> new_dict = NameDictionary::Add(
          dict,
          isolate->factory()->InternalizeUtf8String(name),
          Handle<Smi>(Smi::FromInt(i), isolate),
          PropertyDetails(NONE, NORMAL, Representation::None()));
      // The dictionary does not need to grow.
      CHECK(new_dict.is_identical_to(dict));
    }
  }
  
  
  const Runtime::Function* Runtime::FunctionForName(Handle<String> name) {
    Heap* heap = name->GetHeap();
    int entry = heap->intrinsic_function_names()->FindEntry(name);
    if (entry != kNotFound) {
      Object* smi_index = heap->intrinsic_function_names()->ValueAt(entry);
      int function_index = Smi::cast(smi_index)->value();
      return &(kIntrinsicFunctions[function_index]);
    }
    return NULL;
  }
  
  
  const Runtime::Function* Runtime::FunctionForEntry(Address entry) {
    for (size_t i = 0; i < ARRAY_SIZE(kIntrinsicFunctions); ++i) {
      if (entry == kIntrinsicFunctions[i].entry) {
        return &(kIntrinsicFunctions[i]);
      }
    }
    return NULL;
  }
  
  
  const Runtime::Function* Runtime::FunctionForId(Runtime::FunctionId id) {
    return &(kIntrinsicFunctions[static_cast<int>(id)]);
  }
  
  } }  // namespace v8::internal
  