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.
  
  #ifndef V8_OBJECTS_H_
  #define V8_OBJECTS_H_
  
  #include "src/allocation.h"
  #include "src/assert-scope.h"
  #include "src/bailout-reason.h"
  #include "src/base/bits.h"
  #include "src/builtins.h"
  #include "src/checks.h"
  #include "src/elements-kind.h"
  #include "src/field-index.h"
  #include "src/flags.h"
  #include "src/list.h"
  #include "src/property-details.h"
  #include "src/smart-pointers.h"
  #include "src/unicode-inl.h"
  #include "src/zone.h"
  
  #if V8_TARGET_ARCH_ARM
  #include "src/arm/constants-arm.h"  // NOLINT
  #elif V8_TARGET_ARCH_ARM64
  #include "src/arm64/constants-arm64.h"  // NOLINT
  #elif V8_TARGET_ARCH_MIPS
  #include "src/mips/constants-mips.h"  // NOLINT
  #elif V8_TARGET_ARCH_MIPS64
  #include "src/mips64/constants-mips64.h"  // NOLINT
  #endif
  
  
  //
  // Most object types in the V8 JavaScript are described in this file.
  //
  // Inheritance hierarchy:
  // - Object
  //   - Smi          (immediate small integer)
  //   - HeapObject   (superclass for everything allocated in the heap)
  //     - JSReceiver  (suitable for property access)
  //       - JSObject
  //         - JSArray
  //         - JSArrayBuffer
  //         - JSArrayBufferView
  //           - JSTypedArray
  //           - JSDataView
  //         - JSCollection
  //         - Float32x4
  //         - Float64x2
  //         - Int32x4
  //           - JSSet
  //           - JSMap
  //         - JSSetIterator
  //         - JSMapIterator
  //         - JSWeakCollection
  //           - JSWeakMap
  //           - JSWeakSet
  //         - JSRegExp
  //         - JSFunction
  //         - JSGeneratorObject
  //         - JSModule
  //         - GlobalObject
  //           - JSGlobalObject
  //           - JSBuiltinsObject
  //         - JSGlobalProxy
  //         - JSValue
  //           - JSDate
  //         - JSMessageObject
  //       - JSProxy
  //         - JSFunctionProxy
  //     - FixedArrayBase
  //       - ByteArray
  //       - FixedArray
  //         - DescriptorArray
  //         - HashTable
  //           - Dictionary
  //           - StringTable
  //           - CompilationCacheTable
  //           - CodeCacheHashTable
  //           - MapCache
  //         - OrderedHashTable
  //           - OrderedHashSet
  //           - OrderedHashMap
  //         - Context
  //         - TypeFeedbackVector
  //         - JSFunctionResultCache
  //         - ScopeInfo
  //         - TransitionArray
  //       - FixedDoubleArray
  //       - ExternalArray
  //         - ExternalUint8ClampedArray
  //         - ExternalInt8Array
  //         - ExternalUint8Array
  //         - ExternalInt16Array
  //         - ExternalUint16Array
  //         - ExternalInt32Array
  //         - ExternalUint32Array
  //         - ExternalFloat32Array
  //         - ExternalFloat32x4Array
  //         - ExternalFloat64x2Array
  //         - ExternalInt32x4Array
  //     - Name
  //       - String
  //         - SeqString
  //           - SeqOneByteString
  //           - SeqTwoByteString
  //         - SlicedString
  //         - ConsString
  //         - ExternalString
  //           - ExternalOneByteString
  //           - ExternalTwoByteString
  //         - InternalizedString
  //           - SeqInternalizedString
  //             - SeqOneByteInternalizedString
  //             - SeqTwoByteInternalizedString
  //           - ConsInternalizedString
  //           - ExternalInternalizedString
  //             - ExternalOneByteInternalizedString
  //             - ExternalTwoByteInternalizedString
  //       - Symbol
  //     - HeapNumber
  //     - Cell
  //       - PropertyCell
  //     - Code
  //     - Map
  //     - Oddball
  //     - Foreign
  //     - SharedFunctionInfo
  //     - Struct
  //       - Box
  //       - DeclaredAccessorDescriptor
  //       - AccessorInfo
  //         - DeclaredAccessorInfo
  //         - ExecutableAccessorInfo
  //       - AccessorPair
  //       - AccessCheckInfo
  //       - InterceptorInfo
  //       - CallHandlerInfo
  //       - TemplateInfo
  //         - FunctionTemplateInfo
  //         - ObjectTemplateInfo
  //       - Script
  //       - SignatureInfo
  //       - TypeSwitchInfo
  //       - DebugInfo
  //       - BreakPointInfo
  //       - CodeCache
  //
  // Formats of Object*:
  //  Smi:        [31 bit signed int] 0
  //  HeapObject: [32 bit direct pointer] (4 byte aligned) | 01
  
  namespace v8 {
  namespace internal {
  
  class OStream;
  
  enum KeyedAccessStoreMode {
    STANDARD_STORE,
    STORE_TRANSITION_SMI_TO_OBJECT,
    STORE_TRANSITION_SMI_TO_DOUBLE,
    STORE_TRANSITION_DOUBLE_TO_OBJECT,
    STORE_TRANSITION_HOLEY_SMI_TO_OBJECT,
    STORE_TRANSITION_HOLEY_SMI_TO_DOUBLE,
    STORE_TRANSITION_HOLEY_DOUBLE_TO_OBJECT,
    STORE_AND_GROW_NO_TRANSITION,
    STORE_AND_GROW_TRANSITION_SMI_TO_OBJECT,
    STORE_AND_GROW_TRANSITION_SMI_TO_DOUBLE,
    STORE_AND_GROW_TRANSITION_DOUBLE_TO_OBJECT,
    STORE_AND_GROW_TRANSITION_HOLEY_SMI_TO_OBJECT,
    STORE_AND_GROW_TRANSITION_HOLEY_SMI_TO_DOUBLE,
    STORE_AND_GROW_TRANSITION_HOLEY_DOUBLE_TO_OBJECT,
    STORE_NO_TRANSITION_IGNORE_OUT_OF_BOUNDS,
    STORE_NO_TRANSITION_HANDLE_COW
  };
  
  
  enum ContextualMode {
    NOT_CONTEXTUAL,
    CONTEXTUAL
  };
  
  
  enum MutableMode {
    MUTABLE,
    IMMUTABLE
  };
  
  
  static const int kGrowICDelta = STORE_AND_GROW_NO_TRANSITION -
      STANDARD_STORE;
  STATIC_ASSERT(STANDARD_STORE == 0);
  STATIC_ASSERT(kGrowICDelta ==
                STORE_AND_GROW_TRANSITION_SMI_TO_OBJECT -
                STORE_TRANSITION_SMI_TO_OBJECT);
  STATIC_ASSERT(kGrowICDelta ==
                STORE_AND_GROW_TRANSITION_SMI_TO_DOUBLE -
                STORE_TRANSITION_SMI_TO_DOUBLE);
  STATIC_ASSERT(kGrowICDelta ==
                STORE_AND_GROW_TRANSITION_DOUBLE_TO_OBJECT -
                STORE_TRANSITION_DOUBLE_TO_OBJECT);
  
  
  static inline KeyedAccessStoreMode GetGrowStoreMode(
      KeyedAccessStoreMode store_mode) {
    if (store_mode < STORE_AND_GROW_NO_TRANSITION) {
      store_mode = static_cast<KeyedAccessStoreMode>(
          static_cast<int>(store_mode) + kGrowICDelta);
    }
    return store_mode;
  }
  
  
  static inline bool IsTransitionStoreMode(KeyedAccessStoreMode store_mode) {
    return store_mode > STANDARD_STORE &&
        store_mode <= STORE_AND_GROW_TRANSITION_HOLEY_DOUBLE_TO_OBJECT &&
        store_mode != STORE_AND_GROW_NO_TRANSITION;
  }
  
  
  static inline KeyedAccessStoreMode GetNonTransitioningStoreMode(
      KeyedAccessStoreMode store_mode) {
    if (store_mode >= STORE_NO_TRANSITION_IGNORE_OUT_OF_BOUNDS) {
      return store_mode;
    }
    if (store_mode >= STORE_AND_GROW_NO_TRANSITION) {
      return STORE_AND_GROW_NO_TRANSITION;
    }
    return STANDARD_STORE;
  }
  
  
  static inline bool IsGrowStoreMode(KeyedAccessStoreMode store_mode) {
    return store_mode >= STORE_AND_GROW_NO_TRANSITION &&
        store_mode <= STORE_AND_GROW_TRANSITION_HOLEY_DOUBLE_TO_OBJECT;
  }
  
  
  // Setter that skips the write barrier if mode is SKIP_WRITE_BARRIER.
  enum WriteBarrierMode { SKIP_WRITE_BARRIER, UPDATE_WRITE_BARRIER };
  
  
  // Indicates whether a value can be loaded as a constant.
  enum StoreMode {
    ALLOW_AS_CONSTANT,
    FORCE_FIELD
  };
  
  
  // PropertyNormalizationMode is used to specify whether to keep
  // inobject properties when normalizing properties of a JSObject.
  enum PropertyNormalizationMode {
    CLEAR_INOBJECT_PROPERTIES,
    KEEP_INOBJECT_PROPERTIES
  };
  
  
  // Indicates how aggressively the prototype should be optimized. FAST_PROTOTYPE
  // will give the fastest result by tailoring the map to the prototype, but that
  // will cause polymorphism with other objects. REGULAR_PROTOTYPE is to be used
  // (at least for now) when dynamically modifying the prototype chain of an
  // object using __proto__ or Object.setPrototypeOf.
  enum PrototypeOptimizationMode { REGULAR_PROTOTYPE, FAST_PROTOTYPE };
  
  
  // Indicates whether transitions can be added to a source map or not.
  enum TransitionFlag {
    INSERT_TRANSITION,
    OMIT_TRANSITION
  };
  
  
  enum DebugExtraICState {
    DEBUG_BREAK,
    DEBUG_PREPARE_STEP_IN
  };
  
  
  // Indicates whether the transition is simple: the target map of the transition
  // either extends the current map with a new property, or it modifies the
  // property that was added last to the current map.
  enum SimpleTransitionFlag {
    SIMPLE_TRANSITION,
    FULL_TRANSITION
  };
  
  
  // Indicates whether we are only interested in the descriptors of a particular
  // map, or in all descriptors in the descriptor array.
  enum DescriptorFlag {
    ALL_DESCRIPTORS,
    OWN_DESCRIPTORS
  };
  
  // The GC maintains a bit of information, the MarkingParity, which toggles
  // from odd to even and back every time marking is completed. Incremental
  // marking can visit an object twice during a marking phase, so algorithms that
  // that piggy-back on marking can use the parity to ensure that they only
  // perform an operation on an object once per marking phase: they record the
  // MarkingParity when they visit an object, and only re-visit the object when it
  // is marked again and the MarkingParity changes.
  enum MarkingParity {
    NO_MARKING_PARITY,
    ODD_MARKING_PARITY,
    EVEN_MARKING_PARITY
  };
  
  // ICs store extra state in a Code object. The default extra state is
  // kNoExtraICState.
  typedef int ExtraICState;
  static const ExtraICState kNoExtraICState = 0;
  
  // Instance size sentinel for objects of variable size.
  const int kVariableSizeSentinel = 0;
  
  // We may store the unsigned bit field as signed Smi value and do not
  // use the sign bit.
  const int kStubMajorKeyBits = 7;
  const int kStubMinorKeyBits = kSmiValueSize - kStubMajorKeyBits - 1;
  
  // All Maps have a field instance_type containing a InstanceType.
  // It describes the type of the instances.
  //
  // As an example, a JavaScript object is a heap object and its map
  // instance_type is JS_OBJECT_TYPE.
  //
  // The names of the string instance types are intended to systematically
  // mirror their encoding in the instance_type field of the map.  The default
  // encoding is considered TWO_BYTE.  It is not mentioned in the name.  ONE_BYTE
  // encoding is mentioned explicitly in the name.  Likewise, the default
  // representation is considered sequential.  It is not mentioned in the
  // name.  The other representations (e.g. CONS, EXTERNAL) are explicitly
  // mentioned.  Finally, the string is either a STRING_TYPE (if it is a normal
  // string) or a INTERNALIZED_STRING_TYPE (if it is a internalized string).
  //
  // NOTE: The following things are some that depend on the string types having
  // instance_types that are less than those of all other types:
  // HeapObject::Size, HeapObject::IterateBody, the typeof operator, and
  // Object::IsString.
  //
  // NOTE: Everything following JS_VALUE_TYPE is considered a
  // JSObject for GC purposes. The first four entries here have typeof
  // 'object', whereas JS_FUNCTION_TYPE has typeof 'function'.
  #define INSTANCE_TYPE_LIST(V)                                   \
    V(STRING_TYPE)                                                \
    V(ONE_BYTE_STRING_TYPE)                                       \
    V(CONS_STRING_TYPE)                                           \
    V(CONS_ONE_BYTE_STRING_TYPE)                                  \
    V(SLICED_STRING_TYPE)                                         \
    V(SLICED_ONE_BYTE_STRING_TYPE)                                \
    V(EXTERNAL_STRING_TYPE)                                       \
    V(EXTERNAL_ONE_BYTE_STRING_TYPE)                              \
    V(EXTERNAL_STRING_WITH_ONE_BYTE_DATA_TYPE)                    \
    V(SHORT_EXTERNAL_STRING_TYPE)                                 \
    V(SHORT_EXTERNAL_ONE_BYTE_STRING_TYPE)                        \
    V(SHORT_EXTERNAL_STRING_WITH_ONE_BYTE_DATA_TYPE)              \
                                                                  \
    V(INTERNALIZED_STRING_TYPE)                                   \
    V(ONE_BYTE_INTERNALIZED_STRING_TYPE)                          \
    V(EXTERNAL_INTERNALIZED_STRING_TYPE)                          \
    V(EXTERNAL_ONE_BYTE_INTERNALIZED_STRING_TYPE)                 \
    V(EXTERNAL_INTERNALIZED_STRING_WITH_ONE_BYTE_DATA_TYPE)       \
    V(SHORT_EXTERNAL_INTERNALIZED_STRING_TYPE)                    \
    V(SHORT_EXTERNAL_ONE_BYTE_INTERNALIZED_STRING_TYPE)           \
    V(SHORT_EXTERNAL_INTERNALIZED_STRING_WITH_ONE_BYTE_DATA_TYPE) \
                                                                  \
    V(SYMBOL_TYPE)                                                \
                                                                  \
    V(MAP_TYPE)                                                   \
    V(CODE_TYPE)                                                  \
    V(ODDBALL_TYPE)                                               \
    V(CELL_TYPE)                                                  \
    V(PROPERTY_CELL_TYPE)                                         \
                                                                  \
    V(HEAP_NUMBER_TYPE)                                           \
    V(MUTABLE_HEAP_NUMBER_TYPE)                                   \
    V(FOREIGN_TYPE)                                               \
    V(BYTE_ARRAY_TYPE)                                            \
    V(FREE_SPACE_TYPE)                                            \
    /* Note: the order of these external array */                 \
    /* types is relied upon in */                                 \
    /* Object::IsExternalArray(). */                              \
    V(EXTERNAL_INT8_ARRAY_TYPE)                                   \
    V(EXTERNAL_UINT8_ARRAY_TYPE)                                  \
    V(EXTERNAL_INT16_ARRAY_TYPE)                                  \
    V(EXTERNAL_UINT16_ARRAY_TYPE)                                 \
    V(EXTERNAL_INT32_ARRAY_TYPE)                                  \
    V(EXTERNAL_UINT32_ARRAY_TYPE)                                 \
    V(EXTERNAL_FLOAT32_ARRAY_TYPE)                                \
    V(EXTERNAL_FLOAT32x4_ARRAY_TYPE)                              \
    V(EXTERNAL_FLOAT64x2_ARRAY_TYPE)                              \
    V(EXTERNAL_INT32x4_ARRAY_TYPE)                                \
    V(EXTERNAL_FLOAT64_ARRAY_TYPE)                                \
    V(EXTERNAL_UINT8_CLAMPED_ARRAY_TYPE)                          \
                                                                  \
    V(FIXED_INT8_ARRAY_TYPE)                                      \
    V(FIXED_UINT8_ARRAY_TYPE)                                     \
    V(FIXED_INT16_ARRAY_TYPE)                                     \
    V(FIXED_UINT16_ARRAY_TYPE)                                    \
    V(FIXED_INT32_ARRAY_TYPE)                                     \
    V(FIXED_UINT32_ARRAY_TYPE)                                    \
    V(FIXED_FLOAT32_ARRAY_TYPE)                                   \
    V(FIXED_FLOAT32x4_ARRAY_TYPE)                                 \
    V(FIXED_INT32x4_ARRAY_TYPE)                                   \
    V(FIXED_FLOAT64x2_ARRAY_TYPE)                                 \
    V(FIXED_FLOAT64_ARRAY_TYPE)                                   \
    V(FIXED_UINT8_CLAMPED_ARRAY_TYPE)                             \
                                                                  \
    V(FILLER_TYPE)                                                \
                                                                  \
    V(DECLARED_ACCESSOR_DESCRIPTOR_TYPE)                          \
    V(DECLARED_ACCESSOR_INFO_TYPE)                                \
    V(EXECUTABLE_ACCESSOR_INFO_TYPE)                              \
    V(ACCESSOR_PAIR_TYPE)                                         \
    V(ACCESS_CHECK_INFO_TYPE)                                     \
    V(INTERCEPTOR_INFO_TYPE)                                      \
    V(CALL_HANDLER_INFO_TYPE)                                     \
    V(FUNCTION_TEMPLATE_INFO_TYPE)                                \
    V(OBJECT_TEMPLATE_INFO_TYPE)                                  \
    V(SIGNATURE_INFO_TYPE)                                        \
    V(TYPE_SWITCH_INFO_TYPE)                                      \
    V(ALLOCATION_MEMENTO_TYPE)                                    \
    V(ALLOCATION_SITE_TYPE)                                       \
    V(SCRIPT_TYPE)                                                \
    V(CODE_CACHE_TYPE)                                            \
    V(POLYMORPHIC_CODE_CACHE_TYPE)                                \
    V(TYPE_FEEDBACK_INFO_TYPE)                                    \
    V(ALIASED_ARGUMENTS_ENTRY_TYPE)                               \
    V(BOX_TYPE)                                                   \
                                                                  \
    V(FIXED_ARRAY_TYPE)                                           \
    V(FIXED_DOUBLE_ARRAY_TYPE)                                    \
    V(CONSTANT_POOL_ARRAY_TYPE)                                   \
    V(SHARED_FUNCTION_INFO_TYPE)                                  \
                                                                  \
    V(JS_MESSAGE_OBJECT_TYPE)                                     \
                                                                  \
    V(JS_VALUE_TYPE)                                              \
    V(JS_DATE_TYPE)                                               \
    V(JS_OBJECT_TYPE)                                             \
    V(JS_CONTEXT_EXTENSION_OBJECT_TYPE)                           \
    V(JS_GENERATOR_OBJECT_TYPE)                                   \
    V(JS_MODULE_TYPE)                                             \
    V(JS_GLOBAL_OBJECT_TYPE)                                      \
    V(JS_BUILTINS_OBJECT_TYPE)                                    \
    V(JS_GLOBAL_PROXY_TYPE)                                       \
    V(JS_ARRAY_TYPE)                                              \
    V(JS_ARRAY_BUFFER_TYPE)                                       \
    V(JS_TYPED_ARRAY_TYPE)                                        \
    V(JS_DATA_VIEW_TYPE)                                          \
    V(FLOAT32x4_TYPE)                                             \
    V(FLOAT64x2_TYPE)                                             \
    V(INT32x4_TYPE)                                               \
    V(JS_PROXY_TYPE)                                              \
    V(JS_SET_TYPE)                                                \
    V(JS_MAP_TYPE)                                                \
    V(JS_SET_ITERATOR_TYPE)                                       \
    V(JS_MAP_ITERATOR_TYPE)                                       \
    V(JS_WEAK_MAP_TYPE)                                           \
    V(JS_WEAK_SET_TYPE)                                           \
    V(JS_REGEXP_TYPE)                                             \
                                                                  \
    V(JS_FUNCTION_TYPE)                                           \
    V(JS_FUNCTION_PROXY_TYPE)                                     \
    V(DEBUG_INFO_TYPE)                                            \
    V(BREAK_POINT_INFO_TYPE)
  
  
  // Since string types are not consecutive, this macro is used to
  // iterate over them.
  #define STRING_TYPE_LIST(V)                                                   \
    V(STRING_TYPE, kVariableSizeSentinel, string, String)                       \
    V(ONE_BYTE_STRING_TYPE, kVariableSizeSentinel, one_byte_string,             \
      OneByteString)                                                            \
    V(CONS_STRING_TYPE, ConsString::kSize, cons_string, ConsString)             \
    V(CONS_ONE_BYTE_STRING_TYPE, ConsString::kSize, cons_one_byte_string,       \
      ConsOneByteString)                                                        \
    V(SLICED_STRING_TYPE, SlicedString::kSize, sliced_string, SlicedString)     \
    V(SLICED_ONE_BYTE_STRING_TYPE, SlicedString::kSize, sliced_one_byte_string, \
      SlicedOneByteString)                                                      \
    V(EXTERNAL_STRING_TYPE, ExternalTwoByteString::kSize, external_string,      \
      ExternalString)                                                           \
    V(EXTERNAL_ONE_BYTE_STRING_TYPE, ExternalOneByteString::kSize,              \
      external_one_byte_string, ExternalOneByteString)                          \
    V(EXTERNAL_STRING_WITH_ONE_BYTE_DATA_TYPE, ExternalTwoByteString::kSize,    \
      external_string_with_one_byte_data, ExternalStringWithOneByteData)        \
    V(SHORT_EXTERNAL_STRING_TYPE, ExternalTwoByteString::kShortSize,            \
      short_external_string, ShortExternalString)                               \
    V(SHORT_EXTERNAL_ONE_BYTE_STRING_TYPE, ExternalOneByteString::kShortSize,   \
      short_external_one_byte_string, ShortExternalOneByteString)               \
    V(SHORT_EXTERNAL_STRING_WITH_ONE_BYTE_DATA_TYPE,                            \
      ExternalTwoByteString::kShortSize,                                        \
      short_external_string_with_one_byte_data,                                 \
      ShortExternalStringWithOneByteData)                                       \
                                                                                \
    V(INTERNALIZED_STRING_TYPE, kVariableSizeSentinel, internalized_string,     \
      InternalizedString)                                                       \
    V(ONE_BYTE_INTERNALIZED_STRING_TYPE, kVariableSizeSentinel,                 \
      one_byte_internalized_string, OneByteInternalizedString)                  \
    V(EXTERNAL_INTERNALIZED_STRING_TYPE, ExternalTwoByteString::kSize,          \
      external_internalized_string, ExternalInternalizedString)                 \
    V(EXTERNAL_ONE_BYTE_INTERNALIZED_STRING_TYPE, ExternalOneByteString::kSize, \
      external_one_byte_internalized_string, ExternalOneByteInternalizedString) \
    V(EXTERNAL_INTERNALIZED_STRING_WITH_ONE_BYTE_DATA_TYPE,                     \
      ExternalTwoByteString::kSize,                                             \
      external_internalized_string_with_one_byte_data,                          \
      ExternalInternalizedStringWithOneByteData)                                \
    V(SHORT_EXTERNAL_INTERNALIZED_STRING_TYPE,                                  \
      ExternalTwoByteString::kShortSize, short_external_internalized_string,    \
      ShortExternalInternalizedString)                                          \
    V(SHORT_EXTERNAL_ONE_BYTE_INTERNALIZED_STRING_TYPE,                         \
      ExternalOneByteString::kShortSize,                                        \
      short_external_one_byte_internalized_string,                              \
      ShortExternalOneByteInternalizedString)                                   \
    V(SHORT_EXTERNAL_INTERNALIZED_STRING_WITH_ONE_BYTE_DATA_TYPE,               \
      ExternalTwoByteString::kShortSize,                                        \
      short_external_internalized_string_with_one_byte_data,                    \
      ShortExternalInternalizedStringWithOneByteData)
  
  // A struct is a simple object a set of object-valued fields.  Including an
  // object type in this causes the compiler to generate most of the boilerplate
  // code for the class including allocation and garbage collection routines,
  // casts and predicates.  All you need to define is the class, methods and
  // object verification routines.  Easy, no?
  //
  // Note that for subtle reasons related to the ordering or numerical values of
  // type tags, elements in this list have to be added to the INSTANCE_TYPE_LIST
  // manually.
  #define STRUCT_LIST(V)                                                         \
    V(BOX, Box, box)                                                             \
    V(DECLARED_ACCESSOR_DESCRIPTOR,                                              \
      DeclaredAccessorDescriptor,                                                \
      declared_accessor_descriptor)                                              \
    V(DECLARED_ACCESSOR_INFO, DeclaredAccessorInfo, declared_accessor_info)      \
    V(EXECUTABLE_ACCESSOR_INFO, ExecutableAccessorInfo, executable_accessor_info)\
    V(ACCESSOR_PAIR, AccessorPair, accessor_pair)                                \
    V(ACCESS_CHECK_INFO, AccessCheckInfo, access_check_info)                     \
    V(INTERCEPTOR_INFO, InterceptorInfo, interceptor_info)                       \
    V(CALL_HANDLER_INFO, CallHandlerInfo, call_handler_info)                     \
    V(FUNCTION_TEMPLATE_INFO, FunctionTemplateInfo, function_template_info)      \
    V(OBJECT_TEMPLATE_INFO, ObjectTemplateInfo, object_template_info)            \
    V(SIGNATURE_INFO, SignatureInfo, signature_info)                             \
    V(TYPE_SWITCH_INFO, TypeSwitchInfo, type_switch_info)                        \
    V(SCRIPT, Script, script)                                                    \
    V(ALLOCATION_SITE, AllocationSite, allocation_site)                          \
    V(ALLOCATION_MEMENTO, AllocationMemento, allocation_memento)                 \
    V(CODE_CACHE, CodeCache, code_cache)                                         \
    V(POLYMORPHIC_CODE_CACHE, PolymorphicCodeCache, polymorphic_code_cache)      \
    V(TYPE_FEEDBACK_INFO, TypeFeedbackInfo, type_feedback_info)                  \
    V(ALIASED_ARGUMENTS_ENTRY, AliasedArgumentsEntry, aliased_arguments_entry)   \
    V(DEBUG_INFO, DebugInfo, debug_info)                                         \
    V(BREAK_POINT_INFO, BreakPointInfo, break_point_info)
  
  // We use the full 8 bits of the instance_type field to encode heap object
  // instance types.  The high-order bit (bit 7) is set if the object is not a
  // string, and cleared if it is a string.
  const uint32_t kIsNotStringMask = 0x80;
  const uint32_t kStringTag = 0x0;
  const uint32_t kNotStringTag = 0x80;
  
  // Bit 6 indicates that the object is an internalized string (if set) or not.
  // Bit 7 has to be clear as well.
  const uint32_t kIsNotInternalizedMask = 0x40;
  const uint32_t kNotInternalizedTag = 0x40;
  const uint32_t kInternalizedTag = 0x0;
  
  // If bit 7 is clear then bit 2 indicates whether the string consists of
  // two-byte characters or one-byte characters.
  const uint32_t kStringEncodingMask = 0x4;
  const uint32_t kTwoByteStringTag = 0x0;
  const uint32_t kOneByteStringTag = 0x4;
  
  // If bit 7 is clear, the low-order 2 bits indicate the representation
  // of the string.
  const uint32_t kStringRepresentationMask = 0x03;
  enum StringRepresentationTag {
    kSeqStringTag = 0x0,
    kConsStringTag = 0x1,
    kExternalStringTag = 0x2,
    kSlicedStringTag = 0x3
  };
  const uint32_t kIsIndirectStringMask = 0x1;
  const uint32_t kIsIndirectStringTag = 0x1;
  STATIC_ASSERT((kSeqStringTag & kIsIndirectStringMask) == 0);  // NOLINT
  STATIC_ASSERT((kExternalStringTag & kIsIndirectStringMask) == 0);  // NOLINT
  STATIC_ASSERT((kConsStringTag &
                 kIsIndirectStringMask) == kIsIndirectStringTag);  // NOLINT
  STATIC_ASSERT((kSlicedStringTag &
                 kIsIndirectStringMask) == kIsIndirectStringTag);  // NOLINT
  
  // Use this mask to distinguish between cons and slice only after making
  // sure that the string is one of the two (an indirect string).
  const uint32_t kSlicedNotConsMask = kSlicedStringTag & ~kConsStringTag;
  STATIC_ASSERT(IS_POWER_OF_TWO(kSlicedNotConsMask));
  
  // If bit 7 is clear, then bit 3 indicates whether this two-byte
  // string actually contains one byte data.
  const uint32_t kOneByteDataHintMask = 0x08;
  const uint32_t kOneByteDataHintTag = 0x08;
  
  // If bit 7 is clear and string representation indicates an external string,
  // then bit 4 indicates whether the data pointer is cached.
  const uint32_t kShortExternalStringMask = 0x10;
  const uint32_t kShortExternalStringTag = 0x10;
  
  
  // A ConsString with an empty string as the right side is a candidate
  // for being shortcut by the garbage collector. We don't allocate any
  // non-flat internalized strings, so we do not shortcut them thereby
  // avoiding turning internalized strings into strings. The bit-masks
  // below contain the internalized bit as additional safety.
  // See heap.cc, mark-compact.cc and objects-visiting.cc.
  const uint32_t kShortcutTypeMask =
      kIsNotStringMask |
      kIsNotInternalizedMask |
      kStringRepresentationMask;
  const uint32_t kShortcutTypeTag = kConsStringTag | kNotInternalizedTag;
  
  static inline bool IsShortcutCandidate(int type) {
    return ((type & kShortcutTypeMask) == kShortcutTypeTag);
  }
  
  
  enum InstanceType {
    // String types.
    INTERNALIZED_STRING_TYPE =
        kTwoByteStringTag | kSeqStringTag | kInternalizedTag,
    ONE_BYTE_INTERNALIZED_STRING_TYPE =
        kOneByteStringTag | kSeqStringTag | kInternalizedTag,
    EXTERNAL_INTERNALIZED_STRING_TYPE =
        kTwoByteStringTag | kExternalStringTag | kInternalizedTag,
    EXTERNAL_ONE_BYTE_INTERNALIZED_STRING_TYPE =
        kOneByteStringTag | kExternalStringTag | kInternalizedTag,
    EXTERNAL_INTERNALIZED_STRING_WITH_ONE_BYTE_DATA_TYPE =
        EXTERNAL_INTERNALIZED_STRING_TYPE | kOneByteDataHintTag |
        kInternalizedTag,
    SHORT_EXTERNAL_INTERNALIZED_STRING_TYPE = EXTERNAL_INTERNALIZED_STRING_TYPE |
                                              kShortExternalStringTag |
                                              kInternalizedTag,
    SHORT_EXTERNAL_ONE_BYTE_INTERNALIZED_STRING_TYPE =
        EXTERNAL_ONE_BYTE_INTERNALIZED_STRING_TYPE | kShortExternalStringTag |
        kInternalizedTag,
    SHORT_EXTERNAL_INTERNALIZED_STRING_WITH_ONE_BYTE_DATA_TYPE =
        EXTERNAL_INTERNALIZED_STRING_WITH_ONE_BYTE_DATA_TYPE |
        kShortExternalStringTag | kInternalizedTag,
    STRING_TYPE = INTERNALIZED_STRING_TYPE | kNotInternalizedTag,
    ONE_BYTE_STRING_TYPE =
        ONE_BYTE_INTERNALIZED_STRING_TYPE | kNotInternalizedTag,
    CONS_STRING_TYPE = kTwoByteStringTag | kConsStringTag | kNotInternalizedTag,
    CONS_ONE_BYTE_STRING_TYPE =
        kOneByteStringTag | kConsStringTag | kNotInternalizedTag,
    SLICED_STRING_TYPE =
        kTwoByteStringTag | kSlicedStringTag | kNotInternalizedTag,
    SLICED_ONE_BYTE_STRING_TYPE =
        kOneByteStringTag | kSlicedStringTag | kNotInternalizedTag,
    EXTERNAL_STRING_TYPE =
        EXTERNAL_INTERNALIZED_STRING_TYPE | kNotInternalizedTag,
    EXTERNAL_ONE_BYTE_STRING_TYPE =
        EXTERNAL_ONE_BYTE_INTERNALIZED_STRING_TYPE | kNotInternalizedTag,
    EXTERNAL_STRING_WITH_ONE_BYTE_DATA_TYPE =
        EXTERNAL_INTERNALIZED_STRING_WITH_ONE_BYTE_DATA_TYPE |
        kNotInternalizedTag,
    SHORT_EXTERNAL_STRING_TYPE =
        SHORT_EXTERNAL_INTERNALIZED_STRING_TYPE | kNotInternalizedTag,
    SHORT_EXTERNAL_ONE_BYTE_STRING_TYPE =
        SHORT_EXTERNAL_ONE_BYTE_INTERNALIZED_STRING_TYPE | kNotInternalizedTag,
    SHORT_EXTERNAL_STRING_WITH_ONE_BYTE_DATA_TYPE =
        SHORT_EXTERNAL_INTERNALIZED_STRING_WITH_ONE_BYTE_DATA_TYPE |
        kNotInternalizedTag,
  
    // Non-string names
    SYMBOL_TYPE = kNotStringTag,  // FIRST_NONSTRING_TYPE, LAST_NAME_TYPE
  
    // Objects allocated in their own spaces (never in new space).
    MAP_TYPE,
    CODE_TYPE,
    ODDBALL_TYPE,
    CELL_TYPE,
    PROPERTY_CELL_TYPE,
  
    // "Data", objects that cannot contain non-map-word pointers to heap
    // objects.
    HEAP_NUMBER_TYPE,
    MUTABLE_HEAP_NUMBER_TYPE,
    FOREIGN_TYPE,
    BYTE_ARRAY_TYPE,
    FREE_SPACE_TYPE,
    EXTERNAL_INT8_ARRAY_TYPE,  // FIRST_EXTERNAL_ARRAY_TYPE
    EXTERNAL_UINT8_ARRAY_TYPE,
    EXTERNAL_INT16_ARRAY_TYPE,
    EXTERNAL_UINT16_ARRAY_TYPE,
    EXTERNAL_INT32_ARRAY_TYPE,
    EXTERNAL_UINT32_ARRAY_TYPE,
    EXTERNAL_FLOAT32_ARRAY_TYPE,
    EXTERNAL_FLOAT32x4_ARRAY_TYPE,
    EXTERNAL_FLOAT64x2_ARRAY_TYPE,
    EXTERNAL_INT32x4_ARRAY_TYPE,
    EXTERNAL_FLOAT64_ARRAY_TYPE,
    EXTERNAL_UINT8_CLAMPED_ARRAY_TYPE,  // LAST_EXTERNAL_ARRAY_TYPE
    FIXED_INT8_ARRAY_TYPE,              // FIRST_FIXED_TYPED_ARRAY_TYPE
    FIXED_UINT8_ARRAY_TYPE,
    FIXED_INT16_ARRAY_TYPE,
    FIXED_UINT16_ARRAY_TYPE,
    FIXED_INT32_ARRAY_TYPE,
    FIXED_INT32x4_ARRAY_TYPE,
    FIXED_UINT32_ARRAY_TYPE,
    FIXED_FLOAT32_ARRAY_TYPE,
    FIXED_FLOAT32x4_ARRAY_TYPE,
    FIXED_FLOAT64x2_ARRAY_TYPE,
    FIXED_FLOAT64_ARRAY_TYPE,
    FIXED_UINT8_CLAMPED_ARRAY_TYPE,  // LAST_FIXED_TYPED_ARRAY_TYPE
    FIXED_DOUBLE_ARRAY_TYPE,
    FILLER_TYPE,  // LAST_DATA_TYPE
  
    // Structs.
    DECLARED_ACCESSOR_DESCRIPTOR_TYPE,
    DECLARED_ACCESSOR_INFO_TYPE,
    EXECUTABLE_ACCESSOR_INFO_TYPE,
    ACCESSOR_PAIR_TYPE,
    ACCESS_CHECK_INFO_TYPE,
    INTERCEPTOR_INFO_TYPE,
    CALL_HANDLER_INFO_TYPE,
    FUNCTION_TEMPLATE_INFO_TYPE,
    OBJECT_TEMPLATE_INFO_TYPE,
    SIGNATURE_INFO_TYPE,
    TYPE_SWITCH_INFO_TYPE,
    ALLOCATION_SITE_TYPE,
    ALLOCATION_MEMENTO_TYPE,
    SCRIPT_TYPE,
    CODE_CACHE_TYPE,
    POLYMORPHIC_CODE_CACHE_TYPE,
    TYPE_FEEDBACK_INFO_TYPE,
    ALIASED_ARGUMENTS_ENTRY_TYPE,
    BOX_TYPE,
    DEBUG_INFO_TYPE,
    BREAK_POINT_INFO_TYPE,
    FIXED_ARRAY_TYPE,
    CONSTANT_POOL_ARRAY_TYPE,
    SHARED_FUNCTION_INFO_TYPE,
  
    // All the following types are subtypes of JSReceiver, which corresponds to
    // objects in the JS sense. The first and the last type in this range are
    // the two forms of function. This organization enables using the same
    // compares for checking the JS_RECEIVER/SPEC_OBJECT range and the
    // NONCALLABLE_JS_OBJECT range.
    JS_FUNCTION_PROXY_TYPE,  // FIRST_JS_RECEIVER_TYPE, FIRST_JS_PROXY_TYPE
    JS_PROXY_TYPE,           // LAST_JS_PROXY_TYPE
    JS_VALUE_TYPE,           // FIRST_JS_OBJECT_TYPE
    JS_MESSAGE_OBJECT_TYPE,
    JS_DATE_TYPE,
    JS_OBJECT_TYPE,
    JS_CONTEXT_EXTENSION_OBJECT_TYPE,
    JS_GENERATOR_OBJECT_TYPE,
    JS_MODULE_TYPE,
    JS_GLOBAL_OBJECT_TYPE,
    JS_BUILTINS_OBJECT_TYPE,
    JS_GLOBAL_PROXY_TYPE,
    JS_ARRAY_TYPE,
    JS_ARRAY_BUFFER_TYPE,
    JS_TYPED_ARRAY_TYPE,
    JS_DATA_VIEW_TYPE,
    FLOAT32x4_TYPE,
    FLOAT64x2_TYPE,
    INT32x4_TYPE,
    JS_SET_TYPE,
    JS_MAP_TYPE,
    JS_SET_ITERATOR_TYPE,
    JS_MAP_ITERATOR_TYPE,
    JS_WEAK_MAP_TYPE,
    JS_WEAK_SET_TYPE,
    JS_REGEXP_TYPE,
    JS_FUNCTION_TYPE,  // LAST_JS_OBJECT_TYPE, LAST_JS_RECEIVER_TYPE
  
    // Pseudo-types
    FIRST_TYPE = 0x0,
    LAST_TYPE = JS_FUNCTION_TYPE,
    FIRST_NAME_TYPE = FIRST_TYPE,
    LAST_NAME_TYPE = SYMBOL_TYPE,
    FIRST_UNIQUE_NAME_TYPE = INTERNALIZED_STRING_TYPE,
    LAST_UNIQUE_NAME_TYPE = SYMBOL_TYPE,
    FIRST_NONSTRING_TYPE = SYMBOL_TYPE,
    // Boundaries for testing for an external array.
    FIRST_EXTERNAL_ARRAY_TYPE = EXTERNAL_INT8_ARRAY_TYPE,
    LAST_EXTERNAL_ARRAY_TYPE = EXTERNAL_UINT8_CLAMPED_ARRAY_TYPE,
    // Boundaries for testing for a fixed typed array.
    FIRST_FIXED_TYPED_ARRAY_TYPE = FIXED_INT8_ARRAY_TYPE,
    LAST_FIXED_TYPED_ARRAY_TYPE = FIXED_UINT8_CLAMPED_ARRAY_TYPE,
    // Boundary for promotion to old data space/old pointer space.
    LAST_DATA_TYPE = FILLER_TYPE,
    // Boundary for objects represented as JSReceiver (i.e. JSObject or JSProxy).
    // Note that there is no range for JSObject or JSProxy, since their subtypes
    // are not continuous in this enum! The enum ranges instead reflect the
    // external class names, where proxies are treated as either ordinary objects,
    // or functions.
    FIRST_JS_RECEIVER_TYPE = JS_FUNCTION_PROXY_TYPE,
    LAST_JS_RECEIVER_TYPE = LAST_TYPE,
    // Boundaries for testing the types represented as JSObject
    FIRST_JS_OBJECT_TYPE = JS_VALUE_TYPE,
    LAST_JS_OBJECT_TYPE = LAST_TYPE,
    // Boundaries for testing the types represented as JSProxy
    FIRST_JS_PROXY_TYPE = JS_FUNCTION_PROXY_TYPE,
    LAST_JS_PROXY_TYPE = JS_PROXY_TYPE,
    // Boundaries for testing whether the type is a JavaScript object.
    FIRST_SPEC_OBJECT_TYPE = FIRST_JS_RECEIVER_TYPE,
    LAST_SPEC_OBJECT_TYPE = LAST_JS_RECEIVER_TYPE,
    // Boundaries for testing the types for which typeof is "object".
    FIRST_NONCALLABLE_SPEC_OBJECT_TYPE = JS_PROXY_TYPE,
    LAST_NONCALLABLE_SPEC_OBJECT_TYPE = JS_REGEXP_TYPE,
    // Note that the types for which typeof is "function" are not continuous.
    // Define this so that we can put assertions on discrete checks.
    NUM_OF_CALLABLE_SPEC_OBJECT_TYPES = 2
  };
  
  const int kExternalArrayTypeCount =
      LAST_EXTERNAL_ARRAY_TYPE - FIRST_EXTERNAL_ARRAY_TYPE + 1;
  
  STATIC_ASSERT(JS_OBJECT_TYPE == Internals::kJSObjectType);
  STATIC_ASSERT(FIRST_NONSTRING_TYPE == Internals::kFirstNonstringType);
  STATIC_ASSERT(ODDBALL_TYPE == Internals::kOddballType);
  STATIC_ASSERT(FOREIGN_TYPE == Internals::kForeignType);
  
  
  #define FIXED_ARRAY_SUB_INSTANCE_TYPE_LIST(V) \
    V(FAST_ELEMENTS_SUB_TYPE)                   \
    V(DICTIONARY_ELEMENTS_SUB_TYPE)             \
    V(FAST_PROPERTIES_SUB_TYPE)                 \
    V(DICTIONARY_PROPERTIES_SUB_TYPE)           \
    V(MAP_CODE_CACHE_SUB_TYPE)                  \
    V(SCOPE_INFO_SUB_TYPE)                      \
    V(STRING_TABLE_SUB_TYPE)                    \
    V(DESCRIPTOR_ARRAY_SUB_TYPE)                \
    V(TRANSITION_ARRAY_SUB_TYPE)
  
  enum FixedArraySubInstanceType {
  #define DEFINE_FIXED_ARRAY_SUB_INSTANCE_TYPE(name) name,
    FIXED_ARRAY_SUB_INSTANCE_TYPE_LIST(DEFINE_FIXED_ARRAY_SUB_INSTANCE_TYPE)
  #undef DEFINE_FIXED_ARRAY_SUB_INSTANCE_TYPE
    LAST_FIXED_ARRAY_SUB_TYPE = TRANSITION_ARRAY_SUB_TYPE
  };
  
  
  enum CompareResult {
    LESS      = -1,
    EQUAL     =  0,
    GREATER   =  1,
  
    NOT_EQUAL = GREATER
  };
  
  
  #define DECL_BOOLEAN_ACCESSORS(name)   \
    inline bool name() const;            \
    inline void set_##name(bool value);  \
  
  
  #define DECL_ACCESSORS(name, type)                                      \
    inline type* name() const;                                            \
    inline void set_##name(type* value,                                   \
                           WriteBarrierMode mode = UPDATE_WRITE_BARRIER); \
  
  
  #define DECLARE_CAST(type)                              \
    INLINE(static type* cast(Object* object));            \
    INLINE(static const type* cast(const Object* object));
  
  
  class AccessorPair;
  class AllocationSite;
  class AllocationSiteCreationContext;
  class AllocationSiteUsageContext;
  class DictionaryElementsAccessor;
  class ElementsAccessor;
  class FixedArrayBase;
  class GlobalObject;
  class ObjectVisitor;
  class LookupIterator;
  class StringStream;
  class TypeFeedbackVector;
  // We cannot just say "class HeapType;" if it is created from a template... =8-?
  template<class> class TypeImpl;
  struct HeapTypeConfig;
  typedef TypeImpl<HeapTypeConfig> HeapType;
  
  
  // A template-ized version of the IsXXX functions.
  template <class C> inline bool Is(Object* obj);
  
  #ifdef VERIFY_HEAP
  #define DECLARE_VERIFIER(Name) void Name##Verify();
  #else
  #define DECLARE_VERIFIER(Name)
  #endif
  
  #ifdef OBJECT_PRINT
  #define DECLARE_PRINTER(Name) void Name##Print(OStream& os);  // NOLINT
  #else
  #define DECLARE_PRINTER(Name)
  #endif
  
  
  #define OBJECT_TYPE_LIST(V) \
    V(Smi)                    \
    V(HeapObject)             \
    V(Number)
  
  #define HEAP_OBJECT_TYPE_LIST(V)   \
    V(HeapNumber)                    \
    V(MutableHeapNumber)             \
    V(Name)                          \
    V(UniqueName)                    \
    V(String)                        \
    V(SeqString)                     \
    V(ExternalString)                \
    V(ConsString)                    \
    V(SlicedString)                  \
    V(ExternalTwoByteString)         \
    V(ExternalOneByteString)         \
    V(SeqTwoByteString)              \
    V(SeqOneByteString)              \
    V(InternalizedString)            \
    V(Symbol)                        \
                                     \
    V(ExternalArray)                 \
    V(ExternalInt8Array)             \
    V(ExternalUint8Array)            \
    V(ExternalInt16Array)            \
    V(ExternalUint16Array)           \
    V(ExternalInt32Array)            \
    V(ExternalUint32Array)           \
    V(ExternalFloat32Array)          \
    V(ExternalFloat32x4Array)        \
    V(ExternalFloat64x2Array)        \
    V(ExternalInt32x4Array)          \
    V(ExternalFloat64Array)          \
    V(ExternalUint8ClampedArray)     \
    V(FixedTypedArrayBase)           \
    V(FixedUint8Array)               \
    V(FixedInt8Array)                \
    V(FixedUint16Array)              \
    V(FixedInt16Array)               \
    V(FixedUint32Array)              \
    V(FixedInt32Array)               \
    V(FixedFloat32Array)             \
    V(FixedFloat32x4Array)           \
    V(FixedFloat64x2Array)           \
    V(FixedInt32x4Array)             \
    V(FixedFloat64Array)             \
    V(FixedUint8ClampedArray)        \
    V(ByteArray)                     \
    V(FreeSpace)                     \
    V(JSReceiver)                    \
    V(JSObject)                      \
    V(JSContextExtensionObject)      \
    V(JSGeneratorObject)             \
    V(JSModule)                      \
    V(Map)                           \
    V(DescriptorArray)               \
    V(TransitionArray)               \
    V(TypeFeedbackVector)            \
    V(DeoptimizationInputData)       \
    V(DeoptimizationOutputData)      \
    V(DependentCode)                 \
    V(FixedArray)                    \
    V(FixedDoubleArray)              \
    V(ConstantPoolArray)             \
    V(Context)                       \
    V(NativeContext)                 \
    V(ScopeInfo)                     \
    V(JSFunction)                    \
    V(Code)                          \
    V(Oddball)                       \
    V(SharedFunctionInfo)            \
    V(JSValue)                       \
    V(JSDate)                        \
    V(JSMessageObject)               \
    V(StringWrapper)                 \
    V(Foreign)                       \
    V(Boolean)                       \
    V(JSArray)                       \
    V(JSArrayBuffer)                 \
    V(JSArrayBufferView)             \
    V(JSTypedArray)                  \
    V(JSDataView)                    \
    V(Float32x4)                     \
    V(Float64x2)                     \
    V(Int32x4)                       \
    V(JSProxy)                       \
    V(JSFunctionProxy)               \
    V(JSSet)                         \
    V(JSMap)                         \
    V(JSSetIterator)                 \
    V(JSMapIterator)                 \
    V(JSWeakCollection)              \
    V(JSWeakMap)                     \
    V(JSWeakSet)                     \
    V(JSRegExp)                      \
    V(HashTable)                     \
    V(Dictionary)                    \
    V(StringTable)                   \
    V(JSFunctionResultCache)         \
    V(NormalizedMapCache)            \
    V(CompilationCacheTable)         \
    V(CodeCacheHashTable)            \
    V(PolymorphicCodeCacheHashTable) \
    V(MapCache)                      \
    V(Primitive)                     \
    V(GlobalObject)                  \
    V(JSGlobalObject)                \
    V(JSBuiltinsObject)              \
    V(JSGlobalProxy)                 \
    V(UndetectableObject)            \
    V(AccessCheckNeeded)             \
    V(Cell)                          \
    V(PropertyCell)                  \
    V(ObjectHashTable)               \
    V(WeakHashTable)                 \
    V(OrderedHashTable)
  
  // Object is the abstract superclass for all classes in the
  // object hierarchy.
  // Object does not use any virtual functions to avoid the
  // allocation of the C++ vtable.
  // Since both Smi and HeapObject are subclasses of Object no
  // data members can be present in Object.
  class Object {
   public:
    // Type testing.
    bool IsObject() const { return true; }
  
  #define IS_TYPE_FUNCTION_DECL(type_)  INLINE(bool Is##type_() const);
    OBJECT_TYPE_LIST(IS_TYPE_FUNCTION_DECL)
    HEAP_OBJECT_TYPE_LIST(IS_TYPE_FUNCTION_DECL)
  #undef IS_TYPE_FUNCTION_DECL
  
    // A non-keyed store is of the form a.x = foo or a["x"] = foo whereas
    // a keyed store is of the form a[expression] = foo.
    enum StoreFromKeyed {
      MAY_BE_STORE_FROM_KEYED,
      CERTAINLY_NOT_STORE_FROM_KEYED
    };
  
    INLINE(bool IsFixedArrayBase() const);
    INLINE(bool IsExternal() const);
    INLINE(bool IsAccessorInfo() const);
  
    INLINE(bool IsStruct() const);
  #define DECLARE_STRUCT_PREDICATE(NAME, Name, name) \
    INLINE(bool Is##Name() const);
    STRUCT_LIST(DECLARE_STRUCT_PREDICATE)
  #undef DECLARE_STRUCT_PREDICATE
  
    INLINE(bool IsSpecObject()) const;
    INLINE(bool IsSpecFunction()) const;
    INLINE(bool IsTemplateInfo()) const;
    INLINE(bool IsNameDictionary() const);
    INLINE(bool IsSeededNumberDictionary() const);
    INLINE(bool IsUnseededNumberDictionary() const);
    INLINE(bool IsOrderedHashSet() const);
    INLINE(bool IsOrderedHashMap() const);
    bool IsCallable() const;
  
    // Oddball testing.
    INLINE(bool IsUndefined() const);
    INLINE(bool IsNull() const);
    INLINE(bool IsTheHole() const);
    INLINE(bool IsException() const);
    INLINE(bool IsUninitialized() const);
    INLINE(bool IsTrue() const);
    INLINE(bool IsFalse() const);
    INLINE(bool IsArgumentsMarker() const);
  
    // Filler objects (fillers and free space objects).
    INLINE(bool IsFiller() const);
  
    // Extract the number.
    inline double Number();
    INLINE(bool IsNaN() const);
    INLINE(bool IsMinusZero() const);
    bool ToInt32(int32_t* value);
    bool ToUint32(uint32_t* value);
  
    inline Representation OptimalRepresentation() {
      if (!FLAG_track_fields) return Representation::Tagged();
      if (IsSmi()) {
        return Representation::Smi();
      } else if (FLAG_track_double_fields && IsHeapNumber()) {
        return Representation::Double();
      } else if (FLAG_track_computed_fields && IsUninitialized()) {
        return Representation::None();
      } else if (FLAG_track_heap_object_fields) {
        DCHECK(IsHeapObject());
        return Representation::HeapObject();
      } else {
        return Representation::Tagged();
      }
    }
  
    inline bool FitsRepresentation(Representation representation) {
      if (FLAG_track_fields && representation.IsNone()) {
        return false;
      } else if (FLAG_track_fields && representation.IsSmi()) {
        return IsSmi();
      } else if (FLAG_track_double_fields && representation.IsDouble()) {
        return IsMutableHeapNumber() || IsNumber();
      } else if (FLAG_track_heap_object_fields && representation.IsHeapObject()) {
        return IsHeapObject();
      }
      return true;
    }
  
    Handle<HeapType> OptimalType(Isolate* isolate, Representation representation);
  
    inline static Handle<Object> NewStorageFor(Isolate* isolate,
                                               Handle<Object> object,
                                               Representation representation);
  
    inline static Handle<Object> WrapForRead(Isolate* isolate,
                                             Handle<Object> object,
                                             Representation representation);
  
    // Returns true if the object is of the correct type to be used as a
    // implementation of a JSObject's elements.
    inline bool HasValidElements();
  
    inline bool HasSpecificClassOf(String* name);
  
    bool BooleanValue();                                      // ECMA-262 9.2.
  
    // Convert to a JSObject if needed.
    // native_context is used when creating wrapper object.
    static inline MaybeHandle<JSReceiver> ToObject(Isolate* isolate,
                                                   Handle<Object> object);
    static MaybeHandle<JSReceiver> ToObject(Isolate* isolate,
                                            Handle<Object> object,
                                            Handle<Context> context);
  
    // Converts this to a Smi if possible.
    static MUST_USE_RESULT inline MaybeHandle<Smi> ToSmi(Isolate* isolate,
                                                         Handle<Object> object);
  
    MUST_USE_RESULT static MaybeHandle<Object> GetProperty(LookupIterator* it);
  
    // Implementation of [[Put]], ECMA-262 5th edition, section 8.12.5.
    MUST_USE_RESULT static MaybeHandle<Object> SetProperty(
        Handle<Object> object, Handle<Name> key, Handle<Object> value,
        StrictMode strict_mode,
        StoreFromKeyed store_mode = MAY_BE_STORE_FROM_KEYED);
  
    MUST_USE_RESULT static MaybeHandle<Object> SetProperty(
        LookupIterator* it, Handle<Object> value, StrictMode strict_mode,
        StoreFromKeyed store_mode);
    MUST_USE_RESULT static MaybeHandle<Object> WriteToReadOnlyProperty(
        LookupIterator* it, Handle<Object> value, StrictMode strict_mode);
    static Handle<Object> SetDataProperty(LookupIterator* it,
                                          Handle<Object> value);
    MUST_USE_RESULT static MaybeHandle<Object> AddDataProperty(
        LookupIterator* it, Handle<Object> value, PropertyAttributes attributes,
        StrictMode strict_mode, StoreFromKeyed store_mode);
    MUST_USE_RESULT static inline MaybeHandle<Object> GetPropertyOrElement(
        Handle<Object> object,
        Handle<Name> key);
    MUST_USE_RESULT static inline MaybeHandle<Object> GetProperty(
        Isolate* isolate,
        Handle<Object> object,
        const char* key);
    MUST_USE_RESULT static inline MaybeHandle<Object> GetProperty(
        Handle<Object> object,
        Handle<Name> key);
  
    MUST_USE_RESULT static MaybeHandle<Object> GetPropertyWithAccessor(
        Handle<Object> receiver,
        Handle<Name> name,
        Handle<JSObject> holder,
        Handle<Object> structure);
    MUST_USE_RESULT static MaybeHandle<Object> SetPropertyWithAccessor(
        Handle<Object> receiver, Handle<Name> name, Handle<Object> value,
        Handle<JSObject> holder, Handle<Object> structure,
        StrictMode strict_mode);
  
    MUST_USE_RESULT static MaybeHandle<Object> GetPropertyWithDefinedGetter(
        Handle<Object> receiver,
        Handle<JSReceiver> getter);
    MUST_USE_RESULT static MaybeHandle<Object> SetPropertyWithDefinedSetter(
        Handle<Object> receiver,
        Handle<JSReceiver> setter,
        Handle<Object> value);
  
    MUST_USE_RESULT static inline MaybeHandle<Object> GetElement(
        Isolate* isolate,
        Handle<Object> object,
        uint32_t index);
  
    MUST_USE_RESULT static MaybeHandle<Object> GetElementWithReceiver(
        Isolate* isolate,
        Handle<Object> object,
        Handle<Object> receiver,
        uint32_t index);
  
    // Returns the permanent hash code associated with this object. May return
    // undefined if not yet created.
    Object* GetHash();
  
    // Returns the permanent hash code associated with this object depending on
    // the actual object type. May create and store a hash code if needed and none
    // exists.
    static Handle<Smi> GetOrCreateHash(Isolate* isolate, Handle<Object> object);
  
    // Checks whether this object has the same value as the given one.  This
    // function is implemented according to ES5, section 9.12 and can be used
    // to implement the Harmony "egal" function.
    bool SameValue(Object* other);
  
    // Checks whether this object has the same value as the given one.
    // +0 and -0 are treated equal. Everything else is the same as SameValue.
    // This function is implemented according to ES6, section 7.2.4 and is used
    // by ES6 Map and Set.
    bool SameValueZero(Object* other);
  
    // Tries to convert an object to an array index.  Returns true and sets
    // the output parameter if it succeeds.
    inline bool ToArrayIndex(uint32_t* index);
  
    // Returns true if this is a JSValue containing a string and the index is
    // < the length of the string.  Used to implement [] on strings.
    inline bool IsStringObjectWithCharacterAt(uint32_t index);
  
    DECLARE_VERIFIER(Object)
  #ifdef VERIFY_HEAP
    // Verify a pointer is a valid object pointer.
    static void VerifyPointer(Object* p);
  #endif
  
    inline void VerifyApiCallResultType();
  
    // Prints this object without details.
    void ShortPrint(FILE* out = stdout);
  
    // Prints this object without details to a message accumulator.
    void ShortPrint(StringStream* accumulator);
  
    DECLARE_CAST(Object)
  
    // Layout description.
    static const int kHeaderSize = 0;  // Object does not take up any space.
  
  #ifdef OBJECT_PRINT
    // For our gdb macros, we should perhaps change these in the future.
    void Print();
  
    // Prints this object with details.
    void Print(OStream& os);  // NOLINT
  #endif
  
   private:
    friend class LookupIterator;
    friend class PrototypeIterator;
  
    // Return the map of the root of object's prototype chain.
    Map* GetRootMap(Isolate* isolate);
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(Object);
  };
  
  
  struct Brief {
    explicit Brief(const Object* const v) : value(v) {}
    const Object* value;
  };
  
  
  OStream& operator<<(OStream& os, const Brief& v);
  
  
  // Smi represents integer Numbers that can be stored in 31 bits.
  // Smis are immediate which means they are NOT allocated in the heap.
  // The this pointer has the following format: [31 bit signed int] 0
  // For long smis it has the following format:
  //     [32 bit signed int] [31 bits zero padding] 0
  // Smi stands for small integer.
  class Smi: public Object {
   public:
    // Returns the integer value.
    inline int value() const;
  
    // Convert a value to a Smi object.
    static inline Smi* FromInt(int value);
  
    static inline Smi* FromIntptr(intptr_t value);
  
    // Returns whether value can be represented in a Smi.
    static inline bool IsValid(intptr_t value);
  
    DECLARE_CAST(Smi)
  
    // Dispatched behavior.
    void SmiPrint(OStream& os) const;  // NOLINT
    DECLARE_VERIFIER(Smi)
  
    static const int kMinValue =
        (static_cast<unsigned int>(-1)) << (kSmiValueSize - 1);
    static const int kMaxValue = -(kMinValue + 1);
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(Smi);
  };
  
  
  // Heap objects typically have a map pointer in their first word.  However,
  // during GC other data (e.g. mark bits, forwarding addresses) is sometimes
  // encoded in the first word.  The class MapWord is an abstraction of the
  // value in a heap object's first word.
  class MapWord BASE_EMBEDDED {
   public:
    // Normal state: the map word contains a map pointer.
  
    // Create a map word from a map pointer.
    static inline MapWord FromMap(const Map* map);
  
    // View this map word as a map pointer.
    inline Map* ToMap();
  
  
    // Scavenge collection: the map word of live objects in the from space
    // contains a forwarding address (a heap object pointer in the to space).
  
    // True if this map word is a forwarding address for a scavenge
    // collection.  Only valid during a scavenge collection (specifically,
    // when all map words are heap object pointers, i.e. not during a full GC).
    inline bool IsForwardingAddress();
  
    // Create a map word from a forwarding address.
    static inline MapWord FromForwardingAddress(HeapObject* object);
  
    // View this map word as a forwarding address.
    inline HeapObject* ToForwardingAddress();
  
    static inline MapWord FromRawValue(uintptr_t value) {
      return MapWord(value);
    }
  
    inline uintptr_t ToRawValue() {
      return value_;
    }
  
   private:
    // HeapObject calls the private constructor and directly reads the value.
    friend class HeapObject;
  
    explicit MapWord(uintptr_t value) : value_(value) {}
  
    uintptr_t value_;
  };
  
  
  // HeapObject is the superclass for all classes describing heap allocated
  // objects.
  class HeapObject: public Object {
   public:
    // [map]: Contains a map which contains the object's reflective
    // information.
    inline Map* map() const;
    inline void set_map(Map* value);
    // The no-write-barrier version.  This is OK if the object is white and in
    // new space, or if the value is an immortal immutable object, like the maps
    // of primitive (non-JS) objects like strings, heap numbers etc.
    inline void set_map_no_write_barrier(Map* value);
  
    // Get the map using acquire load.
    inline Map* synchronized_map();
    inline MapWord synchronized_map_word() const;
  
    // Set the map using release store
    inline void synchronized_set_map(Map* value);
    inline void synchronized_set_map_no_write_barrier(Map* value);
    inline void synchronized_set_map_word(MapWord map_word);
  
    // During garbage collection, the map word of a heap object does not
    // necessarily contain a map pointer.
    inline MapWord map_word() const;
    inline void set_map_word(MapWord map_word);
  
    // The Heap the object was allocated in. Used also to access Isolate.
    inline Heap* GetHeap() const;
  
    // Convenience method to get current isolate.
    inline Isolate* GetIsolate() const;
  
    // Converts an address to a HeapObject pointer.
    static inline HeapObject* FromAddress(Address address);
  
    // Returns the address of this HeapObject.
    inline Address address();
  
    // Iterates over pointers contained in the object (including the Map)
    void Iterate(ObjectVisitor* v);
  
    // Iterates over all pointers contained in the object except the
    // first map pointer.  The object type is given in the first
    // parameter. This function does not access the map pointer in the
    // object, and so is safe to call while the map pointer is modified.
    void IterateBody(InstanceType type, int object_size, ObjectVisitor* v);
  
    // Returns the heap object's size in bytes
    inline int Size();
  
    // Returns true if this heap object may contain raw values, i.e., values that
    // look like pointers to heap objects.
    inline bool MayContainRawValues();
  
    // Given a heap object's map pointer, returns the heap size in bytes
    // Useful when the map pointer field is used for other purposes.
    // GC internal.
    inline int SizeFromMap(Map* map);
  
    // Returns the field at offset in obj, as a read/write Object* reference.
    // Does no checking, and is safe to use during GC, while maps are invalid.
    // Does not invoke write barrier, so should only be assigned to
    // during marking GC.
    static inline Object** RawField(HeapObject* obj, int offset);
  
    // Adds the |code| object related to |name| to the code cache of this map. If
    // this map is a dictionary map that is shared, the map copied and installed
    // onto the object.
    static void UpdateMapCodeCache(Handle<HeapObject> object,
                                   Handle<Name> name,
                                   Handle<Code> code);
  
    DECLARE_CAST(HeapObject)
  
    // Return the write barrier mode for this. Callers of this function
    // must be able to present a reference to an DisallowHeapAllocation
    // object as a sign that they are not going to use this function
    // from code that allocates and thus invalidates the returned write
    // barrier mode.
    inline WriteBarrierMode GetWriteBarrierMode(
        const DisallowHeapAllocation& promise);
  
    // Dispatched behavior.
    void HeapObjectShortPrint(OStream& os);  // NOLINT
  #ifdef OBJECT_PRINT
    void PrintHeader(OStream& os, const char* id);  // NOLINT
  #endif
    DECLARE_PRINTER(HeapObject)
    DECLARE_VERIFIER(HeapObject)
  #ifdef VERIFY_HEAP
    inline void VerifyObjectField(int offset);
    inline void VerifySmiField(int offset);
  
    // Verify a pointer is a valid HeapObject pointer that points to object
    // areas in the heap.
    static void VerifyHeapPointer(Object* p);
  #endif
  
    // Layout description.
    // First field in a heap object is map.
    static const int kMapOffset = Object::kHeaderSize;
    static const int kHeaderSize = kMapOffset + kPointerSize;
  
    STATIC_ASSERT(kMapOffset == Internals::kHeapObjectMapOffset);
  
   protected:
    // helpers for calling an ObjectVisitor to iterate over pointers in the
    // half-open range [start, end) specified as integer offsets
    inline void IteratePointers(ObjectVisitor* v, int start, int end);
    // as above, for the single element at "offset"
    inline void IteratePointer(ObjectVisitor* v, int offset);
    // as above, for the next code link of a code object.
    inline void IterateNextCodeLink(ObjectVisitor* v, int offset);
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(HeapObject);
  };
  
  
  // This class describes a body of an object of a fixed size
  // in which all pointer fields are located in the [start_offset, end_offset)
  // interval.
  template<int start_offset, int end_offset, int size>
  class FixedBodyDescriptor {
   public:
    static const int kStartOffset = start_offset;
    static const int kEndOffset = end_offset;
    static const int kSize = size;
  
    static inline void IterateBody(HeapObject* obj, ObjectVisitor* v);
  
    template<typename StaticVisitor>
    static inline void IterateBody(HeapObject* obj) {
      StaticVisitor::VisitPointers(HeapObject::RawField(obj, start_offset),
                                   HeapObject::RawField(obj, end_offset));
    }
  };
  
  
  // This class describes a body of an object of a variable size
  // in which all pointer fields are located in the [start_offset, object_size)
  // interval.
  template<int start_offset>
  class FlexibleBodyDescriptor {
   public:
    static const int kStartOffset = start_offset;
  
    static inline void IterateBody(HeapObject* obj,
                                   int object_size,
                                   ObjectVisitor* v);
  
    template<typename StaticVisitor>
    static inline void IterateBody(HeapObject* obj, int object_size) {
      StaticVisitor::VisitPointers(HeapObject::RawField(obj, start_offset),
                                   HeapObject::RawField(obj, object_size));
    }
  };
  
  
  // The HeapNumber class describes heap allocated numbers that cannot be
  // represented in a Smi (small integer)
  class HeapNumber: public HeapObject {
   public:
    // [value]: number value.
    inline double value() const;
    inline void set_value(double value);
  
    DECLARE_CAST(HeapNumber)
  
    // Dispatched behavior.
    bool HeapNumberBooleanValue();
  
    void HeapNumberPrint(OStream& os);  // NOLINT
    DECLARE_VERIFIER(HeapNumber)
  
    inline int get_exponent();
    inline int get_sign();
  
    // Layout description.
    static const int kValueOffset = HeapObject::kHeaderSize;
    // IEEE doubles are two 32 bit words.  The first is just mantissa, the second
    // is a mixture of sign, exponent and mantissa. The offsets of two 32 bit
    // words within double numbers are endian dependent and they are set
    // accordingly.
  #if defined(V8_TARGET_LITTLE_ENDIAN)
    static const int kMantissaOffset = kValueOffset;
    static const int kExponentOffset = kValueOffset + 4;
  #elif defined(V8_TARGET_BIG_ENDIAN)
    static const int kMantissaOffset = kValueOffset + 4;
    static const int kExponentOffset = kValueOffset;
  #else
  #error Unknown byte ordering
  #endif
  
    static const int kSize = kValueOffset + kDoubleSize;
    static const uint32_t kSignMask = 0x80000000u;
    static const uint32_t kExponentMask = 0x7ff00000u;
    static const uint32_t kMantissaMask = 0xfffffu;
    static const int kMantissaBits = 52;
    static const int kExponentBits = 11;
    static const int kExponentBias = 1023;
    static const int kExponentShift = 20;
    static const int kInfinityOrNanExponent =
        (kExponentMask >> kExponentShift) - kExponentBias;
    static const int kMantissaBitsInTopWord = 20;
    static const int kNonMantissaBitsInTopWord = 12;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(HeapNumber);
  };
  
  
  enum EnsureElementsMode {
    DONT_ALLOW_DOUBLE_ELEMENTS,
    ALLOW_COPIED_DOUBLE_ELEMENTS,
    ALLOW_CONVERTED_DOUBLE_ELEMENTS
  };
  
  
  // Indicates whether a property should be set or (re)defined.  Setting of a
  // property causes attributes to remain unchanged, writability to be checked
  // and callbacks to be called.  Defining of a property causes attributes to
  // be updated and callbacks to be overridden.
  enum SetPropertyMode {
    SET_PROPERTY,
    DEFINE_PROPERTY
  };
  
  
  // Indicator for one component of an AccessorPair.
  enum AccessorComponent {
    ACCESSOR_GETTER,
    ACCESSOR_SETTER
  };
  
  
  // JSReceiver includes types on which properties can be defined, i.e.,
  // JSObject and JSProxy.
  class JSReceiver: public HeapObject {
   public:
    enum DeleteMode {
      NORMAL_DELETION,
      STRICT_DELETION,
      FORCE_DELETION
    };
  
    DECLARE_CAST(JSReceiver)
  
    MUST_USE_RESULT static MaybeHandle<Object> SetElement(
        Handle<JSReceiver> object,
        uint32_t index,
        Handle<Object> value,
        PropertyAttributes attributes,
        StrictMode strict_mode);
  
    // Implementation of [[HasProperty]], ECMA-262 5th edition, section 8.12.6.
    MUST_USE_RESULT static inline Maybe<bool> HasProperty(
        Handle<JSReceiver> object, Handle<Name> name);
    MUST_USE_RESULT static inline Maybe<bool> HasOwnProperty(Handle<JSReceiver>,
                                                             Handle<Name> name);
    MUST_USE_RESULT static inline Maybe<bool> HasElement(
        Handle<JSReceiver> object, uint32_t index);
    MUST_USE_RESULT static inline Maybe<bool> HasOwnElement(
        Handle<JSReceiver> object, uint32_t index);
  
    // Implementation of [[Delete]], ECMA-262 5th edition, section 8.12.7.
    MUST_USE_RESULT static MaybeHandle<Object> DeleteProperty(
        Handle<JSReceiver> object,
        Handle<Name> name,
        DeleteMode mode = NORMAL_DELETION);
    MUST_USE_RESULT static MaybeHandle<Object> DeleteElement(
        Handle<JSReceiver> object,
        uint32_t index,
        DeleteMode mode = NORMAL_DELETION);
  
    // Tests for the fast common case for property enumeration.
    bool IsSimpleEnum();
  
    // Returns the class name ([[Class]] property in the specification).
    String* class_name();
  
    // Returns the constructor name (the name (possibly, inferred name) of the
    // function that was used to instantiate the object).
    String* constructor_name();
  
    MUST_USE_RESULT static inline Maybe<PropertyAttributes> GetPropertyAttributes(
        Handle<JSReceiver> object, Handle<Name> name);
    MUST_USE_RESULT static Maybe<PropertyAttributes> GetPropertyAttributes(
        LookupIterator* it);
    MUST_USE_RESULT static Maybe<PropertyAttributes> GetOwnPropertyAttributes(
        Handle<JSReceiver> object, Handle<Name> name);
  
    MUST_USE_RESULT static inline Maybe<PropertyAttributes> GetElementAttribute(
        Handle<JSReceiver> object, uint32_t index);
    MUST_USE_RESULT static inline Maybe<PropertyAttributes>
        GetOwnElementAttribute(Handle<JSReceiver> object, uint32_t index);
  
    // Return the constructor function (may be Heap::null_value()).
    inline Object* GetConstructor();
  
    // Retrieves a permanent object identity hash code. The undefined value might
    // be returned in case no hash was created yet.
    inline Object* GetIdentityHash();
  
    // Retrieves a permanent object identity hash code. May create and store a
    // hash code if needed and none exists.
    inline static Handle<Smi> GetOrCreateIdentityHash(
        Handle<JSReceiver> object);
  
    enum KeyCollectionType { OWN_ONLY, INCLUDE_PROTOS };
  
    // Computes the enumerable keys for a JSObject. Used for implementing
    // "for (n in object) { }".
    MUST_USE_RESULT static MaybeHandle<FixedArray> GetKeys(
        Handle<JSReceiver> object,
        KeyCollectionType type);
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSReceiver);
  };
  
  // Forward declaration for JSObject::GetOrCreateHiddenPropertiesHashTable.
  class ObjectHashTable;
  
  // Forward declaration for JSObject::Copy.
  class AllocationSite;
  
  
  // The JSObject describes real heap allocated JavaScript objects with
  // properties.
  // Note that the map of JSObject changes during execution to enable inline
  // caching.
  class JSObject: public JSReceiver {
   public:
    // [properties]: Backing storage for properties.
    // properties is a FixedArray in the fast case and a Dictionary in the
    // slow case.
    DECL_ACCESSORS(properties, FixedArray)  // Get and set fast properties.
    inline void initialize_properties();
    inline bool HasFastProperties();
    inline NameDictionary* property_dictionary();  // Gets slow properties.
  
    // [elements]: The elements (properties with names that are integers).
    //
    // Elements can be in two general modes: fast and slow. Each mode
    // corrensponds to a set of object representations of elements that
    // have something in common.
    //
    // In the fast mode elements is a FixedArray and so each element can
    // be quickly accessed. This fact is used in the generated code. The
    // elements array can have one of three maps in this mode:
    // fixed_array_map, sloppy_arguments_elements_map or
    // fixed_cow_array_map (for copy-on-write arrays). In the latter case
    // the elements array may be shared by a few objects and so before
    // writing to any element the array must be copied. Use
    // EnsureWritableFastElements in this case.
    //
    // In the slow mode the elements is either a NumberDictionary, an
    // ExternalArray, or a FixedArray parameter map for a (sloppy)
    // arguments object.
    DECL_ACCESSORS(elements, FixedArrayBase)
    inline void initialize_elements();
    static void ResetElements(Handle<JSObject> object);
    static inline void SetMapAndElements(Handle<JSObject> object,
                                         Handle<Map> map,
                                         Handle<FixedArrayBase> elements);
    inline ElementsKind GetElementsKind();
    inline ElementsAccessor* GetElementsAccessor();
    // Returns true if an object has elements of FAST_SMI_ELEMENTS ElementsKind.
    inline bool HasFastSmiElements();
    // Returns true if an object has elements of FAST_ELEMENTS ElementsKind.
    inline bool HasFastObjectElements();
    // Returns true if an object has elements of FAST_ELEMENTS or
    // FAST_SMI_ONLY_ELEMENTS.
    inline bool HasFastSmiOrObjectElements();
    // Returns true if an object has any of the fast elements kinds.
    inline bool HasFastElements();
    // Returns true if an object has elements of FAST_DOUBLE_ELEMENTS
    // ElementsKind.
    inline bool HasFastDoubleElements();
    // Returns true if an object has elements of FAST_HOLEY_*_ELEMENTS
    // ElementsKind.
    inline bool HasFastHoleyElements();
    inline bool HasSloppyArgumentsElements();
    inline bool HasDictionaryElements();
  
    inline bool HasExternalUint8ClampedElements();
    inline bool HasExternalArrayElements();
    inline bool HasExternalInt8Elements();
    inline bool HasExternalUint8Elements();
    inline bool HasExternalInt16Elements();
    inline bool HasExternalUint16Elements();
    inline bool HasExternalInt32Elements();
    inline bool HasExternalUint32Elements();
    inline bool HasExternalFloat32Elements();
    inline bool HasExternalFloat32x4Elements();
    inline bool HasExternalFloat64x2Elements();
    inline bool HasExternalInt32x4Elements();
    inline bool HasExternalFloat64Elements();
  
    inline bool HasFixedTypedArrayElements();
  
    inline bool HasFixedUint8ClampedElements();
    inline bool HasFixedArrayElements();
    inline bool HasFixedInt8Elements();
    inline bool HasFixedUint8Elements();
    inline bool HasFixedInt16Elements();
    inline bool HasFixedUint16Elements();
    inline bool HasFixedInt32Elements();
    inline bool HasFixedUint32Elements();
    inline bool HasFixedFloat32Elements();
    inline bool HasFixedFloat64Elements();
    inline bool HasFixedFloat32x4Elements();
    inline bool HasFixedFloat64x2Elements();
    inline bool HasFixedInt32x4Elements();
  
    bool HasFastArgumentsElements();
    bool HasDictionaryArgumentsElements();
    inline SeededNumberDictionary* element_dictionary();  // Gets slow elements.
  
    // Requires: HasFastElements().
    static Handle<FixedArray> EnsureWritableFastElements(
        Handle<JSObject> object);
  
    // Collects elements starting at index 0.
    // Undefined values are placed after non-undefined values.
    // Returns the number of non-undefined values.
    static Handle<Object> PrepareElementsForSort(Handle<JSObject> object,
                                                 uint32_t limit);
    // As PrepareElementsForSort, but only on objects where elements is
    // a dictionary, and it will stay a dictionary.  Collates undefined and
    // unexisting elements below limit from position zero of the elements.
    static Handle<Object> PrepareSlowElementsForSort(Handle<JSObject> object,
                                                     uint32_t limit);
  
    MUST_USE_RESULT static MaybeHandle<Object> SetPropertyWithInterceptor(
        LookupIterator* it, Handle<Object> value);
  
    // SetLocalPropertyIgnoreAttributes converts callbacks to fields. We need to
    // grant an exemption to ExecutableAccessor callbacks in some cases.
    enum ExecutableAccessorInfoHandling {
      DEFAULT_HANDLING,
      DONT_FORCE_FIELD
    };
  
    MUST_USE_RESULT static MaybeHandle<Object> SetOwnPropertyIgnoreAttributes(
        Handle<JSObject> object,
        Handle<Name> key,
        Handle<Object> value,
        PropertyAttributes attributes,
        ExecutableAccessorInfoHandling handling = DEFAULT_HANDLING);
  
    static void AddProperty(Handle<JSObject> object, Handle<Name> key,
                            Handle<Object> value, PropertyAttributes attributes);
  
    // Extend the receiver with a single fast property appeared first in the
    // passed map. This also extends the property backing store if necessary.
    static void AllocateStorageForMap(Handle<JSObject> object, Handle<Map> map);
  
    // Migrates the given object to a map whose field representations are the
    // lowest upper bound of all known representations for that field.
    static void MigrateInstance(Handle<JSObject> instance);
  
    // Migrates the given object only if the target map is already available,
    // or returns false if such a map is not yet available.
    static bool TryMigrateInstance(Handle<JSObject> instance);
  
    // Sets the property value in a normalized object given (key, value, details).
    // Handles the special representation of JS global objects.
    static void SetNormalizedProperty(Handle<JSObject> object,
                                      Handle<Name> key,
                                      Handle<Object> value,
                                      PropertyDetails details);
  
    static void OptimizeAsPrototype(Handle<JSObject> object,
                                    PrototypeOptimizationMode mode);
    static void ReoptimizeIfPrototype(Handle<JSObject> object);
  
    // Retrieve interceptors.
    InterceptorInfo* GetNamedInterceptor();
    InterceptorInfo* GetIndexedInterceptor();
  
    // Used from JSReceiver.
    MUST_USE_RESULT static Maybe<PropertyAttributes>
        GetPropertyAttributesWithInterceptor(Handle<JSObject> holder,
                                             Handle<Object> receiver,
                                             Handle<Name> name);
    MUST_USE_RESULT static Maybe<PropertyAttributes>
        GetPropertyAttributesWithFailedAccessCheck(LookupIterator* it);
    MUST_USE_RESULT static Maybe<PropertyAttributes>
        GetElementAttributeWithReceiver(Handle<JSObject> object,
                                        Handle<JSReceiver> receiver,
                                        uint32_t index, bool check_prototype);
  
    // Retrieves an AccessorPair property from the given object. Might return
    // undefined if the property doesn't exist or is of a different kind.
    MUST_USE_RESULT static MaybeHandle<Object> GetAccessor(
        Handle<JSObject> object,
        Handle<Name> name,
        AccessorComponent component);
  
    // Defines an AccessorPair property on the given object.
    // TODO(mstarzinger): Rename to SetAccessor().
    static MaybeHandle<Object> DefineAccessor(Handle<JSObject> object,
                                              Handle<Name> name,
                                              Handle<Object> getter,
                                              Handle<Object> setter,
                                              PropertyAttributes attributes);
  
    // Defines an AccessorInfo property on the given object.
    MUST_USE_RESULT static MaybeHandle<Object> SetAccessor(
        Handle<JSObject> object,
        Handle<AccessorInfo> info);
  
    MUST_USE_RESULT static MaybeHandle<Object> GetPropertyWithInterceptor(
        Handle<JSObject> object,
        Handle<Object> receiver,
        Handle<Name> name);
  
    // Returns true if this is an instance of an api function and has
    // been modified since it was created.  May give false positives.
    bool IsDirty();
  
    // Accessors for hidden properties object.
    //
    // Hidden properties are not own properties of the object itself.
    // Instead they are stored in an auxiliary structure kept as an own
    // property with a special name Heap::hidden_string(). But if the
    // receiver is a JSGlobalProxy then the auxiliary object is a property
    // of its prototype, and if it's a detached proxy, then you can't have
    // hidden properties.
  
    // Sets a hidden property on this object. Returns this object if successful,
    // undefined if called on a detached proxy.
    static Handle<Object> SetHiddenProperty(Handle<JSObject> object,
                                            Handle<Name> key,
                                            Handle<Object> value);
    // Gets the value of a hidden property with the given key. Returns the hole
    // if the property doesn't exist (or if called on a detached proxy),
    // otherwise returns the value set for the key.
    Object* GetHiddenProperty(Handle<Name> key);
    // Deletes a hidden property. Deleting a non-existing property is
    // considered successful.
    static void DeleteHiddenProperty(Handle<JSObject> object,
                                     Handle<Name> key);
    // Returns true if the object has a property with the hidden string as name.
    static bool HasHiddenProperties(Handle<JSObject> object);
  
    static void SetIdentityHash(Handle<JSObject> object, Handle<Smi> hash);
  
    static inline void ValidateElements(Handle<JSObject> object);
  
    // Makes sure that this object can contain HeapObject as elements.
    static inline void EnsureCanContainHeapObjectElements(Handle<JSObject> obj);
  
    // Makes sure that this object can contain the specified elements.
    static inline void EnsureCanContainElements(
        Handle<JSObject> object,
        Object** elements,
        uint32_t count,
        EnsureElementsMode mode);
    static inline void EnsureCanContainElements(
        Handle<JSObject> object,
        Handle<FixedArrayBase> elements,
        uint32_t length,
        EnsureElementsMode mode);
    static void EnsureCanContainElements(
        Handle<JSObject> object,
        Arguments* arguments,
        uint32_t first_arg,
        uint32_t arg_count,
        EnsureElementsMode mode);
  
    // Would we convert a fast elements array to dictionary mode given
    // an access at key?
    bool WouldConvertToSlowElements(Handle<Object> key);
    // Do we want to keep the elements in fast case when increasing the
    // capacity?
    bool ShouldConvertToSlowElements(int new_capacity);
    // Returns true if the backing storage for the slow-case elements of
    // this object takes up nearly as much space as a fast-case backing
    // storage would.  In that case the JSObject should have fast
    // elements.
    bool ShouldConvertToFastElements();
    // Returns true if the elements of JSObject contains only values that can be
    // represented in a FixedDoubleArray and has at least one value that can only
    // be represented as a double and not a Smi.
    bool ShouldConvertToFastDoubleElements(bool* has_smi_only_elements);
  
    // Computes the new capacity when expanding the elements of a JSObject.
    static int NewElementsCapacity(int old_capacity) {
      // (old_capacity + 50%) + 16
      return old_capacity + (old_capacity >> 1) + 16;
    }
  
    // These methods do not perform access checks!
    MUST_USE_RESULT static MaybeHandle<AccessorPair> GetOwnElementAccessorPair(
        Handle<JSObject> object,
        uint32_t index);
  
    MUST_USE_RESULT static MaybeHandle<Object> SetFastElement(
        Handle<JSObject> object,
        uint32_t index,
        Handle<Object> value,
        StrictMode strict_mode,
        bool check_prototype);
  
    MUST_USE_RESULT static MaybeHandle<Object> SetOwnElement(
        Handle<JSObject> object,
        uint32_t index,
        Handle<Object> value,
        StrictMode strict_mode);
  
    // Empty handle is returned if the element cannot be set to the given value.
    MUST_USE_RESULT static MaybeHandle<Object> SetElement(
        Handle<JSObject> object,
        uint32_t index,
        Handle<Object> value,
        PropertyAttributes attributes,
        StrictMode strict_mode,
        bool check_prototype = true,
        SetPropertyMode set_mode = SET_PROPERTY);
  
    // Returns the index'th element.
    // The undefined object if index is out of bounds.
    MUST_USE_RESULT static MaybeHandle<Object> GetElementWithInterceptor(
        Handle<JSObject> object,
        Handle<Object> receiver,
        uint32_t index);
  
    enum SetFastElementsCapacitySmiMode {
      kAllowSmiElements,
      kForceSmiElements,
      kDontAllowSmiElements
    };
  
    // Replace the elements' backing store with fast elements of the given
    // capacity.  Update the length for JSArrays.  Returns the new backing
    // store.
    static Handle<FixedArray> SetFastElementsCapacityAndLength(
        Handle<JSObject> object,
        int capacity,
        int length,
        SetFastElementsCapacitySmiMode smi_mode);
    static void SetFastDoubleElementsCapacityAndLength(
        Handle<JSObject> object,
        int capacity,
        int length);
  
    // Lookup interceptors are used for handling properties controlled by host
    // objects.
    inline bool HasNamedInterceptor();
    inline bool HasIndexedInterceptor();
  
    // Computes the enumerable keys from interceptors. Used for debug mirrors and
    // by JSReceiver::GetKeys.
    MUST_USE_RESULT static MaybeHandle<JSObject> GetKeysForNamedInterceptor(
        Handle<JSObject> object,
        Handle<JSReceiver> receiver);
    MUST_USE_RESULT static MaybeHandle<JSObject> GetKeysForIndexedInterceptor(
        Handle<JSObject> object,
        Handle<JSReceiver> receiver);
  
    // Support functions for v8 api (needed for correct interceptor behavior).
    MUST_USE_RESULT static Maybe<bool> HasRealNamedProperty(
        Handle<JSObject> object, Handle<Name> key);
    MUST_USE_RESULT static Maybe<bool> HasRealElementProperty(
        Handle<JSObject> object, uint32_t index);
    MUST_USE_RESULT static Maybe<bool> HasRealNamedCallbackProperty(
        Handle<JSObject> object, Handle<Name> key);
  
    // Get the header size for a JSObject.  Used to compute the index of
    // internal fields as well as the number of internal fields.
    inline int GetHeaderSize();
  
    inline int GetInternalFieldCount();
    inline int GetInternalFieldOffset(int index);
    inline Object* GetInternalField(int index);
    inline void SetInternalField(int index, Object* value);
    inline void SetInternalField(int index, Smi* value);
  
    // Returns the number of properties on this object filtering out properties
    // with the specified attributes (ignoring interceptors).
    int NumberOfOwnProperties(PropertyAttributes filter = NONE);
    // Fill in details for properties into storage starting at the specified
    // index.
    void GetOwnPropertyNames(
        FixedArray* storage, int index, PropertyAttributes filter = NONE);
  
    // Returns the number of properties on this object filtering out properties
    // with the specified attributes (ignoring interceptors).
    int NumberOfOwnElements(PropertyAttributes filter);
    // Returns the number of enumerable elements (ignoring interceptors).
    int NumberOfEnumElements();
    // Returns the number of elements on this object filtering out elements
    // with the specified attributes (ignoring interceptors).
    int GetOwnElementKeys(FixedArray* storage, PropertyAttributes filter);
    // Count and fill in the enumerable elements into storage.
    // (storage->length() == NumberOfEnumElements()).
    // If storage is NULL, will count the elements without adding
    // them to any storage.
    // Returns the number of enumerable elements.
    int GetEnumElementKeys(FixedArray* storage);
  
    // Returns a new map with all transitions dropped from the object's current
    // map and the ElementsKind set.
    static Handle<Map> GetElementsTransitionMap(Handle<JSObject> object,
                                                ElementsKind to_kind);
    static void TransitionElementsKind(Handle<JSObject> object,
                                       ElementsKind to_kind);
  
    static void MigrateToMap(Handle<JSObject> object, Handle<Map> new_map);
  
    // Convert the object to use the canonical dictionary
    // representation. If the object is expected to have additional properties
    // added this number can be indicated to have the backing store allocated to
    // an initial capacity for holding these properties.
    static void NormalizeProperties(Handle<JSObject> object,
                                    PropertyNormalizationMode mode,
                                    int expected_additional_properties);
  
    // Convert and update the elements backing store to be a
    // SeededNumberDictionary dictionary.  Returns the backing after conversion.
    static Handle<SeededNumberDictionary> NormalizeElements(
        Handle<JSObject> object);
  
    // Transform slow named properties to fast variants.
    static void MigrateSlowToFast(Handle<JSObject> object,
                                  int unused_property_fields);
  
    // Access fast-case object properties at index.
    static Handle<Object> FastPropertyAt(Handle<JSObject> object,
                                         Representation representation,
                                         FieldIndex index);
    inline Object* RawFastPropertyAt(FieldIndex index);
    inline void FastPropertyAtPut(FieldIndex index, Object* value);
    void WriteToField(int descriptor, Object* value);
  
    // Access to in object properties.
    inline int GetInObjectPropertyOffset(int index);
    inline Object* InObjectPropertyAt(int index);
    inline Object* InObjectPropertyAtPut(int index,
                                         Object* value,
                                         WriteBarrierMode mode
                                         = UPDATE_WRITE_BARRIER);
  
    // Set the object's prototype (only JSReceiver and null are allowed values).
    MUST_USE_RESULT static MaybeHandle<Object> SetPrototype(
        Handle<JSObject> object, Handle<Object> value, bool from_javascript);
  
    // Initializes the body after properties slot, properties slot is
    // initialized by set_properties.  Fill the pre-allocated fields with
    // pre_allocated_value and the rest with filler_value.
    // Note: this call does not update write barrier, the caller is responsible
    // to ensure that |filler_value| can be collected without WB here.
    inline void InitializeBody(Map* map,
                               Object* pre_allocated_value,
                               Object* filler_value);
  
    // Check whether this object references another object
    bool ReferencesObject(Object* obj);
  
    // Disalow further properties to be added to the object.
    MUST_USE_RESULT static MaybeHandle<Object> PreventExtensions(
        Handle<JSObject> object);
  
    // ES5 Object.freeze
    MUST_USE_RESULT static MaybeHandle<Object> Freeze(Handle<JSObject> object);
  
    // Called the first time an object is observed with ES7 Object.observe.
    static void SetObserved(Handle<JSObject> object);
  
    // Copy object.
    enum DeepCopyHints { kNoHints = 0, kObjectIsShallow = 1 };
  
    static Handle<JSObject> Copy(Handle<JSObject> object);
    MUST_USE_RESULT static MaybeHandle<JSObject> DeepCopy(
        Handle<JSObject> object,
        AllocationSiteUsageContext* site_context,
        DeepCopyHints hints = kNoHints);
    MUST_USE_RESULT static MaybeHandle<JSObject> DeepWalk(
        Handle<JSObject> object,
        AllocationSiteCreationContext* site_context);
  
    static Handle<Object> GetDataProperty(Handle<JSObject> object,
                                          Handle<Name> key);
    static Handle<Object> GetDataProperty(LookupIterator* it);
  
    DECLARE_CAST(JSObject)
  
    // Dispatched behavior.
    void JSObjectShortPrint(StringStream* accumulator);
    DECLARE_PRINTER(JSObject)
    DECLARE_VERIFIER(JSObject)
  #ifdef OBJECT_PRINT
    void PrintProperties(OStream& os);   // NOLINT
    void PrintElements(OStream& os);     // NOLINT
    void PrintTransitions(OStream& os);  // NOLINT
  #endif
  
    static void PrintElementsTransition(
        FILE* file, Handle<JSObject> object,
        ElementsKind from_kind, Handle<FixedArrayBase> from_elements,
        ElementsKind to_kind, Handle<FixedArrayBase> to_elements);
  
    void PrintInstanceMigration(FILE* file, Map* original_map, Map* new_map);
  
  #ifdef DEBUG
    // Structure for collecting spill information about JSObjects.
    class SpillInformation {
     public:
      void Clear();
      void Print();
      int number_of_objects_;
      int number_of_objects_with_fast_properties_;
      int number_of_objects_with_fast_elements_;
      int number_of_fast_used_fields_;
      int number_of_fast_unused_fields_;
      int number_of_slow_used_properties_;
      int number_of_slow_unused_properties_;
      int number_of_fast_used_elements_;
      int number_of_fast_unused_elements_;
      int number_of_slow_used_elements_;
      int number_of_slow_unused_elements_;
    };
  
    void IncrementSpillStatistics(SpillInformation* info);
  #endif
  
  #ifdef VERIFY_HEAP
    // If a GC was caused while constructing this object, the elements pointer
    // may point to a one pointer filler map. The object won't be rooted, but
    // our heap verification code could stumble across it.
    bool ElementsAreSafeToExamine();
  #endif
  
    Object* SlowReverseLookup(Object* value);
  
    // Maximal number of elements (numbered 0 .. kMaxElementCount - 1).
    // Also maximal value of JSArray's length property.
    static const uint32_t kMaxElementCount = 0xffffffffu;
  
    // Constants for heuristics controlling conversion of fast elements
    // to slow elements.
  
    // Maximal gap that can be introduced by adding an element beyond
    // the current elements length.
    static const uint32_t kMaxGap = 1024;
  
    // Maximal length of fast elements array that won't be checked for
    // being dense enough on expansion.
    static const int kMaxUncheckedFastElementsLength = 5000;
  
    // Same as above but for old arrays. This limit is more strict. We
    // don't want to be wasteful with long lived objects.
    static const int kMaxUncheckedOldFastElementsLength = 500;
  
    // Note that Page::kMaxRegularHeapObjectSize puts a limit on
    // permissible values (see the DCHECK in heap.cc).
    static const int kInitialMaxFastElementArray = 100000;
  
    // This constant applies only to the initial map of "$Object" aka
    // "global.Object" and not to arbitrary other JSObject maps.
    static const int kInitialGlobalObjectUnusedPropertiesCount = 4;
  
    static const int kMaxInstanceSize = 255 * kPointerSize;
    // When extending the backing storage for property values, we increase
    // its size by more than the 1 entry necessary, so sequentially adding fields
    // to the same object requires fewer allocations and copies.
    static const int kFieldsAdded = 3;
  
    // Layout description.
    static const int kPropertiesOffset = HeapObject::kHeaderSize;
    static const int kElementsOffset = kPropertiesOffset + kPointerSize;
    static const int kHeaderSize = kElementsOffset + kPointerSize;
  
    STATIC_ASSERT(kHeaderSize == Internals::kJSObjectHeaderSize);
  
    class BodyDescriptor : public FlexibleBodyDescriptor<kPropertiesOffset> {
     public:
      static inline int SizeOf(Map* map, HeapObject* object);
    };
  
    Context* GetCreationContext();
  
    // Enqueue change record for Object.observe. May cause GC.
    static void EnqueueChangeRecord(Handle<JSObject> object,
                                    const char* type,
                                    Handle<Name> name,
                                    Handle<Object> old_value);
  
    static void MigrateToNewProperty(Handle<JSObject> object,
                                     Handle<Map> transition,
                                     Handle<Object> value);
  
   private:
    friend class DictionaryElementsAccessor;
    friend class JSReceiver;
    friend class Object;
  
    static void MigrateFastToFast(Handle<JSObject> object, Handle<Map> new_map);
    static void MigrateFastToSlow(Handle<JSObject> object,
                                  Handle<Map> new_map,
                                  int expected_additional_properties);
  
    static void GeneralizeFieldRepresentation(Handle<JSObject> object,
                                              int modify_index,
                                              Representation new_representation,
                                              Handle<HeapType> new_field_type);
  
    static void UpdateAllocationSite(Handle<JSObject> object,
                                     ElementsKind to_kind);
  
    // Used from Object::GetProperty().
    MUST_USE_RESULT static MaybeHandle<Object> GetPropertyWithFailedAccessCheck(
        LookupIterator* it);
  
    MUST_USE_RESULT static MaybeHandle<Object> GetElementWithCallback(
        Handle<JSObject> object,
        Handle<Object> receiver,
        Handle<Object> structure,
        uint32_t index,
        Handle<Object> holder);
  
    MUST_USE_RESULT static Maybe<PropertyAttributes>
        GetElementAttributeWithInterceptor(Handle<JSObject> object,
                                           Handle<JSReceiver> receiver,
                                           uint32_t index, bool continue_search);
    MUST_USE_RESULT static Maybe<PropertyAttributes>
        GetElementAttributeWithoutInterceptor(Handle<JSObject> object,
                                              Handle<JSReceiver> receiver,
                                              uint32_t index,
                                              bool continue_search);
    MUST_USE_RESULT static MaybeHandle<Object> SetElementWithCallback(
        Handle<JSObject> object,
        Handle<Object> structure,
        uint32_t index,
        Handle<Object> value,
        Handle<JSObject> holder,
        StrictMode strict_mode);
    MUST_USE_RESULT static MaybeHandle<Object> SetElementWithInterceptor(
        Handle<JSObject> object,
        uint32_t index,
        Handle<Object> value,
        PropertyAttributes attributes,
        StrictMode strict_mode,
        bool check_prototype,
        SetPropertyMode set_mode);
    MUST_USE_RESULT static MaybeHandle<Object> SetElementWithoutInterceptor(
        Handle<JSObject> object,
        uint32_t index,
        Handle<Object> value,
        PropertyAttributes attributes,
        StrictMode strict_mode,
        bool check_prototype,
        SetPropertyMode set_mode);
    MUST_USE_RESULT
    static MaybeHandle<Object> SetElementWithCallbackSetterInPrototypes(
        Handle<JSObject> object,
        uint32_t index,
        Handle<Object> value,
        bool* found,
        StrictMode strict_mode);
    MUST_USE_RESULT static MaybeHandle<Object> SetDictionaryElement(
        Handle<JSObject> object,
        uint32_t index,
        Handle<Object> value,
        PropertyAttributes attributes,
        StrictMode strict_mode,
        bool check_prototype,
        SetPropertyMode set_mode = SET_PROPERTY);
    MUST_USE_RESULT static MaybeHandle<Object> SetFastDoubleElement(
        Handle<JSObject> object,
        uint32_t index,
        Handle<Object> value,
        StrictMode strict_mode,
        bool check_prototype = true);
  
    MUST_USE_RESULT static MaybeHandle<Object> SetPropertyWithFailedAccessCheck(
        LookupIterator* it, Handle<Object> value, StrictMode strict_mode);
  
    // Add a property to a slow-case object.
    static void AddSlowProperty(Handle<JSObject> object,
                                Handle<Name> name,
                                Handle<Object> value,
                                PropertyAttributes attributes);
  
    MUST_USE_RESULT static MaybeHandle<Object> DeleteProperty(
        Handle<JSObject> object,
        Handle<Name> name,
        DeleteMode mode);
    MUST_USE_RESULT static MaybeHandle<Object> DeletePropertyWithInterceptor(
        Handle<JSObject> holder, Handle<JSObject> receiver, Handle<Name> name);
  
    // Deletes the named property in a normalized object.
    static Handle<Object> DeleteNormalizedProperty(Handle<JSObject> object,
                                                   Handle<Name> name,
                                                   DeleteMode mode);
  
    MUST_USE_RESULT static MaybeHandle<Object> DeleteElement(
        Handle<JSObject> object,
        uint32_t index,
        DeleteMode mode);
    MUST_USE_RESULT static MaybeHandle<Object> DeleteElementWithInterceptor(
        Handle<JSObject> object,
        uint32_t index);
  
    bool ReferencesObjectFromElements(FixedArray* elements,
                                      ElementsKind kind,
                                      Object* object);
  
    // Returns true if most of the elements backing storage is used.
    bool HasDenseElements();
  
    // Gets the current elements capacity and the number of used elements.
    void GetElementsCapacityAndUsage(int* capacity, int* used);
  
    static bool CanSetCallback(Handle<JSObject> object, Handle<Name> name);
    static void SetElementCallback(Handle<JSObject> object,
                                   uint32_t index,
                                   Handle<Object> structure,
                                   PropertyAttributes attributes);
    static void SetPropertyCallback(Handle<JSObject> object,
                                    Handle<Name> name,
                                    Handle<Object> structure,
                                    PropertyAttributes attributes);
    static void DefineElementAccessor(Handle<JSObject> object,
                                      uint32_t index,
                                      Handle<Object> getter,
                                      Handle<Object> setter,
                                      PropertyAttributes attributes);
  
    // Return the hash table backing store or the inline stored identity hash,
    // whatever is found.
    MUST_USE_RESULT Object* GetHiddenPropertiesHashTable();
  
    // Return the hash table backing store for hidden properties.  If there is no
    // backing store, allocate one.
    static Handle<ObjectHashTable> GetOrCreateHiddenPropertiesHashtable(
        Handle<JSObject> object);
  
    // Set the hidden property backing store to either a hash table or
    // the inline-stored identity hash.
    static Handle<Object> SetHiddenPropertiesHashTable(
        Handle<JSObject> object,
        Handle<Object> value);
  
    MUST_USE_RESULT Object* GetIdentityHash();
  
    static Handle<Smi> GetOrCreateIdentityHash(Handle<JSObject> object);
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSObject);
  };
  
  
  // Common superclass for FixedArrays that allow implementations to share
  // common accessors and some code paths.
  class FixedArrayBase: public HeapObject {
   public:
    // [length]: length of the array.
    inline int length() const;
    inline void set_length(int value);
  
    // Get and set the length using acquire loads and release stores.
    inline int synchronized_length() const;
    inline void synchronized_set_length(int value);
  
    DECLARE_CAST(FixedArrayBase)
  
    // Layout description.
    // Length is smi tagged when it is stored.
    static const int kLengthOffset = HeapObject::kHeaderSize;
    static const int kHeaderSize = kLengthOffset + kPointerSize;
  };
  
  
  class FixedDoubleArray;
  class IncrementalMarking;
  
  
  // FixedArray describes fixed-sized arrays with element type Object*.
  class FixedArray: public FixedArrayBase {
   public:
    // Setter and getter for elements.
    inline Object* get(int index);
    static inline Handle<Object> get(Handle<FixedArray> array, int index);
    // Setter that uses write barrier.
    inline void set(int index, Object* value);
    inline bool is_the_hole(int index);
  
    // Setter that doesn't need write barrier.
    inline void set(int index, Smi* value);
    // Setter with explicit barrier mode.
    inline void set(int index, Object* value, WriteBarrierMode mode);
  
    // Setters for frequently used oddballs located in old space.
    inline void set_undefined(int index);
    inline void set_null(int index);
    inline void set_the_hole(int index);
  
    inline Object** GetFirstElementAddress();
    inline bool ContainsOnlySmisOrHoles();
  
    // Gives access to raw memory which stores the array's data.
    inline Object** data_start();
  
    inline void FillWithHoles(int from, int to);
  
    // Shrink length and insert filler objects.
    void Shrink(int length);
  
    // Copy operation.
    static Handle<FixedArray> CopySize(Handle<FixedArray> array,
                                       int new_length,
                                       PretenureFlag pretenure = NOT_TENURED);
  
    // Add the elements of a JSArray to this FixedArray.
    MUST_USE_RESULT static MaybeHandle<FixedArray> AddKeysFromArrayLike(
        Handle<FixedArray> content,
        Handle<JSObject> array);
  
    // Computes the union of keys and return the result.
    // Used for implementing "for (n in object) { }"
    MUST_USE_RESULT static MaybeHandle<FixedArray> UnionOfKeys(
        Handle<FixedArray> first,
        Handle<FixedArray> second);
  
    // Copy a sub array from the receiver to dest.
    void CopyTo(int pos, FixedArray* dest, int dest_pos, int len);
  
    // Garbage collection support.
    static int SizeFor(int length) { return kHeaderSize + length * kPointerSize; }
  
    // Code Generation support.
    static int OffsetOfElementAt(int index) { return SizeFor(index); }
  
    // Garbage collection support.
    Object** RawFieldOfElementAt(int index) {
      return HeapObject::RawField(this, OffsetOfElementAt(index));
    }
  
    DECLARE_CAST(FixedArray)
  
    // Maximal allowed size, in bytes, of a single FixedArray.
    // Prevents overflowing size computations, as well as extreme memory
    // consumption.
    static const int kMaxSize = 128 * MB * kPointerSize;
    // Maximally allowed length of a FixedArray.
    static const int kMaxLength = (kMaxSize - kHeaderSize) / kPointerSize;
  
    // Dispatched behavior.
    DECLARE_PRINTER(FixedArray)
    DECLARE_VERIFIER(FixedArray)
  #ifdef DEBUG
    // Checks if two FixedArrays have identical contents.
    bool IsEqualTo(FixedArray* other);
  #endif
  
    // Swap two elements in a pair of arrays.  If this array and the
    // numbers array are the same object, the elements are only swapped
    // once.
    void SwapPairs(FixedArray* numbers, int i, int j);
  
    // Sort prefix of this array and the numbers array as pairs wrt. the
    // numbers.  If the numbers array and the this array are the same
    // object, the prefix of this array is sorted.
    void SortPairs(FixedArray* numbers, uint32_t len);
  
    class BodyDescriptor : public FlexibleBodyDescriptor<kHeaderSize> {
     public:
      static inline int SizeOf(Map* map, HeapObject* object) {
        return SizeFor(reinterpret_cast<FixedArray*>(object)->length());
      }
    };
  
   protected:
    // Set operation on FixedArray without using write barriers. Can
    // only be used for storing old space objects or smis.
    static inline void NoWriteBarrierSet(FixedArray* array,
                                         int index,
                                         Object* value);
  
    // Set operation on FixedArray without incremental write barrier. Can
    // only be used if the object is guaranteed to be white (whiteness witness
    // is present).
    static inline void NoIncrementalWriteBarrierSet(FixedArray* array,
                                                    int index,
                                                    Object* value);
  
   private:
    STATIC_ASSERT(kHeaderSize == Internals::kFixedArrayHeaderSize);
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(FixedArray);
  };
  
  
  // FixedDoubleArray describes fixed-sized arrays with element type double.
  class FixedDoubleArray: public FixedArrayBase {
   public:
    // Setter and getter for elements.
    inline double get_scalar(int index);
    inline int64_t get_representation(int index);
    static inline Handle<Object> get(Handle<FixedDoubleArray> array, int index);
    inline void set(int index, double value);
    inline void set_the_hole(int index);
  
    // Checking for the hole.
    inline bool is_the_hole(int index);
  
    // Garbage collection support.
    inline static int SizeFor(int length) {
      return kHeaderSize + length * kDoubleSize;
    }
  
    // Gives access to raw memory which stores the array's data.
    inline double* data_start();
  
    inline void FillWithHoles(int from, int to);
  
    // Code Generation support.
    static int OffsetOfElementAt(int index) { return SizeFor(index); }
  
    inline static bool is_the_hole_nan(double value);
    inline static double hole_nan_as_double();
    inline static double canonical_not_the_hole_nan_as_double();
  
    DECLARE_CAST(FixedDoubleArray)
  
    // Maximal allowed size, in bytes, of a single FixedDoubleArray.
    // Prevents overflowing size computations, as well as extreme memory
    // consumption.
    static const int kMaxSize = 512 * MB;
    // Maximally allowed length of a FixedArray.
    static const int kMaxLength = (kMaxSize - kHeaderSize) / kDoubleSize;
  
    // Dispatched behavior.
    DECLARE_PRINTER(FixedDoubleArray)
    DECLARE_VERIFIER(FixedDoubleArray)
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(FixedDoubleArray);
  };
  
  
  // ConstantPoolArray describes a fixed-sized array containing constant pool
  // entries.
  //
  // A ConstantPoolArray can be structured in two different ways depending upon
  // whether it is extended or small. The is_extended_layout() method can be used
  // to discover which layout the constant pool has.
  //
  // The format of a small constant pool is:
  //   [kSmallLayout1Offset]                    : Small section layout bitmap 1
  //   [kSmallLayout2Offset]                    : Small section layout bitmap 2
  //   [first_index(INT64, SMALL_SECTION)]      : 64 bit entries
  //    ...                                     :  ...
  //   [first_index(CODE_PTR, SMALL_SECTION)]   : code pointer entries
  //    ...                                     :  ...
  //   [first_index(HEAP_PTR, SMALL_SECTION)]   : heap pointer entries
  //    ...                                     :  ...
  //   [first_index(INT32, SMALL_SECTION)]      : 32 bit entries
  //    ...                                     :  ...
  //
  // If the constant pool has an extended layout, the extended section constant
  // pool also contains an extended section, which has the following format at
  // location get_extended_section_header_offset():
  //   [kExtendedInt64CountOffset]              : count of extended 64 bit entries
  //   [kExtendedCodePtrCountOffset]            : count of extended code pointers
  //   [kExtendedHeapPtrCountOffset]            : count of extended heap pointers
  //   [kExtendedInt32CountOffset]              : count of extended 32 bit entries
  //   [first_index(INT64, EXTENDED_SECTION)]   : 64 bit entries
  //    ...                                     :  ...
  //   [first_index(CODE_PTR, EXTENDED_SECTION)]: code pointer entries
  //    ...                                     :  ...
  //   [first_index(HEAP_PTR, EXTENDED_SECTION)]: heap pointer entries
  //    ...                                     :  ...
  //   [first_index(INT32, EXTENDED_SECTION)]   : 32 bit entries
  //    ...                                     :  ...
  //
  class ConstantPoolArray: public HeapObject {
   public:
    enum WeakObjectState {
      NO_WEAK_OBJECTS,
      WEAK_OBJECTS_IN_OPTIMIZED_CODE,
      WEAK_OBJECTS_IN_IC
    };
  
    enum Type {
      INT64 = 0,
      CODE_PTR,
      HEAP_PTR,
      INT32,
      // Number of types stored by the ConstantPoolArrays.
      NUMBER_OF_TYPES,
      FIRST_TYPE = INT64,
      LAST_TYPE = INT32
    };
  
    enum LayoutSection {
      SMALL_SECTION = 0,
      EXTENDED_SECTION,
      NUMBER_OF_LAYOUT_SECTIONS
    };
  
    class NumberOfEntries BASE_EMBEDDED {
     public:
      inline NumberOfEntries() {
        for (int i = 0; i < NUMBER_OF_TYPES; i++) {
          element_counts_[i] = 0;
        }
      }
  
      inline NumberOfEntries(int int64_count, int code_ptr_count,
                             int heap_ptr_count, int int32_count) {
        element_counts_[INT64] = int64_count;
        element_counts_[CODE_PTR] = code_ptr_count;
        element_counts_[HEAP_PTR] = heap_ptr_count;
        element_counts_[INT32] = int32_count;
      }
  
      inline NumberOfEntries(ConstantPoolArray* array, LayoutSection section) {
        element_counts_[INT64] = array->number_of_entries(INT64, section);
        element_counts_[CODE_PTR] = array->number_of_entries(CODE_PTR, section);
        element_counts_[HEAP_PTR] = array->number_of_entries(HEAP_PTR, section);
        element_counts_[INT32] = array->number_of_entries(INT32, section);
      }
  
      inline void increment(Type type);
      inline int equals(const NumberOfEntries& other) const;
      inline bool is_empty() const;
      inline int count_of(Type type) const;
      inline int base_of(Type type) const;
      inline int total_count() const;
      inline int are_in_range(int min, int max) const;
  
     private:
      int element_counts_[NUMBER_OF_TYPES];
    };
  
    class Iterator BASE_EMBEDDED {
     public:
      inline Iterator(ConstantPoolArray* array, Type type)
          : array_(array),
            type_(type),
            final_section_(array->final_section()),
            current_section_(SMALL_SECTION),
            next_index_(array->first_index(type, SMALL_SECTION)) {
        update_section();
      }
  
      inline Iterator(ConstantPoolArray* array, Type type, LayoutSection section)
          : array_(array),
            type_(type),
            final_section_(section),
            current_section_(section),
            next_index_(array->first_index(type, section)) {
        update_section();
      }
  
      inline int next_index();
      inline bool is_finished();
  
     private:
      inline void update_section();
      ConstantPoolArray* array_;
      const Type type_;
      const LayoutSection final_section_;
  
      LayoutSection current_section_;
      int next_index_;
    };
  
    // Getters for the first index, the last index and the count of entries of
    // a given type for a given layout section.
    inline int first_index(Type type, LayoutSection layout_section);
    inline int last_index(Type type, LayoutSection layout_section);
    inline int number_of_entries(Type type, LayoutSection layout_section);
  
    // Returns the type of the entry at the given index.
    inline Type get_type(int index);
    inline bool offset_is_type(int offset, Type type);
  
    // Setter and getter for pool elements.
    inline Address get_code_ptr_entry(int index);
    inline Object* get_heap_ptr_entry(int index);
    inline int64_t get_int64_entry(int index);
    inline int32_t get_int32_entry(int index);
    inline double get_int64_entry_as_double(int index);
  
    inline void set(int index, Address value);
    inline void set(int index, Object* value);
    inline void set(int index, int64_t value);
    inline void set(int index, double value);
    inline void set(int index, int32_t value);
  
    // Setters which take a raw offset rather than an index (for code generation).
    inline void set_at_offset(int offset, int32_t value);
    inline void set_at_offset(int offset, int64_t value);
    inline void set_at_offset(int offset, double value);
    inline void set_at_offset(int offset, Address value);
    inline void set_at_offset(int offset, Object* value);
  
    // Setter and getter for weak objects state
    inline void set_weak_object_state(WeakObjectState state);
    inline WeakObjectState get_weak_object_state();
  
    // Returns true if the constant pool has an extended layout, false if it has
    // only the small layout.
    inline bool is_extended_layout();
  
    // Returns the last LayoutSection in this constant pool array.
    inline LayoutSection final_section();
  
    // Set up initial state for a small layout constant pool array.
    inline void Init(const NumberOfEntries& small);
  
    // Set up initial state for an extended layout constant pool array.
    inline void InitExtended(const NumberOfEntries& small,
                             const NumberOfEntries& extended);
  
    // Clears the pointer entries with GC safe values.
    void ClearPtrEntries(Isolate* isolate);
  
    // returns the total number of entries in the constant pool array.
    inline int length();
  
    // Garbage collection support.
    inline int size();
  
  
    inline static int MaxInt64Offset(int number_of_int64) {
      return kFirstEntryOffset + (number_of_int64 * kInt64Size);
    }
  
    inline static int SizeFor(const NumberOfEntries& small) {
      int size = kFirstEntryOffset +
          (small.count_of(INT64)  * kInt64Size) +
          (small.count_of(CODE_PTR) * kPointerSize) +
          (small.count_of(HEAP_PTR) * kPointerSize) +
          (small.count_of(INT32) * kInt32Size);
      return RoundUp(size, kPointerSize);
    }
  
    inline static int SizeForExtended(const NumberOfEntries& small,
                                      const NumberOfEntries& extended) {
      int size = SizeFor(small);
      size = RoundUp(size, kInt64Size);  // Align extended header to 64 bits.
      size += kExtendedFirstOffset +
          (extended.count_of(INT64) * kInt64Size) +
          (extended.count_of(CODE_PTR) * kPointerSize) +
          (extended.count_of(HEAP_PTR) * kPointerSize) +
          (extended.count_of(INT32) * kInt32Size);
      return RoundUp(size, kPointerSize);
    }
  
    inline static int entry_size(Type type) {
      switch (type) {
        case INT32:
          return kInt32Size;
        case INT64:
          return kInt64Size;
        case CODE_PTR:
        case HEAP_PTR:
          return kPointerSize;
        default:
          UNREACHABLE();
          return 0;
      }
    }
  
    // Code Generation support.
    inline int OffsetOfElementAt(int index) {
      int offset;
      LayoutSection section;
      if (is_extended_layout() && index >= first_extended_section_index()) {
        section = EXTENDED_SECTION;
        offset = get_extended_section_header_offset() + kExtendedFirstOffset;
      } else {
        section = SMALL_SECTION;
        offset = kFirstEntryOffset;
      }
  
      // Add offsets for the preceding type sections.
      DCHECK(index <= last_index(LAST_TYPE, section));
      for (Type type = FIRST_TYPE; index > last_index(type, section);
           type = next_type(type)) {
        offset += entry_size(type) * number_of_entries(type, section);
      }
  
      // Add offset for the index in it's type.
      Type type = get_type(index);
      offset += entry_size(type) * (index - first_index(type, section));
      return offset;
    }
  
    DECLARE_CAST(ConstantPoolArray)
  
    // Garbage collection support.
    Object** RawFieldOfElementAt(int index) {
      return HeapObject::RawField(this, OffsetOfElementAt(index));
    }
  
    // Small Layout description.
    static const int kSmallLayout1Offset = HeapObject::kHeaderSize;
    static const int kSmallLayout2Offset = kSmallLayout1Offset + kInt32Size;
    static const int kHeaderSize = kSmallLayout2Offset + kInt32Size;
    static const int kFirstEntryOffset = ROUND_UP(kHeaderSize, kInt64Size);
  
    static const int kSmallLayoutCountBits = 10;
    static const int kMaxSmallEntriesPerType = (1 << kSmallLayoutCountBits) - 1;
  
    // Fields in kSmallLayout1Offset.
    class Int64CountField: public BitField<int, 1, kSmallLayoutCountBits> {};
    class CodePtrCountField: public BitField<int, 11, kSmallLayoutCountBits> {};
    class HeapPtrCountField: public BitField<int, 21, kSmallLayoutCountBits> {};
    class IsExtendedField: public BitField<bool, 31, 1> {};
  
    // Fields in kSmallLayout2Offset.
    class Int32CountField: public BitField<int, 1, kSmallLayoutCountBits> {};
    class TotalCountField: public BitField<int, 11, 12> {};
    class WeakObjectStateField: public BitField<WeakObjectState, 23, 2> {};
  
    // Extended layout description, which starts at
    // get_extended_section_header_offset().
    static const int kExtendedInt64CountOffset = 0;
    static const int kExtendedCodePtrCountOffset =
        kExtendedInt64CountOffset + kPointerSize;
    static const int kExtendedHeapPtrCountOffset =
        kExtendedCodePtrCountOffset + kPointerSize;
    static const int kExtendedInt32CountOffset =
        kExtendedHeapPtrCountOffset + kPointerSize;
    static const int kExtendedFirstOffset =
        kExtendedInt32CountOffset + kPointerSize;
  
    // Dispatched behavior.
    void ConstantPoolIterateBody(ObjectVisitor* v);
  
    DECLARE_PRINTER(ConstantPoolArray)
    DECLARE_VERIFIER(ConstantPoolArray)
  
   private:
    inline int first_extended_section_index();
    inline int get_extended_section_header_offset();
  
    inline static Type next_type(Type type) {
      DCHECK(type >= FIRST_TYPE && type < NUMBER_OF_TYPES);
      int type_int = static_cast<int>(type);
      return static_cast<Type>(++type_int);
    }
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(ConstantPoolArray);
  };
  
  
  // DescriptorArrays are fixed arrays used to hold instance descriptors.
  // The format of the these objects is:
  //   [0]: Number of descriptors
  //   [1]: Either Smi(0) if uninitialized, or a pointer to small fixed array:
  //          [0]: pointer to fixed array with enum cache
  //          [1]: either Smi(0) or pointer to fixed array with indices
  //   [2]: first key
  //   [2 + number of descriptors * kDescriptorSize]: start of slack
  class DescriptorArray: public FixedArray {
   public:
    // Returns true for both shared empty_descriptor_array and for smis, which the
    // map uses to encode additional bit fields when the descriptor array is not
    // yet used.
    inline bool IsEmpty();
  
    // Returns the number of descriptors in the array.
    int number_of_descriptors() {
      DCHECK(length() >= kFirstIndex || IsEmpty());
      int len = length();
      return len == 0 ? 0 : Smi::cast(get(kDescriptorLengthIndex))->value();
    }
  
    int number_of_descriptors_storage() {
      int len = length();
      return len == 0 ? 0 : (len - kFirstIndex) / kDescriptorSize;
    }
  
    int NumberOfSlackDescriptors() {
      return number_of_descriptors_storage() - number_of_descriptors();
    }
  
    inline void SetNumberOfDescriptors(int number_of_descriptors);
    inline int number_of_entries() { return number_of_descriptors(); }
  
    bool HasEnumCache() {
      return !IsEmpty() && !get(kEnumCacheIndex)->IsSmi();
    }
  
    void CopyEnumCacheFrom(DescriptorArray* array) {
      set(kEnumCacheIndex, array->get(kEnumCacheIndex));
    }
  
    FixedArray* GetEnumCache() {
      DCHECK(HasEnumCache());
      FixedArray* bridge = FixedArray::cast(get(kEnumCacheIndex));
      return FixedArray::cast(bridge->get(kEnumCacheBridgeCacheIndex));
    }
  
    bool HasEnumIndicesCache() {
      if (IsEmpty()) return false;
      Object* object = get(kEnumCacheIndex);
      if (object->IsSmi()) return false;
      FixedArray* bridge = FixedArray::cast(object);
      return !bridge->get(kEnumCacheBridgeIndicesCacheIndex)->IsSmi();
    }
  
    FixedArray* GetEnumIndicesCache() {
      DCHECK(HasEnumIndicesCache());
      FixedArray* bridge = FixedArray::cast(get(kEnumCacheIndex));
      return FixedArray::cast(bridge->get(kEnumCacheBridgeIndicesCacheIndex));
    }
  
    Object** GetEnumCacheSlot() {
      DCHECK(HasEnumCache());
      return HeapObject::RawField(reinterpret_cast<HeapObject*>(this),
                                  kEnumCacheOffset);
    }
  
    void ClearEnumCache();
  
    // Initialize or change the enum cache,
    // using the supplied storage for the small "bridge".
    void SetEnumCache(FixedArray* bridge_storage,
                      FixedArray* new_cache,
                      Object* new_index_cache);
  
    bool CanHoldValue(int descriptor, Object* value);
  
    // Accessors for fetching instance descriptor at descriptor number.
    inline Name* GetKey(int descriptor_number);
    inline Object** GetKeySlot(int descriptor_number);
    inline Object* GetValue(int descriptor_number);
    inline void SetValue(int descriptor_number, Object* value);
    inline Object** GetValueSlot(int descriptor_number);
    static inline int GetValueOffset(int descriptor_number);
    inline Object** GetDescriptorStartSlot(int descriptor_number);
    inline Object** GetDescriptorEndSlot(int descriptor_number);
    inline PropertyDetails GetDetails(int descriptor_number);
    inline PropertyType GetType(int descriptor_number);
    inline int GetFieldIndex(int descriptor_number);
    inline HeapType* GetFieldType(int descriptor_number);
    inline Object* GetConstant(int descriptor_number);
    inline Object* GetCallbacksObject(int descriptor_number);
    inline AccessorDescriptor* GetCallbacks(int descriptor_number);
  
    inline Name* GetSortedKey(int descriptor_number);
    inline int GetSortedKeyIndex(int descriptor_number);
    inline void SetSortedKey(int pointer, int descriptor_number);
    inline void SetRepresentation(int descriptor_number,
                                  Representation representation);
  
    // Accessor for complete descriptor.
    inline void Get(int descriptor_number, Descriptor* desc);
    inline void Set(int descriptor_number, Descriptor* desc);
    void Replace(int descriptor_number, Descriptor* descriptor);
  
    // Append automatically sets the enumeration index. This should only be used
    // to add descriptors in bulk at the end, followed by sorting the descriptor
    // array.
    inline void Append(Descriptor* desc);
  
    static Handle<DescriptorArray> CopyUpTo(Handle<DescriptorArray> desc,
                                            int enumeration_index,
                                            int slack = 0);
  
    static Handle<DescriptorArray> CopyUpToAddAttributes(
        Handle<DescriptorArray> desc,
        int enumeration_index,
        PropertyAttributes attributes,
        int slack = 0);
  
    // Sort the instance descriptors by the hash codes of their keys.
    void Sort();
  
    // Search the instance descriptors for given name.
    INLINE(int Search(Name* name, int number_of_own_descriptors));
  
    // As the above, but uses DescriptorLookupCache and updates it when
    // necessary.
    INLINE(int SearchWithCache(Name* name, Map* map));
  
    // Allocates a DescriptorArray, but returns the singleton
    // empty descriptor array object if number_of_descriptors is 0.
    static Handle<DescriptorArray> Allocate(Isolate* isolate,
                                            int number_of_descriptors,
                                            int slack = 0);
  
    DECLARE_CAST(DescriptorArray)
  
    // Constant for denoting key was not found.
    static const int kNotFound = -1;
  
    static const int kDescriptorLengthIndex = 0;
    static const int kEnumCacheIndex = 1;
    static const int kFirstIndex = 2;
  
    // The length of the "bridge" to the enum cache.
    static const int kEnumCacheBridgeLength = 2;
    static const int kEnumCacheBridgeCacheIndex = 0;
    static const int kEnumCacheBridgeIndicesCacheIndex = 1;
  
    // Layout description.
    static const int kDescriptorLengthOffset = FixedArray::kHeaderSize;
    static const int kEnumCacheOffset = kDescriptorLengthOffset + kPointerSize;
    static const int kFirstOffset = kEnumCacheOffset + kPointerSize;
  
    // Layout description for the bridge array.
    static const int kEnumCacheBridgeCacheOffset = FixedArray::kHeaderSize;
  
    // Layout of descriptor.
    static const int kDescriptorKey = 0;
    static const int kDescriptorDetails = 1;
    static const int kDescriptorValue = 2;
    static const int kDescriptorSize = 3;
  
  #ifdef OBJECT_PRINT
    // Print all the descriptors.
    void PrintDescriptors(OStream& os);  // NOLINT
  #endif
  
  #ifdef DEBUG
    // Is the descriptor array sorted and without duplicates?
    bool IsSortedNoDuplicates(int valid_descriptors = -1);
  
    // Is the descriptor array consistent with the back pointers in targets?
    bool IsConsistentWithBackPointers(Map* current_map);
  
    // Are two DescriptorArrays equal?
    bool IsEqualTo(DescriptorArray* other);
  #endif
  
    // Returns the fixed array length required to hold number_of_descriptors
    // descriptors.
    static int LengthFor(int number_of_descriptors) {
      return ToKeyIndex(number_of_descriptors);
    }
  
   private:
    // WhitenessWitness is used to prove that a descriptor array is white
    // (unmarked), so incremental write barriers can be skipped because the
    // marking invariant cannot be broken and slots pointing into evacuation
    // candidates will be discovered when the object is scanned. A witness is
    // always stack-allocated right after creating an array. By allocating a
    // witness, incremental marking is globally disabled. The witness is then
    // passed along wherever needed to statically prove that the array is known to
    // be white.
    class WhitenessWitness {
     public:
      inline explicit WhitenessWitness(DescriptorArray* array);
      inline ~WhitenessWitness();
  
     private:
      IncrementalMarking* marking_;
    };
  
    // An entry in a DescriptorArray, represented as an (array, index) pair.
    class Entry {
     public:
      inline explicit Entry(DescriptorArray* descs, int index) :
          descs_(descs), index_(index) { }
  
      inline PropertyType type() { return descs_->GetType(index_); }
      inline Object* GetCallbackObject() { return descs_->GetValue(index_); }
  
     private:
      DescriptorArray* descs_;
      int index_;
    };
  
    // Conversion from descriptor number to array indices.
    static int ToKeyIndex(int descriptor_number) {
      return kFirstIndex +
             (descriptor_number * kDescriptorSize) +
             kDescriptorKey;
    }
  
    static int ToDetailsIndex(int descriptor_number) {
      return kFirstIndex +
             (descriptor_number * kDescriptorSize) +
             kDescriptorDetails;
    }
  
    static int ToValueIndex(int descriptor_number) {
      return kFirstIndex +
             (descriptor_number * kDescriptorSize) +
             kDescriptorValue;
    }
  
    // Transfer a complete descriptor from the src descriptor array to this
    // descriptor array.
    void CopyFrom(int index,
                  DescriptorArray* src,
                  const WhitenessWitness&);
  
    inline void Set(int descriptor_number,
                    Descriptor* desc,
                    const WhitenessWitness&);
  
    // Swap first and second descriptor.
    inline void SwapSortedKeys(int first, int second);
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(DescriptorArray);
  };
  
  
  enum SearchMode { ALL_ENTRIES, VALID_ENTRIES };
  
  template<SearchMode search_mode, typename T>
  inline int LinearSearch(T* array, Name* name, int len, int valid_entries);
  
  
  template<SearchMode search_mode, typename T>
  inline int Search(T* array, Name* name, int valid_entries = 0);
  
  
  // HashTable is a subclass of FixedArray that implements a hash table
  // that uses open addressing and quadratic probing.
  //
  // In order for the quadratic probing to work, elements that have not
  // yet been used and elements that have been deleted are
  // distinguished.  Probing continues when deleted elements are
  // encountered and stops when unused elements are encountered.
  //
  // - Elements with key == undefined have not been used yet.
  // - Elements with key == the_hole have been deleted.
  //
  // The hash table class is parameterized with a Shape and a Key.
  // Shape must be a class with the following interface:
  //   class ExampleShape {
  //    public:
  //      // Tells whether key matches other.
  //     static bool IsMatch(Key key, Object* other);
  //     // Returns the hash value for key.
  //     static uint32_t Hash(Key key);
  //     // Returns the hash value for object.
  //     static uint32_t HashForObject(Key key, Object* object);
  //     // Convert key to an object.
  //     static inline Handle<Object> AsHandle(Isolate* isolate, Key key);
  //     // The prefix size indicates number of elements in the beginning
  //     // of the backing storage.
  //     static const int kPrefixSize = ..;
  //     // The Element size indicates number of elements per entry.
  //     static const int kEntrySize = ..;
  //   };
  // The prefix size indicates an amount of memory in the
  // beginning of the backing storage that can be used for non-element
  // information by subclasses.
  
  template<typename Key>
  class BaseShape {
   public:
    static const bool UsesSeed = false;
    static uint32_t Hash(Key key) { return 0; }
    static uint32_t SeededHash(Key key, uint32_t seed) {
      DCHECK(UsesSeed);
      return Hash(key);
    }
    static uint32_t HashForObject(Key key, Object* object) { return 0; }
    static uint32_t SeededHashForObject(Key key, uint32_t seed, Object* object) {
      DCHECK(UsesSeed);
      return HashForObject(key, object);
    }
  };
  
  template<typename Derived, typename Shape, typename Key>
  class HashTable: public FixedArray {
   public:
    // Wrapper methods
    inline uint32_t Hash(Key key) {
      if (Shape::UsesSeed) {
        return Shape::SeededHash(key, GetHeap()->HashSeed());
      } else {
        return Shape::Hash(key);
      }
    }
  
    inline uint32_t HashForObject(Key key, Object* object) {
      if (Shape::UsesSeed) {
        return Shape::SeededHashForObject(key, GetHeap()->HashSeed(), object);
      } else {
        return Shape::HashForObject(key, object);
      }
    }
  
    // Returns the number of elements in the hash table.
    int NumberOfElements() {
      return Smi::cast(get(kNumberOfElementsIndex))->value();
    }
  
    // Returns the number of deleted elements in the hash table.
    int NumberOfDeletedElements() {
      return Smi::cast(get(kNumberOfDeletedElementsIndex))->value();
    }
  
    // Returns the capacity of the hash table.
    int Capacity() {
      return Smi::cast(get(kCapacityIndex))->value();
    }
  
    // ElementAdded should be called whenever an element is added to a
    // hash table.
    void ElementAdded() { SetNumberOfElements(NumberOfElements() + 1); }
  
    // ElementRemoved should be called whenever an element is removed from
    // a hash table.
    void ElementRemoved() {
      SetNumberOfElements(NumberOfElements() - 1);
      SetNumberOfDeletedElements(NumberOfDeletedElements() + 1);
    }
    void ElementsRemoved(int n) {
      SetNumberOfElements(NumberOfElements() - n);
      SetNumberOfDeletedElements(NumberOfDeletedElements() + n);
    }
  
    // Returns a new HashTable object.
    MUST_USE_RESULT static Handle<Derived> New(
        Isolate* isolate,
        int at_least_space_for,
        MinimumCapacity capacity_option = USE_DEFAULT_MINIMUM_CAPACITY,
        PretenureFlag pretenure = NOT_TENURED);
  
    // Computes the required capacity for a table holding the given
    // number of elements. May be more than HashTable::kMaxCapacity.
    static int ComputeCapacity(int at_least_space_for);
  
    // Returns the key at entry.
    Object* KeyAt(int entry) { return get(EntryToIndex(entry)); }
  
    // Tells whether k is a real key.  The hole and undefined are not allowed
    // as keys and can be used to indicate missing or deleted elements.
    bool IsKey(Object* k) {
      return !k->IsTheHole() && !k->IsUndefined();
    }
  
    // Garbage collection support.
    void IteratePrefix(ObjectVisitor* visitor);
    void IterateElements(ObjectVisitor* visitor);
  
    DECLARE_CAST(HashTable)
  
    // Compute the probe offset (quadratic probing).
    INLINE(static uint32_t GetProbeOffset(uint32_t n)) {
      return (n + n * n) >> 1;
    }
  
    static const int kNumberOfElementsIndex = 0;
    static const int kNumberOfDeletedElementsIndex = 1;
    static const int kCapacityIndex = 2;
    static const int kPrefixStartIndex = 3;
    static const int kElementsStartIndex =
        kPrefixStartIndex + Shape::kPrefixSize;
    static const int kEntrySize = Shape::kEntrySize;
    static const int kElementsStartOffset =
        kHeaderSize + kElementsStartIndex * kPointerSize;
    static const int kCapacityOffset =
        kHeaderSize + kCapacityIndex * kPointerSize;
  
    // Constant used for denoting a absent entry.
    static const int kNotFound = -1;
  
    // Maximal capacity of HashTable. Based on maximal length of underlying
    // FixedArray. Staying below kMaxCapacity also ensures that EntryToIndex
    // cannot overflow.
    static const int kMaxCapacity =
        (FixedArray::kMaxLength - kElementsStartOffset) / kEntrySize;
  
    // Find entry for key otherwise return kNotFound.
    inline int FindEntry(Key key);
    int FindEntry(Isolate* isolate, Key key);
  
    // Rehashes the table in-place.
    void Rehash(Key key);
  
   protected:
    friend class ObjectHashTable;
  
    // Find the entry at which to insert element with the given key that
    // has the given hash value.
    uint32_t FindInsertionEntry(uint32_t hash);
  
    // Returns the index for an entry (of the key)
    static inline int EntryToIndex(int entry) {
      return (entry * kEntrySize) + kElementsStartIndex;
    }
  
    // Update the number of elements in the hash table.
    void SetNumberOfElements(int nof) {
      set(kNumberOfElementsIndex, Smi::FromInt(nof));
    }
  
    // Update the number of deleted elements in the hash table.
    void SetNumberOfDeletedElements(int nod) {
      set(kNumberOfDeletedElementsIndex, Smi::FromInt(nod));
    }
  
    // Sets the capacity of the hash table.
    void SetCapacity(int capacity) {
      // To scale a computed hash code to fit within the hash table, we
      // use bit-wise AND with a mask, so the capacity must be positive
      // and non-zero.
      DCHECK(capacity > 0);
      DCHECK(capacity <= kMaxCapacity);
      set(kCapacityIndex, Smi::FromInt(capacity));
    }
  
  
    // Returns probe entry.
    static uint32_t GetProbe(uint32_t hash, uint32_t number, uint32_t size) {
      DCHECK(base::bits::IsPowerOfTwo32(size));
      return (hash + GetProbeOffset(number)) & (size - 1);
    }
  
    inline static uint32_t FirstProbe(uint32_t hash, uint32_t size) {
      return hash & (size - 1);
    }
  
    inline static uint32_t NextProbe(
        uint32_t last, uint32_t number, uint32_t size) {
      return (last + number) & (size - 1);
    }
  
    // Attempt to shrink hash table after removal of key.
    MUST_USE_RESULT static Handle<Derived> Shrink(Handle<Derived> table, Key key);
  
    // Ensure enough space for n additional elements.
    MUST_USE_RESULT static Handle<Derived> EnsureCapacity(
        Handle<Derived> table,
        int n,
        Key key,
        PretenureFlag pretenure = NOT_TENURED);
  
   private:
    // Returns _expected_ if one of entries given by the first _probe_ probes is
    // equal to  _expected_. Otherwise, returns the entry given by the probe
    // number _probe_.
    uint32_t EntryForProbe(Key key, Object* k, int probe, uint32_t expected);
  
    void Swap(uint32_t entry1, uint32_t entry2, WriteBarrierMode mode);
  
    // Rehashes this hash-table into the new table.
    void Rehash(Handle<Derived> new_table, Key key);
  };
  
  
  // HashTableKey is an abstract superclass for virtual key behavior.
  class HashTableKey {
   public:
    // Returns whether the other object matches this key.
    virtual bool IsMatch(Object* other) = 0;
    // Returns the hash value for this key.
    virtual uint32_t Hash() = 0;
    // Returns the hash value for object.
    virtual uint32_t HashForObject(Object* key) = 0;
    // Returns the key object for storing into the hash table.
    MUST_USE_RESULT virtual Handle<Object> AsHandle(Isolate* isolate) = 0;
    // Required.
    virtual ~HashTableKey() {}
  };
  
  
  class StringTableShape : public BaseShape<HashTableKey*> {
   public:
    static inline bool IsMatch(HashTableKey* key, Object* value) {
      return key->IsMatch(value);
    }
  
    static inline uint32_t Hash(HashTableKey* key) {
      return key->Hash();
    }
  
    static inline uint32_t HashForObject(HashTableKey* key, Object* object) {
      return key->HashForObject(object);
    }
  
    static inline Handle<Object> AsHandle(Isolate* isolate, HashTableKey* key);
  
    static const int kPrefixSize = 0;
    static const int kEntrySize = 1;
  };
  
  class SeqOneByteString;
  
  // StringTable.
  //
  // No special elements in the prefix and the element size is 1
  // because only the string itself (the key) needs to be stored.
  class StringTable: public HashTable<StringTable,
                                      StringTableShape,
                                      HashTableKey*> {
   public:
    // Find string in the string table. If it is not there yet, it is
    // added. The return value is the string found.
    static Handle<String> LookupString(Isolate* isolate, Handle<String> key);
    static Handle<String> LookupKey(Isolate* isolate, HashTableKey* key);
  
    // Tries to internalize given string and returns string handle on success
    // or an empty handle otherwise.
    MUST_USE_RESULT static MaybeHandle<String> InternalizeStringIfExists(
        Isolate* isolate,
        Handle<String> string);
  
    // Looks up a string that is equal to the given string and returns
    // string handle if it is found, or an empty handle otherwise.
    MUST_USE_RESULT static MaybeHandle<String> LookupStringIfExists(
        Isolate* isolate,
        Handle<String> str);
    MUST_USE_RESULT static MaybeHandle<String> LookupTwoCharsStringIfExists(
        Isolate* isolate,
        uint16_t c1,
        uint16_t c2);
  
    DECLARE_CAST(StringTable)
  
   private:
    template <bool seq_one_byte>
    friend class JsonParser;
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(StringTable);
  };
  
  
  class MapCacheShape : public BaseShape<HashTableKey*> {
   public:
    static inline bool IsMatch(HashTableKey* key, Object* value) {
      return key->IsMatch(value);
    }
  
    static inline uint32_t Hash(HashTableKey* key) {
      return key->Hash();
    }
  
    static inline uint32_t HashForObject(HashTableKey* key, Object* object) {
      return key->HashForObject(object);
    }
  
    static inline Handle<Object> AsHandle(Isolate* isolate, HashTableKey* key);
  
    static const int kPrefixSize = 0;
    static const int kEntrySize = 2;
  };
  
  
  // MapCache.
  //
  // Maps keys that are a fixed array of unique names to a map.
  // Used for canonicalize maps for object literals.
  class MapCache: public HashTable<MapCache, MapCacheShape, HashTableKey*> {
   public:
    // Find cached value for a name key, otherwise return null.
    Object* Lookup(FixedArray* key);
    static Handle<MapCache> Put(
        Handle<MapCache> map_cache, Handle<FixedArray> key, Handle<Map> value);
    DECLARE_CAST(MapCache)
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(MapCache);
  };
  
  
  template <typename Derived, typename Shape, typename Key>
  class Dictionary: public HashTable<Derived, Shape, Key> {
   protected:
    typedef HashTable<Derived, Shape, Key> DerivedHashTable;
  
   public:
    // Returns the value at entry.
    Object* ValueAt(int entry) {
      return this->get(DerivedHashTable::EntryToIndex(entry) + 1);
    }
  
    // Set the value for entry.
    void ValueAtPut(int entry, Object* value) {
      this->set(DerivedHashTable::EntryToIndex(entry) + 1, value);
    }
  
    // Returns the property details for the property at entry.
    PropertyDetails DetailsAt(int entry) {
      DCHECK(entry >= 0);  // Not found is -1, which is not caught by get().
      return PropertyDetails(
          Smi::cast(this->get(DerivedHashTable::EntryToIndex(entry) + 2)));
    }
  
    // Set the details for entry.
    void DetailsAtPut(int entry, PropertyDetails value) {
      this->set(DerivedHashTable::EntryToIndex(entry) + 2, value.AsSmi());
    }
  
    // Sorting support
    void CopyValuesTo(FixedArray* elements);
  
    // Delete a property from the dictionary.
    static Handle<Object> DeleteProperty(
        Handle<Derived> dictionary,
        int entry,
        JSObject::DeleteMode mode);
  
    // Attempt to shrink the dictionary after deletion of key.
    MUST_USE_RESULT static inline Handle<Derived> Shrink(
        Handle<Derived> dictionary,
        Key key) {
      return DerivedHashTable::Shrink(dictionary, key);
    }
  
    // Returns the number of elements in the dictionary filtering out properties
    // with the specified attributes.
    int NumberOfElementsFilterAttributes(PropertyAttributes filter);
  
    // Returns the number of enumerable elements in the dictionary.
    int NumberOfEnumElements();
  
    enum SortMode { UNSORTED, SORTED };
    // Copies keys to preallocated fixed array.
    void CopyKeysTo(FixedArray* storage,
                    PropertyAttributes filter,
                    SortMode sort_mode);
    // Fill in details for properties into storage.
    void CopyKeysTo(FixedArray* storage,
                    int index,
                    PropertyAttributes filter,
                    SortMode sort_mode);
  
    // Accessors for next enumeration index.
    void SetNextEnumerationIndex(int index) {
      DCHECK(index != 0);
      this->set(kNextEnumerationIndexIndex, Smi::FromInt(index));
    }
  
    int NextEnumerationIndex() {
      return Smi::cast(this->get(kNextEnumerationIndexIndex))->value();
    }
  
    // Creates a new dictionary.
    MUST_USE_RESULT static Handle<Derived> New(
        Isolate* isolate,
        int at_least_space_for,
        PretenureFlag pretenure = NOT_TENURED);
  
    // Ensure enough space for n additional elements.
    static Handle<Derived> EnsureCapacity(Handle<Derived> obj, int n, Key key);
  
  #ifdef OBJECT_PRINT
    void Print(OStream& os);  // NOLINT
  #endif
    // Returns the key (slow).
    Object* SlowReverseLookup(Object* value);
  
    // Sets the entry to (key, value) pair.
    inline void SetEntry(int entry,
                         Handle<Object> key,
                         Handle<Object> value);
    inline void SetEntry(int entry,
                         Handle<Object> key,
                         Handle<Object> value,
                         PropertyDetails details);
  
    MUST_USE_RESULT static Handle<Derived> Add(
        Handle<Derived> dictionary,
        Key key,
        Handle<Object> value,
        PropertyDetails details);
  
   protected:
    // Generic at put operation.
    MUST_USE_RESULT static Handle<Derived> AtPut(
        Handle<Derived> dictionary,
        Key key,
        Handle<Object> value);
  
    // Add entry to dictionary.
    static void AddEntry(
        Handle<Derived> dictionary,
        Key key,
        Handle<Object> value,
        PropertyDetails details,
        uint32_t hash);
  
    // Generate new enumeration indices to avoid enumeration index overflow.
    static void GenerateNewEnumerationIndices(Handle<Derived> dictionary);
    static const int kMaxNumberKeyIndex = DerivedHashTable::kPrefixStartIndex;
    static const int kNextEnumerationIndexIndex = kMaxNumberKeyIndex + 1;
  };
  
  
  class NameDictionaryShape : public BaseShape<Handle<Name> > {
   public:
    static inline bool IsMatch(Handle<Name> key, Object* other);
    static inline uint32_t Hash(Handle<Name> key);
    static inline uint32_t HashForObject(Handle<Name> key, Object* object);
    static inline Handle<Object> AsHandle(Isolate* isolate, Handle<Name> key);
    static const int kPrefixSize = 2;
    static const int kEntrySize = 3;
    static const bool kIsEnumerable = true;
  };
  
  
  class NameDictionary: public Dictionary<NameDictionary,
                                          NameDictionaryShape,
                                          Handle<Name> > {
    typedef Dictionary<
        NameDictionary, NameDictionaryShape, Handle<Name> > DerivedDictionary;
  
   public:
    DECLARE_CAST(NameDictionary)
  
    // Copies enumerable keys to preallocated fixed array.
    void CopyEnumKeysTo(FixedArray* storage);
    inline static void DoGenerateNewEnumerationIndices(
        Handle<NameDictionary> dictionary);
  
    // Find entry for key, otherwise return kNotFound. Optimized version of
    // HashTable::FindEntry.
    int FindEntry(Handle<Name> key);
  };
  
  
  class NumberDictionaryShape : public BaseShape<uint32_t> {
   public:
    static inline bool IsMatch(uint32_t key, Object* other);
    static inline Handle<Object> AsHandle(Isolate* isolate, uint32_t key);
    static const int kEntrySize = 3;
    static const bool kIsEnumerable = false;
  };
  
  
  class SeededNumberDictionaryShape : public NumberDictionaryShape {
   public:
    static const bool UsesSeed = true;
    static const int kPrefixSize = 2;
  
    static inline uint32_t SeededHash(uint32_t key, uint32_t seed);
    static inline uint32_t SeededHashForObject(uint32_t key,
                                               uint32_t seed,
                                               Object* object);
  };
  
  
  class UnseededNumberDictionaryShape : public NumberDictionaryShape {
   public:
    static const int kPrefixSize = 0;
  
    static inline uint32_t Hash(uint32_t key);
    static inline uint32_t HashForObject(uint32_t key, Object* object);
  };
  
  
  class SeededNumberDictionary
      : public Dictionary<SeededNumberDictionary,
                          SeededNumberDictionaryShape,
                          uint32_t> {
   public:
    DECLARE_CAST(SeededNumberDictionary)
  
    // Type specific at put (default NONE attributes is used when adding).
    MUST_USE_RESULT static Handle<SeededNumberDictionary> AtNumberPut(
        Handle<SeededNumberDictionary> dictionary,
        uint32_t key,
        Handle<Object> value);
    MUST_USE_RESULT static Handle<SeededNumberDictionary> AddNumberEntry(
        Handle<SeededNumberDictionary> dictionary,
        uint32_t key,
        Handle<Object> value,
        PropertyDetails details);
  
    // Set an existing entry or add a new one if needed.
    // Return the updated dictionary.
    MUST_USE_RESULT static Handle<SeededNumberDictionary> Set(
        Handle<SeededNumberDictionary> dictionary,
        uint32_t key,
        Handle<Object> value,
        PropertyDetails details);
  
    void UpdateMaxNumberKey(uint32_t key);
  
    // If slow elements are required we will never go back to fast-case
    // for the elements kept in this dictionary.  We require slow
    // elements if an element has been added at an index larger than
    // kRequiresSlowElementsLimit or set_requires_slow_elements() has been called
    // when defining a getter or setter with a number key.
    inline bool requires_slow_elements();
    inline void set_requires_slow_elements();
  
    // Get the value of the max number key that has been added to this
    // dictionary.  max_number_key can only be called if
    // requires_slow_elements returns false.
    inline uint32_t max_number_key();
  
    // Bit masks.
    static const int kRequiresSlowElementsMask = 1;
    static const int kRequiresSlowElementsTagSize = 1;
    static const uint32_t kRequiresSlowElementsLimit = (1 << 29) - 1;
  };
  
  
  class UnseededNumberDictionary
      : public Dictionary<UnseededNumberDictionary,
                          UnseededNumberDictionaryShape,
                          uint32_t> {
   public:
    DECLARE_CAST(UnseededNumberDictionary)
  
    // Type specific at put (default NONE attributes is used when adding).
    MUST_USE_RESULT static Handle<UnseededNumberDictionary> AtNumberPut(
        Handle<UnseededNumberDictionary> dictionary,
        uint32_t key,
        Handle<Object> value);
    MUST_USE_RESULT static Handle<UnseededNumberDictionary> AddNumberEntry(
        Handle<UnseededNumberDictionary> dictionary,
        uint32_t key,
        Handle<Object> value);
  
    // Set an existing entry or add a new one if needed.
    // Return the updated dictionary.
    MUST_USE_RESULT static Handle<UnseededNumberDictionary> Set(
        Handle<UnseededNumberDictionary> dictionary,
        uint32_t key,
        Handle<Object> value);
  };
  
  
  class ObjectHashTableShape : public BaseShape<Handle<Object> > {
   public:
    static inline bool IsMatch(Handle<Object> key, Object* other);
    static inline uint32_t Hash(Handle<Object> key);
    static inline uint32_t HashForObject(Handle<Object> key, Object* object);
    static inline Handle<Object> AsHandle(Isolate* isolate, Handle<Object> key);
    static const int kPrefixSize = 0;
    static const int kEntrySize = 2;
  };
  
  
  // ObjectHashTable maps keys that are arbitrary objects to object values by
  // using the identity hash of the key for hashing purposes.
  class ObjectHashTable: public HashTable<ObjectHashTable,
                                          ObjectHashTableShape,
                                          Handle<Object> > {
    typedef HashTable<
        ObjectHashTable, ObjectHashTableShape, Handle<Object> > DerivedHashTable;
   public:
    DECLARE_CAST(ObjectHashTable)
  
    // Attempt to shrink hash table after removal of key.
    MUST_USE_RESULT static inline Handle<ObjectHashTable> Shrink(
        Handle<ObjectHashTable> table,
        Handle<Object> key);
  
    // Looks up the value associated with the given key. The hole value is
    // returned in case the key is not present.
    Object* Lookup(Handle<Object> key);
  
    // Adds (or overwrites) the value associated with the given key.
    static Handle<ObjectHashTable> Put(Handle<ObjectHashTable> table,
                                       Handle<Object> key,
                                       Handle<Object> value);
  
    // Returns an ObjectHashTable (possibly |table|) where |key| has been removed.
    static Handle<ObjectHashTable> Remove(Handle<ObjectHashTable> table,
                                          Handle<Object> key,
                                          bool* was_present);
  
   private:
    friend class MarkCompactCollector;
  
    void AddEntry(int entry, Object* key, Object* value);
    void RemoveEntry(int entry);
  
    // Returns the index to the value of an entry.
    static inline int EntryToValueIndex(int entry) {
      return EntryToIndex(entry) + 1;
    }
  };
  
  
  // OrderedHashTable is a HashTable with Object keys that preserves
  // insertion order. There are Map and Set interfaces (OrderedHashMap
  // and OrderedHashTable, below). It is meant to be used by JSMap/JSSet.
  //
  // Only Object* keys are supported, with Object::SameValueZero() used as the
  // equality operator and Object::GetHash() for the hash function.
  //
  // Based on the "Deterministic Hash Table" as described by Jason Orendorff at
  // https://wiki.mozilla.org/User:Jorend/Deterministic_hash_tables
  // Originally attributed to Tyler Close.
  //
  // Memory layout:
  //   [0]: bucket count
  //   [1]: element count
  //   [2]: deleted element count
  //   [3..(3 + NumberOfBuckets() - 1)]: "hash table", where each item is an
  //                            offset into the data table (see below) where the
  //                            first item in this bucket is stored.
  //   [3 + NumberOfBuckets()..length]: "data table", an array of length
  //                            Capacity() * kEntrySize, where the first entrysize
  //                            items are handled by the derived class and the
  //                            item at kChainOffset is another entry into the
  //                            data table indicating the next entry in this hash
  //                            bucket.
  //
  // When we transition the table to a new version we obsolete it and reuse parts
  // of the memory to store information how to transition an iterator to the new
  // table:
  //
  // Memory layout for obsolete table:
  //   [0]: bucket count
  //   [1]: Next newer table
  //   [2]: Number of removed holes or -1 when the table was cleared.
  //   [3..(3 + NumberOfRemovedHoles() - 1)]: The indexes of the removed holes.
  //   [3 + NumberOfRemovedHoles()..length]: Not used
  //
  template<class Derived, class Iterator, int entrysize>
  class OrderedHashTable: public FixedArray {
   public:
    // Returns an OrderedHashTable with a capacity of at least |capacity|.
    static Handle<Derived> Allocate(
        Isolate* isolate, int capacity, PretenureFlag pretenure = NOT_TENURED);
  
    // Returns an OrderedHashTable (possibly |table|) with enough space
    // to add at least one new element.
    static Handle<Derived> EnsureGrowable(Handle<Derived> table);
  
    // Returns an OrderedHashTable (possibly |table|) that's shrunken
    // if possible.
    static Handle<Derived> Shrink(Handle<Derived> table);
  
    // Returns a new empty OrderedHashTable and records the clearing so that
    // exisiting iterators can be updated.
    static Handle<Derived> Clear(Handle<Derived> table);
  
    // Returns an OrderedHashTable (possibly |table|) where |key| has been
    // removed.
    static Handle<Derived> Remove(Handle<Derived> table, Handle<Object> key,
        bool* was_present);
  
    // Returns kNotFound if the key isn't present.
    int FindEntry(Handle<Object> key, int hash);
  
    // Like the above, but doesn't require the caller to provide a hash.
    int FindEntry(Handle<Object> key);
  
    int NumberOfElements() {
      return Smi::cast(get(kNumberOfElementsIndex))->value();
    }
  
    int NumberOfDeletedElements() {
      return Smi::cast(get(kNumberOfDeletedElementsIndex))->value();
    }
  
    int UsedCapacity() { return NumberOfElements() + NumberOfDeletedElements(); }
  
    int NumberOfBuckets() {
      return Smi::cast(get(kNumberOfBucketsIndex))->value();
    }
  
    // Returns the index into the data table where the new entry
    // should be placed. The table is assumed to have enough space
    // for a new entry.
    int AddEntry(int hash);
  
    // Removes the entry, and puts the_hole in entrysize pointers
    // (leaving the hash table chain intact).
    void RemoveEntry(int entry);
  
    // Returns an index into |this| for the given entry.
    int EntryToIndex(int entry) {
      return kHashTableStartIndex + NumberOfBuckets() + (entry * kEntrySize);
    }
  
    Object* KeyAt(int entry) { return get(EntryToIndex(entry)); }
  
    bool IsObsolete() {
      return !get(kNextTableIndex)->IsSmi();
    }
  
    // The next newer table. This is only valid if the table is obsolete.
    Derived* NextTable() {
      return Derived::cast(get(kNextTableIndex));
    }
  
    // When the table is obsolete we store the indexes of the removed holes.
    int RemovedIndexAt(int index) {
      return Smi::cast(get(kRemovedHolesIndex + index))->value();
    }
  
    static const int kNotFound = -1;
    static const int kMinCapacity = 4;
  
   private:
    static Handle<Derived> Rehash(Handle<Derived> table, int new_capacity);
  
    void SetNumberOfBuckets(int num) {
      set(kNumberOfBucketsIndex, Smi::FromInt(num));
    }
  
    void SetNumberOfElements(int num) {
      set(kNumberOfElementsIndex, Smi::FromInt(num));
    }
  
    void SetNumberOfDeletedElements(int num) {
      set(kNumberOfDeletedElementsIndex, Smi::FromInt(num));
    }
  
    int Capacity() {
      return NumberOfBuckets() * kLoadFactor;
    }
  
    // Returns the next entry for the given entry.
    int ChainAt(int entry) {
      return Smi::cast(get(EntryToIndex(entry) + kChainOffset))->value();
    }
  
    int HashToBucket(int hash) {
      return hash & (NumberOfBuckets() - 1);
    }
  
    int HashToEntry(int hash) {
      int bucket = HashToBucket(hash);
      return Smi::cast(get(kHashTableStartIndex + bucket))->value();
    }
  
    void SetNextTable(Derived* next_table) {
      set(kNextTableIndex, next_table);
    }
  
    void SetRemovedIndexAt(int index, int removed_index) {
      return set(kRemovedHolesIndex + index, Smi::FromInt(removed_index));
    }
  
    static const int kNumberOfBucketsIndex = 0;
    static const int kNumberOfElementsIndex = kNumberOfBucketsIndex + 1;
    static const int kNumberOfDeletedElementsIndex = kNumberOfElementsIndex + 1;
    static const int kHashTableStartIndex = kNumberOfDeletedElementsIndex + 1;
  
    static const int kNextTableIndex = kNumberOfElementsIndex;
    static const int kRemovedHolesIndex = kHashTableStartIndex;
  
    static const int kEntrySize = entrysize + 1;
    static const int kChainOffset = entrysize;
  
    static const int kLoadFactor = 2;
    static const int kMaxCapacity =
        (FixedArray::kMaxLength - kHashTableStartIndex)
        / (1 + (kEntrySize * kLoadFactor));
  };
  
  
  class JSSetIterator;
  
  
  class OrderedHashSet: public OrderedHashTable<
      OrderedHashSet, JSSetIterator, 1> {
   public:
    DECLARE_CAST(OrderedHashSet)
  
    bool Contains(Handle<Object> key);
    static Handle<OrderedHashSet> Add(
        Handle<OrderedHashSet> table, Handle<Object> key);
  };
  
  
  class JSMapIterator;
  
  
  class OrderedHashMap:public OrderedHashTable<
      OrderedHashMap, JSMapIterator, 2> {
   public:
    DECLARE_CAST(OrderedHashMap)
  
    Object* Lookup(Handle<Object> key);
    static Handle<OrderedHashMap> Put(
        Handle<OrderedHashMap> table,
        Handle<Object> key,
        Handle<Object> value);
  
    Object* ValueAt(int entry) {
      return get(EntryToIndex(entry) + kValueOffset);
    }
  
   private:
    static const int kValueOffset = 1;
  };
  
  
  template <int entrysize>
  class WeakHashTableShape : public BaseShape<Handle<Object> > {
   public:
    static inline bool IsMatch(Handle<Object> key, Object* other);
    static inline uint32_t Hash(Handle<Object> key);
    static inline uint32_t HashForObject(Handle<Object> key, Object* object);
    static inline Handle<Object> AsHandle(Isolate* isolate, Handle<Object> key);
    static const int kPrefixSize = 0;
    static const int kEntrySize = entrysize;
  };
  
  
  // WeakHashTable maps keys that are arbitrary objects to object values.
  // It is used for the global weak hash table that maps objects
  // embedded in optimized code to dependent code lists.
  class WeakHashTable: public HashTable<WeakHashTable,
                                        WeakHashTableShape<2>,
                                        Handle<Object> > {
    typedef HashTable<
        WeakHashTable, WeakHashTableShape<2>, Handle<Object> > DerivedHashTable;
   public:
    DECLARE_CAST(WeakHashTable)
  
    // Looks up the value associated with the given key. The hole value is
    // returned in case the key is not present.
    Object* Lookup(Handle<Object> key);
  
    // Adds (or overwrites) the value associated with the given key. Mapping a
    // key to the hole value causes removal of the whole entry.
    MUST_USE_RESULT static Handle<WeakHashTable> Put(Handle<WeakHashTable> table,
                                                     Handle<Object> key,
                                                     Handle<Object> value);
  
    // This function is called when heap verification is turned on.
    void Zap(Object* value) {
      int capacity = Capacity();
      for (int i = 0; i < capacity; i++) {
        set(EntryToIndex(i), value);
        set(EntryToValueIndex(i), value);
      }
    }
  
   private:
    friend class MarkCompactCollector;
  
    void AddEntry(int entry, Handle<Object> key, Handle<Object> value);
  
    // Returns the index to the value of an entry.
    static inline int EntryToValueIndex(int entry) {
      return EntryToIndex(entry) + 1;
    }
  };
  
  
  // JSFunctionResultCache caches results of some JSFunction invocation.
  // It is a fixed array with fixed structure:
  //   [0]: factory function
  //   [1]: finger index
  //   [2]: current cache size
  //   [3]: dummy field.
  // The rest of array are key/value pairs.
  class JSFunctionResultCache: public FixedArray {
   public:
    static const int kFactoryIndex = 0;
    static const int kFingerIndex = kFactoryIndex + 1;
    static const int kCacheSizeIndex = kFingerIndex + 1;
    static const int kDummyIndex = kCacheSizeIndex + 1;
    static const int kEntriesIndex = kDummyIndex + 1;
  
    static const int kEntrySize = 2;  // key + value
  
    static const int kFactoryOffset = kHeaderSize;
    static const int kFingerOffset = kFactoryOffset + kPointerSize;
    static const int kCacheSizeOffset = kFingerOffset + kPointerSize;
  
    inline void MakeZeroSize();
    inline void Clear();
  
    inline int size();
    inline void set_size(int size);
    inline int finger_index();
    inline void set_finger_index(int finger_index);
  
    DECLARE_CAST(JSFunctionResultCache)
  
    DECLARE_VERIFIER(JSFunctionResultCache)
  };
  
  
  // ScopeInfo represents information about different scopes of a source
  // program  and the allocation of the scope's variables. Scope information
  // is stored in a compressed form in ScopeInfo objects and is used
  // at runtime (stack dumps, deoptimization, etc.).
  
  // This object provides quick access to scope info details for runtime
  // routines.
  class ScopeInfo : public FixedArray {
   public:
    DECLARE_CAST(ScopeInfo)
  
    // Return the type of this scope.
    ScopeType scope_type();
  
    // Does this scope call eval?
    bool CallsEval();
  
    // Return the strict mode of this scope.
    StrictMode strict_mode();
  
    // Does this scope make a sloppy eval call?
    bool CallsSloppyEval() { return CallsEval() && strict_mode() == SLOPPY; }
  
    // Return the total number of locals allocated on the stack and in the
    // context. This includes the parameters that are allocated in the context.
    int LocalCount();
  
    // Return the number of stack slots for code. This number consists of two
    // parts:
    //  1. One stack slot per stack allocated local.
    //  2. One stack slot for the function name if it is stack allocated.
    int StackSlotCount();
  
    // Return the number of context slots for code if a context is allocated. This
    // number consists of three parts:
    //  1. Size of fixed header for every context: Context::MIN_CONTEXT_SLOTS
    //  2. One context slot per context allocated local.
    //  3. One context slot for the function name if it is context allocated.
    // Parameters allocated in the context count as context allocated locals. If
    // no contexts are allocated for this scope ContextLength returns 0.
    int ContextLength();
  
    // Is this scope the scope of a named function expression?
    bool HasFunctionName();
  
    // Return if this has context allocated locals.
    bool HasHeapAllocatedLocals();
  
    // Return if contexts are allocated for this scope.
    bool HasContext();
  
    // Return if this is a function scope with "use asm".
    bool IsAsmModule() { return AsmModuleField::decode(Flags()); }
  
    // Return if this is a nested function within an asm module scope.
    bool IsAsmFunction() { return AsmFunctionField::decode(Flags()); }
  
    // Return the function_name if present.
    String* FunctionName();
  
    // Return the name of the given parameter.
    String* ParameterName(int var);
  
    // Return the name of the given local.
    String* LocalName(int var);
  
    // Return the name of the given stack local.
    String* StackLocalName(int var);
  
    // Return the name of the given context local.
    String* ContextLocalName(int var);
  
    // Return the mode of the given context local.
    VariableMode ContextLocalMode(int var);
  
    // Return the initialization flag of the given context local.
    InitializationFlag ContextLocalInitFlag(int var);
  
    // Return the initialization flag of the given context local.
    MaybeAssignedFlag ContextLocalMaybeAssignedFlag(int var);
  
    // Return true if this local was introduced by the compiler, and should not be
    // exposed to the user in a debugger.
    bool LocalIsSynthetic(int var);
  
    // Lookup support for serialized scope info. Returns the
    // the stack slot index for a given slot name if the slot is
    // present; otherwise returns a value < 0. The name must be an internalized
    // string.
    int StackSlotIndex(String* name);
  
    // Lookup support for serialized scope info. Returns the
    // context slot index for a given slot name if the slot is present; otherwise
    // returns a value < 0. The name must be an internalized string.
    // If the slot is present and mode != NULL, sets *mode to the corresponding
    // mode for that variable.
    static int ContextSlotIndex(Handle<ScopeInfo> scope_info, Handle<String> name,
                                VariableMode* mode, InitializationFlag* init_flag,
                                MaybeAssignedFlag* maybe_assigned_flag);
  
    // Lookup support for serialized scope info. Returns the
    // parameter index for a given parameter name if the parameter is present;
    // otherwise returns a value < 0. The name must be an internalized string.
    int ParameterIndex(String* name);
  
    // Lookup support for serialized scope info. Returns the function context
    // slot index if the function name is present and context-allocated (named
    // function expressions, only), otherwise returns a value < 0. The name
    // must be an internalized string.
    int FunctionContextSlotIndex(String* name, VariableMode* mode);
  
  
    // Copies all the context locals into an object used to materialize a scope.
    static bool CopyContextLocalsToScopeObject(Handle<ScopeInfo> scope_info,
                                               Handle<Context> context,
                                               Handle<JSObject> scope_object);
  
  
    static Handle<ScopeInfo> Create(Scope* scope, Zone* zone);
  
    // Serializes empty scope info.
    static ScopeInfo* Empty(Isolate* isolate);
  
  #ifdef DEBUG
    void Print();
  #endif
  
    // The layout of the static part of a ScopeInfo is as follows. Each entry is
    // numeric and occupies one array slot.
    // 1. A set of properties of the scope
    // 2. The number of parameters. This only applies to function scopes. For
    //    non-function scopes this is 0.
    // 3. The number of non-parameter variables allocated on the stack.
    // 4. The number of non-parameter and parameter variables allocated in the
    //    context.
  #define FOR_EACH_NUMERIC_FIELD(V)          \
    V(Flags)                                 \
    V(ParameterCount)                        \
    V(StackLocalCount)                       \
    V(ContextLocalCount)
  
  #define FIELD_ACCESSORS(name)                            \
    void Set##name(int value) {                            \
      set(k##name, Smi::FromInt(value));                   \
    }                                                      \
    int name() {                                           \
      if (length() > 0) {                                  \
        return Smi::cast(get(k##name))->value();           \
      } else {                                             \
        return 0;                                          \
      }                                                    \
    }
    FOR_EACH_NUMERIC_FIELD(FIELD_ACCESSORS)
  #undef FIELD_ACCESSORS
  
   private:
    enum {
  #define DECL_INDEX(name) k##name,
    FOR_EACH_NUMERIC_FIELD(DECL_INDEX)
  #undef DECL_INDEX
  #undef FOR_EACH_NUMERIC_FIELD
      kVariablePartIndex
    };
  
    // The layout of the variable part of a ScopeInfo is as follows:
    // 1. ParameterEntries:
    //    This part stores the names of the parameters for function scopes. One
    //    slot is used per parameter, so in total this part occupies
    //    ParameterCount() slots in the array. For other scopes than function
    //    scopes ParameterCount() is 0.
    // 2. StackLocalEntries:
    //    Contains the names of local variables that are allocated on the stack,
    //    in increasing order of the stack slot index. One slot is used per stack
    //    local, so in total this part occupies StackLocalCount() slots in the
    //    array.
    // 3. ContextLocalNameEntries:
    //    Contains the names of local variables and parameters that are allocated
    //    in the context. They are stored in increasing order of the context slot
    //    index starting with Context::MIN_CONTEXT_SLOTS. One slot is used per
    //    context local, so in total this part occupies ContextLocalCount() slots
    //    in the array.
    // 4. ContextLocalInfoEntries:
    //    Contains the variable modes and initialization flags corresponding to
    //    the context locals in ContextLocalNameEntries. One slot is used per
    //    context local, so in total this part occupies ContextLocalCount()
    //    slots in the array.
    // 5. FunctionNameEntryIndex:
    //    If the scope belongs to a named function expression this part contains
    //    information about the function variable. It always occupies two array
    //    slots:  a. The name of the function variable.
    //            b. The context or stack slot index for the variable.
    int ParameterEntriesIndex();
    int StackLocalEntriesIndex();
    int ContextLocalNameEntriesIndex();
    int ContextLocalInfoEntriesIndex();
    int FunctionNameEntryIndex();
  
    // Location of the function variable for named function expressions.
    enum FunctionVariableInfo {
      NONE,     // No function name present.
      STACK,    // Function
      CONTEXT,
      UNUSED
    };
  
    // Properties of scopes.
    class ScopeTypeField:        public BitField<ScopeType,            0, 3> {};
    class CallsEvalField:        public BitField<bool,                 3, 1> {};
    class StrictModeField:       public BitField<StrictMode,           4, 1> {};
    class FunctionVariableField: public BitField<FunctionVariableInfo, 5, 2> {};
    class FunctionVariableMode:  public BitField<VariableMode,         7, 3> {};
    class AsmModuleField : public BitField<bool, 10, 1> {};
    class AsmFunctionField : public BitField<bool, 11, 1> {};
  
    // BitFields representing the encoded information for context locals in the
    // ContextLocalInfoEntries part.
    class ContextLocalMode:      public BitField<VariableMode,         0, 3> {};
    class ContextLocalInitFlag:  public BitField<InitializationFlag,   3, 1> {};
    class ContextLocalMaybeAssignedFlag
        : public BitField<MaybeAssignedFlag, 4, 1> {};
  };
  
  
  // The cache for maps used by normalized (dictionary mode) objects.
  // Such maps do not have property descriptors, so a typical program
  // needs very limited number of distinct normalized maps.
  class NormalizedMapCache: public FixedArray {
   public:
    static Handle<NormalizedMapCache> New(Isolate* isolate);
  
    MUST_USE_RESULT MaybeHandle<Map> Get(Handle<Map> fast_map,
                                         PropertyNormalizationMode mode);
    void Set(Handle<Map> fast_map, Handle<Map> normalized_map);
  
    void Clear();
  
    DECLARE_CAST(NormalizedMapCache)
  
    static inline bool IsNormalizedMapCache(const Object* obj);
  
    DECLARE_VERIFIER(NormalizedMapCache)
   private:
    static const int kEntries = 64;
  
    static inline int GetIndex(Handle<Map> map);
  
    // The following declarations hide base class methods.
    Object* get(int index);
    void set(int index, Object* value);
  };
  
  
  // ByteArray represents fixed sized byte arrays.  Used for the relocation info
  // that is attached to code objects.
  class ByteArray: public FixedArrayBase {
   public:
    inline int Size() { return RoundUp(length() + kHeaderSize, kPointerSize); }
  
    // Setter and getter.
    inline byte get(int index);
    inline void set(int index, byte value);
  
    // Treat contents as an int array.
    inline int get_int(int index);
  
    static int SizeFor(int length) {
      return OBJECT_POINTER_ALIGN(kHeaderSize + length);
    }
    // We use byte arrays for free blocks in the heap.  Given a desired size in
    // bytes that is a multiple of the word size and big enough to hold a byte
    // array, this function returns the number of elements a byte array should
    // have.
    static int LengthFor(int size_in_bytes) {
      DCHECK(IsAligned(size_in_bytes, kPointerSize));
      DCHECK(size_in_bytes >= kHeaderSize);
      return size_in_bytes - kHeaderSize;
    }
  
    // Returns data start address.
    inline Address GetDataStartAddress();
  
    // Returns a pointer to the ByteArray object for a given data start address.
    static inline ByteArray* FromDataStartAddress(Address address);
  
    DECLARE_CAST(ByteArray)
  
    // Dispatched behavior.
    inline int ByteArraySize() {
      return SizeFor(this->length());
    }
    DECLARE_PRINTER(ByteArray)
    DECLARE_VERIFIER(ByteArray)
  
    // Layout description.
    static const int kAlignedSize = OBJECT_POINTER_ALIGN(kHeaderSize);
  
    // Maximal memory consumption for a single ByteArray.
    static const int kMaxSize = 512 * MB;
    // Maximal length of a single ByteArray.
    static const int kMaxLength = kMaxSize - kHeaderSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(ByteArray);
  };
  
  
  // FreeSpace represents fixed sized areas of the heap that are not currently in
  // use.  Used by the heap and GC.
  class FreeSpace: public HeapObject {
   public:
    // [size]: size of the free space including the header.
    inline int size() const;
    inline void set_size(int value);
  
    inline int nobarrier_size() const;
    inline void nobarrier_set_size(int value);
  
    inline int Size() { return size(); }
  
    DECLARE_CAST(FreeSpace)
  
    // Dispatched behavior.
    DECLARE_PRINTER(FreeSpace)
    DECLARE_VERIFIER(FreeSpace)
  
    // Layout description.
    // Size is smi tagged when it is stored.
    static const int kSizeOffset = HeapObject::kHeaderSize;
    static const int kHeaderSize = kSizeOffset + kPointerSize;
  
    static const int kAlignedSize = OBJECT_POINTER_ALIGN(kHeaderSize);
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(FreeSpace);
  };
  
  
  // V has parameters (Type, type, TYPE, C type, element_size)
  #define BUILTIN_TYPED_ARRAY(V) \
    V(Uint8, uint8, UINT8, uint8_t, 1)                                           \
    V(Int8, int8, INT8, int8_t, 1)                                               \
    V(Uint16, uint16, UINT16, uint16_t, 2)                                       \
    V(Int16, int16, INT16, int16_t, 2)                                           \
    V(Uint32, uint32, UINT32, uint32_t, 4)                                       \
    V(Int32, int32, INT32, int32_t, 4)                                           \
    V(Float32, float32, FLOAT32, float, 4)                                       \
    V(Float64, float64, FLOAT64, double, 8)                                      \
    V(Uint8Clamped, uint8_clamped, UINT8_CLAMPED, uint8_t, 1)
  
  
  #define SIMD128_TYPED_ARRAY(V) \
    V(Float32x4, float32x4, FLOAT32x4, v8::internal::float32x4_value_t, 16)      \
    V(Float64x2, float64x2, FLOAT64x2, v8::internal::float64x2_value_t, 16)      \
    V(Int32x4, int32x4, INT32x4, v8::internal::int32x4_value_t, 16)
  
  
  #define TYPED_ARRAYS(V) \
    BUILTIN_TYPED_ARRAY(V) \
    SIMD128_TYPED_ARRAY(V)
  
  
  // An ExternalArray represents a fixed-size array of primitive values
  // which live outside the JavaScript heap. Its subclasses are used to
  // implement the CanvasArray types being defined in the WebGL
  // specification. As of this writing the first public draft is not yet
  // available, but Khronos members can access the draft at:
  //   https://cvs.khronos.org/svn/repos/3dweb/trunk/doc/spec/WebGL-spec.html
  //
  // The semantics of these arrays differ from CanvasPixelArray.
  // Out-of-range values passed to the setter are converted via a C
  // cast, not clamping. Out-of-range indices cause exceptions to be
  // raised rather than being silently ignored.
  class ExternalArray: public FixedArrayBase {
   public:
    inline bool is_the_hole(int index) { return false; }
  
    // [external_pointer]: The pointer to the external memory area backing this
    // external array.
    DECL_ACCESSORS(external_pointer, void)  // Pointer to the data store.
  
    DECLARE_CAST(ExternalArray)
  
    // Maximal acceptable length for an external array.
    static const int kMaxLength = 0x3fffffff;
  
    // ExternalArray headers are not quadword aligned.
    static const int kExternalPointerOffset =
        POINTER_SIZE_ALIGN(FixedArrayBase::kLengthOffset + kPointerSize);
    static const int kHeaderSize = kExternalPointerOffset + kPointerSize;
    static const int kAlignedSize = OBJECT_POINTER_ALIGN(kHeaderSize);
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalArray);
  };
  
  
  // A ExternalUint8ClampedArray represents a fixed-size byte array with special
  // semantics used for implementing the CanvasPixelArray object. Please see the
  // specification at:
  
  // http://www.whatwg.org/specs/web-apps/current-work/
  //                      multipage/the-canvas-element.html#canvaspixelarray
  // In particular, write access clamps the value written to 0 or 255 if the
  // value written is outside this range.
  class ExternalUint8ClampedArray: public ExternalArray {
   public:
    inline uint8_t* external_uint8_clamped_pointer();
  
    // Setter and getter.
    inline uint8_t get_scalar(int index);
    static inline Handle<Object> get(Handle<ExternalUint8ClampedArray> array,
                                     int index);
    inline void set(int index, uint8_t value);
  
    // This accessor applies the correct conversion from Smi, HeapNumber
    // and undefined and clamps the converted value between 0 and 255.
    static Handle<Object> SetValue(Handle<ExternalUint8ClampedArray> array,
                                   uint32_t index,
                                   Handle<Object> value);
  
    DECLARE_CAST(ExternalUint8ClampedArray)
  
    // Dispatched behavior.
    DECLARE_PRINTER(ExternalUint8ClampedArray)
    DECLARE_VERIFIER(ExternalUint8ClampedArray)
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalUint8ClampedArray);
  };
  
  
  class ExternalInt8Array: public ExternalArray {
   public:
    // Setter and getter.
    inline int8_t get_scalar(int index);
    static inline Handle<Object> get(Handle<ExternalInt8Array> array, int index);
    inline void set(int index, int8_t value);
  
    // This accessor applies the correct conversion from Smi, HeapNumber
    // and undefined.
    static Handle<Object> SetValue(Handle<ExternalInt8Array> array,
                                   uint32_t index,
                                   Handle<Object> value);
  
    DECLARE_CAST(ExternalInt8Array)
  
    // Dispatched behavior.
    DECLARE_PRINTER(ExternalInt8Array)
    DECLARE_VERIFIER(ExternalInt8Array)
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalInt8Array);
  };
  
  
  class ExternalUint8Array: public ExternalArray {
   public:
    // Setter and getter.
    inline uint8_t get_scalar(int index);
    static inline Handle<Object> get(Handle<ExternalUint8Array> array, int index);
    inline void set(int index, uint8_t value);
  
    // This accessor applies the correct conversion from Smi, HeapNumber
    // and undefined.
    static Handle<Object> SetValue(Handle<ExternalUint8Array> array,
                                   uint32_t index,
                                   Handle<Object> value);
  
    DECLARE_CAST(ExternalUint8Array)
  
    // Dispatched behavior.
    DECLARE_PRINTER(ExternalUint8Array)
    DECLARE_VERIFIER(ExternalUint8Array)
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalUint8Array);
  };
  
  
  class ExternalInt16Array: public ExternalArray {
   public:
    // Setter and getter.
    inline int16_t get_scalar(int index);
    static inline Handle<Object> get(Handle<ExternalInt16Array> array, int index);
    inline void set(int index, int16_t value);
  
    // This accessor applies the correct conversion from Smi, HeapNumber
    // and undefined.
    static Handle<Object> SetValue(Handle<ExternalInt16Array> array,
                                   uint32_t index,
                                   Handle<Object> value);
  
    DECLARE_CAST(ExternalInt16Array)
  
    // Dispatched behavior.
    DECLARE_PRINTER(ExternalInt16Array)
    DECLARE_VERIFIER(ExternalInt16Array)
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalInt16Array);
  };
  
  
  class ExternalUint16Array: public ExternalArray {
   public:
    // Setter and getter.
    inline uint16_t get_scalar(int index);
    static inline Handle<Object> get(Handle<ExternalUint16Array> array,
                                     int index);
    inline void set(int index, uint16_t value);
  
    // This accessor applies the correct conversion from Smi, HeapNumber
    // and undefined.
    static Handle<Object> SetValue(Handle<ExternalUint16Array> array,
                                   uint32_t index,
                                   Handle<Object> value);
  
    DECLARE_CAST(ExternalUint16Array)
  
    // Dispatched behavior.
    DECLARE_PRINTER(ExternalUint16Array)
    DECLARE_VERIFIER(ExternalUint16Array)
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalUint16Array);
  };
  
  
  class ExternalInt32Array: public ExternalArray {
   public:
    // Setter and getter.
    inline int32_t get_scalar(int index);
    static inline Handle<Object> get(Handle<ExternalInt32Array> array, int index);
    inline void set(int index, int32_t value);
  
    // This accessor applies the correct conversion from Smi, HeapNumber
    // and undefined.
    static Handle<Object> SetValue(Handle<ExternalInt32Array> array,
                                   uint32_t index,
                                   Handle<Object> value);
  
    DECLARE_CAST(ExternalInt32Array)
  
    // Dispatched behavior.
    DECLARE_PRINTER(ExternalInt32Array)
    DECLARE_VERIFIER(ExternalInt32Array)
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalInt32Array);
  };
  
  
  class ExternalUint32Array: public ExternalArray {
   public:
    // Setter and getter.
    inline uint32_t get_scalar(int index);
    static inline Handle<Object> get(Handle<ExternalUint32Array> array,
                                     int index);
    inline void set(int index, uint32_t value);
  
    // This accessor applies the correct conversion from Smi, HeapNumber
    // and undefined.
    static Handle<Object> SetValue(Handle<ExternalUint32Array> array,
                                   uint32_t index,
                                   Handle<Object> value);
  
    DECLARE_CAST(ExternalUint32Array)
  
    // Dispatched behavior.
    DECLARE_PRINTER(ExternalUint32Array)
    DECLARE_VERIFIER(ExternalUint32Array)
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalUint32Array);
  };
  
  
  class ExternalFloat32Array: public ExternalArray {
   public:
    // Setter and getter.
    inline float get_scalar(int index);
    static inline Handle<Object> get(Handle<ExternalFloat32Array> array,
                                     int index);
    inline void set(int index, float value);
  
    // This accessor applies the correct conversion from Smi, HeapNumber
    // and undefined.
    static Handle<Object> SetValue(Handle<ExternalFloat32Array> array,
                                   uint32_t index,
                                   Handle<Object> value);
  
    DECLARE_CAST(ExternalFloat32Array)
  
    // Dispatched behavior.
    DECLARE_PRINTER(ExternalFloat32Array)
    DECLARE_VERIFIER(ExternalFloat32Array)
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalFloat32Array);
  };
  
  
  class ExternalFloat32x4Array: public ExternalArray {
   public:
    // Setter and getter.
    inline float32x4_value_t get_scalar(int index);
    static inline Handle<Object> get(Handle<ExternalFloat32x4Array> array,
                                     int index);
    inline void set(int index, const float32x4_value_t& value);
  
    // This accessor applies the correct conversion from Smi, HeapNumber
    // and undefined.
    static Handle<Object> SetValue(Handle<ExternalFloat32x4Array> array,
                                   uint32_t index,
                                   Handle<Object> value);
  
    // Casting.
    DECLARE_CAST(ExternalFloat32x4Array)
  
    // Dispatched behavior.
    DECLARE_PRINTER(ExternalFloat32x4Array)
    DECLARE_VERIFIER(ExternalFloat32x4Array)
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalFloat32x4Array);
  };
  
  
  class ExternalFloat64x2Array: public ExternalArray {
   public:
    // Setter and getter.
    inline float64x2_value_t get_scalar(int index);
    static inline Handle<Object> get(Handle<ExternalFloat64x2Array> array,
                                     int index);
    inline void set(int index, const float64x2_value_t& value);
  
    // This accessor applies the correct conversion from Smi, HeapNumber
    // and undefined.
    static Handle<Object> SetValue(Handle<ExternalFloat64x2Array> array,
                                   uint32_t index,
                                   Handle<Object> value);
  
    // Casting.
    DECLARE_CAST(ExternalFloat64x2Array)
  
    // Dispatched behavior.
    DECLARE_PRINTER(ExternalFloat64x2Array)
    DECLARE_VERIFIER(ExternalFloat64x2Array)
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalFloat64x2Array);
  };
  
  
  class ExternalInt32x4Array: public ExternalArray {
   public:
    // Setter and getter.
    inline int32x4_value_t get_scalar(int index);
    static inline Handle<Object> get(Handle<ExternalInt32x4Array> array,
                                     int index);
    inline void set(int index, const int32x4_value_t& value);
  
    // This accessor applies the correct conversion from Smi, HeapNumber
    // and undefined.
    static Handle<Object> SetValue(Handle<ExternalInt32x4Array> array,
                                   uint32_t index,
                                   Handle<Object> value);
  
    // Casting.
    DECLARE_CAST(ExternalInt32x4Array)
  
    // Dispatched behavior.
    DECLARE_PRINTER(ExternalInt32x4Array)
    DECLARE_VERIFIER(ExternalInt32x4Array)
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalInt32x4Array);
  };
  
  
  class ExternalFloat64Array: public ExternalArray {
   public:
    // Setter and getter.
    inline double get_scalar(int index);
    static inline Handle<Object> get(Handle<ExternalFloat64Array> array,
                                     int index);
    inline void set(int index, double value);
  
    // This accessor applies the correct conversion from Smi, HeapNumber
    // and undefined.
    static Handle<Object> SetValue(Handle<ExternalFloat64Array> array,
                                   uint32_t index,
                                   Handle<Object> value);
  
    DECLARE_CAST(ExternalFloat64Array)
  
    // Dispatched behavior.
    DECLARE_PRINTER(ExternalFloat64Array)
    DECLARE_VERIFIER(ExternalFloat64Array)
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalFloat64Array);
  };
  
  
  class FixedTypedArrayBase: public FixedArrayBase {
   public:
    DECLARE_CAST(FixedTypedArrayBase)
  
    static const int kDataOffset = kHeaderSize;
  
    inline int size();
  
    inline int TypedArraySize(InstanceType type);
  
    // Use with care: returns raw pointer into heap.
    inline void* DataPtr();
  
    inline int DataSize();
  
   private:
    inline int DataSize(InstanceType type);
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(FixedTypedArrayBase);
  };
  
  
  template <class Traits>
  class FixedTypedArray: public FixedTypedArrayBase {
   public:
    typedef typename Traits::ElementType ElementType;
    static const InstanceType kInstanceType = Traits::kInstanceType;
  
    DECLARE_CAST(FixedTypedArray<Traits>)
  
    static inline int ElementOffset(int index) {
      return kDataOffset + index * sizeof(ElementType);
    }
  
    static inline int SizeFor(int length) {
      return ElementOffset(length);
    }
  
    inline ElementType get_scalar(int index);
    static inline Handle<Object> get(Handle<FixedTypedArray> array, int index);
    inline void set(int index, ElementType value);
  
    static inline ElementType from_int(int value);
    static inline ElementType from_double(double value);
  
    // This accessor applies the correct conversion from Smi, HeapNumber
    // and undefined.
    static Handle<Object> SetValue(Handle<FixedTypedArray<Traits> > array,
                                   uint32_t index,
                                   Handle<Object> value);
  
    DECLARE_PRINTER(FixedTypedArray)
    DECLARE_VERIFIER(FixedTypedArray)
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(FixedTypedArray);
  };
  
  #define FIXED_TYPED_ARRAY_TRAITS(Type, type, TYPE, elementType, size)         \
    class Type##ArrayTraits {                                                   \
     public:   /* NOLINT */                                                     \
      typedef elementType ElementType;                                          \
      static const InstanceType kInstanceType = FIXED_##TYPE##_ARRAY_TYPE;      \
      static const char* Designator() { return #type " array"; }                \
      static inline Handle<Object> ToHandle(Isolate* isolate,                   \
                                            elementType scalar);                \
      static inline elementType defaultValue();                                 \
    };                                                                          \
                                                                                \
    typedef FixedTypedArray<Type##ArrayTraits> Fixed##Type##Array;
  
  TYPED_ARRAYS(FIXED_TYPED_ARRAY_TRAITS)
  
  #undef FIXED_TYPED_ARRAY_TRAITS
  
  // DeoptimizationInputData is a fixed array used to hold the deoptimization
  // data for code generated by the Hydrogen/Lithium compiler.  It also
  // contains information about functions that were inlined.  If N different
  // functions were inlined then first N elements of the literal array will
  // contain these functions.
  //
  // It can be empty.
  class DeoptimizationInputData: public FixedArray {
   public:
    // Layout description.  Indices in the array.
    static const int kTranslationByteArrayIndex = 0;
    static const int kInlinedFunctionCountIndex = 1;
    static const int kLiteralArrayIndex = 2;
    static const int kOsrAstIdIndex = 3;
    static const int kOsrPcOffsetIndex = 4;
    static const int kOptimizationIdIndex = 5;
    static const int kSharedFunctionInfoIndex = 6;
    static const int kFirstDeoptEntryIndex = 7;
  
    // Offsets of deopt entry elements relative to the start of the entry.
    static const int kAstIdRawOffset = 0;
    static const int kTranslationIndexOffset = 1;
    static const int kArgumentsStackHeightOffset = 2;
    static const int kPcOffset = 3;
    static const int kDeoptEntrySize = 4;
  
    // Simple element accessors.
  #define DEFINE_ELEMENT_ACCESSORS(name, type)      \
    type* name() {                                  \
      return type::cast(get(k##name##Index));       \
    }                                               \
    void Set##name(type* value) {                   \
      set(k##name##Index, value);                   \
    }
  
    DEFINE_ELEMENT_ACCESSORS(TranslationByteArray, ByteArray)
    DEFINE_ELEMENT_ACCESSORS(InlinedFunctionCount, Smi)
    DEFINE_ELEMENT_ACCESSORS(LiteralArray, FixedArray)
    DEFINE_ELEMENT_ACCESSORS(OsrAstId, Smi)
    DEFINE_ELEMENT_ACCESSORS(OsrPcOffset, Smi)
    DEFINE_ELEMENT_ACCESSORS(OptimizationId, Smi)
    DEFINE_ELEMENT_ACCESSORS(SharedFunctionInfo, Object)
  
  #undef DEFINE_ELEMENT_ACCESSORS
  
    // Accessors for elements of the ith deoptimization entry.
  #define DEFINE_ENTRY_ACCESSORS(name, type)                      \
    type* name(int i) {                                           \
      return type::cast(get(IndexForEntry(i) + k##name##Offset)); \
    }                                                             \
    void Set##name(int i, type* value) {                          \
      set(IndexForEntry(i) + k##name##Offset, value);             \
    }
  
    DEFINE_ENTRY_ACCESSORS(AstIdRaw, Smi)
    DEFINE_ENTRY_ACCESSORS(TranslationIndex, Smi)
    DEFINE_ENTRY_ACCESSORS(ArgumentsStackHeight, Smi)
    DEFINE_ENTRY_ACCESSORS(Pc, Smi)
  
  #undef DEFINE_DEOPT_ENTRY_ACCESSORS
  
    BailoutId AstId(int i) {
      return BailoutId(AstIdRaw(i)->value());
    }
  
    void SetAstId(int i, BailoutId value) {
      SetAstIdRaw(i, Smi::FromInt(value.ToInt()));
    }
  
    int DeoptCount() {
      return (length() - kFirstDeoptEntryIndex) / kDeoptEntrySize;
    }
  
    // Allocates a DeoptimizationInputData.
    static Handle<DeoptimizationInputData> New(Isolate* isolate,
                                               int deopt_entry_count,
                                               PretenureFlag pretenure);
  
    DECLARE_CAST(DeoptimizationInputData)
  
  #ifdef ENABLE_DISASSEMBLER
    void DeoptimizationInputDataPrint(OStream& os);  // NOLINT
  #endif
  
   private:
    static int IndexForEntry(int i) {
      return kFirstDeoptEntryIndex + (i * kDeoptEntrySize);
    }
  
  
    static int LengthFor(int entry_count) { return IndexForEntry(entry_count); }
  };
  
  
  // DeoptimizationOutputData is a fixed array used to hold the deoptimization
  // data for code generated by the full compiler.
  // The format of the these objects is
  //   [i * 2]: Ast ID for ith deoptimization.
  //   [i * 2 + 1]: PC and state of ith deoptimization
  class DeoptimizationOutputData: public FixedArray {
   public:
    int DeoptPoints() { return length() / 2; }
  
    BailoutId AstId(int index) {
      return BailoutId(Smi::cast(get(index * 2))->value());
    }
  
    void SetAstId(int index, BailoutId id) {
      set(index * 2, Smi::FromInt(id.ToInt()));
    }
  
    Smi* PcAndState(int index) { return Smi::cast(get(1 + index * 2)); }
    void SetPcAndState(int index, Smi* offset) { set(1 + index * 2, offset); }
  
    static int LengthOfFixedArray(int deopt_points) {
      return deopt_points * 2;
    }
  
    // Allocates a DeoptimizationOutputData.
    static Handle<DeoptimizationOutputData> New(Isolate* isolate,
                                                int number_of_deopt_points,
                                                PretenureFlag pretenure);
  
    DECLARE_CAST(DeoptimizationOutputData)
  
  #if defined(OBJECT_PRINT) || defined(ENABLE_DISASSEMBLER)
    void DeoptimizationOutputDataPrint(OStream& os);  // NOLINT
  #endif
  };
  
  
  // Forward declaration.
  class Cell;
  class PropertyCell;
  class SafepointEntry;
  class TypeFeedbackInfo;
  
  // Code describes objects with on-the-fly generated machine code.
  class Code: public HeapObject {
   public:
    // Opaque data type for encapsulating code flags like kind, inline
    // cache state, and arguments count.
    typedef uint32_t Flags;
  
  #define NON_IC_KIND_LIST(V) \
    V(FUNCTION)               \
    V(OPTIMIZED_FUNCTION)     \
    V(STUB)                   \
    V(HANDLER)                \
    V(BUILTIN)                \
    V(REGEXP)
  
  #define IC_KIND_LIST(V) \
    V(LOAD_IC)            \
    V(KEYED_LOAD_IC)      \
    V(CALL_IC)            \
    V(STORE_IC)           \
    V(KEYED_STORE_IC)     \
    V(BINARY_OP_IC)       \
    V(COMPARE_IC)         \
    V(COMPARE_NIL_IC)     \
    V(TO_BOOLEAN_IC)
  
  #define CODE_KIND_LIST(V) \
    NON_IC_KIND_LIST(V)     \
    IC_KIND_LIST(V)
  
    enum Kind {
  #define DEFINE_CODE_KIND_ENUM(name) name,
      CODE_KIND_LIST(DEFINE_CODE_KIND_ENUM)
  #undef DEFINE_CODE_KIND_ENUM
      NUMBER_OF_KINDS
    };
  
    // No more than 16 kinds. The value is currently encoded in four bits in
    // Flags.
    STATIC_ASSERT(NUMBER_OF_KINDS <= 16);
  
    static const char* Kind2String(Kind kind);
  
    // Types of stubs.
    enum StubType {
      NORMAL,
      FAST
    };
  
    static const int kPrologueOffsetNotSet = -1;
  
  #ifdef ENABLE_DISASSEMBLER
    // Printing
    static const char* ICState2String(InlineCacheState state);
    static const char* StubType2String(StubType type);
    static void PrintExtraICState(OStream& os,  // NOLINT
                                  Kind kind, ExtraICState extra);
    void Disassemble(const char* name, OStream& os);  // NOLINT
  #endif  // ENABLE_DISASSEMBLER
  
    // [instruction_size]: Size of the native instructions
    inline int instruction_size() const;
    inline void set_instruction_size(int value);
  
    // [relocation_info]: Code relocation information
    DECL_ACCESSORS(relocation_info, ByteArray)
    void InvalidateRelocation();
    void InvalidateEmbeddedObjects();
  
    // [handler_table]: Fixed array containing offsets of exception handlers.
    DECL_ACCESSORS(handler_table, FixedArray)
  
    // [deoptimization_data]: Array containing data for deopt.
    DECL_ACCESSORS(deoptimization_data, FixedArray)
  
    // [raw_type_feedback_info]: This field stores various things, depending on
    // the kind of the code object.
    //   FUNCTION           => type feedback information.
    //   STUB and ICs       => major/minor key as Smi.
    DECL_ACCESSORS(raw_type_feedback_info, Object)
    inline Object* type_feedback_info();
    inline void set_type_feedback_info(
        Object* value, WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
    inline uint32_t stub_key();
    inline void set_stub_key(uint32_t key);
  
    // [next_code_link]: Link for lists of optimized or deoptimized code.
    // Note that storage for this field is overlapped with typefeedback_info.
    DECL_ACCESSORS(next_code_link, Object)
  
    // [gc_metadata]: Field used to hold GC related metadata. The contents of this
    // field does not have to be traced during garbage collection since
    // it is only used by the garbage collector itself.
    DECL_ACCESSORS(gc_metadata, Object)
  
    // [ic_age]: Inline caching age: the value of the Heap::global_ic_age
    // at the moment when this object was created.
    inline void set_ic_age(int count);
    inline int ic_age() const;
  
    // [prologue_offset]: Offset of the function prologue, used for aging
    // FUNCTIONs and OPTIMIZED_FUNCTIONs.
    inline int prologue_offset() const;
    inline void set_prologue_offset(int offset);
  
    // Unchecked accessors to be used during GC.
    inline ByteArray* unchecked_relocation_info();
  
    inline int relocation_size();
  
    // [flags]: Various code flags.
    inline Flags flags();
    inline void set_flags(Flags flags);
  
    // [flags]: Access to specific code flags.
    inline Kind kind();
    inline InlineCacheState ic_state();  // Only valid for IC stubs.
    inline ExtraICState extra_ic_state();  // Only valid for IC stubs.
  
    inline StubType type();  // Only valid for monomorphic IC stubs.
  
    // Testers for IC stub kinds.
    inline bool is_inline_cache_stub();
    inline bool is_debug_stub();
    inline bool is_handler() { return kind() == HANDLER; }
    inline bool is_load_stub() { return kind() == LOAD_IC; }
    inline bool is_keyed_load_stub() { return kind() == KEYED_LOAD_IC; }
    inline bool is_store_stub() { return kind() == STORE_IC; }
    inline bool is_keyed_store_stub() { return kind() == KEYED_STORE_IC; }
    inline bool is_call_stub() { return kind() == CALL_IC; }
    inline bool is_binary_op_stub() { return kind() == BINARY_OP_IC; }
    inline bool is_compare_ic_stub() { return kind() == COMPARE_IC; }
    inline bool is_compare_nil_ic_stub() { return kind() == COMPARE_NIL_IC; }
    inline bool is_to_boolean_ic_stub() { return kind() == TO_BOOLEAN_IC; }
    inline bool is_keyed_stub();
    inline bool is_optimized_code() { return kind() == OPTIMIZED_FUNCTION; }
    inline bool is_weak_stub();
    inline void mark_as_weak_stub();
    inline bool is_invalidated_weak_stub();
    inline void mark_as_invalidated_weak_stub();
  
    inline bool CanBeWeakStub() {
      Kind k = kind();
      return (k == LOAD_IC || k == STORE_IC || k == KEYED_LOAD_IC ||
              k == KEYED_STORE_IC || k == COMPARE_NIL_IC) &&
             ic_state() == MONOMORPHIC;
    }
  
    inline bool IsCodeStubOrIC();
  
    inline void set_raw_kind_specific_flags1(int value);
    inline void set_raw_kind_specific_flags2(int value);
  
    // [is_crankshafted]: For kind STUB or ICs, tells whether or not a code
    // object was generated by either the hydrogen or the TurboFan optimizing
    // compiler (but it may not be an optimized function).
    inline bool is_crankshafted();
    inline bool is_hydrogen_stub();  // Crankshafted, but not a function.
    inline void set_is_crankshafted(bool value);
  
    // [is_turbofanned]: For kind STUB or OPTIMIZED_FUNCTION, tells whether the
    // code object was generated by the TurboFan optimizing compiler.
    inline bool is_turbofanned();
    inline void set_is_turbofanned(bool value);
  
    // [optimizable]: For FUNCTION kind, tells if it is optimizable.
    inline bool optimizable();
    inline void set_optimizable(bool value);
  
    // [has_deoptimization_support]: For FUNCTION kind, tells if it has
    // deoptimization support.
    inline bool has_deoptimization_support();
    inline void set_has_deoptimization_support(bool value);
  
    // [has_debug_break_slots]: For FUNCTION kind, tells if it has
    // been compiled with debug break slots.
    inline bool has_debug_break_slots();
    inline void set_has_debug_break_slots(bool value);
  
    // [compiled_with_optimizing]: For FUNCTION kind, tells if it has
    // been compiled with IsOptimizing set to true.
    inline bool is_compiled_optimizable();
    inline void set_compiled_optimizable(bool value);
  
    // [allow_osr_at_loop_nesting_level]: For FUNCTION kind, tells for
    // how long the function has been marked for OSR and therefore which
    // level of loop nesting we are willing to do on-stack replacement
    // for.
    inline void set_allow_osr_at_loop_nesting_level(int level);
    inline int allow_osr_at_loop_nesting_level();
  
    // [profiler_ticks]: For FUNCTION kind, tells for how many profiler ticks
    // the code object was seen on the stack with no IC patching going on.
    inline int profiler_ticks();
    inline void set_profiler_ticks(int ticks);
  
    // [builtin_index]: For BUILTIN kind, tells which builtin index it has.
    inline int builtin_index();
    inline void set_builtin_index(int id);
  
    // [stack_slots]: For kind OPTIMIZED_FUNCTION, the number of stack slots
    // reserved in the code prologue.
    inline unsigned stack_slots();
    inline void set_stack_slots(unsigned slots);
  
    // [safepoint_table_start]: For kind OPTIMIZED_FUNCTION, the offset in
    // the instruction stream where the safepoint table starts.
    inline unsigned safepoint_table_offset();
    inline void set_safepoint_table_offset(unsigned offset);
  
    // [back_edge_table_start]: For kind FUNCTION, the offset in the
    // instruction stream where the back edge table starts.
    inline unsigned back_edge_table_offset();
    inline void set_back_edge_table_offset(unsigned offset);
  
    inline bool back_edges_patched_for_osr();
  
    // [to_boolean_foo]: For kind TO_BOOLEAN_IC tells what state the stub is in.
    inline byte to_boolean_state();
  
    // [has_function_cache]: For kind STUB tells whether there is a function
    // cache is passed to the stub.
    inline bool has_function_cache();
    inline void set_has_function_cache(bool flag);
  
  
    // [marked_for_deoptimization]: For kind OPTIMIZED_FUNCTION tells whether
    // the code is going to be deoptimized because of dead embedded maps.
    inline bool marked_for_deoptimization();
    inline void set_marked_for_deoptimization(bool flag);
  
    // [constant_pool]: The constant pool for this function.
    inline ConstantPoolArray* constant_pool();
    inline void set_constant_pool(Object* constant_pool);
  
    // Get the safepoint entry for the given pc.
    SafepointEntry GetSafepointEntry(Address pc);
  
    // Find an object in a stub with a specified map
    Object* FindNthObject(int n, Map* match_map);
  
    // Find the first allocation site in an IC stub.
    AllocationSite* FindFirstAllocationSite();
  
    // Find the first map in an IC stub.
    Map* FindFirstMap();
    void FindAllMaps(MapHandleList* maps);
  
    // Find the first handler in an IC stub.
    Code* FindFirstHandler();
  
    // Find |length| handlers and put them into |code_list|. Returns false if not
    // enough handlers can be found.
    bool FindHandlers(CodeHandleList* code_list, int length = -1);
  
    // Find the handler for |map|.
    MaybeHandle<Code> FindHandlerForMap(Map* map);
  
    // Find the first name in an IC stub.
    Name* FindFirstName();
  
    class FindAndReplacePattern;
    // For each (map-to-find, object-to-replace) pair in the pattern, this
    // function replaces the corresponding placeholder in the code with the
    // object-to-replace. The function assumes that pairs in the pattern come in
    // the same order as the placeholders in the code.
    void FindAndReplace(const FindAndReplacePattern& pattern);
  
    // The entire code object including its header is copied verbatim to the
    // snapshot so that it can be written in one, fast, memcpy during
    // deserialization. The deserializer will overwrite some pointers, rather
    // like a runtime linker, but the random allocation addresses used in the
    // mksnapshot process would still be present in the unlinked snapshot data,
    // which would make snapshot production non-reproducible. This method wipes
    // out the to-be-overwritten header data for reproducible snapshots.
    inline void WipeOutHeader();
  
    // Flags operations.
    static inline Flags ComputeFlags(
        Kind kind, InlineCacheState ic_state = UNINITIALIZED,
        ExtraICState extra_ic_state = kNoExtraICState, StubType type = NORMAL,
        CacheHolderFlag holder = kCacheOnReceiver);
  
    static inline Flags ComputeMonomorphicFlags(
        Kind kind, ExtraICState extra_ic_state = kNoExtraICState,
        CacheHolderFlag holder = kCacheOnReceiver, StubType type = NORMAL);
  
    static inline Flags ComputeHandlerFlags(
        Kind handler_kind, StubType type = NORMAL,
        CacheHolderFlag holder = kCacheOnReceiver);
  
    static inline InlineCacheState ExtractICStateFromFlags(Flags flags);
    static inline StubType ExtractTypeFromFlags(Flags flags);
    static inline CacheHolderFlag ExtractCacheHolderFromFlags(Flags flags);
    static inline Kind ExtractKindFromFlags(Flags flags);
    static inline ExtraICState ExtractExtraICStateFromFlags(Flags flags);
  
    static inline Flags RemoveTypeFromFlags(Flags flags);
    static inline Flags RemoveTypeAndHolderFromFlags(Flags flags);
  
    // Convert a target address into a code object.
    static inline Code* GetCodeFromTargetAddress(Address address);
  
    // Convert an entry address into an object.
    static inline Object* GetObjectFromEntryAddress(Address location_of_address);
  
    // Returns the address of the first instruction.
    inline byte* instruction_start();
  
    // Returns the address right after the last instruction.
    inline byte* instruction_end();
  
    // Returns the size of the instructions, padding, and relocation information.
    inline int body_size();
  
    // Returns the address of the first relocation info (read backwards!).
    inline byte* relocation_start();
  
    // Code entry point.
    inline byte* entry();
  
    // Returns true if pc is inside this object's instructions.
    inline bool contains(byte* pc);
  
    // Relocate the code by delta bytes. Called to signal that this code
    // object has been moved by delta bytes.
    void Relocate(intptr_t delta);
  
    // Migrate code described by desc.
    void CopyFrom(const CodeDesc& desc);
  
    // Returns the object size for a given body (used for allocation).
    static int SizeFor(int body_size) {
      DCHECK_SIZE_TAG_ALIGNED(body_size);
      return RoundUp(kHeaderSize + body_size, kCodeAlignment);
    }
  
    // Calculate the size of the code object to report for log events. This takes
    // the layout of the code object into account.
    int ExecutableSize() {
      // Check that the assumptions about the layout of the code object holds.
      DCHECK_EQ(static_cast<int>(instruction_start() - address()),
                Code::kHeaderSize);
      return instruction_size() + Code::kHeaderSize;
    }
  
    // Locating source position.
    int SourcePosition(Address pc);
    int SourceStatementPosition(Address pc);
  
    DECLARE_CAST(Code)
  
    // Dispatched behavior.
    int CodeSize() { return SizeFor(body_size()); }
    inline void CodeIterateBody(ObjectVisitor* v);
  
    template<typename StaticVisitor>
    inline void CodeIterateBody(Heap* heap);
  
    DECLARE_PRINTER(Code)
    DECLARE_VERIFIER(Code)
  
    void ClearInlineCaches();
    void ClearInlineCaches(Kind kind);
  
    BailoutId TranslatePcOffsetToAstId(uint32_t pc_offset);
    uint32_t TranslateAstIdToPcOffset(BailoutId ast_id);
  
  #define DECLARE_CODE_AGE_ENUM(X) k##X##CodeAge,
    enum Age {
      kNotExecutedCodeAge = -2,
      kExecutedOnceCodeAge = -1,
      kNoAgeCodeAge = 0,
      CODE_AGE_LIST(DECLARE_CODE_AGE_ENUM)
      kAfterLastCodeAge,
      kFirstCodeAge = kNotExecutedCodeAge,
      kLastCodeAge = kAfterLastCodeAge - 1,
      kCodeAgeCount = kAfterLastCodeAge - kNotExecutedCodeAge - 1,
      kIsOldCodeAge = kSexagenarianCodeAge,
      kPreAgedCodeAge = kIsOldCodeAge - 1
    };
  #undef DECLARE_CODE_AGE_ENUM
  
    // Code aging.  Indicates how many full GCs this code has survived without
    // being entered through the prologue.  Used to determine when it is
    // relatively safe to flush this code object and replace it with the lazy
    // compilation stub.
    static void MakeCodeAgeSequenceYoung(byte* sequence, Isolate* isolate);
    static void MarkCodeAsExecuted(byte* sequence, Isolate* isolate);
    void MakeOlder(MarkingParity);
    static bool IsYoungSequence(Isolate* isolate, byte* sequence);
    bool IsOld();
    Age GetAge();
    // Gets the raw code age, including psuedo code-age values such as
    // kNotExecutedCodeAge and kExecutedOnceCodeAge.
    Age GetRawAge();
    static inline Code* GetPreAgedCodeAgeStub(Isolate* isolate) {
      return GetCodeAgeStub(isolate, kNotExecutedCodeAge, NO_MARKING_PARITY);
    }
  
    void PrintDeoptLocation(FILE* out, int bailout_id);
    bool CanDeoptAt(Address pc);
  
  #ifdef VERIFY_HEAP
    void VerifyEmbeddedObjectsDependency();
  #endif
  
    inline bool CanContainWeakObjects() {
      return is_optimized_code() || is_weak_stub();
    }
  
    inline bool IsWeakObject(Object* object) {
      return (is_optimized_code() && !is_turbofanned() &&
              IsWeakObjectInOptimizedCode(object)) ||
             (is_weak_stub() && IsWeakObjectInIC(object));
    }
  
    static inline bool IsWeakObjectInOptimizedCode(Object* object);
    static inline bool IsWeakObjectInIC(Object* object);
  
    // Max loop nesting marker used to postpose OSR. We don't take loop
    // nesting that is deeper than 5 levels into account.
    static const int kMaxLoopNestingMarker = 6;
  
    // Layout description.
    static const int kInstructionSizeOffset = HeapObject::kHeaderSize;
    static const int kRelocationInfoOffset = kInstructionSizeOffset + kIntSize;
    static const int kHandlerTableOffset = kRelocationInfoOffset + kPointerSize;
    static const int kDeoptimizationDataOffset =
        kHandlerTableOffset + kPointerSize;
    // For FUNCTION kind, we store the type feedback info here.
    static const int kTypeFeedbackInfoOffset =
        kDeoptimizationDataOffset + kPointerSize;
    static const int kNextCodeLinkOffset = kTypeFeedbackInfoOffset + kPointerSize;
    static const int kGCMetadataOffset = kNextCodeLinkOffset + kPointerSize;
    static const int kICAgeOffset =
        kGCMetadataOffset + kPointerSize;
    static const int kFlagsOffset = kICAgeOffset + kIntSize;
    static const int kKindSpecificFlags1Offset = kFlagsOffset + kIntSize;
    static const int kKindSpecificFlags2Offset =
        kKindSpecificFlags1Offset + kIntSize;
    // Note: We might be able to squeeze this into the flags above.
    static const int kPrologueOffset = kKindSpecificFlags2Offset + kIntSize;
    static const int kConstantPoolOffset = kPrologueOffset + kPointerSize;
  
    static const int kHeaderPaddingStart = kConstantPoolOffset + kIntSize;
  
    // Add padding to align the instruction start following right after
    // the Code object header.
    static const int kHeaderSize =
        (kHeaderPaddingStart + kCodeAlignmentMask) & ~kCodeAlignmentMask;
  
    // Byte offsets within kKindSpecificFlags1Offset.
    static const int kOptimizableOffset = kKindSpecificFlags1Offset;
  
    static const int kFullCodeFlags = kOptimizableOffset + 1;
    class FullCodeFlagsHasDeoptimizationSupportField:
        public BitField<bool, 0, 1> {};  // NOLINT
    class FullCodeFlagsHasDebugBreakSlotsField: public BitField<bool, 1, 1> {};
    class FullCodeFlagsIsCompiledOptimizable: public BitField<bool, 2, 1> {};
  
    static const int kProfilerTicksOffset = kFullCodeFlags + 1;
  
    // Flags layout.  BitField<type, shift, size>.
    class ICStateField : public BitField<InlineCacheState, 0, 4> {};
    class TypeField : public BitField<StubType, 4, 1> {};
    class CacheHolderField : public BitField<CacheHolderFlag, 5, 2> {};
    class KindField : public BitField<Kind, 7, 4> {};
    class ExtraICStateField: public BitField<ExtraICState, 11,
        PlatformSmiTagging::kSmiValueSize - 11 + 1> {};  // NOLINT
  
    // KindSpecificFlags1 layout (STUB and OPTIMIZED_FUNCTION)
    static const int kStackSlotsFirstBit = 0;
    static const int kStackSlotsBitCount = 24;
    static const int kHasFunctionCacheBit =
        kStackSlotsFirstBit + kStackSlotsBitCount;
    static const int kMarkedForDeoptimizationBit = kHasFunctionCacheBit + 1;
    static const int kWeakStubBit = kMarkedForDeoptimizationBit + 1;
    static const int kInvalidatedWeakStubBit = kWeakStubBit + 1;
    static const int kIsTurbofannedBit = kInvalidatedWeakStubBit + 1;
  
    STATIC_ASSERT(kStackSlotsFirstBit + kStackSlotsBitCount <= 32);
    STATIC_ASSERT(kIsTurbofannedBit + 1 <= 32);
  
    class StackSlotsField: public BitField<int,
        kStackSlotsFirstBit, kStackSlotsBitCount> {};  // NOLINT
    class HasFunctionCacheField : public BitField<bool, kHasFunctionCacheBit, 1> {
    };  // NOLINT
    class MarkedForDeoptimizationField
        : public BitField<bool, kMarkedForDeoptimizationBit, 1> {};   // NOLINT
    class WeakStubField : public BitField<bool, kWeakStubBit, 1> {};  // NOLINT
    class InvalidatedWeakStubField
        : public BitField<bool, kInvalidatedWeakStubBit, 1> {};  // NOLINT
    class IsTurbofannedField : public BitField<bool, kIsTurbofannedBit, 1> {
    };  // NOLINT
  
    // KindSpecificFlags2 layout (ALL)
    static const int kIsCrankshaftedBit = 0;
    class IsCrankshaftedField: public BitField<bool,
        kIsCrankshaftedBit, 1> {};  // NOLINT
  
    // KindSpecificFlags2 layout (STUB and OPTIMIZED_FUNCTION)
    static const int kSafepointTableOffsetFirstBit = kIsCrankshaftedBit + 1;
    static const int kSafepointTableOffsetBitCount = 24;
  
    STATIC_ASSERT(kSafepointTableOffsetFirstBit +
                  kSafepointTableOffsetBitCount <= 32);
    STATIC_ASSERT(1 + kSafepointTableOffsetBitCount <= 32);
  
    class SafepointTableOffsetField: public BitField<int,
        kSafepointTableOffsetFirstBit,
        kSafepointTableOffsetBitCount> {};  // NOLINT
  
    // KindSpecificFlags2 layout (FUNCTION)
    class BackEdgeTableOffsetField: public BitField<int,
        kIsCrankshaftedBit + 1, 27> {};  // NOLINT
    class AllowOSRAtLoopNestingLevelField: public BitField<int,
        kIsCrankshaftedBit + 1 + 27, 4> {};  // NOLINT
    STATIC_ASSERT(AllowOSRAtLoopNestingLevelField::kMax >= kMaxLoopNestingMarker);
  
    static const int kArgumentsBits = 16;
    static const int kMaxArguments = (1 << kArgumentsBits) - 1;
  
    // This constant should be encodable in an ARM instruction.
    static const int kFlagsNotUsedInLookup =
        TypeField::kMask | CacheHolderField::kMask;
  
   private:
    friend class RelocIterator;
    friend class Deoptimizer;  // For FindCodeAgeSequence.
  
    void ClearInlineCaches(Kind* kind);
  
    // Code aging
    byte* FindCodeAgeSequence();
    static void GetCodeAgeAndParity(Code* code, Age* age,
                                    MarkingParity* parity);
    static void GetCodeAgeAndParity(Isolate* isolate, byte* sequence, Age* age,
                                    MarkingParity* parity);
    static Code* GetCodeAgeStub(Isolate* isolate, Age age, MarkingParity parity);
  
    // Code aging -- platform-specific
    static void PatchPlatformCodeAge(Isolate* isolate,
                                     byte* sequence, Age age,
                                     MarkingParity parity);
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(Code);
  };
  
  
  class CompilationInfo;
  
  // This class describes the layout of dependent codes array of a map. The
  // array is partitioned into several groups of dependent codes. Each group
  // contains codes with the same dependency on the map. The array has the
  // following layout for n dependency groups:
  //
  // +----+----+-----+----+---------+----------+-----+---------+-----------+
  // | C1 | C2 | ... | Cn | group 1 |  group 2 | ... | group n | undefined |
  // +----+----+-----+----+---------+----------+-----+---------+-----------+
  //
  // The first n elements are Smis, each of them specifies the number of codes
  // in the corresponding group. The subsequent elements contain grouped code
  // objects. The suffix of the array can be filled with the undefined value if
  // the number of codes is less than the length of the array. The order of the
  // code objects within a group is not preserved.
  //
  // All code indexes used in the class are counted starting from the first
  // code object of the first group. In other words, code index 0 corresponds
  // to array index n = kCodesStartIndex.
  
  class DependentCode: public FixedArray {
   public:
    enum DependencyGroup {
      // Group of IC stubs that weakly embed this map and depend on being
      // invalidated when the map is garbage collected. Dependent IC stubs form
      // a linked list. This group stores only the head of the list. This means
      // that the number_of_entries(kWeakICGroup) is 0 or 1.
      kWeakICGroup,
      // Group of code that weakly embed this map and depend on being
      // deoptimized when the map is garbage collected.
      kWeakCodeGroup,
      // Group of code that embed a transition to this map, and depend on being
      // deoptimized when the transition is replaced by a new version.
      kTransitionGroup,
      // Group of code that omit run-time prototype checks for prototypes
      // described by this map. The group is deoptimized whenever an object
      // described by this map changes shape (and transitions to a new map),
      // possibly invalidating the assumptions embedded in the code.
      kPrototypeCheckGroup,
      // Group of code that depends on elements not being added to objects with
      // this map.
      kElementsCantBeAddedGroup,
      // Group of code that depends on global property values in property cells
      // not being changed.
      kPropertyCellChangedGroup,
      // Group of code that omit run-time type checks for the field(s) introduced
      // by this map.
      kFieldTypeGroup,
      // Group of code that omit run-time type checks for initial maps of
      // constructors.
      kInitialMapChangedGroup,
      // Group of code that depends on tenuring information in AllocationSites
      // not being changed.
      kAllocationSiteTenuringChangedGroup,
      // Group of code that depends on element transition information in
      // AllocationSites not being changed.
      kAllocationSiteTransitionChangedGroup
    };
  
    static const int kGroupCount = kAllocationSiteTransitionChangedGroup + 1;
  
    // Array for holding the index of the first code object of each group.
    // The last element stores the total number of code objects.
    class GroupStartIndexes {
     public:
      explicit GroupStartIndexes(DependentCode* entries);
      void Recompute(DependentCode* entries);
      int at(int i) { return start_indexes_[i]; }
      int number_of_entries() { return start_indexes_[kGroupCount]; }
     private:
      int start_indexes_[kGroupCount + 1];
    };
  
    bool Contains(DependencyGroup group, Code* code);
    static Handle<DependentCode> Insert(Handle<DependentCode> entries,
                                        DependencyGroup group,
                                        Handle<Object> object);
    void UpdateToFinishedCode(DependencyGroup group,
                              CompilationInfo* info,
                              Code* code);
    void RemoveCompilationInfo(DependentCode::DependencyGroup group,
                               CompilationInfo* info);
  
    void DeoptimizeDependentCodeGroup(Isolate* isolate,
                                      DependentCode::DependencyGroup group);
  
    bool MarkCodeForDeoptimization(Isolate* isolate,
                                   DependentCode::DependencyGroup group);
    void AddToDependentICList(Handle<Code> stub);
  
    // The following low-level accessors should only be used by this class
    // and the mark compact collector.
    inline int number_of_entries(DependencyGroup group);
    inline void set_number_of_entries(DependencyGroup group, int value);
    inline bool is_code_at(int i);
    inline Code* code_at(int i);
    inline CompilationInfo* compilation_info_at(int i);
    inline void set_object_at(int i, Object* object);
    inline Object** slot_at(int i);
    inline Object* object_at(int i);
    inline void clear_at(int i);
    inline void copy(int from, int to);
    DECLARE_CAST(DependentCode)
  
    static DependentCode* ForObject(Handle<HeapObject> object,
                                    DependencyGroup group);
  
    static const char* DependencyGroupName(DependencyGroup group);
    static void SetMarkedForDeoptimization(Code* code, DependencyGroup group);
  
   private:
    // Make a room at the end of the given group by moving out the first
    // code objects of the subsequent groups.
    inline void ExtendGroup(DependencyGroup group);
    static const int kCodesStartIndex = kGroupCount;
  };
  
  
  // All heap objects have a Map that describes their structure.
  //  A Map contains information about:
  //  - Size information about the object
  //  - How to iterate over an object (for garbage collection)
  class Map: public HeapObject {
   public:
    // Instance size.
    // Size in bytes or kVariableSizeSentinel if instances do not have
    // a fixed size.
    inline int instance_size();
    inline void set_instance_size(int value);
  
    // Count of properties allocated in the object.
    inline int inobject_properties();
    inline void set_inobject_properties(int value);
  
    // Count of property fields pre-allocated in the object when first allocated.
    inline int pre_allocated_property_fields();
    inline void set_pre_allocated_property_fields(int value);
  
    // Instance type.
    inline InstanceType instance_type();
    inline void set_instance_type(InstanceType value);
  
    // Tells how many unused property fields are available in the
    // instance (only used for JSObject in fast mode).
    inline int unused_property_fields();
    inline void set_unused_property_fields(int value);
  
    // Bit field.
    inline byte bit_field();
    inline void set_bit_field(byte value);
  
    // Bit field 2.
    inline byte bit_field2();
    inline void set_bit_field2(byte value);
  
    // Bit field 3.
    inline uint32_t bit_field3();
    inline void set_bit_field3(uint32_t bits);
  
    class EnumLengthBits:             public BitField<int,
        0, kDescriptorIndexBitCount> {};  // NOLINT
    class NumberOfOwnDescriptorsBits: public BitField<int,
        kDescriptorIndexBitCount, kDescriptorIndexBitCount> {};  // NOLINT
    STATIC_ASSERT(kDescriptorIndexBitCount + kDescriptorIndexBitCount == 20);
    class DictionaryMap : public BitField<bool, 20, 1> {};
    class OwnsDescriptors : public BitField<bool, 21, 1> {};
    class HasInstanceCallHandler : public BitField<bool, 22, 1> {};
    class Deprecated : public BitField<bool, 23, 1> {};
    class IsFrozen : public BitField<bool, 24, 1> {};
    class IsUnstable : public BitField<bool, 25, 1> {};
    class IsMigrationTarget : public BitField<bool, 26, 1> {};
    class DoneInobjectSlackTracking : public BitField<bool, 27, 1> {};
    // Bit 28 is free.
  
    // Keep this bit field at the very end for better code in
    // Builtins::kJSConstructStubGeneric stub.
    class ConstructionCount:          public BitField<int, 29, 3> {};
  
    // Tells whether the object in the prototype property will be used
    // for instances created from this function.  If the prototype
    // property is set to a value that is not a JSObject, the prototype
    // property will not be used to create instances of the function.
    // See ECMA-262, 13.2.2.
    inline void set_non_instance_prototype(bool value);
    inline bool has_non_instance_prototype();
  
    // Tells whether function has special prototype property. If not, prototype
    // property will not be created when accessed (will return undefined),
    // and construction from this function will not be allowed.
    inline void set_function_with_prototype(bool value);
    inline bool function_with_prototype();
  
    // Tells whether the instance with this map should be ignored by the
    // Object.getPrototypeOf() function and the __proto__ accessor.
    inline void set_is_hidden_prototype() {
      set_bit_field(bit_field() | (1 << kIsHiddenPrototype));
    }
  
    inline bool is_hidden_prototype() {
      return ((1 << kIsHiddenPrototype) & bit_field()) != 0;
    }
  
    // Records and queries whether the instance has a named interceptor.
    inline void set_has_named_interceptor() {
      set_bit_field(bit_field() | (1 << kHasNamedInterceptor));
    }
  
    inline bool has_named_interceptor() {
      return ((1 << kHasNamedInterceptor) & bit_field()) != 0;
    }
  
    // Records and queries whether the instance has an indexed interceptor.
    inline void set_has_indexed_interceptor() {
      set_bit_field(bit_field() | (1 << kHasIndexedInterceptor));
    }
  
    inline bool has_indexed_interceptor() {
      return ((1 << kHasIndexedInterceptor) & bit_field()) != 0;
    }
  
    // Tells whether the instance is undetectable.
    // An undetectable object is a special class of JSObject: 'typeof' operator
    // returns undefined, ToBoolean returns false. Otherwise it behaves like
    // a normal JS object.  It is useful for implementing undetectable
    // document.all in Firefox & Safari.
    // See https://bugzilla.mozilla.org/show_bug.cgi?id=248549.
    inline void set_is_undetectable() {
      set_bit_field(bit_field() | (1 << kIsUndetectable));
    }
  
    inline bool is_undetectable() {
      return ((1 << kIsUndetectable) & bit_field()) != 0;
    }
  
    // Tells whether the instance has a call-as-function handler.
    inline void set_is_observed() {
      set_bit_field(bit_field() | (1 << kIsObserved));
    }
  
    inline bool is_observed() {
      return ((1 << kIsObserved) & bit_field()) != 0;
    }
  
    inline void set_is_extensible(bool value);
    inline bool is_extensible();
    inline void set_is_prototype_map(bool value);
    inline bool is_prototype_map();
  
    inline void set_elements_kind(ElementsKind elements_kind) {
      DCHECK(static_cast<int>(elements_kind) < kElementsKindCount);
      DCHECK(kElementsKindCount <= (1 << Map::ElementsKindBits::kSize));
      set_bit_field2(Map::ElementsKindBits::update(bit_field2(), elements_kind));
      DCHECK(this->elements_kind() == elements_kind);
    }
  
    inline ElementsKind elements_kind() {
      return Map::ElementsKindBits::decode(bit_field2());
    }
  
    // Tells whether the instance has fast elements that are only Smis.
    inline bool has_fast_smi_elements() {
      return IsFastSmiElementsKind(elements_kind());
    }
  
    // Tells whether the instance has fast elements.
    inline bool has_fast_object_elements() {
      return IsFastObjectElementsKind(elements_kind());
    }
  
    inline bool has_fast_smi_or_object_elements() {
      return IsFastSmiOrObjectElementsKind(elements_kind());
    }
  
    inline bool has_fast_double_elements() {
      return IsFastDoubleElementsKind(elements_kind());
    }
  
    inline bool has_fast_elements() {
      return IsFastElementsKind(elements_kind());
    }
  
    inline bool has_sloppy_arguments_elements() {
      return elements_kind() == SLOPPY_ARGUMENTS_ELEMENTS;
    }
  
    inline bool has_external_array_elements() {
      return IsExternalArrayElementsKind(elements_kind());
    }
  
    inline bool has_fixed_typed_array_elements() {
      return IsFixedTypedArrayElementsKind(elements_kind());
    }
  
    inline bool has_dictionary_elements() {
      return IsDictionaryElementsKind(elements_kind());
    }
  
    inline bool has_slow_elements_kind() {
      return elements_kind() == DICTIONARY_ELEMENTS
          || elements_kind() == SLOPPY_ARGUMENTS_ELEMENTS;
    }
  
    static bool IsValidElementsTransition(ElementsKind from_kind,
                                          ElementsKind to_kind);
  
    // Returns true if the current map doesn't have DICTIONARY_ELEMENTS but if a
    // map with DICTIONARY_ELEMENTS was found in the prototype chain.
    bool DictionaryElementsInPrototypeChainOnly();
  
    inline bool HasTransitionArray() const;
    inline bool HasElementsTransition();
    inline Map* elements_transition_map();
  
    inline Map* GetTransition(int transition_index);
    inline int SearchTransition(Name* name);
    inline FixedArrayBase* GetInitialElements();
  
    DECL_ACCESSORS(transitions, TransitionArray)
  
    static inline Handle<String> ExpectedTransitionKey(Handle<Map> map);
    static inline Handle<Map> ExpectedTransitionTarget(Handle<Map> map);
  
    // Try to follow an existing transition to a field with attributes NONE. The
    // return value indicates whether the transition was successful.
    static inline Handle<Map> FindTransitionToField(Handle<Map> map,
                                                    Handle<Name> key);
  
    Map* FindRootMap();
    Map* FindFieldOwner(int descriptor);
  
    inline int GetInObjectPropertyOffset(int index);
  
    int NumberOfFields();
  
    // TODO(ishell): candidate with JSObject::MigrateToMap().
    bool InstancesNeedRewriting(Map* target, int target_number_of_fields,
                                int target_inobject, int target_unused,
                                int* old_number_of_fields);
    // TODO(ishell): moveit!
    static Handle<Map> GeneralizeAllFieldRepresentations(Handle<Map> map);
    MUST_USE_RESULT static Handle<HeapType> GeneralizeFieldType(
        Handle<HeapType> type1,
        Handle<HeapType> type2,
        Isolate* isolate);
    static void GeneralizeFieldType(Handle<Map> map,
                                    int modify_index,
                                    Handle<HeapType> new_field_type);
    static Handle<Map> GeneralizeRepresentation(
        Handle<Map> map,
        int modify_index,
        Representation new_representation,
        Handle<HeapType> new_field_type,
        StoreMode store_mode);
    static Handle<Map> CopyGeneralizeAllRepresentations(
        Handle<Map> map,
        int modify_index,
        StoreMode store_mode,
        PropertyAttributes attributes,
        const char* reason);
    static Handle<Map> CopyGeneralizeAllRepresentations(
        Handle<Map> map,
        int modify_index,
        StoreMode store_mode,
        const char* reason);
  
    static Handle<Map> PrepareForDataProperty(Handle<Map> old_map,
                                              int descriptor_number,
                                              Handle<Object> value);
  
    static Handle<Map> Normalize(Handle<Map> map, PropertyNormalizationMode mode);
  
    // Returns the constructor name (the name (possibly, inferred name) of the
    // function that was used to instantiate the object).
    String* constructor_name();
  
    // Tells whether the map is used for JSObjects in dictionary mode (ie
    // normalized objects, ie objects for which HasFastProperties returns false).
    // A map can never be used for both dictionary mode and fast mode JSObjects.
    // False by default and for HeapObjects that are not JSObjects.
    inline void set_dictionary_map(bool value);
    inline bool is_dictionary_map();
  
    // Tells whether the instance needs security checks when accessing its
    // properties.
    inline void set_is_access_check_needed(bool access_check_needed);
    inline bool is_access_check_needed();
  
    // Returns true if map has a non-empty stub code cache.
    inline bool has_code_cache();
  
    // [prototype]: implicit prototype object.
    DECL_ACCESSORS(prototype, Object)
  
    // [constructor]: points back to the function responsible for this map.
    DECL_ACCESSORS(constructor, Object)
  
    // [instance descriptors]: describes the object.
    DECL_ACCESSORS(instance_descriptors, DescriptorArray)
    inline void InitializeDescriptors(DescriptorArray* descriptors);
  
    // [stub cache]: contains stubs compiled for this map.
    DECL_ACCESSORS(code_cache, Object)
  
    // [dependent code]: list of optimized codes that weakly embed this map.
    DECL_ACCESSORS(dependent_code, DependentCode)
  
    // [back pointer]: points back to the parent map from which a transition
    // leads to this map. The field overlaps with prototype transitions and the
    // back pointer will be moved into the prototype transitions array if
    // required.
    inline Object* GetBackPointer();
    inline void SetBackPointer(Object* value,
                               WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
    inline void init_back_pointer(Object* undefined);
  
    // [prototype transitions]: cache of prototype transitions.
    // Prototype transition is a transition that happens
    // when we change object's prototype to a new one.
    // Cache format:
    //    0: finger - index of the first free cell in the cache
    //    1: back pointer that overlaps with prototype transitions field.
    //    2 + 2 * i: prototype
    //    3 + 2 * i: target map
    inline FixedArray* GetPrototypeTransitions();
    inline bool HasPrototypeTransitions();
  
    static const int kProtoTransitionHeaderSize = 1;
    static const int kProtoTransitionNumberOfEntriesOffset = 0;
    static const int kProtoTransitionElementsPerEntry = 2;
    static const int kProtoTransitionPrototypeOffset = 0;
    static const int kProtoTransitionMapOffset = 1;
  
    inline int NumberOfProtoTransitions() {
      FixedArray* cache = GetPrototypeTransitions();
      if (cache->length() == 0) return 0;
      return
          Smi::cast(cache->get(kProtoTransitionNumberOfEntriesOffset))->value();
    }
  
    inline void SetNumberOfProtoTransitions(int value) {
      FixedArray* cache = GetPrototypeTransitions();
      DCHECK(cache->length() != 0);
      cache->set(kProtoTransitionNumberOfEntriesOffset, Smi::FromInt(value));
    }
  
    // Lookup in the map's instance descriptors and fill out the result
    // with the given holder if the name is found. The holder may be
    // NULL when this function is used from the compiler.
    inline void LookupDescriptor(JSObject* holder,
                                 Name* name,
                                 LookupResult* result);
  
    inline void LookupTransition(JSObject* holder,
                                 Name* name,
                                 LookupResult* result);
  
    inline PropertyDetails GetLastDescriptorDetails();
  
    // The size of transition arrays are limited so they do not end up in large
    // object space. Otherwise ClearNonLiveTransitions would leak memory while
    // applying in-place right trimming.
    inline bool CanHaveMoreTransitions();
  
    int LastAdded() {
      int number_of_own_descriptors = NumberOfOwnDescriptors();
      DCHECK(number_of_own_descriptors > 0);
      return number_of_own_descriptors - 1;
    }
  
    int NumberOfOwnDescriptors() {
      return NumberOfOwnDescriptorsBits::decode(bit_field3());
    }
  
    void SetNumberOfOwnDescriptors(int number) {
      DCHECK(number <= instance_descriptors()->number_of_descriptors());
      set_bit_field3(NumberOfOwnDescriptorsBits::update(bit_field3(), number));
    }
  
    inline Cell* RetrieveDescriptorsPointer();
  
    int EnumLength() {
      return EnumLengthBits::decode(bit_field3());
    }
  
    void SetEnumLength(int length) {
      if (length != kInvalidEnumCacheSentinel) {
        DCHECK(length >= 0);
        DCHECK(length == 0 || instance_descriptors()->HasEnumCache());
        DCHECK(length <= NumberOfOwnDescriptors());
      }
      set_bit_field3(EnumLengthBits::update(bit_field3(), length));
    }
  
    inline bool owns_descriptors();
    inline void set_owns_descriptors(bool owns_descriptors);
    inline bool has_instance_call_handler();
    inline void set_has_instance_call_handler();
    inline void freeze();
    inline bool is_frozen();
    inline void mark_unstable();
    inline bool is_stable();
    inline void set_migration_target(bool value);
    inline bool is_migration_target();
    inline void set_done_inobject_slack_tracking(bool value);
    inline bool done_inobject_slack_tracking();
    inline void set_construction_count(int value);
    inline int construction_count();
    inline void deprecate();
    inline bool is_deprecated();
    inline bool CanBeDeprecated();
    // Returns a non-deprecated version of the input. If the input was not
    // deprecated, it is directly returned. Otherwise, the non-deprecated version
    // is found by re-transitioning from the root of the transition tree using the
    // descriptor array of the map. Returns NULL if no updated map is found.
    // This method also applies any pending migrations along the prototype chain.
    static MaybeHandle<Map> TryUpdate(Handle<Map> map) WARN_UNUSED_RESULT;
    // Same as above, but does not touch the prototype chain.
    static MaybeHandle<Map> TryUpdateInternal(Handle<Map> map)
        WARN_UNUSED_RESULT;
  
    // Returns a non-deprecated version of the input. This method may deprecate
    // existing maps along the way if encodings conflict. Not for use while
    // gathering type feedback. Use TryUpdate in those cases instead.
    static Handle<Map> Update(Handle<Map> map);
  
    static Handle<Map> CopyDropDescriptors(Handle<Map> map);
    static Handle<Map> CopyInsertDescriptor(Handle<Map> map,
                                            Descriptor* descriptor,
                                            TransitionFlag flag);
  
    MUST_USE_RESULT static MaybeHandle<Map> CopyWithField(
        Handle<Map> map,
        Handle<Name> name,
        Handle<HeapType> type,
        PropertyAttributes attributes,
        Representation representation,
        TransitionFlag flag);
  
    MUST_USE_RESULT static MaybeHandle<Map> CopyWithConstant(
        Handle<Map> map,
        Handle<Name> name,
        Handle<Object> constant,
        PropertyAttributes attributes,
        TransitionFlag flag);
  
    // Returns a new map with all transitions dropped from the given map and
    // the ElementsKind set.
    static Handle<Map> TransitionElementsTo(Handle<Map> map,
                                            ElementsKind to_kind);
  
    static Handle<Map> AsElementsKind(Handle<Map> map, ElementsKind kind);
  
    static Handle<Map> CopyAsElementsKind(Handle<Map> map,
                                          ElementsKind kind,
                                          TransitionFlag flag);
  
    static Handle<Map> CopyForObserved(Handle<Map> map);
  
    static Handle<Map> CopyForFreeze(Handle<Map> map);
    // Maximal number of fast properties. Used to restrict the number of map
    // transitions to avoid an explosion in the number of maps for objects used as
    // dictionaries.
    inline bool TooManyFastProperties(StoreFromKeyed store_mode);
    static Handle<Map> TransitionToDataProperty(Handle<Map> map,
                                                Handle<Name> name,
                                                Handle<Object> value,
                                                PropertyAttributes attributes,
                                                StoreFromKeyed store_mode);
    static Handle<Map> TransitionToAccessorProperty(
        Handle<Map> map, Handle<Name> name, AccessorComponent component,
        Handle<Object> accessor, PropertyAttributes attributes);
    static Handle<Map> ReconfigureDataProperty(Handle<Map> map, int descriptor,
                                               PropertyAttributes attributes);
  
    inline void AppendDescriptor(Descriptor* desc);
  
    // Returns a copy of the map, with all transitions dropped from the
    // instance descriptors.
    static Handle<Map> Copy(Handle<Map> map);
    static Handle<Map> Create(Isolate* isolate, int inobject_properties);
  
    // Returns the next free property index (only valid for FAST MODE).
    int NextFreePropertyIndex();
  
    // Returns the number of properties described in instance_descriptors
    // filtering out properties with the specified attributes.
    int NumberOfDescribedProperties(DescriptorFlag which = OWN_DESCRIPTORS,
                                    PropertyAttributes filter = NONE);
  
    // Returns the number of slots allocated for the initial properties
    // backing storage for instances of this map.
    int InitialPropertiesLength() {
      return pre_allocated_property_fields() + unused_property_fields() -
          inobject_properties();
    }
  
    DECLARE_CAST(Map)
  
    // Code cache operations.
  
    // Clears the code cache.
    inline void ClearCodeCache(Heap* heap);
  
    // Update code cache.
    static void UpdateCodeCache(Handle<Map> map,
                                Handle<Name> name,
                                Handle<Code> code);
  
    // Extend the descriptor array of the map with the list of descriptors.
    // In case of duplicates, the latest descriptor is used.
    static void AppendCallbackDescriptors(Handle<Map> map,
                                          Handle<Object> descriptors);
  
    static void EnsureDescriptorSlack(Handle<Map> map, int slack);
  
    // Returns the found code or undefined if absent.
    Object* FindInCodeCache(Name* name, Code::Flags flags);
  
    // Returns the non-negative index of the code object if it is in the
    // cache and -1 otherwise.
    int IndexInCodeCache(Object* name, Code* code);
  
    // Removes a code object from the code cache at the given index.
    void RemoveFromCodeCache(Name* name, Code* code, int index);
  
    // Set all map transitions from this map to dead maps to null.  Also clear
    // back pointers in transition targets so that we do not process this map
    // again while following back pointers.
    void ClearNonLiveTransitions(Heap* heap);
  
    // Computes a hash value for this map, to be used in HashTables and such.
    int Hash();
  
    // Returns the map that this map transitions to if its elements_kind
    // is changed to |elements_kind|, or NULL if no such map is cached yet.
    // |safe_to_add_transitions| is set to false if adding transitions is not
    // allowed.
    Map* LookupElementsTransitionMap(ElementsKind elements_kind);
  
    // Returns the transitioned map for this map with the most generic
    // elements_kind that's found in |candidates|, or null handle if no match is
    // found at all.
    Handle<Map> FindTransitionedMap(MapHandleList* candidates);
  
    bool CanTransition() {
      // Only JSObject and subtypes have map transitions and back pointers.
      STATIC_ASSERT(LAST_TYPE == LAST_JS_OBJECT_TYPE);
      return instance_type() >= FIRST_JS_OBJECT_TYPE;
    }
  
    bool IsJSObjectMap() {
      return instance_type() >= FIRST_JS_OBJECT_TYPE;
    }
    bool IsJSProxyMap() {
      InstanceType type = instance_type();
      return FIRST_JS_PROXY_TYPE <= type && type <= LAST_JS_PROXY_TYPE;
    }
    bool IsJSGlobalProxyMap() {
      return instance_type() == JS_GLOBAL_PROXY_TYPE;
    }
    bool IsJSGlobalObjectMap() {
      return instance_type() == JS_GLOBAL_OBJECT_TYPE;
    }
    bool IsGlobalObjectMap() {
      const InstanceType type = instance_type();
      return type == JS_GLOBAL_OBJECT_TYPE || type == JS_BUILTINS_OBJECT_TYPE;
    }
  
    inline bool CanOmitMapChecks();
  
    static void AddDependentCompilationInfo(Handle<Map> map,
                                            DependentCode::DependencyGroup group,
                                            CompilationInfo* info);
  
    static void AddDependentCode(Handle<Map> map,
                                 DependentCode::DependencyGroup group,
                                 Handle<Code> code);
    static void AddDependentIC(Handle<Map> map,
                               Handle<Code> stub);
  
    bool IsMapInArrayPrototypeChain();
  
    // Dispatched behavior.
    DECLARE_PRINTER(Map)
    DECLARE_VERIFIER(Map)
  
  #ifdef VERIFY_HEAP
    void DictionaryMapVerify();
    void VerifyOmittedMapChecks();
  #endif
  
    inline int visitor_id();
    inline void set_visitor_id(int visitor_id);
  
    typedef void (*TraverseCallback)(Map* map, void* data);
  
    void TraverseTransitionTree(TraverseCallback callback, void* data);
  
    // When you set the prototype of an object using the __proto__ accessor you
    // need a new map for the object (the prototype is stored in the map).  In
    // order not to multiply maps unnecessarily we store these as transitions in
    // the original map.  That way we can transition to the same map if the same
    // prototype is set, rather than creating a new map every time.  The
    // transitions are in the form of a map where the keys are prototype objects
    // and the values are the maps the are transitioned to.
    static const int kMaxCachedPrototypeTransitions = 256;
    static Handle<Map> TransitionToPrototype(Handle<Map> map,
                                             Handle<Object> prototype);
  
    static const int kMaxPreAllocatedPropertyFields = 255;
  
    // Layout description.
    static const int kInstanceSizesOffset = HeapObject::kHeaderSize;
    static const int kInstanceAttributesOffset = kInstanceSizesOffset + kIntSize;
    static const int kBitField3Offset = kInstanceAttributesOffset + kIntSize;
    static const int kPrototypeOffset = kBitField3Offset + kPointerSize;
    static const int kConstructorOffset = kPrototypeOffset + kPointerSize;
    // Storage for the transition array is overloaded to directly contain a back
    // pointer if unused. When the map has transitions, the back pointer is
    // transferred to the transition array and accessed through an extra
    // indirection.
    static const int kTransitionsOrBackPointerOffset =
        kConstructorOffset + kPointerSize;
    static const int kDescriptorsOffset =
        kTransitionsOrBackPointerOffset + kPointerSize;
    static const int kCodeCacheOffset = kDescriptorsOffset + kPointerSize;
    static const int kDependentCodeOffset = kCodeCacheOffset + kPointerSize;
    static const int kSize = kDependentCodeOffset + kPointerSize;
  
    // Layout of pointer fields. Heap iteration code relies on them
    // being continuously allocated.
    static const int kPointerFieldsBeginOffset = Map::kPrototypeOffset;
    static const int kPointerFieldsEndOffset = kSize;
  
    // Byte offsets within kInstanceSizesOffset.
    static const int kInstanceSizeOffset = kInstanceSizesOffset + 0;
    static const int kInObjectPropertiesByte = 1;
    static const int kInObjectPropertiesOffset =
        kInstanceSizesOffset + kInObjectPropertiesByte;
    static const int kPreAllocatedPropertyFieldsByte = 2;
    static const int kPreAllocatedPropertyFieldsOffset =
        kInstanceSizesOffset + kPreAllocatedPropertyFieldsByte;
    static const int kVisitorIdByte = 3;
    static const int kVisitorIdOffset = kInstanceSizesOffset + kVisitorIdByte;
  
    // Byte offsets within kInstanceAttributesOffset attributes.
  #if V8_TARGET_LITTLE_ENDIAN
    // Order instance type and bit field together such that they can be loaded
    // together as a 16-bit word with instance type in the lower 8 bits regardless
    // of endianess. Also provide endian-independent offset to that 16-bit word.
    static const int kInstanceTypeOffset = kInstanceAttributesOffset + 0;
    static const int kBitFieldOffset = kInstanceAttributesOffset + 1;
  #else
    static const int kBitFieldOffset = kInstanceAttributesOffset + 0;
    static const int kInstanceTypeOffset = kInstanceAttributesOffset + 1;
  #endif
    static const int kInstanceTypeAndBitFieldOffset =
        kInstanceAttributesOffset + 0;
    static const int kBitField2Offset = kInstanceAttributesOffset + 2;
    static const int kUnusedPropertyFieldsOffset = kInstanceAttributesOffset + 3;
  
    STATIC_ASSERT(kInstanceTypeAndBitFieldOffset ==
                  Internals::kMapInstanceTypeAndBitFieldOffset);
  
    // Bit positions for bit field.
    static const int kHasNonInstancePrototype = 0;
    static const int kIsHiddenPrototype = 1;
    static const int kHasNamedInterceptor = 2;
    static const int kHasIndexedInterceptor = 3;
    static const int kIsUndetectable = 4;
    static const int kIsObserved = 5;
    static const int kIsAccessCheckNeeded = 6;
    class FunctionWithPrototype: public BitField<bool, 7,  1> {};
  
    // Bit positions for bit field 2
    static const int kIsExtensible = 0;
    static const int kStringWrapperSafeForDefaultValueOf = 1;
    class IsPrototypeMapBits : public BitField<bool, 2, 1> {};
    class ElementsKindBits: public BitField<ElementsKind, 3, 5> {};
  
    // Derived values from bit field 2
    static const int8_t kMaximumBitField2FastElementValue = static_cast<int8_t>(
        (FAST_ELEMENTS + 1) << Map::ElementsKindBits::kShift) - 1;
    static const int8_t kMaximumBitField2FastSmiElementValue =
        static_cast<int8_t>((FAST_SMI_ELEMENTS + 1) <<
                            Map::ElementsKindBits::kShift) - 1;
    static const int8_t kMaximumBitField2FastHoleyElementValue =
        static_cast<int8_t>((FAST_HOLEY_ELEMENTS + 1) <<
                            Map::ElementsKindBits::kShift) - 1;
    static const int8_t kMaximumBitField2FastHoleySmiElementValue =
        static_cast<int8_t>((FAST_HOLEY_SMI_ELEMENTS + 1) <<
                            Map::ElementsKindBits::kShift) - 1;
  
    typedef FixedBodyDescriptor<kPointerFieldsBeginOffset,
                                kPointerFieldsEndOffset,
                                kSize> BodyDescriptor;
  
    // Compares this map to another to see if they describe equivalent objects.
    // If |mode| is set to CLEAR_INOBJECT_PROPERTIES, |other| is treated as if
    // it had exactly zero inobject properties.
    // The "shared" flags of both this map and |other| are ignored.
    bool EquivalentToForNormalization(Map* other, PropertyNormalizationMode mode);
  
   private:
    static void ConnectElementsTransition(Handle<Map> parent, Handle<Map> child);
    static void ConnectTransition(Handle<Map> parent, Handle<Map> child,
                                  Handle<Name> name, SimpleTransitionFlag flag);
  
    bool EquivalentToForTransition(Map* other);
    static Handle<Map> RawCopy(Handle<Map> map, int instance_size);
    static Handle<Map> ShareDescriptor(Handle<Map> map,
                                       Handle<DescriptorArray> descriptors,
                                       Descriptor* descriptor);
    static Handle<Map> CopyInstallDescriptors(
        Handle<Map> map,
        int new_descriptor,
        Handle<DescriptorArray> descriptors);
    static Handle<Map> CopyAddDescriptor(Handle<Map> map,
                                         Descriptor* descriptor,
                                         TransitionFlag flag);
    static Handle<Map> CopyReplaceDescriptors(
        Handle<Map> map,
        Handle<DescriptorArray> descriptors,
        TransitionFlag flag,
        MaybeHandle<Name> maybe_name,
        SimpleTransitionFlag simple_flag = FULL_TRANSITION);
    static Handle<Map> CopyReplaceDescriptor(Handle<Map> map,
                                             Handle<DescriptorArray> descriptors,
                                             Descriptor* descriptor,
                                             int index,
                                             TransitionFlag flag);
  
    static Handle<Map> CopyNormalized(Handle<Map> map,
                                      PropertyNormalizationMode mode);
  
    // Fires when the layout of an object with a leaf map changes.
    // This includes adding transitions to the leaf map or changing
    // the descriptor array.
    inline void NotifyLeafMapLayoutChange();
  
    static Handle<Map> TransitionElementsToSlow(Handle<Map> object,
                                                ElementsKind to_kind);
  
    // Zaps the contents of backing data structures. Note that the
    // heap verifier (i.e. VerifyMarkingVisitor) relies on zapping of objects
    // holding weak references when incremental marking is used, because it also
    // iterates over objects that are otherwise unreachable.
    // In general we only want to call these functions in release mode when
    // heap verification is turned on.
    void ZapPrototypeTransitions();
    void ZapTransitions();
  
    void DeprecateTransitionTree();
    void DeprecateTarget(Name* key, DescriptorArray* new_descriptors);
  
    Map* FindLastMatchMap(int verbatim, int length, DescriptorArray* descriptors);
  
    void UpdateFieldType(int descriptor_number, Handle<Name> name,
                         Handle<HeapType> new_type);
  
    void PrintGeneralization(FILE* file,
                             const char* reason,
                             int modify_index,
                             int split,
                             int descriptors,
                             bool constant_to_field,
                             Representation old_representation,
                             Representation new_representation,
                             HeapType* old_field_type,
                             HeapType* new_field_type);
  
    static inline void SetPrototypeTransitions(
        Handle<Map> map,
        Handle<FixedArray> prototype_transitions);
  
    static Handle<Map> GetPrototypeTransition(Handle<Map> map,
                                              Handle<Object> prototype);
    static Handle<Map> PutPrototypeTransition(Handle<Map> map,
                                              Handle<Object> prototype,
                                              Handle<Map> target_map);
  
    static const int kFastPropertiesSoftLimit = 12;
    static const int kMaxFastProperties = 128;
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(Map);
  };
  
  
  // An abstract superclass, a marker class really, for simple structure classes.
  // It doesn't carry much functionality but allows struct classes to be
  // identified in the type system.
  class Struct: public HeapObject {
   public:
    inline void InitializeBody(int object_size);
    DECLARE_CAST(Struct)
  };
  
  
  // A simple one-element struct, useful where smis need to be boxed.
  class Box : public Struct {
   public:
    // [value]: the boxed contents.
    DECL_ACCESSORS(value, Object)
  
    DECLARE_CAST(Box)
  
    // Dispatched behavior.
    DECLARE_PRINTER(Box)
    DECLARE_VERIFIER(Box)
  
    static const int kValueOffset = HeapObject::kHeaderSize;
    static const int kSize = kValueOffset + kPointerSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(Box);
  };
  
  
  // Script describes a script which has been added to the VM.
  class Script: public Struct {
   public:
    // Script types.
    enum Type {
      TYPE_NATIVE = 0,
      TYPE_EXTENSION = 1,
      TYPE_NORMAL = 2
    };
  
    // Script compilation types.
    enum CompilationType {
      COMPILATION_TYPE_HOST = 0,
      COMPILATION_TYPE_EVAL = 1
    };
  
    // Script compilation state.
    enum CompilationState {
      COMPILATION_STATE_INITIAL = 0,
      COMPILATION_STATE_COMPILED = 1
    };
  
    // [source]: the script source.
    DECL_ACCESSORS(source, Object)
  
    // [name]: the script name.
    DECL_ACCESSORS(name, Object)
  
    // [id]: the script id.
    DECL_ACCESSORS(id, Smi)
  
    // [line_offset]: script line offset in resource from where it was extracted.
    DECL_ACCESSORS(line_offset, Smi)
  
    // [column_offset]: script column offset in resource from where it was
    // extracted.
    DECL_ACCESSORS(column_offset, Smi)
  
    // [context_data]: context data for the context this script was compiled in.
    DECL_ACCESSORS(context_data, Object)
  
    // [wrapper]: the wrapper cache.
    DECL_ACCESSORS(wrapper, Foreign)
  
    // [type]: the script type.
    DECL_ACCESSORS(type, Smi)
  
    // [line_ends]: FixedArray of line ends positions.
    DECL_ACCESSORS(line_ends, Object)
  
    // [eval_from_shared]: for eval scripts the shared funcion info for the
    // function from which eval was called.
    DECL_ACCESSORS(eval_from_shared, Object)
  
    // [eval_from_instructions_offset]: the instruction offset in the code for the
    // function from which eval was called where eval was called.
    DECL_ACCESSORS(eval_from_instructions_offset, Smi)
  
    // [flags]: Holds an exciting bitfield.
    DECL_ACCESSORS(flags, Smi)
  
    // [source_url]: sourceURL from magic comment
    DECL_ACCESSORS(source_url, Object)
  
    // [source_url]: sourceMappingURL magic comment
    DECL_ACCESSORS(source_mapping_url, Object)
  
    // [compilation_type]: how the the script was compiled. Encoded in the
    // 'flags' field.
    inline CompilationType compilation_type();
    inline void set_compilation_type(CompilationType type);
  
    // [compilation_state]: determines whether the script has already been
    // compiled. Encoded in the 'flags' field.
    inline CompilationState compilation_state();
    inline void set_compilation_state(CompilationState state);
  
    // [is_shared_cross_origin]: An opaque boolean set by the embedder via
    // ScriptOrigin, and used by the embedder to make decisions about the
    // script's level of privilege. V8 just passes this through. Encoded in
    // the 'flags' field.
    DECL_BOOLEAN_ACCESSORS(is_shared_cross_origin)
  
    DECLARE_CAST(Script)
  
    // If script source is an external string, check that the underlying
    // resource is accessible. Otherwise, always return true.
    inline bool HasValidSource();
  
    // Convert code position into column number.
    static int GetColumnNumber(Handle<Script> script, int code_pos);
  
    // Convert code position into (zero-based) line number.
    // The non-handlified version does not allocate, but may be much slower.
    static int GetLineNumber(Handle<Script> script, int code_pos);
    int GetLineNumber(int code_pos);
  
    static Handle<Object> GetNameOrSourceURL(Handle<Script> script);
  
    // Init line_ends array with code positions of line ends inside script source.
    static void InitLineEnds(Handle<Script> script);
  
    // Get the JS object wrapping the given script; create it if none exists.
    static Handle<JSObject> GetWrapper(Handle<Script> script);
    void ClearWrapperCache();
  
    // Dispatched behavior.
    DECLARE_PRINTER(Script)
    DECLARE_VERIFIER(Script)
  
    static const int kSourceOffset = HeapObject::kHeaderSize;
    static const int kNameOffset = kSourceOffset + kPointerSize;
    static const int kLineOffsetOffset = kNameOffset + kPointerSize;
    static const int kColumnOffsetOffset = kLineOffsetOffset + kPointerSize;
    static const int kContextOffset = kColumnOffsetOffset + kPointerSize;
    static const int kWrapperOffset = kContextOffset + kPointerSize;
    static const int kTypeOffset = kWrapperOffset + kPointerSize;
    static const int kLineEndsOffset = kTypeOffset + kPointerSize;
    static const int kIdOffset = kLineEndsOffset + kPointerSize;
    static const int kEvalFromSharedOffset = kIdOffset + kPointerSize;
    static const int kEvalFrominstructionsOffsetOffset =
        kEvalFromSharedOffset + kPointerSize;
    static const int kFlagsOffset =
        kEvalFrominstructionsOffsetOffset + kPointerSize;
    static const int kSourceUrlOffset = kFlagsOffset + kPointerSize;
    static const int kSourceMappingUrlOffset = kSourceUrlOffset + kPointerSize;
    static const int kSize = kSourceMappingUrlOffset + kPointerSize;
  
   private:
    int GetLineNumberWithArray(int code_pos);
  
    // Bit positions in the flags field.
    static const int kCompilationTypeBit = 0;
    static const int kCompilationStateBit = 1;
    static const int kIsSharedCrossOriginBit = 2;
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(Script);
  };
  
  
  // List of builtin functions we want to identify to improve code
  // generation.
  //
  // Each entry has a name of a global object property holding an object
  // optionally followed by ".prototype", a name of a builtin function
  // on the object (the one the id is set for), and a label.
  //
  // Installation of ids for the selected builtin functions is handled
  // by the bootstrapper.
  #define FUNCTIONS_WITH_ID_LIST(V)                   \
    V(Array.prototype, indexOf, ArrayIndexOf)         \
    V(Array.prototype, lastIndexOf, ArrayLastIndexOf) \
    V(Array.prototype, push, ArrayPush)               \
    V(Array.prototype, pop, ArrayPop)                 \
    V(Array.prototype, shift, ArrayShift)             \
    V(Function.prototype, apply, FunctionApply)       \
    V(String.prototype, charCodeAt, StringCharCodeAt) \
    V(String.prototype, charAt, StringCharAt)         \
    V(String, fromCharCode, StringFromCharCode)       \
    V(Math, floor, MathFloor)                         \
    V(Math, round, MathRound)                         \
    V(Math, ceil, MathCeil)                           \
    V(Math, abs, MathAbs)                             \
    V(Math, log, MathLog)                             \
    V(Math, exp, MathExp)                             \
    V(Math, sqrt, MathSqrt)                           \
    V(Math, pow, MathPow)                             \
    V(Math, max, MathMax)                             \
    V(Math, min, MathMin)                             \
    V(Math, imul, MathImul)                           \
    V(Math, clz32, MathClz32)                         \
    V(Math, fround, MathFround)
  
  #define SIMD_NULLARY_OPERATIONS(V)                                             \
    V(SIMD.float32x4, zero, Float32x4Zero, Float32x4)                            \
    V(SIMD.float64x2, zero, Float64x2Zero, Float64x2)                            \
    V(SIMD.int32x4, zero, Int32x4Zero, Int32x4)
  
  #define SIMD_UNARY_OPERATIONS(V)                                               \
    V(SIMD, float32x4, Float32x4Coercion, Float32x4, Float32x4)                  \
    V(SIMD, float64x2, Float64x2Coercion, Float64x2, Float64x2)                  \
    V(SIMD, int32x4, Int32x4Coercion, Int32x4, Int32x4)                          \
    V(SIMD.float32x4, abs, Float32x4Abs, Float32x4, Float32x4)                   \
    V(SIMD.float32x4, fromInt32x4, Int32x4ToFloat32x4, Float32x4, Int32x4)       \
    V(SIMD.float32x4, fromInt32x4Bits, Int32x4BitsToFloat32x4, Float32x4,        \
      Int32x4)                                                                   \
    V(SIMD.float32x4, neg, Float32x4Neg, Float32x4, Float32x4)                   \
    V(SIMD.float32x4, reciprocal, Float32x4Reciprocal, Float32x4, Float32x4)     \
    V(SIMD.float32x4, reciprocalSqrt, Float32x4ReciprocalSqrt,                   \
      Float32x4, Float32x4)                                                      \
    V(SIMD.float32x4, splat, Float32x4Splat, Float32x4, Double)                  \
    V(SIMD.float32x4, sqrt, Float32x4Sqrt, Float32x4, Float32x4)                 \
    V(SIMD.float64x2, abs, Float64x2Abs, Float64x2, Float64x2)                   \
    V(SIMD.float64x2, neg, Float64x2Neg, Float64x2, Float64x2)                   \
    V(SIMD.float64x2, sqrt, Float64x2Sqrt, Float64x2, Float64x2)                 \
    V(SIMD.int32x4, fromFloat32x4, Float32x4ToInt32x4, Int32x4, Float32x4)       \
    V(SIMD.int32x4, fromFloat32x4Bits, Float32x4BitsToInt32x4, Int32x4,          \
      Float32x4)                                                                 \
    V(SIMD.int32x4, neg, Int32x4Neg, Int32x4, Int32x4)                           \
    V(SIMD.int32x4, not, Int32x4Not, Int32x4, Int32x4)                           \
    V(SIMD.int32x4, splat, Int32x4Splat, Int32x4, Integer32)
  
  // Do not need to install them in InstallExperimentalSIMDBuiltinFunctionIds.
  #define SIMD_UNARY_OPERATIONS_FOR_PROPERTY_ACCESS(V)                           \
    V(SIMD.float32x4.prototype, signMask, Float32x4GetSignMask, Integer32,       \
      Float32x4)                                                                 \
    V(SIMD.float32x4.prototype, x, Float32x4GetX, Double, Float32x4)             \
    V(SIMD.float32x4.prototype, y, Float32x4GetY, Double, Float32x4)             \
    V(SIMD.float32x4.prototype, z, Float32x4GetZ, Double, Float32x4)             \
    V(SIMD.float32x4.prototype, w, Float32x4GetW, Double, Float32x4)             \
    V(SIMD.float64x2.prototype, signMask, Float64x2GetSignMask, Integer32,       \
      Float64x2)                                                                 \
    V(SIMD.float64x2.prototype, x, Float64x2GetX, Double, Float64x2)             \
    V(SIMD.float64x2.prototype, y, Float64x2GetY, Double, Float64x2)             \
    V(SIMD.int32x4.prototype, signMask, Int32x4GetSignMask, Integer32, Int32x4)  \
    V(SIMD.int32x4.prototype, x, Int32x4GetX, Integer32, Int32x4)                \
    V(SIMD.int32x4.prototype, y, Int32x4GetY, Integer32, Int32x4)                \
    V(SIMD.int32x4.prototype, z, Int32x4GetZ, Integer32, Int32x4)                \
    V(SIMD.int32x4.prototype, w, Int32x4GetW, Integer32, Int32x4)                \
    V(SIMD.int32x4.prototype, flagX, Int32x4GetFlagX, Tagged, Int32x4)           \
    V(SIMD.int32x4.prototype, flagY, Int32x4GetFlagY, Tagged, Int32x4)           \
    V(SIMD.int32x4.prototype, flagZ, Int32x4GetFlagZ, Tagged, Int32x4)           \
    V(SIMD.int32x4.prototype, flagW, Int32x4GetFlagW, Tagged, Int32x4)
  
  #define SIMD_BINARY_OPERATIONS(V)                                              \
    V(SIMD.float32x4, add, Float32x4Add, Float32x4, Float32x4, Float32x4)        \
    V(SIMD.float32x4, div, Float32x4Div, Float32x4, Float32x4, Float32x4)        \
    V(SIMD.float32x4, max, Float32x4Max, Float32x4, Float32x4, Float32x4)        \
    V(SIMD.float32x4, min, Float32x4Min, Float32x4, Float32x4, Float32x4)        \
    V(SIMD.float32x4, mul, Float32x4Mul, Float32x4, Float32x4, Float32x4)        \
    V(SIMD.float32x4, sub, Float32x4Sub, Float32x4, Float32x4, Float32x4)        \
    V(SIMD.float32x4, equal, Float32x4Equal, Int32x4, Float32x4, Float32x4)      \
    V(SIMD.float32x4, notEqual, Float32x4NotEqual, Int32x4, Float32x4,           \
      Float32x4)                                                                 \
    V(SIMD.float32x4, greaterThan, Float32x4GreaterThan, Int32x4, Float32x4,     \
      Float32x4)                                                                 \
    V(SIMD.float32x4, greaterThanOrEqual, Float32x4GreaterThanOrEqual, Int32x4,  \
      Float32x4, Float32x4)                                                      \
    V(SIMD.float32x4, lessThan, Float32x4LessThan, Int32x4, Float32x4,           \
      Float32x4)                                                                 \
    V(SIMD.float32x4, lessThanOrEqual, Float32x4LessThanOrEqual, Int32x4,        \
      Float32x4, Float32x4)                                                      \
    V(SIMD.float32x4, shuffle, Float32x4Shuffle, Float32x4, Float32x4,           \
      Integer32)                                                                 \
    V(SIMD.float32x4, scale, Float32x4Scale, Float32x4, Float32x4, Double)       \
    V(SIMD.float32x4, withX, Float32x4WithX, Float32x4, Float32x4, Double)       \
    V(SIMD.float32x4, withY, Float32x4WithY, Float32x4, Float32x4, Double)       \
    V(SIMD.float32x4, withZ, Float32x4WithZ, Float32x4, Float32x4, Double)       \
    V(SIMD.float32x4, withW, Float32x4WithW, Float32x4, Float32x4, Double)       \
    V(SIMD.float64x2, add, Float64x2Add, Float64x2, Float64x2, Float64x2)        \
    V(SIMD.float64x2, div, Float64x2Div, Float64x2, Float64x2, Float64x2)        \
    V(SIMD.float64x2, max, Float64x2Max, Float64x2, Float64x2, Float64x2)        \
    V(SIMD.float64x2, min, Float64x2Min, Float64x2, Float64x2, Float64x2)        \
    V(SIMD.float64x2, mul, Float64x2Mul, Float64x2, Float64x2, Float64x2)        \
    V(SIMD.float64x2, sub, Float64x2Sub, Float64x2, Float64x2, Float64x2)        \
    V(SIMD.float64x2, scale, Float64x2Scale, Float64x2, Float64x2, Double)       \
    V(SIMD.float64x2, withX, Float64x2WithX, Float64x2, Float64x2, Double)       \
    V(SIMD.float64x2, withY, Float64x2WithY, Float64x2, Float64x2, Double)       \
    V(SIMD, float64x2, Float64x2Constructor, Float64x2, Double, Double)          \
    V(SIMD.int32x4, add, Int32x4Add, Int32x4, Int32x4, Int32x4)                  \
    V(SIMD.int32x4, and, Int32x4And, Int32x4, Int32x4, Int32x4)                  \
    V(SIMD.int32x4, mul, Int32x4Mul, Int32x4, Int32x4, Int32x4)                  \
    V(SIMD.int32x4, or, Int32x4Or, Int32x4, Int32x4, Int32x4)                    \
    V(SIMD.int32x4, sub, Int32x4Sub, Int32x4, Int32x4, Int32x4)                  \
    V(SIMD.int32x4, xor, Int32x4Xor, Int32x4, Int32x4, Int32x4)                  \
    V(SIMD.int32x4, shuffle, Int32x4Shuffle, Int32x4, Int32x4, Integer32)        \
    V(SIMD.int32x4, withX, Int32x4WithX, Int32x4, Int32x4, Integer32)            \
    V(SIMD.int32x4, withY, Int32x4WithY, Int32x4, Int32x4, Integer32)            \
    V(SIMD.int32x4, withZ, Int32x4WithZ, Int32x4, Int32x4, Integer32)            \
    V(SIMD.int32x4, withW, Int32x4WithW, Int32x4, Int32x4, Integer32)            \
    V(SIMD.int32x4, withFlagX, Int32x4WithFlagX, Int32x4, Int32x4, Tagged)       \
    V(SIMD.int32x4, withFlagY, Int32x4WithFlagY, Int32x4, Int32x4, Tagged)       \
    V(SIMD.int32x4, withFlagZ, Int32x4WithFlagZ, Int32x4, Int32x4, Tagged)       \
    V(SIMD.int32x4, withFlagW, Int32x4WithFlagW, Int32x4, Int32x4, Tagged)       \
    V(SIMD.int32x4, greaterThan, Int32x4GreaterThan, Int32x4, Int32x4, Int32x4)  \
    V(SIMD.int32x4, equal, Int32x4Equal, Int32x4, Int32x4, Int32x4)              \
    V(SIMD.int32x4, lessThan, Int32x4LessThan, Int32x4, Int32x4, Int32x4)        \
    V(SIMD.int32x4, shiftLeft, Int32x4ShiftLeft, Int32x4, Int32x4, Integer32)    \
    V(SIMD.int32x4, shiftRight, Int32x4ShiftRight, Int32x4, Int32x4, Integer32)  \
    V(SIMD.int32x4, shiftRightArithmetic, Int32x4ShiftRightArithmetic, Int32x4,  \
      Int32x4, Integer32)
  
  #define SIMD_TERNARY_OPERATIONS(V)                                             \
    V(SIMD.float32x4, clamp, Float32x4Clamp, Float32x4, Float32x4, Float32x4,    \
      Float32x4)                                                                 \
    V(SIMD.float32x4, shuffleMix, Float32x4ShuffleMix, Float32x4, Float32x4,     \
      Float32x4, Integer32)                                                      \
    V(SIMD.float32x4, select, Float32x4Select, Float32x4, Int32x4, Float32x4,    \
      Float32x4)                                                                 \
    V(SIMD.float64x2, clamp, Float64x2Clamp, Float64x2, Float64x2, Float64x2,    \
      Float64x2)                                                                 \
    V(SIMD.int32x4, select, Int32x4Select, Int32x4, Int32x4, Int32x4, Int32x4)
  
  #define SIMD_QUARTERNARY_OPERATIONS(V)                                         \
    V(SIMD, float32x4, Float32x4Constructor, Float32x4, Double, Double, Double,  \
      Double)                                                                    \
    V(SIMD, int32x4, Int32x4Constructor, Int32x4, Integer32, Integer32,          \
      Integer32, Integer32)                                                      \
    V(SIMD.int32x4, bool, Int32x4Bool, Int32x4, Tagged, Tagged, Tagged, Tagged)
  
  #define SIMD_ARRAY_OPERATIONS(V)                                               \
    V(Float32x4Array.prototype, getAt, Float32x4ArrayGetAt)                      \
    V(Float32x4Array.prototype, setAt, Float32x4ArraySetAt)                      \
    V(Float64x2Array.prototype, getAt, Float64x2ArrayGetAt)                      \
    V(Float64x2Array.prototype, setAt, Float64x2ArraySetAt)                      \
    V(Int32x4Array.prototype, getAt, Int32x4ArrayGetAt)                          \
    V(Int32x4Array.prototype, setAt, Int32x4ArraySetAt)
  
  #define TYPED_ARRAYS_SIMD_LOAD_OPERATIONS(V)                                   \
    V(Float32Array.prototype, _getFloat32x4XYZW, Float32ArrayGetFloat32x4XYZW)   \
    V(Float32Array.prototype, _getFloat32x4XYZ, Float32ArrayGetFloat32x4XYZ)     \
    V(Float32Array.prototype, _getFloat32x4XY, Float32ArrayGetFloat32x4XY)       \
    V(Float32Array.prototype, _getFloat32x4X, Float32ArrayGetFloat32x4X)         \
    V(Float64Array.prototype, _getFloat64x2XY, Float64ArrayGetFloat64x2XY)       \
    V(Float64Array.prototype, _getFloat64x2X, Float64ArrayGetFloat64x2X)         \
    V(Int32Array.prototype, _getInt32x4XYZW, Int32ArrayGetInt32x4XYZW)           \
    V(Int32Array.prototype, _getInt32x4XYZ, Int32ArrayGetInt32x4XYZ)             \
    V(Int32Array.prototype, _getInt32x4XY, Int32ArrayGetInt32x4XY)               \
    V(Int32Array.prototype, _getInt32x4X, Int32ArrayGetInt32x4X)                 \
    V(Int8Array.prototype, _getFloat32x4XYZW, Int8ArrayGetFloat32x4XYZW)         \
    V(Int8Array.prototype, _getFloat32x4XYZ, Int8ArrayGetFloat32x4XYZ)           \
    V(Int8Array.prototype, _getFloat32x4XY, Int8ArrayGetFloat32x4XY)             \
    V(Int8Array.prototype, _getFloat32x4X, Int8ArrayGetFloat32x4X)               \
    V(Int8Array.prototype, _getFloat64x2XY, Int8ArrayGetFloat64x2XY)             \
    V(Int8Array.prototype, _getFloat64x2X, Int8ArrayGetFloat64x2X)               \
    V(Int8Array.prototype, _getInt32x4XYZW, Int8ArrayGetInt32x4XYZW)             \
    V(Int8Array.prototype, _getInt32x4XYZ, Int8ArrayGetInt32x4XYZ)               \
    V(Int8Array.prototype, _getInt32x4XY, Int8ArrayGetInt32x4XY)                 \
    V(Int8Array.prototype, _getInt32x4X, Int8ArrayGetInt32x4X)
  
  #define TYPED_ARRAYS_SIMD_STORE_OPERATIONS(V)                                  \
    V(Float32Array.prototype, _setFloat32x4XYZW, Float32ArraySetFloat32x4XYZW)   \
    V(Float32Array.prototype, _setFloat32x4XYZ, Float32ArraySetFloat32x4XYZ)     \
    V(Float32Array.prototype, _setFloat32x4XY, Float32ArraySetFloat32x4XY)       \
    V(Float32Array.prototype, _setFloat32x4X, Float32ArraySetFloat32x4X)         \
    V(Float64Array.prototype, _setFloat64x2XY, Float64ArraySetFloat64x2XY)       \
    V(Float64Array.prototype, _setFloat64x2X, Float64ArraySetFloat64x2X)         \
    V(Int32Array.prototype, _setInt32x4XYZW, Int32ArraySetInt32x4XYZW)           \
    V(Int32Array.prototype, _setInt32x4XYZ, Int32ArraySetInt32x4XYZ)             \
    V(Int32Array.prototype, _setInt32x4XY, Int32ArraySetInt32x4XY)               \
    V(Int32Array.prototype, _setInt32x4X, Int32ArraySetInt32x4X)                 \
    V(Int8Array.prototype, _setFloat32x4XYZW, Int8ArraySetFloat32x4XYZW)         \
    V(Int8Array.prototype, _setFloat32x4XYZ, Int8ArraySetFloat32x4XYZ)           \
    V(Int8Array.prototype, _setFloat32x4XY, Int8ArraySetFloat32x4XY)             \
    V(Int8Array.prototype, _setFloat32x4X, Int8ArraySetFloat32x4X)               \
    V(Int8Array.prototype, _setFloat64x2XY, Int8ArraySetFloat64x2XY)             \
    V(Int8Array.prototype, _setFloat64x2X, Int8ArraySetFloat64x2X)               \
    V(Int8Array.prototype, _setInt32x4XYZW, Int8ArraySetInt32x4XYZW)             \
    V(Int8Array.prototype, _setInt32x4XYZ, Int8ArraySetInt32x4XYZ)               \
    V(Int8Array.prototype, _setInt32x4XY, Int8ArraySetInt32x4XY)                 \
    V(Int8Array.prototype, _setInt32x4X, Int8ArraySetInt32x4X)
  
  // Do not need to install them in InstallExperimentalSIMDBuiltinFunctionIds.
  #define SIMD_FAKE_ID_LISTS(V)                                                  \
    V(SIMD, unreachable, SIMD128Unreachable)                                     \
    V(SIMD, change, SIMD128Change)
  
  enum BuiltinFunctionId {
    kArrayCode,
  #define DECLARE_FUNCTION_ID(ignored1, ignore2, name)    \
    k##name,
    FUNCTIONS_WITH_ID_LIST(DECLARE_FUNCTION_ID)
    // Fake id for a special case of Math.pow. Note, it continues the
    // list of math functions.
    kMathPowHalf,
    SIMD_FAKE_ID_LISTS(DECLARE_FUNCTION_ID)
    SIMD_ARRAY_OPERATIONS(DECLARE_FUNCTION_ID)
    TYPED_ARRAYS_SIMD_LOAD_OPERATIONS(DECLARE_FUNCTION_ID)
    TYPED_ARRAYS_SIMD_STORE_OPERATIONS(DECLARE_FUNCTION_ID)
  #undef DECLARE_FUNCTION_ID
  #define DECLARE_SIMD_NULLARY_FUNCTION_ID(i1, i2, name, i3)                     \
    k##name,
    SIMD_NULLARY_OPERATIONS(DECLARE_SIMD_NULLARY_FUNCTION_ID)
  #undef DECLARE_SIMD_NULLARY_FUNCTION_ID
  #define DECLARE_SIMD_UNARY_FUNCTION_ID(i1, i2, name, i3, i4)                   \
    k##name,
    SIMD_UNARY_OPERATIONS(DECLARE_SIMD_UNARY_FUNCTION_ID)
    SIMD_UNARY_OPERATIONS_FOR_PROPERTY_ACCESS(DECLARE_SIMD_UNARY_FUNCTION_ID)
  #undef DECLARE_SIMD_UNARY_FUNCTION_ID
  #define DECLARE_SIMD_BINARY_FUNCTION_ID(i1, i2, name, i3, i4, i5)              \
    k##name,
    SIMD_BINARY_OPERATIONS(DECLARE_SIMD_BINARY_FUNCTION_ID)
  #undef DECLARE_SIMD_BINARY_FUNCTION_ID
  #define DECLARE_SIMD_TERNARY_FUNCTION_ID(i1, i2, name, i3, i4, i5, i6)         \
    k##name,
    SIMD_TERNARY_OPERATIONS(DECLARE_SIMD_TERNARY_FUNCTION_ID)
  #undef DECLARE_SIMD_TERNARY_FUNCTION_ID
  #define DECLARE_SIMD_QUARTERNARY_FUNCTION_ID(i1, i2, name, i3, i4, i5, i6, i7) \
    k##name,
    SIMD_QUARTERNARY_OPERATIONS(DECLARE_SIMD_QUARTERNARY_FUNCTION_ID)
  #undef DECLARE_SIMD_QUARTERNARY_FUNCTION_ID
    kNumberOfBuiltinFunction
  };
  
  
  // SharedFunctionInfo describes the JSFunction information that can be
  // shared by multiple instances of the function.
  class SharedFunctionInfo: public HeapObject {
   public:
    // [name]: Function name.
    DECL_ACCESSORS(name, Object)
  
    // [code]: Function code.
    DECL_ACCESSORS(code, Code)
    inline void ReplaceCode(Code* code);
  
    // [optimized_code_map]: Map from native context to optimized code
    // and a shared literals array or Smi(0) if none.
    DECL_ACCESSORS(optimized_code_map, Object)
  
    // Returns index i of the entry with the specified context and OSR entry.
    // At position i - 1 is the context, position i the code, and i + 1 the
    // literals array.  Returns -1 when no matching entry is found.
    int SearchOptimizedCodeMap(Context* native_context, BailoutId osr_ast_id);
  
    // Installs optimized code from the code map on the given closure. The
    // index has to be consistent with a search result as defined above.
    FixedArray* GetLiteralsFromOptimizedCodeMap(int index);
  
    Code* GetCodeFromOptimizedCodeMap(int index);
  
    // Clear optimized code map.
    void ClearOptimizedCodeMap();
  
    // Removed a specific optimized code object from the optimized code map.
    void EvictFromOptimizedCodeMap(Code* optimized_code, const char* reason);
  
    void ClearTypeFeedbackInfo();
  
    // Trims the optimized code map after entries have been removed.
    void TrimOptimizedCodeMap(int shrink_by);
  
    // Add a new entry to the optimized code map.
    static void AddToOptimizedCodeMap(Handle<SharedFunctionInfo> shared,
                                      Handle<Context> native_context,
                                      Handle<Code> code,
                                      Handle<FixedArray> literals,
                                      BailoutId osr_ast_id);
  
    // Layout description of the optimized code map.
    static const int kNextMapIndex = 0;
    static const int kEntriesStart = 1;
    static const int kContextOffset = 0;
    static const int kCachedCodeOffset = 1;
    static const int kLiteralsOffset = 2;
    static const int kOsrAstIdOffset = 3;
    static const int kEntryLength = 4;
    static const int kInitialLength = kEntriesStart + kEntryLength;
  
    // [scope_info]: Scope info.
    DECL_ACCESSORS(scope_info, ScopeInfo)
  
    // [construct stub]: Code stub for constructing instances of this function.
    DECL_ACCESSORS(construct_stub, Code)
  
    // Returns if this function has been compiled to native code yet.
    inline bool is_compiled();
  
    // [length]: The function length - usually the number of declared parameters.
    // Use up to 2^30 parameters.
    inline int length() const;
    inline void set_length(int value);
  
    // [formal parameter count]: The declared number of parameters.
    inline int formal_parameter_count() const;
    inline void set_formal_parameter_count(int value);
  
    // Set the formal parameter count so the function code will be
    // called without using argument adaptor frames.
    inline void DontAdaptArguments();
  
    // [expected_nof_properties]: Expected number of properties for the function.
    inline int expected_nof_properties() const;
    inline void set_expected_nof_properties(int value);
  
    // [feedback_vector] - accumulates ast node feedback from full-codegen and
    // (increasingly) from crankshafted code where sufficient feedback isn't
    // available.
    DECL_ACCESSORS(feedback_vector, TypeFeedbackVector)
  
    // [instance class name]: class name for instances.
    DECL_ACCESSORS(instance_class_name, Object)
  
    // [function data]: This field holds some additional data for function.
    // Currently it either has FunctionTemplateInfo to make benefit the API
    // or Smi identifying a builtin function.
    // In the long run we don't want all functions to have this field but
    // we can fix that when we have a better model for storing hidden data
    // on objects.
    DECL_ACCESSORS(function_data, Object)
  
    inline bool IsApiFunction();
    inline FunctionTemplateInfo* get_api_func_data();
    inline bool HasBuiltinFunctionId();
    inline BuiltinFunctionId builtin_function_id();
  
    // [script info]: Script from which the function originates.
    DECL_ACCESSORS(script, Object)
  
    // [num_literals]: Number of literals used by this function.
    inline int num_literals() const;
    inline void set_num_literals(int value);
  
    // [start_position_and_type]: Field used to store both the source code
    // position, whether or not the function is a function expression,
    // and whether or not the function is a toplevel function. The two
    // least significants bit indicates whether the function is an
    // expression and the rest contains the source code position.
    inline int start_position_and_type() const;
    inline void set_start_position_and_type(int value);
  
    // [debug info]: Debug information.
    DECL_ACCESSORS(debug_info, Object)
  
    // [inferred name]: Name inferred from variable or property
    // assignment of this function. Used to facilitate debugging and
    // profiling of JavaScript code written in OO style, where almost
    // all functions are anonymous but are assigned to object
    // properties.
    DECL_ACCESSORS(inferred_name, String)
  
    // The function's name if it is non-empty, otherwise the inferred name.
    String* DebugName();
  
    // Position of the 'function' token in the script source.
    inline int function_token_position() const;
    inline void set_function_token_position(int function_token_position);
  
    // Position of this function in the script source.
    inline int start_position() const;
    inline void set_start_position(int start_position);
  
    // End position of this function in the script source.
    inline int end_position() const;
    inline void set_end_position(int end_position);
  
    // Is this function a function expression in the source code.
    DECL_BOOLEAN_ACCESSORS(is_expression)
  
    // Is this function a top-level function (scripts, evals).
    DECL_BOOLEAN_ACCESSORS(is_toplevel)
  
    // Bit field containing various information collected by the compiler to
    // drive optimization.
    inline int compiler_hints() const;
    inline void set_compiler_hints(int value);
  
    inline int ast_node_count() const;
    inline void set_ast_node_count(int count);
  
    inline int profiler_ticks() const;
    inline void set_profiler_ticks(int ticks);
  
    // Inline cache age is used to infer whether the function survived a context
    // disposal or not. In the former case we reset the opt_count.
    inline int ic_age();
    inline void set_ic_age(int age);
  
    // Indicates if this function can be lazy compiled.
    // This is used to determine if we can safely flush code from a function
    // when doing GC if we expect that the function will no longer be used.
    DECL_BOOLEAN_ACCESSORS(allows_lazy_compilation)
  
    // Indicates if this function can be lazy compiled without a context.
    // This is used to determine if we can force compilation without reaching
    // the function through program execution but through other means (e.g. heap
    // iteration by the debugger).
    DECL_BOOLEAN_ACCESSORS(allows_lazy_compilation_without_context)
  
    // Indicates whether optimizations have been disabled for this
    // shared function info. If a function is repeatedly optimized or if
    // we cannot optimize the function we disable optimization to avoid
    // spending time attempting to optimize it again.
    DECL_BOOLEAN_ACCESSORS(optimization_disabled)
  
    // Indicates the language mode.
    inline StrictMode strict_mode();
    inline void set_strict_mode(StrictMode strict_mode);
  
    // False if the function definitely does not allocate an arguments object.
    DECL_BOOLEAN_ACCESSORS(uses_arguments)
  
    // True if the function has any duplicated parameter names.
    DECL_BOOLEAN_ACCESSORS(has_duplicate_parameters)
  
    // Indicates whether the function is a native function.
    // These needs special treatment in .call and .apply since
    // null passed as the receiver should not be translated to the
    // global object.
    DECL_BOOLEAN_ACCESSORS(native)
  
    // Indicate that this builtin needs to be inlined in crankshaft.
    DECL_BOOLEAN_ACCESSORS(inline_builtin)
  
    // Indicates that the function was created by the Function function.
    // Though it's anonymous, toString should treat it as if it had the name
    // "anonymous".  We don't set the name itself so that the system does not
    // see a binding for it.
    DECL_BOOLEAN_ACCESSORS(name_should_print_as_anonymous)
  
    // Indicates whether the function is a bound function created using
    // the bind function.
    DECL_BOOLEAN_ACCESSORS(bound)
  
    // Indicates that the function is anonymous (the name field can be set
    // through the API, which does not change this flag).
    DECL_BOOLEAN_ACCESSORS(is_anonymous)
  
    // Is this a function or top-level/eval code.
    DECL_BOOLEAN_ACCESSORS(is_function)
  
    // Indicates that code for this function cannot be cached.
    DECL_BOOLEAN_ACCESSORS(dont_cache)
  
    // Indicates that code for this function cannot be flushed.
    DECL_BOOLEAN_ACCESSORS(dont_flush)
  
    // Indicates that this function is a generator.
    DECL_BOOLEAN_ACCESSORS(is_generator)
  
    // Indicates that this function is an arrow function.
    DECL_BOOLEAN_ACCESSORS(is_arrow)
  
    // Indicates that this function is a concise method.
    DECL_BOOLEAN_ACCESSORS(is_concise_method)
  
    // Indicates that this function is an asm function.
    DECL_BOOLEAN_ACCESSORS(asm_function)
  
    inline FunctionKind kind();
    inline void set_kind(FunctionKind kind);
  
    // Indicates whether or not the code in the shared function support
    // deoptimization.
    inline bool has_deoptimization_support();
  
    // Enable deoptimization support through recompiled code.
    void EnableDeoptimizationSupport(Code* recompiled);
  
    // Disable (further) attempted optimization of all functions sharing this
    // shared function info.
    void DisableOptimization(BailoutReason reason);
  
    inline BailoutReason DisableOptimizationReason();
  
    // Lookup the bailout ID and DCHECK that it exists in the non-optimized
    // code, returns whether it asserted (i.e., always true if assertions are
    // disabled).
    bool VerifyBailoutId(BailoutId id);
  
    // [source code]: Source code for the function.
    bool HasSourceCode() const;
    Handle<Object> GetSourceCode();
  
    // Number of times the function was optimized.
    inline int opt_count();
    inline void set_opt_count(int opt_count);
  
    // Number of times the function was deoptimized.
    inline void set_deopt_count(int value);
    inline int deopt_count();
    inline void increment_deopt_count();
  
    // Number of time we tried to re-enable optimization after it
    // was disabled due to high number of deoptimizations.
    inline void set_opt_reenable_tries(int value);
    inline int opt_reenable_tries();
  
    inline void TryReenableOptimization();
  
    // Stores deopt_count, opt_reenable_tries and ic_age as bit-fields.
    inline void set_counters(int value);
    inline int counters() const;
  
    // Stores opt_count and bailout_reason as bit-fields.
    inline void set_opt_count_and_bailout_reason(int value);
    inline int opt_count_and_bailout_reason() const;
  
    void set_bailout_reason(BailoutReason reason) {
      set_opt_count_and_bailout_reason(
          DisabledOptimizationReasonBits::update(opt_count_and_bailout_reason(),
                                                 reason));
    }
  
    // Check whether or not this function is inlineable.
    bool IsInlineable();
  
    // Source size of this function.
    int SourceSize();
  
    // Calculate the instance size.
    int CalculateInstanceSize();
  
    // Calculate the number of in-object properties.
    int CalculateInObjectProperties();
  
    // Dispatched behavior.
    DECLARE_PRINTER(SharedFunctionInfo)
    DECLARE_VERIFIER(SharedFunctionInfo)
  
    void ResetForNewContext(int new_ic_age);
  
    DECLARE_CAST(SharedFunctionInfo)
  
    // Constants.
    static const int kDontAdaptArgumentsSentinel = -1;
  
    // Layout description.
    // Pointer fields.
    static const int kNameOffset = HeapObject::kHeaderSize;
    static const int kCodeOffset = kNameOffset + kPointerSize;
    static const int kOptimizedCodeMapOffset = kCodeOffset + kPointerSize;
    static const int kScopeInfoOffset = kOptimizedCodeMapOffset + kPointerSize;
    static const int kConstructStubOffset = kScopeInfoOffset + kPointerSize;
    static const int kInstanceClassNameOffset =
        kConstructStubOffset + kPointerSize;
    static const int kFunctionDataOffset =
        kInstanceClassNameOffset + kPointerSize;
    static const int kScriptOffset = kFunctionDataOffset + kPointerSize;
    static const int kDebugInfoOffset = kScriptOffset + kPointerSize;
    static const int kInferredNameOffset = kDebugInfoOffset + kPointerSize;
    static const int kFeedbackVectorOffset =
        kInferredNameOffset + kPointerSize;
  #if V8_HOST_ARCH_32_BIT
    // Smi fields.
    static const int kLengthOffset =
        kFeedbackVectorOffset + kPointerSize;
    static const int kFormalParameterCountOffset = kLengthOffset + kPointerSize;
    static const int kExpectedNofPropertiesOffset =
        kFormalParameterCountOffset + kPointerSize;
    static const int kNumLiteralsOffset =
        kExpectedNofPropertiesOffset + kPointerSize;
    static const int kStartPositionAndTypeOffset =
        kNumLiteralsOffset + kPointerSize;
    static const int kEndPositionOffset =
        kStartPositionAndTypeOffset + kPointerSize;
    static const int kFunctionTokenPositionOffset =
        kEndPositionOffset + kPointerSize;
    static const int kCompilerHintsOffset =
        kFunctionTokenPositionOffset + kPointerSize;
    static const int kOptCountAndBailoutReasonOffset =
        kCompilerHintsOffset + kPointerSize;
    static const int kCountersOffset =
        kOptCountAndBailoutReasonOffset + kPointerSize;
    static const int kAstNodeCountOffset =
        kCountersOffset + kPointerSize;
    static const int kProfilerTicksOffset =
        kAstNodeCountOffset + kPointerSize;
  
    // Total size.
    static const int kSize = kProfilerTicksOffset + kPointerSize;
  #else
    // The only reason to use smi fields instead of int fields
    // is to allow iteration without maps decoding during
    // garbage collections.
    // To avoid wasting space on 64-bit architectures we use
    // the following trick: we group integer fields into pairs
    // First integer in each pair is shifted left by 1.
    // By doing this we guarantee that LSB of each kPointerSize aligned
    // word is not set and thus this word cannot be treated as pointer
    // to HeapObject during old space traversal.
    static const int kLengthOffset =
        kFeedbackVectorOffset + kPointerSize;
    static const int kFormalParameterCountOffset =
        kLengthOffset + kIntSize;
  
    static const int kExpectedNofPropertiesOffset =
        kFormalParameterCountOffset + kIntSize;
    static const int kNumLiteralsOffset =
        kExpectedNofPropertiesOffset + kIntSize;
  
    static const int kEndPositionOffset =
        kNumLiteralsOffset + kIntSize;
    static const int kStartPositionAndTypeOffset =
        kEndPositionOffset + kIntSize;
  
    static const int kFunctionTokenPositionOffset =
        kStartPositionAndTypeOffset + kIntSize;
    static const int kCompilerHintsOffset =
        kFunctionTokenPositionOffset + kIntSize;
  
    static const int kOptCountAndBailoutReasonOffset =
        kCompilerHintsOffset + kIntSize;
    static const int kCountersOffset =
        kOptCountAndBailoutReasonOffset + kIntSize;
  
    static const int kAstNodeCountOffset =
        kCountersOffset + kIntSize;
    static const int kProfilerTicksOffset =
        kAstNodeCountOffset + kIntSize;
  
    // Total size.
    static const int kSize = kProfilerTicksOffset + kIntSize;
  
  #endif
  
    static const int kAlignedSize = POINTER_SIZE_ALIGN(kSize);
  
    typedef FixedBodyDescriptor<kNameOffset,
                                kFeedbackVectorOffset + kPointerSize,
                                kSize> BodyDescriptor;
  
    // Bit positions in start_position_and_type.
    // The source code start position is in the 30 most significant bits of
    // the start_position_and_type field.
    static const int kIsExpressionBit    = 0;
    static const int kIsTopLevelBit      = 1;
    static const int kStartPositionShift = 2;
    static const int kStartPositionMask  = ~((1 << kStartPositionShift) - 1);
  
    // Bit positions in compiler_hints.
    enum CompilerHints {
      kAllowLazyCompilation,
      kAllowLazyCompilationWithoutContext,
      kOptimizationDisabled,
      kStrictModeFunction,
      kUsesArguments,
      kHasDuplicateParameters,
      kNative,
      kInlineBuiltin,
      kBoundFunction,
      kIsAnonymous,
      kNameShouldPrintAsAnonymous,
      kIsFunction,
      kDontCache,
      kDontFlush,
      kIsArrow,
      kIsGenerator,
      kIsConciseMethod,
      kIsAsmFunction,
      kCompilerHintsCount  // Pseudo entry
    };
  
    class FunctionKindBits : public BitField<FunctionKind, kIsArrow, 3> {};
  
    class DeoptCountBits : public BitField<int, 0, 4> {};
    class OptReenableTriesBits : public BitField<int, 4, 18> {};
    class ICAgeBits : public BitField<int, 22, 8> {};
  
    class OptCountBits : public BitField<int, 0, 22> {};
    class DisabledOptimizationReasonBits : public BitField<int, 22, 8> {};
  
   private:
  #if V8_HOST_ARCH_32_BIT
    // On 32 bit platforms, compiler hints is a smi.
    static const int kCompilerHintsSmiTagSize = kSmiTagSize;
    static const int kCompilerHintsSize = kPointerSize;
  #else
    // On 64 bit platforms, compiler hints is not a smi, see comment above.
    static const int kCompilerHintsSmiTagSize = 0;
    static const int kCompilerHintsSize = kIntSize;
  #endif
  
    STATIC_ASSERT(SharedFunctionInfo::kCompilerHintsCount <=
                  SharedFunctionInfo::kCompilerHintsSize * kBitsPerByte);
  
   public:
    // Constants for optimizing codegen for strict mode function and
    // native tests.
    // Allows to use byte-width instructions.
    static const int kStrictModeBitWithinByte =
        (kStrictModeFunction + kCompilerHintsSmiTagSize) % kBitsPerByte;
  
    static const int kNativeBitWithinByte =
        (kNative + kCompilerHintsSmiTagSize) % kBitsPerByte;
  
  #if defined(V8_TARGET_LITTLE_ENDIAN)
    static const int kStrictModeByteOffset = kCompilerHintsOffset +
        (kStrictModeFunction + kCompilerHintsSmiTagSize) / kBitsPerByte;
    static const int kNativeByteOffset = kCompilerHintsOffset +
        (kNative + kCompilerHintsSmiTagSize) / kBitsPerByte;
  #elif defined(V8_TARGET_BIG_ENDIAN)
    static const int kStrictModeByteOffset = kCompilerHintsOffset +
        (kCompilerHintsSize - 1) -
        ((kStrictModeFunction + kCompilerHintsSmiTagSize) / kBitsPerByte);
    static const int kNativeByteOffset = kCompilerHintsOffset +
        (kCompilerHintsSize - 1) -
        ((kNative + kCompilerHintsSmiTagSize) / kBitsPerByte);
  #else
  #error Unknown byte ordering
  #endif
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(SharedFunctionInfo);
  };
  
  
  // Printing support.
  struct SourceCodeOf {
    explicit SourceCodeOf(SharedFunctionInfo* v, int max = -1)
        : value(v), max_length(max) {}
    const SharedFunctionInfo* value;
    int max_length;
  };
  
  
  OStream& operator<<(OStream& os, const SourceCodeOf& v);
  
  
  class JSGeneratorObject: public JSObject {
   public:
    // [function]: The function corresponding to this generator object.
    DECL_ACCESSORS(function, JSFunction)
  
    // [context]: The context of the suspended computation.
    DECL_ACCESSORS(context, Context)
  
    // [receiver]: The receiver of the suspended computation.
    DECL_ACCESSORS(receiver, Object)
  
    // [continuation]: Offset into code of continuation.
    //
    // A positive offset indicates a suspended generator.  The special
    // kGeneratorExecuting and kGeneratorClosed values indicate that a generator
    // cannot be resumed.
    inline int continuation() const;
    inline void set_continuation(int continuation);
    inline bool is_closed();
    inline bool is_executing();
    inline bool is_suspended();
  
    // [operand_stack]: Saved operand stack.
    DECL_ACCESSORS(operand_stack, FixedArray)
  
    // [stack_handler_index]: Index of first stack handler in operand_stack, or -1
    // if the captured activation had no stack handler.
    inline int stack_handler_index() const;
    inline void set_stack_handler_index(int stack_handler_index);
  
    DECLARE_CAST(JSGeneratorObject)
  
    // Dispatched behavior.
    DECLARE_PRINTER(JSGeneratorObject)
    DECLARE_VERIFIER(JSGeneratorObject)
  
    // Magic sentinel values for the continuation.
    static const int kGeneratorExecuting = -1;
    static const int kGeneratorClosed = 0;
  
    // Layout description.
    static const int kFunctionOffset = JSObject::kHeaderSize;
    static const int kContextOffset = kFunctionOffset + kPointerSize;
    static const int kReceiverOffset = kContextOffset + kPointerSize;
    static const int kContinuationOffset = kReceiverOffset + kPointerSize;
    static const int kOperandStackOffset = kContinuationOffset + kPointerSize;
    static const int kStackHandlerIndexOffset =
        kOperandStackOffset + kPointerSize;
    static const int kSize = kStackHandlerIndexOffset + kPointerSize;
  
    // Resume mode, for use by runtime functions.
    enum ResumeMode { NEXT, THROW };
  
    // Yielding from a generator returns an object with the following inobject
    // properties.  See Context::iterator_result_map() for the map.
    static const int kResultValuePropertyIndex = 0;
    static const int kResultDonePropertyIndex = 1;
    static const int kResultPropertyCount = 2;
  
    static const int kResultValuePropertyOffset = JSObject::kHeaderSize;
    static const int kResultDonePropertyOffset =
        kResultValuePropertyOffset + kPointerSize;
    static const int kResultSize = kResultDonePropertyOffset + kPointerSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSGeneratorObject);
  };
  
  
  // Representation for module instance objects.
  class JSModule: public JSObject {
   public:
    // [context]: the context holding the module's locals, or undefined if none.
    DECL_ACCESSORS(context, Object)
  
    // [scope_info]: Scope info.
    DECL_ACCESSORS(scope_info, ScopeInfo)
  
    DECLARE_CAST(JSModule)
  
    // Dispatched behavior.
    DECLARE_PRINTER(JSModule)
    DECLARE_VERIFIER(JSModule)
  
    // Layout description.
    static const int kContextOffset = JSObject::kHeaderSize;
    static const int kScopeInfoOffset = kContextOffset + kPointerSize;
    static const int kSize = kScopeInfoOffset + kPointerSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSModule);
  };
  
  
  // JSFunction describes JavaScript functions.
  class JSFunction: public JSObject {
   public:
    // [prototype_or_initial_map]:
    DECL_ACCESSORS(prototype_or_initial_map, Object)
  
    // [shared]: The information about the function that
    // can be shared by instances.
    DECL_ACCESSORS(shared, SharedFunctionInfo)
  
    // [context]: The context for this function.
    inline Context* context();
    inline void set_context(Object* context);
    inline JSObject* global_proxy();
  
    // [code]: The generated code object for this function.  Executed
    // when the function is invoked, e.g. foo() or new foo(). See
    // [[Call]] and [[Construct]] description in ECMA-262, section
    // 8.6.2, page 27.
    inline Code* code();
    inline void set_code(Code* code);
    inline void set_code_no_write_barrier(Code* code);
    inline void ReplaceCode(Code* code);
  
    // Tells whether this function is builtin.
    inline bool IsBuiltin();
  
    // Tells whether this function is defined in a native script.
    inline bool IsFromNativeScript();
  
    // Tells whether this function is defined in an extension script.
    inline bool IsFromExtensionScript();
  
    // Tells whether or not the function needs arguments adaption.
    inline bool NeedsArgumentsAdaption();
  
    // Tells whether or not this function has been optimized.
    inline bool IsOptimized();
  
    // Tells whether or not this function can be optimized.
    inline bool IsOptimizable();
  
    // Mark this function for lazy recompilation. The function will be
    // recompiled the next time it is executed.
    void MarkForOptimization();
    void MarkForConcurrentOptimization();
    void MarkInOptimizationQueue();
  
    // Tells whether or not the function is already marked for lazy
    // recompilation.
    inline bool IsMarkedForOptimization();
    inline bool IsMarkedForConcurrentOptimization();
  
    // Tells whether or not the function is on the concurrent recompilation queue.
    inline bool IsInOptimizationQueue();
  
    // Inobject slack tracking is the way to reclaim unused inobject space.
    //
    // The instance size is initially determined by adding some slack to
    // expected_nof_properties (to allow for a few extra properties added
    // after the constructor). There is no guarantee that the extra space
    // will not be wasted.
    //
    // Here is the algorithm to reclaim the unused inobject space:
    // - Detect the first constructor call for this JSFunction.
    //   When it happens enter the "in progress" state: initialize construction
    //   counter in the initial_map and set the |done_inobject_slack_tracking|
    //   flag.
    // - While the tracking is in progress create objects filled with
    //   one_pointer_filler_map instead of undefined_value. This way they can be
    //   resized quickly and safely.
    // - Once enough (kGenerousAllocationCount) objects have been created
    //   compute the 'slack' (traverse the map transition tree starting from the
    //   initial_map and find the lowest value of unused_property_fields).
    // - Traverse the transition tree again and decrease the instance size
    //   of every map. Existing objects will resize automatically (they are
    //   filled with one_pointer_filler_map). All further allocations will
    //   use the adjusted instance size.
    // - SharedFunctionInfo's expected_nof_properties left unmodified since
    //   allocations made using different closures could actually create different
    //   kind of objects (see prototype inheritance pattern).
    //
    //  Important: inobject slack tracking is not attempted during the snapshot
    //  creation.
  
    static const int kGenerousAllocationCount = Map::ConstructionCount::kMax;
    static const int kFinishSlackTracking     = 1;
    static const int kNoSlackTracking         = 0;
  
    // True if the initial_map is set and the object constructions countdown
    // counter is not zero.
    inline bool IsInobjectSlackTrackingInProgress();
  
    // Starts the tracking.
    // Initializes object constructions countdown counter in the initial map.
    // IsInobjectSlackTrackingInProgress is normally true after this call,
    // except when tracking have not been started (e.g. the map has no unused
    // properties or the snapshot is being built).
    void StartInobjectSlackTracking();
  
    // Completes the tracking.
    // IsInobjectSlackTrackingInProgress is false after this call.
    void CompleteInobjectSlackTracking();
  
    // [literals_or_bindings]: Fixed array holding either
    // the materialized literals or the bindings of a bound function.
    //
    // If the function contains object, regexp or array literals, the
    // literals array prefix contains the object, regexp, and array
    // function to be used when creating these literals.  This is
    // necessary so that we do not dynamically lookup the object, regexp
    // or array functions.  Performing a dynamic lookup, we might end up
    // using the functions from a new context that we should not have
    // access to.
    //
    // On bound functions, the array is a (copy-on-write) fixed-array containing
    // the function that was bound, bound this-value and any bound
    // arguments. Bound functions never contain literals.
    DECL_ACCESSORS(literals_or_bindings, FixedArray)
  
    inline FixedArray* literals();
    inline void set_literals(FixedArray* literals);
  
    inline FixedArray* function_bindings();
    inline void set_function_bindings(FixedArray* bindings);
  
    // The initial map for an object created by this constructor.
    inline Map* initial_map();
    static void SetInitialMap(Handle<JSFunction> function, Handle<Map> map,
                              Handle<Object> prototype);
    inline bool has_initial_map();
    static void EnsureHasInitialMap(Handle<JSFunction> function);
  
    // Get and set the prototype property on a JSFunction. If the
    // function has an initial map the prototype is set on the initial
    // map. Otherwise, the prototype is put in the initial map field
    // until an initial map is needed.
    inline bool has_prototype();
    inline bool has_instance_prototype();
    inline Object* prototype();
    inline Object* instance_prototype();
    static void SetPrototype(Handle<JSFunction> function,
                             Handle<Object> value);
    static void SetInstancePrototype(Handle<JSFunction> function,
                                     Handle<Object> value);
  
    // Creates a new closure for the fucntion with the same bindings,
    // bound values, and prototype. An equivalent of spec operations
    // ``CloneMethod`` and ``CloneBoundFunction``.
    static Handle<JSFunction> CloneClosure(Handle<JSFunction> function);
  
    // After prototype is removed, it will not be created when accessed, and
    // [[Construct]] from this function will not be allowed.
    bool RemovePrototype();
    inline bool should_have_prototype();
  
    // Accessor for this function's initial map's [[class]]
    // property. This is primarily used by ECMA native functions.  This
    // method sets the class_name field of this function's initial map
    // to a given value. It creates an initial map if this function does
    // not have one. Note that this method does not copy the initial map
    // if it has one already, but simply replaces it with the new value.
    // Instances created afterwards will have a map whose [[class]] is
    // set to 'value', but there is no guarantees on instances created
    // before.
    void SetInstanceClassName(String* name);
  
    // Returns if this function has been compiled to native code yet.
    inline bool is_compiled();
  
    // [next_function_link]: Links functions into various lists, e.g. the list
    // of optimized functions hanging off the native_context. The CodeFlusher
    // uses this link to chain together flushing candidates. Treated weakly
    // by the garbage collector.
    DECL_ACCESSORS(next_function_link, Object)
  
    // Prints the name of the function using PrintF.
    void PrintName(FILE* out = stdout);
  
    DECLARE_CAST(JSFunction)
  
    // Iterates the objects, including code objects indirectly referenced
    // through pointers to the first instruction in the code object.
    void JSFunctionIterateBody(int object_size, ObjectVisitor* v);
  
    // Dispatched behavior.
    DECLARE_PRINTER(JSFunction)
    DECLARE_VERIFIER(JSFunction)
  
    // Returns the number of allocated literals.
    inline int NumberOfLiterals();
  
    // Retrieve the native context from a function's literal array.
    static Context* NativeContextFromLiterals(FixedArray* literals);
  
    // Used for flags such as --hydrogen-filter.
    bool PassesFilter(const char* raw_filter);
  
    // Layout descriptors. The last property (from kNonWeakFieldsEndOffset to
    // kSize) is weak and has special handling during garbage collection.
    static const int kCodeEntryOffset = JSObject::kHeaderSize;
    static const int kPrototypeOrInitialMapOffset =
        kCodeEntryOffset + kPointerSize;
    static const int kSharedFunctionInfoOffset =
        kPrototypeOrInitialMapOffset + kPointerSize;
    static const int kContextOffset = kSharedFunctionInfoOffset + kPointerSize;
    static const int kLiteralsOffset = kContextOffset + kPointerSize;
    static const int kNonWeakFieldsEndOffset = kLiteralsOffset + kPointerSize;
    static const int kNextFunctionLinkOffset = kNonWeakFieldsEndOffset;
    static const int kSize = kNextFunctionLinkOffset + kPointerSize;
  
    // Layout of the literals array.
    static const int kLiteralsPrefixSize = 1;
    static const int kLiteralNativeContextIndex = 0;
  
    // Layout of the bound-function binding array.
    static const int kBoundFunctionIndex = 0;
    static const int kBoundThisIndex = 1;
    static const int kBoundArgumentsStartIndex = 2;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSFunction);
  };
  
  
  // JSGlobalProxy's prototype must be a JSGlobalObject or null,
  // and the prototype is hidden. JSGlobalProxy always delegates
  // property accesses to its prototype if the prototype is not null.
  //
  // A JSGlobalProxy can be reinitialized which will preserve its identity.
  //
  // Accessing a JSGlobalProxy requires security check.
  
  class JSGlobalProxy : public JSObject {
   public:
    // [native_context]: the owner native context of this global proxy object.
    // It is null value if this object is not used by any context.
    DECL_ACCESSORS(native_context, Object)
  
    // [hash]: The hash code property (undefined if not initialized yet).
    DECL_ACCESSORS(hash, Object)
  
    DECLARE_CAST(JSGlobalProxy)
  
    inline bool IsDetachedFrom(GlobalObject* global) const;
  
    // Dispatched behavior.
    DECLARE_PRINTER(JSGlobalProxy)
    DECLARE_VERIFIER(JSGlobalProxy)
  
    // Layout description.
    static const int kNativeContextOffset = JSObject::kHeaderSize;
    static const int kHashOffset = kNativeContextOffset + kPointerSize;
    static const int kSize = kHashOffset + kPointerSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSGlobalProxy);
  };
  
  
  // Forward declaration.
  class JSBuiltinsObject;
  
  // Common super class for JavaScript global objects and the special
  // builtins global objects.
  class GlobalObject: public JSObject {
   public:
    // [builtins]: the object holding the runtime routines written in JS.
    DECL_ACCESSORS(builtins, JSBuiltinsObject)
  
    // [native context]: the natives corresponding to this global object.
    DECL_ACCESSORS(native_context, Context)
  
    // [global context]: the most recent (i.e. innermost) global context.
    DECL_ACCESSORS(global_context, Context)
  
    // [global proxy]: the global proxy object of the context
    DECL_ACCESSORS(global_proxy, JSObject)
  
    DECLARE_CAST(GlobalObject)
  
    // Layout description.
    static const int kBuiltinsOffset = JSObject::kHeaderSize;
    static const int kNativeContextOffset = kBuiltinsOffset + kPointerSize;
    static const int kGlobalContextOffset = kNativeContextOffset + kPointerSize;
    static const int kGlobalProxyOffset = kGlobalContextOffset + kPointerSize;
    static const int kHeaderSize = kGlobalProxyOffset + kPointerSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(GlobalObject);
  };
  
  
  // JavaScript global object.
  class JSGlobalObject: public GlobalObject {
   public:
    DECLARE_CAST(JSGlobalObject)
  
    // Ensure that the global object has a cell for the given property name.
    static Handle<PropertyCell> EnsurePropertyCell(Handle<JSGlobalObject> global,
                                                   Handle<Name> name);
  
    inline bool IsDetached();
  
    // Dispatched behavior.
    DECLARE_PRINTER(JSGlobalObject)
    DECLARE_VERIFIER(JSGlobalObject)
  
    // Layout description.
    static const int kSize = GlobalObject::kHeaderSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSGlobalObject);
  };
  
  
  // Builtins global object which holds the runtime routines written in
  // JavaScript.
  class JSBuiltinsObject: public GlobalObject {
   public:
    // Accessors for the runtime routines written in JavaScript.
    inline Object* javascript_builtin(Builtins::JavaScript id);
    inline void set_javascript_builtin(Builtins::JavaScript id, Object* value);
  
    // Accessors for code of the runtime routines written in JavaScript.
    inline Code* javascript_builtin_code(Builtins::JavaScript id);
    inline void set_javascript_builtin_code(Builtins::JavaScript id, Code* value);
  
    DECLARE_CAST(JSBuiltinsObject)
  
    // Dispatched behavior.
    DECLARE_PRINTER(JSBuiltinsObject)
    DECLARE_VERIFIER(JSBuiltinsObject)
  
    // Layout description.  The size of the builtins object includes
    // room for two pointers per runtime routine written in javascript
    // (function and code object).
    static const int kJSBuiltinsCount = Builtins::id_count;
    static const int kJSBuiltinsOffset = GlobalObject::kHeaderSize;
    static const int kJSBuiltinsCodeOffset =
        GlobalObject::kHeaderSize + (kJSBuiltinsCount * kPointerSize);
    static const int kSize =
        kJSBuiltinsCodeOffset + (kJSBuiltinsCount * kPointerSize);
  
    static int OffsetOfFunctionWithId(Builtins::JavaScript id) {
      return kJSBuiltinsOffset + id * kPointerSize;
    }
  
    static int OffsetOfCodeWithId(Builtins::JavaScript id) {
      return kJSBuiltinsCodeOffset + id * kPointerSize;
    }
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSBuiltinsObject);
  };
  
  
  // Representation for JS Wrapper objects, String, Number, Boolean, etc.
  class JSValue: public JSObject {
   public:
    // [value]: the object being wrapped.
    DECL_ACCESSORS(value, Object)
  
    DECLARE_CAST(JSValue)
  
    // Dispatched behavior.
    DECLARE_PRINTER(JSValue)
    DECLARE_VERIFIER(JSValue)
  
    // Layout description.
    static const int kValueOffset = JSObject::kHeaderSize;
    static const int kSize = kValueOffset + kPointerSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSValue);
  };
  
  
  class DateCache;
  
  // Representation for JS date objects.
  class JSDate: public JSObject {
   public:
    // If one component is NaN, all of them are, indicating a NaN time value.
    // [value]: the time value.
    DECL_ACCESSORS(value, Object)
    // [year]: caches year. Either undefined, smi, or NaN.
    DECL_ACCESSORS(year, Object)
    // [month]: caches month. Either undefined, smi, or NaN.
    DECL_ACCESSORS(month, Object)
    // [day]: caches day. Either undefined, smi, or NaN.
    DECL_ACCESSORS(day, Object)
    // [weekday]: caches day of week. Either undefined, smi, or NaN.
    DECL_ACCESSORS(weekday, Object)
    // [hour]: caches hours. Either undefined, smi, or NaN.
    DECL_ACCESSORS(hour, Object)
    // [min]: caches minutes. Either undefined, smi, or NaN.
    DECL_ACCESSORS(min, Object)
    // [sec]: caches seconds. Either undefined, smi, or NaN.
    DECL_ACCESSORS(sec, Object)
    // [cache stamp]: sample of the date cache stamp at the
    // moment when chached fields were cached.
    DECL_ACCESSORS(cache_stamp, Object)
  
    DECLARE_CAST(JSDate)
  
    // Returns the date field with the specified index.
    // See FieldIndex for the list of date fields.
    static Object* GetField(Object* date, Smi* index);
  
    void SetValue(Object* value, bool is_value_nan);
  
  
    // Dispatched behavior.
    DECLARE_PRINTER(JSDate)
    DECLARE_VERIFIER(JSDate)
  
    // The order is important. It must be kept in sync with date macros
    // in macros.py.
    enum FieldIndex {
      kDateValue,
      kYear,
      kMonth,
      kDay,
      kWeekday,
      kHour,
      kMinute,
      kSecond,
      kFirstUncachedField,
      kMillisecond = kFirstUncachedField,
      kDays,
      kTimeInDay,
      kFirstUTCField,
      kYearUTC = kFirstUTCField,
      kMonthUTC,
      kDayUTC,
      kWeekdayUTC,
      kHourUTC,
      kMinuteUTC,
      kSecondUTC,
      kMillisecondUTC,
      kDaysUTC,
      kTimeInDayUTC,
      kTimezoneOffset
    };
  
    // Layout description.
    static const int kValueOffset = JSObject::kHeaderSize;
    static const int kYearOffset = kValueOffset + kPointerSize;
    static const int kMonthOffset = kYearOffset + kPointerSize;
    static const int kDayOffset = kMonthOffset + kPointerSize;
    static const int kWeekdayOffset = kDayOffset + kPointerSize;
    static const int kHourOffset = kWeekdayOffset  + kPointerSize;
    static const int kMinOffset = kHourOffset + kPointerSize;
    static const int kSecOffset = kMinOffset + kPointerSize;
    static const int kCacheStampOffset = kSecOffset + kPointerSize;
    static const int kSize = kCacheStampOffset + kPointerSize;
  
   private:
    inline Object* DoGetField(FieldIndex index);
  
    Object* GetUTCField(FieldIndex index, double value, DateCache* date_cache);
  
    // Computes and caches the cacheable fields of the date.
    inline void SetCachedFields(int64_t local_time_ms, DateCache* date_cache);
  
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSDate);
  };
  
  
  // Representation of message objects used for error reporting through
  // the API. The messages are formatted in JavaScript so this object is
  // a real JavaScript object. The information used for formatting the
  // error messages are not directly accessible from JavaScript to
  // prevent leaking information to user code called during error
  // formatting.
  class JSMessageObject: public JSObject {
   public:
    // [type]: the type of error message.
    DECL_ACCESSORS(type, String)
  
    // [arguments]: the arguments for formatting the error message.
    DECL_ACCESSORS(arguments, JSArray)
  
    // [script]: the script from which the error message originated.
    DECL_ACCESSORS(script, Object)
  
    // [stack_frames]: an array of stack frames for this error object.
    DECL_ACCESSORS(stack_frames, Object)
  
    // [start_position]: the start position in the script for the error message.
    inline int start_position() const;
    inline void set_start_position(int value);
  
    // [end_position]: the end position in the script for the error message.
    inline int end_position() const;
    inline void set_end_position(int value);
  
    DECLARE_CAST(JSMessageObject)
  
    // Dispatched behavior.
    DECLARE_PRINTER(JSMessageObject)
    DECLARE_VERIFIER(JSMessageObject)
  
    // Layout description.
    static const int kTypeOffset = JSObject::kHeaderSize;
    static const int kArgumentsOffset = kTypeOffset + kPointerSize;
    static const int kScriptOffset = kArgumentsOffset + kPointerSize;
    static const int kStackFramesOffset = kScriptOffset + kPointerSize;
    static const int kStartPositionOffset = kStackFramesOffset + kPointerSize;
    static const int kEndPositionOffset = kStartPositionOffset + kPointerSize;
    static const int kSize = kEndPositionOffset + kPointerSize;
  
    typedef FixedBodyDescriptor<HeapObject::kMapOffset,
                                kStackFramesOffset + kPointerSize,
                                kSize> BodyDescriptor;
  };
  
  
  // Regular expressions
  // The regular expression holds a single reference to a FixedArray in
  // the kDataOffset field.
  // The FixedArray contains the following data:
  // - tag : type of regexp implementation (not compiled yet, atom or irregexp)
  // - reference to the original source string
  // - reference to the original flag string
  // If it is an atom regexp
  // - a reference to a literal string to search for
  // If it is an irregexp regexp:
  // - a reference to code for Latin1 inputs (bytecode or compiled), or a smi
  // used for tracking the last usage (used for code flushing).
  // - a reference to code for UC16 inputs (bytecode or compiled), or a smi
  // used for tracking the last usage (used for code flushing)..
  // - max number of registers used by irregexp implementations.
  // - number of capture registers (output values) of the regexp.
  class JSRegExp: public JSObject {
   public:
    // Meaning of Type:
    // NOT_COMPILED: Initial value. No data has been stored in the JSRegExp yet.
    // ATOM: A simple string to match against using an indexOf operation.
    // IRREGEXP: Compiled with Irregexp.
    // IRREGEXP_NATIVE: Compiled to native code with Irregexp.
    enum Type { NOT_COMPILED, ATOM, IRREGEXP };
    enum Flag {
      NONE = 0,
      GLOBAL = 1,
      IGNORE_CASE = 2,
      MULTILINE = 4,
      STICKY = 8
    };
  
    class Flags {
     public:
      explicit Flags(uint32_t value) : value_(value) { }
      bool is_global() { return (value_ & GLOBAL) != 0; }
      bool is_ignore_case() { return (value_ & IGNORE_CASE) != 0; }
      bool is_multiline() { return (value_ & MULTILINE) != 0; }
      bool is_sticky() { return (value_ & STICKY) != 0; }
      uint32_t value() { return value_; }
     private:
      uint32_t value_;
    };
  
    DECL_ACCESSORS(data, Object)
  
    inline Type TypeTag();
    inline int CaptureCount();
    inline Flags GetFlags();
    inline String* Pattern();
    inline Object* DataAt(int index);
    // Set implementation data after the object has been prepared.
    inline void SetDataAt(int index, Object* value);
  
    static int code_index(bool is_latin1) {
      if (is_latin1) {
        return kIrregexpLatin1CodeIndex;
      } else {
        return kIrregexpUC16CodeIndex;
      }
    }
  
    static int saved_code_index(bool is_latin1) {
      if (is_latin1) {
        return kIrregexpLatin1CodeSavedIndex;
      } else {
        return kIrregexpUC16CodeSavedIndex;
      }
    }
  
    DECLARE_CAST(JSRegExp)
  
    // Dispatched behavior.
    DECLARE_VERIFIER(JSRegExp)
  
    static const int kDataOffset = JSObject::kHeaderSize;
    static const int kSize = kDataOffset + kPointerSize;
  
    // Indices in the data array.
    static const int kTagIndex = 0;
    static const int kSourceIndex = kTagIndex + 1;
    static const int kFlagsIndex = kSourceIndex + 1;
    static const int kDataIndex = kFlagsIndex + 1;
    // The data fields are used in different ways depending on the
    // value of the tag.
    // Atom regexps (literal strings).
    static const int kAtomPatternIndex = kDataIndex;
  
    static const int kAtomDataSize = kAtomPatternIndex + 1;
  
    // Irregexp compiled code or bytecode for Latin1. If compilation
    // fails, this fields hold an exception object that should be
    // thrown if the regexp is used again.
    static const int kIrregexpLatin1CodeIndex = kDataIndex;
    // Irregexp compiled code or bytecode for UC16.  If compilation
    // fails, this fields hold an exception object that should be
    // thrown if the regexp is used again.
    static const int kIrregexpUC16CodeIndex = kDataIndex + 1;
  
    // Saved instance of Irregexp compiled code or bytecode for Latin1 that
    // is a potential candidate for flushing.
    static const int kIrregexpLatin1CodeSavedIndex = kDataIndex + 2;
    // Saved instance of Irregexp compiled code or bytecode for UC16 that is
    // a potential candidate for flushing.
    static const int kIrregexpUC16CodeSavedIndex = kDataIndex + 3;
  
    // Maximal number of registers used by either Latin1 or UC16.
    // Only used to check that there is enough stack space
    static const int kIrregexpMaxRegisterCountIndex = kDataIndex + 4;
    // Number of captures in the compiled regexp.
    static const int kIrregexpCaptureCountIndex = kDataIndex + 5;
  
    static const int kIrregexpDataSize = kIrregexpCaptureCountIndex + 1;
  
    // Offsets directly into the data fixed array.
    static const int kDataTagOffset =
        FixedArray::kHeaderSize + kTagIndex * kPointerSize;
    static const int kDataOneByteCodeOffset =
        FixedArray::kHeaderSize + kIrregexpLatin1CodeIndex * kPointerSize;
    static const int kDataUC16CodeOffset =
        FixedArray::kHeaderSize + kIrregexpUC16CodeIndex * kPointerSize;
    static const int kIrregexpCaptureCountOffset =
        FixedArray::kHeaderSize + kIrregexpCaptureCountIndex * kPointerSize;
  
    // In-object fields.
    static const int kSourceFieldIndex = 0;
    static const int kGlobalFieldIndex = 1;
    static const int kIgnoreCaseFieldIndex = 2;
    static const int kMultilineFieldIndex = 3;
    static const int kLastIndexFieldIndex = 4;
    static const int kInObjectFieldCount = 5;
  
    // The uninitialized value for a regexp code object.
    static const int kUninitializedValue = -1;
  
    // The compilation error value for the regexp code object. The real error
    // object is in the saved code field.
    static const int kCompilationErrorValue = -2;
  
    // When we store the sweep generation at which we moved the code from the
    // code index to the saved code index we mask it of to be in the [0:255]
    // range.
    static const int kCodeAgeMask = 0xff;
  };
  
  
  class CompilationCacheShape : public BaseShape<HashTableKey*> {
   public:
    static inline bool IsMatch(HashTableKey* key, Object* value) {
      return key->IsMatch(value);
    }
  
    static inline uint32_t Hash(HashTableKey* key) {
      return key->Hash();
    }
  
    static inline uint32_t HashForObject(HashTableKey* key, Object* object) {
      return key->HashForObject(object);
    }
  
    static inline Handle<Object> AsHandle(Isolate* isolate, HashTableKey* key);
  
    static const int kPrefixSize = 0;
    static const int kEntrySize = 2;
  };
  
  
  class CompilationCacheTable: public HashTable<CompilationCacheTable,
                                                CompilationCacheShape,
                                                HashTableKey*> {
   public:
    // Find cached value for a string key, otherwise return null.
    Handle<Object> Lookup(Handle<String> src, Handle<Context> context);
    Handle<Object> LookupEval(Handle<String> src,
                              Handle<SharedFunctionInfo> shared,
                              StrictMode strict_mode, int scope_position);
    Handle<Object> LookupRegExp(Handle<String> source, JSRegExp::Flags flags);
    static Handle<CompilationCacheTable> Put(
        Handle<CompilationCacheTable> cache, Handle<String> src,
        Handle<Context> context, Handle<Object> value);
    static Handle<CompilationCacheTable> PutEval(
        Handle<CompilationCacheTable> cache, Handle<String> src,
        Handle<SharedFunctionInfo> context, Handle<SharedFunctionInfo> value,
        int scope_position);
    static Handle<CompilationCacheTable> PutRegExp(
        Handle<CompilationCacheTable> cache, Handle<String> src,
        JSRegExp::Flags flags, Handle<FixedArray> value);
    void Remove(Object* value);
  
    DECLARE_CAST(CompilationCacheTable)
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(CompilationCacheTable);
  };
  
  
  class CodeCache: public Struct {
   public:
    DECL_ACCESSORS(default_cache, FixedArray)
    DECL_ACCESSORS(normal_type_cache, Object)
  
    // Add the code object to the cache.
    static void Update(
        Handle<CodeCache> cache, Handle<Name> name, Handle<Code> code);
  
    // Lookup code object in the cache. Returns code object if found and undefined
    // if not.
    Object* Lookup(Name* name, Code::Flags flags);
  
    // Get the internal index of a code object in the cache. Returns -1 if the
    // code object is not in that cache. This index can be used to later call
    // RemoveByIndex. The cache cannot be modified between a call to GetIndex and
    // RemoveByIndex.
    int GetIndex(Object* name, Code* code);
  
    // Remove an object from the cache with the provided internal index.
    void RemoveByIndex(Object* name, Code* code, int index);
  
    DECLARE_CAST(CodeCache)
  
    // Dispatched behavior.
    DECLARE_PRINTER(CodeCache)
    DECLARE_VERIFIER(CodeCache)
  
    static const int kDefaultCacheOffset = HeapObject::kHeaderSize;
    static const int kNormalTypeCacheOffset =
        kDefaultCacheOffset + kPointerSize;
    static const int kSize = kNormalTypeCacheOffset + kPointerSize;
  
   private:
    static void UpdateDefaultCache(
        Handle<CodeCache> code_cache, Handle<Name> name, Handle<Code> code);
    static void UpdateNormalTypeCache(
        Handle<CodeCache> code_cache, Handle<Name> name, Handle<Code> code);
    Object* LookupDefaultCache(Name* name, Code::Flags flags);
    Object* LookupNormalTypeCache(Name* name, Code::Flags flags);
  
    // Code cache layout of the default cache. Elements are alternating name and
    // code objects for non normal load/store/call IC's.
    static const int kCodeCacheEntrySize = 2;
    static const int kCodeCacheEntryNameOffset = 0;
    static const int kCodeCacheEntryCodeOffset = 1;
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(CodeCache);
  };
  
  
  class CodeCacheHashTableShape : public BaseShape<HashTableKey*> {
   public:
    static inline bool IsMatch(HashTableKey* key, Object* value) {
      return key->IsMatch(value);
    }
  
    static inline uint32_t Hash(HashTableKey* key) {
      return key->Hash();
    }
  
    static inline uint32_t HashForObject(HashTableKey* key, Object* object) {
      return key->HashForObject(object);
    }
  
    static inline Handle<Object> AsHandle(Isolate* isolate, HashTableKey* key);
  
    static const int kPrefixSize = 0;
    static const int kEntrySize = 2;
  };
  
  
  class CodeCacheHashTable: public HashTable<CodeCacheHashTable,
                                             CodeCacheHashTableShape,
                                             HashTableKey*> {
   public:
    Object* Lookup(Name* name, Code::Flags flags);
    static Handle<CodeCacheHashTable> Put(
        Handle<CodeCacheHashTable> table,
        Handle<Name> name,
        Handle<Code> code);
  
    int GetIndex(Name* name, Code::Flags flags);
    void RemoveByIndex(int index);
  
    DECLARE_CAST(CodeCacheHashTable)
  
    // Initial size of the fixed array backing the hash table.
    static const int kInitialSize = 64;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(CodeCacheHashTable);
  };
  
  
  class PolymorphicCodeCache: public Struct {
   public:
    DECL_ACCESSORS(cache, Object)
  
    static void Update(Handle<PolymorphicCodeCache> cache,
                       MapHandleList* maps,
                       Code::Flags flags,
                       Handle<Code> code);
  
  
    // Returns an undefined value if the entry is not found.
    Handle<Object> Lookup(MapHandleList* maps, Code::Flags flags);
  
    DECLARE_CAST(PolymorphicCodeCache)
  
    // Dispatched behavior.
    DECLARE_PRINTER(PolymorphicCodeCache)
    DECLARE_VERIFIER(PolymorphicCodeCache)
  
    static const int kCacheOffset = HeapObject::kHeaderSize;
    static const int kSize = kCacheOffset + kPointerSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(PolymorphicCodeCache);
  };
  
  
  class PolymorphicCodeCacheHashTable
      : public HashTable<PolymorphicCodeCacheHashTable,
                         CodeCacheHashTableShape,
                         HashTableKey*> {
   public:
    Object* Lookup(MapHandleList* maps, int code_kind);
  
    static Handle<PolymorphicCodeCacheHashTable> Put(
        Handle<PolymorphicCodeCacheHashTable> hash_table,
        MapHandleList* maps,
        int code_kind,
        Handle<Code> code);
  
    DECLARE_CAST(PolymorphicCodeCacheHashTable)
  
    static const int kInitialSize = 64;
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(PolymorphicCodeCacheHashTable);
  };
  
  
  class TypeFeedbackInfo: public Struct {
   public:
    inline int ic_total_count();
    inline void set_ic_total_count(int count);
  
    inline int ic_with_type_info_count();
    inline void change_ic_with_type_info_count(int delta);
  
    inline int ic_generic_count();
    inline void change_ic_generic_count(int delta);
  
    inline void initialize_storage();
  
    inline void change_own_type_change_checksum();
    inline int own_type_change_checksum();
  
    inline void set_inlined_type_change_checksum(int checksum);
    inline bool matches_inlined_type_change_checksum(int checksum);
  
  
    DECLARE_CAST(TypeFeedbackInfo)
  
    // Dispatched behavior.
    DECLARE_PRINTER(TypeFeedbackInfo)
    DECLARE_VERIFIER(TypeFeedbackInfo)
  
    static const int kStorage1Offset = HeapObject::kHeaderSize;
    static const int kStorage2Offset = kStorage1Offset + kPointerSize;
    static const int kStorage3Offset = kStorage2Offset + kPointerSize;
    static const int kSize = kStorage3Offset + kPointerSize;
  
   private:
    static const int kTypeChangeChecksumBits = 7;
  
    class ICTotalCountField: public BitField<int, 0,
        kSmiValueSize - kTypeChangeChecksumBits> {};  // NOLINT
    class OwnTypeChangeChecksum: public BitField<int,
        kSmiValueSize - kTypeChangeChecksumBits,
        kTypeChangeChecksumBits> {};  // NOLINT
    class ICsWithTypeInfoCountField: public BitField<int, 0,
        kSmiValueSize - kTypeChangeChecksumBits> {};  // NOLINT
    class InlinedTypeChangeChecksum: public BitField<int,
        kSmiValueSize - kTypeChangeChecksumBits,
        kTypeChangeChecksumBits> {};  // NOLINT
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(TypeFeedbackInfo);
  };
  
  
  enum AllocationSiteMode {
    DONT_TRACK_ALLOCATION_SITE,
    TRACK_ALLOCATION_SITE,
    LAST_ALLOCATION_SITE_MODE = TRACK_ALLOCATION_SITE
  };
  
  
  class AllocationSite: public Struct {
   public:
    static const uint32_t kMaximumArrayBytesToPretransition = 8 * 1024;
    static const double kPretenureRatio;
    static const int kPretenureMinimumCreated = 100;
  
    // Values for pretenure decision field.
    enum PretenureDecision {
      kUndecided = 0,
      kDontTenure = 1,
      kMaybeTenure = 2,
      kTenure = 3,
      kZombie = 4,
      kLastPretenureDecisionValue = kZombie
    };
  
    const char* PretenureDecisionName(PretenureDecision decision);
  
    DECL_ACCESSORS(transition_info, Object)
    // nested_site threads a list of sites that represent nested literals
    // walked in a particular order. So [[1, 2], 1, 2] will have one
    // nested_site, but [[1, 2], 3, [4]] will have a list of two.
    DECL_ACCESSORS(nested_site, Object)
    DECL_ACCESSORS(pretenure_data, Smi)
    DECL_ACCESSORS(pretenure_create_count, Smi)
    DECL_ACCESSORS(dependent_code, DependentCode)
    DECL_ACCESSORS(weak_next, Object)
  
    inline void Initialize();
  
    // This method is expensive, it should only be called for reporting.
    bool IsNestedSite();
  
    // transition_info bitfields, for constructed array transition info.
    class ElementsKindBits:       public BitField<ElementsKind, 0,  15> {};
    class UnusedBits:             public BitField<int,          15, 14> {};
    class DoNotInlineBit:         public BitField<bool,         29,  1> {};
  
    // Bitfields for pretenure_data
    class MementoFoundCountBits:  public BitField<int,               0, 26> {};
    class PretenureDecisionBits:  public BitField<PretenureDecision, 26, 3> {};
    class DeoptDependentCodeBit:  public BitField<bool,              29, 1> {};
    STATIC_ASSERT(PretenureDecisionBits::kMax >= kLastPretenureDecisionValue);
  
    // Increments the mementos found counter and returns true when the first
    // memento was found for a given allocation site.
    inline bool IncrementMementoFoundCount();
  
    inline void IncrementMementoCreateCount();
  
    PretenureFlag GetPretenureMode();
  
    void ResetPretenureDecision();
  
    PretenureDecision pretenure_decision() {
      int value = pretenure_data()->value();
      return PretenureDecisionBits::decode(value);
    }
  
    void set_pretenure_decision(PretenureDecision decision) {
      int value = pretenure_data()->value();
      set_pretenure_data(
          Smi::FromInt(PretenureDecisionBits::update(value, decision)),
          SKIP_WRITE_BARRIER);
    }
  
    bool deopt_dependent_code() {
      int value = pretenure_data()->value();
      return DeoptDependentCodeBit::decode(value);
    }
  
    void set_deopt_dependent_code(bool deopt) {
      int value = pretenure_data()->value();
      set_pretenure_data(
          Smi::FromInt(DeoptDependentCodeBit::update(value, deopt)),
          SKIP_WRITE_BARRIER);
    }
  
    int memento_found_count() {
      int value = pretenure_data()->value();
      return MementoFoundCountBits::decode(value);
    }
  
    inline void set_memento_found_count(int count);
  
    int memento_create_count() {
      return pretenure_create_count()->value();
    }
  
    void set_memento_create_count(int count) {
      set_pretenure_create_count(Smi::FromInt(count), SKIP_WRITE_BARRIER);
    }
  
    // The pretenuring decision is made during gc, and the zombie state allows
    // us to recognize when an allocation site is just being kept alive because
    // a later traversal of new space may discover AllocationMementos that point
    // to this AllocationSite.
    bool IsZombie() {
      return pretenure_decision() == kZombie;
    }
  
    bool IsMaybeTenure() {
      return pretenure_decision() == kMaybeTenure;
    }
  
    inline void MarkZombie();
  
    inline bool MakePretenureDecision(PretenureDecision current_decision,
                                      double ratio,
                                      bool maximum_size_scavenge);
  
    inline bool DigestPretenuringFeedback(bool maximum_size_scavenge);
  
    ElementsKind GetElementsKind() {
      DCHECK(!SitePointsToLiteral());
      int value = Smi::cast(transition_info())->value();
      return ElementsKindBits::decode(value);
    }
  
    void SetElementsKind(ElementsKind kind) {
      int value = Smi::cast(transition_info())->value();
      set_transition_info(Smi::FromInt(ElementsKindBits::update(value, kind)),
                          SKIP_WRITE_BARRIER);
    }
  
    bool CanInlineCall() {
      int value = Smi::cast(transition_info())->value();
      return DoNotInlineBit::decode(value) == 0;
    }
  
    void SetDoNotInlineCall() {
      int value = Smi::cast(transition_info())->value();
      set_transition_info(Smi::FromInt(DoNotInlineBit::update(value, true)),
                          SKIP_WRITE_BARRIER);
    }
  
    bool SitePointsToLiteral() {
      // If transition_info is a smi, then it represents an ElementsKind
      // for a constructed array. Otherwise, it must be a boilerplate
      // for an object or array literal.
      return transition_info()->IsJSArray() || transition_info()->IsJSObject();
    }
  
    static void DigestTransitionFeedback(Handle<AllocationSite> site,
                                         ElementsKind to_kind);
  
    enum Reason {
      TENURING,
      TRANSITIONS
    };
  
    static void AddDependentCompilationInfo(Handle<AllocationSite> site,
                                            Reason reason,
                                            CompilationInfo* info);
  
    DECLARE_PRINTER(AllocationSite)
    DECLARE_VERIFIER(AllocationSite)
  
    DECLARE_CAST(AllocationSite)
    static inline AllocationSiteMode GetMode(
        ElementsKind boilerplate_elements_kind);
    static inline AllocationSiteMode GetMode(ElementsKind from, ElementsKind to);
    static inline bool CanTrack(InstanceType type);
  
    static const int kTransitionInfoOffset = HeapObject::kHeaderSize;
    static const int kNestedSiteOffset = kTransitionInfoOffset + kPointerSize;
    static const int kPretenureDataOffset = kNestedSiteOffset + kPointerSize;
    static const int kPretenureCreateCountOffset =
        kPretenureDataOffset + kPointerSize;
    static const int kDependentCodeOffset =
        kPretenureCreateCountOffset + kPointerSize;
    static const int kWeakNextOffset = kDependentCodeOffset + kPointerSize;
    static const int kSize = kWeakNextOffset + kPointerSize;
  
    // During mark compact we need to take special care for the dependent code
    // field.
    static const int kPointerFieldsBeginOffset = kTransitionInfoOffset;
    static const int kPointerFieldsEndOffset = kDependentCodeOffset;
  
    // For other visitors, use the fixed body descriptor below.
    typedef FixedBodyDescriptor<HeapObject::kHeaderSize,
                                kDependentCodeOffset + kPointerSize,
                                kSize> BodyDescriptor;
  
   private:
    inline DependentCode::DependencyGroup ToDependencyGroup(Reason reason);
    bool PretenuringDecisionMade() {
      return pretenure_decision() != kUndecided;
    }
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(AllocationSite);
  };
  
  
  class AllocationMemento: public Struct {
   public:
    static const int kAllocationSiteOffset = HeapObject::kHeaderSize;
    static const int kSize = kAllocationSiteOffset + kPointerSize;
  
    DECL_ACCESSORS(allocation_site, Object)
  
    bool IsValid() {
      return allocation_site()->IsAllocationSite() &&
          !AllocationSite::cast(allocation_site())->IsZombie();
    }
    AllocationSite* GetAllocationSite() {
      DCHECK(IsValid());
      return AllocationSite::cast(allocation_site());
    }
  
    DECLARE_PRINTER(AllocationMemento)
    DECLARE_VERIFIER(AllocationMemento)
  
    DECLARE_CAST(AllocationMemento)
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(AllocationMemento);
  };
  
  
  // Representation of a slow alias as part of a sloppy arguments objects.
  // For fast aliases (if HasSloppyArgumentsElements()):
  // - the parameter map contains an index into the context
  // - all attributes of the element have default values
  // For slow aliases (if HasDictionaryArgumentsElements()):
  // - the parameter map contains no fast alias mapping (i.e. the hole)
  // - this struct (in the slow backing store) contains an index into the context
  // - all attributes are available as part if the property details
  class AliasedArgumentsEntry: public Struct {
   public:
    inline int aliased_context_slot() const;
    inline void set_aliased_context_slot(int count);
  
    DECLARE_CAST(AliasedArgumentsEntry)
  
    // Dispatched behavior.
    DECLARE_PRINTER(AliasedArgumentsEntry)
    DECLARE_VERIFIER(AliasedArgumentsEntry)
  
    static const int kAliasedContextSlot = HeapObject::kHeaderSize;
    static const int kSize = kAliasedContextSlot + kPointerSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(AliasedArgumentsEntry);
  };
  
  
  enum AllowNullsFlag {ALLOW_NULLS, DISALLOW_NULLS};
  enum RobustnessFlag {ROBUST_STRING_TRAVERSAL, FAST_STRING_TRAVERSAL};
  
  
  class StringHasher {
   public:
    explicit inline StringHasher(int length, uint32_t seed);
  
    template <typename schar>
    static inline uint32_t HashSequentialString(const schar* chars,
                                                int length,
                                                uint32_t seed);
  
    // Reads all the data, even for long strings and computes the utf16 length.
    static uint32_t ComputeUtf8Hash(Vector<const char> chars,
                                    uint32_t seed,
                                    int* utf16_length_out);
  
    // Calculated hash value for a string consisting of 1 to
    // String::kMaxArrayIndexSize digits with no leading zeros (except "0").
    // value is represented decimal value.
    static uint32_t MakeArrayIndexHash(uint32_t value, int length);
  
    // No string is allowed to have a hash of zero.  That value is reserved
    // for internal properties.  If the hash calculation yields zero then we
    // use 27 instead.
    static const int kZeroHash = 27;
  
    // Reusable parts of the hashing algorithm.
    INLINE(static uint32_t AddCharacterCore(uint32_t running_hash, uint16_t c));
    INLINE(static uint32_t GetHashCore(uint32_t running_hash));
  
   protected:
    // Returns the value to store in the hash field of a string with
    // the given length and contents.
    uint32_t GetHashField();
    // Returns true if the hash of this string can be computed without
    // looking at the contents.
    inline bool has_trivial_hash();
    // Adds a block of characters to the hash.
    template<typename Char>
    inline void AddCharacters(const Char* chars, int len);
  
   private:
    // Add a character to the hash.
    inline void AddCharacter(uint16_t c);
    // Update index. Returns true if string is still an index.
    inline bool UpdateIndex(uint16_t c);
  
    int length_;
    uint32_t raw_running_hash_;
    uint32_t array_index_;
    bool is_array_index_;
    bool is_first_char_;
    DISALLOW_COPY_AND_ASSIGN(StringHasher);
  };
  
  
  class IteratingStringHasher : public StringHasher {
   public:
    static inline uint32_t Hash(String* string, uint32_t seed);
    inline void VisitOneByteString(const uint8_t* chars, int length);
    inline void VisitTwoByteString(const uint16_t* chars, int length);
  
   private:
    inline IteratingStringHasher(int len, uint32_t seed)
        : StringHasher(len, seed) {}
    DISALLOW_COPY_AND_ASSIGN(IteratingStringHasher);
  };
  
  
  // The characteristics of a string are stored in its map.  Retrieving these
  // few bits of information is moderately expensive, involving two memory
  // loads where the second is dependent on the first.  To improve efficiency
  // the shape of the string is given its own class so that it can be retrieved
  // once and used for several string operations.  A StringShape is small enough
  // to be passed by value and is immutable, but be aware that flattening a
  // string can potentially alter its shape.  Also be aware that a GC caused by
  // something else can alter the shape of a string due to ConsString
  // shortcutting.  Keeping these restrictions in mind has proven to be error-
  // prone and so we no longer put StringShapes in variables unless there is a
  // concrete performance benefit at that particular point in the code.
  class StringShape BASE_EMBEDDED {
   public:
    inline explicit StringShape(const String* s);
    inline explicit StringShape(Map* s);
    inline explicit StringShape(InstanceType t);
    inline bool IsSequential();
    inline bool IsExternal();
    inline bool IsCons();
    inline bool IsSliced();
    inline bool IsIndirect();
    inline bool IsExternalOneByte();
    inline bool IsExternalTwoByte();
    inline bool IsSequentialOneByte();
    inline bool IsSequentialTwoByte();
    inline bool IsInternalized();
    inline StringRepresentationTag representation_tag();
    inline uint32_t encoding_tag();
    inline uint32_t full_representation_tag();
    inline uint32_t size_tag();
  #ifdef DEBUG
    inline uint32_t type() { return type_; }
    inline void invalidate() { valid_ = false; }
    inline bool valid() { return valid_; }
  #else
    inline void invalidate() { }
  #endif
  
   private:
    uint32_t type_;
  #ifdef DEBUG
    inline void set_valid() { valid_ = true; }
    bool valid_;
  #else
    inline void set_valid() { }
  #endif
  };
  
  
  // The Name abstract class captures anything that can be used as a property
  // name, i.e., strings and symbols.  All names store a hash value.
  class Name: public HeapObject {
   public:
    // Get and set the hash field of the name.
    inline uint32_t hash_field();
    inline void set_hash_field(uint32_t value);
  
    // Tells whether the hash code has been computed.
    inline bool HasHashCode();
  
    // Returns a hash value used for the property table
    inline uint32_t Hash();
  
    // Equality operations.
    inline bool Equals(Name* other);
    inline static bool Equals(Handle<Name> one, Handle<Name> two);
  
    // Conversion.
    inline bool AsArrayIndex(uint32_t* index);
  
    // Whether name can only name own properties.
    inline bool IsOwn();
  
    DECLARE_CAST(Name)
  
    DECLARE_PRINTER(Name)
  
    // Layout description.
    static const int kHashFieldOffset = HeapObject::kHeaderSize;
    static const int kSize = kHashFieldOffset + kPointerSize;
  
    // Mask constant for checking if a name has a computed hash code
    // and if it is a string that is an array index.  The least significant bit
    // indicates whether a hash code has been computed.  If the hash code has
    // been computed the 2nd bit tells whether the string can be used as an
    // array index.
    static const int kHashNotComputedMask = 1;
    static const int kIsNotArrayIndexMask = 1 << 1;
    static const int kNofHashBitFields = 2;
  
    // Shift constant retrieving hash code from hash field.
    static const int kHashShift = kNofHashBitFields;
  
    // Only these bits are relevant in the hash, since the top two are shifted
    // out.
    static const uint32_t kHashBitMask = 0xffffffffu >> kHashShift;
  
    // Array index strings this short can keep their index in the hash field.
    static const int kMaxCachedArrayIndexLength = 7;
  
    // For strings which are array indexes the hash value has the string length
    // mixed into the hash, mainly to avoid a hash value of zero which would be
    // the case for the string '0'. 24 bits are used for the array index value.
    static const int kArrayIndexValueBits = 24;
    static const int kArrayIndexLengthBits =
        kBitsPerInt - kArrayIndexValueBits - kNofHashBitFields;
  
    STATIC_ASSERT((kArrayIndexLengthBits > 0));
  
    class ArrayIndexValueBits : public BitField<unsigned int, kNofHashBitFields,
        kArrayIndexValueBits> {};  // NOLINT
    class ArrayIndexLengthBits : public BitField<unsigned int,
        kNofHashBitFields + kArrayIndexValueBits,
        kArrayIndexLengthBits> {};  // NOLINT
  
    // Check that kMaxCachedArrayIndexLength + 1 is a power of two so we
    // could use a mask to test if the length of string is less than or equal to
    // kMaxCachedArrayIndexLength.
    STATIC_ASSERT(IS_POWER_OF_TWO(kMaxCachedArrayIndexLength + 1));
  
    static const unsigned int kContainsCachedArrayIndexMask =
        (~static_cast<unsigned>(kMaxCachedArrayIndexLength)
         << ArrayIndexLengthBits::kShift) |
        kIsNotArrayIndexMask;
  
    // Value of empty hash field indicating that the hash is not computed.
    static const int kEmptyHashField =
        kIsNotArrayIndexMask | kHashNotComputedMask;
  
   protected:
    static inline bool IsHashFieldComputed(uint32_t field);
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(Name);
  };
  
  
  // ES6 symbols.
  class Symbol: public Name {
   public:
    // [name]: the print name of a symbol, or undefined if none.
    DECL_ACCESSORS(name, Object)
  
    DECL_ACCESSORS(flags, Smi)
  
    // [is_private]: whether this is a private symbol.
    DECL_BOOLEAN_ACCESSORS(is_private)
  
    // [is_own]: whether this is an own symbol, that is, only used to designate
    // own properties of objects.
    DECL_BOOLEAN_ACCESSORS(is_own)
  
    DECLARE_CAST(Symbol)
  
    // Dispatched behavior.
    DECLARE_PRINTER(Symbol)
    DECLARE_VERIFIER(Symbol)
  
    // Layout description.
    static const int kNameOffset = Name::kSize;
    static const int kFlagsOffset = kNameOffset + kPointerSize;
    static const int kSize = kFlagsOffset + kPointerSize;
  
    typedef FixedBodyDescriptor<kNameOffset, kFlagsOffset, kSize> BodyDescriptor;
  
   private:
    static const int kPrivateBit = 0;
    static const int kOwnBit = 1;
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(Symbol);
  };
  
  
  class ConsString;
  
  // The String abstract class captures JavaScript string values:
  //
  // Ecma-262:
  //  4.3.16 String Value
  //    A string value is a member of the type String and is a finite
  //    ordered sequence of zero or more 16-bit unsigned integer values.
  //
  // All string values have a length field.
  class String: public Name {
   public:
    enum Encoding { ONE_BYTE_ENCODING, TWO_BYTE_ENCODING };
  
    // Array index strings this short can keep their index in the hash field.
    static const int kMaxCachedArrayIndexLength = 7;
  
    // For strings which are array indexes the hash value has the string length
    // mixed into the hash, mainly to avoid a hash value of zero which would be
    // the case for the string '0'. 24 bits are used for the array index value.
    static const int kArrayIndexValueBits = 24;
    static const int kArrayIndexLengthBits =
        kBitsPerInt - kArrayIndexValueBits - kNofHashBitFields;
  
    STATIC_ASSERT((kArrayIndexLengthBits > 0));
  
    class ArrayIndexValueBits : public BitField<unsigned int, kNofHashBitFields,
        kArrayIndexValueBits> {};  // NOLINT
    class ArrayIndexLengthBits : public BitField<unsigned int,
        kNofHashBitFields + kArrayIndexValueBits,
        kArrayIndexLengthBits> {};  // NOLINT
  
    // Check that kMaxCachedArrayIndexLength + 1 is a power of two so we
    // could use a mask to test if the length of string is less than or equal to
    // kMaxCachedArrayIndexLength.
    STATIC_ASSERT(IS_POWER_OF_TWO(kMaxCachedArrayIndexLength + 1));
  
    static const unsigned int kContainsCachedArrayIndexMask =
        (~static_cast<unsigned>(kMaxCachedArrayIndexLength)
         << ArrayIndexLengthBits::kShift) |
        kIsNotArrayIndexMask;
  
    // Representation of the flat content of a String.
    // A non-flat string doesn't have flat content.
    // A flat string has content that's encoded as a sequence of either
    // one-byte chars or two-byte UC16.
    // Returned by String::GetFlatContent().
    class FlatContent {
     public:
      // Returns true if the string is flat and this structure contains content.
      bool IsFlat() { return state_ != NON_FLAT; }
      // Returns true if the structure contains one-byte content.
      bool IsOneByte() { return state_ == ONE_BYTE; }
      // Returns true if the structure contains two-byte content.
      bool IsTwoByte() { return state_ == TWO_BYTE; }
  
      // Return the one byte content of the string. Only use if IsOneByte()
      // returns true.
      Vector<const uint8_t> ToOneByteVector() {
        DCHECK_EQ(ONE_BYTE, state_);
        return Vector<const uint8_t>(onebyte_start, length_);
      }
      // Return the two-byte content of the string. Only use if IsTwoByte()
      // returns true.
      Vector<const uc16> ToUC16Vector() {
        DCHECK_EQ(TWO_BYTE, state_);
        return Vector<const uc16>(twobyte_start, length_);
      }
  
      uc16 Get(int i) {
        DCHECK(i < length_);
        DCHECK(state_ != NON_FLAT);
        if (state_ == ONE_BYTE) return onebyte_start[i];
        return twobyte_start[i];
      }
  
     private:
      enum State { NON_FLAT, ONE_BYTE, TWO_BYTE };
  
      // Constructors only used by String::GetFlatContent().
      explicit FlatContent(const uint8_t* start, int length)
          : onebyte_start(start), length_(length), state_(ONE_BYTE) {}
      explicit FlatContent(const uc16* start, int length)
          : twobyte_start(start), length_(length), state_(TWO_BYTE) { }
      FlatContent() : onebyte_start(NULL), length_(0), state_(NON_FLAT) { }
  
      union {
        const uint8_t* onebyte_start;
        const uc16* twobyte_start;
      };
      int length_;
      State state_;
  
      friend class String;
    };
  
    // Get and set the length of the string.
    inline int length() const;
    inline void set_length(int value);
  
    // Get and set the length of the string using acquire loads and release
    // stores.
    inline int synchronized_length() const;
    inline void synchronized_set_length(int value);
  
    // Returns whether this string has only one-byte chars, i.e. all of them can
    // be one-byte encoded.  This might be the case even if the string is
    // two-byte.  Such strings may appear when the embedder prefers
    // two-byte external representations even for one-byte data.
    inline bool IsOneByteRepresentation() const;
    inline bool IsTwoByteRepresentation() const;
  
    // Cons and slices have an encoding flag that may not represent the actual
    // encoding of the underlying string.  This is taken into account here.
    // Requires: this->IsFlat()
    inline bool IsOneByteRepresentationUnderneath();
    inline bool IsTwoByteRepresentationUnderneath();
  
    // NOTE: this should be considered only a hint.  False negatives are
    // possible.
    inline bool HasOnlyOneByteChars();
  
    // Get and set individual two byte chars in the string.
    inline void Set(int index, uint16_t value);
    // Get individual two byte char in the string.  Repeated calls
    // to this method are not efficient unless the string is flat.
    INLINE(uint16_t Get(int index));
  
    // Flattens the string.  Checks first inline to see if it is
    // necessary.  Does nothing if the string is not a cons string.
    // Flattening allocates a sequential string with the same data as
    // the given string and mutates the cons string to a degenerate
    // form, where the first component is the new sequential string and
    // the second component is the empty string.  If allocation fails,
    // this function returns a failure.  If flattening succeeds, this
    // function returns the sequential string that is now the first
    // component of the cons string.
    //
    // Degenerate cons strings are handled specially by the garbage
    // collector (see IsShortcutCandidate).
  
    static inline Handle<String> Flatten(Handle<String> string,
                                         PretenureFlag pretenure = NOT_TENURED);
  
    // Tries to return the content of a flat string as a structure holding either
    // a flat vector of char or of uc16.
    // If the string isn't flat, and therefore doesn't have flat content, the
    // returned structure will report so, and can't provide a vector of either
    // kind.
    FlatContent GetFlatContent();
  
    // Returns the parent of a sliced string or first part of a flat cons string.
    // Requires: StringShape(this).IsIndirect() && this->IsFlat()
    inline String* GetUnderlying();
  
    // Mark the string as an undetectable object. It only applies to
    // one-byte and two-byte string types.
    bool MarkAsUndetectable();
  
    // String equality operations.
    inline bool Equals(String* other);
    inline static bool Equals(Handle<String> one, Handle<String> two);
    bool IsUtf8EqualTo(Vector<const char> str, bool allow_prefix_match = false);
    bool IsOneByteEqualTo(Vector<const uint8_t> str);
    bool IsTwoByteEqualTo(Vector<const uc16> str);
  
    // Return a UTF8 representation of the string.  The string is null
    // terminated but may optionally contain nulls.  Length is returned
    // in length_output if length_output is not a null pointer  The string
    // should be nearly flat, otherwise the performance of this method may
    // be very slow (quadratic in the length).  Setting robustness_flag to
    // ROBUST_STRING_TRAVERSAL invokes behaviour that is robust  This means it
    // handles unexpected data without causing assert failures and it does not
    // do any heap allocations.  This is useful when printing stack traces.
    SmartArrayPointer<char> ToCString(AllowNullsFlag allow_nulls,
                                      RobustnessFlag robustness_flag,
                                      int offset,
                                      int length,
                                      int* length_output = 0);
    SmartArrayPointer<char> ToCString(
        AllowNullsFlag allow_nulls = DISALLOW_NULLS,
        RobustnessFlag robustness_flag = FAST_STRING_TRAVERSAL,
        int* length_output = 0);
  
    // Return a 16 bit Unicode representation of the string.
    // The string should be nearly flat, otherwise the performance of
    // of this method may be very bad.  Setting robustness_flag to
    // ROBUST_STRING_TRAVERSAL invokes behaviour that is robust  This means it
    // handles unexpected data without causing assert failures and it does not
    // do any heap allocations.  This is useful when printing stack traces.
    SmartArrayPointer<uc16> ToWideCString(
        RobustnessFlag robustness_flag = FAST_STRING_TRAVERSAL);
  
    bool ComputeArrayIndex(uint32_t* index);
  
    // Externalization.
    bool MakeExternal(v8::String::ExternalStringResource* resource);
    bool MakeExternal(v8::String::ExternalOneByteStringResource* resource);
  
    // Conversion.
    inline bool AsArrayIndex(uint32_t* index);
  
    DECLARE_CAST(String)
  
    void PrintOn(FILE* out);
  
    // For use during stack traces.  Performs rudimentary sanity check.
    bool LooksValid();
  
    // Dispatched behavior.
    void StringShortPrint(StringStream* accumulator);
    void PrintUC16(OStream& os, int start = 0, int end = -1);  // NOLINT
  #ifdef OBJECT_PRINT
    char* ToAsciiArray();
  #endif
    DECLARE_PRINTER(String)
    DECLARE_VERIFIER(String)
  
    inline bool IsFlat();
  
    // Layout description.
    static const int kLengthOffset = Name::kSize;
    static const int kSize = kLengthOffset + kPointerSize;
  
    // Maximum number of characters to consider when trying to convert a string
    // value into an array index.
    static const int kMaxArrayIndexSize = 10;
    STATIC_ASSERT(kMaxArrayIndexSize < (1 << kArrayIndexLengthBits));
  
    // Max char codes.
    static const int32_t kMaxOneByteCharCode = unibrow::Latin1::kMaxChar;
    static const uint32_t kMaxOneByteCharCodeU = unibrow::Latin1::kMaxChar;
    static const int kMaxUtf16CodeUnit = 0xffff;
    static const uint32_t kMaxUtf16CodeUnitU = kMaxUtf16CodeUnit;
  
    // Value of hash field containing computed hash equal to zero.
    static const int kEmptyStringHash = kIsNotArrayIndexMask;
  
    // Maximal string length.
    static const int kMaxLength = (1 << 28) - 16;
  
    // Max length for computing hash. For strings longer than this limit the
    // string length is used as the hash value.
    static const int kMaxHashCalcLength = 16383;
  
    // Limit for truncation in short printing.
    static const int kMaxShortPrintLength = 1024;
  
    // Support for regular expressions.
    const uc16* GetTwoByteData(unsigned start);
  
    // Helper function for flattening strings.
    template <typename sinkchar>
    static void WriteToFlat(String* source,
                            sinkchar* sink,
                            int from,
                            int to);
  
    // The return value may point to the first aligned word containing the first
    // non-one-byte character, rather than directly to the non-one-byte character.
    // If the return value is >= the passed length, the entire string was
    // one-byte.
    static inline int NonAsciiStart(const char* chars, int length) {
      const char* start = chars;
      const char* limit = chars + length;
  
      if (length >= kIntptrSize) {
        // Check unaligned bytes.
        while (!IsAligned(reinterpret_cast<intptr_t>(chars), sizeof(uintptr_t))) {
          if (static_cast<uint8_t>(*chars) > unibrow::Utf8::kMaxOneByteChar) {
            return static_cast<int>(chars - start);
          }
          ++chars;
        }
        // Check aligned words.
        DCHECK(unibrow::Utf8::kMaxOneByteChar == 0x7F);
        const uintptr_t non_one_byte_mask = kUintptrAllBitsSet / 0xFF * 0x80;
        while (chars + sizeof(uintptr_t) <= limit) {
          if (*reinterpret_cast<const uintptr_t*>(chars) & non_one_byte_mask) {
            return static_cast<int>(chars - start);
          }
          chars += sizeof(uintptr_t);
        }
      }
      // Check remaining unaligned bytes.
      while (chars < limit) {
        if (static_cast<uint8_t>(*chars) > unibrow::Utf8::kMaxOneByteChar) {
          return static_cast<int>(chars - start);
        }
        ++chars;
      }
  
      return static_cast<int>(chars - start);
    }
  
    static inline bool IsAscii(const char* chars, int length) {
      return NonAsciiStart(chars, length) >= length;
    }
  
    static inline bool IsAscii(const uint8_t* chars, int length) {
      return
          NonAsciiStart(reinterpret_cast<const char*>(chars), length) >= length;
    }
  
    static inline int NonOneByteStart(const uc16* chars, int length) {
      const uc16* limit = chars + length;
      const uc16* start = chars;
      while (chars < limit) {
        if (*chars > kMaxOneByteCharCodeU) return static_cast<int>(chars - start);
        ++chars;
      }
      return static_cast<int>(chars - start);
    }
  
    static inline bool IsOneByte(const uc16* chars, int length) {
      return NonOneByteStart(chars, length) >= length;
    }
  
    template<class Visitor>
    static inline ConsString* VisitFlat(Visitor* visitor,
                                        String* string,
                                        int offset = 0);
  
    static Handle<FixedArray> CalculateLineEnds(Handle<String> string,
                                                bool include_ending_line);
  
    // Use the hash field to forward to the canonical internalized string
    // when deserializing an internalized string.
    inline void SetForwardedInternalizedString(String* string);
    inline String* GetForwardedInternalizedString();
  
   private:
    friend class Name;
    friend class StringTableInsertionKey;
  
    static Handle<String> SlowFlatten(Handle<ConsString> cons,
                                      PretenureFlag tenure);
  
    // Slow case of String::Equals.  This implementation works on any strings
    // but it is most efficient on strings that are almost flat.
    bool SlowEquals(String* other);
  
    static bool SlowEquals(Handle<String> one, Handle<String> two);
  
    // Slow case of AsArrayIndex.
    bool SlowAsArrayIndex(uint32_t* index);
  
    // Compute and set the hash code.
    uint32_t ComputeAndSetHash();
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(String);
  };
  
  
  // The SeqString abstract class captures sequential string values.
  class SeqString: public String {
   public:
    DECLARE_CAST(SeqString)
  
    // Layout description.
    static const int kHeaderSize = String::kSize;
  
    // Truncate the string in-place if possible and return the result.
    // In case of new_length == 0, the empty string is returned without
    // truncating the original string.
    MUST_USE_RESULT static Handle<String> Truncate(Handle<SeqString> string,
                                                   int new_length);
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(SeqString);
  };
  
  
  // The OneByteString class captures sequential one-byte string objects.
  // Each character in the OneByteString is an one-byte character.
  class SeqOneByteString: public SeqString {
   public:
    static const bool kHasOneByteEncoding = true;
  
    // Dispatched behavior.
    inline uint16_t SeqOneByteStringGet(int index);
    inline void SeqOneByteStringSet(int index, uint16_t value);
  
    // Get the address of the characters in this string.
    inline Address GetCharsAddress();
  
    inline uint8_t* GetChars();
  
    DECLARE_CAST(SeqOneByteString)
  
    // Garbage collection support.  This method is called by the
    // garbage collector to compute the actual size of an OneByteString
    // instance.
    inline int SeqOneByteStringSize(InstanceType instance_type);
  
    // Computes the size for an OneByteString instance of a given length.
    static int SizeFor(int length) {
      return OBJECT_POINTER_ALIGN(kHeaderSize + length * kCharSize);
    }
  
    // Maximal memory usage for a single sequential one-byte string.
    static const int kMaxSize = 512 * MB - 1;
    STATIC_ASSERT((kMaxSize - kHeaderSize) >= String::kMaxLength);
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(SeqOneByteString);
  };
  
  
  // The TwoByteString class captures sequential unicode string objects.
  // Each character in the TwoByteString is a two-byte uint16_t.
  class SeqTwoByteString: public SeqString {
   public:
    static const bool kHasOneByteEncoding = false;
  
    // Dispatched behavior.
    inline uint16_t SeqTwoByteStringGet(int index);
    inline void SeqTwoByteStringSet(int index, uint16_t value);
  
    // Get the address of the characters in this string.
    inline Address GetCharsAddress();
  
    inline uc16* GetChars();
  
    // For regexp code.
    const uint16_t* SeqTwoByteStringGetData(unsigned start);
  
    DECLARE_CAST(SeqTwoByteString)
  
    // Garbage collection support.  This method is called by the
    // garbage collector to compute the actual size of a TwoByteString
    // instance.
    inline int SeqTwoByteStringSize(InstanceType instance_type);
  
    // Computes the size for a TwoByteString instance of a given length.
    static int SizeFor(int length) {
      return OBJECT_POINTER_ALIGN(kHeaderSize + length * kShortSize);
    }
  
    // Maximal memory usage for a single sequential two-byte string.
    static const int kMaxSize = 512 * MB - 1;
    STATIC_ASSERT(static_cast<int>((kMaxSize - kHeaderSize)/sizeof(uint16_t)) >=
                 String::kMaxLength);
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(SeqTwoByteString);
  };
  
  
  // The ConsString class describes string values built by using the
  // addition operator on strings.  A ConsString is a pair where the
  // first and second components are pointers to other string values.
  // One or both components of a ConsString can be pointers to other
  // ConsStrings, creating a binary tree of ConsStrings where the leaves
  // are non-ConsString string values.  The string value represented by
  // a ConsString can be obtained by concatenating the leaf string
  // values in a left-to-right depth-first traversal of the tree.
  class ConsString: public String {
   public:
    // First string of the cons cell.
    inline String* first();
    // Doesn't check that the result is a string, even in debug mode.  This is
    // useful during GC where the mark bits confuse the checks.
    inline Object* unchecked_first();
    inline void set_first(String* first,
                          WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
  
    // Second string of the cons cell.
    inline String* second();
    // Doesn't check that the result is a string, even in debug mode.  This is
    // useful during GC where the mark bits confuse the checks.
    inline Object* unchecked_second();
    inline void set_second(String* second,
                           WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
  
    // Dispatched behavior.
    uint16_t ConsStringGet(int index);
  
    DECLARE_CAST(ConsString)
  
    // Layout description.
    static const int kFirstOffset = POINTER_SIZE_ALIGN(String::kSize);
    static const int kSecondOffset = kFirstOffset + kPointerSize;
    static const int kSize = kSecondOffset + kPointerSize;
  
    // Minimum length for a cons string.
    static const int kMinLength = 13;
  
    typedef FixedBodyDescriptor<kFirstOffset, kSecondOffset + kPointerSize, kSize>
            BodyDescriptor;
  
    DECLARE_VERIFIER(ConsString)
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(ConsString);
  };
  
  
  // The Sliced String class describes strings that are substrings of another
  // sequential string.  The motivation is to save time and memory when creating
  // a substring.  A Sliced String is described as a pointer to the parent,
  // the offset from the start of the parent string and the length.  Using
  // a Sliced String therefore requires unpacking of the parent string and
  // adding the offset to the start address.  A substring of a Sliced String
  // are not nested since the double indirection is simplified when creating
  // such a substring.
  // Currently missing features are:
  //  - handling externalized parent strings
  //  - external strings as parent
  //  - truncating sliced string to enable otherwise unneeded parent to be GC'ed.
  class SlicedString: public String {
   public:
    inline String* parent();
    inline void set_parent(String* parent,
                           WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
    inline int offset() const;
    inline void set_offset(int offset);
  
    // Dispatched behavior.
    uint16_t SlicedStringGet(int index);
  
    DECLARE_CAST(SlicedString)
  
    // Layout description.
    static const int kParentOffset = POINTER_SIZE_ALIGN(String::kSize);
    static const int kOffsetOffset = kParentOffset + kPointerSize;
    static const int kSize = kOffsetOffset + kPointerSize;
  
    // Minimum length for a sliced string.
    static const int kMinLength = 13;
  
    typedef FixedBodyDescriptor<kParentOffset,
                                kOffsetOffset + kPointerSize, kSize>
            BodyDescriptor;
  
    DECLARE_VERIFIER(SlicedString)
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(SlicedString);
  };
  
  
  // The ExternalString class describes string values that are backed by
  // a string resource that lies outside the V8 heap.  ExternalStrings
  // consist of the length field common to all strings, a pointer to the
  // external resource.  It is important to ensure (externally) that the
  // resource is not deallocated while the ExternalString is live in the
  // V8 heap.
  //
  // The API expects that all ExternalStrings are created through the
  // API.  Therefore, ExternalStrings should not be used internally.
  class ExternalString: public String {
   public:
    DECLARE_CAST(ExternalString)
  
    // Layout description.
    static const int kResourceOffset = POINTER_SIZE_ALIGN(String::kSize);
    static const int kShortSize = kResourceOffset + kPointerSize;
    static const int kResourceDataOffset = kResourceOffset + kPointerSize;
    static const int kSize = kResourceDataOffset + kPointerSize;
  
    static const int kMaxShortLength =
        (kShortSize - SeqString::kHeaderSize) / kCharSize;
  
    // Return whether external string is short (data pointer is not cached).
    inline bool is_short();
  
    STATIC_ASSERT(kResourceOffset == Internals::kStringResourceOffset);
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalString);
  };
  
  
  // The ExternalOneByteString class is an external string backed by an
  // one-byte string.
  class ExternalOneByteString : public ExternalString {
   public:
    static const bool kHasOneByteEncoding = true;
  
    typedef v8::String::ExternalOneByteStringResource Resource;
  
    // The underlying resource.
    inline const Resource* resource();
    inline void set_resource(const Resource* buffer);
  
    // Update the pointer cache to the external character array.
    // The cached pointer is always valid, as the external character array does =
    // not move during lifetime.  Deserialization is the only exception, after
    // which the pointer cache has to be refreshed.
    inline void update_data_cache();
  
    inline const uint8_t* GetChars();
  
    // Dispatched behavior.
    inline uint16_t ExternalOneByteStringGet(int index);
  
    DECLARE_CAST(ExternalOneByteString)
  
    // Garbage collection support.
    inline void ExternalOneByteStringIterateBody(ObjectVisitor* v);
  
    template <typename StaticVisitor>
    inline void ExternalOneByteStringIterateBody();
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalOneByteString);
  };
  
  
  // The ExternalTwoByteString class is an external string backed by a UTF-16
  // encoded string.
  class ExternalTwoByteString: public ExternalString {
   public:
    static const bool kHasOneByteEncoding = false;
  
    typedef v8::String::ExternalStringResource Resource;
  
    // The underlying string resource.
    inline const Resource* resource();
    inline void set_resource(const Resource* buffer);
  
    // Update the pointer cache to the external character array.
    // The cached pointer is always valid, as the external character array does =
    // not move during lifetime.  Deserialization is the only exception, after
    // which the pointer cache has to be refreshed.
    inline void update_data_cache();
  
    inline const uint16_t* GetChars();
  
    // Dispatched behavior.
    inline uint16_t ExternalTwoByteStringGet(int index);
  
    // For regexp code.
    inline const uint16_t* ExternalTwoByteStringGetData(unsigned start);
  
    DECLARE_CAST(ExternalTwoByteString)
  
    // Garbage collection support.
    inline void ExternalTwoByteStringIterateBody(ObjectVisitor* v);
  
    template<typename StaticVisitor>
    inline void ExternalTwoByteStringIterateBody();
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalTwoByteString);
  };
  
  
  // Utility superclass for stack-allocated objects that must be updated
  // on gc.  It provides two ways for the gc to update instances, either
  // iterating or updating after gc.
  class Relocatable BASE_EMBEDDED {
   public:
    explicit inline Relocatable(Isolate* isolate);
    inline virtual ~Relocatable();
    virtual void IterateInstance(ObjectVisitor* v) { }
    virtual void PostGarbageCollection() { }
  
    static void PostGarbageCollectionProcessing(Isolate* isolate);
    static int ArchiveSpacePerThread();
    static char* ArchiveState(Isolate* isolate, char* to);
    static char* RestoreState(Isolate* isolate, char* from);
    static void Iterate(Isolate* isolate, ObjectVisitor* v);
    static void Iterate(ObjectVisitor* v, Relocatable* top);
    static char* Iterate(ObjectVisitor* v, char* t);
  
   private:
    Isolate* isolate_;
    Relocatable* prev_;
  };
  
  
  // A flat string reader provides random access to the contents of a
  // string independent of the character width of the string.  The handle
  // must be valid as long as the reader is being used.
  class FlatStringReader : public Relocatable {
   public:
    FlatStringReader(Isolate* isolate, Handle<String> str);
    FlatStringReader(Isolate* isolate, Vector<const char> input);
    void PostGarbageCollection();
    inline uc32 Get(int index);
    int length() { return length_; }
   private:
    String** str_;
    bool is_one_byte_;
    int length_;
    const void* start_;
  };
  
  
  // A ConsStringOp that returns null.
  // Useful when the operation to apply on a ConsString
  // requires an expensive data structure.
  class ConsStringNullOp {
   public:
    inline ConsStringNullOp() {}
    static inline String* Operate(String*, unsigned*, int32_t*, unsigned*);
   private:
    DISALLOW_COPY_AND_ASSIGN(ConsStringNullOp);
  };
  
  
  // This maintains an off-stack representation of the stack frames required
  // to traverse a ConsString, allowing an entirely iterative and restartable
  // traversal of the entire string
  class ConsStringIteratorOp {
   public:
    inline ConsStringIteratorOp() {}
    inline explicit ConsStringIteratorOp(ConsString* cons_string,
                                         int offset = 0) {
      Reset(cons_string, offset);
    }
    inline void Reset(ConsString* cons_string, int offset = 0) {
      depth_ = 0;
      // Next will always return NULL.
      if (cons_string == NULL) return;
      Initialize(cons_string, offset);
    }
    // Returns NULL when complete.
    inline String* Next(int* offset_out) {
      *offset_out = 0;
      if (depth_ == 0) return NULL;
      return Continue(offset_out);
    }
  
   private:
    static const int kStackSize = 32;
    // Use a mask instead of doing modulo operations for stack wrapping.
    static const int kDepthMask = kStackSize-1;
    STATIC_ASSERT(IS_POWER_OF_TWO(kStackSize));
    static inline int OffsetForDepth(int depth);
  
    inline void PushLeft(ConsString* string);
    inline void PushRight(ConsString* string);
    inline void AdjustMaximumDepth();
    inline void Pop();
    inline bool StackBlown() { return maximum_depth_ - depth_ == kStackSize; }
    void Initialize(ConsString* cons_string, int offset);
    String* Continue(int* offset_out);
    String* NextLeaf(bool* blew_stack);
    String* Search(int* offset_out);
  
    // Stack must always contain only frames for which right traversal
    // has not yet been performed.
    ConsString* frames_[kStackSize];
    ConsString* root_;
    int depth_;
    int maximum_depth_;
    int consumed_;
    DISALLOW_COPY_AND_ASSIGN(ConsStringIteratorOp);
  };
  
  
  class StringCharacterStream {
   public:
    inline StringCharacterStream(String* string,
                                 ConsStringIteratorOp* op,
                                 int offset = 0);
    inline uint16_t GetNext();
    inline bool HasMore();
    inline void Reset(String* string, int offset = 0);
    inline void VisitOneByteString(const uint8_t* chars, int length);
    inline void VisitTwoByteString(const uint16_t* chars, int length);
  
   private:
    bool is_one_byte_;
    union {
      const uint8_t* buffer8_;
      const uint16_t* buffer16_;
    };
    const uint8_t* end_;
    ConsStringIteratorOp* op_;
    DISALLOW_COPY_AND_ASSIGN(StringCharacterStream);
  };
  
  
  template <typename T>
  class VectorIterator {
   public:
    VectorIterator(T* d, int l) : data_(Vector<const T>(d, l)), index_(0) { }
    explicit VectorIterator(Vector<const T> data) : data_(data), index_(0) { }
    T GetNext() { return data_[index_++]; }
    bool has_more() { return index_ < data_.length(); }
   private:
    Vector<const T> data_;
    int index_;
  };
  
  
  // The Oddball describes objects null, undefined, true, and false.
  class Oddball: public HeapObject {
   public:
    // [to_string]: Cached to_string computed at startup.
    DECL_ACCESSORS(to_string, String)
  
    // [to_number]: Cached to_number computed at startup.
    DECL_ACCESSORS(to_number, Object)
  
    inline byte kind() const;
    inline void set_kind(byte kind);
  
    DECLARE_CAST(Oddball)
  
    // Dispatched behavior.
    DECLARE_VERIFIER(Oddball)
  
    // Initialize the fields.
    static void Initialize(Isolate* isolate,
                           Handle<Oddball> oddball,
                           const char* to_string,
                           Handle<Object> to_number,
                           byte kind);
  
    // Layout description.
    static const int kToStringOffset = HeapObject::kHeaderSize;
    static const int kToNumberOffset = kToStringOffset + kPointerSize;
    static const int kKindOffset = kToNumberOffset + kPointerSize;
    static const int kSize = kKindOffset + kPointerSize;
  
    static const byte kFalse = 0;
    static const byte kTrue = 1;
    static const byte kNotBooleanMask = ~1;
    static const byte kTheHole = 2;
    static const byte kNull = 3;
    static const byte kArgumentMarker = 4;
    static const byte kUndefined = 5;
    static const byte kUninitialized = 6;
    static const byte kOther = 7;
    static const byte kException = 8;
  
    typedef FixedBodyDescriptor<kToStringOffset,
                                kToNumberOffset + kPointerSize,
                                kSize> BodyDescriptor;
  
    STATIC_ASSERT(kKindOffset == Internals::kOddballKindOffset);
    STATIC_ASSERT(kNull == Internals::kNullOddballKind);
    STATIC_ASSERT(kUndefined == Internals::kUndefinedOddballKind);
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(Oddball);
  };
  
  
  class Cell: public HeapObject {
   public:
    // [value]: value of the global property.
    DECL_ACCESSORS(value, Object)
  
    DECLARE_CAST(Cell)
  
    static inline Cell* FromValueAddress(Address value) {
      Object* result = FromAddress(value - kValueOffset);
      DCHECK(result->IsCell() || result->IsPropertyCell());
      return static_cast<Cell*>(result);
    }
  
    inline Address ValueAddress() {
      return address() + kValueOffset;
    }
  
    // Dispatched behavior.
    DECLARE_PRINTER(Cell)
    DECLARE_VERIFIER(Cell)
  
    // Layout description.
    static const int kValueOffset = HeapObject::kHeaderSize;
    static const int kSize = kValueOffset + kPointerSize;
  
    typedef FixedBodyDescriptor<kValueOffset,
                                kValueOffset + kPointerSize,
                                kSize> BodyDescriptor;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(Cell);
  };
  
  
  class PropertyCell: public Cell {
   public:
    // [type]: type of the global property.
    HeapType* type();
    void set_type(HeapType* value, WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
  
    // [dependent_code]: dependent code that depends on the type of the global
    // property.
    DECL_ACCESSORS(dependent_code, DependentCode)
  
    // Sets the value of the cell and updates the type field to be the union
    // of the cell's current type and the value's type. If the change causes
    // a change of the type of the cell's contents, code dependent on the cell
    // will be deoptimized.
    static void SetValueInferType(Handle<PropertyCell> cell,
                                  Handle<Object> value);
  
    // Computes the new type of the cell's contents for the given value, but
    // without actually modifying the 'type' field.
    static Handle<HeapType> UpdatedType(Handle<PropertyCell> cell,
                                        Handle<Object> value);
  
    static void AddDependentCompilationInfo(Handle<PropertyCell> cell,
                                            CompilationInfo* info);
  
    DECLARE_CAST(PropertyCell)
  
    inline Address TypeAddress() {
      return address() + kTypeOffset;
    }
  
    // Dispatched behavior.
    DECLARE_PRINTER(PropertyCell)
    DECLARE_VERIFIER(PropertyCell)
  
    // Layout description.
    static const int kTypeOffset = kValueOffset + kPointerSize;
    static const int kDependentCodeOffset = kTypeOffset + kPointerSize;
    static const int kSize = kDependentCodeOffset + kPointerSize;
  
    static const int kPointerFieldsBeginOffset = kValueOffset;
    static const int kPointerFieldsEndOffset = kDependentCodeOffset;
  
    typedef FixedBodyDescriptor<kValueOffset,
                                kSize,
                                kSize> BodyDescriptor;
  
   private:
    DECL_ACCESSORS(type_raw, Object)
    DISALLOW_IMPLICIT_CONSTRUCTORS(PropertyCell);
  };
  
  
  // The JSProxy describes EcmaScript Harmony proxies
  class JSProxy: public JSReceiver {
   public:
    // [handler]: The handler property.
    DECL_ACCESSORS(handler, Object)
  
    // [hash]: The hash code property (undefined if not initialized yet).
    DECL_ACCESSORS(hash, Object)
  
    DECLARE_CAST(JSProxy)
  
    MUST_USE_RESULT static MaybeHandle<Object> GetPropertyWithHandler(
        Handle<JSProxy> proxy,
        Handle<Object> receiver,
        Handle<Name> name);
    MUST_USE_RESULT static inline MaybeHandle<Object> GetElementWithHandler(
        Handle<JSProxy> proxy,
        Handle<Object> receiver,
        uint32_t index);
  
    // If the handler defines an accessor property with a setter, invoke it.
    // If it defines an accessor property without a setter, or a data property
    // that is read-only, throw. In all these cases set '*done' to true,
    // otherwise set it to false.
    MUST_USE_RESULT
    static MaybeHandle<Object> SetPropertyViaPrototypesWithHandler(
        Handle<JSProxy> proxy, Handle<Object> receiver, Handle<Name> name,
        Handle<Object> value, StrictMode strict_mode, bool* done);
  
    MUST_USE_RESULT static Maybe<PropertyAttributes>
        GetPropertyAttributesWithHandler(Handle<JSProxy> proxy,
                                         Handle<Object> receiver,
                                         Handle<Name> name);
    MUST_USE_RESULT static Maybe<PropertyAttributes>
        GetElementAttributeWithHandler(Handle<JSProxy> proxy,
                                       Handle<JSReceiver> receiver,
                                       uint32_t index);
    MUST_USE_RESULT static MaybeHandle<Object> SetPropertyWithHandler(
        Handle<JSProxy> proxy, Handle<Object> receiver, Handle<Name> name,
        Handle<Object> value, StrictMode strict_mode);
  
    // Turn the proxy into an (empty) JSObject.
    static void Fix(Handle<JSProxy> proxy);
  
    // Initializes the body after the handler slot.
    inline void InitializeBody(int object_size, Object* value);
  
    // Invoke a trap by name. If the trap does not exist on this's handler,
    // but derived_trap is non-NULL, invoke that instead.  May cause GC.
    MUST_USE_RESULT static MaybeHandle<Object> CallTrap(
        Handle<JSProxy> proxy,
        const char* name,
        Handle<Object> derived_trap,
        int argc,
        Handle<Object> args[]);
  
    // Dispatched behavior.
    DECLARE_PRINTER(JSProxy)
    DECLARE_VERIFIER(JSProxy)
  
    // Layout description. We add padding so that a proxy has the same
    // size as a virgin JSObject. This is essential for becoming a JSObject
    // upon freeze.
    static const int kHandlerOffset = HeapObject::kHeaderSize;
    static const int kHashOffset = kHandlerOffset + kPointerSize;
    static const int kPaddingOffset = kHashOffset + kPointerSize;
    static const int kSize = JSObject::kHeaderSize;
    static const int kHeaderSize = kPaddingOffset;
    static const int kPaddingSize = kSize - kPaddingOffset;
  
    STATIC_ASSERT(kPaddingSize >= 0);
  
    typedef FixedBodyDescriptor<kHandlerOffset,
                                kPaddingOffset,
                                kSize> BodyDescriptor;
  
   private:
    friend class JSReceiver;
  
    MUST_USE_RESULT static inline MaybeHandle<Object> SetElementWithHandler(
        Handle<JSProxy> proxy,
        Handle<JSReceiver> receiver,
        uint32_t index,
        Handle<Object> value,
        StrictMode strict_mode);
  
    MUST_USE_RESULT static Maybe<bool> HasPropertyWithHandler(
        Handle<JSProxy> proxy, Handle<Name> name);
    MUST_USE_RESULT static inline Maybe<bool> HasElementWithHandler(
        Handle<JSProxy> proxy, uint32_t index);
  
    MUST_USE_RESULT static MaybeHandle<Object> DeletePropertyWithHandler(
        Handle<JSProxy> proxy,
        Handle<Name> name,
        DeleteMode mode);
    MUST_USE_RESULT static MaybeHandle<Object> DeleteElementWithHandler(
        Handle<JSProxy> proxy,
        uint32_t index,
        DeleteMode mode);
  
    MUST_USE_RESULT Object* GetIdentityHash();
  
    static Handle<Smi> GetOrCreateIdentityHash(Handle<JSProxy> proxy);
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSProxy);
  };
  
  
  class JSFunctionProxy: public JSProxy {
   public:
    // [call_trap]: The call trap.
    DECL_ACCESSORS(call_trap, Object)
  
    // [construct_trap]: The construct trap.
    DECL_ACCESSORS(construct_trap, Object)
  
    DECLARE_CAST(JSFunctionProxy)
  
    // Dispatched behavior.
    DECLARE_PRINTER(JSFunctionProxy)
    DECLARE_VERIFIER(JSFunctionProxy)
  
    // Layout description.
    static const int kCallTrapOffset = JSProxy::kPaddingOffset;
    static const int kConstructTrapOffset = kCallTrapOffset + kPointerSize;
    static const int kPaddingOffset = kConstructTrapOffset + kPointerSize;
    static const int kSize = JSFunction::kSize;
    static const int kPaddingSize = kSize - kPaddingOffset;
  
    STATIC_ASSERT(kPaddingSize >= 0);
  
    typedef FixedBodyDescriptor<kHandlerOffset,
                                kConstructTrapOffset + kPointerSize,
                                kSize> BodyDescriptor;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSFunctionProxy);
  };
  
  
  class JSCollection : public JSObject {
   public:
    // [table]: the backing hash table
    DECL_ACCESSORS(table, Object)
  
    static const int kTableOffset = JSObject::kHeaderSize;
    static const int kSize = kTableOffset + kPointerSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSCollection);
  };
  
  
  // The JSSet describes EcmaScript Harmony sets
  class JSSet : public JSCollection {
   public:
    DECLARE_CAST(JSSet)
  
    // Dispatched behavior.
    DECLARE_PRINTER(JSSet)
    DECLARE_VERIFIER(JSSet)
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSSet);
  };
  
  
  // The JSMap describes EcmaScript Harmony maps
  class JSMap : public JSCollection {
   public:
    DECLARE_CAST(JSMap)
  
    // Dispatched behavior.
    DECLARE_PRINTER(JSMap)
    DECLARE_VERIFIER(JSMap)
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSMap);
  };
  
  
  // OrderedHashTableIterator is an iterator that iterates over the keys and
  // values of an OrderedHashTable.
  //
  // The iterator has a reference to the underlying OrderedHashTable data,
  // [table], as well as the current [index] the iterator is at.
  //
  // When the OrderedHashTable is rehashed it adds a reference from the old table
  // to the new table as well as storing enough data about the changes so that the
  // iterator [index] can be adjusted accordingly.
  //
  // When the [Next] result from the iterator is requested, the iterator checks if
  // there is a newer table that it needs to transition to.
  template<class Derived, class TableType>
  class OrderedHashTableIterator: public JSObject {
   public:
    // [table]: the backing hash table mapping keys to values.
    DECL_ACCESSORS(table, Object)
  
    // [index]: The index into the data table.
    DECL_ACCESSORS(index, Object)
  
    // [kind]: The kind of iteration this is. One of the [Kind] enum values.
    DECL_ACCESSORS(kind, Object)
  
  #ifdef OBJECT_PRINT
    void OrderedHashTableIteratorPrint(OStream& os);  // NOLINT
  #endif
  
    static const int kTableOffset = JSObject::kHeaderSize;
    static const int kIndexOffset = kTableOffset + kPointerSize;
    static const int kKindOffset = kIndexOffset + kPointerSize;
    static const int kSize = kKindOffset + kPointerSize;
  
    enum Kind {
      kKindKeys = 1,
      kKindValues = 2,
      kKindEntries = 3
    };
  
    // Whether the iterator has more elements. This needs to be called before
    // calling |CurrentKey| and/or |CurrentValue|.
    bool HasMore();
  
    // Move the index forward one.
    void MoveNext() {
      set_index(Smi::FromInt(Smi::cast(index())->value() + 1));
    }
  
    // Populates the array with the next key and value and then moves the iterator
    // forward.
    // This returns the |kind| or 0 if the iterator is already at the end.
    Smi* Next(JSArray* value_array);
  
    // Returns the current key of the iterator. This should only be called when
    // |HasMore| returns true.
    inline Object* CurrentKey();
  
   private:
    // Transitions the iterator to the non obsolete backing store. This is a NOP
    // if the [table] is not obsolete.
    void Transition();
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(OrderedHashTableIterator);
  };
  
  
  class JSSetIterator: public OrderedHashTableIterator<JSSetIterator,
                                                       OrderedHashSet> {
   public:
    // Dispatched behavior.
    DECLARE_PRINTER(JSSetIterator)
    DECLARE_VERIFIER(JSSetIterator)
  
    DECLARE_CAST(JSSetIterator)
  
    // Called by |Next| to populate the array. This allows the subclasses to
    // populate the array differently.
    inline void PopulateValueArray(FixedArray* array);
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSSetIterator);
  };
  
  
  class JSMapIterator: public OrderedHashTableIterator<JSMapIterator,
                                                       OrderedHashMap> {
   public:
    // Dispatched behavior.
    DECLARE_PRINTER(JSMapIterator)
    DECLARE_VERIFIER(JSMapIterator)
  
    DECLARE_CAST(JSMapIterator)
  
    // Called by |Next| to populate the array. This allows the subclasses to
    // populate the array differently.
    inline void PopulateValueArray(FixedArray* array);
  
   private:
    // Returns the current value of the iterator. This should only be called when
    // |HasMore| returns true.
    inline Object* CurrentValue();
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSMapIterator);
  };
  
  
  // Base class for both JSWeakMap and JSWeakSet
  class JSWeakCollection: public JSObject {
   public:
    // [table]: the backing hash table mapping keys to values.
    DECL_ACCESSORS(table, Object)
  
    // [next]: linked list of encountered weak maps during GC.
    DECL_ACCESSORS(next, Object)
  
    static const int kTableOffset = JSObject::kHeaderSize;
    static const int kNextOffset = kTableOffset + kPointerSize;
    static const int kSize = kNextOffset + kPointerSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSWeakCollection);
  };
  
  
  // The JSWeakMap describes EcmaScript Harmony weak maps
  class JSWeakMap: public JSWeakCollection {
   public:
    DECLARE_CAST(JSWeakMap)
  
    // Dispatched behavior.
    DECLARE_PRINTER(JSWeakMap)
    DECLARE_VERIFIER(JSWeakMap)
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSWeakMap);
  };
  
  
  // The JSWeakSet describes EcmaScript Harmony weak sets
  class JSWeakSet: public JSWeakCollection {
   public:
    DECLARE_CAST(JSWeakSet)
  
    // Dispatched behavior.
    DECLARE_PRINTER(JSWeakSet)
    DECLARE_VERIFIER(JSWeakSet)
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSWeakSet);
  };
  
  
  class JSArrayBuffer: public JSObject {
   public:
    // [backing_store]: backing memory for this array
    DECL_ACCESSORS(backing_store, void)
  
    // [byte_length]: length in bytes
    DECL_ACCESSORS(byte_length, Object)
  
    // [flags]
    DECL_ACCESSORS(flag, Smi)
  
    inline bool is_external();
    inline void set_is_external(bool value);
  
    inline bool should_be_freed();
    inline void set_should_be_freed(bool value);
  
    // [weak_next]: linked list of array buffers.
    DECL_ACCESSORS(weak_next, Object)
  
    // [weak_first_array]: weak linked list of views.
    DECL_ACCESSORS(weak_first_view, Object)
  
    DECLARE_CAST(JSArrayBuffer)
  
    // Neutering. Only neuters the buffer, not associated typed arrays.
    void Neuter();
  
    // Dispatched behavior.
    DECLARE_PRINTER(JSArrayBuffer)
    DECLARE_VERIFIER(JSArrayBuffer)
  
    static const int kBackingStoreOffset = JSObject::kHeaderSize;
    static const int kByteLengthOffset = kBackingStoreOffset + kPointerSize;
    static const int kFlagOffset = kByteLengthOffset + kPointerSize;
    static const int kWeakNextOffset = kFlagOffset + kPointerSize;
    static const int kWeakFirstViewOffset = kWeakNextOffset + kPointerSize;
    static const int kSize = kWeakFirstViewOffset + kPointerSize;
  
    static const int kSizeWithInternalFields =
        kSize + v8::ArrayBuffer::kInternalFieldCount * kPointerSize;
  
   private:
    // Bit position in a flag
    static const int kIsExternalBit = 0;
    static const int kShouldBeFreed = 1;
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSArrayBuffer);
  };
  
  
  class JSArrayBufferView: public JSObject {
   public:
    // [buffer]: ArrayBuffer that this typed array views.
    DECL_ACCESSORS(buffer, Object)
  
    // [byte_length]: offset of typed array in bytes.
    DECL_ACCESSORS(byte_offset, Object)
  
    // [byte_length]: length of typed array in bytes.
    DECL_ACCESSORS(byte_length, Object)
  
    // [weak_next]: linked list of typed arrays over the same array buffer.
    DECL_ACCESSORS(weak_next, Object)
  
    DECLARE_CAST(JSArrayBufferView)
  
    DECLARE_VERIFIER(JSArrayBufferView)
  
    static const int kBufferOffset = JSObject::kHeaderSize;
    static const int kByteOffsetOffset = kBufferOffset + kPointerSize;
    static const int kByteLengthOffset = kByteOffsetOffset + kPointerSize;
    static const int kWeakNextOffset = kByteLengthOffset + kPointerSize;
    static const int kViewSize = kWeakNextOffset + kPointerSize;
  
   protected:
    void NeuterView();
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSArrayBufferView);
  };
  
  
  class JSTypedArray: public JSArrayBufferView {
   public:
    // [length]: length of typed array in elements.
    DECL_ACCESSORS(length, Object)
  
    // Neutering. Only neuters this typed array.
    void Neuter();
  
    DECLARE_CAST(JSTypedArray)
  
    ExternalArrayType type();
    size_t element_size();
  
    Handle<JSArrayBuffer> GetBuffer();
  
    // Dispatched behavior.
    DECLARE_PRINTER(JSTypedArray)
    DECLARE_VERIFIER(JSTypedArray)
  
    static const int kLengthOffset = kViewSize + kPointerSize;
    static const int kSize = kLengthOffset + kPointerSize;
  
    static const int kSizeWithInternalFields =
        kSize + v8::ArrayBufferView::kInternalFieldCount * kPointerSize;
  
   private:
    static Handle<JSArrayBuffer> MaterializeArrayBuffer(
        Handle<JSTypedArray> typed_array);
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSTypedArray);
  };
  
  
  class JSDataView: public JSArrayBufferView {
   public:
    // Only neuters this DataView
    void Neuter();
  
    DECLARE_CAST(JSDataView)
  
    // Dispatched behavior.
    DECLARE_PRINTER(JSDataView)
    DECLARE_VERIFIER(JSDataView)
  
    static const int kSize = kViewSize;
  
    static const int kSizeWithInternalFields =
        kSize + v8::ArrayBufferView::kInternalFieldCount * kPointerSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSDataView);
  };
  
  
  class Float32x4: public JSObject {
   public:
    typedef float32x4_value_t value_t;
    static const int kValueSize = kFloat32x4Size;
    static const InstanceType kInstanceType = FLOAT32x4_TYPE;
    static inline const char* Name();
    static inline int kRuntimeAllocatorId();
  
    // [value]: the FixedFloat32x4Array with length 1.
    DECL_ACCESSORS(value, Object)
  
    // Casting.
    DECLARE_CAST(Float32x4)
  
    // Dispatched behavior.
    void Float32x4Print(OStream& os);
    DECLARE_VERIFIER(Float32x4)
  
    // Helpers.
    static const int kLanes = 4;
    inline float getAt(int index);
    inline float x() { return getAt(0); }
    inline float y() { return getAt(1); }
    inline float z() { return getAt(2); }
    inline float w() { return getAt(3); }
    inline float32x4_value_t get();
    inline void set(float32x4_value_t f32x4);
  
    // Layout description.
    static const int kValueOffset = JSObject::kHeaderSize;
    static const int kSize = kValueOffset + kPointerSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(Float32x4);
  };
  
  
  class Float64x2: public JSObject {
   public:
    typedef float64x2_value_t value_t;
    static const int kValueSize = kFloat64x2Size;
    static const InstanceType kInstanceType = FLOAT64x2_TYPE;
    static inline const char* Name();
    static inline int kRuntimeAllocatorId();
  
    // [value]: the FixedFloat64x2Array with length 1.
    DECL_ACCESSORS(value, Object)
  
    // Casting.
    DECLARE_CAST(Float64x2)
  
    // Dispatched behavior.
    void Float64x2Print(OStream& os);
    DECLARE_VERIFIER(Float64x2)
  
    // Helpers.
    static const int kLanes = 2;
    inline double getAt(int index);
    inline double x() { return getAt(0); }
    inline double y() { return getAt(1); }
    inline float64x2_value_t get();
    inline void set(float64x2_value_t f64x2);
  
    // Layout description.
    static const int kValueOffset = JSObject::kHeaderSize;
    static const int kSize = kValueOffset + kPointerSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(Float64x2);
  };
  
  
  class Int32x4: public JSObject {
   public:
    typedef int32x4_value_t value_t;
    static const int kValueSize = kInt32x4Size;
    static const InstanceType kInstanceType = INT32x4_TYPE;
    static inline const char* Name();
    static inline int kRuntimeAllocatorId();
  
    // [value]: the FixedInt32x4Array with length 1.
    DECL_ACCESSORS(value, Object)
  
    // Casting.
    DECLARE_CAST(Int32x4)
  
    // Dispatched behavior.
    void Int32x4Print(OStream& os);
    DECLARE_VERIFIER(Int32x4)
  
    // Helpers.
    static const int kLanes = 4;
    inline int32_t getAt(int32_t index);
    inline int32_t x() { return getAt(0); }
    inline int32_t y() { return getAt(1); }
    inline int32_t z() { return getAt(2); }
    inline int32_t w() { return getAt(3); }
    inline int32x4_value_t get();
    inline void set(int32x4_value_t i32x4);
  
    // Layout description.
    static const int kValueOffset = JSObject::kHeaderSize;
    static const int kSize = kValueOffset + kPointerSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(Int32x4);
  };
  
  
  // Foreign describes objects pointing from JavaScript to C structures.
  // Since they cannot contain references to JS HeapObjects they can be
  // placed in old_data_space.
  class Foreign: public HeapObject {
   public:
    // [address]: field containing the address.
    inline Address foreign_address();
    inline void set_foreign_address(Address value);
  
    DECLARE_CAST(Foreign)
  
    // Dispatched behavior.
    inline void ForeignIterateBody(ObjectVisitor* v);
  
    template<typename StaticVisitor>
    inline void ForeignIterateBody();
  
    // Dispatched behavior.
    DECLARE_PRINTER(Foreign)
    DECLARE_VERIFIER(Foreign)
  
    // Layout description.
  
    static const int kForeignAddressOffset = HeapObject::kHeaderSize;
    static const int kSize = kForeignAddressOffset + kPointerSize;
  
    STATIC_ASSERT(kForeignAddressOffset == Internals::kForeignAddressOffset);
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(Foreign);
  };
  
  
  // The JSArray describes JavaScript Arrays
  //  Such an array can be in one of two modes:
  //    - fast, backing storage is a FixedArray and length <= elements.length();
  //       Please note: push and pop can be used to grow and shrink the array.
  //    - slow, backing storage is a HashTable with numbers as keys.
  class JSArray: public JSObject {
   public:
    // [length]: The length property.
    DECL_ACCESSORS(length, Object)
  
    // Overload the length setter to skip write barrier when the length
    // is set to a smi. This matches the set function on FixedArray.
    inline void set_length(Smi* length);
  
    static void JSArrayUpdateLengthFromIndex(Handle<JSArray> array,
                                             uint32_t index,
                                             Handle<Object> value);
  
    static bool IsReadOnlyLengthDescriptor(Handle<Map> jsarray_map);
    static bool WouldChangeReadOnlyLength(Handle<JSArray> array, uint32_t index);
    static MaybeHandle<Object> ReadOnlyLengthError(Handle<JSArray> array);
  
    // Initialize the array with the given capacity. The function may
    // fail due to out-of-memory situations, but only if the requested
    // capacity is non-zero.
    static void Initialize(Handle<JSArray> array, int capacity, int length = 0);
  
    // Initializes the array to a certain length.
    inline bool AllowsSetElementsLength();
    // Can cause GC.
    MUST_USE_RESULT static MaybeHandle<Object> SetElementsLength(
        Handle<JSArray> array,
        Handle<Object> length);
  
    // Set the content of the array to the content of storage.
    static inline void SetContent(Handle<JSArray> array,
                                  Handle<FixedArrayBase> storage);
  
    DECLARE_CAST(JSArray)
  
    // Ensures that the fixed array backing the JSArray has at
    // least the stated size.
    static inline void EnsureSize(Handle<JSArray> array,
                                  int minimum_size_of_backing_fixed_array);
  
    // Expand the fixed array backing of a fast-case JSArray to at least
    // the requested size.
    static void Expand(Handle<JSArray> array,
                       int minimum_size_of_backing_fixed_array);
  
    // Dispatched behavior.
    DECLARE_PRINTER(JSArray)
    DECLARE_VERIFIER(JSArray)
  
    // Number of element slots to pre-allocate for an empty array.
    static const int kPreallocatedArrayElements = 4;
  
    // Layout description.
    static const int kLengthOffset = JSObject::kHeaderSize;
    static const int kSize = kLengthOffset + kPointerSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSArray);
  };
  
  
  Handle<Object> CacheInitialJSArrayMaps(Handle<Context> native_context,
                                         Handle<Map> initial_map);
  
  
  // JSRegExpResult is just a JSArray with a specific initial map.
  // This initial map adds in-object properties for "index" and "input"
  // properties, as assigned by RegExp.prototype.exec, which allows
  // faster creation of RegExp exec results.
  // This class just holds constants used when creating the result.
  // After creation the result must be treated as a JSArray in all regards.
  class JSRegExpResult: public JSArray {
   public:
    // Offsets of object fields.
    static const int kIndexOffset = JSArray::kSize;
    static const int kInputOffset = kIndexOffset + kPointerSize;
    static const int kSize = kInputOffset + kPointerSize;
    // Indices of in-object properties.
    static const int kIndexIndex = 0;
    static const int kInputIndex = 1;
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(JSRegExpResult);
  };
  
  
  class AccessorInfo: public Struct {
   public:
    DECL_ACCESSORS(name, Object)
    DECL_ACCESSORS(flag, Smi)
    DECL_ACCESSORS(expected_receiver_type, Object)
  
    inline bool all_can_read();
    inline void set_all_can_read(bool value);
  
    inline bool all_can_write();
    inline void set_all_can_write(bool value);
  
    inline PropertyAttributes property_attributes();
    inline void set_property_attributes(PropertyAttributes attributes);
  
    // Checks whether the given receiver is compatible with this accessor.
    static bool IsCompatibleReceiverType(Isolate* isolate,
                                         Handle<AccessorInfo> info,
                                         Handle<HeapType> type);
    inline bool IsCompatibleReceiver(Object* receiver);
  
    DECLARE_CAST(AccessorInfo)
  
    // Dispatched behavior.
    DECLARE_VERIFIER(AccessorInfo)
  
    // Append all descriptors to the array that are not already there.
    // Return number added.
    static int AppendUnique(Handle<Object> descriptors,
                            Handle<FixedArray> array,
                            int valid_descriptors);
  
    static const int kNameOffset = HeapObject::kHeaderSize;
    static const int kFlagOffset = kNameOffset + kPointerSize;
    static const int kExpectedReceiverTypeOffset = kFlagOffset + kPointerSize;
    static const int kSize = kExpectedReceiverTypeOffset + kPointerSize;
  
   private:
    inline bool HasExpectedReceiverType() {
      return expected_receiver_type()->IsFunctionTemplateInfo();
    }
    // Bit positions in flag.
    static const int kAllCanReadBit = 0;
    static const int kAllCanWriteBit = 1;
    class AttributesField: public BitField<PropertyAttributes, 2, 3> {};
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(AccessorInfo);
  };
  
  
  enum AccessorDescriptorType {
    kDescriptorBitmaskCompare,
    kDescriptorPointerCompare,
    kDescriptorPrimitiveValue,
    kDescriptorObjectDereference,
    kDescriptorPointerDereference,
    kDescriptorPointerShift,
    kDescriptorReturnObject
  };
  
  
  struct BitmaskCompareDescriptor {
    uint32_t bitmask;
    uint32_t compare_value;
    uint8_t size;  // Must be in {1,2,4}.
  };
  
  
  struct PointerCompareDescriptor {
    void* compare_value;
  };
  
  
  struct PrimitiveValueDescriptor {
    v8::DeclaredAccessorDescriptorDataType data_type;
    uint8_t bool_offset;  // Must be in [0,7], used for kDescriptorBoolType.
  };
  
  
  struct ObjectDerefenceDescriptor {
    uint8_t internal_field;
  };
  
  
  struct PointerShiftDescriptor {
    int16_t byte_offset;
  };
  
  
  struct DeclaredAccessorDescriptorData {
    AccessorDescriptorType type;
    union {
      struct BitmaskCompareDescriptor bitmask_compare_descriptor;
      struct PointerCompareDescriptor pointer_compare_descriptor;
      struct PrimitiveValueDescriptor primitive_value_descriptor;
      struct ObjectDerefenceDescriptor object_dereference_descriptor;
      struct PointerShiftDescriptor pointer_shift_descriptor;
    };
  };
  
  
  class DeclaredAccessorDescriptor;
  
  
  class DeclaredAccessorDescriptorIterator {
   public:
    explicit DeclaredAccessorDescriptorIterator(
        DeclaredAccessorDescriptor* descriptor);
    const DeclaredAccessorDescriptorData* Next();
    bool Complete() const { return length_ == offset_; }
   private:
    uint8_t* array_;
    const int length_;
    int offset_;
    DISALLOW_IMPLICIT_CONSTRUCTORS(DeclaredAccessorDescriptorIterator);
  };
  
  
  class DeclaredAccessorDescriptor: public Struct {
   public:
    DECL_ACCESSORS(serialized_data, ByteArray)
  
    DECLARE_CAST(DeclaredAccessorDescriptor)
  
    static Handle<DeclaredAccessorDescriptor> Create(
        Isolate* isolate,
        const DeclaredAccessorDescriptorData& data,
        Handle<DeclaredAccessorDescriptor> previous);
  
    // Dispatched behavior.
    DECLARE_PRINTER(DeclaredAccessorDescriptor)
    DECLARE_VERIFIER(DeclaredAccessorDescriptor)
  
    static const int kSerializedDataOffset = HeapObject::kHeaderSize;
    static const int kSize = kSerializedDataOffset + kPointerSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(DeclaredAccessorDescriptor);
  };
  
  
  class DeclaredAccessorInfo: public AccessorInfo {
   public:
    DECL_ACCESSORS(descriptor, DeclaredAccessorDescriptor)
  
    DECLARE_CAST(DeclaredAccessorInfo)
  
    // Dispatched behavior.
    DECLARE_PRINTER(DeclaredAccessorInfo)
    DECLARE_VERIFIER(DeclaredAccessorInfo)
  
    static const int kDescriptorOffset = AccessorInfo::kSize;
    static const int kSize = kDescriptorOffset + kPointerSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(DeclaredAccessorInfo);
  };
  
  
  // An accessor must have a getter, but can have no setter.
  //
  // When setting a property, V8 searches accessors in prototypes.
  // If an accessor was found and it does not have a setter,
  // the request is ignored.
  //
  // If the accessor in the prototype has the READ_ONLY property attribute, then
  // a new value is added to the derived object when the property is set.
  // This shadows the accessor in the prototype.
  class ExecutableAccessorInfo: public AccessorInfo {
   public:
    DECL_ACCESSORS(getter, Object)
    DECL_ACCESSORS(setter, Object)
    DECL_ACCESSORS(data, Object)
  
    DECLARE_CAST(ExecutableAccessorInfo)
  
    // Dispatched behavior.
    DECLARE_PRINTER(ExecutableAccessorInfo)
    DECLARE_VERIFIER(ExecutableAccessorInfo)
  
    static const int kGetterOffset = AccessorInfo::kSize;
    static const int kSetterOffset = kGetterOffset + kPointerSize;
    static const int kDataOffset = kSetterOffset + kPointerSize;
    static const int kSize = kDataOffset + kPointerSize;
  
    inline void clear_setter();
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(ExecutableAccessorInfo);
  };
  
  
  // Support for JavaScript accessors: A pair of a getter and a setter. Each
  // accessor can either be
  //   * a pointer to a JavaScript function or proxy: a real accessor
  //   * undefined: considered an accessor by the spec, too, strangely enough
  //   * the hole: an accessor which has not been set
  //   * a pointer to a map: a transition used to ensure map sharing
  class AccessorPair: public Struct {
   public:
    DECL_ACCESSORS(getter, Object)
    DECL_ACCESSORS(setter, Object)
  
    DECLARE_CAST(AccessorPair)
  
    static Handle<AccessorPair> Copy(Handle<AccessorPair> pair);
  
    Object* get(AccessorComponent component) {
      return component == ACCESSOR_GETTER ? getter() : setter();
    }
  
    void set(AccessorComponent component, Object* value) {
      if (component == ACCESSOR_GETTER) {
        set_getter(value);
      } else {
        set_setter(value);
      }
    }
  
    // Note: Returns undefined instead in case of a hole.
    Object* GetComponent(AccessorComponent component);
  
    // Set both components, skipping arguments which are a JavaScript null.
    void SetComponents(Object* getter, Object* setter) {
      if (!getter->IsNull()) set_getter(getter);
      if (!setter->IsNull()) set_setter(setter);
    }
  
    bool ContainsAccessor() {
      return IsJSAccessor(getter()) || IsJSAccessor(setter());
    }
  
    // Dispatched behavior.
    DECLARE_PRINTER(AccessorPair)
    DECLARE_VERIFIER(AccessorPair)
  
    static const int kGetterOffset = HeapObject::kHeaderSize;
    static const int kSetterOffset = kGetterOffset + kPointerSize;
    static const int kSize = kSetterOffset + kPointerSize;
  
   private:
    // Strangely enough, in addition to functions and harmony proxies, the spec
    // requires us to consider undefined as a kind of accessor, too:
    //    var obj = {};
    //    Object.defineProperty(obj, "foo", {get: undefined});
    //    assertTrue("foo" in obj);
    bool IsJSAccessor(Object* obj) {
      return obj->IsSpecFunction() || obj->IsUndefined();
    }
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(AccessorPair);
  };
  
  
  class AccessCheckInfo: public Struct {
   public:
    DECL_ACCESSORS(named_callback, Object)
    DECL_ACCESSORS(indexed_callback, Object)
    DECL_ACCESSORS(data, Object)
  
    DECLARE_CAST(AccessCheckInfo)
  
    // Dispatched behavior.
    DECLARE_PRINTER(AccessCheckInfo)
    DECLARE_VERIFIER(AccessCheckInfo)
  
    static const int kNamedCallbackOffset   = HeapObject::kHeaderSize;
    static const int kIndexedCallbackOffset = kNamedCallbackOffset + kPointerSize;
    static const int kDataOffset = kIndexedCallbackOffset + kPointerSize;
    static const int kSize = kDataOffset + kPointerSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(AccessCheckInfo);
  };
  
  
  class InterceptorInfo: public Struct {
   public:
    DECL_ACCESSORS(getter, Object)
    DECL_ACCESSORS(setter, Object)
    DECL_ACCESSORS(query, Object)
    DECL_ACCESSORS(deleter, Object)
    DECL_ACCESSORS(enumerator, Object)
    DECL_ACCESSORS(data, Object)
  
    DECLARE_CAST(InterceptorInfo)
  
    // Dispatched behavior.
    DECLARE_PRINTER(InterceptorInfo)
    DECLARE_VERIFIER(InterceptorInfo)
  
    static const int kGetterOffset = HeapObject::kHeaderSize;
    static const int kSetterOffset = kGetterOffset + kPointerSize;
    static const int kQueryOffset = kSetterOffset + kPointerSize;
    static const int kDeleterOffset = kQueryOffset + kPointerSize;
    static const int kEnumeratorOffset = kDeleterOffset + kPointerSize;
    static const int kDataOffset = kEnumeratorOffset + kPointerSize;
    static const int kSize = kDataOffset + kPointerSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(InterceptorInfo);
  };
  
  
  class CallHandlerInfo: public Struct {
   public:
    DECL_ACCESSORS(callback, Object)
    DECL_ACCESSORS(data, Object)
  
    DECLARE_CAST(CallHandlerInfo)
  
    // Dispatched behavior.
    DECLARE_PRINTER(CallHandlerInfo)
    DECLARE_VERIFIER(CallHandlerInfo)
  
    static const int kCallbackOffset = HeapObject::kHeaderSize;
    static const int kDataOffset = kCallbackOffset + kPointerSize;
    static const int kSize = kDataOffset + kPointerSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(CallHandlerInfo);
  };
  
  
  class TemplateInfo: public Struct {
   public:
    DECL_ACCESSORS(tag, Object)
    DECL_ACCESSORS(property_list, Object)
    DECL_ACCESSORS(property_accessors, Object)
  
    DECLARE_VERIFIER(TemplateInfo)
  
    static const int kTagOffset = HeapObject::kHeaderSize;
    static const int kPropertyListOffset = kTagOffset + kPointerSize;
    static const int kPropertyAccessorsOffset =
        kPropertyListOffset + kPointerSize;
    static const int kHeaderSize = kPropertyAccessorsOffset + kPointerSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(TemplateInfo);
  };
  
  
  class FunctionTemplateInfo: public TemplateInfo {
   public:
    DECL_ACCESSORS(serial_number, Object)
    DECL_ACCESSORS(call_code, Object)
    DECL_ACCESSORS(prototype_template, Object)
    DECL_ACCESSORS(parent_template, Object)
    DECL_ACCESSORS(named_property_handler, Object)
    DECL_ACCESSORS(indexed_property_handler, Object)
    DECL_ACCESSORS(instance_template, Object)
    DECL_ACCESSORS(class_name, Object)
    DECL_ACCESSORS(signature, Object)
    DECL_ACCESSORS(instance_call_handler, Object)
    DECL_ACCESSORS(access_check_info, Object)
    DECL_ACCESSORS(flag, Smi)
  
    inline int length() const;
    inline void set_length(int value);
  
    // Following properties use flag bits.
    DECL_BOOLEAN_ACCESSORS(hidden_prototype)
    DECL_BOOLEAN_ACCESSORS(undetectable)
    // If the bit is set, object instances created by this function
    // requires access check.
    DECL_BOOLEAN_ACCESSORS(needs_access_check)
    DECL_BOOLEAN_ACCESSORS(read_only_prototype)
    DECL_BOOLEAN_ACCESSORS(remove_prototype)
    DECL_BOOLEAN_ACCESSORS(do_not_cache)
  
    DECLARE_CAST(FunctionTemplateInfo)
  
    // Dispatched behavior.
    DECLARE_PRINTER(FunctionTemplateInfo)
    DECLARE_VERIFIER(FunctionTemplateInfo)
  
    static const int kSerialNumberOffset = TemplateInfo::kHeaderSize;
    static const int kCallCodeOffset = kSerialNumberOffset + kPointerSize;
    static const int kPrototypeTemplateOffset =
        kCallCodeOffset + kPointerSize;
    static const int kParentTemplateOffset =
        kPrototypeTemplateOffset + kPointerSize;
    static const int kNamedPropertyHandlerOffset =
        kParentTemplateOffset + kPointerSize;
    static const int kIndexedPropertyHandlerOffset =
        kNamedPropertyHandlerOffset + kPointerSize;
    static const int kInstanceTemplateOffset =
        kIndexedPropertyHandlerOffset + kPointerSize;
    static const int kClassNameOffset = kInstanceTemplateOffset + kPointerSize;
    static const int kSignatureOffset = kClassNameOffset + kPointerSize;
    static const int kInstanceCallHandlerOffset = kSignatureOffset + kPointerSize;
    static const int kAccessCheckInfoOffset =
        kInstanceCallHandlerOffset + kPointerSize;
    static const int kFlagOffset = kAccessCheckInfoOffset + kPointerSize;
    static const int kLengthOffset = kFlagOffset + kPointerSize;
    static const int kSize = kLengthOffset + kPointerSize;
  
    // Returns true if |object| is an instance of this function template.
    bool IsTemplateFor(Object* object);
    bool IsTemplateFor(Map* map);
  
   private:
    // Bit position in the flag, from least significant bit position.
    static const int kHiddenPrototypeBit   = 0;
    static const int kUndetectableBit      = 1;
    static const int kNeedsAccessCheckBit  = 2;
    static const int kReadOnlyPrototypeBit = 3;
    static const int kRemovePrototypeBit   = 4;
    static const int kDoNotCacheBit        = 5;
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(FunctionTemplateInfo);
  };
  
  
  class ObjectTemplateInfo: public TemplateInfo {
   public:
    DECL_ACCESSORS(constructor, Object)
    DECL_ACCESSORS(internal_field_count, Object)
  
    DECLARE_CAST(ObjectTemplateInfo)
  
    // Dispatched behavior.
    DECLARE_PRINTER(ObjectTemplateInfo)
    DECLARE_VERIFIER(ObjectTemplateInfo)
  
    static const int kConstructorOffset = TemplateInfo::kHeaderSize;
    static const int kInternalFieldCountOffset =
        kConstructorOffset + kPointerSize;
    static const int kSize = kInternalFieldCountOffset + kPointerSize;
  };
  
  
  class SignatureInfo: public Struct {
   public:
    DECL_ACCESSORS(receiver, Object)
    DECL_ACCESSORS(args, Object)
  
    DECLARE_CAST(SignatureInfo)
  
    // Dispatched behavior.
    DECLARE_PRINTER(SignatureInfo)
    DECLARE_VERIFIER(SignatureInfo)
  
    static const int kReceiverOffset = Struct::kHeaderSize;
    static const int kArgsOffset     = kReceiverOffset + kPointerSize;
    static const int kSize           = kArgsOffset + kPointerSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(SignatureInfo);
  };
  
  
  class TypeSwitchInfo: public Struct {
   public:
    DECL_ACCESSORS(types, Object)
  
    DECLARE_CAST(TypeSwitchInfo)
  
    // Dispatched behavior.
    DECLARE_PRINTER(TypeSwitchInfo)
    DECLARE_VERIFIER(TypeSwitchInfo)
  
    static const int kTypesOffset = Struct::kHeaderSize;
    static const int kSize        = kTypesOffset + kPointerSize;
  };
  
  
  // The DebugInfo class holds additional information for a function being
  // debugged.
  class DebugInfo: public Struct {
   public:
    // The shared function info for the source being debugged.
    DECL_ACCESSORS(shared, SharedFunctionInfo)
    // Code object for the original code.
    DECL_ACCESSORS(original_code, Code)
    // Code object for the patched code. This code object is the code object
    // currently active for the function.
    DECL_ACCESSORS(code, Code)
    // Fixed array holding status information for each active break point.
    DECL_ACCESSORS(break_points, FixedArray)
  
    // Check if there is a break point at a code position.
    bool HasBreakPoint(int code_position);
    // Get the break point info object for a code position.
    Object* GetBreakPointInfo(int code_position);
    // Clear a break point.
    static void ClearBreakPoint(Handle<DebugInfo> debug_info,
                                int code_position,
                                Handle<Object> break_point_object);
    // Set a break point.
    static void SetBreakPoint(Handle<DebugInfo> debug_info, int code_position,
                              int source_position, int statement_position,
                              Handle<Object> break_point_object);
    // Get the break point objects for a code position.
    Object* GetBreakPointObjects(int code_position);
    // Find the break point info holding this break point object.
    static Object* FindBreakPointInfo(Handle<DebugInfo> debug_info,
                                      Handle<Object> break_point_object);
    // Get the number of break points for this function.
    int GetBreakPointCount();
  
    DECLARE_CAST(DebugInfo)
  
    // Dispatched behavior.
    DECLARE_PRINTER(DebugInfo)
    DECLARE_VERIFIER(DebugInfo)
  
    static const int kSharedFunctionInfoIndex = Struct::kHeaderSize;
    static const int kOriginalCodeIndex = kSharedFunctionInfoIndex + kPointerSize;
    static const int kPatchedCodeIndex = kOriginalCodeIndex + kPointerSize;
    static const int kActiveBreakPointsCountIndex =
        kPatchedCodeIndex + kPointerSize;
    static const int kBreakPointsStateIndex =
        kActiveBreakPointsCountIndex + kPointerSize;
    static const int kSize = kBreakPointsStateIndex + kPointerSize;
  
    static const int kEstimatedNofBreakPointsInFunction = 16;
  
   private:
    static const int kNoBreakPointInfo = -1;
  
    // Lookup the index in the break_points array for a code position.
    int GetBreakPointInfoIndex(int code_position);
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(DebugInfo);
  };
  
  
  // The BreakPointInfo class holds information for break points set in a
  // function. The DebugInfo object holds a BreakPointInfo object for each code
  // position with one or more break points.
  class BreakPointInfo: public Struct {
   public:
    // The position in the code for the break point.
    DECL_ACCESSORS(code_position, Smi)
    // The position in the source for the break position.
    DECL_ACCESSORS(source_position, Smi)
    // The position in the source for the last statement before this break
    // position.
    DECL_ACCESSORS(statement_position, Smi)
    // List of related JavaScript break points.
    DECL_ACCESSORS(break_point_objects, Object)
  
    // Removes a break point.
    static void ClearBreakPoint(Handle<BreakPointInfo> info,
                                Handle<Object> break_point_object);
    // Set a break point.
    static void SetBreakPoint(Handle<BreakPointInfo> info,
                              Handle<Object> break_point_object);
    // Check if break point info has this break point object.
    static bool HasBreakPointObject(Handle<BreakPointInfo> info,
                                    Handle<Object> break_point_object);
    // Get the number of break points for this code position.
    int GetBreakPointCount();
  
    DECLARE_CAST(BreakPointInfo)
  
    // Dispatched behavior.
    DECLARE_PRINTER(BreakPointInfo)
    DECLARE_VERIFIER(BreakPointInfo)
  
    static const int kCodePositionIndex = Struct::kHeaderSize;
    static const int kSourcePositionIndex = kCodePositionIndex + kPointerSize;
    static const int kStatementPositionIndex =
        kSourcePositionIndex + kPointerSize;
    static const int kBreakPointObjectsIndex =
        kStatementPositionIndex + kPointerSize;
    static const int kSize = kBreakPointObjectsIndex + kPointerSize;
  
   private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(BreakPointInfo);
  };
  
  
  #undef DECL_BOOLEAN_ACCESSORS
  #undef DECL_ACCESSORS
  #undef DECLARE_CAST
  #undef DECLARE_VERIFIER
  
  #define VISITOR_SYNCHRONIZATION_TAGS_LIST(V)                            \
    V(kStringTable, "string_table", "(Internalized strings)")             \
    V(kExternalStringsTable, "external_strings_table", "(External strings)") \
    V(kStrongRootList, "strong_root_list", "(Strong roots)")              \
    V(kSmiRootList, "smi_root_list", "(Smi roots)")                       \
    V(kInternalizedString, "internalized_string", "(Internal string)")    \
    V(kBootstrapper, "bootstrapper", "(Bootstrapper)")                    \
    V(kTop, "top", "(Isolate)")                                           \
    V(kRelocatable, "relocatable", "(Relocatable)")                       \
    V(kDebug, "debug", "(Debugger)")                                      \
    V(kCompilationCache, "compilationcache", "(Compilation cache)")       \
    V(kHandleScope, "handlescope", "(Handle scope)")                      \
    V(kBuiltins, "builtins", "(Builtins)")                                \
    V(kGlobalHandles, "globalhandles", "(Global handles)")                \
    V(kEternalHandles, "eternalhandles", "(Eternal handles)")             \
    V(kThreadManager, "threadmanager", "(Thread manager)")                \
    V(kExtensions, "Extensions", "(Extensions)")
  
  class VisitorSynchronization : public AllStatic {
   public:
  #define DECLARE_ENUM(enum_item, ignore1, ignore2) enum_item,
    enum SyncTag {
      VISITOR_SYNCHRONIZATION_TAGS_LIST(DECLARE_ENUM)
      kNumberOfSyncTags
    };
  #undef DECLARE_ENUM
  
    static const char* const kTags[kNumberOfSyncTags];
    static const char* const kTagNames[kNumberOfSyncTags];
  };
  
  // Abstract base class for visiting, and optionally modifying, the
  // pointers contained in Objects. Used in GC and serialization/deserialization.
  class ObjectVisitor BASE_EMBEDDED {
   public:
    virtual ~ObjectVisitor() {}
  
    // Visits a contiguous arrays of pointers in the half-open range
    // [start, end). Any or all of the values may be modified on return.
    virtual void VisitPointers(Object** start, Object** end) = 0;
  
    // Handy shorthand for visiting a single pointer.
    virtual void VisitPointer(Object** p) { VisitPointers(p, p + 1); }
  
    // Visit weak next_code_link in Code object.
    virtual void VisitNextCodeLink(Object** p) { VisitPointers(p, p + 1); }
  
    // To allow lazy clearing of inline caches the visitor has
    // a rich interface for iterating over Code objects..
  
    // Visits a code target in the instruction stream.
    virtual void VisitCodeTarget(RelocInfo* rinfo);
  
    // Visits a code entry in a JS function.
    virtual void VisitCodeEntry(Address entry_address);
  
    // Visits a global property cell reference in the instruction stream.
    virtual void VisitCell(RelocInfo* rinfo);
  
    // Visits a runtime entry in the instruction stream.
    virtual void VisitRuntimeEntry(RelocInfo* rinfo) {}
  
    // Visits the resource of an one-byte or two-byte string.
    virtual void VisitExternalOneByteString(
        v8::String::ExternalOneByteStringResource** resource) {}
    virtual void VisitExternalTwoByteString(
        v8::String::ExternalStringResource** resource) {}
  
    // Visits a debug call target in the instruction stream.
    virtual void VisitDebugTarget(RelocInfo* rinfo);
  
    // Visits the byte sequence in a function's prologue that contains information
    // about the code's age.
    virtual void VisitCodeAgeSequence(RelocInfo* rinfo);
  
    // Visit pointer embedded into a code object.
    virtual void VisitEmbeddedPointer(RelocInfo* rinfo);
  
    // Visits an external reference embedded into a code object.
    virtual void VisitExternalReference(RelocInfo* rinfo);
  
    // Visits an external reference. The value may be modified on return.
    virtual void VisitExternalReference(Address* p) {}
  
    // Visits a handle that has an embedder-assigned class ID.
    virtual void VisitEmbedderReference(Object** p, uint16_t class_id) {}
  
    // Intended for serialization/deserialization checking: insert, or
    // check for the presence of, a tag at this position in the stream.
    // Also used for marking up GC roots in heap snapshots.
    virtual void Synchronize(VisitorSynchronization::SyncTag tag) {}
  };
  
  
  class StructBodyDescriptor : public
    FlexibleBodyDescriptor<HeapObject::kHeaderSize> {
   public:
    static inline int SizeOf(Map* map, HeapObject* object) {
      return map->instance_size();
    }
  };
  
  
  // BooleanBit is a helper class for setting and getting a bit in an
  // integer or Smi.
  class BooleanBit : public AllStatic {
   public:
    static inline bool get(Smi* smi, int bit_position) {
      return get(smi->value(), bit_position);
    }
  
    static inline bool get(int value, int bit_position) {
      return (value & (1 << bit_position)) != 0;
    }
  
    static inline Smi* set(Smi* smi, int bit_position, bool v) {
      return Smi::FromInt(set(smi->value(), bit_position, v));
    }
  
    static inline int set(int value, int bit_position, bool v) {
      if (v) {
        value |= (1 << bit_position);
      } else {
        value &= ~(1 << bit_position);
      }
      return value;
    }
  };
  
  } }  // namespace v8::internal
  
  #endif  // V8_OBJECTS_H_
  