text: //===---- CGBuiltin.cpp - Emit LLVM Code for builtins ---------------------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This contains code to emit Objective-C code as LLVM code.
  //
  //===----------------------------------------------------------------------===//
  
  #include "CGDebugInfo.h"
  #include "CGObjCRuntime.h"
  #include "CodeGenFunction.h"
  #include "CodeGenModule.h"
  #include "TargetInfo.h"
  #include "clang/AST/ASTContext.h"
  #include "clang/AST/DeclObjC.h"
  #include "clang/AST/StmtObjC.h"
  #include "clang/Basic/Diagnostic.h"
  #include "clang/CodeGen/CGFunctionInfo.h"
  #include "llvm/ADT/STLExtras.h"
  #include "llvm/IR/CallSite.h"
  #include "llvm/IR/DataLayout.h"
  #include "llvm/IR/InlineAsm.h"
  using namespace clang;
  using namespace CodeGen;
  
  typedef llvm::PointerIntPair<llvm::Value*,1,bool> TryEmitResult;
  static TryEmitResult
  tryEmitARCRetainScalarExpr(CodeGenFunction &CGF, const Expr *e);
  static RValue AdjustObjCObjectType(CodeGenFunction &CGF,
                                     QualType ET,
                                     RValue Result);
  
  /// Given the address of a variable of pointer type, find the correct
  /// null to store into it.
  static llvm::Constant *getNullForVariable(Address addr) {
    llvm::Type *type = addr.getElementType();
    return llvm::ConstantPointerNull::get(cast<llvm::PointerType>(type));
  }
  
  /// Emits an instance of NSConstantString representing the object.
  llvm::Value *CodeGenFunction::EmitObjCStringLiteral(const ObjCStringLiteral *E)
  {
    llvm::Constant *C = 
        CGM.getObjCRuntime().GenerateConstantString(E->getString()).getPointer();
    // FIXME: This bitcast should just be made an invariant on the Runtime.
    return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType()));
  }
  
  /// EmitObjCBoxedExpr - This routine generates code to call
  /// the appropriate expression boxing method. This will either be
  /// one of +[NSNumber numberWith<Type>:], or +[NSString stringWithUTF8String:],
  /// or [NSValue valueWithBytes:objCType:].
  ///
  llvm::Value *
  CodeGenFunction::EmitObjCBoxedExpr(const ObjCBoxedExpr *E) {
    // Generate the correct selector for this literal's concrete type.
    // Get the method.
    const ObjCMethodDecl *BoxingMethod = E->getBoxingMethod();
    const Expr *SubExpr = E->getSubExpr();
    assert(BoxingMethod && "BoxingMethod is null");
    assert(BoxingMethod->isClassMethod() && "BoxingMethod must be a class method");
    Selector Sel = BoxingMethod->getSelector();
    
    // Generate a reference to the class pointer, which will be the receiver.
    // Assumes that the method was introduced in the class that should be
    // messaged (avoids pulling it out of the result type).
    CGObjCRuntime &Runtime = CGM.getObjCRuntime();
    const ObjCInterfaceDecl *ClassDecl = BoxingMethod->getClassInterface();
    llvm::Value *Receiver = Runtime.GetClass(*this, ClassDecl);
  
    CallArgList Args;
    const ParmVarDecl *ArgDecl = *BoxingMethod->param_begin();
    QualType ArgQT = ArgDecl->getType().getUnqualifiedType();
    
    // ObjCBoxedExpr supports boxing of structs and unions 
    // via [NSValue valueWithBytes:objCType:]
    const QualType ValueType(SubExpr->getType().getCanonicalType());
    if (ValueType->isObjCBoxableRecordType()) {
      // Emit CodeGen for first parameter
      // and cast value to correct type
      Address Temporary = CreateMemTemp(SubExpr->getType());
      EmitAnyExprToMem(SubExpr, Temporary, Qualifiers(), /*isInit*/ true);
      Address BitCast = Builder.CreateBitCast(Temporary, ConvertType(ArgQT));
      Args.add(RValue::get(BitCast.getPointer()), ArgQT);
  
      // Create char array to store type encoding
      std::string Str;
      getContext().getObjCEncodingForType(ValueType, Str);
      llvm::Constant *GV = CGM.GetAddrOfConstantCString(Str).getPointer();
      
      // Cast type encoding to correct type
      const ParmVarDecl *EncodingDecl = BoxingMethod->parameters()[1];
      QualType EncodingQT = EncodingDecl->getType().getUnqualifiedType();
      llvm::Value *Cast = Builder.CreateBitCast(GV, ConvertType(EncodingQT));
  
      Args.add(RValue::get(Cast), EncodingQT);
    } else {
      Args.add(EmitAnyExpr(SubExpr), ArgQT);
    }
  
    RValue result = Runtime.GenerateMessageSend(
        *this, ReturnValueSlot(), BoxingMethod->getReturnType(), Sel, Receiver,
        Args, ClassDecl, BoxingMethod);
    return Builder.CreateBitCast(result.getScalarVal(), 
                                 ConvertType(E->getType()));
  }
  
  llvm::Value *CodeGenFunction::EmitObjCCollectionLiteral(const Expr *E,
                                      const ObjCMethodDecl *MethodWithObjects) {
    ASTContext &Context = CGM.getContext();
    const ObjCDictionaryLiteral *DLE = nullptr;
    const ObjCArrayLiteral *ALE = dyn_cast<ObjCArrayLiteral>(E);
    if (!ALE)
      DLE = cast<ObjCDictionaryLiteral>(E);
    
    // Compute the type of the array we're initializing.
    uint64_t NumElements = 
      ALE ? ALE->getNumElements() : DLE->getNumElements();
    llvm::APInt APNumElements(Context.getTypeSize(Context.getSizeType()),
                              NumElements);
    QualType ElementType = Context.getObjCIdType().withConst();
    QualType ElementArrayType 
      = Context.getConstantArrayType(ElementType, APNumElements, 
                                     ArrayType::Normal, /*IndexTypeQuals=*/0);
  
    // Allocate the temporary array(s).
    Address Objects = CreateMemTemp(ElementArrayType, "objects");
    Address Keys = Address::invalid();
    if (DLE)
      Keys = CreateMemTemp(ElementArrayType, "keys");
    
    // In ARC, we may need to do extra work to keep all the keys and
    // values alive until after the call.
    SmallVector<llvm::Value *, 16> NeededObjects;
    bool TrackNeededObjects =
      (getLangOpts().ObjCAutoRefCount &&
      CGM.getCodeGenOpts().OptimizationLevel != 0);
  
    // Perform the actual initialialization of the array(s).
    for (uint64_t i = 0; i < NumElements; i++) {
      if (ALE) {
        // Emit the element and store it to the appropriate array slot.
        const Expr *Rhs = ALE->getElement(i);
        LValue LV = MakeAddrLValue(
            Builder.CreateConstArrayGEP(Objects, i, getPointerSize()),
            ElementType, AlignmentSource::Decl);
  
        llvm::Value *value = EmitScalarExpr(Rhs);
        EmitStoreThroughLValue(RValue::get(value), LV, true);
        if (TrackNeededObjects) {
          NeededObjects.push_back(value);
        }
      } else {      
        // Emit the key and store it to the appropriate array slot.
        const Expr *Key = DLE->getKeyValueElement(i).Key;
        LValue KeyLV = MakeAddrLValue(
            Builder.CreateConstArrayGEP(Keys, i, getPointerSize()),
            ElementType, AlignmentSource::Decl);
        llvm::Value *keyValue = EmitScalarExpr(Key);
        EmitStoreThroughLValue(RValue::get(keyValue), KeyLV, /*isInit=*/true);
  
        // Emit the value and store it to the appropriate array slot.
        const Expr *Value = DLE->getKeyValueElement(i).Value;
        LValue ValueLV = MakeAddrLValue(
            Builder.CreateConstArrayGEP(Objects, i, getPointerSize()),
            ElementType, AlignmentSource::Decl);
        llvm::Value *valueValue = EmitScalarExpr(Value);
        EmitStoreThroughLValue(RValue::get(valueValue), ValueLV, /*isInit=*/true);
        if (TrackNeededObjects) {
          NeededObjects.push_back(keyValue);
          NeededObjects.push_back(valueValue);
        }
      }
    }
    
    // Generate the argument list.
    CallArgList Args;  
    ObjCMethodDecl::param_const_iterator PI = MethodWithObjects->param_begin();
    const ParmVarDecl *argDecl = *PI++;
    QualType ArgQT = argDecl->getType().getUnqualifiedType();
    Args.add(RValue::get(Objects.getPointer()), ArgQT);
    if (DLE) {
      argDecl = *PI++;
      ArgQT = argDecl->getType().getUnqualifiedType();
      Args.add(RValue::get(Keys.getPointer()), ArgQT);
    }
    argDecl = *PI;
    ArgQT = argDecl->getType().getUnqualifiedType();
    llvm::Value *Count = 
      llvm::ConstantInt::get(CGM.getTypes().ConvertType(ArgQT), NumElements);
    Args.add(RValue::get(Count), ArgQT);
  
    // Generate a reference to the class pointer, which will be the receiver.
    Selector Sel = MethodWithObjects->getSelector();
    QualType ResultType = E->getType();
    const ObjCObjectPointerType *InterfacePointerType
      = ResultType->getAsObjCInterfacePointerType();
    ObjCInterfaceDecl *Class 
      = InterfacePointerType->getObjectType()->getInterface();
    CGObjCRuntime &Runtime = CGM.getObjCRuntime();
    llvm::Value *Receiver = Runtime.GetClass(*this, Class);
  
    // Generate the message send.
    RValue result = Runtime.GenerateMessageSend(
        *this, ReturnValueSlot(), MethodWithObjects->getReturnType(), Sel,
        Receiver, Args, Class, MethodWithObjects);
  
    // The above message send needs these objects, but in ARC they are
    // passed in a buffer that is essentially __unsafe_unretained.
    // Therefore we must prevent the optimizer from releasing them until
    // after the call.
    if (TrackNeededObjects) {
      EmitARCIntrinsicUse(NeededObjects);
    }
  
    return Builder.CreateBitCast(result.getScalarVal(), 
                                 ConvertType(E->getType()));
  }
  
  llvm::Value *CodeGenFunction::EmitObjCArrayLiteral(const ObjCArrayLiteral *E) {
    return EmitObjCCollectionLiteral(E, E->getArrayWithObjectsMethod());
  }
  
  llvm::Value *CodeGenFunction::EmitObjCDictionaryLiteral(
                                              const ObjCDictionaryLiteral *E) {
    return EmitObjCCollectionLiteral(E, E->getDictWithObjectsMethod());
  }
  
  /// Emit a selector.
  llvm::Value *CodeGenFunction::EmitObjCSelectorExpr(const ObjCSelectorExpr *E) {
    // Untyped selector.
    // Note that this implementation allows for non-constant strings to be passed
    // as arguments to @selector().  Currently, the only thing preventing this
    // behaviour is the type checking in the front end.
    return CGM.getObjCRuntime().GetSelector(*this, E->getSelector());
  }
  
  llvm::Value *CodeGenFunction::EmitObjCProtocolExpr(const ObjCProtocolExpr *E) {
    // FIXME: This should pass the Decl not the name.
    return CGM.getObjCRuntime().GenerateProtocolRef(*this, E->getProtocol());
  }
  
  /// \brief Adjust the type of an Objective-C object that doesn't match up due
  /// to type erasure at various points, e.g., related result types or the use
  /// of parameterized classes.
  static RValue AdjustObjCObjectType(CodeGenFunction &CGF, QualType ExpT,
                                     RValue Result) {
    if (!ExpT->isObjCRetainableType())
      return Result;
  
    // If the converted types are the same, we're done.
    llvm::Type *ExpLLVMTy = CGF.ConvertType(ExpT);
    if (ExpLLVMTy == Result.getScalarVal()->getType())
      return Result;
  
    // We have applied a substitution. Cast the rvalue appropriately.
    return RValue::get(CGF.Builder.CreateBitCast(Result.getScalarVal(),
                                                 ExpLLVMTy));
  }
  
  /// Decide whether to extend the lifetime of the receiver of a
  /// returns-inner-pointer message.
  static bool
  shouldExtendReceiverForInnerPointerMessage(const ObjCMessageExpr *message) {
    switch (message->getReceiverKind()) {
  
    // For a normal instance message, we should extend unless the
    // receiver is loaded from a variable with precise lifetime.
    case ObjCMessageExpr::Instance: {
      const Expr *receiver = message->getInstanceReceiver();
  
      // Look through OVEs.
      if (auto opaque = dyn_cast<OpaqueValueExpr>(receiver)) {
        if (opaque->getSourceExpr())
          receiver = opaque->getSourceExpr()->IgnoreParens();
      }
  
      const ImplicitCastExpr *ice = dyn_cast<ImplicitCastExpr>(receiver);
      if (!ice || ice->getCastKind() != CK_LValueToRValue) return true;
      receiver = ice->getSubExpr()->IgnoreParens();
  
      // Look through OVEs.
      if (auto opaque = dyn_cast<OpaqueValueExpr>(receiver)) {
        if (opaque->getSourceExpr())
          receiver = opaque->getSourceExpr()->IgnoreParens();
      }
  
      // Only __strong variables.
      if (receiver->getType().getObjCLifetime() != Qualifiers::OCL_Strong)
        return true;
  
      // All ivars and fields have precise lifetime.
      if (isa<MemberExpr>(receiver) || isa<ObjCIvarRefExpr>(receiver))
        return false;
  
      // Otherwise, check for variables.
      const DeclRefExpr *declRef = dyn_cast<DeclRefExpr>(ice->getSubExpr());
      if (!declRef) return true;
      const VarDecl *var = dyn_cast<VarDecl>(declRef->getDecl());
      if (!var) return true;
  
      // All variables have precise lifetime except local variables with
      // automatic storage duration that aren't specially marked.
      return (var->hasLocalStorage() &&
              !var->hasAttr<ObjCPreciseLifetimeAttr>());
    }
  
    case ObjCMessageExpr::Class:
    case ObjCMessageExpr::SuperClass:
      // It's never necessary for class objects.
      return false;
  
    case ObjCMessageExpr::SuperInstance:
      // We generally assume that 'self' lives throughout a method call.
      return false;
    }
  
    llvm_unreachable("invalid receiver kind");
  }
  
  /// Given an expression of ObjC pointer type, check whether it was
  /// immediately loaded from an ARC __weak l-value.
  static const Expr *findWeakLValue(const Expr *E) {
    assert(E->getType()->isObjCRetainableType());
    E = E->IgnoreParens();
    if (auto CE = dyn_cast<CastExpr>(E)) {
      if (CE->getCastKind() == CK_LValueToRValue) {
        if (CE->getSubExpr()->getType().getObjCLifetime() == Qualifiers::OCL_Weak)
          return CE->getSubExpr();
      }
    }
  
    return nullptr;
  }
  
  RValue CodeGenFunction::EmitObjCMessageExpr(const ObjCMessageExpr *E,
                                              ReturnValueSlot Return) {
    // Only the lookup mechanism and first two arguments of the method
    // implementation vary between runtimes.  We can get the receiver and
    // arguments in generic code.
  
    bool isDelegateInit = E->isDelegateInitCall();
  
    const ObjCMethodDecl *method = E->getMethodDecl();
  
    // If the method is -retain, and the receiver's being loaded from
    // a __weak variable, peephole the entire operation to objc_loadWeakRetained.
    if (method && E->getReceiverKind() == ObjCMessageExpr::Instance &&
        method->getMethodFamily() == OMF_retain) {
      if (auto lvalueExpr = findWeakLValue(E->getInstanceReceiver())) {
        LValue lvalue = EmitLValue(lvalueExpr);
        llvm::Value *result = EmitARCLoadWeakRetained(lvalue.getAddress());
        return AdjustObjCObjectType(*this, E->getType(), RValue::get(result));
      }
    }
  
    // We don't retain the receiver in delegate init calls, and this is
    // safe because the receiver value is always loaded from 'self',
    // which we zero out.  We don't want to Block_copy block receivers,
    // though.
    bool retainSelf =
      (!isDelegateInit &&
       CGM.getLangOpts().ObjCAutoRefCount &&
       method &&
       method->hasAttr<NSConsumesSelfAttr>());
  
    CGObjCRuntime &Runtime = CGM.getObjCRuntime();
    bool isSuperMessage = false;
    bool isClassMessage = false;
    ObjCInterfaceDecl *OID = nullptr;
    // Find the receiver
    QualType ReceiverType;
    llvm::Value *Receiver = nullptr;
    switch (E->getReceiverKind()) {
    case ObjCMessageExpr::Instance:
      ReceiverType = E->getInstanceReceiver()->getType();
      if (retainSelf) {
        TryEmitResult ter = tryEmitARCRetainScalarExpr(*this,
                                                     E->getInstanceReceiver());
        Receiver = ter.getPointer();
        if (ter.getInt()) retainSelf = false;
      } else
        Receiver = EmitScalarExpr(E->getInstanceReceiver());
      break;
  
    case ObjCMessageExpr::Class: {
      ReceiverType = E->getClassReceiver();
      const ObjCObjectType *ObjTy = ReceiverType->getAs<ObjCObjectType>();
      assert(ObjTy && "Invalid Objective-C class message send");
      OID = ObjTy->getInterface();
      assert(OID && "Invalid Objective-C class message send");
      Receiver = Runtime.GetClass(*this, OID);
      isClassMessage = true;
      break;
    }
  
    case ObjCMessageExpr::SuperInstance:
      ReceiverType = E->getSuperType();
      Receiver = LoadObjCSelf();
      isSuperMessage = true;
      break;
  
    case ObjCMessageExpr::SuperClass:
      ReceiverType = E->getSuperType();
      Receiver = LoadObjCSelf();
      isSuperMessage = true;
      isClassMessage = true;
      break;
    }
  
    if (retainSelf)
      Receiver = EmitARCRetainNonBlock(Receiver);
  
    // In ARC, we sometimes want to "extend the lifetime"
    // (i.e. retain+autorelease) of receivers of returns-inner-pointer
    // messages.
    if (getLangOpts().ObjCAutoRefCount && method &&
        method->hasAttr<ObjCReturnsInnerPointerAttr>() &&
        shouldExtendReceiverForInnerPointerMessage(E))
      Receiver = EmitARCRetainAutorelease(ReceiverType, Receiver);
  
    QualType ResultType = method ? method->getReturnType() : E->getType();
  
    CallArgList Args;
    EmitCallArgs(Args, method, E->arguments());
  
    // For delegate init calls in ARC, do an unsafe store of null into
    // self.  This represents the call taking direct ownership of that
    // value.  We have to do this after emitting the other call
    // arguments because they might also reference self, but we don't
    // have to worry about any of them modifying self because that would
    // be an undefined read and write of an object in unordered
    // expressions.
    if (isDelegateInit) {
      assert(getLangOpts().ObjCAutoRefCount &&
             "delegate init calls should only be marked in ARC");
  
      // Do an unsafe store of null into self.
      Address selfAddr =
        GetAddrOfLocalVar(cast<ObjCMethodDecl>(CurCodeDecl)->getSelfDecl());
      Builder.CreateStore(getNullForVariable(selfAddr), selfAddr);
    }
  
    RValue result;
    if (isSuperMessage) {
      // super is only valid in an Objective-C method
      const ObjCMethodDecl *OMD = cast<ObjCMethodDecl>(CurFuncDecl);
      bool isCategoryImpl = isa<ObjCCategoryImplDecl>(OMD->getDeclContext());
      result = Runtime.GenerateMessageSendSuper(*this, Return, ResultType,
                                                E->getSelector(),
                                                OMD->getClassInterface(),
                                                isCategoryImpl,
                                                Receiver,
                                                isClassMessage,
                                                Args,
                                                method);
    } else {
      result = Runtime.GenerateMessageSend(*this, Return, ResultType,
                                           E->getSelector(),
                                           Receiver, Args, OID,
                                           method);
    }
  
    // For delegate init calls in ARC, implicitly store the result of
    // the call back into self.  This takes ownership of the value.
    if (isDelegateInit) {
      Address selfAddr =
        GetAddrOfLocalVar(cast<ObjCMethodDecl>(CurCodeDecl)->getSelfDecl());
      llvm::Value *newSelf = result.getScalarVal();
  
      // The delegate return type isn't necessarily a matching type; in
      // fact, it's quite likely to be 'id'.
      llvm::Type *selfTy = selfAddr.getElementType();
      newSelf = Builder.CreateBitCast(newSelf, selfTy);
  
      Builder.CreateStore(newSelf, selfAddr);
    }
  
    return AdjustObjCObjectType(*this, E->getType(), result);
  }
  
  namespace {
  struct FinishARCDealloc final : EHScopeStack::Cleanup {
    void Emit(CodeGenFunction &CGF, Flags flags) override {
      const ObjCMethodDecl *method = cast<ObjCMethodDecl>(CGF.CurCodeDecl);
  
      const ObjCImplDecl *impl = cast<ObjCImplDecl>(method->getDeclContext());
      const ObjCInterfaceDecl *iface = impl->getClassInterface();
      if (!iface->getSuperClass()) return;
  
      bool isCategory = isa<ObjCCategoryImplDecl>(impl);
  
      // Call [super dealloc] if we have a superclass.
      llvm::Value *self = CGF.LoadObjCSelf();
  
      CallArgList args;
      CGF.CGM.getObjCRuntime().GenerateMessageSendSuper(CGF, ReturnValueSlot(),
                                                        CGF.getContext().VoidTy,
                                                        method->getSelector(),
                                                        iface,
                                                        isCategory,
                                                        self,
                                                        /*is class msg*/ false,
                                                        args,
                                                        method);
    }
  };
  }
  
  /// StartObjCMethod - Begin emission of an ObjCMethod. This generates
  /// the LLVM function and sets the other context used by
  /// CodeGenFunction.
  void CodeGenFunction::StartObjCMethod(const ObjCMethodDecl *OMD,
                                        const ObjCContainerDecl *CD) {
    SourceLocation StartLoc = OMD->getLocStart();
    FunctionArgList args;
    // Check if we should generate debug info for this method.
    if (OMD->hasAttr<NoDebugAttr>())
      DebugInfo = nullptr; // disable debug info indefinitely for this function
  
    llvm::Function *Fn = CGM.getObjCRuntime().GenerateMethod(OMD, CD);
  
    const CGFunctionInfo &FI = CGM.getTypes().arrangeObjCMethodDeclaration(OMD);
    CGM.SetInternalFunctionAttributes(OMD, Fn, FI);
  
    args.push_back(OMD->getSelfDecl());
    args.push_back(OMD->getCmdDecl());
  
    args.append(OMD->param_begin(), OMD->param_end());
  
    CurGD = OMD;
    CurEHLocation = OMD->getLocEnd();
  
    StartFunction(OMD, OMD->getReturnType(), Fn, FI, args,
                  OMD->getLocation(), StartLoc);
  
    // In ARC, certain methods get an extra cleanup.
    if (CGM.getLangOpts().ObjCAutoRefCount &&
        OMD->isInstanceMethod() &&
        OMD->getSelector().isUnarySelector()) {
      const IdentifierInfo *ident = 
        OMD->getSelector().getIdentifierInfoForSlot(0);
      if (ident->isStr("dealloc"))
        EHStack.pushCleanup<FinishARCDealloc>(getARCCleanupKind());
    }
  }
  
  static llvm::Value *emitARCRetainLoadOfScalar(CodeGenFunction &CGF,
                                                LValue lvalue, QualType type);
  
  /// Generate an Objective-C method.  An Objective-C method is a C function with
  /// its pointer, name, and types registered in the class struture.
  void CodeGenFunction::GenerateObjCMethod(const ObjCMethodDecl *OMD) {
    StartObjCMethod(OMD, OMD->getClassInterface());
    PGO.assignRegionCounters(GlobalDecl(OMD), CurFn);
    assert(isa<CompoundStmt>(OMD->getBody()));
    incrementProfileCounter(OMD->getBody());
    EmitCompoundStmtWithoutScope(*cast<CompoundStmt>(OMD->getBody()));
    FinishFunction(OMD->getBodyRBrace());
  }
  
  /// emitStructGetterCall - Call the runtime function to load a property
  /// into the return value slot.
  static void emitStructGetterCall(CodeGenFunction &CGF, ObjCIvarDecl *ivar, 
                                   bool isAtomic, bool hasStrong) {
    ASTContext &Context = CGF.getContext();
  
    Address src =
      CGF.EmitLValueForIvar(CGF.TypeOfSelfObject(), CGF.LoadObjCSelf(), ivar, 0)
         .getAddress();
  
    // objc_copyStruct (ReturnValue, &structIvar, 
    //                  sizeof (Type of Ivar), isAtomic, false);
    CallArgList args;
  
    Address dest = CGF.Builder.CreateBitCast(CGF.ReturnValue, CGF.VoidPtrTy);
    args.add(RValue::get(dest.getPointer()), Context.VoidPtrTy);
  
    src = CGF.Builder.CreateBitCast(src, CGF.VoidPtrTy);
    args.add(RValue::get(src.getPointer()), Context.VoidPtrTy);
  
    CharUnits size = CGF.getContext().getTypeSizeInChars(ivar->getType());
    args.add(RValue::get(CGF.CGM.getSize(size)), Context.getSizeType());
    args.add(RValue::get(CGF.Builder.getInt1(isAtomic)), Context.BoolTy);
    args.add(RValue::get(CGF.Builder.getInt1(hasStrong)), Context.BoolTy);
  
    llvm::Constant *fn = CGF.CGM.getObjCRuntime().GetGetStructFunction();
    CGCallee callee = CGCallee::forDirect(fn);
    CGF.EmitCall(CGF.getTypes().arrangeBuiltinFunctionCall(Context.VoidTy, args),
                 callee, ReturnValueSlot(), args);
  }
  
  /// Determine whether the given architecture supports unaligned atomic
  /// accesses.  They don't have to be fast, just faster than a function
  /// call and a mutex.
  static bool hasUnalignedAtomics(llvm::Triple::ArchType arch) {
    // FIXME: Allow unaligned atomic load/store on x86.  (It is not
    // currently supported by the backend.)
    return 0;
  }
  
  /// Return the maximum size that permits atomic accesses for the given
  /// architecture.
  static CharUnits getMaxAtomicAccessSize(CodeGenModule &CGM,
                                          llvm::Triple::ArchType arch) {
    // ARM has 8-byte atomic accesses, but it's not clear whether we
    // want to rely on them here.
  
    // In the default case, just assume that any size up to a pointer is
    // fine given adequate alignment.
    return CharUnits::fromQuantity(CGM.PointerSizeInBytes);
  }
  
  namespace {
    class PropertyImplStrategy {
    public:
      enum StrategyKind {
        /// The 'native' strategy is to use the architecture's provided
        /// reads and writes.
        Native,
  
        /// Use objc_setProperty and objc_getProperty.
        GetSetProperty,
  
        /// Use objc_setProperty for the setter, but use expression
        /// evaluation for the getter.
        SetPropertyAndExpressionGet,
  
        /// Use objc_copyStruct.
        CopyStruct,
  
        /// The 'expression' strategy is to emit normal assignment or
        /// lvalue-to-rvalue expressions.
        Expression
      };
  
      StrategyKind getKind() const { return StrategyKind(Kind); }
  
      bool hasStrongMember() const { return HasStrong; }
      bool isAtomic() const { return IsAtomic; }
      bool isCopy() const { return IsCopy; }
  
      CharUnits getIvarSize() const { return IvarSize; }
      CharUnits getIvarAlignment() const { return IvarAlignment; }
  
      PropertyImplStrategy(CodeGenModule &CGM,
                           const ObjCPropertyImplDecl *propImpl);
  
    private:
      unsigned Kind : 8;
      unsigned IsAtomic : 1;
      unsigned IsCopy : 1;
      unsigned HasStrong : 1;
  
      CharUnits IvarSize;
      CharUnits IvarAlignment;
    };
  }
  
  /// Pick an implementation strategy for the given property synthesis.
  PropertyImplStrategy::PropertyImplStrategy(CodeGenModule &CGM,
                                       const ObjCPropertyImplDecl *propImpl) {
    const ObjCPropertyDecl *prop = propImpl->getPropertyDecl();
    ObjCPropertyDecl::SetterKind setterKind = prop->getSetterKind();
  
    IsCopy = (setterKind == ObjCPropertyDecl::Copy);
    IsAtomic = prop->isAtomic();
    HasStrong = false; // doesn't matter here.
  
    // Evaluate the ivar's size and alignment.
    ObjCIvarDecl *ivar = propImpl->getPropertyIvarDecl();
    QualType ivarType = ivar->getType();
    std::tie(IvarSize, IvarAlignment) =
        CGM.getContext().getTypeInfoInChars(ivarType);
  
    // If we have a copy property, we always have to use getProperty/setProperty.
    // TODO: we could actually use setProperty and an expression for non-atomics.
    if (IsCopy) {
      Kind = GetSetProperty;
      return;
    }
  
    // Handle retain.
    if (setterKind == ObjCPropertyDecl::Retain) {
      // In GC-only, there's nothing special that needs to be done.
      if (CGM.getLangOpts().getGC() == LangOptions::GCOnly) {
        // fallthrough
  
      // In ARC, if the property is non-atomic, use expression emission,
      // which translates to objc_storeStrong.  This isn't required, but
      // it's slightly nicer.
      } else if (CGM.getLangOpts().ObjCAutoRefCount && !IsAtomic) {
        // Using standard expression emission for the setter is only
        // acceptable if the ivar is __strong, which won't be true if
        // the property is annotated with __attribute__((NSObject)).
        // TODO: falling all the way back to objc_setProperty here is
        // just laziness, though;  we could still use objc_storeStrong
        // if we hacked it right.
        if (ivarType.getObjCLifetime() == Qualifiers::OCL_Strong)
          Kind = Expression;
        else
          Kind = SetPropertyAndExpressionGet;
        return;
  
      // Otherwise, we need to at least use setProperty.  However, if
      // the property isn't atomic, we can use normal expression
      // emission for the getter.
      } else if (!IsAtomic) {
        Kind = SetPropertyAndExpressionGet;
        return;
  
      // Otherwise, we have to use both setProperty and getProperty.
      } else {
        Kind = GetSetProperty;
        return;
      }
    }
  
    // If we're not atomic, just use expression accesses.
    if (!IsAtomic) {
      Kind = Expression;
      return;
    }
  
    // Properties on bitfield ivars need to be emitted using expression
    // accesses even if they're nominally atomic.
    if (ivar->isBitField()) {
      Kind = Expression;
      return;
    }
  
    // GC-qualified or ARC-qualified ivars need to be emitted as
    // expressions.  This actually works out to being atomic anyway,
    // except for ARC __strong, but that should trigger the above code.
    if (ivarType.hasNonTrivialObjCLifetime() ||
        (CGM.getLangOpts().getGC() &&
         CGM.getContext().getObjCGCAttrKind(ivarType))) {
      Kind = Expression;
      return;
    }
  
    // Compute whether the ivar has strong members.
    if (CGM.getLangOpts().getGC())
      if (const RecordType *recordType = ivarType->getAs<RecordType>())
        HasStrong = recordType->getDecl()->hasObjectMember();
  
    // We can never access structs with object members with a native
    // access, because we need to use write barriers.  This is what
    // objc_copyStruct is for.
    if (HasStrong) {
      Kind = CopyStruct;
      return;
    }
  
    // Otherwise, this is target-dependent and based on the size and
    // alignment of the ivar.
  
    // If the size of the ivar is not a power of two, give up.  We don't
    // want to get into the business of doing compare-and-swaps.
    if (!IvarSize.isPowerOfTwo()) {
      Kind = CopyStruct;
      return;
    }
  
    llvm::Triple::ArchType arch =
      CGM.getTarget().getTriple().getArch();
  
    // Most architectures require memory to fit within a single cache
    // line, so the alignment has to be at least the size of the access.
    // Otherwise we have to grab a lock.
    if (IvarAlignment < IvarSize && !hasUnalignedAtomics(arch)) {
      Kind = CopyStruct;
      return;
    }
  
    // If the ivar's size exceeds the architecture's maximum atomic
    // access size, we have to use CopyStruct.
    if (IvarSize > getMaxAtomicAccessSize(CGM, arch)) {
      Kind = CopyStruct;
      return;
    }
  
    // Otherwise, we can use native loads and stores.
    Kind = Native;
  }
  
  /// \brief Generate an Objective-C property getter function.
  ///
  /// The given Decl must be an ObjCImplementationDecl. \@synthesize
  /// is illegal within a category.
  void CodeGenFunction::GenerateObjCGetter(ObjCImplementationDecl *IMP,
                                           const ObjCPropertyImplDecl *PID) {
    llvm::Constant *AtomicHelperFn =
        CodeGenFunction(CGM).GenerateObjCAtomicGetterCopyHelperFunction(PID);
    const ObjCPropertyDecl *PD = PID->getPropertyDecl();
    ObjCMethodDecl *OMD = PD->getGetterMethodDecl();
    assert(OMD && "Invalid call to generate getter (empty method)");
    StartObjCMethod(OMD, IMP->getClassInterface());
  
    generateObjCGetterBody(IMP, PID, OMD, AtomicHelperFn);
  
    FinishFunction();
  }
  
  static bool hasTrivialGetExpr(const ObjCPropertyImplDecl *propImpl) {
    const Expr *getter = propImpl->getGetterCXXConstructor();
    if (!getter) return true;
  
    // Sema only makes only of these when the ivar has a C++ class type,
    // so the form is pretty constrained.
  
    // If the property has a reference type, we might just be binding a
    // reference, in which case the result will be a gl-value.  We should
    // treat this as a non-trivial operation.
    if (getter->isGLValue())
      return false;
  
    // If we selected a trivial copy-constructor, we're okay.
    if (const CXXConstructExpr *construct = dyn_cast<CXXConstructExpr>(getter))
      return (construct->getConstructor()->isTrivial());
  
    // The constructor might require cleanups (in which case it's never
    // trivial).
    assert(isa<ExprWithCleanups>(getter));
    return false;
  }
  
  /// emitCPPObjectAtomicGetterCall - Call the runtime function to 
  /// copy the ivar into the resturn slot.
  static void emitCPPObjectAtomicGetterCall(CodeGenFunction &CGF, 
                                            llvm::Value *returnAddr,
                                            ObjCIvarDecl *ivar,
                                            llvm::Constant *AtomicHelperFn) {
    // objc_copyCppObjectAtomic (&returnSlot, &CppObjectIvar,
    //                           AtomicHelperFn);
    CallArgList args;
    
    // The 1st argument is the return Slot.
    args.add(RValue::get(returnAddr), CGF.getContext().VoidPtrTy);
    
    // The 2nd argument is the address of the ivar.
    llvm::Value *ivarAddr = 
      CGF.EmitLValueForIvar(CGF.TypeOfSelfObject(), 
                            CGF.LoadObjCSelf(), ivar, 0).getPointer();
    ivarAddr = CGF.Builder.CreateBitCast(ivarAddr, CGF.Int8PtrTy);
    args.add(RValue::get(ivarAddr), CGF.getContext().VoidPtrTy);
    
    // Third argument is the helper function.
    args.add(RValue::get(AtomicHelperFn), CGF.getContext().VoidPtrTy);
    
    llvm::Constant *copyCppAtomicObjectFn = 
      CGF.CGM.getObjCRuntime().GetCppAtomicObjectGetFunction();
    CGCallee callee = CGCallee::forDirect(copyCppAtomicObjectFn);
    CGF.EmitCall(
        CGF.getTypes().arrangeBuiltinFunctionCall(CGF.getContext().VoidTy, args),
                 callee, ReturnValueSlot(), args);
  }
  
  void
  CodeGenFunction::generateObjCGetterBody(const ObjCImplementationDecl *classImpl,
                                          const ObjCPropertyImplDecl *propImpl,
                                          const ObjCMethodDecl *GetterMethodDecl,
                                          llvm::Constant *AtomicHelperFn) {
    // If there's a non-trivial 'get' expression, we just have to emit that.
    if (!hasTrivialGetExpr(propImpl)) {
      if (!AtomicHelperFn) {
        ReturnStmt ret(SourceLocation(), propImpl->getGetterCXXConstructor(),
                       /*nrvo*/ nullptr);
        EmitReturnStmt(ret);
      }
      else {
        ObjCIvarDecl *ivar = propImpl->getPropertyIvarDecl();
        emitCPPObjectAtomicGetterCall(*this, ReturnValue.getPointer(), 
                                      ivar, AtomicHelperFn);
      }
      return;
    }
  
    const ObjCPropertyDecl *prop = propImpl->getPropertyDecl();
    QualType propType = prop->getType();
    ObjCMethodDecl *getterMethod = prop->getGetterMethodDecl();
  
    ObjCIvarDecl *ivar = propImpl->getPropertyIvarDecl();  
  
    // Pick an implementation strategy.
    PropertyImplStrategy strategy(CGM, propImpl);
    switch (strategy.getKind()) {
    case PropertyImplStrategy::Native: {
      // We don't need to do anything for a zero-size struct.
      if (strategy.getIvarSize().isZero())
        return;
  
      LValue LV = EmitLValueForIvar(TypeOfSelfObject(), LoadObjCSelf(), ivar, 0);
  
      // Currently, all atomic accesses have to be through integer
      // types, so there's no point in trying to pick a prettier type.
      uint64_t ivarSize = getContext().toBits(strategy.getIvarSize());
      llvm::Type *bitcastType = llvm::Type::getIntNTy(getLLVMContext(), ivarSize);
      bitcastType = bitcastType->getPointerTo(); // addrspace 0 okay
  
      // Perform an atomic load.  This does not impose ordering constraints.
      Address ivarAddr = LV.getAddress();
      ivarAddr = Builder.CreateBitCast(ivarAddr, bitcastType);
      llvm::LoadInst *load = Builder.CreateLoad(ivarAddr, "load");
      load->setAtomic(llvm::AtomicOrdering::Unordered);
  
      // Store that value into the return address.  Doing this with a
      // bitcast is likely to produce some pretty ugly IR, but it's not
      // the *most* terrible thing in the world.
      llvm::Type *retTy = ConvertType(getterMethod->getReturnType());
      uint64_t retTySize = CGM.getDataLayout().getTypeSizeInBits(retTy);
      llvm::Value *ivarVal = load;
      if (ivarSize > retTySize) {
        llvm::Type *newTy = llvm::Type::getIntNTy(getLLVMContext(), retTySize);
        ivarVal = Builder.CreateTrunc(load, newTy);
        bitcastType = newTy->getPointerTo();
      }
      Builder.CreateStore(ivarVal,
                          Builder.CreateBitCast(ReturnValue, bitcastType));
  
      // Make sure we don't do an autorelease.
      AutoreleaseResult = false;
      return;
    }
  
    case PropertyImplStrategy::GetSetProperty: {
      llvm::Constant *getPropertyFn =
        CGM.getObjCRuntime().GetPropertyGetFunction();
      if (!getPropertyFn) {
        CGM.ErrorUnsupported(propImpl, "Obj-C getter requiring atomic copy");
        return;
      }
      CGCallee callee = CGCallee::forDirect(getPropertyFn);
  
      // Return (ivar-type) objc_getProperty((id) self, _cmd, offset, true).
      // FIXME: Can't this be simpler? This might even be worse than the
      // corresponding gcc code.
      llvm::Value *cmd =
        Builder.CreateLoad(GetAddrOfLocalVar(getterMethod->getCmdDecl()), "cmd");
      llvm::Value *self = Builder.CreateBitCast(LoadObjCSelf(), VoidPtrTy);
      llvm::Value *ivarOffset =
        EmitIvarOffset(classImpl->getClassInterface(), ivar);
  
      CallArgList args;
      args.add(RValue::get(self), getContext().getObjCIdType());
      args.add(RValue::get(cmd), getContext().getObjCSelType());
      args.add(RValue::get(ivarOffset), getContext().getPointerDiffType());
      args.add(RValue::get(Builder.getInt1(strategy.isAtomic())),
               getContext().BoolTy);
  
      // FIXME: We shouldn't need to get the function info here, the
      // runtime already should have computed it to build the function.
      llvm::Instruction *CallInstruction;
      RValue RV = EmitCall(
          getTypes().arrangeBuiltinFunctionCall(propType, args),
          callee, ReturnValueSlot(), args, &CallInstruction);
      if (llvm::CallInst *call = dyn_cast<llvm::CallInst>(CallInstruction))
        call->setTailCall();
  
      // We need to fix the type here. Ivars with copy & retain are
      // always objects so we don't need to worry about complex or
      // aggregates.
      RV = RValue::get(Builder.CreateBitCast(
          RV.getScalarVal(),
          getTypes().ConvertType(getterMethod->getReturnType())));
  
      EmitReturnOfRValue(RV, propType);
  
      // objc_getProperty does an autorelease, so we should suppress ours.
      AutoreleaseResult = false;
  
      return;
    }
  
    case PropertyImplStrategy::CopyStruct:
      emitStructGetterCall(*this, ivar, strategy.isAtomic(),
                           strategy.hasStrongMember());
      return;
  
    case PropertyImplStrategy::Expression:
    case PropertyImplStrategy::SetPropertyAndExpressionGet: {
      LValue LV = EmitLValueForIvar(TypeOfSelfObject(), LoadObjCSelf(), ivar, 0);
  
      QualType ivarType = ivar->getType();
      switch (getEvaluationKind(ivarType)) {
      case TEK_Complex: {
        ComplexPairTy pair = EmitLoadOfComplex(LV, SourceLocation());
        EmitStoreOfComplex(pair, MakeAddrLValue(ReturnValue, ivarType),
                           /*init*/ true);
        return;
      }
      case TEK_Aggregate:
        // The return value slot is guaranteed to not be aliased, but
        // that's not necessarily the same as "on the stack", so
        // we still potentially need objc_memmove_collectable.
        EmitAggregateCopy(ReturnValue, LV.getAddress(), ivarType);
        return;
      case TEK_Scalar: {
        llvm::Value *value;
        if (propType->isReferenceType()) {
          value = LV.getAddress().getPointer();
        } else {
          // We want to load and autoreleaseReturnValue ARC __weak ivars.
          if (LV.getQuals().getObjCLifetime() == Qualifiers::OCL_Weak) {
            if (getLangOpts().ObjCAutoRefCount) {
              value = emitARCRetainLoadOfScalar(*this, LV, ivarType);
            } else {
              value = EmitARCLoadWeak(LV.getAddress());
            }
  
          // Otherwise we want to do a simple load, suppressing the
          // final autorelease.
          } else {
            value = EmitLoadOfLValue(LV, SourceLocation()).getScalarVal();
            AutoreleaseResult = false;
          }
  
          value = Builder.CreateBitCast(
              value, ConvertType(GetterMethodDecl->getReturnType()));
        }
        
        EmitReturnOfRValue(RValue::get(value), propType);
        return;
      }
      }
      llvm_unreachable("bad evaluation kind");
    }
  
    }
    llvm_unreachable("bad @property implementation strategy!");
  }
  
  /// emitStructSetterCall - Call the runtime function to store the value
  /// from the first formal parameter into the given ivar.
  static void emitStructSetterCall(CodeGenFunction &CGF, ObjCMethodDecl *OMD,
                                   ObjCIvarDecl *ivar) {
    // objc_copyStruct (&structIvar, &Arg, 
    //                  sizeof (struct something), true, false);
    CallArgList args;
  
    // The first argument is the address of the ivar.
    llvm::Value *ivarAddr = CGF.EmitLValueForIvar(CGF.TypeOfSelfObject(),
                                                  CGF.LoadObjCSelf(), ivar, 0)
      .getPointer();
    ivarAddr = CGF.Builder.CreateBitCast(ivarAddr, CGF.Int8PtrTy);
    args.add(RValue::get(ivarAddr), CGF.getContext().VoidPtrTy);
  
    // The second argument is the address of the parameter variable.
    ParmVarDecl *argVar = *OMD->param_begin();
    DeclRefExpr argRef(argVar, false, argVar->getType().getNonReferenceType(), 
                       VK_LValue, SourceLocation());
    llvm::Value *argAddr = CGF.EmitLValue(&argRef).getPointer();
    argAddr = CGF.Builder.CreateBitCast(argAddr, CGF.Int8PtrTy);
    args.add(RValue::get(argAddr), CGF.getContext().VoidPtrTy);
  
    // The third argument is the sizeof the type.
    llvm::Value *size =
      CGF.CGM.getSize(CGF.getContext().getTypeSizeInChars(ivar->getType()));
    args.add(RValue::get(size), CGF.getContext().getSizeType());
  
    // The fourth argument is the 'isAtomic' flag.
    args.add(RValue::get(CGF.Builder.getTrue()), CGF.getContext().BoolTy);
  
    // The fifth argument is the 'hasStrong' flag.
    // FIXME: should this really always be false?
    args.add(RValue::get(CGF.Builder.getFalse()), CGF.getContext().BoolTy);
  
    llvm::Constant *fn = CGF.CGM.getObjCRuntime().GetSetStructFunction();
    CGCallee callee = CGCallee::forDirect(fn);
    CGF.EmitCall(
        CGF.getTypes().arrangeBuiltinFunctionCall(CGF.getContext().VoidTy, args),
                 callee, ReturnValueSlot(), args);
  }
  
  /// emitCPPObjectAtomicSetterCall - Call the runtime function to store 
  /// the value from the first formal parameter into the given ivar, using 
  /// the Cpp API for atomic Cpp objects with non-trivial copy assignment.
  static void emitCPPObjectAtomicSetterCall(CodeGenFunction &CGF, 
                                            ObjCMethodDecl *OMD,
                                            ObjCIvarDecl *ivar,
                                            llvm::Constant *AtomicHelperFn) {
    // objc_copyCppObjectAtomic (&CppObjectIvar, &Arg, 
    //                           AtomicHelperFn);
    CallArgList args;
    
    // The first argument is the address of the ivar.
    llvm::Value *ivarAddr = 
      CGF.EmitLValueForIvar(CGF.TypeOfSelfObject(), 
                            CGF.LoadObjCSelf(), ivar, 0).getPointer();
    ivarAddr = CGF.Builder.CreateBitCast(ivarAddr, CGF.Int8PtrTy);
    args.add(RValue::get(ivarAddr), CGF.getContext().VoidPtrTy);
    
    // The second argument is the address of the parameter variable.
    ParmVarDecl *argVar = *OMD->param_begin();
    DeclRefExpr argRef(argVar, false, argVar->getType().getNonReferenceType(), 
                       VK_LValue, SourceLocation());
    llvm::Value *argAddr = CGF.EmitLValue(&argRef).getPointer();
    argAddr = CGF.Builder.CreateBitCast(argAddr, CGF.Int8PtrTy);
    args.add(RValue::get(argAddr), CGF.getContext().VoidPtrTy);
    
    // Third argument is the helper function.
    args.add(RValue::get(AtomicHelperFn), CGF.getContext().VoidPtrTy);
    
    llvm::Constant *fn = 
      CGF.CGM.getObjCRuntime().GetCppAtomicObjectSetFunction();
    CGCallee callee = CGCallee::forDirect(fn);
    CGF.EmitCall(
        CGF.getTypes().arrangeBuiltinFunctionCall(CGF.getContext().VoidTy, args),
                 callee, ReturnValueSlot(), args);
  }
  
  
  static bool hasTrivialSetExpr(const ObjCPropertyImplDecl *PID) {
    Expr *setter = PID->getSetterCXXAssignment();
    if (!setter) return true;
  
    // Sema only makes only of these when the ivar has a C++ class type,
    // so the form is pretty constrained.
  
    // An operator call is trivial if the function it calls is trivial.
    // This also implies that there's nothing non-trivial going on with
    // the arguments, because operator= can only be trivial if it's a
    // synthesized assignment operator and therefore both parameters are
    // references.
    if (CallExpr *call = dyn_cast<CallExpr>(setter)) {
      if (const FunctionDecl *callee
            = dyn_cast_or_null<FunctionDecl>(call->getCalleeDecl()))
        if (callee->isTrivial())
          return true;
      return false;
    }
  
    assert(isa<ExprWithCleanups>(setter));
    return false;
  }
  
  static bool UseOptimizedSetter(CodeGenModule &CGM) {
    if (CGM.getLangOpts().getGC() != LangOptions::NonGC)
      return false;
    return CGM.getLangOpts().ObjCRuntime.hasOptimizedSetter();
  }
  
  void
  CodeGenFunction::generateObjCSetterBody(const ObjCImplementationDecl *classImpl,
                                          const ObjCPropertyImplDecl *propImpl,
                                          llvm::Constant *AtomicHelperFn) {
    const ObjCPropertyDecl *prop = propImpl->getPropertyDecl();
    ObjCIvarDecl *ivar = propImpl->getPropertyIvarDecl();
    ObjCMethodDecl *setterMethod = prop->getSetterMethodDecl();
    
    // Just use the setter expression if Sema gave us one and it's
    // non-trivial.
    if (!hasTrivialSetExpr(propImpl)) {
      if (!AtomicHelperFn)
        // If non-atomic, assignment is called directly.
        EmitStmt(propImpl->getSetterCXXAssignment());
      else
        // If atomic, assignment is called via a locking api.
        emitCPPObjectAtomicSetterCall(*this, setterMethod, ivar,
                                      AtomicHelperFn);
      return;
    }
  
    PropertyImplStrategy strategy(CGM, propImpl);
    switch (strategy.getKind()) {
    case PropertyImplStrategy::Native: {
      // We don't need to do anything for a zero-size struct.
      if (strategy.getIvarSize().isZero())
        return;
  
      Address argAddr = GetAddrOfLocalVar(*setterMethod->param_begin());
  
      LValue ivarLValue =
        EmitLValueForIvar(TypeOfSelfObject(), LoadObjCSelf(), ivar, /*quals*/ 0);
      Address ivarAddr = ivarLValue.getAddress();
  
      // Currently, all atomic accesses have to be through integer
      // types, so there's no point in trying to pick a prettier type.
      llvm::Type *bitcastType =
        llvm::Type::getIntNTy(getLLVMContext(),
                              getContext().toBits(strategy.getIvarSize()));
  
      // Cast both arguments to the chosen operation type.
      argAddr = Builder.CreateElementBitCast(argAddr, bitcastType);
      ivarAddr = Builder.CreateElementBitCast(ivarAddr, bitcastType);
  
      // This bitcast load is likely to cause some nasty IR.
      llvm::Value *load = Builder.CreateLoad(argAddr);
  
      // Perform an atomic store.  There are no memory ordering requirements.
      llvm::StoreInst *store = Builder.CreateStore(load, ivarAddr);
      store->setAtomic(llvm::AtomicOrdering::Unordered);
      return;
    }
  
    case PropertyImplStrategy::GetSetProperty:
    case PropertyImplStrategy::SetPropertyAndExpressionGet: {
  
      llvm::Constant *setOptimizedPropertyFn = nullptr;
      llvm::Constant *setPropertyFn = nullptr;
      if (UseOptimizedSetter(CGM)) {
        // 10.8 and iOS 6.0 code and GC is off
        setOptimizedPropertyFn = 
          CGM.getObjCRuntime()
             .GetOptimizedPropertySetFunction(strategy.isAtomic(),
                                              strategy.isCopy());
        if (!setOptimizedPropertyFn) {
          CGM.ErrorUnsupported(propImpl, "Obj-C optimized setter - NYI");
          return;
        }
      }
      else {
        setPropertyFn = CGM.getObjCRuntime().GetPropertySetFunction();
        if (!setPropertyFn) {
          CGM.ErrorUnsupported(propImpl, "Obj-C setter requiring atomic copy");
          return;
        }
      }
     
      // Emit objc_setProperty((id) self, _cmd, offset, arg,
      //                       <is-atomic>, <is-copy>).
      llvm::Value *cmd =
        Builder.CreateLoad(GetAddrOfLocalVar(setterMethod->getCmdDecl()));
      llvm::Value *self =
        Builder.CreateBitCast(LoadObjCSelf(), VoidPtrTy);
      llvm::Value *ivarOffset =
        EmitIvarOffset(classImpl->getClassInterface(), ivar);
      Address argAddr = GetAddrOfLocalVar(*setterMethod->param_begin());
      llvm::Value *arg = Builder.CreateLoad(argAddr, "arg");
      arg = Builder.CreateBitCast(arg, VoidPtrTy);
  
      CallArgList args;
      args.add(RValue::get(self), getContext().getObjCIdType());
      args.add(RValue::get(cmd), getContext().getObjCSelType());
      if (setOptimizedPropertyFn) {
        args.add(RValue::get(arg), getContext().getObjCIdType());
        args.add(RValue::get(ivarOffset), getContext().getPointerDiffType());
        CGCallee callee = CGCallee::forDirect(setOptimizedPropertyFn);
        EmitCall(getTypes().arrangeBuiltinFunctionCall(getContext().VoidTy, args),
                 callee, ReturnValueSlot(), args);
      } else {
        args.add(RValue::get(ivarOffset), getContext().getPointerDiffType());
        args.add(RValue::get(arg), getContext().getObjCIdType());
        args.add(RValue::get(Builder.getInt1(strategy.isAtomic())),
                 getContext().BoolTy);
        args.add(RValue::get(Builder.getInt1(strategy.isCopy())),
                 getContext().BoolTy);
        // FIXME: We shouldn't need to get the function info here, the runtime
        // already should have computed it to build the function.
        CGCallee callee = CGCallee::forDirect(setPropertyFn);
        EmitCall(getTypes().arrangeBuiltinFunctionCall(getContext().VoidTy, args),
                 callee, ReturnValueSlot(), args);
      }
      
      return;
    }
  
    case PropertyImplStrategy::CopyStruct:
      emitStructSetterCall(*this, setterMethod, ivar);
      return;
  
    case PropertyImplStrategy::Expression:
      break;
    }
  
    // Otherwise, fake up some ASTs and emit a normal assignment.
    ValueDecl *selfDecl = setterMethod->getSelfDecl();
    DeclRefExpr self(selfDecl, false, selfDecl->getType(),
                     VK_LValue, SourceLocation());
    ImplicitCastExpr selfLoad(ImplicitCastExpr::OnStack,
                              selfDecl->getType(), CK_LValueToRValue, &self,
                              VK_RValue);
    ObjCIvarRefExpr ivarRef(ivar, ivar->getType().getNonReferenceType(),
                            SourceLocation(), SourceLocation(),
                            &selfLoad, true, true);
  
    ParmVarDecl *argDecl = *setterMethod->param_begin();
    QualType argType = argDecl->getType().getNonReferenceType();
    DeclRefExpr arg(argDecl, false, argType, VK_LValue, SourceLocation());
    ImplicitCastExpr argLoad(ImplicitCastExpr::OnStack,
                             argType.getUnqualifiedType(), CK_LValueToRValue,
                             &arg, VK_RValue);
      
    // The property type can differ from the ivar type in some situations with
    // Objective-C pointer types, we can always bit cast the RHS in these cases.
    // The following absurdity is just to ensure well-formed IR.
    CastKind argCK = CK_NoOp;
    if (ivarRef.getType()->isObjCObjectPointerType()) {
      if (argLoad.getType()->isObjCObjectPointerType())
        argCK = CK_BitCast;
      else if (argLoad.getType()->isBlockPointerType())
        argCK = CK_BlockPointerToObjCPointerCast;
      else
        argCK = CK_CPointerToObjCPointerCast;
    } else if (ivarRef.getType()->isBlockPointerType()) {
       if (argLoad.getType()->isBlockPointerType())
        argCK = CK_BitCast;
      else
        argCK = CK_AnyPointerToBlockPointerCast;
    } else if (ivarRef.getType()->isPointerType()) {
      argCK = CK_BitCast;
    }
    ImplicitCastExpr argCast(ImplicitCastExpr::OnStack,
                             ivarRef.getType(), argCK, &argLoad,
                             VK_RValue);
    Expr *finalArg = &argLoad;
    if (!getContext().hasSameUnqualifiedType(ivarRef.getType(),
                                             argLoad.getType()))
      finalArg = &argCast;
  
  
    BinaryOperator assign(&ivarRef, finalArg, BO_Assign,
                          ivarRef.getType(), VK_RValue, OK_Ordinary,
                          SourceLocation(), false);
    EmitStmt(&assign);
  }
  
  /// \brief Generate an Objective-C property setter function.
  ///
  /// The given Decl must be an ObjCImplementationDecl. \@synthesize
  /// is illegal within a category.
  void CodeGenFunction::GenerateObjCSetter(ObjCImplementationDecl *IMP,
                                           const ObjCPropertyImplDecl *PID) {
    llvm::Constant *AtomicHelperFn =
        CodeGenFunction(CGM).GenerateObjCAtomicSetterCopyHelperFunction(PID);
    const ObjCPropertyDecl *PD = PID->getPropertyDecl();
    ObjCMethodDecl *OMD = PD->getSetterMethodDecl();
    assert(OMD && "Invalid call to generate setter (empty method)");
    StartObjCMethod(OMD, IMP->getClassInterface());
  
    generateObjCSetterBody(IMP, PID, AtomicHelperFn);
  
    FinishFunction();
  }
  
  namespace {
    struct DestroyIvar final : EHScopeStack::Cleanup {
    private:
      llvm::Value *addr;
      const ObjCIvarDecl *ivar;
      CodeGenFunction::Destroyer *destroyer;
      bool useEHCleanupForArray;
    public:
      DestroyIvar(llvm::Value *addr, const ObjCIvarDecl *ivar,
                  CodeGenFunction::Destroyer *destroyer,
                  bool useEHCleanupForArray)
        : addr(addr), ivar(ivar), destroyer(destroyer),
          useEHCleanupForArray(useEHCleanupForArray) {}
  
      void Emit(CodeGenFunction &CGF, Flags flags) override {
        LValue lvalue
          = CGF.EmitLValueForIvar(CGF.TypeOfSelfObject(), addr, ivar, /*CVR*/ 0);
        CGF.emitDestroy(lvalue.getAddress(), ivar->getType(), destroyer,
                        flags.isForNormalCleanup() && useEHCleanupForArray);
      }
    };
  }
  
  /// Like CodeGenFunction::destroyARCStrong, but do it with a call.
  static void destroyARCStrongWithStore(CodeGenFunction &CGF,
                                        Address addr,
                                        QualType type) {
    llvm::Value *null = getNullForVariable(addr);
    CGF.EmitARCStoreStrongCall(addr, null, /*ignored*/ true);
  }
  
  static void emitCXXDestructMethod(CodeGenFunction &CGF,
                                    ObjCImplementationDecl *impl) {
    CodeGenFunction::RunCleanupsScope scope(CGF);
  
    llvm::Value *self = CGF.LoadObjCSelf();
  
    const ObjCInterfaceDecl *iface = impl->getClassInterface();
    for (const ObjCIvarDecl *ivar = iface->all_declared_ivar_begin();
         ivar; ivar = ivar->getNextIvar()) {
      QualType type = ivar->getType();
  
      // Check whether the ivar is a destructible type.
      QualType::DestructionKind dtorKind = type.isDestructedType();
      if (!dtorKind) continue;
  
      CodeGenFunction::Destroyer *destroyer = nullptr;
  
      // Use a call to objc_storeStrong to destroy strong ivars, for the
      // general benefit of the tools.
      if (dtorKind == QualType::DK_objc_strong_lifetime) {
        destroyer = destroyARCStrongWithStore;
  
      // Otherwise use the default for the destruction kind.
      } else {
        destroyer = CGF.getDestroyer(dtorKind);
      }
  
      CleanupKind cleanupKind = CGF.getCleanupKind(dtorKind);
  
      CGF.EHStack.pushCleanup<DestroyIvar>(cleanupKind, self, ivar, destroyer,
                                           cleanupKind & EHCleanup);
    }
  
    assert(scope.requiresCleanups() && "nothing to do in .cxx_destruct?");
  }
  
  void CodeGenFunction::GenerateObjCCtorDtorMethod(ObjCImplementationDecl *IMP,
                                                   ObjCMethodDecl *MD,
                                                   bool ctor) {
    MD->createImplicitParams(CGM.getContext(), IMP->getClassInterface());
    StartObjCMethod(MD, IMP->getClassInterface());
  
    // Emit .cxx_construct.
    if (ctor) {
      // Suppress the final autorelease in ARC.
      AutoreleaseResult = false;
  
      for (const auto *IvarInit : IMP->inits()) {
        FieldDecl *Field = IvarInit->getAnyMember();
        ObjCIvarDecl *Ivar = cast<ObjCIvarDecl>(Field);
        LValue LV = EmitLValueForIvar(TypeOfSelfObject(), 
                                      LoadObjCSelf(), Ivar, 0);
        EmitAggExpr(IvarInit->getInit(),
                    AggValueSlot::forLValue(LV, AggValueSlot::IsDestructed,
                                            AggValueSlot::DoesNotNeedGCBarriers,
                                            AggValueSlot::IsNotAliased));
      }
      // constructor returns 'self'.
      CodeGenTypes &Types = CGM.getTypes();
      QualType IdTy(CGM.getContext().getObjCIdType());
      llvm::Value *SelfAsId =
        Builder.CreateBitCast(LoadObjCSelf(), Types.ConvertType(IdTy));
      EmitReturnOfRValue(RValue::get(SelfAsId), IdTy);
  
    // Emit .cxx_destruct.
    } else {
      emitCXXDestructMethod(*this, IMP);
    }
    FinishFunction();
  }
  
  llvm::Value *CodeGenFunction::LoadObjCSelf() {
    VarDecl *Self = cast<ObjCMethodDecl>(CurFuncDecl)->getSelfDecl();
    DeclRefExpr DRE(Self, /*is enclosing local*/ (CurFuncDecl != CurCodeDecl),
                    Self->getType(), VK_LValue, SourceLocation());
    return EmitLoadOfScalar(EmitDeclRefLValue(&DRE), SourceLocation());
  }
  
  QualType CodeGenFunction::TypeOfSelfObject() {
    const ObjCMethodDecl *OMD = cast<ObjCMethodDecl>(CurFuncDecl);
    ImplicitParamDecl *selfDecl = OMD->getSelfDecl();
    const ObjCObjectPointerType *PTy = cast<ObjCObjectPointerType>(
      getContext().getCanonicalType(selfDecl->getType()));
    return PTy->getPointeeType();
  }
  
  void CodeGenFunction::EmitObjCForCollectionStmt(const ObjCForCollectionStmt &S){
    llvm::Constant *EnumerationMutationFnPtr =
      CGM.getObjCRuntime().EnumerationMutationFunction();
    if (!EnumerationMutationFnPtr) {
      CGM.ErrorUnsupported(&S, "Obj-C fast enumeration for this runtime");
      return;
    }
    CGCallee EnumerationMutationFn =
      CGCallee::forDirect(EnumerationMutationFnPtr);
  
    CGDebugInfo *DI = getDebugInfo();
    if (DI)
      DI->EmitLexicalBlockStart(Builder, S.getSourceRange().getBegin());
  
    // The local variable comes into scope immediately.
    AutoVarEmission variable = AutoVarEmission::invalid();
    if (const DeclStmt *SD = dyn_cast<DeclStmt>(S.getElement()))
      variable = EmitAutoVarAlloca(*cast<VarDecl>(SD->getSingleDecl()));
  
    JumpDest LoopEnd = getJumpDestInCurrentScope("forcoll.end");
  
    // Fast enumeration state.
    QualType StateTy = CGM.getObjCFastEnumerationStateType();
    Address StatePtr = CreateMemTemp(StateTy, "state.ptr");
    EmitNullInitialization(StatePtr, StateTy);
  
    // Number of elements in the items array.
    static const unsigned NumItems = 16;
  
    // Fetch the countByEnumeratingWithState:objects:count: selector.
    IdentifierInfo *II[] = {
      &CGM.getContext().Idents.get("countByEnumeratingWithState"),
      &CGM.getContext().Idents.get("objects"),
      &CGM.getContext().Idents.get("count")
    };
    Selector FastEnumSel =
      CGM.getContext().Selectors.getSelector(llvm::array_lengthof(II), &II[0]);
  
    QualType ItemsTy =
      getContext().getConstantArrayType(getContext().getObjCIdType(),
                                        llvm::APInt(32, NumItems),
                                        ArrayType::Normal, 0);
    Address ItemsPtr = CreateMemTemp(ItemsTy, "items.ptr");
  
    RunCleanupsScope ForScope(*this);
  
    // Emit the collection pointer.  In ARC, we do a retain.
    llvm::Value *Collection;
    if (getLangOpts().ObjCAutoRefCount) {
      Collection = EmitARCRetainScalarExpr(S.getCollection());
  
      // Enter a cleanup to do the release.
      EmitObjCConsumeObject(S.getCollection()->getType(), Collection);
    } else {
      Collection = EmitScalarExpr(S.getCollection());
    }
  
    // The 'continue' label needs to appear within the cleanup for the
    // collection object.
    JumpDest AfterBody = getJumpDestInCurrentScope("forcoll.next");
  
    // Send it our message:
    CallArgList Args;
  
    // The first argument is a temporary of the enumeration-state type.
    Args.add(RValue::get(StatePtr.getPointer()),
             getContext().getPointerType(StateTy));
  
    // The second argument is a temporary array with space for NumItems
    // pointers.  We'll actually be loading elements from the array
    // pointer written into the control state; this buffer is so that
    // collections that *aren't* backed by arrays can still queue up
    // batches of elements.
    Args.add(RValue::get(ItemsPtr.getPointer()),
             getContext().getPointerType(ItemsTy));
  
    // The third argument is the capacity of that temporary array.
    llvm::Type *UnsignedLongLTy = ConvertType(getContext().UnsignedLongTy);
    llvm::Constant *Count = llvm::ConstantInt::get(UnsignedLongLTy, NumItems);
    Args.add(RValue::get(Count), getContext().UnsignedLongTy);
  
    // Start the enumeration.
    RValue CountRV =
      CGM.getObjCRuntime().GenerateMessageSend(*this, ReturnValueSlot(),
                                               getContext().UnsignedLongTy,
                                               FastEnumSel,
                                               Collection, Args);
  
    // The initial number of objects that were returned in the buffer.
    llvm::Value *initialBufferLimit = CountRV.getScalarVal();
  
    llvm::BasicBlock *EmptyBB = createBasicBlock("forcoll.empty");
    llvm::BasicBlock *LoopInitBB = createBasicBlock("forcoll.loopinit");
  
    llvm::Value *zero = llvm::Constant::getNullValue(UnsignedLongLTy);
  
    // If the limit pointer was zero to begin with, the collection is
    // empty; skip all this. Set the branch weight assuming this has the same
    // probability of exiting the loop as any other loop exit.
    uint64_t EntryCount = getCurrentProfileCount();
    Builder.CreateCondBr(
        Builder.CreateICmpEQ(initialBufferLimit, zero, "iszero"), EmptyBB,
        LoopInitBB,
        createProfileWeights(EntryCount, getProfileCount(S.getBody())));
  
    // Otherwise, initialize the loop.
    EmitBlock(LoopInitBB);
  
    // Save the initial mutations value.  This is the value at an
    // address that was written into the state object by
    // countByEnumeratingWithState:objects:count:.
    Address StateMutationsPtrPtr = Builder.CreateStructGEP(
        StatePtr, 2, 2 * getPointerSize(), "mutationsptr.ptr");
    llvm::Value *StateMutationsPtr
      = Builder.CreateLoad(StateMutationsPtrPtr, "mutationsptr");
  
    llvm::Value *initialMutations =
      Builder.CreateAlignedLoad(StateMutationsPtr, getPointerAlign(),
                                "forcoll.initial-mutations");
  
    // Start looping.  This is the point we return to whenever we have a
    // fresh, non-empty batch of objects.
    llvm::BasicBlock *LoopBodyBB = createBasicBlock("forcoll.loopbody");
    EmitBlock(LoopBodyBB);
  
    // The current index into the buffer.
    llvm::PHINode *index = Builder.CreatePHI(UnsignedLongLTy, 3, "forcoll.index");
    index->addIncoming(zero, LoopInitBB);
  
    // The current buffer size.
    llvm::PHINode *count = Builder.CreatePHI(UnsignedLongLTy, 3, "forcoll.count");
    count->addIncoming(initialBufferLimit, LoopInitBB);
  
    incrementProfileCounter(&S);
  
    // Check whether the mutations value has changed from where it was
    // at start.  StateMutationsPtr should actually be invariant between
    // refreshes.
    StateMutationsPtr = Builder.CreateLoad(StateMutationsPtrPtr, "mutationsptr");
    llvm::Value *currentMutations
      = Builder.CreateAlignedLoad(StateMutationsPtr, getPointerAlign(),
                                  "statemutations");
  
    llvm::BasicBlock *WasMutatedBB = createBasicBlock("forcoll.mutated");
    llvm::BasicBlock *WasNotMutatedBB = createBasicBlock("forcoll.notmutated");
  
    Builder.CreateCondBr(Builder.CreateICmpEQ(currentMutations, initialMutations),
                         WasNotMutatedBB, WasMutatedBB);
  
    // If so, call the enumeration-mutation function.
    EmitBlock(WasMutatedBB);
    llvm::Value *V =
      Builder.CreateBitCast(Collection,
                            ConvertType(getContext().getObjCIdType()));
    CallArgList Args2;
    Args2.add(RValue::get(V), getContext().getObjCIdType());
    // FIXME: We shouldn't need to get the function info here, the runtime already
    // should have computed it to build the function.
    EmitCall(
            CGM.getTypes().arrangeBuiltinFunctionCall(getContext().VoidTy, Args2),
             EnumerationMutationFn, ReturnValueSlot(), Args2);
  
    // Otherwise, or if the mutation function returns, just continue.
    EmitBlock(WasNotMutatedBB);
  
    // Initialize the element variable.
    RunCleanupsScope elementVariableScope(*this);
    bool elementIsVariable;
    LValue elementLValue;
    QualType elementType;
    if (const DeclStmt *SD = dyn_cast<DeclStmt>(S.getElement())) {
      // Initialize the variable, in case it's a __block variable or something.
      EmitAutoVarInit(variable);
  
      const VarDecl* D = cast<VarDecl>(SD->getSingleDecl());
      DeclRefExpr tempDRE(const_cast<VarDecl*>(D), false, D->getType(),
                          VK_LValue, SourceLocation());
      elementLValue = EmitLValue(&tempDRE);
      elementType = D->getType();
      elementIsVariable = true;
  
      if (D->isARCPseudoStrong())
        elementLValue.getQuals().setObjCLifetime(Qualifiers::OCL_ExplicitNone);
    } else {
      elementLValue = LValue(); // suppress warning
      elementType = cast<Expr>(S.getElement())->getType();
      elementIsVariable = false;
    }
    llvm::Type *convertedElementType = ConvertType(elementType);
  
    // Fetch the buffer out of the enumeration state.
    // TODO: this pointer should actually be invariant between
    // refreshes, which would help us do certain loop optimizations.
    Address StateItemsPtr = Builder.CreateStructGEP(
        StatePtr, 1, getPointerSize(), "stateitems.ptr");
    llvm::Value *EnumStateItems =
      Builder.CreateLoad(StateItemsPtr, "stateitems");
  
    // Fetch the value at the current index from the buffer.
    llvm::Value *CurrentItemPtr =
      Builder.CreateGEP(EnumStateItems, index, "currentitem.ptr");
    llvm::Value *CurrentItem =
      Builder.CreateAlignedLoad(CurrentItemPtr, getPointerAlign());
  
    // Cast that value to the right type.
    CurrentItem = Builder.CreateBitCast(CurrentItem, convertedElementType,
                                        "currentitem");
  
    // Make sure we have an l-value.  Yes, this gets evaluated every
    // time through the loop.
    if (!elementIsVariable) {
      elementLValue = EmitLValue(cast<Expr>(S.getElement()));
      EmitStoreThroughLValue(RValue::get(CurrentItem), elementLValue);
    } else {
      EmitStoreThroughLValue(RValue::get(CurrentItem), elementLValue,
                             /*isInit*/ true);
    }
  
    // If we do have an element variable, this assignment is the end of
    // its initialization.
    if (elementIsVariable)
      EmitAutoVarCleanups(variable);
  
    // Perform the loop body, setting up break and continue labels.
    BreakContinueStack.push_back(BreakContinue(LoopEnd, AfterBody));
    {
      RunCleanupsScope Scope(*this);
      EmitStmt(S.getBody());
    }
    BreakContinueStack.pop_back();
  
    // Destroy the element variable now.
    elementVariableScope.ForceCleanup();
  
    // Check whether there are more elements.
    EmitBlock(AfterBody.getBlock());
  
    llvm::BasicBlock *FetchMoreBB = createBasicBlock("forcoll.refetch");
  
    // First we check in the local buffer.
    llvm::Value *indexPlusOne
      = Builder.CreateAdd(index, llvm::ConstantInt::get(UnsignedLongLTy, 1));
  
    // If we haven't overrun the buffer yet, we can continue.
    // Set the branch weights based on the simplifying assumption that this is
    // like a while-loop, i.e., ignoring that the false branch fetches more
    // elements and then returns to the loop.
    Builder.CreateCondBr(
        Builder.CreateICmpULT(indexPlusOne, count), LoopBodyBB, FetchMoreBB,
        createProfileWeights(getProfileCount(S.getBody()), EntryCount));
  
    index->addIncoming(indexPlusOne, AfterBody.getBlock());
    count->addIncoming(count, AfterBody.getBlock());
  
    // Otherwise, we have to fetch more elements.
    EmitBlock(FetchMoreBB);
  
    CountRV =
      CGM.getObjCRuntime().GenerateMessageSend(*this, ReturnValueSlot(),
                                               getContext().UnsignedLongTy,
                                               FastEnumSel,
                                               Collection, Args);
  
    // If we got a zero count, we're done.
    llvm::Value *refetchCount = CountRV.getScalarVal();
  
    // (note that the message send might split FetchMoreBB)
    index->addIncoming(zero, Builder.GetInsertBlock());
    count->addIncoming(refetchCount, Builder.GetInsertBlock());
  
    Builder.CreateCondBr(Builder.CreateICmpEQ(refetchCount, zero),
                         EmptyBB, LoopBodyBB);
  
    // No more elements.
    EmitBlock(EmptyBB);
  
    if (!elementIsVariable) {
      // If the element was not a declaration, set it to be null.
  
      llvm::Value *null = llvm::Constant::getNullValue(convertedElementType);
      elementLValue = EmitLValue(cast<Expr>(S.getElement()));
      EmitStoreThroughLValue(RValue::get(null), elementLValue);
    }
  
    if (DI)
      DI->EmitLexicalBlockEnd(Builder, S.getSourceRange().getEnd());
  
    ForScope.ForceCleanup();
    EmitBlock(LoopEnd.getBlock());
  }
  
  void CodeGenFunction::EmitObjCAtTryStmt(const ObjCAtTryStmt &S) {
    CGM.getObjCRuntime().EmitTryStmt(*this, S);
  }
  
  void CodeGenFunction::EmitObjCAtThrowStmt(const ObjCAtThrowStmt &S) {
    CGM.getObjCRuntime().EmitThrowStmt(*this, S);
  }
  
  void CodeGenFunction::EmitObjCAtSynchronizedStmt(
                                                const ObjCAtSynchronizedStmt &S) {
    CGM.getObjCRuntime().EmitSynchronizedStmt(*this, S);
  }
  
  namespace {
    struct CallObjCRelease final : EHScopeStack::Cleanup {
      CallObjCRelease(llvm::Value *object) : object(object) {}
      llvm::Value *object;
  
      void Emit(CodeGenFunction &CGF, Flags flags) override {
        // Releases at the end of the full-expression are imprecise.
        CGF.EmitARCRelease(object, ARCImpreciseLifetime);
      }
    };
  }
  
  /// Produce the code for a CK_ARCConsumeObject.  Does a primitive
  /// release at the end of the full-expression.
  llvm::Value *CodeGenFunction::EmitObjCConsumeObject(QualType type,
                                                      llvm::Value *object) {
    // If we're in a conditional branch, we need to make the cleanup
    // conditional.
    pushFullExprCleanup<CallObjCRelease>(getARCCleanupKind(), object);
    return object;
  }
  
  llvm::Value *CodeGenFunction::EmitObjCExtendObjectLifetime(QualType type,
                                                             llvm::Value *value) {
    return EmitARCRetainAutorelease(type, value);
  }
  
  /// Given a number of pointers, inform the optimizer that they're
  /// being intrinsically used up until this point in the program.
  void CodeGenFunction::EmitARCIntrinsicUse(ArrayRef<llvm::Value*> values) {
    llvm::Constant *&fn = CGM.getObjCEntrypoints().clang_arc_use;
    if (!fn) {
      llvm::FunctionType *fnType =
        llvm::FunctionType::get(CGM.VoidTy, None, true);
      fn = CGM.CreateRuntimeFunction(fnType, "clang.arc.use");
    }
  
    // This isn't really a "runtime" function, but as an intrinsic it
    // doesn't really matter as long as we align things up.
    EmitNounwindRuntimeCall(fn, values);
  }
  
  
  static llvm::Constant *createARCRuntimeFunction(CodeGenModule &CGM,
                                                  llvm::FunctionType *type,
                                                  StringRef fnName) {
    llvm::Constant *fn = CGM.CreateRuntimeFunction(type, fnName);
  
    if (llvm::Function *f = dyn_cast<llvm::Function>(fn)) {
      // If the target runtime doesn't naturally support ARC, emit weak
      // references to the runtime support library.  We don't really
      // permit this to fail, but we need a particular relocation style.
      if (!CGM.getLangOpts().ObjCRuntime.hasNativeARC() &&
          !CGM.getTriple().isOSBinFormatCOFF()) {
        f->setLinkage(llvm::Function::ExternalWeakLinkage);
      } else if (fnName == "objc_retain" || fnName  == "objc_release") {
        // If we have Native ARC, set nonlazybind attribute for these APIs for
        // performance.
        f->addFnAttr(llvm::Attribute::NonLazyBind);
      }
    }
  
    return fn;
  }
  
  /// Perform an operation having the signature
  ///   i8* (i8*)
  /// where a null input causes a no-op and returns null.
  static llvm::Value *emitARCValueOperation(CodeGenFunction &CGF,
                                            llvm::Value *value,
                                            llvm::Constant *&fn,
                                            StringRef fnName,
                                            bool isTailCall = false) {
    if (isa<llvm::ConstantPointerNull>(value)) return value;
  
    if (!fn) {
      llvm::FunctionType *fnType =
        llvm::FunctionType::get(CGF.Int8PtrTy, CGF.Int8PtrTy, false);
      fn = createARCRuntimeFunction(CGF.CGM, fnType, fnName);
    }
  
    // Cast the argument to 'id'.
    llvm::Type *origType = value->getType();
    value = CGF.Builder.CreateBitCast(value, CGF.Int8PtrTy);
  
    // Call the function.
    llvm::CallInst *call = CGF.EmitNounwindRuntimeCall(fn, value);
    if (isTailCall)
      call->setTailCall();
  
    // Cast the result back to the original type.
    return CGF.Builder.CreateBitCast(call, origType);
  }
  
  /// Perform an operation having the following signature:
  ///   i8* (i8**)
  static llvm::Value *emitARCLoadOperation(CodeGenFunction &CGF,
                                           Address addr,
                                           llvm::Constant *&fn,
                                           StringRef fnName) {
    if (!fn) {
      llvm::FunctionType *fnType =
        llvm::FunctionType::get(CGF.Int8PtrTy, CGF.Int8PtrPtrTy, false);
      fn = createARCRuntimeFunction(CGF.CGM, fnType, fnName);
    }
  
    // Cast the argument to 'id*'.
    llvm::Type *origType = addr.getElementType();
    addr = CGF.Builder.CreateBitCast(addr, CGF.Int8PtrPtrTy);
  
    // Call the function.
    llvm::Value *result = CGF.EmitNounwindRuntimeCall(fn, addr.getPointer());
  
    // Cast the result back to a dereference of the original type.
    if (origType != CGF.Int8PtrTy)
      result = CGF.Builder.CreateBitCast(result, origType);
  
    return result;
  }
  
  /// Perform an operation having the following signature:
  ///   i8* (i8**, i8*)
  static llvm::Value *emitARCStoreOperation(CodeGenFunction &CGF,
                                            Address addr,
                                            llvm::Value *value,
                                            llvm::Constant *&fn,
                                            StringRef fnName,
                                            bool ignored) {
    assert(addr.getElementType() == value->getType());
  
    if (!fn) {
      llvm::Type *argTypes[] = { CGF.Int8PtrPtrTy, CGF.Int8PtrTy };
  
      llvm::FunctionType *fnType
        = llvm::FunctionType::get(CGF.Int8PtrTy, argTypes, false);
      fn = createARCRuntimeFunction(CGF.CGM, fnType, fnName);
    }
  
    llvm::Type *origType = value->getType();
  
    llvm::Value *args[] = {
      CGF.Builder.CreateBitCast(addr.getPointer(), CGF.Int8PtrPtrTy),
      CGF.Builder.CreateBitCast(value, CGF.Int8PtrTy)
    };
    llvm::CallInst *result = CGF.EmitNounwindRuntimeCall(fn, args);
  
    if (ignored) return nullptr;
  
    return CGF.Builder.CreateBitCast(result, origType);
  }
  
  /// Perform an operation having the following signature:
  ///   void (i8**, i8**)
  static void emitARCCopyOperation(CodeGenFunction &CGF,
                                   Address dst,
                                   Address src,
                                   llvm::Constant *&fn,
                                   StringRef fnName) {
    assert(dst.getType() == src.getType());
  
    if (!fn) {
      llvm::Type *argTypes[] = { CGF.Int8PtrPtrTy, CGF.Int8PtrPtrTy };
  
      llvm::FunctionType *fnType
        = llvm::FunctionType::get(CGF.Builder.getVoidTy(), argTypes, false);
      fn = createARCRuntimeFunction(CGF.CGM, fnType, fnName);
    }
  
    llvm::Value *args[] = {
      CGF.Builder.CreateBitCast(dst.getPointer(), CGF.Int8PtrPtrTy),
      CGF.Builder.CreateBitCast(src.getPointer(), CGF.Int8PtrPtrTy)
    };
    CGF.EmitNounwindRuntimeCall(fn, args);
  }
  
  /// Produce the code to do a retain.  Based on the type, calls one of:
  ///   call i8* \@objc_retain(i8* %value)
  ///   call i8* \@objc_retainBlock(i8* %value)
  llvm::Value *CodeGenFunction::EmitARCRetain(QualType type, llvm::Value *value) {
    if (type->isBlockPointerType())
      return EmitARCRetainBlock(value, /*mandatory*/ false);
    else
      return EmitARCRetainNonBlock(value);
  }
  
  /// Retain the given object, with normal retain semantics.
  ///   call i8* \@objc_retain(i8* %value)
  llvm::Value *CodeGenFunction::EmitARCRetainNonBlock(llvm::Value *value) {
    return emitARCValueOperation(*this, value,
                                 CGM.getObjCEntrypoints().objc_retain,
                                 "objc_retain");
  }
  
  /// Retain the given block, with _Block_copy semantics.
  ///   call i8* \@objc_retainBlock(i8* %value)
  ///
  /// \param mandatory - If false, emit the call with metadata
  /// indicating that it's okay for the optimizer to eliminate this call
  /// if it can prove that the block never escapes except down the stack.
  llvm::Value *CodeGenFunction::EmitARCRetainBlock(llvm::Value *value,
                                                   bool mandatory) {
    llvm::Value *result
      = emitARCValueOperation(*this, value,
                              CGM.getObjCEntrypoints().objc_retainBlock,
                              "objc_retainBlock");
  
    // If the copy isn't mandatory, add !clang.arc.copy_on_escape to
    // tell the optimizer that it doesn't need to do this copy if the
    // block doesn't escape, where being passed as an argument doesn't
    // count as escaping.
    if (!mandatory && isa<llvm::Instruction>(result)) {
      llvm::CallInst *call
        = cast<llvm::CallInst>(result->stripPointerCasts());
      assert(call->getCalledValue() == CGM.getObjCEntrypoints().objc_retainBlock);
  
      call->setMetadata("clang.arc.copy_on_escape",
                        llvm::MDNode::get(Builder.getContext(), None));
    }
  
    return result;
  }
  
  static void emitAutoreleasedReturnValueMarker(CodeGenFunction &CGF) {
    // Fetch the void(void) inline asm which marks that we're going to
    // do something with the autoreleased return value.
    llvm::InlineAsm *&marker
      = CGF.CGM.getObjCEntrypoints().retainAutoreleasedReturnValueMarker;
    if (!marker) {
      StringRef assembly
        = CGF.CGM.getTargetCodeGenInfo()
             .getARCRetainAutoreleasedReturnValueMarker();
  
      // If we have an empty assembly string, there's nothing to do.
      if (assembly.empty()) {
  
      // Otherwise, at -O0, build an inline asm that we're going to call
      // in a moment.
      } else if (CGF.CGM.getCodeGenOpts().OptimizationLevel == 0) {
        llvm::FunctionType *type =
          llvm::FunctionType::get(CGF.VoidTy, /*variadic*/false);
        
        marker = llvm::InlineAsm::get(type, assembly, "", /*sideeffects*/ true);
  
      // If we're at -O1 and above, we don't want to litter the code
      // with this marker yet, so leave a breadcrumb for the ARC
      // optimizer to pick up.
      } else {
        llvm::NamedMDNode *metadata =
          CGF.CGM.getModule().getOrInsertNamedMetadata(
                              "clang.arc.retainAutoreleasedReturnValueMarker");
        assert(metadata->getNumOperands() <= 1);
        if (metadata->getNumOperands() == 0) {
          auto &ctx = CGF.getLLVMContext();
          metadata->addOperand(llvm::MDNode::get(ctx,
                                       llvm::MDString::get(ctx, assembly)));
        }
      }
    }
  
    // Call the marker asm if we made one, which we do only at -O0.
    if (marker)
      CGF.Builder.CreateCall(marker);
  }
  
  /// Retain the given object which is the result of a function call.
  ///   call i8* \@objc_retainAutoreleasedReturnValue(i8* %value)
  ///
  /// Yes, this function name is one character away from a different
  /// call with completely different semantics.
  llvm::Value *
  CodeGenFunction::EmitARCRetainAutoreleasedReturnValue(llvm::Value *value) {
    emitAutoreleasedReturnValueMarker(*this);
    return emitARCValueOperation(*this, value,
                CGM.getObjCEntrypoints().objc_retainAutoreleasedReturnValue,
                                 "objc_retainAutoreleasedReturnValue");
  }
  
  /// Claim a possibly-autoreleased return value at +0.  This is only
  /// valid to do in contexts which do not rely on the retain to keep
  /// the object valid for for all of its uses; for example, when
  /// the value is ignored, or when it is being assigned to an
  /// __unsafe_unretained variable.
  ///
  ///   call i8* \@objc_unsafeClaimAutoreleasedReturnValue(i8* %value)
  llvm::Value *
  CodeGenFunction::EmitARCUnsafeClaimAutoreleasedReturnValue(llvm::Value *value) {
    emitAutoreleasedReturnValueMarker(*this);
    return emitARCValueOperation(*this, value,
                CGM.getObjCEntrypoints().objc_unsafeClaimAutoreleasedReturnValue,
                                 "objc_unsafeClaimAutoreleasedReturnValue");
  }
  
  /// Release the given object.
  ///   call void \@objc_release(i8* %value)
  void CodeGenFunction::EmitARCRelease(llvm::Value *value,
                                       ARCPreciseLifetime_t precise) {
    if (isa<llvm::ConstantPointerNull>(value)) return;
  
    llvm::Constant *&fn = CGM.getObjCEntrypoints().objc_release;
    if (!fn) {
      llvm::FunctionType *fnType =
        llvm::FunctionType::get(Builder.getVoidTy(), Int8PtrTy, false);
      fn = createARCRuntimeFunction(CGM, fnType, "objc_release");
    }
  
    // Cast the argument to 'id'.
    value = Builder.CreateBitCast(value, Int8PtrTy);
  
    // Call objc_release.
    llvm::CallInst *call = EmitNounwindRuntimeCall(fn, value);
  
    if (precise == ARCImpreciseLifetime) {
      call->setMetadata("clang.imprecise_release",
                        llvm::MDNode::get(Builder.getContext(), None));
    }
  }
  
  /// Destroy a __strong variable.
  ///
  /// At -O0, emit a call to store 'null' into the address;
  /// instrumenting tools prefer this because the address is exposed,
  /// but it's relatively cumbersome to optimize.
  ///
  /// At -O1 and above, just load and call objc_release.
  ///
  ///   call void \@objc_storeStrong(i8** %addr, i8* null)
  void CodeGenFunction::EmitARCDestroyStrong(Address addr,
                                             ARCPreciseLifetime_t precise) {
    if (CGM.getCodeGenOpts().OptimizationLevel == 0) {
      llvm::Value *null = getNullForVariable(addr);
      EmitARCStoreStrongCall(addr, null, /*ignored*/ true);
      return;
    }
  
    llvm::Value *value = Builder.CreateLoad(addr);
    EmitARCRelease(value, precise);
  }
  
  /// Store into a strong object.  Always calls this:
  ///   call void \@objc_storeStrong(i8** %addr, i8* %value)
  llvm::Value *CodeGenFunction::EmitARCStoreStrongCall(Address addr,
                                                       llvm::Value *value,
                                                       bool ignored) {
    assert(addr.getElementType() == value->getType());
  
    llvm::Constant *&fn = CGM.getObjCEntrypoints().objc_storeStrong;
    if (!fn) {
      llvm::Type *argTypes[] = { Int8PtrPtrTy, Int8PtrTy };
      llvm::FunctionType *fnType
        = llvm::FunctionType::get(Builder.getVoidTy(), argTypes, false);
      fn = createARCRuntimeFunction(CGM, fnType, "objc_storeStrong");
    }
  
    llvm::Value *args[] = {
      Builder.CreateBitCast(addr.getPointer(), Int8PtrPtrTy),
      Builder.CreateBitCast(value, Int8PtrTy)
    };
    EmitNounwindRuntimeCall(fn, args);
  
    if (ignored) return nullptr;
    return value;
  }
  
  /// Store into a strong object.  Sometimes calls this:
  ///   call void \@objc_storeStrong(i8** %addr, i8* %value)
  /// Other times, breaks it down into components.
  llvm::Value *CodeGenFunction::EmitARCStoreStrong(LValue dst,
                                                   llvm::Value *newValue,
                                                   bool ignored) {
    QualType type = dst.getType();
    bool isBlock = type->isBlockPointerType();
  
    // Use a store barrier at -O0 unless this is a block type or the
    // lvalue is inadequately aligned.
    if (shouldUseFusedARCCalls() &&
        !isBlock &&
        (dst.getAlignment().isZero() ||
         dst.getAlignment() >= CharUnits::fromQuantity(PointerAlignInBytes))) {
      return EmitARCStoreStrongCall(dst.getAddress(), newValue, ignored);
    }
  
    // Otherwise, split it out.
  
    // Retain the new value.
    newValue = EmitARCRetain(type, newValue);
  
    // Read the old value.
    llvm::Value *oldValue = EmitLoadOfScalar(dst, SourceLocation());
  
    // Store.  We do this before the release so that any deallocs won't
    // see the old value.
    EmitStoreOfScalar(newValue, dst);
  
    // Finally, release the old value.
    EmitARCRelease(oldValue, dst.isARCPreciseLifetime());
  
    return newValue;
  }
  
  /// Autorelease the given object.
  ///   call i8* \@objc_autorelease(i8* %value)
  llvm::Value *CodeGenFunction::EmitARCAutorelease(llvm::Value *value) {
    return emitARCValueOperation(*this, value,
                                 CGM.getObjCEntrypoints().objc_autorelease,
                                 "objc_autorelease");
  }
  
  /// Autorelease the given object.
  ///   call i8* \@objc_autoreleaseReturnValue(i8* %value)
  llvm::Value *
  CodeGenFunction::EmitARCAutoreleaseReturnValue(llvm::Value *value) {
    return emitARCValueOperation(*this, value,
                              CGM.getObjCEntrypoints().objc_autoreleaseReturnValue,
                                 "objc_autoreleaseReturnValue",
                                 /*isTailCall*/ true);
  }
  
  /// Do a fused retain/autorelease of the given object.
  ///   call i8* \@objc_retainAutoreleaseReturnValue(i8* %value)
  llvm::Value *
  CodeGenFunction::EmitARCRetainAutoreleaseReturnValue(llvm::Value *value) {
    return emitARCValueOperation(*this, value,
                       CGM.getObjCEntrypoints().objc_retainAutoreleaseReturnValue,
                                 "objc_retainAutoreleaseReturnValue",
                                 /*isTailCall*/ true);
  }
  
  /// Do a fused retain/autorelease of the given object.
  ///   call i8* \@objc_retainAutorelease(i8* %value)
  /// or
  ///   %retain = call i8* \@objc_retainBlock(i8* %value)
  ///   call i8* \@objc_autorelease(i8* %retain)
  llvm::Value *CodeGenFunction::EmitARCRetainAutorelease(QualType type,
                                                         llvm::Value *value) {
    if (!type->isBlockPointerType())
      return EmitARCRetainAutoreleaseNonBlock(value);
  
    if (isa<llvm::ConstantPointerNull>(value)) return value;
  
    llvm::Type *origType = value->getType();
    value = Builder.CreateBitCast(value, Int8PtrTy);
    value = EmitARCRetainBlock(value, /*mandatory*/ true);
    value = EmitARCAutorelease(value);
    return Builder.CreateBitCast(value, origType);
  }
  
  /// Do a fused retain/autorelease of the given object.
  ///   call i8* \@objc_retainAutorelease(i8* %value)
  llvm::Value *
  CodeGenFunction::EmitARCRetainAutoreleaseNonBlock(llvm::Value *value) {
    return emitARCValueOperation(*this, value,
                                 CGM.getObjCEntrypoints().objc_retainAutorelease,
                                 "objc_retainAutorelease");
  }
  
  /// i8* \@objc_loadWeak(i8** %addr)
  /// Essentially objc_autorelease(objc_loadWeakRetained(addr)).
  llvm::Value *CodeGenFunction::EmitARCLoadWeak(Address addr) {
    return emitARCLoadOperation(*this, addr,
                                CGM.getObjCEntrypoints().objc_loadWeak,
                                "objc_loadWeak");
  }
  
  /// i8* \@objc_loadWeakRetained(i8** %addr)
  llvm::Value *CodeGenFunction::EmitARCLoadWeakRetained(Address addr) {
    return emitARCLoadOperation(*this, addr,
                                CGM.getObjCEntrypoints().objc_loadWeakRetained,
                                "objc_loadWeakRetained");
  }
  
  /// i8* \@objc_storeWeak(i8** %addr, i8* %value)
  /// Returns %value.
  llvm::Value *CodeGenFunction::EmitARCStoreWeak(Address addr,
                                                 llvm::Value *value,
                                                 bool ignored) {
    return emitARCStoreOperation(*this, addr, value,
                                 CGM.getObjCEntrypoints().objc_storeWeak,
                                 "objc_storeWeak", ignored);
  }
  
  /// i8* \@objc_initWeak(i8** %addr, i8* %value)
  /// Returns %value.  %addr is known to not have a current weak entry.
  /// Essentially equivalent to:
  ///   *addr = nil; objc_storeWeak(addr, value);
  void CodeGenFunction::EmitARCInitWeak(Address addr, llvm::Value *value) {
    // If we're initializing to null, just write null to memory; no need
    // to get the runtime involved.  But don't do this if optimization
    // is enabled, because accounting for this would make the optimizer
    // much more complicated.
    if (isa<llvm::ConstantPointerNull>(value) &&
        CGM.getCodeGenOpts().OptimizationLevel == 0) {
      Builder.CreateStore(value, addr);
      return;
    }
  
    emitARCStoreOperation(*this, addr, value,
                          CGM.getObjCEntrypoints().objc_initWeak,
                          "objc_initWeak", /*ignored*/ true);
  }
  
  /// void \@objc_destroyWeak(i8** %addr)
  /// Essentially objc_storeWeak(addr, nil).
  void CodeGenFunction::EmitARCDestroyWeak(Address addr) {
    llvm::Constant *&fn = CGM.getObjCEntrypoints().objc_destroyWeak;
    if (!fn) {
      llvm::FunctionType *fnType =
        llvm::FunctionType::get(Builder.getVoidTy(), Int8PtrPtrTy, false);
      fn = createARCRuntimeFunction(CGM, fnType, "objc_destroyWeak");
    }
  
    // Cast the argument to 'id*'.
    addr = Builder.CreateBitCast(addr, Int8PtrPtrTy);
  
    EmitNounwindRuntimeCall(fn, addr.getPointer());
  }
  
  /// void \@objc_moveWeak(i8** %dest, i8** %src)
  /// Disregards the current value in %dest.  Leaves %src pointing to nothing.
  /// Essentially (objc_copyWeak(dest, src), objc_destroyWeak(src)).
  void CodeGenFunction::EmitARCMoveWeak(Address dst, Address src) {
    emitARCCopyOperation(*this, dst, src,
                         CGM.getObjCEntrypoints().objc_moveWeak,
                         "objc_moveWeak");
  }
  
  /// void \@objc_copyWeak(i8** %dest, i8** %src)
  /// Disregards the current value in %dest.  Essentially
  ///   objc_release(objc_initWeak(dest, objc_readWeakRetained(src)))
  void CodeGenFunction::EmitARCCopyWeak(Address dst, Address src) {
    emitARCCopyOperation(*this, dst, src,
                         CGM.getObjCEntrypoints().objc_copyWeak,
                         "objc_copyWeak");
  }
  
  /// Produce the code to do a objc_autoreleasepool_push.
  ///   call i8* \@objc_autoreleasePoolPush(void)
  llvm::Value *CodeGenFunction::EmitObjCAutoreleasePoolPush() {
    llvm::Constant *&fn = CGM.getObjCEntrypoints().objc_autoreleasePoolPush;
    if (!fn) {
      llvm::FunctionType *fnType =
        llvm::FunctionType::get(Int8PtrTy, false);
      fn = createARCRuntimeFunction(CGM, fnType, "objc_autoreleasePoolPush");
    }
  
    return EmitNounwindRuntimeCall(fn);
  }
  
  /// Produce the code to do a primitive release.
  ///   call void \@objc_autoreleasePoolPop(i8* %ptr)
  void CodeGenFunction::EmitObjCAutoreleasePoolPop(llvm::Value *value) {
    assert(value->getType() == Int8PtrTy);
  
    llvm::Constant *&fn = CGM.getObjCEntrypoints().objc_autoreleasePoolPop;
    if (!fn) {
      llvm::FunctionType *fnType =
        llvm::FunctionType::get(Builder.getVoidTy(), Int8PtrTy, false);
  
      // We don't want to use a weak import here; instead we should not
      // fall into this path.
      fn = createARCRuntimeFunction(CGM, fnType, "objc_autoreleasePoolPop");
    }
  
    // objc_autoreleasePoolPop can throw.
    EmitRuntimeCallOrInvoke(fn, value);
  }
  
  /// Produce the code to do an MRR version objc_autoreleasepool_push.
  /// Which is: [[NSAutoreleasePool alloc] init];
  /// Where alloc is declared as: + (id) alloc; in NSAutoreleasePool class.
  /// init is declared as: - (id) init; in its NSObject super class.
  ///
  llvm::Value *CodeGenFunction::EmitObjCMRRAutoreleasePoolPush() {
    CGObjCRuntime &Runtime = CGM.getObjCRuntime();
    llvm::Value *Receiver = Runtime.EmitNSAutoreleasePoolClassRef(*this);
    // [NSAutoreleasePool alloc]
    IdentifierInfo *II = &CGM.getContext().Idents.get("alloc");
    Selector AllocSel = getContext().Selectors.getSelector(0, &II);
    CallArgList Args;
    RValue AllocRV =  
      Runtime.GenerateMessageSend(*this, ReturnValueSlot(), 
                                  getContext().getObjCIdType(),
                                  AllocSel, Receiver, Args); 
  
    // [Receiver init]
    Receiver = AllocRV.getScalarVal();
    II = &CGM.getContext().Idents.get("init");
    Selector InitSel = getContext().Selectors.getSelector(0, &II);
    RValue InitRV =
      Runtime.GenerateMessageSend(*this, ReturnValueSlot(),
                                  getContext().getObjCIdType(),
                                  InitSel, Receiver, Args); 
    return InitRV.getScalarVal();
  }
  
  /// Produce the code to do a primitive release.
  /// [tmp drain];
  void CodeGenFunction::EmitObjCMRRAutoreleasePoolPop(llvm::Value *Arg) {
    IdentifierInfo *II = &CGM.getContext().Idents.get("drain");
    Selector DrainSel = getContext().Selectors.getSelector(0, &II);
    CallArgList Args;
    CGM.getObjCRuntime().GenerateMessageSend(*this, ReturnValueSlot(),
                                getContext().VoidTy, DrainSel, Arg, Args); 
  }
  
  void CodeGenFunction::destroyARCStrongPrecise(CodeGenFunction &CGF,
                                                Address addr,
                                                QualType type) {
    CGF.EmitARCDestroyStrong(addr, ARCPreciseLifetime);
  }
  
  void CodeGenFunction::destroyARCStrongImprecise(CodeGenFunction &CGF,
                                                  Address addr,
                                                  QualType type) {
    CGF.EmitARCDestroyStrong(addr, ARCImpreciseLifetime);
  }
  
  void CodeGenFunction::destroyARCWeak(CodeGenFunction &CGF,
                                       Address addr,
                                       QualType type) {
    CGF.EmitARCDestroyWeak(addr);
  }
  
  namespace {
    struct CallObjCAutoreleasePoolObject final : EHScopeStack::Cleanup {
      llvm::Value *Token;
  
      CallObjCAutoreleasePoolObject(llvm::Value *token) : Token(token) {}
  
      void Emit(CodeGenFunction &CGF, Flags flags) override {
        CGF.EmitObjCAutoreleasePoolPop(Token);
      }
    };
    struct CallObjCMRRAutoreleasePoolObject final : EHScopeStack::Cleanup {
      llvm::Value *Token;
  
      CallObjCMRRAutoreleasePoolObject(llvm::Value *token) : Token(token) {}
  
      void Emit(CodeGenFunction &CGF, Flags flags) override {
        CGF.EmitObjCMRRAutoreleasePoolPop(Token);
      }
    };
  }
  
  void CodeGenFunction::EmitObjCAutoreleasePoolCleanup(llvm::Value *Ptr) {
    if (CGM.getLangOpts().ObjCAutoRefCount)
      EHStack.pushCleanup<CallObjCAutoreleasePoolObject>(NormalCleanup, Ptr);
    else
      EHStack.pushCleanup<CallObjCMRRAutoreleasePoolObject>(NormalCleanup, Ptr);
  }
  
  static TryEmitResult tryEmitARCRetainLoadOfScalar(CodeGenFunction &CGF,
                                                    LValue lvalue,
                                                    QualType type) {
    switch (type.getObjCLifetime()) {
    case Qualifiers::OCL_None:
    case Qualifiers::OCL_ExplicitNone:
    case Qualifiers::OCL_Strong:
    case Qualifiers::OCL_Autoreleasing:
      return TryEmitResult(CGF.EmitLoadOfLValue(lvalue,
                                                SourceLocation()).getScalarVal(),
                           false);
  
    case Qualifiers::OCL_Weak:
      return TryEmitResult(CGF.EmitARCLoadWeakRetained(lvalue.getAddress()),
                           true);
    }
  
    llvm_unreachable("impossible lifetime!");
  }
  
  static TryEmitResult tryEmitARCRetainLoadOfScalar(CodeGenFunction &CGF,
                                                    const Expr *e) {
    e = e->IgnoreParens();
    QualType type = e->getType();
  
    // If we're loading retained from a __strong xvalue, we can avoid 
    // an extra retain/release pair by zeroing out the source of this
    // "move" operation.
    if (e->isXValue() &&
        !type.isConstQualified() &&
        type.getObjCLifetime() == Qualifiers::OCL_Strong) {
      // Emit the lvalue.
      LValue lv = CGF.EmitLValue(e);
      
      // Load the object pointer.
      llvm::Value *result = CGF.EmitLoadOfLValue(lv,
                                                 SourceLocation()).getScalarVal();
      
      // Set the source pointer to NULL.
      CGF.EmitStoreOfScalar(getNullForVariable(lv.getAddress()), lv);
      
      return TryEmitResult(result, true);
    }
  
    // As a very special optimization, in ARC++, if the l-value is the
    // result of a non-volatile assignment, do a simple retain of the
    // result of the call to objc_storeWeak instead of reloading.
    if (CGF.getLangOpts().CPlusPlus &&
        !type.isVolatileQualified() &&
        type.getObjCLifetime() == Qualifiers::OCL_Weak &&
        isa<BinaryOperator>(e) &&
        cast<BinaryOperator>(e)->getOpcode() == BO_Assign)
      return TryEmitResult(CGF.EmitScalarExpr(e), false);
  
    return tryEmitARCRetainLoadOfScalar(CGF, CGF.EmitLValue(e), type);
  }
  
  typedef llvm::function_ref<llvm::Value *(CodeGenFunction &CGF,
                                           llvm::Value *value)>
    ValueTransform;
  
  /// Insert code immediately after a call.
  static llvm::Value *emitARCOperationAfterCall(CodeGenFunction &CGF,
                                                llvm::Value *value,
                                                ValueTransform doAfterCall,
                                                ValueTransform doFallback) {
    if (llvm::CallInst *call = dyn_cast<llvm::CallInst>(value)) {
      CGBuilderTy::InsertPoint ip = CGF.Builder.saveIP();
  
      // Place the retain immediately following the call.
      CGF.Builder.SetInsertPoint(call->getParent(),
                                 ++llvm::BasicBlock::iterator(call));
      value = doAfterCall(CGF, value);
  
      CGF.Builder.restoreIP(ip);
      return value;
    } else if (llvm::InvokeInst *invoke = dyn_cast<llvm::InvokeInst>(value)) {
      CGBuilderTy::InsertPoint ip = CGF.Builder.saveIP();
  
      // Place the retain at the beginning of the normal destination block.
      llvm::BasicBlock *BB = invoke->getNormalDest();
      CGF.Builder.SetInsertPoint(BB, BB->begin());
      value = doAfterCall(CGF, value);
  
      CGF.Builder.restoreIP(ip);
      return value;
  
    // Bitcasts can arise because of related-result returns.  Rewrite
    // the operand.
    } else if (llvm::BitCastInst *bitcast = dyn_cast<llvm::BitCastInst>(value)) {
      llvm::Value *operand = bitcast->getOperand(0);
      operand = emitARCOperationAfterCall(CGF, operand, doAfterCall, doFallback);
      bitcast->setOperand(0, operand);
      return bitcast;
  
    // Generic fall-back case.
    } else {
      // Retain using the non-block variant: we never need to do a copy
      // of a block that's been returned to us.
      return doFallback(CGF, value);
    }
  }
  
  /// Given that the given expression is some sort of call (which does
  /// not return retained), emit a retain following it.
  static llvm::Value *emitARCRetainCallResult(CodeGenFunction &CGF,
                                              const Expr *e) {
    llvm::Value *value = CGF.EmitScalarExpr(e);
    return emitARCOperationAfterCall(CGF, value,
             [](CodeGenFunction &CGF, llvm::Value *value) {
               return CGF.EmitARCRetainAutoreleasedReturnValue(value);
             },
             [](CodeGenFunction &CGF, llvm::Value *value) {
               return CGF.EmitARCRetainNonBlock(value);
             });
  }
  
  /// Given that the given expression is some sort of call (which does
  /// not return retained), perform an unsafeClaim following it.
  static llvm::Value *emitARCUnsafeClaimCallResult(CodeGenFunction &CGF,
                                                   const Expr *e) {
    llvm::Value *value = CGF.EmitScalarExpr(e);
    return emitARCOperationAfterCall(CGF, value,
             [](CodeGenFunction &CGF, llvm::Value *value) {
               return CGF.EmitARCUnsafeClaimAutoreleasedReturnValue(value);
             },
             [](CodeGenFunction &CGF, llvm::Value *value) {
               return value;
             });
  }
  
  llvm::Value *CodeGenFunction::EmitARCReclaimReturnedObject(const Expr *E,
                                                        bool allowUnsafeClaim) {
    if (allowUnsafeClaim &&
        CGM.getLangOpts().ObjCRuntime.hasARCUnsafeClaimAutoreleasedReturnValue()) {
      return emitARCUnsafeClaimCallResult(*this, E);
    } else {
      llvm::Value *value = emitARCRetainCallResult(*this, E);
      return EmitObjCConsumeObject(E->getType(), value);
    }
  }
  
  /// Determine whether it might be important to emit a separate
  /// objc_retain_block on the result of the given expression, or
  /// whether it's okay to just emit it in a +1 context.
  static bool shouldEmitSeparateBlockRetain(const Expr *e) {
    assert(e->getType()->isBlockPointerType());
    e = e->IgnoreParens();
  
    // For future goodness, emit block expressions directly in +1
    // contexts if we can.
    if (isa<BlockExpr>(e))
      return false;
  
    if (const CastExpr *cast = dyn_cast<CastExpr>(e)) {
      switch (cast->getCastKind()) {
      // Emitting these operations in +1 contexts is goodness.
      case CK_LValueToRValue:
      case CK_ARCReclaimReturnedObject:
      case CK_ARCConsumeObject:
      case CK_ARCProduceObject:
        return false;
  
      // These operations preserve a block type.
      case CK_NoOp:
      case CK_BitCast:
        return shouldEmitSeparateBlockRetain(cast->getSubExpr());
  
      // These operations are known to be bad (or haven't been considered).
      case CK_AnyPointerToBlockPointerCast:
      default:
        return true;
      }
    }
  
    return true;
  }
  
  namespace {
  /// A CRTP base class for emitting expressions of retainable object
  /// pointer type in ARC.
  template <typename Impl, typename Result> class ARCExprEmitter {
  protected:
    CodeGenFunction &CGF;
    Impl &asImpl() { return *static_cast<Impl*>(this); }
  
    ARCExprEmitter(CodeGenFunction &CGF) : CGF(CGF) {}
  
  public:
    Result visit(const Expr *e);
    Result visitCastExpr(const CastExpr *e);
    Result visitPseudoObjectExpr(const PseudoObjectExpr *e);
    Result visitBinaryOperator(const BinaryOperator *e);
    Result visitBinAssign(const BinaryOperator *e);
    Result visitBinAssignUnsafeUnretained(const BinaryOperator *e);
    Result visitBinAssignAutoreleasing(const BinaryOperator *e);
    Result visitBinAssignWeak(const BinaryOperator *e);
    Result visitBinAssignStrong(const BinaryOperator *e);
  
    // Minimal implementation:
    //   Result visitLValueToRValue(const Expr *e)
    //   Result visitConsumeObject(const Expr *e)
    //   Result visitExtendBlockObject(const Expr *e)
    //   Result visitReclaimReturnedObject(const Expr *e)
    //   Result visitCall(const Expr *e)
    //   Result visitExpr(const Expr *e)
    //
    //   Result emitBitCast(Result result, llvm::Type *resultType)
    //   llvm::Value *getValueOfResult(Result result)
  };
  }
  
  /// Try to emit a PseudoObjectExpr under special ARC rules.
  ///
  /// This massively duplicates emitPseudoObjectRValue.
  template <typename Impl, typename Result>
  Result
  ARCExprEmitter<Impl,Result>::visitPseudoObjectExpr(const PseudoObjectExpr *E) {
    SmallVector<CodeGenFunction::OpaqueValueMappingData, 4> opaques;
  
    // Find the result expression.
    const Expr *resultExpr = E->getResultExpr();
    assert(resultExpr);
    Result result;
  
    for (PseudoObjectExpr::const_semantics_iterator
           i = E->semantics_begin(), e = E->semantics_end(); i != e; ++i) {
      const Expr *semantic = *i;
  
      // If this semantic expression is an opaque value, bind it
      // to the result of its source expression.
      if (const OpaqueValueExpr *ov = dyn_cast<OpaqueValueExpr>(semantic)) {
        typedef CodeGenFunction::OpaqueValueMappingData OVMA;
        OVMA opaqueData;
  
        // If this semantic is the result of the pseudo-object
        // expression, try to evaluate the source as +1.
        if (ov == resultExpr) {
          assert(!OVMA::shouldBindAsLValue(ov));
          result = asImpl().visit(ov->getSourceExpr());
          opaqueData = OVMA::bind(CGF, ov,
                              RValue::get(asImpl().getValueOfResult(result)));
  
        // Otherwise, just bind it.
        } else {
          opaqueData = OVMA::bind(CGF, ov, ov->getSourceExpr());
        }
        opaques.push_back(opaqueData);
  
      // Otherwise, if the expression is the result, evaluate it
      // and remember the result.
      } else if (semantic == resultExpr) {
        result = asImpl().visit(semantic);
  
      // Otherwise, evaluate the expression in an ignored context.
      } else {
        CGF.EmitIgnoredExpr(semantic);
      }
    }
  
    // Unbind all the opaques now.
    for (unsigned i = 0, e = opaques.size(); i != e; ++i)
      opaques[i].unbind(CGF);
  
    return result;
  }
  
  template <typename Impl, typename Result>
  Result ARCExprEmitter<Impl,Result>::visitCastExpr(const CastExpr *e) {
    switch (e->getCastKind()) {
  
    // No-op casts don't change the type, so we just ignore them.
    case CK_NoOp:
      return asImpl().visit(e->getSubExpr());
  
    // These casts can change the type.
    case CK_CPointerToObjCPointerCast:
    case CK_BlockPointerToObjCPointerCast:
    case CK_AnyPointerToBlockPointerCast:
    case CK_BitCast: {
      llvm::Type *resultType = CGF.ConvertType(e->getType());
      assert(e->getSubExpr()->getType()->hasPointerRepresentation());
      Result result = asImpl().visit(e->getSubExpr());
      return asImpl().emitBitCast(result, resultType);
    }
  
    // Handle some casts specially.
    case CK_LValueToRValue:
      return asImpl().visitLValueToRValue(e->getSubExpr());
    case CK_ARCConsumeObject:
      return asImpl().visitConsumeObject(e->getSubExpr());
    case CK_ARCExtendBlockObject:
      return asImpl().visitExtendBlockObject(e->getSubExpr());
    case CK_ARCReclaimReturnedObject:
      return asImpl().visitReclaimReturnedObject(e->getSubExpr());
  
    // Otherwise, use the default logic.
    default:
      return asImpl().visitExpr(e);
    }
  }
  
  template <typename Impl, typename Result>
  Result
  ARCExprEmitter<Impl,Result>::visitBinaryOperator(const BinaryOperator *e) {
    switch (e->getOpcode()) {
    case BO_Comma:
      CGF.EmitIgnoredExpr(e->getLHS());
      CGF.EnsureInsertPoint();
      return asImpl().visit(e->getRHS());
  
    case BO_Assign:
      return asImpl().visitBinAssign(e);
  
    default:
      return asImpl().visitExpr(e);
    }
  }
  
  template <typename Impl, typename Result>
  Result ARCExprEmitter<Impl,Result>::visitBinAssign(const BinaryOperator *e) {
    switch (e->getLHS()->getType().getObjCLifetime()) {
    case Qualifiers::OCL_ExplicitNone:
      return asImpl().visitBinAssignUnsafeUnretained(e);
  
    case Qualifiers::OCL_Weak:
      return asImpl().visitBinAssignWeak(e);
  
    case Qualifiers::OCL_Autoreleasing:
      return asImpl().visitBinAssignAutoreleasing(e);
  
    case Qualifiers::OCL_Strong:
      return asImpl().visitBinAssignStrong(e);
  
    case Qualifiers::OCL_None:
      return asImpl().visitExpr(e);
    }
    llvm_unreachable("bad ObjC ownership qualifier");
  }
  
  /// The default rule for __unsafe_unretained emits the RHS recursively,
  /// stores into the unsafe variable, and propagates the result outward.
  template <typename Impl, typename Result>
  Result ARCExprEmitter<Impl,Result>::
                      visitBinAssignUnsafeUnretained(const BinaryOperator *e) {
    // Recursively emit the RHS.
    // For __block safety, do this before emitting the LHS.
    Result result = asImpl().visit(e->getRHS());
  
    // Perform the store.
    LValue lvalue =
      CGF.EmitCheckedLValue(e->getLHS(), CodeGenFunction::TCK_Store);
    CGF.EmitStoreThroughLValue(RValue::get(asImpl().getValueOfResult(result)),
                               lvalue);
  
    return result;
  }
  
  template <typename Impl, typename Result>
  Result
  ARCExprEmitter<Impl,Result>::visitBinAssignAutoreleasing(const BinaryOperator *e) {
    return asImpl().visitExpr(e);
  }
  
  template <typename Impl, typename Result>
  Result
  ARCExprEmitter<Impl,Result>::visitBinAssignWeak(const BinaryOperator *e) {
    return asImpl().visitExpr(e);
  }
  
  template <typename Impl, typename Result>
  Result
  ARCExprEmitter<Impl,Result>::visitBinAssignStrong(const BinaryOperator *e) {
    return asImpl().visitExpr(e);
  }
  
  /// The general expression-emission logic.
  template <typename Impl, typename Result>
  Result ARCExprEmitter<Impl,Result>::visit(const Expr *e) {
    // We should *never* see a nested full-expression here, because if
    // we fail to emit at +1, our caller must not retain after we close
    // out the full-expression.  This isn't as important in the unsafe
    // emitter.
    assert(!isa<ExprWithCleanups>(e));
  
    // Look through parens, __extension__, generic selection, etc.
    e = e->IgnoreParens();
  
    // Handle certain kinds of casts.
    if (const CastExpr *ce = dyn_cast<CastExpr>(e)) {
      return asImpl().visitCastExpr(ce);
  
    // Handle the comma operator.
    } else if (auto op = dyn_cast<BinaryOperator>(e)) {
      return asImpl().visitBinaryOperator(op);
  
    // TODO: handle conditional operators here
  
    // For calls and message sends, use the retained-call logic.
    // Delegate inits are a special case in that they're the only
    // returns-retained expression that *isn't* surrounded by
    // a consume.
    } else if (isa<CallExpr>(e) ||
               (isa<ObjCMessageExpr>(e) &&
                !cast<ObjCMessageExpr>(e)->isDelegateInitCall())) {
      return asImpl().visitCall(e);
  
    // Look through pseudo-object expressions.
    } else if (const PseudoObjectExpr *pseudo = dyn_cast<PseudoObjectExpr>(e)) {
      return asImpl().visitPseudoObjectExpr(pseudo);
    }
  
    return asImpl().visitExpr(e);
  }
  
  namespace {
  
  /// An emitter for +1 results.
  struct ARCRetainExprEmitter :
    public ARCExprEmitter<ARCRetainExprEmitter, TryEmitResult> {
  
    ARCRetainExprEmitter(CodeGenFunction &CGF) : ARCExprEmitter(CGF) {}
  
    llvm::Value *getValueOfResult(TryEmitResult result) {
      return result.getPointer();
    }
  
    TryEmitResult emitBitCast(TryEmitResult result, llvm::Type *resultType) {
      llvm::Value *value = result.getPointer();
      value = CGF.Builder.CreateBitCast(value, resultType);
      result.setPointer(value);
      return result;
    }
  
    TryEmitResult visitLValueToRValue(const Expr *e) {
      return tryEmitARCRetainLoadOfScalar(CGF, e);
    }
  
    /// For consumptions, just emit the subexpression and thus elide
    /// the retain/release pair.
    TryEmitResult visitConsumeObject(const Expr *e) {
      llvm::Value *result = CGF.EmitScalarExpr(e);
      return TryEmitResult(result, true);
    }
  
    /// Block extends are net +0.  Naively, we could just recurse on
    /// the subexpression, but actually we need to ensure that the
    /// value is copied as a block, so there's a little filter here.
    TryEmitResult visitExtendBlockObject(const Expr *e) {
      llvm::Value *result; // will be a +0 value
  
      // If we can't safely assume the sub-expression will produce a
      // block-copied value, emit the sub-expression at +0.
      if (shouldEmitSeparateBlockRetain(e)) {
        result = CGF.EmitScalarExpr(e);
  
      // Otherwise, try to emit the sub-expression at +1 recursively.
      } else {
        TryEmitResult subresult = asImpl().visit(e);
  
        // If that produced a retained value, just use that.
        if (subresult.getInt()) {
          return subresult;
        }
  
        // Otherwise it's +0.
        result = subresult.getPointer();
      }
  
      // Retain the object as a block.
      result = CGF.EmitARCRetainBlock(result, /*mandatory*/ true);
      return TryEmitResult(result, true);
    }
  
    /// For reclaims, emit the subexpression as a retained call and
    /// skip the consumption.
    TryEmitResult visitReclaimReturnedObject(const Expr *e) {
      llvm::Value *result = emitARCRetainCallResult(CGF, e);
      return TryEmitResult(result, true);
    }
  
    /// When we have an undecorated call, retroactively do a claim.
    TryEmitResult visitCall(const Expr *e) {
      llvm::Value *result = emitARCRetainCallResult(CGF, e);
      return TryEmitResult(result, true);
    }
  
    // TODO: maybe special-case visitBinAssignWeak?
  
    TryEmitResult visitExpr(const Expr *e) {
      // We didn't find an obvious production, so emit what we've got and
      // tell the caller that we didn't manage to retain.
      llvm::Value *result = CGF.EmitScalarExpr(e);
      return TryEmitResult(result, false);
    }
  };
  }
  
  static TryEmitResult
  tryEmitARCRetainScalarExpr(CodeGenFunction &CGF, const Expr *e) {
    return ARCRetainExprEmitter(CGF).visit(e);
  }
  
  static llvm::Value *emitARCRetainLoadOfScalar(CodeGenFunction &CGF,
                                                  LValue lvalue,
                                                  QualType type) {
    TryEmitResult result = tryEmitARCRetainLoadOfScalar(CGF, lvalue, type);
    llvm::Value *value = result.getPointer();
    if (!result.getInt())
      value = CGF.EmitARCRetain(type, value);
    return value;
  }
  
  /// EmitARCRetainScalarExpr - Semantically equivalent to
  /// EmitARCRetainObject(e->getType(), EmitScalarExpr(e)), but making a
  /// best-effort attempt to peephole expressions that naturally produce
  /// retained objects.
  llvm::Value *CodeGenFunction::EmitARCRetainScalarExpr(const Expr *e) {
    // The retain needs to happen within the full-expression.
    if (const ExprWithCleanups *cleanups = dyn_cast<ExprWithCleanups>(e)) {
      enterFullExpression(cleanups);
      RunCleanupsScope scope(*this);
      return EmitARCRetainScalarExpr(cleanups->getSubExpr());
    }
  
    TryEmitResult result = tryEmitARCRetainScalarExpr(*this, e);
    llvm::Value *value = result.getPointer();
    if (!result.getInt())
      value = EmitARCRetain(e->getType(), value);
    return value;
  }
  
  llvm::Value *
  CodeGenFunction::EmitARCRetainAutoreleaseScalarExpr(const Expr *e) {
    // The retain needs to happen within the full-expression.
    if (const ExprWithCleanups *cleanups = dyn_cast<ExprWithCleanups>(e)) {
      enterFullExpression(cleanups);
      RunCleanupsScope scope(*this);
      return EmitARCRetainAutoreleaseScalarExpr(cleanups->getSubExpr());
    }
  
    TryEmitResult result = tryEmitARCRetainScalarExpr(*this, e);
    llvm::Value *value = result.getPointer();
    if (result.getInt())
      value = EmitARCAutorelease(value);
    else
      value = EmitARCRetainAutorelease(e->getType(), value);
    return value;
  }
  
  llvm::Value *CodeGenFunction::EmitARCExtendBlockObject(const Expr *e) {
    llvm::Value *result;
    bool doRetain;
  
    if (shouldEmitSeparateBlockRetain(e)) {
      result = EmitScalarExpr(e);
      doRetain = true;
    } else {
      TryEmitResult subresult = tryEmitARCRetainScalarExpr(*this, e);
      result = subresult.getPointer();
      doRetain = !subresult.getInt();
    }
  
    if (doRetain)
      result = EmitARCRetainBlock(result, /*mandatory*/ true);
    return EmitObjCConsumeObject(e->getType(), result);
  }
  
  llvm::Value *CodeGenFunction::EmitObjCThrowOperand(const Expr *expr) {
    // In ARC, retain and autorelease the expression.
    if (getLangOpts().ObjCAutoRefCount) {
      // Do so before running any cleanups for the full-expression.
      // EmitARCRetainAutoreleaseScalarExpr does this for us.
      return EmitARCRetainAutoreleaseScalarExpr(expr);
    }
  
    // Otherwise, use the normal scalar-expression emission.  The
    // exception machinery doesn't do anything special with the
    // exception like retaining it, so there's no safety associated with
    // only running cleanups after the throw has started, and when it
    // matters it tends to be substantially inferior code.
    return EmitScalarExpr(expr);
  }
  
  namespace {
  
  /// An emitter for assigning into an __unsafe_unretained context.
  struct ARCUnsafeUnretainedExprEmitter :
    public ARCExprEmitter<ARCUnsafeUnretainedExprEmitter, llvm::Value*> {
  
    ARCUnsafeUnretainedExprEmitter(CodeGenFunction &CGF) : ARCExprEmitter(CGF) {}
  
    llvm::Value *getValueOfResult(llvm::Value *value) {
      return value;
    }
  
    llvm::Value *emitBitCast(llvm::Value *value, llvm::Type *resultType) {
      return CGF.Builder.CreateBitCast(value, resultType);
    }
  
    llvm::Value *visitLValueToRValue(const Expr *e) {
      return CGF.EmitScalarExpr(e);
    }
  
    /// For consumptions, just emit the subexpression and perform the
    /// consumption like normal.
    llvm::Value *visitConsumeObject(const Expr *e) {
      llvm::Value *value = CGF.EmitScalarExpr(e);
      return CGF.EmitObjCConsumeObject(e->getType(), value);
    }
  
    /// No special logic for block extensions.  (This probably can't
    /// actually happen in this emitter, though.)
    llvm::Value *visitExtendBlockObject(const Expr *e) {
      return CGF.EmitARCExtendBlockObject(e);
    }
  
    /// For reclaims, perform an unsafeClaim if that's enabled.
    llvm::Value *visitReclaimReturnedObject(const Expr *e) {
      return CGF.EmitARCReclaimReturnedObject(e, /*unsafe*/ true);
    }
  
    /// When we have an undecorated call, just emit it without adding
    /// the unsafeClaim.
    llvm::Value *visitCall(const Expr *e) {
      return CGF.EmitScalarExpr(e);
    }
  
    /// Just do normal scalar emission in the default case.
    llvm::Value *visitExpr(const Expr *e) {
      return CGF.EmitScalarExpr(e);
    }
  };
  }
  
  static llvm::Value *emitARCUnsafeUnretainedScalarExpr(CodeGenFunction &CGF,
                                                        const Expr *e) {
    return ARCUnsafeUnretainedExprEmitter(CGF).visit(e);
  }
  
  /// EmitARCUnsafeUnretainedScalarExpr - Semantically equivalent to
  /// immediately releasing the resut of EmitARCRetainScalarExpr, but
  /// avoiding any spurious retains, including by performing reclaims
  /// with objc_unsafeClaimAutoreleasedReturnValue.
  llvm::Value *CodeGenFunction::EmitARCUnsafeUnretainedScalarExpr(const Expr *e) {
    // Look through full-expressions.
    if (const ExprWithCleanups *cleanups = dyn_cast<ExprWithCleanups>(e)) {
      enterFullExpression(cleanups);
      RunCleanupsScope scope(*this);
      return emitARCUnsafeUnretainedScalarExpr(*this, cleanups->getSubExpr());
    }
  
    return emitARCUnsafeUnretainedScalarExpr(*this, e);
  }
  
  std::pair<LValue,llvm::Value*>
  CodeGenFunction::EmitARCStoreUnsafeUnretained(const BinaryOperator *e,
                                                bool ignored) {
    // Evaluate the RHS first.  If we're ignoring the result, assume
    // that we can emit at an unsafe +0.
    llvm::Value *value;
    if (ignored) {
      value = EmitARCUnsafeUnretainedScalarExpr(e->getRHS());
    } else {
      value = EmitScalarExpr(e->getRHS());
    }
  
    // Emit the LHS and perform the store.
    LValue lvalue = EmitLValue(e->getLHS());
    EmitStoreOfScalar(value, lvalue);
  
    return std::pair<LValue,llvm::Value*>(std::move(lvalue), value);
  }
  
  std::pair<LValue,llvm::Value*>
  CodeGenFunction::EmitARCStoreStrong(const BinaryOperator *e,
                                      bool ignored) {
    // Evaluate the RHS first.
    TryEmitResult result = tryEmitARCRetainScalarExpr(*this, e->getRHS());
    llvm::Value *value = result.getPointer();
  
    bool hasImmediateRetain = result.getInt();
  
    // If we didn't emit a retained object, and the l-value is of block
    // type, then we need to emit the block-retain immediately in case
    // it invalidates the l-value.
    if (!hasImmediateRetain && e->getType()->isBlockPointerType()) {
      value = EmitARCRetainBlock(value, /*mandatory*/ false);
      hasImmediateRetain = true;
    }
  
    LValue lvalue = EmitLValue(e->getLHS());
  
    // If the RHS was emitted retained, expand this.
    if (hasImmediateRetain) {
      llvm::Value *oldValue = EmitLoadOfScalar(lvalue, SourceLocation());
      EmitStoreOfScalar(value, lvalue);
      EmitARCRelease(oldValue, lvalue.isARCPreciseLifetime());
    } else {
      value = EmitARCStoreStrong(lvalue, value, ignored);
    }
  
    return std::pair<LValue,llvm::Value*>(lvalue, value);
  }
  
  std::pair<LValue,llvm::Value*>
  CodeGenFunction::EmitARCStoreAutoreleasing(const BinaryOperator *e) {
    llvm::Value *value = EmitARCRetainAutoreleaseScalarExpr(e->getRHS());
    LValue lvalue = EmitLValue(e->getLHS());
  
    EmitStoreOfScalar(value, lvalue);
  
    return std::pair<LValue,llvm::Value*>(lvalue, value);
  }
  
  void CodeGenFunction::EmitObjCAutoreleasePoolStmt(
                                            const ObjCAutoreleasePoolStmt &ARPS) {
    const Stmt *subStmt = ARPS.getSubStmt();
    const CompoundStmt &S = cast<CompoundStmt>(*subStmt);
  
    CGDebugInfo *DI = getDebugInfo();
    if (DI)
      DI->EmitLexicalBlockStart(Builder, S.getLBracLoc());
  
    // Keep track of the current cleanup stack depth.
    RunCleanupsScope Scope(*this);
    if (CGM.getLangOpts().ObjCRuntime.hasNativeARC()) {
      llvm::Value *token = EmitObjCAutoreleasePoolPush();
      EHStack.pushCleanup<CallObjCAutoreleasePoolObject>(NormalCleanup, token);
    } else {
      llvm::Value *token = EmitObjCMRRAutoreleasePoolPush();
      EHStack.pushCleanup<CallObjCMRRAutoreleasePoolObject>(NormalCleanup, token);
    }
  
    for (const auto *I : S.body())
      EmitStmt(I);
  
    if (DI)
      DI->EmitLexicalBlockEnd(Builder, S.getRBracLoc());
  }
  
  /// EmitExtendGCLifetime - Given a pointer to an Objective-C object,
  /// make sure it survives garbage collection until this point.
  void CodeGenFunction::EmitExtendGCLifetime(llvm::Value *object) {
    // We just use an inline assembly.
    llvm::FunctionType *extenderType
      = llvm::FunctionType::get(VoidTy, VoidPtrTy, RequiredArgs::All);
    llvm::Value *extender
      = llvm::InlineAsm::get(extenderType,
                             /* assembly */ "",
                             /* constraints */ "r",
                             /* side effects */ true);
  
    object = Builder.CreateBitCast(object, VoidPtrTy);
    EmitNounwindRuntimeCall(extender, object);
  }
  
  /// GenerateObjCAtomicSetterCopyHelperFunction - Given a c++ object type with
  /// non-trivial copy assignment function, produce following helper function.
  /// static void copyHelper(Ty *dest, const Ty *source) { *dest = *source; }
  ///
  llvm::Constant *
  CodeGenFunction::GenerateObjCAtomicSetterCopyHelperFunction(
                                          const ObjCPropertyImplDecl *PID) {
    if (!getLangOpts().CPlusPlus ||
        !getLangOpts().ObjCRuntime.hasAtomicCopyHelper())
      return nullptr;
    QualType Ty = PID->getPropertyIvarDecl()->getType();
    if (!Ty->isRecordType())
      return nullptr;
    const ObjCPropertyDecl *PD = PID->getPropertyDecl();
    if ((!(PD->getPropertyAttributes() & ObjCPropertyDecl::OBJC_PR_atomic)))
      return nullptr;
    llvm::Constant *HelperFn = nullptr;
    if (hasTrivialSetExpr(PID))
      return nullptr;
    assert(PID->getSetterCXXAssignment() && "SetterCXXAssignment - null");
    if ((HelperFn = CGM.getAtomicSetterHelperFnMap(Ty)))
      return HelperFn;
    
    ASTContext &C = getContext();
    IdentifierInfo *II
      = &CGM.getContext().Idents.get("__assign_helper_atomic_property_");
    FunctionDecl *FD = FunctionDecl::Create(C,
                                            C.getTranslationUnitDecl(),
                                            SourceLocation(),
                                            SourceLocation(), II, C.VoidTy,
                                            nullptr, SC_Static,
                                            false,
                                            false);
  
    QualType DestTy = C.getPointerType(Ty);
    QualType SrcTy = Ty;
    SrcTy.addConst();
    SrcTy = C.getPointerType(SrcTy);
    
    FunctionArgList args;
    ImplicitParamDecl dstDecl(getContext(), FD, SourceLocation(), nullptr,DestTy);
    args.push_back(&dstDecl);
    ImplicitParamDecl srcDecl(getContext(), FD, SourceLocation(), nullptr, SrcTy);
    args.push_back(&srcDecl);
  
    const CGFunctionInfo &FI =
      CGM.getTypes().arrangeBuiltinFunctionDeclaration(C.VoidTy, args);
  
    llvm::FunctionType *LTy = CGM.getTypes().GetFunctionType(FI);
    
    llvm::Function *Fn =
      llvm::Function::Create(LTy, llvm::GlobalValue::InternalLinkage,
                             "__assign_helper_atomic_property_",
                             &CGM.getModule());
  
    CGM.SetInternalFunctionAttributes(nullptr, Fn, FI);
  
    StartFunction(FD, C.VoidTy, Fn, FI, args);
    
    DeclRefExpr DstExpr(&dstDecl, false, DestTy,
                        VK_RValue, SourceLocation());
    UnaryOperator DST(&DstExpr, UO_Deref, DestTy->getPointeeType(),
                      VK_LValue, OK_Ordinary, SourceLocation());
    
    DeclRefExpr SrcExpr(&srcDecl, false, SrcTy,
                        VK_RValue, SourceLocation());
    UnaryOperator SRC(&SrcExpr, UO_Deref, SrcTy->getPointeeType(),
                      VK_LValue, OK_Ordinary, SourceLocation());
    
    Expr *Args[2] = { &DST, &SRC };
    CallExpr *CalleeExp = cast<CallExpr>(PID->getSetterCXXAssignment());
    CXXOperatorCallExpr TheCall(C, OO_Equal, CalleeExp->getCallee(),
                                Args, DestTy->getPointeeType(),
                                VK_LValue, SourceLocation(), false);
    
    EmitStmt(&TheCall);
  
    FinishFunction();
    HelperFn = llvm::ConstantExpr::getBitCast(Fn, VoidPtrTy);
    CGM.setAtomicSetterHelperFnMap(Ty, HelperFn);
    return HelperFn;
  }
  
  llvm::Constant *
  CodeGenFunction::GenerateObjCAtomicGetterCopyHelperFunction(
                                              const ObjCPropertyImplDecl *PID) {
    if (!getLangOpts().CPlusPlus ||
        !getLangOpts().ObjCRuntime.hasAtomicCopyHelper())
      return nullptr;
    const ObjCPropertyDecl *PD = PID->getPropertyDecl();
    QualType Ty = PD->getType();
    if (!Ty->isRecordType())
      return nullptr;
    if ((!(PD->getPropertyAttributes() & ObjCPropertyDecl::OBJC_PR_atomic)))
      return nullptr;
    llvm::Constant *HelperFn = nullptr;
  
    if (hasTrivialGetExpr(PID))
      return nullptr;
    assert(PID->getGetterCXXConstructor() && "getGetterCXXConstructor - null");
    if ((HelperFn = CGM.getAtomicGetterHelperFnMap(Ty)))
      return HelperFn;
    
    
    ASTContext &C = getContext();
    IdentifierInfo *II
    = &CGM.getContext().Idents.get("__copy_helper_atomic_property_");
    FunctionDecl *FD = FunctionDecl::Create(C,
                                            C.getTranslationUnitDecl(),
                                            SourceLocation(),
                                            SourceLocation(), II, C.VoidTy,
                                            nullptr, SC_Static,
                                            false,
                                            false);
  
    QualType DestTy = C.getPointerType(Ty);
    QualType SrcTy = Ty;
    SrcTy.addConst();
    SrcTy = C.getPointerType(SrcTy);
    
    FunctionArgList args;
    ImplicitParamDecl dstDecl(getContext(), FD, SourceLocation(), nullptr,DestTy);
    args.push_back(&dstDecl);
    ImplicitParamDecl srcDecl(getContext(), FD, SourceLocation(), nullptr, SrcTy);
    args.push_back(&srcDecl);
  
    const CGFunctionInfo &FI =
      CGM.getTypes().arrangeBuiltinFunctionDeclaration(C.VoidTy, args);
  
    llvm::FunctionType *LTy = CGM.getTypes().GetFunctionType(FI);
    
    llvm::Function *Fn =
    llvm::Function::Create(LTy, llvm::GlobalValue::InternalLinkage,
                           "__copy_helper_atomic_property_", &CGM.getModule());
    
    CGM.SetInternalFunctionAttributes(nullptr, Fn, FI);
  
    StartFunction(FD, C.VoidTy, Fn, FI, args);
    
    DeclRefExpr SrcExpr(&srcDecl, false, SrcTy,
                        VK_RValue, SourceLocation());
    
    UnaryOperator SRC(&SrcExpr, UO_Deref, SrcTy->getPointeeType(),
                      VK_LValue, OK_Ordinary, SourceLocation());
    
    CXXConstructExpr *CXXConstExpr = 
      cast<CXXConstructExpr>(PID->getGetterCXXConstructor());
    
    SmallVector<Expr*, 4> ConstructorArgs;
    ConstructorArgs.push_back(&SRC);
    ConstructorArgs.append(std::next(CXXConstExpr->arg_begin()),
                           CXXConstExpr->arg_end());
  
    CXXConstructExpr *TheCXXConstructExpr =
      CXXConstructExpr::Create(C, Ty, SourceLocation(),
                               CXXConstExpr->getConstructor(),
                               CXXConstExpr->isElidable(),
                               ConstructorArgs,
                               CXXConstExpr->hadMultipleCandidates(),
                               CXXConstExpr->isListInitialization(),
                               CXXConstExpr->isStdInitListInitialization(),
                               CXXConstExpr->requiresZeroInitialization(),
                               CXXConstExpr->getConstructionKind(),
                               SourceRange());
    
    DeclRefExpr DstExpr(&dstDecl, false, DestTy,
                        VK_RValue, SourceLocation());
    
    RValue DV = EmitAnyExpr(&DstExpr);
    CharUnits Alignment
      = getContext().getTypeAlignInChars(TheCXXConstructExpr->getType());
    EmitAggExpr(TheCXXConstructExpr, 
                AggValueSlot::forAddr(Address(DV.getScalarVal(), Alignment),
                                      Qualifiers(),
                                      AggValueSlot::IsDestructed,
                                      AggValueSlot::DoesNotNeedGCBarriers,
                                      AggValueSlot::IsNotAliased));
    
    FinishFunction();
    HelperFn = llvm::ConstantExpr::getBitCast(Fn, VoidPtrTy);
    CGM.setAtomicGetterHelperFnMap(Ty, HelperFn);
    return HelperFn;
  }
  
  llvm::Value *
  CodeGenFunction::EmitBlockCopyAndAutorelease(llvm::Value *Block, QualType Ty) {
    // Get selectors for retain/autorelease.
    IdentifierInfo *CopyID = &getContext().Idents.get("copy");
    Selector CopySelector =
        getContext().Selectors.getNullarySelector(CopyID);
    IdentifierInfo *AutoreleaseID = &getContext().Idents.get("autorelease");
    Selector AutoreleaseSelector =
        getContext().Selectors.getNullarySelector(AutoreleaseID);
  
    // Emit calls to retain/autorelease.
    CGObjCRuntime &Runtime = CGM.getObjCRuntime();
    llvm::Value *Val = Block;
    RValue Result;
    Result = Runtime.GenerateMessageSend(*this, ReturnValueSlot(),
                                         Ty, CopySelector,
                                         Val, CallArgList(), nullptr, nullptr);
    Val = Result.getScalarVal();
    Result = Runtime.GenerateMessageSend(*this, ReturnValueSlot(),
                                         Ty, AutoreleaseSelector,
                                         Val, CallArgList(), nullptr, nullptr);
    Val = Result.getScalarVal();
    return Val;
  }
  
  
  CGObjCRuntime::~CGObjCRuntime() {}
  