clang/lib/CodeGen/CGExprCXX.cpp

//===--- CGExprCXX.cpp - Emit LLVM Code for C++ expressions ---------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This contains code dealing with code generation of C++ expressions
//
//===----------------------------------------------------------------------===//

#include "CodeGenFunction.h"
#include "CGCXXABI.h"
#include "CGObjCRuntime.h"
#include "llvm/Intrinsics.h"
using namespace clang;
using namespace CodeGen;

RValue CodeGenFunction::EmitCXXMemberCall(const CXXMethodDecl *MD,
                                          llvm::Value *Callee,
                                          ReturnValueSlot ReturnValue,
                                          llvm::Value *This,
                                          llvm::Value *VTT,
                                          CallExpr::const_arg_iterator ArgBeg,
                                          CallExpr::const_arg_iterator ArgEnd) {
  assert(MD->isInstance() &&
         "Trying to emit a member call expr on a static method!");

  const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();

  CallArgList Args;

  // Push the this ptr.
  Args.push_back(std::make_pair(RValue::get(This),
                                MD->getThisType(getContext())));

  // If there is a VTT parameter, emit it.
  if (VTT) {
    QualType T = getContext().getPointerType(getContext().VoidPtrTy);
    Args.push_back(std::make_pair(RValue::get(VTT), T));
  }
  
  // And the rest of the call args
  EmitCallArgs(Args, FPT, ArgBeg, ArgEnd);

  QualType ResultType = FPT->getResultType();
  return EmitCall(CGM.getTypes().getFunctionInfo(ResultType, Args,
                                                 FPT->getExtInfo()),
                  Callee, ReturnValue, Args, MD);
}

/// canDevirtualizeMemberFunctionCalls - Checks whether virtual calls on given
/// expr can be devirtualized.
static bool canDevirtualizeMemberFunctionCalls(const Expr *Base) {
  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Base)) {
    if (const VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl())) {
      // This is a record decl. We know the type and can devirtualize it.
      return VD->getType()->isRecordType();
    }
    
    return false;
  }
  
  // We can always devirtualize calls on temporary object expressions.
  if (isa<CXXConstructExpr>(Base))
    return true;
  
  // And calls on bound temporaries.
  if (isa<CXXBindTemporaryExpr>(Base))
    return true;
  
  // Check if this is a call expr that returns a record type.
  if (const CallExpr *CE = dyn_cast<CallExpr>(Base))
    return CE->getCallReturnType()->isRecordType();
  
  // We can't devirtualize the call.
  return false;
}

RValue CodeGenFunction::EmitCXXMemberCallExpr(const CXXMemberCallExpr *CE,
                                              ReturnValueSlot ReturnValue) {
  if (isa<BinaryOperator>(CE->getCallee()->IgnoreParens())) 
    return EmitCXXMemberPointerCallExpr(CE, ReturnValue);
      
  const MemberExpr *ME = cast<MemberExpr>(CE->getCallee()->IgnoreParens());
  const CXXMethodDecl *MD = cast<CXXMethodDecl>(ME->getMemberDecl());

  if (MD->isStatic()) {
    // The method is static, emit it as we would a regular call.
    llvm::Value *Callee = CGM.GetAddrOfFunction(MD);
    return EmitCall(getContext().getPointerType(MD->getType()), Callee,
                    ReturnValue, CE->arg_begin(), CE->arg_end());
  }

  // Compute the object pointer.
  llvm::Value *This;
  if (ME->isArrow())
    This = EmitScalarExpr(ME->getBase());
  else {
    LValue BaseLV = EmitLValue(ME->getBase());
    if (BaseLV.isPropertyRef() || BaseLV.isKVCRef()) {
      QualType QT = ME->getBase()->getType();
      RValue RV = 
        BaseLV.isPropertyRef() ? EmitLoadOfPropertyRefLValue(BaseLV, QT)
          : EmitLoadOfKVCRefLValue(BaseLV, QT);
      This = RV.isScalar() ? RV.getScalarVal() : RV.getAggregateAddr();
    }
    else
      This = BaseLV.getAddress();
  }

  if (MD->isTrivial()) {
    if (isa<CXXDestructorDecl>(MD)) return RValue::get(0);

    assert(MD->isCopyAssignment() && "unknown trivial member function");
    // We don't like to generate the trivial copy assignment operator when
    // it isn't necessary; just produce the proper effect here.
    llvm::Value *RHS = EmitLValue(*CE->arg_begin()).getAddress();
    EmitAggregateCopy(This, RHS, CE->getType());
    return RValue::get(This);
  }

  // Compute the function type we're calling.
  const CGFunctionInfo &FInfo =
    (isa<CXXDestructorDecl>(MD)
     ? CGM.getTypes().getFunctionInfo(cast<CXXDestructorDecl>(MD),
                                      Dtor_Complete)
     : CGM.getTypes().getFunctionInfo(MD));

  const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
  const llvm::Type *Ty
    = CGM.getTypes().GetFunctionType(FInfo, FPT->isVariadic());

  // C++ [class.virtual]p12:
  //   Explicit qualification with the scope operator (5.1) suppresses the
  //   virtual call mechanism.
  //
  // We also don't emit a virtual call if the base expression has a record type
  // because then we know what the type is.
  bool UseVirtualCall = MD->isVirtual() && !ME->hasQualifier()
                     && !canDevirtualizeMemberFunctionCalls(ME->getBase());

  llvm::Value *Callee;
  if (const CXXDestructorDecl *Dtor = dyn_cast<CXXDestructorDecl>(MD)) {
    if (UseVirtualCall) {
      Callee = BuildVirtualCall(Dtor, Dtor_Complete, This, Ty);
    } else {
      Callee = CGM.GetAddrOfFunction(GlobalDecl(Dtor, Dtor_Complete), Ty);
    }
  } else if (UseVirtualCall) {
    Callee = BuildVirtualCall(MD, This, Ty); 
  } else {
    Callee = CGM.GetAddrOfFunction(MD, Ty);
  }

  return EmitCXXMemberCall(MD, Callee, ReturnValue, This, /*VTT=*/0,
                           CE->arg_begin(), CE->arg_end());
}

RValue
CodeGenFunction::EmitCXXMemberPointerCallExpr(const CXXMemberCallExpr *E,
                                              ReturnValueSlot ReturnValue) {
  const BinaryOperator *BO =
      cast<BinaryOperator>(E->getCallee()->IgnoreParens());
  const Expr *BaseExpr = BO->getLHS();
  const Expr *MemFnExpr = BO->getRHS();
  
  const MemberPointerType *MPT = 
    MemFnExpr->getType()->getAs<MemberPointerType>();

  const FunctionProtoType *FPT = 
    MPT->getPointeeType()->getAs<FunctionProtoType>();
  const CXXRecordDecl *RD = 
    cast<CXXRecordDecl>(MPT->getClass()->getAs<RecordType>()->getDecl());

  // Get the member function pointer.
  llvm::Value *MemFnPtr = EmitScalarExpr(MemFnExpr);

  // Emit the 'this' pointer.
  llvm::Value *This;
  
  if (BO->getOpcode() == BO_PtrMemI)
    This = EmitScalarExpr(BaseExpr);
  else 
    This = EmitLValue(BaseExpr).getAddress();

  // Ask the ABI to load the callee.  Note that This is modified.
  llvm::Value *Callee =
    CGM.getCXXABI().EmitLoadOfMemberFunctionPointer(CGF, This, MemFnPtr, MPT);
  
  CallArgList Args;

  QualType ThisType = 
    getContext().getPointerType(getContext().getTagDeclType(RD));

  // Push the this ptr.
  Args.push_back(std::make_pair(RValue::get(This), ThisType));
  
  // And the rest of the call args
  EmitCallArgs(Args, FPT, E->arg_begin(), E->arg_end());
  const FunctionType *BO_FPT = BO->getType()->getAs<FunctionProtoType>();
  return EmitCall(CGM.getTypes().getFunctionInfo(Args, BO_FPT), Callee, 
                  ReturnValue, Args);
}

RValue
CodeGenFunction::EmitCXXOperatorMemberCallExpr(const CXXOperatorCallExpr *E,
                                               const CXXMethodDecl *MD,
                                               ReturnValueSlot ReturnValue) {
  assert(MD->isInstance() &&
         "Trying to emit a member call expr on a static method!");
  if (MD->isCopyAssignment()) {
    const CXXRecordDecl *ClassDecl = cast<CXXRecordDecl>(MD->getDeclContext());
    if (ClassDecl->hasTrivialCopyAssignment()) {
      assert(!ClassDecl->hasUserDeclaredCopyAssignment() &&
             "EmitCXXOperatorMemberCallExpr - user declared copy assignment");
      LValue LV = EmitLValue(E->getArg(0));
      llvm::Value *This;
      if (LV.isPropertyRef() || LV.isKVCRef()) {
        llvm::Value *AggLoc  = CreateMemTemp(E->getArg(1)->getType());
        EmitAggExpr(E->getArg(1), AggLoc, false /*VolatileDest*/);
        if (LV.isPropertyRef())
          EmitObjCPropertySet(LV.getPropertyRefExpr(),
                              RValue::getAggregate(AggLoc, 
                                                   false /*VolatileDest*/));
        else
          EmitObjCPropertySet(LV.getKVCRefExpr(),
                              RValue::getAggregate(AggLoc, 
                                                   false /*VolatileDest*/));
        return RValue::getAggregate(0, false);
      }
      else
        This = LV.getAddress();
      
      llvm::Value *Src = EmitLValue(E->getArg(1)).getAddress();
      QualType Ty = E->getType();
      EmitAggregateCopy(This, Src, Ty);
      return RValue::get(This);
    }
  }

  const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
  const llvm::Type *Ty =
    CGM.getTypes().GetFunctionType(CGM.getTypes().getFunctionInfo(MD),
                                   FPT->isVariadic());
  LValue LV = EmitLValue(E->getArg(0));
  llvm::Value *This;
  if (LV.isPropertyRef() || LV.isKVCRef()) {
    QualType QT = E->getArg(0)->getType();
    RValue RV = 
      LV.isPropertyRef() ? EmitLoadOfPropertyRefLValue(LV, QT)
                         : EmitLoadOfKVCRefLValue(LV, QT);
    assert (!RV.isScalar() && "EmitCXXOperatorMemberCallExpr");
    This = RV.getAggregateAddr();
  }
  else
    This = LV.getAddress();

  llvm::Value *Callee;
  if (MD->isVirtual() && !canDevirtualizeMemberFunctionCalls(E->getArg(0)))
    Callee = BuildVirtualCall(MD, This, Ty);
  else
    Callee = CGM.GetAddrOfFunction(MD, Ty);

  return EmitCXXMemberCall(MD, Callee, ReturnValue, This, /*VTT=*/0,
                           E->arg_begin() + 1, E->arg_end());
}

void
CodeGenFunction::EmitCXXConstructExpr(llvm::Value *Dest,
                                      const CXXConstructExpr *E) {
  assert(Dest && "Must have a destination!");
  const CXXConstructorDecl *CD = E->getConstructor();
  
  // If we require zero initialization before (or instead of) calling the
  // constructor, as can be the case with a non-user-provided default
  // constructor, emit the zero initialization now.
  if (E->requiresZeroInitialization())
    EmitNullInitialization(Dest, E->getType());

  
  // If this is a call to a trivial default constructor, do nothing.
  if (CD->isTrivial() && CD->isDefaultConstructor())
    return;
  
  // Code gen optimization to eliminate copy constructor and return
  // its first argument instead, if in fact that argument is a temporary 
  // object.
  if (getContext().getLangOptions().ElideConstructors && E->isElidable()) {
    if (const Expr *Arg = E->getArg(0)->getTemporaryObject()) {
      EmitAggExpr(Arg, Dest, false);
      return;
    }
  }
  
  const ConstantArrayType *Array 
    = getContext().getAsConstantArrayType(E->getType());
  if (Array) {
    QualType BaseElementTy = getContext().getBaseElementType(Array);
    const llvm::Type *BasePtr = ConvertType(BaseElementTy);
    BasePtr = llvm::PointerType::getUnqual(BasePtr);
    llvm::Value *BaseAddrPtr =
      Builder.CreateBitCast(Dest, BasePtr);
    
    EmitCXXAggrConstructorCall(CD, Array, BaseAddrPtr, 
                               E->arg_begin(), E->arg_end());
  }
  else {
    CXXCtorType Type = 
      (E->getConstructionKind() == CXXConstructExpr::CK_Complete) 
      ? Ctor_Complete : Ctor_Base;
    bool ForVirtualBase = 
      E->getConstructionKind() == CXXConstructExpr::CK_VirtualBase;
    
    // Call the constructor.
    EmitCXXConstructorCall(CD, Type, ForVirtualBase, Dest,
                           E->arg_begin(), E->arg_end());
  }
}

/// Check whether the given operator new[] is the global placement
/// operator new[].
static bool IsPlacementOperatorNewArray(ASTContext &Ctx,
                                        const FunctionDecl *Fn) {
  // Must be in global scope.  Note that allocation functions can't be
  // declared in namespaces.
  if (!Fn->getDeclContext()->getRedeclContext()->isFileContext())
    return false;

  // Signature must be void *operator new[](size_t, void*).
  // The size_t is common to all operator new[]s.
  if (Fn->getNumParams() != 2)
    return false;

  CanQualType ParamType = Ctx.getCanonicalType(Fn->getParamDecl(1)->getType());
  return (ParamType == Ctx.VoidPtrTy);
}

static CharUnits CalculateCookiePadding(CodeGenFunction &CGF,
                                        const CXXNewExpr *E) {
  if (!E->isArray())
    return CharUnits::Zero();

  // No cookie is required if the new operator being used is 
  // ::operator new[](size_t, void*).
  const FunctionDecl *OperatorNew = E->getOperatorNew();
  if (IsPlacementOperatorNewArray(CGF.getContext(), OperatorNew))
    return CharUnits::Zero();

  return CGF.CGM.getCXXABI().GetArrayCookieSize(E->getAllocatedType());
}

static llvm::Value *EmitCXXNewAllocSize(ASTContext &Context,
                                        CodeGenFunction &CGF,
                                        const CXXNewExpr *E,
                                        llvm::Value *&NumElements,
                                        llvm::Value *&SizeWithoutCookie) {
  QualType ElemType = E->getAllocatedType();

  const llvm::IntegerType *SizeTy =
    cast<llvm::IntegerType>(CGF.ConvertType(CGF.getContext().getSizeType()));
  
  CharUnits TypeSize = CGF.getContext().getTypeSizeInChars(ElemType);

  if (!E->isArray()) {
    SizeWithoutCookie = llvm::ConstantInt::get(SizeTy, TypeSize.getQuantity());
    return SizeWithoutCookie;
  }

  // Figure out the cookie size.
  CharUnits CookieSize = CalculateCookiePadding(CGF, E);

  // Emit the array size expression.
  // We multiply the size of all dimensions for NumElements.
  // e.g for 'int[2][3]', ElemType is 'int' and NumElements is 6.
  NumElements = CGF.EmitScalarExpr(E->getArraySize());
  assert(NumElements->getType() == SizeTy && "element count not a size_t");

  uint64_t ArraySizeMultiplier = 1;
  while (const ConstantArrayType *CAT
             = CGF.getContext().getAsConstantArrayType(ElemType)) {
    ElemType = CAT->getElementType();
    ArraySizeMultiplier *= CAT->getSize().getZExtValue();
  }

  llvm::Value *Size;
  
  // If someone is doing 'new int[42]' there is no need to do a dynamic check.
  // Don't bloat the -O0 code.
  if (llvm::ConstantInt *NumElementsC =
        dyn_cast<llvm::ConstantInt>(NumElements)) {
    llvm::APInt NEC = NumElementsC->getValue();
    unsigned SizeWidth = NEC.getBitWidth();

    // Determine if there is an overflow here by doing an extended multiply.
    NEC.zext(SizeWidth*2);
    llvm::APInt SC(SizeWidth*2, TypeSize.getQuantity());
    SC *= NEC;

    if (!CookieSize.isZero()) {
      // Save the current size without a cookie.  We don't care if an
      // overflow's already happened because SizeWithoutCookie isn't
      // used if the allocator returns null or throws, as it should
      // always do on an overflow.
      llvm::APInt SWC = SC;
      SWC.trunc(SizeWidth);
      SizeWithoutCookie = llvm::ConstantInt::get(SizeTy, SWC);

      // Add the cookie size.
      SC += llvm::APInt(SizeWidth*2, CookieSize.getQuantity());
    }
    
    if (SC.countLeadingZeros() >= SizeWidth) {
      SC.trunc(SizeWidth);
      Size = llvm::ConstantInt::get(SizeTy, SC);
    } else {
      // On overflow, produce a -1 so operator new throws.
      Size = llvm::Constant::getAllOnesValue(SizeTy);
    }

    // Scale NumElements while we're at it.
    uint64_t N = NEC.getZExtValue() * ArraySizeMultiplier;
    NumElements = llvm::ConstantInt::get(SizeTy, N);

  // Otherwise, we don't need to do an overflow-checked multiplication if
  // we're multiplying by one.
  } else if (TypeSize.isOne()) {
    assert(ArraySizeMultiplier == 1);

    Size = NumElements;

    // If we need a cookie, add its size in with an overflow check.
    // This is maybe a little paranoid.
    if (!CookieSize.isZero()) {
      SizeWithoutCookie = Size;

      llvm::Value *CookieSizeV
        = llvm::ConstantInt::get(SizeTy, CookieSize.getQuantity());

      const llvm::Type *Types[] = { SizeTy };
      llvm::Value *UAddF
        = CGF.CGM.getIntrinsic(llvm::Intrinsic::uadd_with_overflow, Types, 1);
      llvm::Value *AddRes
        = CGF.Builder.CreateCall2(UAddF, Size, CookieSizeV);

      Size = CGF.Builder.CreateExtractValue(AddRes, 0);
      llvm::Value *DidOverflow = CGF.Builder.CreateExtractValue(AddRes, 1);
      Size = CGF.Builder.CreateSelect(DidOverflow,
                                      llvm::ConstantInt::get(SizeTy, -1),
                                      Size);
    }

  // Otherwise use the int.umul.with.overflow intrinsic.
  } else {
    llvm::Value *OutermostElementSize
      = llvm::ConstantInt::get(SizeTy, TypeSize.getQuantity());

    llvm::Value *NumOutermostElements = NumElements;

    // Scale NumElements by the array size multiplier.  This might
    // overflow, but only if the multiplication below also overflows,
    // in which case this multiplication isn't used.
    if (ArraySizeMultiplier != 1)
      NumElements = CGF.Builder.CreateMul(NumElements,
                         llvm::ConstantInt::get(SizeTy, ArraySizeMultiplier));

    // The requested size of the outermost array is non-constant.
    // Multiply that by the static size of the elements of that array;
    // on unsigned overflow, set the size to -1 to trigger an
    // exception from the allocation routine.  This is sufficient to
    // prevent buffer overruns from the allocator returning a
    // seemingly valid pointer to insufficient space.  This idea comes
    // originally from MSVC, and GCC has an open bug requesting
    // similar behavior:
    //   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19351
    //
    // This will not be sufficient for C++0x, which requires a
    // specific exception class (std::bad_array_new_length).
    // That will require ABI support that has not yet been specified.
    const llvm::Type *Types[] = { SizeTy };
    llvm::Value *UMulF
      = CGF.CGM.getIntrinsic(llvm::Intrinsic::umul_with_overflow, Types, 1);
    llvm::Value *MulRes = CGF.Builder.CreateCall2(UMulF, NumOutermostElements,
                                                  OutermostElementSize);

    // The overflow bit.
    llvm::Value *DidOverflow = CGF.Builder.CreateExtractValue(MulRes, 1);

    // The result of the multiplication.
    Size = CGF.Builder.CreateExtractValue(MulRes, 0);

    // If we have a cookie, we need to add that size in, too.
    if (!CookieSize.isZero()) {
      SizeWithoutCookie = Size;

      llvm::Value *CookieSizeV
        = llvm::ConstantInt::get(SizeTy, CookieSize.getQuantity());
      llvm::Value *UAddF
        = CGF.CGM.getIntrinsic(llvm::Intrinsic::uadd_with_overflow, Types, 1);
      llvm::Value *AddRes
        = CGF.Builder.CreateCall2(UAddF, SizeWithoutCookie, CookieSizeV);

      Size = CGF.Builder.CreateExtractValue(AddRes, 0);

      llvm::Value *AddDidOverflow = CGF.Builder.CreateExtractValue(AddRes, 1);
      DidOverflow = CGF.Builder.CreateAnd(DidOverflow, AddDidOverflow);
    }

    Size = CGF.Builder.CreateSelect(DidOverflow,
                                    llvm::ConstantInt::get(SizeTy, -1),
                                    Size);
  }

  if (CookieSize.isZero())
    SizeWithoutCookie = Size;
  else
    assert(SizeWithoutCookie && "didn't set SizeWithoutCookie?");

  return Size;
}

static void StoreAnyExprIntoOneUnit(CodeGenFunction &CGF, const CXXNewExpr *E,
                                    llvm::Value *NewPtr) {
  
  assert(E->getNumConstructorArgs() == 1 &&
         "Can only have one argument to initializer of POD type.");
  
  const Expr *Init = E->getConstructorArg(0);
  QualType AllocType = E->getAllocatedType();

  unsigned Alignment =
    CGF.getContext().getTypeAlignInChars(AllocType).getQuantity();
  if (!CGF.hasAggregateLLVMType(AllocType)) 
    CGF.EmitStoreOfScalar(CGF.EmitScalarExpr(Init), NewPtr,
                          AllocType.isVolatileQualified(), Alignment,
                          AllocType);
  else if (AllocType->isAnyComplexType())
    CGF.EmitComplexExprIntoAddr(Init, NewPtr, 
                                AllocType.isVolatileQualified());
  else
    CGF.EmitAggExpr(Init, NewPtr, AllocType.isVolatileQualified());
}

void
CodeGenFunction::EmitNewArrayInitializer(const CXXNewExpr *E, 
                                         llvm::Value *NewPtr,
                                         llvm::Value *NumElements) {
  // We have a POD type.
  if (E->getNumConstructorArgs() == 0)
    return;
  
  const llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
  
  // Create a temporary for the loop index and initialize it with 0.
  llvm::Value *IndexPtr = CreateTempAlloca(SizeTy, "loop.index");
  llvm::Value *Zero = llvm::Constant::getNullValue(SizeTy);
  Builder.CreateStore(Zero, IndexPtr);
  
  // Start the loop with a block that tests the condition.
  llvm::BasicBlock *CondBlock = createBasicBlock("for.cond");
  llvm::BasicBlock *AfterFor = createBasicBlock("for.end");
  
  EmitBlock(CondBlock);
  
  llvm::BasicBlock *ForBody = createBasicBlock("for.body");
  
  // Generate: if (loop-index < number-of-elements fall to the loop body,
  // otherwise, go to the block after the for-loop.
  llvm::Value *Counter = Builder.CreateLoad(IndexPtr);
  llvm::Value *IsLess = Builder.CreateICmpULT(Counter, NumElements, "isless");
  // If the condition is true, execute the body.
  Builder.CreateCondBr(IsLess, ForBody, AfterFor);
  
  EmitBlock(ForBody);
  
  llvm::BasicBlock *ContinueBlock = createBasicBlock("for.inc");
  // Inside the loop body, emit the constructor call on the array element.
  Counter = Builder.CreateLoad(IndexPtr);
  llvm::Value *Address = Builder.CreateInBoundsGEP(NewPtr, Counter, 
                                                   "arrayidx");
  StoreAnyExprIntoOneUnit(*this, E, Address);
  
  EmitBlock(ContinueBlock);
  
  // Emit the increment of the loop counter.
  llvm::Value *NextVal = llvm::ConstantInt::get(SizeTy, 1);
  Counter = Builder.CreateLoad(IndexPtr);
  NextVal = Builder.CreateAdd(Counter, NextVal, "inc");
  Builder.CreateStore(NextVal, IndexPtr);
  
  // Finally, branch back up to the condition for the next iteration.
  EmitBranch(CondBlock);
  
  // Emit the fall-through block.
  EmitBlock(AfterFor, true);
}

static void EmitZeroMemSet(CodeGenFunction &CGF, QualType T,
                           llvm::Value *NewPtr, llvm::Value *Size) {
  llvm::LLVMContext &VMContext = CGF.CGM.getLLVMContext();
  const llvm::Type *BP = llvm::Type::getInt8PtrTy(VMContext);
  if (NewPtr->getType() != BP)
    NewPtr = CGF.Builder.CreateBitCast(NewPtr, BP, "tmp");
  
  CGF.Builder.CreateCall5(CGF.CGM.getMemSetFn(BP, CGF.IntPtrTy), NewPtr,
                llvm::Constant::getNullValue(llvm::Type::getInt8Ty(VMContext)),
                          Size,
                    llvm::ConstantInt::get(CGF.Int32Ty, 
                                           CGF.getContext().getTypeAlign(T)/8),
                          llvm::ConstantInt::get(llvm::Type::getInt1Ty(VMContext),
                                                 0));
}
                       
static void EmitNewInitializer(CodeGenFunction &CGF, const CXXNewExpr *E,
                               llvm::Value *NewPtr,
                               llvm::Value *NumElements,
                               llvm::Value *AllocSizeWithoutCookie) {
  if (E->isArray()) {
    if (CXXConstructorDecl *Ctor = E->getConstructor()) {
      bool RequiresZeroInitialization = false;
      if (Ctor->getParent()->hasTrivialConstructor()) {
        // If new expression did not specify value-initialization, then there
        // is no initialization.
        if (!E->hasInitializer() || Ctor->getParent()->isEmpty())
          return;
      
        if (CGF.CGM.getTypes().isZeroInitializable(E->getAllocatedType())) {
          // Optimization: since zero initialization will just set the memory
          // to all zeroes, generate a single memset to do it in one shot.
          EmitZeroMemSet(CGF, E->getAllocatedType(), NewPtr, 
                         AllocSizeWithoutCookie);
          return;
        }

        RequiresZeroInitialization = true;
      }
      
      CGF.EmitCXXAggrConstructorCall(Ctor, NumElements, NewPtr, 
                                     E->constructor_arg_begin(), 
                                     E->constructor_arg_end(),
                                     RequiresZeroInitialization);
      return;
    } else if (E->getNumConstructorArgs() == 1 &&
               isa<ImplicitValueInitExpr>(E->getConstructorArg(0))) {
      // Optimization: since zero initialization will just set the memory
      // to all zeroes, generate a single memset to do it in one shot.
      EmitZeroMemSet(CGF, E->getAllocatedType(), NewPtr, 
                     AllocSizeWithoutCookie);
      return;      
    } else {
      CGF.EmitNewArrayInitializer(E, NewPtr, NumElements);
      return;
    }
  }

  if (CXXConstructorDecl *Ctor = E->getConstructor()) {
    // Per C++ [expr.new]p15, if we have an initializer, then we're performing
    // direct initialization. C++ [dcl.init]p5 requires that we 
    // zero-initialize storage if there are no user-declared constructors.
    if (E->hasInitializer() && 
        !Ctor->getParent()->hasUserDeclaredConstructor() &&
        !Ctor->getParent()->isEmpty())
      CGF.EmitNullInitialization(NewPtr, E->getAllocatedType());
      
    CGF.EmitCXXConstructorCall(Ctor, Ctor_Complete, /*ForVirtualBase=*/false, 
                               NewPtr, E->constructor_arg_begin(),
                               E->constructor_arg_end());

    return;
  }
  // We have a POD type.
  if (E->getNumConstructorArgs() == 0)
    return;
  
  StoreAnyExprIntoOneUnit(CGF, E, NewPtr);
}

llvm::Value *CodeGenFunction::EmitCXXNewExpr(const CXXNewExpr *E) {
  QualType AllocType = E->getAllocatedType();
  if (AllocType->isArrayType())
    while (const ArrayType *AType = getContext().getAsArrayType(AllocType))
      AllocType = AType->getElementType();

  FunctionDecl *NewFD = E->getOperatorNew();
  const FunctionProtoType *NewFTy = NewFD->getType()->getAs<FunctionProtoType>();

  CallArgList NewArgs;

  // The allocation size is the first argument.
  QualType SizeTy = getContext().getSizeType();

  llvm::Value *NumElements = 0;
  llvm::Value *AllocSizeWithoutCookie = 0;
  llvm::Value *AllocSize = EmitCXXNewAllocSize(getContext(),
                                               *this, E, NumElements,
                                               AllocSizeWithoutCookie);
  
  NewArgs.push_back(std::make_pair(RValue::get(AllocSize), SizeTy));

  // Emit the rest of the arguments.
  // FIXME: Ideally, this should just use EmitCallArgs.
  CXXNewExpr::const_arg_iterator NewArg = E->placement_arg_begin();

  // First, use the types from the function type.
  // We start at 1 here because the first argument (the allocation size)
  // has already been emitted.
  for (unsigned i = 1, e = NewFTy->getNumArgs(); i != e; ++i, ++NewArg) {
    QualType ArgType = NewFTy->getArgType(i);

    assert(getContext().getCanonicalType(ArgType.getNonReferenceType()).
           getTypePtr() ==
           getContext().getCanonicalType(NewArg->getType()).getTypePtr() &&
           "type mismatch in call argument!");

    NewArgs.push_back(std::make_pair(EmitCallArg(*NewArg, ArgType),
                                     ArgType));

  }

  // Either we've emitted all the call args, or we have a call to a
  // variadic function.
  assert((NewArg == E->placement_arg_end() || NewFTy->isVariadic()) &&
         "Extra arguments in non-variadic function!");

  // If we still have any arguments, emit them using the type of the argument.
  for (CXXNewExpr::const_arg_iterator NewArgEnd = E->placement_arg_end();
       NewArg != NewArgEnd; ++NewArg) {
    QualType ArgType = NewArg->getType();
    NewArgs.push_back(std::make_pair(EmitCallArg(*NewArg, ArgType),
                                     ArgType));
  }

  // Emit the call to new.
  RValue RV =
    EmitCall(CGM.getTypes().getFunctionInfo(NewArgs, NewFTy),
             CGM.GetAddrOfFunction(NewFD), ReturnValueSlot(), NewArgs, NewFD);

  // If an allocation function is declared with an empty exception specification
  // it returns null to indicate failure to allocate storage. [expr.new]p13.
  // (We don't need to check for null when there's no new initializer and
  // we're allocating a POD type).
  bool NullCheckResult = NewFTy->hasEmptyExceptionSpec() &&
    !(AllocType->isPODType() && !E->hasInitializer());

  llvm::BasicBlock *NullCheckSource = 0;
  llvm::BasicBlock *NewNotNull = 0;
  llvm::BasicBlock *NewEnd = 0;

  llvm::Value *NewPtr = RV.getScalarVal();
  unsigned AS = cast<llvm::PointerType>(NewPtr->getType())->getAddressSpace();

  if (NullCheckResult) {
    NullCheckSource = Builder.GetInsertBlock();
    NewNotNull = createBasicBlock("new.notnull");
    NewEnd = createBasicBlock("new.end");

    llvm::Value *IsNull = Builder.CreateIsNull(NewPtr, "new.isnull");
    Builder.CreateCondBr(IsNull, NewEnd, NewNotNull);
    EmitBlock(NewNotNull);
  }
  
  assert((AllocSize == AllocSizeWithoutCookie) ==
         CalculateCookiePadding(*this, E).isZero());
  if (AllocSize != AllocSizeWithoutCookie) {
    assert(E->isArray());
    NewPtr = CGM.getCXXABI().InitializeArrayCookie(CGF, NewPtr, NumElements,
                                                   AllocType);
  }

  const llvm::Type *ElementPtrTy
    = ConvertTypeForMem(AllocType)->getPointerTo(AS);
  NewPtr = Builder.CreateBitCast(NewPtr, ElementPtrTy);
  if (E->isArray()) {
    EmitNewInitializer(*this, E, NewPtr, NumElements, AllocSizeWithoutCookie);

    // NewPtr is a pointer to the base element type.  If we're
    // allocating an array of arrays, we'll need to cast back to the
    // array pointer type.
    const llvm::Type *ResultTy = ConvertTypeForMem(E->getType());
    if (NewPtr->getType() != ResultTy)
      NewPtr = Builder.CreateBitCast(NewPtr, ResultTy);
  } else {
    EmitNewInitializer(*this, E, NewPtr, NumElements, AllocSizeWithoutCookie);
  }
  
  if (NullCheckResult) {
    Builder.CreateBr(NewEnd);
    llvm::BasicBlock *NotNullSource = Builder.GetInsertBlock();
    EmitBlock(NewEnd);

    llvm::PHINode *PHI = Builder.CreatePHI(NewPtr->getType());
    PHI->reserveOperandSpace(2);
    PHI->addIncoming(NewPtr, NotNullSource);
    PHI->addIncoming(llvm::Constant::getNullValue(NewPtr->getType()),
                     NullCheckSource);

    NewPtr = PHI;
  }
  
  return NewPtr;
}

void CodeGenFunction::EmitDeleteCall(const FunctionDecl *DeleteFD,
                                     llvm::Value *Ptr,
                                     QualType DeleteTy) {
  assert(DeleteFD->getOverloadedOperator() == OO_Delete);

  const FunctionProtoType *DeleteFTy =
    DeleteFD->getType()->getAs<FunctionProtoType>();

  CallArgList DeleteArgs;

  // Check if we need to pass the size to the delete operator.
  llvm::Value *Size = 0;
  QualType SizeTy;
  if (DeleteFTy->getNumArgs() == 2) {
    SizeTy = DeleteFTy->getArgType(1);
    CharUnits DeleteTypeSize = getContext().getTypeSizeInChars(DeleteTy);
    Size = llvm::ConstantInt::get(ConvertType(SizeTy), 
                                  DeleteTypeSize.getQuantity());
  }
  
  QualType ArgTy = DeleteFTy->getArgType(0);
  llvm::Value *DeletePtr = Builder.CreateBitCast(Ptr, ConvertType(ArgTy));
  DeleteArgs.push_back(std::make_pair(RValue::get(DeletePtr), ArgTy));

  if (Size)
    DeleteArgs.push_back(std::make_pair(RValue::get(Size), SizeTy));

  // Emit the call to delete.
  EmitCall(CGM.getTypes().getFunctionInfo(DeleteArgs, DeleteFTy),
           CGM.GetAddrOfFunction(DeleteFD), ReturnValueSlot(), 
           DeleteArgs, DeleteFD);
}

namespace {
  /// Calls the given 'operator delete' on a single object.
  struct CallObjectDelete : EHScopeStack::Cleanup {
    llvm::Value *Ptr;
    const FunctionDecl *OperatorDelete;
    QualType ElementType;

    CallObjectDelete(llvm::Value *Ptr,
                     const FunctionDecl *OperatorDelete,
                     QualType ElementType)
      : Ptr(Ptr), OperatorDelete(OperatorDelete), ElementType(ElementType) {}

    void Emit(CodeGenFunction &CGF, bool IsForEH) {
      CGF.EmitDeleteCall(OperatorDelete, Ptr, ElementType);
    }
  };
}

/// Emit the code for deleting a single object.
static void EmitObjectDelete(CodeGenFunction &CGF,
                             const FunctionDecl *OperatorDelete,
                             llvm::Value *Ptr,
                             QualType ElementType) {
  // Find the destructor for the type, if applicable.  If the
  // destructor is virtual, we'll just emit the vcall and return.
  const CXXDestructorDecl *Dtor = 0;
  if (const RecordType *RT = ElementType->getAs<RecordType>()) {
    CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
    if (!RD->hasTrivialDestructor()) {
      Dtor = RD->getDestructor();

      if (Dtor->isVirtual()) {
        const llvm::Type *Ty =
          CGF.getTypes().GetFunctionType(CGF.getTypes().getFunctionInfo(Dtor,
                                                               Dtor_Complete),
                                         /*isVariadic=*/false);
          
        llvm::Value *Callee
          = CGF.BuildVirtualCall(Dtor, Dtor_Deleting, Ptr, Ty);
        CGF.EmitCXXMemberCall(Dtor, Callee, ReturnValueSlot(), Ptr, /*VTT=*/0,
                              0, 0);

        // The dtor took care of deleting the object.
        return;
      }
    }
  }

  // Make sure that we call delete even if the dtor throws.
  CGF.EHStack.pushCleanup<CallObjectDelete>(NormalAndEHCleanup,
                                            Ptr, OperatorDelete, ElementType);

  if (Dtor)
    CGF.EmitCXXDestructorCall(Dtor, Dtor_Complete,
                              /*ForVirtualBase=*/false, Ptr);

  CGF.PopCleanupBlock();
}

namespace {
  /// Calls the given 'operator delete' on an array of objects.
  struct CallArrayDelete : EHScopeStack::Cleanup {
    llvm::Value *Ptr;
    const FunctionDecl *OperatorDelete;
    llvm::Value *NumElements;
    QualType ElementType;
    CharUnits CookieSize;

    CallArrayDelete(llvm::Value *Ptr,
                    const FunctionDecl *OperatorDelete,
                    llvm::Value *NumElements,
                    QualType ElementType,
                    CharUnits CookieSize)
      : Ptr(Ptr), OperatorDelete(OperatorDelete), NumElements(NumElements),
        ElementType(ElementType), CookieSize(CookieSize) {}

    void Emit(CodeGenFunction &CGF, bool IsForEH) {
      const FunctionProtoType *DeleteFTy =
        OperatorDelete->getType()->getAs<FunctionProtoType>();
      assert(DeleteFTy->getNumArgs() == 1 || DeleteFTy->getNumArgs() == 2);

      CallArgList Args;
      
      // Pass the pointer as the first argument.
      QualType VoidPtrTy = DeleteFTy->getArgType(0);
      llvm::Value *DeletePtr
        = CGF.Builder.CreateBitCast(Ptr, CGF.ConvertType(VoidPtrTy));
      Args.push_back(std::make_pair(RValue::get(DeletePtr), VoidPtrTy));

      // Pass the original requested size as the second argument.
      if (DeleteFTy->getNumArgs() == 2) {
        QualType size_t = DeleteFTy->getArgType(1);
        const llvm::IntegerType *SizeTy
          = cast<llvm::IntegerType>(CGF.ConvertType(size_t));
        
        CharUnits ElementTypeSize =
          CGF.CGM.getContext().getTypeSizeInChars(ElementType);

        // The size of an element, multiplied by the number of elements.
        llvm::Value *Size
          = llvm::ConstantInt::get(SizeTy, ElementTypeSize.getQuantity());
        Size = CGF.Builder.CreateMul(Size, NumElements);

        // Plus the size of the cookie if applicable.
        if (!CookieSize.isZero()) {
          llvm::Value *CookieSizeV
            = llvm::ConstantInt::get(SizeTy, CookieSize.getQuantity());
          Size = CGF.Builder.CreateAdd(Size, CookieSizeV);
        }

        Args.push_back(std::make_pair(RValue::get(Size), size_t));
      }

      // Emit the call to delete.
      CGF.EmitCall(CGF.getTypes().getFunctionInfo(Args, DeleteFTy),
                   CGF.CGM.GetAddrOfFunction(OperatorDelete),
                   ReturnValueSlot(), Args, OperatorDelete);
    }
  };
}

/// Emit the code for deleting an array of objects.
static void EmitArrayDelete(CodeGenFunction &CGF,
                            const FunctionDecl *OperatorDelete,
                            llvm::Value *Ptr,
                            QualType ElementType) {
  llvm::Value *NumElements = 0;
  llvm::Value *AllocatedPtr = 0;
  CharUnits CookieSize;
  CGF.CGM.getCXXABI().ReadArrayCookie(CGF, Ptr, ElementType,
                                      NumElements, AllocatedPtr, CookieSize);

  assert(AllocatedPtr && "ReadArrayCookie didn't set AllocatedPtr");

  // Make sure that we call delete even if one of the dtors throws.
  CGF.EHStack.pushCleanup<CallArrayDelete>(NormalAndEHCleanup,
                                           AllocatedPtr, OperatorDelete,
                                           NumElements, ElementType,
                                           CookieSize);

  if (const CXXRecordDecl *RD = ElementType->getAsCXXRecordDecl()) {
    if (!RD->hasTrivialDestructor()) {
      assert(NumElements && "ReadArrayCookie didn't find element count"
                            " for a class with destructor");
      CGF.EmitCXXAggrDestructorCall(RD->getDestructor(), NumElements, Ptr);
    }
  }

  CGF.PopCleanupBlock();
}

void CodeGenFunction::EmitCXXDeleteExpr(const CXXDeleteExpr *E) {
  
  // Get at the argument before we performed the implicit conversion
  // to void*.
  const Expr *Arg = E->getArgument();
  while (const ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(Arg)) {
    if (ICE->getCastKind() != CK_UserDefinedConversion &&
        ICE->getType()->isVoidPointerType())
      Arg = ICE->getSubExpr();
    else
      break;
  }

  llvm::Value *Ptr = EmitScalarExpr(Arg);

  // Null check the pointer.
  llvm::BasicBlock *DeleteNotNull = createBasicBlock("delete.notnull");
  llvm::BasicBlock *DeleteEnd = createBasicBlock("delete.end");

  llvm::Value *IsNull =
    Builder.CreateICmpEQ(Ptr, llvm::Constant::getNullValue(Ptr->getType()),
                         "isnull");

  Builder.CreateCondBr(IsNull, DeleteEnd, DeleteNotNull);
  EmitBlock(DeleteNotNull);

  // We might be deleting a pointer to array.  If so, GEP down to the
  // first non-array element.
  // (this assumes that A(*)[3][7] is converted to [3 x [7 x %A]]*)
  QualType DeleteTy = Arg->getType()->getAs<PointerType>()->getPointeeType();
  if (DeleteTy->isConstantArrayType()) {
    llvm::Value *Zero = Builder.getInt32(0);
    llvm::SmallVector<llvm::Value*,8> GEP;

    GEP.push_back(Zero); // point at the outermost array

    // For each layer of array type we're pointing at:
    while (const ConstantArrayType *Arr
             = getContext().getAsConstantArrayType(DeleteTy)) {
      // 1. Unpeel the array type.
      DeleteTy = Arr->getElementType();

      // 2. GEP to the first element of the array.
      GEP.push_back(Zero);
    }

    Ptr = Builder.CreateInBoundsGEP(Ptr, GEP.begin(), GEP.end(), "del.first");
  }

  assert(ConvertTypeForMem(DeleteTy) ==
         cast<llvm::PointerType>(Ptr->getType())->getElementType());

  if (E->isArrayForm()) {
    EmitArrayDelete(*this, E->getOperatorDelete(), Ptr, DeleteTy);
  } else {
    EmitObjectDelete(*this, E->getOperatorDelete(), Ptr, DeleteTy);
  }

  EmitBlock(DeleteEnd);
}

llvm::Value * CodeGenFunction::EmitCXXTypeidExpr(const CXXTypeidExpr *E) {
  QualType Ty = E->getType();
  const llvm::Type *LTy = ConvertType(Ty)->getPointerTo();
  
  if (E->isTypeOperand()) {
    llvm::Constant *TypeInfo = 
      CGM.GetAddrOfRTTIDescriptor(E->getTypeOperand());
    return Builder.CreateBitCast(TypeInfo, LTy);
  }
  
  Expr *subE = E->getExprOperand();
  Ty = subE->getType();
  CanQualType CanTy = CGM.getContext().getCanonicalType(Ty);
  Ty = CanTy.getUnqualifiedType().getNonReferenceType();
  if (const RecordType *RT = Ty->getAs<RecordType>()) {
    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
    if (RD->isPolymorphic()) {
      // FIXME: if subE is an lvalue do
      LValue Obj = EmitLValue(subE);
      llvm::Value *This = Obj.getAddress();
      LTy = LTy->getPointerTo()->getPointerTo();
      llvm::Value *V = Builder.CreateBitCast(This, LTy);
      // We need to do a zero check for *p, unless it has NonNullAttr.
      // FIXME: PointerType->hasAttr<NonNullAttr>()
      bool CanBeZero = false;
      if (UnaryOperator *UO = dyn_cast<UnaryOperator>(subE->IgnoreParens()))
        if (UO->getOpcode() == UO_Deref)
          CanBeZero = true;
      if (CanBeZero) {
        llvm::BasicBlock *NonZeroBlock = createBasicBlock();
        llvm::BasicBlock *ZeroBlock = createBasicBlock();
        
        llvm::Value *Zero = llvm::Constant::getNullValue(LTy);
        Builder.CreateCondBr(Builder.CreateICmpNE(V, Zero),
                             NonZeroBlock, ZeroBlock);
        EmitBlock(ZeroBlock);
        /// Call __cxa_bad_typeid
        const llvm::Type *ResultType = llvm::Type::getVoidTy(VMContext);
        const llvm::FunctionType *FTy;
        FTy = llvm::FunctionType::get(ResultType, false);
        llvm::Value *F = CGM.CreateRuntimeFunction(FTy, "__cxa_bad_typeid");
        Builder.CreateCall(F)->setDoesNotReturn();
        Builder.CreateUnreachable();
        EmitBlock(NonZeroBlock);
      }
      V = Builder.CreateLoad(V, "vtable");
      V = Builder.CreateConstInBoundsGEP1_64(V, -1ULL);
      V = Builder.CreateLoad(V);
      return V;
    }
  }
  return Builder.CreateBitCast(CGM.GetAddrOfRTTIDescriptor(Ty), LTy);
}

llvm::Value *CodeGenFunction::EmitDynamicCast(llvm::Value *V,
                                              const CXXDynamicCastExpr *DCE) {
  QualType SrcTy = DCE->getSubExpr()->getType();
  QualType DestTy = DCE->getTypeAsWritten();
  QualType InnerType = DestTy->getPointeeType();
  
  const llvm::Type *LTy = ConvertType(DCE->getType());

  bool CanBeZero = false;
  bool ToVoid = false;
  bool ThrowOnBad = false;
  if (DestTy->isPointerType()) {
    // FIXME: if PointerType->hasAttr<NonNullAttr>(), we don't set this
    CanBeZero = true;
    if (InnerType->isVoidType())
      ToVoid = true;
  } else {
    LTy = LTy->getPointerTo();
    
    // FIXME: What if exceptions are disabled?
    ThrowOnBad = true;
  }

  if (SrcTy->isPointerType() || SrcTy->isReferenceType())
    SrcTy = SrcTy->getPointeeType();
  SrcTy = SrcTy.getUnqualifiedType();

  if (DestTy->isPointerType() || DestTy->isReferenceType())
    DestTy = DestTy->getPointeeType();
  DestTy = DestTy.getUnqualifiedType();

  llvm::BasicBlock *ContBlock = createBasicBlock();
  llvm::BasicBlock *NullBlock = 0;
  llvm::BasicBlock *NonZeroBlock = 0;
  if (CanBeZero) {
    NonZeroBlock = createBasicBlock();
    NullBlock = createBasicBlock();
    Builder.CreateCondBr(Builder.CreateIsNotNull(V), NonZeroBlock, NullBlock);
    EmitBlock(NonZeroBlock);
  }

  llvm::BasicBlock *BadCastBlock = 0;

  const llvm::Type *PtrDiffTy = ConvertType(getContext().getPointerDiffType());

  // See if this is a dynamic_cast(void*)
  if (ToVoid) {
    llvm::Value *This = V;
    V = Builder.CreateBitCast(This, PtrDiffTy->getPointerTo()->getPointerTo());
    V = Builder.CreateLoad(V, "vtable");
    V = Builder.CreateConstInBoundsGEP1_64(V, -2ULL);
    V = Builder.CreateLoad(V, "offset to top");
    This = Builder.CreateBitCast(This, llvm::Type::getInt8PtrTy(VMContext));
    V = Builder.CreateInBoundsGEP(This, V);
    V = Builder.CreateBitCast(V, LTy);
  } else {
    /// Call __dynamic_cast
    const llvm::Type *ResultType = llvm::Type::getInt8PtrTy(VMContext);
    const llvm::FunctionType *FTy;
    std::vector<const llvm::Type*> ArgTys;
    const llvm::Type *PtrToInt8Ty
      = llvm::Type::getInt8Ty(VMContext)->getPointerTo();
    ArgTys.push_back(PtrToInt8Ty);
    ArgTys.push_back(PtrToInt8Ty);
    ArgTys.push_back(PtrToInt8Ty);
    ArgTys.push_back(PtrDiffTy);
    FTy = llvm::FunctionType::get(ResultType, ArgTys, false);

    // FIXME: Calculate better hint.
    llvm::Value *hint = llvm::ConstantInt::get(PtrDiffTy, -1ULL);
    
    assert(SrcTy->isRecordType() && "Src type must be record type!");
    assert(DestTy->isRecordType() && "Dest type must be record type!");
    
    llvm::Value *SrcArg
      = CGM.GetAddrOfRTTIDescriptor(SrcTy.getUnqualifiedType());
    llvm::Value *DestArg
      = CGM.GetAddrOfRTTIDescriptor(DestTy.getUnqualifiedType());
    
    V = Builder.CreateBitCast(V, PtrToInt8Ty);
    V = Builder.CreateCall4(CGM.CreateRuntimeFunction(FTy, "__dynamic_cast"),
                            V, SrcArg, DestArg, hint);
    V = Builder.CreateBitCast(V, LTy);

    if (ThrowOnBad) {
      BadCastBlock = createBasicBlock();
      Builder.CreateCondBr(Builder.CreateIsNotNull(V), ContBlock, BadCastBlock);
      EmitBlock(BadCastBlock);
      /// Invoke __cxa_bad_cast
      ResultType = llvm::Type::getVoidTy(VMContext);
      const llvm::FunctionType *FBadTy;
      FBadTy = llvm::FunctionType::get(ResultType, false);
      llvm::Value *F = CGM.CreateRuntimeFunction(FBadTy, "__cxa_bad_cast");
      if (llvm::BasicBlock *InvokeDest = getInvokeDest()) {
        llvm::BasicBlock *Cont = createBasicBlock("invoke.cont");
        Builder.CreateInvoke(F, Cont, InvokeDest)->setDoesNotReturn();
        EmitBlock(Cont);
      } else {
        // FIXME: Does this ever make sense?
        Builder.CreateCall(F)->setDoesNotReturn();
      }
      Builder.CreateUnreachable();
    }
  }
  
  if (CanBeZero) {
    Builder.CreateBr(ContBlock);
    EmitBlock(NullBlock);
    Builder.CreateBr(ContBlock);
  }
  EmitBlock(ContBlock);
  if (CanBeZero) {
    llvm::PHINode *PHI = Builder.CreatePHI(LTy);
    PHI->reserveOperandSpace(2);
    PHI->addIncoming(V, NonZeroBlock);
    PHI->addIncoming(llvm::Constant::getNullValue(LTy), NullBlock);
    V = PHI;
  }

  return V;
}