lib/CodeGen/CGExpr.cpp

//===--- CGExpr.cpp - Emit LLVM Code from 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 to emit Expr nodes as LLVM code.
//
//===----------------------------------------------------------------------===//

#include "CodeGenFunction.h"
#include "CGCXXABI.h"
#include "CGCall.h"
#include "CGDebugInfo.h"
#include "CGObjCRuntime.h"
#include "CGRecordLayout.h"
#include "CodeGenModule.h"
#include "TargetInfo.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/DeclObjC.h"
#include "clang/Frontend/CodeGenOptions.h"
#include "llvm/ADT/Hashing.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/MDBuilder.h"
#include "llvm/Support/ConvertUTF.h"

using namespace clang;
using namespace CodeGen;

//===--------------------------------------------------------------------===//
//                        Miscellaneous Helper Methods
//===--------------------------------------------------------------------===//

llvm::Value *CodeGenFunction::EmitCastToVoidPtr(llvm::Value *value) {
  unsigned addressSpace =
    cast<llvm::PointerType>(value->getType())->getAddressSpace();

  llvm::PointerType *destType = Int8PtrTy;
  if (addressSpace)
    destType = llvm::Type::getInt8PtrTy(getLLVMContext(), addressSpace);

  if (value->getType() == destType) return value;
  return Builder.CreateBitCast(value, destType);
}

/// CreateTempAlloca - This creates a alloca and inserts it into the entry
/// block.
llvm::AllocaInst *CodeGenFunction::CreateTempAlloca(llvm::Type *Ty,
                                                    const Twine &Name) {
  if (!Builder.isNamePreserving())
    return new llvm::AllocaInst(Ty, 0, "", AllocaInsertPt);
  return new llvm::AllocaInst(Ty, 0, Name, AllocaInsertPt);
}

void CodeGenFunction::InitTempAlloca(llvm::AllocaInst *Var,
                                     llvm::Value *Init) {
  llvm::StoreInst *Store = new llvm::StoreInst(Init, Var);
  llvm::BasicBlock *Block = AllocaInsertPt->getParent();
  Block->getInstList().insertAfter(&*AllocaInsertPt, Store);
}

llvm::AllocaInst *CodeGenFunction::CreateIRTemp(QualType Ty,
                                                const Twine &Name) {
  llvm::AllocaInst *Alloc = CreateTempAlloca(ConvertType(Ty), Name);
  // FIXME: Should we prefer the preferred type alignment here?
  CharUnits Align = getContext().getTypeAlignInChars(Ty);
  Alloc->setAlignment(Align.getQuantity());
  return Alloc;
}

llvm::AllocaInst *CodeGenFunction::CreateMemTemp(QualType Ty,
                                                 const Twine &Name) {
  llvm::AllocaInst *Alloc = CreateTempAlloca(ConvertTypeForMem(Ty), Name);
  // FIXME: Should we prefer the preferred type alignment here?
  CharUnits Align = getContext().getTypeAlignInChars(Ty);
  Alloc->setAlignment(Align.getQuantity());
  return Alloc;
}

/// EvaluateExprAsBool - Perform the usual unary conversions on the specified
/// expression and compare the result against zero, returning an Int1Ty value.
llvm::Value *CodeGenFunction::EvaluateExprAsBool(const Expr *E) {
  if (const MemberPointerType *MPT = E->getType()->getAs<MemberPointerType>()) {
    llvm::Value *MemPtr = EmitScalarExpr(E);
    return CGM.getCXXABI().EmitMemberPointerIsNotNull(*this, MemPtr, MPT);
  }

  QualType BoolTy = getContext().BoolTy;
  if (!E->getType()->isAnyComplexType())
    return EmitScalarConversion(EmitScalarExpr(E), E->getType(), BoolTy);

  return EmitComplexToScalarConversion(EmitComplexExpr(E), E->getType(),BoolTy);
}

/// EmitIgnoredExpr - Emit code to compute the specified expression,
/// ignoring the result.
void CodeGenFunction::EmitIgnoredExpr(const Expr *E) {
  if (E->isRValue())
    return (void) EmitAnyExpr(E, AggValueSlot::ignored(), true);

  // Just emit it as an l-value and drop the result.
  EmitLValue(E);
}

/// EmitAnyExpr - Emit code to compute the specified expression which
/// can have any type.  The result is returned as an RValue struct.
/// If this is an aggregate expression, AggSlot indicates where the
/// result should be returned.
RValue CodeGenFunction::EmitAnyExpr(const Expr *E,
                                    AggValueSlot aggSlot,
                                    bool ignoreResult) {
  switch (getEvaluationKind(E->getType())) {
  case TEK_Scalar:
    return RValue::get(EmitScalarExpr(E, ignoreResult));
  case TEK_Complex:
    return RValue::getComplex(EmitComplexExpr(E, ignoreResult, ignoreResult));
  case TEK_Aggregate:
    if (!ignoreResult && aggSlot.isIgnored())
      aggSlot = CreateAggTemp(E->getType(), "agg-temp");
    EmitAggExpr(E, aggSlot);
    return aggSlot.asRValue();
  }
  llvm_unreachable("bad evaluation kind");
}

/// EmitAnyExprToTemp - Similary to EmitAnyExpr(), however, the result will
/// always be accessible even if no aggregate location is provided.
RValue CodeGenFunction::EmitAnyExprToTemp(const Expr *E) {
  AggValueSlot AggSlot = AggValueSlot::ignored();

  if (hasAggregateEvaluationKind(E->getType()))
    AggSlot = CreateAggTemp(E->getType(), "agg.tmp");
  return EmitAnyExpr(E, AggSlot);
}

/// EmitAnyExprToMem - Evaluate an expression into a given memory
/// location.
void CodeGenFunction::EmitAnyExprToMem(const Expr *E,
                                       llvm::Value *Location,
                                       Qualifiers Quals,
                                       bool IsInit) {
  // FIXME: This function should take an LValue as an argument.
  switch (getEvaluationKind(E->getType())) {
  case TEK_Complex:
    EmitComplexExprIntoLValue(E,
                         MakeNaturalAlignAddrLValue(Location, E->getType()),
                              /*isInit*/ false);
    return;

  case TEK_Aggregate: {
    CharUnits Alignment = getContext().getTypeAlignInChars(E->getType());
    EmitAggExpr(E, AggValueSlot::forAddr(Location, Alignment, Quals,
                                         AggValueSlot::IsDestructed_t(IsInit),
                                         AggValueSlot::DoesNotNeedGCBarriers,
                                         AggValueSlot::IsAliased_t(!IsInit)));
    return;
  }

  case TEK_Scalar: {
    RValue RV = RValue::get(EmitScalarExpr(E, /*Ignore*/ false));
    LValue LV = MakeAddrLValue(Location, E->getType());
    EmitStoreThroughLValue(RV, LV);
    return;
  }
  }
  llvm_unreachable("bad evaluation kind");
}

static llvm::Value *
CreateReferenceTemporary(CodeGenFunction &CGF, QualType Type,
                         const NamedDecl *InitializedDecl) {
  if (const VarDecl *VD = dyn_cast_or_null<VarDecl>(InitializedDecl)) {
    if (VD->hasGlobalStorage()) {
      SmallString<256> Name;
      llvm::raw_svector_ostream Out(Name);
      CGF.CGM.getCXXABI().getMangleContext().mangleReferenceTemporary(VD, Out);
      Out.flush();

      llvm::Type *RefTempTy = CGF.ConvertTypeForMem(Type);
  
      // Create the reference temporary.
      llvm::GlobalVariable *RefTemp =
        new llvm::GlobalVariable(CGF.CGM.getModule(), 
                                 RefTempTy, /*isConstant=*/false,
                                 llvm::GlobalValue::InternalLinkage,
                                 llvm::Constant::getNullValue(RefTempTy),
                                 Name.str());
      // If we're binding to a thread_local variable, the temporary is also
      // thread local.
      if (VD->getTLSKind())
        CGF.CGM.setTLSMode(RefTemp, *VD);
      return RefTemp;
    }
  }

  return CGF.CreateMemTemp(Type, "ref.tmp");
}

static llvm::Value *
EmitExprForReferenceBinding(CodeGenFunction &CGF, const Expr *E,
                            llvm::Value *&ReferenceTemporary,
                            const CXXDestructorDecl *&ReferenceTemporaryDtor,
                            const InitListExpr *&ReferenceInitializerList,
                            QualType &ObjCARCReferenceLifetimeType,
                            const NamedDecl *InitializedDecl) {
  const MaterializeTemporaryExpr *M = NULL;
  E = E->findMaterializedTemporary(M);
  // Objective-C++ ARC:
  //   If we are binding a reference to a temporary that has ownership, we
  //   need to perform retain/release operations on the temporary.
  if (M && CGF.getLangOpts().ObjCAutoRefCount &&
      M->getType()->isObjCLifetimeType() &&
      (M->getType().getObjCLifetime() == Qualifiers::OCL_Strong ||
       M->getType().getObjCLifetime() == Qualifiers::OCL_Weak ||
       M->getType().getObjCLifetime() == Qualifiers::OCL_Autoreleasing))
    ObjCARCReferenceLifetimeType = M->getType();

  if (const ExprWithCleanups *EWC = dyn_cast<ExprWithCleanups>(E)) {
    CGF.enterFullExpression(EWC);
    CodeGenFunction::RunCleanupsScope Scope(CGF);

    return EmitExprForReferenceBinding(CGF, EWC->getSubExpr(), 
                                       ReferenceTemporary, 
                                       ReferenceTemporaryDtor,
                                       ReferenceInitializerList,
                                       ObjCARCReferenceLifetimeType,
                                       InitializedDecl);
  }

  if (E->isGLValue()) {
    // Emit the expression as an lvalue.
    LValue LV = CGF.EmitLValue(E);
    assert(LV.isSimple());
    return LV.getAddress();
  }
  
  if (!ObjCARCReferenceLifetimeType.isNull()) {
    ReferenceTemporary = CreateReferenceTemporary(CGF, 
                                                ObjCARCReferenceLifetimeType, 
                                                  InitializedDecl);
    
    
    LValue RefTempDst = CGF.MakeAddrLValue(ReferenceTemporary, 
                                           ObjCARCReferenceLifetimeType);

    CGF.EmitScalarInit(E, dyn_cast_or_null<ValueDecl>(InitializedDecl),
                       RefTempDst, false);
    
    bool ExtendsLifeOfTemporary = false;
    if (const VarDecl *Var = dyn_cast_or_null<VarDecl>(InitializedDecl)) {
      if (Var->extendsLifetimeOfTemporary())
        ExtendsLifeOfTemporary = true;
    } else if (InitializedDecl && isa<FieldDecl>(InitializedDecl)) {
      ExtendsLifeOfTemporary = true;
    }
    
    if (!ExtendsLifeOfTemporary) {
      // Since the lifetime of this temporary isn't going to be extended,
      // we need to clean it up ourselves at the end of the full expression.
      switch (ObjCARCReferenceLifetimeType.getObjCLifetime()) {
      case Qualifiers::OCL_None:
      case Qualifiers::OCL_ExplicitNone:
      case Qualifiers::OCL_Autoreleasing:
        break;
          
      case Qualifiers::OCL_Strong: {
        assert(!ObjCARCReferenceLifetimeType->isArrayType());
        CleanupKind cleanupKind = CGF.getARCCleanupKind();
        CGF.pushDestroy(cleanupKind, 
                        ReferenceTemporary,
                        ObjCARCReferenceLifetimeType,
                        CodeGenFunction::destroyARCStrongImprecise,
                        cleanupKind & EHCleanup);
        break;
      }
        
      case Qualifiers::OCL_Weak:
        assert(!ObjCARCReferenceLifetimeType->isArrayType());
        CGF.pushDestroy(NormalAndEHCleanup, 
                        ReferenceTemporary,
                        ObjCARCReferenceLifetimeType,
                        CodeGenFunction::destroyARCWeak,
                        /*useEHCleanupForArray*/ true);
        break;
      }
      
      ObjCARCReferenceLifetimeType = QualType();
    }
    
    return ReferenceTemporary;
  }

  SmallVector<SubobjectAdjustment, 2> Adjustments;
  E = E->skipRValueSubobjectAdjustments(Adjustments);
  if (const OpaqueValueExpr *opaque = dyn_cast<OpaqueValueExpr>(E))
    if (opaque->getType()->isRecordType())
      return CGF.EmitOpaqueValueLValue(opaque).getAddress();

  // Create a reference temporary if necessary.
  AggValueSlot AggSlot = AggValueSlot::ignored();
  if (CGF.hasAggregateEvaluationKind(E->getType())) {
    ReferenceTemporary = CreateReferenceTemporary(CGF, E->getType(), 
                                                  InitializedDecl);
    CharUnits Alignment = CGF.getContext().getTypeAlignInChars(E->getType());
    AggValueSlot::IsDestructed_t isDestructed
      = AggValueSlot::IsDestructed_t(InitializedDecl != 0);
    AggSlot = AggValueSlot::forAddr(ReferenceTemporary, Alignment,
                                    Qualifiers(), isDestructed,
                                    AggValueSlot::DoesNotNeedGCBarriers,
                                    AggValueSlot::IsNotAliased);
  }
  
  if (InitializedDecl) {
    if (const InitListExpr *ILE = dyn_cast<InitListExpr>(E)) {
      if (ILE->initializesStdInitializerList()) {
        ReferenceInitializerList = ILE;
      }
    }
    else if (const RecordType *RT =
               E->getType()->getBaseElementTypeUnsafe()->getAs<RecordType>()){
      // Get the destructor for the reference temporary.
      CXXRecordDecl *ClassDecl = cast<CXXRecordDecl>(RT->getDecl());
      if (!ClassDecl->hasTrivialDestructor())
        ReferenceTemporaryDtor = ClassDecl->getDestructor();
    }
  }

  RValue RV = CGF.EmitAnyExpr(E, AggSlot);

  // Check if need to perform derived-to-base casts and/or field accesses, to
  // get from the temporary object we created (and, potentially, for which we
  // extended the lifetime) to the subobject we're binding the reference to.
  if (!Adjustments.empty()) {
    llvm::Value *Object = RV.getAggregateAddr();
    for (unsigned I = Adjustments.size(); I != 0; --I) {
      SubobjectAdjustment &Adjustment = Adjustments[I-1];
      switch (Adjustment.Kind) {
      case SubobjectAdjustment::DerivedToBaseAdjustment:
        Object = 
            CGF.GetAddressOfBaseClass(Object, 
                                      Adjustment.DerivedToBase.DerivedClass, 
                            Adjustment.DerivedToBase.BasePath->path_begin(),
                            Adjustment.DerivedToBase.BasePath->path_end(),
                                      /*NullCheckValue=*/false);
        break;
          
      case SubobjectAdjustment::FieldAdjustment: {
        LValue LV = CGF.MakeAddrLValue(Object, E->getType());
        LV = CGF.EmitLValueForField(LV, Adjustment.Field);
        if (LV.isSimple()) {
          Object = LV.getAddress();
          break;
        }
        
        // For non-simple lvalues, we actually have to create a copy of
        // the object we're binding to.
        QualType T = Adjustment.Field->getType().getNonReferenceType()
                                                .getUnqualifiedType();
        Object = CreateReferenceTemporary(CGF, T, InitializedDecl);
        LValue TempLV = CGF.MakeAddrLValue(Object,
                                           Adjustment.Field->getType());
        CGF.EmitStoreThroughLValue(CGF.EmitLoadOfLValue(LV), TempLV);
        break;
      }

      case SubobjectAdjustment::MemberPointerAdjustment: {
        llvm::Value *Ptr = CGF.EmitScalarExpr(Adjustment.Ptr.RHS);
        Object = CGF.CGM.getCXXABI().EmitMemberDataPointerAddress(
                      CGF, Object, Ptr, Adjustment.Ptr.MPT);
        break;
      }
      }
    }

    return Object;
  }

  if (RV.isAggregate())
    return RV.getAggregateAddr();

  // Create a temporary variable that we can bind the reference to.
  ReferenceTemporary = CreateReferenceTemporary(CGF, E->getType(), 
                                                InitializedDecl);


  LValue tempLV = CGF.MakeNaturalAlignAddrLValue(ReferenceTemporary,
                                                 E->getType());
  if (RV.isScalar())
    CGF.EmitStoreOfScalar(RV.getScalarVal(), tempLV, /*init*/ true);
  else
    CGF.EmitStoreOfComplex(RV.getComplexVal(), tempLV, /*init*/ true);
  return ReferenceTemporary;
}

RValue
CodeGenFunction::EmitReferenceBindingToExpr(const Expr *E,
                                            const NamedDecl *InitializedDecl) {
  llvm::Value *ReferenceTemporary = 0;
  const CXXDestructorDecl *ReferenceTemporaryDtor = 0;
  const InitListExpr *ReferenceInitializerList = 0;
  QualType ObjCARCReferenceLifetimeType;
  llvm::Value *Value = EmitExprForReferenceBinding(*this, E, ReferenceTemporary,
                                                   ReferenceTemporaryDtor,
                                                   ReferenceInitializerList,
                                                   ObjCARCReferenceLifetimeType,
                                                   InitializedDecl);
  if (SanitizePerformTypeCheck && !E->getType()->isFunctionType()) {
    // C++11 [dcl.ref]p5 (as amended by core issue 453):
    //   If a glvalue to which a reference is directly bound designates neither
    //   an existing object or function of an appropriate type nor a region of
    //   storage of suitable size and alignment to contain an object of the
    //   reference's type, the behavior is undefined.
    QualType Ty = E->getType();
    EmitTypeCheck(TCK_ReferenceBinding, E->getExprLoc(), Value, Ty);
  }
  if (!ReferenceTemporaryDtor && !ReferenceInitializerList &&
      ObjCARCReferenceLifetimeType.isNull())
    return RValue::get(Value);
  
  // Make sure to call the destructor for the reference temporary.
  const VarDecl *VD = dyn_cast_or_null<VarDecl>(InitializedDecl);
  if (VD && VD->hasGlobalStorage()) {
    if (ReferenceTemporaryDtor) {
      llvm::Constant *CleanupFn;
      llvm::Constant *CleanupArg;
      if (E->getType()->isArrayType()) {
        CleanupFn = CodeGenFunction(CGM).generateDestroyHelper(
            cast<llvm::Constant>(ReferenceTemporary), E->getType(),
            destroyCXXObject, getLangOpts().Exceptions);
        CleanupArg = llvm::Constant::getNullValue(Int8PtrTy);
      } else {
        CleanupFn =
          CGM.GetAddrOfCXXDestructor(ReferenceTemporaryDtor, Dtor_Complete);
        CleanupArg = cast<llvm::Constant>(ReferenceTemporary);
      }
      CGM.getCXXABI().registerGlobalDtor(*this, *VD, CleanupFn, CleanupArg);
    } else if (ReferenceInitializerList) {
      // FIXME: This is wrong. We need to register a global destructor to clean
      // up the initializer_list object, rather than adding it as a local
      // cleanup.
      EmitStdInitializerListCleanup(ReferenceTemporary,
                                    ReferenceInitializerList);
    } else {
      assert(!ObjCARCReferenceLifetimeType.isNull() && !VD->getTLSKind());
      // Note: We intentionally do not register a global "destructor" to
      // release the object.
    }
    
    return RValue::get(Value);
  }

  if (ReferenceTemporaryDtor) {
    if (E->getType()->isArrayType())
      pushDestroy(NormalAndEHCleanup, ReferenceTemporary, E->getType(),
                  destroyCXXObject, getLangOpts().Exceptions);
    else
      PushDestructorCleanup(ReferenceTemporaryDtor, ReferenceTemporary);
  } else if (ReferenceInitializerList) {
    EmitStdInitializerListCleanup(ReferenceTemporary,
                                  ReferenceInitializerList);
  } else {
    switch (ObjCARCReferenceLifetimeType.getObjCLifetime()) {
    case Qualifiers::OCL_None:
      llvm_unreachable(
                      "Not a reference temporary that needs to be deallocated");
    case Qualifiers::OCL_ExplicitNone:
    case Qualifiers::OCL_Autoreleasing:
      // Nothing to do.
      break;        
        
    case Qualifiers::OCL_Strong: {
      bool precise = VD && VD->hasAttr<ObjCPreciseLifetimeAttr>();
      CleanupKind cleanupKind = getARCCleanupKind();
      pushDestroy(cleanupKind, ReferenceTemporary, ObjCARCReferenceLifetimeType,
                  precise ? destroyARCStrongPrecise : destroyARCStrongImprecise,
                  cleanupKind & EHCleanup);
      break;
    }
        
    case Qualifiers::OCL_Weak: {
      // __weak objects always get EH cleanups; otherwise, exceptions
      // could cause really nasty crashes instead of mere leaks.
      pushDestroy(NormalAndEHCleanup, ReferenceTemporary,
                  ObjCARCReferenceLifetimeType, destroyARCWeak, true);
      break;        
    }
    }
  }
  
  return RValue::get(Value);
}


/// getAccessedFieldNo - Given an encoded value and a result number, return the
/// input field number being accessed.
unsigned CodeGenFunction::getAccessedFieldNo(unsigned Idx,
                                             const llvm::Constant *Elts) {
  return cast<llvm::ConstantInt>(Elts->getAggregateElement(Idx))
      ->getZExtValue();
}

/// Emit the hash_16_bytes function from include/llvm/ADT/Hashing.h.
static llvm::Value *emitHash16Bytes(CGBuilderTy &Builder, llvm::Value *Low,
                                    llvm::Value *High) {
  llvm::Value *KMul = Builder.getInt64(0x9ddfea08eb382d69ULL);
  llvm::Value *K47 = Builder.getInt64(47);
  llvm::Value *A0 = Builder.CreateMul(Builder.CreateXor(Low, High), KMul);
  llvm::Value *A1 = Builder.CreateXor(Builder.CreateLShr(A0, K47), A0);
  llvm::Value *B0 = Builder.CreateMul(Builder.CreateXor(High, A1), KMul);
  llvm::Value *B1 = Builder.CreateXor(Builder.CreateLShr(B0, K47), B0);
  return Builder.CreateMul(B1, KMul);
}

void CodeGenFunction::EmitTypeCheck(TypeCheckKind TCK, SourceLocation Loc,
                                    llvm::Value *Address,
                                    QualType Ty, CharUnits Alignment) {
  if (!SanitizePerformTypeCheck)
    return;

  // Don't check pointers outside the default address space. The null check
  // isn't correct, the object-size check isn't supported by LLVM, and we can't
  // communicate the addresses to the runtime handler for the vptr check.
  if (Address->getType()->getPointerAddressSpace())
    return;

  llvm::Value *Cond = 0;
  llvm::BasicBlock *Done = 0;

  if (SanOpts->Null) {
    // The glvalue must not be an empty glvalue.
    Cond = Builder.CreateICmpNE(
        Address, llvm::Constant::getNullValue(Address->getType()));

    if (TCK == TCK_DowncastPointer) {
      // When performing a pointer downcast, it's OK if the value is null.
      // Skip the remaining checks in that case.
      Done = createBasicBlock("null");
      llvm::BasicBlock *Rest = createBasicBlock("not.null");
      Builder.CreateCondBr(Cond, Rest, Done);
      EmitBlock(Rest);
      Cond = 0;
    }
  }

  if (SanOpts->ObjectSize && !Ty->isIncompleteType()) {
    uint64_t Size = getContext().getTypeSizeInChars(Ty).getQuantity();

    // The glvalue must refer to a large enough storage region.
    // FIXME: If Address Sanitizer is enabled, insert dynamic instrumentation
    //        to check this.
    llvm::Value *F = CGM.getIntrinsic(llvm::Intrinsic::objectsize, IntPtrTy);
    llvm::Value *Min = Builder.getFalse();
    llvm::Value *CastAddr = Builder.CreateBitCast(Address, Int8PtrTy);
    llvm::Value *LargeEnough =
        Builder.CreateICmpUGE(Builder.CreateCall2(F, CastAddr, Min),
                              llvm::ConstantInt::get(IntPtrTy, Size));
    Cond = Cond ? Builder.CreateAnd(Cond, LargeEnough) : LargeEnough;
  }

  uint64_t AlignVal = 0;

  if (SanOpts->Alignment) {
    AlignVal = Alignment.getQuantity();
    if (!Ty->isIncompleteType() && !AlignVal)
      AlignVal = getContext().getTypeAlignInChars(Ty).getQuantity();

    // The glvalue must be suitably aligned.
    if (AlignVal) {
      llvm::Value *Align =
          Builder.CreateAnd(Builder.CreatePtrToInt(Address, IntPtrTy),
                            llvm::ConstantInt::get(IntPtrTy, AlignVal - 1));
      llvm::Value *Aligned =
        Builder.CreateICmpEQ(Align, llvm::ConstantInt::get(IntPtrTy, 0));
      Cond = Cond ? Builder.CreateAnd(Cond, Aligned) : Aligned;
    }
  }

  if (Cond) {
    llvm::Constant *StaticData[] = {
      EmitCheckSourceLocation(Loc),
      EmitCheckTypeDescriptor(Ty),
      llvm::ConstantInt::get(SizeTy, AlignVal),
      llvm::ConstantInt::get(Int8Ty, TCK)
    };
    EmitCheck(Cond, "type_mismatch", StaticData, Address, CRK_Recoverable);
  }

  // If possible, check that the vptr indicates that there is a subobject of
  // type Ty at offset zero within this object.
  //
  // C++11 [basic.life]p5,6:
  //   [For storage which does not refer to an object within its lifetime]
  //   The program has undefined behavior if:
  //    -- the [pointer or glvalue] is used to access a non-static data member
  //       or call a non-static member function
  CXXRecordDecl *RD = Ty->getAsCXXRecordDecl();
  if (SanOpts->Vptr &&
      (TCK == TCK_MemberAccess || TCK == TCK_MemberCall ||
       TCK == TCK_DowncastPointer || TCK == TCK_DowncastReference) &&
      RD && RD->hasDefinition() && RD->isDynamicClass()) {
    // Compute a hash of the mangled name of the type.
    //
    // FIXME: This is not guaranteed to be deterministic! Move to a
    //        fingerprinting mechanism once LLVM provides one. For the time
    //        being the implementation happens to be deterministic.
    SmallString<64> MangledName;
    llvm::raw_svector_ostream Out(MangledName);
    CGM.getCXXABI().getMangleContext().mangleCXXRTTI(Ty.getUnqualifiedType(),
                                                     Out);
    llvm::hash_code TypeHash = hash_value(Out.str());

    // Load the vptr, and compute hash_16_bytes(TypeHash, vptr).
    llvm::Value *Low = llvm::ConstantInt::get(Int64Ty, TypeHash);
    llvm::Type *VPtrTy = llvm::PointerType::get(IntPtrTy, 0);
    llvm::Value *VPtrAddr = Builder.CreateBitCast(Address, VPtrTy);
    llvm::Value *VPtrVal = Builder.CreateLoad(VPtrAddr);
    llvm::Value *High = Builder.CreateZExt(VPtrVal, Int64Ty);

    llvm::Value *Hash = emitHash16Bytes(Builder, Low, High);
    Hash = Builder.CreateTrunc(Hash, IntPtrTy);

    // Look the hash up in our cache.
    const int CacheSize = 128;
    llvm::Type *HashTable = llvm::ArrayType::get(IntPtrTy, CacheSize);
    llvm::Value *Cache = CGM.CreateRuntimeVariable(HashTable,
                                                   "__ubsan_vptr_type_cache");
    llvm::Value *Slot = Builder.CreateAnd(Hash,
                                          llvm::ConstantInt::get(IntPtrTy,
                                                                 CacheSize-1));
    llvm::Value *Indices[] = { Builder.getInt32(0), Slot };
    llvm::Value *CacheVal =
      Builder.CreateLoad(Builder.CreateInBoundsGEP(Cache, Indices));

    // If the hash isn't in the cache, call a runtime handler to perform the
    // hard work of checking whether the vptr is for an object of the right
    // type. This will either fill in the cache and return, or produce a
    // diagnostic.
    llvm::Constant *StaticData[] = {
      EmitCheckSourceLocation(Loc),
      EmitCheckTypeDescriptor(Ty),
      CGM.GetAddrOfRTTIDescriptor(Ty.getUnqualifiedType()),
      llvm::ConstantInt::get(Int8Ty, TCK)
    };
    llvm::Value *DynamicData[] = { Address, Hash };
    EmitCheck(Builder.CreateICmpEQ(CacheVal, Hash),
              "dynamic_type_cache_miss", StaticData, DynamicData,
              CRK_AlwaysRecoverable);
  }

  if (Done) {
    Builder.CreateBr(Done);
    EmitBlock(Done);
  }
}

/// Determine whether this expression refers to a flexible array member in a
/// struct. We disable array bounds checks for such members.
static bool isFlexibleArrayMemberExpr(const Expr *E) {
  // For compatibility with existing code, we treat arrays of length 0 or
  // 1 as flexible array members.
  const ArrayType *AT = E->getType()->castAsArrayTypeUnsafe();
  if (const ConstantArrayType *CAT = dyn_cast<ConstantArrayType>(AT)) {
    if (CAT->getSize().ugt(1))
      return false;
  } else if (!isa<IncompleteArrayType>(AT))
    return false;

  E = E->IgnoreParens();

  // A flexible array member must be the last member in the class.
  if (const MemberExpr *ME = dyn_cast<MemberExpr>(E)) {
    // FIXME: If the base type of the member expr is not FD->getParent(),
    // this should not be treated as a flexible array member access.
    if (const FieldDecl *FD = dyn_cast<FieldDecl>(ME->getMemberDecl())) {
      RecordDecl::field_iterator FI(
          DeclContext::decl_iterator(const_cast<FieldDecl *>(FD)));
      return ++FI == FD->getParent()->field_end();
    }
  }

  return false;
}

/// If Base is known to point to the start of an array, return the length of
/// that array. Return 0 if the length cannot be determined.
static llvm::Value *getArrayIndexingBound(
    CodeGenFunction &CGF, const Expr *Base, QualType &IndexedType) {
  // For the vector indexing extension, the bound is the number of elements.
  if (const VectorType *VT = Base->getType()->getAs<VectorType>()) {
    IndexedType = Base->getType();
    return CGF.Builder.getInt32(VT->getNumElements());
  }

  Base = Base->IgnoreParens();

  if (const CastExpr *CE = dyn_cast<CastExpr>(Base)) {
    if (CE->getCastKind() == CK_ArrayToPointerDecay &&
        !isFlexibleArrayMemberExpr(CE->getSubExpr())) {
      IndexedType = CE->getSubExpr()->getType();
      const ArrayType *AT = IndexedType->castAsArrayTypeUnsafe();
      if (const ConstantArrayType *CAT = dyn_cast<ConstantArrayType>(AT))
        return CGF.Builder.getInt(CAT->getSize());
      else if (const VariableArrayType *VAT = dyn_cast<VariableArrayType>(AT))
        return CGF.getVLASize(VAT).first;
    }
  }

  return 0;
}

void CodeGenFunction::EmitBoundsCheck(const Expr *E, const Expr *Base,
                                      llvm::Value *Index, QualType IndexType,
                                      bool Accessed) {
  assert(SanOpts->Bounds && "should not be called unless adding bounds checks");

  QualType IndexedType;
  llvm::Value *Bound = getArrayIndexingBound(*this, Base, IndexedType);
  if (!Bound)
    return;

  bool IndexSigned = IndexType->isSignedIntegerOrEnumerationType();
  llvm::Value *IndexVal = Builder.CreateIntCast(Index, SizeTy, IndexSigned);
  llvm::Value *BoundVal = Builder.CreateIntCast(Bound, SizeTy, false);

  llvm::Constant *StaticData[] = {
    EmitCheckSourceLocation(E->getExprLoc()),
    EmitCheckTypeDescriptor(IndexedType),
    EmitCheckTypeDescriptor(IndexType)
  };
  llvm::Value *Check = Accessed ? Builder.CreateICmpULT(IndexVal, BoundVal)
                                : Builder.CreateICmpULE(IndexVal, BoundVal);
  EmitCheck(Check, "out_of_bounds", StaticData, Index, CRK_Recoverable);
}


CodeGenFunction::ComplexPairTy CodeGenFunction::
EmitComplexPrePostIncDec(const UnaryOperator *E, LValue LV,
                         bool isInc, bool isPre) {
  ComplexPairTy InVal = EmitLoadOfComplex(LV);
  
  llvm::Value *NextVal;
  if (isa<llvm::IntegerType>(InVal.first->getType())) {
    uint64_t AmountVal = isInc ? 1 : -1;
    NextVal = llvm::ConstantInt::get(InVal.first->getType(), AmountVal, true);
    
    // Add the inc/dec to the real part.
    NextVal = Builder.CreateAdd(InVal.first, NextVal, isInc ? "inc" : "dec");
  } else {
    QualType ElemTy = E->getType()->getAs<ComplexType>()->getElementType();
    llvm::APFloat FVal(getContext().getFloatTypeSemantics(ElemTy), 1);
    if (!isInc)
      FVal.changeSign();
    NextVal = llvm::ConstantFP::get(getLLVMContext(), FVal);
    
    // Add the inc/dec to the real part.
    NextVal = Builder.CreateFAdd(InVal.first, NextVal, isInc ? "inc" : "dec");
  }
  
  ComplexPairTy IncVal(NextVal, InVal.second);
  
  // Store the updated result through the lvalue.
  EmitStoreOfComplex(IncVal, LV, /*init*/ false);
  
  // If this is a postinc, return the value read from memory, otherwise use the
  // updated value.
  return isPre ? IncVal : InVal;
}


//===----------------------------------------------------------------------===//
//                         LValue Expression Emission
//===----------------------------------------------------------------------===//

RValue CodeGenFunction::GetUndefRValue(QualType Ty) {
  if (Ty->isVoidType())
    return RValue::get(0);

  switch (getEvaluationKind(Ty)) {
  case TEK_Complex: {
    llvm::Type *EltTy =
      ConvertType(Ty->castAs<ComplexType>()->getElementType());
    llvm::Value *U = llvm::UndefValue::get(EltTy);
    return RValue::getComplex(std::make_pair(U, U));
  }
  
  // If this is a use of an undefined aggregate type, the aggregate must have an
  // identifiable address.  Just because the contents of the value are undefined
  // doesn't mean that the address can't be taken and compared.
  case TEK_Aggregate: {
    llvm::Value *DestPtr = CreateMemTemp(Ty, "undef.agg.tmp");
    return RValue::getAggregate(DestPtr);
  }

  case TEK_Scalar:
    return RValue::get(llvm::UndefValue::get(ConvertType(Ty)));
  }
  llvm_unreachable("bad evaluation kind");
}

RValue CodeGenFunction::EmitUnsupportedRValue(const Expr *E,
                                              const char *Name) {
  ErrorUnsupported(E, Name);
  return GetUndefRValue(E->getType());
}

LValue CodeGenFunction::EmitUnsupportedLValue(const Expr *E,
                                              const char *Name) {
  ErrorUnsupported(E, Name);
  llvm::Type *Ty = llvm::PointerType::getUnqual(ConvertType(E->getType()));
  return MakeAddrLValue(llvm::UndefValue::get(Ty), E->getType());
}

LValue CodeGenFunction::EmitCheckedLValue(const Expr *E, TypeCheckKind TCK) {
  LValue LV;
  if (SanOpts->Bounds && isa<ArraySubscriptExpr>(E))
    LV = EmitArraySubscriptExpr(cast<ArraySubscriptExpr>(E), /*Accessed*/true);
  else
    LV = EmitLValue(E);
  if (!isa<DeclRefExpr>(E) && !LV.isBitField() && LV.isSimple())
    EmitTypeCheck(TCK, E->getExprLoc(), LV.getAddress(),
                  E->getType(), LV.getAlignment());
  return LV;
}

/// EmitLValue - Emit code to compute a designator that specifies the location
/// of the expression.
///
/// This can return one of two things: a simple address or a bitfield reference.
/// In either case, the LLVM Value* in the LValue structure is guaranteed to be
/// an LLVM pointer type.
///
/// If this returns a bitfield reference, nothing about the pointee type of the
/// LLVM value is known: For example, it may not be a pointer to an integer.
///
/// If this returns a normal address, and if the lvalue's C type is fixed size,
/// this method guarantees that the returned pointer type will point to an LLVM
/// type of the same size of the lvalue's type.  If the lvalue has a variable
/// length type, this is not possible.
///
LValue CodeGenFunction::EmitLValue(const Expr *E) {
  switch (E->getStmtClass()) {
  default: return EmitUnsupportedLValue(E, "l-value expression");

  case Expr::ObjCPropertyRefExprClass:
    llvm_unreachable("cannot emit a property reference directly");

  case Expr::ObjCSelectorExprClass:
    return EmitObjCSelectorLValue(cast<ObjCSelectorExpr>(E));
  case Expr::ObjCIsaExprClass:
    return EmitObjCIsaExpr(cast<ObjCIsaExpr>(E));
  case Expr::BinaryOperatorClass:
    return EmitBinaryOperatorLValue(cast<BinaryOperator>(E));
  case Expr::CompoundAssignOperatorClass:
    if (!E->getType()->isAnyComplexType())
      return EmitCompoundAssignmentLValue(cast<CompoundAssignOperator>(E));
    return EmitComplexCompoundAssignmentLValue(cast<CompoundAssignOperator>(E));
  case Expr::CallExprClass:
  case Expr::CXXMemberCallExprClass:
  case Expr::CXXOperatorCallExprClass:
  case Expr::UserDefinedLiteralClass:
    return EmitCallExprLValue(cast<CallExpr>(E));
  case Expr::VAArgExprClass:
    return EmitVAArgExprLValue(cast<VAArgExpr>(E));
  case Expr::DeclRefExprClass:
    return EmitDeclRefLValue(cast<DeclRefExpr>(E));
  case Expr::ParenExprClass:
    return EmitLValue(cast<ParenExpr>(E)->getSubExpr());
  case Expr::GenericSelectionExprClass:
    return EmitLValue(cast<GenericSelectionExpr>(E)->getResultExpr());
  case Expr::PredefinedExprClass:
    return EmitPredefinedLValue(cast<PredefinedExpr>(E));
  case Expr::StringLiteralClass:
    return EmitStringLiteralLValue(cast<StringLiteral>(E));
  case Expr::ObjCEncodeExprClass:
    return EmitObjCEncodeExprLValue(cast<ObjCEncodeExpr>(E));
  case Expr::PseudoObjectExprClass:
    return EmitPseudoObjectLValue(cast<PseudoObjectExpr>(E));
  case Expr::InitListExprClass:
    return EmitInitListLValue(cast<InitListExpr>(E));
  case Expr::CXXTemporaryObjectExprClass:
  case Expr::CXXConstructExprClass:
    return EmitCXXConstructLValue(cast<CXXConstructExpr>(E));
  case Expr::CXXBindTemporaryExprClass:
    return EmitCXXBindTemporaryLValue(cast<CXXBindTemporaryExpr>(E));
  case Expr::CXXUuidofExprClass:
    return EmitCXXUuidofLValue(cast<CXXUuidofExpr>(E));
  case Expr::LambdaExprClass:
    return EmitLambdaLValue(cast<LambdaExpr>(E));

  case Expr::ExprWithCleanupsClass: {
    const ExprWithCleanups *cleanups = cast<ExprWithCleanups>(E);
    enterFullExpression(cleanups);
    RunCleanupsScope Scope(*this);
    return EmitLValue(cleanups->getSubExpr());
  }

  case Expr::CXXScalarValueInitExprClass:
    return EmitNullInitializationLValue(cast<CXXScalarValueInitExpr>(E));
  case Expr::CXXDefaultArgExprClass:
    return EmitLValue(cast<CXXDefaultArgExpr>(E)->getExpr());
  case Expr::CXXDefaultInitExprClass: {
    CXXDefaultInitExprScope Scope(*this);
    return EmitLValue(cast<CXXDefaultInitExpr>(E)->getExpr());
  }
  case Expr::CXXTypeidExprClass:
    return EmitCXXTypeidLValue(cast<CXXTypeidExpr>(E));

  case Expr::ObjCMessageExprClass:
    return EmitObjCMessageExprLValue(cast<ObjCMessageExpr>(E));
  case Expr::ObjCIvarRefExprClass:
    return EmitObjCIvarRefLValue(cast<ObjCIvarRefExpr>(E));
  case Expr::StmtExprClass:
    return EmitStmtExprLValue(cast<StmtExpr>(E));
  case Expr::UnaryOperatorClass:
    return EmitUnaryOpLValue(cast<UnaryOperator>(E));
  case Expr::ArraySubscriptExprClass:
    return EmitArraySubscriptExpr(cast<ArraySubscriptExpr>(E));
  case Expr::ExtVectorElementExprClass:
    return EmitExtVectorElementExpr(cast<ExtVectorElementExpr>(E));
  case Expr::MemberExprClass:
    return EmitMemberExpr(cast<MemberExpr>(E));
  case Expr::CompoundLiteralExprClass:
    return EmitCompoundLiteralLValue(cast<CompoundLiteralExpr>(E));
  case Expr::ConditionalOperatorClass:
    return EmitConditionalOperatorLValue(cast<ConditionalOperator>(E));
  case Expr::BinaryConditionalOperatorClass:
    return EmitConditionalOperatorLValue(cast<BinaryConditionalOperator>(E));
  case Expr::ChooseExprClass:
    return EmitLValue(cast<ChooseExpr>(E)->getChosenSubExpr(getContext()));
  case Expr::OpaqueValueExprClass:
    return EmitOpaqueValueLValue(cast<OpaqueValueExpr>(E));
  case Expr::SubstNonTypeTemplateParmExprClass:
    return EmitLValue(cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement());
  case Expr::ImplicitCastExprClass:
  case Expr::CStyleCastExprClass:
  case Expr::CXXFunctionalCastExprClass:
  case Expr::CXXStaticCastExprClass:
  case Expr::CXXDynamicCastExprClass:
  case Expr::CXXReinterpretCastExprClass:
  case Expr::CXXConstCastExprClass:
  case Expr::ObjCBridgedCastExprClass:
    return EmitCastLValue(cast<CastExpr>(E));

  case Expr::MaterializeTemporaryExprClass:
    return EmitMaterializeTemporaryExpr(cast<MaterializeTemporaryExpr>(E));
  }
}

/// Given an object of the given canonical type, can we safely copy a
/// value out of it based on its initializer?
static bool isConstantEmittableObjectType(QualType type) {
  assert(type.isCanonical());
  assert(!type->isReferenceType());

  // Must be const-qualified but non-volatile.
  Qualifiers qs = type.getLocalQualifiers();
  if (!qs.hasConst() || qs.hasVolatile()) return false;

  // Otherwise, all object types satisfy this except C++ classes with
  // mutable subobjects or non-trivial copy/destroy behavior.
  if (const RecordType *RT = dyn_cast<RecordType>(type))
    if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(RT->getDecl()))
      if (RD->hasMutableFields() || !RD->isTrivial())
        return false;

  return true;
}

/// Can we constant-emit a load of a reference to a variable of the
/// given type?  This is different from predicates like
/// Decl::isUsableInConstantExpressions because we do want it to apply
/// in situations that don't necessarily satisfy the language's rules
/// for this (e.g. C++'s ODR-use rules).  For example, we want to able
/// to do this with const float variables even if those variables
/// aren't marked 'constexpr'.
enum ConstantEmissionKind {
  CEK_None,
  CEK_AsReferenceOnly,
  CEK_AsValueOrReference,
  CEK_AsValueOnly
};
static ConstantEmissionKind checkVarTypeForConstantEmission(QualType type) {
  type = type.getCanonicalType();
  if (const ReferenceType *ref = dyn_cast<ReferenceType>(type)) {
    if (isConstantEmittableObjectType(ref->getPointeeType()))
      return CEK_AsValueOrReference;
    return CEK_AsReferenceOnly;
  }
  if (isConstantEmittableObjectType(type))
    return CEK_AsValueOnly;
  return CEK_None;
}

/// Try to emit a reference to the given value without producing it as
/// an l-value.  This is actually more than an optimization: we can't
/// produce an l-value for variables that we never actually captured
/// in a block or lambda, which means const int variables or constexpr
/// literals or similar.
CodeGenFunction::ConstantEmission
CodeGenFunction::tryEmitAsConstant(DeclRefExpr *refExpr) {
  ValueDecl *value = refExpr->getDecl();

  // The value needs to be an enum constant or a constant variable.
  ConstantEmissionKind CEK;
  if (isa<ParmVarDecl>(value)) {
    CEK = CEK_None;
  } else if (VarDecl *var = dyn_cast<VarDecl>(value)) {
    CEK = checkVarTypeForConstantEmission(var->getType());
  } else if (isa<EnumConstantDecl>(value)) {
    CEK = CEK_AsValueOnly;
  } else {
    CEK = CEK_None;
  }
  if (CEK == CEK_None) return ConstantEmission();

  Expr::EvalResult result;
  bool resultIsReference;
  QualType resultType;

  // It's best to evaluate all the way as an r-value if that's permitted.
  if (CEK != CEK_AsReferenceOnly &&
      refExpr->EvaluateAsRValue(result, getContext())) {
    resultIsReference = false;
    resultType = refExpr->getType();

  // Otherwise, try to evaluate as an l-value.
  } else if (CEK != CEK_AsValueOnly &&
             refExpr->EvaluateAsLValue(result, getContext())) {
    resultIsReference = true;
    resultType = value->getType();

  // Failure.
  } else {
    return ConstantEmission();
  }

  // In any case, if the initializer has side-effects, abandon ship.
  if (result.HasSideEffects)
    return ConstantEmission();

  // Emit as a constant.
  llvm::Constant *C = CGM.EmitConstantValue(result.Val, resultType, this);

  // Make sure we emit a debug reference to the global variable.
  // This should probably fire even for 
  if (isa<VarDecl>(value)) {
    if (!getContext().DeclMustBeEmitted(cast<VarDecl>(value)))
      EmitDeclRefExprDbgValue(refExpr, C);
  } else {
    assert(isa<EnumConstantDecl>(value));
    EmitDeclRefExprDbgValue(refExpr, C);
  }

  // If we emitted a reference constant, we need to dereference that.
  if (resultIsReference)
    return ConstantEmission::forReference(C);

  return ConstantEmission::forValue(C);
}

llvm::Value *CodeGenFunction::EmitLoadOfScalar(LValue lvalue) {
  return EmitLoadOfScalar(lvalue.getAddress(), lvalue.isVolatile(),
                          lvalue.getAlignment().getQuantity(),
                          lvalue.getType(), lvalue.getTBAAInfo(),
                          lvalue.getTBAABaseType(), lvalue.getTBAAOffset());
}

static bool hasBooleanRepresentation(QualType Ty) {
  if (Ty->isBooleanType())
    return true;

  if (const EnumType *ET = Ty->getAs<EnumType>())
    return ET->getDecl()->getIntegerType()->isBooleanType();

  if (const AtomicType *AT = Ty->getAs<AtomicType>())
    return hasBooleanRepresentation(AT->getValueType());

  return false;
}

static bool getRangeForType(CodeGenFunction &CGF, QualType Ty,
                            llvm::APInt &Min, llvm::APInt &End,
                            bool StrictEnums) {
  const EnumType *ET = Ty->getAs<EnumType>();
  bool IsRegularCPlusPlusEnum = CGF.getLangOpts().CPlusPlus && StrictEnums &&
                                ET && !ET->getDecl()->isFixed();
  bool IsBool = hasBooleanRepresentation(Ty);
  if (!IsBool && !IsRegularCPlusPlusEnum)
    return false;

  if (IsBool) {
    Min = llvm::APInt(CGF.getContext().getTypeSize(Ty), 0);
    End = llvm::APInt(CGF.getContext().getTypeSize(Ty), 2);
  } else {
    const EnumDecl *ED = ET->getDecl();
    llvm::Type *LTy = CGF.ConvertTypeForMem(ED->getIntegerType());
    unsigned Bitwidth = LTy->getScalarSizeInBits();
    unsigned NumNegativeBits = ED->getNumNegativeBits();
    unsigned NumPositiveBits = ED->getNumPositiveBits();

    if (NumNegativeBits) {
      unsigned NumBits = std::max(NumNegativeBits, NumPositiveBits + 1);
      assert(NumBits <= Bitwidth);
      End = llvm::APInt(Bitwidth, 1) << (NumBits - 1);
      Min = -End;
    } else {
      assert(NumPositiveBits <= Bitwidth);
      End = llvm::APInt(Bitwidth, 1) << NumPositiveBits;
      Min = llvm::APInt(Bitwidth, 0);
    }
  }
  return true;
}

llvm::MDNode *CodeGenFunction::getRangeForLoadFromType(QualType Ty) {
  llvm::APInt Min, End;
  if (!getRangeForType(*this, Ty, Min, End,
                       CGM.getCodeGenOpts().StrictEnums))
    return 0;

  llvm::MDBuilder MDHelper(getLLVMContext());
  return MDHelper.createRange(Min, End);
}

llvm::Value *CodeGenFunction::EmitLoadOfScalar(llvm::Value *Addr, bool Volatile,
                                              unsigned Alignment, QualType Ty,
                                              llvm::MDNode *TBAAInfo,
                                              QualType TBAABaseType,
                                              uint64_t TBAAOffset) {
  // For better performance, handle vector loads differently.
  if (Ty->isVectorType()) {
    llvm::Value *V;
    const llvm::Type *EltTy =
    cast<llvm::PointerType>(Addr->getType())->getElementType();
    
    const llvm::VectorType *VTy = cast<llvm::VectorType>(EltTy);
      
    // Handle vectors of size 3, like size 4 for better performance.
    if (VTy->getNumElements() == 3) {
        
      // Bitcast to vec4 type.
      llvm::VectorType *vec4Ty = llvm::VectorType::get(VTy->getElementType(),
                                                         4);
      llvm::PointerType *ptVec4Ty =
      llvm::PointerType::get(vec4Ty,
                             (cast<llvm::PointerType>(
                                      Addr->getType()))->getAddressSpace());
      llvm::Value *Cast = Builder.CreateBitCast(Addr, ptVec4Ty,
                                                "castToVec4");
      // Now load value.
      llvm::Value *LoadVal = Builder.CreateLoad(Cast, Volatile, "loadVec4");

      // Shuffle vector to get vec3.
      llvm::Constant *Mask[] = {
        llvm::ConstantInt::get(llvm::Type::getInt32Ty(getLLVMContext()), 0),
        llvm::ConstantInt::get(llvm::Type::getInt32Ty(getLLVMContext()), 1),
        llvm::ConstantInt::get(llvm::Type::getInt32Ty(getLLVMContext()), 2)
      };

      llvm::Value *MaskV = llvm::ConstantVector::get(Mask);
      V = Builder.CreateShuffleVector(LoadVal,
                                      llvm::UndefValue::get(vec4Ty),
                                      MaskV, "extractVec");
      return EmitFromMemory(V, Ty);
    }
  }

  // Atomic operations have to be done on integral types.
  if (Ty->isAtomicType()) {
    LValue lvalue = LValue::MakeAddr(Addr, Ty,
                                     CharUnits::fromQuantity(Alignment),
                                     getContext(), TBAAInfo);
    return EmitAtomicLoad(lvalue).getScalarVal();
  }
  
  llvm::LoadInst *Load = Builder.CreateLoad(Addr);
  if (Volatile)
    Load->setVolatile(true);
  if (Alignment)
    Load->setAlignment(Alignment);
  if (TBAAInfo) {
    llvm::MDNode *TBAAPath = CGM.getTBAAStructTagInfo(TBAABaseType, TBAAInfo,
                                                      TBAAOffset);
    CGM.DecorateInstruction(Load, TBAAPath, false/*ConvertTypeToTag*/);
  }

  if ((SanOpts->Bool && hasBooleanRepresentation(Ty)) ||
      (SanOpts->Enum && Ty->getAs<EnumType>())) {
    llvm::APInt Min, End;
    if (getRangeForType(*this, Ty, Min, End, true)) {
      --End;
      llvm::Value *Check;
      if (!Min)
        Check = Builder.CreateICmpULE(
          Load, llvm::ConstantInt::get(getLLVMContext(), End));
      else {
        llvm::Value *Upper = Builder.CreateICmpSLE(
          Load, llvm::ConstantInt::get(getLLVMContext(), End));
        llvm::Value *Lower = Builder.CreateICmpSGE(
          Load, llvm::ConstantInt::get(getLLVMContext(), Min));
        Check = Builder.CreateAnd(Upper, Lower);
      }
      // FIXME: Provide a SourceLocation.
      EmitCheck(Check, "load_invalid_value", EmitCheckTypeDescriptor(Ty),
                EmitCheckValue(Load), CRK_Recoverable);
    }
  } else if (CGM.getCodeGenOpts().OptimizationLevel > 0)
    if (llvm::MDNode *RangeInfo = getRangeForLoadFromType(Ty))
      Load->setMetadata(llvm::LLVMContext::MD_range, RangeInfo);

  return EmitFromMemory(Load, Ty);
}

llvm::Value *CodeGenFunction::EmitToMemory(llvm::Value *Value, QualType Ty) {
  // Bool has a different representation in memory than in registers.
  if (hasBooleanRepresentation(Ty)) {
    // This should really always be an i1, but sometimes it's already
    // an i8, and it's awkward to track those cases down.
    if (Value->getType()->isIntegerTy(1))
      return Builder.CreateZExt(Value, ConvertTypeForMem(Ty), "frombool");
    assert(Value->getType()->isIntegerTy(getContext().getTypeSize(Ty)) &&
           "wrong value rep of bool");
  }

  return Value;
}

llvm::Value *CodeGenFunction::EmitFromMemory(llvm::Value *Value, QualType Ty) {
  // Bool has a different representation in memory than in registers.
  if (hasBooleanRepresentation(Ty)) {
    assert(Value->getType()->isIntegerTy(getContext().getTypeSize(Ty)) &&
           "wrong value rep of bool");
    return Builder.CreateTrunc(Value, Builder.getInt1Ty(), "tobool");
  }

  return Value;
}

void CodeGenFunction::EmitStoreOfScalar(llvm::Value *Value, llvm::Value *Addr,
                                        bool Volatile, unsigned Alignment,
                                        QualType Ty,
                                        llvm::MDNode *TBAAInfo,
                                        bool isInit, QualType TBAABaseType,
                                        uint64_t TBAAOffset) {
  
  // Handle vectors differently to get better performance.
  if (Ty->isVectorType()) {
    llvm::Type *SrcTy = Value->getType();
    llvm::VectorType *VecTy = cast<llvm::VectorType>(SrcTy);
    // Handle vec3 special.
    if (VecTy->getNumElements() == 3) {
      llvm::LLVMContext &VMContext = getLLVMContext();
      
      // Our source is a vec3, do a shuffle vector to make it a vec4.
      SmallVector<llvm::Constant*, 4> Mask;
      Mask.push_back(llvm::ConstantInt::get(
                                            llvm::Type::getInt32Ty(VMContext),
                                            0));
      Mask.push_back(llvm::ConstantInt::get(
                                            llvm::Type::getInt32Ty(VMContext),
                                            1));
      Mask.push_back(llvm::ConstantInt::get(
                                            llvm::Type::getInt32Ty(VMContext),
                                            2));
      Mask.push_back(llvm::UndefValue::get(llvm::Type::getInt32Ty(VMContext)));
      
      llvm::Value *MaskV = llvm::ConstantVector::get(Mask);
      Value = Builder.CreateShuffleVector(Value,
                                          llvm::UndefValue::get(VecTy),
                                          MaskV, "extractVec");
      SrcTy = llvm::VectorType::get(VecTy->getElementType(), 4);
    }
    llvm::PointerType *DstPtr = cast<llvm::PointerType>(Addr->getType());
    if (DstPtr->getElementType() != SrcTy) {
      llvm::Type *MemTy =
      llvm::PointerType::get(SrcTy, DstPtr->getAddressSpace());
      Addr = Builder.CreateBitCast(Addr, MemTy, "storetmp");
    }
  }
  
  Value = EmitToMemory(Value, Ty);

  if (Ty->isAtomicType()) {
    EmitAtomicStore(RValue::get(Value),
                    LValue::MakeAddr(Addr, Ty,
                                     CharUnits::fromQuantity(Alignment),
                                     getContext(), TBAAInfo),
                    isInit);
    return;
  }

  llvm::StoreInst *Store = Builder.CreateStore(Value, Addr, Volatile);
  if (Alignment)
    Store->setAlignment(Alignment);
  if (TBAAInfo) {
    llvm::MDNode *TBAAPath = CGM.getTBAAStructTagInfo(TBAABaseType, TBAAInfo,
                                                      TBAAOffset);
    CGM.DecorateInstruction(Store, TBAAPath, false/*ConvertTypeToTag*/);
  }
}

void CodeGenFunction::EmitStoreOfScalar(llvm::Value *value, LValue lvalue,
                                        bool isInit) {
  EmitStoreOfScalar(value, lvalue.getAddress(), lvalue.isVolatile(),
                    lvalue.getAlignment().getQuantity(), lvalue.getType(),
                    lvalue.getTBAAInfo(), isInit, lvalue.getTBAABaseType(),
                    lvalue.getTBAAOffset());
}

/// EmitLoadOfLValue - Given an expression that represents a value lvalue, this
/// method emits the address of the lvalue, then loads the result as an rvalue,
/// returning the rvalue.
RValue CodeGenFunction::EmitLoadOfLValue(LValue LV) {
  if (LV.isObjCWeak()) {
    // load of a __weak object.
    llvm::Value *AddrWeakObj = LV.getAddress();
    return RValue::get(CGM.getObjCRuntime().EmitObjCWeakRead(*this,
                                                             AddrWeakObj));
  }
  if (LV.getQuals().getObjCLifetime() == Qualifiers::OCL_Weak) {
    llvm::Value *Object = EmitARCLoadWeakRetained(LV.getAddress());
    Object = EmitObjCConsumeObject(LV.getType(), Object);
    return RValue::get(Object);
  }

  if (LV.isSimple()) {
    assert(!LV.getType()->isFunctionType());

    // Everything needs a load.
    return RValue::get(EmitLoadOfScalar(LV));
  }

  if (LV.isVectorElt()) {
    llvm::LoadInst *Load = Builder.CreateLoad(LV.getVectorAddr(),
                                              LV.isVolatileQualified());
    Load->setAlignment(LV.getAlignment().getQuantity());
    return RValue::get(Builder.CreateExtractElement(Load, LV.getVectorIdx(),
                                                    "vecext"));
  }

  // If this is a reference to a subset of the elements of a vector, either
  // shuffle the input or extract/insert them as appropriate.
  if (LV.isExtVectorElt())
    return EmitLoadOfExtVectorElementLValue(LV);

  assert(LV.isBitField() && "Unknown LValue type!");
  return EmitLoadOfBitfieldLValue(LV);
}

RValue CodeGenFunction::EmitLoadOfBitfieldLValue(LValue LV) {
  const CGBitFieldInfo &Info = LV.getBitFieldInfo();

  // Get the output type.
  llvm::Type *ResLTy = ConvertType(LV.getType());

  llvm::Value *Ptr = LV.getBitFieldAddr();
  llvm::Value *Val = Builder.CreateLoad(Ptr, LV.isVolatileQualified(),
                                        "bf.load");
  cast<llvm::LoadInst>(Val)->setAlignment(Info.StorageAlignment);

  if (Info.IsSigned) {
    assert(static_cast<unsigned>(Info.Offset + Info.Size) <= Info.StorageSize);
    unsigned HighBits = Info.StorageSize - Info.Offset - Info.Size;
    if (HighBits)
      Val = Builder.CreateShl(Val, HighBits, "bf.shl");
    if (Info.Offset + HighBits)
      Val = Builder.CreateAShr(Val, Info.Offset + HighBits, "bf.ashr");
  } else {
    if (Info.Offset)
      Val = Builder.CreateLShr(Val, Info.Offset, "bf.lshr");
    if (static_cast<unsigned>(Info.Offset) + Info.Size < Info.StorageSize)
      Val = Builder.CreateAnd(Val, llvm::APInt::getLowBitsSet(Info.StorageSize,
                                                              Info.Size),
                              "bf.clear");
  }
  Val = Builder.CreateIntCast(Val, ResLTy, Info.IsSigned, "bf.cast");

  return RValue::get(Val);
}

// If this is a reference to a subset of the elements of a vector, create an
// appropriate shufflevector.
RValue CodeGenFunction::EmitLoadOfExtVectorElementLValue(LValue LV) {
  llvm::LoadInst *Load = Builder.CreateLoad(LV.getExtVectorAddr(),
                                            LV.isVolatileQualified());
  Load->setAlignment(LV.getAlignment().getQuantity());
  llvm::Value *Vec = Load;

  const llvm::Constant *Elts = LV.getExtVectorElts();

  // If the result of the expression is a non-vector type, we must be extracting
  // a single element.  Just codegen as an extractelement.
  const VectorType *ExprVT = LV.getType()->getAs<VectorType>();
  if (!ExprVT) {
    unsigned InIdx = getAccessedFieldNo(0, Elts);
    llvm::Value *Elt = llvm::ConstantInt::get(Int32Ty, InIdx);
    return RValue::get(Builder.CreateExtractElement(Vec, Elt));
  }

  // Always use shuffle vector to try to retain the original program structure
  unsigned NumResultElts = ExprVT->getNumElements();

  SmallVector<llvm::Constant*, 4> Mask;
  for (unsigned i = 0; i != NumResultElts; ++i)
    Mask.push_back(Builder.getInt32(getAccessedFieldNo(i, Elts)));

  llvm::Value *MaskV = llvm::ConstantVector::get(Mask);
  Vec = Builder.CreateShuffleVector(Vec, llvm::UndefValue::get(Vec->getType()),
                                    MaskV);
  return RValue::get(Vec);
}



/// EmitStoreThroughLValue - Store the specified rvalue into the specified
/// lvalue, where both are guaranteed to the have the same type, and that type
/// is 'Ty'.
void CodeGenFunction::EmitStoreThroughLValue(RValue Src, LValue Dst, bool isInit) {
  if (!Dst.isSimple()) {
    if (Dst.isVectorElt()) {
      // Read/modify/write the vector, inserting the new element.
      llvm::LoadInst *Load = Builder.CreateLoad(Dst.getVectorAddr(),
                                                Dst.isVolatileQualified());
      Load->setAlignment(Dst.getAlignment().getQuantity());
      llvm::Value *Vec = Load;
      Vec = Builder.CreateInsertElement(Vec, Src.getScalarVal(),
                                        Dst.getVectorIdx(), "vecins");
      llvm::StoreInst *Store = Builder.CreateStore(Vec, Dst.getVectorAddr(),
                                                   Dst.isVolatileQualified());
      Store->setAlignment(Dst.getAlignment().getQuantity());
      return;
    }

    // If this is an update of extended vector elements, insert them as
    // appropriate.
    if (Dst.isExtVectorElt())
      return EmitStoreThroughExtVectorComponentLValue(Src, Dst);

    assert(Dst.isBitField() && "Unknown LValue type");
    return EmitStoreThroughBitfieldLValue(Src, Dst);
  }

  // There's special magic for assigning into an ARC-qualified l-value.
  if (Qualifiers::ObjCLifetime Lifetime = Dst.getQuals().getObjCLifetime()) {
    switch (Lifetime) {
    case Qualifiers::OCL_None:
      llvm_unreachable("present but none");

    case Qualifiers::OCL_ExplicitNone:
      // nothing special
      break;

    case Qualifiers::OCL_Strong:
      EmitARCStoreStrong(Dst, Src.getScalarVal(), /*ignore*/ true);
      return;

    case Qualifiers::OCL_Weak:
      EmitARCStoreWeak(Dst.getAddress(), Src.getScalarVal(), /*ignore*/ true);
      return;

    case Qualifiers::OCL_Autoreleasing:
      Src = RValue::get(EmitObjCExtendObjectLifetime(Dst.getType(),
                                                     Src.getScalarVal()));
      // fall into the normal path
      break;
    }
  }

  if (Dst.isObjCWeak() && !Dst.isNonGC()) {
    // load of a __weak object.
    llvm::Value *LvalueDst = Dst.getAddress();
    llvm::Value *src = Src.getScalarVal();
     CGM.getObjCRuntime().EmitObjCWeakAssign(*this, src, LvalueDst);
    return;
  }

  if (Dst.isObjCStrong() && !Dst.isNonGC()) {
    // load of a __strong object.
    llvm::Value *LvalueDst = Dst.getAddress();
    llvm::Value *src = Src.getScalarVal();
    if (Dst.isObjCIvar()) {
      assert(Dst.getBaseIvarExp() && "BaseIvarExp is NULL");
      llvm::Type *ResultType = ConvertType(getContext().LongTy);
      llvm::Value *RHS = EmitScalarExpr(Dst.getBaseIvarExp());
      llvm::Value *dst = RHS;
      RHS = Builder.CreatePtrToInt(RHS, ResultType, "sub.ptr.rhs.cast");
      llvm::Value *LHS = 
        Builder.CreatePtrToInt(LvalueDst, ResultType, "sub.ptr.lhs.cast");
      llvm::Value *BytesBetween = Builder.CreateSub(LHS, RHS, "ivar.offset");
      CGM.getObjCRuntime().EmitObjCIvarAssign(*this, src, dst,
                                              BytesBetween);
    } else if (Dst.isGlobalObjCRef()) {
      CGM.getObjCRuntime().EmitObjCGlobalAssign(*this, src, LvalueDst,
                                                Dst.isThreadLocalRef());
    }
    else
      CGM.getObjCRuntime().EmitObjCStrongCastAssign(*this, src, LvalueDst);
    return;
  }

  assert(Src.isScalar() && "Can't emit an agg store with this method");
  EmitStoreOfScalar(Src.getScalarVal(), Dst, isInit);
}

void CodeGenFunction::EmitStoreThroughBitfieldLValue(RValue Src, LValue Dst,
                                                     llvm::Value **Result) {
  const CGBitFieldInfo &Info = Dst.getBitFieldInfo();
  llvm::Type *ResLTy = ConvertTypeForMem(Dst.getType());
  llvm::Value *Ptr = Dst.getBitFieldAddr();

  // Get the source value, truncated to the width of the bit-field.
  llvm::Value *SrcVal = Src.getScalarVal();

  // Cast the source to the storage type and shift it into place.
  SrcVal = Builder.CreateIntCast(SrcVal,
                                 Ptr->getType()->getPointerElementType(),
                                 /*IsSigned=*/false);
  llvm::Value *MaskedVal = SrcVal;

  // See if there are other bits in the bitfield's storage we'll need to load
  // and mask together with source before storing.
  if (Info.StorageSize != Info.Size) {
    assert(Info.StorageSize > Info.Size && "Invalid bitfield size.");
    llvm::Value *Val = Builder.CreateLoad(Ptr, Dst.isVolatileQualified(),
                                          "bf.load");
    cast<llvm::LoadInst>(Val)->setAlignment(Info.StorageAlignment);

    // Mask the source value as needed.
    if (!hasBooleanRepresentation(Dst.getType()))
      SrcVal = Builder.CreateAnd(SrcVal,
                                 llvm::APInt::getLowBitsSet(Info.StorageSize,
                                                            Info.Size),
                                 "bf.value");
    MaskedVal = SrcVal;
    if (Info.Offset)
      SrcVal = Builder.CreateShl(SrcVal, Info.Offset, "bf.shl");

    // Mask out the original value.
    Val = Builder.CreateAnd(Val,
                            ~llvm::APInt::getBitsSet(Info.StorageSize,
                                                     Info.Offset,
                                                     Info.Offset + Info.Size),
                            "bf.clear");

    // Or together the unchanged values and the source value.
    SrcVal = Builder.CreateOr(Val, SrcVal, "bf.set");
  } else {
    assert(Info.Offset == 0);
  }

  // Write the new value back out.
  llvm::StoreInst *Store = Builder.CreateStore(SrcVal, Ptr,
                                               Dst.isVolatileQualified());
  Store->setAlignment(Info.StorageAlignment);

  // Return the new value of the bit-field, if requested.
  if (Result) {
    llvm::Value *ResultVal = MaskedVal;

    // Sign extend the value if needed.
    if (Info.IsSigned) {
      assert(Info.Size <= Info.StorageSize);
      unsigned HighBits = Info.StorageSize - Info.Size;
      if (HighBits) {
        ResultVal = Builder.CreateShl(ResultVal, HighBits, "bf.result.shl");
        ResultVal = Builder.CreateAShr(ResultVal, HighBits, "bf.result.ashr");
      }
    }

    ResultVal = Builder.CreateIntCast(ResultVal, ResLTy, Info.IsSigned,
                                      "bf.result.cast");
    *Result = EmitFromMemory(ResultVal, Dst.getType());
  }
}

void CodeGenFunction::EmitStoreThroughExtVectorComponentLValue(RValue Src,
                                                               LValue Dst) {
  // This access turns into a read/modify/write of the vector.  Load the input
  // value now.
  llvm::LoadInst *Load = Builder.CreateLoad(Dst.getExtVectorAddr(),
                                            Dst.isVolatileQualified());
  Load->setAlignment(Dst.getAlignment().getQuantity());
  llvm::Value *Vec = Load;
  const llvm::Constant *Elts = Dst.getExtVectorElts();

  llvm::Value *SrcVal = Src.getScalarVal();

  if (const VectorType *VTy = Dst.getType()->getAs<VectorType>()) {
    unsigned NumSrcElts = VTy->getNumElements();
    unsigned NumDstElts =
       cast<llvm::VectorType>(Vec->getType())->getNumElements();
    if (NumDstElts == NumSrcElts) {
      // Use shuffle vector is the src and destination are the same number of
      // elements and restore the vector mask since it is on the side it will be
      // stored.
      SmallVector<llvm::Constant*, 4> Mask(NumDstElts);
      for (unsigned i = 0; i != NumSrcElts; ++i)
        Mask[getAccessedFieldNo(i, Elts)] = Builder.getInt32(i);

      llvm::Value *MaskV = llvm::ConstantVector::get(Mask);
      Vec = Builder.CreateShuffleVector(SrcVal,
                                        llvm::UndefValue::get(Vec->getType()),
                                        MaskV);
    } else if (NumDstElts > NumSrcElts) {
      // Extended the source vector to the same length and then shuffle it
      // into the destination.
      // FIXME: since we're shuffling with undef, can we just use the indices
      //        into that?  This could be simpler.
      SmallVector<llvm::Constant*, 4> ExtMask;
      for (unsigned i = 0; i != NumSrcElts; ++i)
        ExtMask.push_back(Builder.getInt32(i));
      ExtMask.resize(NumDstElts, llvm::UndefValue::get(Int32Ty));
      llvm::Value *ExtMaskV = llvm::ConstantVector::get(ExtMask);
      llvm::Value *ExtSrcVal =
        Builder.CreateShuffleVector(SrcVal,
                                    llvm::UndefValue::get(SrcVal->getType()),
                                    ExtMaskV);
      // build identity
      SmallVector<llvm::Constant*, 4> Mask;
      for (unsigned i = 0; i != NumDstElts; ++i)
        Mask.push_back(Builder.getInt32(i));

      // modify when what gets shuffled in
      for (unsigned i = 0; i != NumSrcElts; ++i)
        Mask[getAccessedFieldNo(i, Elts)] = Builder.getInt32(i+NumDstElts);
      llvm::Value *MaskV = llvm::ConstantVector::get(Mask);
      Vec = Builder.CreateShuffleVector(Vec, ExtSrcVal, MaskV);
    } else {
      // We should never shorten the vector
      llvm_unreachable("unexpected shorten vector length");
    }
  } else {
    // If the Src is a scalar (not a vector) it must be updating one element.
    unsigned InIdx = getAccessedFieldNo(0, Elts);
    llvm::Value *Elt = llvm::ConstantInt::get(Int32Ty, InIdx);
    Vec = Builder.CreateInsertElement(Vec, SrcVal, Elt);
  }

  llvm::StoreInst *Store = Builder.CreateStore(Vec, Dst.getExtVectorAddr(),
                                               Dst.isVolatileQualified());
  Store->setAlignment(Dst.getAlignment().getQuantity());
}

// setObjCGCLValueClass - sets class of he lvalue for the purpose of
// generating write-barries API. It is currently a global, ivar,
// or neither.
static void setObjCGCLValueClass(const ASTContext &Ctx, const Expr *E,
                                 LValue &LV,
                                 bool IsMemberAccess=false) {
  if (Ctx.getLangOpts().getGC() == LangOptions::NonGC)
    return;
  
  if (isa<ObjCIvarRefExpr>(E)) {
    QualType ExpTy = E->getType();
    if (IsMemberAccess && ExpTy->isPointerType()) {
      // If ivar is a structure pointer, assigning to field of
      // this struct follows gcc's behavior and makes it a non-ivar 
      // writer-barrier conservatively.
      ExpTy = ExpTy->getAs<PointerType>()->getPointeeType();
      if (ExpTy->isRecordType()) {
        LV.setObjCIvar(false);
        return;
      }
    }
    LV.setObjCIvar(true);
    ObjCIvarRefExpr *Exp = cast<ObjCIvarRefExpr>(const_cast<Expr*>(E));
    LV.setBaseIvarExp(Exp->getBase());
    LV.setObjCArray(E->getType()->isArrayType());
    return;
  }
  
  if (const DeclRefExpr *Exp = dyn_cast<DeclRefExpr>(E)) {
    if (const VarDecl *VD = dyn_cast<VarDecl>(Exp->getDecl())) {
      if (VD->hasGlobalStorage()) {
        LV.setGlobalObjCRef(true);
        LV.setThreadLocalRef(VD->getTLSKind() != VarDecl::TLS_None);
      }
    }
    LV.setObjCArray(E->getType()->isArrayType());
    return;
  }
  
  if (const UnaryOperator *Exp = dyn_cast<UnaryOperator>(E)) {
    setObjCGCLValueClass(Ctx, Exp->getSubExpr(), LV, IsMemberAccess);
    return;
  }
  
  if (const ParenExpr *Exp = dyn_cast<ParenExpr>(E)) {
    setObjCGCLValueClass(Ctx, Exp->getSubExpr(), LV, IsMemberAccess);
    if (LV.isObjCIvar()) {
      // If cast is to a structure pointer, follow gcc's behavior and make it
      // a non-ivar write-barrier.
      QualType ExpTy = E->getType();
      if (ExpTy->isPointerType())
        ExpTy = ExpTy->getAs<PointerType>()->getPointeeType();
      if (ExpTy->isRecordType())
        LV.setObjCIvar(false); 
    }
    return;
  }

  if (const GenericSelectionExpr *Exp = dyn_cast<GenericSelectionExpr>(E)) {
    setObjCGCLValueClass(Ctx, Exp->getResultExpr(), LV);
    return;
  }

  if (const ImplicitCastExpr *Exp = dyn_cast<ImplicitCastExpr>(E)) {
    setObjCGCLValueClass(Ctx, Exp->getSubExpr(), LV, IsMemberAccess);
    return;
  }
  
  if (const CStyleCastExpr *Exp = dyn_cast<CStyleCastExpr>(E)) {
    setObjCGCLValueClass(Ctx, Exp->getSubExpr(), LV, IsMemberAccess);
    return;
  }

  if (const ObjCBridgedCastExpr *Exp = dyn_cast<ObjCBridgedCastExpr>(E)) {
    setObjCGCLValueClass(Ctx, Exp->getSubExpr(), LV, IsMemberAccess);
    return;
  }

  if (const ArraySubscriptExpr *Exp = dyn_cast<ArraySubscriptExpr>(E)) {
    setObjCGCLValueClass(Ctx, Exp->getBase(), LV);
    if (LV.isObjCIvar() && !LV.isObjCArray()) 
      // Using array syntax to assigning to what an ivar points to is not 
      // same as assigning to the ivar itself. {id *Names;} Names[i] = 0;
      LV.setObjCIvar(false); 
    else if (LV.isGlobalObjCRef() && !LV.isObjCArray())
      // Using array syntax to assigning to what global points to is not 
      // same as assigning to the global itself. {id *G;} G[i] = 0;
      LV.setGlobalObjCRef(false);
    return;
  }

  if (const MemberExpr *Exp = dyn_cast<MemberExpr>(E)) {
    setObjCGCLValueClass(Ctx, Exp->getBase(), LV, true);
    // We don't know if member is an 'ivar', but this flag is looked at
    // only in the context of LV.isObjCIvar().
    LV.setObjCArray(E->getType()->isArrayType());
    return;
  }
}

static llvm::Value *
EmitBitCastOfLValueToProperType(CodeGenFunction &CGF,
                                llvm::Value *V, llvm::Type *IRType,
                                StringRef Name = StringRef()) {
  unsigned AS = cast<llvm::PointerType>(V->getType())->getAddressSpace();
  return CGF.Builder.CreateBitCast(V, IRType->getPointerTo(AS), Name);
}

static LValue EmitGlobalVarDeclLValue(CodeGenFunction &CGF,
                                      const Expr *E, const VarDecl *VD) {
  llvm::Value *V = CGF.CGM.GetAddrOfGlobalVar(VD);
  llvm::Type *RealVarTy = CGF.getTypes().ConvertTypeForMem(VD->getType());
  V = EmitBitCastOfLValueToProperType(CGF, V, RealVarTy);
  CharUnits Alignment = CGF.getContext().getDeclAlign(VD);
  QualType T = E->getType();
  LValue LV;
  if (VD->getType()->isReferenceType()) {
    llvm::LoadInst *LI = CGF.Builder.CreateLoad(V);
    LI->setAlignment(Alignment.getQuantity());
    V = LI;
    LV = CGF.MakeNaturalAlignAddrLValue(V, T);
  } else {
    LV = CGF.MakeAddrLValue(V, E->getType(), Alignment);
  }
  setObjCGCLValueClass(CGF.getContext(), E, LV);
  return LV;
}

static LValue EmitFunctionDeclLValue(CodeGenFunction &CGF,
                                     const Expr *E, const FunctionDecl *FD) {
  llvm::Value *V = CGF.CGM.GetAddrOfFunction(FD);
  if (!FD->hasPrototype()) {
    if (const FunctionProtoType *Proto =
            FD->getType()->getAs<FunctionProtoType>()) {
      // Ugly case: for a K&R-style definition, the type of the definition
      // isn't the same as the type of a use.  Correct for this with a
      // bitcast.
      QualType NoProtoType =
          CGF.getContext().getFunctionNoProtoType(Proto->getResultType());
      NoProtoType = CGF.getContext().getPointerType(NoProtoType);
      V = CGF.Builder.CreateBitCast(V, CGF.ConvertType(NoProtoType));
    }
  }
  CharUnits Alignment = CGF.getContext().getDeclAlign(FD);
  return CGF.MakeAddrLValue(V, E->getType(), Alignment);
}

LValue CodeGenFunction::EmitDeclRefLValue(const DeclRefExpr *E) {
  const NamedDecl *ND = E->getDecl();
  CharUnits Alignment = getContext().getDeclAlign(ND);
  QualType T = E->getType();

  // A DeclRefExpr for a reference initialized by a constant expression can
  // appear without being odr-used. Directly emit the constant initializer.
  if (const VarDecl *VD = dyn_cast<VarDecl>(ND)) {
    const Expr *Init = VD->getAnyInitializer(VD);
    if (Init && !isa<ParmVarDecl>(VD) && VD->getType()->isReferenceType() &&
        VD->isUsableInConstantExpressions(getContext()) &&
        VD->checkInitIsICE()) {
      llvm::Constant *Val =
        CGM.EmitConstantValue(*VD->evaluateValue(), VD->getType(), this);
      assert(Val && "failed to emit reference constant expression");
      // FIXME: Eventually we will want to emit vector element references.
      return MakeAddrLValue(Val, T, Alignment);
    }
  }

  // FIXME: We should be able to assert this for FunctionDecls as well!
  // FIXME: We should be able to assert this for all DeclRefExprs, not just
  // those with a valid source location.
  assert((ND->isUsed(false) || !isa<VarDecl>(ND) ||
          !E->getLocation().isValid()) &&
         "Should not use decl without marking it used!");

  if (ND->hasAttr<WeakRefAttr>()) {
    const ValueDecl *VD = cast<ValueDecl>(ND);
    llvm::Constant *Aliasee = CGM.GetWeakRefReference(VD);
    return MakeAddrLValue(Aliasee, T, Alignment);
  }

  if (const VarDecl *VD = dyn_cast<VarDecl>(ND)) {
    // Check if this is a global variable.
    if (VD->hasLinkage() || VD->isStaticDataMember()) {
      // If it's thread_local, emit a call to its wrapper function instead.
      if (VD->getTLSKind() == VarDecl::TLS_Dynamic)
        return CGM.getCXXABI().EmitThreadLocalDeclRefExpr(*this, E);
      return EmitGlobalVarDeclLValue(*this, E, VD);
    }

    bool isBlockVariable = VD->hasAttr<BlocksAttr>();

    llvm::Value *V = LocalDeclMap.lookup(VD);
    if (!V && VD->isStaticLocal()) 
      V = CGM.getStaticLocalDeclAddress(VD);

    // Use special handling for lambdas.
    if (!V) {
      if (FieldDecl *FD = LambdaCaptureFields.lookup(VD)) {
        QualType LambdaTagType = getContext().getTagDeclType(FD->getParent());
        LValue LambdaLV = MakeNaturalAlignAddrLValue(CXXABIThisValue,
                                                     LambdaTagType);
        return EmitLValueForField(LambdaLV, FD);
      }

      assert(isa<BlockDecl>(CurCodeDecl) && E->refersToEnclosingLocal());
      return MakeAddrLValue(GetAddrOfBlockDecl(VD, isBlockVariable),
                            T, Alignment);
    }

    assert(V && "DeclRefExpr not entered in LocalDeclMap?");

    if (isBlockVariable)
      V = BuildBlockByrefAddress(V, VD);

    LValue LV;
    if (VD->getType()->isReferenceType()) {
      llvm::LoadInst *LI = Builder.CreateLoad(V);
      LI->setAlignment(Alignment.getQuantity());
      V = LI;
      LV = MakeNaturalAlignAddrLValue(V, T);
    } else {
      LV = MakeAddrLValue(V, T, Alignment);
    }

    bool isLocalStorage = VD->hasLocalStorage();

    bool NonGCable = isLocalStorage &&
                     !VD->getType()->isReferenceType() &&
                     !isBlockVariable;
    if (NonGCable) {
      LV.getQuals().removeObjCGCAttr();
      LV.setNonGC(true);
    }

    bool isImpreciseLifetime =
      (isLocalStorage && !VD->hasAttr<ObjCPreciseLifetimeAttr>());
    if (isImpreciseLifetime)
      LV.setARCPreciseLifetime(ARCImpreciseLifetime);
    setObjCGCLValueClass(getContext(), E, LV);
    return LV;
  }

  if (const FunctionDecl *fn = dyn_cast<FunctionDecl>(ND))
    return EmitFunctionDeclLValue(*this, E, fn);

  llvm_unreachable("Unhandled DeclRefExpr");
}

LValue CodeGenFunction::EmitUnaryOpLValue(const UnaryOperator *E) {
  // __extension__ doesn't affect lvalue-ness.
  if (E->getOpcode() == UO_Extension)
    return EmitLValue(E->getSubExpr());

  QualType ExprTy = getContext().getCanonicalType(E->getSubExpr()->getType());
  switch (E->getOpcode()) {
  default: llvm_unreachable("Unknown unary operator lvalue!");
  case UO_Deref: {
    QualType T = E->getSubExpr()->getType()->getPointeeType();
    assert(!T.isNull() && "CodeGenFunction::EmitUnaryOpLValue: Illegal type");

    LValue LV = MakeNaturalAlignAddrLValue(EmitScalarExpr(E->getSubExpr()), T);
    LV.getQuals().setAddressSpace(ExprTy.getAddressSpace());

    // We should not generate __weak write barrier on indirect reference
    // of a pointer to object; as in void foo (__weak id *param); *param = 0;
    // But, we continue to generate __strong write barrier on indirect write
    // into a pointer to object.
    if (getLangOpts().ObjC1 &&
        getLangOpts().getGC() != LangOptions::NonGC &&
        LV.isObjCWeak())
      LV.setNonGC(!E->isOBJCGCCandidate(getContext()));
    return LV;
  }
  case UO_Real:
  case UO_Imag: {
    LValue LV = EmitLValue(E->getSubExpr());
    assert(LV.isSimple() && "real/imag on non-ordinary l-value");
    llvm::Value *Addr = LV.getAddress();

    // __real is valid on scalars.  This is a faster way of testing that.
    // __imag can only produce an rvalue on scalars.
    if (E->getOpcode() == UO_Real &&
        !cast<llvm::PointerType>(Addr->getType())
           ->getElementType()->isStructTy()) {
      assert(E->getSubExpr()->getType()->isArithmeticType());
      return LV;
    }

    assert(E->getSubExpr()->getType()->isAnyComplexType());

    unsigned Idx = E->getOpcode() == UO_Imag;
    return MakeAddrLValue(Builder.CreateStructGEP(LV.getAddress(),
                                                  Idx, "idx"),
                          ExprTy);
  }
  case UO_PreInc:
  case UO_PreDec: {
    LValue LV = EmitLValue(E->getSubExpr());
    bool isInc = E->getOpcode() == UO_PreInc;
    
    if (E->getType()->isAnyComplexType())
      EmitComplexPrePostIncDec(E, LV, isInc, true/*isPre*/);
    else
      EmitScalarPrePostIncDec(E, LV, isInc, true/*isPre*/);
    return LV;
  }
  }
}

LValue CodeGenFunction::EmitStringLiteralLValue(const StringLiteral *E) {
  return MakeAddrLValue(CGM.GetAddrOfConstantStringFromLiteral(E),
                        E->getType());
}

LValue CodeGenFunction::EmitObjCEncodeExprLValue(const ObjCEncodeExpr *E) {
  return MakeAddrLValue(CGM.GetAddrOfConstantStringFromObjCEncode(E),
                        E->getType());
}

static llvm::Constant*
GetAddrOfConstantWideString(StringRef Str,
                            const char *GlobalName,
                            ASTContext &Context,
                            QualType Ty, SourceLocation Loc,
                            CodeGenModule &CGM) {

  StringLiteral *SL = StringLiteral::Create(Context,
                                            Str,
                                            StringLiteral::Wide,
                                            /*Pascal = */false,
                                            Ty, Loc);
  llvm::Constant *C = CGM.GetConstantArrayFromStringLiteral(SL);
  llvm::GlobalVariable *GV =
    new llvm::GlobalVariable(CGM.getModule(), C->getType(),
                             !CGM.getLangOpts().WritableStrings,
                             llvm::GlobalValue::PrivateLinkage,
                             C, GlobalName);
  const unsigned WideAlignment =
    Context.getTypeAlignInChars(Ty).getQuantity();
  GV->setAlignment(WideAlignment);
  return GV;
}

static void ConvertUTF8ToWideString(unsigned CharByteWidth, StringRef Source,
                                    SmallString<32>& Target) {
  Target.resize(CharByteWidth * (Source.size() + 1));
  char *ResultPtr = &Target[0];
  const UTF8 *ErrorPtr;
  bool success = ConvertUTF8toWide(CharByteWidth, Source, ResultPtr, ErrorPtr);
  (void)success;
  assert(success);
  Target.resize(ResultPtr - &Target[0]);
}

LValue CodeGenFunction::EmitPredefinedLValue(const PredefinedExpr *E) {
  switch (E->getIdentType()) {
  default:
    return EmitUnsupportedLValue(E, "predefined expression");

  case PredefinedExpr::Func:
  case PredefinedExpr::Function:
  case PredefinedExpr::LFunction:
  case PredefinedExpr::PrettyFunction: {
    unsigned IdentType = E->getIdentType();
    std::string GlobalVarName;

    switch (IdentType) {
    default: llvm_unreachable("Invalid type");
    case PredefinedExpr::Func:
      GlobalVarName = "__func__.";
      break;
    case PredefinedExpr::Function:
      GlobalVarName = "__FUNCTION__.";
      break;
    case PredefinedExpr::LFunction:
      GlobalVarName = "L__FUNCTION__.";
      break;
    case PredefinedExpr::PrettyFunction:
      GlobalVarName = "__PRETTY_FUNCTION__.";
      break;
    }

    StringRef FnName = CurFn->getName();
    if (FnName.startswith("\01"))
      FnName = FnName.substr(1);
    GlobalVarName += FnName;

    const Decl *CurDecl = CurCodeDecl;
    if (CurDecl == 0)
      CurDecl = getContext().getTranslationUnitDecl();

    std::string FunctionName =
        (isa<BlockDecl>(CurDecl)
         ? FnName.str()
         : PredefinedExpr::ComputeName((PredefinedExpr::IdentType)IdentType,
                                       CurDecl));

    const Type* ElemType = E->getType()->getArrayElementTypeNoTypeQual();
    llvm::Constant *C;
    if (ElemType->isWideCharType()) {
      SmallString<32> RawChars;
      ConvertUTF8ToWideString(
          getContext().getTypeSizeInChars(ElemType).getQuantity(),
          FunctionName, RawChars);
      C = GetAddrOfConstantWideString(RawChars,
                                      GlobalVarName.c_str(),
                                      getContext(),
                                      E->getType(),
                                      E->getLocation(),
                                      CGM);
    } else {
      C = CGM.GetAddrOfConstantCString(FunctionName,
                                       GlobalVarName.c_str(),
                                       1);
    }
    return MakeAddrLValue(C, E->getType());
  }
  }
}

/// Emit a type description suitable for use by a runtime sanitizer library. The
/// format of a type descriptor is
///
/// \code
///   { i16 TypeKind, i16 TypeInfo }
/// \endcode
///
/// followed by an array of i8 containing the type name. TypeKind is 0 for an
/// integer, 1 for a floating point value, and -1 for anything else.
llvm::Constant *CodeGenFunction::EmitCheckTypeDescriptor(QualType T) {
  // FIXME: Only emit each type's descriptor once.
  uint16_t TypeKind = -1;
  uint16_t TypeInfo = 0;

  if (T->isIntegerType()) {
    TypeKind = 0;
    TypeInfo = (llvm::Log2_32(getContext().getTypeSize(T)) << 1) |
               (T->isSignedIntegerType() ? 1 : 0);
  } else if (T->isFloatingType()) {
    TypeKind = 1;
    TypeInfo = getContext().getTypeSize(T);
  }

  // Format the type name as if for a diagnostic, including quotes and
  // optionally an 'aka'.
  SmallString<32> Buffer;
  CGM.getDiags().ConvertArgToString(DiagnosticsEngine::ak_qualtype,
                                    (intptr_t)T.getAsOpaquePtr(),
                                    0, 0, 0, 0, 0, 0, Buffer,
                                    ArrayRef<intptr_t>());

  llvm::Constant *Components[] = {
    Builder.getInt16(TypeKind), Builder.getInt16(TypeInfo),
    llvm::ConstantDataArray::getString(getLLVMContext(), Buffer)
  };
  llvm::Constant *Descriptor = llvm::ConstantStruct::getAnon(Components);

  llvm::GlobalVariable *GV =
    new llvm::GlobalVariable(CGM.getModule(), Descriptor->getType(),
                             /*isConstant=*/true,
                             llvm::GlobalVariable::PrivateLinkage,
                             Descriptor);
  GV->setUnnamedAddr(true);
  return GV;
}

llvm::Value *CodeGenFunction::EmitCheckValue(llvm::Value *V) {
  llvm::Type *TargetTy = IntPtrTy;

  // Floating-point types which fit into intptr_t are bitcast to integers
  // and then passed directly (after zero-extension, if necessary).
  if (V->getType()->isFloatingPointTy()) {
    unsigned Bits = V->getType()->getPrimitiveSizeInBits();
    if (Bits <= TargetTy->getIntegerBitWidth())
      V = Builder.CreateBitCast(V, llvm::Type::getIntNTy(getLLVMContext(),
                                                         Bits));
  }

  // Integers which fit in intptr_t are zero-extended and passed directly.
  if (V->getType()->isIntegerTy() &&
      V->getType()->getIntegerBitWidth() <= TargetTy->getIntegerBitWidth())
    return Builder.CreateZExt(V, TargetTy);

  // Pointers are passed directly, everything else is passed by address.
  if (!V->getType()->isPointerTy()) {
    llvm::Value *Ptr = CreateTempAlloca(V->getType());
    Builder.CreateStore(V, Ptr);
    V = Ptr;
  }
  return Builder.CreatePtrToInt(V, TargetTy);
}

/// \brief Emit a representation of a SourceLocation for passing to a handler
/// in a sanitizer runtime library. The format for this data is:
/// \code
///   struct SourceLocation {
///     const char *Filename;
///     int32_t Line, Column;
///   };
/// \endcode
/// For an invalid SourceLocation, the Filename pointer is null.
llvm::Constant *CodeGenFunction::EmitCheckSourceLocation(SourceLocation Loc) {
  PresumedLoc PLoc = getContext().getSourceManager().getPresumedLoc(Loc);

  llvm::Constant *Data[] = {
    // FIXME: Only emit each file name once.
    PLoc.isValid() ? cast<llvm::Constant>(
                       Builder.CreateGlobalStringPtr(PLoc.getFilename()))
                   : llvm::Constant::getNullValue(Int8PtrTy),
    Builder.getInt32(PLoc.getLine()),
    Builder.getInt32(PLoc.getColumn())
  };

  return llvm::ConstantStruct::getAnon(Data);
}

void CodeGenFunction::EmitCheck(llvm::Value *Checked, StringRef CheckName,
                                ArrayRef<llvm::Constant *> StaticArgs,
                                ArrayRef<llvm::Value *> DynamicArgs,
                                CheckRecoverableKind RecoverKind) {
  assert(SanOpts != &SanitizerOptions::Disabled);

  if (CGM.getCodeGenOpts().SanitizeUndefinedTrapOnError) {
    assert (RecoverKind != CRK_AlwaysRecoverable &&
            "Runtime call required for AlwaysRecoverable kind!");
    return EmitTrapCheck(Checked);
  }

  llvm::BasicBlock *Cont = createBasicBlock("cont");

  llvm::BasicBlock *Handler = createBasicBlock("handler." + CheckName);

  llvm::Instruction *Branch = Builder.CreateCondBr(Checked, Cont, Handler);

  // Give hint that we very much don't expect to execute the handler
  // Value chosen to match UR_NONTAKEN_WEIGHT, see BranchProbabilityInfo.cpp
  llvm::MDBuilder MDHelper(getLLVMContext());
  llvm::MDNode *Node = MDHelper.createBranchWeights((1U << 20) - 1, 1);
  Branch->setMetadata(llvm::LLVMContext::MD_prof, Node);

  EmitBlock(Handler);

  llvm::Constant *Info = llvm::ConstantStruct::getAnon(StaticArgs);
  llvm::GlobalValue *InfoPtr =
      new llvm::GlobalVariable(CGM.getModule(), Info->getType(), false,
                               llvm::GlobalVariable::PrivateLinkage, Info);
  InfoPtr->setUnnamedAddr(true);

  SmallVector<llvm::Value *, 4> Args;
  SmallVector<llvm::Type *, 4> ArgTypes;
  Args.reserve(DynamicArgs.size() + 1);
  ArgTypes.reserve(DynamicArgs.size() + 1);

  // Handler functions take an i8* pointing to the (handler-specific) static
  // information block, followed by a sequence of intptr_t arguments
  // representing operand values.
  Args.push_back(Builder.CreateBitCast(InfoPtr, Int8PtrTy));
  ArgTypes.push_back(Int8PtrTy);
  for (size_t i = 0, n = DynamicArgs.size(); i != n; ++i) {
    Args.push_back(EmitCheckValue(DynamicArgs[i]));
    ArgTypes.push_back(IntPtrTy);
  }

  bool Recover = (RecoverKind == CRK_AlwaysRecoverable) ||
                 ((RecoverKind == CRK_Recoverable) &&
                   CGM.getCodeGenOpts().SanitizeRecover);

  llvm::FunctionType *FnType =
    llvm::FunctionType::get(CGM.VoidTy, ArgTypes, false);
  llvm::AttrBuilder B;
  if (!Recover) {
    B.addAttribute(llvm::Attribute::NoReturn)
     .addAttribute(llvm::Attribute::NoUnwind);
  }
  B.addAttribute(llvm::Attribute::UWTable);

  // Checks that have two variants use a suffix to differentiate them
  bool NeedsAbortSuffix = (RecoverKind != CRK_Unrecoverable) &&
                           !CGM.getCodeGenOpts().SanitizeRecover;
  std::string FunctionName = ("__ubsan_handle_" + CheckName +
                              (NeedsAbortSuffix? "_abort" : "")).str();
  llvm::Value *Fn =
    CGM.CreateRuntimeFunction(FnType, FunctionName,
                              llvm::AttributeSet::get(getLLVMContext(),
                                              llvm::AttributeSet::FunctionIndex,
                                                      B));
  llvm::CallInst *HandlerCall = EmitNounwindRuntimeCall(Fn, Args);
  if (Recover) {
    Builder.CreateBr(Cont);
  } else {
    HandlerCall->setDoesNotReturn();
    Builder.CreateUnreachable();
  }

  EmitBlock(Cont);
}

void CodeGenFunction::EmitTrapCheck(llvm::Value *Checked) {
  llvm::BasicBlock *Cont = createBasicBlock("cont");

  // If we're optimizing, collapse all calls to trap down to just one per
  // function to save on code size.
  if (!CGM.getCodeGenOpts().OptimizationLevel || !TrapBB) {
    TrapBB = createBasicBlock("trap");
    Builder.CreateCondBr(Checked, Cont, TrapBB);
    EmitBlock(TrapBB);
    llvm::Value *F = CGM.getIntrinsic(llvm::Intrinsic::trap);
    llvm::CallInst *TrapCall = Builder.CreateCall(F);
    TrapCall->setDoesNotReturn();
    TrapCall->setDoesNotThrow();
    Builder.CreateUnreachable();
  } else {
    Builder.CreateCondBr(Checked, Cont, TrapBB);
  }

  EmitBlock(Cont);
}

/// isSimpleArrayDecayOperand - If the specified expr is a simple decay from an
/// array to pointer, return the array subexpression.
static const Expr *isSimpleArrayDecayOperand(const Expr *E) {
  // If this isn't just an array->pointer decay, bail out.
  const CastExpr *CE = dyn_cast<CastExpr>(E);
  if (CE == 0 || CE->getCastKind() != CK_ArrayToPointerDecay)
    return 0;
  
  // If this is a decay from variable width array, bail out.
  const Expr *SubExpr = CE->getSubExpr();
  if (SubExpr->getType()->isVariableArrayType())
    return 0;
  
  return SubExpr;
}

LValue CodeGenFunction::EmitArraySubscriptExpr(const ArraySubscriptExpr *E,
                                               bool Accessed) {
  // The index must always be an integer, which is not an aggregate.  Emit it.
  llvm::Value *Idx = EmitScalarExpr(E->getIdx());
  QualType IdxTy  = E->getIdx()->getType();
  bool IdxSigned = IdxTy->isSignedIntegerOrEnumerationType();

  if (SanOpts->Bounds)
    EmitBoundsCheck(E, E->getBase(), Idx, IdxTy, Accessed);

  // If the base is a vector type, then we are forming a vector element lvalue
  // with this subscript.
  if (E->getBase()->getType()->isVectorType()) {
    // Emit the vector as an lvalue to get its address.
    LValue LHS = EmitLValue(E->getBase());
    assert(LHS.isSimple() && "Can only subscript lvalue vectors here!");
    Idx = Builder.CreateIntCast(Idx, Int32Ty, IdxSigned, "vidx");
    return LValue::MakeVectorElt(LHS.getAddress(), Idx,
                                 E->getBase()->getType(), LHS.getAlignment());
  }

  // Extend or truncate the index type to 32 or 64-bits.
  if (Idx->getType() != IntPtrTy)
    Idx = Builder.CreateIntCast(Idx, IntPtrTy, IdxSigned, "idxprom");

  // We know that the pointer points to a type of the correct size, unless the
  // size is a VLA or Objective-C interface.
  llvm::Value *Address = 0;
  CharUnits ArrayAlignment;
  if (const VariableArrayType *vla =
        getContext().getAsVariableArrayType(E->getType())) {
    // The base must be a pointer, which is not an aggregate.  Emit
    // it.  It needs to be emitted first in case it's what captures
    // the VLA bounds.
    Address = EmitScalarExpr(E->getBase());

    // The element count here is the total number of non-VLA elements.
    llvm::Value *numElements = getVLASize(vla).first;

    // Effectively, the multiply by the VLA size is part of the GEP.
    // GEP indexes are signed, and scaling an index isn't permitted to
    // signed-overflow, so we use the same semantics for our explicit
    // multiply.  We suppress this if overflow is not undefined behavior.
    if (getLangOpts().isSignedOverflowDefined()) {
      Idx = Builder.CreateMul(Idx, numElements);
      Address = Builder.CreateGEP(Address, Idx, "arrayidx");
    } else {
      Idx = Builder.CreateNSWMul(Idx, numElements);
      Address = Builder.CreateInBoundsGEP(Address, Idx, "arrayidx");
    }
  } else if (const ObjCObjectType *OIT = E->getType()->getAs<ObjCObjectType>()){
    // Indexing over an interface, as in "NSString *P; P[4];"
    llvm::Value *InterfaceSize =
      llvm::ConstantInt::get(Idx->getType(),
          getContext().getTypeSizeInChars(OIT).getQuantity());

    Idx = Builder.CreateMul(Idx, InterfaceSize);

    // The base must be a pointer, which is not an aggregate.  Emit it.
    llvm::Value *Base = EmitScalarExpr(E->getBase());
    Address = EmitCastToVoidPtr(Base);
    Address = Builder.CreateGEP(Address, Idx, "arrayidx");
    Address = Builder.CreateBitCast(Address, Base->getType());
  } else if (const Expr *Array = isSimpleArrayDecayOperand(E->getBase())) {
    // If this is A[i] where A is an array, the frontend will have decayed the
    // base to be a ArrayToPointerDecay implicit cast.  While correct, it is
    // inefficient at -O0 to emit a "gep A, 0, 0" when codegen'ing it, then a
    // "gep x, i" here.  Emit one "gep A, 0, i".
    assert(Array->getType()->isArrayType() &&
           "Array to pointer decay must have array source type!");
    LValue ArrayLV;
    // For simple multidimensional array indexing, set the 'accessed' flag for
    // better bounds-checking of the base expression.
    if (const ArraySubscriptExpr *ASE = dyn_cast<ArraySubscriptExpr>(Array))
      ArrayLV = EmitArraySubscriptExpr(ASE, /*Accessed*/ true);
    else
      ArrayLV = EmitLValue(Array);
    llvm::Value *ArrayPtr = ArrayLV.getAddress();
    llvm::Value *Zero = llvm::ConstantInt::get(Int32Ty, 0);
    llvm::Value *Args[] = { Zero, Idx };
    
    // Propagate the alignment from the array itself to the result.
    ArrayAlignment = ArrayLV.getAlignment();

    if (getLangOpts().isSignedOverflowDefined())
      Address = Builder.CreateGEP(ArrayPtr, Args, "arrayidx");
    else
      Address = Builder.CreateInBoundsGEP(ArrayPtr, Args, "arrayidx");
  } else {
    // The base must be a pointer, which is not an aggregate.  Emit it.
    llvm::Value *Base = EmitScalarExpr(E->getBase());
    if (getLangOpts().isSignedOverflowDefined())
      Address = Builder.CreateGEP(Base, Idx, "arrayidx");
    else
      Address = Builder.CreateInBoundsGEP(Base, Idx, "arrayidx");
  }

  QualType T = E->getBase()->getType()->getPointeeType();
  assert(!T.isNull() &&
         "CodeGenFunction::EmitArraySubscriptExpr(): Illegal base type");

  
  // Limit the alignment to that of the result type.
  LValue LV;
  if (!ArrayAlignment.isZero()) {
    CharUnits Align = getContext().getTypeAlignInChars(T);
    ArrayAlignment = std::min(Align, ArrayAlignment);
    LV = MakeAddrLValue(Address, T, ArrayAlignment);
  } else {
    LV = MakeNaturalAlignAddrLValue(Address, T);
  }

  LV.getQuals().setAddressSpace(E->getBase()->getType().getAddressSpace());

  if (getLangOpts().ObjC1 &&
      getLangOpts().getGC() != LangOptions::NonGC) {
    LV.setNonGC(!E->isOBJCGCCandidate(getContext()));
    setObjCGCLValueClass(getContext(), E, LV);
  }
  return LV;
}

static
llvm::Constant *GenerateConstantVector(CGBuilderTy &Builder,
                                       SmallVector<unsigned, 4> &Elts) {
  SmallVector<llvm::Constant*, 4> CElts;
  for (unsigned i = 0, e = Elts.size(); i != e; ++i)
    CElts.push_back(Builder.getInt32(Elts[i]));

  return llvm::ConstantVector::get(CElts);
}

LValue CodeGenFunction::
EmitExtVectorElementExpr(const ExtVectorElementExpr *E) {
  // Emit the base vector as an l-value.
  LValue Base;

  // ExtVectorElementExpr's base can either be a vector or pointer to vector.
  if (E->isArrow()) {
    // If it is a pointer to a vector, emit the address and form an lvalue with
    // it.
    llvm::Value *Ptr = EmitScalarExpr(E->getBase());
    const PointerType *PT = E->getBase()->getType()->getAs<PointerType>();
    Base = MakeAddrLValue(Ptr, PT->getPointeeType());
    Base.getQuals().removeObjCGCAttr();
  } else if (E->getBase()->isGLValue()) {
    // Otherwise, if the base is an lvalue ( as in the case of foo.x.x),
    // emit the base as an lvalue.
    assert(E->getBase()->getType()->isVectorType());
    Base = EmitLValue(E->getBase());
  } else {
    // Otherwise, the base is a normal rvalue (as in (V+V).x), emit it as such.
    assert(E->getBase()->getType()->isVectorType() &&
           "Result must be a vector");
    llvm::Value *Vec = EmitScalarExpr(E->getBase());
    
    // Store the vector to memory (because LValue wants an address).
    llvm::Value *VecMem = CreateMemTemp(E->getBase()->getType());
    Builder.CreateStore(Vec, VecMem);
    Base = MakeAddrLValue(VecMem, E->getBase()->getType());
  }

  QualType type =
    E->getType().withCVRQualifiers(Base.getQuals().getCVRQualifiers());
  
  // Encode the element access list into a vector of unsigned indices.
  SmallVector<unsigned, 4> Indices;
  E->getEncodedElementAccess(Indices);

  if (Base.isSimple()) {
    llvm::Constant *CV = GenerateConstantVector(Builder, Indices);
    return LValue::MakeExtVectorElt(Base.getAddress(), CV, type,
                                    Base.getAlignment());
  }
  assert(Base.isExtVectorElt() && "Can only subscript lvalue vec elts here!");

  llvm::Constant *BaseElts = Base.getExtVectorElts();
  SmallVector<llvm::Constant *, 4> CElts;

  for (unsigned i = 0, e = Indices.size(); i != e; ++i)
    CElts.push_back(BaseElts->getAggregateElement(Indices[i]));
  llvm::Constant *CV = llvm::ConstantVector::get(CElts);
  return LValue::MakeExtVectorElt(Base.getExtVectorAddr(), CV, type,
                                  Base.getAlignment());
}

LValue CodeGenFunction::EmitMemberExpr(const MemberExpr *E) {
  Expr *BaseExpr = E->getBase();

  // If this is s.x, emit s as an lvalue.  If it is s->x, emit s as a scalar.
  LValue BaseLV;
  if (E->isArrow()) {
    llvm::Value *Ptr = EmitScalarExpr(BaseExpr);
    QualType PtrTy = BaseExpr->getType()->getPointeeType();
    EmitTypeCheck(TCK_MemberAccess, E->getExprLoc(), Ptr, PtrTy);
    BaseLV = MakeNaturalAlignAddrLValue(Ptr, PtrTy);
  } else
    BaseLV = EmitCheckedLValue(BaseExpr, TCK_MemberAccess);

  NamedDecl *ND = E->getMemberDecl();
  if (FieldDecl *Field = dyn_cast<FieldDecl>(ND)) {
    LValue LV = EmitLValueForField(BaseLV, Field);
    setObjCGCLValueClass(getContext(), E, LV);
    return LV;
  }
  
  if (VarDecl *VD = dyn_cast<VarDecl>(ND))
    return EmitGlobalVarDeclLValue(*this, E, VD);

  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(ND))
    return EmitFunctionDeclLValue(*this, E, FD);

  llvm_unreachable("Unhandled member declaration!");
}

LValue CodeGenFunction::EmitLValueForField(LValue base,
                                           const FieldDecl *field) {
  if (field->isBitField()) {
    const CGRecordLayout &RL =
      CGM.getTypes().getCGRecordLayout(field->getParent());
    const CGBitFieldInfo &Info = RL.getBitFieldInfo(field);
    llvm::Value *Addr = base.getAddress();
    unsigned Idx = RL.getLLVMFieldNo(field);
    if (Idx != 0)
      // For structs, we GEP to the field that the record layout suggests.
      Addr = Builder.CreateStructGEP(Addr, Idx, field->getName());
    // Get the access type.
    llvm::Type *PtrTy = llvm::Type::getIntNPtrTy(
      getLLVMContext(), Info.StorageSize,
      CGM.getContext().getTargetAddressSpace(base.getType()));
    if (Addr->getType() != PtrTy)
      Addr = Builder.CreateBitCast(Addr, PtrTy);

    QualType fieldType =
      field->getType().withCVRQualifiers(base.getVRQualifiers());
    return LValue::MakeBitfield(Addr, Info, fieldType, base.getAlignment());
  }

  const RecordDecl *rec = field->getParent();
  QualType type = field->getType();
  CharUnits alignment = getContext().getDeclAlign(field);

  // FIXME: It should be impossible to have an LValue without alignment for a
  // complete type.
  if (!base.getAlignment().isZero())
    alignment = std::min(alignment, base.getAlignment());

  bool mayAlias = rec->hasAttr<MayAliasAttr>();

  llvm::Value *addr = base.getAddress();
  unsigned cvr = base.getVRQualifiers();
  bool TBAAPath = CGM.getCodeGenOpts().StructPathTBAA;
  if (rec->isUnion()) {
    // For unions, there is no pointer adjustment.
    assert(!type->isReferenceType() && "union has reference member");
    // TODO: handle path-aware TBAA for union.
    TBAAPath = false;
  } else {
    // For structs, we GEP to the field that the record layout suggests.
    unsigned idx = CGM.getTypes().getCGRecordLayout(rec).getLLVMFieldNo(field);
    addr = Builder.CreateStructGEP(addr, idx, field->getName());

    // If this is a reference field, load the reference right now.
    if (const ReferenceType *refType = type->getAs<ReferenceType>()) {
      llvm::LoadInst *load = Builder.CreateLoad(addr, "ref");
      if (cvr & Qualifiers::Volatile) load->setVolatile(true);
      load->setAlignment(alignment.getQuantity());

      // Loading the reference will disable path-aware TBAA.
      TBAAPath = false;
      if (CGM.shouldUseTBAA()) {
        llvm::MDNode *tbaa;
        if (mayAlias)
          tbaa = CGM.getTBAAInfo(getContext().CharTy);
        else
          tbaa = CGM.getTBAAInfo(type);
        CGM.DecorateInstruction(load, tbaa);
      }

      addr = load;
      mayAlias = false;
      type = refType->getPointeeType();
      if (type->isIncompleteType())
        alignment = CharUnits();
      else
        alignment = getContext().getTypeAlignInChars(type);
      cvr = 0; // qualifiers don't recursively apply to referencee
    }
  }
  
  // Make sure that the address is pointing to the right type.  This is critical
  // for both unions and structs.  A union needs a bitcast, a struct element
  // will need a bitcast if the LLVM type laid out doesn't match the desired
  // type.
  addr = EmitBitCastOfLValueToProperType(*this, addr,
                                         CGM.getTypes().ConvertTypeForMem(type),
                                         field->getName());

  if (field->hasAttr<AnnotateAttr>())
    addr = EmitFieldAnnotations(field, addr);

  LValue LV = MakeAddrLValue(addr, type, alignment);
  LV.getQuals().addCVRQualifiers(cvr);
  if (TBAAPath) {
    const ASTRecordLayout &Layout =
        getContext().getASTRecordLayout(field->getParent());
    // Set the base type to be the base type of the base LValue and
    // update offset to be relative to the base type.
    LV.setTBAABaseType(mayAlias ? getContext().CharTy : base.getTBAABaseType());
    LV.setTBAAOffset(mayAlias ? 0 : base.getTBAAOffset() +
                     Layout.getFieldOffset(field->getFieldIndex()) /
                                           getContext().getCharWidth());
  }

  // __weak attribute on a field is ignored.
  if (LV.getQuals().getObjCGCAttr() == Qualifiers::Weak)
    LV.getQuals().removeObjCGCAttr();

  // Fields of may_alias structs act like 'char' for TBAA purposes.
  // FIXME: this should get propagated down through anonymous structs
  // and unions.
  if (mayAlias && LV.getTBAAInfo())
    LV.setTBAAInfo(CGM.getTBAAInfo(getContext().CharTy));

  return LV;
}

LValue 
CodeGenFunction::EmitLValueForFieldInitialization(LValue Base, 
                                                  const FieldDecl *Field) {
  QualType FieldType = Field->getType();
  
  if (!FieldType->isReferenceType())
    return EmitLValueForField(Base, Field);

  const CGRecordLayout &RL =
    CGM.getTypes().getCGRecordLayout(Field->getParent());
  unsigned idx = RL.getLLVMFieldNo(Field);
  llvm::Value *V = Builder.CreateStructGEP(Base.getAddress(), idx);
  assert(!FieldType.getObjCGCAttr() && "fields cannot have GC attrs");

  // Make sure that the address is pointing to the right type.  This is critical
  // for both unions and structs.  A union needs a bitcast, a struct element
  // will need a bitcast if the LLVM type laid out doesn't match the desired
  // type.
  llvm::Type *llvmType = ConvertTypeForMem(FieldType);
  V = EmitBitCastOfLValueToProperType(*this, V, llvmType, Field->getName());

  CharUnits Alignment = getContext().getDeclAlign(Field);

  // FIXME: It should be impossible to have an LValue without alignment for a
  // complete type.
  if (!Base.getAlignment().isZero())
    Alignment = std::min(Alignment, Base.getAlignment());

  return MakeAddrLValue(V, FieldType, Alignment);
}

LValue CodeGenFunction::EmitCompoundLiteralLValue(const CompoundLiteralExpr *E){
  if (E->isFileScope()) {
    llvm::Value *GlobalPtr = CGM.GetAddrOfConstantCompoundLiteral(E);
    return MakeAddrLValue(GlobalPtr, E->getType());
  }
  if (E->getType()->isVariablyModifiedType())
    // make sure to emit the VLA size.
    EmitVariablyModifiedType(E->getType());
  
  llvm::Value *DeclPtr = CreateMemTemp(E->getType(), ".compoundliteral");
  const Expr *InitExpr = E->getInitializer();
  LValue Result = MakeAddrLValue(DeclPtr, E->getType());

  EmitAnyExprToMem(InitExpr, DeclPtr, E->getType().getQualifiers(),
                   /*Init*/ true);

  return Result;
}

LValue CodeGenFunction::EmitInitListLValue(const InitListExpr *E) {
  if (!E->isGLValue())
    // Initializing an aggregate temporary in C++11: T{...}.
    return EmitAggExprToLValue(E);

  // An lvalue initializer list must be initializing a reference.
  assert(E->getNumInits() == 1 && "reference init with multiple values");
  return EmitLValue(E->getInit(0));
}

LValue CodeGenFunction::
EmitConditionalOperatorLValue(const AbstractConditionalOperator *expr) {
  if (!expr->isGLValue()) {
    // ?: here should be an aggregate.
    assert(hasAggregateEvaluationKind(expr->getType()) &&
           "Unexpected conditional operator!");
    return EmitAggExprToLValue(expr);
  }

  OpaqueValueMapping binding(*this, expr);

  const Expr *condExpr = expr->getCond();
  bool CondExprBool;
  if (ConstantFoldsToSimpleInteger(condExpr, CondExprBool)) {
    const Expr *live = expr->getTrueExpr(), *dead = expr->getFalseExpr();
    if (!CondExprBool) std::swap(live, dead);

    if (!ContainsLabel(dead))
      return EmitLValue(live);
  }

  llvm::BasicBlock *lhsBlock = createBasicBlock("cond.true");
  llvm::BasicBlock *rhsBlock = createBasicBlock("cond.false");
  llvm::BasicBlock *contBlock = createBasicBlock("cond.end");

  ConditionalEvaluation eval(*this);
  EmitBranchOnBoolExpr(condExpr, lhsBlock, rhsBlock);
    
  // Any temporaries created here are conditional.
  EmitBlock(lhsBlock);
  eval.begin(*this);
  LValue lhs = EmitLValue(expr->getTrueExpr());
  eval.end(*this);
    
  if (!lhs.isSimple())
    return EmitUnsupportedLValue(expr, "conditional operator");

  lhsBlock = Builder.GetInsertBlock();
  Builder.CreateBr(contBlock);
    
  // Any temporaries created here are conditional.
  EmitBlock(rhsBlock);
  eval.begin(*this);
  LValue rhs = EmitLValue(expr->getFalseExpr());
  eval.end(*this);
  if (!rhs.isSimple())
    return EmitUnsupportedLValue(expr, "conditional operator");
  rhsBlock = Builder.GetInsertBlock();

  EmitBlock(contBlock);

  llvm::PHINode *phi = Builder.CreatePHI(lhs.getAddress()->getType(), 2,
                                         "cond-lvalue");
  phi->addIncoming(lhs.getAddress(), lhsBlock);
  phi->addIncoming(rhs.getAddress(), rhsBlock);
  return MakeAddrLValue(phi, expr->getType());
}

/// EmitCastLValue - Casts are never lvalues unless that cast is to a reference
/// type. If the cast is to a reference, we can have the usual lvalue result,
/// otherwise if a cast is needed by the code generator in an lvalue context,
/// then it must mean that we need the address of an aggregate in order to
/// access one of its members.  This can happen for all the reasons that casts
/// are permitted with aggregate result, including noop aggregate casts, and
/// cast from scalar to union.
LValue CodeGenFunction::EmitCastLValue(const CastExpr *E) {
  switch (E->getCastKind()) {
  case CK_ToVoid:
    return EmitUnsupportedLValue(E, "unexpected cast lvalue");

  case CK_Dependent:
    llvm_unreachable("dependent cast kind in IR gen!");

  case CK_BuiltinFnToFnPtr:
    llvm_unreachable("builtin functions are handled elsewhere");

  // These two casts are currently treated as no-ops, although they could
  // potentially be real operations depending on the target's ABI.
  case CK_NonAtomicToAtomic:
  case CK_AtomicToNonAtomic:

  case CK_NoOp:
  case CK_LValueToRValue:
    if (!E->getSubExpr()->Classify(getContext()).isPRValue() 
        || E->getType()->isRecordType())
      return EmitLValue(E->getSubExpr());
    // Fall through to synthesize a temporary.

  case CK_BitCast:
  case CK_ArrayToPointerDecay:
  case CK_FunctionToPointerDecay:
  case CK_NullToMemberPointer:
  case CK_NullToPointer:
  case CK_IntegralToPointer:
  case CK_PointerToIntegral:
  case CK_PointerToBoolean:
  case CK_VectorSplat:
  case CK_IntegralCast:
  case CK_IntegralToBoolean:
  case CK_IntegralToFloating:
  case CK_FloatingToIntegral:
  case CK_FloatingToBoolean:
  case CK_FloatingCast:
  case CK_FloatingRealToComplex:
  case CK_FloatingComplexToReal:
  case CK_FloatingComplexToBoolean:
  case CK_FloatingComplexCast:
  case CK_FloatingComplexToIntegralComplex:
  case CK_IntegralRealToComplex:
  case CK_IntegralComplexToReal:
  case CK_IntegralComplexToBoolean:
  case CK_IntegralComplexCast:
  case CK_IntegralComplexToFloatingComplex:
  case CK_DerivedToBaseMemberPointer:
  case CK_BaseToDerivedMemberPointer:
  case CK_MemberPointerToBoolean:
  case CK_ReinterpretMemberPointer:
  case CK_AnyPointerToBlockPointerCast:
  case CK_ARCProduceObject:
  case CK_ARCConsumeObject:
  case CK_ARCReclaimReturnedObject:
  case CK_ARCExtendBlockObject: 
  case CK_CopyAndAutoreleaseBlockObject: {
    // These casts only produce lvalues when we're binding a reference to a 
    // temporary realized from a (converted) pure rvalue. Emit the expression
    // as a value, copy it into a temporary, and return an lvalue referring to
    // that temporary.
    llvm::Value *V = CreateMemTemp(E->getType(), "ref.temp");
    EmitAnyExprToMem(E, V, E->getType().getQualifiers(), false);
    return MakeAddrLValue(V, E->getType());
  }

  case CK_Dynamic: {
    LValue LV = EmitLValue(E->getSubExpr());
    llvm::Value *V = LV.getAddress();
    const CXXDynamicCastExpr *DCE = cast<CXXDynamicCastExpr>(E);
    return MakeAddrLValue(EmitDynamicCast(V, DCE), E->getType());
  }

  case CK_ConstructorConversion:
  case CK_UserDefinedConversion:
  case CK_CPointerToObjCPointerCast:
  case CK_BlockPointerToObjCPointerCast:
    return EmitLValue(E->getSubExpr());
  
  case CK_UncheckedDerivedToBase:
  case CK_DerivedToBase: {
    const RecordType *DerivedClassTy = 
      E->getSubExpr()->getType()->getAs<RecordType>();
    CXXRecordDecl *DerivedClassDecl = 
      cast<CXXRecordDecl>(DerivedClassTy->getDecl());
    
    LValue LV = EmitLValue(E->getSubExpr());
    llvm::Value *This = LV.getAddress();
    
    // Perform the derived-to-base conversion
    llvm::Value *Base = 
      GetAddressOfBaseClass(This, DerivedClassDecl, 
                            E->path_begin(), E->path_end(),
                            /*NullCheckValue=*/false);
    
    return MakeAddrLValue(Base, E->getType());
  }
  case CK_ToUnion:
    return EmitAggExprToLValue(E);
  case CK_BaseToDerived: {
    const RecordType *DerivedClassTy = E->getType()->getAs<RecordType>();
    CXXRecordDecl *DerivedClassDecl = 
      cast<CXXRecordDecl>(DerivedClassTy->getDecl());
    
    LValue LV = EmitLValue(E->getSubExpr());

    // C++11 [expr.static.cast]p2: Behavior is undefined if a downcast is
    // performed and the object is not of the derived type.
    if (SanitizePerformTypeCheck)
      EmitTypeCheck(TCK_DowncastReference, E->getExprLoc(),
                    LV.getAddress(), E->getType());

    // Perform the base-to-derived conversion
    llvm::Value *Derived = 
      GetAddressOfDerivedClass(LV.getAddress(), DerivedClassDecl, 
                               E->path_begin(), E->path_end(),
                               /*NullCheckValue=*/false);
    
    return MakeAddrLValue(Derived, E->getType());
  }
  case CK_LValueBitCast: {
    // This must be a reinterpret_cast (or c-style equivalent).
    const ExplicitCastExpr *CE = cast<ExplicitCastExpr>(E);
    
    LValue LV = EmitLValue(E->getSubExpr());
    llvm::Value *V = Builder.CreateBitCast(LV.getAddress(),
                                           ConvertType(CE->getTypeAsWritten()));
    return MakeAddrLValue(V, E->getType());
  }
  case CK_ObjCObjectLValueCast: {
    LValue LV = EmitLValue(E->getSubExpr());
    QualType ToType = getContext().getLValueReferenceType(E->getType());
    llvm::Value *V = Builder.CreateBitCast(LV.getAddress(), 
                                           ConvertType(ToType));
    return MakeAddrLValue(V, E->getType());
  }
  case CK_ZeroToOCLEvent:
    llvm_unreachable("NULL to OpenCL event lvalue cast is not valid");
  }
  
  llvm_unreachable("Unhandled lvalue cast kind?");
}

LValue CodeGenFunction::EmitNullInitializationLValue(
                                              const CXXScalarValueInitExpr *E) {
  QualType Ty = E->getType();
  LValue LV = MakeAddrLValue(CreateMemTemp(Ty), Ty);
  EmitNullInitialization(LV.getAddress(), Ty);
  return LV;
}

LValue CodeGenFunction::EmitOpaqueValueLValue(const OpaqueValueExpr *e) {
  assert(OpaqueValueMappingData::shouldBindAsLValue(e));
  return getOpaqueLValueMapping(e);
}

LValue CodeGenFunction::EmitMaterializeTemporaryExpr(
                                           const MaterializeTemporaryExpr *E) {
  RValue RV = EmitReferenceBindingToExpr(E, /*InitializedDecl=*/0);
  return MakeAddrLValue(RV.getScalarVal(), E->getType());
}

RValue CodeGenFunction::EmitRValueForField(LValue LV,
                                           const FieldDecl *FD) {
  QualType FT = FD->getType();
  LValue FieldLV = EmitLValueForField(LV, FD);
  switch (getEvaluationKind(FT)) {
  case TEK_Complex:
    return RValue::getComplex(EmitLoadOfComplex(FieldLV));
  case TEK_Aggregate:
    return FieldLV.asAggregateRValue();
  case TEK_Scalar:
    return EmitLoadOfLValue(FieldLV);
  }
  llvm_unreachable("bad evaluation kind");
}

//===--------------------------------------------------------------------===//
//                             Expression Emission
//===--------------------------------------------------------------------===//

RValue CodeGenFunction::EmitCallExpr(const CallExpr *E, 
                                     ReturnValueSlot ReturnValue) {
  if (CGDebugInfo *DI = getDebugInfo()) {
    SourceLocation Loc = E->getLocStart();
    // Force column info to be generated so we can differentiate
    // multiple call sites on the same line in the debug info.
    const FunctionDecl* Callee = E->getDirectCallee();
    bool ForceColumnInfo = Callee && Callee->isInlineSpecified();
    DI->EmitLocation(Builder, Loc, ForceColumnInfo);
  }

  // Builtins never have block type.
  if (E->getCallee()->getType()->isBlockPointerType())
    return EmitBlockCallExpr(E, ReturnValue);

  if (const CXXMemberCallExpr *CE = dyn_cast<CXXMemberCallExpr>(E))
    return EmitCXXMemberCallExpr(CE, ReturnValue);

  if (const CUDAKernelCallExpr *CE = dyn_cast<CUDAKernelCallExpr>(E))
    return EmitCUDAKernelCallExpr(CE, ReturnValue);

  const Decl *TargetDecl = E->getCalleeDecl();
  if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(TargetDecl)) {
    if (unsigned builtinID = FD->getBuiltinID())
      return EmitBuiltinExpr(FD, builtinID, E);
  }

  if (const CXXOperatorCallExpr *CE = dyn_cast<CXXOperatorCallExpr>(E))
    if (const CXXMethodDecl *MD = dyn_cast_or_null<CXXMethodDecl>(TargetDecl))
      return EmitCXXOperatorMemberCallExpr(CE, MD, ReturnValue);

  if (const CXXPseudoDestructorExpr *PseudoDtor 
          = dyn_cast<CXXPseudoDestructorExpr>(E->getCallee()->IgnoreParens())) {
    QualType DestroyedType = PseudoDtor->getDestroyedType();
    if (getLangOpts().ObjCAutoRefCount &&
        DestroyedType->isObjCLifetimeType() &&
        (DestroyedType.getObjCLifetime() == Qualifiers::OCL_Strong ||
         DestroyedType.getObjCLifetime() == Qualifiers::OCL_Weak)) {
      // Automatic Reference Counting:
      //   If the pseudo-expression names a retainable object with weak or
      //   strong lifetime, the object shall be released.
      Expr *BaseExpr = PseudoDtor->getBase();
      llvm::Value *BaseValue = NULL;
      Qualifiers BaseQuals;
      
      // If this is s.x, emit s as an lvalue. If it is s->x, emit s as a scalar.
      if (PseudoDtor->isArrow()) {
        BaseValue = EmitScalarExpr(BaseExpr);
        const PointerType *PTy = BaseExpr->getType()->getAs<PointerType>();
        BaseQuals = PTy->getPointeeType().getQualifiers();
      } else {
        LValue BaseLV = EmitLValue(BaseExpr);
        BaseValue = BaseLV.getAddress();
        QualType BaseTy = BaseExpr->getType();
        BaseQuals = BaseTy.getQualifiers();
      }
          
      switch (PseudoDtor->getDestroyedType().getObjCLifetime()) {
      case Qualifiers::OCL_None:
      case Qualifiers::OCL_ExplicitNone:
      case Qualifiers::OCL_Autoreleasing:
        break;
        
      case Qualifiers::OCL_Strong:
        EmitARCRelease(Builder.CreateLoad(BaseValue, 
                          PseudoDtor->getDestroyedType().isVolatileQualified()),
                       ARCPreciseLifetime);
        break;

      case Qualifiers::OCL_Weak:
        EmitARCDestroyWeak(BaseValue);
        break;
      }
    } else {
      // C++ [expr.pseudo]p1:
      //   The result shall only be used as the operand for the function call
      //   operator (), and the result of such a call has type void. The only
      //   effect is the evaluation of the postfix-expression before the dot or
      //   arrow.      
      EmitScalarExpr(E->getCallee());
    }
    
    return RValue::get(0);
  }

  llvm::Value *Callee = EmitScalarExpr(E->getCallee());
  return EmitCall(E->getCallee()->getType(), Callee, ReturnValue,
                  E->arg_begin(), E->arg_end(), TargetDecl);
}

LValue CodeGenFunction::EmitBinaryOperatorLValue(const BinaryOperator *E) {
  // Comma expressions just emit their LHS then their RHS as an l-value.
  if (E->getOpcode() == BO_Comma) {
    EmitIgnoredExpr(E->getLHS());
    EnsureInsertPoint();
    return EmitLValue(E->getRHS());
  }

  if (E->getOpcode() == BO_PtrMemD ||
      E->getOpcode() == BO_PtrMemI)
    return EmitPointerToDataMemberBinaryExpr(E);

  assert(E->getOpcode() == BO_Assign && "unexpected binary l-value");

  // Note that in all of these cases, __block variables need the RHS
  // evaluated first just in case the variable gets moved by the RHS.

  switch (getEvaluationKind(E->getType())) {
  case TEK_Scalar: {
    switch (E->getLHS()->getType().getObjCLifetime()) {
    case Qualifiers::OCL_Strong:
      return EmitARCStoreStrong(E, /*ignored*/ false).first;

    case Qualifiers::OCL_Autoreleasing:
      return EmitARCStoreAutoreleasing(E).first;

    // No reason to do any of these differently.
    case Qualifiers::OCL_None:
    case Qualifiers::OCL_ExplicitNone:
    case Qualifiers::OCL_Weak:
      break;
    }

    RValue RV = EmitAnyExpr(E->getRHS());
    LValue LV = EmitCheckedLValue(E->getLHS(), TCK_Store);
    EmitStoreThroughLValue(RV, LV);
    return LV;
  }

  case TEK_Complex:
    return EmitComplexAssignmentLValue(E);

  case TEK_Aggregate:
    return EmitAggExprToLValue(E);
  }
  llvm_unreachable("bad evaluation kind");
}

LValue CodeGenFunction::EmitCallExprLValue(const CallExpr *E) {
  RValue RV = EmitCallExpr(E);

  if (!RV.isScalar())
    return MakeAddrLValue(RV.getAggregateAddr(), E->getType());
    
  assert(E->getCallReturnType()->isReferenceType() &&
         "Can't have a scalar return unless the return type is a "
         "reference type!");

  return MakeAddrLValue(RV.getScalarVal(), E->getType());
}

LValue CodeGenFunction::EmitVAArgExprLValue(const VAArgExpr *E) {
  // FIXME: This shouldn't require another copy.
  return EmitAggExprToLValue(E);
}

LValue CodeGenFunction::EmitCXXConstructLValue(const CXXConstructExpr *E) {
  assert(E->getType()->getAsCXXRecordDecl()->hasTrivialDestructor()
         && "binding l-value to type which needs a temporary");
  AggValueSlot Slot = CreateAggTemp(E->getType());
  EmitCXXConstructExpr(E, Slot);
  return MakeAddrLValue(Slot.getAddr(), E->getType());
}

LValue
CodeGenFunction::EmitCXXTypeidLValue(const CXXTypeidExpr *E) {
  return MakeAddrLValue(EmitCXXTypeidExpr(E), E->getType());
}

llvm::Value *CodeGenFunction::EmitCXXUuidofExpr(const CXXUuidofExpr *E) {
  return CGM.GetAddrOfUuidDescriptor(E);
}

LValue CodeGenFunction::EmitCXXUuidofLValue(const CXXUuidofExpr *E) {
  return MakeAddrLValue(EmitCXXUuidofExpr(E), E->getType());
}

LValue
CodeGenFunction::EmitCXXBindTemporaryLValue(const CXXBindTemporaryExpr *E) {
  AggValueSlot Slot = CreateAggTemp(E->getType(), "temp.lvalue");
  Slot.setExternallyDestructed();
  EmitAggExpr(E->getSubExpr(), Slot);
  EmitCXXTemporary(E->getTemporary(), E->getType(), Slot.getAddr());
  return MakeAddrLValue(Slot.getAddr(), E->getType());
}

LValue
CodeGenFunction::EmitLambdaLValue(const LambdaExpr *E) {
  AggValueSlot Slot = CreateAggTemp(E->getType(), "temp.lvalue");
  EmitLambdaExpr(E, Slot);
  return MakeAddrLValue(Slot.getAddr(), E->getType());
}

LValue CodeGenFunction::EmitObjCMessageExprLValue(const ObjCMessageExpr *E) {
  RValue RV = EmitObjCMessageExpr(E);
  
  if (!RV.isScalar())
    return MakeAddrLValue(RV.getAggregateAddr(), E->getType());
  
  assert(E->getMethodDecl()->getResultType()->isReferenceType() &&
         "Can't have a scalar return unless the return type is a "
         "reference type!");
  
  return MakeAddrLValue(RV.getScalarVal(), E->getType());
}

LValue CodeGenFunction::EmitObjCSelectorLValue(const ObjCSelectorExpr *E) {
  llvm::Value *V = 
    CGM.getObjCRuntime().GetSelector(*this, E->getSelector(), true);
  return MakeAddrLValue(V, E->getType());
}

llvm::Value *CodeGenFunction::EmitIvarOffset(const ObjCInterfaceDecl *Interface,
                                             const ObjCIvarDecl *Ivar) {
  return CGM.getObjCRuntime().EmitIvarOffset(*this, Interface, Ivar);
}

LValue CodeGenFunction::EmitLValueForIvar(QualType ObjectTy,
                                          llvm::Value *BaseValue,
                                          const ObjCIvarDecl *Ivar,
                                          unsigned CVRQualifiers) {
  return CGM.getObjCRuntime().EmitObjCValueForIvar(*this, ObjectTy, BaseValue,
                                                   Ivar, CVRQualifiers);
}

LValue CodeGenFunction::EmitObjCIvarRefLValue(const ObjCIvarRefExpr *E) {
  // FIXME: A lot of the code below could be shared with EmitMemberExpr.
  llvm::Value *BaseValue = 0;
  const Expr *BaseExpr = E->getBase();
  Qualifiers BaseQuals;
  QualType ObjectTy;
  if (E->isArrow()) {
    BaseValue = EmitScalarExpr(BaseExpr);
    ObjectTy = BaseExpr->getType()->getPointeeType();
    BaseQuals = ObjectTy.getQualifiers();
  } else {
    LValue BaseLV = EmitLValue(BaseExpr);
    // FIXME: this isn't right for bitfields.
    BaseValue = BaseLV.getAddress();
    ObjectTy = BaseExpr->getType();
    BaseQuals = ObjectTy.getQualifiers();
  }

  LValue LV = 
    EmitLValueForIvar(ObjectTy, BaseValue, E->getDecl(),
                      BaseQuals.getCVRQualifiers());
  setObjCGCLValueClass(getContext(), E, LV);
  return LV;
}

LValue CodeGenFunction::EmitStmtExprLValue(const StmtExpr *E) {
  // Can only get l-value for message expression returning aggregate type
  RValue RV = EmitAnyExprToTemp(E);
  return MakeAddrLValue(RV.getAggregateAddr(), E->getType());
}

RValue CodeGenFunction::EmitCall(QualType CalleeType, llvm::Value *Callee,
                                 ReturnValueSlot ReturnValue,
                                 CallExpr::const_arg_iterator ArgBeg,
                                 CallExpr::const_arg_iterator ArgEnd,
                                 const Decl *TargetDecl) {
  // Get the actual function type. The callee type will always be a pointer to
  // function type or a block pointer type.
  assert(CalleeType->isFunctionPointerType() &&
         "Call must have function pointer type!");

  CalleeType = getContext().getCanonicalType(CalleeType);

  const FunctionType *FnType
    = cast<FunctionType>(cast<PointerType>(CalleeType)->getPointeeType());

  CallArgList Args;
  EmitCallArgs(Args, dyn_cast<FunctionProtoType>(FnType), ArgBeg, ArgEnd);

  const CGFunctionInfo &FnInfo =
    CGM.getTypes().arrangeFreeFunctionCall(Args, FnType);

  // C99 6.5.2.2p6:
  //   If the expression that denotes the called function has a type
  //   that does not include a prototype, [the default argument
  //   promotions are performed]. If the number of arguments does not
  //   equal the number of parameters, the behavior is undefined. If
  //   the function is defined with a type that includes a prototype,
  //   and either the prototype ends with an ellipsis (, ...) or the
  //   types of the arguments after promotion are not compatible with
  //   the types of the parameters, the behavior is undefined. If the
  //   function is defined with a type that does not include a
  //   prototype, and the types of the arguments after promotion are
  //   not compatible with those of the parameters after promotion,
  //   the behavior is undefined [except in some trivial cases].
  // That is, in the general case, we should assume that a call
  // through an unprototyped function type works like a *non-variadic*
  // call.  The way we make this work is to cast to the exact type
  // of the promoted arguments.
  if (isa<FunctionNoProtoType>(FnType)) {
    llvm::Type *CalleeTy = getTypes().GetFunctionType(FnInfo);
    CalleeTy = CalleeTy->getPointerTo();
    Callee = Builder.CreateBitCast(Callee, CalleeTy, "callee.knr.cast");
  }

  return EmitCall(FnInfo, Callee, ReturnValue, Args, TargetDecl);
}

LValue CodeGenFunction::
EmitPointerToDataMemberBinaryExpr(const BinaryOperator *E) {
  llvm::Value *BaseV;
  if (E->getOpcode() == BO_PtrMemI)
    BaseV = EmitScalarExpr(E->getLHS());
  else
    BaseV = EmitLValue(E->getLHS()).getAddress();

  llvm::Value *OffsetV = EmitScalarExpr(E->getRHS());

  const MemberPointerType *MPT
    = E->getRHS()->getType()->getAs<MemberPointerType>();

  llvm::Value *AddV =
    CGM.getCXXABI().EmitMemberDataPointerAddress(*this, BaseV, OffsetV, MPT);

  return MakeAddrLValue(AddV, MPT->getPointeeType());
}

/// Given the address of a temporary variable, produce an r-value of
/// its type.
RValue CodeGenFunction::convertTempToRValue(llvm::Value *addr,
                                            QualType type) {
  LValue lvalue = MakeNaturalAlignAddrLValue(addr, type);
  switch (getEvaluationKind(type)) {
  case TEK_Complex:
    return RValue::getComplex(EmitLoadOfComplex(lvalue));
  case TEK_Aggregate:
    return lvalue.asAggregateRValue();
  case TEK_Scalar:
    return RValue::get(EmitLoadOfScalar(lvalue));
  }
  llvm_unreachable("bad evaluation kind");
}

void CodeGenFunction::SetFPAccuracy(llvm::Value *Val, float Accuracy) {
  assert(Val->getType()->isFPOrFPVectorTy());
  if (Accuracy == 0.0 || !isa<llvm::Instruction>(Val))
    return;

  llvm::MDBuilder MDHelper(getLLVMContext());
  llvm::MDNode *Node = MDHelper.createFPMath(Accuracy);

  cast<llvm::Instruction>(Val)->setMetadata(llvm::LLVMContext::MD_fpmath, Node);
}

namespace {
  struct LValueOrRValue {
    LValue LV;
    RValue RV;
  };
}

static LValueOrRValue emitPseudoObjectExpr(CodeGenFunction &CGF,
                                           const PseudoObjectExpr *E,
                                           bool forLValue,
                                           AggValueSlot slot) {
  SmallVector<CodeGenFunction::OpaqueValueMappingData, 4> opaques;

  // Find the result expression, if any.
  const Expr *resultExpr = E->getResultExpr();
  LValueOrRValue 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)) {

      // If this is the result expression, we may need to evaluate
      // directly into the slot.
      typedef CodeGenFunction::OpaqueValueMappingData OVMA;
      OVMA opaqueData;
      if (ov == resultExpr && ov->isRValue() && !forLValue &&
          CodeGenFunction::hasAggregateEvaluationKind(ov->getType())) {
        CGF.EmitAggExpr(ov->getSourceExpr(), slot);

        LValue LV = CGF.MakeAddrLValue(slot.getAddr(), ov->getType());
        opaqueData = OVMA::bind(CGF, ov, LV);
        result.RV = slot.asRValue();

      // Otherwise, emit as normal.
      } else {
        opaqueData = OVMA::bind(CGF, ov, ov->getSourceExpr());

        // If this is the result, also evaluate the result now.
        if (ov == resultExpr) {
          if (forLValue)
            result.LV = CGF.EmitLValue(ov);
          else
            result.RV = CGF.EmitAnyExpr(ov, slot);
        }
      }

      opaques.push_back(opaqueData);

    // Otherwise, if the expression is the result, evaluate it
    // and remember the result.
    } else if (semantic == resultExpr) {
      if (forLValue)
        result.LV = CGF.EmitLValue(semantic);
      else
        result.RV = CGF.EmitAnyExpr(semantic, slot);

    // 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;
}

RValue CodeGenFunction::EmitPseudoObjectRValue(const PseudoObjectExpr *E,
                                               AggValueSlot slot) {
  return emitPseudoObjectExpr(*this, E, false, slot).RV;
}

LValue CodeGenFunction::EmitPseudoObjectLValue(const PseudoObjectExpr *E) {
  return emitPseudoObjectExpr(*this, E, true, AggValueSlot::ignored()).LV;
}