Merge branch 'master' of ssh://bitbucket.org/czan/honours

1 files changed, 1496 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGExprConstant.cpp b/clang/lib/CodeGen/CGExprConstant.cpp
new file mode 100644
index 0000000..bc9f9ef
--- /dev/null
+++ b/clang/lib/CodeGen/CGExprConstant.cpp
@@ -0,0 +1,1496 @@
+//===--- CGExprConstant.cpp - Emit LLVM Code from Constant 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 Constant Expr nodes as LLVM code.
+//
+//===----------------------------------------------------------------------===//
+
+#include "CodeGenFunction.h"
+#include "CodeGenModule.h"
+#include "CGCXXABI.h"
+#include "CGObjCRuntime.h"
+#include "CGRecordLayout.h"
+#include "clang/AST/APValue.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/RecordLayout.h"
+#include "clang/AST/StmtVisitor.h"
+#include "clang/Basic/Builtins.h"
+#include "llvm/Constants.h"
+#include "llvm/Function.h"
+#include "llvm/GlobalVariable.h"
+#include "llvm/Target/TargetData.h"
+using namespace clang;
+using namespace CodeGen;
+
+//===----------------------------------------------------------------------===//
+//                            ConstStructBuilder
+//===----------------------------------------------------------------------===//
+
+namespace {
+class ConstStructBuilder {
+  CodeGenModule &CGM;
+  CodeGenFunction *CGF;
+
+  bool Packed;
+  CharUnits NextFieldOffsetInChars;
+  CharUnits LLVMStructAlignment;
+  SmallVector<llvm::Constant *, 32> Elements;
+public:
+  static llvm::Constant *BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF,
+                                     InitListExpr *ILE);
+  static llvm::Constant *BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF,
+                                     const APValue &Value, QualType ValTy);
+
+private:
+  ConstStructBuilder(CodeGenModule &CGM, CodeGenFunction *CGF)
+    : CGM(CGM), CGF(CGF), Packed(false), 
+    NextFieldOffsetInChars(CharUnits::Zero()),
+    LLVMStructAlignment(CharUnits::One()) { }
+
+  void AppendVTablePointer(BaseSubobject Base, llvm::Constant *VTable,
+                           const CXXRecordDecl *VTableClass);
+
+  void AppendField(const FieldDecl *Field, uint64_t FieldOffset,
+                   llvm::Constant *InitExpr);
+
+  void AppendBytes(CharUnits FieldOffsetInChars, llvm::Constant *InitCst);
+
+  void AppendBitField(const FieldDecl *Field, uint64_t FieldOffset,
+                      llvm::ConstantInt *InitExpr);
+
+  void AppendPadding(CharUnits PadSize);
+
+  void AppendTailPadding(CharUnits RecordSize);
+
+  void ConvertStructToPacked();
+
+  bool Build(InitListExpr *ILE);
+  void Build(const APValue &Val, const RecordDecl *RD, bool IsPrimaryBase,
+             llvm::Constant *VTable, const CXXRecordDecl *VTableClass,
+             CharUnits BaseOffset);
+  llvm::Constant *Finalize(QualType Ty);
+
+  CharUnits getAlignment(const llvm::Constant *C) const {
+    if (Packed)  return CharUnits::One();
+    return CharUnits::fromQuantity(
+        CGM.getTargetData().getABITypeAlignment(C->getType()));
+  }
+
+  CharUnits getSizeInChars(const llvm::Constant *C) const {
+    return CharUnits::fromQuantity(
+        CGM.getTargetData().getTypeAllocSize(C->getType()));
+  }
+};
+
+void ConstStructBuilder::AppendVTablePointer(BaseSubobject Base,
+                                             llvm::Constant *VTable,
+                                             const CXXRecordDecl *VTableClass) {
+  // Find the appropriate vtable within the vtable group.
+  uint64_t AddressPoint =
+    CGM.getVTableContext().getVTableLayout(VTableClass).getAddressPoint(Base);
+  llvm::Value *Indices[] = {
+    llvm::ConstantInt::get(CGM.Int64Ty, 0),
+    llvm::ConstantInt::get(CGM.Int64Ty, AddressPoint)
+  };
+  llvm::Constant *VTableAddressPoint =
+    llvm::ConstantExpr::getInBoundsGetElementPtr(VTable, Indices);
+
+  // Add the vtable at the start of the object.
+  AppendBytes(Base.getBaseOffset(), VTableAddressPoint);
+}
+
+void ConstStructBuilder::
+AppendField(const FieldDecl *Field, uint64_t FieldOffset,
+            llvm::Constant *InitCst) {
+  const ASTContext &Context = CGM.getContext();
+
+  CharUnits FieldOffsetInChars = Context.toCharUnitsFromBits(FieldOffset);
+
+  AppendBytes(FieldOffsetInChars, InitCst);
+}
+
+void ConstStructBuilder::
+AppendBytes(CharUnits FieldOffsetInChars, llvm::Constant *InitCst) {
+
+  assert(NextFieldOffsetInChars <= FieldOffsetInChars
+         && "Field offset mismatch!");
+
+  CharUnits FieldAlignment = getAlignment(InitCst);
+
+  // Round up the field offset to the alignment of the field type.
+  CharUnits AlignedNextFieldOffsetInChars =
+    NextFieldOffsetInChars.RoundUpToAlignment(FieldAlignment);
+
+  if (AlignedNextFieldOffsetInChars > FieldOffsetInChars) {
+    assert(!Packed && "Alignment is wrong even with a packed struct!");
+
+    // Convert the struct to a packed struct.
+    ConvertStructToPacked();
+
+    AlignedNextFieldOffsetInChars = NextFieldOffsetInChars;
+  }
+
+  if (AlignedNextFieldOffsetInChars < FieldOffsetInChars) {
+    // We need to append padding.
+    AppendPadding(FieldOffsetInChars - NextFieldOffsetInChars);
+
+    assert(NextFieldOffsetInChars == FieldOffsetInChars &&
+           "Did not add enough padding!");
+
+    AlignedNextFieldOffsetInChars = NextFieldOffsetInChars;
+  }
+
+  // Add the field.
+  Elements.push_back(InitCst);
+  NextFieldOffsetInChars = AlignedNextFieldOffsetInChars +
+                           getSizeInChars(InitCst);
+
+  if (Packed)
+    assert(LLVMStructAlignment == CharUnits::One() &&
+           "Packed struct not byte-aligned!");
+  else
+    LLVMStructAlignment = std::max(LLVMStructAlignment, FieldAlignment);
+}
+
+void ConstStructBuilder::AppendBitField(const FieldDecl *Field,
+                                        uint64_t FieldOffset,
+                                        llvm::ConstantInt *CI) {
+  const ASTContext &Context = CGM.getContext();
+  const uint64_t CharWidth = Context.getCharWidth();
+  uint64_t NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars);
+  if (FieldOffset > NextFieldOffsetInBits) {
+    // We need to add padding.
+    CharUnits PadSize = Context.toCharUnitsFromBits(
+      llvm::RoundUpToAlignment(FieldOffset - NextFieldOffsetInBits, 
+                               Context.getTargetInfo().getCharAlign()));
+
+    AppendPadding(PadSize);
+  }
+
+  uint64_t FieldSize = Field->getBitWidthValue(Context);
+
+  llvm::APInt FieldValue = CI->getValue();
+
+  // Promote the size of FieldValue if necessary
+  // FIXME: This should never occur, but currently it can because initializer
+  // constants are cast to bool, and because clang is not enforcing bitfield
+  // width limits.
+  if (FieldSize > FieldValue.getBitWidth())
+    FieldValue = FieldValue.zext(FieldSize);
+
+  // Truncate the size of FieldValue to the bit field size.
+  if (FieldSize < FieldValue.getBitWidth())
+    FieldValue = FieldValue.trunc(FieldSize);
+
+  NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars);
+  if (FieldOffset < NextFieldOffsetInBits) {
+    // Either part of the field or the entire field can go into the previous
+    // byte.
+    assert(!Elements.empty() && "Elements can't be empty!");
+
+    unsigned BitsInPreviousByte = NextFieldOffsetInBits - FieldOffset;
+
+    bool FitsCompletelyInPreviousByte =
+      BitsInPreviousByte >= FieldValue.getBitWidth();
+
+    llvm::APInt Tmp = FieldValue;
+
+    if (!FitsCompletelyInPreviousByte) {
+      unsigned NewFieldWidth = FieldSize - BitsInPreviousByte;
+
+      if (CGM.getTargetData().isBigEndian()) {
+        Tmp = Tmp.lshr(NewFieldWidth);
+        Tmp = Tmp.trunc(BitsInPreviousByte);
+
+        // We want the remaining high bits.
+        FieldValue = FieldValue.trunc(NewFieldWidth);
+      } else {
+        Tmp = Tmp.trunc(BitsInPreviousByte);
+
+        // We want the remaining low bits.
+        FieldValue = FieldValue.lshr(BitsInPreviousByte);
+        FieldValue = FieldValue.trunc(NewFieldWidth);
+      }
+    }
+
+    Tmp = Tmp.zext(CharWidth);
+    if (CGM.getTargetData().isBigEndian()) {
+      if (FitsCompletelyInPreviousByte)
+        Tmp = Tmp.shl(BitsInPreviousByte - FieldValue.getBitWidth());
+    } else {
+      Tmp = Tmp.shl(CharWidth - BitsInPreviousByte);
+    }
+
+    // 'or' in the bits that go into the previous byte.
+    llvm::Value *LastElt = Elements.back();
+    if (llvm::ConstantInt *Val = dyn_cast<llvm::ConstantInt>(LastElt))
+      Tmp |= Val->getValue();
+    else {
+      assert(isa<llvm::UndefValue>(LastElt));
+      // If there is an undef field that we're adding to, it can either be a
+      // scalar undef (in which case, we just replace it with our field) or it
+      // is an array.  If it is an array, we have to pull one byte off the
+      // array so that the other undef bytes stay around.
+      if (!isa<llvm::IntegerType>(LastElt->getType())) {
+        // The undef padding will be a multibyte array, create a new smaller
+        // padding and then an hole for our i8 to get plopped into.
+        assert(isa<llvm::ArrayType>(LastElt->getType()) &&
+               "Expected array padding of undefs");
+        llvm::ArrayType *AT = cast<llvm::ArrayType>(LastElt->getType());
+        assert(AT->getElementType()->isIntegerTy(CharWidth) &&
+               AT->getNumElements() != 0 &&
+               "Expected non-empty array padding of undefs");
+        
+        // Remove the padding array.
+        NextFieldOffsetInChars -= CharUnits::fromQuantity(AT->getNumElements());
+        Elements.pop_back();
+        
+        // Add the padding back in two chunks.
+        AppendPadding(CharUnits::fromQuantity(AT->getNumElements()-1));
+        AppendPadding(CharUnits::One());
+        assert(isa<llvm::UndefValue>(Elements.back()) &&
+               Elements.back()->getType()->isIntegerTy(CharWidth) &&
+               "Padding addition didn't work right");
+      }
+    }
+
+    Elements.back() = llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp);
+
+    if (FitsCompletelyInPreviousByte)
+      return;
+  }
+
+  while (FieldValue.getBitWidth() > CharWidth) {
+    llvm::APInt Tmp;
+
+    if (CGM.getTargetData().isBigEndian()) {
+      // We want the high bits.
+      Tmp = 
+        FieldValue.lshr(FieldValue.getBitWidth() - CharWidth).trunc(CharWidth);
+    } else {
+      // We want the low bits.
+      Tmp = FieldValue.trunc(CharWidth);
+
+      FieldValue = FieldValue.lshr(CharWidth);
+    }
+
+    Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp));
+    ++NextFieldOffsetInChars;
+
+    FieldValue = FieldValue.trunc(FieldValue.getBitWidth() - CharWidth);
+  }
+
+  assert(FieldValue.getBitWidth() > 0 &&
+         "Should have at least one bit left!");
+  assert(FieldValue.getBitWidth() <= CharWidth &&
+         "Should not have more than a byte left!");
+
+  if (FieldValue.getBitWidth() < CharWidth) {
+    if (CGM.getTargetData().isBigEndian()) {
+      unsigned BitWidth = FieldValue.getBitWidth();
+
+      FieldValue = FieldValue.zext(CharWidth) << (CharWidth - BitWidth);
+    } else
+      FieldValue = FieldValue.zext(CharWidth);
+  }
+
+  // Append the last element.
+  Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(),
+                                            FieldValue));
+  ++NextFieldOffsetInChars;
+}
+
+void ConstStructBuilder::AppendPadding(CharUnits PadSize) {
+  if (PadSize.isZero())
+    return;
+
+  llvm::Type *Ty = CGM.Int8Ty;
+  if (PadSize > CharUnits::One())
+    Ty = llvm::ArrayType::get(Ty, PadSize.getQuantity());
+
+  llvm::Constant *C = llvm::UndefValue::get(Ty);
+  Elements.push_back(C);
+  assert(getAlignment(C) == CharUnits::One() && 
+         "Padding must have 1 byte alignment!");
+
+  NextFieldOffsetInChars += getSizeInChars(C);
+}
+
+void ConstStructBuilder::AppendTailPadding(CharUnits RecordSize) {
+  assert(NextFieldOffsetInChars <= RecordSize && 
+         "Size mismatch!");
+
+  AppendPadding(RecordSize - NextFieldOffsetInChars);
+}
+
+void ConstStructBuilder::ConvertStructToPacked() {
+  SmallVector<llvm::Constant *, 16> PackedElements;
+  CharUnits ElementOffsetInChars = CharUnits::Zero();
+
+  for (unsigned i = 0, e = Elements.size(); i != e; ++i) {
+    llvm::Constant *C = Elements[i];
+
+    CharUnits ElementAlign = CharUnits::fromQuantity(
+      CGM.getTargetData().getABITypeAlignment(C->getType()));
+    CharUnits AlignedElementOffsetInChars =
+      ElementOffsetInChars.RoundUpToAlignment(ElementAlign);
+
+    if (AlignedElementOffsetInChars > ElementOffsetInChars) {
+      // We need some padding.
+      CharUnits NumChars =
+        AlignedElementOffsetInChars - ElementOffsetInChars;
+
+      llvm::Type *Ty = CGM.Int8Ty;
+      if (NumChars > CharUnits::One())
+        Ty = llvm::ArrayType::get(Ty, NumChars.getQuantity());
+
+      llvm::Constant *Padding = llvm::UndefValue::get(Ty);
+      PackedElements.push_back(Padding);
+      ElementOffsetInChars += getSizeInChars(Padding);
+    }
+
+    PackedElements.push_back(C);
+    ElementOffsetInChars += getSizeInChars(C);
+  }
+
+  assert(ElementOffsetInChars == NextFieldOffsetInChars &&
+         "Packing the struct changed its size!");
+
+  Elements.swap(PackedElements);
+  LLVMStructAlignment = CharUnits::One();
+  Packed = true;
+}
+                            
+bool ConstStructBuilder::Build(InitListExpr *ILE) {
+  if (ILE->initializesStdInitializerList()) {
+    //CGM.ErrorUnsupported(ILE, "global std::initializer_list");
+    return false;
+  }
+
+  RecordDecl *RD = ILE->getType()->getAs<RecordType>()->getDecl();
+  const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
+
+  unsigned FieldNo = 0;
+  unsigned ElementNo = 0;
+  const FieldDecl *LastFD = 0;
+  bool IsMsStruct = RD->hasAttr<MsStructAttr>();
+  
+  for (RecordDecl::field_iterator Field = RD->field_begin(),
+       FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) {
+    if (IsMsStruct) {
+      // Zero-length bitfields following non-bitfield members are
+      // ignored:
+      if (CGM.getContext().ZeroBitfieldFollowsNonBitfield((*Field), LastFD)) {
+        --FieldNo;
+        continue;
+      }
+      LastFD = (*Field);
+    }
+    
+    // If this is a union, skip all the fields that aren't being initialized.
+    if (RD->isUnion() && ILE->getInitializedFieldInUnion() != *Field)
+      continue;
+
+    // Don't emit anonymous bitfields, they just affect layout.
+    if (Field->isUnnamedBitfield()) {
+      LastFD = (*Field);
+      continue;
+    }
+
+    // Get the initializer.  A struct can include fields without initializers,
+    // we just use explicit null values for them.
+    llvm::Constant *EltInit;
+    if (ElementNo < ILE->getNumInits())
+      EltInit = CGM.EmitConstantExpr(ILE->getInit(ElementNo++),
+                                     Field->getType(), CGF);
+    else
+      EltInit = CGM.EmitNullConstant(Field->getType());
+
+    if (!EltInit)
+      return false;
+    
+    if (!Field->isBitField()) {
+      // Handle non-bitfield members.
+      AppendField(*Field, Layout.getFieldOffset(FieldNo), EltInit);
+    } else {
+      // Otherwise we have a bitfield.
+      AppendBitField(*Field, Layout.getFieldOffset(FieldNo),
+                     cast<llvm::ConstantInt>(EltInit));
+    }
+  }
+
+  return true;
+}
+
+namespace {
+struct BaseInfo {
+  BaseInfo(const CXXRecordDecl *Decl, CharUnits Offset, unsigned Index)
+    : Decl(Decl), Offset(Offset), Index(Index) {
+  }
+
+  const CXXRecordDecl *Decl;
+  CharUnits Offset;
+  unsigned Index;
+
+  bool operator<(const BaseInfo &O) const { return Offset < O.Offset; }
+};
+}
+
+void ConstStructBuilder::Build(const APValue &Val, const RecordDecl *RD,
+                               bool IsPrimaryBase, llvm::Constant *VTable,
+                               const CXXRecordDecl *VTableClass,
+                               CharUnits Offset) {
+  const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
+
+  if (const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(RD)) {
+    // Add a vtable pointer, if we need one and it hasn't already been added.
+    if (CD->isDynamicClass() && !IsPrimaryBase)
+      AppendVTablePointer(BaseSubobject(CD, Offset), VTable, VTableClass);
+
+    // Accumulate and sort bases, in order to visit them in address order, which
+    // may not be the same as declaration order.
+    llvm::SmallVector<BaseInfo, 8> Bases;
+    Bases.reserve(CD->getNumBases());
+    unsigned BaseNo = 0;
+    for (CXXRecordDecl::base_class_const_iterator Base = CD->bases_begin(),
+         BaseEnd = CD->bases_end(); Base != BaseEnd; ++Base, ++BaseNo) {
+      assert(!Base->isVirtual() && "should not have virtual bases here");
+      const CXXRecordDecl *BD = Base->getType()->getAsCXXRecordDecl();
+      CharUnits BaseOffset = Layout.getBaseClassOffset(BD);
+      Bases.push_back(BaseInfo(BD, BaseOffset, BaseNo));
+    }
+    std::stable_sort(Bases.begin(), Bases.end());
+
+    for (unsigned I = 0, N = Bases.size(); I != N; ++I) {
+      BaseInfo &Base = Bases[I];
+
+      bool IsPrimaryBase = Layout.getPrimaryBase() == Base.Decl;
+      Build(Val.getStructBase(Base.Index), Base.Decl, IsPrimaryBase,
+            VTable, VTableClass, Offset + Base.Offset);
+    }
+  }
+
+  unsigned FieldNo = 0;
+  const FieldDecl *LastFD = 0;
+  bool IsMsStruct = RD->hasAttr<MsStructAttr>();
+  uint64_t OffsetBits = CGM.getContext().toBits(Offset);
+
+  for (RecordDecl::field_iterator Field = RD->field_begin(),
+       FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) {
+    if (IsMsStruct) {
+      // Zero-length bitfields following non-bitfield members are
+      // ignored:
+      if (CGM.getContext().ZeroBitfieldFollowsNonBitfield((*Field), LastFD)) {
+        --FieldNo;
+        continue;
+      }
+      LastFD = (*Field);
+    }
+
+    // If this is a union, skip all the fields that aren't being initialized.
+    if (RD->isUnion() && Val.getUnionField() != *Field)
+      continue;
+
+    // Don't emit anonymous bitfields, they just affect layout.
+    if (Field->isUnnamedBitfield()) {
+      LastFD = (*Field);
+      continue;
+    }
+
+    // Emit the value of the initializer.
+    const APValue &FieldValue =
+      RD->isUnion() ? Val.getUnionValue() : Val.getStructField(FieldNo);
+    llvm::Constant *EltInit =
+      CGM.EmitConstantValueForMemory(FieldValue, Field->getType(), CGF);
+    assert(EltInit && "EmitConstantValue can't fail");
+
+    if (!Field->isBitField()) {
+      // Handle non-bitfield members.
+      AppendField(*Field, Layout.getFieldOffset(FieldNo) + OffsetBits, EltInit);
+    } else {
+      // Otherwise we have a bitfield.
+      AppendBitField(*Field, Layout.getFieldOffset(FieldNo) + OffsetBits,
+                     cast<llvm::ConstantInt>(EltInit));
+    }
+  }
+}
+
+llvm::Constant *ConstStructBuilder::Finalize(QualType Ty) {
+  RecordDecl *RD = Ty->getAs<RecordType>()->getDecl();
+  const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
+
+  CharUnits LayoutSizeInChars = Layout.getSize();
+
+  if (NextFieldOffsetInChars > LayoutSizeInChars) {
+    // If the struct is bigger than the size of the record type,
+    // we must have a flexible array member at the end.
+    assert(RD->hasFlexibleArrayMember() &&
+           "Must have flexible array member if struct is bigger than type!");
+
+    // No tail padding is necessary.
+  } else {
+    // Append tail padding if necessary.
+    AppendTailPadding(LayoutSizeInChars);
+
+    CharUnits LLVMSizeInChars =
+      NextFieldOffsetInChars.RoundUpToAlignment(LLVMStructAlignment);
+
+    // Check if we need to convert the struct to a packed struct.
+    if (NextFieldOffsetInChars <= LayoutSizeInChars &&
+        LLVMSizeInChars > LayoutSizeInChars) {
+      assert(!Packed && "Size mismatch!");
+
+      ConvertStructToPacked();
+      assert(NextFieldOffsetInChars <= LayoutSizeInChars &&
+             "Converting to packed did not help!");
+    }
+
+    assert(LayoutSizeInChars == NextFieldOffsetInChars &&
+           "Tail padding mismatch!");
+  }
+
+  // Pick the type to use.  If the type is layout identical to the ConvertType
+  // type then use it, otherwise use whatever the builder produced for us.
+  llvm::StructType *STy =
+      llvm::ConstantStruct::getTypeForElements(CGM.getLLVMContext(),
+                                               Elements, Packed);
+  llvm::Type *ValTy = CGM.getTypes().ConvertType(Ty);
+  if (llvm::StructType *ValSTy = dyn_cast<llvm::StructType>(ValTy)) {
+    if (ValSTy->isLayoutIdentical(STy))
+      STy = ValSTy;
+  }
+
+  llvm::Constant *Result = llvm::ConstantStruct::get(STy, Elements);
+
+  assert(NextFieldOffsetInChars.RoundUpToAlignment(getAlignment(Result)) ==
+         getSizeInChars(Result) && "Size mismatch!");
+
+  return Result;
+}
+
+llvm::Constant *ConstStructBuilder::BuildStruct(CodeGenModule &CGM,
+                                                CodeGenFunction *CGF,
+                                                InitListExpr *ILE) {
+  ConstStructBuilder Builder(CGM, CGF);
+
+  if (!Builder.Build(ILE))
+    return 0;
+
+  return Builder.Finalize(ILE->getType());
+}
+
+llvm::Constant *ConstStructBuilder::BuildStruct(CodeGenModule &CGM,
+                                                CodeGenFunction *CGF,
+                                                const APValue &Val,
+                                                QualType ValTy) {
+  ConstStructBuilder Builder(CGM, CGF);
+
+  const RecordDecl *RD = ValTy->castAs<RecordType>()->getDecl();
+  const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(RD);
+  llvm::Constant *VTable = 0;
+  if (CD && CD->isDynamicClass())
+    VTable = CGM.getVTables().GetAddrOfVTable(CD);
+
+  Builder.Build(Val, RD, false, VTable, CD, CharUnits::Zero());
+
+  return Builder.Finalize(ValTy);
+}
+
+
+//===----------------------------------------------------------------------===//
+//                             ConstExprEmitter
+//===----------------------------------------------------------------------===//
+
+/// This class only needs to handle two cases:
+/// 1) Literals (this is used by APValue emission to emit literals).
+/// 2) Arrays, structs and unions (outside C++11 mode, we don't currently
+///    constant fold these types).
+class ConstExprEmitter :
+  public StmtVisitor<ConstExprEmitter, llvm::Constant*> {
+  CodeGenModule &CGM;
+  CodeGenFunction *CGF;
+  llvm::LLVMContext &VMContext;
+public:
+  ConstExprEmitter(CodeGenModule &cgm, CodeGenFunction *cgf)
+    : CGM(cgm), CGF(cgf), VMContext(cgm.getLLVMContext()) {
+  }
+
+  //===--------------------------------------------------------------------===//
+  //                            Visitor Methods
+  //===--------------------------------------------------------------------===//
+
+  llvm::Constant *VisitStmt(Stmt *S) {
+    return 0;
+  }
+
+  llvm::Constant *VisitParenExpr(ParenExpr *PE) {
+    return Visit(PE->getSubExpr());
+  }
+
+  llvm::Constant *
+  VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *PE) {
+    return Visit(PE->getReplacement());
+  }
+
+  llvm::Constant *VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
+    return Visit(GE->getResultExpr());
+  }
+
+  llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
+    return Visit(E->getInitializer());
+  }
+
+  llvm::Constant *VisitCastExpr(CastExpr* E) {
+    Expr *subExpr = E->getSubExpr();
+    llvm::Constant *C = CGM.EmitConstantExpr(subExpr, subExpr->getType(), CGF);
+    if (!C) return 0;
+
+    llvm::Type *destType = ConvertType(E->getType());
+
+    switch (E->getCastKind()) {
+    case CK_ToUnion: {
+      // GCC cast to union extension
+      assert(E->getType()->isUnionType() &&
+             "Destination type is not union type!");
+
+      // Build a struct with the union sub-element as the first member,
+      // and padded to the appropriate size
+      SmallVector<llvm::Constant*, 2> Elts;
+      SmallVector<llvm::Type*, 2> Types;
+      Elts.push_back(C);
+      Types.push_back(C->getType());
+      unsigned CurSize = CGM.getTargetData().getTypeAllocSize(C->getType());
+      unsigned TotalSize = CGM.getTargetData().getTypeAllocSize(destType);
+
+      assert(CurSize <= TotalSize && "Union size mismatch!");
+      if (unsigned NumPadBytes = TotalSize - CurSize) {
+        llvm::Type *Ty = CGM.Int8Ty;
+        if (NumPadBytes > 1)
+          Ty = llvm::ArrayType::get(Ty, NumPadBytes);
+
+        Elts.push_back(llvm::UndefValue::get(Ty));
+        Types.push_back(Ty);
+      }
+
+      llvm::StructType* STy =
+        llvm::StructType::get(C->getType()->getContext(), Types, false);
+      return llvm::ConstantStruct::get(STy, Elts);
+    }
+
+    case CK_LValueToRValue:
+    case CK_AtomicToNonAtomic:
+    case CK_NonAtomicToAtomic:
+    case CK_NoOp:
+      return C;
+
+    case CK_Dependent: llvm_unreachable("saw dependent cast!");
+
+    case CK_ReinterpretMemberPointer:
+    case CK_DerivedToBaseMemberPointer:
+    case CK_BaseToDerivedMemberPointer:
+      return CGM.getCXXABI().EmitMemberPointerConversion(E, C);
+
+    // These will never be supported.
+    case CK_ObjCObjectLValueCast:
+    case CK_ARCProduceObject:
+    case CK_ARCConsumeObject:
+    case CK_ARCReclaimReturnedObject:
+    case CK_ARCExtendBlockObject:
+    case CK_CopyAndAutoreleaseBlockObject:
+      return 0;
+
+    // These don't need to be handled here because Evaluate knows how to
+    // evaluate them in the cases where they can be folded.
+    case CK_BitCast:
+    case CK_ToVoid:
+    case CK_Dynamic:
+    case CK_LValueBitCast:
+    case CK_NullToMemberPointer:
+    case CK_UserDefinedConversion:
+    case CK_ConstructorConversion:
+    case CK_CPointerToObjCPointerCast:
+    case CK_BlockPointerToObjCPointerCast:
+    case CK_AnyPointerToBlockPointerCast:
+    case CK_ArrayToPointerDecay:
+    case CK_FunctionToPointerDecay:
+    case CK_BaseToDerived:
+    case CK_DerivedToBase:
+    case CK_UncheckedDerivedToBase:
+    case CK_MemberPointerToBoolean:
+    case CK_VectorSplat:
+    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_PointerToIntegral:
+    case CK_PointerToBoolean:
+    case CK_NullToPointer:
+    case CK_IntegralCast:
+    case CK_IntegralToPointer:
+    case CK_IntegralToBoolean:
+    case CK_IntegralToFloating:
+    case CK_FloatingToIntegral:
+    case CK_FloatingToBoolean:
+    case CK_FloatingCast:
+      return 0;
+    }
+    llvm_unreachable("Invalid CastKind");
+  }
+
+  llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
+    return Visit(DAE->getExpr());
+  }
+
+  llvm::Constant *VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E) {
+    return Visit(E->GetTemporaryExpr());
+  }
+
+  llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) {
+    if (ILE->isStringLiteralInit())
+      return Visit(ILE->getInit(0));
+
+    llvm::ArrayType *AType =
+        cast<llvm::ArrayType>(ConvertType(ILE->getType()));
+    llvm::Type *ElemTy = AType->getElementType();
+    unsigned NumInitElements = ILE->getNumInits();
+    unsigned NumElements = AType->getNumElements();
+
+    // Initialising an array requires us to automatically
+    // initialise any elements that have not been initialised explicitly
+    unsigned NumInitableElts = std::min(NumInitElements, NumElements);
+
+    // Copy initializer elements.
+    std::vector<llvm::Constant*> Elts;
+    Elts.reserve(NumInitableElts + NumElements);
+
+    bool RewriteType = false;
+    for (unsigned i = 0; i < NumInitableElts; ++i) {
+      Expr *Init = ILE->getInit(i);
+      llvm::Constant *C = CGM.EmitConstantExpr(Init, Init->getType(), CGF);
+      if (!C)
+        return 0;
+      RewriteType |= (C->getType() != ElemTy);
+      Elts.push_back(C);
+    }
+
+    // Initialize remaining array elements.
+    // FIXME: This doesn't handle member pointers correctly!
+    llvm::Constant *fillC;
+    if (Expr *filler = ILE->getArrayFiller())
+      fillC = CGM.EmitConstantExpr(filler, filler->getType(), CGF);
+    else
+      fillC = llvm::Constant::getNullValue(ElemTy);
+    if (!fillC)
+      return 0;
+    RewriteType |= (fillC->getType() != ElemTy);
+    Elts.resize(NumElements, fillC);
+
+    if (RewriteType) {
+      // FIXME: Try to avoid packing the array
+      std::vector<llvm::Type*> Types;
+      Types.reserve(NumInitableElts + NumElements);
+      for (unsigned i = 0, e = Elts.size(); i < e; ++i)
+        Types.push_back(Elts[i]->getType());
+      llvm::StructType *SType = llvm::StructType::get(AType->getContext(),
+                                                            Types, true);
+      return llvm::ConstantStruct::get(SType, Elts);
+    }
+
+    return llvm::ConstantArray::get(AType, Elts);
+  }
+
+  llvm::Constant *EmitStructInitialization(InitListExpr *ILE) {
+    return ConstStructBuilder::BuildStruct(CGM, CGF, ILE);
+  }
+
+  llvm::Constant *EmitUnionInitialization(InitListExpr *ILE) {
+    return ConstStructBuilder::BuildStruct(CGM, CGF, ILE);
+  }
+
+  llvm::Constant *VisitImplicitValueInitExpr(ImplicitValueInitExpr* E) {
+    return CGM.EmitNullConstant(E->getType());
+  }
+
+  llvm::Constant *VisitInitListExpr(InitListExpr *ILE) {
+    if (ILE->getType()->isArrayType())
+      return EmitArrayInitialization(ILE);
+
+    if (ILE->getType()->isRecordType())
+      return EmitStructInitialization(ILE);
+
+    if (ILE->getType()->isUnionType())
+      return EmitUnionInitialization(ILE);
+
+    return 0;
+  }
+
+  llvm::Constant *VisitCXXConstructExpr(CXXConstructExpr *E) {
+    if (!E->getConstructor()->isTrivial())
+      return 0;
+
+    QualType Ty = E->getType();
+
+    // FIXME: We should not have to call getBaseElementType here.
+    const RecordType *RT = 
+      CGM.getContext().getBaseElementType(Ty)->getAs<RecordType>();
+    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
+    
+    // If the class doesn't have a trivial destructor, we can't emit it as a
+    // constant expr.
+    if (!RD->hasTrivialDestructor())
+      return 0;
+    
+    // Only copy and default constructors can be trivial.
+
+
+    if (E->getNumArgs()) {
+      assert(E->getNumArgs() == 1 && "trivial ctor with > 1 argument");
+      assert(E->getConstructor()->isCopyOrMoveConstructor() &&
+             "trivial ctor has argument but isn't a copy/move ctor");
+
+      Expr *Arg = E->getArg(0);
+      assert(CGM.getContext().hasSameUnqualifiedType(Ty, Arg->getType()) &&
+             "argument to copy ctor is of wrong type");
+
+      return Visit(Arg);
+    }
+
+    return CGM.EmitNullConstant(Ty);
+  }
+
+  llvm::Constant *VisitStringLiteral(StringLiteral *E) {
+    return CGM.GetConstantArrayFromStringLiteral(E);
+  }
+
+  llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E) {
+    // This must be an @encode initializing an array in a static initializer.
+    // Don't emit it as the address of the string, emit the string data itself
+    // as an inline array.
+    std::string Str;
+    CGM.getContext().getObjCEncodingForType(E->getEncodedType(), Str);
+    const ConstantArrayType *CAT = cast<ConstantArrayType>(E->getType());
+
+    // Resize the string to the right size, adding zeros at the end, or
+    // truncating as needed.
+    Str.resize(CAT->getSize().getZExtValue(), '\0');
+    return llvm::ConstantDataArray::getString(VMContext, Str, false);
+  }
+
+  llvm::Constant *VisitUnaryExtension(const UnaryOperator *E) {
+    return Visit(E->getSubExpr());
+  }
+
+  // Utility methods
+  llvm::Type *ConvertType(QualType T) {
+    return CGM.getTypes().ConvertType(T);
+  }
+
+public:
+  llvm::Constant *EmitLValue(APValue::LValueBase LVBase) {
+    if (const ValueDecl *Decl = LVBase.dyn_cast<const ValueDecl*>()) {
+      if (Decl->hasAttr<WeakRefAttr>())
+        return CGM.GetWeakRefReference(Decl);
+      if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl))
+        return CGM.GetAddrOfFunction(FD);
+      if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) {
+        // We can never refer to a variable with local storage.
+        if (!VD->hasLocalStorage()) {
+          if (VD->isFileVarDecl() || VD->hasExternalStorage())
+            return CGM.GetAddrOfGlobalVar(VD);
+          else if (VD->isLocalVarDecl()) {
+            assert(CGF && "Can't access static local vars without CGF");
+            return CGF->GetAddrOfStaticLocalVar(VD);
+          }
+        }
+      }
+      return 0;
+    }
+
+    Expr *E = const_cast<Expr*>(LVBase.get<const Expr*>());
+    switch (E->getStmtClass()) {
+    default: break;
+    case Expr::CompoundLiteralExprClass: {
+      // Note that due to the nature of compound literals, this is guaranteed
+      // to be the only use of the variable, so we just generate it here.
+      CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E);
+      llvm::Constant* C = CGM.EmitConstantExpr(CLE->getInitializer(),
+                                               CLE->getType(), CGF);
+      // FIXME: "Leaked" on failure.
+      if (C)
+        C = new llvm::GlobalVariable(CGM.getModule(), C->getType(),
+                                     E->getType().isConstant(CGM.getContext()),
+                                     llvm::GlobalValue::InternalLinkage,
+                                     C, ".compoundliteral", 0, false,
+                          CGM.getContext().getTargetAddressSpace(E->getType()));
+      return C;
+    }
+    case Expr::StringLiteralClass:
+      return CGM.GetAddrOfConstantStringFromLiteral(cast<StringLiteral>(E));
+    case Expr::ObjCEncodeExprClass:
+      return CGM.GetAddrOfConstantStringFromObjCEncode(cast<ObjCEncodeExpr>(E));
+    case Expr::ObjCStringLiteralClass: {
+      ObjCStringLiteral* SL = cast<ObjCStringLiteral>(E);
+      llvm::Constant *C =
+          CGM.getObjCRuntime().GenerateConstantString(SL->getString());
+      return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType()));
+    }
+    case Expr::PredefinedExprClass: {
+      unsigned Type = cast<PredefinedExpr>(E)->getIdentType();
+      if (CGF) {
+        LValue Res = CGF->EmitPredefinedLValue(cast<PredefinedExpr>(E));
+        return cast<llvm::Constant>(Res.getAddress());
+      } else if (Type == PredefinedExpr::PrettyFunction) {
+        return CGM.GetAddrOfConstantCString("top level", ".tmp");
+      }
+
+      return CGM.GetAddrOfConstantCString("", ".tmp");
+    }
+    case Expr::AddrLabelExprClass: {
+      assert(CGF && "Invalid address of label expression outside function.");
+      llvm::Constant *Ptr =
+        CGF->GetAddrOfLabel(cast<AddrLabelExpr>(E)->getLabel());
+      return llvm::ConstantExpr::getBitCast(Ptr, ConvertType(E->getType()));
+    }
+    case Expr::CallExprClass: {
+      CallExpr* CE = cast<CallExpr>(E);
+      unsigned builtin = CE->isBuiltinCall();
+      if (builtin !=
+            Builtin::BI__builtin___CFStringMakeConstantString &&
+          builtin !=
+            Builtin::BI__builtin___NSStringMakeConstantString)
+        break;
+      const Expr *Arg = CE->getArg(0)->IgnoreParenCasts();
+      const StringLiteral *Literal = cast<StringLiteral>(Arg);
+      if (builtin ==
+            Builtin::BI__builtin___NSStringMakeConstantString) {
+        return CGM.getObjCRuntime().GenerateConstantString(Literal);
+      }
+      // FIXME: need to deal with UCN conversion issues.
+      return CGM.GetAddrOfConstantCFString(Literal);
+    }
+    case Expr::BlockExprClass: {
+      std::string FunctionName;
+      if (CGF)
+        FunctionName = CGF->CurFn->getName();
+      else
+        FunctionName = "global";
+
+      return CGM.GetAddrOfGlobalBlock(cast<BlockExpr>(E), FunctionName.c_str());
+    }
+    case Expr::CXXTypeidExprClass: {
+      CXXTypeidExpr *Typeid = cast<CXXTypeidExpr>(E);
+      QualType T;
+      if (Typeid->isTypeOperand())
+        T = Typeid->getTypeOperand();
+      else
+        T = Typeid->getExprOperand()->getType();
+      return CGM.GetAddrOfRTTIDescriptor(T);
+    }
+    }
+
+    return 0;
+  }
+};
+
+}  // end anonymous namespace.
+
+llvm::Constant *CodeGenModule::EmitConstantInit(const VarDecl &D,
+                                                CodeGenFunction *CGF) {
+  if (const APValue *Value = D.evaluateValue())
+    return EmitConstantValueForMemory(*Value, D.getType(), CGF);
+
+  // FIXME: Implement C++11 [basic.start.init]p2: if the initializer of a
+  // reference is a constant expression, and the reference binds to a temporary,
+  // then constant initialization is performed. ConstExprEmitter will
+  // incorrectly emit a prvalue constant in this case, and the calling code
+  // interprets that as the (pointer) value of the reference, rather than the
+  // desired value of the referee.
+  if (D.getType()->isReferenceType())
+    return 0;
+
+  const Expr *E = D.getInit();
+  assert(E && "No initializer to emit");
+
+  llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E));
+  if (C && C->getType()->isIntegerTy(1)) {
+    llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
+    C = llvm::ConstantExpr::getZExt(C, BoolTy);
+  }
+  return C;
+}
+
+llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E,
+                                                QualType DestType,
+                                                CodeGenFunction *CGF) {
+  Expr::EvalResult Result;
+
+  bool Success = false;
+
+  if (DestType->isReferenceType())
+    Success = E->EvaluateAsLValue(Result, Context);
+  else
+    Success = E->EvaluateAsRValue(Result, Context);
+
+  llvm::Constant *C = 0;
+  if (Success && !Result.HasSideEffects)
+    C = EmitConstantValue(Result.Val, DestType, CGF);
+  else
+    C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E));
+
+  if (C && C->getType()->isIntegerTy(1)) {
+    llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
+    C = llvm::ConstantExpr::getZExt(C, BoolTy);
+  }
+  return C;
+}
+
+llvm::Constant *CodeGenModule::EmitConstantValue(const APValue &Value,
+                                                 QualType DestType,
+                                                 CodeGenFunction *CGF) {
+  switch (Value.getKind()) {
+  case APValue::Uninitialized:
+    llvm_unreachable("Constant expressions should be initialized.");
+  case APValue::LValue: {
+    llvm::Type *DestTy = getTypes().ConvertTypeForMem(DestType);
+    llvm::Constant *Offset =
+      llvm::ConstantInt::get(Int64Ty, Value.getLValueOffset().getQuantity());
+
+    llvm::Constant *C;
+    if (APValue::LValueBase LVBase = Value.getLValueBase()) {
+      // An array can be represented as an lvalue referring to the base.
+      if (isa<llvm::ArrayType>(DestTy)) {
+        assert(Offset->isNullValue() && "offset on array initializer");
+        return ConstExprEmitter(*this, CGF).Visit(
+          const_cast<Expr*>(LVBase.get<const Expr*>()));
+      }
+
+      C = ConstExprEmitter(*this, CGF).EmitLValue(LVBase);
+
+      // Apply offset if necessary.
+      if (!Offset->isNullValue()) {
+        llvm::Constant *Casted = llvm::ConstantExpr::getBitCast(C, Int8PtrTy);
+        Casted = llvm::ConstantExpr::getGetElementPtr(Casted, Offset);
+        C = llvm::ConstantExpr::getBitCast(Casted, C->getType());
+      }
+
+      // Convert to the appropriate type; this could be an lvalue for
+      // an integer.
+      if (isa<llvm::PointerType>(DestTy))
+        return llvm::ConstantExpr::getBitCast(C, DestTy);
+
+      return llvm::ConstantExpr::getPtrToInt(C, DestTy);
+    } else {
+      C = Offset;
+
+      // Convert to the appropriate type; this could be an lvalue for
+      // an integer.
+      if (isa<llvm::PointerType>(DestTy))
+        return llvm::ConstantExpr::getIntToPtr(C, DestTy);
+
+      // If the types don't match this should only be a truncate.
+      if (C->getType() != DestTy)
+        return llvm::ConstantExpr::getTrunc(C, DestTy);
+
+      return C;
+    }
+  }
+  case APValue::Int:
+    return llvm::ConstantInt::get(VMContext, Value.getInt());
+  case APValue::ComplexInt: {
+    llvm::Constant *Complex[2];
+
+    Complex[0] = llvm::ConstantInt::get(VMContext,
+                                        Value.getComplexIntReal());
+    Complex[1] = llvm::ConstantInt::get(VMContext,
+                                        Value.getComplexIntImag());
+
+    // FIXME: the target may want to specify that this is packed.
+    llvm::StructType *STy = llvm::StructType::get(Complex[0]->getType(),
+                                                  Complex[1]->getType(),
+                                                  NULL);
+    return llvm::ConstantStruct::get(STy, Complex);
+  }
+  case APValue::Float: {
+    const llvm::APFloat &Init = Value.getFloat();
+    if (&Init.getSemantics() == &llvm::APFloat::IEEEhalf)
+      return llvm::ConstantInt::get(VMContext, Init.bitcastToAPInt());
+    else
+      return llvm::ConstantFP::get(VMContext, Init);
+  }
+  case APValue::ComplexFloat: {
+    llvm::Constant *Complex[2];
+
+    Complex[0] = llvm::ConstantFP::get(VMContext,
+                                       Value.getComplexFloatReal());
+    Complex[1] = llvm::ConstantFP::get(VMContext,
+                                       Value.getComplexFloatImag());
+
+    // FIXME: the target may want to specify that this is packed.
+    llvm::StructType *STy = llvm::StructType::get(Complex[0]->getType(),
+                                                  Complex[1]->getType(),
+                                                  NULL);
+    return llvm::ConstantStruct::get(STy, Complex);
+  }
+  case APValue::Vector: {
+    SmallVector<llvm::Constant *, 4> Inits;
+    unsigned NumElts = Value.getVectorLength();
+
+    for (unsigned i = 0; i != NumElts; ++i) {
+      const APValue &Elt = Value.getVectorElt(i);
+      if (Elt.isInt())
+        Inits.push_back(llvm::ConstantInt::get(VMContext, Elt.getInt()));
+      else
+        Inits.push_back(llvm::ConstantFP::get(VMContext, Elt.getFloat()));
+    }
+    return llvm::ConstantVector::get(Inits);
+  }
+  case APValue::AddrLabelDiff: {
+    const AddrLabelExpr *LHSExpr = Value.getAddrLabelDiffLHS();
+    const AddrLabelExpr *RHSExpr = Value.getAddrLabelDiffRHS();
+    llvm::Constant *LHS = EmitConstantExpr(LHSExpr, LHSExpr->getType(), CGF);
+    llvm::Constant *RHS = EmitConstantExpr(RHSExpr, RHSExpr->getType(), CGF);
+
+    // Compute difference
+    llvm::Type *ResultType = getTypes().ConvertType(DestType);
+    LHS = llvm::ConstantExpr::getPtrToInt(LHS, IntPtrTy);
+    RHS = llvm::ConstantExpr::getPtrToInt(RHS, IntPtrTy);
+    llvm::Constant *AddrLabelDiff = llvm::ConstantExpr::getSub(LHS, RHS);
+
+    // LLVM is a bit sensitive about the exact format of the
+    // address-of-label difference; make sure to truncate after
+    // the subtraction.
+    return llvm::ConstantExpr::getTruncOrBitCast(AddrLabelDiff, ResultType);
+  }
+  case APValue::Struct:
+  case APValue::Union:
+    return ConstStructBuilder::BuildStruct(*this, CGF, Value, DestType);
+  case APValue::Array: {
+    const ArrayType *CAT = Context.getAsArrayType(DestType);
+    unsigned NumElements = Value.getArraySize();
+    unsigned NumInitElts = Value.getArrayInitializedElts();
+
+    std::vector<llvm::Constant*> Elts;
+    Elts.reserve(NumElements);
+
+    // Emit array filler, if there is one.
+    llvm::Constant *Filler = 0;
+    if (Value.hasArrayFiller())
+      Filler = EmitConstantValueForMemory(Value.getArrayFiller(),
+                                          CAT->getElementType(), CGF);
+
+    // Emit initializer elements.
+    llvm::Type *CommonElementType = 0;
+    for (unsigned I = 0; I < NumElements; ++I) {
+      llvm::Constant *C = Filler;
+      if (I < NumInitElts)
+        C = EmitConstantValueForMemory(Value.getArrayInitializedElt(I),
+                                       CAT->getElementType(), CGF);
+      if (I == 0)
+        CommonElementType = C->getType();
+      else if (C->getType() != CommonElementType)
+        CommonElementType = 0;
+      Elts.push_back(C);
+    }
+
+    if (!CommonElementType) {
+      // FIXME: Try to avoid packing the array
+      std::vector<llvm::Type*> Types;
+      Types.reserve(NumElements);
+      for (unsigned i = 0, e = Elts.size(); i < e; ++i)
+        Types.push_back(Elts[i]->getType());
+      llvm::StructType *SType = llvm::StructType::get(VMContext, Types, true);
+      return llvm::ConstantStruct::get(SType, Elts);
+    }
+
+    llvm::ArrayType *AType =
+      llvm::ArrayType::get(CommonElementType, NumElements);
+    return llvm::ConstantArray::get(AType, Elts);
+  }
+  case APValue::MemberPointer:
+    return getCXXABI().EmitMemberPointer(Value, DestType);
+  }
+  llvm_unreachable("Unknown APValue kind");
+}
+
+llvm::Constant *
+CodeGenModule::EmitConstantValueForMemory(const APValue &Value,
+                                          QualType DestType,
+                                          CodeGenFunction *CGF) {
+  llvm::Constant *C = EmitConstantValue(Value, DestType, CGF);
+  if (C->getType()->isIntegerTy(1)) {
+    llvm::Type *BoolTy = getTypes().ConvertTypeForMem(DestType);
+    C = llvm::ConstantExpr::getZExt(C, BoolTy);
+  }
+  return C;
+}
+
+llvm::Constant *
+CodeGenModule::GetAddrOfConstantCompoundLiteral(const CompoundLiteralExpr *E) {
+  assert(E->isFileScope() && "not a file-scope compound literal expr");
+  return ConstExprEmitter(*this, 0).EmitLValue(E);
+}
+
+llvm::Constant *
+CodeGenModule::getMemberPointerConstant(const UnaryOperator *uo) {
+  // Member pointer constants always have a very particular form.
+  const MemberPointerType *type = cast<MemberPointerType>(uo->getType());
+  const ValueDecl *decl = cast<DeclRefExpr>(uo->getSubExpr())->getDecl();
+
+  // A member function pointer.
+  if (const CXXMethodDecl *method = dyn_cast<CXXMethodDecl>(decl))
+    return getCXXABI().EmitMemberPointer(method);
+
+  // Otherwise, a member data pointer.
+  uint64_t fieldOffset = getContext().getFieldOffset(decl);
+  CharUnits chars = getContext().toCharUnitsFromBits((int64_t) fieldOffset);
+  return getCXXABI().EmitMemberDataPointer(type, chars);
+}
+
+static void
+FillInNullDataMemberPointers(CodeGenModule &CGM, QualType T,
+                             SmallVectorImpl<llvm::Constant *> &Elements,
+                             uint64_t StartOffset) {
+  assert(StartOffset % CGM.getContext().getCharWidth() == 0 && 
+         "StartOffset not byte aligned!");
+
+  if (CGM.getTypes().isZeroInitializable(T))
+    return;
+
+  if (const ConstantArrayType *CAT = 
+        CGM.getContext().getAsConstantArrayType(T)) {
+    QualType ElementTy = CAT->getElementType();
+    uint64_t ElementSize = CGM.getContext().getTypeSize(ElementTy);
+    
+    for (uint64_t I = 0, E = CAT->getSize().getZExtValue(); I != E; ++I) {
+      FillInNullDataMemberPointers(CGM, ElementTy, Elements,
+                                   StartOffset + I * ElementSize);
+    }
+  } else if (const RecordType *RT = T->getAs<RecordType>()) {
+    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
+    const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
+
+    // Go through all bases and fill in any null pointer to data members.
+    for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
+         E = RD->bases_end(); I != E; ++I) {
+      if (I->isVirtual()) {
+        // Ignore virtual bases.
+        continue;
+      }
+      
+      const CXXRecordDecl *BaseDecl = 
+      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
+      
+      // Ignore empty bases.
+      if (BaseDecl->isEmpty())
+        continue;
+      
+      // Ignore bases that don't have any pointer to data members.
+      if (CGM.getTypes().isZeroInitializable(BaseDecl))
+        continue;
+
+      uint64_t BaseOffset = Layout.getBaseClassOffsetInBits(BaseDecl);
+      FillInNullDataMemberPointers(CGM, I->getType(),
+                                   Elements, StartOffset + BaseOffset);
+    }
+    
+    // Visit all fields.
+    unsigned FieldNo = 0;
+    for (RecordDecl::field_iterator I = RD->field_begin(),
+         E = RD->field_end(); I != E; ++I, ++FieldNo) {
+      QualType FieldType = I->getType();
+      
+      if (CGM.getTypes().isZeroInitializable(FieldType))
+        continue;
+
+      uint64_t FieldOffset = StartOffset + Layout.getFieldOffset(FieldNo);
+      FillInNullDataMemberPointers(CGM, FieldType, Elements, FieldOffset);
+    }
+  } else {
+    assert(T->isMemberPointerType() && "Should only see member pointers here!");
+    assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() &&
+           "Should only see pointers to data members here!");
+  
+    CharUnits StartIndex = CGM.getContext().toCharUnitsFromBits(StartOffset);
+    CharUnits EndIndex = StartIndex + CGM.getContext().getTypeSizeInChars(T);
+
+    // FIXME: hardcodes Itanium member pointer representation!
+    llvm::Constant *NegativeOne =
+      llvm::ConstantInt::get(CGM.Int8Ty, -1ULL, /*isSigned*/true);
+
+    // Fill in the null data member pointer.
+    for (CharUnits I = StartIndex; I != EndIndex; ++I)
+      Elements[I.getQuantity()] = NegativeOne;
+  }
+}
+
+static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM,
+                                               llvm::Type *baseType,
+                                               const CXXRecordDecl *base);
+
+static llvm::Constant *EmitNullConstant(CodeGenModule &CGM,
+                                        const CXXRecordDecl *record,
+                                        bool asCompleteObject) {
+  const CGRecordLayout &layout = CGM.getTypes().getCGRecordLayout(record);
+  llvm::StructType *structure =
+    (asCompleteObject ? layout.getLLVMType()
+                      : layout.getBaseSubobjectLLVMType());
+
+  unsigned numElements = structure->getNumElements();
+  std::vector<llvm::Constant *> elements(numElements);
+
+  // Fill in all the bases.
+  for (CXXRecordDecl::base_class_const_iterator
+         I = record->bases_begin(), E = record->bases_end(); I != E; ++I) {
+    if (I->isVirtual()) {
+      // Ignore virtual bases; if we're laying out for a complete
+      // object, we'll lay these out later.
+      continue;
+    }
+
+    const CXXRecordDecl *base = 
+      cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl());
+
+    // Ignore empty bases.
+    if (base->isEmpty())
+      continue;
+    
+    unsigned fieldIndex = layout.getNonVirtualBaseLLVMFieldNo(base);
+    llvm::Type *baseType = structure->getElementType(fieldIndex);
+    elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base);
+  }
+
+  // Fill in all the fields.
+  for (RecordDecl::field_iterator I = record->field_begin(),
+         E = record->field_end(); I != E; ++I) {
+    const FieldDecl *field = *I;
+
+    // Fill in non-bitfields. (Bitfields always use a zero pattern, which we
+    // will fill in later.)
+    if (!field->isBitField()) {
+      unsigned fieldIndex = layout.getLLVMFieldNo(field);
+      elements[fieldIndex] = CGM.EmitNullConstant(field->getType());
+    }
+
+    // For unions, stop after the first named field.
+    if (record->isUnion() && field->getDeclName())
+      break;
+  }
+
+  // Fill in the virtual bases, if we're working with the complete object.
+  if (asCompleteObject) {
+    for (CXXRecordDecl::base_class_const_iterator
+           I = record->vbases_begin(), E = record->vbases_end(); I != E; ++I) {
+      const CXXRecordDecl *base = 
+        cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl());
+
+      // Ignore empty bases.
+      if (base->isEmpty())
+        continue;
+
+      unsigned fieldIndex = layout.getVirtualBaseIndex(base);
+
+      // We might have already laid this field out.
+      if (elements[fieldIndex]) continue;
+
+      llvm::Type *baseType = structure->getElementType(fieldIndex);
+      elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base);
+    }
+  }
+
+  // Now go through all other fields and zero them out.
+  for (unsigned i = 0; i != numElements; ++i) {
+    if (!elements[i])
+      elements[i] = llvm::Constant::getNullValue(structure->getElementType(i));
+  }
+  
+  return llvm::ConstantStruct::get(structure, elements);
+}
+
+/// Emit the null constant for a base subobject.
+static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM,
+                                               llvm::Type *baseType,
+                                               const CXXRecordDecl *base) {
+  const CGRecordLayout &baseLayout = CGM.getTypes().getCGRecordLayout(base);
+
+  // Just zero out bases that don't have any pointer to data members.
+  if (baseLayout.isZeroInitializableAsBase())
+    return llvm::Constant::getNullValue(baseType);
+
+  // If the base type is a struct, we can just use its null constant.
+  if (isa<llvm::StructType>(baseType)) {
+    return EmitNullConstant(CGM, base, /*complete*/ false);
+  }
+
+  // Otherwise, some bases are represented as arrays of i8 if the size
+  // of the base is smaller than its corresponding LLVM type.  Figure
+  // out how many elements this base array has.
+  llvm::ArrayType *baseArrayType = cast<llvm::ArrayType>(baseType);
+  unsigned numBaseElements = baseArrayType->getNumElements();
+
+  // Fill in null data member pointers.
+  SmallVector<llvm::Constant *, 16> baseElements(numBaseElements);
+  FillInNullDataMemberPointers(CGM, CGM.getContext().getTypeDeclType(base),
+                               baseElements, 0);
+
+  // Now go through all other elements and zero them out.
+  if (numBaseElements) {
+    llvm::Constant *i8_zero = llvm::Constant::getNullValue(CGM.Int8Ty);
+    for (unsigned i = 0; i != numBaseElements; ++i) {
+      if (!baseElements[i])
+        baseElements[i] = i8_zero;
+    }
+  }
+      
+  return llvm::ConstantArray::get(baseArrayType, baseElements);
+}
+
+llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) {
+  if (getTypes().isZeroInitializable(T))
+    return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T));
+    
+  if (const ConstantArrayType *CAT = Context.getAsConstantArrayType(T)) {
+    llvm::ArrayType *ATy =
+      cast<llvm::ArrayType>(getTypes().ConvertTypeForMem(T));
+
+    QualType ElementTy = CAT->getElementType();
+
+    llvm::Constant *Element = EmitNullConstant(ElementTy);
+    unsigned NumElements = CAT->getSize().getZExtValue();
+    
+    if (Element->isNullValue())
+      return llvm::ConstantAggregateZero::get(ATy);
+    
+    SmallVector<llvm::Constant *, 8> Array(NumElements, Element);
+    return llvm::ConstantArray::get(ATy, Array);
+  }
+
+  if (const RecordType *RT = T->getAs<RecordType>()) {
+    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
+    return ::EmitNullConstant(*this, RD, /*complete object*/ true);
+  }
+
+  assert(T->isMemberPointerType() && "Should only see member pointers here!");
+  assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() &&
+         "Should only see pointers to data members here!");
+  
+  // Itanium C++ ABI 2.3:
+  //   A NULL pointer is represented as -1.
+  return getCXXABI().EmitNullMemberPointer(T->castAs<MemberPointerType>());
+}
+
+llvm::Constant *
+CodeGenModule::EmitNullConstantForBase(const CXXRecordDecl *Record) {
+  return ::EmitNullConstant(*this, Record, false);
+}