xref: /llvm-project-15.0.7/clang/lib/AST/ASTContext.cpp (revision 7a017c6f)

//===--- ASTContext.cpp - Context to hold long-lived AST nodes ------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//  This file implements the ASTContext interface.
//
//===----------------------------------------------------------------------===//

#include "clang/AST/ASTContext.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExternalASTSource.h"
#include "clang/AST/RecordLayout.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Basic/TargetInfo.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/MemoryBuffer.h"
using namespace clang;

enum FloatingRank {
  FloatRank, DoubleRank, LongDoubleRank
};

ASTContext::ASTContext(const LangOptions& LOpts, SourceManager &SM,
                       TargetInfo &t,
                       IdentifierTable &idents, SelectorTable &sels,
                       bool FreeMem, unsigned size_reserve,
                       bool InitializeBuiltins) :
  GlobalNestedNameSpecifier(0), CFConstantStringTypeDecl(0),
  ObjCFastEnumerationStateTypeDecl(0), SourceMgr(SM), LangOpts(LOpts),
  FreeMemory(FreeMem), Target(t), Idents(idents), Selectors(sels),
  ExternalSource(0) {
  if (size_reserve > 0) Types.reserve(size_reserve);
  InitBuiltinTypes();
  TUDecl = TranslationUnitDecl::Create(*this);
  BuiltinInfo.InitializeTargetBuiltins(Target);
  if (InitializeBuiltins)
    this->InitializeBuiltins(idents);
  PrintingPolicy.CPlusPlus = LangOpts.CPlusPlus;
}

ASTContext::~ASTContext() {
  // Deallocate all the types.
  while (!Types.empty()) {
    Types.back()->Destroy(*this);
    Types.pop_back();
  }

  {
    llvm::DenseMap<const RecordDecl*, const ASTRecordLayout*>::iterator
      I = ASTRecordLayouts.begin(), E = ASTRecordLayouts.end();
    while (I != E) {
      ASTRecordLayout *R = const_cast<ASTRecordLayout*>((I++)->second);
      delete R;
    }
  }

  {
    llvm::DenseMap<const ObjCContainerDecl*, const ASTRecordLayout*>::iterator
      I = ObjCLayouts.begin(), E = ObjCLayouts.end();
    while (I != E) {
      ASTRecordLayout *R = const_cast<ASTRecordLayout*>((I++)->second);
      delete R;
    }
  }

  // Destroy nested-name-specifiers.
  for (llvm::FoldingSet<NestedNameSpecifier>::iterator
         NNS = NestedNameSpecifiers.begin(),
         NNSEnd = NestedNameSpecifiers.end();
       NNS != NNSEnd;
       /* Increment in loop */)
    (*NNS++).Destroy(*this);

  if (GlobalNestedNameSpecifier)
    GlobalNestedNameSpecifier->Destroy(*this);

  TUDecl->Destroy(*this);
}

void ASTContext::InitializeBuiltins(IdentifierTable &idents) {
  BuiltinInfo.InitializeBuiltins(idents, LangOpts.NoBuiltin);
}

void
ASTContext::setExternalSource(llvm::OwningPtr<ExternalASTSource> &Source) {
  ExternalSource.reset(Source.take());
}

void ASTContext::PrintStats() const {
  fprintf(stderr, "*** AST Context Stats:\n");
  fprintf(stderr, "  %d types total.\n", (int)Types.size());

  unsigned counts[] = {
#define TYPE(Name, Parent) 0,
#define ABSTRACT_TYPE(Name, Parent)
#include "clang/AST/TypeNodes.def"
    0 // Extra
  };

  for (unsigned i = 0, e = Types.size(); i != e; ++i) {
    Type *T = Types[i];
    counts[(unsigned)T->getTypeClass()]++;
  }

  unsigned Idx = 0;
  unsigned TotalBytes = 0;
#define TYPE(Name, Parent)                                              \
  if (counts[Idx])                                                      \
    fprintf(stderr, "    %d %s types\n", (int)counts[Idx], #Name);      \
  TotalBytes += counts[Idx] * sizeof(Name##Type);                       \
  ++Idx;
#define ABSTRACT_TYPE(Name, Parent)
#include "clang/AST/TypeNodes.def"

  fprintf(stderr, "Total bytes = %d\n", int(TotalBytes));

  if (ExternalSource.get()) {
    fprintf(stderr, "\n");
    ExternalSource->PrintStats();
  }
}


void ASTContext::InitBuiltinType(QualType &R, BuiltinType::Kind K) {
  Types.push_back((R = QualType(new (*this,8) BuiltinType(K),0)).getTypePtr());
}

void ASTContext::InitBuiltinTypes() {
  assert(VoidTy.isNull() && "Context reinitialized?");

  // C99 6.2.5p19.
  InitBuiltinType(VoidTy,              BuiltinType::Void);

  // C99 6.2.5p2.
  InitBuiltinType(BoolTy,              BuiltinType::Bool);
  // C99 6.2.5p3.
  if (LangOpts.CharIsSigned)
    InitBuiltinType(CharTy,            BuiltinType::Char_S);
  else
    InitBuiltinType(CharTy,            BuiltinType::Char_U);
  // C99 6.2.5p4.
  InitBuiltinType(SignedCharTy,        BuiltinType::SChar);
  InitBuiltinType(ShortTy,             BuiltinType::Short);
  InitBuiltinType(IntTy,               BuiltinType::Int);
  InitBuiltinType(LongTy,              BuiltinType::Long);
  InitBuiltinType(LongLongTy,          BuiltinType::LongLong);

  // C99 6.2.5p6.
  InitBuiltinType(UnsignedCharTy,      BuiltinType::UChar);
  InitBuiltinType(UnsignedShortTy,     BuiltinType::UShort);
  InitBuiltinType(UnsignedIntTy,       BuiltinType::UInt);
  InitBuiltinType(UnsignedLongTy,      BuiltinType::ULong);
  InitBuiltinType(UnsignedLongLongTy,  BuiltinType::ULongLong);

  // C99 6.2.5p10.
  InitBuiltinType(FloatTy,             BuiltinType::Float);
  InitBuiltinType(DoubleTy,            BuiltinType::Double);
  InitBuiltinType(LongDoubleTy,        BuiltinType::LongDouble);

  // GNU extension, 128-bit integers.
  InitBuiltinType(Int128Ty,            BuiltinType::Int128);
  InitBuiltinType(UnsignedInt128Ty,    BuiltinType::UInt128);

  if (LangOpts.CPlusPlus) // C++ 3.9.1p5
    InitBuiltinType(WCharTy,           BuiltinType::WChar);
  else // C99
    WCharTy = getFromTargetType(Target.getWCharType());

  // Placeholder type for functions.
  InitBuiltinType(OverloadTy,          BuiltinType::Overload);

  // Placeholder type for type-dependent expressions whose type is
  // completely unknown. No code should ever check a type against
  // DependentTy and users should never see it; however, it is here to
  // help diagnose failures to properly check for type-dependent
  // expressions.
  InitBuiltinType(DependentTy,         BuiltinType::Dependent);

  // C99 6.2.5p11.
  FloatComplexTy      = getComplexType(FloatTy);
  DoubleComplexTy     = getComplexType(DoubleTy);
  LongDoubleComplexTy = getComplexType(LongDoubleTy);

  BuiltinVaListType = QualType();
  ObjCIdType = QualType();
  IdStructType = 0;
  ObjCClassType = QualType();
  ClassStructType = 0;

  ObjCConstantStringType = QualType();

  // void * type
  VoidPtrTy = getPointerType(VoidTy);

  // nullptr type (C++0x 2.14.7)
  InitBuiltinType(NullPtrTy,           BuiltinType::NullPtr);
}

//===----------------------------------------------------------------------===//
//                         Type Sizing and Analysis
//===----------------------------------------------------------------------===//

/// getFloatTypeSemantics - Return the APFloat 'semantics' for the specified
/// scalar floating point type.
const llvm::fltSemantics &ASTContext::getFloatTypeSemantics(QualType T) const {
  const BuiltinType *BT = T->getAsBuiltinType();
  assert(BT && "Not a floating point type!");
  switch (BT->getKind()) {
  default: assert(0 && "Not a floating point type!");
  case BuiltinType::Float:      return Target.getFloatFormat();
  case BuiltinType::Double:     return Target.getDoubleFormat();
  case BuiltinType::LongDouble: return Target.getLongDoubleFormat();
  }
}

/// getDeclAlign - Return a conservative estimate of the alignment of the
/// specified decl.  Note that bitfields do not have a valid alignment, so
/// this method will assert on them.
unsigned ASTContext::getDeclAlignInBytes(const Decl *D) {
  unsigned Align = Target.getCharWidth();

  if (const AlignedAttr* AA = D->getAttr<AlignedAttr>())
    Align = std::max(Align, AA->getAlignment());

  if (const ValueDecl *VD = dyn_cast<ValueDecl>(D)) {
    QualType T = VD->getType();
    if (const ReferenceType* RT = T->getAsReferenceType()) {
      unsigned AS = RT->getPointeeType().getAddressSpace();
      Align = Target.getPointerAlign(AS);
    } else if (!T->isIncompleteType() && !T->isFunctionType()) {
      // Incomplete or function types default to 1.
      while (isa<VariableArrayType>(T) || isa<IncompleteArrayType>(T))
        T = cast<ArrayType>(T)->getElementType();

      Align = std::max(Align, getPreferredTypeAlign(T.getTypePtr()));
    }
  }

  return Align / Target.getCharWidth();
}

/// getTypeSize - Return the size of the specified type, in bits.  This method
/// does not work on incomplete types.
std::pair<uint64_t, unsigned>
ASTContext::getTypeInfo(const Type *T) {
  uint64_t Width=0;
  unsigned Align=8;
  switch (T->getTypeClass()) {
#define TYPE(Class, Base)
#define ABSTRACT_TYPE(Class, Base)
#define NON_CANONICAL_TYPE(Class, Base)
#define DEPENDENT_TYPE(Class, Base) case Type::Class:
#include "clang/AST/TypeNodes.def"
    assert(false && "Should not see dependent types");
    break;

  case Type::FunctionNoProto:
  case Type::FunctionProto:
    // GCC extension: alignof(function) = 32 bits
    Width = 0;
    Align = 32;
    break;

  case Type::IncompleteArray:
  case Type::VariableArray:
    Width = 0;
    Align = getTypeAlign(cast<ArrayType>(T)->getElementType());
    break;

  case Type::ConstantArray: {
    const ConstantArrayType *CAT = cast<ConstantArrayType>(T);

    std::pair<uint64_t, unsigned> EltInfo = getTypeInfo(CAT->getElementType());
    Width = EltInfo.first*CAT->getSize().getZExtValue();
    Align = EltInfo.second;
    break;
  }
  case Type::ExtVector:
  case Type::Vector: {
    std::pair<uint64_t, unsigned> EltInfo =
      getTypeInfo(cast<VectorType>(T)->getElementType());
    Width = EltInfo.first*cast<VectorType>(T)->getNumElements();
    Align = Width;
    // If the alignment is not a power of 2, round up to the next power of 2.
    // This happens for non-power-of-2 length vectors.
    // FIXME: this should probably be a target property.
    Align = 1 << llvm::Log2_32_Ceil(Align);
    break;
  }

  case Type::Builtin:
    switch (cast<BuiltinType>(T)->getKind()) {
    default: assert(0 && "Unknown builtin type!");
    case BuiltinType::Void:
      // GCC extension: alignof(void) = 8 bits.
      Width = 0;
      Align = 8;
      break;

    case BuiltinType::Bool:
      Width = Target.getBoolWidth();
      Align = Target.getBoolAlign();
      break;
    case BuiltinType::Char_S:
    case BuiltinType::Char_U:
    case BuiltinType::UChar:
    case BuiltinType::SChar:
      Width = Target.getCharWidth();
      Align = Target.getCharAlign();
      break;
    case BuiltinType::WChar:
      Width = Target.getWCharWidth();
      Align = Target.getWCharAlign();
      break;
    case BuiltinType::UShort:
    case BuiltinType::Short:
      Width = Target.getShortWidth();
      Align = Target.getShortAlign();
      break;
    case BuiltinType::UInt:
    case BuiltinType::Int:
      Width = Target.getIntWidth();
      Align = Target.getIntAlign();
      break;
    case BuiltinType::ULong:
    case BuiltinType::Long:
      Width = Target.getLongWidth();
      Align = Target.getLongAlign();
      break;
    case BuiltinType::ULongLong:
    case BuiltinType::LongLong:
      Width = Target.getLongLongWidth();
      Align = Target.getLongLongAlign();
      break;
    case BuiltinType::Int128:
    case BuiltinType::UInt128:
      Width = 128;
      Align = 128; // int128_t is 128-bit aligned on all targets.
      break;
    case BuiltinType::Float:
      Width = Target.getFloatWidth();
      Align = Target.getFloatAlign();
      break;
    case BuiltinType::Double:
      Width = Target.getDoubleWidth();
      Align = Target.getDoubleAlign();
      break;
    case BuiltinType::LongDouble:
      Width = Target.getLongDoubleWidth();
      Align = Target.getLongDoubleAlign();
      break;
    case BuiltinType::NullPtr:
      Width = Target.getPointerWidth(0); // C++ 3.9.1p11: sizeof(nullptr_t)
      Align = Target.getPointerAlign(0); //   == sizeof(void*)
      break;
    }
    break;
  case Type::FixedWidthInt:
    // FIXME: This isn't precisely correct; the width/alignment should depend
    // on the available types for the target
    Width = cast<FixedWidthIntType>(T)->getWidth();
    Width = std::max(llvm::NextPowerOf2(Width - 1), (uint64_t)8);
    Align = Width;
    break;
  case Type::ExtQual:
    // FIXME: Pointers into different addr spaces could have different sizes and
    // alignment requirements: getPointerInfo should take an AddrSpace.
    return getTypeInfo(QualType(cast<ExtQualType>(T)->getBaseType(), 0));
  case Type::ObjCQualifiedId:
  case Type::ObjCQualifiedInterface:
    Width = Target.getPointerWidth(0);
    Align = Target.getPointerAlign(0);
    break;
  case Type::BlockPointer: {
    unsigned AS = cast<BlockPointerType>(T)->getPointeeType().getAddressSpace();
    Width = Target.getPointerWidth(AS);
    Align = Target.getPointerAlign(AS);
    break;
  }
  case Type::Pointer: {
    unsigned AS = cast<PointerType>(T)->getPointeeType().getAddressSpace();
    Width = Target.getPointerWidth(AS);
    Align = Target.getPointerAlign(AS);
    break;
  }
  case Type::LValueReference:
  case Type::RValueReference:
    // "When applied to a reference or a reference type, the result is the size
    // of the referenced type." C++98 5.3.3p2: expr.sizeof.
    // FIXME: This is wrong for struct layout: a reference in a struct has
    // pointer size.
    return getTypeInfo(cast<ReferenceType>(T)->getPointeeType());
  case Type::MemberPointer: {
    // FIXME: This is ABI dependent. We use the Itanium C++ ABI.
    // http://www.codesourcery.com/public/cxx-abi/abi.html#member-pointers
    // If we ever want to support other ABIs this needs to be abstracted.

    QualType Pointee = cast<MemberPointerType>(T)->getPointeeType();
    std::pair<uint64_t, unsigned> PtrDiffInfo =
      getTypeInfo(getPointerDiffType());
    Width = PtrDiffInfo.first;
    if (Pointee->isFunctionType())
      Width *= 2;
    Align = PtrDiffInfo.second;
    break;
  }
  case Type::Complex: {
    // Complex types have the same alignment as their elements, but twice the
    // size.
    std::pair<uint64_t, unsigned> EltInfo =
      getTypeInfo(cast<ComplexType>(T)->getElementType());
    Width = EltInfo.first*2;
    Align = EltInfo.second;
    break;
  }
  case Type::ObjCInterface: {
    const ObjCInterfaceType *ObjCI = cast<ObjCInterfaceType>(T);
    const ASTRecordLayout &Layout = getASTObjCInterfaceLayout(ObjCI->getDecl());
    Width = Layout.getSize();
    Align = Layout.getAlignment();
    break;
  }
  case Type::Record:
  case Type::Enum: {
    const TagType *TT = cast<TagType>(T);

    if (TT->getDecl()->isInvalidDecl()) {
      Width = 1;
      Align = 1;
      break;
    }

    if (const EnumType *ET = dyn_cast<EnumType>(TT))
      return getTypeInfo(ET->getDecl()->getIntegerType());

    const RecordType *RT = cast<RecordType>(TT);
    const ASTRecordLayout &Layout = getASTRecordLayout(RT->getDecl());
    Width = Layout.getSize();
    Align = Layout.getAlignment();
    break;
  }

  case Type::Typedef: {
    const TypedefDecl *Typedef = cast<TypedefType>(T)->getDecl();
    if (const AlignedAttr *Aligned = Typedef->getAttr<AlignedAttr>()) {
      Align = Aligned->getAlignment();
      Width = getTypeSize(Typedef->getUnderlyingType().getTypePtr());
    } else
      return getTypeInfo(Typedef->getUnderlyingType().getTypePtr());
    break;
  }

  case Type::TypeOfExpr:
    return getTypeInfo(cast<TypeOfExprType>(T)->getUnderlyingExpr()->getType()
                         .getTypePtr());

  case Type::TypeOf:
    return getTypeInfo(cast<TypeOfType>(T)->getUnderlyingType().getTypePtr());

  case Type::QualifiedName:
    return getTypeInfo(cast<QualifiedNameType>(T)->getNamedType().getTypePtr());

  case Type::TemplateSpecialization:
    assert(getCanonicalType(T) != T &&
           "Cannot request the size of a dependent type");
    // FIXME: this is likely to be wrong once we support template
    // aliases, since a template alias could refer to a typedef that
    // has an __aligned__ attribute on it.
    return getTypeInfo(getCanonicalType(T));
  }

  assert(Align && (Align & (Align-1)) == 0 && "Alignment must be power of 2");
  return std::make_pair(Width, Align);
}

/// getPreferredTypeAlign - Return the "preferred" alignment of the specified
/// type for the current target in bits.  This can be different than the ABI
/// alignment in cases where it is beneficial for performance to overalign
/// a data type.
unsigned ASTContext::getPreferredTypeAlign(const Type *T) {
  unsigned ABIAlign = getTypeAlign(T);

  // Double and long long should be naturally aligned if possible.
  if (const ComplexType* CT = T->getAsComplexType())
    T = CT->getElementType().getTypePtr();
  if (T->isSpecificBuiltinType(BuiltinType::Double) ||
      T->isSpecificBuiltinType(BuiltinType::LongLong))
    return std::max(ABIAlign, (unsigned)getTypeSize(T));

  return ABIAlign;
}


/// LayoutField - Field layout.
void ASTRecordLayout::LayoutField(const FieldDecl *FD, unsigned FieldNo,
                                  bool IsUnion, unsigned StructPacking,
                                  ASTContext &Context) {
  unsigned FieldPacking = StructPacking;
  uint64_t FieldOffset = IsUnion ? 0 : Size;
  uint64_t FieldSize;
  unsigned FieldAlign;

  // FIXME: Should this override struct packing? Probably we want to
  // take the minimum?
  if (const PackedAttr *PA = FD->getAttr<PackedAttr>())
    FieldPacking = PA->getAlignment();

  if (const Expr *BitWidthExpr = FD->getBitWidth()) {
    // TODO: Need to check this algorithm on other targets!
    //       (tested on Linux-X86)
    FieldSize = BitWidthExpr->EvaluateAsInt(Context).getZExtValue();

    std::pair<uint64_t, unsigned> FieldInfo =
      Context.getTypeInfo(FD->getType());
    uint64_t TypeSize = FieldInfo.first;

    // Determine the alignment of this bitfield. The packing
    // attributes define a maximum and the alignment attribute defines
    // a minimum.
    // FIXME: What is the right behavior when the specified alignment
    // is smaller than the specified packing?
    FieldAlign = FieldInfo.second;
    if (FieldPacking)
      FieldAlign = std::min(FieldAlign, FieldPacking);
    if (const AlignedAttr *AA = FD->getAttr<AlignedAttr>())
      FieldAlign = std::max(FieldAlign, AA->getAlignment());

    // Check if we need to add padding to give the field the correct
    // alignment.
    if (FieldSize == 0 || (FieldOffset & (FieldAlign-1)) + FieldSize > TypeSize)
      FieldOffset = (FieldOffset + (FieldAlign-1)) & ~(FieldAlign-1);

    // Padding members don't affect overall alignment
    if (!FD->getIdentifier())
      FieldAlign = 1;
  } else {
    if (FD->getType()->isIncompleteArrayType()) {
      // This is a flexible array member; we can't directly
      // query getTypeInfo about these, so we figure it out here.
      // Flexible array members don't have any size, but they
      // have to be aligned appropriately for their element type.
      FieldSize = 0;
      const ArrayType* ATy = Context.getAsArrayType(FD->getType());
      FieldAlign = Context.getTypeAlign(ATy->getElementType());
    } else if (const ReferenceType *RT = FD->getType()->getAsReferenceType()) {
      unsigned AS = RT->getPointeeType().getAddressSpace();
      FieldSize = Context.Target.getPointerWidth(AS);
      FieldAlign = Context.Target.getPointerAlign(AS);
    } else {
      std::pair<uint64_t, unsigned> FieldInfo =
        Context.getTypeInfo(FD->getType());
      FieldSize = FieldInfo.first;
      FieldAlign = FieldInfo.second;
    }

    // Determine the alignment of this bitfield. The packing
    // attributes define a maximum and the alignment attribute defines
    // a minimum. Additionally, the packing alignment must be at least
    // a byte for non-bitfields.
    //
    // FIXME: What is the right behavior when the specified alignment
    // is smaller than the specified packing?
    if (FieldPacking)
      FieldAlign = std::min(FieldAlign, std::max(8U, FieldPacking));
    if (const AlignedAttr *AA = FD->getAttr<AlignedAttr>())
      FieldAlign = std::max(FieldAlign, AA->getAlignment());

    // Round up the current record size to the field's alignment boundary.
    FieldOffset = (FieldOffset + (FieldAlign-1)) & ~(FieldAlign-1);
  }

  // Place this field at the current location.
  FieldOffsets[FieldNo] = FieldOffset;

  // Reserve space for this field.
  if (IsUnion) {
    Size = std::max(Size, FieldSize);
  } else {
    Size = FieldOffset + FieldSize;
  }

  // Remember the next available offset.
  NextOffset = Size;

  // Remember max struct/class alignment.
  Alignment = std::max(Alignment, FieldAlign);
}

static void CollectLocalObjCIvars(ASTContext *Ctx,
                                  const ObjCInterfaceDecl *OI,
                                  llvm::SmallVectorImpl<FieldDecl*> &Fields) {
  for (ObjCInterfaceDecl::ivar_iterator I = OI->ivar_begin(),
       E = OI->ivar_end(); I != E; ++I) {
    ObjCIvarDecl *IVDecl = *I;
    if (!IVDecl->isInvalidDecl())
      Fields.push_back(cast<FieldDecl>(IVDecl));
  }
}

void ASTContext::CollectObjCIvars(const ObjCInterfaceDecl *OI,
                             llvm::SmallVectorImpl<FieldDecl*> &Fields) {
  if (const ObjCInterfaceDecl *SuperClass = OI->getSuperClass())
    CollectObjCIvars(SuperClass, Fields);
  CollectLocalObjCIvars(this, OI, Fields);
}

/// ShallowCollectObjCIvars -
/// Collect all ivars, including those synthesized, in the current class.
///
void ASTContext::ShallowCollectObjCIvars(const ObjCInterfaceDecl *OI,
                                 llvm::SmallVectorImpl<ObjCIvarDecl*> &Ivars,
                                 bool CollectSynthesized) {
  for (ObjCInterfaceDecl::ivar_iterator I = OI->ivar_begin(),
         E = OI->ivar_end(); I != E; ++I) {
     Ivars.push_back(*I);
  }
  if (CollectSynthesized)
    CollectSynthesizedIvars(OI, Ivars);
}

void ASTContext::CollectProtocolSynthesizedIvars(const ObjCProtocolDecl *PD,
                                llvm::SmallVectorImpl<ObjCIvarDecl*> &Ivars) {
  for (ObjCContainerDecl::prop_iterator I = PD->prop_begin(*this),
       E = PD->prop_end(*this); I != E; ++I)
    if (ObjCIvarDecl *Ivar = (*I)->getPropertyIvarDecl())
      Ivars.push_back(Ivar);

  // Also look into nested protocols.
  for (ObjCProtocolDecl::protocol_iterator P = PD->protocol_begin(),
       E = PD->protocol_end(); P != E; ++P)
    CollectProtocolSynthesizedIvars(*P, Ivars);
}

/// CollectSynthesizedIvars -
/// This routine collect synthesized ivars for the designated class.
///
void ASTContext::CollectSynthesizedIvars(const ObjCInterfaceDecl *OI,
                                llvm::SmallVectorImpl<ObjCIvarDecl*> &Ivars) {
  for (ObjCInterfaceDecl::prop_iterator I = OI->prop_begin(*this),
       E = OI->prop_end(*this); I != E; ++I) {
    if (ObjCIvarDecl *Ivar = (*I)->getPropertyIvarDecl())
      Ivars.push_back(Ivar);
  }
  // Also look into interface's protocol list for properties declared
  // in the protocol and whose ivars are synthesized.
  for (ObjCInterfaceDecl::protocol_iterator P = OI->protocol_begin(),
       PE = OI->protocol_end(); P != PE; ++P) {
    ObjCProtocolDecl *PD = (*P);
    CollectProtocolSynthesizedIvars(PD, Ivars);
  }
}

unsigned ASTContext::CountProtocolSynthesizedIvars(const ObjCProtocolDecl *PD) {
  unsigned count = 0;
  for (ObjCContainerDecl::prop_iterator I = PD->prop_begin(*this),
       E = PD->prop_end(*this); I != E; ++I)
    if ((*I)->getPropertyIvarDecl())
      ++count;

  // Also look into nested protocols.
  for (ObjCProtocolDecl::protocol_iterator P = PD->protocol_begin(),
       E = PD->protocol_end(); P != E; ++P)
    count += CountProtocolSynthesizedIvars(*P);
  return count;
}

unsigned ASTContext::CountSynthesizedIvars(const ObjCInterfaceDecl *OI)
{
  unsigned count = 0;
  for (ObjCInterfaceDecl::prop_iterator I = OI->prop_begin(*this),
       E = OI->prop_end(*this); I != E; ++I) {
    if ((*I)->getPropertyIvarDecl())
      ++count;
  }
  // Also look into interface's protocol list for properties declared
  // in the protocol and whose ivars are synthesized.
  for (ObjCInterfaceDecl::protocol_iterator P = OI->protocol_begin(),
       PE = OI->protocol_end(); P != PE; ++P) {
    ObjCProtocolDecl *PD = (*P);
    count += CountProtocolSynthesizedIvars(PD);
  }
  return count;
}

/// getInterfaceLayoutImpl - Get or compute information about the
/// layout of the given interface.
///
/// \param Impl - If given, also include the layout of the interface's
/// implementation. This may differ by including synthesized ivars.
const ASTRecordLayout &
ASTContext::getObjCLayout(const ObjCInterfaceDecl *D,
                          const ObjCImplementationDecl *Impl) {
  assert(!D->isForwardDecl() && "Invalid interface decl!");

  // Look up this layout, if already laid out, return what we have.
  ObjCContainerDecl *Key =
    Impl ? (ObjCContainerDecl*) Impl : (ObjCContainerDecl*) D;
  if (const ASTRecordLayout *Entry = ObjCLayouts[Key])
    return *Entry;

  unsigned FieldCount = D->ivar_size();
  // Add in synthesized ivar count if laying out an implementation.
  if (Impl) {
    unsigned SynthCount = CountSynthesizedIvars(D);
    FieldCount += SynthCount;
    // If there aren't any sythesized ivars then reuse the interface
    // entry. Note we can't cache this because we simply free all
    // entries later; however we shouldn't look up implementations
    // frequently.
    if (SynthCount == 0)
      return getObjCLayout(D, 0);
  }

  ASTRecordLayout *NewEntry = NULL;
  if (ObjCInterfaceDecl *SD = D->getSuperClass()) {
    const ASTRecordLayout &SL = getASTObjCInterfaceLayout(SD);
    unsigned Alignment = SL.getAlignment();

    // We start laying out ivars not at the end of the superclass
    // structure, but at the next byte following the last field.
    uint64_t Size = llvm::RoundUpToAlignment(SL.NextOffset, 8);

    ObjCLayouts[Key] = NewEntry = new ASTRecordLayout(Size, Alignment);
    NewEntry->InitializeLayout(FieldCount);
  } else {
    ObjCLayouts[Key] = NewEntry = new ASTRecordLayout();
    NewEntry->InitializeLayout(FieldCount);
  }

  unsigned StructPacking = 0;
  if (const PackedAttr *PA = D->getAttr<PackedAttr>())
    StructPacking = PA->getAlignment();

  if (const AlignedAttr *AA = D->getAttr<AlignedAttr>())
    NewEntry->SetAlignment(std::max(NewEntry->getAlignment(),
                                    AA->getAlignment()));

  // Layout each ivar sequentially.
  unsigned i = 0;
  llvm::SmallVector<ObjCIvarDecl*, 16> Ivars;
  ShallowCollectObjCIvars(D, Ivars, Impl);
  for (unsigned k = 0, e = Ivars.size(); k != e; ++k)
       NewEntry->LayoutField(Ivars[k], i++, false, StructPacking, *this);

  // Finally, round the size of the total struct up to the alignment of the
  // struct itself.
  NewEntry->FinalizeLayout();
  return *NewEntry;
}

const ASTRecordLayout &
ASTContext::getASTObjCInterfaceLayout(const ObjCInterfaceDecl *D) {
  return getObjCLayout(D, 0);
}

const ASTRecordLayout &
ASTContext::getASTObjCImplementationLayout(const ObjCImplementationDecl *D) {
  return getObjCLayout(D->getClassInterface(), D);
}

/// getASTRecordLayout - Get or compute information about the layout of the
/// specified record (struct/union/class), which indicates its size and field
/// position information.
const ASTRecordLayout &ASTContext::getASTRecordLayout(const RecordDecl *D) {
  D = D->getDefinition(*this);
  assert(D && "Cannot get layout of forward declarations!");

  // Look up this layout, if already laid out, return what we have.
  const ASTRecordLayout *&Entry = ASTRecordLayouts[D];
  if (Entry) return *Entry;

  // Allocate and assign into ASTRecordLayouts here.  The "Entry" reference can
  // be invalidated (dangle) if the ASTRecordLayouts hashtable is inserted into.
  ASTRecordLayout *NewEntry = new ASTRecordLayout();
  Entry = NewEntry;

  // FIXME: Avoid linear walk through the fields, if possible.
  NewEntry->InitializeLayout(std::distance(D->field_begin(*this),
                                           D->field_end(*this)));
  bool IsUnion = D->isUnion();

  unsigned StructPacking = 0;
  if (const PackedAttr *PA = D->getAttr<PackedAttr>())
    StructPacking = PA->getAlignment();

  if (const AlignedAttr *AA = D->getAttr<AlignedAttr>())
    NewEntry->SetAlignment(std::max(NewEntry->getAlignment(),
                                    AA->getAlignment()));

  // Layout each field, for now, just sequentially, respecting alignment.  In
  // the future, this will need to be tweakable by targets.
  unsigned FieldIdx = 0;
  for (RecordDecl::field_iterator Field = D->field_begin(*this),
                               FieldEnd = D->field_end(*this);
       Field != FieldEnd; (void)++Field, ++FieldIdx)
    NewEntry->LayoutField(*Field, FieldIdx, IsUnion, StructPacking, *this);

  // Finally, round the size of the total struct up to the alignment of the
  // struct itself.
  NewEntry->FinalizeLayout(getLangOptions().CPlusPlus);
  return *NewEntry;
}

//===----------------------------------------------------------------------===//
//                   Type creation/memoization methods
//===----------------------------------------------------------------------===//

QualType ASTContext::getAddrSpaceQualType(QualType T, unsigned AddressSpace) {
  QualType CanT = getCanonicalType(T);
  if (CanT.getAddressSpace() == AddressSpace)
    return T;

  // If we are composing extended qualifiers together, merge together into one
  // ExtQualType node.
  unsigned CVRQuals = T.getCVRQualifiers();
  QualType::GCAttrTypes GCAttr = QualType::GCNone;
  Type *TypeNode = T.getTypePtr();

  if (ExtQualType *EQT = dyn_cast<ExtQualType>(TypeNode)) {
    // If this type already has an address space specified, it cannot get
    // another one.
    assert(EQT->getAddressSpace() == 0 &&
           "Type cannot be in multiple addr spaces!");
    GCAttr = EQT->getObjCGCAttr();
    TypeNode = EQT->getBaseType();
  }

  // Check if we've already instantiated this type.
  llvm::FoldingSetNodeID ID;
  ExtQualType::Profile(ID, TypeNode, AddressSpace, GCAttr);
  void *InsertPos = 0;
  if (ExtQualType *EXTQy = ExtQualTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(EXTQy, CVRQuals);

  // If the base type isn't canonical, this won't be a canonical type either,
  // so fill in the canonical type field.
  QualType Canonical;
  if (!TypeNode->isCanonical()) {
    Canonical = getAddrSpaceQualType(CanT, AddressSpace);

    // Update InsertPos, the previous call could have invalidated it.
    ExtQualType *NewIP = ExtQualTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(NewIP == 0 && "Shouldn't be in the map!"); NewIP = NewIP;
  }
  ExtQualType *New =
    new (*this, 8) ExtQualType(TypeNode, Canonical, AddressSpace, GCAttr);
  ExtQualTypes.InsertNode(New, InsertPos);
  Types.push_back(New);
  return QualType(New, CVRQuals);
}

QualType ASTContext::getObjCGCQualType(QualType T,
                                       QualType::GCAttrTypes GCAttr) {
  QualType CanT = getCanonicalType(T);
  if (CanT.getObjCGCAttr() == GCAttr)
    return T;

  if (T->isPointerType()) {
    QualType Pointee = T->getAsPointerType()->getPointeeType();
    if (Pointee->isPointerType()) {
      QualType ResultType = getObjCGCQualType(Pointee, GCAttr);
      return getPointerType(ResultType);
    }
  }
  // If we are composing extended qualifiers together, merge together into one
  // ExtQualType node.
  unsigned CVRQuals = T.getCVRQualifiers();
  Type *TypeNode = T.getTypePtr();
  unsigned AddressSpace = 0;

  if (ExtQualType *EQT = dyn_cast<ExtQualType>(TypeNode)) {
    // If this type already has an address space specified, it cannot get
    // another one.
    assert(EQT->getObjCGCAttr() == QualType::GCNone &&
           "Type cannot be in multiple addr spaces!");
    AddressSpace = EQT->getAddressSpace();
    TypeNode = EQT->getBaseType();
  }

  // Check if we've already instantiated an gc qual'd type of this type.
  llvm::FoldingSetNodeID ID;
  ExtQualType::Profile(ID, TypeNode, AddressSpace, GCAttr);
  void *InsertPos = 0;
  if (ExtQualType *EXTQy = ExtQualTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(EXTQy, CVRQuals);

  // If the base type isn't canonical, this won't be a canonical type either,
  // so fill in the canonical type field.
  // FIXME: Isn't this also not canonical if the base type is a array
  // or pointer type?  I can't find any documentation for objc_gc, though...
  QualType Canonical;
  if (!T->isCanonical()) {
    Canonical = getObjCGCQualType(CanT, GCAttr);

    // Update InsertPos, the previous call could have invalidated it.
    ExtQualType *NewIP = ExtQualTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(NewIP == 0 && "Shouldn't be in the map!"); NewIP = NewIP;
  }
  ExtQualType *New =
    new (*this, 8) ExtQualType(TypeNode, Canonical, AddressSpace, GCAttr);
  ExtQualTypes.InsertNode(New, InsertPos);
  Types.push_back(New);
  return QualType(New, CVRQuals);
}

/// getComplexType - Return the uniqued reference to the type for a complex
/// number with the specified element type.
QualType ASTContext::getComplexType(QualType T) {
  // Unique pointers, to guarantee there is only one pointer of a particular
  // structure.
  llvm::FoldingSetNodeID ID;
  ComplexType::Profile(ID, T);

  void *InsertPos = 0;
  if (ComplexType *CT = ComplexTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(CT, 0);

  // If the pointee type isn't canonical, this won't be a canonical type either,
  // so fill in the canonical type field.
  QualType Canonical;
  if (!T->isCanonical()) {
    Canonical = getComplexType(getCanonicalType(T));

    // Get the new insert position for the node we care about.
    ComplexType *NewIP = ComplexTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(NewIP == 0 && "Shouldn't be in the map!"); NewIP = NewIP;
  }
  ComplexType *New = new (*this,8) ComplexType(T, Canonical);
  Types.push_back(New);
  ComplexTypes.InsertNode(New, InsertPos);
  return QualType(New, 0);
}

QualType ASTContext::getFixedWidthIntType(unsigned Width, bool Signed) {
  llvm::DenseMap<unsigned, FixedWidthIntType*> &Map = Signed ?
     SignedFixedWidthIntTypes : UnsignedFixedWidthIntTypes;
  FixedWidthIntType *&Entry = Map[Width];
  if (!Entry)
    Entry = new FixedWidthIntType(Width, Signed);
  return QualType(Entry, 0);
}

/// getPointerType - Return the uniqued reference to the type for a pointer to
/// the specified type.
QualType ASTContext::getPointerType(QualType T) {
  // Unique pointers, to guarantee there is only one pointer of a particular
  // structure.
  llvm::FoldingSetNodeID ID;
  PointerType::Profile(ID, T);

  void *InsertPos = 0;
  if (PointerType *PT = PointerTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(PT, 0);

  // If the pointee type isn't canonical, this won't be a canonical type either,
  // so fill in the canonical type field.
  QualType Canonical;
  if (!T->isCanonical()) {
    Canonical = getPointerType(getCanonicalType(T));

    // Get the new insert position for the node we care about.
    PointerType *NewIP = PointerTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(NewIP == 0 && "Shouldn't be in the map!"); NewIP = NewIP;
  }
  PointerType *New = new (*this,8) PointerType(T, Canonical);
  Types.push_back(New);
  PointerTypes.InsertNode(New, InsertPos);
  return QualType(New, 0);
}

/// getBlockPointerType - Return the uniqued reference to the type for
/// a pointer to the specified block.
QualType ASTContext::getBlockPointerType(QualType T) {
  assert(T->isFunctionType() && "block of function types only");
  // Unique pointers, to guarantee there is only one block of a particular
  // structure.
  llvm::FoldingSetNodeID ID;
  BlockPointerType::Profile(ID, T);

  void *InsertPos = 0;
  if (BlockPointerType *PT =
        BlockPointerTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(PT, 0);

  // If the block pointee type isn't canonical, this won't be a canonical
  // type either so fill in the canonical type field.
  QualType Canonical;
  if (!T->isCanonical()) {
    Canonical = getBlockPointerType(getCanonicalType(T));

    // Get the new insert position for the node we care about.
    BlockPointerType *NewIP =
      BlockPointerTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(NewIP == 0 && "Shouldn't be in the map!"); NewIP = NewIP;
  }
  BlockPointerType *New = new (*this,8) BlockPointerType(T, Canonical);
  Types.push_back(New);
  BlockPointerTypes.InsertNode(New, InsertPos);
  return QualType(New, 0);
}

/// getLValueReferenceType - Return the uniqued reference to the type for an
/// lvalue reference to the specified type.
QualType ASTContext::getLValueReferenceType(QualType T) {
  // Unique pointers, to guarantee there is only one pointer of a particular
  // structure.
  llvm::FoldingSetNodeID ID;
  ReferenceType::Profile(ID, T);

  void *InsertPos = 0;
  if (LValueReferenceType *RT =
        LValueReferenceTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(RT, 0);

  // If the referencee type isn't canonical, this won't be a canonical type
  // either, so fill in the canonical type field.
  QualType Canonical;
  if (!T->isCanonical()) {
    Canonical = getLValueReferenceType(getCanonicalType(T));

    // Get the new insert position for the node we care about.
    LValueReferenceType *NewIP =
      LValueReferenceTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(NewIP == 0 && "Shouldn't be in the map!"); NewIP = NewIP;
  }

  LValueReferenceType *New = new (*this,8) LValueReferenceType(T, Canonical);
  Types.push_back(New);
  LValueReferenceTypes.InsertNode(New, InsertPos);
  return QualType(New, 0);
}

/// getRValueReferenceType - Return the uniqued reference to the type for an
/// rvalue reference to the specified type.
QualType ASTContext::getRValueReferenceType(QualType T) {
  // Unique pointers, to guarantee there is only one pointer of a particular
  // structure.
  llvm::FoldingSetNodeID ID;
  ReferenceType::Profile(ID, T);

  void *InsertPos = 0;
  if (RValueReferenceType *RT =
        RValueReferenceTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(RT, 0);

  // If the referencee type isn't canonical, this won't be a canonical type
  // either, so fill in the canonical type field.
  QualType Canonical;
  if (!T->isCanonical()) {
    Canonical = getRValueReferenceType(getCanonicalType(T));

    // Get the new insert position for the node we care about.
    RValueReferenceType *NewIP =
      RValueReferenceTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(NewIP == 0 && "Shouldn't be in the map!"); NewIP = NewIP;
  }

  RValueReferenceType *New = new (*this,8) RValueReferenceType(T, Canonical);
  Types.push_back(New);
  RValueReferenceTypes.InsertNode(New, InsertPos);
  return QualType(New, 0);
}

/// getMemberPointerType - Return the uniqued reference to the type for a
/// member pointer to the specified type, in the specified class.
QualType ASTContext::getMemberPointerType(QualType T, const Type *Cls)
{
  // Unique pointers, to guarantee there is only one pointer of a particular
  // structure.
  llvm::FoldingSetNodeID ID;
  MemberPointerType::Profile(ID, T, Cls);

  void *InsertPos = 0;
  if (MemberPointerType *PT =
      MemberPointerTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(PT, 0);

  // If the pointee or class type isn't canonical, this won't be a canonical
  // type either, so fill in the canonical type field.
  QualType Canonical;
  if (!T->isCanonical()) {
    Canonical = getMemberPointerType(getCanonicalType(T),getCanonicalType(Cls));

    // Get the new insert position for the node we care about.
    MemberPointerType *NewIP =
      MemberPointerTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(NewIP == 0 && "Shouldn't be in the map!"); NewIP = NewIP;
  }
  MemberPointerType *New = new (*this,8) MemberPointerType(T, Cls, Canonical);
  Types.push_back(New);
  MemberPointerTypes.InsertNode(New, InsertPos);
  return QualType(New, 0);
}

/// getConstantArrayType - Return the unique reference to the type for an
/// array of the specified element type.
QualType ASTContext::getConstantArrayType(QualType EltTy,
                                          const llvm::APInt &ArySizeIn,
                                          ArrayType::ArraySizeModifier ASM,
                                          unsigned EltTypeQuals) {
  assert((EltTy->isDependentType() || EltTy->isConstantSizeType()) &&
         "Constant array of VLAs is illegal!");

  // Convert the array size into a canonical width matching the pointer size for
  // the target.
  llvm::APInt ArySize(ArySizeIn);
  ArySize.zextOrTrunc(Target.getPointerWidth(EltTy.getAddressSpace()));

  llvm::FoldingSetNodeID ID;
  ConstantArrayType::Profile(ID, EltTy, ArySize, ASM, EltTypeQuals);

  void *InsertPos = 0;
  if (ConstantArrayType *ATP =
      ConstantArrayTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(ATP, 0);

  // If the element type isn't canonical, this won't be a canonical type either,
  // so fill in the canonical type field.
  QualType Canonical;
  if (!EltTy->isCanonical()) {
    Canonical = getConstantArrayType(getCanonicalType(EltTy), ArySize,
                                     ASM, EltTypeQuals);
    // Get the new insert position for the node we care about.
    ConstantArrayType *NewIP =
      ConstantArrayTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(NewIP == 0 && "Shouldn't be in the map!"); NewIP = NewIP;
  }

  ConstantArrayType *New =
    new(*this,8)ConstantArrayType(EltTy, Canonical, ArySize, ASM, EltTypeQuals);
  ConstantArrayTypes.InsertNode(New, InsertPos);
  Types.push_back(New);
  return QualType(New, 0);
}

/// getVariableArrayType - Returns a non-unique reference to the type for a
/// variable array of the specified element type.
QualType ASTContext::getVariableArrayType(QualType EltTy, Expr *NumElts,
                                          ArrayType::ArraySizeModifier ASM,
                                          unsigned EltTypeQuals) {
  // Since we don't unique expressions, it isn't possible to unique VLA's
  // that have an expression provided for their size.

  VariableArrayType *New =
    new(*this,8)VariableArrayType(EltTy,QualType(), NumElts, ASM, EltTypeQuals);

  VariableArrayTypes.push_back(New);
  Types.push_back(New);
  return QualType(New, 0);
}

/// getDependentSizedArrayType - Returns a non-unique reference to
/// the type for a dependently-sized array of the specified element
/// type. FIXME: We will need these to be uniqued, or at least
/// comparable, at some point.
QualType ASTContext::getDependentSizedArrayType(QualType EltTy, Expr *NumElts,
                                                ArrayType::ArraySizeModifier ASM,
                                                unsigned EltTypeQuals) {
  assert((NumElts->isTypeDependent() || NumElts->isValueDependent()) &&
         "Size must be type- or value-dependent!");

  // Since we don't unique expressions, it isn't possible to unique
  // dependently-sized array types.

  DependentSizedArrayType *New =
      new (*this,8) DependentSizedArrayType(EltTy, QualType(), NumElts,
                                            ASM, EltTypeQuals);

  DependentSizedArrayTypes.push_back(New);
  Types.push_back(New);
  return QualType(New, 0);
}

QualType ASTContext::getIncompleteArrayType(QualType EltTy,
                                            ArrayType::ArraySizeModifier ASM,
                                            unsigned EltTypeQuals) {
  llvm::FoldingSetNodeID ID;
  IncompleteArrayType::Profile(ID, EltTy, ASM, EltTypeQuals);

  void *InsertPos = 0;
  if (IncompleteArrayType *ATP =
       IncompleteArrayTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(ATP, 0);

  // If the element type isn't canonical, this won't be a canonical type
  // either, so fill in the canonical type field.
  QualType Canonical;

  if (!EltTy->isCanonical()) {
    Canonical = getIncompleteArrayType(getCanonicalType(EltTy),
                                       ASM, EltTypeQuals);

    // Get the new insert position for the node we care about.
    IncompleteArrayType *NewIP =
      IncompleteArrayTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(NewIP == 0 && "Shouldn't be in the map!"); NewIP = NewIP;
  }

  IncompleteArrayType *New = new (*this,8) IncompleteArrayType(EltTy, Canonical,
                                                           ASM, EltTypeQuals);

  IncompleteArrayTypes.InsertNode(New, InsertPos);
  Types.push_back(New);
  return QualType(New, 0);
}

/// getVectorType - Return the unique reference to a vector type of
/// the specified element type and size. VectorType must be a built-in type.
QualType ASTContext::getVectorType(QualType vecType, unsigned NumElts) {
  BuiltinType *baseType;

  baseType = dyn_cast<BuiltinType>(getCanonicalType(vecType).getTypePtr());
  assert(baseType != 0 && "getVectorType(): Expecting a built-in type");

  // Check if we've already instantiated a vector of this type.
  llvm::FoldingSetNodeID ID;
  VectorType::Profile(ID, vecType, NumElts, Type::Vector);
  void *InsertPos = 0;
  if (VectorType *VTP = VectorTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(VTP, 0);

  // If the element type isn't canonical, this won't be a canonical type either,
  // so fill in the canonical type field.
  QualType Canonical;
  if (!vecType->isCanonical()) {
    Canonical = getVectorType(getCanonicalType(vecType), NumElts);

    // Get the new insert position for the node we care about.
    VectorType *NewIP = VectorTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(NewIP == 0 && "Shouldn't be in the map!"); NewIP = NewIP;
  }
  VectorType *New = new (*this,8) VectorType(vecType, NumElts, Canonical);
  VectorTypes.InsertNode(New, InsertPos);
  Types.push_back(New);
  return QualType(New, 0);
}

/// getExtVectorType - Return the unique reference to an extended vector type of
/// the specified element type and size. VectorType must be a built-in type.
QualType ASTContext::getExtVectorType(QualType vecType, unsigned NumElts) {
  BuiltinType *baseType;

  baseType = dyn_cast<BuiltinType>(getCanonicalType(vecType).getTypePtr());
  assert(baseType != 0 && "getExtVectorType(): Expecting a built-in type");

  // Check if we've already instantiated a vector of this type.
  llvm::FoldingSetNodeID ID;
  VectorType::Profile(ID, vecType, NumElts, Type::ExtVector);
  void *InsertPos = 0;
  if (VectorType *VTP = VectorTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(VTP, 0);

  // If the element type isn't canonical, this won't be a canonical type either,
  // so fill in the canonical type field.
  QualType Canonical;
  if (!vecType->isCanonical()) {
    Canonical = getExtVectorType(getCanonicalType(vecType), NumElts);

    // Get the new insert position for the node we care about.
    VectorType *NewIP = VectorTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(NewIP == 0 && "Shouldn't be in the map!"); NewIP = NewIP;
  }
  ExtVectorType *New = new (*this,8) ExtVectorType(vecType, NumElts, Canonical);
  VectorTypes.InsertNode(New, InsertPos);
  Types.push_back(New);
  return QualType(New, 0);
}

/// getFunctionNoProtoType - Return a K&R style C function type like 'int()'.
///
QualType ASTContext::getFunctionNoProtoType(QualType ResultTy) {
  // Unique functions, to guarantee there is only one function of a particular
  // structure.
  llvm::FoldingSetNodeID ID;
  FunctionNoProtoType::Profile(ID, ResultTy);

  void *InsertPos = 0;
  if (FunctionNoProtoType *FT =
        FunctionNoProtoTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(FT, 0);

  QualType Canonical;
  if (!ResultTy->isCanonical()) {
    Canonical = getFunctionNoProtoType(getCanonicalType(ResultTy));

    // Get the new insert position for the node we care about.
    FunctionNoProtoType *NewIP =
      FunctionNoProtoTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(NewIP == 0 && "Shouldn't be in the map!"); NewIP = NewIP;
  }

  FunctionNoProtoType *New =new(*this,8)FunctionNoProtoType(ResultTy,Canonical);
  Types.push_back(New);
  FunctionNoProtoTypes.InsertNode(New, InsertPos);
  return QualType(New, 0);
}

/// getFunctionType - Return a normal function type with a typed argument
/// list.  isVariadic indicates whether the argument list includes '...'.
QualType ASTContext::getFunctionType(QualType ResultTy,const QualType *ArgArray,
                                     unsigned NumArgs, bool isVariadic,
                                     unsigned TypeQuals, bool hasExceptionSpec,
                                     bool hasAnyExceptionSpec, unsigned NumExs,
                                     const QualType *ExArray) {
  // Unique functions, to guarantee there is only one function of a particular
  // structure.
  llvm::FoldingSetNodeID ID;
  FunctionProtoType::Profile(ID, ResultTy, ArgArray, NumArgs, isVariadic,
                             TypeQuals, hasExceptionSpec, hasAnyExceptionSpec,
                             NumExs, ExArray);

  void *InsertPos = 0;
  if (FunctionProtoType *FTP =
        FunctionProtoTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(FTP, 0);

  // Determine whether the type being created is already canonical or not.
  bool isCanonical = ResultTy->isCanonical();
  if (hasExceptionSpec)
    isCanonical = false;
  for (unsigned i = 0; i != NumArgs && isCanonical; ++i)
    if (!ArgArray[i]->isCanonical())
      isCanonical = false;

  // If this type isn't canonical, get the canonical version of it.
  // The exception spec is not part of the canonical type.
  QualType Canonical;
  if (!isCanonical) {
    llvm::SmallVector<QualType, 16> CanonicalArgs;
    CanonicalArgs.reserve(NumArgs);
    for (unsigned i = 0; i != NumArgs; ++i)
      CanonicalArgs.push_back(getCanonicalType(ArgArray[i]));

    Canonical = getFunctionType(getCanonicalType(ResultTy),
                                CanonicalArgs.data(), NumArgs,
                                isVariadic, TypeQuals);

    // Get the new insert position for the node we care about.
    FunctionProtoType *NewIP =
      FunctionProtoTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(NewIP == 0 && "Shouldn't be in the map!"); NewIP = NewIP;
  }

  // FunctionProtoType objects are allocated with extra bytes after them
  // for two variable size arrays (for parameter and exception types) at the
  // end of them.
  FunctionProtoType *FTP =
    (FunctionProtoType*)Allocate(sizeof(FunctionProtoType) +
                                 NumArgs*sizeof(QualType) +
                                 NumExs*sizeof(QualType), 8);
  new (FTP) FunctionProtoType(ResultTy, ArgArray, NumArgs, isVariadic,
                              TypeQuals, hasExceptionSpec, hasAnyExceptionSpec,
                              ExArray, NumExs, Canonical);
  Types.push_back(FTP);
  FunctionProtoTypes.InsertNode(FTP, InsertPos);
  return QualType(FTP, 0);
}

/// getTypeDeclType - Return the unique reference to the type for the
/// specified type declaration.
QualType ASTContext::getTypeDeclType(TypeDecl *Decl, TypeDecl* PrevDecl) {
  assert(Decl && "Passed null for Decl param");
  if (Decl->TypeForDecl) return QualType(Decl->TypeForDecl, 0);

  if (TypedefDecl *Typedef = dyn_cast<TypedefDecl>(Decl))
    return getTypedefType(Typedef);
  else if (isa<TemplateTypeParmDecl>(Decl)) {
    assert(false && "Template type parameter types are always available.");
  } else if (ObjCInterfaceDecl *ObjCInterface = dyn_cast<ObjCInterfaceDecl>(Decl))
    return getObjCInterfaceType(ObjCInterface);

  if (RecordDecl *Record = dyn_cast<RecordDecl>(Decl)) {
    if (PrevDecl)
      Decl->TypeForDecl = PrevDecl->TypeForDecl;
    else
      Decl->TypeForDecl = new (*this,8) RecordType(Record);
  }
  else if (EnumDecl *Enum = dyn_cast<EnumDecl>(Decl)) {
    if (PrevDecl)
      Decl->TypeForDecl = PrevDecl->TypeForDecl;
    else
      Decl->TypeForDecl = new (*this,8) EnumType(Enum);
  }
  else
    assert(false && "TypeDecl without a type?");

  if (!PrevDecl) Types.push_back(Decl->TypeForDecl);
  return QualType(Decl->TypeForDecl, 0);
}

/// getTypedefType - Return the unique reference to the type for the
/// specified typename decl.
QualType ASTContext::getTypedefType(TypedefDecl *Decl) {
  if (Decl->TypeForDecl) return QualType(Decl->TypeForDecl, 0);

  QualType Canonical = getCanonicalType(Decl->getUnderlyingType());
  Decl->TypeForDecl = new(*this,8) TypedefType(Type::Typedef, Decl, Canonical);
  Types.push_back(Decl->TypeForDecl);
  return QualType(Decl->TypeForDecl, 0);
}

/// getObjCInterfaceType - Return the unique reference to the type for the
/// specified ObjC interface decl.
QualType ASTContext::getObjCInterfaceType(const ObjCInterfaceDecl *Decl) {
  if (Decl->TypeForDecl) return QualType(Decl->TypeForDecl, 0);

  ObjCInterfaceDecl *OID = const_cast<ObjCInterfaceDecl*>(Decl);
  Decl->TypeForDecl = new(*this,8) ObjCInterfaceType(Type::ObjCInterface, OID);
  Types.push_back(Decl->TypeForDecl);
  return QualType(Decl->TypeForDecl, 0);
}

/// \brief Retrieve the template type parameter type for a template
/// parameter with the given depth, index, and (optionally) name.
QualType ASTContext::getTemplateTypeParmType(unsigned Depth, unsigned Index,
                                             IdentifierInfo *Name) {
  llvm::FoldingSetNodeID ID;
  TemplateTypeParmType::Profile(ID, Depth, Index, Name);
  void *InsertPos = 0;
  TemplateTypeParmType *TypeParm
    = TemplateTypeParmTypes.FindNodeOrInsertPos(ID, InsertPos);

  if (TypeParm)
    return QualType(TypeParm, 0);

  if (Name)
    TypeParm = new (*this, 8) TemplateTypeParmType(Depth, Index, Name,
                                         getTemplateTypeParmType(Depth, Index));
  else
    TypeParm = new (*this, 8) TemplateTypeParmType(Depth, Index);

  Types.push_back(TypeParm);
  TemplateTypeParmTypes.InsertNode(TypeParm, InsertPos);

  return QualType(TypeParm, 0);
}

QualType
ASTContext::getTemplateSpecializationType(TemplateName Template,
                                          const TemplateArgument *Args,
                                          unsigned NumArgs,
                                          QualType Canon) {
  if (!Canon.isNull())
    Canon = getCanonicalType(Canon);

  llvm::FoldingSetNodeID ID;
  TemplateSpecializationType::Profile(ID, Template, Args, NumArgs);

  void *InsertPos = 0;
  TemplateSpecializationType *Spec
    = TemplateSpecializationTypes.FindNodeOrInsertPos(ID, InsertPos);

  if (Spec)
    return QualType(Spec, 0);

  void *Mem = Allocate((sizeof(TemplateSpecializationType) +
                        sizeof(TemplateArgument) * NumArgs),
                       8);
  Spec = new (Mem) TemplateSpecializationType(Template, Args, NumArgs, Canon);
  Types.push_back(Spec);
  TemplateSpecializationTypes.InsertNode(Spec, InsertPos);

  return QualType(Spec, 0);
}

QualType
ASTContext::getQualifiedNameType(NestedNameSpecifier *NNS,
                                 QualType NamedType) {
  llvm::FoldingSetNodeID ID;
  QualifiedNameType::Profile(ID, NNS, NamedType);

  void *InsertPos = 0;
  QualifiedNameType *T
    = QualifiedNameTypes.FindNodeOrInsertPos(ID, InsertPos);
  if (T)
    return QualType(T, 0);

  T = new (*this) QualifiedNameType(NNS, NamedType,
                                    getCanonicalType(NamedType));
  Types.push_back(T);
  QualifiedNameTypes.InsertNode(T, InsertPos);
  return QualType(T, 0);
}

QualType ASTContext::getTypenameType(NestedNameSpecifier *NNS,
                                     const IdentifierInfo *Name,
                                     QualType Canon) {
  assert(NNS->isDependent() && "nested-name-specifier must be dependent");

  if (Canon.isNull()) {
    NestedNameSpecifier *CanonNNS = getCanonicalNestedNameSpecifier(NNS);
    if (CanonNNS != NNS)
      Canon = getTypenameType(CanonNNS, Name);
  }

  llvm::FoldingSetNodeID ID;
  TypenameType::Profile(ID, NNS, Name);

  void *InsertPos = 0;
  TypenameType *T
    = TypenameTypes.FindNodeOrInsertPos(ID, InsertPos);
  if (T)
    return QualType(T, 0);

  T = new (*this) TypenameType(NNS, Name, Canon);
  Types.push_back(T);
  TypenameTypes.InsertNode(T, InsertPos);
  return QualType(T, 0);
}

QualType
ASTContext::getTypenameType(NestedNameSpecifier *NNS,
                            const TemplateSpecializationType *TemplateId,
                            QualType Canon) {
  assert(NNS->isDependent() && "nested-name-specifier must be dependent");

  if (Canon.isNull()) {
    NestedNameSpecifier *CanonNNS = getCanonicalNestedNameSpecifier(NNS);
    QualType CanonType = getCanonicalType(QualType(TemplateId, 0));
    if (CanonNNS != NNS || CanonType != QualType(TemplateId, 0)) {
      const TemplateSpecializationType *CanonTemplateId
        = CanonType->getAsTemplateSpecializationType();
      assert(CanonTemplateId &&
             "Canonical type must also be a template specialization type");
      Canon = getTypenameType(CanonNNS, CanonTemplateId);
    }
  }

  llvm::FoldingSetNodeID ID;
  TypenameType::Profile(ID, NNS, TemplateId);

  void *InsertPos = 0;
  TypenameType *T
    = TypenameTypes.FindNodeOrInsertPos(ID, InsertPos);
  if (T)
    return QualType(T, 0);

  T = new (*this) TypenameType(NNS, TemplateId, Canon);
  Types.push_back(T);
  TypenameTypes.InsertNode(T, InsertPos);
  return QualType(T, 0);
}

/// CmpProtocolNames - Comparison predicate for sorting protocols
/// alphabetically.
static bool CmpProtocolNames(const ObjCProtocolDecl *LHS,
                            const ObjCProtocolDecl *RHS) {
  return LHS->getDeclName() < RHS->getDeclName();
}

static void SortAndUniqueProtocols(ObjCProtocolDecl **&Protocols,
                                   unsigned &NumProtocols) {
  ObjCProtocolDecl **ProtocolsEnd = Protocols+NumProtocols;

  // Sort protocols, keyed by name.
  std::sort(Protocols, Protocols+NumProtocols, CmpProtocolNames);

  // Remove duplicates.
  ProtocolsEnd = std::unique(Protocols, ProtocolsEnd);
  NumProtocols = ProtocolsEnd-Protocols;
}


/// getObjCQualifiedInterfaceType - Return a ObjCQualifiedInterfaceType type for
/// the given interface decl and the conforming protocol list.
QualType ASTContext::getObjCQualifiedInterfaceType(ObjCInterfaceDecl *Decl,
                       ObjCProtocolDecl **Protocols, unsigned NumProtocols) {
  // Sort the protocol list alphabetically to canonicalize it.
  SortAndUniqueProtocols(Protocols, NumProtocols);

  llvm::FoldingSetNodeID ID;
  ObjCQualifiedInterfaceType::Profile(ID, Decl, Protocols, NumProtocols);

  void *InsertPos = 0;
  if (ObjCQualifiedInterfaceType *QT =
      ObjCQualifiedInterfaceTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(QT, 0);

  // No Match;
  ObjCQualifiedInterfaceType *QType =
    new (*this,8) ObjCQualifiedInterfaceType(Decl, Protocols, NumProtocols);

  Types.push_back(QType);
  ObjCQualifiedInterfaceTypes.InsertNode(QType, InsertPos);
  return QualType(QType, 0);
}

/// getObjCQualifiedIdType - Return an ObjCQualifiedIdType for the 'id' decl
/// and the conforming protocol list.
QualType ASTContext::getObjCQualifiedIdType(ObjCProtocolDecl **Protocols,
                                            unsigned NumProtocols) {
  // Sort the protocol list alphabetically to canonicalize it.
  SortAndUniqueProtocols(Protocols, NumProtocols);

  llvm::FoldingSetNodeID ID;
  ObjCQualifiedIdType::Profile(ID, Protocols, NumProtocols);

  void *InsertPos = 0;
  if (ObjCQualifiedIdType *QT =
        ObjCQualifiedIdTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(QT, 0);

  // No Match;
  ObjCQualifiedIdType *QType =
    new (*this,8) ObjCQualifiedIdType(Protocols, NumProtocols);
  Types.push_back(QType);
  ObjCQualifiedIdTypes.InsertNode(QType, InsertPos);
  return QualType(QType, 0);
}

/// getTypeOfExprType - Unlike many "get<Type>" functions, we can't unique
/// TypeOfExprType AST's (since expression's are never shared). For example,
/// multiple declarations that refer to "typeof(x)" all contain different
/// DeclRefExpr's. This doesn't effect the type checker, since it operates
/// on canonical type's (which are always unique).
QualType ASTContext::getTypeOfExprType(Expr *tofExpr) {
  QualType Canonical = getCanonicalType(tofExpr->getType());
  TypeOfExprType *toe = new (*this,8) TypeOfExprType(tofExpr, Canonical);
  Types.push_back(toe);
  return QualType(toe, 0);
}

/// getTypeOfType -  Unlike many "get<Type>" functions, we don't unique
/// TypeOfType AST's. The only motivation to unique these nodes would be
/// memory savings. Since typeof(t) is fairly uncommon, space shouldn't be
/// an issue. This doesn't effect the type checker, since it operates
/// on canonical type's (which are always unique).
QualType ASTContext::getTypeOfType(QualType tofType) {
  QualType Canonical = getCanonicalType(tofType);
  TypeOfType *tot = new (*this,8) TypeOfType(tofType, Canonical);
  Types.push_back(tot);
  return QualType(tot, 0);
}

/// getTagDeclType - Return the unique reference to the type for the
/// specified TagDecl (struct/union/class/enum) decl.
QualType ASTContext::getTagDeclType(TagDecl *Decl) {
  assert (Decl);
  return getTypeDeclType(Decl);
}

/// getSizeType - Return the unique type for "size_t" (C99 7.17), the result
/// of the sizeof operator (C99 6.5.3.4p4). The value is target dependent and
/// needs to agree with the definition in <stddef.h>.
QualType ASTContext::getSizeType() const {
  return getFromTargetType(Target.getSizeType());
}

/// getSignedWCharType - Return the type of "signed wchar_t".
/// Used when in C++, as a GCC extension.
QualType ASTContext::getSignedWCharType() const {
  // FIXME: derive from "Target" ?
  return WCharTy;
}

/// getUnsignedWCharType - Return the type of "unsigned wchar_t".
/// Used when in C++, as a GCC extension.
QualType ASTContext::getUnsignedWCharType() const {
  // FIXME: derive from "Target" ?
  return UnsignedIntTy;
}

/// getPointerDiffType - Return the unique type for "ptrdiff_t" (ref?)
/// defined in <stddef.h>. Pointer - pointer requires this (C99 6.5.6p9).
QualType ASTContext::getPointerDiffType() const {
  return getFromTargetType(Target.getPtrDiffType(0));
}

//===----------------------------------------------------------------------===//
//                              Type Operators
//===----------------------------------------------------------------------===//

/// getCanonicalType - Return the canonical (structural) type corresponding to
/// the specified potentially non-canonical type.  The non-canonical version
/// of a type may have many "decorated" versions of types.  Decorators can
/// include typedefs, 'typeof' operators, etc. The returned type is guaranteed
/// to be free of any of these, allowing two canonical types to be compared
/// for exact equality with a simple pointer comparison.
QualType ASTContext::getCanonicalType(QualType T) {
  QualType CanType = T.getTypePtr()->getCanonicalTypeInternal();

  // If the result has type qualifiers, make sure to canonicalize them as well.
  unsigned TypeQuals = T.getCVRQualifiers() | CanType.getCVRQualifiers();
  if (TypeQuals == 0) return CanType;

  // If the type qualifiers are on an array type, get the canonical type of the
  // array with the qualifiers applied to the element type.
  ArrayType *AT = dyn_cast<ArrayType>(CanType);
  if (!AT)
    return CanType.getQualifiedType(TypeQuals);

  // Get the canonical version of the element with the extra qualifiers on it.
  // This can recursively sink qualifiers through multiple levels of arrays.
  QualType NewEltTy=AT->getElementType().getWithAdditionalQualifiers(TypeQuals);
  NewEltTy = getCanonicalType(NewEltTy);

  if (ConstantArrayType *CAT = dyn_cast<ConstantArrayType>(AT))
    return getConstantArrayType(NewEltTy, CAT->getSize(),CAT->getSizeModifier(),
                                CAT->getIndexTypeQualifier());
  if (IncompleteArrayType *IAT = dyn_cast<IncompleteArrayType>(AT))
    return getIncompleteArrayType(NewEltTy, IAT->getSizeModifier(),
                                  IAT->getIndexTypeQualifier());

  if (DependentSizedArrayType *DSAT = dyn_cast<DependentSizedArrayType>(AT))
    return getDependentSizedArrayType(NewEltTy, DSAT->getSizeExpr(),
                                      DSAT->getSizeModifier(),
                                      DSAT->getIndexTypeQualifier());

  VariableArrayType *VAT = cast<VariableArrayType>(AT);
  return getVariableArrayType(NewEltTy, VAT->getSizeExpr(),
                              VAT->getSizeModifier(),
                              VAT->getIndexTypeQualifier());
}

Decl *ASTContext::getCanonicalDecl(Decl *D) {
  if (!D)
    return 0;

  if (TagDecl *Tag = dyn_cast<TagDecl>(D)) {
    QualType T = getTagDeclType(Tag);
    return cast<TagDecl>(cast<TagType>(T.getTypePtr()->CanonicalType)
                         ->getDecl());
  }

  if (ClassTemplateDecl *Template = dyn_cast<ClassTemplateDecl>(D)) {
    while (Template->getPreviousDeclaration())
      Template = Template->getPreviousDeclaration();
    return Template;
  }

  if (const FunctionDecl *Function = dyn_cast<FunctionDecl>(D)) {
    while (Function->getPreviousDeclaration())
      Function = Function->getPreviousDeclaration();
    return const_cast<FunctionDecl *>(Function);
  }

  if (const VarDecl *Var = dyn_cast<VarDecl>(D)) {
    while (Var->getPreviousDeclaration())
      Var = Var->getPreviousDeclaration();
    return const_cast<VarDecl *>(Var);
  }

  return D;
}

TemplateName ASTContext::getCanonicalTemplateName(TemplateName Name) {
  // If this template name refers to a template, the canonical
  // template name merely stores the template itself.
  if (TemplateDecl *Template = Name.getAsTemplateDecl())
    return TemplateName(cast<TemplateDecl>(getCanonicalDecl(Template)));

  DependentTemplateName *DTN = Name.getAsDependentTemplateName();
  assert(DTN && "Non-dependent template names must refer to template decls.");
  return DTN->CanonicalTemplateName;
}

NestedNameSpecifier *
ASTContext::getCanonicalNestedNameSpecifier(NestedNameSpecifier *NNS) {
  if (!NNS)
    return 0;

  switch (NNS->getKind()) {
  case NestedNameSpecifier::Identifier:
    // Canonicalize the prefix but keep the identifier the same.
    return NestedNameSpecifier::Create(*this,
                         getCanonicalNestedNameSpecifier(NNS->getPrefix()),
                                       NNS->getAsIdentifier());

  case NestedNameSpecifier::Namespace:
    // A namespace is canonical; build a nested-name-specifier with
    // this namespace and no prefix.
    return NestedNameSpecifier::Create(*this, 0, NNS->getAsNamespace());

  case NestedNameSpecifier::TypeSpec:
  case NestedNameSpecifier::TypeSpecWithTemplate: {
    QualType T = getCanonicalType(QualType(NNS->getAsType(), 0));
    NestedNameSpecifier *Prefix = 0;

    // FIXME: This isn't the right check!
    if (T->isDependentType())
      Prefix = getCanonicalNestedNameSpecifier(NNS->getPrefix());

    return NestedNameSpecifier::Create(*this, Prefix,
                 NNS->getKind() == NestedNameSpecifier::TypeSpecWithTemplate,
                                       T.getTypePtr());
  }

  case NestedNameSpecifier::Global:
    // The global specifier is canonical and unique.
    return NNS;
  }

  // Required to silence a GCC warning
  return 0;
}


const ArrayType *ASTContext::getAsArrayType(QualType T) {
  // Handle the non-qualified case efficiently.
  if (T.getCVRQualifiers() == 0) {
    // Handle the common positive case fast.
    if (const ArrayType *AT = dyn_cast<ArrayType>(T))
      return AT;
  }

  // Handle the common negative case fast, ignoring CVR qualifiers.
  QualType CType = T->getCanonicalTypeInternal();

  // Make sure to look through type qualifiers (like ExtQuals) for the negative
  // test.
  if (!isa<ArrayType>(CType) &&
      !isa<ArrayType>(CType.getUnqualifiedType()))
    return 0;

  // Apply any CVR qualifiers from the array type to the element type.  This
  // implements C99 6.7.3p8: "If the specification of an array type includes
  // any type qualifiers, the element type is so qualified, not the array type."

  // If we get here, we either have type qualifiers on the type, or we have
  // sugar such as a typedef in the way.  If we have type qualifiers on the type
  // we must propagate them down into the elemeng type.
  unsigned CVRQuals = T.getCVRQualifiers();
  unsigned AddrSpace = 0;
  Type *Ty = T.getTypePtr();

  // Rip through ExtQualType's and typedefs to get to a concrete type.
  while (1) {
    if (const ExtQualType *EXTQT = dyn_cast<ExtQualType>(Ty)) {
      AddrSpace = EXTQT->getAddressSpace();
      Ty = EXTQT->getBaseType();
    } else {
      T = Ty->getDesugaredType();
      if (T.getTypePtr() == Ty && T.getCVRQualifiers() == 0)
        break;
      CVRQuals |= T.getCVRQualifiers();
      Ty = T.getTypePtr();
    }
  }

  // If we have a simple case, just return now.
  const ArrayType *ATy = dyn_cast<ArrayType>(Ty);
  if (ATy == 0 || (AddrSpace == 0 && CVRQuals == 0))
    return ATy;

  // Otherwise, we have an array and we have qualifiers on it.  Push the
  // qualifiers into the array element type and return a new array type.
  // Get the canonical version of the element with the extra qualifiers on it.
  // This can recursively sink qualifiers through multiple levels of arrays.
  QualType NewEltTy = ATy->getElementType();
  if (AddrSpace)
    NewEltTy = getAddrSpaceQualType(NewEltTy, AddrSpace);
  NewEltTy = NewEltTy.getWithAdditionalQualifiers(CVRQuals);

  if (const ConstantArrayType *CAT = dyn_cast<ConstantArrayType>(ATy))
    return cast<ArrayType>(getConstantArrayType(NewEltTy, CAT->getSize(),
                                                CAT->getSizeModifier(),
                                                CAT->getIndexTypeQualifier()));
  if (const IncompleteArrayType *IAT = dyn_cast<IncompleteArrayType>(ATy))
    return cast<ArrayType>(getIncompleteArrayType(NewEltTy,
                                                  IAT->getSizeModifier(),
                                                 IAT->getIndexTypeQualifier()));

  if (const DependentSizedArrayType *DSAT
        = dyn_cast<DependentSizedArrayType>(ATy))
    return cast<ArrayType>(
                     getDependentSizedArrayType(NewEltTy,
                                                DSAT->getSizeExpr(),
                                                DSAT->getSizeModifier(),
                                                DSAT->getIndexTypeQualifier()));

  const VariableArrayType *VAT = cast<VariableArrayType>(ATy);
  return cast<ArrayType>(getVariableArrayType(NewEltTy, VAT->getSizeExpr(),
                                              VAT->getSizeModifier(),
                                              VAT->getIndexTypeQualifier()));
}


/// getArrayDecayedType - Return the properly qualified result of decaying the
/// specified array type to a pointer.  This operation is non-trivial when
/// handling typedefs etc.  The canonical type of "T" must be an array type,
/// this returns a pointer to a properly qualified element of the array.
///
/// See C99 6.7.5.3p7 and C99 6.3.2.1p3.
QualType ASTContext::getArrayDecayedType(QualType Ty) {
  // Get the element type with 'getAsArrayType' so that we don't lose any
  // typedefs in the element type of the array.  This also handles propagation
  // of type qualifiers from the array type into the element type if present
  // (C99 6.7.3p8).
  const ArrayType *PrettyArrayType = getAsArrayType(Ty);
  assert(PrettyArrayType && "Not an array type!");

  QualType PtrTy = getPointerType(PrettyArrayType->getElementType());

  // int x[restrict 4] ->  int *restrict
  return PtrTy.getQualifiedType(PrettyArrayType->getIndexTypeQualifier());
}

QualType ASTContext::getBaseElementType(const VariableArrayType *VAT) {
  QualType ElemTy = VAT->getElementType();

  if (const VariableArrayType *VAT = getAsVariableArrayType(ElemTy))
    return getBaseElementType(VAT);

  return ElemTy;
}

/// getFloatingRank - Return a relative rank for floating point types.
/// This routine will assert if passed a built-in type that isn't a float.
static FloatingRank getFloatingRank(QualType T) {
  if (const ComplexType *CT = T->getAsComplexType())
    return getFloatingRank(CT->getElementType());

  assert(T->getAsBuiltinType() && "getFloatingRank(): not a floating type");
  switch (T->getAsBuiltinType()->getKind()) {
  default: assert(0 && "getFloatingRank(): not a floating type");
  case BuiltinType::Float:      return FloatRank;
  case BuiltinType::Double:     return DoubleRank;
  case BuiltinType::LongDouble: return LongDoubleRank;
  }
}

/// getFloatingTypeOfSizeWithinDomain - Returns a real floating
/// point or a complex type (based on typeDomain/typeSize).
/// 'typeDomain' is a real floating point or complex type.
/// 'typeSize' is a real floating point or complex type.
QualType ASTContext::getFloatingTypeOfSizeWithinDomain(QualType Size,
                                                       QualType Domain) const {
  FloatingRank EltRank = getFloatingRank(Size);
  if (Domain->isComplexType()) {
    switch (EltRank) {
    default: assert(0 && "getFloatingRank(): illegal value for rank");
    case FloatRank:      return FloatComplexTy;
    case DoubleRank:     return DoubleComplexTy;
    case LongDoubleRank: return LongDoubleComplexTy;
    }
  }

  assert(Domain->isRealFloatingType() && "Unknown domain!");
  switch (EltRank) {
  default: assert(0 && "getFloatingRank(): illegal value for rank");
  case FloatRank:      return FloatTy;
  case DoubleRank:     return DoubleTy;
  case LongDoubleRank: return LongDoubleTy;
  }
}

/// getFloatingTypeOrder - Compare the rank of the two specified floating
/// point types, ignoring the domain of the type (i.e. 'double' ==
/// '_Complex double').  If LHS > RHS, return 1.  If LHS == RHS, return 0. If
/// LHS < RHS, return -1.
int ASTContext::getFloatingTypeOrder(QualType LHS, QualType RHS) {
  FloatingRank LHSR = getFloatingRank(LHS);
  FloatingRank RHSR = getFloatingRank(RHS);

  if (LHSR == RHSR)
    return 0;
  if (LHSR > RHSR)
    return 1;
  return -1;
}

/// getIntegerRank - Return an integer conversion rank (C99 6.3.1.1p1). This
/// routine will assert if passed a built-in type that isn't an integer or enum,
/// or if it is not canonicalized.
unsigned ASTContext::getIntegerRank(Type *T) {
  assert(T->isCanonical() && "T should be canonicalized");
  if (EnumType* ET = dyn_cast<EnumType>(T))
    T = ET->getDecl()->getIntegerType().getTypePtr();

  // There are two things which impact the integer rank: the width, and
  // the ordering of builtins.  The builtin ordering is encoded in the
  // bottom three bits; the width is encoded in the bits above that.
  if (FixedWidthIntType* FWIT = dyn_cast<FixedWidthIntType>(T)) {
    return FWIT->getWidth() << 3;
  }

  switch (cast<BuiltinType>(T)->getKind()) {
  default: assert(0 && "getIntegerRank(): not a built-in integer");
  case BuiltinType::Bool:
    return 1 + (getIntWidth(BoolTy) << 3);
  case BuiltinType::Char_S:
  case BuiltinType::Char_U:
  case BuiltinType::SChar:
  case BuiltinType::UChar:
    return 2 + (getIntWidth(CharTy) << 3);
  case BuiltinType::Short:
  case BuiltinType::UShort:
    return 3 + (getIntWidth(ShortTy) << 3);
  case BuiltinType::Int:
  case BuiltinType::UInt:
    return 4 + (getIntWidth(IntTy) << 3);
  case BuiltinType::Long:
  case BuiltinType::ULong:
    return 5 + (getIntWidth(LongTy) << 3);
  case BuiltinType::LongLong:
  case BuiltinType::ULongLong:
    return 6 + (getIntWidth(LongLongTy) << 3);
  case BuiltinType::Int128:
  case BuiltinType::UInt128:
    return 7 + (getIntWidth(Int128Ty) << 3);
  }
}

/// getIntegerTypeOrder - Returns the highest ranked integer type:
/// C99 6.3.1.8p1.  If LHS > RHS, return 1.  If LHS == RHS, return 0. If
/// LHS < RHS, return -1.
int ASTContext::getIntegerTypeOrder(QualType LHS, QualType RHS) {
  Type *LHSC = getCanonicalType(LHS).getTypePtr();
  Type *RHSC = getCanonicalType(RHS).getTypePtr();
  if (LHSC == RHSC) return 0;

  bool LHSUnsigned = LHSC->isUnsignedIntegerType();
  bool RHSUnsigned = RHSC->isUnsignedIntegerType();

  unsigned LHSRank = getIntegerRank(LHSC);
  unsigned RHSRank = getIntegerRank(RHSC);

  if (LHSUnsigned == RHSUnsigned) {  // Both signed or both unsigned.
    if (LHSRank == RHSRank) return 0;
    return LHSRank > RHSRank ? 1 : -1;
  }

  // Otherwise, the LHS is signed and the RHS is unsigned or visa versa.
  if (LHSUnsigned) {
    // If the unsigned [LHS] type is larger, return it.
    if (LHSRank >= RHSRank)
      return 1;

    // If the signed type can represent all values of the unsigned type, it
    // wins.  Because we are dealing with 2's complement and types that are
    // powers of two larger than each other, this is always safe.
    return -1;
  }

  // If the unsigned [RHS] type is larger, return it.
  if (RHSRank >= LHSRank)
    return -1;

  // If the signed type can represent all values of the unsigned type, it
  // wins.  Because we are dealing with 2's complement and types that are
  // powers of two larger than each other, this is always safe.
  return 1;
}

// getCFConstantStringType - Return the type used for constant CFStrings.
QualType ASTContext::getCFConstantStringType() {
  if (!CFConstantStringTypeDecl) {
    CFConstantStringTypeDecl =
      RecordDecl::Create(*this, TagDecl::TK_struct, TUDecl, SourceLocation(),
                         &Idents.get("NSConstantString"));
    QualType FieldTypes[4];

    // const int *isa;
    FieldTypes[0] = getPointerType(IntTy.getQualifiedType(QualType::Const));
    // int flags;
    FieldTypes[1] = IntTy;
    // const char *str;
    FieldTypes[2] = getPointerType(CharTy.getQualifiedType(QualType::Const));
    // long length;
    FieldTypes[3] = LongTy;

    // Create fields
    for (unsigned i = 0; i < 4; ++i) {
      FieldDecl *Field = FieldDecl::Create(*this, CFConstantStringTypeDecl,
                                           SourceLocation(), 0,
                                           FieldTypes[i], /*BitWidth=*/0,
                                           /*Mutable=*/false);
      CFConstantStringTypeDecl->addDecl(*this, Field);
    }

    CFConstantStringTypeDecl->completeDefinition(*this);
  }

  return getTagDeclType(CFConstantStringTypeDecl);
}

void ASTContext::setCFConstantStringType(QualType T) {
  const RecordType *Rec = T->getAsRecordType();
  assert(Rec && "Invalid CFConstantStringType");
  CFConstantStringTypeDecl = Rec->getDecl();
}

QualType ASTContext::getObjCFastEnumerationStateType()
{
  if (!ObjCFastEnumerationStateTypeDecl) {
    ObjCFastEnumerationStateTypeDecl =
      RecordDecl::Create(*this, TagDecl::TK_struct, TUDecl, SourceLocation(),
                         &Idents.get("__objcFastEnumerationState"));

    QualType FieldTypes[] = {
      UnsignedLongTy,
      getPointerType(ObjCIdType),
      getPointerType(UnsignedLongTy),
      getConstantArrayType(UnsignedLongTy,
                           llvm::APInt(32, 5), ArrayType::Normal, 0)
    };

    for (size_t i = 0; i < 4; ++i) {
      FieldDecl *Field = FieldDecl::Create(*this,
                                           ObjCFastEnumerationStateTypeDecl,
                                           SourceLocation(), 0,
                                           FieldTypes[i], /*BitWidth=*/0,
                                           /*Mutable=*/false);
      ObjCFastEnumerationStateTypeDecl->addDecl(*this, Field);
    }

    ObjCFastEnumerationStateTypeDecl->completeDefinition(*this);
  }

  return getTagDeclType(ObjCFastEnumerationStateTypeDecl);
}

void ASTContext::setObjCFastEnumerationStateType(QualType T) {
  const RecordType *Rec = T->getAsRecordType();
  assert(Rec && "Invalid ObjCFAstEnumerationStateType");
  ObjCFastEnumerationStateTypeDecl = Rec->getDecl();
}

// This returns true if a type has been typedefed to BOOL:
// typedef <type> BOOL;
static bool isTypeTypedefedAsBOOL(QualType T) {
  if (const TypedefType *TT = dyn_cast<TypedefType>(T))
    if (IdentifierInfo *II = TT->getDecl()->getIdentifier())
      return II->isStr("BOOL");

  return false;
}

/// getObjCEncodingTypeSize returns size of type for objective-c encoding
/// purpose.
int ASTContext::getObjCEncodingTypeSize(QualType type) {
  uint64_t sz = getTypeSize(type);

  // Make all integer and enum types at least as large as an int
  if (sz > 0 && type->isIntegralType())
    sz = std::max(sz, getTypeSize(IntTy));
  // Treat arrays as pointers, since that's how they're passed in.
  else if (type->isArrayType())
    sz = getTypeSize(VoidPtrTy);
  return sz / getTypeSize(CharTy);
}

/// getObjCEncodingForMethodDecl - Return the encoded type for this method
/// declaration.
void ASTContext::getObjCEncodingForMethodDecl(const ObjCMethodDecl *Decl,
                                              std::string& S) {
  // FIXME: This is not very efficient.
  // Encode type qualifer, 'in', 'inout', etc. for the return type.
  getObjCEncodingForTypeQualifier(Decl->getObjCDeclQualifier(), S);
  // Encode result type.
  getObjCEncodingForType(Decl->getResultType(), S);
  // Compute size of all parameters.
  // Start with computing size of a pointer in number of bytes.
  // FIXME: There might(should) be a better way of doing this computation!
  SourceLocation Loc;
  int PtrSize = getTypeSize(VoidPtrTy) / getTypeSize(CharTy);
  // The first two arguments (self and _cmd) are pointers; account for
  // their size.
  int ParmOffset = 2 * PtrSize;
  for (ObjCMethodDecl::param_iterator PI = Decl->param_begin(),
       E = Decl->param_end(); PI != E; ++PI) {
    QualType PType = (*PI)->getType();
    int sz = getObjCEncodingTypeSize(PType);
    assert (sz > 0 && "getObjCEncodingForMethodDecl - Incomplete param type");
    ParmOffset += sz;
  }
  S += llvm::utostr(ParmOffset);
  S += "@0:";
  S += llvm::utostr(PtrSize);

  // Argument types.
  ParmOffset = 2 * PtrSize;
  for (ObjCMethodDecl::param_iterator PI = Decl->param_begin(),
       E = Decl->param_end(); PI != E; ++PI) {
    ParmVarDecl *PVDecl = *PI;
    QualType PType = PVDecl->getOriginalType();
    if (const ArrayType *AT =
          dyn_cast<ArrayType>(PType->getCanonicalTypeInternal())) {
      // Use array's original type only if it has known number of
      // elements.
      if (!isa<ConstantArrayType>(AT))
        PType = PVDecl->getType();
    } else if (PType->isFunctionType())
      PType = PVDecl->getType();
    // Process argument qualifiers for user supplied arguments; such as,
    // 'in', 'inout', etc.
    getObjCEncodingForTypeQualifier(PVDecl->getObjCDeclQualifier(), S);
    getObjCEncodingForType(PType, S);
    S += llvm::utostr(ParmOffset);
    ParmOffset += getObjCEncodingTypeSize(PType);
  }
}

/// getObjCEncodingForPropertyDecl - Return the encoded type for this
/// property declaration. If non-NULL, Container must be either an
/// ObjCCategoryImplDecl or ObjCImplementationDecl; it should only be
/// NULL when getting encodings for protocol properties.
/// Property attributes are stored as a comma-delimited C string. The simple
/// attributes readonly and bycopy are encoded as single characters. The
/// parametrized attributes, getter=name, setter=name, and ivar=name, are
/// encoded as single characters, followed by an identifier. Property types
/// are also encoded as a parametrized attribute. The characters used to encode
/// these attributes are defined by the following enumeration:
/// @code
/// enum PropertyAttributes {
/// kPropertyReadOnly = 'R',   // property is read-only.
/// kPropertyBycopy = 'C',     // property is a copy of the value last assigned
/// kPropertyByref = '&',  // property is a reference to the value last assigned
/// kPropertyDynamic = 'D',    // property is dynamic
/// kPropertyGetter = 'G',     // followed by getter selector name
/// kPropertySetter = 'S',     // followed by setter selector name
/// kPropertyInstanceVariable = 'V'  // followed by instance variable  name
/// kPropertyType = 't'              // followed by old-style type encoding.
/// kPropertyWeak = 'W'              // 'weak' property
/// kPropertyStrong = 'P'            // property GC'able
/// kPropertyNonAtomic = 'N'         // property non-atomic
/// };
/// @endcode
void ASTContext::getObjCEncodingForPropertyDecl(const ObjCPropertyDecl *PD,
                                                const Decl *Container,
                                                std::string& S) {
  // Collect information from the property implementation decl(s).
  bool Dynamic = false;
  ObjCPropertyImplDecl *SynthesizePID = 0;

  // FIXME: Duplicated code due to poor abstraction.
  if (Container) {
    if (const ObjCCategoryImplDecl *CID =
        dyn_cast<ObjCCategoryImplDecl>(Container)) {
      for (ObjCCategoryImplDecl::propimpl_iterator
             i = CID->propimpl_begin(*this), e = CID->propimpl_end(*this);
           i != e; ++i) {
        ObjCPropertyImplDecl *PID = *i;
        if (PID->getPropertyDecl() == PD) {
          if (PID->getPropertyImplementation()==ObjCPropertyImplDecl::Dynamic) {
            Dynamic = true;
          } else {
            SynthesizePID = PID;
          }
        }
      }
    } else {
      const ObjCImplementationDecl *OID=cast<ObjCImplementationDecl>(Container);
      for (ObjCCategoryImplDecl::propimpl_iterator
             i = OID->propimpl_begin(*this), e = OID->propimpl_end(*this);
           i != e; ++i) {
        ObjCPropertyImplDecl *PID = *i;
        if (PID->getPropertyDecl() == PD) {
          if (PID->getPropertyImplementation()==ObjCPropertyImplDecl::Dynamic) {
            Dynamic = true;
          } else {
            SynthesizePID = PID;
          }
        }
      }
    }
  }

  // FIXME: This is not very efficient.
  S = "T";

  // Encode result type.
  // GCC has some special rules regarding encoding of properties which
  // closely resembles encoding of ivars.
  getObjCEncodingForTypeImpl(PD->getType(), S, true, true, 0,
                             true /* outermost type */,
                             true /* encoding for property */);

  if (PD->isReadOnly()) {
    S += ",R";
  } else {
    switch (PD->getSetterKind()) {
    case ObjCPropertyDecl::Assign: break;
    case ObjCPropertyDecl::Copy:   S += ",C"; break;
    case ObjCPropertyDecl::Retain: S += ",&"; break;
    }
  }

  // It really isn't clear at all what this means, since properties
  // are "dynamic by default".
  if (Dynamic)
    S += ",D";

  if (PD->getPropertyAttributes() & ObjCPropertyDecl::OBJC_PR_nonatomic)
    S += ",N";

  if (PD->getPropertyAttributes() & ObjCPropertyDecl::OBJC_PR_getter) {
    S += ",G";
    S += PD->getGetterName().getAsString();
  }

  if (PD->getPropertyAttributes() & ObjCPropertyDecl::OBJC_PR_setter) {
    S += ",S";
    S += PD->getSetterName().getAsString();
  }

  if (SynthesizePID) {
    const ObjCIvarDecl *OID = SynthesizePID->getPropertyIvarDecl();
    S += ",V";
    S += OID->getNameAsString();
  }

  // FIXME: OBJCGC: weak & strong
}

/// getLegacyIntegralTypeEncoding -
/// Another legacy compatibility encoding: 32-bit longs are encoded as
/// 'l' or 'L' , but not always.  For typedefs, we need to use
/// 'i' or 'I' instead if encoding a struct field, or a pointer!
///
void ASTContext::getLegacyIntegralTypeEncoding (QualType &PointeeTy) const {
  if (dyn_cast<TypedefType>(PointeeTy.getTypePtr())) {
    if (const BuiltinType *BT = PointeeTy->getAsBuiltinType()) {
      if (BT->getKind() == BuiltinType::ULong &&
          ((const_cast<ASTContext *>(this))->getIntWidth(PointeeTy) == 32))
        PointeeTy = UnsignedIntTy;
      else
        if (BT->getKind() == BuiltinType::Long &&
            ((const_cast<ASTContext *>(this))->getIntWidth(PointeeTy) == 32))
          PointeeTy = IntTy;
    }
  }
}

void ASTContext::getObjCEncodingForType(QualType T, std::string& S,
                                        const FieldDecl *Field) {
  // We follow the behavior of gcc, expanding structures which are
  // directly pointed to, and expanding embedded structures. Note that
  // these rules are sufficient to prevent recursive encoding of the
  // same type.
  getObjCEncodingForTypeImpl(T, S, true, true, Field,
                             true /* outermost type */);
}

static void EncodeBitField(const ASTContext *Context, std::string& S,
                           const FieldDecl *FD) {
  const Expr *E = FD->getBitWidth();
  assert(E && "bitfield width not there - getObjCEncodingForTypeImpl");
  ASTContext *Ctx = const_cast<ASTContext*>(Context);
  unsigned N = E->EvaluateAsInt(*Ctx).getZExtValue();
  S += 'b';
  S += llvm::utostr(N);
}

void ASTContext::getObjCEncodingForTypeImpl(QualType T, std::string& S,
                                            bool ExpandPointedToStructures,
                                            bool ExpandStructures,
                                            const FieldDecl *FD,
                                            bool OutermostType,
                                            bool EncodingProperty) {
  if (const BuiltinType *BT = T->getAsBuiltinType()) {
    if (FD && FD->isBitField()) {
      EncodeBitField(this, S, FD);
    }
    else {
      char encoding;
      switch (BT->getKind()) {
      default: assert(0 && "Unhandled builtin type kind");
      case BuiltinType::Void:       encoding = 'v'; break;
      case BuiltinType::Bool:       encoding = 'B'; break;
      case BuiltinType::Char_U:
      case BuiltinType::UChar:      encoding = 'C'; break;
      case BuiltinType::UShort:     encoding = 'S'; break;
      case BuiltinType::UInt:       encoding = 'I'; break;
      case BuiltinType::ULong:
          encoding =
            (const_cast<ASTContext *>(this))->getIntWidth(T) == 32 ? 'L' : 'Q';
          break;
      case BuiltinType::UInt128:    encoding = 'T'; break;
      case BuiltinType::ULongLong:  encoding = 'Q'; break;
      case BuiltinType::Char_S:
      case BuiltinType::SChar:      encoding = 'c'; break;
      case BuiltinType::Short:      encoding = 's'; break;
      case BuiltinType::Int:        encoding = 'i'; break;
      case BuiltinType::Long:
        encoding =
          (const_cast<ASTContext *>(this))->getIntWidth(T) == 32 ? 'l' : 'q';
        break;
      case BuiltinType::LongLong:   encoding = 'q'; break;
      case BuiltinType::Int128:     encoding = 't'; break;
      case BuiltinType::Float:      encoding = 'f'; break;
      case BuiltinType::Double:     encoding = 'd'; break;
      case BuiltinType::LongDouble: encoding = 'd'; break;
      }

      S += encoding;
    }
  } else if (const ComplexType *CT = T->getAsComplexType()) {
    S += 'j';
    getObjCEncodingForTypeImpl(CT->getElementType(), S, false, false, 0, false,
                               false);
  } else if (T->isObjCQualifiedIdType()) {
    getObjCEncodingForTypeImpl(getObjCIdType(), S,
                               ExpandPointedToStructures,
                               ExpandStructures, FD);
    if (FD || EncodingProperty) {
      // Note that we do extended encoding of protocol qualifer list
      // Only when doing ivar or property encoding.
      const ObjCQualifiedIdType *QIDT = T->getAsObjCQualifiedIdType();
      S += '"';
      for (ObjCQualifiedIdType::qual_iterator I = QIDT->qual_begin(),
           E = QIDT->qual_end(); I != E; ++I) {
        S += '<';
        S += (*I)->getNameAsString();
        S += '>';
      }
      S += '"';
    }
    return;
  }
  else if (const PointerType *PT = T->getAsPointerType()) {
    QualType PointeeTy = PT->getPointeeType();
    bool isReadOnly = false;
    // For historical/compatibility reasons, the read-only qualifier of the
    // pointee gets emitted _before_ the '^'.  The read-only qualifier of
    // the pointer itself gets ignored, _unless_ we are looking at a typedef!
    // Also, do not emit the 'r' for anything but the outermost type!
    if (dyn_cast<TypedefType>(T.getTypePtr())) {
      if (OutermostType && T.isConstQualified()) {
        isReadOnly = true;
        S += 'r';
      }
    }
    else if (OutermostType) {
      QualType P = PointeeTy;
      while (P->getAsPointerType())
        P = P->getAsPointerType()->getPointeeType();
      if (P.isConstQualified()) {
        isReadOnly = true;
        S += 'r';
      }
    }
    if (isReadOnly) {
      // Another legacy compatibility encoding. Some ObjC qualifier and type
      // combinations need to be rearranged.
      // Rewrite "in const" from "nr" to "rn"
      const char * s = S.c_str();
      int len = S.length();
      if (len >= 2 && s[len-2] == 'n' && s[len-1] == 'r') {
        std::string replace = "rn";
        S.replace(S.end()-2, S.end(), replace);
      }
    }
    if (isObjCIdStructType(PointeeTy)) {
      S += '@';
      return;
    }
    else if (PointeeTy->isObjCInterfaceType()) {
      if (!EncodingProperty &&
          isa<TypedefType>(PointeeTy.getTypePtr())) {
        // Another historical/compatibility reason.
        // We encode the underlying type which comes out as
        // {...};
        S += '^';
        getObjCEncodingForTypeImpl(PointeeTy, S,
                                   false, ExpandPointedToStructures,
                                   NULL);
        return;
      }
      S += '@';
      if (FD || EncodingProperty) {
        const ObjCInterfaceType *OIT =
                PointeeTy.getUnqualifiedType()->getAsObjCInterfaceType();
        ObjCInterfaceDecl *OI = OIT->getDecl();
        S += '"';
        S += OI->getNameAsCString();
        for (ObjCInterfaceType::qual_iterator I = OIT->qual_begin(),
             E = OIT->qual_end(); I != E; ++I) {
          S += '<';
          S += (*I)->getNameAsString();
          S += '>';
        }
        S += '"';
      }
      return;
    } else if (isObjCClassStructType(PointeeTy)) {
      S += '#';
      return;
    } else if (isObjCSelType(PointeeTy)) {
      S += ':';
      return;
    }

    if (PointeeTy->isCharType()) {
      // char pointer types should be encoded as '*' unless it is a
      // type that has been typedef'd to 'BOOL'.
      if (!isTypeTypedefedAsBOOL(PointeeTy)) {
        S += '*';
        return;
      }
    }

    S += '^';
    getLegacyIntegralTypeEncoding(PointeeTy);

    getObjCEncodingForTypeImpl(PointeeTy, S,
                               false, ExpandPointedToStructures,
                               NULL);
  } else if (const ArrayType *AT =
               // Ignore type qualifiers etc.
               dyn_cast<ArrayType>(T->getCanonicalTypeInternal())) {
    if (isa<IncompleteArrayType>(AT)) {
      // Incomplete arrays are encoded as a pointer to the array element.
      S += '^';

      getObjCEncodingForTypeImpl(AT->getElementType(), S,
                                 false, ExpandStructures, FD);
    } else {
      S += '[';

      if (const ConstantArrayType *CAT = dyn_cast<ConstantArrayType>(AT))
        S += llvm::utostr(CAT->getSize().getZExtValue());
      else {
        //Variable length arrays are encoded as a regular array with 0 elements.
        assert(isa<VariableArrayType>(AT) && "Unknown array type!");
        S += '0';
      }

      getObjCEncodingForTypeImpl(AT->getElementType(), S,
                                 false, ExpandStructures, FD);
      S += ']';
    }
  } else if (T->getAsFunctionType()) {
    S += '?';
  } else if (const RecordType *RTy = T->getAsRecordType()) {
    RecordDecl *RDecl = RTy->getDecl();
    S += RDecl->isUnion() ? '(' : '{';
    // Anonymous structures print as '?'
    if (const IdentifierInfo *II = RDecl->getIdentifier()) {
      S += II->getName();
    } else {
      S += '?';
    }
    if (ExpandStructures) {
      S += '=';
      for (RecordDecl::field_iterator Field = RDecl->field_begin(*this),
                                   FieldEnd = RDecl->field_end(*this);
           Field != FieldEnd; ++Field) {
        if (FD) {
          S += '"';
          S += Field->getNameAsString();
          S += '"';
        }

        // Special case bit-fields.
        if (Field->isBitField()) {
          getObjCEncodingForTypeImpl(Field->getType(), S, false, true,
                                     (*Field));
        } else {
          QualType qt = Field->getType();
          getLegacyIntegralTypeEncoding(qt);
          getObjCEncodingForTypeImpl(qt, S, false, true,
                                     FD);
        }
      }
    }
    S += RDecl->isUnion() ? ')' : '}';
  } else if (T->isEnumeralType()) {
    if (FD && FD->isBitField())
      EncodeBitField(this, S, FD);
    else
      S += 'i';
  } else if (T->isBlockPointerType()) {
    S += "@?"; // Unlike a pointer-to-function, which is "^?".
  } else if (T->isObjCInterfaceType()) {
    // @encode(class_name)
    ObjCInterfaceDecl *OI = T->getAsObjCInterfaceType()->getDecl();
    S += '{';
    const IdentifierInfo *II = OI->getIdentifier();
    S += II->getName();
    S += '=';
    llvm::SmallVector<FieldDecl*, 32> RecFields;
    CollectObjCIvars(OI, RecFields);
    for (unsigned i = 0, e = RecFields.size(); i != e; ++i) {
      if (RecFields[i]->isBitField())
        getObjCEncodingForTypeImpl(RecFields[i]->getType(), S, false, true,
                                   RecFields[i]);
      else
        getObjCEncodingForTypeImpl(RecFields[i]->getType(), S, false, true,
                                   FD);
    }
    S += '}';
  }
  else
    assert(0 && "@encode for type not implemented!");
}

void ASTContext::getObjCEncodingForTypeQualifier(Decl::ObjCDeclQualifier QT,
                                                 std::string& S) const {
  if (QT & Decl::OBJC_TQ_In)
    S += 'n';
  if (QT & Decl::OBJC_TQ_Inout)
    S += 'N';
  if (QT & Decl::OBJC_TQ_Out)
    S += 'o';
  if (QT & Decl::OBJC_TQ_Bycopy)
    S += 'O';
  if (QT & Decl::OBJC_TQ_Byref)
    S += 'R';
  if (QT & Decl::OBJC_TQ_Oneway)
    S += 'V';
}

void ASTContext::setBuiltinVaListType(QualType T)
{
  assert(BuiltinVaListType.isNull() && "__builtin_va_list type already set!");

  BuiltinVaListType = T;
}

void ASTContext::setObjCIdType(QualType T)
{
  ObjCIdType = T;

  const TypedefType *TT = T->getAsTypedefType();
  if (!TT)
    return;

  TypedefDecl *TD = TT->getDecl();

  // typedef struct objc_object *id;
  const PointerType *ptr = TD->getUnderlyingType()->getAsPointerType();
  // User error - caller will issue diagnostics.
  if (!ptr)
    return;
  const RecordType *rec = ptr->getPointeeType()->getAsStructureType();
  // User error - caller will issue diagnostics.
  if (!rec)
    return;
  IdStructType = rec;
}

void ASTContext::setObjCSelType(QualType T)
{
  ObjCSelType = T;

  const TypedefType *TT = T->getAsTypedefType();
  if (!TT)
    return;
  TypedefDecl *TD = TT->getDecl();

  // typedef struct objc_selector *SEL;
  const PointerType *ptr = TD->getUnderlyingType()->getAsPointerType();
  if (!ptr)
    return;
  const RecordType *rec = ptr->getPointeeType()->getAsStructureType();
  if (!rec)
    return;
  SelStructType = rec;
}

void ASTContext::setObjCProtoType(QualType QT)
{
  ObjCProtoType = QT;
}

void ASTContext::setObjCClassType(QualType T)
{
  ObjCClassType = T;

  const TypedefType *TT = T->getAsTypedefType();
  if (!TT)
    return;
  TypedefDecl *TD = TT->getDecl();

  // typedef struct objc_class *Class;
  const PointerType *ptr = TD->getUnderlyingType()->getAsPointerType();
  assert(ptr && "'Class' incorrectly typed");
  const RecordType *rec = ptr->getPointeeType()->getAsStructureType();
  assert(rec && "'Class' incorrectly typed");
  ClassStructType = rec;
}

void ASTContext::setObjCConstantStringInterface(ObjCInterfaceDecl *Decl) {
  assert(ObjCConstantStringType.isNull() &&
         "'NSConstantString' type already set!");

  ObjCConstantStringType = getObjCInterfaceType(Decl);
}

/// \brief Retrieve the template name that represents a qualified
/// template name such as \c std::vector.
TemplateName ASTContext::getQualifiedTemplateName(NestedNameSpecifier *NNS,
                                                  bool TemplateKeyword,
                                                  TemplateDecl *Template) {
  llvm::FoldingSetNodeID ID;
  QualifiedTemplateName::Profile(ID, NNS, TemplateKeyword, Template);

  void *InsertPos = 0;
  QualifiedTemplateName *QTN =
    QualifiedTemplateNames.FindNodeOrInsertPos(ID, InsertPos);
  if (!QTN) {
    QTN = new (*this,4) QualifiedTemplateName(NNS, TemplateKeyword, Template);
    QualifiedTemplateNames.InsertNode(QTN, InsertPos);
  }

  return TemplateName(QTN);
}

/// \brief Retrieve the template name that represents a dependent
/// template name such as \c MetaFun::template apply.
TemplateName ASTContext::getDependentTemplateName(NestedNameSpecifier *NNS,
                                                  const IdentifierInfo *Name) {
  assert(NNS->isDependent() && "Nested name specifier must be dependent");

  llvm::FoldingSetNodeID ID;
  DependentTemplateName::Profile(ID, NNS, Name);

  void *InsertPos = 0;
  DependentTemplateName *QTN =
    DependentTemplateNames.FindNodeOrInsertPos(ID, InsertPos);

  if (QTN)
    return TemplateName(QTN);

  NestedNameSpecifier *CanonNNS = getCanonicalNestedNameSpecifier(NNS);
  if (CanonNNS == NNS) {
    QTN = new (*this,4) DependentTemplateName(NNS, Name);
  } else {
    TemplateName Canon = getDependentTemplateName(CanonNNS, Name);
    QTN = new (*this,4) DependentTemplateName(NNS, Name, Canon);
  }

  DependentTemplateNames.InsertNode(QTN, InsertPos);
  return TemplateName(QTN);
}

/// getFromTargetType - Given one of the integer types provided by
/// TargetInfo, produce the corresponding type. The unsigned @p Type
/// is actually a value of type @c TargetInfo::IntType.
QualType ASTContext::getFromTargetType(unsigned Type) const {
  switch (Type) {
  case TargetInfo::NoInt: return QualType();
  case TargetInfo::SignedShort: return ShortTy;
  case TargetInfo::UnsignedShort: return UnsignedShortTy;
  case TargetInfo::SignedInt: return IntTy;
  case TargetInfo::UnsignedInt: return UnsignedIntTy;
  case TargetInfo::SignedLong: return LongTy;
  case TargetInfo::UnsignedLong: return UnsignedLongTy;
  case TargetInfo::SignedLongLong: return LongLongTy;
  case TargetInfo::UnsignedLongLong: return UnsignedLongLongTy;
  }

  assert(false && "Unhandled TargetInfo::IntType value");
  return QualType();
}

//===----------------------------------------------------------------------===//
//                        Type Predicates.
//===----------------------------------------------------------------------===//

/// isObjCNSObjectType - Return true if this is an NSObject object using
/// NSObject attribute on a c-style pointer type.
/// FIXME - Make it work directly on types.
///
bool ASTContext::isObjCNSObjectType(QualType Ty) const {
  if (TypedefType *TDT = dyn_cast<TypedefType>(Ty)) {
    if (TypedefDecl *TD = TDT->getDecl())
      if (TD->getAttr<ObjCNSObjectAttr>())
        return true;
  }
  return false;
}

/// isObjCObjectPointerType - Returns true if type is an Objective-C pointer
/// to an object type.  This includes "id" and "Class" (two 'special' pointers
/// to struct), Interface* (pointer to ObjCInterfaceType) and id<P> (qualified
/// ID type).
bool ASTContext::isObjCObjectPointerType(QualType Ty) const {
  if (Ty->isObjCQualifiedIdType())
    return true;

  // Blocks are objects.
  if (Ty->isBlockPointerType())
    return true;

  // All other object types are pointers.
  const PointerType *PT = Ty->getAsPointerType();
  if (PT == 0)
    return false;

  // If this a pointer to an interface (e.g. NSString*), it is ok.
  if (PT->getPointeeType()->isObjCInterfaceType() ||
      // If is has NSObject attribute, OK as well.
      isObjCNSObjectType(Ty))
    return true;

  // Check to see if this is 'id' or 'Class', both of which are typedefs for
  // pointer types.  This looks for the typedef specifically, not for the
  // underlying type.  Iteratively strip off typedefs so that we can handle
  // typedefs of typedefs.
  while (TypedefType *TDT = dyn_cast<TypedefType>(Ty)) {
    if (Ty.getUnqualifiedType() == getObjCIdType() ||
        Ty.getUnqualifiedType() == getObjCClassType())
      return true;

    Ty = TDT->getDecl()->getUnderlyingType();
  }

  return false;
}

/// getObjCGCAttr - Returns one of GCNone, Weak or Strong objc's
/// garbage collection attribute.
///
QualType::GCAttrTypes ASTContext::getObjCGCAttrKind(const QualType &Ty) const {
  QualType::GCAttrTypes GCAttrs = QualType::GCNone;
  if (getLangOptions().ObjC1 &&
      getLangOptions().getGCMode() != LangOptions::NonGC) {
    GCAttrs = Ty.getObjCGCAttr();
    // Default behavious under objective-c's gc is for objective-c pointers
    // (or pointers to them) be treated as though they were declared
    // as __strong.
    if (GCAttrs == QualType::GCNone) {
      if (isObjCObjectPointerType(Ty))
        GCAttrs = QualType::Strong;
      else if (Ty->isPointerType())
        return getObjCGCAttrKind(Ty->getAsPointerType()->getPointeeType());
    }
    // Non-pointers have none gc'able attribute regardless of the attribute
    // set on them.
    else if (!Ty->isPointerType() && !isObjCObjectPointerType(Ty))
      return QualType::GCNone;
  }
  return GCAttrs;
}

//===----------------------------------------------------------------------===//
//                        Type Compatibility Testing
//===----------------------------------------------------------------------===//

/// areCompatVectorTypes - Return true if the two specified vector types are
/// compatible.
static bool areCompatVectorTypes(const VectorType *LHS,
                                 const VectorType *RHS) {
  assert(LHS->isCanonical() && RHS->isCanonical());
  return LHS->getElementType() == RHS->getElementType() &&
         LHS->getNumElements() == RHS->getNumElements();
}

/// canAssignObjCInterfaces - Return true if the two interface types are
/// compatible for assignment from RHS to LHS.  This handles validation of any
/// protocol qualifiers on the LHS or RHS.
///
bool ASTContext::canAssignObjCInterfaces(const ObjCInterfaceType *LHS,
                                         const ObjCInterfaceType *RHS) {
  // Verify that the base decls are compatible: the RHS must be a subclass of
  // the LHS.
  if (!LHS->getDecl()->isSuperClassOf(RHS->getDecl()))
    return false;

  // RHS must have a superset of the protocols in the LHS.  If the LHS is not
  // protocol qualified at all, then we are good.
  if (!isa<ObjCQualifiedInterfaceType>(LHS))
    return true;

  // Okay, we know the LHS has protocol qualifiers.  If the RHS doesn't, then it
  // isn't a superset.
  if (!isa<ObjCQualifiedInterfaceType>(RHS))
    return true;  // FIXME: should return false!

  // Finally, we must have two protocol-qualified interfaces.
  const ObjCQualifiedInterfaceType *LHSP =cast<ObjCQualifiedInterfaceType>(LHS);
  const ObjCQualifiedInterfaceType *RHSP =cast<ObjCQualifiedInterfaceType>(RHS);

  // All LHS protocols must have a presence on the RHS.
  assert(LHSP->qual_begin() != LHSP->qual_end() && "Empty LHS protocol list?");

  for (ObjCQualifiedInterfaceType::qual_iterator LHSPI = LHSP->qual_begin(),
                                                 LHSPE = LHSP->qual_end();
       LHSPI != LHSPE; LHSPI++) {
    bool RHSImplementsProtocol = false;

    // If the RHS doesn't implement the protocol on the left, the types
    // are incompatible.
    for (ObjCQualifiedInterfaceType::qual_iterator RHSPI = RHSP->qual_begin(),
                                                   RHSPE = RHSP->qual_end();
         !RHSImplementsProtocol && (RHSPI != RHSPE); RHSPI++) {
      if ((*RHSPI)->lookupProtocolNamed((*LHSPI)->getIdentifier()))
        RHSImplementsProtocol = true;
    }
    // FIXME: For better diagnostics, consider passing back the protocol name.
    if (!RHSImplementsProtocol)
      return false;
  }
  // The RHS implements all protocols listed on the LHS.
  return true;
}

bool ASTContext::areComparableObjCPointerTypes(QualType LHS, QualType RHS) {
  // get the "pointed to" types
  const PointerType *LHSPT = LHS->getAsPointerType();
  const PointerType *RHSPT = RHS->getAsPointerType();

  if (!LHSPT || !RHSPT)
    return false;

  QualType lhptee = LHSPT->getPointeeType();
  QualType rhptee = RHSPT->getPointeeType();
  const ObjCInterfaceType* LHSIface = lhptee->getAsObjCInterfaceType();
  const ObjCInterfaceType* RHSIface = rhptee->getAsObjCInterfaceType();
  // ID acts sort of like void* for ObjC interfaces
  if (LHSIface && isObjCIdStructType(rhptee))
    return true;
  if (RHSIface && isObjCIdStructType(lhptee))
    return true;
  if (!LHSIface || !RHSIface)
    return false;
  return canAssignObjCInterfaces(LHSIface, RHSIface) ||
         canAssignObjCInterfaces(RHSIface, LHSIface);
}

/// typesAreCompatible - C99 6.7.3p9: For two qualified types to be compatible,
/// both shall have the identically qualified version of a compatible type.
/// C99 6.2.7p1: Two types have compatible types if their types are the
/// same. See 6.7.[2,3,5] for additional rules.
bool ASTContext::typesAreCompatible(QualType LHS, QualType RHS) {
  return !mergeTypes(LHS, RHS).isNull();
}

QualType ASTContext::mergeFunctionTypes(QualType lhs, QualType rhs) {
  const FunctionType *lbase = lhs->getAsFunctionType();
  const FunctionType *rbase = rhs->getAsFunctionType();
  const FunctionProtoType *lproto = dyn_cast<FunctionProtoType>(lbase);
  const FunctionProtoType *rproto = dyn_cast<FunctionProtoType>(rbase);
  bool allLTypes = true;
  bool allRTypes = true;

  // Check return type
  QualType retType = mergeTypes(lbase->getResultType(), rbase->getResultType());
  if (retType.isNull()) return QualType();
  if (getCanonicalType(retType) != getCanonicalType(lbase->getResultType()))
    allLTypes = false;
  if (getCanonicalType(retType) != getCanonicalType(rbase->getResultType()))
    allRTypes = false;

  if (lproto && rproto) { // two C99 style function prototypes
    assert(!lproto->hasExceptionSpec() && !rproto->hasExceptionSpec() &&
           "C++ shouldn't be here");
    unsigned lproto_nargs = lproto->getNumArgs();
    unsigned rproto_nargs = rproto->getNumArgs();

    // Compatible functions must have the same number of arguments
    if (lproto_nargs != rproto_nargs)
      return QualType();

    // Variadic and non-variadic functions aren't compatible
    if (lproto->isVariadic() != rproto->isVariadic())
      return QualType();

    if (lproto->getTypeQuals() != rproto->getTypeQuals())
      return QualType();

    // Check argument compatibility
    llvm::SmallVector<QualType, 10> types;
    for (unsigned i = 0; i < lproto_nargs; i++) {
      QualType largtype = lproto->getArgType(i).getUnqualifiedType();
      QualType rargtype = rproto->getArgType(i).getUnqualifiedType();
      QualType argtype = mergeTypes(largtype, rargtype);
      if (argtype.isNull()) return QualType();
      types.push_back(argtype);
      if (getCanonicalType(argtype) != getCanonicalType(largtype))
        allLTypes = false;
      if (getCanonicalType(argtype) != getCanonicalType(rargtype))
        allRTypes = false;
    }
    if (allLTypes) return lhs;
    if (allRTypes) return rhs;
    return getFunctionType(retType, types.begin(), types.size(),
                           lproto->isVariadic(), lproto->getTypeQuals());
  }

  if (lproto) allRTypes = false;
  if (rproto) allLTypes = false;

  const FunctionProtoType *proto = lproto ? lproto : rproto;
  if (proto) {
    assert(!proto->hasExceptionSpec() && "C++ shouldn't be here");
    if (proto->isVariadic()) return QualType();
    // Check that the types are compatible with the types that
    // would result from default argument promotions (C99 6.7.5.3p15).
    // The only types actually affected are promotable integer
    // types and floats, which would be passed as a different
    // type depending on whether the prototype is visible.
    unsigned proto_nargs = proto->getNumArgs();
    for (unsigned i = 0; i < proto_nargs; ++i) {
      QualType argTy = proto->getArgType(i);
      if (argTy->isPromotableIntegerType() ||
          getCanonicalType(argTy).getUnqualifiedType() == FloatTy)
        return QualType();
    }

    if (allLTypes) return lhs;
    if (allRTypes) return rhs;
    return getFunctionType(retType, proto->arg_type_begin(),
                           proto->getNumArgs(), lproto->isVariadic(),
                           lproto->getTypeQuals());
  }

  if (allLTypes) return lhs;
  if (allRTypes) return rhs;
  return getFunctionNoProtoType(retType);
}

QualType ASTContext::mergeTypes(QualType LHS, QualType RHS) {
  // C++ [expr]: If an expression initially has the type "reference to T", the
  // type is adjusted to "T" prior to any further analysis, the expression
  // designates the object or function denoted by the reference, and the
  // expression is an lvalue unless the reference is an rvalue reference and
  // the expression is a function call (possibly inside parentheses).
  // FIXME: C++ shouldn't be going through here!  The rules are different
  // enough that they should be handled separately.
  // FIXME: Merging of lvalue and rvalue references is incorrect. C++ *really*
  // shouldn't be going through here!
  if (const ReferenceType *RT = LHS->getAsReferenceType())
    LHS = RT->getPointeeType();
  if (const ReferenceType *RT = RHS->getAsReferenceType())
    RHS = RT->getPointeeType();

  QualType LHSCan = getCanonicalType(LHS),
           RHSCan = getCanonicalType(RHS);

  // If two types are identical, they are compatible.
  if (LHSCan == RHSCan)
    return LHS;

  // If the qualifiers are different, the types aren't compatible
  // Note that we handle extended qualifiers later, in the
  // case for ExtQualType.
  if (LHSCan.getCVRQualifiers() != RHSCan.getCVRQualifiers())
    return QualType();

  Type::TypeClass LHSClass = LHSCan->getTypeClass();
  Type::TypeClass RHSClass = RHSCan->getTypeClass();

  // We want to consider the two function types to be the same for these
  // comparisons, just force one to the other.
  if (LHSClass == Type::FunctionProto) LHSClass = Type::FunctionNoProto;
  if (RHSClass == Type::FunctionProto) RHSClass = Type::FunctionNoProto;

  // Strip off objc_gc attributes off the top level so they can be merged.
  // This is a complete mess, but the attribute itself doesn't make much sense.
  if (RHSClass == Type::ExtQual) {
    QualType::GCAttrTypes GCAttr = RHSCan.getObjCGCAttr();
    if (GCAttr != QualType::GCNone) {
      QualType::GCAttrTypes GCLHSAttr = LHSCan.getObjCGCAttr();
      // __weak attribute must appear on both declarations.
      // __strong attribue is redundant if other decl is an objective-c
      // object pointer (or decorated with __strong attribute); otherwise
      // issue error.
      if ((GCAttr == QualType::Weak && GCLHSAttr != GCAttr) ||
          (GCAttr == QualType::Strong && GCLHSAttr != GCAttr &&
           LHSCan->isPointerType() && !isObjCObjectPointerType(LHSCan) &&
           !isObjCIdStructType(LHSCan->getAsPointerType()->getPointeeType())))
        return QualType();

      RHS = QualType(cast<ExtQualType>(RHS.getDesugaredType())->getBaseType(),
                     RHS.getCVRQualifiers());
      QualType Result = mergeTypes(LHS, RHS);
      if (!Result.isNull()) {
        if (Result.getObjCGCAttr() == QualType::GCNone)
          Result = getObjCGCQualType(Result, GCAttr);
        else if (Result.getObjCGCAttr() != GCAttr)
          Result = QualType();
      }
      return Result;
    }
  }
  if (LHSClass == Type::ExtQual) {
    QualType::GCAttrTypes GCAttr = LHSCan.getObjCGCAttr();
    if (GCAttr != QualType::GCNone) {
      QualType::GCAttrTypes GCRHSAttr = RHSCan.getObjCGCAttr();
      // __weak attribute must appear on both declarations. __strong
      // __strong attribue is redundant if other decl is an objective-c
      // object pointer (or decorated with __strong attribute); otherwise
      // issue error.
      if ((GCAttr == QualType::Weak && GCRHSAttr != GCAttr) ||
          (GCAttr == QualType::Strong && GCRHSAttr != GCAttr &&
           RHSCan->isPointerType() && !isObjCObjectPointerType(RHSCan) &&
           !isObjCIdStructType(RHSCan->getAsPointerType()->getPointeeType())))
        return QualType();

      LHS = QualType(cast<ExtQualType>(LHS.getDesugaredType())->getBaseType(),
                     LHS.getCVRQualifiers());
      QualType Result = mergeTypes(LHS, RHS);
      if (!Result.isNull()) {
        if (Result.getObjCGCAttr() == QualType::GCNone)
          Result = getObjCGCQualType(Result, GCAttr);
        else if (Result.getObjCGCAttr() != GCAttr)
          Result = QualType();
      }
      return Result;
    }
  }

  // Same as above for arrays
  if (LHSClass == Type::VariableArray || LHSClass == Type::IncompleteArray)
    LHSClass = Type::ConstantArray;
  if (RHSClass == Type::VariableArray || RHSClass == Type::IncompleteArray)
    RHSClass = Type::ConstantArray;

  // Canonicalize ExtVector -> Vector.
  if (LHSClass == Type::ExtVector) LHSClass = Type::Vector;
  if (RHSClass == Type::ExtVector) RHSClass = Type::Vector;

  // Consider qualified interfaces and interfaces the same.
  if (LHSClass == Type::ObjCQualifiedInterface) LHSClass = Type::ObjCInterface;
  if (RHSClass == Type::ObjCQualifiedInterface) RHSClass = Type::ObjCInterface;

  // If the canonical type classes don't match.
  if (LHSClass != RHSClass) {
    const ObjCInterfaceType* LHSIface = LHS->getAsObjCInterfaceType();
    const ObjCInterfaceType* RHSIface = RHS->getAsObjCInterfaceType();

    // 'id' and 'Class' act sort of like void* for ObjC interfaces
    if (LHSIface && (isObjCIdStructType(RHS) || isObjCClassStructType(RHS)))
      return LHS;
    if (RHSIface && (isObjCIdStructType(LHS) || isObjCClassStructType(LHS)))
      return RHS;

    // ID is compatible with all qualified id types.
    if (LHS->isObjCQualifiedIdType()) {
      if (const PointerType *PT = RHS->getAsPointerType()) {
        QualType pType = PT->getPointeeType();
        if (isObjCIdStructType(pType) || isObjCClassStructType(pType))
          return LHS;
        // FIXME: need to use ObjCQualifiedIdTypesAreCompatible(LHS, RHS, true).
        // Unfortunately, this API is part of Sema (which we don't have access
        // to. Need to refactor. The following check is insufficient, since we
        // need to make sure the class implements the protocol.
        if (pType->isObjCInterfaceType())
          return LHS;
      }
    }
    if (RHS->isObjCQualifiedIdType()) {
      if (const PointerType *PT = LHS->getAsPointerType()) {
        QualType pType = PT->getPointeeType();
        if (isObjCIdStructType(pType) || isObjCClassStructType(pType))
          return RHS;
        // FIXME: need to use ObjCQualifiedIdTypesAreCompatible(LHS, RHS, true).
        // Unfortunately, this API is part of Sema (which we don't have access
        // to. Need to refactor. The following check is insufficient, since we
        // need to make sure the class implements the protocol.
        if (pType->isObjCInterfaceType())
          return RHS;
      }
    }
    // C99 6.7.2.2p4: Each enumerated type shall be compatible with char,
    // a signed integer type, or an unsigned integer type.
    if (const EnumType* ETy = LHS->getAsEnumType()) {
      if (ETy->getDecl()->getIntegerType() == RHSCan.getUnqualifiedType())
        return RHS;
    }
    if (const EnumType* ETy = RHS->getAsEnumType()) {
      if (ETy->getDecl()->getIntegerType() == LHSCan.getUnqualifiedType())
        return LHS;
    }

    return QualType();
  }

  // The canonical type classes match.
  switch (LHSClass) {
#define TYPE(Class, Base)
#define ABSTRACT_TYPE(Class, Base)
#define NON_CANONICAL_TYPE(Class, Base) case Type::Class:
#define DEPENDENT_TYPE(Class, Base) case Type::Class:
#include "clang/AST/TypeNodes.def"
    assert(false && "Non-canonical and dependent types shouldn't get here");
    return QualType();

  case Type::LValueReference:
  case Type::RValueReference:
  case Type::MemberPointer:
    assert(false && "C++ should never be in mergeTypes");
    return QualType();

  case Type::IncompleteArray:
  case Type::VariableArray:
  case Type::FunctionProto:
  case Type::ExtVector:
  case Type::ObjCQualifiedInterface:
    assert(false && "Types are eliminated above");
    return QualType();

  case Type::Pointer:
  {
    // Merge two pointer types, while trying to preserve typedef info
    QualType LHSPointee = LHS->getAsPointerType()->getPointeeType();
    QualType RHSPointee = RHS->getAsPointerType()->getPointeeType();
    QualType ResultType = mergeTypes(LHSPointee, RHSPointee);
    if (ResultType.isNull()) return QualType();
    if (getCanonicalType(LHSPointee) == getCanonicalType(ResultType))
      return LHS;
    if (getCanonicalType(RHSPointee) == getCanonicalType(ResultType))
      return RHS;
    return getPointerType(ResultType);
  }
  case Type::BlockPointer:
  {
    // Merge two block pointer types, while trying to preserve typedef info
    QualType LHSPointee = LHS->getAsBlockPointerType()->getPointeeType();
    QualType RHSPointee = RHS->getAsBlockPointerType()->getPointeeType();
    QualType ResultType = mergeTypes(LHSPointee, RHSPointee);
    if (ResultType.isNull()) return QualType();
    if (getCanonicalType(LHSPointee) == getCanonicalType(ResultType))
      return LHS;
    if (getCanonicalType(RHSPointee) == getCanonicalType(ResultType))
      return RHS;
    return getBlockPointerType(ResultType);
  }
  case Type::ConstantArray:
  {
    const ConstantArrayType* LCAT = getAsConstantArrayType(LHS);
    const ConstantArrayType* RCAT = getAsConstantArrayType(RHS);
    if (LCAT && RCAT && RCAT->getSize() != LCAT->getSize())
      return QualType();

    QualType LHSElem = getAsArrayType(LHS)->getElementType();
    QualType RHSElem = getAsArrayType(RHS)->getElementType();
    QualType ResultType = mergeTypes(LHSElem, RHSElem);
    if (ResultType.isNull()) return QualType();
    if (LCAT && getCanonicalType(LHSElem) == getCanonicalType(ResultType))
      return LHS;
    if (RCAT && getCanonicalType(RHSElem) == getCanonicalType(ResultType))
      return RHS;
    if (LCAT) return getConstantArrayType(ResultType, LCAT->getSize(),
                                          ArrayType::ArraySizeModifier(), 0);
    if (RCAT) return getConstantArrayType(ResultType, RCAT->getSize(),
                                          ArrayType::ArraySizeModifier(), 0);
    const VariableArrayType* LVAT = getAsVariableArrayType(LHS);
    const VariableArrayType* RVAT = getAsVariableArrayType(RHS);
    if (LVAT && getCanonicalType(LHSElem) == getCanonicalType(ResultType))
      return LHS;
    if (RVAT && getCanonicalType(RHSElem) == getCanonicalType(ResultType))
      return RHS;
    if (LVAT) {
      // FIXME: This isn't correct! But tricky to implement because
      // the array's size has to be the size of LHS, but the type
      // has to be different.
      return LHS;
    }
    if (RVAT) {
      // FIXME: This isn't correct! But tricky to implement because
      // the array's size has to be the size of RHS, but the type
      // has to be different.
      return RHS;
    }
    if (getCanonicalType(LHSElem) == getCanonicalType(ResultType)) return LHS;
    if (getCanonicalType(RHSElem) == getCanonicalType(ResultType)) return RHS;
    return getIncompleteArrayType(ResultType, ArrayType::ArraySizeModifier(),0);
  }
  case Type::FunctionNoProto:
    return mergeFunctionTypes(LHS, RHS);
  case Type::Record:
  case Type::Enum:
    // FIXME: Why are these compatible?
    if (isObjCIdStructType(LHS) && isObjCClassStructType(RHS)) return LHS;
    if (isObjCClassStructType(LHS) && isObjCIdStructType(RHS)) return LHS;
    return QualType();
  case Type::Builtin:
    // Only exactly equal builtin types are compatible, which is tested above.
    return QualType();
  case Type::Complex:
    // Distinct complex types are incompatible.
    return QualType();
  case Type::Vector:
    // FIXME: The merged type should be an ExtVector!
    if (areCompatVectorTypes(LHS->getAsVectorType(), RHS->getAsVectorType()))
      return LHS;
    return QualType();
  case Type::ObjCInterface: {
    // Check if the interfaces are assignment compatible.
    // FIXME: This should be type compatibility, e.g. whether
    // "LHS x; RHS x;" at global scope is legal.
    const ObjCInterfaceType* LHSIface = LHS->getAsObjCInterfaceType();
    const ObjCInterfaceType* RHSIface = RHS->getAsObjCInterfaceType();
    if (LHSIface && RHSIface &&
        canAssignObjCInterfaces(LHSIface, RHSIface))
      return LHS;

    return QualType();
  }
  case Type::ObjCQualifiedId:
    // Distinct qualified id's are not compatible.
    return QualType();
  case Type::FixedWidthInt:
    // Distinct fixed-width integers are not compatible.
    return QualType();
  case Type::ExtQual:
    // FIXME: ExtQual types can be compatible even if they're not
    // identical!
    return QualType();
    // First attempt at an implementation, but I'm not really sure it's
    // right...
#if 0
    ExtQualType* LQual = cast<ExtQualType>(LHSCan);
    ExtQualType* RQual = cast<ExtQualType>(RHSCan);
    if (LQual->getAddressSpace() != RQual->getAddressSpace() ||
        LQual->getObjCGCAttr() != RQual->getObjCGCAttr())
      return QualType();
    QualType LHSBase, RHSBase, ResultType, ResCanUnqual;
    LHSBase = QualType(LQual->getBaseType(), 0);
    RHSBase = QualType(RQual->getBaseType(), 0);
    ResultType = mergeTypes(LHSBase, RHSBase);
    if (ResultType.isNull()) return QualType();
    ResCanUnqual = getCanonicalType(ResultType).getUnqualifiedType();
    if (LHSCan.getUnqualifiedType() == ResCanUnqual)
      return LHS;
    if (RHSCan.getUnqualifiedType() == ResCanUnqual)
      return RHS;
    ResultType = getAddrSpaceQualType(ResultType, LQual->getAddressSpace());
    ResultType = getObjCGCQualType(ResultType, LQual->getObjCGCAttr());
    ResultType.setCVRQualifiers(LHSCan.getCVRQualifiers());
    return ResultType;
#endif

  case Type::TemplateSpecialization:
    assert(false && "Dependent types have no size");
    break;
  }

  return QualType();
}

//===----------------------------------------------------------------------===//
//                         Integer Predicates
//===----------------------------------------------------------------------===//

unsigned ASTContext::getIntWidth(QualType T) {
  if (T == BoolTy)
    return 1;
  if (FixedWidthIntType* FWIT = dyn_cast<FixedWidthIntType>(T)) {
    return FWIT->getWidth();
  }
  // For builtin types, just use the standard type sizing method
  return (unsigned)getTypeSize(T);
}

QualType ASTContext::getCorrespondingUnsignedType(QualType T) {
  assert(T->isSignedIntegerType() && "Unexpected type");
  if (const EnumType* ETy = T->getAsEnumType())
    T = ETy->getDecl()->getIntegerType();
  const BuiltinType* BTy = T->getAsBuiltinType();
  assert (BTy && "Unexpected signed integer type");
  switch (BTy->getKind()) {
  case BuiltinType::Char_S:
  case BuiltinType::SChar:
    return UnsignedCharTy;
  case BuiltinType::Short:
    return UnsignedShortTy;
  case BuiltinType::Int:
    return UnsignedIntTy;
  case BuiltinType::Long:
    return UnsignedLongTy;
  case BuiltinType::LongLong:
    return UnsignedLongLongTy;
  case BuiltinType::Int128:
    return UnsignedInt128Ty;
  default:
    assert(0 && "Unexpected signed integer type");
    return QualType();
  }
}

ExternalASTSource::~ExternalASTSource() { }

void ExternalASTSource::PrintStats() { }