ASTContext.cpp

//===--- 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/Decl.h"
#include "clang/AST/DeclObjC.h"
#include "clang/Basic/TargetInfo.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Bitcode/Serialize.h"
#include "llvm/Bitcode/Deserialize.h"

using namespace clang;

enum FloatingRank {
  FloatRank, DoubleRank, LongDoubleRank
};

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

  TUDecl->Destroy(*this);
}

void ASTContext::PrintStats() const {
  fprintf(stderr, "*** AST Context Stats:\n");
  fprintf(stderr, "  %d types total.\n", (int)Types.size());
  unsigned NumBuiltin = 0, NumPointer = 0, NumArray = 0, NumFunctionP = 0;
  unsigned NumVector = 0, NumComplex = 0;
  unsigned NumFunctionNP = 0, NumTypeName = 0, NumTagged = 0, NumReference = 0;
  
  unsigned NumTagStruct = 0, NumTagUnion = 0, NumTagEnum = 0, NumTagClass = 0;
  unsigned NumObjCInterfaces = 0, NumObjCQualifiedInterfaces = 0;
  unsigned NumObjCQualifiedIds = 0;
  unsigned NumTypeOfTypes = 0, NumTypeOfExprs = 0;
  
  for (unsigned i = 0, e = Types.size(); i != e; ++i) {
    Type *T = Types[i];
    if (isa<BuiltinType>(T))
      ++NumBuiltin;
    else if (isa<PointerType>(T))
      ++NumPointer;
    else if (isa<ReferenceType>(T))
      ++NumReference;
    else if (isa<ComplexType>(T))
      ++NumComplex;
    else if (isa<ArrayType>(T))
      ++NumArray;
    else if (isa<VectorType>(T))
      ++NumVector;
    else if (isa<FunctionTypeNoProto>(T))
      ++NumFunctionNP;
    else if (isa<FunctionTypeProto>(T))
      ++NumFunctionP;
    else if (isa<TypedefType>(T))
      ++NumTypeName;
    else if (TagType *TT = dyn_cast<TagType>(T)) {
      ++NumTagged;
      switch (TT->getDecl()->getKind()) {
      default: assert(0 && "Unknown tagged type!");
      case Decl::Struct: ++NumTagStruct; break;
      case Decl::Union:  ++NumTagUnion; break;
      case Decl::Class:  ++NumTagClass; break; 
      case Decl::Enum:   ++NumTagEnum; break;
      }
    } else if (isa<ObjCInterfaceType>(T))
      ++NumObjCInterfaces;
    else if (isa<ObjCQualifiedInterfaceType>(T))
      ++NumObjCQualifiedInterfaces;
    else if (isa<ObjCQualifiedIdType>(T))
      ++NumObjCQualifiedIds;
    else if (isa<TypeOfType>(T))
      ++NumTypeOfTypes;
    else if (isa<TypeOfExpr>(T))
      ++NumTypeOfExprs;
    else {
      QualType(T, 0).dump();
      assert(0 && "Unknown type!");
    }
  }

  fprintf(stderr, "    %d builtin types\n", NumBuiltin);
  fprintf(stderr, "    %d pointer types\n", NumPointer);
  fprintf(stderr, "    %d reference types\n", NumReference);
  fprintf(stderr, "    %d complex types\n", NumComplex);
  fprintf(stderr, "    %d array types\n", NumArray);
  fprintf(stderr, "    %d vector types\n", NumVector);
  fprintf(stderr, "    %d function types with proto\n", NumFunctionP);
  fprintf(stderr, "    %d function types with no proto\n", NumFunctionNP);
  fprintf(stderr, "    %d typename (typedef) types\n", NumTypeName);
  fprintf(stderr, "    %d tagged types\n", NumTagged);
  fprintf(stderr, "      %d struct types\n", NumTagStruct);
  fprintf(stderr, "      %d union types\n", NumTagUnion);
  fprintf(stderr, "      %d class types\n", NumTagClass);
  fprintf(stderr, "      %d enum types\n", NumTagEnum);
  fprintf(stderr, "    %d interface types\n", NumObjCInterfaces);
  fprintf(stderr, "    %d protocol qualified interface types\n",
          NumObjCQualifiedInterfaces);
  fprintf(stderr, "    %d protocol qualified id types\n",
          NumObjCQualifiedIds);
  fprintf(stderr, "    %d typeof types\n", NumTypeOfTypes);
  fprintf(stderr, "    %d typeof exprs\n", NumTypeOfExprs);
  
  fprintf(stderr, "Total bytes = %d\n", int(NumBuiltin*sizeof(BuiltinType)+
    NumPointer*sizeof(PointerType)+NumArray*sizeof(ArrayType)+
    NumComplex*sizeof(ComplexType)+NumVector*sizeof(VectorType)+
    NumFunctionP*sizeof(FunctionTypeProto)+
    NumFunctionNP*sizeof(FunctionTypeNoProto)+
    NumTypeName*sizeof(TypedefType)+NumTagged*sizeof(TagType)+
    NumTypeOfTypes*sizeof(TypeOfType)+NumTypeOfExprs*sizeof(TypeOfExpr)));
}


void ASTContext::InitBuiltinType(QualType &R, BuiltinType::Kind K) {
  Types.push_back((R = QualType(new 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 (Target.isCharSigned())
    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);
  
  // 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);
}

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

/// 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(QualType T) {
  T = getCanonicalType(T);
  uint64_t Width;
  unsigned Align;
  switch (T->getTypeClass()) {
  case Type::TypeName: assert(0 && "Not a canonical type!");
  case Type::FunctionNoProto:
  case Type::FunctionProto:
  default:
    assert(0 && "Incomplete types have no size!");
  case Type::VariableArray:
    assert(0 && "VLAs not implemented yet!");
  case Type::ConstantArray: {
    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();
    // FIXME: This isn't right for unusual vectors
    Align = Width;
    break;
  }

  case Type::Builtin:
    switch (cast<BuiltinType>(T)->getKind()) {
    default: assert(0 && "Unknown builtin type!");
    case BuiltinType::Void:
      assert(0 && "Incomplete types have no size!");
    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::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::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;
    }
    break;
  case Type::ASQual:
    // FIXME: Pointers into different addr spaces could have different sizes and
    // alignment requirements: getPointerInfo should take an AddrSpace.
    return getTypeInfo(QualType(cast<ASQualType>(T)->getBaseType(), 0));
  case Type::ObjCQualifiedId:
    Width = Target.getPointerWidth(0);
    Align = Target.getPointerAlign(0);
    break;
  case Type::Pointer: {
    unsigned AS = cast<PointerType>(T)->getPointeeType().getAddressSpace();
    Width = Target.getPointerWidth(AS);
    Align = Target.getPointerAlign(AS);
    break;
  }
  case Type::Reference:
    // "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::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: {
    ObjCInterfaceType *ObjCI = cast<ObjCInterfaceType>(T);
    const ASTRecordLayout &Layout = getASTObjCInterfaceLayout(ObjCI->getDecl());
    Width = Layout.getSize();
    Align = Layout.getAlignment();
    break;
  }
  case Type::Tagged: {
    if (EnumType *ET = dyn_cast<EnumType>(cast<TagType>(T)))
      return getTypeInfo(ET->getDecl()->getIntegerType());

    RecordType *RT = cast<RecordType>(T);
    const ASTRecordLayout &Layout = getASTRecordLayout(RT->getDecl());
    Width = Layout.getSize();
    Align = Layout.getAlignment();
    break;
  }
  }
  
  assert(Align && (Align & (Align-1)) == 0 && "Alignment must be power of 2");
  return std::make_pair(Width, Align);
}

/// LayoutField - Field layout.
void ASTRecordLayout::LayoutField(const FieldDecl *FD, unsigned FieldNo,
                                  bool IsUnion, bool StructIsPacked,
                                  ASTContext &Context) {
  bool FieldIsPacked = StructIsPacked || FD->getAttr<PackedAttr>();
  uint64_t FieldOffset = IsUnion ? 0 : Size;
  uint64_t FieldSize;
  unsigned FieldAlign;
  
  if (const Expr *BitWidthExpr = FD->getBitWidth()) {
    // TODO: Need to check this algorithm on other targets!
    //       (tested on Linux-X86)
    llvm::APSInt I(32);
    bool BitWidthIsICE = 
      BitWidthExpr->isIntegerConstantExpr(I, Context);
    assert (BitWidthIsICE  && "Invalid BitField size expression");
    FieldSize = I.getZExtValue();
    
    std::pair<uint64_t, unsigned> FieldInfo = 
      Context.getTypeInfo(FD->getType());
    uint64_t TypeSize = FieldInfo.first;
    
    FieldAlign = FieldInfo.second;
    if (FieldIsPacked)
      FieldAlign = 1;
    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()->isIncompleteType()) {
      // This must be 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 = FD->getType()->getAsArrayType();
      FieldAlign = Context.getTypeAlign(ATy->getElementType());
    } else {
      std::pair<uint64_t, unsigned> FieldInfo = 
        Context.getTypeInfo(FD->getType());
      FieldSize = FieldInfo.first;
      FieldAlign = FieldInfo.second;
    }
    
    if (FieldIsPacked)
      FieldAlign = 8;
    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 max struct/class alignment.
  Alignment = std::max(Alignment, FieldAlign);
}


/// getASTObjcInterfaceLayout - Get or compute information about the layout of the
/// specified Objective C, which indicates its size and ivar
/// position information.
const ASTRecordLayout &
ASTContext::getASTObjCInterfaceLayout(const ObjCInterfaceDecl *D) {
  // Look up this layout, if already laid out, return what we have.
  const ASTRecordLayout *&Entry = ASTObjCInterfaces[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 = NULL;
  unsigned FieldCount = D->ivar_size();
  if (ObjCInterfaceDecl *SD = D->getSuperClass()) {
    FieldCount++;
    const ASTRecordLayout &SL = getASTObjCInterfaceLayout(SD);
    unsigned Alignment = SL.getAlignment();
    uint64_t Size = SL.getSize();
    NewEntry = new ASTRecordLayout(Size, Alignment);
    NewEntry->InitializeLayout(FieldCount);
    NewEntry->SetFieldOffset(0, 0); // Super class is at the beginning of the layout.
  } else {
    NewEntry = new ASTRecordLayout();
    NewEntry->InitializeLayout(FieldCount);
  }
  Entry = NewEntry;

  bool IsPacked = D->getAttr<PackedAttr>();

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

  // Layout each ivar sequentially.
  unsigned i = 0;
  for (ObjCInterfaceDecl::ivar_iterator IVI = D->ivar_begin(), 
       IVE = D->ivar_end(); IVI != IVE; ++IVI) {
    const ObjCIvarDecl* Ivar = (*IVI);
    NewEntry->LayoutField(Ivar, i++, false, IsPacked, *this);
  }

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

/// 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) {
  assert(D->isDefinition() && "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;

  NewEntry->InitializeLayout(D->getNumMembers());
  bool StructIsPacked = D->getAttr<PackedAttr>();
  bool IsUnion = (D->getKind() == Decl::Union);

  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.
  for (unsigned i = 0, e = D->getNumMembers(); i != e; ++i) {
    const FieldDecl *FD = D->getMember(i);
    NewEntry->LayoutField(FD, i, IsUnion, StructIsPacked, *this);
  }

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

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

QualType ASTContext::getASQualType(QualType T, unsigned AddressSpace) {
  QualType CanT = getCanonicalType(T);
  if (CanT.getAddressSpace() == AddressSpace)
    return T;
  
  // Type's cannot have multiple ASQuals, therefore we know we only have to deal
  // with CVR qualifiers from here on out.
  assert(CanT.getAddressSpace() == 0 &&
         "Type is already address space qualified");
  
  // Check if we've already instantiated an address space qual'd type of this
  // type.
  llvm::FoldingSetNodeID ID;
  ASQualType::Profile(ID, T.getTypePtr(), AddressSpace);      
  void *InsertPos = 0;
  if (ASQualType *ASQy = ASQualTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(ASQy, 0);
    
  // 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 (!T->isCanonical()) {
    Canonical = getASQualType(CanT, AddressSpace);
    
    // Get the new insert position for the node we care about.
    ASQualType *NewIP = ASQualTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(NewIP == 0 && "Shouldn't be in the map!");
  }
  ASQualType *New = new ASQualType(T.getTypePtr(), Canonical, AddressSpace);
  ASQualTypes.InsertNode(New, InsertPos);
  Types.push_back(New);
  return QualType(New, T.getCVRQualifiers());
}


/// 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!");
  }
  ComplexType *New = new ComplexType(T, Canonical);
  Types.push_back(New);
  ComplexTypes.InsertNode(New, InsertPos);
  return QualType(New, 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!");
  }
  PointerType *New = new PointerType(T, Canonical);
  Types.push_back(New);
  PointerTypes.InsertNode(New, InsertPos);
  return QualType(New, 0);
}

/// getReferenceType - Return the uniqued reference to the type for a reference
/// to the specified type.
QualType ASTContext::getReferenceType(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 (ReferenceType *RT = ReferenceTypes.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 = getReferenceType(getCanonicalType(T));
   
    // Get the new insert position for the node we care about.
    ReferenceType *NewIP = ReferenceTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(NewIP == 0 && "Shouldn't be in the map!");
  }

  ReferenceType *New = new ReferenceType(T, Canonical);
  Types.push_back(New);
  ReferenceTypes.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 &ArySize,
                                          ArrayType::ArraySizeModifier ASM,
                                          unsigned EltTypeQuals) {
  llvm::FoldingSetNodeID ID;
  ConstantArrayType::Profile(ID, EltTy, ArySize);
      
  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!");
  }
  
  ConstantArrayType *New = new 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 VariableArrayType(EltTy, QualType(), NumElts, 
                                                 ASM, EltTypeQuals);

  VariableArrayTypes.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);

  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!");
  }

  IncompleteArrayType *New = new 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!");
  }
  VectorType *New = new 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!");
  }
  ExtVectorType *New = new ExtVectorType(vecType, NumElts, Canonical);
  VectorTypes.InsertNode(New, InsertPos);
  Types.push_back(New);
  return QualType(New, 0);
}

/// getFunctionTypeNoProto - Return a K&R style C function type like 'int()'.
///
QualType ASTContext::getFunctionTypeNoProto(QualType ResultTy) {
  // Unique functions, to guarantee there is only one function of a particular
  // structure.
  llvm::FoldingSetNodeID ID;
  FunctionTypeNoProto::Profile(ID, ResultTy);
  
  void *InsertPos = 0;
  if (FunctionTypeNoProto *FT = 
        FunctionTypeNoProtos.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(FT, 0);
  
  QualType Canonical;
  if (!ResultTy->isCanonical()) {
    Canonical = getFunctionTypeNoProto(getCanonicalType(ResultTy));
    
    // Get the new insert position for the node we care about.
    FunctionTypeNoProto *NewIP =
      FunctionTypeNoProtos.FindNodeOrInsertPos(ID, InsertPos);
    assert(NewIP == 0 && "Shouldn't be in the map!");
  }
  
  FunctionTypeNoProto *New = new FunctionTypeNoProto(ResultTy, Canonical);
  Types.push_back(New);
  FunctionTypeNoProtos.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, QualType *ArgArray,
                                     unsigned NumArgs, bool isVariadic) {
  // Unique functions, to guarantee there is only one function of a particular
  // structure.
  llvm::FoldingSetNodeID ID;
  FunctionTypeProto::Profile(ID, ResultTy, ArgArray, NumArgs, isVariadic);

  void *InsertPos = 0;
  if (FunctionTypeProto *FTP = 
        FunctionTypeProtos.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(FTP, 0);
    
  // Determine whether the type being created is already canonical or not.  
  bool isCanonical = ResultTy->isCanonical();
  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.
  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[0], NumArgs,
                                isVariadic);
    
    // Get the new insert position for the node we care about.
    FunctionTypeProto *NewIP =
      FunctionTypeProtos.FindNodeOrInsertPos(ID, InsertPos);
    assert(NewIP == 0 && "Shouldn't be in the map!");
  }
  
  // FunctionTypeProto objects are not allocated with new because they have a
  // variable size array (for parameter types) at the end of them.
  FunctionTypeProto *FTP = 
    (FunctionTypeProto*)malloc(sizeof(FunctionTypeProto) + 
                               NumArgs*sizeof(QualType));
  new (FTP) FunctionTypeProto(ResultTy, ArgArray, NumArgs, isVariadic,
                              Canonical);
  Types.push_back(FTP);
  FunctionTypeProtos.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) {
  if (Decl->TypeForDecl) return QualType(Decl->TypeForDecl, 0);
  
  if (TypedefDecl *Typedef = dyn_cast_or_null<TypedefDecl>(Decl))
    return getTypedefType(Typedef);
  else if (ObjCInterfaceDecl *ObjCInterface 
             = dyn_cast_or_null<ObjCInterfaceDecl>(Decl))
    return getObjCInterfaceType(ObjCInterface);
  else if (RecordDecl *Record = dyn_cast_or_null<RecordDecl>(Decl)) {
    Decl->TypeForDecl = new RecordType(Record);
    Types.push_back(Decl->TypeForDecl);
    return QualType(Decl->TypeForDecl, 0);
  } else if (EnumDecl *Enum = dyn_cast_or_null<EnumDecl>(Decl)) {
    Decl->TypeForDecl = new EnumType(Enum);
    Types.push_back(Decl->TypeForDecl);
    return QualType(Decl->TypeForDecl, 0);    
  } else
    assert(false && "TypeDecl without a type?");
}

/// 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 TypedefType(Type::TypeName, 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(ObjCInterfaceDecl *Decl) {
  if (Decl->TypeForDecl) return QualType(Decl->TypeForDecl, 0);
  
  Decl->TypeForDecl = new ObjCInterfaceType(Type::ObjCInterface, Decl);
  Types.push_back(Decl->TypeForDecl);
  return QualType(Decl->TypeForDecl, 0);
}

/// CmpProtocolNames - Comparison predicate for sorting protocols
/// alphabetically.
static bool CmpProtocolNames(const ObjCProtocolDecl *LHS,
                            const ObjCProtocolDecl *RHS) {
  return strcmp(LHS->getName(), RHS->getName()) < 0;
}

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 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(QualType idType,
                                            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;
  QualType Canonical;
  if (!idType->isCanonical()) {
    Canonical = getObjCQualifiedIdType(getCanonicalType(idType), 
                                       Protocols, NumProtocols);
    ObjCQualifiedIdType *NewQT = 
      ObjCQualifiedIdTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(NewQT == 0 && "Shouldn't be in the map!");
  }
  
  ObjCQualifiedIdType *QType = 
    new ObjCQualifiedIdType(Canonical, Protocols, NumProtocols);
  Types.push_back(QType);
  ObjCQualifiedIdTypes.InsertNode(QType, InsertPos);
  return QualType(QType, 0);
}

/// getTypeOfExpr - Unlike many "get<Type>" functions, we can't unique
/// TypeOfExpr 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::getTypeOfExpr(Expr *tofExpr) {
  QualType Canonical = getCanonicalType(tofExpr->getType());
  TypeOfExpr *toe = new TypeOfExpr(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 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 {
  // On Darwin, size_t is defined as a "long unsigned int". 
  // FIXME: should derive from "Target".
  return UnsignedLongTy; 
}

/// getWcharType - Return the unique type for "wchar_t" (C99 7.17), the
/// width of characters in wide strings, The value is target dependent and 
/// needs to agree with the definition in <stddef.h>.
QualType ASTContext::getWcharType() const {
  // On Darwin, wchar_t is defined as a "int". 
  // FIXME: should derive from "Target".
  return IntTy; 
}

/// 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 {