text: //===-- Type.cpp - Implement the Type class -------------------------------===//
  //
  //                     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 Type class for the VMCore library.
  //
  //===----------------------------------------------------------------------===//
  
  #include "LLVMContextImpl.h"
  #include "llvm/DerivedTypes.h"
  #include "llvm/Constants.h"
  #include "llvm/Assembly/Writer.h"
  #include "llvm/LLVMContext.h"
  #include "llvm/Metadata.h"
  #include "llvm/ADT/DepthFirstIterator.h"
  #include "llvm/ADT/StringExtras.h"
  #include "llvm/ADT/SCCIterator.h"
  #include "llvm/ADT/STLExtras.h"
  #include "llvm/Support/Compiler.h"
  #include "llvm/Support/Debug.h"
  #include "llvm/Support/ErrorHandling.h"
  #include "llvm/Support/ManagedStatic.h"
  #include "llvm/Support/MathExtras.h"
  #include "llvm/Support/raw_ostream.h"
  #include "llvm/Support/Threading.h"
  #include <algorithm>
  #include <cstdarg>
  using namespace llvm;
  
  // DEBUG_MERGE_TYPES - Enable this #define to see how and when derived types are
  // created and later destroyed, all in an effort to make sure that there is only
  // a single canonical version of a type.
  //
  // #define DEBUG_MERGE_TYPES 1
  
  AbstractTypeUser::~AbstractTypeUser() {}
  
  void AbstractTypeUser::setType(Value *V, const Type *NewTy) {
    V->VTy = NewTy;
  }
  
  //===----------------------------------------------------------------------===//
  //                         Type Class Implementation
  //===----------------------------------------------------------------------===//
  
  /// Because of the way Type subclasses are allocated, this function is necessary
  /// to use the correct kind of "delete" operator to deallocate the Type object.
  /// Some type objects (FunctionTy, StructTy) allocate additional space
  /// after the space for their derived type to hold the contained types array of
  /// PATypeHandles. Using this allocation scheme means all the PATypeHandles are
  /// allocated with the type object, decreasing allocations and eliminating the
  /// need for a std::vector to be used in the Type class itself. 
  /// @brief Type destruction function
  void Type::destroy() const {
    // Nothing calls getForwardedType from here on.
    if (ForwardType && ForwardType->isAbstract()) {
      ForwardType->dropRef();
      ForwardType = NULL;
    }
  
    // Structures and Functions allocate their contained types past the end of
    // the type object itself. These need to be destroyed differently than the
    // other types.
    if (this->isFunctionTy() || this->isStructTy()) {
      // First, make sure we destruct any PATypeHandles allocated by these
      // subclasses.  They must be manually destructed. 
      for (unsigned i = 0; i < NumContainedTys; ++i)
        ContainedTys[i].PATypeHandle::~PATypeHandle();
  
      // Now call the destructor for the subclass directly because we're going
      // to delete this as an array of char.
      if (this->isFunctionTy())
        static_cast<const FunctionType*>(this)->FunctionType::~FunctionType();
      else {
        assert(isStructTy());
        static_cast<const StructType*>(this)->StructType::~StructType();
      }
  
      // Finally, remove the memory as an array deallocation of the chars it was
      // constructed from.
      operator delete(const_cast<Type *>(this));
  
      return;
    } else if (const OpaqueType *opaque_this = dyn_cast<OpaqueType>(this)) {
      LLVMContextImpl *pImpl = this->getContext().pImpl;
      pImpl->OpaqueTypes.erase(opaque_this);
    }
  
    // For all the other type subclasses, there is either no contained types or 
    // just one (all Sequentials). For Sequentials, the PATypeHandle is not
    // allocated past the type object, its included directly in the SequentialType
    // class. This means we can safely just do "normal" delete of this object and
    // all the destructors that need to run will be run.
    delete this; 
  }
  
  const Type *Type::getPrimitiveType(LLVMContext &C, TypeID IDNumber) {
    switch (IDNumber) {
    case VoidTyID      : return getVoidTy(C);
    case FloatTyID     : return getFloatTy(C);
    case DoubleTyID    : return getDoubleTy(C);
    case X86_FP80TyID  : return getX86_FP80Ty(C);
    case FP128TyID     : return getFP128Ty(C);
    case PPC_FP128TyID : return getPPC_FP128Ty(C);
    case LabelTyID     : return getLabelTy(C);
    case MetadataTyID  : return getMetadataTy(C);
    case X86_MMXTyID   : return getX86_MMXTy(C);
    default:
      return 0;
    }
  }
  
  const Type *Type::getVAArgsPromotedType(LLVMContext &C) const {
    if (ID == IntegerTyID && getSubclassData() < 32)
      return Type::getInt32Ty(C);
    else if (ID == FloatTyID)
      return Type::getDoubleTy(C);
    else
      return this;
  }
  
  /// getScalarType - If this is a vector type, return the element type,
  /// otherwise return this.
  const Type *Type::getScalarType() const {
    if (const VectorType *VTy = dyn_cast<VectorType>(this))
      return VTy->getElementType();
    return this;
  }
  
  /// isIntegerTy - Return true if this is an IntegerType of the specified width.
  bool Type::isIntegerTy(unsigned Bitwidth) const {
    return isIntegerTy() && cast<IntegerType>(this)->getBitWidth() == Bitwidth;
  }
  
  /// isIntOrIntVectorTy - Return true if this is an integer type or a vector of
  /// integer types.
  ///
  bool Type::isIntOrIntVectorTy() const {
    if (isIntegerTy())
      return true;
    if (ID != Type::VectorTyID) return false;
    
    return cast<VectorType>(this)->getElementType()->isIntegerTy();
  }
  
  /// isFPOrFPVectorTy - Return true if this is a FP type or a vector of FP types.
  ///
  bool Type::isFPOrFPVectorTy() const {
    if (ID == Type::FloatTyID || ID == Type::DoubleTyID || 
        ID == Type::FP128TyID || ID == Type::X86_FP80TyID || 
        ID == Type::PPC_FP128TyID)
      return true;
    if (ID != Type::VectorTyID) return false;
    
    return cast<VectorType>(this)->getElementType()->isFloatingPointTy();
  }
  
  // canLosslesslyBitCastTo - Return true if this type can be converted to
  // 'Ty' without any reinterpretation of bits.  For example, i8* to i32*.
  //
  bool Type::canLosslesslyBitCastTo(const Type *Ty) const {
    // Identity cast means no change so return true
    if (this == Ty) 
      return true;
    
    // They are not convertible unless they are at least first class types
    if (!this->isFirstClassType() || !Ty->isFirstClassType())
      return false;
  
    // Vector -> Vector conversions are always lossless if the two vector types
    // have the same size, otherwise not.  Also, 64-bit vector types can be
    // converted to x86mmx.
    if (const VectorType *thisPTy = dyn_cast<VectorType>(this)) {
      if (const VectorType *thatPTy = dyn_cast<VectorType>(Ty))
        return thisPTy->getBitWidth() == thatPTy->getBitWidth();
      if (Ty->getTypeID() == Type::X86_MMXTyID &&
          thisPTy->getBitWidth() == 64)
        return true;
    }
  
    if (this->getTypeID() == Type::X86_MMXTyID)
      if (const VectorType *thatPTy = dyn_cast<VectorType>(Ty))
        if (thatPTy->getBitWidth() == 64)
          return true;
  
    // At this point we have only various mismatches of the first class types
    // remaining and ptr->ptr. Just select the lossless conversions. Everything
    // else is not lossless.
    if (this->isPointerTy())
      return Ty->isPointerTy();
    return false;  // Other types have no identity values
  }
  
  unsigned Type::getPrimitiveSizeInBits() const {
    switch (getTypeID()) {
    case Type::FloatTyID: return 32;
    case Type::DoubleTyID: return 64;
    case Type::X86_FP80TyID: return 80;
    case Type::FP128TyID: return 128;
    case Type::PPC_FP128TyID: return 128;
    case Type::X86_MMXTyID: return 64;
    case Type::IntegerTyID: return cast<IntegerType>(this)->getBitWidth();
    case Type::VectorTyID:  return cast<VectorType>(this)->getBitWidth();
    default: return 0;
    }
  }
  
  /// getScalarSizeInBits - If this is a vector type, return the
  /// getPrimitiveSizeInBits value for the element type. Otherwise return the
  /// getPrimitiveSizeInBits value for this type.
  unsigned Type::getScalarSizeInBits() const {
    return getScalarType()->getPrimitiveSizeInBits();
  }
  
  /// getFPMantissaWidth - Return the width of the mantissa of this type.  This
  /// is only valid on floating point types.  If the FP type does not
  /// have a stable mantissa (e.g. ppc long double), this method returns -1.
  int Type::getFPMantissaWidth() const {
    if (const VectorType *VTy = dyn_cast<VectorType>(this))
      return VTy->getElementType()->getFPMantissaWidth();
    assert(isFloatingPointTy() && "Not a floating point type!");
    if (ID == FloatTyID) return 24;
    if (ID == DoubleTyID) return 53;
    if (ID == X86_FP80TyID) return 64;
    if (ID == FP128TyID) return 113;
    assert(ID == PPC_FP128TyID && "unknown fp type");
    return -1;
  }
  
  /// isSizedDerivedType - Derived types like structures and arrays are sized
  /// iff all of the members of the type are sized as well.  Since asking for
  /// their size is relatively uncommon, move this operation out of line.
  bool Type::isSizedDerivedType() const {
    if (this->isIntegerTy())
      return true;
  
    if (const ArrayType *ATy = dyn_cast<ArrayType>(this))
      return ATy->getElementType()->isSized();
  
    if (const VectorType *PTy = dyn_cast<VectorType>(this))
      return PTy->getElementType()->isSized();
  
    if (!this->isStructTy()) 
      return false;
  
    // Okay, our struct is sized if all of the elements are...
    for (subtype_iterator I = subtype_begin(), E = subtype_end(); I != E; ++I)
      if (!(*I)->isSized()) 
        return false;
  
    return true;
  }
  
  /// getForwardedTypeInternal - This method is used to implement the union-find
  /// algorithm for when a type is being forwarded to another type.
  const Type *Type::getForwardedTypeInternal() const {
    assert(ForwardType && "This type is not being forwarded to another type!");
  
    // Check to see if the forwarded type has been forwarded on.  If so, collapse
    // the forwarding links.
    const Type *RealForwardedType = ForwardType->getForwardedType();
    if (!RealForwardedType)
      return ForwardType;  // No it's not forwarded again
  
    // Yes, it is forwarded again.  First thing, add the reference to the new
    // forward type.
    if (RealForwardedType->isAbstract())
      RealForwardedType->addRef();
  
    // Now drop the old reference.  This could cause ForwardType to get deleted.
    // ForwardType must be abstract because only abstract types can have their own
    // ForwardTypes.
    ForwardType->dropRef();
  
    // Return the updated type.
    ForwardType = RealForwardedType;
    return ForwardType;
  }
  
  void Type::refineAbstractType(const DerivedType *OldTy, const Type *NewTy) {
    llvm_unreachable("Attempting to refine a derived type!");
  }
  void Type::typeBecameConcrete(const DerivedType *AbsTy) {
    llvm_unreachable("DerivedType is already a concrete type!");
  }
  
  
  std::string Type::getDescription() const {
    LLVMContextImpl *pImpl = getContext().pImpl;
    TypePrinting &Map =
      isAbstract() ?
        pImpl->AbstractTypeDescriptions :
        pImpl->ConcreteTypeDescriptions;
    
    std::string DescStr;
    raw_string_ostream DescOS(DescStr);
    Map.print(this, DescOS);
    return DescOS.str();
  }
  
  
  bool StructType::indexValid(const Value *V) const {
    // Structure indexes require 32-bit integer constants.
    if (V->getType()->isIntegerTy(32))
      if (const ConstantInt *CU = dyn_cast<ConstantInt>(V))
        return indexValid(CU->getZExtValue());
    return false;
  }
  
  bool StructType::indexValid(unsigned V) const {
    return V < NumContainedTys;
  }
  
  // getTypeAtIndex - Given an index value into the type, return the type of the
  // element.  For a structure type, this must be a constant value...
  //
  const Type *StructType::getTypeAtIndex(const Value *V) const {
    unsigned Idx = (unsigned)cast<ConstantInt>(V)->getZExtValue();
    return getTypeAtIndex(Idx);
  }
  
  const Type *StructType::getTypeAtIndex(unsigned Idx) const {
    assert(indexValid(Idx) && "Invalid structure index!");
    return ContainedTys[Idx];
  }
  
  
  //===----------------------------------------------------------------------===//
  //                          Primitive 'Type' data
  //===----------------------------------------------------------------------===//
  
  const Type *Type::getVoidTy(LLVMContext &C) {
    return &C.pImpl->VoidTy;
  }
  
  const Type *Type::getLabelTy(LLVMContext &C) {
    return &C.pImpl->LabelTy;
  }
  
  const Type *Type::getFloatTy(LLVMContext &C) {
    return &C.pImpl->FloatTy;
  }
  
  const Type *Type::getDoubleTy(LLVMContext &C) {
    return &C.pImpl->DoubleTy;
  }
  
  const Type *Type::getMetadataTy(LLVMContext &C) {
    return &C.pImpl->MetadataTy;
  }
  
  const Type *Type::getX86_FP80Ty(LLVMContext &C) {
    return &C.pImpl->X86_FP80Ty;
  }
  
  const Type *Type::getFP128Ty(LLVMContext &C) {
    return &C.pImpl->FP128Ty;
  }
  
  const Type *Type::getPPC_FP128Ty(LLVMContext &C) {
    return &C.pImpl->PPC_FP128Ty;
  }
  
  const Type *Type::getX86_MMXTy(LLVMContext &C) {
    return &C.pImpl->X86_MMXTy;
  }
  
  const IntegerType *Type::getIntNTy(LLVMContext &C, unsigned N) {
    return IntegerType::get(C, N);
  }
  
  const IntegerType *Type::getInt1Ty(LLVMContext &C) {
    return &C.pImpl->Int1Ty;
  }
  
  const IntegerType *Type::getInt8Ty(LLVMContext &C) {
    return &C.pImpl->Int8Ty;
  }
  
  const IntegerType *Type::getInt16Ty(LLVMContext &C) {
    return &C.pImpl->Int16Ty;
  }
  
  const IntegerType *Type::getInt32Ty(LLVMContext &C) {
    return &C.pImpl->Int32Ty;
  }
  
  const IntegerType *Type::getInt64Ty(LLVMContext &C) {
    return &C.pImpl->Int64Ty;
  }
  
  const PointerType *Type::getFloatPtrTy(LLVMContext &C, unsigned AS) {
    return getFloatTy(C)->getPointerTo(AS);
  }
  
  const PointerType *Type::getDoublePtrTy(LLVMContext &C, unsigned AS) {
    return getDoubleTy(C)->getPointerTo(AS);
  }
  
  const PointerType *Type::getX86_FP80PtrTy(LLVMContext &C, unsigned AS) {
    return getX86_FP80Ty(C)->getPointerTo(AS);
  }
  
  const PointerType *Type::getFP128PtrTy(LLVMContext &C, unsigned AS) {
    return getFP128Ty(C)->getPointerTo(AS);
  }
  
  const PointerType *Type::getPPC_FP128PtrTy(LLVMContext &C, unsigned AS) {
    return getPPC_FP128Ty(C)->getPointerTo(AS);
  }
  
  const PointerType *Type::getX86_MMXPtrTy(LLVMContext &C, unsigned AS) {
    return getX86_MMXTy(C)->getPointerTo(AS);
  }
  
  const PointerType *Type::getIntNPtrTy(LLVMContext &C, unsigned N, unsigned AS) {
    return getIntNTy(C, N)->getPointerTo(AS);
  }
  
  const PointerType *Type::getInt1PtrTy(LLVMContext &C, unsigned AS) {
    return getInt1Ty(C)->getPointerTo(AS);
  }
  
  const PointerType *Type::getInt8PtrTy(LLVMContext &C, unsigned AS) {
    return getInt8Ty(C)->getPointerTo(AS);
  }
  
  const PointerType *Type::getInt16PtrTy(LLVMContext &C, unsigned AS) {
    return getInt16Ty(C)->getPointerTo(AS);
  }
  
  const PointerType *Type::getInt32PtrTy(LLVMContext &C, unsigned AS) {
    return getInt32Ty(C)->getPointerTo(AS);
  }
  
  const PointerType *Type::getInt64PtrTy(LLVMContext &C, unsigned AS) {
    return getInt64Ty(C)->getPointerTo(AS);
  }
  
  //===----------------------------------------------------------------------===//
  //                          Derived Type Constructors
  //===----------------------------------------------------------------------===//
  
  /// isValidReturnType - Return true if the specified type is valid as a return
  /// type.
  bool FunctionType::isValidReturnType(const Type *RetTy) {
    return !RetTy->isFunctionTy() && !RetTy->isLabelTy() &&
           !RetTy->isMetadataTy();
  }
  
  /// isValidArgumentType - Return true if the specified type is valid as an
  /// argument type.
  bool FunctionType::isValidArgumentType(const Type *ArgTy) {
    return ArgTy->isFirstClassType() || ArgTy->isOpaqueTy();
  }
  
  FunctionType::FunctionType(const Type *Result,
                             const std::vector<const Type*> &Params,
                             bool IsVarArgs)
    : DerivedType(Result->getContext(), FunctionTyID), isVarArgs(IsVarArgs) {
    ContainedTys = reinterpret_cast<PATypeHandle*>(this+1);
    NumContainedTys = Params.size() + 1; // + 1 for result type
    assert(isValidReturnType(Result) && "invalid return type for function");
  
  
    bool isAbstract = Result->isAbstract();
    new (&ContainedTys[0]) PATypeHandle(Result, this);
  
    for (unsigned i = 0; i != Params.size(); ++i) {
      assert(isValidArgumentType(Params[i]) &&
             "Not a valid type for function argument!");
      new (&ContainedTys[i+1]) PATypeHandle(Params[i], this);
      isAbstract |= Params[i]->isAbstract();
    }
  
    // Calculate whether or not this type is abstract
    setAbstract(isAbstract);
  }
  
  StructType::StructType(LLVMContext &C, 
                         const std::vector<const Type*> &Types, bool isPacked)
    : CompositeType(C, StructTyID) {
    ContainedTys = reinterpret_cast<PATypeHandle*>(this + 1);
    NumContainedTys = Types.size();
    setSubclassData(isPacked);
    bool isAbstract = false;
    for (unsigned i = 0; i < Types.size(); ++i) {
      assert(Types[i] && "<null> type for structure field!");
      assert(isValidElementType(Types[i]) &&
             "Invalid type for structure element!");
      new (&ContainedTys[i]) PATypeHandle(Types[i], this);
      isAbstract |= Types[i]->isAbstract();
    }
  
    // Calculate whether or not this type is abstract
    setAbstract(isAbstract);
  }
  
  ArrayType::ArrayType(const Type *ElType, uint64_t NumEl)
    : SequentialType(ArrayTyID, ElType) {
    NumElements = NumEl;
  
    // Calculate whether or not this type is abstract
    setAbstract(ElType->isAbstract());
  }
  
  VectorType::VectorType(const Type *ElType, unsigned NumEl)
    : SequentialType(VectorTyID, ElType) {
    NumElements = NumEl;
    setAbstract(ElType->isAbstract());
    assert(NumEl > 0 && "NumEl of a VectorType must be greater than 0");
    assert(isValidElementType(ElType) &&
           "Elements of a VectorType must be a primitive type");
  
  }
  
  
  PointerType::PointerType(const Type *E, unsigned AddrSpace)
    : SequentialType(PointerTyID, E) {
    AddressSpace = AddrSpace;
    // Calculate whether or not this type is abstract
    setAbstract(E->isAbstract());
  }
  
  OpaqueType::OpaqueType(LLVMContext &C) : DerivedType(C, OpaqueTyID) {
    setAbstract(true);
  #ifdef DEBUG_MERGE_TYPES
    DEBUG(dbgs() << "Derived new type: " << *this << "\n");
  #endif
  }
  
  void PATypeHolder::destroy() {
    Ty = 0;
  }
  
  // dropAllTypeUses - When this (abstract) type is resolved to be equal to
  // another (more concrete) type, we must eliminate all references to other
  // types, to avoid some circular reference problems.
  void DerivedType::dropAllTypeUses() {
    if (NumContainedTys != 0) {
      // The type must stay abstract.  To do this, we insert a pointer to a type
      // that will never get resolved, thus will always be abstract.
      ContainedTys[0] = getContext().pImpl->AlwaysOpaqueTy;
  
      // Change the rest of the types to be Int32Ty's.  It doesn't matter what we
      // pick so long as it doesn't point back to this type.  We choose something
      // concrete to avoid overhead for adding to AbstractTypeUser lists and
      // stuff.
      const Type *ConcreteTy = Type::getInt32Ty(getContext());
      for (unsigned i = 1, e = NumContainedTys; i != e; ++i)
        ContainedTys[i] = ConcreteTy;
    }
  }
  
  
  namespace {
  
  /// TypePromotionGraph and graph traits - this is designed to allow us to do
  /// efficient SCC processing of type graphs.  This is the exact same as
  /// GraphTraits<Type*>, except that we pretend that concrete types have no
  /// children to avoid processing them.
  struct TypePromotionGraph {
    Type *Ty;
    TypePromotionGraph(Type *T) : Ty(T) {}
  };
  
  }
  
  namespace llvm {
    template <> struct GraphTraits<TypePromotionGraph> {
      typedef Type NodeType;
      typedef Type::subtype_iterator ChildIteratorType;
  
      static inline NodeType *getEntryNode(TypePromotionGraph G) { return G.Ty; }
      static inline ChildIteratorType child_begin(NodeType *N) {
        if (N->isAbstract())
          return N->subtype_begin();
        // No need to process children of concrete types.
        return N->subtype_end();
      }
      static inline ChildIteratorType child_end(NodeType *N) {
        return N->subtype_end();
      }
    };
  }
  
  
  // PromoteAbstractToConcrete - This is a recursive function that walks a type
  // graph calculating whether or not a type is abstract.
  //
  void Type::PromoteAbstractToConcrete() {
    if (!isAbstract()) return;
  
    scc_iterator<TypePromotionGraph> SI = scc_begin(TypePromotionGraph(this));
    scc_iterator<TypePromotionGraph> SE = scc_end  (TypePromotionGraph(this));
  
    for (; SI != SE; ++SI) {
      std::vector<Type*> &SCC = *SI;
  
      // Concrete types are leaves in the tree.  Since an SCC will either be all
      // abstract or all concrete, we only need to check one type.
      if (!SCC[0]->isAbstract()) continue;
      
      if (SCC[0]->isOpaqueTy())
        return;     // Not going to be concrete, sorry.
  
      // If all of the children of all of the types in this SCC are concrete,
      // then this SCC is now concrete as well.  If not, neither this SCC, nor
      // any parent SCCs will be concrete, so we might as well just exit.
      for (unsigned i = 0, e = SCC.size(); i != e; ++i)
        for (Type::subtype_iterator CI = SCC[i]->subtype_begin(),
               E = SCC[i]->subtype_end(); CI != E; ++CI)
          if ((*CI)->isAbstract())
            // If the child type is in our SCC, it doesn't make the entire SCC
            // abstract unless there is a non-SCC abstract type.
            if (std::find(SCC.begin(), SCC.end(), *CI) == SCC.end())
              return;               // Not going to be concrete, sorry.
  
      // Okay, we just discovered this whole SCC is now concrete, mark it as
      // such!
      for (unsigned i = 0, e = SCC.size(); i != e; ++i) {
        assert(SCC[i]->isAbstract() && "Why are we processing concrete types?");
  
        SCC[i]->setAbstract(false);
      }
  
      for (unsigned i = 0, e = SCC.size(); i != e; ++i) {
        assert(!SCC[i]->isAbstract() && "Concrete type became abstract?");
        // The type just became concrete, notify all users!
        cast<DerivedType>(SCC[i])->notifyUsesThatTypeBecameConcrete();
      }
    }
  }
  
  
  //===----------------------------------------------------------------------===//
  //                      Type Structural Equality Testing
  //===----------------------------------------------------------------------===//
  
  // TypesEqual - Two types are considered structurally equal if they have the
  // same "shape": Every level and element of the types have identical primitive
  // ID's, and the graphs have the same edges/nodes in them.  Nodes do not have to
  // be pointer equals to be equivalent though.  This uses an optimistic algorithm
  // that assumes that two graphs are the same until proven otherwise.
  //
  static bool TypesEqual(const Type *Ty, const Type *Ty2,
                         std::map<const Type *, const Type *> &EqTypes) {
    if (Ty == Ty2) return true;
    if (Ty->getTypeID() != Ty2->getTypeID()) return false;
    if (Ty->isOpaqueTy())
      return false;  // Two unequal opaque types are never equal
  
    std::map<const Type*, const Type*>::iterator It = EqTypes.find(Ty);
    if (It != EqTypes.end())
      return It->second == Ty2;    // Looping back on a type, check for equality
  
    // Otherwise, add the mapping to the table to make sure we don't get
    // recursion on the types...
    EqTypes.insert(It, std::make_pair(Ty, Ty2));
  
    // Two really annoying special cases that breaks an otherwise nice simple
    // algorithm is the fact that arraytypes have sizes that differentiates types,
    // and that function types can be varargs or not.  Consider this now.
    //
    if (const IntegerType *ITy = dyn_cast<IntegerType>(Ty)) {
      const IntegerType *ITy2 = cast<IntegerType>(Ty2);
      return ITy->getBitWidth() == ITy2->getBitWidth();
    }
    
    if (const PointerType *PTy = dyn_cast<PointerType>(Ty)) {
      const PointerType *PTy2 = cast<PointerType>(Ty2);
      return PTy->getAddressSpace() == PTy2->getAddressSpace() &&
             TypesEqual(PTy->getElementType(), PTy2->getElementType(), EqTypes);
    }
    
    if (const StructType *STy = dyn_cast<StructType>(Ty)) {
      const StructType *STy2 = cast<StructType>(Ty2);
      if (STy->getNumElements() != STy2->getNumElements()) return false;
      if (STy->isPacked() != STy2->isPacked()) return false;
      for (unsigned i = 0, e = STy2->getNumElements(); i != e; ++i)
        if (!TypesEqual(STy->getElementType(i), STy2->getElementType(i), EqTypes))
          return false;
      return true;
    }
    
    if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
      const ArrayType *ATy2 = cast<ArrayType>(Ty2);
      return ATy->getNumElements() == ATy2->getNumElements() &&
             TypesEqual(ATy->getElementType(), ATy2->getElementType(), EqTypes);
    }
    
    if (const VectorType *PTy = dyn_cast<VectorType>(Ty)) {
      const VectorType *PTy2 = cast<VectorType>(Ty2);
      return PTy->getNumElements() == PTy2->getNumElements() &&
             TypesEqual(PTy->getElementType(), PTy2->getElementType(), EqTypes);
    }
    
    if (const FunctionType *FTy = dyn_cast<FunctionType>(Ty)) {
      const FunctionType *FTy2 = cast<FunctionType>(Ty2);
      if (FTy->isVarArg() != FTy2->isVarArg() ||
          FTy->getNumParams() != FTy2->getNumParams() ||
          !TypesEqual(FTy->getReturnType(), FTy2->getReturnType(), EqTypes))
        return false;
      for (unsigned i = 0, e = FTy2->getNumParams(); i != e; ++i) {
        if (!TypesEqual(FTy->getParamType(i), FTy2->getParamType(i), EqTypes))
          return false;
      }
      return true;
    }
    
    llvm_unreachable("Unknown derived type!");
    return false;
  }
  
  namespace llvm { // in namespace llvm so findable by ADL
  static bool TypesEqual(const Type *Ty, const Type *Ty2) {
    std::map<const Type *, const Type *> EqTypes;
    return ::TypesEqual(Ty, Ty2, EqTypes);
  }
  }
  
  // AbstractTypeHasCycleThrough - Return true there is a path from CurTy to
  // TargetTy in the type graph.  We know that Ty is an abstract type, so if we
  // ever reach a non-abstract type, we know that we don't need to search the
  // subgraph.
  static bool AbstractTypeHasCycleThrough(const Type *TargetTy, const Type *CurTy,
                                  SmallPtrSet<const Type*, 128> &VisitedTypes) {
    if (TargetTy == CurTy) return true;
    if (!CurTy->isAbstract()) return false;
  
    if (!VisitedTypes.insert(CurTy))
      return false;  // Already been here.
  
    for (Type::subtype_iterator I = CurTy->subtype_begin(),
         E = CurTy->subtype_end(); I != E; ++I)
      if (AbstractTypeHasCycleThrough(TargetTy, *I, VisitedTypes))
        return true;
    return false;
  }
  
  static bool ConcreteTypeHasCycleThrough(const Type *TargetTy, const Type *CurTy,
                                  SmallPtrSet<const Type*, 128> &VisitedTypes) {
    if (TargetTy == CurTy) return true;
  
    if (!VisitedTypes.insert(CurTy))
      return false;  // Already been here.
  
    for (Type::subtype_iterator I = CurTy->subtype_begin(),
         E = CurTy->subtype_end(); I != E; ++I)
      if (ConcreteTypeHasCycleThrough(TargetTy, *I, VisitedTypes))
        return true;
    return false;
  }
  
  /// TypeHasCycleThroughItself - Return true if the specified type has
  /// a cycle back to itself.
  
  namespace llvm { // in namespace llvm so it's findable by ADL
  static bool TypeHasCycleThroughItself(const Type *Ty) {
    SmallPtrSet<const Type*, 128> VisitedTypes;
  
    if (Ty->isAbstract()) {  // Optimized case for abstract types.
      for (Type::subtype_iterator I = Ty->subtype_begin(), E = Ty->subtype_end();
           I != E; ++I)
        if (AbstractTypeHasCycleThrough(Ty, *I, VisitedTypes))
          return true;
    } else {
      for (Type::subtype_iterator I = Ty->subtype_begin(), E = Ty->subtype_end();
           I != E; ++I)
        if (ConcreteTypeHasCycleThrough(Ty, *I, VisitedTypes))
          return true;
    }
    return false;
  }
  }
  
  //===----------------------------------------------------------------------===//
  // Function Type Factory and Value Class...
  //
  const IntegerType *IntegerType::get(LLVMContext &C, unsigned NumBits) {
    assert(NumBits >= MIN_INT_BITS && "bitwidth too small");
    assert(NumBits <= MAX_INT_BITS && "bitwidth too large");
  
    // Check for the built-in integer types
    switch (NumBits) {
    case  1: return cast<IntegerType>(Type::getInt1Ty(C));
    case  8: return cast<IntegerType>(Type::getInt8Ty(C));
    case 16: return cast<IntegerType>(Type::getInt16Ty(C));
    case 32: return cast<IntegerType>(Type::getInt32Ty(C));
    case 64: return cast<IntegerType>(Type::getInt64Ty(C));
    default: 
      break;
    }
  
    LLVMContextImpl *pImpl = C.pImpl;
    
    IntegerValType IVT(NumBits);
    IntegerType *ITy = 0;
    
    // First, see if the type is already in the table, for which
    // a reader lock suffices.
    ITy = pImpl->IntegerTypes.get(IVT);
      
    if (!ITy) {
      // Value not found.  Derive a new type!
      ITy = new IntegerType(C, NumBits);
      pImpl->IntegerTypes.add(IVT, ITy);
    }
  #ifdef DEBUG_MERGE_TYPES
    DEBUG(dbgs() << "Derived new type: " << *ITy << "\n");
  #endif
    return ITy;
  }
  
  bool IntegerType::isPowerOf2ByteWidth() const {
    unsigned BitWidth = getBitWidth();
    return (BitWidth > 7) && isPowerOf2_32(BitWidth);
  }
  
  APInt IntegerType::getMask() const {
    return APInt::getAllOnesValue(getBitWidth());
  }
  
  FunctionValType FunctionValType::get(const FunctionType *FT) {
    // Build up a FunctionValType
    std::vector<const Type *> ParamTypes;
    ParamTypes.reserve(FT->getNumParams());
    for (unsigned i = 0, e = FT->getNumParams(); i != e; ++i)
      ParamTypes.push_back(FT->getParamType(i));
    return FunctionValType(FT->getReturnType(), ParamTypes, FT->isVarArg());
  }
  
  
  // FunctionType::get - The factory function for the FunctionType class...
  FunctionType *FunctionType::get(const Type *ReturnType,
                                  const std::vector<const Type*> &Params,
                                  bool isVarArg) {
    FunctionValType VT(ReturnType, Params, isVarArg);
    FunctionType *FT = 0;
    
    LLVMContextImpl *pImpl = ReturnType->getContext().pImpl;
    
    FT = pImpl->FunctionTypes.get(VT);
    
    if (!FT) {
      FT = (FunctionType*) operator new(sizeof(FunctionType) +
                                      sizeof(PATypeHandle)*(Params.size()+1));
      new (FT) FunctionType(ReturnType, Params, isVarArg);
      pImpl->FunctionTypes.add(VT, FT);
    }
  
  #ifdef DEBUG_MERGE_TYPES
    DEBUG(dbgs() << "Derived new type: " << FT << "\n");
  #endif
    return FT;
  }
  
  ArrayType *ArrayType::get(const Type *ElementType, uint64_t NumElements) {
    assert(ElementType && "Can't get array of <null> types!");
    assert(isValidElementType(ElementType) && "Invalid type for array element!");
  
    ArrayValType AVT(ElementType, NumElements);
    ArrayType *AT = 0;
  
    LLVMContextImpl *pImpl = ElementType->getContext().pImpl;
    
    AT = pImpl->ArrayTypes.get(AVT);
        
    if (!AT) {
      // Value not found.  Derive a new type!
      pImpl->ArrayTypes.add(AVT, AT = new ArrayType(ElementType, NumElements));
    }
  #ifdef DEBUG_MERGE_TYPES
    DEBUG(dbgs() << "Derived new type: " << *AT << "\n");
  #endif
    return AT;
  }
  
  bool ArrayType::isValidElementType(const Type *ElemTy) {
    return !ElemTy->isVoidTy() && !ElemTy->isLabelTy() &&
           !ElemTy->isMetadataTy() && !ElemTy->isFunctionTy();
  }
  
  VectorType *VectorType::get(const Type *ElementType, unsigned NumElements) {
    assert(ElementType && "Can't get vector of <null> types!");
  
    VectorValType PVT(ElementType, NumElements);
    VectorType *PT = 0;
    
    LLVMContextImpl *pImpl = ElementType->getContext().pImpl;
    
    PT = pImpl->VectorTypes.get(PVT);
      
    if (!PT) {
      pImpl->VectorTypes.add(PVT, PT = new VectorType(ElementType, NumElements));
    }
  #ifdef DEBUG_MERGE_TYPES
    DEBUG(dbgs() << "Derived new type: " << *PT << "\n");
  #endif
    return PT;
  }
  
  bool VectorType::isValidElementType(const Type *ElemTy) {
    return ElemTy->isIntegerTy() || ElemTy->isFloatingPointTy() ||
           ElemTy->isOpaqueTy();
  }
  
  //===----------------------------------------------------------------------===//
  // Struct Type Factory...
  //
  
  StructType *StructType::get(LLVMContext &Context,
                              const std::vector<const Type*> &ETypes, 
                              bool isPacked) {
    StructValType STV(ETypes, isPacked);
    StructType *ST = 0;
    
    LLVMContextImpl *pImpl = Context.pImpl;
    
    ST = pImpl->StructTypes.get(STV);
      
    if (!ST) {
      // Value not found.  Derive a new type!
      ST = (StructType*) operator new(sizeof(StructType) +
                                      sizeof(PATypeHandle) * ETypes.size());
      new (ST) StructType(Context, ETypes, isPacked);
      pImpl->StructTypes.add(STV, ST);
    }
  #ifdef DEBUG_MERGE_TYPES
    DEBUG(dbgs() << "Derived new type: " << *ST << "\n");
  #endif
    return ST;
  }
  
  StructType *StructType::get(LLVMContext &Context, const Type *type, ...) {
    va_list ap;
    std::vector<const llvm::Type*> StructFields;
    va_start(ap, type);
    while (type) {
      StructFields.push_back(type);
      type = va_arg(ap, llvm::Type*);
    }
    return llvm::StructType::get(Context, StructFields);
  }
  
  bool StructType::isValidElementType(const Type *ElemTy) {
    return !ElemTy->isVoidTy() && !ElemTy->isLabelTy() &&
           !ElemTy->isMetadataTy() && !ElemTy->isFunctionTy();
  }
  
  
  //===----------------------------------------------------------------------===//
  // Pointer Type Factory...
  //
  
  PointerType *PointerType::get(const Type *ValueType, unsigned AddressSpace) {
    assert(ValueType && "Can't get a pointer to <null> type!");
    assert(ValueType->getTypeID() != VoidTyID &&
           "Pointer to void is not valid, use i8* instead!");
    assert(isValidElementType(ValueType) && "Invalid type for pointer element!");
    PointerValType PVT(ValueType, AddressSpace);
  
    PointerType *PT = 0;
    
    LLVMContextImpl *pImpl = ValueType->getContext().pImpl;
    
    PT = pImpl->PointerTypes.get(PVT);
    
    if (!PT) {
      // Value not found.  Derive a new type!
      pImpl->PointerTypes.add(PVT, PT = new PointerType(ValueType, AddressSpace));
    }
  #ifdef DEBUG_MERGE_TYPES
    DEBUG(dbgs() << "Derived new type: " << *PT << "\n");
  #endif
    return PT;
  }
  
  const PointerType *Type::getPointerTo(unsigned addrs) const {
    return PointerType::get(this, addrs);
  }
  
  bool PointerType::isValidElementType(const Type *ElemTy) {
    return !ElemTy->isVoidTy() && !ElemTy->isLabelTy() &&
           !ElemTy->isMetadataTy();
  }
  
  
  //===----------------------------------------------------------------------===//
  // Opaque Type Factory...
  //
  
  OpaqueType *OpaqueType::get(LLVMContext &C) {
    OpaqueType *OT = new OpaqueType(C);       // All opaque types are distinct.
    LLVMContextImpl *pImpl = C.pImpl;
    pImpl->OpaqueTypes.insert(OT);
    return OT;
  }
  
  
  
  //===----------------------------------------------------------------------===//
  //                     Derived Type Refinement Functions
  //===----------------------------------------------------------------------===//
  
  // addAbstractTypeUser - Notify an abstract type that there is a new user of
  // it.  This function is called primarily by the PATypeHandle class.
  void Type::addAbstractTypeUser(AbstractTypeUser *U) const {
    assert(isAbstract() && "addAbstractTypeUser: Current type not abstract!");
    AbstractTypeUsers.push_back(U);
  }
  
  
  // removeAbstractTypeUser - Notify an abstract type that a user of the class
  // no longer has a handle to the type.  This function is called primarily by
  // the PATypeHandle class.  When there are no users of the abstract type, it
  // is annihilated, because there is no way to get a reference to it ever again.
  //
  void Type::removeAbstractTypeUser(AbstractTypeUser *U) const {
    
    // Search from back to front because we will notify users from back to
    // front.  Also, it is likely that there will be a stack like behavior to
    // users that register and unregister users.
    //
    unsigned i;
    for (i = AbstractTypeUsers.size(); AbstractTypeUsers[i-1] != U; --i)
      assert(i != 0 && "AbstractTypeUser not in user list!");
  
    --i;  // Convert to be in range 0 <= i < size()
    assert(i < AbstractTypeUsers.size() && "Index out of range!");  // Wraparound?
  
    AbstractTypeUsers.erase(AbstractTypeUsers.begin()+i);
  
  #ifdef DEBUG_MERGE_TYPES
    DEBUG(dbgs() << "  remAbstractTypeUser[" << (void*)this << ", "
                 << *this << "][" << i << "] User = " << U << "\n");
  #endif
  
    if (AbstractTypeUsers.empty() && getRefCount() == 0 && isAbstract()) {
  #ifdef DEBUG_MERGE_TYPES
      DEBUG(dbgs() << "DELETEing unused abstract type: <" << *this
                   << ">[" << (void*)this << "]" << "\n");
  #endif
    
      this->destroy();
    }
  }
  
  // refineAbstractTypeTo - This function is used when it is discovered
  // that the 'this' abstract type is actually equivalent to the NewType
  // specified. This causes all users of 'this' to switch to reference the more 
  // concrete type NewType and for 'this' to be deleted.  Only used for internal
  // callers.
  //
  void DerivedType::refineAbstractTypeTo(const Type *NewType) {
    assert(isAbstract() && "refineAbstractTypeTo: Current type is not abstract!");
    assert(this != NewType && "Can't refine to myself!");
    assert(ForwardType == 0 && "This type has already been refined!");
  
    LLVMContextImpl *pImpl = getContext().pImpl;
  
    // The descriptions may be out of date.  Conservatively clear them all!
    pImpl->AbstractTypeDescriptions.clear();
  
  #ifdef DEBUG_MERGE_TYPES
    DEBUG(dbgs() << "REFINING abstract type [" << (void*)this << " "
                 << *this << "] to [" << (void*)NewType << " "
                 << *NewType << "]!\n");
  #endif
  
    // Make sure to put the type to be refined to into a holder so that if IT gets
    // refined, that we will not continue using a dead reference...
    //
    PATypeHolder NewTy(NewType);
    // Any PATypeHolders referring to this type will now automatically forward to
    // the type we are resolved to.
    ForwardType = NewType;
    if (ForwardType->isAbstract())
      ForwardType->addRef();
  
    // Add a self use of the current type so that we don't delete ourself until
    // after the function exits.
    //
    PATypeHolder CurrentTy(this);
  
    // To make the situation simpler, we ask the subclass to remove this type from
    // the type map, and to replace any type uses with uses of non-abstract types.
    // This dramatically limits the amount of recursive type trouble we can find
    // ourselves in.
    dropAllTypeUses();
  
    // Iterate over all of the uses of this type, invoking callback.  Each user
    // should remove itself from our use list automatically.  We have to check to
    // make sure that NewTy doesn't _become_ 'this'.  If it does, resolving types
    // will not cause users to drop off of the use list.  If we resolve to ourself
    // we succeed!
    //
    while (!AbstractTypeUsers.empty() && NewTy != this) {
      AbstractTypeUser *User = AbstractTypeUsers.back();
  
      unsigned OldSize = AbstractTypeUsers.size(); (void)OldSize;
  #ifdef DEBUG_MERGE_TYPES
      DEBUG(dbgs() << " REFINING user " << OldSize-1 << "[" << (void*)User
                   << "] of abstract type [" << (void*)this << " "
                   << *this << "] to [" << (void*)NewTy.get() << " "
                   << *NewTy << "]!\n");
  #endif
      User->refineAbstractType(this, NewTy);
  
      assert(AbstractTypeUsers.size() != OldSize &&
             "AbsTyUser did not remove self from user list!");
    }
  
    // If we were successful removing all users from the type, 'this' will be
    // deleted when the last PATypeHolder is destroyed or updated from this type.
    // This may occur on exit of this function, as the CurrentTy object is
    // destroyed.
  }
  
  // notifyUsesThatTypeBecameConcrete - Notify AbstractTypeUsers of this type that
  // the current type has transitioned from being abstract to being concrete.
  //
  void DerivedType::notifyUsesThatTypeBecameConcrete() {
  #ifdef DEBUG_MERGE_TYPES
    DEBUG(dbgs() << "typeIsREFINED type: " << (void*)this << " " << *this <<"\n");
  #endif
  
    unsigned OldSize = AbstractTypeUsers.size(); (void)OldSize;
    while (!AbstractTypeUsers.empty()) {
      AbstractTypeUser *ATU = AbstractTypeUsers.back();
      ATU->typeBecameConcrete(this);
  
      assert(AbstractTypeUsers.size() < OldSize-- &&
             "AbstractTypeUser did not remove itself from the use list!");
    }
  }
  
  // refineAbstractType - Called when a contained type is found to be more
  // concrete - this could potentially change us from an abstract type to a
  // concrete type.
  //
  void FunctionType::refineAbstractType(const DerivedType *OldType,
                                        const Type *NewType) {
    LLVMContextImpl *pImpl = OldType->getContext().pImpl;
    pImpl->FunctionTypes.RefineAbstractType(this, OldType, NewType);
  }
  
  void FunctionType::typeBecameConcrete(const DerivedType *AbsTy) {
    LLVMContextImpl *pImpl = AbsTy->getContext().pImpl;
    pImpl->FunctionTypes.TypeBecameConcrete(this, AbsTy);
  }
  
  
  // refineAbstractType - Called when a contained type is found to be more
  // concrete - this could potentially change us from an abstract type to a
  // concrete type.
  //
  void ArrayType::refineAbstractType(const DerivedType *OldType,
                                     const Type *NewType) {
    LLVMContextImpl *pImpl = OldType->getContext().pImpl;
    pImpl->ArrayTypes.RefineAbstractType(this, OldType, NewType);
  }
  
  void ArrayType::typeBecameConcrete(const DerivedType *AbsTy) {
    LLVMContextImpl *pImpl = AbsTy->getContext().pImpl;
    pImpl->ArrayTypes.TypeBecameConcrete(this, AbsTy);
  }
  
  // refineAbstractType - Called when a contained type is found to be more
  // concrete - this could potentially change us from an abstract type to a
  // concrete type.
  //
  void VectorType::refineAbstractType(const DerivedType *OldType,
                                     const Type *NewType) {
    LLVMContextImpl *pImpl = OldType->getContext().pImpl;
    pImpl->VectorTypes.RefineAbstractType(this, OldType, NewType);
  }
  
  void VectorType::typeBecameConcrete(const DerivedType *AbsTy) {
    LLVMContextImpl *pImpl = AbsTy->getContext().pImpl;
    pImpl->VectorTypes.TypeBecameConcrete(this, AbsTy);
  }
  
  // refineAbstractType - Called when a contained type is found to be more
  // concrete - this could potentially change us from an abstract type to a
  // concrete type.
  //
  void StructType::refineAbstractType(const DerivedType *OldType,
                                      const Type *NewType) {
    LLVMContextImpl *pImpl = OldType->getContext().pImpl;
    pImpl->StructTypes.RefineAbstractType(this, OldType, NewType);
  }
  
  void StructType::typeBecameConcrete(const DerivedType *AbsTy) {
    LLVMContextImpl *pImpl = AbsTy->getContext().pImpl;
    pImpl->StructTypes.TypeBecameConcrete(this, AbsTy);
  }
  
  // refineAbstractType - Called when a contained type is found to be more
  // concrete - this could potentially change us from an abstract type to a
  // concrete type.
  //
  void PointerType::refineAbstractType(const DerivedType *OldType,
                                       const Type *NewType) {
    LLVMContextImpl *pImpl = OldType->getContext().pImpl;
    pImpl->PointerTypes.RefineAbstractType(this, OldType, NewType);
  }
  
  void PointerType::typeBecameConcrete(const DerivedType *AbsTy) {
    LLVMContextImpl *pImpl = AbsTy->getContext().pImpl;
    pImpl->PointerTypes.TypeBecameConcrete(this, AbsTy);
  }
  
  bool SequentialType::indexValid(const Value *V) const {
    if (V->getType()->isIntegerTy()) 
      return true;
    return false;
  }
  
  namespace llvm {
  raw_ostream &operator<<(raw_ostream &OS, const Type &T) {
    T.print(OS);
    return OS;
  }
  }
  