Type.cpp

Go to the documentation of this file.

//===-- 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 "llvm/DerivedTypes.h"
#include "llvm/Constants.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/SCCIterator.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/ManagedStatic.h"
#include "llvm/Support/Debug.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() {}


//===----------------------------------------------------------------------===//
//                         Type Class Implementation
//===----------------------------------------------------------------------===//

// Concrete/Abstract TypeDescriptions - We lazily calculate type descriptions
// for types as they are needed.  Because resolution of types must invalidate
// all of the abstract type descriptions, we keep them in a seperate map to make
// this easy.
static ManagedStatic<std::map<const Type*, 
                              std::string> > ConcreteTypeDescriptions;
static ManagedStatic<std::map<const Type*,
                              std::string> > AbstractTypeDescriptions;

/// 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 {

  // 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 (isa<FunctionType>(this) || isa<StructType>(this)) {
    // 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 (isa<FunctionType>(this))
      static_cast<const FunctionType*>(this)->FunctionType::~FunctionType();
    else
      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;
  }

  // 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(TypeID IDNumber) {
  switch (IDNumber) {
  case VoidTyID      : return VoidTy;
  case FloatTyID     : return FloatTy;
  case DoubleTyID    : return DoubleTy;
  case X86_FP80TyID  : return X86_FP80Ty;
  case FP128TyID     : return FP128Ty;
  case PPC_FP128TyID : return PPC_FP128Ty;
  case LabelTyID     : return LabelTy;
  default:
    return 0;
  }
}

const Type *Type::getVAArgsPromotedType() const {
  if (ID == IntegerTyID && getSubclassData() < 32)
    return Type::Int32Ty;
  else if (ID == FloatTyID)
    return Type::DoubleTy;
  else
    return this;
}

/// isIntOrIntVector - Return true if this is an integer type or a vector of
/// integer types.
///
bool Type::isIntOrIntVector() const {
  if (isInteger())
    return true;
  if (ID != Type::VectorTyID) return false;
  
  return cast<VectorType>(this)->getElementType()->isInteger();
}

/// isFPOrFPVector - Return true if this is a FP type or a vector of FP types.
///
bool Type::isFPOrFPVector() 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()->isFloatingPoint();
}

// canLosslesllyBitCastTo - Return true if this type can be converted to
// 'Ty' without any reinterpretation of bits.  For example, uint to int.
//
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.
  if (const VectorType *thisPTy = dyn_cast<VectorType>(this))
    if (const VectorType *thatPTy = dyn_cast<VectorType>(Ty))
      return thisPTy->getBitWidth() == thatPTy->getBitWidth();

  // 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 (isa<PointerType>(this))
    return isa<PointerType>(Ty);
  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::IntegerTyID: return cast<IntegerType>(this)->getBitWidth();
  case Type::VectorTyID:  return cast<VectorType>(this)->getBitWidth();
  default: return 0;
  }
}

/// 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 (isa<IntegerType>(this))
    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 (!isa<StructType>(this)) 
    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())
    cast<DerivedType>(RealForwardedType)->addRef();

  // Now drop the old reference.  This could cause ForwardType to get deleted.
  cast<DerivedType>(ForwardType)->dropRef();

  // Return the updated type.
  ForwardType = RealForwardedType;
  return ForwardType;
}

void Type::refineAbstractType(const DerivedType *OldTy, const Type *NewTy) {
  abort();
}
void Type::typeBecameConcrete(const DerivedType *AbsTy) {
  abort();
}


// getTypeDescription - This is a recursive function that walks a type hierarchy
// calculating the description for a type.
//
static std::string getTypeDescription(const Type *Ty,
                                      std::vector<const Type *> &TypeStack) {
  if (isa<OpaqueType>(Ty)) {                     // Base case for the recursion
    std::map<const Type*, std::string>::iterator I =
      AbstractTypeDescriptions->find(Ty);
    if (I != AbstractTypeDescriptions->end())
      return I->second;
    std::string Desc = "opaque";
    AbstractTypeDescriptions->insert(std::make_pair(Ty, Desc));
    return Desc;
  }

  if (!Ty->isAbstract()) {                       // Base case for the recursion
    std::map<const Type*, std::string>::iterator I =
      ConcreteTypeDescriptions->find(Ty);
    if (I != ConcreteTypeDescriptions->end()) 
      return I->second;
    
    if (Ty->isPrimitiveType()) {
      switch (Ty->getTypeID()) {
      default: assert(0 && "Unknown prim type!");
      case Type::VoidTyID:   return (*ConcreteTypeDescriptions)[Ty] = "void";
      case Type::FloatTyID:  return (*ConcreteTypeDescriptions)[Ty] = "float";
      case Type::DoubleTyID: return (*ConcreteTypeDescriptions)[Ty] = "double";
      case Type::X86_FP80TyID: 
            return (*ConcreteTypeDescriptions)[Ty] = "x86_fp80";
      case Type::FP128TyID: return (*ConcreteTypeDescriptions)[Ty] = "fp128";
      case Type::PPC_FP128TyID: 
          return (*ConcreteTypeDescriptions)[Ty] = "ppc_fp128";
      case Type::LabelTyID:  return (*ConcreteTypeDescriptions)[Ty] = "label";
      }
    }
  }

  // Check to see if the Type is already on the stack...
  unsigned Slot = 0, CurSize = TypeStack.size();
  while (Slot < CurSize && TypeStack[Slot] != Ty) ++Slot; // Scan for type

  // This is another base case for the recursion.  In this case, we know
  // that we have looped back to a type that we have previously visited.
  // Generate the appropriate upreference to handle this.
  //
  if (Slot < CurSize)
    return "\\" + utostr(CurSize-Slot);         // Here's the upreference

  // Recursive case: derived types...
  std::string Result;
  TypeStack.push_back(Ty);    // Add us to the stack..

  switch (Ty->getTypeID()) {
  case Type::IntegerTyID: {
    const IntegerType *ITy = cast<IntegerType>(Ty);
    Result = "i" + utostr(ITy->getBitWidth());
    break;
  }
  case Type::FunctionTyID: {
    const FunctionType *FTy = cast<FunctionType>(Ty);
    if (!Result.empty())
      Result += " ";
    Result += getTypeDescription(FTy->getReturnType(), TypeStack) + " (";
    for (FunctionType::param_iterator I = FTy->param_begin(),
         E = FTy->param_end(); I != E; ++I) {
      if (I != FTy->param_begin())
        Result += ", ";
      Result += getTypeDescription(*I, TypeStack);
    }
    if (FTy->isVarArg()) {
      if (FTy->getNumParams()) Result += ", ";
      Result += "...";
    }
    Result += ")";
    break;
  }
  case Type::StructTyID: {
    const StructType *STy = cast<StructType>(Ty);
    if (STy->isPacked())
      Result = "<{ ";
    else
      Result = "{ ";
    for (StructType::element_iterator I = STy->element_begin(),
           E = STy->element_end(); I != E; ++I) {
      if (I != STy->element_begin())
        Result += ", ";
      Result += getTypeDescription(*I, TypeStack);
    }
    Result += " }";
    if (STy->isPacked())
      Result += ">";
    break;
  }
  case Type::PointerTyID: {
    const PointerType *PTy = cast<PointerType>(Ty);
    Result = getTypeDescription(PTy->getElementType(), TypeStack);
    if (unsigned AddressSpace = PTy->getAddressSpace())
      Result += " addrspace(" + utostr(AddressSpace) + ")";
    Result += " *";
    break;
  }
  case Type::ArrayTyID: {
    const ArrayType *ATy = cast<ArrayType>(Ty);
    unsigned NumElements = ATy->getNumElements();
    Result = "[";
    Result += utostr(NumElements) + " x ";
    Result += getTypeDescription(ATy->getElementType(), TypeStack) + "]";
    break;
  }
  case Type::VectorTyID: {
    const VectorType *PTy = cast<VectorType>(Ty);
    unsigned NumElements = PTy->getNumElements();
    Result = "<";
    Result += utostr(NumElements) + " x ";
    Result += getTypeDescription(PTy->getElementType(), TypeStack) + ">";
    break;
  }
  default:
    Result = "<error>";
    assert(0 && "Unhandled type in getTypeDescription!");
  }

  TypeStack.pop_back();       // Remove self from stack...

  return Result;
}



static const std::string &getOrCreateDesc(std::map<const Type*,std::string>&Map,
                                          const Type *Ty) {
  std::map<const Type*, std::string>::iterator I = Map.find(Ty);
  if (I != Map.end()) return I->second;

  std::vector<const Type *> TypeStack;
  std::string Result = getTypeDescription(Ty, TypeStack);
  return Map[Ty] = Result;
}


const std::string &Type::getDescription() const {
  if (isAbstract())
    return getOrCreateDesc(*AbstractTypeDescriptions, this);
  else
    return getOrCreateDesc(*ConcreteTypeDescriptions, this);
}


bool StructType::indexValid(const Value *V) const {
  // Structure indexes require 32-bit integer constants.
  if (V->getType() == Type::Int32Ty)
    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::VoidTy       = new Type(Type::VoidTyID);
const Type *Type::FloatTy      = new Type(Type::FloatTyID);
const Type *Type::DoubleTy     = new Type(Type::DoubleTyID);
const Type *Type::X86_FP80Ty   = new Type(Type::X86_FP80TyID);
const Type *Type::FP128Ty      = new Type(Type::FP128TyID);
const Type *Type::PPC_FP128Ty  = new Type(Type::PPC_FP128TyID);
const Type *Type::LabelTy      = new Type(Type::LabelTyID);

namespace {
  struct BuiltinIntegerType : public IntegerType {
    explicit BuiltinIntegerType(unsigned W) : IntegerType(W) {}
  };
}
const IntegerType *Type::Int1Ty  = new BuiltinIntegerType(1);
const IntegerType *Type::Int8Ty  = new BuiltinIntegerType(8);
const IntegerType *Type::Int16Ty = new BuiltinIntegerType(16);
const IntegerType *Type::Int32Ty = new BuiltinIntegerType(32);
const IntegerType *Type::Int64Ty = new BuiltinIntegerType(64);


//===----------------------------------------------------------------------===//
//                          Derived Type Constructors
//===----------------------------------------------------------------------===//

/// isValidReturnType - Return true if the specified type is valid as a return
/// type.
bool FunctionType::isValidReturnType(const Type *RetTy) {
  if (RetTy->isFirstClassType())
    return true;
  if (RetTy == Type::VoidTy || isa<OpaqueType>(RetTy))
    return true;
  
  // If this is a multiple return case, verify that each return is a first class
  // value and that there is at least one value.
  const StructType *SRetTy = dyn_cast<StructType>(RetTy);
  if (SRetTy == 0 || SRetTy->getNumElements() == 0)
    return false;
  
  for (unsigned i = 0, e = SRetTy->getNumElements(); i != e; ++i)
    if (!SRetTy->getElementType(i)->isFirstClassType())
      return false;
  return true;
}

FunctionType::FunctionType(const Type *Result,
                           const std::vector<const Type*> &Params,
                           bool IsVarArgs)
  : DerivedType(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((Params[i]->isFirstClassType() || isa<OpaqueType>(Params[i])) &&
           "Function arguments must be value types!");
    new (&ContainedTys[i+1]) PATypeHandle(Params[i],this);
    isAbstract |= Params[i]->isAbstract();
  }

  // Calculate whether or not this type is abstract
  setAbstract(isAbstract);
}

StructType::StructType(const std::vector<const Type*> &Types, bool isPacked)
  : CompositeType(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] != Type::VoidTy && "Void type for structure field!!");
     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((ElType->isInteger() || ElType->isFloatingPoint() || 
          isa<OpaqueType>(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() : DerivedType(OpaqueTyID) {
  setAbstract(true);
#ifdef DEBUG_MERGE_TYPES
  DOUT << "Derived new type: " << *this << "\n";
#endif
}

// 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.
    static Type *AlwaysOpaqueTy = OpaqueType::get();
    static PATypeHolder Holder(AlwaysOpaqueTy);
    ContainedTys[0] = 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 AbstracTypeUser lists and stuff.
    for (unsigned i = 1, e = NumContainedTys; i != e; ++i)
      ContainedTys[i] = Type::Int32Ty;
  }
}


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();
      else           // 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()) {
      if (isa<OpaqueType>(SCC[0]))
        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 (isa<OpaqueType>(Ty))
    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();
  } else 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);
  } else 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;
  } else 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);
  } else 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);
  } else 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;
  } else {
    assert(0 && "Unknown derived type!");
    return false;
  }
}

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.
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;
}

/// getSubElementHash - Generate a hash value for all of the SubType's of this
/// type.  The hash value is guaranteed to be zero if any of the subtypes are 
/// an opaque type.  Otherwise we try to mix them in as well as possible, but do
/// not look at the subtype's subtype's.
static unsigned getSubElementHash(const Type *Ty) {
  unsigned HashVal = 0;
  for (Type::subtype_iterator I = Ty->subtype_begin(), E = Ty->subtype_end();
       I != E; ++I) {
    HashVal *= 32;
    const Type *SubTy = I->get();
    HashVal += SubTy->getTypeID();
    switch (SubTy->getTypeID()) {
    default: break;
    case Type::OpaqueTyID: return 0;    // Opaque -> hash = 0 no matter what.
    case Type::IntegerTyID:
      HashVal ^= (cast<IntegerType>(SubTy)->getBitWidth() << 3);
      break;
    case Type::FunctionTyID:
      HashVal ^= cast<FunctionType>(SubTy)->getNumParams()*2 + 
                 cast<FunctionType>(SubTy)->isVarArg();
      break;
    case Type::ArrayTyID:
      HashVal ^= cast<ArrayType>(SubTy)->getNumElements();
      break;
    case Type::VectorTyID:
      HashVal ^= cast<VectorType>(SubTy)->getNumElements();
      break;
    case Type::StructTyID:
      HashVal ^= cast<StructType>(SubTy)->getNumElements();
      break;
    case Type::PointerTyID:
      HashVal ^= cast<PointerType>(SubTy)->getAddressSpace();
      break;
    }
  }
  return HashVal ? HashVal : 1;  // Do not return zero unless opaque subty.
}

//===----------------------------------------------------------------------===//
//                       Derived Type Factory Functions
//===----------------------------------------------------------------------===//

namespace llvm {
class TypeMapBase {
protected:
  /// TypesByHash - Keep track of types by their structure hash value.  Note
  /// that we only keep track of types that have cycles through themselves in
  /// this map.
  ///
  std::multimap<unsigned, PATypeHolder> TypesByHash;

public:
  void RemoveFromTypesByHash(unsigned Hash, const Type *Ty) {
    std::multimap<unsigned, PATypeHolder>::iterator I =
      TypesByHash.lower_bound(Hash);
    for (; I != TypesByHash.end() && I->first == Hash; ++I) {
      if (I->second == Ty) {
        TypesByHash.erase(I);
        return;
      }
    }
    
    // This must be do to an opaque type that was resolved.  Switch down to hash
    // code of zero.
    assert(Hash && "Didn't find type entry!");
    RemoveFromTypesByHash(0, Ty);
  }
  
  /// TypeBecameConcrete - When Ty gets a notification that TheType just became
  /// concrete, drop uses and make Ty non-abstract if we should.
  void TypeBecameConcrete(DerivedType *Ty, const DerivedType *TheType) {
    // If the element just became concrete, remove 'ty' from the abstract
    // type user list for the type.  Do this for as many times as Ty uses
    // OldType.
    for (Type::subtype_iterator I = Ty->subtype_begin(), E = Ty->subtype_end();
         I != E; ++I)
      if (I->get() == TheType)
        TheType->removeAbstractTypeUser(Ty);
    
    // If the type is currently thought to be abstract, rescan all of our
    // subtypes to see if the type has just become concrete!  Note that this
    // may send out notifications to AbstractTypeUsers that types become
    // concrete.
    if (Ty->isAbstract())
      Ty->PromoteAbstractToConcrete();
  }
};
}


// TypeMap - Make sure that only one instance of a particular type may be
// created on any given run of the compiler... note that this involves updating
// our map if an abstract type gets refined somehow.
//
namespace llvm {
template<class ValType, class TypeClass>
class TypeMap : public TypeMapBase {
  std::map<ValType, PATypeHolder> Map;
public:
  typedef typename std::map<ValType, PATypeHolder>::iterator iterator;
  ~TypeMap() { print(