It helps if I remember to actually add the file...

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78116 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 774 insertions, 0 deletions

diff --git a/lib/VMCore/ConstantsContext.h b/lib/VMCore/ConstantsContext.h
new file mode 100644
index 0000000000..90a2b6295a
--- /dev/null
+++ b/lib/VMCore/ConstantsContext.h
@@ -0,0 +1,774 @@
+//===---------------- ConstantsContext.h - Implementation ------*- C++ -*--===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file defines various helper methods and classes used by
+// LLVMContextImpl for creating and managing constants.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CONSTANTSCONTEXT_H
+#define LLVM_CONSTANTSCONTEXT_H
+
+#include "llvm/Instructions.h"
+#include "llvm/Operator.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/System/Mutex.h"
+#include "llvm/System/RWMutex.h"
+#include <map>
+
+namespace llvm {
+template<class ValType>
+struct ConstantTraits;
+
+/// UnaryConstantExpr - This class is private to Constants.cpp, and is used
+/// behind the scenes to implement unary constant exprs.
+class UnaryConstantExpr : public ConstantExpr {
+  void *operator new(size_t, unsigned);  // DO NOT IMPLEMENT
+public:
+  // allocate space for exactly one operand
+  void *operator new(size_t s) {
+    return User::operator new(s, 1);
+  }
+  UnaryConstantExpr(unsigned Opcode, Constant *C, const Type *Ty)
+    : ConstantExpr(Ty, Opcode, &Op<0>(), 1) {
+    Op<0>() = C;
+  }
+  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
+};
+
+/// BinaryConstantExpr - This class is private to Constants.cpp, and is used
+/// behind the scenes to implement binary constant exprs.
+class BinaryConstantExpr : public ConstantExpr {
+  void *operator new(size_t, unsigned);  // DO NOT IMPLEMENT
+public:
+  // allocate space for exactly two operands
+  void *operator new(size_t s) {
+    return User::operator new(s, 2);
+  }
+  BinaryConstantExpr(unsigned Opcode, Constant *C1, Constant *C2)
+    : ConstantExpr(C1->getType(), Opcode, &Op<0>(), 2) {
+    Op<0>() = C1;
+    Op<1>() = C2;
+  }
+  /// Transparently provide more efficient getOperand methods.
+  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
+};
+
+/// SelectConstantExpr - This class is private to Constants.cpp, and is used
+/// behind the scenes to implement select constant exprs.
+class SelectConstantExpr : public ConstantExpr {
+  void *operator new(size_t, unsigned);  // DO NOT IMPLEMENT
+public:
+  // allocate space for exactly three operands
+  void *operator new(size_t s) {
+    return User::operator new(s, 3);
+  }
+  SelectConstantExpr(Constant *C1, Constant *C2, Constant *C3)
+    : ConstantExpr(C2->getType(), Instruction::Select, &Op<0>(), 3) {
+    Op<0>() = C1;
+    Op<1>() = C2;
+    Op<2>() = C3;
+  }
+  /// Transparently provide more efficient getOperand methods.
+  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
+};
+
+/// ExtractElementConstantExpr - This class is private to
+/// Constants.cpp, and is used behind the scenes to implement
+/// extractelement constant exprs.
+class ExtractElementConstantExpr : public ConstantExpr {
+  void *operator new(size_t, unsigned);  // DO NOT IMPLEMENT
+public:
+  // allocate space for exactly two operands
+  void *operator new(size_t s) {
+    return User::operator new(s, 2);
+  }
+  ExtractElementConstantExpr(Constant *C1, Constant *C2)
+    : ConstantExpr(cast<VectorType>(C1->getType())->getElementType(), 
+                   Instruction::ExtractElement, &Op<0>(), 2) {
+    Op<0>() = C1;
+    Op<1>() = C2;
+  }
+  /// Transparently provide more efficient getOperand methods.
+  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
+};
+
+/// InsertElementConstantExpr - This class is private to
+/// Constants.cpp, and is used behind the scenes to implement
+/// insertelement constant exprs.
+class InsertElementConstantExpr : public ConstantExpr {
+  void *operator new(size_t, unsigned);  // DO NOT IMPLEMENT
+public:
+  // allocate space for exactly three operands
+  void *operator new(size_t s) {
+    return User::operator new(s, 3);
+  }
+  InsertElementConstantExpr(Constant *C1, Constant *C2, Constant *C3)
+    : ConstantExpr(C1->getType(), Instruction::InsertElement, 
+                   &Op<0>(), 3) {
+    Op<0>() = C1;
+    Op<1>() = C2;
+    Op<2>() = C3;
+  }
+  /// Transparently provide more efficient getOperand methods.
+  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
+};
+
+/// ShuffleVectorConstantExpr - This class is private to
+/// Constants.cpp, and is used behind the scenes to implement
+/// shufflevector constant exprs.
+class ShuffleVectorConstantExpr : public ConstantExpr {
+  void *operator new(size_t, unsigned);  // DO NOT IMPLEMENT
+public:
+  // allocate space for exactly three operands
+  void *operator new(size_t s) {
+    return User::operator new(s, 3);
+  }
+  ShuffleVectorConstantExpr(Constant *C1, Constant *C2, Constant *C3)
+  : ConstantExpr(VectorType::get(
+                   cast<VectorType>(C1->getType())->getElementType(),
+                   cast<VectorType>(C3->getType())->getNumElements()),
+                 Instruction::ShuffleVector, 
+                 &Op<0>(), 3) {
+    Op<0>() = C1;
+    Op<1>() = C2;
+    Op<2>() = C3;
+  }
+  /// Transparently provide more efficient getOperand methods.
+  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
+};
+
+/// ExtractValueConstantExpr - This class is private to
+/// Constants.cpp, and is used behind the scenes to implement
+/// extractvalue constant exprs.
+class ExtractValueConstantExpr : public ConstantExpr {
+  void *operator new(size_t, unsigned);  // DO NOT IMPLEMENT
+public:
+  // allocate space for exactly one operand
+  void *operator new(size_t s) {
+    return User::operator new(s, 1);
+  }
+  ExtractValueConstantExpr(Constant *Agg,
+                           const SmallVector<unsigned, 4> &IdxList,
+                           const Type *DestTy)
+    : ConstantExpr(DestTy, Instruction::ExtractValue, &Op<0>(), 1),
+      Indices(IdxList) {
+    Op<0>() = Agg;
+  }
+
+  /// Indices - These identify which value to extract.
+  const SmallVector<unsigned, 4> Indices;
+
+  /// Transparently provide more efficient getOperand methods.
+  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
+};
+
+/// InsertValueConstantExpr - This class is private to
+/// Constants.cpp, and is used behind the scenes to implement
+/// insertvalue constant exprs.
+class InsertValueConstantExpr : public ConstantExpr {
+  void *operator new(size_t, unsigned);  // DO NOT IMPLEMENT
+public:
+  // allocate space for exactly one operand
+  void *operator new(size_t s) {
+    return User::operator new(s, 2);
+  }
+  InsertValueConstantExpr(Constant *Agg, Constant *Val,
+                          const SmallVector<unsigned, 4> &IdxList,
+                          const Type *DestTy)
+    : ConstantExpr(DestTy, Instruction::InsertValue, &Op<0>(), 2),
+      Indices(IdxList) {
+    Op<0>() = Agg;
+    Op<1>() = Val;
+  }
+
+  /// Indices - These identify the position for the insertion.
+  const SmallVector<unsigned, 4> Indices;
+
+  /// Transparently provide more efficient getOperand methods.
+  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
+};
+
+
+/// GetElementPtrConstantExpr - This class is private to Constants.cpp, and is
+/// used behind the scenes to implement getelementpr constant exprs.
+class GetElementPtrConstantExpr : public ConstantExpr {
+  GetElementPtrConstantExpr(Constant *C, const std::vector<Constant*> &IdxList,
+                            const Type *DestTy);
+public:
+  static GetElementPtrConstantExpr *Create(Constant *C,
+                                           const std::vector<Constant*>&IdxList,
+                                           const Type *DestTy) {
+    return
+      new(IdxList.size() + 1) GetElementPtrConstantExpr(C, IdxList, DestTy);
+  }
+  /// Transparently provide more efficient getOperand methods.
+  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
+};
+
+// CompareConstantExpr - This class is private to Constants.cpp, and is used
+// behind the scenes to implement ICmp and FCmp constant expressions. This is
+// needed in order to store the predicate value for these instructions.
+struct CompareConstantExpr : public ConstantExpr {
+  void *operator new(size_t, unsigned);  // DO NOT IMPLEMENT
+  // allocate space for exactly two operands
+  void *operator new(size_t s) {
+    return User::operator new(s, 2);
+  }
+  unsigned short predicate;
+  CompareConstantExpr(const Type *ty, Instruction::OtherOps opc,
+                      unsigned short pred,  Constant* LHS, Constant* RHS)
+    : ConstantExpr(ty, opc, &Op<0>(), 2), predicate(pred) {
+    Op<0>() = LHS;
+    Op<1>() = RHS;
+  }
+  /// Transparently provide more efficient getOperand methods.
+  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
+};
+
+template <>
+struct OperandTraits<UnaryConstantExpr> : FixedNumOperandTraits<1> {
+};
+DEFINE_TRANSPARENT_OPERAND_ACCESSORS(UnaryConstantExpr, Value)
+
+template <>
+struct OperandTraits<BinaryConstantExpr> : FixedNumOperandTraits<2> {
+};
+DEFINE_TRANSPARENT_OPERAND_ACCESSORS(BinaryConstantExpr, Value)
+
+template <>
+struct OperandTraits<SelectConstantExpr> : FixedNumOperandTraits<3> {
+};
+DEFINE_TRANSPARENT_OPERAND_ACCESSORS(SelectConstantExpr, Value)
+
+template <>
+struct OperandTraits<ExtractElementConstantExpr> : FixedNumOperandTraits<2> {
+};
+DEFINE_TRANSPARENT_OPERAND_ACCESSORS(ExtractElementConstantExpr, Value)
+
+template <>
+struct OperandTraits<InsertElementConstantExpr> : FixedNumOperandTraits<3> {
+};
+DEFINE_TRANSPARENT_OPERAND_ACCESSORS(InsertElementConstantExpr, Value)
+
+template <>
+struct OperandTraits<ShuffleVectorConstantExpr> : FixedNumOperandTraits<3> {
+};
+DEFINE_TRANSPARENT_OPERAND_ACCESSORS(ShuffleVectorConstantExpr, Value)
+
+template <>
+struct OperandTraits<ExtractValueConstantExpr> : FixedNumOperandTraits<1> {
+};
+DEFINE_TRANSPARENT_OPERAND_ACCESSORS(ExtractValueConstantExpr, Value)
+
+template <>
+struct OperandTraits<InsertValueConstantExpr> : FixedNumOperandTraits<2> {
+};
+DEFINE_TRANSPARENT_OPERAND_ACCESSORS(InsertValueConstantExpr, Value)
+
+template <>
+struct OperandTraits<GetElementPtrConstantExpr> : VariadicOperandTraits<1> {
+};
+
+DEFINE_TRANSPARENT_OPERAND_ACCESSORS(GetElementPtrConstantExpr, Value)
+
+
+template <>
+struct OperandTraits<CompareConstantExpr> : FixedNumOperandTraits<2> {
+};
+DEFINE_TRANSPARENT_OPERAND_ACCESSORS(CompareConstantExpr, Value)
+
+struct ExprMapKeyType {
+  typedef SmallVector<unsigned, 4> IndexList;
+
+  ExprMapKeyType(unsigned opc,
+      const std::vector<Constant*> &ops,
+      unsigned short pred = 0,
+      const IndexList &inds = IndexList())
+        : opcode(opc), predicate(pred), operands(ops), indices(inds) {}
+  uint16_t opcode;
+  uint16_t predicate;
+  std::vector<Constant*> operands;
+  IndexList indices;
+  bool operator==(const ExprMapKeyType& that) const {
+    return this->opcode == that.opcode &&
+           this->predicate == that.predicate &&
+           this->operands == that.operands &&
+           this->indices == that.indices;
+  }
+  bool operator<(const ExprMapKeyType & that) const {
+    return this->opcode < that.opcode ||
+      (this->opcode == that.opcode && this->predicate < that.predicate) ||
+      (this->opcode == that.opcode && this->predicate == that.predicate &&
+       this->operands < that.operands) ||
+      (this->opcode == that.opcode && this->predicate == that.predicate &&
+       this->operands == that.operands && this->indices < that.indices);
+  }
+
+  bool operator!=(const ExprMapKeyType& that) const {
+    return !(*this == that);
+  }
+};
+
+// The number of operands for each ConstantCreator::create method is
+// determined by the ConstantTraits template.
+// ConstantCreator - A class that is used to create constants by
+// ValueMap*.  This class should be partially specialized if there is
+// something strange that needs to be done to interface to the ctor for the
+// constant.
+//
+template<typename T, typename Alloc>
+struct ConstantTraits< std::vector<T, Alloc> > {
+  static unsigned uses(const std::vector<T, Alloc>& v) {
+    return v.size();
+  }
+};
+
+template<class ConstantClass, class TypeClass, class ValType>
+struct ConstantCreator {
+  static ConstantClass *create(const TypeClass *Ty, const ValType &V) {
+    return new(ConstantTraits<ValType>::uses(V)) ConstantClass(Ty, V);
+  }
+};
+
+template<class ConstantClass, class TypeClass>
+struct ConvertConstantType {
+  static void convert(ConstantClass *OldC, const TypeClass *NewTy) {
+    llvm_unreachable("This type cannot be converted!");
+  }
+};
+
+template<>
+struct ConstantCreator<ConstantExpr, Type, ExprMapKeyType> {
+  static ConstantExpr *create(const Type *Ty, const ExprMapKeyType &V,
+      unsigned short pred = 0) {
+    if (Instruction::isCast(V.opcode))
+      return new UnaryConstantExpr(V.opcode, V.operands[0], Ty);
+    if ((V.opcode >= Instruction::BinaryOpsBegin &&
+         V.opcode < Instruction::BinaryOpsEnd))
+      return new BinaryConstantExpr(V.opcode, V.operands[0], V.operands[1]);
+    if (V.opcode == Instruction::Select)
+      return new SelectConstantExpr(V.operands[0], V.operands[1], 
+                                    V.operands[2]);
+    if (V.opcode == Instruction::ExtractElement)
+      return new ExtractElementConstantExpr(V.operands[0], V.operands[1]);
+    if (V.opcode == Instruction::InsertElement)
+      return new InsertElementConstantExpr(V.operands[0], V.operands[1],
+                                           V.operands[2]);
+    if (V.opcode == Instruction::ShuffleVector)
+      return new ShuffleVectorConstantExpr(V.operands[0], V.operands[1],
+                                           V.operands[2]);
+    if (V.opcode == Instruction::InsertValue)
+      return new InsertValueConstantExpr(V.operands[0], V.operands[1],
+                                         V.indices, Ty);
+    if (V.opcode == Instruction::ExtractValue)
+      return new ExtractValueConstantExpr(V.operands[0], V.indices, Ty);
+    if (V.opcode == Instruction::GetElementPtr) {
+      std::vector<Constant*> IdxList(V.operands.begin()+1, V.operands.end());
+      return GetElementPtrConstantExpr::Create(V.operands[0], IdxList, Ty);
+    }
+
+    // The compare instructions are weird. We have to encode the predicate
+    // value and it is combined with the instruction opcode by multiplying
+    // the opcode by one hundred. We must decode this to get the predicate.
+    if (V.opcode == Instruction::ICmp)
+      return new CompareConstantExpr(Ty, Instruction::ICmp, V.predicate, 
+                                     V.operands[0], V.operands[1]);
+    if (V.opcode == Instruction::FCmp) 
+      return new CompareConstantExpr(Ty, Instruction::FCmp, V.predicate, 
+                                     V.operands[0], V.operands[1]);
+    llvm_unreachable("Invalid ConstantExpr!");
+    return 0;
+  }
+};
+
+template<>
+struct ConvertConstantType<ConstantExpr, Type> {
+  static void convert(ConstantExpr *OldC, const Type *NewTy) {
+    Constant *New;
+    switch (OldC->getOpcode()) {
+    case Instruction::Trunc:
+    case Instruction::ZExt:
+    case Instruction::SExt:
+    case Instruction::FPTrunc:
+    case Instruction::FPExt:
+    case Instruction::UIToFP:
+    case Instruction::SIToFP:
+    case Instruction::FPToUI:
+    case Instruction::FPToSI:
+    case Instruction::PtrToInt:
+    case Instruction::IntToPtr:
+    case Instruction::BitCast:
+      New = ConstantExpr::getCast(OldC->getOpcode(), OldC->getOperand(0), 
+                                  NewTy);
+      break;
+    case Instruction::Select:
+      New = ConstantExpr::getSelectTy(NewTy, OldC->getOperand(0),
+                                      OldC->getOperand(1),
+                                      OldC->getOperand(2));
+      break;
+    default:
+      assert(OldC->getOpcode() >= Instruction::BinaryOpsBegin &&
+             OldC->getOpcode() <  Instruction::BinaryOpsEnd);
+      New = ConstantExpr::getTy(NewTy, OldC->getOpcode(), OldC->getOperand(0),
+                                OldC->getOperand(1));
+      break;
+    case Instruction::GetElementPtr:
+      // Make everyone now use a constant of the new type...
+      std::vector<Value*> Idx(OldC->op_begin()+1, OldC->op_end());
+      New = ConstantExpr::getGetElementPtrTy(NewTy, OldC->getOperand(0),
+                                             &Idx[0], Idx.size());
+      break;
+    }
+
+    assert(New != OldC && "Didn't replace constant??");
+    OldC->uncheckedReplaceAllUsesWith(New);
+    OldC->destroyConstant();    // This constant is now dead, destroy it.
+  }
+};
+
+// ConstantAggregateZero does not take extra "value" argument...
+template<class ValType>
+struct ConstantCreator<ConstantAggregateZero, Type, ValType> {
+  static ConstantAggregateZero *create(const Type *Ty, const ValType &V){
+    return new ConstantAggregateZero(Ty);
+  }
+};
+
+template<>
+struct ConvertConstantType<ConstantVector, VectorType> {
+  static void convert(ConstantVector *OldC, const VectorType *NewTy) {
+    // Make everyone now use a constant of the new type...
+    std::vector<Constant*> C;
+    for (unsigned i = 0, e = OldC->getNumOperands(); i != e; ++i)
+      C.push_back(cast<Constant>(OldC->getOperand(i)));
+    Constant *New = ConstantVector::get(NewTy, C);
+    assert(New != OldC && "Didn't replace constant??");
+    OldC->uncheckedReplaceAllUsesWith(New);
+    OldC->destroyConstant();    // This constant is now dead, destroy it.
+  }
+};
+
+template<>
+struct ConvertConstantType<ConstantAggregateZero, Type> {
+  static void convert(ConstantAggregateZero *OldC, const Type *NewTy) {
+    // Make everyone now use a constant of the new type...
+    Constant *New = ConstantAggregateZero::get(NewTy);
+    assert(New != OldC && "Didn't replace constant??");
+    OldC->uncheckedReplaceAllUsesWith(New);
+    OldC->destroyConstant();     // This constant is now dead, destroy it.
+  }
+};
+
+template<>
+struct ConvertConstantType<ConstantArray, ArrayType> {
+  static void convert(ConstantArray *OldC, const ArrayType *NewTy) {
+    // Make everyone now use a constant of the new type...
+    std::vector<Constant*> C;
+    for (unsigned i = 0, e = OldC->getNumOperands(); i != e; ++i)
+      C.push_back(cast<Constant>(OldC->getOperand(i)));
+    Constant *New = ConstantArray::get(NewTy, C);
+    assert(New != OldC && "Didn't replace constant??");
+    OldC->uncheckedReplaceAllUsesWith(New);
+    OldC->destroyConstant();    // This constant is now dead, destroy it.
+  }
+};
+
+template<>
+struct ConvertConstantType<ConstantStruct, StructType> {
+  static void convert(ConstantStruct *OldC, const StructType *NewTy) {
+    // Make everyone now use a constant of the new type...
+    std::vector<Constant*> C;
+    for (unsigned i = 0, e = OldC->getNumOperands(); i != e; ++i)
+      C.push_back(cast<Constant>(OldC->getOperand(i)));
+    Constant *New = ConstantStruct::get(NewTy, C);
+    assert(New != OldC && "Didn't replace constant??");
+
+    OldC->uncheckedReplaceAllUsesWith(New);
+    OldC->destroyConstant();    // This constant is now dead, destroy it.
+  }
+};
+
+// ConstantPointerNull does not take extra "value" argument...
+template<class ValType>
+struct ConstantCreator<ConstantPointerNull, PointerType, ValType> {
+  static ConstantPointerNull *create(const PointerType *Ty, const ValType &V){
+    return new ConstantPointerNull(Ty);
+  }
+};
+
+template<>
+struct ConvertConstantType<ConstantPointerNull, PointerType> {
+  static void convert(ConstantPointerNull *OldC, const PointerType *NewTy) {
+    // Make everyone now use a constant of the new type...
+    Constant *New = ConstantPointerNull::get(NewTy);
+    assert(New != OldC && "Didn't replace constant??");
+    OldC->uncheckedReplaceAllUsesWith(New);
+    OldC->destroyConstant();     // This constant is now dead, destroy it.
+  }
+};
+
+// UndefValue does not take extra "value" argument...
+template<class ValType>
+struct ConstantCreator<UndefValue, Type, ValType> {
+  static UndefValue *create(const Type *Ty, const ValType &V) {
+    return new UndefValue(Ty);
+  }
+};
+
+template<>
+struct ConvertConstantType<UndefValue, Type> {
+  static void convert(UndefValue *OldC, const Type *NewTy) {
+    // Make everyone now use a constant of the new type.
+    Constant *New = UndefValue::get(NewTy);
+    assert(New != OldC && "Didn't replace constant??");
+    OldC->uncheckedReplaceAllUsesWith(New);
+    OldC->destroyConstant();     // This constant is now dead, destroy it.
+  }
+};
+
+template<class ValType, class TypeClass, class ConstantClass,
+         bool HasLargeKey = false /*true for arrays and structs*/ >
+class ValueMap : public AbstractTypeUser {
+public:
+  typedef std::pair<const Type*, ValType> MapKey;
+  typedef std::map<MapKey, Constant *> MapTy;
+  typedef std::map<Constant*, typename MapTy::iterator> InverseMapTy;
+  typedef std::map<const Type*, typename MapTy::iterator> AbstractTypeMapTy;
+private:
+  /// Map - This is the main map from the element descriptor to the Constants.
+  /// This is the primary way we avoid creating two of the same shape
+  /// constant.
+  MapTy Map;
+    
+  /// InverseMap - If "HasLargeKey" is true, this contains an inverse mapping
+  /// from the constants to their element in Map.  This is important for
+  /// removal of constants from the array, which would otherwise have to scan
+  /// through the map with very large keys.
+  InverseMapTy InverseMap;
+
+  /// AbstractTypeMap - Map for abstract type constants.
+  ///
+  AbstractTypeMapTy AbstractTypeMap;
+    
+  /// ValueMapLock - Mutex for this map.
+  sys::SmartMutex<true> ValueMapLock;
+
+public:
+  // NOTE: This function is not locked.  It is the caller's responsibility
+  // to enforce proper synchronization.
+  typename MapTy::iterator map_end() { return Map.end(); }
+    
+  /// InsertOrGetItem - Return an iterator for the specified element.
+  /// If the element exists in the map, the returned iterator points to the
+  /// entry and Exists=true.  If not, the iterator points to the newly
+  /// inserted entry and returns Exists=false.  Newly inserted entries have
+  /// I->second == 0, and should be filled in.
+  /// NOTE: This function is not locked.  It is the caller's responsibility
+  // to enforce proper synchronization.
+  typename MapTy::iterator InsertOrGetItem(std::pair<MapKey, Constant *>
+                                 &InsertVal,
+                                 bool &Exists) {
+    std::pair<typename MapTy::iterator, bool> IP = Map.insert(InsertVal);
+    Exists = !IP.second;
+    return IP.first;
+  }
+    
+private:
+  typename MapTy::iterator FindExistingElement(ConstantClass *CP) {
+    if (HasLargeKey) {
+      typename InverseMapTy::iterator IMI = InverseMap.find(CP);
+      assert(IMI != InverseMap.end() && IMI->second != Map.end() &&
+             IMI->second->second == CP &&
+             "InverseMap corrupt!");
+      return IMI->second;
+    }
+      
+    typename MapTy::iterator I =
+      Map.find(MapKey(static_cast<const TypeClass*>(CP->getRawType()),
+                      getValType(CP)));
+    if (I == Map.end() || I->second != CP) {
+      // FIXME: This should not use a linear scan.  If this gets to be a
+      // performance problem, someone should look at this.
+      for (I = Map.begin(); I != Map.end() && I->second != CP; ++I)
+        /* empty */;
+    }
+    return I;
+  }
+    
+  ConstantClass* Create(const TypeClass *Ty, const ValType &V,
+                        typename MapTy::iterator I) {
+    ConstantClass* Result =
+      ConstantCreator<ConstantClass,TypeClass,ValType>::create(Ty, V);
+
+    assert(Result->getType() == Ty && "Type specified is not correct!");
+    I = Map.insert(I, std::make_pair(MapKey(Ty, V), Result));
+
+    if (HasLargeKey)  // Remember the reverse mapping if needed.
+      InverseMap.insert(std::make_pair(Result, I));
+
+    // If the type of the constant is abstract, make sure that an entry
+    // exists for it in the AbstractTypeMap.
+    if (Ty->isAbstract()) {
+      typename AbstractTypeMapTy::iterator TI = 
+                                               AbstractTypeMap.find(Ty);
+
+      if (TI == AbstractTypeMap.end()) {
+        // Add ourselves to the ATU list of the type.
+        cast<DerivedType>(Ty)->addAbstractTypeUser(this);
+
+        AbstractTypeMap.insert(TI, std::make_pair(Ty, I));
+      }
+    }
+      
+    return Result;
+  }
+public:
+    
+  /// getOrCreate - Return the specified constant from the map, creating it if
+  /// necessary.
+  ConstantClass *getOrCreate(const TypeClass *Ty, const ValType &V) {
+    sys::SmartScopedLock<true> Lock(ValueMapLock);
+    MapKey Lookup(Ty, V);
+    ConstantClass* Result = 0;
+    
+    typename MapTy::iterator I = Map.find(Lookup);
+    // Is it in the map?  
+    if (I != Map.end())
+      Result = static_cast<ConstantClass *>(I->second);
+        
+    if (!Result) {
+      // If no preexisting value, create one now...
+      Result = Create(Ty, V, I);
+    }
+        
+    return Result;
+  }
+
+  void remove(ConstantClass *CP) {
+    sys::SmartScopedLock<true> Lock(ValueMapLock);
+    typename MapTy::iterator I = FindExistingElement(CP);
+    assert(I != Map.end() && "Constant not found in constant table!");
+    assert(I->second == CP && "Didn't find correct element?");
+
+    if (HasLargeKey)  // Remember the reverse mapping if needed.
+      InverseMap.erase(CP);
+      
+    // Now that we found the entry, make sure this isn't the entry that
+    // the AbstractTypeMap points to.
+    const TypeClass *Ty = static_cast<const TypeClass *>(I->first.first);
+    if (Ty->isAbstract()) {
+      assert(AbstractTypeMap.count(Ty) &&
+             "Abstract type not in AbstractTypeMap?");
+      typename MapTy::iterator &ATMEntryIt = AbstractTypeMap[Ty];
+      if (ATMEntryIt == I) {
+        // Yes, we are removing the representative entry for this type.
+        // See if there are any other entries of the same type.
+        typename MapTy::iterator TmpIt = ATMEntryIt;
+
+        // First check the entry before this one...
+        if (TmpIt != Map.begin()) {
+          --TmpIt;
+          if (TmpIt->first.first != Ty) // Not the same type, move back...
+            ++TmpIt;
+        }
+
+        // If we didn't find the same type, try to move forward...
+        if (TmpIt == ATMEntryIt) {
+          ++TmpIt;
+          if (TmpIt == Map.end() || TmpIt->first.first != Ty)
+            --TmpIt;   // No entry afterwards with the same type
+        }
+
+        // If there is another entry in the map of the same abstract type,
+        // update the AbstractTypeMap entry now.
+        if (TmpIt != ATMEntryIt) {
+          ATMEntryIt = TmpIt;
+        } else {
+          // Otherwise, we are removing the last instance of this type
+          // from the table.  Remove from the ATM, and from user list.
+          cast<DerivedType>(Ty)->removeAbstractTypeUser(this);
+          AbstractTypeMap.erase(Ty);
+        }
+      }
+    }
+
+    Map.erase(I);
+  }
+
+    
+  /// MoveConstantToNewSlot - If we are about to change C to be the element
+  /// specified by I, update our internal data structures to reflect this
+  /// fact.
+  /// NOTE: This function is not locked. It is the responsibility of the
+  /// caller to enforce proper synchronization if using this method.
+  void MoveConstantToNewSlot(ConstantClass *C, typename MapTy::iterator I) {
+    // First, remove the old location of the specified constant in the map.
+    typename MapTy::iterator OldI = FindExistingElement(C);
+    assert(OldI != Map.end() && "Constant not found in constant table!");
+    assert(OldI->second == C && "Didn't find correct element?");
+      
+    // If this constant is the representative element for its abstract type,
+    // update the AbstractTypeMap so that the representative element is I.
+    if (C->getType()->isAbstract()) {
+      typename AbstractTypeMapTy::iterator ATI =
+          AbstractTypeMap.find(C->getType());
+      assert(ATI != AbstractTypeMap.end() &&
+             "Abstract type not in AbstractTypeMap?");
+      if (ATI->second == OldI)
+        ATI->second = I;
+    }
+      
+    // Remove the old entry from the map.
+    Map.erase(OldI);
+    
+    // Update the inverse map so that we know that this constant is now
+    // located at descriptor I.
+    if (HasLargeKey) {
+      assert(I->second == C && "Bad inversemap entry!");
+      InverseMap[C] = I;
+    }
+  }
+    
+  void refineAbstractType(const DerivedType *OldTy, const Type *NewTy) {
+    sys::SmartScopedLock<true> Lock(ValueMapLock);
+    typename AbstractTypeMapTy::iterator I =
+      AbstractTypeMap.find(cast<Type>(OldTy));
+
+    assert(I != AbstractTypeMap.end() &&
+           "Abstract type not in AbstractTypeMap?");
+
+    // Convert a constant at a time until the last one is gone.  The last one
+    // leaving will remove() itself, causing the AbstractTypeMapEntry to be
+    // eliminated eventually.
+    do {
+      ConvertConstantType<ConstantClass,
+                          TypeClass>::convert(
+                              static_cast<ConstantClass *>(I->second->second),
+                                              cast<TypeClass>(NewTy));
+
+      I = AbstractTypeMap.find(cast<Type>(OldTy));
+    } while (I != AbstractTypeMap.end());
+  }
+
+  // If the type became concrete without being refined to any other existing
+  // type, we just remove ourselves from the ATU list.
+  void typeBecameConcrete(const DerivedType *AbsTy) {
+    AbsTy->removeAbstractTypeUser(this);
+  }
+
+  void dump() const {
+    DOUT << "Constant.cpp: ValueMap\n";
+  }
+};
+
+}
+
+#endif