ConstantsContext.h

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//===-- ConstantsContext.h - Constants-related Context Interals -*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
//  This file defines various helper methods and classes used by
// LLVMContextImpl for creating and managing constants.
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_LIB_IR_CONSTANTSCONTEXT_H
#define LLVM_LIB_IR_CONSTANTSCONTEXT_H
 
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMapInfo.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/Hashing.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/OperandTraits.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <utility>
 
#define DEBUG_TYPE "ir"
 
namespace llvm {
 
/// CastConstantExpr - This class is private to Constants.cpp, and is used
/// behind the scenes to implement cast constant exprs.
class CastConstantExpr final : public ConstantExpr {
  constexpr static IntrusiveOperandsAllocMarker AllocMarker{1};
 
public:
  CastConstantExpr(unsigned Opcode, Constant *C, Type *Ty)
      : ConstantExpr(Ty, Opcode, AllocMarker) {
    Op<0>() = C;
  }
 
  // allocate space for exactly one operand
  void *operator new(size_t S) { return User::operator new(S, AllocMarker); }
  void operator delete(void *Ptr) { User::operator delete(Ptr, AllocMarker); }
 
  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
 
  static bool classof(const ConstantExpr *CE) {
    return Instruction::isCast(CE->getOpcode());
  }
  static bool classof(const Value *V) {
    return isa<ConstantExpr>(V) && classof(cast<ConstantExpr>(V));
  }
};
 
/// BinaryConstantExpr - This class is private to Constants.cpp, and is used
/// behind the scenes to implement binary constant exprs.
class BinaryConstantExpr final : public ConstantExpr {
  constexpr static IntrusiveOperandsAllocMarker AllocMarker{2};
 
public:
  BinaryConstantExpr(unsigned Opcode, Constant *C1, Constant *C2,
                     unsigned Flags)
      : ConstantExpr(C1->getType(), Opcode, AllocMarker) {
    Op<0>() = C1;
    Op<1>() = C2;
    assert((Flags & ConstantSubclassBits) == 0 && "invalid flags");
    SubclassOptionalData = Flags;
  }
 
  // allocate space for exactly two operands
  void *operator new(size_t S) { return User::operator new(S, AllocMarker); }
  void operator delete(void *Ptr) { User::operator delete(Ptr, AllocMarker); }
 
  /// Transparently provide more efficient getOperand methods.
  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
 
  static bool classof(const ConstantExpr *CE) {
    return Instruction::isBinaryOp(CE->getOpcode());
  }
  static bool classof(const Value *V) {
    return isa<ConstantExpr>(V) && classof(cast<ConstantExpr>(V));
  }
};
 
/// ExtractElementConstantExpr - This class is private to
/// Constants.cpp, and is used behind the scenes to implement
/// extractelement constant exprs.
class ExtractElementConstantExpr final : public ConstantExpr {
  constexpr static IntrusiveOperandsAllocMarker AllocMarker{2};
 
public:
  ExtractElementConstantExpr(Constant *C1, Constant *C2)
      : ConstantExpr(cast<VectorType>(C1->getType())->getElementType(),
                     Instruction::ExtractElement, AllocMarker) {
    Op<0>() = C1;
    Op<1>() = C2;
  }
 
  // allocate space for exactly two operands
  void *operator new(size_t S) { return User::operator new(S, AllocMarker); }
  void operator delete(void *Ptr) { User::operator delete(Ptr, AllocMarker); }
 
  /// Transparently provide more efficient getOperand methods.
  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
 
  static bool classof(const ConstantExpr *CE) {
    return CE->getOpcode() == Instruction::ExtractElement;
  }
  static bool classof(const Value *V) {
    return isa<ConstantExpr>(V) && classof(cast<ConstantExpr>(V));
  }
};
 
/// InsertElementConstantExpr - This class is private to
/// Constants.cpp, and is used behind the scenes to implement
/// insertelement constant exprs.
class InsertElementConstantExpr final : public ConstantExpr {
  constexpr static IntrusiveOperandsAllocMarker AllocMarker{3};
 
public:
  InsertElementConstantExpr(Constant *C1, Constant *C2, Constant *C3)
      : ConstantExpr(C1->getType(), Instruction::InsertElement, AllocMarker) {
    Op<0>() = C1;
    Op<1>() = C2;
    Op<2>() = C3;
  }
 
  // allocate space for exactly three operands
  void *operator new(size_t S) { return User::operator new(S, AllocMarker); }
  void operator delete(void *Ptr) { User::operator delete(Ptr, AllocMarker); }
 
  /// Transparently provide more efficient getOperand methods.
  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
 
  static bool classof(const ConstantExpr *CE) {
    return CE->getOpcode() == Instruction::InsertElement;
  }
  static bool classof(const Value *V) {
    return isa<ConstantExpr>(V) && classof(cast<ConstantExpr>(V));
  }
};
 
/// ShuffleVectorConstantExpr - This class is private to
/// Constants.cpp, and is used behind the scenes to implement
/// shufflevector constant exprs.
class ShuffleVectorConstantExpr final : public ConstantExpr {
  constexpr static IntrusiveOperandsAllocMarker AllocMarker{2};
 
public:
  ShuffleVectorConstantExpr(Constant *C1, Constant *C2, ArrayRef<int> Mask)
      : ConstantExpr(VectorType::get(
                         cast<VectorType>(C1->getType())->getElementType(),
                         Mask.size(), isa<ScalableVectorType>(C1->getType())),
                     Instruction::ShuffleVector, AllocMarker) {
    assert(ShuffleVectorInst::isValidOperands(C1, C2, Mask) &&
           "Invalid shuffle vector instruction operands!");
    Op<0>() = C1;
    Op<1>() = C2;
    ShuffleMask.assign(Mask.begin(), Mask.end());
    ShuffleMaskForBitcode =
        ShuffleVectorInst::convertShuffleMaskForBitcode(Mask, getType());
  }
 
  SmallVector<int, 4> ShuffleMask;
  Constant *ShuffleMaskForBitcode;
 
  void *operator new(size_t S) { return User::operator new(S, AllocMarker); }
  void operator delete(void *Ptr) {
    return User::operator delete(Ptr, AllocMarker);
  }
 
  /// Transparently provide more efficient getOperand methods.
  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
 
  static bool classof(const ConstantExpr *CE) {
    return CE->getOpcode() == Instruction::ShuffleVector;
  }
  static bool classof(const Value *V) {
    return isa<ConstantExpr>(V) && classof(cast<ConstantExpr>(V));
  }
};
 
/// GetElementPtrConstantExpr - This class is private to Constants.cpp, and is
/// used behind the scenes to implement getelementptr constant exprs.
class GetElementPtrConstantExpr : public ConstantExpr {
  Type *SrcElementTy;
  Type *ResElementTy;
  std::optional<ConstantRange> InRange;
 
  GetElementPtrConstantExpr(Type *SrcElementTy, Constant *C,
                            ArrayRef<Constant *> IdxList, Type *DestTy,
                            std::optional<ConstantRange> InRange,
                            AllocInfo AllocInfo);
 
public:
  static GetElementPtrConstantExpr *
  Create(Type *SrcElementTy, Constant *C, ArrayRef<Constant *> IdxList,
         Type *DestTy, unsigned Flags, std::optional<ConstantRange> InRange) {
    IntrusiveOperandsAllocMarker AllocMarker{unsigned(IdxList.size() + 1)};
    GetElementPtrConstantExpr *Result = new (AllocMarker)
        GetElementPtrConstantExpr(SrcElementTy, C, IdxList, DestTy,
                                  std::move(InRange), AllocMarker);
    assert((Flags & ConstantSubclassBits) == 0 && "invalid flags");
    Result->SubclassOptionalData = Flags;
    return Result;
  }
 
  Type *getSourceElementType() const;
  Type *getResultElementType() const;
  std::optional<ConstantRange> getInRange() const;
 
  /// Transparently provide more efficient getOperand methods.
  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
 
  static bool classof(const ConstantExpr *CE) {
    return CE->getOpcode() == Instruction::GetElementPtr;
  }
  static bool classof(const Value *V) {
    return isa<ConstantExpr>(V) && classof(cast<ConstantExpr>(V));
  }
};
 
template <>
struct OperandTraits<CastConstantExpr>
    : public FixedNumOperandTraits<CastConstantExpr, 1> {};
DEFINE_TRANSPARENT_OPERAND_ACCESSORS(CastConstantExpr, Value)
 
template <>
struct OperandTraits<BinaryConstantExpr>
    : public FixedNumOperandTraits<BinaryConstantExpr, 2> {};
DEFINE_TRANSPARENT_OPERAND_ACCESSORS(BinaryConstantExpr, Value)
 
template <>
struct OperandTraits<ExtractElementConstantExpr>
    : public FixedNumOperandTraits<ExtractElementConstantExpr, 2> {};
DEFINE_TRANSPARENT_OPERAND_ACCESSORS(ExtractElementConstantExpr, Value)
 
template <>
struct OperandTraits<InsertElementConstantExpr>
    : public FixedNumOperandTraits<InsertElementConstantExpr, 3> {};
DEFINE_TRANSPARENT_OPERAND_ACCESSORS(InsertElementConstantExpr, Value)
 
template <>
struct OperandTraits<ShuffleVectorConstantExpr>
    : public FixedNumOperandTraits<ShuffleVectorConstantExpr, 2> {};
DEFINE_TRANSPARENT_OPERAND_ACCESSORS(ShuffleVectorConstantExpr, Value)
 
template <>
struct OperandTraits<GetElementPtrConstantExpr>
    : public VariadicOperandTraits<GetElementPtrConstantExpr> {};
 
DEFINE_TRANSPARENT_OPERAND_ACCESSORS(GetElementPtrConstantExpr, Value)
 
template <class ConstantClass> struct ConstantAggrKeyType;
struct InlineAsmKeyType;
struct ConstantExprKeyType;
struct ConstantPtrAuthKeyType;
 
template <class ConstantClass> struct ConstantInfo;
template <> struct ConstantInfo<ConstantExpr> {
  using ValType = ConstantExprKeyType;
  using TypeClass = Type;
};
template <> struct ConstantInfo<InlineAsm> {
  using ValType = InlineAsmKeyType;
  using TypeClass = PointerType;
};
template <> struct ConstantInfo<ConstantArray> {
  using ValType = ConstantAggrKeyType<ConstantArray>;
  using TypeClass = ArrayType;
};
template <> struct ConstantInfo<ConstantStruct> {
  using ValType = ConstantAggrKeyType<ConstantStruct>;
  using TypeClass = StructType;
};
template <> struct ConstantInfo<ConstantVector> {
  using ValType = ConstantAggrKeyType<ConstantVector>;
  using TypeClass = VectorType;
};
template <> struct ConstantInfo<ConstantPtrAuth> {
  using ValType = ConstantPtrAuthKeyType;
  using TypeClass = Type;
};
 
template <class ConstantClass> struct ConstantAggrKeyType {
  ArrayRef<Constant *> Operands;
 
  ConstantAggrKeyType(ArrayRef<Constant *> Operands) : Operands(Operands) {}
 
  ConstantAggrKeyType(ArrayRef<Constant *> Operands, const ConstantClass *)
      : Operands(Operands) {}
 
  ConstantAggrKeyType(const ConstantClass *C,
                      SmallVectorImpl<Constant *> &Storage) {
    assert(Storage.empty() && "Expected empty storage");
    Storage.reserve(C->getNumOperands());
    for (unsigned I = 0, E = C->getNumOperands(); I != E; ++I)
      Storage.push_back(C->getOperand(I));
    Operands = Storage;
  }
 
  bool operator==(const ConstantAggrKeyType &X) const {
    return Operands == X.Operands;
  }
 
  bool operator==(const ConstantClass *C) const {
    if (Operands.size() != C->getNumOperands())
      return false;
    for (unsigned I = 0, E = Operands.size(); I != E; ++I)
      if (Operands[I] != C->getOperand(I))
        return false;
    return true;
  }
 
  unsigned getHash() const { return hash_combine_range(Operands); }
 
  using TypeClass = typename ConstantInfo<ConstantClass>::TypeClass;
 
  ConstantClass *create(TypeClass *Ty) const {
    User::IntrusiveOperandsAllocMarker AllocMarker{unsigned(Operands.size())};
    return new (AllocMarker) ConstantClass(Ty, Operands, AllocMarker);
  }
};
 
struct InlineAsmKeyType {
  StringRef AsmString;
  StringRef Constraints;
  FunctionType *FTy;
  bool HasSideEffects;
  bool IsAlignStack;
  InlineAsm::AsmDialect AsmDialect;
  bool CanThrow;
 
  InlineAsmKeyType(StringRef AsmString, StringRef Constraints,
                   FunctionType *FTy, bool HasSideEffects, bool IsAlignStack,
                   InlineAsm::AsmDialect AsmDialect, bool canThrow)
      : AsmString(AsmString), Constraints(Constraints), FTy(FTy),
        HasSideEffects(HasSideEffects), IsAlignStack(IsAlignStack),
        AsmDialect(AsmDialect), CanThrow(canThrow) {}
 
  InlineAsmKeyType(const InlineAsm *Asm, SmallVectorImpl<Constant *> &)
      : AsmString(Asm->getAsmString()), Constraints(Asm->getConstraintString()),
        FTy(Asm->getFunctionType()), HasSideEffects(Asm->hasSideEffects()),
        IsAlignStack(Asm->isAlignStack()), AsmDialect(Asm->getDialect()),
        CanThrow(Asm->canThrow()) {}
 
  bool operator==(const InlineAsmKeyType &X) const {
    return HasSideEffects == X.HasSideEffects &&
           IsAlignStack == X.IsAlignStack && AsmDialect == X.AsmDialect &&
           AsmString == X.AsmString && Constraints == X.Constraints &&
           FTy == X.FTy && CanThrow == X.CanThrow;
  }
 
  bool operator==(const InlineAsm *Asm) const {
    return HasSideEffects == Asm->hasSideEffects() &&
           IsAlignStack == Asm->isAlignStack() &&
           AsmDialect == Asm->getDialect() &&
           AsmString == Asm->getAsmString() &&
           Constraints == Asm->getConstraintString() &&
           FTy == Asm->getFunctionType() && CanThrow == Asm->canThrow();
  }
 
  unsigned getHash() const {
    return hash_combine(AsmString, Constraints, HasSideEffects, IsAlignStack,
                        AsmDialect, FTy, CanThrow);
  }
 
  using TypeClass = ConstantInfo<InlineAsm>::TypeClass;
 
  InlineAsm *create(TypeClass *Ty) const {
    assert(PointerType::getUnqual(FTy->getContext()) == Ty);
    return new InlineAsm(FTy, std::string(AsmString), std::string(Constraints),
                         HasSideEffects, IsAlignStack, AsmDialect, CanThrow);
  }
};
 
struct ConstantExprKeyType {
private:
  uint8_t Opcode;
  uint8_t SubclassOptionalData;
  ArrayRef<Constant *> Ops;
  ArrayRef<int> ShuffleMask;
  Type *ExplicitTy;
  std::optional<ConstantRange> InRange;
 
  static ArrayRef<int> getShuffleMaskIfValid(const ConstantExpr *CE) {
    if (CE->getOpcode() == Instruction::ShuffleVector)
      return CE->getShuffleMask();
    return {};
  }
 
  static Type *getSourceElementTypeIfValid(const ConstantExpr *CE) {
    if (auto *GEPCE = dyn_cast<GetElementPtrConstantExpr>(CE))
      return GEPCE->getSourceElementType();
    return nullptr;
  }
 
  static std::optional<ConstantRange>
  getInRangeIfValid(const ConstantExpr *CE) {
    if (auto *GEPCE = dyn_cast<GetElementPtrConstantExpr>(CE))
      return GEPCE->getInRange();
    return std::nullopt;
  }
 
public:
  ConstantExprKeyType(unsigned Opcode, ArrayRef<Constant *> Ops,
                      unsigned short SubclassOptionalData = 0,
                      ArrayRef<int> ShuffleMask = {},
                      Type *ExplicitTy = nullptr,
                      std::optional<ConstantRange> InRange = std::nullopt)
      : Opcode(Opcode), SubclassOptionalData(SubclassOptionalData), Ops(Ops),
        ShuffleMask(ShuffleMask), ExplicitTy(ExplicitTy),
        InRange(std::move(InRange)) {}
 
  ConstantExprKeyType(ArrayRef<Constant *> Operands, const ConstantExpr *CE)
      : Opcode(CE->getOpcode()),
        SubclassOptionalData(CE->getRawSubclassOptionalData()), Ops(Operands),
        ShuffleMask(getShuffleMaskIfValid(CE)),
        ExplicitTy(getSourceElementTypeIfValid(CE)),
        InRange(getInRangeIfValid(CE)) {}
 
  ConstantExprKeyType(const ConstantExpr *CE,
                      SmallVectorImpl<Constant *> &Storage)
      : Opcode(CE->getOpcode()),
        SubclassOptionalData(CE->getRawSubclassOptionalData()),
        ShuffleMask(getShuffleMaskIfValid(CE)),
        ExplicitTy(getSourceElementTypeIfValid(CE)),
        InRange(getInRangeIfValid(CE)) {
    assert(Storage.empty() && "Expected empty storage");
    for (unsigned I = 0, E = CE->getNumOperands(); I != E; ++I)
      Storage.push_back(CE->getOperand(I));
    Ops = Storage;
  }
 
  static bool rangesEqual(const std::optional<ConstantRange> &A,
                          const std::optional<ConstantRange> &B) {
    if (!A.has_value() || !B.has_value())
      return A.has_value() == B.has_value();
    return A->getBitWidth() == B->getBitWidth() && A == B;
  }
 
  bool operator==(const ConstantExprKeyType &X) const {
    return Opcode == X.Opcode &&
           SubclassOptionalData == X.SubclassOptionalData && Ops == X.Ops &&
           ShuffleMask == X.ShuffleMask && ExplicitTy == X.ExplicitTy &&
           rangesEqual(InRange, X.InRange);
  }
 
  bool operator==(const ConstantExpr *CE) const {
    if (Opcode != CE->getOpcode())
      return false;
    if (SubclassOptionalData != CE->getRawSubclassOptionalData())
      return false;
    if (Ops.size() != CE->getNumOperands())
      return false;
    for (unsigned I = 0, E = Ops.size(); I != E; ++I)
      if (Ops[I] != CE->getOperand(I))
        return false;
    if (ShuffleMask != getShuffleMaskIfValid(CE))
      return false;
    if (ExplicitTy != getSourceElementTypeIfValid(CE))
      return false;
    if (!rangesEqual(InRange, getInRangeIfValid(CE)))
      return false;
    return true;
  }
 
  unsigned getHash() const {
    return hash_combine(Opcode, SubclassOptionalData, hash_combine_range(Ops),
                        hash_combine_range(ShuffleMask), ExplicitTy);
  }
 
  using TypeClass = ConstantInfo<ConstantExpr>::TypeClass;
 
  ConstantExpr *create(TypeClass *Ty) const {
    switch (Opcode) {
    default:
      if (Instruction::isCast(Opcode))
        return new CastConstantExpr(Opcode, Ops[0], Ty);
      if (Instruction::isBinaryOp(Opcode))
        return new BinaryConstantExpr(Opcode, Ops[0], Ops[1],
                                      SubclassOptionalData);
      llvm_unreachable("Invalid ConstantExpr!");
    case Instruction::ExtractElement:
      return new ExtractElementConstantExpr(Ops[0], Ops[1]);
    case Instruction::InsertElement:
      return new InsertElementConstantExpr(Ops[0], Ops[1], Ops[2]);
    case Instruction::ShuffleVector:
      return new ShuffleVectorConstantExpr(Ops[0], Ops[1], ShuffleMask);
    case Instruction::GetElementPtr:
      return GetElementPtrConstantExpr::Create(
          ExplicitTy, Ops[0], Ops.slice(1), Ty, SubclassOptionalData, InRange);
    }
  }
};
 
struct ConstantPtrAuthKeyType {
  ArrayRef<Constant *> Operands;
 
  ConstantPtrAuthKeyType(ArrayRef<Constant *> Operands) : Operands(Operands) {}
 
  ConstantPtrAuthKeyType(ArrayRef<Constant *> Operands, const ConstantPtrAuth *)
      : Operands(Operands) {}
 
  ConstantPtrAuthKeyType(const ConstantPtrAuth *C,
                         SmallVectorImpl<Constant *> &Storage) {
    assert(Storage.empty() && "Expected empty storage");
    for (unsigned I = 0, E = C->getNumOperands(); I != E; ++I)
      Storage.push_back(cast<Constant>(C->getOperand(I)));
    Operands = Storage;
  }
 
  bool operator==(const ConstantPtrAuthKeyType &X) const {
    return Operands == X.Operands;
  }
 
  bool operator==(const ConstantPtrAuth *C) const {
    if (Operands.size() != C->getNumOperands())
      return false;
    for (unsigned I = 0, E = Operands.size(); I != E; ++I)
      if (Operands[I] != C->getOperand(I))
        return false;
    return true;
  }
 
  unsigned getHash() const { return hash_combine_range(Operands); }
 
  using TypeClass = ConstantInfo<ConstantPtrAuth>::TypeClass;
 
  ConstantPtrAuth *create(TypeClass *Ty) const {
    return new ConstantPtrAuth(Operands[0], cast<ConstantInt>(Operands[1]),
                               cast<ConstantInt>(Operands[2]), Operands[3],
                               Operands[4]);
  }
};
 
// Free memory for a given constant.  Assumes the constant has already been
// removed from all relevant maps.
void deleteConstant(Constant *C);
 
template <class ConstantClass> class ConstantUniqueMap {
public:
  using ValType = typename ConstantInfo<ConstantClass>::ValType;
  using TypeClass = typename ConstantInfo<ConstantClass>::TypeClass;
  using LookupKey = std::pair<TypeClass *, ValType>;
 
  /// Key and hash together, so that we compute the hash only once and reuse it.
  using LookupKeyHashed = std::pair<unsigned, LookupKey>;
 
private:
  struct MapInfo {
    using ConstantClassInfo = DenseMapInfo<ConstantClass *>;
 
    static inline ConstantClass *getEmptyKey() {
      return ConstantClassInfo::getEmptyKey();
    }
 
    static inline ConstantClass *getTombstoneKey() {
      return ConstantClassInfo::getTombstoneKey();
    }
 
    static unsigned getHashValue(const ConstantClass *CP) {
      SmallVector<Constant *, 32> Storage;
      return getHashValue(LookupKey(CP->getType(), ValType(CP, Storage)));
    }
 
    static bool isEqual(const ConstantClass *LHS, const ConstantClass *RHS) {
      return LHS == RHS;
    }
 
    static unsigned getHashValue(const LookupKey &Val) {
      return hash_combine(Val.first, Val.second.getHash());
    }
 
    static unsigned getHashValue(const LookupKeyHashed &Val) {
      return Val.first;
    }
 
    static bool isEqual(const LookupKey &LHS, const ConstantClass *RHS) {
      if (RHS == getEmptyKey() || RHS == getTombstoneKey())
        return false;
      if (LHS.first != RHS->getType())
        return false;
      return LHS.second == RHS;
    }
 
    static bool isEqual(const LookupKeyHashed &LHS, const ConstantClass *RHS) {
      return isEqual(LHS.second, RHS);
    }
  };
 
public:
  using MapTy = DenseSet<ConstantClass *, MapInfo>;
 
private:
  MapTy Map;
 
public:
  typename MapTy::iterator begin() { return Map.begin(); }
  typename MapTy::iterator end() { return Map.end(); }
 
  void freeConstants() {
    for (auto &I : Map)
      deleteConstant(I);
  }
 
private:
  ConstantClass *create(TypeClass *Ty, ValType V, LookupKeyHashed &HashKey) {
    ConstantClass *Result = V.create(Ty);
 
    assert(Result->getType() == Ty && "Type specified is not correct!");
    Map.insert_as(Result, HashKey);
 
    return Result;
  }
 
public:
  /// Return the specified constant from the map, creating it if necessary.
  ConstantClass *getOrCreate(TypeClass *Ty, ValType V) {
    LookupKey Key(Ty, V);
    /// Hash once, and reuse it for the lookup and the insertion if needed.
    LookupKeyHashed Lookup(MapInfo::getHashValue(Key), Key);
 
    ConstantClass *Result = nullptr;
 
    auto I = Map.find_as(Lookup);
    if (I == Map.end())
      Result = create(Ty, V, Lookup);
    else
      Result = *I;
    assert(Result && "Unexpected nullptr");
 
    return Result;
  }
 
  /// Remove this constant from the map
  void remove(ConstantClass *CP) {
    typename MapTy::iterator I = Map.find(CP);
    assert(I != Map.end() && "Constant not found in constant table!");
    assert(*I == CP && "Didn't find correct element?");
    Map.erase(I);
  }
 
  ConstantClass *replaceOperandsInPlace(ArrayRef<Constant *> Operands,
                                        ConstantClass *CP, Value *From,
                                        Constant *To, unsigned NumUpdated = 0,
                                        unsigned OperandNo = ~0u) {
    LookupKey Key(CP->getType(), ValType(Operands, CP));
    /// Hash once, and reuse it for the lookup and the insertion if needed.
    LookupKeyHashed Lookup(MapInfo::getHashValue(Key), Key);
 
    auto ItMap = Map.find_as(Lookup);
    if (ItMap != Map.end())
      return *ItMap;
 
    // Update to the new value.  Optimize for the case when we have a single
    // operand that we're changing, but handle bulk updates efficiently.
    remove(CP);
    if (NumUpdated == 1) {
      assert(OperandNo < CP->getNumOperands() && "Invalid index");
      assert(CP->getOperand(OperandNo) != To && "I didn't contain From!");
      CP->setOperand(OperandNo, To);
    } else {
      for (unsigned I = 0, E = CP->getNumOperands(); I != E; ++I)
        if (CP->getOperand(I) == From)
          CP->setOperand(I, To);
    }
    Map.insert_as(CP, Lookup);
    return nullptr;
  }
 
  void dump() const {
    LLVM_DEBUG(dbgs() << "Constant.cpp: ConstantUniqueMap\n");
  }
};
 
template <> inline void ConstantUniqueMap<InlineAsm>::freeConstants() {
  for (auto &I : Map)
    delete I;
}
 
} // end namespace llvm
 
#endif // LLVM_LIB_IR_CONSTANTSCONTEXT_H