Subversion Repositories QNX 8.QNX8 LLVM/Clang compiler suite

//===-- llvm/Instruction.h - Instruction class definition -------*- 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 contains the declaration of the Instruction class, which is the

// base class for all of the LLVM instructions.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_IR_INSTRUCTION_H

#define LLVM_IR_INSTRUCTION_H

#include "llvm/ADT/ArrayRef.h"

#include "llvm/ADT/Bitfields.h"

#include "llvm/ADT/StringRef.h"

#include "llvm/ADT/ilist_node.h"

#include "llvm/IR/DebugLoc.h"

#include "llvm/IR/SymbolTableListTraits.h"

#include "llvm/IR/User.h"

#include "llvm/IR/Value.h"

#include "llvm/Support/AtomicOrdering.h"

#include <cstdint>

#include <utility>

namespace llvm {

class BasicBlock;

class FastMathFlags;

class MDNode;

class Module;

struct AAMDNodes;

template <> struct ilist_alloc_traits<Instruction> {

  static inline void deleteNode(Instruction *V);

};

class Instruction : public User,

                    public ilist_node_with_parent<Instruction, BasicBlock> {

  BasicBlock *Parent;

  DebugLoc DbgLoc;                         // 'dbg' Metadata cache.

  /// Relative order of this instruction in its parent basic block. Used for

  /// O(1) local dominance checks between instructions.

  mutable unsigned Order = 0;

protected:

  // The 15 first bits of `Value::SubclassData` are available for subclasses of

  // `Instruction` to use.

  using OpaqueField = Bitfield::Element<uint16_t, 0, 15>;

  // Template alias so that all Instruction storing alignment use the same

  // definiton.

  // Valid alignments are powers of two from 2^0 to 2^MaxAlignmentExponent =

  // 2^32. We store them as Log2(Alignment), so we need 6 bits to encode the 33

  // possible values.

  template <unsigned Offset>

  using AlignmentBitfieldElementT =

      typename Bitfield::Element<unsigned, Offset, 6,

                                 Value::MaxAlignmentExponent>;

  template <unsigned Offset>

  using BoolBitfieldElementT = typename Bitfield::Element<bool, Offset, 1>;

  template <unsigned Offset>

  using AtomicOrderingBitfieldElementT =

      typename Bitfield::Element<AtomicOrdering, Offset, 3,

                                 AtomicOrdering::LAST>;

private:

  // The last bit is used to store whether the instruction has metadata attached

  // or not.

  using HasMetadataField = Bitfield::Element<bool, 15, 1>;

protected:

  ~Instruction(); // Use deleteValue() to delete a generic Instruction.

public:

  Instruction(const Instruction &) = delete;

  Instruction &operator=(const Instruction &) = delete;

  /// Specialize the methods defined in Value, as we know that an instruction

  /// can only be used by other instructions.

  Instruction       *user_back()       { return cast<Instruction>(*user_begin());}

  const Instruction *user_back() const { return cast<Instruction>(*user_begin());}

  inline const BasicBlock *getParent() const { return Parent; }

  inline       BasicBlock *getParent()       { return Parent; }

  /// Return the module owning the function this instruction belongs to

  /// or nullptr it the function does not have a module.

  ///

  /// Note: this is undefined behavior if the instruction does not have a

  /// parent, or the parent basic block does not have a parent function.

  const Module *getModule() const;

  Module *getModule() {

    return const_cast<Module *>(

                           static_cast<const Instruction *>(this)->getModule());

  }

  /// Return the function this instruction belongs to.

  ///

  /// Note: it is undefined behavior to call this on an instruction not

  /// currently inserted into a function.

  const Function *getFunction() const;

  Function *getFunction() {

    return const_cast<Function *>(

                         static_cast<const Instruction *>(this)->getFunction());

  }

  /// This method unlinks 'this' from the containing basic block, but does not

  /// delete it.

  void removeFromParent();

  /// This method unlinks 'this' from the containing basic block and deletes it.

  ///

  /// \returns an iterator pointing to the element after the erased one

  SymbolTableList<Instruction>::iterator eraseFromParent();

  /// Insert an unlinked instruction into a basic block immediately before

  /// the specified instruction.

  void insertBefore(Instruction *InsertPos);

  /// Insert an unlinked instruction into a basic block immediately after the

  /// specified instruction.

  void insertAfter(Instruction *InsertPos);

  /// Inserts an unlinked instruction into \p ParentBB at position \p It and

  /// returns the iterator of the inserted instruction.

  SymbolTableList<Instruction>::iterator

  insertInto(BasicBlock *ParentBB, SymbolTableList<Instruction>::iterator It);

  /// Unlink this instruction from its current basic block and insert it into

  /// the basic block that MovePos lives in, right before MovePos.

  void moveBefore(Instruction *MovePos);

  /// Unlink this instruction and insert into BB before I.

  ///

  /// \pre I is a valid iterator into BB.

  void moveBefore(BasicBlock &BB, SymbolTableList<Instruction>::iterator I);

  /// Unlink this instruction from its current basic block and insert it into

  /// the basic block that MovePos lives in, right after MovePos.

  void moveAfter(Instruction *MovePos);

  /// Given an instruction Other in the same basic block as this instruction,

  /// return true if this instruction comes before Other. In this worst case,

  /// this takes linear time in the number of instructions in the block. The

  /// results are cached, so in common cases when the block remains unmodified,

  /// it takes constant time.

  bool comesBefore(const Instruction *Other) const;

  /// Get the first insertion point at which the result of this instruction

  /// is defined. This is *not* the directly following instruction in a number

  /// of cases, e.g. phi nodes or terminators that return values. This function

  /// may return null if the insertion after the definition is not possible,

  /// e.g. due to a catchswitch terminator.

  Instruction *getInsertionPointAfterDef();

  //===--------------------------------------------------------------------===//

  // Subclass classification.

  //===--------------------------------------------------------------------===//

  /// Returns a member of one of the enums like Instruction::Add.

  unsigned getOpcode() const { return getValueID() - InstructionVal; }

  const char *getOpcodeName() const { return getOpcodeName(getOpcode()); }

  bool isTerminator() const { return isTerminator(getOpcode()); }

  bool isUnaryOp() const { return isUnaryOp(getOpcode()); }

  bool isBinaryOp() const { return isBinaryOp(getOpcode()); }

  bool isIntDivRem() const { return isIntDivRem(getOpcode()); }

  bool isShift() const { return isShift(getOpcode()); }

  bool isCast() const { return isCast(getOpcode()); }

  bool isFuncletPad() const { return isFuncletPad(getOpcode()); }

  bool isExceptionalTerminator() const {

    return isExceptionalTerminator(getOpcode());

  }

  /// It checks if this instruction is the only user of at least one of

  /// its operands.

  bool isOnlyUserOfAnyOperand();

  static const char* getOpcodeName(unsigned OpCode);

  static inline bool isTerminator(unsigned OpCode) {

    return OpCode >= TermOpsBegin && OpCode < TermOpsEnd;

  }

  static inline bool isUnaryOp(unsigned Opcode) {

    return Opcode >= UnaryOpsBegin && Opcode < UnaryOpsEnd;

  }

  static inline bool isBinaryOp(unsigned Opcode) {

    return Opcode >= BinaryOpsBegin && Opcode < BinaryOpsEnd;

  }

  static inline bool isIntDivRem(unsigned Opcode) {

    return Opcode == UDiv || Opcode == SDiv || Opcode == URem || Opcode == SRem;

  }

  /// Determine if the Opcode is one of the shift instructions.

  static inline bool isShift(unsigned Opcode) {

    return Opcode >= Shl && Opcode <= AShr;

  }

  /// Return true if this is a logical shift left or a logical shift right.

  inline bool isLogicalShift() const {

    return getOpcode() == Shl || getOpcode() == LShr;

  }

  /// Return true if this is an arithmetic shift right.

  inline bool isArithmeticShift() const {

    return getOpcode() == AShr;

  }

  /// Determine if the Opcode is and/or/xor.

  static inline bool isBitwiseLogicOp(unsigned Opcode) {

    return Opcode == And || Opcode == Or || Opcode == Xor;

  }

  /// Return true if this is and/or/xor.

  inline bool isBitwiseLogicOp() const {

    return isBitwiseLogicOp(getOpcode());

  }

  /// Determine if the OpCode is one of the CastInst instructions.

  static inline bool isCast(unsigned OpCode) {

    return OpCode >= CastOpsBegin && OpCode < CastOpsEnd;

  }

  /// Determine if the OpCode is one of the FuncletPadInst instructions.

  static inline bool isFuncletPad(unsigned OpCode) {

    return OpCode >= FuncletPadOpsBegin && OpCode < FuncletPadOpsEnd;

  }

  /// Returns true if the OpCode is a terminator related to exception handling.

  static inline bool isExceptionalTerminator(unsigned OpCode) {

    switch (OpCode) {

    case Instruction::CatchSwitch:

    case Instruction::CatchRet:

    case Instruction::CleanupRet:

    case Instruction::Invoke:

    case Instruction::Resume:

      return true;

    default:

      return false;

    }

  }

  //===--------------------------------------------------------------------===//

  // Metadata manipulation.

  //===--------------------------------------------------------------------===//

  /// Return true if this instruction has any metadata attached to it.

  bool hasMetadata() const { return DbgLoc || Value::hasMetadata(); }

  /// Return true if this instruction has metadata attached to it other than a

  /// debug location.

  bool hasMetadataOtherThanDebugLoc() const { return Value::hasMetadata(); }

  /// Return true if this instruction has the given type of metadata attached.

  bool hasMetadata(unsigned KindID) const {

    return getMetadata(KindID) != nullptr;

  }

  /// Return true if this instruction has the given type of metadata attached.

  bool hasMetadata(StringRef Kind) const {

    return getMetadata(Kind) != nullptr;

  }

  /// Get the metadata of given kind attached to this Instruction.

  /// If the metadata is not found then return null.

  MDNode *getMetadata(unsigned KindID) const {

    if (!hasMetadata()) return nullptr;

    return getMetadataImpl(KindID);

  }

  /// Get the metadata of given kind attached to this Instruction.

  /// If the metadata is not found then return null.

  MDNode *getMetadata(StringRef Kind) const {

    if (!hasMetadata()) return nullptr;

    return getMetadataImpl(Kind);

  }

  /// Get all metadata attached to this Instruction. The first element of each

  /// pair returned is the KindID, the second element is the metadata value.

  /// This list is returned sorted by the KindID.

  void

  getAllMetadata(SmallVectorImpl<std::pair<unsigned, MDNode *>> &MDs) const {

    if (hasMetadata())

      getAllMetadataImpl(MDs);

  }

  /// This does the same thing as getAllMetadata, except that it filters out the

  /// debug location.

  void getAllMetadataOtherThanDebugLoc(

      SmallVectorImpl<std::pair<unsigned, MDNode *>> &MDs) const {

    Value::getAllMetadata(MDs);

  }

  /// Set the metadata of the specified kind to the specified node. This updates

  /// or replaces metadata if already present, or removes it if Node is null.

  void setMetadata(unsigned KindID, MDNode *Node);

  void setMetadata(StringRef Kind, MDNode *Node);

  /// Copy metadata from \p SrcInst to this instruction. \p WL, if not empty,

  /// specifies the list of meta data that needs to be copied. If \p WL is

  /// empty, all meta data will be copied.

  void copyMetadata(const Instruction &SrcInst,

                    ArrayRef<unsigned> WL = ArrayRef<unsigned>());

  /// If the instruction has "branch_weights" MD_prof metadata and the MDNode

  /// has three operands (including name string), swap the order of the

  /// metadata.

  void swapProfMetadata();

  /// Drop all unknown metadata except for debug locations.

  /// @{

  /// Passes are required to drop metadata they don't understand. This is a

  /// convenience method for passes to do so.

  /// dropUndefImplyingAttrsAndUnknownMetadata should be used instead of

  /// this API if the Instruction being modified is a call.

  void dropUnknownNonDebugMetadata(ArrayRef<unsigned> KnownIDs);

  void dropUnknownNonDebugMetadata() {

    return dropUnknownNonDebugMetadata(std::nullopt);

  }

  void dropUnknownNonDebugMetadata(unsigned ID1) {

    return dropUnknownNonDebugMetadata(ArrayRef(ID1));

  }

  void dropUnknownNonDebugMetadata(unsigned ID1, unsigned ID2) {

    unsigned IDs[] = {ID1, ID2};

    return dropUnknownNonDebugMetadata(IDs);

  }

  /// @}

  /// Adds an !annotation metadata node with \p Annotation to this instruction.

  /// If this instruction already has !annotation metadata, append \p Annotation

  /// to the existing node.

  void addAnnotationMetadata(StringRef Annotation);

  /// Returns the AA metadata for this instruction.

  AAMDNodes getAAMetadata() const;

  /// Sets the AA metadata on this instruction from the AAMDNodes structure.

  void setAAMetadata(const AAMDNodes &N);

  /// Retrieve total raw weight values of a branch.

  /// Returns true on success with profile total weights filled in.

  /// Returns false if no metadata was found.

  bool extractProfTotalWeight(uint64_t &TotalVal) const;

  /// Set the debug location information for this instruction.

  void setDebugLoc(DebugLoc Loc) { DbgLoc = std::move(Loc); }

  /// Return the debug location for this node as a DebugLoc.

  const DebugLoc &getDebugLoc() const { return DbgLoc; }

  /// Set or clear the nuw flag on this instruction, which must be an operator

  /// which supports this flag. See LangRef.html for the meaning of this flag.

  void setHasNoUnsignedWrap(bool b = true);

  /// Set or clear the nsw flag on this instruction, which must be an operator

  /// which supports this flag. See LangRef.html for the meaning of this flag.

  void setHasNoSignedWrap(bool b = true);

  /// Set or clear the exact flag on this instruction, which must be an operator

  /// which supports this flag. See LangRef.html for the meaning of this flag.

  void setIsExact(bool b = true);

  /// Determine whether the no unsigned wrap flag is set.

  bool hasNoUnsignedWrap() const LLVM_READONLY;

  /// Determine whether the no signed wrap flag is set.

  bool hasNoSignedWrap() const LLVM_READONLY;

  /// Return true if this operator has flags which may cause this instruction

  /// to evaluate to poison despite having non-poison inputs.

  bool hasPoisonGeneratingFlags() const LLVM_READONLY;

  /// Drops flags that may cause this instruction to evaluate to poison despite

  /// having non-poison inputs.

  void dropPoisonGeneratingFlags();

  /// Return true if this instruction has poison-generating metadata.

  bool hasPoisonGeneratingMetadata() const LLVM_READONLY;

  /// Drops metadata that may generate poison.

  void dropPoisonGeneratingMetadata();

  /// Return true if this instruction has poison-generating flags or metadata.

  bool hasPoisonGeneratingFlagsOrMetadata() const {

    return hasPoisonGeneratingFlags() || hasPoisonGeneratingMetadata();

  }

  /// Drops flags and metadata that may generate poison.

  void dropPoisonGeneratingFlagsAndMetadata() {

    dropPoisonGeneratingFlags();

    dropPoisonGeneratingMetadata();

  }

  /// This function drops non-debug unknown metadata (through

  /// dropUnknownNonDebugMetadata). For calls, it also drops parameter and 

  /// return attributes that can cause undefined behaviour. Both of these should

  /// be done by passes which move instructions in IR.

  void

  dropUndefImplyingAttrsAndUnknownMetadata(ArrayRef<unsigned> KnownIDs = {});

  /// Determine whether the exact flag is set.

  bool isExact() const LLVM_READONLY;

  /// Set or clear all fast-math-flags on this instruction, which must be an

  /// operator which supports this flag. See LangRef.html for the meaning of

  /// this flag.

  void setFast(bool B);

  /// Set or clear the reassociation flag on this instruction, which must be

  /// an operator which supports this flag. See LangRef.html for the meaning of

  /// this flag.

  void setHasAllowReassoc(bool B);

  /// Set or clear the no-nans flag on this instruction, which must be an

  /// operator which supports this flag. See LangRef.html for the meaning of

  /// this flag.

  void setHasNoNaNs(bool B);

  /// Set or clear the no-infs flag on this instruction, which must be an

  /// operator which supports this flag. See LangRef.html for the meaning of

  /// this flag.

  void setHasNoInfs(bool B);

  /// Set or clear the no-signed-zeros flag on this instruction, which must be

  /// an operator which supports this flag. See LangRef.html for the meaning of

  /// this flag.

  void setHasNoSignedZeros(bool B);

  /// Set or clear the allow-reciprocal flag on this instruction, which must be

  /// an operator which supports this flag. See LangRef.html for the meaning of

  /// this flag.

  void setHasAllowReciprocal(bool B);

  /// Set or clear the allow-contract flag on this instruction, which must be

  /// an operator which supports this flag. See LangRef.html for the meaning of

  /// this flag.

  void setHasAllowContract(bool B);

  /// Set or clear the approximate-math-functions flag on this instruction,

  /// which must be an operator which supports this flag. See LangRef.html for

  /// the meaning of this flag.

  void setHasApproxFunc(bool B);

  /// Convenience function for setting multiple fast-math flags on this

  /// instruction, which must be an operator which supports these flags. See

  /// LangRef.html for the meaning of these flags.

  void setFastMathFlags(FastMathFlags FMF);

  /// Convenience function for transferring all fast-math flag values to this

  /// instruction, which must be an operator which supports these flags. See

  /// LangRef.html for the meaning of these flags.

  void copyFastMathFlags(FastMathFlags FMF);

  /// Determine whether all fast-math-flags are set.

  bool isFast() const LLVM_READONLY;

  /// Determine whether the allow-reassociation flag is set.

  bool hasAllowReassoc() const LLVM_READONLY;

  /// Determine whether the no-NaNs flag is set.

  bool hasNoNaNs() const LLVM_READONLY;

  /// Determine whether the no-infs flag is set.

  bool hasNoInfs() const LLVM_READONLY;

  /// Determine whether the no-signed-zeros flag is set.

  bool hasNoSignedZeros() const LLVM_READONLY;

  /// Determine whether the allow-reciprocal flag is set.

  bool hasAllowReciprocal() const LLVM_READONLY;

  /// Determine whether the allow-contract flag is set.

  bool hasAllowContract() const LLVM_READONLY;

  /// Determine whether the approximate-math-functions flag is set.

  bool hasApproxFunc() const LLVM_READONLY;

  /// Convenience function for getting all the fast-math flags, which must be an

  /// operator which supports these flags. See LangRef.html for the meaning of

  /// these flags.

  FastMathFlags getFastMathFlags() const LLVM_READONLY;

  /// Copy I's fast-math flags

  void copyFastMathFlags(const Instruction *I);

  /// Convenience method to copy supported exact, fast-math, and (optionally)

  /// wrapping flags from V to this instruction.

  void copyIRFlags(const Value *V, bool IncludeWrapFlags = true);

  /// Logical 'and' of any supported wrapping, exact, and fast-math flags of

  /// V and this instruction.

  void andIRFlags(const Value *V);

  /// Merge 2 debug locations and apply it to the Instruction. If the

  /// instruction is a CallIns, we need to traverse the inline chain to find

  /// the common scope. This is not efficient for N-way merging as each time

  /// you merge 2 iterations, you need to rebuild the hashmap to find the

  /// common scope. However, we still choose this API because:

  ///  1) Simplicity: it takes 2 locations instead of a list of locations.

  ///  2) In worst case, it increases the complexity from O(N*I) to

  ///     O(2*N*I), where N is # of Instructions to merge, and I is the

  ///     maximum level of inline stack. So it is still linear.

  ///  3) Merging of call instructions should be extremely rare in real

  ///     applications, thus the N-way merging should be in code path.

  /// The DebugLoc attached to this instruction will be overwritten by the

  /// merged DebugLoc.

  void applyMergedLocation(const DILocation *LocA, const DILocation *LocB);

  /// Updates the debug location given that the instruction has been hoisted

  /// from a block to a predecessor of that block.

  /// Note: it is undefined behavior to call this on an instruction not

  /// currently inserted into a function.

  void updateLocationAfterHoist();

  /// Drop the instruction's debug location. This does not guarantee removal

  /// of the !dbg source location attachment, as it must set a line 0 location

  /// with scope information attached on call instructions. To guarantee

  /// removal of the !dbg attachment, use the \ref setDebugLoc() API.

  /// Note: it is undefined behavior to call this on an instruction not

  /// currently inserted into a function.

  void dropLocation();

  /// Merge the DIAssignID metadata from this instruction and those attached to

  /// instructions in \p SourceInstructions. This process performs a RAUW on

  /// the MetadataAsValue uses of the merged DIAssignID nodes. Not every

  /// instruction in \p SourceInstructions needs to have DIAssignID

  /// metadata. If none of them do then nothing happens. If this instruction

  /// does not have a DIAssignID attachment but at least one in \p

  /// SourceInstructions does then the merged one will be attached to

  /// it. However, instructions without attachments in \p SourceInstructions

  /// are not modified.

  void mergeDIAssignID(ArrayRef<const Instruction *> SourceInstructions);

private:

  // These are all implemented in Metadata.cpp.

  MDNode *getMetadataImpl(unsigned KindID) const;

  MDNode *getMetadataImpl(StringRef Kind) const;

  void

  getAllMetadataImpl(SmallVectorImpl<std::pair<unsigned, MDNode *>> &) const;

  /// Update the LLVMContext ID-to-Instruction(s) mapping. If \p ID is nullptr

  /// then clear the mapping for this instruction.

  void updateDIAssignIDMapping(DIAssignID *ID);

public:

  //===--------------------------------------------------------------------===//

  // Predicates and helper methods.

  //===--------------------------------------------------------------------===//

  /// Return true if the instruction is associative:

  ///

  ///   Associative operators satisfy:  x op (y op z) === (x op y) op z

  ///

  /// In LLVM, the Add, Mul, And, Or, and Xor operators are associative.

  ///

  bool isAssociative() const LLVM_READONLY;

  static bool isAssociative(unsigned Opcode) {

    return Opcode == And || Opcode == Or || Opcode == Xor ||

           Opcode == Add || Opcode == Mul;

  }

  /// Return true if the instruction is commutative:

  ///

  ///   Commutative operators satisfy: (x op y) === (y op x)

  ///

  /// In LLVM, these are the commutative operators, plus SetEQ and SetNE, when

  /// applied to any type.

  ///

  bool isCommutative() const LLVM_READONLY;

  static bool isCommutative(unsigned Opcode) {

    switch (Opcode) {

    case Add: case FAdd:

    case Mul: case FMul:

    case And: case Or: case Xor:

      return true;

    default:

      return false;

  }

  }

  /// Return true if the instruction is idempotent:

  ///

  ///   Idempotent operators satisfy:  x op x === x

  ///

  /// In LLVM, the And and Or operators are idempotent.

  ///

  bool isIdempotent() const { return isIdempotent(getOpcode()); }

  static bool isIdempotent(unsigned Opcode) {

    return Opcode == And || Opcode == Or;

  }

  /// Return true if the instruction is nilpotent:

  ///

  ///   Nilpotent operators satisfy:  x op x === Id,

  ///

  ///   where Id is the identity for the operator, i.e. a constant such that

  ///     x op Id === x and Id op x === x for all x.

  ///

  /// In LLVM, the Xor operator is nilpotent.

  ///

  bool isNilpotent() const { return isNilpotent(getOpcode()); }

  static bool isNilpotent(unsigned Opcode) {

    return Opcode == Xor;

  }

  /// Return true if this instruction may modify memory.

  bool mayWriteToMemory() const LLVM_READONLY;

  /// Return true if this instruction may read memory.

  bool mayReadFromMemory() const LLVM_READONLY;

  /// Return true if this instruction may read or write memory.

  bool mayReadOrWriteMemory() const {

    return mayReadFromMemory() || mayWriteToMemory();

  }

  /// Return true if this instruction has an AtomicOrdering of unordered or

  /// higher.

  bool isAtomic() const LLVM_READONLY;

  /// Return true if this atomic instruction loads from memory.

  bool hasAtomicLoad() const LLVM_READONLY;

  /// Return true if this atomic instruction stores to memory.

  bool hasAtomicStore() const LLVM_READONLY;

  /// Return true if this instruction has a volatile memory access.

  bool isVolatile() const LLVM_READONLY;

  /// Return true if this instruction may throw an exception.

  bool mayThrow() const LLVM_READONLY;

  /// Return true if this instruction behaves like a memory fence: it can load

  /// or store to memory location without being given a memory location.

  bool isFenceLike() const {

    switch (getOpcode()) {

    default:

      return false;

    // This list should be kept in sync with the list in mayWriteToMemory for

    // all opcodes which don't have a memory location.

    case Instruction::Fence:

    case Instruction::CatchPad:

    case Instruction::CatchRet:

    case Instruction::Call:

    case Instruction::Invoke:

      return true;

    }

  }

  /// Return true if the instruction may have side effects.

  ///

  /// Side effects are:

  ///  * Writing to memory.

  ///  * Unwinding.

  ///  * Not returning (e.g. an infinite loop).

  ///

  /// Note that this does not consider malloc and alloca to have side

  /// effects because the newly allocated memory is completely invisible to

  /// instructions which don't use the returned value.  For cases where this

  /// matters, isSafeToSpeculativelyExecute may be more appropriate.

  bool mayHaveSideEffects() const LLVM_READONLY;

  /// Return true if the instruction can be removed if the result is unused.

  ///

  /// When constant folding some instructions cannot be removed even if their

  /// results are unused. Specifically terminator instructions and calls that

  /// may have side effects cannot be removed without semantically changing the

  /// generated program.

  bool isSafeToRemove() const LLVM_READONLY;

  /// Return true if the instruction will return (unwinding is considered as

  /// a form of returning control flow here).

  bool willReturn() const LLVM_READONLY;

  /// Return true if the instruction is a variety of EH-block.

  bool isEHPad() const {

    switch (getOpcode()) {

    case Instruction::CatchSwitch:

    case Instruction::CatchPad:

    case Instruction::CleanupPad:

    case Instruction::LandingPad:

      return true;

    default:

      return false;

    }

  }

  /// Return true if the instruction is a llvm.lifetime.start or

  /// llvm.lifetime.end marker.

  bool isLifetimeStartOrEnd() const LLVM_READONLY;

  /// Return true if the instruction is a llvm.launder.invariant.group or

  /// llvm.strip.invariant.group.

  bool isLaunderOrStripInvariantGroup() const LLVM_READONLY;

  /// Return true if the instruction is a DbgInfoIntrinsic or PseudoProbeInst.

  bool isDebugOrPseudoInst() const LLVM_READONLY;

  /// Return a pointer to the next non-debug instruction in the same basic

  /// block as 'this', or nullptr if no such instruction exists. Skip any pseudo

  /// operations if \c SkipPseudoOp is true.

  const Instruction *

  getNextNonDebugInstruction(bool SkipPseudoOp = false) const;

  Instruction *getNextNonDebugInstruction(bool SkipPseudoOp = false) {

    return const_cast<Instruction *>(

        static_cast<const Instruction *>(this)->getNextNonDebugInstruction(

            SkipPseudoOp));

  }

  /// Return a pointer to the previous non-debug instruction in the same basic

  /// block as 'this', or nullptr if no such instruction exists. Skip any pseudo

  /// operations if \c SkipPseudoOp is true.

  const Instruction *

  getPrevNonDebugInstruction(bool SkipPseudoOp = false) const;

  Instruction *getPrevNonDebugInstruction(bool SkipPseudoOp = false) {

    return const_cast<Instruction *>(

        static_cast<const Instruction *>(this)->getPrevNonDebugInstruction(

            SkipPseudoOp));

  }

  /// Create a copy of 'this' instruction that is identical in all ways except

  /// the following:

  ///   * The instruction has no parent

  ///   * The instruction has no name

  ///

  Instruction *clone() const;

  /// Return true if the specified instruction is exactly identical to the

  /// current one. This means that all operands match and any extra information

  /// (e.g. load is volatile) agree.

  bool isIdenticalTo(const Instruction *I) const LLVM_READONLY;

  /// This is like isIdenticalTo, except that it ignores the

  /// SubclassOptionalData flags, which may specify conditions under which the

  /// instruction's result is undefined.

  bool isIdenticalToWhenDefined(const Instruction *I) const LLVM_READONLY;

  /// When checking for operation equivalence (using isSameOperationAs) it is

  /// sometimes useful to ignore certain attributes.

  enum OperationEquivalenceFlags {

    /// Check for equivalence ignoring load/store alignment.

    CompareIgnoringAlignment = 1<<0,

    /// Check for equivalence treating a type and a vector of that type

    /// as equivalent.

    CompareUsingScalarTypes = 1<<1

  };

  /// This function determines if the specified instruction executes the same

  /// operation as the current one. This means that the opcodes, type, operand

  /// types and any other factors affecting the operation must be the same. This

  /// is similar to isIdenticalTo except the operands themselves don't have to

  /// be identical.

  /// @returns true if the specified instruction is the same operation as

  /// the current one.

  /// Determine if one instruction is the same operation as another.

  bool isSameOperationAs(const Instruction *I, unsigned flags = 0) const LLVM_READONLY;

  /// Return true if there are any uses of this instruction in blocks other than

  /// the specified block. Note that PHI nodes are considered to evaluate their

  /// operands in the corresponding predecessor block.

  bool isUsedOutsideOfBlock(const BasicBlock *BB) const LLVM_READONLY;

  /// Return the number of successors that this instruction has. The instruction

  /// must be a terminator.

  unsigned getNumSuccessors() const LLVM_READONLY;

  /// Return the specified successor. This instruction must be a terminator.

  BasicBlock *getSuccessor(unsigned Idx) const LLVM_READONLY;

  /// Update the specified successor to point at the provided block. This

  /// instruction must be a terminator.

  void setSuccessor(unsigned Idx, BasicBlock *BB);

  /// Replace specified successor OldBB to point at the provided block.

  /// This instruction must be a terminator.

  void replaceSuccessorWith(BasicBlock *OldBB, BasicBlock *NewBB);

  /// Methods for support type inquiry through isa, cast, and dyn_cast:

  static bool classof(const Value *V) {

    return V->getValueID() >= Value::InstructionVal;

  }

  //----------------------------------------------------------------------

  // Exported enumerations.

  //

  enum TermOps {       // These terminate basic blocks

#define  FIRST_TERM_INST(N)             TermOpsBegin = N,

#define HANDLE_TERM_INST(N, OPC, CLASS) OPC = N,

#define   LAST_TERM_INST(N)             TermOpsEnd = N+1

#include "llvm/IR/Instruction.def"

  };

  enum UnaryOps {

#define  FIRST_UNARY_INST(N)             UnaryOpsBegin = N,

#define HANDLE_UNARY_INST(N, OPC, CLASS) OPC = N,

#define   LAST_UNARY_INST(N)             UnaryOpsEnd = N+1

#include "llvm/IR/Instruction.def"

  };

  enum BinaryOps {

#define  FIRST_BINARY_INST(N)             BinaryOpsBegin = N,

#define HANDLE_BINARY_INST(N, OPC, CLASS) OPC = N,

#define   LAST_BINARY_INST(N)             BinaryOpsEnd = N+1

#include "llvm/IR/Instruction.def"

  };

  enum MemoryOps {

#define  FIRST_MEMORY_INST(N)             MemoryOpsBegin = N,

#define HANDLE_MEMORY_INST(N, OPC, CLASS) OPC = N,

#define   LAST_MEMORY_INST(N)             MemoryOpsEnd = N+1

#include "llvm/IR/Instruction.def"

  };

  enum CastOps {

#define  FIRST_CAST_INST(N)             CastOpsBegin = N,

#define HANDLE_CAST_INST(N, OPC, CLASS) OPC = N,

#define   LAST_CAST_INST(N)             CastOpsEnd = N+1

#include "llvm/IR/Instruction.def"

  };

  enum FuncletPadOps {

#define  FIRST_FUNCLETPAD_INST(N)             FuncletPadOpsBegin = N,

#define HANDLE_FUNCLETPAD_INST(N, OPC, CLASS) OPC = N,

#define   LAST_FUNCLETPAD_INST(N)             FuncletPadOpsEnd = N+1

#include "llvm/IR/Instruction.def"

  };

  enum OtherOps {

#define  FIRST_OTHER_INST(N)             OtherOpsBegin = N,

#define HANDLE_OTHER_INST(N, OPC, CLASS) OPC = N,

#define   LAST_OTHER_INST(N)             OtherOpsEnd = N+1

#include "llvm/IR/Instruction.def"

  };

private:

  friend class SymbolTableListTraits<Instruction>;

  friend class BasicBlock; // For renumbering.

  // Shadow Value::setValueSubclassData with a private forwarding method so that