xref: /external/llvm/include/llvm/CodeGen/MachineInstr.h

//===-- llvm/CodeGen/MachineInstr.h - MachineInstr class --------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the declaration of the MachineInstr class, which is the
// basic representation for all target dependent machine instructions used by
// the back end.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CODEGEN_MACHINEINSTR_H
#define LLVM_CODEGEN_MACHINEINSTR_H

#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/MC/MCInstrDesc.h"
#include "llvm/Target/TargetOpcodes.h"
#include "llvm/ADT/ilist.h"
#include "llvm/ADT/ilist_node.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/DenseMapInfo.h"
#include "llvm/Support/DebugLoc.h"
#include <vector>

namespace llvm {

template <typename T> class SmallVectorImpl;
class AliasAnalysis;
class TargetInstrInfo;
class TargetRegisterClass;
class TargetRegisterInfo;
class MachineFunction;
class MachineMemOperand;

//===----------------------------------------------------------------------===//
/// MachineInstr - Representation of each machine instruction.
///
class MachineInstr : public ilist_node<MachineInstr> {
public:
  typedef MachineMemOperand **mmo_iterator;

  /// Flags to specify different kinds of comments to output in
  /// assembly code.  These flags carry semantic information not
  /// otherwise easily derivable from the IR text.
  ///
  enum CommentFlag {
    ReloadReuse = 0x1
  };

  enum MIFlag {
    NoFlags      = 0,
    FrameSetup   = 1 << 0,              // Instruction is used as a part of
                                        // function frame setup code.
    InsideBundle = 1 << 1               // Instruction is inside a bundle (not
                                        // the first MI in a bundle)
  };
private:
  const MCInstrDesc *MCID;              // Instruction descriptor.

  uint8_t Flags;                        // Various bits of additional
                                        // information about machine
                                        // instruction.

  uint8_t AsmPrinterFlags;              // Various bits of information used by
                                        // the AsmPrinter to emit helpful
                                        // comments.  This is *not* semantic
                                        // information.  Do not use this for
                                        // anything other than to convey comment
                                        // information to AsmPrinter.

  std::vector<MachineOperand> Operands; // the operands
  mmo_iterator MemRefs;                 // information on memory references
  mmo_iterator MemRefsEnd;
  MachineBasicBlock *Parent;            // Pointer to the owning basic block.
  DebugLoc debugLoc;                    // Source line information.

  MachineInstr(const MachineInstr&);   // DO NOT IMPLEMENT
  void operator=(const MachineInstr&); // DO NOT IMPLEMENT

  // Intrusive list support
  friend struct ilist_traits<MachineInstr>;
  friend struct ilist_traits<MachineBasicBlock>;
  void setParent(MachineBasicBlock *P) { Parent = P; }

  /// MachineInstr ctor - This constructor creates a copy of the given
  /// MachineInstr in the given MachineFunction.
  MachineInstr(MachineFunction &, const MachineInstr &);

  /// MachineInstr ctor - This constructor creates a dummy MachineInstr with
  /// MCID NULL and no operands.
  MachineInstr();

  // The next two constructors have DebugLoc and non-DebugLoc versions;
  // over time, the non-DebugLoc versions should be phased out and eventually
  // removed.

  /// MachineInstr ctor - This constructor creates a MachineInstr and adds the
  /// implicit operands.  It reserves space for the number of operands specified
  /// by the MCInstrDesc.  The version with a DebugLoc should be preferred.
  explicit MachineInstr(const MCInstrDesc &MCID, bool NoImp = false);

  /// MachineInstr ctor - Work exactly the same as the ctor above, except that
  /// the MachineInstr is created and added to the end of the specified basic
  /// block.  The version with a DebugLoc should be preferred.
  MachineInstr(MachineBasicBlock *MBB, const MCInstrDesc &MCID);

  /// MachineInstr ctor - This constructor create a MachineInstr and add the
  /// implicit operands.  It reserves space for number of operands specified by
  /// MCInstrDesc.  An explicit DebugLoc is supplied.
  explicit MachineInstr(const MCInstrDesc &MCID, const DebugLoc dl,
                        bool NoImp = false);

  /// MachineInstr ctor - Work exactly the same as the ctor above, except that
  /// the MachineInstr is created and added to the end of the specified basic
  /// block.
  MachineInstr(MachineBasicBlock *MBB, const DebugLoc dl,
               const MCInstrDesc &MCID);

  ~MachineInstr();

  // MachineInstrs are pool-allocated and owned by MachineFunction.
  friend class MachineFunction;

public:
  const MachineBasicBlock* getParent() const { return Parent; }
  MachineBasicBlock* getParent() { return Parent; }

  /// getAsmPrinterFlags - Return the asm printer flags bitvector.
  ///
  uint8_t getAsmPrinterFlags() const { return AsmPrinterFlags; }

  /// clearAsmPrinterFlags - clear the AsmPrinter bitvector
  ///
  void clearAsmPrinterFlags() { AsmPrinterFlags = 0; }

  /// getAsmPrinterFlag - Return whether an AsmPrinter flag is set.
  ///
  bool getAsmPrinterFlag(CommentFlag Flag) const {
    return AsmPrinterFlags & Flag;
  }

  /// setAsmPrinterFlag - Set a flag for the AsmPrinter.
  ///
  void setAsmPrinterFlag(CommentFlag Flag) {
    AsmPrinterFlags |= (uint8_t)Flag;
  }

  /// clearAsmPrinterFlag - clear specific AsmPrinter flags
  ///
  void clearAsmPrinterFlag(CommentFlag Flag) {
    AsmPrinterFlags &= ~Flag;
  }

  /// getFlags - Return the MI flags bitvector.
  uint8_t getFlags() const {
    return Flags;
  }

  /// getFlag - Return whether an MI flag is set.
  bool getFlag(MIFlag Flag) const {
    return Flags & Flag;
  }

  /// setFlag - Set a MI flag.
  void setFlag(MIFlag Flag) {
    Flags |= (uint8_t)Flag;
  }

  void setFlags(unsigned flags) {
    Flags = flags;
  }

  /// isInsideBundle - Return true if MI is in a bundle (but not the first MI
  /// in a bundle).
  ///
  /// A bundle looks like this before it's finalized:
  ///   ----------------
  ///   |      MI      |
  ///   ----------------
  ///          |
  ///   ----------------
  ///   |      MI    * |
  ///   ----------------
  ///          |
  ///   ----------------
  ///   |      MI    * |
  ///   ----------------
  /// In this case, the first MI starts a bundle but is not inside a bundle, the
  /// next 2 MIs are considered "inside" the bundle.
  ///
  /// After a bundle is finalized, it looks like this:
  ///   ----------------
  ///   |    Bundle    |
  ///   ----------------
  ///          |
  ///   ----------------
  ///   |      MI    * |
  ///   ----------------
  ///          |
  ///   ----------------
  ///   |      MI    * |
  ///   ----------------
  ///          |
  ///   ----------------
  ///   |      MI    * |
  ///   ----------------
  /// The first instruction has the special opcode "BUNDLE". It's not "inside"
  /// a bundle, but the next three MIs are.
  bool isInsideBundle() const {
    return getFlag(InsideBundle);
  }

  /// getDebugLoc - Returns the debug location id of this MachineInstr.
  ///
  DebugLoc getDebugLoc() const { return debugLoc; }

  /// emitError - Emit an error referring to the source location of this
  /// instruction. This should only be used for inline assembly that is somehow
  /// impossible to compile. Other errors should have been handled much
  /// earlier.
  ///
  /// If this method returns, the caller should try to recover from the error.
  ///
  void emitError(StringRef Msg) const;

  /// getDesc - Returns the target instruction descriptor of this
  /// MachineInstr.
  const MCInstrDesc &getDesc() const { return *MCID; }

  /// getOpcode - Returns the opcode of this MachineInstr.
  ///
  int getOpcode() const { return MCID->Opcode; }

  /// Access to explicit operands of the instruction.
  ///
  unsigned getNumOperands() const { return (unsigned)Operands.size(); }

  const MachineOperand& getOperand(unsigned i) const {
    assert(i < getNumOperands() && "getOperand() out of range!");
    return Operands[i];
  }
  MachineOperand& getOperand(unsigned i) {
    assert(i < getNumOperands() && "getOperand() out of range!");
    return Operands[i];
  }

  /// getNumExplicitOperands - Returns the number of non-implicit operands.
  ///
  unsigned getNumExplicitOperands() const;

  /// iterator/begin/end - Iterate over all operands of a machine instruction.
  typedef std::vector<MachineOperand>::iterator mop_iterator;
  typedef std::vector<MachineOperand>::const_iterator const_mop_iterator;

  mop_iterator operands_begin() { return Operands.begin(); }
  mop_iterator operands_end() { return Operands.end(); }

  const_mop_iterator operands_begin() const { return Operands.begin(); }
  const_mop_iterator operands_end() const { return Operands.end(); }

  /// Access to memory operands of the instruction
  mmo_iterator memoperands_begin() const { return MemRefs; }
  mmo_iterator memoperands_end() const { return MemRefsEnd; }
  bool memoperands_empty() const { return MemRefsEnd == MemRefs; }

  /// hasOneMemOperand - Return true if this instruction has exactly one
  /// MachineMemOperand.
  bool hasOneMemOperand() const {
    return MemRefsEnd - MemRefs == 1;
  }

  /// API for querying MachineInstr properties. These are bundle aware.
  ///
  bool hasProperty(unsigned short Flag) const;

  bool isTerminator() const {
    return hasProperty(MCID::Terminator);
  }

  enum MICheckType {
    CheckDefs,      // Check all operands for equality
    CheckKillDead,  // Check all operands including kill / dead markers
    IgnoreDefs,     // Ignore all definitions
    IgnoreVRegDefs  // Ignore virtual register definitions
  };

  /// isIdenticalTo - Return true if this instruction is identical to (same
  /// opcode and same operands as) the specified instruction.
  bool isIdenticalTo(const MachineInstr *Other,
                     MICheckType Check = CheckDefs) const;

  /// removeFromParent - This method unlinks 'this' from the containing basic
  /// block, and returns it, but does not delete it.
  MachineInstr *removeFromParent();

  /// eraseFromParent - This method unlinks 'this' from the containing basic
  /// block and deletes it.
  void eraseFromParent();

  /// isLabel - Returns true if the MachineInstr represents a label.
  ///
  bool isLabel() const {
    return getOpcode() == TargetOpcode::PROLOG_LABEL ||
           getOpcode() == TargetOpcode::EH_LABEL ||
           getOpcode() == TargetOpcode::GC_LABEL;
  }

  bool isPrologLabel() const {
    return getOpcode() == TargetOpcode::PROLOG_LABEL;
  }
  bool isEHLabel() const { return getOpcode() == TargetOpcode::EH_LABEL; }
  bool isGCLabel() const { return getOpcode() == TargetOpcode::GC_LABEL; }
  bool isDebugValue() const { return getOpcode() == TargetOpcode::DBG_VALUE; }

  bool isPHI() const { return getOpcode() == TargetOpcode::PHI; }
  bool isKill() const { return getOpcode() == TargetOpcode::KILL; }
  bool isImplicitDef() const { return getOpcode()==TargetOpcode::IMPLICIT_DEF; }
  bool isInlineAsm() const { return getOpcode() == TargetOpcode::INLINEASM; }
  bool isStackAligningInlineAsm() const;
  bool isInsertSubreg() const {
    return getOpcode() == TargetOpcode::INSERT_SUBREG;
  }
  bool isSubregToReg() const {
    return getOpcode() == TargetOpcode::SUBREG_TO_REG;
  }
  bool isRegSequence() const {
    return getOpcode() == TargetOpcode::REG_SEQUENCE;
  }
  bool isCopy() const {
    return getOpcode() == TargetOpcode::COPY;
  }
  bool isFullCopy() const {
    return isCopy() && !getOperand(0).getSubReg() && !getOperand(1).getSubReg();
  }

  /// isCopyLike - Return true if the instruction behaves like a copy.
  /// This does not include native copy instructions.
  bool isCopyLike() const {
    return isCopy() || isSubregToReg();
  }

  /// isIdentityCopy - Return true is the instruction is an identity copy.
  bool isIdentityCopy() const {
    return isCopy() && getOperand(0).getReg() == getOperand(1).getReg() &&
      getOperand(0).getSubReg() == getOperand(1).getSubReg();
  }

  /// readsRegister - Return true if the MachineInstr reads the specified
  /// register. If TargetRegisterInfo is passed, then it also checks if there
  /// is a read of a super-register.
  /// This does not count partial redefines of virtual registers as reads:
  ///   %reg1024:6 = OP.
  bool readsRegister(unsigned Reg, const TargetRegisterInfo *TRI = NULL) const {
    return findRegisterUseOperandIdx(Reg, false, TRI) != -1;
  }

  /// readsVirtualRegister - Return true if the MachineInstr reads the specified
  /// virtual register. Take into account that a partial define is a
  /// read-modify-write operation.
  bool readsVirtualRegister(unsigned Reg) const {
    return readsWritesVirtualRegister(Reg).first;
  }

  /// readsWritesVirtualRegister - Return a pair of bools (reads, writes)
  /// indicating if this instruction reads or writes Reg. This also considers
  /// partial defines.
  /// If Ops is not null, all operand indices for Reg are added.
  std::pair<bool,bool> readsWritesVirtualRegister(unsigned Reg,
                                      SmallVectorImpl<unsigned> *Ops = 0) const;

  /// killsRegister - Return true if the MachineInstr kills the specified
  /// register. If TargetRegisterInfo is passed, then it also checks if there is
  /// a kill of a super-register.
  bool killsRegister(unsigned Reg, const TargetRegisterInfo *TRI = NULL) const {
    return findRegisterUseOperandIdx(Reg, true, TRI) != -1;
  }

  /// definesRegister - Return true if the MachineInstr fully defines the
  /// specified register. If TargetRegisterInfo is passed, then it also checks
  /// if there is a def of a super-register.
  /// NOTE: It's ignoring subreg indices on virtual registers.
  bool definesRegister(unsigned Reg, const TargetRegisterInfo *TRI=NULL) const {
    return findRegisterDefOperandIdx(Reg, false, false, TRI) != -1;
  }

  /// modifiesRegister - Return true if the MachineInstr modifies (fully define
  /// or partially define) the specified register.
  /// NOTE: It's ignoring subreg indices on virtual registers.
  bool modifiesRegister(unsigned Reg, const TargetRegisterInfo *TRI) const {
    return findRegisterDefOperandIdx(Reg, false, true, TRI) != -1;
  }

  /// registerDefIsDead - Returns true if the register is dead in this machine
  /// instruction. If TargetRegisterInfo is passed, then it also checks
  /// if there is a dead def of a super-register.
  bool registerDefIsDead(unsigned Reg,
                         const TargetRegisterInfo *TRI = NULL) const {
    return findRegisterDefOperandIdx(Reg, true, false, TRI) != -1;
  }

  /// findRegisterUseOperandIdx() - Returns the operand index that is a use of
  /// the specific register or -1 if it is not found. It further tightens
  /// the search criteria to a use that kills the register if isKill is true.
  int findRegisterUseOperandIdx(unsigned Reg, bool isKill = false,
                                const TargetRegisterInfo *TRI = NULL) const;

  /// findRegisterUseOperand - Wrapper for findRegisterUseOperandIdx, it returns
  /// a pointer to the MachineOperand rather than an index.
  MachineOperand *findRegisterUseOperand(unsigned Reg, bool isKill = false,
                                         const TargetRegisterInfo *TRI = NULL) {
    int Idx = findRegisterUseOperandIdx(Reg, isKill, TRI);
    return (Idx == -1) ? NULL : &getOperand(Idx);
  }

  /// findRegisterDefOperandIdx() - Returns the operand index that is a def of
  /// the specified register or -1 if it is not found. If isDead is true, defs
  /// that are not dead are skipped. If Overlap is true, then it also looks for
  /// defs that merely overlap the specified register. If TargetRegisterInfo is
  /// non-null, then it also checks if there is a def of a super-register.
  int findRegisterDefOperandIdx(unsigned Reg,
                                bool isDead = false, bool Overlap = false,
                                const TargetRegisterInfo *TRI = NULL) const;

  /// findRegisterDefOperand - Wrapper for findRegisterDefOperandIdx, it returns
  /// a pointer to the MachineOperand rather than an index.
  MachineOperand *findRegisterDefOperand(unsigned Reg, bool isDead = false,
                                         const TargetRegisterInfo *TRI = NULL) {
    int Idx = findRegisterDefOperandIdx(Reg, isDead, false, TRI);
    return (Idx == -1) ? NULL : &getOperand(Idx);
  }

  /// findFirstPredOperandIdx() - Find the index of the first operand in the
  /// operand list that is used to represent the predicate. It returns -1 if
  /// none is found.
  int findFirstPredOperandIdx() const;

  /// findInlineAsmFlagIdx() - Find the index of the flag word operand that
  /// corresponds to operand OpIdx on an inline asm instruction.  Returns -1 if
  /// getOperand(OpIdx) does not belong to an inline asm operand group.
  ///
  /// If GroupNo is not NULL, it will receive the number of the operand group
  /// containing OpIdx.
  ///
  /// The flag operand is an immediate that can be decoded with methods like
  /// InlineAsm::hasRegClassConstraint().
  ///
  int findInlineAsmFlagIdx(unsigned OpIdx, unsigned *GroupNo = 0) const;

  /// getRegClassConstraint - Compute the static register class constraint for
  /// operand OpIdx.  For normal instructions, this is derived from the
  /// MCInstrDesc.  For inline assembly it is derived from the flag words.
  ///
  /// Returns NULL if the static register classs constraint cannot be
  /// determined.
  ///
  const TargetRegisterClass*
  getRegClassConstraint(unsigned OpIdx,
                        const TargetInstrInfo *TII,
                        const TargetRegisterInfo *TRI) const;

  /// isRegTiedToUseOperand - Given the index of a register def operand,
  /// check if the register def is tied to a source operand, due to either
  /// two-address elimination or inline assembly constraints. Returns the
  /// first tied use operand index by reference is UseOpIdx is not null.
  bool isRegTiedToUseOperand(unsigned DefOpIdx, unsigned *UseOpIdx = 0) const;

  /// isRegTiedToDefOperand - Return true if the use operand of the specified
  /// index is tied to an def operand. It also returns the def operand index by
  /// reference if DefOpIdx is not null.
  bool isRegTiedToDefOperand(unsigned UseOpIdx, unsigned *DefOpIdx = 0) const;

  /// clearKillInfo - Clears kill flags on all operands.
  ///
  void clearKillInfo();

  /// copyKillDeadInfo - Copies kill / dead operand properties from MI.
  ///
  void copyKillDeadInfo(const MachineInstr *MI);

  /// copyPredicates - Copies predicate operand(s) from MI.
  void copyPredicates(const MachineInstr *MI);

  /// substituteRegister - Replace all occurrences of FromReg with ToReg:SubIdx,
  /// properly composing subreg indices where necessary.
  void substituteRegister(unsigned FromReg, unsigned ToReg, unsigned SubIdx,
                          const TargetRegisterInfo &RegInfo);

  /// addRegisterKilled - We have determined MI kills a register. Look for the
  /// operand that uses it and mark it as IsKill. If AddIfNotFound is true,
  /// add a implicit operand if it's not found. Returns true if the operand
  /// exists / is added.
  bool addRegisterKilled(unsigned IncomingReg,
                         const TargetRegisterInfo *RegInfo,
                         bool AddIfNotFound = false);

  /// addRegisterDead - We have determined MI defined a register without a use.
  /// Look for the operand that defines it and mark it as IsDead. If
  /// AddIfNotFound is true, add a implicit operand if it's not found. Returns
  /// true if the operand exists / is added.
  bool addRegisterDead(unsigned IncomingReg, const TargetRegisterInfo *RegInfo,
                       bool AddIfNotFound = false);

  /// addRegisterDefined - We have determined MI defines a register. Make sure
  /// there is an operand defining Reg.
  void addRegisterDefined(unsigned IncomingReg,
                          const TargetRegisterInfo *RegInfo = 0);

  /// setPhysRegsDeadExcept - Mark every physreg used by this instruction as
  /// dead except those in the UsedRegs list.
  void setPhysRegsDeadExcept(const SmallVectorImpl<unsigned> &UsedRegs,
                             const TargetRegisterInfo &TRI);

  /// isSafeToMove - Return true if it is safe to move this instruction. If
  /// SawStore is set to true, it means that there is a store (or call) between
  /// the instruction's location and its intended destination.
  bool isSafeToMove(const TargetInstrInfo *TII, AliasAnalysis *AA,
                    bool &SawStore) const;

  /// isSafeToReMat - Return true if it's safe to rematerialize the specified
  /// instruction which defined the specified register instead of copying it.
  bool isSafeToReMat(const TargetInstrInfo *TII, AliasAnalysis *AA,
                     unsigned DstReg) const;

  /// hasVolatileMemoryRef - Return true if this instruction may have a
  /// volatile memory reference, or if the information describing the
  /// memory reference is not available. Return false if it is known to
  /// have no volatile memory references.
  bool hasVolatileMemoryRef() const;

  /// isInvariantLoad - Return true if this instruction is loading from a
  /// location whose value is invariant across the function.  For example,
  /// loading a value from the constant pool or from the argument area of
  /// a function if it does not change.  This should only return true of *all*
  /// loads the instruction does are invariant (if it does multiple loads).
  bool isInvariantLoad(AliasAnalysis *AA) const;

  /// isConstantValuePHI - If the specified instruction is a PHI that always
  /// merges together the same virtual register, return the register, otherwise
  /// return 0.
  unsigned isConstantValuePHI() const;

  /// hasUnmodeledSideEffects - Return true if this instruction has side
  /// effects that are not modeled by mayLoad / mayStore, etc.
  /// For all instructions, the property is encoded in MCInstrDesc::Flags
  /// (see MCInstrDesc::hasUnmodeledSideEffects(). The only exception is
  /// INLINEASM instruction, in which case the side effect property is encoded
  /// in one of its operands (see InlineAsm::Extra_HasSideEffect).
  ///
  bool hasUnmodeledSideEffects() const;

  /// allDefsAreDead - Return true if all the defs of this instruction are dead.
  ///
  bool allDefsAreDead() const;

  /// copyImplicitOps - Copy implicit register operands from specified
  /// instruction to this instruction.
  void copyImplicitOps(const MachineInstr *MI);

  //
  // Debugging support
  //
  void print(raw_ostream &OS, const TargetMachine *TM = 0) const;
  void dump() const;

  //===--------------------------------------------------------------------===//
  // Accessors used to build up machine instructions.

  /// addOperand - Add the specified operand to the instruction.  If it is an
  /// implicit operand, it is added to the end of the operand list.  If it is
  /// an explicit operand it is added at the end of the explicit operand list
  /// (before the first implicit operand).
  void addOperand(const MachineOperand &Op);

  /// setDesc - Replace the instruction descriptor (thus opcode) of
  /// the current instruction with a new one.
  ///
  void setDesc(const MCInstrDesc &tid) { MCID = &tid; }

  /// setDebugLoc - Replace current source information with new such.
  /// Avoid using this, the constructor argument is preferable.
  ///
  void setDebugLoc(const DebugLoc dl) { debugLoc = dl; }

  /// RemoveOperand - Erase an operand  from an instruction, leaving it with one
  /// fewer operand than it started with.
  ///
  void RemoveOperand(unsigned i);

  /// addMemOperand - Add a MachineMemOperand to the machine instruction.
  /// This function should be used only occasionally. The setMemRefs function
  /// is the primary method for setting up a MachineInstr's MemRefs list.
  void addMemOperand(MachineFunction &MF, MachineMemOperand *MO);

  /// setMemRefs - Assign this MachineInstr's memory reference descriptor
  /// list. This does not transfer ownership.
  void setMemRefs(mmo_iterator NewMemRefs, mmo_iterator NewMemRefsEnd) {
    MemRefs = NewMemRefs;
    MemRefsEnd = NewMemRefsEnd;
  }

private:
  /// getRegInfo - If this instruction is embedded into a MachineFunction,
  /// return the MachineRegisterInfo object for the current function, otherwise
  /// return null.
  MachineRegisterInfo *getRegInfo();

  /// addImplicitDefUseOperands - Add all implicit def and use operands to
  /// this instruction.
  void addImplicitDefUseOperands();

  /// RemoveRegOperandsFromUseLists - Unlink all of the register operands in
  /// this instruction from their respective use lists.  This requires that the
  /// operands already be on their use lists.
  void RemoveRegOperandsFromUseLists();

  /// AddRegOperandsToUseLists - Add all of the register operands in
  /// this instruction from their respective use lists.  This requires that the
  /// operands not be on their use lists yet.
  void AddRegOperandsToUseLists(MachineRegisterInfo &RegInfo);
};

/// MachineInstrExpressionTrait - Special DenseMapInfo traits to compare
/// MachineInstr* by *value* of the instruction rather than by pointer value.
/// The hashing and equality testing functions ignore definitions so this is
/// useful for CSE, etc.
struct MachineInstrExpressionTrait : DenseMapInfo<MachineInstr*> {
  static inline MachineInstr *getEmptyKey() {
    return 0;
  }

  static inline MachineInstr *getTombstoneKey() {
    return reinterpret_cast<MachineInstr*>(-1);
  }

  static unsigned getHashValue(const MachineInstr* const &MI);

  static bool isEqual(const MachineInstr* const &LHS,
                      const MachineInstr* const &RHS) {
    if (RHS == getEmptyKey() || RHS == getTombstoneKey() ||
        LHS == getEmptyKey() || LHS == getTombstoneKey())
      return LHS == RHS;
    return LHS->isIdenticalTo(RHS, MachineInstr::IgnoreVRegDefs);
  }
};

//===----------------------------------------------------------------------===//
// Debugging Support

inline raw_ostream& operator<<(raw_ostream &OS, const MachineInstr &MI) {
  MI.print(OS);
  return OS;
}

} // End llvm namespace

#endif