lib/CodeGen/MachineInstr.cpp

//===-- lib/CodeGen/MachineInstr.cpp --------------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Methods common to all machine instructions.
//
//===----------------------------------------------------------------------===//

#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/Value.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetInstrDesc.h"
#include "llvm/Target/MRegisterInfo.h"
#include "llvm/Support/LeakDetector.h"
#include "llvm/Support/Streams.h"
#include <ostream>
using namespace llvm;

//===----------------------------------------------------------------------===//
// MachineOperand Implementation
//===----------------------------------------------------------------------===//

/// AddRegOperandToRegInfo - Add this register operand to the specified
/// MachineRegisterInfo.  If it is null, then the next/prev fields should be
/// explicitly nulled out.
void MachineOperand::AddRegOperandToRegInfo(MachineRegisterInfo *RegInfo) {
  assert(isReg() && "Can only add reg operand to use lists");

  // If the reginfo pointer is null, just explicitly null out or next/prev
  // pointers, to ensure they are not garbage.
  if (RegInfo == 0) {
    Contents.Reg.Prev = 0;
    Contents.Reg.Next = 0;
    return;
  }

  // Otherwise, add this operand to the head of the registers use/def list.
  MachineOperand **Head = &RegInfo->getRegUseDefListHead(getReg());

  // For SSA values, we prefer to keep the definition at the start of the list.
  // we do this by skipping over the definition if it is at the head of the
  // list.
  if (*Head && (*Head)->isDef())
    Head = &(*Head)->Contents.Reg.Next;

  Contents.Reg.Next = *Head;
  if (Contents.Reg.Next) {
    assert(getReg() == Contents.Reg.Next->getReg() &&
           "Different regs on the same list!");
    Contents.Reg.Next->Contents.Reg.Prev = &Contents.Reg.Next;
  }

  Contents.Reg.Prev = Head;
  *Head = this;
}

void MachineOperand::setReg(unsigned Reg) {
  if (getReg() == Reg) return; // No change.

  // Otherwise, we have to change the register.  If this operand is embedded
  // into a machine function, we need to update the old and new register's
  // use/def lists.
  if (MachineInstr *MI = getParent())
    if (MachineBasicBlock *MBB = MI->getParent())
      if (MachineFunction *MF = MBB->getParent()) {
        RemoveRegOperandFromRegInfo();
        Contents.Reg.RegNo = Reg;
        AddRegOperandToRegInfo(&MF->getRegInfo());
        return;
      }

  // Otherwise, just change the register, no problem.  :)
  Contents.Reg.RegNo = Reg;
}

/// ChangeToImmediate - Replace this operand with a new immediate operand of
/// the specified value.  If an operand is known to be an immediate already,
/// the setImm method should be used.
void MachineOperand::ChangeToImmediate(int64_t ImmVal) {
  // If this operand is currently a register operand, and if this is in a
  // function, deregister the operand from the register's use/def list.
  if (isReg() && getParent() && getParent()->getParent() &&
      getParent()->getParent()->getParent())
    RemoveRegOperandFromRegInfo();

  OpKind = MO_Immediate;
  Contents.ImmVal = ImmVal;
}

/// ChangeToRegister - Replace this operand with a new register operand of
/// the specified value.  If an operand is known to be an register already,
/// the setReg method should be used.
void MachineOperand::ChangeToRegister(unsigned Reg, bool isDef, bool isImp,
                                      bool isKill, bool isDead) {
  // If this operand is already a register operand, use setReg to update the
  // register's use/def lists.
  if (isReg()) {
    setReg(Reg);
  } else {
    // Otherwise, change this to a register and set the reg#.
    OpKind = MO_Register;
    Contents.Reg.RegNo = Reg;

    // If this operand is embedded in a function, add the operand to the
    // register's use/def list.
    if (MachineInstr *MI = getParent())
      if (MachineBasicBlock *MBB = MI->getParent())
        if (MachineFunction *MF = MBB->getParent())
          AddRegOperandToRegInfo(&MF->getRegInfo());
  }

  IsDef = isDef;
  IsImp = isImp;
  IsKill = isKill;
  IsDead = isDead;
  SubReg = 0;
}

/// isIdenticalTo - Return true if this operand is identical to the specified
/// operand.
bool MachineOperand::isIdenticalTo(const MachineOperand &Other) const {
  if (getType() != Other.getType()) return false;

  switch (getType()) {
  default: assert(0 && "Unrecognized operand type");
  case MachineOperand::MO_Register:
    return getReg() == Other.getReg() && isDef() == Other.isDef() &&
           getSubReg() == Other.getSubReg();
  case MachineOperand::MO_Immediate:
    return getImm() == Other.getImm();
  case MachineOperand::MO_MachineBasicBlock:
    return getMBB() == Other.getMBB();
  case MachineOperand::MO_FrameIndex:
    return getIndex() == Other.getIndex();
  case MachineOperand::MO_ConstantPoolIndex:
    return getIndex() == Other.getIndex() && getOffset() == Other.getOffset();
  case MachineOperand::MO_JumpTableIndex:
    return getIndex() == Other.getIndex();
  case MachineOperand::MO_GlobalAddress:
    return getGlobal() == Other.getGlobal() && getOffset() == Other.getOffset();
  case MachineOperand::MO_ExternalSymbol:
    return !strcmp(getSymbolName(), Other.getSymbolName()) &&
           getOffset() == Other.getOffset();
  }
}

/// print - Print the specified machine operand.
///
void MachineOperand::print(std::ostream &OS, const TargetMachine *TM) const {
  switch (getType()) {
  case MachineOperand::MO_Register:
    if (getReg() == 0 || MRegisterInfo::isVirtualRegister(getReg())) {
      OS << "%reg" << getReg();
    } else {
      // If the instruction is embedded into a basic block, we can find the
      // target info for the instruction.
      if (TM == 0)
        if (const MachineInstr *MI = getParent())
          if (const MachineBasicBlock *MBB = MI->getParent())
            if (const MachineFunction *MF = MBB->getParent())
              TM = &MF->getTarget();

      if (TM)
        OS << "%" << TM->getRegisterInfo()->get(getReg()).Name;
      else
        OS << "%mreg" << getReg();
    }

    if (isDef() || isKill() || isDead() || isImplicit()) {
      OS << "<";
      bool NeedComma = false;
      if (isImplicit()) {
        OS << (isDef() ? "imp-def" : "imp-use");
        NeedComma = true;
      } else if (isDef()) {
        OS << "def";
        NeedComma = true;
      }
      if (isKill() || isDead()) {
        if (NeedComma)    OS << ",";
        if (isKill()) OS << "kill";
        if (isDead()) OS << "dead";
      }
      OS << ">";
    }
    break;
  case MachineOperand::MO_Immediate:
    OS << getImm();
    break;
  case MachineOperand::MO_MachineBasicBlock:
    OS << "mbb<"
       << ((Value*)getMBB()->getBasicBlock())->getName()
       << "," << (void*)getMBB() << ">";
    break;
  case MachineOperand::MO_FrameIndex:
    OS << "<fi#" << getIndex() << ">";
    break;
  case MachineOperand::MO_ConstantPoolIndex:
    OS << "<cp#" << getIndex();
    if (getOffset()) OS << "+" << getOffset();
    OS << ">";
    break;
  case MachineOperand::MO_JumpTableIndex:
    OS << "<jt#" << getIndex() << ">";
    break;
  case MachineOperand::MO_GlobalAddress:
    OS << "<ga:" << ((Value*)getGlobal())->getName();
    if (getOffset()) OS << "+" << getOffset();
    OS << ">";
    break;
  case MachineOperand::MO_ExternalSymbol:
    OS << "<es:" << getSymbolName();
    if (getOffset()) OS << "+" << getOffset();
    OS << ">";
    break;
  default:
    assert(0 && "Unrecognized operand type");
  }
}

//===----------------------------------------------------------------------===//
// MachineInstr Implementation
//===----------------------------------------------------------------------===//

/// MachineInstr ctor - This constructor creates a dummy MachineInstr with
/// TID NULL and no operands.
MachineInstr::MachineInstr()
  : TID(0), NumImplicitOps(0), Parent(0) {
  // Make sure that we get added to a machine basicblock
  LeakDetector::addGarbageObject(this);
}

void MachineInstr::addImplicitDefUseOperands() {
  if (TID->ImplicitDefs)
    for (const unsigned *ImpDefs = TID->ImplicitDefs; *ImpDefs; ++ImpDefs)
      addOperand(MachineOperand::CreateReg(*ImpDefs, true, true));
  if (TID->ImplicitUses)
    for (const unsigned *ImpUses = TID->ImplicitUses; *ImpUses; ++ImpUses)
      addOperand(MachineOperand::CreateReg(*ImpUses, false, true));
}

/// MachineInstr ctor - This constructor create a MachineInstr and add the
/// implicit operands. It reserves space for number of operands specified by
/// TargetInstrDesc or the numOperands if it is not zero. (for
/// instructions with variable number of operands).
MachineInstr::MachineInstr(const TargetInstrDesc &tid, bool NoImp)
  : TID(&tid), NumImplicitOps(0), Parent(0) {
  if (!NoImp && TID->getImplicitDefs())
    for (const unsigned *ImpDefs = TID->getImplicitDefs(); *ImpDefs; ++ImpDefs)
      NumImplicitOps++;
  if (!NoImp && TID->getImplicitUses())
    for (const unsigned *ImpUses = TID->getImplicitUses(); *ImpUses; ++ImpUses)
      NumImplicitOps++;
  Operands.reserve(NumImplicitOps + TID->getNumOperands());
  if (!NoImp)
    addImplicitDefUseOperands();
  // Make sure that we get added to a machine basicblock
  LeakDetector::addGarbageObject(this);
}

/// 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::MachineInstr(MachineBasicBlock *MBB,
                           const TargetInstrDesc &tid)
  : TID(&tid), NumImplicitOps(0), Parent(0) {
  assert(MBB && "Cannot use inserting ctor with null basic block!");
  if (TID->ImplicitDefs)
    for (const unsigned *ImpDefs = TID->getImplicitDefs(); *ImpDefs; ++ImpDefs)
      NumImplicitOps++;
  if (TID->ImplicitUses)
    for (const unsigned *ImpUses = TID->getImplicitUses(); *ImpUses; ++ImpUses)
      NumImplicitOps++;
  Operands.reserve(NumImplicitOps + TID->getNumOperands());
  addImplicitDefUseOperands();
  // Make sure that we get added to a machine basicblock
  LeakDetector::addGarbageObject(this);
  MBB->push_back(this);  // Add instruction to end of basic block!
}

/// MachineInstr ctor - Copies MachineInstr arg exactly
///
MachineInstr::MachineInstr(const MachineInstr &MI) {
  TID = &MI.getDesc();
  NumImplicitOps = MI.NumImplicitOps;
  Operands.reserve(MI.getNumOperands());

  // Add operands
  for (unsigned i = 0; i != MI.getNumOperands(); ++i) {
    Operands.push_back(MI.getOperand(i));
    Operands.back().ParentMI = this;
  }

  // Set parent, next, and prev to null
  Parent = 0;
  Prev = 0;
  Next = 0;
}


MachineInstr::~MachineInstr() {
  LeakDetector::removeGarbageObject(this);
#ifndef NDEBUG
  for (unsigned i = 0, e = Operands.size(); i != e; ++i) {
    assert(Operands[i].ParentMI == this && "ParentMI mismatch!");
    assert((!Operands[i].isReg() || !Operands[i].isOnRegUseList()) &&
           "Reg operand def/use list corrupted");
  }
#endif
}

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

/// getRegInfo - If this instruction is embedded into a MachineFunction,
/// return the MachineRegisterInfo object for the current function, otherwise
/// return null.
MachineRegisterInfo *MachineInstr::getRegInfo() {
  if (MachineBasicBlock *MBB = getParent())
    if (MachineFunction *MF = MBB->getParent())
      return &MF->getRegInfo();
  return 0;
}

/// 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 MachineInstr::RemoveRegOperandsFromUseLists() {
  for (unsigned i = 0, e = Operands.size(); i != e; ++i) {
    if (Operands[i].isReg())
      Operands[i].RemoveRegOperandFromRegInfo();
  }
}

/// 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 MachineInstr::AddRegOperandsToUseLists(MachineRegisterInfo &RegInfo) {
  for (unsigned i = 0, e = Operands.size(); i != e; ++i) {
    if (Operands[i].isReg())
      Operands[i].AddRegOperandToRegInfo(&RegInfo);
  }
}


/// 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 MachineInstr::addOperand(const MachineOperand &Op) {
  bool isImpReg = Op.isReg() && Op.isImplicit();
  assert((isImpReg || !OperandsComplete()) &&
         "Trying to add an operand to a machine instr that is already done!");

  // If we are adding the operand to the end of the list, our job is simpler.
  // This is true most of the time, so this is a reasonable optimization.
  if (isImpReg || NumImplicitOps == 0) {
    // We can only do this optimization if we know that the operand list won't
    // reallocate.
    if (Operands.empty() || Operands.size()+1 <= Operands.capacity()) {
      Operands.push_back(Op);

      // Set the parent of the operand.
      Operands.back().ParentMI = this;

      // If the operand is a register, update the operand's use list.
      if (Op.isReg())
        Operands.back().AddRegOperandToRegInfo(getRegInfo());
      return;
    }
  }

  // Otherwise, we have to insert a real operand before any implicit ones.
  unsigned OpNo = Operands.size()-NumImplicitOps;

  MachineRegisterInfo *RegInfo = getRegInfo();

  // If this instruction isn't embedded into a function, then we don't need to
  // update any operand lists.
  if (RegInfo == 0) {
    // Simple insertion, no reginfo update needed for other register operands.
    Operands.insert(Operands.begin()+OpNo, Op);
    Operands[OpNo].ParentMI = this;

    // Do explicitly set the reginfo for this operand though, to ensure the
    // next/prev fields are properly nulled out.
    if (Operands[OpNo].isReg())
      Operands[OpNo].AddRegOperandToRegInfo(0);

  } else if (Operands.size()+1 <= Operands.capacity()) {
    // Otherwise, we have to remove register operands from their register use
    // list, add the operand, then add the register operands back to their use
    // list.  This also must handle the case when the operand list reallocates
    // to somewhere else.

    // If insertion of this operand won't cause reallocation of the operand
    // list, just remove the implicit operands, add the operand, then re-add all
    // the rest of the operands.
    for (unsigned i = OpNo, e = Operands.size(); i != e; ++i) {
      assert(Operands[i].isReg() && "Should only be an implicit reg!");
      Operands[i].RemoveRegOperandFromRegInfo();
    }

    // Add the operand.  If it is a register, add it to the reg list.
    Operands.insert(Operands.begin()+OpNo, Op);
    Operands[OpNo].ParentMI = this;

    if (Operands[OpNo].isReg())
      Operands[OpNo].AddRegOperandToRegInfo(RegInfo);

    // Re-add all the implicit ops.
    for (unsigned i = OpNo+1, e = Operands.size(); i != e; ++i) {
      assert(Operands[i].isReg() && "Should only be an implicit reg!");
      Operands[i].AddRegOperandToRegInfo(RegInfo);
    }
  } else {
    // Otherwise, we will be reallocating the operand list.  Remove all reg
    // operands from their list, then readd them after the operand list is
    // reallocated.
    RemoveRegOperandsFromUseLists();

    Operands.insert(Operands.begin()+OpNo, Op);
    Operands[OpNo].ParentMI = this;

    // Re-add all the operands.
    AddRegOperandsToUseLists(*RegInfo);
  }
}

/// RemoveOperand - Erase an operand  from an instruction, leaving it with one
/// fewer operand than it started with.
///
void MachineInstr::RemoveOperand(unsigned OpNo) {
  assert(OpNo < Operands.size() && "Invalid operand number");

  // Special case removing the last one.
  if (OpNo == Operands.size()-1) {
    // If needed, remove from the reg def/use list.
    if (Operands.back().isReg() && Operands.back().isOnRegUseList())
      Operands.back().RemoveRegOperandFromRegInfo();

    Operands.pop_back();
    return;
  }

  // Otherwise, we are removing an interior operand.  If we have reginfo to
  // update, remove all operands that will be shifted down from their reg lists,
  // move everything down, then re-add them.
  MachineRegisterInfo *RegInfo = getRegInfo();
  if (RegInfo) {
    for (unsigned i = OpNo, e = Operands.size(); i != e; ++i) {
      if (Operands[i].isReg())
        Operands[i].RemoveRegOperandFromRegInfo();
    }
  }

  Operands.erase(Operands.begin()+OpNo);

  if (RegInfo) {
    for (unsigned i = OpNo, e = Operands.size(); i != e; ++i) {
      if (Operands[i].isReg())
        Operands[i].AddRegOperandToRegInfo(RegInfo);
    }
  }
}


/// removeFromParent - This method unlinks 'this' from the containing basic
/// block, and returns it, but does not delete it.
MachineInstr *MachineInstr::removeFromParent() {
  assert(getParent() && "Not embedded in a basic block!");
  getParent()->remove(this);
  return this;
}


/// OperandComplete - Return true if it's illegal to add a new operand
///
bool MachineInstr::OperandsComplete() const {
  unsigned short NumOperands = TID->getNumOperands();
  if (!TID->isVariadic() && getNumOperands()-NumImplicitOps >= NumOperands)
    return true;  // Broken: we have all the operands of this instruction!
  return false;
}

/// getNumExplicitOperands - Returns the number of non-implicit operands.
///
unsigned MachineInstr::getNumExplicitOperands() const {
  unsigned NumOperands = TID->getNumOperands();
  if (!TID->isVariadic())
    return NumOperands;

  for (unsigned e = getNumOperands(); NumOperands != e; ++NumOperands) {
    const MachineOperand &MO = getOperand(NumOperands);
    if (!MO.isRegister() || !MO.isImplicit())
      NumOperands++;
  }
  return NumOperands;
}


/// isDebugLabel - Returns true if the MachineInstr represents a debug label.
///
bool MachineInstr::isDebugLabel() const {
  return getOpcode() == TargetInstrInfo::LABEL && getOperand(1).getImm() == 0;
}

/// findRegisterUseOperandIdx() - Returns the MachineOperand that is a use of
/// the specific register or -1 if it is not found. It further tightening
/// the search criteria to a use that kills the register if isKill is true.
int MachineInstr::findRegisterUseOperandIdx(unsigned Reg, bool isKill) const {
  for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
    const MachineOperand &MO = getOperand(i);
    if (MO.isRegister() && MO.isUse() && MO.getReg() == Reg)
      if (!isKill || MO.isKill())
        return i;
  }
  return -1;
}

/// findRegisterDefOperand() - Returns the MachineOperand that is a def of
/// the specific register or NULL if it is not found.
MachineOperand *MachineInstr::findRegisterDefOperand(unsigned Reg) {
  for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
    MachineOperand &MO = getOperand(i);
    if (MO.isRegister() && MO.isDef() && MO.getReg() == Reg)
      return &MO;
  }
  return NULL;
}

/// 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 MachineInstr::findFirstPredOperandIdx() const {
  const TargetInstrDesc &TID = getDesc();
  if (TID.isPredicable()) {
    for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
      if (TID.OpInfo[i].isPredicate())
        return i;
  }

  return -1;
}

/// isRegReDefinedByTwoAddr - Returns true if the Reg re-definition is due
/// to two addr elimination.
bool MachineInstr::isRegReDefinedByTwoAddr(unsigned Reg) const {
  const TargetInstrDesc &TID = getDesc();
  for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
    const MachineOperand &MO1 = getOperand(i);
    if (MO1.isRegister() && MO1.isDef() && MO1.getReg() == Reg) {
      for (unsigned j = i+1; j < e; ++j) {
        const MachineOperand &MO2 = getOperand(j);
        if (MO2.isRegister() && MO2.isUse() && MO2.getReg() == Reg &&
            TID.getOperandConstraint(j, TOI::TIED_TO) == (int)i)
          return true;
      }
    }
  }
  return false;
}

/// copyKillDeadInfo - Copies kill / dead operand properties from MI.
///
void MachineInstr::copyKillDeadInfo(const MachineInstr *MI) {
  for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
    const MachineOperand &MO = MI->getOperand(i);
    if (!MO.isRegister() || (!MO.isKill() && !MO.isDead()))
      continue;
    for (unsigned j = 0, ee = getNumOperands(); j != ee; ++j) {
      MachineOperand &MOp = getOperand(j);
      if (!MOp.isIdenticalTo(MO))
        continue;
      if (MO.isKill())
        MOp.setIsKill();
      else
        MOp.setIsDead();
      break;
    }
  }
}

/// copyPredicates - Copies predicate operand(s) from MI.
void MachineInstr::copyPredicates(const MachineInstr *MI) {
  const TargetInstrDesc &TID = MI->getDesc();
  if (TID.isPredicable()) {
    for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
      if (TID.OpInfo[i].isPredicate()) {
        // Predicated operands must be last operands.
        addOperand(MI->getOperand(i));
      }
    }
  }
}

void MachineInstr::dump() const {
  cerr << "  " << *this;
}

void MachineInstr::print(std::ostream &OS, const TargetMachine *TM) const {
  // Specialize printing if op#0 is definition
  unsigned StartOp = 0;
  if (getNumOperands() && getOperand(0).isRegister() && getOperand(0).isDef()) {
    getOperand(0).print(OS, TM);
    OS << " = ";
    ++StartOp;   // Don't print this operand again!
  }

  OS << getDesc().getName();

  for (unsigned i = StartOp, e = getNumOperands(); i != e; ++i) {
    if (i != StartOp)
      OS << ",";
    OS << " ";
    getOperand(i).print(OS, TM);
  }

  OS << "\n";
}

bool MachineInstr::addRegisterKilled(unsigned IncomingReg,
                                     const MRegisterInfo *RegInfo,
                                     bool AddIfNotFound) {
  bool Found = false;
  for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
    MachineOperand &MO = getOperand(i);
    if (MO.isRegister() && MO.isUse()) {
      unsigned Reg = MO.getReg();
      if (!Reg)
        continue;
      if (Reg == IncomingReg) {
        MO.setIsKill();
        Found = true;
        break;
      } else if (MRegisterInfo::isPhysicalRegister(Reg) &&
                 MRegisterInfo::isPhysicalRegister(IncomingReg) &&
                 RegInfo->isSuperRegister(IncomingReg, Reg) &&
                 MO.isKill())
        // A super-register kill already exists.
        Found = true;
    }
  }

  // If not found, this means an alias of one of the operand is killed. Add a
  // new implicit operand if required.
  if (!Found && AddIfNotFound) {
    addOperand(MachineOperand::CreateReg(IncomingReg, false/*IsDef*/,
                                         true/*IsImp*/,true/*IsKill*/));
    return true;
  }
  return Found;
}

bool MachineInstr::addRegisterDead(unsigned IncomingReg,
                                   const MRegisterInfo *RegInfo,
                                   bool AddIfNotFound) {
  bool Found = false;
  for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
    MachineOperand &MO = getOperand(i);
    if (MO.isRegister() && MO.isDef()) {
      unsigned Reg = MO.getReg();
      if (!Reg)
        continue;
      if (Reg == IncomingReg) {
        MO.setIsDead();
        Found = true;
        break;
      } else if (MRegisterInfo::isPhysicalRegister(Reg) &&
                 MRegisterInfo::isPhysicalRegister(IncomingReg) &&
                 RegInfo->isSuperRegister(IncomingReg, Reg) &&
                 MO.isDead())
        // There exists a super-register that's marked dead.
        return true;
    }
  }

  // If not found, this means an alias of one of the operand is dead. Add a
  // new implicit operand.
  if (!Found && AddIfNotFound) {
    addOperand(MachineOperand::CreateReg(IncomingReg, true/*IsDef*/,
                                         true/*IsImp*/,false/*IsKill*/,
                                         true/*IsDead*/));
    return true;
  }
  return Found;
}

/// copyKillDeadInfo - copies killed/dead information from one instr to another
void MachineInstr::copyKillDeadInfo(MachineInstr *OldMI,
                                    const MRegisterInfo *RegInfo) {
  // If the instruction defines any virtual registers, update the VarInfo,
  // kill and dead information for the instruction.
  for (unsigned i = 0, e = OldMI->getNumOperands(); i != e; ++i) {
    MachineOperand &MO = OldMI->getOperand(i);
    if (MO.isRegister() && MO.getReg() &&
        MRegisterInfo::isVirtualRegister(MO.getReg())) {
      unsigned Reg = MO.getReg();
      if (MO.isDef()) {
        if (MO.isDead()) {
          MO.setIsDead(false);
          addRegisterDead(Reg, RegInfo);
        }
      }
      if (MO.isKill()) {
        MO.setIsKill(false);
        addRegisterKilled(Reg, RegInfo);
      }
    }
  }
}