MachineInstr.cpp

    OS << " ";
    getOperand(i).print(OS, TM);
  }

  if (!memoperands_empty()) {
    OS << ", Mem:";
    for (std::list<MachineMemOperand>::const_iterator i = memoperands_begin(),
         e = memoperands_end(); i != e; ++i) {
      OS << *i;
      if (next(i) != e)
        OS << " ";
    }
  }

  if (!debugLoc.isUnknown()) {
    const MachineFunction *MF = getParent()->getParent();
    DebugLocTuple DLT = MF->getDebugLocTuple(debugLoc);
    DICompileUnit CU(DLT.CompileUnit);
    std::string Dir, Fn;
    OS << " [dbg: "
       << CU.getDirectory(Dir) << '/' << CU.getFilename(Fn) << ","
       << DLT.Line << ","
       << DLT.Col  << "]";
  }

  OS << "\n";
}

bool MachineInstr::addRegisterKilled(unsigned IncomingReg,
                                     const TargetRegisterInfo *RegInfo,
                                     bool AddIfNotFound) {
  bool isPhysReg = TargetRegisterInfo::isPhysicalRegister(IncomingReg);
  bool hasAliases = isPhysReg && RegInfo->getAliasSet(IncomingReg);
  bool Found = false;
  SmallVector<unsigned,4> DeadOps;
  for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
    MachineOperand &MO = getOperand(i);
    if (!MO.isReg() || !MO.isUse() || MO.isUndef())
      continue;
    unsigned Reg = MO.getReg();
    if (!Reg)
      continue;

    if (Reg == IncomingReg) {
      if (!Found) {
        if (MO.isKill())
          // The register is already marked kill.
          return true;
        if (isPhysReg && isRegTiedToDefOperand(i))
          // Two-address uses of physregs must not be marked kill.
          return true;
        MO.setIsKill();
        Found = true;
      }
    } else if (hasAliases && MO.isKill() &&
               TargetRegisterInfo::isPhysicalRegister(Reg)) {
      // A super-register kill already exists.
      if (RegInfo->isSuperRegister(IncomingReg, Reg))
        return true;
      if (RegInfo->isSubRegister(IncomingReg, Reg))
        DeadOps.push_back(i);
    }
  }

  // Trim unneeded kill operands.
  while (!DeadOps.empty()) {
    unsigned OpIdx = DeadOps.back();
    if (getOperand(OpIdx).isImplicit())
      RemoveOperand(OpIdx);
    else
      getOperand(OpIdx).setIsKill(false);
    DeadOps.pop_back();
  }

  // If not found, this means an alias of one of the operands 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 TargetRegisterInfo *RegInfo,
                                   bool AddIfNotFound) {
  bool isPhysReg = TargetRegisterInfo::isPhysicalRegister(IncomingReg);
  bool hasAliases = isPhysReg && RegInfo->getAliasSet(IncomingReg);
  bool Found = false;
  SmallVector<unsigned,4> DeadOps;
  for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
    MachineOperand &MO = getOperand(i);
    if (!MO.isReg() || !MO.isDef())
      continue;
    unsigned Reg = MO.getReg();
    if (!Reg)
      continue;

    if (Reg == IncomingReg) {
      if (!Found) {
        if (MO.isDead())
          // The register is already marked dead.
          return true;
        MO.setIsDead();
        Found = true;
      }
    } else if (hasAliases && MO.isDead() &&
               TargetRegisterInfo::isPhysicalRegister(Reg)) {
      // There exists a super-register that's marked dead.
      if (RegInfo->isSuperRegister(IncomingReg, Reg))
        return true;
      if (RegInfo->getSubRegisters(IncomingReg) &&
          RegInfo->getSuperRegisters(Reg) &&
          RegInfo->isSubRegister(IncomingReg, Reg))
        DeadOps.push_back(i);
    }
  }

  // Trim unneeded dead operands.
  while (!DeadOps.empty()) {
    unsigned OpIdx = DeadOps.back();
    if (getOperand(OpIdx).isImplicit())
      RemoveOperand(OpIdx);
    else
      getOperand(OpIdx).setIsDead(false);
    DeadOps.pop_back();
  }

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