bool NoUseAfterLastDef(unsigned Reg, MachineBasicBlock *MBB, unsigned Dist,
unsigned &LastDef);
+ MachineInstr *FindLastUseInMBB(unsigned Reg, MachineBasicBlock *MBB,
+ unsigned Dist);
+
bool isProfitableToCommute(unsigned regB, unsigned regC,
MachineInstr *MI, MachineBasicBlock *MBB,
unsigned Dist);
return !(LastUse > LastDef && LastUse < Dist);
}
+MachineInstr *TwoAddressInstructionPass::FindLastUseInMBB(unsigned Reg,
+ MachineBasicBlock *MBB,
+ unsigned Dist) {
+ unsigned LastUseDist = 0;
+ MachineInstr *LastUse = 0;
+ for (MachineRegisterInfo::reg_iterator I = MRI->reg_begin(Reg),
+ E = MRI->reg_end(); I != E; ++I) {
+ MachineOperand &MO = I.getOperand();
+ MachineInstr *MI = MO.getParent();
+ if (MI->getParent() != MBB)
+ continue;
+ DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(MI);
+ if (DI == DistanceMap.end())
+ continue;
+ if (DI->second >= Dist)
+ continue;
+
+ if (MO.isUse() && DI->second > LastUseDist) {
+ LastUse = DI->first;
+ LastUseDist = DI->second;
+ }
+ }
+ return LastUse;
+}
+
/// isCopyToReg - Return true if the specified MI is a copy instruction or
/// a extract_subreg instruction. It also returns the source and destination
/// registers and whether they are physical registers by reference.
/// isSafeToDelete - If the specified instruction does not produce any side
/// effects and all of its defs are dead, then it's safe to delete.
-static bool isSafeToDelete(MachineInstr *MI, const TargetInstrInfo *TII) {
+static bool isSafeToDelete(MachineInstr *MI, unsigned Reg,
+ const TargetInstrInfo *TII,
+ SmallVector<unsigned, 4> &Kills) {
const TargetInstrDesc &TID = MI->getDesc();
if (TID.mayStore() || TID.isCall())
return false;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
- if (!MO.isReg() || !MO.isDef())
+ if (!MO.isReg())
continue;
- if (!MO.isDead())
+ if (MO.isDef() && !MO.isDead())
return false;
+ if (MO.isUse() && MO.getReg() != Reg && MO.isKill())
+ Kills.push_back(MO.getReg());
}
return true;
if (!isKilled(*mi, regB, MRI, TII)) {
// If regA is dead and the instruction can be deleted, just delete
// it so it doesn't clobber regB.
- if (mi->getOperand(ti).isDead() && isSafeToDelete(mi, TII)) {
- mbbi->erase(mi); // Nuke the old inst.
- mi = nmi;
- ++NumDeletes;
- break; // Done with this instruction.
+ SmallVector<unsigned, 4> Kills;
+ if (mi->getOperand(ti).isDead() &&
+ isSafeToDelete(mi, regB, TII, Kills)) {
+ SmallVector<std::pair<std::pair<unsigned, bool>
+ ,MachineInstr*>, 4> NewKills;
+ bool ReallySafe = true;
+ // If this instruction kills some virtual registers, we need
+ // update the kill information. If it's not possible to do so,
+ // then bail out.
+ while (!Kills.empty()) {
+ unsigned Kill = Kills.back();
+ Kills.pop_back();
+ if (TargetRegisterInfo::isPhysicalRegister(Kill)) {
+ ReallySafe = false;
+ break;
+ }
+ MachineInstr *LastKill = FindLastUseInMBB(Kill, &*mbbi, Dist);
+ if (LastKill) {
+ bool isModRef = LastKill->modifiesRegister(Kill);
+ NewKills.push_back(std::make_pair(std::make_pair(Kill,isModRef),
+ LastKill));
+ } else {
+ ReallySafe = false;
+ break;
+ }
+ }
+
+ if (ReallySafe) {
+ if (LV) {
+ while (!NewKills.empty()) {
+ MachineInstr *NewKill = NewKills.back().second;
+ unsigned Kill = NewKills.back().first.first;
+ bool isDead = NewKills.back().first.second;
+ NewKills.pop_back();
+ if (LV->removeVirtualRegisterKilled(Kill, mi)) {
+ if (isDead)
+ LV->addVirtualRegisterDead(Kill, NewKill);
+ else
+ LV->addVirtualRegisterKilled(Kill, NewKill);
+ }
+ }
+ }
+
+ // We're really going to nuke the old inst. If regB was marked
+ // as a kill we need to update its Kills list.
+ if (mi->getOperand(si).isKill())
+ LV->removeVirtualRegisterKilled(regB, mi);
+
+ mbbi->erase(mi); // Nuke the old inst.
+ mi = nmi;
+ ++NumDeletes;
+ break; // Done with this instruction.
+ }
}
// If this instruction is commutative, check to see if C dies. If
++NumReMats;
} else {
bool Emitted = TII->copyRegToReg(*mbbi, mi, regA, regB, rc, rc);
+ (void)Emitted;
assert(Emitted && "Unable to issue a copy instruction!\n");
}
// Update live variables for regB.
if (LV) {
- LiveVariables::VarInfo& varInfoB = LV->getVarInfo(regB);
-
- // regB is used in this BB.
- varInfoB.UsedBlocks[mbbi->getNumber()] = true;
-
if (LV->removeVirtualRegisterKilled(regB, mi))
LV->addVirtualRegisterKilled(regB, prevMI);