+/// RescheduleMIBelowKill - If there is one more local instruction that reads
+/// 'Reg' and it kills 'Reg, consider moving the instruction below the kill
+/// instruction in order to eliminate the need for the copy.
+bool
+TwoAddressInstructionPass::RescheduleMIBelowKill(MachineBasicBlock *MBB,
+ MachineBasicBlock::iterator &mi,
+ MachineBasicBlock::iterator &nmi,
+ unsigned Reg) {
+ MachineInstr *MI = &*mi;
+ DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(MI);
+ if (DI == DistanceMap.end())
+ // Must be created from unfolded load. Don't waste time trying this.
+ return false;
+
+ MachineInstr *KillMI = findLocalKill(Reg, MBB, mi, MRI, DistanceMap);
+ if (!KillMI || KillMI->isCopy() || KillMI->isCopyLike())
+ // Don't mess with copies, they may be coalesced later.
+ return false;
+
+ const MCInstrDesc &MCID = KillMI->getDesc();
+ if (MCID.hasUnmodeledSideEffects() || MCID.isCall() || MCID.isBranch() ||
+ MCID.isTerminator())
+ // Don't move pass calls, etc.
+ return false;
+
+ unsigned DstReg;
+ if (isTwoAddrUse(*KillMI, Reg, DstReg))
+ return false;
+
+ bool SeenStore;
+ if (!MI->isSafeToMove(TII, AA, SeenStore))
+ return false;
+
+ if (TII->getInstrLatency(InstrItins, MI) > 1)
+ // FIXME: Needs more sophisticated heuristics.
+ return false;
+
+ SmallSet<unsigned, 2> Uses;
+ SmallSet<unsigned, 2> Defs;
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ const MachineOperand &MO = MI->getOperand(i);
+ if (!MO.isReg())
+ continue;
+ unsigned MOReg = MO.getReg();
+ if (!MOReg)
+ continue;
+ if (MO.isDef())
+ Defs.insert(MOReg);
+ else
+ Uses.insert(MOReg);
+ }
+
+ // Move the copies connected to MI down as well.
+ MachineBasicBlock::iterator From = MI;
+ MachineBasicBlock::iterator To = llvm::next(From);
+ while (To->isCopy() && Defs.count(To->getOperand(1).getReg())) {
+ Defs.insert(To->getOperand(0).getReg());
+ ++To;
+ }
+
+ // Check if the reschedule will not break depedencies.
+ unsigned NumVisited = 0;
+ MachineBasicBlock::iterator KillPos = KillMI;
+ ++KillPos;
+ for (MachineBasicBlock::iterator I = To; I != KillPos; ++I) {
+ MachineInstr *OtherMI = I;
+ // DBG_VALUE cannot be counted against the limit.
+ if (OtherMI->isDebugValue())
+ continue;
+ if (NumVisited > 10) // FIXME: Arbitrary limit to reduce compile time cost.
+ return false;
+ ++NumVisited;
+ const MCInstrDesc &OMCID = OtherMI->getDesc();
+ if (OMCID.hasUnmodeledSideEffects() || OMCID.isCall() || OMCID.isBranch() ||
+ OMCID.isTerminator())
+ // Don't move pass calls, etc.
+ return false;
+ for (unsigned i = 0, e = OtherMI->getNumOperands(); i != e; ++i) {
+ const MachineOperand &MO = OtherMI->getOperand(i);
+ if (!MO.isReg())
+ continue;
+ unsigned MOReg = MO.getReg();
+ if (!MOReg)
+ continue;
+ if (MO.isDef()) {
+ if (Uses.count(MOReg))
+ // Physical register use would be clobbered.
+ return false;
+ if (!MO.isDead() && Defs.count(MOReg))
+ // May clobber a physical register def.
+ // FIXME: This may be too conservative. It's ok if the instruction
+ // is sunken completely below the use.
+ return false;
+ } else {
+ if (Defs.count(MOReg))
+ return false;
+ if (MOReg != Reg && MO.isKill() && Uses.count(MOReg))
+ // Don't want to extend other live ranges and update kills.
+ return false;
+ }
+ }
+ }
+
+ // Move debug info as well.
+ if (From != MBB->begin()) {
+ while (llvm::prior(From)->isDebugValue())
+ --From;
+ }
+
+ // Copies following MI may have been moved as well.
+ nmi = To;
+ MBB->splice(KillPos, MBB, From, To);
+ DistanceMap.erase(DI);
+
+ if (LV) {
+ // Update live variables
+ LV->removeVirtualRegisterKilled(Reg, KillMI);
+ LV->addVirtualRegisterKilled(Reg, MI);
+ } else {
+ for (unsigned i = 0, e = KillMI->getNumOperands(); i != e; ++i) {
+ MachineOperand &MO = KillMI->getOperand(i);
+ if (!MO.isReg() || !MO.isUse() || MO.getReg() != Reg)
+ continue;
+ MO.setIsKill(false);
+ }
+ MI->addRegisterKilled(Reg, 0);
+ }
+
+ return true;
+}
+
+/// isDefTooClose - Return true if the re-scheduling will put the given
+/// instruction too close to the defs of its register dependencies.
+bool TwoAddressInstructionPass::isDefTooClose(unsigned Reg, unsigned Dist,
+ MachineInstr *MI,
+ MachineBasicBlock *MBB) {
+ for (MachineRegisterInfo::def_iterator DI = MRI->def_begin(Reg),
+ DE = MRI->def_end(); DI != DE; ++DI) {
+ MachineInstr *DefMI = &*DI;
+ if (DefMI->getParent() != MBB || DefMI->isCopy() || DefMI->isCopyLike())
+ continue;
+ if (DefMI == MI)
+ return true; // MI is defining something KillMI uses
+ DenseMap<MachineInstr*, unsigned>::iterator DDI = DistanceMap.find(DefMI);
+ if (DDI == DistanceMap.end())
+ return true; // Below MI
+ unsigned DefDist = DDI->second;
+ assert(Dist > DefDist && "Visited def already?");
+ if (TII->getInstrLatency(InstrItins, DefMI) > (int)(Dist - DefDist))
+ return true;
+ }
+ return false;
+}
+
+/// RescheduleKillAboveMI - If there is one more local instruction that reads
+/// 'Reg' and it kills 'Reg, consider moving the kill instruction above the
+/// current two-address instruction in order to eliminate the need for the
+/// copy.
+bool
+TwoAddressInstructionPass::RescheduleKillAboveMI(MachineBasicBlock *MBB,
+ MachineBasicBlock::iterator &mi,
+ MachineBasicBlock::iterator &nmi,
+ unsigned Reg) {
+ MachineInstr *MI = &*mi;
+ DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(MI);
+ if (DI == DistanceMap.end())
+ // Must be created from unfolded load. Don't waste time trying this.
+ return false;
+
+ MachineInstr *KillMI = findLocalKill(Reg, MBB, mi, MRI, DistanceMap);
+ if (!KillMI || KillMI->isCopy() || KillMI->isCopyLike())
+ // Don't mess with copies, they may be coalesced later.
+ return false;
+
+ unsigned DstReg;
+ if (isTwoAddrUse(*KillMI, Reg, DstReg))
+ return false;
+
+ bool SeenStore;
+ if (!KillMI->isSafeToMove(TII, AA, SeenStore))
+ return false;
+
+ SmallSet<unsigned, 2> Uses;
+ SmallSet<unsigned, 2> Kills;
+ SmallSet<unsigned, 2> Defs;
+ SmallSet<unsigned, 2> LiveDefs;
+ for (unsigned i = 0, e = KillMI->getNumOperands(); i != e; ++i) {
+ const MachineOperand &MO = KillMI->getOperand(i);
+ if (!MO.isReg())
+ continue;
+ unsigned MOReg = MO.getReg();
+ if (MO.isUse()) {
+ if (!MOReg)
+ continue;
+ if (isDefTooClose(MOReg, DI->second, MI, MBB))
+ return false;
+ Uses.insert(MOReg);
+ if (MO.isKill() && MOReg != Reg)
+ Kills.insert(MOReg);
+ } else if (TargetRegisterInfo::isPhysicalRegister(MOReg)) {
+ Defs.insert(MOReg);
+ if (!MO.isDead())
+ LiveDefs.insert(MOReg);
+ }
+ }
+
+ // Check if the reschedule will not break depedencies.
+ unsigned NumVisited = 0;
+ MachineBasicBlock::iterator KillPos = KillMI;
+ for (MachineBasicBlock::iterator I = mi; I != KillPos; ++I) {
+ MachineInstr *OtherMI = I;
+ // DBG_VALUE cannot be counted against the limit.
+ if (OtherMI->isDebugValue())
+ continue;
+ if (NumVisited > 10) // FIXME: Arbitrary limit to reduce compile time cost.
+ return false;
+ ++NumVisited;
+ const MCInstrDesc &MCID = OtherMI->getDesc();
+ if (MCID.hasUnmodeledSideEffects() || MCID.isCall() || MCID.isBranch() ||
+ MCID.isTerminator())
+ // Don't move pass calls, etc.
+ return false;
+ for (unsigned i = 0, e = OtherMI->getNumOperands(); i != e; ++i) {
+ const MachineOperand &MO = OtherMI->getOperand(i);
+ if (!MO.isReg())
+ continue;
+ unsigned MOReg = MO.getReg();
+ if (!MOReg)
+ continue;
+ if (MO.isUse()) {
+ if (Defs.count(MOReg))
+ // Moving KillMI can clobber the physical register if the def has
+ // not been seen.
+ return false;
+ if (Kills.count(MOReg))
+ // Don't want to extend other live ranges and update kills.
+ return false;
+ } else {
+ if (Uses.count(MOReg))
+ return false;
+ if (TargetRegisterInfo::isPhysicalRegister(MOReg) &&
+ LiveDefs.count(MOReg))
+ return false;
+ // Physical register def is seen.
+ Defs.erase(MOReg);
+ }
+ }
+ }
+
+ // Move the old kill above MI, don't forget to move debug info as well.
+ MachineBasicBlock::iterator InsertPos = mi;
+ if (InsertPos != MBB->begin())
+ while (llvm::prior(InsertPos)->isDebugValue())
+ --InsertPos;
+ MachineBasicBlock::iterator From = KillMI;
+ MachineBasicBlock::iterator To = llvm::next(From);
+ while (llvm::prior(From)->isDebugValue())
+ --From;
+ MBB->splice(InsertPos, MBB, From, To);
+
+ nmi = llvm::prior(mi); // Backtrack so we process the moved instruction.
+ DistanceMap.erase(DI);
+
+ if (LV) {
+ // Update live variables
+ LV->removeVirtualRegisterKilled(Reg, KillMI);
+ LV->addVirtualRegisterKilled(Reg, MI);
+ } else {
+ for (unsigned i = 0, e = KillMI->getNumOperands(); i != e; ++i) {
+ MachineOperand &MO = KillMI->getOperand(i);
+ if (!MO.isReg() || !MO.isUse() || MO.getReg() != Reg)
+ continue;
+ MO.setIsKill(false);
+ }
+ MI->addRegisterKilled(Reg, 0);
+ }
+ return true;
+}
+