lib/CodeGen/MachineCSE.cpp

83     bool PerformTrivialCopyPropagation(MachineInstr *MI,
88     bool hasLivePhysRegDefUses(const MachineInstr *MI,
93     bool PhysRegDefsReach(MachineInstr *CSMI, MachineInstr *MI,
97     bool isCSECandidate(MachineInstr *MI);
99                            MachineInstr *CSMI, MachineInstr *MI);
122 bool MachineCSE::PerformTrivialCopyPropagation(MachineInstr *MI,
125   for (MachineOperand &MO : MI->operands()) {
158     DEBUG(dbgs() << "***     to: " << *MI);
159     // Propagate SrcReg of copies to MI.
215 bool MachineCSE::hasLivePhysRegDefUses(const MachineInstr *MI,
221   for (const MachineOperand &MO : MI->operands()) {
238   MachineBasicBlock::const_iterator I = MI; I = std::next(I);
239   for (const MachineOperand &MO : MI->operands()) {
265 bool MachineCSE::PhysRegDefsReach(MachineInstr *CSMI, MachineInstr *MI,
272   const MachineBasicBlock *MBB = MI->getParent();
289   MachineBasicBlock::const_iterator E = MI;
298       assert(CrossMBB && "Reaching end-of-MBB without finding MI?");
331 bool MachineCSE::isCSECandidate(MachineInstr *MI) {
332   if (MI->isPosition() || MI->isPHI() || MI->isImplicitDef() || MI->isKill() ||
333       MI->isInlineAsm() || MI->isDebugValue())
337   if (MI->isCopyLike())
341   if (MI->mayStore() || MI->isCall() || MI->isTerminator() ||
342       MI->hasUnmodeledSideEffects())
345   if (MI->mayLoad()) {
349     if (!MI->isInvariantLoad(AA))
358 /// isProfitableToCSE - Return true if it's profitable to eliminate MI with a
361                                    MachineInstr *CSMI, MachineInstr *MI) {
371     for (MachineInstr &MI : MRI->use_nodbg_instructions(CSReg)) {
372       CSUses.insert(&MI);
374     for (MachineInstr &MI : MRI->use_nodbg_instructions(Reg)) {
375       if (!CSUses.count(&MI)) {
386   if (TII->isAsCheapAsAMove(MI)) {
388     MachineBasicBlock *BB = MI->getParent();
396   for (const MachineOperand &MO : MI->operands()) {
405     for (MachineInstr &MI : MRI->use_nodbg_instructions(Reg)) {
407       if (!MI.isCopyLike()) {
420   for (MachineInstr &MI : MRI->use_nodbg_instructions(CSReg)) {
421     HasPHI |= MI.isPHI();
422     CSBBs.insert(MI.getParent());
427   return CSBBs.count(MI->getParent());
451     MachineInstr *MI = &*I;
454     if (!isCSECandidate(MI))
457     bool FoundCSE = VNT.count(MI);
460       if (PerformTrivialCopyPropagation(MI, MBB)) {
463         // After coalescing MI itself may become a copy.
464         if (MI->isCopyLike())
468         FoundCSE = VNT.count(MI);
474     if (!FoundCSE && MI->isCommutable()) {
475       MachineInstr *NewMI = TII->commuteInstruction(MI);
479         if (NewMI != MI) {
484           // MI was changed but it didn't help, commute it back!
485           (void)TII->commuteInstruction(MI);
496     if (FoundCSE && hasLivePhysRegDefUses(MI, MBB, PhysRefs,
506         unsigned CSVN = VNT.lookup(MI);
508         if (PhysRegDefsReach(CSMI, MI, PhysRefs, PhysDefs, CrossMBBPhysDef))
514       VNT.insert(MI, CurrVN++);
515       Exps.push_back(MI);
520     unsigned CSVN = VNT.lookup(MI);
522     DEBUG(dbgs() << "Examining: " << *MI);
527     unsigned NumDefs = MI->getDesc().getNumDefs() +
528                        MI->getDesc().getNumImplicitDefs();
530     for (unsigned i = 0, e = MI->getNumOperands(); NumDefs && i != e; ++i) {
531       MachineOperand &MO = MI->getOperand(i);
537       // Go through implicit defs of CSMI and MI, if a def is not dead at MI,
542       // Keep track of implicit defs of CSMI and MI, to clear possibly
556       if (!isProfitableToCSE(NewReg, OldReg, CSMI, MI)) {
589       // Go through implicit defs of CSMI and MI, if a def is not dead at MI,
594       // Go through implicit defs of CSMI and MI, and clear the kill flags on
595       // their uses in all the instructions between CSMI and MI.
599       //   subs  ... %NZCV<imp-def>        <- MI, to be eliminated
601       // Since we eliminated MI, and reused a register imp-def'd by CSMI
602       // (here %NZCV), that register, if it was killed before MI, should have
604       if (CSMI->getParent() == MI->getParent()) {
605         for (MachineBasicBlock::iterator II = CSMI, IE = MI; II != IE; ++II)
628       MI->eraseFromParent();
636       VNT.insert(MI, CurrVN++);
637       Exps.push_back(MI);