-/// PropagateBackward - Traverse backward and look for the definition of
-/// OldReg. If it can successfully update all of the references with NewReg,
-/// do so and return true.
-bool StackSlotColoring::PropagateBackward(MachineBasicBlock::iterator MII,
- MachineBasicBlock *MBB,
- unsigned OldReg, unsigned NewReg) {
- if (MII == MBB->begin())
- return false;
-
- SmallVector<MachineOperand*, 4> Uses;
- SmallVector<MachineOperand*, 4> Refs;
- while (--MII != MBB->begin()) {
- bool FoundDef = false; // Not counting 2address def.
-
- Uses.clear();
- const MCInstrDesc &MCID = MII->getDesc();
- for (unsigned i = 0, e = MII->getNumOperands(); i != e; ++i) {
- MachineOperand &MO = MII->getOperand(i);
- if (!MO.isReg())
- continue;
- unsigned Reg = MO.getReg();
- if (Reg == 0)
- continue;
- if (Reg == OldReg) {
- if (MO.isImplicit())
- return false;
-
- // Abort the use is actually a sub-register def. We don't have enough
- // information to figure out if it is really legal.
- if (MO.getSubReg() || MII->isSubregToReg())
- return false;
-
- const TargetRegisterClass *RC = TII->getRegClass(MCID, i, TRI);
- if (RC && !RC->contains(NewReg))
- return false;
-
- if (MO.isUse()) {
- Uses.push_back(&MO);
- } else {
- Refs.push_back(&MO);
- if (!MII->isRegTiedToUseOperand(i))
- FoundDef = true;
- }
- } else if (TRI->regsOverlap(Reg, NewReg)) {
- return false;
- } else if (TRI->regsOverlap(Reg, OldReg)) {
- if (!MO.isUse() || !MO.isKill())
- return false;
- }
- }
-
- if (FoundDef) {
- // Found non-two-address def. Stop here.
- for (unsigned i = 0, e = Refs.size(); i != e; ++i)
- Refs[i]->setReg(NewReg);
- return true;
- }
-
- // Two-address uses must be updated as well.
- for (unsigned i = 0, e = Uses.size(); i != e; ++i)
- Refs.push_back(Uses[i]);
- }
- return false;
-}
-
-/// PropagateForward - Traverse forward and look for the kill of OldReg. If
-/// it can successfully update all of the uses with NewReg, do so and
-/// return true.
-bool StackSlotColoring::PropagateForward(MachineBasicBlock::iterator MII,
- MachineBasicBlock *MBB,
- unsigned OldReg, unsigned NewReg) {
- if (MII == MBB->end())
- return false;
-
- SmallVector<MachineOperand*, 4> Uses;
- while (++MII != MBB->end()) {
- bool FoundKill = false;
- const MCInstrDesc &MCID = MII->getDesc();
- for (unsigned i = 0, e = MII->getNumOperands(); i != e; ++i) {
- MachineOperand &MO = MII->getOperand(i);
- if (!MO.isReg())
- continue;
- unsigned Reg = MO.getReg();
- if (Reg == 0)
- continue;
- if (Reg == OldReg) {
- if (MO.isDef() || MO.isImplicit())
- return false;
-
- // Abort the use is actually a sub-register use. We don't have enough
- // information to figure out if it is really legal.
- if (MO.getSubReg())
- return false;
-
- const TargetRegisterClass *RC = TII->getRegClass(MCID, i, TRI);
- if (RC && !RC->contains(NewReg))
- return false;
- if (MO.isKill())
- FoundKill = true;
-
- Uses.push_back(&MO);
- } else if (TRI->regsOverlap(Reg, NewReg) ||
- TRI->regsOverlap(Reg, OldReg))
- return false;
- }
- if (FoundKill) {
- for (unsigned i = 0, e = Uses.size(); i != e; ++i)
- Uses[i]->setReg(NewReg);
- return true;
- }
- }
- return false;
-}
-
-/// UnfoldAndRewriteInstruction - Rewrite specified instruction by unfolding
-/// folded memory references and replacing those references with register
-/// references instead.
-void
-StackSlotColoring::UnfoldAndRewriteInstruction(MachineInstr *MI, int OldFI,
- unsigned Reg,
- const TargetRegisterClass *RC,
- SmallSet<unsigned, 4> &Defs,
- MachineFunction &MF) {
- MachineBasicBlock *MBB = MI->getParent();
- if (unsigned DstReg = TII->isLoadFromStackSlot(MI, OldFI)) {
- if (PropagateForward(MI, MBB, DstReg, Reg)) {
- DEBUG(dbgs() << "Eliminated load: ");
- DEBUG(MI->dump());
- ++NumLoadElim;
- } else {
- BuildMI(*MBB, MI, MI->getDebugLoc(), TII->get(TargetOpcode::COPY),
- DstReg).addReg(Reg);
- ++NumRegRepl;
- }
-
- if (!Defs.count(Reg)) {
- // If this is the first use of Reg in this MBB and it wasn't previously
- // defined in MBB, add it to livein.
- MBB->addLiveIn(Reg);
- Defs.insert(Reg);
- }
- } else if (unsigned SrcReg = TII->isStoreToStackSlot(MI, OldFI)) {
- if (MI->killsRegister(SrcReg) && PropagateBackward(MI, MBB, SrcReg, Reg)) {
- DEBUG(dbgs() << "Eliminated store: ");
- DEBUG(MI->dump());
- ++NumStoreElim;
- } else {
- BuildMI(*MBB, MI, MI->getDebugLoc(), TII->get(TargetOpcode::COPY), Reg)
- .addReg(SrcReg);
- ++NumRegRepl;
- }
-
- // Remember reg has been defined in MBB.
- Defs.insert(Reg);
- } else {
- SmallVector<MachineInstr*, 4> NewMIs;
- bool Success = TII->unfoldMemoryOperand(MF, MI, Reg, false, false, NewMIs);
- (void)Success; // Silence compiler warning.
- assert(Success && "Failed to unfold!");
- MachineInstr *NewMI = NewMIs[0];
- MBB->insert(MI, NewMI);
- ++NumRegRepl;
-
- if (NewMI->readsRegister(Reg)) {
- if (!Defs.count(Reg))
- // If this is the first use of Reg in this MBB and it wasn't previously
- // defined in MBB, add it to livein.
- MBB->addLiveIn(Reg);
- Defs.insert(Reg);
- }
- }
- MBB->erase(MI);
-}