+/// Find all live intervals that need to shrink, then remove the instruction.
+void LiveRangeEdit::eliminateDeadDef(MachineInstr *MI, ToShrinkSet &ToShrink) {
+ assert(MI->allDefsAreDead() && "Def isn't really dead");
+ SlotIndex Idx = LIS.getInstructionIndex(MI).getRegSlot();
+
+ // Never delete a bundled instruction.
+ if (MI->isBundled()) {
+ return;
+ }
+ // Never delete inline asm.
+ if (MI->isInlineAsm()) {
+ DEBUG(dbgs() << "Won't delete: " << Idx << '\t' << *MI);
+ return;
+ }
+
+ // Use the same criteria as DeadMachineInstructionElim.
+ bool SawStore = false;
+ if (!MI->isSafeToMove(&TII, 0, SawStore)) {
+ DEBUG(dbgs() << "Can't delete: " << Idx << '\t' << *MI);
+ return;
+ }
+
+ DEBUG(dbgs() << "Deleting dead def " << Idx << '\t' << *MI);
+
+ // Collect virtual registers to be erased after MI is gone.
+ SmallVector<unsigned, 8> RegsToErase;
+ bool ReadsPhysRegs = false;
+
+ // Check for live intervals that may shrink
+ for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
+ MOE = MI->operands_end(); MOI != MOE; ++MOI) {
+ if (!MOI->isReg())
+ continue;
+ unsigned Reg = MOI->getReg();
+ if (!TargetRegisterInfo::isVirtualRegister(Reg)) {
+ // Check if MI reads any unreserved physregs.
+ if (Reg && MOI->readsReg() && !MRI.isReserved(Reg))
+ ReadsPhysRegs = true;
+ else if (MOI->isDef()) {
+ for (MCRegUnitIterator Units(Reg, MRI.getTargetRegisterInfo());
+ Units.isValid(); ++Units) {
+ if (LiveInterval *LI = LIS.getCachedRegUnit(*Units)) {
+ if (VNInfo *VNI = LI->getVNInfoAt(Idx))
+ LI->removeValNo(VNI);
+ }
+ }
+ }
+ continue;
+ }
+ LiveInterval &LI = LIS.getInterval(Reg);
+
+ // Shrink read registers, unless it is likely to be expensive and
+ // unlikely to change anything. We typically don't want to shrink the
+ // PIC base register that has lots of uses everywhere.
+ // Always shrink COPY uses that probably come from live range splitting.
+ if (MI->readsVirtualRegister(Reg) &&
+ (MI->isCopy() || MOI->isDef() || MRI.hasOneNonDBGUse(Reg) ||
+ LI.killedAt(Idx)))
+ ToShrink.insert(&LI);
+
+ // Remove defined value.
+ if (MOI->isDef()) {
+ if (VNInfo *VNI = LI.getVNInfoAt(Idx)) {
+ if (TheDelegate)
+ TheDelegate->LRE_WillShrinkVirtReg(LI.reg);
+ LI.removeValNo(VNI);
+ if (LI.empty())
+ RegsToErase.push_back(Reg);
+ }
+ }
+ }
+
+ // Currently, we don't support DCE of physreg live ranges. If MI reads
+ // any unreserved physregs, don't erase the instruction, but turn it into
+ // a KILL instead. This way, the physreg live ranges don't end up
+ // dangling.
+ // FIXME: It would be better to have something like shrinkToUses() for
+ // physregs. That could potentially enable more DCE and it would free up
+ // the physreg. It would not happen often, though.
+ if (ReadsPhysRegs) {
+ MI->setDesc(TII.get(TargetOpcode::KILL));
+ // Remove all operands that aren't physregs.
+ for (unsigned i = MI->getNumOperands(); i; --i) {
+ const MachineOperand &MO = MI->getOperand(i-1);
+ if (MO.isReg() && TargetRegisterInfo::isPhysicalRegister(MO.getReg()))
+ continue;
+ MI->RemoveOperand(i-1);
+ }
+ DEBUG(dbgs() << "Converted physregs to:\t" << *MI);
+ } else {
+ if (TheDelegate)
+ TheDelegate->LRE_WillEraseInstruction(MI);
+ LIS.RemoveMachineInstrFromMaps(MI);
+ MI->eraseFromParent();
+ ++NumDCEDeleted;
+ }
+
+ // Erase any virtregs that are now empty and unused. There may be <undef>
+ // uses around. Keep the empty live range in that case.
+ for (unsigned i = 0, e = RegsToErase.size(); i != e; ++i) {
+ unsigned Reg = RegsToErase[i];
+ if (LIS.hasInterval(Reg) && MRI.reg_nodbg_empty(Reg)) {
+ ToShrink.remove(&LIS.getInterval(Reg));
+ eraseVirtReg(Reg);
+ }
+ }
+}
+
+void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
+ ArrayRef<unsigned> RegsBeingSpilled) {
+ ToShrinkSet ToShrink;
+
+ for (;;) {
+ // Erase all dead defs.
+ while (!Dead.empty())
+ eliminateDeadDef(Dead.pop_back_val(), ToShrink);
+
+ if (ToShrink.empty())
+ break;
+
+ // Shrink just one live interval. Then delete new dead defs.
+ LiveInterval *LI = ToShrink.back();
+ ToShrink.pop_back();
+ if (foldAsLoad(LI, Dead))
+ continue;
+ if (TheDelegate)
+ TheDelegate->LRE_WillShrinkVirtReg(LI->reg);
+ if (!LIS.shrinkToUses(LI, &Dead))
+ continue;
+
+ // Don't create new intervals for a register being spilled.
+ // The new intervals would have to be spilled anyway so its not worth it.
+ // Also they currently aren't spilled so creating them and not spilling
+ // them results in incorrect code.
+ bool BeingSpilled = false;
+ for (unsigned i = 0, e = RegsBeingSpilled.size(); i != e; ++i) {
+ if (LI->reg == RegsBeingSpilled[i]) {
+ BeingSpilled = true;
+ break;
+ }
+ }
+
+ if (BeingSpilled) continue;
+
+ // LI may have been separated, create new intervals.
+ LI->RenumberValues(LIS);
+ ConnectedVNInfoEqClasses ConEQ(LIS);
+ unsigned NumComp = ConEQ.Classify(LI);
+ if (NumComp <= 1)
+ continue;
+ ++NumFracRanges;
+ bool IsOriginal = VRM && VRM->getOriginal(LI->reg) == LI->reg;
+ DEBUG(dbgs() << NumComp << " components: " << *LI << '\n');
+ SmallVector<LiveInterval*, 8> Dups(1, LI);
+ for (unsigned i = 1; i != NumComp; ++i) {
+ Dups.push_back(&createFrom(LI->reg));
+ // If LI is an original interval that hasn't been split yet, make the new
+ // intervals their own originals instead of referring to LI. The original
+ // interval must contain all the split products, and LI doesn't.
+ if (IsOriginal)
+ VRM->setIsSplitFromReg(Dups.back()->reg, 0);
+ if (TheDelegate)
+ TheDelegate->LRE_DidCloneVirtReg(Dups.back()->reg, LI->reg);
+ }
+ ConEQ.Distribute(&Dups[0], MRI);
+ DEBUG({
+ for (unsigned i = 0; i != NumComp; ++i)
+ dbgs() << '\t' << *Dups[i] << '\n';
+ });
+ }
+}
+
+void
+LiveRangeEdit::calculateRegClassAndHint(MachineFunction &MF,
+ const MachineLoopInfo &Loops,
+ const MachineBlockFrequencyInfo &MBFI) {
+ VirtRegAuxInfo VRAI(MF, LIS, Loops, MBFI);
+ for (iterator I = begin(), E = end(); I != E; ++I) {
+ LiveInterval &LI = **I;
+ if (MRI.recomputeRegClass(LI.reg, MF.getTarget()))
+ DEBUG(dbgs() << "Inflated " << PrintReg(LI.reg) << " to "
+ << MRI.getRegClass(LI.reg)->getName() << '\n');
+ VRAI.CalculateWeightAndHint(LI);
+ }
+}