1 //===-- LiveRangeEdit.cpp - Basic tools for editing a register live range -===//
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 // The LiveRangeEdit class represents changes done to a virtual register when it
11 //===----------------------------------------------------------------------===//
29 STATISTIC(NumFracRanges,        "Number of live ranges fractured by DCE");
38     VRM->setIsSplitFromReg(VReg, VRM->getOriginal(OldReg));  in createEmptyIntervalFrom()
41   if (Parent && !Parent->isSpillable())  in createEmptyIntervalFrom()
45     // the main range here---it will be constructed later after the subranges  in createEmptyIntervalFrom()
58     VRM->setIsSplitFromReg(VReg, VRM->getOriginal(OldReg));  in createFrom()
66   if (Parent && !Parent->isSpillable())  in createFrom()
83     if (VNI->isUnused())  in scanRemattable()
85     Register Original = VRM->getOriginal(getReg());  in scanRemattable()
87     VNInfo *OrigVNI = OrigLI.getVNInfoAt(VNI->def);  in scanRemattable()
90     MachineInstr *DefMI = LIS.getInstructionFromIndex(OrigVNI->def);  in scanRemattable()
104 /// allUsesAvailableAt - Return true if all registers used by OrigMI at
111   for (const MachineOperand &MO : OrigMI->operands()) {  in allUsesAvailableAt()
115     // We can't remat physreg uses, unless it is a constant or target wants  in allUsesAvailableAt()
137     // Check that subrange is live at UseIdx.  in allUsesAvailableAt()
141       LaneBitmask LM = SubReg ? TRI->getSubRegIndexLaneMask(SubReg)  in allUsesAvailableAt()
193   (*--MI).clearRegisterDeads(DestReg);  in rematerializeAt()
199   return LIS.getSlotIndexes()->insertMachineInstrInMaps(*MI, Late).getRegSlot();  in rematerializeAt()
203   if (TheDelegate && TheDelegate->LRE_CanEraseVirtReg(Reg))  in eraseVirtReg()
211   // Check that there is a single def and a single use.  in foldAsLoad()
212   for (MachineOperand &MO : MRI.reg_nodbg_operands(LI->reg())) {  in foldAsLoad()
217       if (!MI->canFoldAsLoad())  in foldAsLoad()
232   // Since we're moving the DefMI load, make sure we're not extending any live  in foldAsLoad()
241   if (!DefMI->isSafeToMove(nullptr, SawStore))  in foldAsLoad()
248   if (UseMI->readsWritesVirtualRegister(LI->reg(), &Ops).second)  in foldAsLoad()
257   if (UseMI->shouldUpdateCallSiteInfo())  in foldAsLoad()
258     UseMI->getMF()->moveCallSiteInfo(UseMI, FoldMI);  in foldAsLoad()
259   UseMI->eraseFromParent();  in foldAsLoad()
260   DefMI->addRegisterDead(LI->reg(), nullptr);  in foldAsLoad()
282 /// Find all live intervals that need to shrink, then remove the instruction.
284   assert(MI->allDefsAreDead() && "Def isn't really dead");  in eliminateDeadDef()
287   // Never delete a bundled instruction.  in eliminateDeadDef()
288   if (MI->isBundled()) {  in eliminateDeadDef()
296   if (MI->isInlineAsm()) {  in eliminateDeadDef()
303   if (!MI->isSafeToMove(nullptr, SawStore)) {  in eliminateDeadDef()
319   if (VRM && MI->getOperand(0).isReg() && MI->getOperand(0).isDef() &&  in eliminateDeadDef()
320       MI->getDesc().getNumDefs() == 1) {  in eliminateDeadDef()
321     Dest = MI->getOperand(0).getReg();  in eliminateDeadDef()
322     DestSubReg = MI->getOperand(0).getSubReg();  in eliminateDeadDef()
323     Register Original = VRM->getOriginal(Dest);  in eliminateDeadDef()
326     // The original live-range may have been shrunk to  in eliminateDeadDef()
327     // an empty live-range. It happens when it is dead, but  in eliminateDeadDef()
328     // we still keep it around to be able to rematerialize  in eliminateDeadDef()
331       isOrigDef = SlotIndex::isSameInstr(OrigVNI->def, Idx);  in eliminateDeadDef()
336   // Check for live intervals that may shrink  in eliminateDeadDef()
337   for (const MachineOperand &MO : MI->operands()) {  in eliminateDeadDef()
354     // Always shrink COPY uses that probably come from live range splitting.  in eliminateDeadDef()
355     if ((MI->readsVirtualRegister(Reg) &&  in eliminateDeadDef()
365         TheDelegate->LRE_WillShrinkVirtReg(LI.reg());  in eliminateDeadDef()
372   // Currently, we don't support DCE of physreg live ranges. If MI reads  in eliminateDeadDef()
374   // a KILL instead. This way, the physreg live ranges don't end up  in eliminateDeadDef()
380     MI->setDesc(TII.get(TargetOpcode::KILL));  in eliminateDeadDef()
382     for (unsigned i = MI->getNumOperands(); i; --i) {  in eliminateDeadDef()
383       const MachineOperand &MO = MI->getOperand(i-1);  in eliminateDeadDef()
386       MI->removeOperand(i-1);  in eliminateDeadDef()
391     // don't delete the inst. Replace the dest with a new reg, and keep  in eliminateDeadDef()
397     // and later result in an invalid live segment end.  in eliminateDeadDef()
408             Alloc, TRI->getSubRegIndexLaneMask(DestSubReg));  in eliminateDeadDef()
409         SR->addSegment(LiveInterval::Segment(Idx, Idx.getDeadSlot(),  in eliminateDeadDef()
410                                              SR->getNextValue(Idx, Alloc)));  in eliminateDeadDef()
414       DeadRemats->insert(MI);  in eliminateDeadDef()
416       MI->substituteRegister(Dest, NewLI.reg(), 0, TRI);  in eliminateDeadDef()
417       assert(MI->registerDefIsDead(NewLI.reg(), &TRI));  in eliminateDeadDef()
420         TheDelegate->LRE_WillEraseInstruction(MI);  in eliminateDeadDef()
422       MI->eraseFromParent();  in eliminateDeadDef()
428   // uses around. Keep the empty live range in that case.  in eliminateDeadDef()
449     // Shrink just one live interval. Then delete new dead defs.  in eliminateDeadDefs()
453     Register VReg = LI->reg();  in eliminateDeadDefs()
455       TheDelegate->LRE_WillShrinkVirtReg(VReg);  in eliminateDeadDefs()
459     // Don't create new intervals for a register being spilled.  in eliminateDeadDefs()
467     LI->RenumberValues();  in eliminateDeadDefs()
473     Register Original = VRM ? VRM->getOriginal(VReg) : Register();  in eliminateDeadDefs()
479         VRM->setIsSplitFromReg(SplitLI->reg(), Original);  in eliminateDeadDefs()
481         TheDelegate->LRE_DidCloneVirtReg(SplitLI->reg(), VReg);  in eliminateDeadDefs()
486 // Keep track of new virtual registers created via
491     VRM->grow();  in MRI_NoteNewVirtualRegister()
504                << TRI->getRegClassName(MRI.getRegClass(LI.reg())) << '\n';  in calculateRegClassAndHint()