| //===-- LiveRangeEdit.cpp - Basic tools for editing a register live range -===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // The LiveRangeEdit class represents changes done to a virtual register when it |
| // is spilled or split. |
| //===----------------------------------------------------------------------===// |
| |
| #define DEBUG_TYPE "regalloc" |
| #include "llvm/CodeGen/LiveRangeEdit.h" |
| #include "llvm/ADT/SetVector.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/CodeGen/CalcSpillWeights.h" |
| #include "llvm/CodeGen/LiveIntervalAnalysis.h" |
| #include "llvm/CodeGen/MachineRegisterInfo.h" |
| #include "llvm/CodeGen/VirtRegMap.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/Target/TargetInstrInfo.h" |
| |
| using namespace llvm; |
| |
| STATISTIC(NumDCEDeleted, "Number of instructions deleted by DCE"); |
| STATISTIC(NumDCEFoldedLoads, "Number of single use loads folded after DCE"); |
| STATISTIC(NumFracRanges, "Number of live ranges fractured by DCE"); |
| |
| void LiveRangeEdit::Delegate::anchor() { } |
| |
| LiveInterval &LiveRangeEdit::createFrom(unsigned OldReg) { |
| unsigned VReg = MRI.createVirtualRegister(MRI.getRegClass(OldReg)); |
| if (VRM) { |
| VRM->grow(); |
| VRM->setIsSplitFromReg(VReg, VRM->getOriginal(OldReg)); |
| } |
| LiveInterval &LI = LIS.getOrCreateInterval(VReg); |
| NewRegs.push_back(&LI); |
| return LI; |
| } |
| |
| bool LiveRangeEdit::checkRematerializable(VNInfo *VNI, |
| const MachineInstr *DefMI, |
| AliasAnalysis *aa) { |
| assert(DefMI && "Missing instruction"); |
| ScannedRemattable = true; |
| if (!TII.isTriviallyReMaterializable(DefMI, aa)) |
| return false; |
| Remattable.insert(VNI); |
| return true; |
| } |
| |
| void LiveRangeEdit::scanRemattable(AliasAnalysis *aa) { |
| for (LiveInterval::vni_iterator I = getParent().vni_begin(), |
| E = getParent().vni_end(); I != E; ++I) { |
| VNInfo *VNI = *I; |
| if (VNI->isUnused()) |
| continue; |
| MachineInstr *DefMI = LIS.getInstructionFromIndex(VNI->def); |
| if (!DefMI) |
| continue; |
| checkRematerializable(VNI, DefMI, aa); |
| } |
| ScannedRemattable = true; |
| } |
| |
| bool LiveRangeEdit::anyRematerializable(AliasAnalysis *aa) { |
| if (!ScannedRemattable) |
| scanRemattable(aa); |
| return !Remattable.empty(); |
| } |
| |
| /// allUsesAvailableAt - Return true if all registers used by OrigMI at |
| /// OrigIdx are also available with the same value at UseIdx. |
| bool LiveRangeEdit::allUsesAvailableAt(const MachineInstr *OrigMI, |
| SlotIndex OrigIdx, |
| SlotIndex UseIdx) const { |
| OrigIdx = OrigIdx.getRegSlot(true); |
| UseIdx = UseIdx.getRegSlot(true); |
| for (unsigned i = 0, e = OrigMI->getNumOperands(); i != e; ++i) { |
| const MachineOperand &MO = OrigMI->getOperand(i); |
| if (!MO.isReg() || !MO.getReg() || !MO.readsReg()) |
| continue; |
| |
| // We can't remat physreg uses, unless it is a constant. |
| if (TargetRegisterInfo::isPhysicalRegister(MO.getReg())) { |
| if (MRI.isConstantPhysReg(MO.getReg(), *OrigMI->getParent()->getParent())) |
| continue; |
| return false; |
| } |
| |
| LiveInterval &li = LIS.getInterval(MO.getReg()); |
| const VNInfo *OVNI = li.getVNInfoAt(OrigIdx); |
| if (!OVNI) |
| continue; |
| |
| // Don't allow rematerialization immediately after the original def. |
| // It would be incorrect if OrigMI redefines the register. |
| // See PR14098. |
| if (SlotIndex::isSameInstr(OrigIdx, UseIdx)) |
| return false; |
| |
| if (OVNI != li.getVNInfoAt(UseIdx)) |
| return false; |
| } |
| return true; |
| } |
| |
| bool LiveRangeEdit::canRematerializeAt(Remat &RM, |
| SlotIndex UseIdx, |
| bool cheapAsAMove) { |
| assert(ScannedRemattable && "Call anyRematerializable first"); |
| |
| // Use scanRemattable info. |
| if (!Remattable.count(RM.ParentVNI)) |
| return false; |
| |
| // No defining instruction provided. |
| SlotIndex DefIdx; |
| if (RM.OrigMI) |
| DefIdx = LIS.getInstructionIndex(RM.OrigMI); |
| else { |
| DefIdx = RM.ParentVNI->def; |
| RM.OrigMI = LIS.getInstructionFromIndex(DefIdx); |
| assert(RM.OrigMI && "No defining instruction for remattable value"); |
| } |
| |
| // If only cheap remats were requested, bail out early. |
| if (cheapAsAMove && !RM.OrigMI->isAsCheapAsAMove()) |
| return false; |
| |
| // Verify that all used registers are available with the same values. |
| if (!allUsesAvailableAt(RM.OrigMI, DefIdx, UseIdx)) |
| return false; |
| |
| return true; |
| } |
| |
| SlotIndex LiveRangeEdit::rematerializeAt(MachineBasicBlock &MBB, |
| MachineBasicBlock::iterator MI, |
| unsigned DestReg, |
| const Remat &RM, |
| const TargetRegisterInfo &tri, |
| bool Late) { |
| assert(RM.OrigMI && "Invalid remat"); |
| TII.reMaterialize(MBB, MI, DestReg, 0, RM.OrigMI, tri); |
| Rematted.insert(RM.ParentVNI); |
| return LIS.getSlotIndexes()->insertMachineInstrInMaps(--MI, Late) |
| .getRegSlot(); |
| } |
| |
| void LiveRangeEdit::eraseVirtReg(unsigned Reg) { |
| if (TheDelegate && TheDelegate->LRE_CanEraseVirtReg(Reg)) |
| LIS.removeInterval(Reg); |
| } |
| |
| bool LiveRangeEdit::foldAsLoad(LiveInterval *LI, |
| SmallVectorImpl<MachineInstr*> &Dead) { |
| MachineInstr *DefMI = 0, *UseMI = 0; |
| |
| // Check that there is a single def and a single use. |
| for (MachineRegisterInfo::reg_nodbg_iterator I = MRI.reg_nodbg_begin(LI->reg), |
| E = MRI.reg_nodbg_end(); I != E; ++I) { |
| MachineOperand &MO = I.getOperand(); |
| MachineInstr *MI = MO.getParent(); |
| if (MO.isDef()) { |
| if (DefMI && DefMI != MI) |
| return false; |
| if (!MI->canFoldAsLoad()) |
| return false; |
| DefMI = MI; |
| } else if (!MO.isUndef()) { |
| if (UseMI && UseMI != MI) |
| return false; |
| // FIXME: Targets don't know how to fold subreg uses. |
| if (MO.getSubReg()) |
| return false; |
| UseMI = MI; |
| } |
| } |
| if (!DefMI || !UseMI) |
| return false; |
| |
| // Since we're moving the DefMI load, make sure we're not extending any live |
| // ranges. |
| if (!allUsesAvailableAt(DefMI, |
| LIS.getInstructionIndex(DefMI), |
| LIS.getInstructionIndex(UseMI))) |
| return false; |
| |
| // We also need to make sure it is safe to move the load. |
| // Assume there are stores between DefMI and UseMI. |
| bool SawStore = true; |
| if (!DefMI->isSafeToMove(&TII, 0, SawStore)) |
| return false; |
| |
| DEBUG(dbgs() << "Try to fold single def: " << *DefMI |
| << " into single use: " << *UseMI); |
| |
| SmallVector<unsigned, 8> Ops; |
| if (UseMI->readsWritesVirtualRegister(LI->reg, &Ops).second) |
| return false; |
| |
| MachineInstr *FoldMI = TII.foldMemoryOperand(UseMI, Ops, DefMI); |
| if (!FoldMI) |
| return false; |
| DEBUG(dbgs() << " folded: " << *FoldMI); |
| LIS.ReplaceMachineInstrInMaps(UseMI, FoldMI); |
| UseMI->eraseFromParent(); |
| DefMI->addRegisterDead(LI->reg, 0); |
| Dead.push_back(DefMI); |
| ++NumDCEFoldedLoads; |
| return true; |
| } |
| |
| void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead, |
| ArrayRef<unsigned> RegsBeingSpilled) { |
| SetVector<LiveInterval*, |
| SmallVector<LiveInterval*, 8>, |
| SmallPtrSet<LiveInterval*, 8> > ToShrink; |
| |
| for (;;) { |
| // Erase all dead defs. |
| while (!Dead.empty()) { |
| MachineInstr *MI = Dead.pop_back_val(); |
| assert(MI->allDefsAreDead() && "Def isn't really dead"); |
| SlotIndex Idx = LIS.getInstructionIndex(MI).getRegSlot(); |
| |
| // Never delete inline asm. |
| if (MI->isInlineAsm()) { |
| DEBUG(dbgs() << "Won't delete: " << Idx << '\t' << *MI); |
| continue; |
| } |
| |
| // Use the same criteria as DeadMachineInstructionElim. |
| bool SawStore = false; |
| if (!MI->isSafeToMove(&TII, 0, SawStore)) { |
| DEBUG(dbgs() << "Can't delete: " << Idx << '\t' << *MI); |
| continue; |
| } |
| |
| 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; |
| 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); |
| } |
| } |
| } |
| |
| 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) { |
| VirtRegAuxInfo VRAI(MF, LIS, Loops); |
| 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); |
| } |
| } |
