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Diffstat (limited to 'contrib/llvm/lib/CodeGen/LiveRangeEdit.cpp')
| -rw-r--r-- | contrib/llvm/lib/CodeGen/LiveRangeEdit.cpp | 327 |
1 files changed, 327 insertions, 0 deletions
diff --git a/contrib/llvm/lib/CodeGen/LiveRangeEdit.cpp b/contrib/llvm/lib/CodeGen/LiveRangeEdit.cpp new file mode 100644 index 000000000000..b385fb36bbf1 --- /dev/null +++ b/contrib/llvm/lib/CodeGen/LiveRangeEdit.cpp @@ -0,0 +1,327 @@ +//===--- 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 "LiveRangeEdit.h" +#include "VirtRegMap.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/Target/TargetInstrInfo.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/raw_ostream.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"); + +LiveInterval &LiveRangeEdit::createFrom(unsigned OldReg, + LiveIntervals &LIS, + VirtRegMap &VRM) { + MachineRegisterInfo &MRI = VRM.getRegInfo(); + unsigned VReg = MRI.createVirtualRegister(MRI.getRegClass(OldReg)); + 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, + const TargetInstrInfo &tii, + AliasAnalysis *aa) { + assert(DefMI && "Missing instruction"); + scannedRemattable_ = true; + if (!tii.isTriviallyReMaterializable(DefMI, aa)) + return false; + remattable_.insert(VNI); + return true; +} + +void LiveRangeEdit::scanRemattable(LiveIntervals &lis, + const TargetInstrInfo &tii, + AliasAnalysis *aa) { + for (LiveInterval::vni_iterator I = parent_.vni_begin(), + E = parent_.vni_end(); I != E; ++I) { + VNInfo *VNI = *I; + if (VNI->isUnused()) + continue; + MachineInstr *DefMI = lis.getInstructionFromIndex(VNI->def); + if (!DefMI) + continue; + checkRematerializable(VNI, DefMI, tii, aa); + } + scannedRemattable_ = true; +} + +bool LiveRangeEdit::anyRematerializable(LiveIntervals &lis, + const TargetInstrInfo &tii, + AliasAnalysis *aa) { + if (!scannedRemattable_) + scanRemattable(lis, tii, 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, + LiveIntervals &lis) { + OrigIdx = OrigIdx.getUseIndex(); + UseIdx = UseIdx.getUseIndex(); + for (unsigned i = 0, e = OrigMI->getNumOperands(); i != e; ++i) { + const MachineOperand &MO = OrigMI->getOperand(i); + if (!MO.isReg() || !MO.getReg() || MO.isDef()) + continue; + // Reserved registers are OK. + if (MO.isUndef() || !lis.hasInterval(MO.getReg())) + continue; + // We cannot depend on virtual registers in uselessRegs_. + if (uselessRegs_) + for (unsigned ui = 0, ue = uselessRegs_->size(); ui != ue; ++ui) + if ((*uselessRegs_)[ui]->reg == MO.getReg()) + return false; + + LiveInterval &li = lis.getInterval(MO.getReg()); + const VNInfo *OVNI = li.getVNInfoAt(OrigIdx); + if (!OVNI) + continue; + if (OVNI != li.getVNInfoAt(UseIdx)) + return false; + } + return true; +} + +bool LiveRangeEdit::canRematerializeAt(Remat &RM, + SlotIndex UseIdx, + bool cheapAsAMove, + LiveIntervals &lis) { + 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->getDesc().isAsCheapAsAMove()) + return false; + + // Verify that all used registers are available with the same values. + if (!allUsesAvailableAt(RM.OrigMI, DefIdx, UseIdx, lis)) + return false; + + return true; +} + +SlotIndex LiveRangeEdit::rematerializeAt(MachineBasicBlock &MBB, + MachineBasicBlock::iterator MI, + unsigned DestReg, + const Remat &RM, + LiveIntervals &lis, + const TargetInstrInfo &tii, + 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) + .getDefIndex(); +} + +void LiveRangeEdit::eraseVirtReg(unsigned Reg, LiveIntervals &LIS) { + if (delegate_ && delegate_->LRE_CanEraseVirtReg(Reg)) + LIS.removeInterval(Reg); +} + +bool LiveRangeEdit::foldAsLoad(LiveInterval *LI, + SmallVectorImpl<MachineInstr*> &Dead, + MachineRegisterInfo &MRI, + LiveIntervals &LIS, + const TargetInstrInfo &TII) { + 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->getDesc().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; + + 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, + LiveIntervals &LIS, VirtRegMap &VRM, + const TargetInstrInfo &TII) { + SetVector<LiveInterval*, + SmallVector<LiveInterval*, 8>, + SmallPtrSet<LiveInterval*, 8> > ToShrink; + MachineRegisterInfo &MRI = VRM.getRegInfo(); + + 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).getDefIndex(); + + // 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); + + // 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)) + 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 (delegate_) + delegate_->LRE_WillShrinkVirtReg(LI.reg); + LI.removeValNo(VNI); + if (LI.empty()) { + ToShrink.remove(&LI); + eraseVirtReg(Reg, LIS); + } + } + } + } + + if (delegate_) + delegate_->LRE_WillEraseInstruction(MI); + LIS.RemoveMachineInstrFromMaps(MI); + MI->eraseFromParent(); + ++NumDCEDeleted; + } + + 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, MRI, LIS, TII)) + continue; + if (delegate_) + delegate_->LRE_WillShrinkVirtReg(LI->reg); + if (!LIS.shrinkToUses(LI, &Dead)) + 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.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, LIS, VRM)); + // 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 (delegate_) + delegate_->LRE_DidCloneVirtReg(Dups.back()->reg, LI->reg); + } + ConEQ.Distribute(&Dups[0], MRI); + } +} + +void LiveRangeEdit::calculateRegClassAndHint(MachineFunction &MF, + LiveIntervals &LIS, + const MachineLoopInfo &Loops) { + VirtRegAuxInfo VRAI(MF, LIS, Loops); + for (iterator I = begin(), E = end(); I != E; ++I) { + LiveInterval &LI = **I; + VRAI.CalculateRegClass(LI.reg); + VRAI.CalculateWeightAndHint(LI); + } +} |