diff --git a/llvm/lib/CodeGen/PHIElimination.cpp b/llvm/lib/CodeGen/PHIElimination.cpp index 3f459b701293..b952aab16f7d 100644 --- a/llvm/lib/CodeGen/PHIElimination.cpp +++ b/llvm/lib/CodeGen/PHIElimination.cpp @@ -19,6 +19,7 @@ #include "llvm/ADT/STLExtras.h" #include "llvm/ADT/SmallPtrSet.h" #include "llvm/ADT/Statistic.h" +#include "llvm/CodeGen/LiveIntervalAnalysis.h" #include "llvm/CodeGen/LiveVariables.h" #include "llvm/CodeGen/MachineDominators.h" #include "llvm/CodeGen/MachineInstr.h" @@ -43,6 +44,7 @@ namespace { class PHIElimination : public MachineFunctionPass { MachineRegisterInfo *MRI; // Machine register information LiveVariables *LV; + LiveIntervals *LIS; public: static char ID; // Pass identification, replacement for typeid @@ -104,6 +106,7 @@ INITIALIZE_PASS_END(PHIElimination, "phi-node-elimination", void PHIElimination::getAnalysisUsage(AnalysisUsage &AU) const { AU.addPreserved(); + AU.addPreserved(); AU.addPreserved(); AU.addPreserved(); MachineFunctionPass::getAnalysisUsage(AU); @@ -112,14 +115,16 @@ void PHIElimination::getAnalysisUsage(AnalysisUsage &AU) const { bool PHIElimination::runOnMachineFunction(MachineFunction &MF) { MRI = &MF.getRegInfo(); LV = getAnalysisIfAvailable(); + LIS = getAnalysisIfAvailable(); bool Changed = false; // This pass takes the function out of SSA form. MRI->leaveSSA(); - // Split critical edges to help the coalescer - if (!DisableEdgeSplitting && LV) { + // Split critical edges to help the coalescer. This does not yet support + // updating LiveIntervals, so we disable it. + if (!DisableEdgeSplitting && LV && !LIS) { MachineLoopInfo *MLI = getAnalysisIfAvailable(); for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) Changed |= SplitPHIEdges(MF, *I, MLI); @@ -137,19 +142,28 @@ bool PHIElimination::runOnMachineFunction(MachineFunction &MF) { E = ImpDefs.end(); I != E; ++I) { MachineInstr *DefMI = *I; unsigned DefReg = DefMI->getOperand(0).getReg(); - if (MRI->use_nodbg_empty(DefReg)) + if (MRI->use_nodbg_empty(DefReg)) { + if (LIS) + LIS->RemoveMachineInstrFromMaps(DefMI); DefMI->eraseFromParent(); + } } // Clean up the lowered PHI instructions. for (LoweredPHIMap::iterator I = LoweredPHIs.begin(), E = LoweredPHIs.end(); - I != E; ++I) + I != E; ++I) { + if (LIS) + LIS->RemoveMachineInstrFromMaps(I->first); MF.DeleteMachineInstr(I->first); + } LoweredPHIs.clear(); ImpDefs.clear(); VRegPHIUseCount.clear(); + if (LIS) + MF.verify(this, "After PHI elimination"); + return Changed; } @@ -278,6 +292,47 @@ void PHIElimination::LowerPHINode(MachineBasicBlock &MBB, } } + // Update LiveIntervals for the new copy or implicit def. + if (LIS) { + MachineInstr *NewInstr = prior(AfterPHIsIt); + LIS->InsertMachineInstrInMaps(NewInstr); + + SlotIndex MBBStartIndex = LIS->getMBBStartIdx(&MBB); + SlotIndex DestCopyIndex = LIS->getInstructionIndex(NewInstr); + if (IncomingReg) { + // Add the region from the beginning of MBB to the copy instruction to + // IncomingReg's live interval. + LiveInterval &IncomingLI = LIS->getOrCreateInterval(IncomingReg); + VNInfo *IncomingVNI = IncomingLI.getVNInfoAt(MBBStartIndex); + if (!IncomingVNI) + IncomingVNI = IncomingLI.getNextValue(MBBStartIndex, + LIS->getVNInfoAllocator()); + IncomingLI.addRange(LiveRange(MBBStartIndex, + DestCopyIndex.getRegSlot(), + IncomingVNI)); + } + + LiveInterval &DestLI = LIS->getOrCreateInterval(DestReg); + if (NewInstr->getOperand(0).isDead()) { + // A dead PHI's live range begins and ends at the start of the MBB, but + // the lowered copy, which will still be dead, needs to begin and end at + // the copy instruction. + VNInfo *OrigDestVNI = DestLI.getVNInfoAt(MBBStartIndex); + assert(OrigDestVNI && "PHI destination should be live at block entry."); + DestLI.removeRange(MBBStartIndex, MBBStartIndex.getDeadSlot()); + DestLI.createDeadDef(DestCopyIndex.getRegSlot(), + LIS->getVNInfoAllocator()); + DestLI.removeValNo(OrigDestVNI); + } else { + // Otherwise, remove the region from the beginning of MBB to the copy + // instruction from DestReg's live interval. + DestLI.removeRange(MBBStartIndex, DestCopyIndex.getRegSlot()); + VNInfo *DestVNI = DestLI.getVNInfoAt(DestCopyIndex.getRegSlot()); + assert(DestVNI && "PHI destination should be live at its definition."); + DestVNI->def = DestCopyIndex.getRegSlot(); + } + } + // Adjust the VRegPHIUseCount map to account for the removal of this PHI node. for (unsigned i = 1; i != MPhi->getNumOperands(); i += 2) --VRegPHIUseCount[BBVRegPair(MPhi->getOperand(i+1).getMBB()->getNumber(), @@ -310,45 +365,44 @@ void PHIElimination::LowerPHINode(MachineBasicBlock &MBB, findPHICopyInsertPoint(&opBlock, &MBB, SrcReg); // Insert the copy. + MachineInstr *NewSrcInstr = 0; if (!reusedIncoming && IncomingReg) { if (SrcUndef) { // The source register is undefined, so there is no need for a real // COPY, but we still need to ensure joint dominance by defs. // Insert an IMPLICIT_DEF instruction. - BuildMI(opBlock, InsertPos, MPhi->getDebugLoc(), - TII->get(TargetOpcode::IMPLICIT_DEF), IncomingReg); + NewSrcInstr = BuildMI(opBlock, InsertPos, MPhi->getDebugLoc(), + TII->get(TargetOpcode::IMPLICIT_DEF), + IncomingReg); // Clean up the old implicit-def, if there even was one. if (MachineInstr *DefMI = MRI->getVRegDef(SrcReg)) if (DefMI->isImplicitDef()) ImpDefs.insert(DefMI); } else { - BuildMI(opBlock, InsertPos, MPhi->getDebugLoc(), - TII->get(TargetOpcode::COPY), IncomingReg) - .addReg(SrcReg, 0, SrcSubReg); + NewSrcInstr = BuildMI(opBlock, InsertPos, MPhi->getDebugLoc(), + TII->get(TargetOpcode::COPY), IncomingReg) + .addReg(SrcReg, 0, SrcSubReg); } } - // Now update live variable information if we have it. Otherwise we're done - if (SrcUndef || !LV) continue; + // We only need to update the LiveVariables kill of SrcReg if this was the + // last PHI use of SrcReg to be lowered on this CFG edge and it is not live + // out of the predecessor. We can also ignore undef sources. + if (LV && !SrcUndef && + !VRegPHIUseCount[BBVRegPair(opBlock.getNumber(), SrcReg)] && + !LV->isLiveOut(SrcReg, opBlock)) { + // We want to be able to insert a kill of the register if this PHI (aka, + // the copy we just inserted) is the last use of the source value. Live + // variable analysis conservatively handles this by saying that the value + // is live until the end of the block the PHI entry lives in. If the value + // really is dead at the PHI copy, there will be no successor blocks which + // have the value live-in. - // We want to be able to insert a kill of the register if this PHI (aka, the - // copy we just inserted) is the last use of the source value. Live - // variable analysis conservatively handles this by saying that the value is - // live until the end of the block the PHI entry lives in. If the value - // really is dead at the PHI copy, there will be no successor blocks which - // have the value live-in. + // Okay, if we now know that the value is not live out of the block, we + // can add a kill marker in this block saying that it kills the incoming + // value! - // Also check to see if this register is in use by another PHI node which - // has not yet been eliminated. If so, it will be killed at an appropriate - // point later. - - // Is it used by any PHI instructions in this block? - bool ValueIsUsed = VRegPHIUseCount[BBVRegPair(opBlock.getNumber(), SrcReg)]; - - // Okay, if we now know that the value is not live out of the block, we can - // add a kill marker in this block saying that it kills the incoming value! - if (!ValueIsUsed && !LV->isLiveOut(SrcReg, opBlock)) { // In our final twist, we have to decide which instruction kills the // register. In most cases this is the copy, however, terminator // instructions at the end of the block may also use the value. In this @@ -389,11 +443,70 @@ void PHIElimination::LowerPHINode(MachineBasicBlock &MBB, unsigned opBlockNum = opBlock.getNumber(); LV->getVarInfo(SrcReg).AliveBlocks.reset(opBlockNum); } + + if (LIS) { + if (NewSrcInstr) { + LIS->InsertMachineInstrInMaps(NewSrcInstr); + LIS->addLiveRangeToEndOfBlock(IncomingReg, NewSrcInstr); + } + + if (!SrcUndef && + !VRegPHIUseCount[BBVRegPair(opBlock.getNumber(), SrcReg)]) { + LiveInterval &SrcLI = LIS->getInterval(SrcReg); + + bool isLiveOut = false; + for (MachineBasicBlock::succ_iterator SI = opBlock.succ_begin(), + SE = opBlock.succ_end(); SI != SE; ++SI) { + if (SrcLI.liveAt(LIS->getMBBStartIdx(*SI))) { + isLiveOut = true; + break; + } + } + + if (!isLiveOut) { + MachineBasicBlock::iterator KillInst = opBlock.end(); + MachineBasicBlock::iterator FirstTerm = opBlock.getFirstTerminator(); + for (MachineBasicBlock::iterator Term = FirstTerm; + Term != opBlock.end(); ++Term) { + if (Term->readsRegister(SrcReg)) + KillInst = Term; + } + + if (KillInst == opBlock.end()) { + // No terminator uses the register. + + if (reusedIncoming || !IncomingReg) { + // We may have to rewind a bit if we didn't just insert a copy. + KillInst = FirstTerm; + while (KillInst != opBlock.begin()) { + --KillInst; + if (KillInst->isDebugValue()) + continue; + if (KillInst->readsRegister(SrcReg)) + break; + } + } else { + // We just inserted this copy. + KillInst = prior(InsertPos); + } + } + assert(KillInst->readsRegister(SrcReg) && + "Cannot find kill instruction"); + + SlotIndex LastUseIndex = LIS->getInstructionIndex(KillInst); + SrcLI.removeRange(LastUseIndex.getRegSlot(), + LIS->getMBBEndIdx(&opBlock)); + } + } + } } // Really delete the PHI instruction now, if it is not in the LoweredPHIs map. - if (reusedIncoming || !IncomingReg) + if (reusedIncoming || !IncomingReg) { + if (LIS) + LIS->RemoveMachineInstrFromMaps(MPhi); MF.DeleteMachineInstr(MPhi); + } } /// analyzePHINodes - Gather information about the PHI nodes in here. In