From 0f28c3f0c30769c1a96e5664eea4acbc48eed6a4 Mon Sep 17 00:00:00 2001 From: Rafael Espindola Date: Thu, 9 Jun 2011 22:53:47 +0000 Subject: [PATCH] Also consider phi nodes when deciding if a register is live out. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132814 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/TailDuplication.cpp | 44 +++++++++++++++++++++++++++++++---------- 1 file changed, 34 insertions(+), 10 deletions(-) diff --git a/lib/CodeGen/TailDuplication.cpp b/lib/CodeGen/TailDuplication.cpp index 93acd5826f..79c93def02 100644 --- a/lib/CodeGen/TailDuplication.cpp +++ b/lib/CodeGen/TailDuplication.cpp @@ -81,12 +81,14 @@ namespace { void ProcessPHI(MachineInstr *MI, MachineBasicBlock *TailBB, MachineBasicBlock *PredBB, DenseMap &LocalVRMap, - SmallVector, 4> &Copies); + SmallVector, 4> &Copies, + const DenseSet &UsedByPhi); void DuplicateInstruction(MachineInstr *MI, MachineBasicBlock *TailBB, MachineBasicBlock *PredBB, MachineFunction &MF, - DenseMap &LocalVRMap); + DenseMap &LocalVRMap, + const DenseSet &UsedByPhi); void UpdateSuccessorsPHIs(MachineBasicBlock *FromBB, bool isDead, SmallVector &TDBBs, SmallSetVector &Succs); @@ -293,6 +295,24 @@ static unsigned getPHISrcRegOpIdx(MachineInstr *MI, MachineBasicBlock *SrcBB) { return 0; } + +// Remember which registers are used by phis in this block. This is +// used to determine which registers are liveout while modifying the +// block (which is why we need to copy the information). +static void getRegsUsedByPHIs(const MachineBasicBlock &BB, + DenseSet *UsedByPhi) { + for(MachineBasicBlock::const_iterator I = BB.begin(), E = BB.end(); + I != E; ++I) { + const MachineInstr &MI = *I; + if (!MI.isPHI()) + break; + for (unsigned i = 1, e = MI.getNumOperands(); i != e; i += 2) { + unsigned SrcReg = MI.getOperand(i).getReg(); + UsedByPhi->insert(SrcReg); + } + } +} + /// AddSSAUpdateEntry - Add a definition and source virtual registers pair for /// SSA update. void TailDuplicatePass::AddSSAUpdateEntry(unsigned OrigReg, unsigned NewReg, @@ -315,7 +335,8 @@ void TailDuplicatePass::ProcessPHI(MachineInstr *MI, MachineBasicBlock *TailBB, MachineBasicBlock *PredBB, DenseMap &LocalVRMap, - SmallVector, 4> &Copies) { + SmallVector, 4> &Copies, + const DenseSet &RegsUsedByPhi) { unsigned DefReg = MI->getOperand(0).getReg(); unsigned SrcOpIdx = getPHISrcRegOpIdx(MI, PredBB); assert(SrcOpIdx && "Unable to find matching PHI source?"); @@ -327,7 +348,7 @@ void TailDuplicatePass::ProcessPHI(MachineInstr *MI, // available value liveout of the block. unsigned NewDef = MRI->createVirtualRegister(RC); Copies.push_back(std::make_pair(NewDef, SrcReg)); - if (isDefLiveOut(DefReg, TailBB, MRI)) + if (isDefLiveOut(DefReg, TailBB, MRI) || RegsUsedByPhi.count(DefReg)) AddSSAUpdateEntry(DefReg, NewDef, PredBB); // Remove PredBB from the PHI node. @@ -343,7 +364,8 @@ void TailDuplicatePass::DuplicateInstruction(MachineInstr *MI, MachineBasicBlock *TailBB, MachineBasicBlock *PredBB, MachineFunction &MF, - DenseMap &LocalVRMap) { + DenseMap &LocalVRMap, + const DenseSet &UsedByPhi) { MachineInstr *NewMI = TII->duplicate(MI, MF); for (unsigned i = 0, e = NewMI->getNumOperands(); i != e; ++i) { MachineOperand &MO = NewMI->getOperand(i); @@ -357,7 +379,7 @@ void TailDuplicatePass::DuplicateInstruction(MachineInstr *MI, unsigned NewReg = MRI->createVirtualRegister(RC); MO.setReg(NewReg); LocalVRMap.insert(std::make_pair(Reg, NewReg)); - if (isDefLiveOut(Reg, TailBB, MRI)) + if (isDefLiveOut(Reg, TailBB, MRI) || UsedByPhi.count(Reg)) AddSSAUpdateEntry(Reg, NewReg, PredBB); } else { DenseMap::iterator VI = LocalVRMap.find(Reg); @@ -531,6 +553,8 @@ TailDuplicatePass::TailDuplicate(MachineBasicBlock *TailBB, MachineFunction &MF, bool Changed = false; SmallSetVector Preds(TailBB->pred_begin(), TailBB->pred_end()); + DenseSet UsedByPhi; + getRegsUsedByPHIs(*TailBB, &UsedByPhi); for (SmallSetVector::iterator PI = Preds.begin(), PE = Preds.end(); PI != PE; ++PI) { MachineBasicBlock *PredBB = *PI; @@ -570,11 +594,11 @@ TailDuplicatePass::TailDuplicate(MachineBasicBlock *TailBB, MachineFunction &MF, if (MI->isPHI()) { // Replace the uses of the def of the PHI with the register coming // from PredBB. - ProcessPHI(MI, TailBB, PredBB, LocalVRMap, CopyInfos); + ProcessPHI(MI, TailBB, PredBB, LocalVRMap, CopyInfos, UsedByPhi); } else { // Replace def of virtual registers with new registers, and update // uses with PHI source register or the new registers. - DuplicateInstruction(MI, TailBB, PredBB, MF, LocalVRMap); + DuplicateInstruction(MI, TailBB, PredBB, MF, LocalVRMap, UsedByPhi); } } MachineBasicBlock::iterator Loc = PredBB->getFirstTerminator(); @@ -620,7 +644,7 @@ TailDuplicatePass::TailDuplicate(MachineBasicBlock *TailBB, MachineFunction &MF, // Replace the uses of the def of the PHI with the register coming // from PredBB. MachineInstr *MI = &*I++; - ProcessPHI(MI, TailBB, PrevBB, LocalVRMap, CopyInfos); + ProcessPHI(MI, TailBB, PrevBB, LocalVRMap, CopyInfos, UsedByPhi); if (MI->getParent()) MI->eraseFromParent(); } @@ -630,7 +654,7 @@ TailDuplicatePass::TailDuplicate(MachineBasicBlock *TailBB, MachineFunction &MF, // Replace def of virtual registers with new registers, and update // uses with PHI source register or the new registers. MachineInstr *MI = &*I++; - DuplicateInstruction(MI, TailBB, PrevBB, MF, LocalVRMap); + DuplicateInstruction(MI, TailBB, PrevBB, MF, LocalVRMap, UsedByPhi); MI->eraseFromParent(); } MachineBasicBlock::iterator Loc = PrevBB->getFirstTerminator(); -- 2.11.4.GIT