diff --git a/llvm/lib/CodeGen/TailDuplication.cpp b/llvm/lib/CodeGen/TailDuplication.cpp index 95ce2a664892..6b801cbf6e1e 100644 --- a/llvm/lib/CodeGen/TailDuplication.cpp +++ b/llvm/lib/CodeGen/TailDuplication.cpp @@ -102,9 +102,15 @@ namespace { SmallVector &TDBBs, const DenseSet &RegsUsedByPhi, SmallVector &Copies); - bool TailDuplicate(MachineBasicBlock *TailBB, MachineFunction &MF, + bool TailDuplicate(MachineBasicBlock *TailBB, + bool IsSimple, + MachineFunction &MF, SmallVector &TDBBs, SmallVector &Copies); + bool TailDuplicateAndUpdate(MachineBasicBlock *MBB, + bool IsSimple, + MachineFunction &MF); + void RemoveDeadBlock(MachineBasicBlock *MBB); }; @@ -175,6 +181,109 @@ static void VerifyPHIs(MachineFunction &MF, bool CheckExtra) { } } +/// TailDuplicateAndUpdate - Tail duplicate the block and cleanup. +bool +TailDuplicatePass::TailDuplicateAndUpdate(MachineBasicBlock *MBB, + bool IsSimple, + MachineFunction &MF) { + // Save the successors list. + SmallSetVector Succs(MBB->succ_begin(), + MBB->succ_end()); + + SmallVector TDBBs; + SmallVector Copies; + if (!TailDuplicate(MBB, IsSimple, MF, TDBBs, Copies)) + return false; + + ++NumTails; + + SmallVector NewPHIs; + MachineSSAUpdater SSAUpdate(MF, &NewPHIs); + + // TailBB's immediate successors are now successors of those predecessors + // which duplicated TailBB. Add the predecessors as sources to the PHI + // instructions. + bool isDead = MBB->pred_empty() && !MBB->hasAddressTaken(); + if (PreRegAlloc) + UpdateSuccessorsPHIs(MBB, isDead, TDBBs, Succs); + + // If it is dead, remove it. + if (isDead) { + NumInstrDups -= MBB->size(); + RemoveDeadBlock(MBB); + ++NumDeadBlocks; + } + + // Update SSA form. + if (!SSAUpdateVRs.empty()) { + for (unsigned i = 0, e = SSAUpdateVRs.size(); i != e; ++i) { + unsigned VReg = SSAUpdateVRs[i]; + SSAUpdate.Initialize(VReg); + + // If the original definition is still around, add it as an available + // value. + MachineInstr *DefMI = MRI->getVRegDef(VReg); + MachineBasicBlock *DefBB = 0; + if (DefMI) { + DefBB = DefMI->getParent(); + SSAUpdate.AddAvailableValue(DefBB, VReg); + } + + // Add the new vregs as available values. + DenseMap::iterator LI = + SSAUpdateVals.find(VReg); + for (unsigned j = 0, ee = LI->second.size(); j != ee; ++j) { + MachineBasicBlock *SrcBB = LI->second[j].first; + unsigned SrcReg = LI->second[j].second; + SSAUpdate.AddAvailableValue(SrcBB, SrcReg); + } + + // Rewrite uses that are outside of the original def's block. + MachineRegisterInfo::use_iterator UI = MRI->use_begin(VReg); + while (UI != MRI->use_end()) { + MachineOperand &UseMO = UI.getOperand(); + MachineInstr *UseMI = &*UI; + ++UI; + if (UseMI->isDebugValue()) { + // SSAUpdate can replace the use with an undef. That creates + // a debug instruction that is a kill. + // FIXME: Should it SSAUpdate job to delete debug instructions + // instead of replacing the use with undef? + UseMI->eraseFromParent(); + continue; + } + if (UseMI->getParent() == DefBB && !UseMI->isPHI()) + continue; + SSAUpdate.RewriteUse(UseMO); + } + } + + SSAUpdateVRs.clear(); + SSAUpdateVals.clear(); + } + + // Eliminate some of the copies inserted by tail duplication to maintain + // SSA form. + for (unsigned i = 0, e = Copies.size(); i != e; ++i) { + MachineInstr *Copy = Copies[i]; + if (!Copy->isCopy()) + continue; + unsigned Dst = Copy->getOperand(0).getReg(); + unsigned Src = Copy->getOperand(1).getReg(); + MachineRegisterInfo::use_iterator UI = MRI->use_begin(Src); + if (++UI == MRI->use_end()) { + // Copy is the only use. Do trivial copy propagation here. + MRI->replaceRegWith(Dst, Src); + Copy->eraseFromParent(); + } + } + + if (NewPHIs.size()) + NumAddedPHIs += NewPHIs.size(); + + return true; +} + /// TailDuplicateBlocks - Look for small blocks that are unconditionally /// branched to and do not fall through. Tail-duplicate their instructions /// into their predecessors to eliminate (dynamic) branches. @@ -186,113 +295,22 @@ bool TailDuplicatePass::TailDuplicateBlocks(MachineFunction &MF) { VerifyPHIs(MF, true); } - SmallVector NewPHIs; - MachineSSAUpdater SSAUpdate(MF, &NewPHIs); - for (MachineFunction::iterator I = ++MF.begin(), E = MF.end(); I != E; ) { MachineBasicBlock *MBB = I++; if (NumTails == TailDupLimit) break; - // Save the successors list. - SmallSetVector Succs(MBB->succ_begin(), - MBB->succ_end()); + bool IsSimple = isSimpleBB(MBB); - SmallVector TDBBs; - SmallVector Copies; - if (!TailDuplicate(MBB, MF, TDBBs, Copies)) + if (!shouldTailDuplicate(MF, IsSimple, *MBB)) continue; - ++NumTails; - - // TailBB's immediate successors are now successors of those predecessors - // which duplicated TailBB. Add the predecessors as sources to the PHI - // instructions. - bool isDead = MBB->pred_empty() && !MBB->hasAddressTaken(); - if (PreRegAlloc) - UpdateSuccessorsPHIs(MBB, isDead, TDBBs, Succs); - - // If it is dead, remove it. - if (isDead) { - NumInstrDups -= MBB->size(); - RemoveDeadBlock(MBB); - ++NumDeadBlocks; - } - - // Update SSA form. - if (!SSAUpdateVRs.empty()) { - NewPHIs.clear(); - for (unsigned i = 0, e = SSAUpdateVRs.size(); i != e; ++i) { - unsigned VReg = SSAUpdateVRs[i]; - SSAUpdate.Initialize(VReg); - - // If the original definition is still around, add it as an available - // value. - MachineInstr *DefMI = MRI->getVRegDef(VReg); - MachineBasicBlock *DefBB = 0; - if (DefMI) { - DefBB = DefMI->getParent(); - SSAUpdate.AddAvailableValue(DefBB, VReg); - } - - // Add the new vregs as available values. - DenseMap::iterator LI = - SSAUpdateVals.find(VReg); - for (unsigned j = 0, ee = LI->second.size(); j != ee; ++j) { - MachineBasicBlock *SrcBB = LI->second[j].first; - unsigned SrcReg = LI->second[j].second; - SSAUpdate.AddAvailableValue(SrcBB, SrcReg); - } - - // Rewrite uses that are outside of the original def's block. - MachineRegisterInfo::use_iterator UI = MRI->use_begin(VReg); - while (UI != MRI->use_end()) { - MachineOperand &UseMO = UI.getOperand(); - MachineInstr *UseMI = &*UI; - ++UI; - if (UseMI->isDebugValue()) { - // SSAUpdate can replace the use with an undef. That creates - // a debug instruction that is a kill. - // FIXME: Should it SSAUpdate job to delete debug instructions - // instead of replacing the use with undef? - UseMI->eraseFromParent(); - continue; - } - if (UseMI->getParent() == DefBB && !UseMI->isPHI()) - continue; - SSAUpdate.RewriteUse(UseMO); - } - } - - SSAUpdateVRs.clear(); - SSAUpdateVals.clear(); - } - - // Eliminate some of the copies inserted by tail duplication to maintain - // SSA form. - for (unsigned i = 0, e = Copies.size(); i != e; ++i) { - MachineInstr *Copy = Copies[i]; - if (!Copy->isCopy()) - continue; - unsigned Dst = Copy->getOperand(0).getReg(); - unsigned Src = Copy->getOperand(1).getReg(); - MachineRegisterInfo::use_iterator UI = MRI->use_begin(Src); - if (++UI == MRI->use_end()) { - // Copy is the only use. Do trivial copy propagation here. - MRI->replaceRegWith(Dst, Src); - Copy->eraseFromParent(); - } - } - - if (PreRegAlloc && TailDupVerify) - VerifyPHIs(MF, false); - MadeChange = true; - - if (NewPHIs.size()) - NumAddedPHIs += NewPHIs.size(); + MadeChange |= TailDuplicateAndUpdate(MBB, IsSimple, MF); } + if (PreRegAlloc && TailDupVerify) + VerifyPHIs(MF, false); return MadeChange; } @@ -532,14 +550,12 @@ TailDuplicatePass::shouldTailDuplicate(const MachineFunction &MF, // to allow undoing the effects of tail merging and other optimizations // that rearrange the predecessors of the indirect branch. - bool hasIndirectBR = false; - if (PreRegAlloc && !TailBB.empty()) { - const MCInstrDesc &MCID = TailBB.back().getDesc(); - if (MCID.isIndirectBranch()) { - MaxDuplicateCount = 20; - hasIndirectBR = true; - } - } + bool HasIndirectbr = false; + if (!TailBB.empty()) + HasIndirectbr = TailBB.back().getDesc().isIndirectBranch(); + + if (HasIndirectbr && PreRegAlloc) + MaxDuplicateCount = 20; // Check the instructions in the block to determine whether tail-duplication // is invalid or unlikely to be profitable. @@ -569,7 +585,7 @@ TailDuplicatePass::shouldTailDuplicate(const MachineFunction &MF, return false; } - if (hasIndirectBR) + if (HasIndirectbr && PreRegAlloc) return true; if (IsSimple) @@ -711,14 +727,11 @@ TailDuplicatePass::duplicateSimpleBB(MachineBasicBlock *TailBB, /// TailDuplicate - If it is profitable, duplicate TailBB's contents in each /// of its predecessors. bool -TailDuplicatePass::TailDuplicate(MachineBasicBlock *TailBB, MachineFunction &MF, +TailDuplicatePass::TailDuplicate(MachineBasicBlock *TailBB, + bool IsSimple, + MachineFunction &MF, SmallVector &TDBBs, SmallVector &Copies) { - bool IsSimple = isSimpleBB(TailBB); - - if (!shouldTailDuplicate(MF, IsSimple, *TailBB)) - return false; - DEBUG(dbgs() << "\n*** Tail-duplicating BB#" << TailBB->getNumber() << '\n'); DenseSet UsedByPhi;