X-Git-Url: http://plrg.eecs.uci.edu/git/?p=oota-llvm.git;a=blobdiff_plain;f=lib%2FCodeGen%2FBranchFolding.cpp;h=e41926a819c2e1202755cabf562c62418e366148;hp=99090a8269d40005d32cef569fa8fabf0ba275a8;hb=d8ba62ab992b9e142e002aee220354c9f09d92b7;hpb=a38cfb2fceb266bd78164021c08284dc59a1e8a3 diff --git a/lib/CodeGen/BranchFolding.cpp b/lib/CodeGen/BranchFolding.cpp index 99090a8269d..e41926a819c 100644 --- a/lib/CodeGen/BranchFolding.cpp +++ b/lib/CodeGen/BranchFolding.cpp @@ -12,32 +12,38 @@ // it then removes. // // Note that this pass must be run after register allocation, it cannot handle -// SSA form. +// SSA form. It also must handle virtual registers for targets that emit virtual +// ISA (e.g. NVPTX). // //===----------------------------------------------------------------------===// -#define DEBUG_TYPE "branchfolding" #include "BranchFolding.h" -#include "llvm/Function.h" -#include "llvm/CodeGen/Passes.h" -#include "llvm/CodeGen/MachineModuleInfo.h" +#include "llvm/ADT/STLExtras.h" +#include "llvm/ADT/SmallSet.h" +#include "llvm/ADT/Statistic.h" +#include "llvm/CodeGen/Analysis.h" +#include "llvm/CodeGen/MachineBlockFrequencyInfo.h" +#include "llvm/CodeGen/MachineBranchProbabilityInfo.h" #include "llvm/CodeGen/MachineFunctionPass.h" #include "llvm/CodeGen/MachineJumpTableInfo.h" +#include "llvm/CodeGen/MachineMemOperand.h" +#include "llvm/CodeGen/MachineModuleInfo.h" +#include "llvm/CodeGen/MachineRegisterInfo.h" +#include "llvm/CodeGen/Passes.h" #include "llvm/CodeGen/RegisterScavenging.h" -#include "llvm/Target/TargetInstrInfo.h" -#include "llvm/Target/TargetMachine.h" -#include "llvm/Target/TargetRegisterInfo.h" +#include "llvm/IR/Function.h" #include "llvm/Support/CommandLine.h" #include "llvm/Support/Debug.h" #include "llvm/Support/ErrorHandling.h" #include "llvm/Support/raw_ostream.h" -#include "llvm/ADT/SmallSet.h" -#include "llvm/ADT/SetVector.h" -#include "llvm/ADT/Statistic.h" -#include "llvm/ADT/STLExtras.h" +#include "llvm/Target/TargetInstrInfo.h" +#include "llvm/Target/TargetRegisterInfo.h" +#include "llvm/Target/TargetSubtargetInfo.h" #include using namespace llvm; +#define DEBUG_TYPE "branchfolding" + STATISTIC(NumDeadBlocks, "Number of dead blocks removed"); STATISTIC(NumBranchOpts, "Number of branches optimized"); STATISTIC(NumTailMerge , "Number of block tails merged"); @@ -61,40 +67,55 @@ TailMergeSize("tail-merge-size", namespace { /// BranchFolderPass - Wrap branch folder in a machine function pass. - class BranchFolderPass : public MachineFunctionPass, - public BranchFolder { + class BranchFolderPass : public MachineFunctionPass { public: static char ID; - explicit BranchFolderPass(bool defaultEnableTailMerge) - : MachineFunctionPass(ID), BranchFolder(defaultEnableTailMerge, true) {} + explicit BranchFolderPass(): MachineFunctionPass(ID) {} + + bool runOnMachineFunction(MachineFunction &MF) override; - virtual bool runOnMachineFunction(MachineFunction &MF); - virtual const char *getPassName() const { return "Control Flow Optimizer"; } + void getAnalysisUsage(AnalysisUsage &AU) const override { + AU.addRequired(); + AU.addRequired(); + AU.addRequired(); + MachineFunctionPass::getAnalysisUsage(AU); + } }; } char BranchFolderPass::ID = 0; +char &llvm::BranchFolderPassID = BranchFolderPass::ID; -FunctionPass *llvm::createBranchFoldingPass(bool DefaultEnableTailMerge) { - return new BranchFolderPass(DefaultEnableTailMerge); -} +INITIALIZE_PASS(BranchFolderPass, "branch-folder", + "Control Flow Optimizer", false, false) bool BranchFolderPass::runOnMachineFunction(MachineFunction &MF) { - return OptimizeFunction(MF, - MF.getTarget().getInstrInfo(), - MF.getTarget().getRegisterInfo(), - getAnalysisIfAvailable()); -} + if (skipOptnoneFunction(*MF.getFunction())) + return false; + TargetPassConfig *PassConfig = &getAnalysis(); + // TailMerge can create jump into if branches that make CFG irreducible for + // HW that requires structurized CFG. + bool EnableTailMerge = !MF.getTarget().requiresStructuredCFG() && + PassConfig->getEnableTailMerge(); + BranchFolder Folder(EnableTailMerge, /*CommonHoist=*/true, + getAnalysis(), + getAnalysis()); + return Folder.OptimizeFunction(MF, MF.getSubtarget().getInstrInfo(), + MF.getSubtarget().getRegisterInfo(), + getAnalysisIfAvailable()); +} -BranchFolder::BranchFolder(bool defaultEnableTailMerge, bool CommonHoist) { +BranchFolder::BranchFolder(bool defaultEnableTailMerge, bool CommonHoist, + const MachineBlockFrequencyInfo &FreqInfo, + const MachineBranchProbabilityInfo &ProbInfo) + : EnableHoistCommonCode(CommonHoist), MBBFreqInfo(FreqInfo), + MBPI(ProbInfo) { switch (FlagEnableTailMerge) { case cl::BOU_UNSET: EnableTailMerge = defaultEnableTailMerge; break; case cl::BOU_TRUE: EnableTailMerge = true; break; case cl::BOU_FALSE: EnableTailMerge = false; break; } - - EnableHoistCommonCode = CommonHoist; } /// RemoveDeadBlock - Remove the specified dead machine basic block from the @@ -113,6 +134,7 @@ void BranchFolder::RemoveDeadBlock(MachineBasicBlock *MBB) { // Remove the block. MF->erase(MBB); + FuncletMembership.erase(MBB); } /// OptimizeImpDefsBlock - If a basic block is just a bunch of implicit_def @@ -131,10 +153,13 @@ bool BranchFolder::OptimizeImpDefsBlock(MachineBasicBlock *MBB) { if (!I->isImplicitDef()) break; unsigned Reg = I->getOperand(0).getReg(); - ImpDefRegs.insert(Reg); - for (const unsigned *SubRegs = TRI->getSubRegisters(Reg); - unsigned SubReg = *SubRegs; ++SubRegs) - ImpDefRegs.insert(SubReg); + if (TargetRegisterInfo::isPhysicalRegister(Reg)) { + for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true); + SubRegs.isValid(); ++SubRegs) + ImpDefRegs.insert(*SubRegs); + } else { + ImpDefRegs.insert(Reg); + } ++I; } if (ImpDefRegs.empty()) @@ -145,8 +170,7 @@ bool BranchFolder::OptimizeImpDefsBlock(MachineBasicBlock *MBB) { if (!TII->isUnpredicatedTerminator(I)) return false; // See if it uses any of the implicitly defined registers. - for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) { - MachineOperand &MO = I->getOperand(i); + for (const MachineOperand &MO : I->operands()) { if (!MO.isReg() || !MO.isUse()) continue; unsigned Reg = MO.getReg(); @@ -179,19 +203,28 @@ bool BranchFolder::OptimizeFunction(MachineFunction &MF, TII = tii; TRI = tri; MMI = mmi; + RS = nullptr; - RS = TRI->requiresRegisterScavenging(MF) ? new RegScavenger() : NULL; + // Use a RegScavenger to help update liveness when required. + MachineRegisterInfo &MRI = MF.getRegInfo(); + if (MRI.tracksLiveness() && TRI->trackLivenessAfterRegAlloc(MF)) + RS = new RegScavenger(); + else + MRI.invalidateLiveness(); // Fix CFG. The later algorithms expect it to be right. bool MadeChange = false; - for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; I++) { - MachineBasicBlock *MBB = I, *TBB = 0, *FBB = 0; + for (MachineBasicBlock &MBB : MF) { + MachineBasicBlock *TBB = nullptr, *FBB = nullptr; SmallVector Cond; - if (!TII->AnalyzeBranch(*MBB, TBB, FBB, Cond, true)) - MadeChange |= MBB->CorrectExtraCFGEdges(TBB, FBB, !Cond.empty()); - MadeChange |= OptimizeImpDefsBlock(MBB); + if (!TII->AnalyzeBranch(MBB, TBB, FBB, Cond, true)) + MadeChange |= MBB.CorrectExtraCFGEdges(TBB, FBB, !Cond.empty()); + MadeChange |= OptimizeImpDefsBlock(&MBB); } + // Recalculate funclet membership. + FuncletMembership = getFuncletMembership(MF); + bool MadeChangeThisIteration = true; while (MadeChangeThisIteration) { MadeChangeThisIteration = TailMergeBlocks(MF); @@ -204,19 +237,16 @@ bool BranchFolder::OptimizeFunction(MachineFunction &MF, // See if any jump tables have become dead as the code generator // did its thing. MachineJumpTableInfo *JTI = MF.getJumpTableInfo(); - if (JTI == 0) { + if (!JTI) { delete RS; return MadeChange; } - + // Walk the function to find jump tables that are live. BitVector JTIsLive(JTI->getJumpTables().size()); - for (MachineFunction::iterator BB = MF.begin(), E = MF.end(); - BB != E; ++BB) { - for (MachineBasicBlock::iterator I = BB->begin(), E = BB->end(); - I != E; ++I) - for (unsigned op = 0, e = I->getNumOperands(); op != e; ++op) { - MachineOperand &Op = I->getOperand(op); + for (const MachineBasicBlock &BB : MF) { + for (const MachineInstr &I : BB) + for (const MachineOperand &Op : I.operands()) { if (!Op.isJTI()) continue; // Remember that this JT is live. @@ -246,11 +276,17 @@ static unsigned HashMachineInstr(const MachineInstr *MI) { for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { const MachineOperand &Op = MI->getOperand(i); - // Merge in bits from the operand if easy. + // Merge in bits from the operand if easy. We can't use MachineOperand's + // hash_code here because it's not deterministic and we sort by hash value + // later. unsigned OperandHash = 0; switch (Op.getType()) { - case MachineOperand::MO_Register: OperandHash = Op.getReg(); break; - case MachineOperand::MO_Immediate: OperandHash = Op.getImm(); break; + case MachineOperand::MO_Register: + OperandHash = Op.getReg(); + break; + case MachineOperand::MO_Immediate: + OperandHash = Op.getImm(); + break; case MachineOperand::MO_MachineBasicBlock: OperandHash = Op.getMBB()->getNumber(); break; @@ -265,27 +301,20 @@ static unsigned HashMachineInstr(const MachineInstr *MI) { // pull in the offset. OperandHash = Op.getOffset(); break; - default: break; + default: + break; } - Hash += ((OperandHash << 3) | Op.getType()) << (i&31); + Hash += ((OperandHash << 3) | Op.getType()) << (i & 31); } return Hash; } /// HashEndOfMBB - Hash the last instruction in the MBB. static unsigned HashEndOfMBB(const MachineBasicBlock *MBB) { - MachineBasicBlock::const_iterator I = MBB->end(); - if (I == MBB->begin()) - return 0; // Empty MBB. - - --I; - // Skip debug info so it will not affect codegen. - while (I->isDebugValue()) { - if (I==MBB->begin()) - return 0; // MBB empty except for debug info. - --I; - } + MachineBasicBlock::const_iterator I = MBB->getLastNonDebugInstr(); + if (I == MBB->end()) + return 0; return HashMachineInstr(I); } @@ -342,14 +371,13 @@ static unsigned ComputeCommonTailLength(MachineBasicBlock *MBB1, } // Back past possible debugging pseudos at beginning of block. This matters // when one block differs from the other only by whether debugging pseudos - // are present at the beginning. (This way, the various checks later for + // are present at the beginning. (This way, the various checks later for // I1==MBB1->begin() work as expected.) if (I1 == MBB1->begin() && I2 != MBB2->begin()) { --I2; while (I2->isDebugValue()) { - if (I2 == MBB2->begin()) { + if (I2 == MBB2->begin()) return TailLen; - } --I2; } ++I2; @@ -371,11 +399,9 @@ void BranchFolder::MaintainLiveIns(MachineBasicBlock *CurMBB, if (RS) { RS->enterBasicBlock(CurMBB); if (!CurMBB->empty()) - RS->forward(prior(CurMBB->end())); - BitVector RegsLiveAtExit(TRI->getNumRegs()); - RS->getRegsUsed(RegsLiveAtExit, false); - for (unsigned int i = 0, e = TRI->getNumRegs(); i != e; i++) - if (RegsLiveAtExit[i]) + RS->forward(std::prev(CurMBB->end())); + for (unsigned int i = 1, e = TRI->getNumRegs(); i != e; i++) + if (RS->isRegUsed(i, false)) NewMBB->addLiveIn(i); } } @@ -398,15 +424,16 @@ void BranchFolder::ReplaceTailWithBranchTo(MachineBasicBlock::iterator OldInst, /// MBB so that the part before the iterator falls into the part starting at the /// iterator. This returns the new MBB. MachineBasicBlock *BranchFolder::SplitMBBAt(MachineBasicBlock &CurMBB, - MachineBasicBlock::iterator BBI1) { + MachineBasicBlock::iterator BBI1, + const BasicBlock *BB) { if (!TII->isLegalToSplitMBBAt(CurMBB, BBI1)) - return 0; + return nullptr; MachineFunction &MF = *CurMBB.getParent(); // Create the fall-through block. - MachineFunction::iterator MBBI = &CurMBB; - MachineBasicBlock *NewMBB =MF.CreateMachineBasicBlock(CurMBB.getBasicBlock()); + MachineFunction::iterator MBBI = CurMBB.getIterator(); + MachineBasicBlock *NewMBB =MF.CreateMachineBasicBlock(BB); CurMBB.getParent()->insert(++MBBI, NewMBB); // Move all the successors of this block to the specified block. @@ -418,9 +445,17 @@ MachineBasicBlock *BranchFolder::SplitMBBAt(MachineBasicBlock &CurMBB, // Splice the code over. NewMBB->splice(NewMBB->end(), &CurMBB, BBI1, CurMBB.end()); + // NewMBB inherits CurMBB's block frequency. + MBBFreqInfo.setBlockFreq(NewMBB, MBBFreqInfo.getBlockFreq(&CurMBB)); + // For targets that use the register scavenger, we must maintain LiveIns. MaintainLiveIns(&CurMBB, NewMBB); + // Add the new block to the funclet. + const auto &FuncletI = FuncletMembership.find(&CurMBB); + if (FuncletI != FuncletMembership.end()) + FuncletMembership[NewMBB] = FuncletI->second; + return NewMBB; } @@ -432,10 +467,9 @@ static unsigned EstimateRuntime(MachineBasicBlock::iterator I, for (; I != E; ++I) { if (I->isDebugValue()) continue; - const MCInstrDesc &MCID = I->getDesc(); - if (MCID.isCall()) + if (I->isCall()) Time += 10; - else if (MCID.mayLoad() || MCID.mayStore()) + else if (I->mayLoad() || I->mayStore()) Time += 2; else ++Time; @@ -450,22 +484,22 @@ static unsigned EstimateRuntime(MachineBasicBlock::iterator I, static void FixTail(MachineBasicBlock *CurMBB, MachineBasicBlock *SuccBB, const TargetInstrInfo *TII) { MachineFunction *MF = CurMBB->getParent(); - MachineFunction::iterator I = llvm::next(MachineFunction::iterator(CurMBB)); - MachineBasicBlock *TBB = 0, *FBB = 0; + MachineFunction::iterator I = std::next(MachineFunction::iterator(CurMBB)); + MachineBasicBlock *TBB = nullptr, *FBB = nullptr; SmallVector Cond; DebugLoc dl; // FIXME: this is nowhere if (I != MF->end() && !TII->AnalyzeBranch(*CurMBB, TBB, FBB, Cond, true)) { - MachineBasicBlock *NextBB = I; + MachineBasicBlock *NextBB = &*I; if (TBB == NextBB && !Cond.empty() && !FBB) { if (!TII->ReverseBranchCondition(Cond)) { TII->RemoveBranch(*CurMBB); - TII->InsertBranch(*CurMBB, SuccBB, NULL, Cond, dl); + TII->InsertBranch(*CurMBB, SuccBB, nullptr, Cond, dl); return; } } } - TII->InsertBranch(*CurMBB, SuccBB, NULL, + TII->InsertBranch(*CurMBB, SuccBB, nullptr, SmallVector(), dl); } @@ -473,20 +507,34 @@ bool BranchFolder::MergePotentialsElt::operator<(const MergePotentialsElt &o) const { if (getHash() < o.getHash()) return true; - else if (getHash() > o.getHash()) + if (getHash() > o.getHash()) return false; - else if (getBlock()->getNumber() < o.getBlock()->getNumber()) + if (getBlock()->getNumber() < o.getBlock()->getNumber()) return true; - else if (getBlock()->getNumber() > o.getBlock()->getNumber()) + if (getBlock()->getNumber() > o.getBlock()->getNumber()) return false; - else { - // _GLIBCXX_DEBUG checks strict weak ordering, which involves comparing - // an object with itself. + // _GLIBCXX_DEBUG checks strict weak ordering, which involves comparing + // an object with itself. #ifndef _GLIBCXX_DEBUG - llvm_unreachable("Predecessor appears twice"); + llvm_unreachable("Predecessor appears twice"); +#else + return false; #endif - return false; - } +} + +BlockFrequency +BranchFolder::MBFIWrapper::getBlockFreq(const MachineBasicBlock *MBB) const { + auto I = MergedBBFreq.find(MBB); + + if (I != MergedBBFreq.end()) + return I->second; + + return MBFI.getBlockFreq(MBB); +} + +void BranchFolder::MBFIWrapper::setBlockFreq(const MachineBasicBlock *MBB, + BlockFrequency F) { + MergedBBFreq[MBB] = F; } /// CountTerminators - Count the number of terminators in the given @@ -502,7 +550,7 @@ static unsigned CountTerminators(MachineBasicBlock *MBB, break; } --I; - if (!I->getDesc().isTerminator()) break; + if (!I->isTerminator()) break; ++NumTerms; } return NumTerms; @@ -512,14 +560,23 @@ static unsigned CountTerminators(MachineBasicBlock *MBB, /// and decide if it would be profitable to merge those tails. Return the /// length of the common tail and iterators to the first common instruction /// in each block. -static bool ProfitableToMerge(MachineBasicBlock *MBB1, - MachineBasicBlock *MBB2, - unsigned minCommonTailLength, - unsigned &CommonTailLen, - MachineBasicBlock::iterator &I1, - MachineBasicBlock::iterator &I2, - MachineBasicBlock *SuccBB, - MachineBasicBlock *PredBB) { +static bool +ProfitableToMerge(MachineBasicBlock *MBB1, MachineBasicBlock *MBB2, + unsigned minCommonTailLength, unsigned &CommonTailLen, + MachineBasicBlock::iterator &I1, + MachineBasicBlock::iterator &I2, MachineBasicBlock *SuccBB, + MachineBasicBlock *PredBB, + DenseMap &FuncletMembership) { + // It is never profitable to tail-merge blocks from two different funclets. + if (!FuncletMembership.empty()) { + auto Funclet1 = FuncletMembership.find(MBB1); + assert(Funclet1 != FuncletMembership.end()); + auto Funclet2 = FuncletMembership.find(MBB2); + assert(Funclet2 != FuncletMembership.end()); + if (Funclet1->second != Funclet2->second) + return false; + } + CommonTailLen = ComputeCommonTailLength(MBB1, MBB2, I1, I2); if (CommonTailLen == 0) return false; @@ -550,8 +607,8 @@ static bool ProfitableToMerge(MachineBasicBlock *MBB1, // heuristics. unsigned EffectiveTailLen = CommonTailLen; if (SuccBB && MBB1 != PredBB && MBB2 != PredBB && - !MBB1->back().getDesc().isBarrier() && - !MBB2->back().getDesc().isBarrier()) + !MBB1->back().isBarrier() && + !MBB2->back().isBarrier()) ++EffectiveTailLen; // Check if the common tail is long enough to be worthwhile. @@ -563,12 +620,8 @@ static bool ProfitableToMerge(MachineBasicBlock *MBB1, // branch instruction, which is likely to be smaller than the 2 // instructions that would be deleted in the merge. MachineFunction *MF = MBB1->getParent(); - if (EffectiveTailLen >= 2 && - MF->getFunction()->hasFnAttr(Attribute::OptimizeForSize) && - (I1 == MBB1->begin() || I2 == MBB2->begin())) - return true; - - return false; + return EffectiveTailLen >= 2 && MF->getFunction()->optForSize() && + (I1 == MBB1->begin() || I2 == MBB2->begin()); } /// ComputeSameTails - Look through all the blocks in MergePotentials that have @@ -588,17 +641,17 @@ unsigned BranchFolder::ComputeSameTails(unsigned CurHash, unsigned maxCommonTailLength = 0U; SameTails.clear(); MachineBasicBlock::iterator TrialBBI1, TrialBBI2; - MPIterator HighestMPIter = prior(MergePotentials.end()); - for (MPIterator CurMPIter = prior(MergePotentials.end()), + MPIterator HighestMPIter = std::prev(MergePotentials.end()); + for (MPIterator CurMPIter = std::prev(MergePotentials.end()), B = MergePotentials.begin(); - CurMPIter != B && CurMPIter->getHash() == CurHash; - --CurMPIter) { - for (MPIterator I = prior(CurMPIter); I->getHash() == CurHash ; --I) { + CurMPIter != B && CurMPIter->getHash() == CurHash; --CurMPIter) { + for (MPIterator I = std::prev(CurMPIter); I->getHash() == CurHash; --I) { unsigned CommonTailLen; if (ProfitableToMerge(CurMPIter->getBlock(), I->getBlock(), minCommonTailLength, CommonTailLen, TrialBBI1, TrialBBI2, - SuccBB, PredBB)) { + SuccBB, PredBB, + FuncletMembership)) { if (CommonTailLen > maxCommonTailLength) { SameTails.clear(); maxCommonTailLength = CommonTailLen; @@ -622,9 +675,9 @@ void BranchFolder::RemoveBlocksWithHash(unsigned CurHash, MachineBasicBlock *SuccBB, MachineBasicBlock *PredBB) { MPIterator CurMPIter, B; - for (CurMPIter = prior(MergePotentials.end()), B = MergePotentials.begin(); - CurMPIter->getHash() == CurHash; - --CurMPIter) { + for (CurMPIter = std::prev(MergePotentials.end()), + B = MergePotentials.begin(); + CurMPIter->getHash() == CurHash; --CurMPIter) { // Put the unconditional branch back, if we need one. MachineBasicBlock *CurMBB = CurMPIter->getBlock(); if (SuccBB && CurMBB != PredBB) @@ -640,6 +693,7 @@ void BranchFolder::RemoveBlocksWithHash(unsigned CurHash, /// CreateCommonTailOnlyBlock - None of the blocks to be tail-merged consist /// only of the common tail. Create a block that does by splitting one. bool BranchFolder::CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB, + MachineBasicBlock *SuccBB, unsigned maxCommonTailLength, unsigned &commonTailIndex) { commonTailIndex = 0; @@ -669,7 +723,12 @@ bool BranchFolder::CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB, DEBUG(dbgs() << "\nSplitting BB#" << MBB->getNumber() << ", size " << maxCommonTailLength); - MachineBasicBlock *newMBB = SplitMBBAt(*MBB, BBI); + // If the split block unconditionally falls-thru to SuccBB, it will be + // merged. In control flow terms it should then take SuccBB's name. e.g. If + // SuccBB is an inner loop, the common tail is still part of the inner loop. + const BasicBlock *BB = (SuccBB && MBB->succ_size() == 1) ? + SuccBB->getBasicBlock() : MBB->getBasicBlock(); + MachineBasicBlock *newMBB = SplitMBBAt(*MBB, BBI, BB); if (!newMBB) { DEBUG(dbgs() << "... failed!"); return false; @@ -685,6 +744,62 @@ bool BranchFolder::CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB, return true; } +static bool hasIdenticalMMOs(const MachineInstr *MI1, const MachineInstr *MI2) { + auto I1 = MI1->memoperands_begin(), E1 = MI1->memoperands_end(); + auto I2 = MI2->memoperands_begin(), E2 = MI2->memoperands_end(); + if ((E1 - I1) != (E2 - I2)) + return false; + for (; I1 != E1; ++I1, ++I2) { + if (**I1 != **I2) + return false; + } + return true; +} + +static void +removeMMOsFromMemoryOperations(MachineBasicBlock::iterator MBBIStartPos, + MachineBasicBlock &MBBCommon) { + // Remove MMOs from memory operations in the common block + // when they do not match the ones from the block being tail-merged. + // This ensures later passes conservatively compute dependencies. + MachineBasicBlock *MBB = MBBIStartPos->getParent(); + // Note CommonTailLen does not necessarily matches the size of + // the common BB nor all its instructions because of debug + // instructions differences. + unsigned CommonTailLen = 0; + for (auto E = MBB->end(); MBBIStartPos != E; ++MBBIStartPos) + ++CommonTailLen; + + MachineBasicBlock::reverse_iterator MBBI = MBB->rbegin(); + MachineBasicBlock::reverse_iterator MBBIE = MBB->rend(); + MachineBasicBlock::reverse_iterator MBBICommon = MBBCommon.rbegin(); + MachineBasicBlock::reverse_iterator MBBIECommon = MBBCommon.rend(); + + while (CommonTailLen--) { + assert(MBBI != MBBIE && "Reached BB end within common tail length!"); + (void)MBBIE; + + if (MBBI->isDebugValue()) { + ++MBBI; + continue; + } + + while ((MBBICommon != MBBIECommon) && MBBICommon->isDebugValue()) + ++MBBICommon; + + assert(MBBICommon != MBBIECommon && + "Reached BB end within common tail length!"); + assert(MBBICommon->isIdenticalTo(&*MBBI) && "Expected matching MIIs!"); + + if (MBBICommon->mayLoad() || MBBICommon->mayStore()) + if (!hasIdenticalMMOs(&*MBBI, &*MBBICommon)) + MBBICommon->clearMemRefs(); + + ++MBBI; + ++MBBICommon; + } +} + // See if any of the blocks in MergePotentials (which all have a common single // successor, or all have no successor) can be tail-merged. If there is a // successor, any blocks in MergePotentials that are not tail-merged and @@ -719,7 +834,7 @@ bool BranchFolder::TryTailMergeBlocks(MachineBasicBlock *SuccBB, // Sort by hash value so that blocks with identical end sequences sort // together. - std::stable_sort(MergePotentials.begin(), MergePotentials.end()); + array_pod_sort(MergePotentials.begin(), MergePotentials.end()); // Walk through equivalence sets looking for actual exact matches. while (MergePotentials.size() > 1) { @@ -742,8 +857,8 @@ bool BranchFolder::TryTailMergeBlocks(MachineBasicBlock *SuccBB, // block, which we can't jump to), we can treat all blocks with this same // tail at once. Use PredBB if that is one of the possibilities, as that // will not introduce any extra branches. - MachineBasicBlock *EntryBB = MergePotentials.begin()->getBlock()-> - getParent()->begin(); + MachineBasicBlock *EntryBB = + &MergePotentials.front().getBlock()->getParent()->front(); unsigned commonTailIndex = SameTails.size(); // If there are two blocks, check to see if one can be made to fall through // into the other. @@ -777,7 +892,7 @@ bool BranchFolder::TryTailMergeBlocks(MachineBasicBlock *SuccBB, !SameTails[commonTailIndex].tailIsWholeBlock())) { // None of the blocks consist entirely of the common tail. // Split a block so that one does. - if (!CreateCommonTailOnlyBlock(PredBB, + if (!CreateCommonTailOnlyBlock(PredBB, SuccBB, maxCommonTailLength, commonTailIndex)) { RemoveBlocksWithHash(CurHash, SuccBB, PredBB); continue; @@ -785,6 +900,10 @@ bool BranchFolder::TryTailMergeBlocks(MachineBasicBlock *SuccBB, } MachineBasicBlock *MBB = SameTails[commonTailIndex].getBlock(); + + // Recompute commont tail MBB's edge weights and block frequency. + setCommonTailEdgeWeights(*MBB); + // MBB is common tail. Adjust all other BB's to jump to this one. // Traversal must be forwards so erases work. DEBUG(dbgs() << "\nUsing common tail in BB#" << MBB->getNumber() @@ -794,6 +913,8 @@ bool BranchFolder::TryTailMergeBlocks(MachineBasicBlock *SuccBB, continue; DEBUG(dbgs() << "BB#" << SameTails[i].getBlock()->getNumber() << (i == e-1 ? "" : ", ")); + // Remove MMOs from memory operations as needed. + removeMMOsFromMemoryOperations(SameTails[i].getTailStartPos(), *MBB); // Hack the end off BB i, making it jump to BB commonTailIndex instead. ReplaceTailWithBranchTo(SameTails[i].getTailStartPos(), MBB); // BB i is no longer a predecessor of SuccBB; remove it from the worklist. @@ -808,19 +929,16 @@ bool BranchFolder::TryTailMergeBlocks(MachineBasicBlock *SuccBB, } bool BranchFolder::TailMergeBlocks(MachineFunction &MF) { - - if (!EnableTailMerge) return false; - bool MadeChange = false; + if (!EnableTailMerge) return MadeChange; // First find blocks with no successors. MergePotentials.clear(); - for (MachineFunction::iterator I = MF.begin(), E = MF.end(); - I != E && MergePotentials.size() < TailMergeThreshold; ++I) { - if (TriedMerging.count(I)) - continue; - if (I->succ_empty()) - MergePotentials.push_back(MergePotentialsElt(HashEndOfMBB(I), I)); + for (MachineBasicBlock &MBB : MF) { + if (MergePotentials.size() == TailMergeThreshold) + break; + if (!TriedMerging.count(&MBB) && MBB.succ_empty()) + MergePotentials.push_back(MergePotentialsElt(HashEndOfMBB(&MBB), &MBB)); } // If this is a large problem, avoid visiting the same basic blocks @@ -828,9 +946,10 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) { if (MergePotentials.size() == TailMergeThreshold) for (unsigned i = 0, e = MergePotentials.size(); i != e; ++i) TriedMerging.insert(MergePotentials[i].getBlock()); + // See if we can do any tail merging on those. if (MergePotentials.size() >= 2) - MadeChange |= TryTailMergeBlocks(NULL, NULL); + MadeChange |= TryTailMergeBlocks(nullptr, nullptr); // Look at blocks (IBB) with multiple predecessors (PBB). // We change each predecessor to a canonical form, by @@ -851,89 +970,150 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) { // a compile-time infinite loop repeatedly doing and undoing the same // transformations.) - for (MachineFunction::iterator I = llvm::next(MF.begin()), E = MF.end(); + for (MachineFunction::iterator I = std::next(MF.begin()), E = MF.end(); I != E; ++I) { - if (I->pred_size() >= 2) { - SmallPtrSet UniquePreds; - MachineBasicBlock *IBB = I; - MachineBasicBlock *PredBB = prior(I); - MergePotentials.clear(); - for (MachineBasicBlock::pred_iterator P = I->pred_begin(), - E2 = I->pred_end(); - P != E2 && MergePotentials.size() < TailMergeThreshold; ++P) { - MachineBasicBlock *PBB = *P; - if (TriedMerging.count(PBB)) - continue; - // Skip blocks that loop to themselves, can't tail merge these. - if (PBB == IBB) - continue; - // Visit each predecessor only once. - if (!UniquePreds.insert(PBB)) - continue; - MachineBasicBlock *TBB = 0, *FBB = 0; - SmallVector Cond; - if (!TII->AnalyzeBranch(*PBB, TBB, FBB, Cond, true)) { - // Failing case: IBB is the target of a cbr, and - // we cannot reverse the branch. - SmallVector NewCond(Cond); - if (!Cond.empty() && TBB == IBB) { - if (TII->ReverseBranchCondition(NewCond)) - continue; - // This is the QBB case described above - if (!FBB) - FBB = llvm::next(MachineFunction::iterator(PBB)); - } - // Failing case: the only way IBB can be reached from PBB is via - // exception handling. Happens for landing pads. Would be nice - // to have a bit in the edge so we didn't have to do all this. - if (IBB->isLandingPad()) { - MachineFunction::iterator IP = PBB; IP++; - MachineBasicBlock *PredNextBB = NULL; - if (IP != MF.end()) - PredNextBB = IP; - if (TBB == NULL) { - if (IBB != PredNextBB) // fallthrough - continue; - } else if (FBB) { - if (TBB != IBB && FBB != IBB) // cbr then ubr - continue; - } else if (Cond.empty()) { - if (TBB != IBB) // ubr - continue; - } else { - if (TBB != IBB && IBB != PredNextBB) // cbr - continue; - } + if (I->pred_size() < 2) continue; + SmallPtrSet UniquePreds; + MachineBasicBlock *IBB = &*I; + MachineBasicBlock *PredBB = &*std::prev(I); + MergePotentials.clear(); + for (MachineBasicBlock *PBB : I->predecessors()) { + if (MergePotentials.size() == TailMergeThreshold) + break; + + if (TriedMerging.count(PBB)) + continue; + + // Skip blocks that loop to themselves, can't tail merge these. + if (PBB == IBB) + continue; + + // Visit each predecessor only once. + if (!UniquePreds.insert(PBB).second) + continue; + + // Skip blocks which may jump to a landing pad. Can't tail merge these. + if (PBB->hasEHPadSuccessor()) + continue; + + MachineBasicBlock *TBB = nullptr, *FBB = nullptr; + SmallVector Cond; + if (!TII->AnalyzeBranch(*PBB, TBB, FBB, Cond, true)) { + // Failing case: IBB is the target of a cbr, and we cannot reverse the + // branch. + SmallVector NewCond(Cond); + if (!Cond.empty() && TBB == IBB) { + if (TII->ReverseBranchCondition(NewCond)) + continue; + // This is the QBB case described above + if (!FBB) { + auto Next = ++PBB->getIterator(); + if (Next != MF.end()) + FBB = &*Next; } - // Remove the unconditional branch at the end, if any. - if (TBB && (Cond.empty() || FBB)) { - DebugLoc dl; // FIXME: this is nowhere - TII->RemoveBranch(*PBB); - if (!Cond.empty()) - // reinsert conditional branch only, for now - TII->InsertBranch(*PBB, (TBB == IBB) ? FBB : TBB, 0, NewCond, dl); + } + + // Failing case: the only way IBB can be reached from PBB is via + // exception handling. Happens for landing pads. Would be nice to have + // a bit in the edge so we didn't have to do all this. + if (IBB->isEHPad()) { + MachineFunction::iterator IP = ++PBB->getIterator(); + MachineBasicBlock *PredNextBB = nullptr; + if (IP != MF.end()) + PredNextBB = &*IP; + if (!TBB) { + if (IBB != PredNextBB) // fallthrough + continue; + } else if (FBB) { + if (TBB != IBB && FBB != IBB) // cbr then ubr + continue; + } else if (Cond.empty()) { + if (TBB != IBB) // ubr + continue; + } else { + if (TBB != IBB && IBB != PredNextBB) // cbr + continue; } - MergePotentials.push_back(MergePotentialsElt(HashEndOfMBB(PBB), *P)); } + + // Remove the unconditional branch at the end, if any. + if (TBB && (Cond.empty() || FBB)) { + DebugLoc dl; // FIXME: this is nowhere + TII->RemoveBranch(*PBB); + if (!Cond.empty()) + // reinsert conditional branch only, for now + TII->InsertBranch(*PBB, (TBB == IBB) ? FBB : TBB, nullptr, + NewCond, dl); + } + + MergePotentials.push_back(MergePotentialsElt(HashEndOfMBB(PBB), PBB)); } - // If this is a large problem, avoid visiting the same basic blocks - // multiple times. - if (MergePotentials.size() == TailMergeThreshold) - for (unsigned i = 0, e = MergePotentials.size(); i != e; ++i) - TriedMerging.insert(MergePotentials[i].getBlock()); - if (MergePotentials.size() >= 2) - MadeChange |= TryTailMergeBlocks(IBB, PredBB); - // Reinsert an unconditional branch if needed. - // The 1 below can occur as a result of removing blocks in TryTailMergeBlocks. - PredBB = prior(I); // this may have been changed in TryTailMergeBlocks - if (MergePotentials.size() == 1 && - MergePotentials.begin()->getBlock() != PredBB) - FixTail(MergePotentials.begin()->getBlock(), IBB, TII); } + + // If this is a large problem, avoid visiting the same basic blocks multiple + // times. + if (MergePotentials.size() == TailMergeThreshold) + for (unsigned i = 0, e = MergePotentials.size(); i != e; ++i) + TriedMerging.insert(MergePotentials[i].getBlock()); + + if (MergePotentials.size() >= 2) + MadeChange |= TryTailMergeBlocks(IBB, PredBB); + + // Reinsert an unconditional branch if needed. The 1 below can occur as a + // result of removing blocks in TryTailMergeBlocks. + PredBB = &*std::prev(I); // this may have been changed in TryTailMergeBlocks + if (MergePotentials.size() == 1 && + MergePotentials.begin()->getBlock() != PredBB) + FixTail(MergePotentials.begin()->getBlock(), IBB, TII); } + return MadeChange; } +void BranchFolder::setCommonTailEdgeWeights(MachineBasicBlock &TailMBB) { + SmallVector EdgeFreqLs(TailMBB.succ_size()); + BlockFrequency AccumulatedMBBFreq; + + // Aggregate edge frequency of successor edge j: + // edgeFreq(j) = sum (freq(bb) * edgeProb(bb, j)), + // where bb is a basic block that is in SameTails. + for (const auto &Src : SameTails) { + const MachineBasicBlock *SrcMBB = Src.getBlock(); + BlockFrequency BlockFreq = MBBFreqInfo.getBlockFreq(SrcMBB); + AccumulatedMBBFreq += BlockFreq; + + // It is not necessary to recompute edge weights if TailBB has less than two + // successors. + if (TailMBB.succ_size() <= 1) + continue; + + auto EdgeFreq = EdgeFreqLs.begin(); + + for (auto SuccI = TailMBB.succ_begin(), SuccE = TailMBB.succ_end(); + SuccI != SuccE; ++SuccI, ++EdgeFreq) + *EdgeFreq += BlockFreq * MBPI.getEdgeProbability(SrcMBB, *SuccI); + } + + MBBFreqInfo.setBlockFreq(&TailMBB, AccumulatedMBBFreq); + + if (TailMBB.succ_size() <= 1) + return; + + auto SumEdgeFreq = + std::accumulate(EdgeFreqLs.begin(), EdgeFreqLs.end(), BlockFrequency(0)) + .getFrequency(); + auto EdgeFreq = EdgeFreqLs.begin(); + + if (SumEdgeFreq > 0) { + for (auto SuccI = TailMBB.succ_begin(), SuccE = TailMBB.succ_end(); + SuccI != SuccE; ++SuccI, ++EdgeFreq) { + auto Prob = BranchProbability::getBranchProbability( + EdgeFreq->getFrequency(), SumEdgeFreq); + TailMBB.setSuccProbability(SuccI, Prob); + } + } +} + //===----------------------------------------------------------------------===// // Branch Optimization //===----------------------------------------------------------------------===// @@ -943,10 +1123,12 @@ bool BranchFolder::OptimizeBranches(MachineFunction &MF) { // Make sure blocks are numbered in order MF.RenumberBlocks(); + // Renumbering blocks alters funclet membership, recalculate it. + FuncletMembership = getFuncletMembership(MF); - for (MachineFunction::iterator I = llvm::next(MF.begin()), E = MF.end(); + for (MachineFunction::iterator I = std::next(MF.begin()), E = MF.end(); I != E; ) { - MachineBasicBlock *MBB = I++; + MachineBasicBlock *MBB = &*I++; MadeChange |= OptimizeBlock(MBB); // If it is dead, remove it. @@ -956,31 +1138,22 @@ bool BranchFolder::OptimizeBranches(MachineFunction &MF) { ++NumDeadBlocks; } } + return MadeChange; } // Blocks should be considered empty if they contain only debug info; // else the debug info would affect codegen. static bool IsEmptyBlock(MachineBasicBlock *MBB) { - if (MBB->empty()) - return true; - for (MachineBasicBlock::iterator MBBI = MBB->begin(), MBBE = MBB->end(); - MBBI!=MBBE; ++MBBI) { - if (!MBBI->isDebugValue()) - return false; - } - return true; + return MBB->getFirstNonDebugInstr() == MBB->end(); } // Blocks with only debug info and branches should be considered the same // as blocks with only branches. static bool IsBranchOnlyBlock(MachineBasicBlock *MBB) { - MachineBasicBlock::iterator MBBI, MBBE; - for (MBBI = MBB->begin(), MBBE = MBB->end(); MBBI!=MBBE; ++MBBI) { - if (!MBBI->isDebugValue()) - break; - } - return (MBBI->getDesc().isBranch()); + MachineBasicBlock::iterator I = MBB->getFirstNonDebugInstr(); + assert(I != MBB->end() && "empty block!"); + return I->isBranch(); } /// IsBetterFallthrough - Return true if it would be clearly better to @@ -993,22 +1166,26 @@ static bool IsBetterFallthrough(MachineBasicBlock *MBB1, // MBB1 doesn't, we prefer to fall through into MBB1. This allows us to // optimize branches that branch to either a return block or an assert block // into a fallthrough to the return. - if (IsEmptyBlock(MBB1) || IsEmptyBlock(MBB2)) return false; + MachineBasicBlock::iterator MBB1I = MBB1->getLastNonDebugInstr(); + MachineBasicBlock::iterator MBB2I = MBB2->getLastNonDebugInstr(); + if (MBB1I == MBB1->end() || MBB2I == MBB2->end()) + return false; // If there is a clear successor ordering we make sure that one block // will fall through to the next if (MBB1->isSuccessor(MBB2)) return true; if (MBB2->isSuccessor(MBB1)) return false; - // Neither block consists entirely of debug info (per IsEmptyBlock check), - // so we needn't test for falling off the beginning here. - MachineBasicBlock::iterator MBB1I = --MBB1->end(); - while (MBB1I->isDebugValue()) - --MBB1I; - MachineBasicBlock::iterator MBB2I = --MBB2->end(); - while (MBB2I->isDebugValue()) - --MBB2I; - return MBB2I->getDesc().isCall() && !MBB1I->getDesc().isCall(); + return MBB2I->isCall() && !MBB1I->isCall(); +} + +/// getBranchDebugLoc - Find and return, if any, the DebugLoc of the branch +/// instructions on the block. +static DebugLoc getBranchDebugLoc(MachineBasicBlock &MBB) { + MachineBasicBlock::iterator I = MBB.getLastNonDebugInstr(); + if (I != MBB.end() && I->isBranch()) + return I->getDebugLoc(); + return DebugLoc(); } /// OptimizeBlock - Analyze and optimize control flow related to the specified @@ -1016,33 +1193,48 @@ static bool IsBetterFallthrough(MachineBasicBlock *MBB1, bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) { bool MadeChange = false; MachineFunction &MF = *MBB->getParent(); - DebugLoc dl; // FIXME: this is nowhere ReoptimizeBlock: - MachineFunction::iterator FallThrough = MBB; + MachineFunction::iterator FallThrough = MBB->getIterator(); ++FallThrough; + // Make sure MBB and FallThrough belong to the same funclet. + bool SameFunclet = true; + if (!FuncletMembership.empty() && FallThrough != MF.end()) { + auto MBBFunclet = FuncletMembership.find(MBB); + assert(MBBFunclet != FuncletMembership.end()); + auto FallThroughFunclet = FuncletMembership.find(&*FallThrough); + assert(FallThroughFunclet != FuncletMembership.end()); + SameFunclet = MBBFunclet->second == FallThroughFunclet->second; + } + // If this block is empty, make everyone use its fall-through, not the block // explicitly. Landing pads should not do this since the landing-pad table // points to this block. Blocks with their addresses taken shouldn't be // optimized away. - if (IsEmptyBlock(MBB) && !MBB->isLandingPad() && !MBB->hasAddressTaken()) { + if (IsEmptyBlock(MBB) && !MBB->isEHPad() && !MBB->hasAddressTaken() && + SameFunclet) { // Dead block? Leave for cleanup later. if (MBB->pred_empty()) return MadeChange; if (FallThrough == MF.end()) { // TODO: Simplify preds to not branch here if possible! + } else if (FallThrough->isEHPad()) { + // Don't rewrite to a landing pad fallthough. That could lead to the case + // where a BB jumps to more than one landing pad. + // TODO: Is it ever worth rewriting predecessors which don't already + // jump to a landing pad, and so can safely jump to the fallthrough? } else { // Rewrite all predecessors of the old block to go to the fallthrough // instead. while (!MBB->pred_empty()) { MachineBasicBlock *Pred = *(MBB->pred_end()-1); - Pred->ReplaceUsesOfBlockWith(MBB, FallThrough); + Pred->ReplaceUsesOfBlockWith(MBB, &*FallThrough); } // If MBB was the target of a jump table, update jump tables to go to the // fallthrough instead. if (MachineJumpTableInfo *MJTI = MF.getJumpTableInfo()) - MJTI->ReplaceMBBInJumpTables(MBB, FallThrough); + MJTI->ReplaceMBBInJumpTables(MBB, &*FallThrough); MadeChange = true; } return MadeChange; @@ -1050,9 +1242,9 @@ ReoptimizeBlock: // Check to see if we can simplify the terminator of the block before this // one. - MachineBasicBlock &PrevBB = *prior(MachineFunction::iterator(MBB)); + MachineBasicBlock &PrevBB = *std::prev(MachineFunction::iterator(MBB)); - MachineBasicBlock *PriorTBB = 0, *PriorFBB = 0; + MachineBasicBlock *PriorTBB = nullptr, *PriorFBB = nullptr; SmallVector PriorCond; bool PriorUnAnalyzable = TII->AnalyzeBranch(PrevBB, PriorTBB, PriorFBB, PriorCond, true); @@ -1065,10 +1257,11 @@ ReoptimizeBlock: // destination, remove the branch, replacing it with an unconditional one or // a fall-through. if (PriorTBB && PriorTBB == PriorFBB) { + DebugLoc dl = getBranchDebugLoc(PrevBB); TII->RemoveBranch(PrevBB); PriorCond.clear(); if (PriorTBB != MBB) - TII->InsertBranch(PrevBB, PriorTBB, 0, PriorCond, dl); + TII->InsertBranch(PrevBB, PriorTBB, nullptr, PriorCond, dl); MadeChange = true; ++NumBranchOpts; goto ReoptimizeBlock; @@ -1083,7 +1276,7 @@ ReoptimizeBlock: // AnalyzeBranch. if (PriorCond.empty() && !PriorTBB && MBB->pred_size() == 1 && PrevBB.succ_size() == 1 && - !MBB->hasAddressTaken() && !MBB->isLandingPad()) { + !MBB->hasAddressTaken() && !MBB->isEHPad()) { DEBUG(dbgs() << "\nMerging into block: " << PrevBB << "From MBB: " << *MBB); // Remove redundant DBG_VALUEs first. @@ -1091,7 +1284,7 @@ ReoptimizeBlock: MachineBasicBlock::iterator PrevBBIter = PrevBB.end(); --PrevBBIter; MachineBasicBlock::iterator MBBIter = MBB->begin(); - // Check if DBG_VALUE at the end of PrevBB is identical to the + // Check if DBG_VALUE at the end of PrevBB is identical to the // DBG_VALUE at the beginning of MBB. while (PrevBBIter != PrevBB.begin() && MBBIter != MBB->end() && PrevBBIter->isDebugValue() && MBBIter->isDebugValue()) { @@ -1103,7 +1296,7 @@ ReoptimizeBlock: } } PrevBB.splice(PrevBB.end(), MBB, MBB->begin(), MBB->end()); - PrevBB.removeSuccessor(PrevBB.succ_begin());; + PrevBB.removeSuccessor(PrevBB.succ_begin()); assert(PrevBB.succ_empty()); PrevBB.transferSuccessors(MBB); MadeChange = true; @@ -1112,7 +1305,7 @@ ReoptimizeBlock: // If the previous branch *only* branches to *this* block (conditional or // not) remove the branch. - if (PriorTBB == MBB && PriorFBB == 0) { + if (PriorTBB == MBB && !PriorFBB) { TII->RemoveBranch(PrevBB); MadeChange = true; ++NumBranchOpts; @@ -1122,8 +1315,9 @@ ReoptimizeBlock: // If the prior block branches somewhere else on the condition and here if // the condition is false, remove the uncond second branch. if (PriorFBB == MBB) { + DebugLoc dl = getBranchDebugLoc(PrevBB); TII->RemoveBranch(PrevBB); - TII->InsertBranch(PrevBB, PriorTBB, 0, PriorCond, dl); + TII->InsertBranch(PrevBB, PriorTBB, nullptr, PriorCond, dl); MadeChange = true; ++NumBranchOpts; goto ReoptimizeBlock; @@ -1135,8 +1329,9 @@ ReoptimizeBlock: if (PriorTBB == MBB) { SmallVector NewPriorCond(PriorCond); if (!TII->ReverseBranchCondition(NewPriorCond)) { + DebugLoc dl = getBranchDebugLoc(PrevBB); TII->RemoveBranch(PrevBB); - TII->InsertBranch(PrevBB, PriorFBB, 0, NewPriorCond, dl); + TII->InsertBranch(PrevBB, PriorFBB, nullptr, NewPriorCond, dl); MadeChange = true; ++NumBranchOpts; goto ReoptimizeBlock; @@ -1151,7 +1346,7 @@ ReoptimizeBlock: // We consider it more likely that execution will stay in the function (e.g. // due to loops) than it is to exit it. This asserts in loops etc, moving // the assert condition out of the loop body. - if (MBB->succ_empty() && !PriorCond.empty() && PriorFBB == 0 && + if (MBB->succ_empty() && !PriorCond.empty() && !PriorFBB && MachineFunction::iterator(PriorTBB) == FallThrough && !MBB->canFallThrough()) { bool DoTransform = true; @@ -1172,11 +1367,12 @@ ReoptimizeBlock: DEBUG(dbgs() << "\nMoving MBB: " << *MBB << "To make fallthrough to: " << *PriorTBB << "\n"); + DebugLoc dl = getBranchDebugLoc(PrevBB); TII->RemoveBranch(PrevBB); - TII->InsertBranch(PrevBB, MBB, 0, NewPriorCond, dl); + TII->InsertBranch(PrevBB, MBB, nullptr, NewPriorCond, dl); // Move this block to the end of the function. - MBB->moveAfter(--MF.end()); + MBB->moveAfter(&MF.back()); MadeChange = true; ++NumBranchOpts; return MadeChange; @@ -1186,7 +1382,7 @@ ReoptimizeBlock: } // Analyze the branch in the current block. - MachineBasicBlock *CurTBB = 0, *CurFBB = 0; + MachineBasicBlock *CurTBB = nullptr, *CurFBB = nullptr; SmallVector CurCond; bool CurUnAnalyzable= TII->AnalyzeBranch(*MBB, CurTBB, CurFBB, CurCond, true); if (!CurUnAnalyzable) { @@ -1201,6 +1397,7 @@ ReoptimizeBlock: if (CurTBB && CurFBB && CurFBB == MBB && CurTBB != MBB) { SmallVector NewCond(CurCond); if (!TII->ReverseBranchCondition(NewCond)) { + DebugLoc dl = getBranchDebugLoc(*MBB); TII->RemoveBranch(*MBB); TII->InsertBranch(*MBB, CurFBB, CurTBB, NewCond, dl); MadeChange = true; @@ -1211,9 +1408,10 @@ ReoptimizeBlock: // If this branch is the only thing in its block, see if we can forward // other blocks across it. - if (CurTBB && CurCond.empty() && CurFBB == 0 && + if (CurTBB && CurCond.empty() && !CurFBB && IsBranchOnlyBlock(MBB) && CurTBB != MBB && - !MBB->hasAddressTaken()) { + !MBB->hasAddressTaken() && !MBB->isEHPad()) { + DebugLoc dl = getBranchDebugLoc(*MBB); // This block may contain just an unconditional branch. Because there can // be 'non-branch terminators' in the block, try removing the branch and // then seeing if the block is empty. @@ -1221,19 +1419,10 @@ ReoptimizeBlock: // If the only things remaining in the block are debug info, remove these // as well, so this will behave the same as an empty block in non-debug // mode. - if (!MBB->empty()) { - bool NonDebugInfoFound = false; - for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); - I != E; ++I) { - if (!I->isDebugValue()) { - NonDebugInfoFound = true; - break; - } - } - if (!NonDebugInfoFound) - // Make the block empty, losing the debug info (we could probably - // improve this in some cases.) - MBB->erase(MBB->begin(), MBB->end()); + if (IsEmptyBlock(MBB)) { + // Make the block empty, losing the debug info (we could probably + // improve this in some cases.) + MBB->erase(MBB->begin(), MBB->end()); } // If this block is just an unconditional branch to CurTBB, we can // usually completely eliminate the block. The only case we cannot @@ -1248,16 +1437,17 @@ ReoptimizeBlock: // explicit branch to us to make updates simpler. if (!PredHasNoFallThrough && PrevBB.isSuccessor(MBB) && PriorTBB != MBB && PriorFBB != MBB) { - if (PriorTBB == 0) { - assert(PriorCond.empty() && PriorFBB == 0 && + if (!PriorTBB) { + assert(PriorCond.empty() && !PriorFBB && "Bad branch analysis"); PriorTBB = MBB; } else { - assert(PriorFBB == 0 && "Machine CFG out of date!"); + assert(!PriorFBB && "Machine CFG out of date!"); PriorFBB = MBB; } + DebugLoc pdl = getBranchDebugLoc(PrevBB); TII->RemoveBranch(PrevBB); - TII->InsertBranch(PrevBB, PriorTBB, PriorFBB, PriorCond, dl); + TII->InsertBranch(PrevBB, PriorTBB, PriorFBB, PriorCond, pdl); } // Iterate through all the predecessors, revectoring each in-turn. @@ -1276,17 +1466,18 @@ ReoptimizeBlock: // If this change resulted in PMBB ending in a conditional // branch where both conditions go to the same destination, // change this to an unconditional branch (and fix the CFG). - MachineBasicBlock *NewCurTBB = 0, *NewCurFBB = 0; + MachineBasicBlock *NewCurTBB = nullptr, *NewCurFBB = nullptr; SmallVector NewCurCond; bool NewCurUnAnalyzable = TII->AnalyzeBranch(*PMBB, NewCurTBB, NewCurFBB, NewCurCond, true); if (!NewCurUnAnalyzable && NewCurTBB && NewCurTBB == NewCurFBB) { + DebugLoc pdl = getBranchDebugLoc(*PMBB); TII->RemoveBranch(*PMBB); NewCurCond.clear(); - TII->InsertBranch(*PMBB, NewCurTBB, 0, NewCurCond, dl); + TII->InsertBranch(*PMBB, NewCurTBB, nullptr, NewCurCond, pdl); MadeChange = true; ++NumBranchOpts; - PMBB->CorrectExtraCFGEdges(NewCurTBB, 0, false); + PMBB->CorrectExtraCFGEdges(NewCurTBB, nullptr, false); } } } @@ -1303,7 +1494,7 @@ ReoptimizeBlock: } // Add the branch back if the block is more than just an uncond branch. - TII->InsertBranch(*MBB, CurTBB, 0, CurCond, dl); + TII->InsertBranch(*MBB, CurTBB, nullptr, CurCond, dl); } } @@ -1316,15 +1507,12 @@ ReoptimizeBlock: // see if it has a fall-through into its successor. bool CurFallsThru = MBB->canFallThrough(); - if (!MBB->isLandingPad()) { + if (!MBB->isEHPad()) { // Check all the predecessors of this block. If one of them has no fall // throughs, move this block right after it. - for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(), - E = MBB->pred_end(); PI != E; ++PI) { + for (MachineBasicBlock *PredBB : MBB->predecessors()) { // Analyze the branch at the end of the pred. - MachineBasicBlock *PredBB = *PI; - MachineFunction::iterator PredFallthrough = PredBB; ++PredFallthrough; - MachineBasicBlock *PredTBB = 0, *PredFBB = 0; + MachineBasicBlock *PredTBB = nullptr, *PredFBB = nullptr; SmallVector PredCond; if (PredBB != MBB && !PredBB->canFallThrough() && !TII->AnalyzeBranch(*PredBB, PredTBB, PredFBB, PredCond, true) @@ -1341,9 +1529,9 @@ ReoptimizeBlock: // B elsewhere // next: if (CurFallsThru) { - MachineBasicBlock *NextBB = llvm::next(MachineFunction::iterator(MBB)); + MachineBasicBlock *NextBB = &*std::next(MBB->getIterator()); CurCond.clear(); - TII->InsertBranch(*MBB, NextBB, 0, CurCond, dl); + TII->InsertBranch(*MBB, NextBB, nullptr, CurCond, DebugLoc()); } MBB->moveAfter(PredBB); MadeChange = true; @@ -1354,11 +1542,9 @@ ReoptimizeBlock: if (!CurFallsThru) { // Check all successors to see if we can move this block before it. - for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(), - E = MBB->succ_end(); SI != E; ++SI) { + for (MachineBasicBlock *SuccBB : MBB->successors()) { // Analyze the branch at the end of the block before the succ. - MachineBasicBlock *SuccBB = *SI; - MachineFunction::iterator SuccPrev = SuccBB; --SuccPrev; + MachineFunction::iterator SuccPrev = --SuccBB->getIterator(); // If this block doesn't already fall-through to that successor, and if // the succ doesn't already have a block that can fall through into it, @@ -1366,7 +1552,7 @@ ReoptimizeBlock: // fallthrough to happen. if (SuccBB != MBB && &*SuccPrev != MBB && !SuccPrev->canFallThrough() && !CurUnAnalyzable && - !SuccBB->isLandingPad()) { + !SuccBB->isEHPad()) { MBB->moveBefore(SuccBB); MadeChange = true; goto ReoptimizeBlock; @@ -1376,12 +1562,20 @@ ReoptimizeBlock: // Okay, there is no really great place to put this block. If, however, // the block before this one would be a fall-through if this block were // removed, move this block to the end of the function. - MachineBasicBlock *PrevTBB = 0, *PrevFBB = 0; + MachineBasicBlock *PrevTBB = nullptr, *PrevFBB = nullptr; SmallVector PrevCond; + // We're looking for cases where PrevBB could possibly fall through to + // FallThrough, but if FallThrough is an EH pad that wouldn't be useful + // so here we skip over any EH pads so we might have a chance to find + // a branch target from PrevBB. + while (FallThrough != MF.end() && FallThrough->isEHPad()) + ++FallThrough; + // Now check to see if the current block is sitting between PrevBB and + // a block to which it could fall through. if (FallThrough != MF.end() && !TII->AnalyzeBranch(PrevBB, PrevTBB, PrevFBB, PrevCond, true) && - PrevBB.isSuccessor(FallThrough)) { - MBB->moveAfter(--MF.end()); + PrevBB.isSuccessor(&*FallThrough)) { + MBB->moveAfter(&MF.back()); MadeChange = true; return MadeChange; } @@ -1400,7 +1594,7 @@ ReoptimizeBlock: bool BranchFolder::HoistCommonCode(MachineFunction &MF) { bool MadeChange = false; for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ) { - MachineBasicBlock *MBB = I++; + MachineBasicBlock *MBB = &*I++; MadeChange |= HoistCommonCodeInSuccs(MBB); } @@ -1411,17 +1605,25 @@ bool BranchFolder::HoistCommonCode(MachineFunction &MF) { /// its 'true' successor. static MachineBasicBlock *findFalseBlock(MachineBasicBlock *BB, MachineBasicBlock *TrueBB) { - for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(), - E = BB->succ_end(); SI != E; ++SI) { - MachineBasicBlock *SuccBB = *SI; + for (MachineBasicBlock *SuccBB : BB->successors()) if (SuccBB != TrueBB) return SuccBB; + return nullptr; +} + +template +static void addRegAndItsAliases(unsigned Reg, const TargetRegisterInfo *TRI, + Container &Set) { + if (TargetRegisterInfo::isPhysicalRegister(Reg)) { + for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI) + Set.insert(*AI); + } else { + Set.insert(Reg); } - return NULL; } /// findHoistingInsertPosAndDeps - Find the location to move common instructions -/// in successors to. The location is ususally just before the terminator, +/// in successors to. The location is usually just before the terminator, /// however if the terminator is a conditional branch and its previous /// instruction is the flag setting instruction, the previous instruction is /// the preferred location. This function also gathers uses and defs of the @@ -1437,21 +1639,24 @@ MachineBasicBlock::iterator findHoistingInsertPosAndDeps(MachineBasicBlock *MBB, if (!TII->isUnpredicatedTerminator(Loc)) return MBB->end(); - for (unsigned i = 0, e = Loc->getNumOperands(); i != e; ++i) { - const MachineOperand &MO = Loc->getOperand(i); + for (const MachineOperand &MO : Loc->operands()) { if (!MO.isReg()) continue; unsigned Reg = MO.getReg(); if (!Reg) continue; if (MO.isUse()) { - Uses.insert(Reg); - for (const unsigned *AS = TRI->getAliasSet(Reg); *AS; ++AS) - Uses.insert(*AS); - } else if (!MO.isDead()) - // Don't try to hoist code in the rare case the terminator defines a - // register that is later used. - return MBB->end(); + addRegAndItsAliases(Reg, TRI, Uses); + } else { + if (!MO.isDead()) + // Don't try to hoist code in the rare case the terminator defines a + // register that is later used. + return MBB->end(); + + // If the terminator defines a register, make sure we don't hoist + // the instruction whose def might be clobbered by the terminator. + addRegAndItsAliases(Reg, TRI, Defs); + } } if (Uses.empty()) @@ -1463,19 +1668,23 @@ MachineBasicBlock::iterator findHoistingInsertPosAndDeps(MachineBasicBlock *MBB, // branch from condition setting instruction. MachineBasicBlock::iterator PI = Loc; --PI; - while (PI != MBB->begin() && Loc->isDebugValue()) + while (PI != MBB->begin() && PI->isDebugValue()) --PI; bool IsDef = false; - for (unsigned i = 0, e = PI->getNumOperands(); !IsDef && i != e; ++i) { - const MachineOperand &MO = PI->getOperand(i); + for (const MachineOperand &MO : PI->operands()) { + // If PI has a regmask operand, it is probably a call. Separate away. + if (MO.isRegMask()) + return Loc; if (!MO.isReg() || MO.isUse()) continue; unsigned Reg = MO.getReg(); if (!Reg) continue; - if (Uses.count(Reg)) + if (Uses.count(Reg)) { IsDef = true; + break; + } } if (!IsDef) // The condition setting instruction is not just before the conditional @@ -1489,33 +1698,28 @@ MachineBasicBlock::iterator findHoistingInsertPosAndDeps(MachineBasicBlock *MBB, // Also avoid moving code above predicated instruction since it's hard to // reason about register liveness with predicated instruction. bool DontMoveAcrossStore = true; - if (!PI->isSafeToMove(TII, 0, DontMoveAcrossStore) || - TII->isPredicated(PI)) + if (!PI->isSafeToMove(nullptr, DontMoveAcrossStore) || TII->isPredicated(PI)) return MBB->end(); // Find out what registers are live. Note this routine is ignoring other live // registers which are only used by instructions in successor blocks. - for (unsigned i = 0, e = PI->getNumOperands(); i != e; ++i) { - const MachineOperand &MO = PI->getOperand(i); + for (const MachineOperand &MO : PI->operands()) { if (!MO.isReg()) continue; unsigned Reg = MO.getReg(); if (!Reg) continue; if (MO.isUse()) { - Uses.insert(Reg); - for (const unsigned *AS = TRI->getAliasSet(Reg); *AS; ++AS) - Uses.insert(*AS); + addRegAndItsAliases(Reg, TRI, Uses); } else { - if (Uses.count(Reg)) { - Uses.erase(Reg); - for (const unsigned *SR = TRI->getSubRegisters(Reg); *SR; ++SR) - Uses.erase(*SR); // Use getSubRegisters to be conservative + if (Uses.erase(Reg)) { + if (TargetRegisterInfo::isPhysicalRegister(Reg)) { + for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) + Uses.erase(*SubRegs); // Use sub-registers to be conservative + } } - Defs.insert(Reg); - for (const unsigned *AS = TRI->getAliasSet(Reg); *AS; ++AS) - Defs.insert(*AS); + addRegAndItsAliases(Reg, TRI, Defs); } } @@ -1526,7 +1730,7 @@ MachineBasicBlock::iterator findHoistingInsertPosAndDeps(MachineBasicBlock *MBB, /// sequence at the start of the function, move the instructions before MBB /// terminator if it's legal. bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) { - MachineBasicBlock *TBB = 0, *FBB = 0; + MachineBasicBlock *TBB = nullptr, *FBB = nullptr; SmallVector Cond; if (TII->AnalyzeBranch(*MBB, TBB, FBB, Cond, true) || !TBB || Cond.empty()) return false; @@ -1579,8 +1783,12 @@ bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) { break; bool IsSafe = true; - for (unsigned i = 0, e = TIB->getNumOperands(); i != e; ++i) { - MachineOperand &MO = TIB->getOperand(i); + for (MachineOperand &MO : TIB->operands()) { + // Don't attempt to hoist instructions with register masks. + if (MO.isRegMask()) { + IsSafe = false; + break; + } if (!MO.isReg()) continue; unsigned Reg = MO.getReg(); @@ -1615,38 +1823,47 @@ bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) { IsSafe = false; break; } + + if (MO.isKill() && Uses.count(Reg)) + // Kills a register that's read by the instruction at the point of + // insertion. Remove the kill marker. + MO.setIsKill(false); } } if (!IsSafe) break; bool DontMoveAcrossStore = true; - if (!TIB->isSafeToMove(TII, 0, DontMoveAcrossStore)) + if (!TIB->isSafeToMove(nullptr, DontMoveAcrossStore)) break; - // Track local defs so we can update liveins. - for (unsigned i = 0, e = TIB->getNumOperands(); i != e; ++i) { - MachineOperand &MO = TIB->getOperand(i); - if (!MO.isReg()) + // Remove kills from LocalDefsSet, these registers had short live ranges. + for (const MachineOperand &MO : TIB->operands()) { + if (!MO.isReg() || !MO.isUse() || !MO.isKill()) continue; unsigned Reg = MO.getReg(); - if (!Reg) + if (!Reg || !LocalDefsSet.count(Reg)) continue; - if (MO.isDef()) { - if (!MO.isDead()) { - LocalDefs.push_back(Reg); - LocalDefsSet.insert(Reg); - for (const unsigned *SR = TRI->getSubRegisters(Reg); *SR; ++SR) - LocalDefsSet.insert(*SR); - } - } else if (MO.isKill() && LocalDefsSet.count(Reg)) { + if (TargetRegisterInfo::isPhysicalRegister(Reg)) { + for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI) + LocalDefsSet.erase(*AI); + } else { LocalDefsSet.erase(Reg); - for (const unsigned *SR = TRI->getSubRegisters(Reg); *SR; ++SR) - LocalDefsSet.erase(*SR); } } - HasDups = true;; + // Track local defs so we can update liveins. + for (const MachineOperand &MO : TIB->operands()) { + if (!MO.isReg() || !MO.isDef() || MO.isDead()) + continue; + unsigned Reg = MO.getReg(); + if (!Reg) + continue; + LocalDefs.push_back(Reg); + addRegAndItsAliases(Reg, TRI, LocalDefsSet); + } + + HasDups = true; ++TIB; ++FIB; }