X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FIfConversion.cpp;h=e2d0eb44da06d45ec68fc42d217e7de67f14896a;hb=b59d46efa521801a3d42fc5f53fedf3e81b070ce;hp=ce7ed293daacdd0cf14b774d4d1af1b83b570ad1;hpb=6b598748b1e03b6b188726d5a0fef2a6abc29562;p=oota-llvm.git diff --git a/lib/CodeGen/IfConversion.cpp b/lib/CodeGen/IfConversion.cpp index ce7ed293daa..e2d0eb44da0 100644 --- a/lib/CodeGen/IfConversion.cpp +++ b/lib/CodeGen/IfConversion.cpp @@ -12,24 +12,29 @@ //===----------------------------------------------------------------------===// #define DEBUG_TYPE "ifcvt" -#include "BranchFolding.h" -#include "llvm/Function.h" #include "llvm/CodeGen/Passes.h" -#include "llvm/CodeGen/MachineModuleInfo.h" +#include "BranchFolding.h" +#include "llvm/ADT/STLExtras.h" +#include "llvm/ADT/SmallSet.h" +#include "llvm/ADT/Statistic.h" #include "llvm/CodeGen/MachineBranchProbabilityInfo.h" #include "llvm/CodeGen/MachineFunctionPass.h" +#include "llvm/CodeGen/MachineInstrBuilder.h" +#include "llvm/CodeGen/MachineModuleInfo.h" +#include "llvm/CodeGen/MachineRegisterInfo.h" +#include "llvm/CodeGen/TargetSchedule.h" +#include "llvm/CodeGen/LiveRegUnits.h" #include "llvm/MC/MCInstrItineraries.h" -#include "llvm/Target/TargetInstrInfo.h" -#include "llvm/Target/TargetLowering.h" -#include "llvm/Target/TargetMachine.h" -#include "llvm/Target/TargetRegisterInfo.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/Statistic.h" -#include "llvm/ADT/STLExtras.h" +#include "llvm/Target/TargetInstrInfo.h" +#include "llvm/Target/TargetLowering.h" +#include "llvm/Target/TargetMachine.h" +#include "llvm/Target/TargetRegisterInfo.h" +#include "llvm/Target/TargetSubtargetInfo.h" + using namespace llvm; // Hidden options for help debugging. @@ -62,6 +67,7 @@ STATISTIC(NumTriangleFRev, "Number of triangle (F/R) if-conversions performed"); STATISTIC(NumDiamonds, "Number of diamond if-conversions performed"); STATISTIC(NumIfConvBBs, "Number of if-converted blocks"); STATISTIC(NumDupBBs, "Number of duplicated blocks"); +STATISTIC(NumUnpred, "Number of true blocks of diamonds unpredicated"); namespace { class IfConverter : public MachineFunctionPass { @@ -148,13 +154,18 @@ namespace { /// BBAnalysis - Results of if-conversion feasibility analysis indexed by /// basic block number. std::vector BBAnalysis; + TargetSchedModel SchedModel; - const TargetLowering *TLI; + const TargetLoweringBase *TLI; const TargetInstrInfo *TII; const TargetRegisterInfo *TRI; - const InstrItineraryData *InstrItins; const MachineBranchProbabilityInfo *MBPI; + MachineRegisterInfo *MRI; + + LiveRegUnits Redefs; + LiveRegUnits DontKill; + bool PreRegAlloc; bool MadeChange; int FnNum; public: @@ -169,7 +180,6 @@ namespace { } virtual bool runOnMachineFunction(MachineFunction &MF); - virtual const char *getPassName() const { return "If Converter"; } private: bool ReverseBranchCondition(BBInfo &BBI); @@ -195,10 +205,9 @@ namespace { void PredicateBlock(BBInfo &BBI, MachineBasicBlock::iterator E, SmallVectorImpl &Cond, - SmallSet &Redefs); + SmallSet *LaterRedefs = 0); void CopyAndPredicateBlock(BBInfo &ToBBI, BBInfo &FromBBI, SmallVectorImpl &Cond, - SmallSet &Redefs, bool IgnoreBr = false); void MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI, bool AddEdges = true); @@ -251,28 +260,38 @@ namespace { char IfConverter::ID = 0; } +char &llvm::IfConverterID = IfConverter::ID; + INITIALIZE_PASS_BEGIN(IfConverter, "if-converter", "If Converter", false, false) INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo) INITIALIZE_PASS_END(IfConverter, "if-converter", "If Converter", false, false) -FunctionPass *llvm::createIfConverterPass() { return new IfConverter(); } - bool IfConverter::runOnMachineFunction(MachineFunction &MF) { TLI = MF.getTarget().getTargetLowering(); TII = MF.getTarget().getInstrInfo(); TRI = MF.getTarget().getRegisterInfo(); MBPI = &getAnalysis(); - InstrItins = MF.getTarget().getInstrItineraryData(); + MRI = &MF.getRegInfo(); + + const TargetSubtargetInfo &ST = + MF.getTarget().getSubtarget(); + SchedModel.init(*ST.getSchedModel(), &ST, TII); + if (!TII) return false; - // Tail merge tend to expose more if-conversion opportunities. - BranchFolder BF(true, false); - bool BFChange = BF.OptimizeFunction(MF, TII, + PreRegAlloc = MRI->isSSA(); + + bool BFChange = false; + if (!PreRegAlloc) { + // Tail merge tend to expose more if-conversion opportunities. + BranchFolder BF(true, false); + BFChange = BF.OptimizeFunction(MF, TII, MF.getTarget().getRegisterInfo(), getAnalysisIfAvailable()); + } DEBUG(dbgs() << "\nIfcvt: function (" << ++FnNum << ") \'" - << MF.getFunction()->getName() << "\'"); + << MF.getName() << "\'"); if (FnNum < IfCvtFnStart || (IfCvtFnStop != -1 && FnNum > IfCvtFnStop)) { DEBUG(dbgs() << " skipped\n"); @@ -313,8 +332,7 @@ bool IfConverter::runOnMachineFunction(MachineFunction &MF) { bool RetVal = false; switch (Kind) { - default: assert(false && "Unexpected!"); - break; + default: llvm_unreachable("Unexpected!"); case ICSimple: case ICSimpleFalse: { bool isFalse = Kind == ICSimpleFalse; @@ -573,12 +591,12 @@ bool IfConverter::ValidDiamond(BBInfo &TrueBBI, BBInfo &FalseBBI, // blocks, move the end iterators up past any branch instructions. while (TIE != TIB) { --TIE; - if (!TIE->getDesc().isBranch()) + if (!TIE->isBranch()) break; } while (FIE != FIB) { --FIE; - if (!FIE->getDesc().isBranch()) + if (!FIE->isBranch()) break; } @@ -621,7 +639,7 @@ void IfConverter::ScanInstructions(BBInfo &BBI) { if (BBI.IsDone) return; - bool AlreadyPredicated = BBI.Predicate.size() > 0; + bool AlreadyPredicated = !BBI.Predicate.empty(); // First analyze the end of BB branches. BBI.TrueBB = BBI.FalseBB = NULL; BBI.BrCond.clear(); @@ -651,39 +669,34 @@ void IfConverter::ScanInstructions(BBInfo &BBI) { if (I->isDebugValue()) continue; - const MCInstrDesc &MCID = I->getDesc(); - if (MCID.isNotDuplicable()) + if (I->isNotDuplicable()) BBI.CannotBeCopied = true; bool isPredicated = TII->isPredicated(I); - bool isCondBr = BBI.IsBrAnalyzable && MCID.isConditionalBranch(); - - if (!isCondBr) { - if (!isPredicated) { - BBI.NonPredSize++; - unsigned ExtraPredCost = 0; - unsigned NumCycles = TII->getInstrLatency(InstrItins, &*I, - &ExtraPredCost); - if (NumCycles > 1) - BBI.ExtraCost += NumCycles-1; - BBI.ExtraCost2 += ExtraPredCost; - } else if (!AlreadyPredicated) { - // FIXME: This instruction is already predicated before the - // if-conversion pass. It's probably something like a conditional move. - // Mark this block unpredicable for now. - BBI.IsUnpredicable = true; - return; - } + bool isCondBr = BBI.IsBrAnalyzable && I->isConditionalBranch(); + + // A conditional branch is not predicable, but it may be eliminated. + if (isCondBr) + continue; + + if (!isPredicated) { + BBI.NonPredSize++; + unsigned ExtraPredCost = TII->getPredicationCost(&*I); + unsigned NumCycles = SchedModel.computeInstrLatency(&*I, false); + if (NumCycles > 1) + BBI.ExtraCost += NumCycles-1; + BBI.ExtraCost2 += ExtraPredCost; + } else if (!AlreadyPredicated) { + // FIXME: This instruction is already predicated before the + // if-conversion pass. It's probably something like a conditional move. + // Mark this block unpredicable for now. + BBI.IsUnpredicable = true; + return; } if (BBI.ClobbersPred && !isPredicated) { // Predicate modification instruction should end the block (except for // already predicated instructions and end of block branches). - if (isCondBr) { - // A conditional branch is not predicable, but it may be eliminated. - continue; - } - // Predicate may have been modified, the subsequent (currently) // unpredicated instructions cannot be correctly predicated. BBI.IsUnpredicable = true; @@ -712,9 +725,9 @@ bool IfConverter::FeasibilityAnalysis(BBInfo &BBI, if (BBI.IsDone || BBI.IsUnpredicable) return false; - // If it is already predicated, check if its predicate subsumes the new - // predicate. - if (BBI.Predicate.size() && !TII->SubsumesPredicate(BBI.Predicate, Pred)) + // If it is already predicated, check if the new predicate subsumes + // its predicate. + if (BBI.Predicate.size() && !TII->SubsumesPredicate(Pred, BBI.Predicate)) return false; if (BBI.BrCond.size()) { @@ -787,8 +800,8 @@ IfConverter::BBInfo &IfConverter::AnalyzeBlock(MachineBasicBlock *BB, unsigned Dups = 0; unsigned Dups2 = 0; - bool TNeedSub = TrueBBI.Predicate.size() > 0; - bool FNeedSub = FalseBBI.Predicate.size() > 0; + bool TNeedSub = !TrueBBI.Predicate.empty(); + bool FNeedSub = !FalseBBI.Predicate.empty(); bool Enqueued = false; BranchProbability Prediction = MBPI->getEdgeProbability(BB, TrueBBI.BB); @@ -953,66 +966,58 @@ void IfConverter::RemoveExtraEdges(BBInfo &BBI) { BBI.BB->CorrectExtraCFGEdges(TBB, FBB, !Cond.empty()); } -/// InitPredRedefs / UpdatePredRedefs - Defs by predicated instructions are -/// modeled as read + write (sort like two-address instructions). These -/// routines track register liveness and add implicit uses to if-converted -/// instructions to conform to the model. -static void InitPredRedefs(MachineBasicBlock *BB, SmallSet &Redefs, - const TargetRegisterInfo *TRI) { - for (MachineBasicBlock::livein_iterator I = BB->livein_begin(), - E = BB->livein_end(); I != E; ++I) { - unsigned Reg = *I; - Redefs.insert(Reg); - for (const unsigned *Subreg = TRI->getSubRegisters(Reg); - *Subreg; ++Subreg) - Redefs.insert(*Subreg); - } -} - -static void UpdatePredRedefs(MachineInstr *MI, SmallSet &Redefs, - const TargetRegisterInfo *TRI, - bool AddImpUse = false) { - SmallVector Defs; - for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { - const MachineOperand &MO = MI->getOperand(i); - if (!MO.isReg()) +/// Behaves like LiveRegUnits::StepForward() but also adds implicit uses to all +/// values defined in MI which are not live/used by MI. +static void UpdatePredRedefs(MachineInstr *MI, LiveRegUnits &Redefs, + const TargetRegisterInfo *TRI) { + for (ConstMIBundleOperands Ops(MI); Ops.isValid(); ++Ops) { + if (!Ops->isReg() || !Ops->isKill()) continue; - unsigned Reg = MO.getReg(); - if (!Reg) + unsigned Reg = Ops->getReg(); + if (Reg == 0) continue; - if (MO.isDef()) - Defs.push_back(Reg); - else if (MO.isKill()) { - Redefs.erase(Reg); - for (const unsigned *SR = TRI->getSubRegisters(Reg); *SR; ++SR) - Redefs.erase(*SR); - } + Redefs.removeReg(Reg, *TRI); } - for (unsigned i = 0, e = Defs.size(); i != e; ++i) { - unsigned Reg = Defs[i]; - if (Redefs.count(Reg)) { - if (AddImpUse) - // Treat predicated update as read + write. - MI->addOperand(MachineOperand::CreateReg(Reg, false/*IsDef*/, - true/*IsImp*/,false/*IsKill*/)); - } else { - Redefs.insert(Reg); - for (const unsigned *SR = TRI->getSubRegisters(Reg); *SR; ++SR) - Redefs.insert(*SR); - } + for (MIBundleOperands Ops(MI); Ops.isValid(); ++Ops) { + if (!Ops->isReg() || !Ops->isDef()) + continue; + unsigned Reg = Ops->getReg(); + if (Reg == 0 || Redefs.contains(Reg, *TRI)) + continue; + Redefs.addReg(Reg, *TRI); + + MachineOperand &Op = *Ops; + MachineInstr *MI = Op.getParent(); + MachineInstrBuilder MIB(*MI->getParent()->getParent(), MI); + MIB.addReg(Reg, RegState::Implicit | RegState::Undef); } } -static void UpdatePredRedefs(MachineBasicBlock::iterator I, - MachineBasicBlock::iterator E, - SmallSet &Redefs, - const TargetRegisterInfo *TRI) { - while (I != E) { - UpdatePredRedefs(I, Redefs, TRI); - ++I; +/** + * Remove kill flags from operands with a registers in the @p DontKill set. + */ +static void RemoveKills(MachineInstr &MI, const LiveRegUnits &DontKill, + const MCRegisterInfo &MCRI) { + for (MIBundleOperands O(&MI); O.isValid(); ++O) { + if (!O->isReg() || !O->isKill()) + continue; + if (DontKill.contains(O->getReg(), MCRI)) + O->setIsKill(false); } } +/** + * Walks a range of machine instructions and removes kill flags for registers + * in the @p DontKill set. + */ +static void RemoveKills(MachineBasicBlock::iterator I, + MachineBasicBlock::iterator E, + const LiveRegUnits &DontKill, + const MCRegisterInfo &MCRI) { + for ( ; I != E; ++I) + RemoveKills(*I, DontKill, MCRI); +} + /// IfConvertSimple - If convert a simple (split, no rejoin) sub-CFG. /// bool IfConverter::IfConvertSimple(BBInfo &BBI, IfcvtKind Kind) { @@ -1033,23 +1038,37 @@ bool IfConverter::IfConvertSimple(BBInfo &BBI, IfcvtKind Kind) { return false; } + if (CvtBBI->BB->hasAddressTaken()) + // Conservatively abort if-conversion if BB's address is taken. + return false; + if (Kind == ICSimpleFalse) if (TII->ReverseBranchCondition(Cond)) - assert(false && "Unable to reverse branch condition!"); + llvm_unreachable("Unable to reverse branch condition!"); // Initialize liveins to the first BB. These are potentiall redefined by // predicated instructions. - SmallSet Redefs; - InitPredRedefs(CvtBBI->BB, Redefs, TRI); - InitPredRedefs(NextBBI->BB, Redefs, TRI); + Redefs.init(TRI); + Redefs.addLiveIns(CvtBBI->BB, *TRI); + Redefs.addLiveIns(NextBBI->BB, *TRI); + + // Compute a set of registers which must not be killed by instructions in + // BB1: This is everything live-in to BB2. + DontKill.init(TRI); + DontKill.addLiveIns(NextBBI->BB, *TRI); if (CvtBBI->BB->pred_size() > 1) { BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB); // Copy instructions in the true block, predicate them, and add them to // the entry block. - CopyAndPredicateBlock(BBI, *CvtBBI, Cond, Redefs); + CopyAndPredicateBlock(BBI, *CvtBBI, Cond); + + // RemoveExtraEdges won't work if the block has an unanalyzable branch, so + // explicitly remove CvtBBI as a successor. + BBI.BB->removeSuccessor(CvtBBI->BB); } else { - PredicateBlock(*CvtBBI, CvtBBI->BB->end(), Cond, Redefs); + RemoveKills(CvtBBI->BB->begin(), CvtBBI->BB->end(), DontKill, *TRI); + PredicateBlock(*CvtBBI, CvtBBI->BB->end(), Cond); // Merge converted block into entry block. BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB); @@ -1106,9 +1125,13 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind) { return false; } + if (CvtBBI->BB->hasAddressTaken()) + // Conservatively abort if-conversion if BB's address is taken. + return false; + if (Kind == ICTriangleFalse || Kind == ICTriangleFRev) if (TII->ReverseBranchCondition(Cond)) - assert(false && "Unable to reverse branch condition!"); + llvm_unreachable("Unable to reverse branch condition!"); if (Kind == ICTriangleRev || Kind == ICTriangleFRev) { if (ReverseBranchCondition(*CvtBBI)) { @@ -1130,20 +1153,26 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind) { // Initialize liveins to the first BB. These are potentially redefined by // predicated instructions. - SmallSet Redefs; - InitPredRedefs(CvtBBI->BB, Redefs, TRI); - InitPredRedefs(NextBBI->BB, Redefs, TRI); + Redefs.init(TRI); + Redefs.addLiveIns(CvtBBI->BB, *TRI); + Redefs.addLiveIns(NextBBI->BB, *TRI); + + DontKill.clear(); bool HasEarlyExit = CvtBBI->FalseBB != NULL; if (CvtBBI->BB->pred_size() > 1) { BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB); // Copy instructions in the true block, predicate them, and add them to // the entry block. - CopyAndPredicateBlock(BBI, *CvtBBI, Cond, Redefs, true); + CopyAndPredicateBlock(BBI, *CvtBBI, Cond, true); + + // RemoveExtraEdges won't work if the block has an unanalyzable branch, so + // explicitly remove CvtBBI as a successor. + BBI.BB->removeSuccessor(CvtBBI->BB); } else { // Predicate the 'true' block after removing its branch. CvtBBI->NonPredSize -= TII->RemoveBranch(*CvtBBI->BB); - PredicateBlock(*CvtBBI, CvtBBI->BB->end(), Cond, Redefs); + PredicateBlock(*CvtBBI, CvtBBI->BB->end(), Cond); // Now merge the entry of the triangle with the true block. BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB); @@ -1155,7 +1184,7 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind) { SmallVector RevCond(CvtBBI->BrCond.begin(), CvtBBI->BrCond.end()); if (TII->ReverseBranchCondition(RevCond)) - assert(false && "Unable to reverse branch condition!"); + llvm_unreachable("Unable to reverse branch condition!"); TII->InsertBranch(*BBI.BB, CvtBBI->FalseBB, NULL, RevCond, dl); BBI.BB->addSuccessor(CvtBBI->FalseBB); } @@ -1170,7 +1199,8 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind) { // block. By not merging them, we make it possible to iteratively // ifcvt the blocks. if (!HasEarlyExit && - NextBBI->BB->pred_size() == 1 && !NextBBI->HasFallThrough) { + NextBBI->BB->pred_size() == 1 && !NextBBI->HasFallThrough && + !NextBBI->BB->hasAddressTaken()) { MergeBlocks(BBI, *NextBBI); FalseBBDead = true; } else { @@ -1220,6 +1250,10 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind, return false; } + if (TrueBBI.BB->hasAddressTaken() || FalseBBI.BB->hasAddressTaken()) + // Conservatively abort if-conversion if either BB has its address taken. + return false; + // Put the predicated instructions from the 'true' block before the // instructions from the 'false' block, unless the true block would clobber // the predicate, in which case, do the opposite. @@ -1227,7 +1261,7 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind, BBInfo *BBI2 = &FalseBBI; SmallVector RevCond(BBI.BrCond.begin(), BBI.BrCond.end()); if (TII->ReverseBranchCondition(RevCond)) - assert(false && "Unable to reverse branch condition!"); + llvm_unreachable("Unable to reverse branch condition!"); SmallVector *Cond1 = &BBI.BrCond; SmallVector *Cond2 = &RevCond; @@ -1249,8 +1283,8 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind, // Initialize liveins to the first BB. These are potentially redefined by // predicated instructions. - SmallSet Redefs; - InitPredRedefs(BBI1->BB, Redefs, TRI); + Redefs.init(TRI); + Redefs.addLiveIns(BBI1->BB, *TRI); // Remove the duplicated instructions at the beginnings of both paths. MachineBasicBlock::iterator DI1 = BBI1->BB->begin(); @@ -1277,11 +1311,23 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind, --NumDups1; } - UpdatePredRedefs(BBI1->BB->begin(), DI1, Redefs, TRI); + // Compute a set of registers which must not be killed by instructions in BB1: + // This is everything used+live in BB2 after the duplicated instructions. We + // can compute this set by simulating liveness backwards from the end of BB2. + DontKill.init(TRI); + for (MachineBasicBlock::reverse_iterator I = BBI2->BB->rbegin(), + E = MachineBasicBlock::reverse_iterator(DI2); I != E; ++I) { + DontKill.stepBackward(*I, *TRI); + } + + for (MachineBasicBlock::const_iterator I = BBI1->BB->begin(), E = DI1; I != E; + ++I) { + Redefs.stepForward(*I, *TRI); + } BBI.BB->splice(BBI.BB->end(), BBI1->BB, BBI1->BB->begin(), DI1); BBI2->BB->erase(BBI2->BB->begin(), DI2); - // Predicate the 'true' block after removing its branch. + // Remove branch from 'true' block and remove duplicated instructions. BBI1->NonPredSize -= TII->RemoveBranch(*BBI1->BB); DI1 = BBI1->BB->end(); for (unsigned i = 0; i != NumDups2; ) { @@ -1294,9 +1340,12 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind, ++i; } BBI1->BB->erase(DI1, BBI1->BB->end()); - PredicateBlock(*BBI1, BBI1->BB->end(), *Cond1, Redefs); - // Predicate the 'false' block. + // Kill flags in the true block for registers living into the false block + // must be removed. + RemoveKills(BBI1->BB->begin(), BBI1->BB->end(), DontKill, *TRI); + + // Remove 'false' block branch and find the last instruction to predicate. BBI2->NonPredSize -= TII->RemoveBranch(*BBI2->BB); DI2 = BBI2->BB->end(); while (NumDups2 != 0) { @@ -1308,7 +1357,56 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind, if (!DI2->isDebugValue()) --NumDups2; } - PredicateBlock(*BBI2, DI2, *Cond2, Redefs); + + // Remember which registers would later be defined by the false block. + // This allows us not to predicate instructions in the true block that would + // later be re-defined. That is, rather than + // subeq r0, r1, #1 + // addne r0, r1, #1 + // generate: + // sub r0, r1, #1 + // addne r0, r1, #1 + SmallSet RedefsByFalse; + SmallSet ExtUses; + if (TII->isProfitableToUnpredicate(*BBI1->BB, *BBI2->BB)) { + for (MachineBasicBlock::iterator FI = BBI2->BB->begin(); FI != DI2; ++FI) { + if (FI->isDebugValue()) + continue; + SmallVector Defs; + for (unsigned i = 0, e = FI->getNumOperands(); i != e; ++i) { + const MachineOperand &MO = FI->getOperand(i); + if (!MO.isReg()) + continue; + unsigned Reg = MO.getReg(); + if (!Reg) + continue; + if (MO.isDef()) { + Defs.push_back(Reg); + } else if (!RedefsByFalse.count(Reg)) { + // These are defined before ctrl flow reach the 'false' instructions. + // They cannot be modified by the 'true' instructions. + for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true); + SubRegs.isValid(); ++SubRegs) + ExtUses.insert(*SubRegs); + } + } + + for (unsigned i = 0, e = Defs.size(); i != e; ++i) { + unsigned Reg = Defs[i]; + if (!ExtUses.count(Reg)) { + for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true); + SubRegs.isValid(); ++SubRegs) + RedefsByFalse.insert(*SubRegs); + } + } + } + } + + // Predicate the 'true' block. + PredicateBlock(*BBI1, BBI1->BB->end(), *Cond1, &RedefsByFalse); + + // Predicate the 'false' block. + PredicateBlock(*BBI2, DI2, *Cond2); // Merge the true block into the entry of the diamond. MergeBlocks(BBI, *BBI1, TailBB == 0); @@ -1319,8 +1417,9 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind, // fold the tail block in as well. Otherwise, unless it falls through to the // tail, add a unconditional branch to it. if (TailBB) { - BBInfo TailBBI = BBAnalysis[TailBB->getNumber()]; - bool CanMergeTail = !TailBBI.HasFallThrough; + BBInfo &TailBBI = BBAnalysis[TailBB->getNumber()]; + bool CanMergeTail = !TailBBI.HasFallThrough && + !TailBBI.BB->hasAddressTaken(); // There may still be a fall-through edge from BBI1 or BBI2 to TailBB; // check if there are any other predecessors besides those. unsigned NumPreds = TailBB->pred_size(); @@ -1356,15 +1455,48 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind, return true; } +static bool MaySpeculate(const MachineInstr *MI, + SmallSet &LaterRedefs, + const TargetInstrInfo *TII) { + bool SawStore = true; + if (!MI->isSafeToMove(TII, 0, SawStore)) + return false; + + for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { + const MachineOperand &MO = MI->getOperand(i); + if (!MO.isReg()) + continue; + unsigned Reg = MO.getReg(); + if (!Reg) + continue; + if (MO.isDef() && !LaterRedefs.count(Reg)) + return false; + } + + return true; +} + /// PredicateBlock - Predicate instructions from the start of the block to the /// specified end with the specified condition. void IfConverter::PredicateBlock(BBInfo &BBI, MachineBasicBlock::iterator E, SmallVectorImpl &Cond, - SmallSet &Redefs) { + SmallSet *LaterRedefs) { + bool AnyUnpred = false; + bool MaySpec = LaterRedefs != 0; for (MachineBasicBlock::iterator I = BBI.BB->begin(); I != E; ++I) { if (I->isDebugValue() || TII->isPredicated(I)) continue; + // It may be possible not to predicate an instruction if it's the 'true' + // side of a diamond and the 'false' side may re-define the instruction's + // defs. + if (MaySpec && MaySpeculate(I, *LaterRedefs, TII)) { + AnyUnpred = true; + continue; + } + // If any instruction is predicated, then every instruction after it must + // be predicated. + MaySpec = false; if (!TII->PredicateInstruction(I, Cond)) { #ifndef NDEBUG dbgs() << "Unable to predicate " << *I << "!\n"; @@ -1374,7 +1506,7 @@ void IfConverter::PredicateBlock(BBInfo &BBI, // If the predicated instruction now redefines a register as the result of // if-conversion, add an implicit kill. - UpdatePredRedefs(I, Redefs, TRI, true); + UpdatePredRedefs(I, Redefs, TRI); } std::copy(Cond.begin(), Cond.end(), std::back_inserter(BBI.Predicate)); @@ -1383,28 +1515,28 @@ void IfConverter::PredicateBlock(BBInfo &BBI, BBI.NonPredSize = 0; ++NumIfConvBBs; + if (AnyUnpred) + ++NumUnpred; } /// CopyAndPredicateBlock - Copy and predicate instructions from source BB to /// the destination block. Skip end of block branches if IgnoreBr is true. void IfConverter::CopyAndPredicateBlock(BBInfo &ToBBI, BBInfo &FromBBI, SmallVectorImpl &Cond, - SmallSet &Redefs, bool IgnoreBr) { MachineFunction &MF = *ToBBI.BB->getParent(); for (MachineBasicBlock::iterator I = FromBBI.BB->begin(), E = FromBBI.BB->end(); I != E; ++I) { - const MCInstrDesc &MCID = I->getDesc(); // Do not copy the end of the block branches. - if (IgnoreBr && MCID.isBranch()) + if (IgnoreBr && I->isBranch()) break; MachineInstr *MI = MF.CloneMachineInstr(I); ToBBI.BB->insert(ToBBI.BB->end(), MI); ToBBI.NonPredSize++; - unsigned ExtraPredCost = 0; - unsigned NumCycles = TII->getInstrLatency(InstrItins, &*I, &ExtraPredCost); + unsigned ExtraPredCost = TII->getPredicationCost(&*I); + unsigned NumCycles = SchedModel.computeInstrLatency(&*I, false); if (NumCycles > 1) ToBBI.ExtraCost += NumCycles-1; ToBBI.ExtraCost2 += ExtraPredCost; @@ -1420,7 +1552,11 @@ void IfConverter::CopyAndPredicateBlock(BBInfo &ToBBI, BBInfo &FromBBI, // If the predicated instruction now redefines a register as the result of // if-conversion, add an implicit kill. - UpdatePredRedefs(MI, Redefs, TRI, true); + UpdatePredRedefs(MI, Redefs, TRI); + + // Some kill flags may not be correct anymore. + if (!DontKill.empty()) + RemoveKills(*MI, DontKill, *TRI); } if (!IgnoreBr) { @@ -1454,6 +1590,9 @@ void IfConverter::CopyAndPredicateBlock(BBInfo &ToBBI, BBInfo &FromBBI, /// i.e., when FromBBI's branch is being moved, add those successor edges to /// ToBBI. void IfConverter::MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI, bool AddEdges) { + assert(!FromBBI.BB->hasAddressTaken() && + "Removing a BB whose address is taken!"); + ToBBI.BB->splice(ToBBI.BB->end(), FromBBI.BB, FromBBI.BB->begin(), FromBBI.BB->end()); @@ -1468,7 +1607,7 @@ void IfConverter::MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI, bool AddEdges) { if (Succ == FallThrough) continue; FromBBI.BB->removeSuccessor(Succ); - if (AddEdges) + if (AddEdges && !ToBBI.BB->isSuccessor(Succ)) ToBBI.BB->addSuccessor(Succ); }