Index: lib/CodeGen/IfConversion.cpp =================================================================== --- lib/CodeGen/IfConversion.cpp +++ lib/CodeGen/IfConversion.cpp @@ -15,6 +15,7 @@ #include "llvm/CodeGen/Passes.h" #include "BranchFolding.h" #include "llvm/ADT/STLExtras.h" +#include "llvm/ADT/ScopeExit.h" #include "llvm/ADT/SmallSet.h" #include "llvm/ADT/Statistic.h" #include "llvm/CodeGen/LivePhysRegs.h" @@ -58,6 +59,8 @@ cl::init(false), cl::Hidden); static cl::opt DisableDiamond("disable-ifcvt-diamond", cl::init(false), cl::Hidden); +static cl::opt DisableForkedDiamond("disable-ifcvt-forked-diamond", + cl::init(false), cl::Hidden); static cl::opt IfCvtBranchFold("ifcvt-branch-fold", cl::init(true), cl::Hidden); @@ -68,6 +71,7 @@ STATISTIC(NumTriangleFalse,"Number of triangle (F) if-conversions performed"); STATISTIC(NumTriangleFRev, "Number of triangle (F/R) if-conversions performed"); STATISTIC(NumDiamonds, "Number of diamond if-conversions performed"); +STATISTIC(NumForkedDiamonds, "Number of forked-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"); @@ -82,7 +86,9 @@ ICTriangleRev, // Same as ICTriangle, but true path rev condition. ICTriangleFalse, // Same as ICTriangle, but on the false path. ICTriangle, // BB is entry of a triangle sub-CFG. - ICDiamond // BB is entry of a diamond sub-CFG. + ICDiamond, // BB is entry of a diamond sub-CFG. + ICForkedDiamond // BB is entry of an almost diamond sub-CFG, with a + // common tail that can be shared. }; /// BBInfo - One per MachineBasicBlock, this is used to cache the result @@ -114,6 +120,7 @@ bool IsAnalyzed : 1; bool IsEnqueued : 1; bool IsBrAnalyzable : 1; + bool IsBrReversible : 1; bool HasFallThrough : 1; bool IsUnpredicable : 1; bool CannotBeCopied : 1; @@ -128,9 +135,10 @@ SmallVector Predicate; BBInfo() : IsDone(false), IsBeingAnalyzed(false), IsAnalyzed(false), IsEnqueued(false), IsBrAnalyzable(false), - HasFallThrough(false), IsUnpredicable(false), - CannotBeCopied(false), ClobbersPred(false), NonPredSize(0), - ExtraCost(0), ExtraCost2(0), BB(nullptr), TrueBB(nullptr), + IsBrReversible(false), HasFallThrough(false), + IsUnpredicable(false), CannotBeCopied(false), + ClobbersPred(false), NonPredSize(0), ExtraCost(0), + ExtraCost2(0), BB(nullptr), TrueBB(nullptr), FalseBB(nullptr) {} }; @@ -148,11 +156,15 @@ struct IfcvtToken { BBInfo &BBI; IfcvtKind Kind; - bool NeedSubsumption; unsigned NumDups; unsigned NumDups2; - IfcvtToken(BBInfo &b, IfcvtKind k, bool s, unsigned d, unsigned d2 = 0) - : BBI(b), Kind(k), NeedSubsumption(s), NumDups(d), NumDups2(d2) {} + bool NeedSubsumption : 1; + bool TClobbersPred : 1; + bool FClobbersPred : 1; + IfcvtToken(BBInfo &b, IfcvtKind k, bool s, unsigned d, unsigned d2 = 0, + bool tc = false, bool fc = false) + : BBI(b), Kind(k), NumDups(d), NumDups2(d2), NeedSubsumption(s), + TClobbersPred(tc), FClobbersPred(fc) {} }; /// BBAnalysis - Results of if-conversion feasibility analysis indexed by @@ -202,23 +214,40 @@ bool FalseBranch, unsigned &Dups, BranchProbability Prediction) const; bool ValidDiamond(BBInfo &TrueBBI, BBInfo &FalseBBI, - unsigned &Dups1, unsigned &Dups2) const; + unsigned &Dups1, unsigned &Dups2, + BBInfo &TrueBBICalc, BBInfo &FalseBBICalc) const; + bool ValidForkedDiamond(BBInfo &TrueBBI, BBInfo &FalseBBI, + unsigned &Dups1, unsigned &Dups2, + BBInfo &TrueBBICalc, BBInfo &FalseBBICalc) const; void AnalyzeBranches(BBInfo &BBI); void ScanInstructions(BBInfo &BBI, MachineBasicBlock::iterator &Begin, MachineBasicBlock::iterator &End) const; + bool RescanInstructions( + MachineBasicBlock::iterator &TIB, MachineBasicBlock::iterator &FIB, + MachineBasicBlock::iterator &TIE, MachineBasicBlock::iterator &FIE, + BBInfo &TrueBBI, BBInfo &FalseBBI) const; void AnalyzeBlock(MachineBasicBlock *MBB, std::vector> &Tokens); bool FeasibilityAnalysis(BBInfo &BBI, SmallVectorImpl &Cond, - bool isTriangle = false, bool RevBranch = false); + bool isTriangle = false, bool RevBranch = false, + bool hasCommonTail = false); void AnalyzeBlocks(MachineFunction &MF, std::vector> &Tokens); void InvalidatePreds(MachineBasicBlock *BB); void RemoveExtraEdges(BBInfo &BBI); bool IfConvertSimple(BBInfo &BBI, IfcvtKind Kind); bool IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind); + bool IfConvertDiamondCommon(BBInfo &BBI, BBInfo &TrueBBI, BBInfo &FalseBBI, + unsigned NumDups1, unsigned NumDups2, + bool TClobbersPred, bool FClobbersPred, + bool RemoveTrueBranch, bool RemoveFalseBranch, + bool MergeAddEdges); bool IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind, unsigned NumDups1, unsigned NumDups2); + bool IfConvertForkedDiamond(BBInfo &BBI, IfcvtKind Kind, + unsigned NumDups1, unsigned NumDups2, + bool TClobbers, bool FClobbers); void PredicateBlock(BBInfo &BBI, MachineBasicBlock::iterator E, SmallVectorImpl &Cond, @@ -410,6 +439,19 @@ if (RetVal) ++NumDiamonds; break; } + case ICForkedDiamond: { + if (DisableForkedDiamond) break; + DEBUG(dbgs() << "Ifcvt (Forked Diamond): BB#" + << BBI.BB->getNumber() << " (T:" + << BBI.TrueBB->getNumber() << ",F:" + << BBI.FalseBB->getNumber() << ") "); + RetVal = IfConvertForkedDiamond(BBI, Kind, NumDups, NumDups2, + Token->TClobbersPred, + Token->FClobbersPred); + DEBUG(dbgs() << (RetVal ? "succeeded!" : "failed!") << "\n"); + if (RetVal) ++NumForkedDiamonds; + break; + } } Change |= RetVal; @@ -611,6 +653,13 @@ return; --TIE; --FIE; + // Upon exit TIE and FIE will both point at the last non-shared instruction, + // they need to be moved forward to point past the last non-shared + // instruction. + auto IncrementEndIteratorsOnExit = make_scope_exit([&]() { + ++TIE; ++FIE; + }); + if (!TBB.succ_empty() || !FBB.succ_empty()) { if (SkipConditionalBranches) { while (TIE != TIB && TIE->isBranch()) @@ -648,10 +697,125 @@ } } +/// RescanInstructions - Run ScanInstructions on a pair of blocks. +/// @param TIB - True Iterator Begin, points to first non-shared instruction +/// @param FIB - False Iterator Begin, points to first non-shared instruction +/// @param TIE - True Iterator End, points past last non-shared instruction +/// @param FIE - False Iterator End, points past last non-shared instruction +/// @param TrueBBI - BBInfo to update for the true block. +/// @param FalseBBI - BBInfo to update for the false block. +/// @returns - false if either block cannot be predicated or if both blocks end +/// with a predicate-clobbering instruction. +bool IfConverter::RescanInstructions( + MachineBasicBlock::iterator &TIB, MachineBasicBlock::iterator &FIB, + MachineBasicBlock::iterator &TIE, MachineBasicBlock::iterator &FIE, + BBInfo &TrueBBI, BBInfo &FalseBBI) const { + ScanInstructions(TrueBBI, TIB, TIE); + if (TrueBBI.IsUnpredicable) + return false; + ScanInstructions(FalseBBI, FIB, FIE); + if (FalseBBI.IsUnpredicable) + return false; + if (TrueBBI.ClobbersPred && FalseBBI.ClobbersPred) + return false; + return true; +} + +/// ValidForkedDiamond - Returns true if the 'true' and 'false' blocks (along +/// with their common predecessor) form a diamond if a common tail block is +/// extracted. +/// While not strictly a diamond, this pattern would form a diamond if +/// tail-merging had merged the shared tails. +/// EBB +/// _/ \_ +/// | | +/// TBB FBB +/// / \ / \ +/// FalseBB TrueBB FalseBB +/// Currently only handles analyzable branches. +/// Specifically excludes actual diamonds to avoid overlap. +bool IfConverter::ValidForkedDiamond( + BBInfo &TrueBBI, BBInfo &FalseBBI, + unsigned &Dups1, unsigned &Dups2, + BBInfo &TrueBBICalc, BBInfo &FalseBBICalc) const { + Dups1 = Dups2 = 0; + if (TrueBBI.IsBeingAnalyzed || TrueBBI.IsDone || + FalseBBI.IsBeingAnalyzed || FalseBBI.IsDone) + return false; + + if (!TrueBBI.IsBrAnalyzable || !FalseBBI.IsBrAnalyzable) + return false; + // Don't IfConvert blocks that can't be folded into their predecessor. + if (TrueBBI.BB->pred_size() > 1 || FalseBBI.BB->pred_size() > 1) + return false; + + // This function is specifically looking for conditional tails, as + // unconditional tails are already handled by the standard diamond case. + if (TrueBBI.BrCond.size() == 0 || + FalseBBI.BrCond.size() == 0) + return false; + + MachineBasicBlock *TT = TrueBBI.TrueBB; + MachineBasicBlock *TF = TrueBBI.FalseBB; + MachineBasicBlock *FT = FalseBBI.TrueBB; + MachineBasicBlock *FF = FalseBBI.FalseBB; + + if (!TT) + TT = getNextBlock(TrueBBI.BB); + if (!TF) + TF = getNextBlock(TrueBBI.BB); + if (!FT) + FT = getNextBlock(FalseBBI.BB); + if (!FF) + FF = getNextBlock(FalseBBI.BB); + + if (!TT || !TF) + return false; + + // Check successors. If they don't match, bail. + if (!((TT == FT && TF == FF) || (TF == FT && TT == FF))) + return false; + + bool FalseReversed = false; + if (TF == FT && TT == FF) { + // If the branches are opposing, but we can't reverse, don't do it. + if (!FalseBBI.IsBrReversible) + return false; + FalseReversed = true; + ReverseBranchCondition(FalseBBI); + } + auto UnReverseOnExit = make_scope_exit([&]() { + if (FalseReversed) + ReverseBranchCondition(FalseBBI); + }); + + // Count duplicate instructions at the beginning of the true and false blocks. + MachineBasicBlock::iterator TIB = TrueBBI.BB->begin(); + MachineBasicBlock::iterator FIB = FalseBBI.BB->begin(); + MachineBasicBlock::iterator TIE = TrueBBI.BB->end(); + MachineBasicBlock::iterator FIE = FalseBBI.BB->end(); + countDuplicatedInstructions(TIB, FIB, TIE, FIE, Dups1, Dups2, + *TrueBBI.BB, *FalseBBI.BB, + /* SkipConditionalBranches */ false); + + TrueBBICalc.BB = TrueBBI.BB; + FalseBBICalc.BB = FalseBBI.BB; + if (!RescanInstructions(TIB, FIB, TIE, FIE, TrueBBICalc, FalseBBICalc)) + return false; + // The size is used to decide whether to if-convert, and the shared portions + // are subtracted off. Because of the subtraction, we just use the size that + // was calculated by the original ScanInstructions, as it is correct. + TrueBBICalc.NonPredSize = TrueBBI.NonPredSize; + FalseBBICalc.NonPredSize = FalseBBI.NonPredSize; + return true; +} + /// ValidDiamond - Returns true if the 'true' and 'false' blocks (along /// with their common predecessor) forms a valid diamond shape for ifcvt. -bool IfConverter::ValidDiamond(BBInfo &TrueBBI, BBInfo &FalseBBI, - unsigned &Dups1, unsigned &Dups2) const { +bool IfConverter::ValidDiamond( + BBInfo &TrueBBI, BBInfo &FalseBBI, + unsigned &Dups1, unsigned &Dups2, + BBInfo &TrueBBICalc, BBInfo &FalseBBICalc) const { Dups1 = Dups2 = 0; if (TrueBBI.IsBeingAnalyzed || TrueBBI.IsDone || FalseBBI.IsBeingAnalyzed || FalseBBI.IsDone) @@ -672,8 +836,7 @@ return false; // FIXME: Allow true block to have an early exit? - if (TrueBBI.FalseBB || FalseBBI.FalseBB || - (TrueBBI.ClobbersPred && FalseBBI.ClobbersPred)) + if (TrueBBI.FalseBB || FalseBBI.FalseBB) return false; // Count duplicate instructions at the beginning and end of the true and @@ -685,6 +848,16 @@ countDuplicatedInstructions(TIB, FIB, TIE, FIE, Dups1, Dups2, *TrueBBI.BB, *FalseBBI.BB, /* SkipConditionalBranches */ true); + + TrueBBICalc.BB = TrueBBI.BB; + FalseBBICalc.BB = FalseBBI.BB; + if (!RescanInstructions(TIB, FIB, TIE, FIE, TrueBBICalc, FalseBBICalc)) + return false; + // The size is used to decide whether to if-convert, and the shared portions + // are subtracted off. Because of the subtraction, we just use the size that + // was calculated by the original ScanInstructions, as it is correct. + TrueBBICalc.NonPredSize = TrueBBI.NonPredSize; + FalseBBICalc.NonPredSize = FalseBBI.NonPredSize; return true; } @@ -698,6 +871,9 @@ BBI.BrCond.clear(); BBI.IsBrAnalyzable = !TII->analyzeBranch(*BBI.BB, BBI.TrueBB, BBI.FalseBB, BBI.BrCond); + SmallVector RevCond(BBI.BrCond.begin(), BBI.BrCond.end()); + BBI.IsBrReversible = (RevCond.size() == 0) || + !TII->ReverseBranchCondition(RevCond); BBI.HasFallThrough = BBI.IsBrAnalyzable && BBI.FalseBB == nullptr; if (BBI.BrCond.size()) { @@ -813,11 +989,22 @@ /// FeasibilityAnalysis - Determine if the block is a suitable candidate to be /// predicated by the specified predicate. +/// @param BBI BBInfo for the block to check +/// @param Pred Predicate array for the branch that leads to BBI +/// @param isTriangle true if the Analysis is for a triangle +/// @param RevBranch true if Reverse(Pred) leads to BBI (e.g. BBI is the false +/// case +/// @param hasCommonTail true if BBI shares a tail with a sibling block that +/// contains any instruction that would make the block unpredicable. bool IfConverter::FeasibilityAnalysis(BBInfo &BBI, SmallVectorImpl &Pred, - bool isTriangle, bool RevBranch) { + bool isTriangle, bool RevBranch, + bool hasCommonTail) { // If the block is dead or unpredicable, then it cannot be predicated. - if (BBI.IsDone || BBI.IsUnpredicable) + // Two blocks may share a common unpredicable tail, but this doesn't prevent + // them from being if-converted. The non-shared portion is assumed to have + // been checked + if (BBI.IsDone || (BBI.IsUnpredicable && !hasCommonTail)) return false; // If it is already predicated but we couldn't analyze its terminator, the @@ -831,7 +1018,7 @@ if (BBI.Predicate.size() && !TII->SubsumesPredicate(Pred, BBI.Predicate)) return false; - if (BBI.BrCond.size()) { + if (!hasCommonTail && BBI.BrCond.size()) { if (!isTriangle) return false; @@ -939,25 +1126,58 @@ BranchProbability Prediction = MBPI->getEdgeProbability(BB, TrueBBI.BB); - if (CanRevCond && ValidDiamond(TrueBBI, FalseBBI, Dups, Dups2) && - MeetIfcvtSizeLimit(*TrueBBI.BB, (TrueBBI.NonPredSize - (Dups + Dups2) + - TrueBBI.ExtraCost), TrueBBI.ExtraCost2, - *FalseBBI.BB, (FalseBBI.NonPredSize - (Dups + Dups2) + - FalseBBI.ExtraCost),FalseBBI.ExtraCost2, - Prediction) && - FeasibilityAnalysis(TrueBBI, BBI.BrCond) && - FeasibilityAnalysis(FalseBBI, RevCond)) { - // Diamond: - // EBB - // / \_ - // | | - // TBB FBB - // \ / - // TailBB - // Note TailBB can be empty. - Tokens.push_back(llvm::make_unique( - BBI, ICDiamond, TNeedSub | FNeedSub, Dups, Dups2)); - Enqueued = true; + if (CanRevCond) { + BBInfo TrueBBICalc, FalseBBICalc; + auto feasibleDiamond = [&]() { + return ( + MeetIfcvtSizeLimit( + *TrueBBI.BB, (TrueBBICalc.NonPredSize - (Dups + Dups2) + + TrueBBICalc.ExtraCost), TrueBBICalc.ExtraCost2, + *FalseBBI.BB, (FalseBBICalc.NonPredSize - (Dups + Dups2) + + FalseBBICalc.ExtraCost), FalseBBICalc.ExtraCost2, + Prediction) && + FeasibilityAnalysis(TrueBBI, BBI.BrCond, + /* IsTriangle */ false, /* RevCond */ false, + /* hasCommonTail */ true) && + FeasibilityAnalysis(FalseBBI, RevCond, + /* IsTriangle */ false, /* RevCond */ false, + /* hasCommonTail */ true)); + }; + + if (ValidDiamond(TrueBBI, FalseBBI, Dups, Dups2, + TrueBBICalc, FalseBBICalc)) { + if (feasibleDiamond()) { + // Diamond: + // EBB + // / \_ + // | | + // TBB FBB + // \ / + // TailBB + // Note TailBB can be empty. + Tokens.push_back(llvm::make_unique( + BBI, ICDiamond, TNeedSub | FNeedSub, Dups, Dups2)); + Enqueued = true; + } + } else if (ValidForkedDiamond(TrueBBI, FalseBBI, Dups, Dups2, + TrueBBICalc, FalseBBICalc)) { + if (feasibleDiamond()) { + // ForkedDiamond: + // if TBB and FBB have a common tail that includes their conditional + // branch instructions, then we can If Convert this pattern. + // EBB + // _/ \_ + // | | + // TBB FBB + // / \ / \ + // FalseBB TrueBB FalseBB + // + Tokens.push_back(llvm::make_unique( + BBI, ICForkedDiamond, TNeedSub | FNeedSub, Dups, Dups2, + (bool) TrueBBICalc.ClobbersPred, (bool) FalseBBICalc.ClobbersPred)); + Enqueued = true; + } + } } if (ValidTriangle(TrueBBI, FalseBBI, false, Dups, Prediction) && @@ -1410,23 +1630,26 @@ return true; } -/// IfConvertDiamond - If convert a diamond sub-CFG. -/// -bool IfConverter::IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind, - unsigned NumDups1, unsigned NumDups2) { - BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()]; - BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()]; - MachineBasicBlock *TailBB = TrueBBI.TrueBB; - // True block must fall through or end with an unanalyzable terminator. - if (!TailBB) { - if (blockAlwaysFallThrough(TrueBBI)) - TailBB = FalseBBI.TrueBB; - assert((TailBB || !TrueBBI.IsBrAnalyzable) && "Unexpected!"); - } +/// IfConvertDiamondCommon - Common code shared between diamond conversions. +/// BBI, TrueBBI, and FalseBBI form the diamond shape. +/// NumDups1 - number of shared instructions at the beginning of TrueBBI and +/// FalseBBI +/// NumDups2 - number of shared instructions at the end of TrueBBI and FalseBBI +/// RemoveTrueBranch - Remove the branch of the true block before predicating +/// Only false for unanalyzable fallthrough cases. +/// RemoveFalseBranch - Remove the branch of the false block before predicating +/// Only false for unanalyzable fallthrough cases. +/// MergeAddEdges - Add successor edges when merging blocks. Only false for +/// unanalyzable fallthrough +bool IfConverter::IfConvertDiamondCommon( + BBInfo &BBI, BBInfo &TrueBBI, BBInfo &FalseBBI, + unsigned NumDups1, unsigned NumDups2, + bool TClobbersPred, bool FClobbersPred, + bool RemoveTrueBranch, bool RemoveFalseBranch, + bool MergeAddEdges) { if (TrueBBI.IsDone || FalseBBI.IsDone || - TrueBBI.BB->pred_size() > 1 || - FalseBBI.BB->pred_size() > 1) { + TrueBBI.BB->pred_size() > 1 || FalseBBI.BB->pred_size() > 1) { // Something has changed. It's no longer safe to predicate these blocks. BBI.IsAnalyzed = false; TrueBBI.IsAnalyzed = false; @@ -1451,15 +1674,16 @@ // Figure out the more profitable ordering. bool DoSwap = false; - if (TrueBBI.ClobbersPred && !FalseBBI.ClobbersPred) + if (TClobbersPred && !FClobbersPred) DoSwap = true; - else if (TrueBBI.ClobbersPred == FalseBBI.ClobbersPred) { + else if (TClobbersPred == FClobbersPred) { if (TrueBBI.NonPredSize > FalseBBI.NonPredSize) DoSwap = true; } if (DoSwap) { std::swap(BBI1, BBI2); std::swap(Cond1, Cond2); + std::swap(RemoveTrueBranch, RemoveFalseBranch); } // Remove the conditional branch from entry to the blocks. @@ -1506,11 +1730,7 @@ BBI.BB->splice(BBI.BB->end(), BBI1->BB, BBI1->BB->begin(), DI1); BBI2->BB->erase(BBI2->BB->begin(), DI2); - // Remove branch from the 'true' block, unless it was not analyzable. - // Non-analyzable branches need to be preserved, since in such cases, - // the CFG structure is not an actual diamond (the join block may not - // be present). - if (BBI1->IsBrAnalyzable) + if (RemoveTrueBranch) BBI1->NonPredSize -= TII->RemoveBranch(*BBI1->BB); // Remove duplicated instructions. DI1 = BBI1->BB->end(); @@ -1529,9 +1749,9 @@ // must be removed. RemoveKills(BBI1->BB->begin(), BBI1->BB->end(), DontKill, *TRI); - // Remove 'false' block branch (unless it was not analyzable), and find - // the last instruction to predicate. - if (BBI2->IsBrAnalyzable) + // Remove 'false' block branch, and find the last instruction to predicate. + // Save the debug location. + if (RemoveFalseBranch) BBI2->NonPredSize -= TII->RemoveBranch(*BBI2->BB); DI2 = BBI2->BB->end(); while (NumDups2 != 0) { @@ -1607,8 +1827,74 @@ PredicateBlock(*BBI2, DI2, *Cond2); // Merge the true block into the entry of the diamond. - MergeBlocks(BBI, *BBI1, TailBB == nullptr); - MergeBlocks(BBI, *BBI2, TailBB == nullptr); + MergeBlocks(BBI, *BBI1, MergeAddEdges); + MergeBlocks(BBI, *BBI2, MergeAddEdges); + return true; +} + +/// IfConvertForkedDiamond - If convert an almost-diamond sub-CFG where the true +/// and false blocks share a common tail. +bool IfConverter::IfConvertForkedDiamond( + BBInfo &BBI, IfcvtKind Kind, + unsigned NumDups1, unsigned NumDups2, + bool TClobbersPred, bool FClobbersPred) { + BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()]; + BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()]; + + // Save the debug location for later. + DebugLoc dl; + MachineBasicBlock::iterator TIE = TrueBBI.BB->getFirstTerminator(); + if (TIE != TrueBBI.BB->end()) + dl = TIE->getDebugLoc(); + // Removing branches from both blocks is safe, because we have already + // determined that both blocks have the same branch instructions. The branch + // will be added back at the end, unpredicated. + if (!IfConvertDiamondCommon( + BBI, TrueBBI, FalseBBI, + NumDups1, NumDups2, + TClobbersPred, FClobbersPred, + /* RemoveTrueBranch */ true, /* RemoveFalseBranch */ true, + /* MergeAddEdges */ true)) + return false; + + // Add back the branch. + // Debug location saved above when removing the branch from BBI2 + TII->InsertBranch(*BBI.BB, TrueBBI.TrueBB, TrueBBI.FalseBB, + TrueBBI.BrCond, dl); + + RemoveExtraEdges(BBI); + + // Update block info. + BBI.IsDone = TrueBBI.IsDone = FalseBBI.IsDone = true; + InvalidatePreds(BBI.BB); + + // FIXME: Must maintain LiveIns. + return true; +} + +/// IfConvertDiamond - If convert a diamond sub-CFG. +/// +bool IfConverter::IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind, + unsigned NumDups1, unsigned NumDups2) { + BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()]; + BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()]; + MachineBasicBlock *TailBB = TrueBBI.TrueBB; + + // True block must fall through or end with an unanalyzable terminator. + if (!TailBB) { + if (blockAlwaysFallThrough(TrueBBI)) + TailBB = FalseBBI.TrueBB; + assert((TailBB || !TrueBBI.IsBrAnalyzable) && "Unexpected!"); + } + + if (!IfConvertDiamondCommon( + BBI, TrueBBI, FalseBBI, + NumDups1, NumDups2, + TrueBBI.ClobbersPred, FalseBBI.ClobbersPred, + /* RemoveTrueBranch */ TrueBBI.IsBrAnalyzable, + /* RemoveFalseBranch */ FalseBBI.IsBrAnalyzable, + /* MergeAddEdges */ TailBB == nullptr)) + return false; // If the if-converted block falls through or unconditionally branches into // the tail block, and the tail block does not have other predecessors, then @@ -1631,7 +1917,7 @@ CanMergeTail = false; else if (NumPreds == 1 && CanMergeTail) { MachineBasicBlock::pred_iterator PI = TailBB->pred_begin(); - if (*PI != BBI1->BB && *PI != BBI2->BB) + if (*PI != TrueBBI.BB && *PI != FalseBBI.BB) CanMergeTail = false; } if (CanMergeTail) { @@ -1647,8 +1933,8 @@ // RemoveExtraEdges won't work if the block has an unanalyzable branch, // which can happen here if TailBB is unanalyzable and is merged, so // explicitly remove BBI1 and BBI2 as successors. - BBI.BB->removeSuccessor(BBI1->BB); - BBI.BB->removeSuccessor(BBI2->BB, true); + BBI.BB->removeSuccessor(TrueBBI.BB); + BBI.BB->removeSuccessor(FalseBBI.BB, /* NormalizeSuccessProbs */ true); RemoveExtraEdges(BBI); // Update block info. Index: test/CodeGen/PowerPC/ifcvt-forked-bug-2016-08-08.ll =================================================================== --- /dev/null +++ test/CodeGen/PowerPC/ifcvt-forked-bug-2016-08-08.ll @@ -0,0 +1,36 @@ +; ModuleID = 'bugpoint-reduced-instructions.bc' +; RUN: llc -O2 -o - %s | FileCheck %s +source_filename = "bugpoint-output-9ad75f8.bc" +target datalayout = "e-m:e-i64:64-n32:64" +target triple = "powerpc64le-unknown-linux-gnu" + +; Function Attrs: nounwind uwtable +define hidden void @_ZN11__sanitizer25MaybeStartBackgroudThreadEv() local_unnamed_addr #0 { +entry: + br i1 undef, label %land.lhs.true, label %if.end + +; CHECK: # %land.lhs.true +; CHECK-NEXT: bclr +; CHECK-NEXT: # %if.end4 +land.lhs.true: ; preds = %entry + br i1 undef, label %return, label %if.end4 + +if.end: ; preds = %entry + br i1 icmp ne (i32 (i8*, i8*, i8* (i8*)*, i8*)* @_ZN11__sanitizer19real_pthread_createEPvS0_PFS0_S0_ES0_, i32 (i8*, i8*, i8* (i8*)*, i8*)* null), label %if.end4, label %return + +if.end4: ; preds = %if.end, %land.lhs.true + %call5 = tail call i8* @_ZN11__sanitizer21internal_start_threadEPFvPvES0_(void (i8*)* nonnull @_ZN11__sanitizer16BackgroundThreadEPv, i8* null) #7 + unreachable + +return: ; preds = %if.end, %land.lhs.true + ret void +} + +declare extern_weak signext i32 @_ZN11__sanitizer19real_pthread_createEPvS0_PFS0_S0_ES0_(i8*, i8*, i8* (i8*)*, i8*) #2 + +declare i8* @_ZN11__sanitizer21internal_start_threadEPFvPvES0_(void (i8*)*, i8*) local_unnamed_addr #2 + +declare hidden void @_ZN11__sanitizer16BackgroundThreadEPv(i8* nocapture readnone) #5 + +attributes #0 = { nounwind uwtable "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="ppc64le" "target-features"="+altivec,+bpermd,+crypto,+direct-move,+extdiv,+power8-vector,+vsx,-qpx" "unsafe-fp-math"="false" "use-soft-float"="false" } +attributes #7 = { nobuiltin nounwind } Index: test/CodeGen/Thumb2/thumb2-ifcvt1.ll =================================================================== --- test/CodeGen/Thumb2/thumb2-ifcvt1.ll +++ test/CodeGen/Thumb2/thumb2-ifcvt1.ll @@ -1,6 +1,7 @@ ; RUN: llc < %s -mtriple=thumbv7-apple-darwin | FileCheck %s ; RUN: llc < %s -mtriple=thumbv7-apple-darwin -arm-default-it | FileCheck %s -; RUN: llc < %s -mtriple=thumbv8 -arm-no-restrict-it |FileCheck %s +; RUN: llc < %s -mtriple=thumbv8 -arm-no-restrict-it | FileCheck %s +; RUN: llc < %s -mtriple=thumbv8 -arm-no-restrict-it -enable-tail-merge=0 | FileCheck %s define i32 @t1(i32 %a, i32 %b, i32 %c, i32 %d) nounwind { ; CHECK-LABEL: t1: ; CHECK: ittt ne @@ -25,9 +26,9 @@ define i32 @t2(i32 %a, i32 %b) nounwind { entry: ; CHECK-LABEL: t2: -; CHECK: ite gt -; CHECK: subgt -; CHECK: suble +; CHECK: ite {{gt|le}} +; CHECK-DAG: suble +; CHECK-DAG: subgt %tmp1434 = icmp eq i32 %a, %b ; [#uses=1] br i1 %tmp1434, label %bb17, label %bb.outer @@ -60,6 +61,44 @@ ret i32 %a_addr.026.1 } +define i32 @t2_nomerge(i32 %a, i32 %b) nounwind { +entry: +; CHECK-LABEL: t2_nomerge: +; CHECK-NOT: ite {{gt|le}} +; CHECK-NOT: suble +; CHECK-NOT: subgt + %tmp1434 = icmp eq i32 %a, %b ; [#uses=1] + br i1 %tmp1434, label %bb17, label %bb.outer + +bb.outer: ; preds = %cond_false, %entry + %b_addr.021.0.ph = phi i32 [ %b, %entry ], [ %tmp10, %cond_false ] ; [#uses=5] + %a_addr.026.0.ph = phi i32 [ %a, %entry ], [ %a_addr.026.0, %cond_false ] ; [#uses=1] + br label %bb + +bb: ; preds = %cond_true, %bb.outer + %indvar = phi i32 [ 0, %bb.outer ], [ %indvar.next, %cond_true ] ; [#uses=2] + %tmp. = sub i32 0, %b_addr.021.0.ph ; [#uses=1] + %tmp.40 = mul i32 %indvar, %tmp. ; [#uses=1] + %a_addr.026.0 = add i32 %tmp.40, %a_addr.026.0.ph ; [#uses=6] + %tmp3 = icmp sgt i32 %a_addr.026.0, %b_addr.021.0.ph ; [#uses=1] + br i1 %tmp3, label %cond_true, label %cond_false + +cond_true: ; preds = %bb + %tmp7 = sub i32 %a_addr.026.0, %b_addr.021.0.ph ; [#uses=2] + %tmp1437 = icmp eq i32 %tmp7, %b_addr.021.0.ph ; [#uses=1] + %indvar.next = add i32 %indvar, 1 ; [#uses=1] + br i1 %tmp1437, label %bb17, label %bb + +cond_false: ; preds = %bb + %tmp10 = sub i32 %b_addr.021.0.ph, %a_addr.026.0 ; [#uses=2] + %tmp14 = icmp eq i32 %b_addr.021.0.ph, %tmp10 ; [#uses=1] + br i1 %tmp14, label %bb17, label %bb.outer + +bb17: ; preds = %cond_false, %cond_true, %entry + %a_addr.026.1 = phi i32 [ %a, %entry ], [ %tmp7, %cond_true ], [ %a_addr.026.0, %cond_false ] ; [#uses=1] + ret i32 %a_addr.026.1 +} + @x = external global i32* ; [#uses=1] define void @foo(i32 %a) nounwind {