diff options
Diffstat (limited to 'lib/Transforms/Utils/SimplifyCFG.cpp')
| -rw-r--r-- | lib/Transforms/Utils/SimplifyCFG.cpp | 781 |
1 files changed, 611 insertions, 170 deletions
diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp index 518df7cdda..3df309958b 100644 --- a/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/lib/Transforms/Utils/SimplifyCFG.cpp @@ -22,6 +22,7 @@ #include "llvm/LLVMContext.h" #include "llvm/MDBuilder.h" #include "llvm/Metadata.h" +#include "llvm/Module.h" #include "llvm/Operator.h" #include "llvm/Type.h" #include "llvm/ADT/DenseMap.h" @@ -54,6 +55,7 @@ DupRet("simplifycfg-dup-ret", cl::Hidden, cl::init(false), cl::desc("Duplicate return instructions into unconditional branches")); STATISTIC(NumSpeculations, "Number of speculative executed instructions"); +STATISTIC(NumLookupTables, "Number of switch instructions turned into lookup tables"); namespace { /// ValueEqualityComparisonCase - Represents a case of a switch. @@ -101,14 +103,14 @@ public: /// static bool SafeToMergeTerminators(TerminatorInst *SI1, TerminatorInst *SI2) { if (SI1 == SI2) return false; // Can't merge with self! - + // It is not safe to merge these two switch instructions if they have a common // successor, and if that successor has a PHI node, and if *that* PHI node has // conflicting incoming values from the two switch blocks. BasicBlock *SI1BB = SI1->getParent(); BasicBlock *SI2BB = SI2->getParent(); SmallPtrSet<BasicBlock*, 16> SI1Succs(succ_begin(SI1BB), succ_end(SI1BB)); - + for (succ_iterator I = succ_begin(SI2BB), E = succ_end(SI2BB); I != E; ++I) if (SI1Succs.count(*I)) for (BasicBlock::iterator BBI = (*I)->begin(); @@ -118,7 +120,7 @@ static bool SafeToMergeTerminators(TerminatorInst *SI1, TerminatorInst *SI2) { PN->getIncomingValueForBlock(SI2BB)) return false; } - + return true; } @@ -135,7 +137,7 @@ static bool isProfitableToFoldUnconditional(BranchInst *SI1, assert(SI1->isUnconditional() && SI2->isConditional()); // We fold the unconditional branch if we can easily update all PHI nodes in - // common successors: + // common successors: // 1> We have a constant incoming value for the conditional branch; // 2> We have "Cond" as the incoming value for the unconditional branch; // 3> SI2->getCondition() and Cond have same operands. @@ -170,7 +172,7 @@ static bool isProfitableToFoldUnconditional(BranchInst *SI1, static void AddPredecessorToBlock(BasicBlock *Succ, BasicBlock *NewPred, BasicBlock *ExistPred) { if (!isa<PHINode>(Succ->begin())) return; // Quick exit if nothing to do - + PHINode *PN; for (BasicBlock::iterator I = Succ->begin(); (PN = dyn_cast<PHINode>(I)); ++I) @@ -222,7 +224,7 @@ static Value *GetIfCondition(BasicBlock *BB, BasicBlock *&IfTrue, // doesn't dominate BB. if (Pred2->getSinglePredecessor() == 0) return 0; - + // If we found a conditional branch predecessor, make sure that it branches // to BB and Pred2Br. If it doesn't, this isn't an "if statement". if (Pred1Br->getSuccessor(0) == BB && @@ -252,7 +254,7 @@ static Value *GetIfCondition(BasicBlock *BB, BasicBlock *&IfTrue, // Otherwise, if this is a conditional branch, then we can use it! BranchInst *BI = dyn_cast<BranchInst>(CommonPred->getTerminator()); if (BI == 0) return 0; - + assert(BI->isConditional() && "Two successors but not conditional?"); if (BI->getSuccessor(0) == Pred1) { IfTrue = Pred1; @@ -345,7 +347,7 @@ static bool DominatesMergePoint(Value *V, BasicBlock *BB, // If we aren't allowing aggressive promotion anymore, then don't consider // instructions in the 'if region'. if (AggressiveInsts == 0) return false; - + // If we have seen this instruction before, don't count it again. if (AggressiveInsts->count(I)) return true; @@ -411,7 +413,7 @@ GatherConstantCompares(Value *V, std::vector<ConstantInt*> &Vals, Value *&Extra, const TargetData *TD, bool isEQ, unsigned &UsedICmps) { Instruction *I = dyn_cast<Instruction>(V); if (I == 0) return 0; - + // If this is an icmp against a constant, handle this as one of the cases. if (ICmpInst *ICI = dyn_cast<ICmpInst>(I)) { if (ConstantInt *C = GetConstantInt(I->getOperand(1), TD)) { @@ -420,21 +422,21 @@ GatherConstantCompares(Value *V, std::vector<ConstantInt*> &Vals, Value *&Extra, Vals.push_back(C); return I->getOperand(0); } - + // If we have "x ult 3" comparison, for example, then we can add 0,1,2 to // the set. ConstantRange Span = ConstantRange::makeICmpRegion(ICI->getPredicate(), C->getValue()); - + // If this is an and/!= check then we want to optimize "x ugt 2" into // x != 0 && x != 1. if (!isEQ) Span = Span.inverse(); - + // If there are a ton of values, we don't want to make a ginormous switch. if (Span.getSetSize().ugt(8) || Span.isEmptySet()) return 0; - + for (APInt Tmp = Span.getLower(); Tmp != Span.getUpper(); ++Tmp) Vals.push_back(ConstantInt::get(V->getContext(), Tmp)); UsedICmps++; @@ -442,11 +444,11 @@ GatherConstantCompares(Value *V, std::vector<ConstantInt*> &Vals, Value *&Extra, } return 0; } - + // Otherwise, we can only handle an | or &, depending on isEQ. if (I->getOpcode() != (isEQ ? Instruction::Or : Instruction::And)) return 0; - + unsigned NumValsBeforeLHS = Vals.size(); unsigned UsedICmpsBeforeLHS = UsedICmps; if (Value *LHS = GatherConstantCompares(I->getOperand(0), Vals, Extra, TD, @@ -467,12 +469,12 @@ GatherConstantCompares(Value *V, std::vector<ConstantInt*> &Vals, Value *&Extra, Extra = I->getOperand(1); return LHS; } - + Vals.resize(NumValsBeforeLHS); UsedICmps = UsedICmpsBeforeLHS; return 0; } - + // If the LHS can't be folded in, but Extra is available and RHS can, try to // use LHS as Extra. if (Extra == 0 || Extra == I->getOperand(0)) { @@ -484,7 +486,7 @@ GatherConstantCompares(Value *V, std::vector<ConstantInt*> &Vals, Value *&Extra, assert(Vals.size() == NumValsBeforeLHS); Extra = OldExtra; } - + return 0; } @@ -615,6 +617,9 @@ SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI, assert(ThisVal && "This isn't a value comparison!!"); if (ThisVal != PredVal) return false; // Different predicates. + // TODO: Preserve branch weight metadata, similarly to how + // FoldValueComparisonIntoPredecessors preserves it. + // Find out information about when control will move from Pred to TI's block. std::vector<ValueEqualityComparisonCase> PredCases; BasicBlock *PredDef = GetValueEqualityComparisonCases(Pred->getTerminator(), @@ -634,7 +639,7 @@ SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI, // can simplify TI. if (!ValuesOverlap(PredCases, ThisCases)) return false; - + if (isa<BranchInst>(TI)) { // Okay, one of the successors of this condbr is dead. Convert it to a // uncond br. @@ -652,7 +657,7 @@ SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI, EraseTerminatorInstAndDCECond(TI); return true; } - + SwitchInst *SI = cast<SwitchInst>(TI); // Okay, TI has cases that are statically dead, prune them away. SmallPtrSet<Constant*, 16> DeadCases; @@ -673,7 +678,7 @@ SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI, DEBUG(dbgs() << "Leaving: " << *TI << "\n"); return true; } - + // Otherwise, TI's block must correspond to some matched value. Find out // which value (or set of values) this is. ConstantInt *TIV = 0; @@ -729,8 +734,8 @@ namespace { } static int ConstantIntSortPredicate(const void *P1, const void *P2) { - const ConstantInt *LHS = *(const ConstantInt**)P1; - const ConstantInt *RHS = *(const ConstantInt**)P2; + const ConstantInt *LHS = *(const ConstantInt*const*)P1; + const ConstantInt *RHS = *(const ConstantInt*const*)P2; if (LHS->getValue().ult(RHS->getValue())) return 1; if (LHS->getValue() == RHS->getValue()) @@ -738,6 +743,67 @@ static int ConstantIntSortPredicate(const void *P1, const void *P2) { return -1; } +static inline bool HasBranchWeights(const Instruction* I) { + MDNode* ProfMD = I->getMetadata(LLVMContext::MD_prof); + if (ProfMD && ProfMD->getOperand(0)) + if (MDString* MDS = dyn_cast<MDString>(ProfMD->getOperand(0))) + return MDS->getString().equals("branch_weights"); + + return false; +} + +/// Tries to get a branch weight for the given instruction, returns NULL if it +/// can't. Pos starts at 0. +static ConstantInt* GetWeight(Instruction* I, int Pos) { + MDNode* ProfMD = I->getMetadata(LLVMContext::MD_prof); + if (ProfMD && ProfMD->getOperand(0)) { + if (MDString* MDS = dyn_cast<MDString>(ProfMD->getOperand(0))) { + if (MDS->getString().equals("branch_weights")) { + assert(ProfMD->getNumOperands() >= 3); + return dyn_cast<ConstantInt>(ProfMD->getOperand(1 + Pos)); + } + } + } + + return 0; +} + +/// Scale the given weights based on the successor TI's metadata. Scaling is +/// done by multiplying every weight by the sum of the successor's weights. +static void ScaleWeights(Instruction* STI, MutableArrayRef<uint64_t> Weights) { + // Sum the successor's weights + assert(HasBranchWeights(STI)); + unsigned Scale = 0; + MDNode* ProfMD = STI->getMetadata(LLVMContext::MD_prof); + for (unsigned i = 1; i < ProfMD->getNumOperands(); ++i) { + ConstantInt* CI = dyn_cast<ConstantInt>(ProfMD->getOperand(i)); + assert(CI); + Scale += CI->getValue().getZExtValue(); + } + + // Skip default, as it's replaced during the folding + for (unsigned i = 1; i < Weights.size(); ++i) { + Weights[i] *= Scale; + } +} + +/// Sees if any of the weights are too big for a uint32_t, and halves all the +/// weights if any are. +static void FitWeights(MutableArrayRef<uint64_t> Weights) { + bool Halve = false; + for (unsigned i = 0; i < Weights.size(); ++i) + if (Weights[i] > UINT_MAX) { + Halve = true; + break; + } + + if (! Halve) + return; + + for (unsigned i = 0; i < Weights.size(); ++i) + Weights[i] /= 2; +} + /// FoldValueComparisonIntoPredecessors - The specified terminator is a value /// equality comparison instruction (either a switch or a branch on "X == c"). /// See if any of the predecessors of the terminator block are value comparisons @@ -770,6 +836,55 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI, // build. SmallVector<BasicBlock*, 8> NewSuccessors; + // Update the branch weight metadata along the way + SmallVector<uint64_t, 8> Weights; + uint64_t PredDefaultWeight = 0; + bool PredHasWeights = HasBranchWeights(PTI); + bool SuccHasWeights = HasBranchWeights(TI); + + if (PredHasWeights) { + MDNode* MD = PTI->getMetadata(LLVMContext::MD_prof); + assert(MD); + for (unsigned i = 1, e = MD->getNumOperands(); i < e; ++i) { + ConstantInt* CI = dyn_cast<ConstantInt>(MD->getOperand(i)); + assert(CI); + Weights.push_back(CI->getValue().getZExtValue()); + } + + // If the predecessor is a conditional eq, then swap the default weight + // to be the first entry. + if (BranchInst* BI = dyn_cast<BranchInst>(PTI)) { + assert(Weights.size() == 2); + ICmpInst *ICI = cast<ICmpInst>(BI->getCondition()); + + if (ICI->getPredicate() == ICmpInst::ICMP_EQ) { + std::swap(Weights.front(), Weights.back()); + } + } + + PredDefaultWeight = Weights.front(); + } else if (SuccHasWeights) { + // If there are no predecessor weights but there are successor weights, + // populate Weights with 1, which will later be scaled to the sum of + // successor's weights + Weights.assign(1 + PredCases.size(), 1); + PredDefaultWeight = 1; + } + + uint64_t SuccDefaultWeight = 0; + if (SuccHasWeights) { + int Index = 0; + if (BranchInst* BI = dyn_cast<BranchInst>(TI)) { + ICmpInst* ICI = dyn_cast<ICmpInst>(BI->getCondition()); + assert(ICI); + + if (ICI->getPredicate() == ICmpInst::ICMP_EQ) + Index = 1; + } + + SuccDefaultWeight = GetWeight(TI, Index)->getValue().getZExtValue(); + } + if (PredDefault == BB) { // If this is the default destination from PTI, only the edges in TI // that don't occur in PTI, or that branch to BB will be activated. @@ -780,6 +895,12 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI, else { // The default destination is BB, we don't need explicit targets. std::swap(PredCases[i], PredCases.back()); + + if (PredHasWeights) { + std::swap(Weights[i+1], Weights.back()); + Weights.pop_back(); + } + PredCases.pop_back(); --i; --e; } @@ -790,14 +911,35 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI, PredDefault = BBDefault; NewSuccessors.push_back(BBDefault); } + + if (SuccHasWeights) { + ScaleWeights(TI, Weights); + Weights.front() *= SuccDefaultWeight; + } else if (PredHasWeights) { + Weights.front() /= (1 + BBCases.size()); + } + for (unsigned i = 0, e = BBCases.size(); i != e; ++i) if (!PTIHandled.count(BBCases[i].Value) && BBCases[i].Dest != BBDefault) { PredCases.push_back(BBCases[i]); NewSuccessors.push_back(BBCases[i].Dest); + if (SuccHasWeights) { + Weights.push_back(PredDefaultWeight * + GetWeight(TI, i)->getValue().getZExtValue()); + } else if (PredHasWeights) { + // Split the old default's weight amongst the children + assert(PredDefaultWeight != 0); + Weights.push_back(PredDefaultWeight / (1 + BBCases.size())); + } } } else { + // FIXME: preserve branch weight metadata, similarly to the 'then' + // above. For now, drop it. + PredHasWeights = false; + SuccHasWeights = false; + // If this is not the default destination from PSI, only the edges // in SI that occur in PSI with a destination of BB will be // activated. @@ -822,7 +964,7 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI, // If there are any constants vectored to BB that TI doesn't handle, // they must go to the default destination of TI. - for (std::set<ConstantInt*, ConstantIntOrdering>::iterator I = + for (std::set<ConstantInt*, ConstantIntOrdering>::iterator I = PTIHandled.begin(), E = PTIHandled.end(); I != E; ++I) { PredCases.push_back(ValueEqualityComparisonCase(*I, BBDefault)); @@ -851,6 +993,17 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI, for (unsigned i = 0, e = PredCases.size(); i != e; ++i) NewSI->addCase(PredCases[i].Value, PredCases[i].Dest); + if (PredHasWeights || SuccHasWeights) { + // Halve the weights if any of them cannot fit in an uint32_t + FitWeights(Weights); + + SmallVector<uint32_t, 8> MDWeights(Weights.begin(), Weights.end()); + + NewSI->setMetadata(LLVMContext::MD_prof, + MDBuilder(BB->getContext()). + createBranchWeights(MDWeights)); + } + EraseTerminatorInstAndDCECond(PTI); // Okay, last check. If BB is still a successor of PSI, then we must @@ -984,11 +1137,11 @@ HoistTerminator: Value *BB1V = PN->getIncomingValueForBlock(BB1); Value *BB2V = PN->getIncomingValueForBlock(BB2); if (BB1V == BB2V) continue; - + // These values do not agree. Insert a select instruction before NT // that determines the right value. SelectInst *&SI = InsertedSelects[std::make_pair(BB1V, BB2V)]; - if (SI == 0) + if (SI == 0) SI = cast<SelectInst> (Builder.CreateSelect(BI->getCondition(), BB1V, BB2V, BB1V->getName()+"."+BB2V->getName())); @@ -1056,7 +1209,7 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) { // Do not hoist the instruction if any of its operands are defined but not // used in this BB. The transformation will prevent the operand from // being sunk into the use block. - for (User::op_iterator i = HInst->op_begin(), e = HInst->op_end(); + for (User::op_iterator i = HInst->op_begin(), e = HInst->op_end(); i != e; ++i) { Instruction *OpI = dyn_cast<Instruction>(*i); if (OpI && OpI->getParent() == BIParent && @@ -1112,7 +1265,7 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) { // as well. if (PHIs.empty()) return false; - + // If we get here, we can hoist the instruction and if-convert. DEBUG(dbgs() << "SPECULATIVELY EXECUTING BB" << *BB1 << "\n";); @@ -1162,13 +1315,13 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) { static bool BlockIsSimpleEnoughToThreadThrough(BasicBlock *BB) { BranchInst *BI = cast<BranchInst>(BB->getTerminator()); unsigned Size = 0; - + for (BasicBlock::iterator BBI = BB->begin(); &*BBI != BI; ++BBI) { if (isa<DbgInfoIntrinsic>(BBI)) continue; if (Size > 10) return false; // Don't clone large BB's. ++Size; - + // We can only support instructions that do not define values that are // live outside of the current basic block. for (Value::use_iterator UI = BBI->use_begin(), E = BBI->use_end(); @@ -1176,7 +1329,7 @@ static bool BlockIsSimpleEnoughToThreadThrough(BasicBlock *BB) { Instruction *U = cast<Instruction>(*UI); if (U->getParent() != BB || isa<PHINode>(U)) return false; } - + // Looks ok, continue checking. } @@ -1194,31 +1347,31 @@ static bool FoldCondBranchOnPHI(BranchInst *BI, const TargetData *TD) { // outside of the block. if (!PN || PN->getParent() != BB || !PN->hasOneUse()) return false; - + // Degenerate case of a single entry PHI. if (PN->getNumIncomingValues() == 1) { FoldSingleEntryPHINodes(PN->getParent()); - return true; + return true; } // Now we know that this block has multiple preds and two succs. if (!BlockIsSimpleEnoughToThreadThrough(BB)) return false; - + // Okay, this is a simple enough basic block. See if any phi values are // constants. for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { ConstantInt *CB = dyn_cast<ConstantInt>(PN->getIncomingValue(i)); if (CB == 0 || !CB->getType()->isIntegerTy(1)) continue; - + // Okay, we now know that all edges from PredBB should be revectored to // branch to RealDest. BasicBlock *PredBB = PN->getIncomingBlock(i); BasicBlock *RealDest = BI->getSuccessor(!CB->getZExtValue()); - + if (RealDest == BB) continue; // Skip self loops. // Skip if the predecessor's terminator is an indirect branch. if (isa<IndirectBrInst>(PredBB->getTerminator())) continue; - + // The dest block might have PHI nodes, other predecessors and other // difficult cases. Instead of being smart about this, just insert a new // block that jumps to the destination block, effectively splitting @@ -1227,7 +1380,7 @@ static bool FoldCondBranchOnPHI(BranchInst *BI, const TargetData *TD) { RealDest->getName()+".critedge", RealDest->getParent(), RealDest); BranchInst::Create(RealDest, EdgeBB); - + // Update PHI nodes. AddPredecessorToBlock(RealDest, EdgeBB, BB); @@ -1244,7 +1397,7 @@ static bool FoldCondBranchOnPHI(BranchInst *BI, const TargetData *TD) { // Clone the instruction. Instruction *N = BBI->clone(); if (BBI->hasName()) N->setName(BBI->getName()+".c"); - + // Update operands due to translation. for (User::op_iterator i = N->op_begin(), e = N->op_end(); i != e; ++i) { @@ -1252,7 +1405,7 @@ static bool FoldCondBranchOnPHI(BranchInst *BI, const TargetData *TD) { if (PI != TranslateMap.end()) *i = PI->second; } - + // Check for trivial simplification. if (Value *V = SimplifyInstruction(N, TD)) { TranslateMap[BBI] = V; @@ -1297,7 +1450,7 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) { // Don't bother if the branch will be constant folded trivially. isa<ConstantInt>(IfCond)) return false; - + // Okay, we found that we can merge this two-entry phi node into a select. // Doing so would require us to fold *all* two entry phi nodes in this block. // At some point this becomes non-profitable (particularly if the target @@ -1307,14 +1460,14 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) { for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ++NumPhis, ++I) if (NumPhis > 2) return false; - + // Loop over the PHI's seeing if we can promote them all to select // instructions. While we are at it, keep track of the instructions // that need to be moved to the dominating block. SmallPtrSet<Instruction*, 4> AggressiveInsts; unsigned MaxCostVal0 = PHINodeFoldingThreshold, MaxCostVal1 = PHINodeFoldingThreshold; - + for (BasicBlock::iterator II = BB->begin(); isa<PHINode>(II);) { PHINode *PN = cast<PHINode>(II++); if (Value *V = SimplifyInstruction(PN, TD)) { @@ -1322,19 +1475,19 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) { PN->eraseFromParent(); continue; } - + if (!DominatesMergePoint(PN->getIncomingValue(0), BB, &AggressiveInsts, MaxCostVal0) || !DominatesMergePoint(PN->getIncomingValue(1), BB, &AggressiveInsts, MaxCostVal1)) return false; } - + // If we folded the first phi, PN dangles at this point. Refresh it. If // we ran out of PHIs then we simplified them all. PN = dyn_cast<PHINode>(BB->begin()); if (PN == 0) return true; - + // Don't fold i1 branches on PHIs which contain binary operators. These can // often be turned into switches and other things. if (PN->getType()->isIntegerTy(1) && @@ -1342,7 +1495,7 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) { isa<BinaryOperator>(PN->getIncomingValue(1)) || isa<BinaryOperator>(IfCond))) return false; - + // If we all PHI nodes are promotable, check to make sure that all // instructions in the predecessor blocks can be promoted as well. If // not, we won't be able to get rid of the control flow, so it's not @@ -1362,7 +1515,7 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) { return false; } } - + if (cast<BranchInst>(IfBlock2->getTerminator())->isConditional()) { IfBlock2 = 0; } else { @@ -1375,15 +1528,15 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) { return false; } } - + DEBUG(dbgs() << "FOUND IF CONDITION! " << *IfCond << " T: " << IfTrue->getName() << " F: " << IfFalse->getName() << "\n"); - + // If we can still promote the PHI nodes after this gauntlet of tests, // do all of the PHI's now. Instruction *InsertPt = DomBlock->getTerminator(); IRBuilder<true, NoFolder> Builder(InsertPt); - + // Move all 'aggressive' instructions, which are defined in the // conditional parts of the if's up to the dominating block. if (IfBlock1) @@ -1394,19 +1547,19 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) { DomBlock->getInstList().splice(InsertPt, IfBlock2->getInstList(), IfBlock2->begin(), IfBlock2->getTerminator()); - + while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) { // Change the PHI node into a select instruction. Value *TrueVal = PN->getIncomingValue(PN->getIncomingBlock(0) == IfFalse); Value *FalseVal = PN->getIncomingValue(PN->getIncomingBlock(0) == IfTrue); - - SelectInst *NV = + + SelectInst *NV = cast<SelectInst>(Builder.CreateSelect(IfCond, TrueVal, FalseVal, "")); PN->replaceAllUsesWith(NV); NV->takeName(PN); PN->eraseFromParent(); } - + // At this point, IfBlock1 and IfBlock2 are both empty, so our if statement // has been flattened. Change DomBlock to jump directly to our new block to // avoid other simplifycfg's kicking in on the diamond. @@ -1420,14 +1573,14 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) { /// SimplifyCondBranchToTwoReturns - If we found a conditional branch that goes /// to two returning blocks, try to merge them together into one return, /// introducing a select if the return values disagree. -static bool SimplifyCondBranchToTwoReturns(BranchInst *BI, +static bool SimplifyCondBranchToTwoReturns(BranchInst *BI, IRBuilder<> &Builder) { assert(BI->isConditional() && "Must be a conditional branch"); BasicBlock *TrueSucc = BI->getSuccessor(0); BasicBlock *FalseSucc = BI->getSuccessor(1); ReturnInst *TrueRet = cast<ReturnInst>(TrueSucc->getTerminator()); ReturnInst *FalseRet = cast<ReturnInst>(FalseSucc->getTerminator()); - + // Check to ensure both blocks are empty (just a return) or optionally empty // with PHI nodes. If there are other instructions, merging would cause extra // computation on one path or the other. @@ -1447,12 +1600,12 @@ static bool SimplifyCondBranchToTwoReturns(BranchInst *BI, EraseTerminatorInstAndDCECond(BI); return true; } - + // Otherwise, figure out what the true and false return values are // so we can insert a new select instruction. Value *TrueValue = TrueRet->getReturnValue(); Value *FalseValue = FalseRet->getReturnValue(); - + // Unwrap any PHI nodes in the return blocks. if (PHINode *TVPN = dyn_cast_or_null<PHINode>(TrueValue)) if (TVPN->getParent() == TrueSucc) @@ -1460,7 +1613,7 @@ static bool SimplifyCondBranchToTwoReturns(BranchInst *BI, if (PHINode *FVPN = dyn_cast_or_null<PHINode>(FalseValue)) if (FVPN->getParent() == FalseSucc) FalseValue = FVPN->getIncomingValueForBlock(BI->getParent()); - + // In order for this transformation to be safe, we must be able to // unconditionally execute both operands to the return. This is // normally the case, but we could have a potentially-trapping @@ -1472,12 +1625,12 @@ static bool SimplifyCondBranchToTwoReturns(BranchInst *BI, if (ConstantExpr *FCV = dyn_cast_or_null<ConstantExpr>(FalseValue)) if (FCV->canTrap()) return false; - + // Okay, we collected all the mapped values and checked them for sanity, and // defined to really do this transformation. First, update the CFG. TrueSucc->removePredecessor(BI->getParent()); FalseSucc->removePredecessor(BI->getParent()); - + // Insert select instructions where needed. Value *BrCond = BI->getCondition(); if (TrueValue) { @@ -1491,15 +1644,15 @@ static bool SimplifyCondBranchToTwoReturns(BranchInst *BI, } } - Value *RI = !TrueValue ? + Value *RI = !TrueValue ? Builder.CreateRetVoid() : Builder.CreateRet(TrueValue); (void) RI; - + DEBUG(dbgs() << "\nCHANGING BRANCH TO TWO RETURNS INTO SELECT:" << "\n " << *BI << "NewRet = " << *RI << "TRUEBLOCK: " << *TrueSucc << "FALSEBLOCK: "<< *FalseSucc); - + EraseTerminatorInstAndDCECond(BI); return true; @@ -1600,7 +1753,7 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { if (Cond == 0) return false; } - + if (Cond == 0 || (!isa<CmpInst>(Cond) && !isa<BinaryOperator>(Cond)) || Cond->getParent() != BB || !Cond->hasOneUse()) return false; @@ -1623,7 +1776,7 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { isSafeToSpeculativelyExecute(FrontIt)) { BonusInst = &*FrontIt; ++FrontIt; - + // Ignore dbg intrinsics. while (isa<DbgInfoIntrinsic>(FrontIt)) ++FrontIt; } @@ -1631,13 +1784,13 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { // Only a single bonus inst is allowed. if (&*FrontIt != Cond) return false; - + // Make sure the instruction after the condition is the cond branch. BasicBlock::iterator CondIt = Cond; ++CondIt; // Ingore dbg intrinsics. while (isa<DbgInfoIntrinsic>(CondIt)) ++CondIt; - + if (&*CondIt != BI) return false; @@ -1649,7 +1802,7 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Cond->getOperand(1))) if (CE->canTrap()) return false; - + // Finally, don't infinitely unroll conditional loops. BasicBlock *TrueDest = BI->getSuccessor(0); BasicBlock *FalseDest = (BI->isConditional()) ? BI->getSuccessor(1) : 0; @@ -1659,22 +1812,22 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) { BasicBlock *PredBlock = *PI; BranchInst *PBI = dyn_cast<BranchInst>(PredBlock->getTerminator()); - + // Check that we have two conditional branches. If there is a PHI node in // the common successor, verify that the same value flows in from both // blocks. SmallVector<PHINode*, 4> PHIs; if (PBI == 0 || PBI->isUnconditional() || - (BI->isConditional() && + (BI->isConditional() && !SafeToMergeTerminators(BI, PBI)) || (!BI->isConditional() && !isProfitableToFoldUnconditional(BI, PBI, Cond, PHIs))) continue; - + // Determine if the two branches share a common destination. Instruction::BinaryOps Opc; bool InvertPredCond = false; - + if (BI->isConditional()) { if (PBI->getSuccessor(0) == TrueDest) Opc = Instruction::Or; @@ -1693,7 +1846,7 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { // Ensure that any values used in the bonus instruction are also used // by the terminator of the predecessor. This means that those values - // must already have been resolved, so we won't be inhibiting the + // must already have been resolved, so we won't be inhibiting the // out-of-order core by speculating them earlier. if (BonusInst) { // Collect the values used by the bonus inst @@ -1707,47 +1860,47 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { SmallVector<std::pair<Value*, unsigned>, 4> Worklist; Worklist.push_back(std::make_pair(PBI->getOperand(0), 0)); - + // Walk up to four levels back up the use-def chain of the predecessor's // terminator to see if all those values were used. The choice of four // levels is arbitrary, to provide a compile-time-cost bound. while (!Worklist.empty()) { std::pair<Value*, unsigned> Pair = Worklist.back(); Worklist.pop_back(); - + if (Pair.second >= 4) continue; UsedValues.erase(Pair.first); if (UsedValues.empty()) break; - + if (Instruction *I = dyn_cast<Instruction>(Pair.first)) { for (Instruction::op_iterator OI = I->op_begin(), OE = I->op_end(); OI != OE; ++OI) Worklist.push_back(std::make_pair(OI->get(), Pair.second+1)); - } + } } - + if (!UsedValues.empty()) return false; } DEBUG(dbgs() << "FOLDING BRANCH TO COMMON DEST:\n" << *PBI << *BB); - IRBuilder<> Builder(PBI); + IRBuilder<> Builder(PBI); // If we need to invert the condition in the pred block to match, do so now. if (InvertPredCond) { Value *NewCond = PBI->getCondition(); - + if (NewCond->hasOneUse() && isa<CmpInst>(NewCond)) { CmpInst *CI = cast<CmpInst>(NewCond); CI->setPredicate(CI->getInversePredicate()); } else { - NewCond = Builder.CreateNot(NewCond, + NewCond = Builder.CreateNot(NewCond, PBI->getCondition()->getName()+".not"); } - + PBI->setCondition(NewCond); PBI->swapSuccessors(); } - + // If we have a bonus inst, clone it into the predecessor block. Instruction *NewBonus = 0; if (BonusInst) { @@ -1756,7 +1909,7 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { NewBonus->takeName(BonusInst); BonusInst->setName(BonusInst->getName()+".old"); } - + // Clone Cond into the predecessor basic block, and or/and the // two conditions together. Instruction *New = Cond->clone(); @@ -1764,9 +1917,9 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { PredBlock->getInstList().insert(PBI, New); New->takeName(Cond); Cond->setName(New->getName()+".old"); - + if (BI->isConditional()) { - Instruction *NewCond = + Instruction *NewCond = cast<Instruction>(Builder.CreateBinOp(Opc, PBI->getCondition(), New, "or.cond")); PBI->setCondition(NewCond); @@ -1806,7 +1959,7 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { // Create (PBI_Cond and BI_Value) or (!PBI_Cond and PBI_C) // PBI_C is true: (PBI_Cond and BI_Value) or (!PBI_Cond) // is false: PBI_Cond and BI_Value - MergedCond = + MergedCond = cast<Instruction>(Builder.CreateBinOp(Instruction::And, PBI->getCondition(), New, "and.cond")); @@ -1814,7 +1967,7 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { Instruction *NotCond = cast<Instruction>(Builder.CreateNot(PBI->getCondition(), "not.cond")); - MergedCond = + MergedCond = cast<Instruction>(Builder.CreateBinOp(Instruction::Or, NotCond, MergedCond, "or.cond")); @@ -1921,7 +2074,7 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) if (isa<DbgInfoIntrinsic>(*I)) I->clone()->insertBefore(PBI); - + return true; } return false; @@ -1936,7 +2089,7 @@ static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI) { BasicBlock *BB = BI->getParent(); // If this block ends with a branch instruction, and if there is a - // predecessor that ends on a branch of the same condition, make + // predecessor that ends on a branch of the same condition, make // this conditional branch redundant. if (PBI->getCondition() == BI->getCondition() && PBI->getSuccessor(0) != PBI->getSuccessor(1)) { @@ -1945,11 +2098,11 @@ static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI) { if (BB->getSinglePredecessor()) { // Turn this into a branch on constant. bool CondIsTrue = PBI->getSuccessor(0) == BB; - BI->setCondition(ConstantInt::get(Type::getInt1Ty(BB->getContext()), + BI->setCondition(ConstantInt::get(Type::getInt1Ty(BB->getContext()), CondIsTrue)); return true; // Nuke the branch on constant. } - + // Otherwise, if there are multiple predecessors, insert a PHI that merges // in the constant and simplify the block result. Subsequent passes of // simplifycfg will thread the block. @@ -1969,18 +2122,18 @@ static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI) { PBI->getCondition() == BI->getCondition() && PBI->getSuccessor(0) != PBI->getSuccessor(1)) { bool CondIsTrue = PBI->getSuccessor(0) == BB; - NewPN->addIncoming(ConstantInt::get(Type::getInt1Ty(BB->getContext()), + NewPN->addIncoming(ConstantInt::get(Type::getInt1Ty(BB->getContext()), CondIsTrue), P); } else { NewPN->addIncoming(BI->getCondition(), P); } } - + BI->setCondition(NewPN); return true; } } |