diff options
| -rw-r--r-- | llvm/lib/Transforms/Utils/SimplifyCFG.cpp | 83 |
1 files changed, 54 insertions, 29 deletions
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp index 458413d2f8a..5e972b16e28 100644 --- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp @@ -173,6 +173,7 @@ class SimplifyCFGOpt { const DataLayout &DL; SmallPtrSetImpl<BasicBlock *> *LoopHeaders; const SimplifyCFGOptions &Options; + bool Resimplify; Value *isValueEqualityComparison(TerminatorInst *TI); BasicBlock *GetValueEqualityComparisonCases( @@ -194,6 +195,9 @@ class SimplifyCFGOpt { bool SimplifyUncondBranch(BranchInst *BI, IRBuilder<> &Builder); bool SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder); + bool tryToSimplifyUncondBranchWithICmpInIt(ICmpInst *ICI, + IRBuilder<> &Builder); + public: SimplifyCFGOpt(const TargetTransformInfo &TTI, const DataLayout &DL, SmallPtrSetImpl<BasicBlock *> *LoopHeaders, @@ -201,6 +205,13 @@ public: : TTI(TTI), DL(DL), LoopHeaders(LoopHeaders), Options(Opts) {} bool run(BasicBlock *BB); + bool simplifyOnce(BasicBlock *BB); + + // Helper to set Resimplify and return change indication. + bool requestResimplify() { + Resimplify = true; + return true; + } }; } // end anonymous namespace @@ -3543,9 +3554,8 @@ static bool SimplifyIndirectBrOnSelect(IndirectBrInst *IBI, SelectInst *SI) { /// /// We prefer to split the edge to 'end' so that there is a true/false entry to /// the PHI, merging the third icmp into the switch. -static bool tryToSimplifyUncondBranchWithICmpInIt( - ICmpInst *ICI, IRBuilder<> &Builder, const DataLayout &DL, - const TargetTransformInfo &TTI, const SimplifyCFGOptions &Options) { +bool SimplifyCFGOpt::tryToSimplifyUncondBranchWithICmpInIt( + ICmpInst *ICI, IRBuilder<> &Builder) { BasicBlock *BB = ICI->getParent(); // If the block has any PHIs in it or the icmp has multiple uses, it is too @@ -3580,7 +3590,7 @@ static bool tryToSimplifyUncondBranchWithICmpInIt( ICI->eraseFromParent(); } // BB is now empty, so it is likely to simplify away. - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); } // Ok, the block is reachable from the default dest. If the constant we're @@ -3596,7 +3606,7 @@ static bool tryToSimplifyUncondBranchWithICmpInIt( ICI->replaceAllUsesWith(V); ICI->eraseFromParent(); // BB is now empty, so it is likely to simplify away. - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); } // The use of the icmp has to be in the 'end' block, by the only PHI node in @@ -5595,33 +5605,33 @@ bool SimplifyCFGOpt::SimplifySwitch(SwitchInst *SI, IRBuilder<> &Builder) { // see if that predecessor totally determines the outcome of this switch. if (BasicBlock *OnlyPred = BB->getSinglePredecessor()) if (SimplifyEqualityComparisonWithOnlyPredecessor(SI, OnlyPred, Builder)) - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); Value *Cond = SI->getCondition(); if (SelectInst *Select = dyn_cast<SelectInst>(Cond)) if (SimplifySwitchOnSelect(SI, Select)) - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); // If the block only contains the switch, see if we can fold the block // away into any preds. if (SI == &*BB->instructionsWithoutDebug().begin()) if (FoldValueComparisonIntoPredecessors(SI, Builder)) - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); } // Try to transform the switch into an icmp and a branch. if (TurnSwitchRangeIntoICmp(SI, Builder)) - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); // Remove unreachable cases. if (eliminateDeadSwitchCases(SI, Options.AC, DL)) - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); if (switchToSelect(SI, Builder, DL, TTI)) - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); if (Options.ForwardSwitchCondToPhi && ForwardSwitchConditionToPHI(SI)) - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); // The conversion from switch to lookup tables results in difficult-to-analyze // code and makes pruning branches much harder. This is a problem if the @@ -5630,10 +5640,10 @@ bool SimplifyCFGOpt::SimplifySwitch(SwitchInst *SI, IRBuilder<> &Builder) { // optimisation pipeline. if (Options.ConvertSwitchToLookupTable && SwitchToLookupTable(SI, Builder, DL, TTI)) - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); if (ReduceSwitchRange(SI, Builder, DL, TTI)) - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); return false; } @@ -5671,7 +5681,7 @@ bool SimplifyCFGOpt::SimplifyIndirectBr(IndirectBrInst *IBI) { if (SelectInst *SI = dyn_cast<SelectInst>(IBI->getAddress())) { if (SimplifyIndirectBrOnSelect(IBI, SI)) - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); } return Changed; } @@ -5781,7 +5791,7 @@ bool SimplifyCFGOpt::SimplifyUncondBranch(BranchInst *BI, for (++I; isa<DbgInfoIntrinsic>(I); ++I) ; if (I->isTerminator() && - tryToSimplifyUncondBranchWithICmpInIt(ICI, Builder, DL, TTI, Options)) + tryToSimplifyUncondBranchWithICmpInIt(ICI, Builder)) return true; } @@ -5799,7 +5809,7 @@ bool SimplifyCFGOpt::SimplifyUncondBranch(BranchInst *BI, // predecessor and use logical operations to update the incoming value // for PHI nodes in common successor. if (FoldBranchToCommonDest(BI, Options.BonusInstThreshold)) - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); return false; } @@ -5827,18 +5837,18 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) { // switch. if (BasicBlock *OnlyPred = BB->getSinglePredecessor()) if (SimplifyEqualityComparisonWithOnlyPredecessor(BI, OnlyPred, Builder)) - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); // This block must be empty, except for the setcond inst, if it exists. // Ignore dbg intrinsics. auto I = BB->instructionsWithoutDebug().begin(); if (&*I == BI) { if (FoldValueComparisonIntoPredecessors(BI, Builder)) - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); } else if (&*I == cast<Instruction>(BI->getCondition())) { ++I; if (&*I == BI && FoldValueComparisonIntoPredecessors(BI, Builder)) - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); } } @@ -5865,7 +5875,7 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) { : ConstantInt::getFalse(BB->getContext()); BI->setCondition(CI); RecursivelyDeleteTriviallyDeadInstructions(OldCond); - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); } } } @@ -5874,7 +5884,7 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) { // branches to us and one of our successors, fold the comparison into the // predecessor and use logical operations to pick the right destination. if (FoldBranchToCommonDest(BI, Options.BonusInstThreshold)) - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); // We have a conditional branch to two blocks that are only reachable // from BI. We know that the condbr dominates the two blocks, so see if @@ -5883,7 +5893,7 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) { if (BI->getSuccessor(0)->getSinglePredecessor()) { if (BI->getSuccessor(1)->getSinglePredecessor()) { if (HoistThenElseCodeToIf(BI, TTI)) - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); } else { // If Successor #1 has multiple preds, we may be able to conditionally // execute Successor #0 if it branches to Successor #1. @@ -5891,7 +5901,7 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) { if (Succ0TI->getNumSuccessors() == 1 && Succ0TI->getSuccessor(0) == BI->getSuccessor(1)) if (SpeculativelyExecuteBB(BI, BI->getSuccessor(0), TTI)) - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); } } else if (BI->getSuccessor(1)->getSinglePredecessor()) { // If Successor #0 has multiple preds, we may be able to conditionally @@ -5900,7 +5910,7 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) { if (Succ1TI->getNumSuccessors() == 1 && Succ1TI->getSuccessor(0) == BI->getSuccessor(0)) if (SpeculativelyExecuteBB(BI, BI->getSuccessor(1), TTI)) - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); } // If this is a branch on a phi node in the current block, thread control @@ -5908,14 +5918,14 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) { if (PHINode *PN = dyn_cast<PHINode>(BI->getCondition())) if (PN->getParent() == BI->getParent()) if (FoldCondBranchOnPHI(BI, DL, Options.AC)) - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); // Scan predecessor blocks for conditional branches. for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) if (BranchInst *PBI = dyn_cast<BranchInst>((*PI)->getTerminator())) if (PBI != BI && PBI->isConditional()) if (SimplifyCondBranchToCondBranch(PBI, BI, DL)) - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); // Look for diamond patterns. if (MergeCondStores) @@ -5923,7 +5933,7 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) { if (BranchInst *PBI = dyn_cast<BranchInst>(PrevBB->getTerminator())) if (PBI != BI && PBI->isConditional()) if (mergeConditionalStores(PBI, BI, DL)) - return simplifyCFG(BB, TTI, Options) || true; + return requestResimplify(); return false; } @@ -6006,7 +6016,7 @@ static bool removeUndefIntroducingPredecessor(BasicBlock *BB) { return false; } -bool SimplifyCFGOpt::run(BasicBlock *BB) { +bool SimplifyCFGOpt::simplifyOnce(BasicBlock *BB) { bool Changed = false; assert(BB && BB->getParent() && "Block not embedded in function!"); @@ -6080,6 +6090,21 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) { return Changed; } +bool SimplifyCFGOpt::run(BasicBlock *BB) { + bool Changed = false; + + // Repeated simplify BB as long as resimplification is requested. + do { + Resimplify = false; + + // Perform one round of simplifcation. Resimplify flag will be set if + // another iteration is requested. + Changed |= simplifyOnce(BB); + } while (Resimplify); + + return Changed; +} + bool llvm::simplifyCFG(BasicBlock *BB, const TargetTransformInfo &TTI, const SimplifyCFGOptions &Options, SmallPtrSetImpl<BasicBlock *> *LoopHeaders) { |