diff options
Diffstat (limited to 'lib/Transforms/Scalar/LICM.cpp')
| -rw-r--r-- | lib/Transforms/Scalar/LICM.cpp | 401 |
1 files changed, 222 insertions, 179 deletions
diff --git a/lib/Transforms/Scalar/LICM.cpp b/lib/Transforms/Scalar/LICM.cpp index 5f00bb9..14af38b 100644 --- a/lib/Transforms/Scalar/LICM.cpp +++ b/lib/Transforms/Scalar/LICM.cpp @@ -52,7 +52,7 @@ #include "llvm/Support/CommandLine.h" #include "llvm/Support/Debug.h" #include "llvm/Support/raw_ostream.h" -#include "llvm/Target/TargetLibraryInfo.h" +#include "llvm/Analysis/TargetLibraryInfo.h" #include "llvm/Transforms/Utils/Local.h" #include "llvm/Transforms/Utils/LoopUtils.h" #include "llvm/Transforms/Utils/SSAUpdater.h" @@ -71,6 +71,27 @@ static cl::opt<bool> DisablePromotion("disable-licm-promotion", cl::Hidden, cl::desc("Disable memory promotion in LICM pass")); +static bool inSubLoop(BasicBlock *BB, Loop *CurLoop, LoopInfo *LI); +static bool isNotUsedInLoop(Instruction &I, Loop *CurLoop); +static bool hoist(Instruction &I, BasicBlock *Preheader); +static bool sink(Instruction &I, LoopInfo *LI, DominatorTree *DT, + Loop *CurLoop, AliasSetTracker *CurAST ); +static bool isGuaranteedToExecute(Instruction &Inst, DominatorTree *DT, + Loop *CurLoop, LICMSafetyInfo * SafetyInfo); +static bool isSafeToExecuteUnconditionally(Instruction &Inst,DominatorTree *DT, + const DataLayout *DL, Loop *CurLoop, + LICMSafetyInfo * SafetyInfo); +static bool pointerInvalidatedByLoop(Value *V, uint64_t Size, + const AAMDNodes &AAInfo, + AliasSetTracker *CurAST); +static Instruction *CloneInstructionInExitBlock(Instruction &I, + BasicBlock &ExitBlock, + PHINode &PN, LoopInfo *LI); +static bool canSinkOrHoistInst(Instruction &I, AliasAnalysis *AA, + DominatorTree *DT, const DataLayout *DL, + Loop *CurLoop, AliasSetTracker *CurAST, + LICMSafetyInfo * SafetyInfo); + namespace { struct LICM : public LoopPass { static char ID; // Pass identification, replacement for typeid @@ -86,7 +107,7 @@ namespace { void getAnalysisUsage(AnalysisUsage &AU) const override { AU.setPreservesCFG(); AU.addRequired<DominatorTreeWrapperPass>(); - AU.addRequired<LoopInfo>(); + AU.addRequired<LoopInfoWrapperPass>(); AU.addRequiredID(LoopSimplifyID); AU.addPreservedID(LoopSimplifyID); AU.addRequiredID(LCSSAID); @@ -94,7 +115,7 @@ namespace { AU.addRequired<AliasAnalysis>(); AU.addPreserved<AliasAnalysis>(); AU.addPreserved<ScalarEvolution>(); - AU.addRequired<TargetLibraryInfo>(); + AU.addRequired<TargetLibraryInfoWrapperPass>(); } using llvm::Pass::doFinalization; @@ -117,9 +138,6 @@ namespace { BasicBlock *Preheader; // The preheader block of the current loop... Loop *CurLoop; // The current loop we are working on... AliasSetTracker *CurAST; // AliasSet information for the current loop... - bool MayThrow; // The current loop contains an instruction which - // may throw, thus preventing code motion of - // instructions with side effects. DenseMap<Loop*, AliasSetTracker*> LoopToAliasSetMap; /// cloneBasicBlockAnalysis - Simple Analysis hook. Clone alias set info. @@ -132,88 +150,17 @@ namespace { /// Simple Analysis hook. Delete loop L from alias set map. void deleteAnalysisLoop(Loop *L) override; - - /// SinkRegion - Walk the specified region of the CFG (defined by all blocks - /// dominated by the specified block, and that are in the current loop) in - /// reverse depth first order w.r.t the DominatorTree. This allows us to - /// visit uses before definitions, allowing us to sink a loop body in one - /// pass without iteration. - /// - void SinkRegion(DomTreeNode *N); - - /// HoistRegion - Walk the specified region of the CFG (defined by all - /// blocks dominated by the specified block, and that are in the current - /// loop) in depth first order w.r.t the DominatorTree. This allows us to - /// visit definitions before uses, allowing us to hoist a loop body in one - /// pass without iteration. - /// - void HoistRegion(DomTreeNode *N); - - /// inSubLoop - Little predicate that returns true if the specified basic - /// block is in a subloop of the current one, not the current one itself. - /// - bool inSubLoop(BasicBlock *BB) { - assert(CurLoop->contains(BB) && "Only valid if BB is IN the loop"); - return LI->getLoopFor(BB) != CurLoop; - } - - /// sink - When an instruction is found to only be used outside of the loop, - /// this function moves it to the exit blocks and patches up SSA form as - /// needed. - /// - void sink(Instruction &I); - - /// hoist - When an instruction is found to only use loop invariant operands - /// that is safe to hoist, this instruction is called to do the dirty work. - /// - void hoist(Instruction &I); - - /// isSafeToExecuteUnconditionally - Only sink or hoist an instruction if it - /// is not a trapping instruction or if it is a trapping instruction and is - /// guaranteed to execute. - /// - bool isSafeToExecuteUnconditionally(Instruction &I); - - /// isGuaranteedToExecute - Check that the instruction is guaranteed to - /// execute. - /// - bool isGuaranteedToExecute(Instruction &I); - - /// pointerInvalidatedByLoop - Return true if the body of this loop may - /// store into the memory location pointed to by V. - /// - bool pointerInvalidatedByLoop(Value *V, uint64_t Size, - const AAMDNodes &AAInfo) { - // Check to see if any of the basic blocks in CurLoop invalidate *V. - return CurAST->getAliasSetForPointer(V, Size, AAInfo).isMod(); - } - - bool canSinkOrHoistInst(Instruction &I); - bool isNotUsedInLoop(Instruction &I); - - void PromoteAliasSet(AliasSet &AS, - SmallVectorImpl<BasicBlock*> &ExitBlocks, - SmallVectorImpl<Instruction*> &InsertPts, - PredIteratorCache &PIC); - - /// \brief Create a copy of the instruction in the exit block and patch up - /// SSA. - /// PN is a user of I in ExitBlock that can be used to get the number and - /// list of predecessors fast. - Instruction *CloneInstructionInExitBlock(Instruction &I, - BasicBlock &ExitBlock, - PHINode &PN); }; } char LICM::ID = 0; INITIALIZE_PASS_BEGIN(LICM, "licm", "Loop Invariant Code Motion", false, false) INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) -INITIALIZE_PASS_DEPENDENCY(LoopInfo) +INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass) INITIALIZE_PASS_DEPENDENCY(LoopSimplify) INITIALIZE_PASS_DEPENDENCY(LCSSA) INITIALIZE_PASS_DEPENDENCY(ScalarEvolution) -INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo) +INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass) INITIALIZE_AG_DEPENDENCY(AliasAnalysis) INITIALIZE_PASS_END(LICM, "licm", "Loop Invariant Code Motion", false, false) @@ -230,13 +177,13 @@ bool LICM::runOnLoop(Loop *L, LPPassManager &LPM) { Changed = false; // Get our Loop and Alias Analysis information... - LI = &getAnalysis<LoopInfo>(); + LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo(); AA = &getAnalysis<AliasAnalysis>(); DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree(); DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>(); DL = DLP ? &DLP->getDataLayout() : nullptr; - TLI = &getAnalysis<TargetLibraryInfo>(); + TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(); assert(L->isLCSSAForm(*DT) && "Loop is not in LCSSA form."); @@ -273,14 +220,9 @@ bool LICM::runOnLoop(Loop *L, LPPassManager &LPM) { CurAST->add(*BB); // Incorporate the specified basic block } - MayThrow = false; - // TODO: We've already searched for instructions which may throw in subloops. - // We may want to reuse this information. - for (Loop::block_iterator BB = L->block_begin(), BBE = L->block_end(); - (BB != BBE) && !MayThrow ; ++BB) - for (BasicBlock::iterator I = (*BB)->begin(), E = (*BB)->end(); - (I != E) && !MayThrow; ++I) - MayThrow |= I->mayThrow(); + // Compute loop safety information. + LICMSafetyInfo SafetyInfo; + computeLICMSafetyInfo(&SafetyInfo, CurLoop); // We want to visit all of the instructions in this loop... that are not parts // of our subloops (they have already had their invariants hoisted out of @@ -293,9 +235,11 @@ bool LICM::runOnLoop(Loop *L, LPPassManager &LPM) { // instructions, we perform another pass to hoist them out of the loop. // if (L->hasDedicatedExits()) - SinkRegion(DT->getNode(L->getHeader())); + Changed |= sinkRegion(DT->getNode(L->getHeader()), AA, LI, DT, DL, TLI, + CurLoop, CurAST, &SafetyInfo); if (Preheader) - HoistRegion(DT->getNode(L->getHeader())); + Changed |= hoistRegion(DT->getNode(L->getHeader()), AA, LI, DT, DL, TLI, + CurLoop, CurAST, &SafetyInfo); // Now that all loop invariants have been removed from the loop, promote any // memory references to scalars that we can. @@ -307,7 +251,9 @@ bool LICM::runOnLoop(Loop *L, LPPassManager &LPM) { // Loop over all of the alias sets in the tracker object. for (AliasSetTracker::iterator I = CurAST->begin(), E = CurAST->end(); I != E; ++I) - PromoteAliasSet(*I, ExitBlocks, InsertPts, PIC); + Changed |= promoteLoopAccessesToScalars(*I, ExitBlocks, InsertPts, + PIC, LI, DT, CurLoop, + CurAST, &SafetyInfo); // Once we have promoted values across the loop body we have to recursively // reform LCSSA as any nested loop may now have values defined within the @@ -316,7 +262,8 @@ bool LICM::runOnLoop(Loop *L, LPPassManager &LPM) { // SSAUpdater strategy during promotion that was LCSSA aware and reformed // it as it went. if (Changed) - formLCSSARecursively(*L, *DT, getAnalysisIfAvailable<ScalarEvolution>()); + formLCSSARecursively(*L, *DT, LI, + getAnalysisIfAvailable<ScalarEvolution>()); } // Check that neither this loop nor its parent have had LCSSA broken. LICM is @@ -339,27 +286,36 @@ bool LICM::runOnLoop(Loop *L, LPPassManager &LPM) { return Changed; } -/// SinkRegion - Walk the specified region of the CFG (defined by all blocks -/// dominated by the specified block, and that are in the current loop) in -/// reverse depth first order w.r.t the DominatorTree. This allows us to visit -/// uses before definitions, allowing us to sink a loop body in one pass without -/// iteration. +/// Walk the specified region of the CFG (defined by all blocks dominated by +/// the specified block, and that are in the current loop) in reverse depth +/// first order w.r.t the DominatorTree. This allows us to visit uses before +/// definitions, allowing us to sink a loop body in one pass without iteration. /// -void LICM::SinkRegion(DomTreeNode *N) { - assert(N != nullptr && "Null dominator tree node?"); +bool llvm::sinkRegion(DomTreeNode *N, AliasAnalysis *AA, LoopInfo *LI, + DominatorTree *DT, const DataLayout *DL, + TargetLibraryInfo *TLI, Loop *CurLoop, + AliasSetTracker *CurAST, LICMSafetyInfo * SafetyInfo) { + + // Verify inputs. + assert(N != nullptr && AA != nullptr && LI != nullptr && + DT != nullptr && CurLoop != nullptr && CurAST != nullptr && + SafetyInfo != nullptr && "Unexpected input to sinkRegion"); + + // Set changed as false. + bool Changed = false; + // Get basic block BasicBlock *BB = N->getBlock(); - // If this subregion is not in the top level loop at all, exit. - if (!CurLoop->contains(BB)) return; + if (!CurLoop->contains(BB)) return Changed; // We are processing blocks in reverse dfo, so process children first. const std::vector<DomTreeNode*> &Children = N->getChildren(); for (unsigned i = 0, e = Children.size(); i != e; ++i) - SinkRegion(Children[i]); - + Changed |= sinkRegion(Children[i], AA, LI, DT, DL, TLI, CurLoop, + CurAST, SafetyInfo); // Only need to process the contents of this block if it is not part of a // subloop (which would already have been processed). - if (inSubLoop(BB)) return; + if (inSubLoop(BB,CurLoop,LI)) return Changed; for (BasicBlock::iterator II = BB->end(); II != BB->begin(); ) { Instruction &I = *--II; @@ -380,31 +336,39 @@ void LICM::SinkRegion(DomTreeNode *N) { // outside of the loop. In this case, it doesn't even matter if the // operands of the instruction are loop invariant. // - if (isNotUsedInLoop(I) && canSinkOrHoistInst(I)) { + if (isNotUsedInLoop(I, CurLoop) && + canSinkOrHoistInst(I, AA, DT, DL, CurLoop, CurAST, SafetyInfo)) { ++II; - sink(I); + Changed |= sink(I, LI, DT, CurLoop, CurAST); } } + return Changed; } -/// HoistRegion - Walk the specified region of the CFG (defined by all blocks -/// dominated by the specified block, and that are in the current loop) in depth -/// first order w.r.t the DominatorTree. This allows us to visit definitions -/// before uses, allowing us to hoist a loop body in one pass without iteration. +/// Walk the specified region of the CFG (defined by all blocks dominated by +/// the specified block, and that are in the current loop) in depth first +/// order w.r.t the DominatorTree. This allows us to visit definitions before +/// uses, allowing us to hoist a loop body in one pass without iteration. /// -void LICM::HoistRegion(DomTreeNode *N) { - assert(N != nullptr && "Null dominator tree node?"); +bool llvm::hoistRegion(DomTreeNode *N, AliasAnalysis *AA, LoopInfo *LI, + DominatorTree *DT, const DataLayout *DL, + TargetLibraryInfo *TLI, Loop *CurLoop, + AliasSetTracker *CurAST, LICMSafetyInfo *SafetyInfo) { + // Verify inputs. + assert(N != nullptr && AA != nullptr && LI != nullptr && + DT != nullptr && CurLoop != nullptr && CurAST != nullptr && + SafetyInfo != nullptr && "Unexpected input to hoistRegion"); + // Set changed as false. + bool Changed = false; + // Get basic block BasicBlock *BB = N->getBlock(); - // If this subregion is not in the top level loop at all, exit. - if (!CurLoop->contains(BB)) return; - + if (!CurLoop->contains(BB)) return Changed; // Only need to process the contents of this block if it is not part of a // subloop (which would already have been processed). - if (!inSubLoop(BB)) + if (!inSubLoop(BB, CurLoop, LI)) for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ) { Instruction &I = *II++; - // Try constant folding this instruction. If all the operands are // constants, it is technically hoistable, but it would be better to just // fold it. @@ -421,20 +385,49 @@ void LICM::HoistRegion(DomTreeNode *N) { // if all of the operands of the instruction are loop invariant and if it // is safe to hoist the instruction. // - if (CurLoop->hasLoopInvariantOperands(&I) && canSinkOrHoistInst(I) && - isSafeToExecuteUnconditionally(I)) - hoist(I); + if (CurLoop->hasLoopInvariantOperands(&I) && + canSinkOrHoistInst(I, AA, DT, DL, CurLoop, CurAST, SafetyInfo) && + isSafeToExecuteUnconditionally(I, DT, DL, CurLoop, SafetyInfo)) + Changed |= hoist(I, CurLoop->getLoopPreheader()); } const std::vector<DomTreeNode*> &Children = N->getChildren(); for (unsigned i = 0, e = Children.size(); i != e; ++i) - HoistRegion(Children[i]); + Changed |= hoistRegion(Children[i], AA, LI, DT, DL, TLI, CurLoop, + CurAST, SafetyInfo); + return Changed; +} + +/// Computes loop safety information, checks loop body & header +/// for the possiblity of may throw exception. +/// +void llvm::computeLICMSafetyInfo(LICMSafetyInfo * SafetyInfo, Loop * CurLoop) { + assert(CurLoop != nullptr && "CurLoop cant be null"); + BasicBlock *Header = CurLoop->getHeader(); + // Setting default safety values. + SafetyInfo->MayThrow = false; + SafetyInfo->HeaderMayThrow = false; + // Iterate over header and compute dafety info. + for (BasicBlock::iterator I = Header->begin(), E = Header->end(); + (I != E) && !SafetyInfo->HeaderMayThrow; ++I) + SafetyInfo->HeaderMayThrow |= I->mayThrow(); + + SafetyInfo->MayThrow = SafetyInfo->HeaderMayThrow; + // Iterate over loop instructions and compute safety info. + for (Loop::block_iterator BB = CurLoop->block_begin(), + BBE = CurLoop->block_end(); (BB != BBE) && !SafetyInfo->MayThrow ; ++BB) + for (BasicBlock::iterator I = (*BB)->begin(), E = (*BB)->end(); + (I != E) && !SafetyInfo->MayThrow; ++I) + SafetyInfo->MayThrow |= I->mayThrow(); } /// canSinkOrHoistInst - Return true if the hoister and sinker can handle this /// instruction. /// -bool LICM::canSinkOrHoistInst(Instruction &I) { +bool canSinkOrHoistInst(Instruction &I, AliasAnalysis *AA, + DominatorTree *DT, const DataLayout *DL, + Loop *CurLoop, AliasSetTracker *CurAST, + LICMSafetyInfo * SafetyInfo) { // Loads have extra constraints we have to verify before we can hoist them. if (LoadInst *LI = dyn_cast<LoadInst>(&I)) { if (!LI->isUnordered()) @@ -455,7 +448,7 @@ bool LICM::canSinkOrHoistInst(Instruction &I) { AAMDNodes AAInfo; LI->getAAMetadata(AAInfo); - return !pointerInvalidatedByLoop(LI->getOperand(0), Size, AAInfo); + return !pointerInvalidatedByLoop(LI->getOperand(0), Size, AAInfo, CurAST); } else if (CallInst *CI = dyn_cast<CallInst>(&I)) { // Don't sink or hoist dbg info; it's legal, but not useful. if (isa<DbgInfoIntrinsic>(I)) @@ -494,14 +487,14 @@ bool LICM::canSinkOrHoistInst(Instruction &I) { !isa<InsertValueInst>(I)) return false; - return isSafeToExecuteUnconditionally(I); + return isSafeToExecuteUnconditionally(I, DT, DL, CurLoop, SafetyInfo); } -/// \brief Returns true if a PHINode is a trivially replaceable with an +/// Returns true if a PHINode is a trivially replaceable with an /// Instruction. +/// This is true when all incoming values are that instruction. +/// This pattern occurs most often with LCSSA PHI nodes. /// -/// This is true when all incoming values are that instruction. This pattern -/// occurs most often with LCSSA PHI nodes. static bool isTriviallyReplacablePHI(PHINode &PN, Instruction &I) { for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) if (PN.getIncomingValue(i) != &I) @@ -510,11 +503,11 @@ static bool isTriviallyReplacablePHI(PHINode &PN, Instruction &I) { return true; } -/// isNotUsedInLoop - Return true if the only users of this instruction are -/// outside of the loop. If this is true, we can sink the instruction to the -/// exit blocks of the loop. +/// Return true if the only users of this instruction are outside of +/// the loop. If this is true, we can sink the instruction to the exit +/// blocks of the loop. /// -bool LICM::isNotUsedInLoop(Instruction &I) { +static bool isNotUsedInLoop(Instruction &I, Loop *CurLoop) { for (User *U : I.users()) { Instruction *UI = cast<Instruction>(U); if (PHINode *PN = dyn_cast<PHINode>(UI)) { @@ -545,9 +538,9 @@ bool LICM::isNotUsedInLoop(Instruction &I) { return true; } -Instruction *LICM::CloneInstructionInExitBlock(Instruction &I, - BasicBlock &ExitBlock, - PHINode &PN) { +static Instruction *CloneInstructionInExitBlock(Instruction &I, + BasicBlock &ExitBlock, + PHINode &PN, LoopInfo *LI) { Instruction *New = I.clone(); ExitBlock.getInstList().insert(ExitBlock.getFirstInsertionPt(), New); if (!I.getName().empty()) New->setName(I.getName() + ".le"); @@ -574,14 +567,15 @@ Instruction *LICM::CloneInstructionInExitBlock(Instruction &I, return New; } -/// sink - When an instruction is found to only be used outside of the loop, -/// this function moves it to the exit blocks and patches up SSA form as needed. +/// When an instruction is found to only be used outside of the loop, this +/// function moves it to the exit blocks and patches up SSA form as needed. /// This method is guaranteed to remove the original instruction from its /// position, and may either delete it or move it to outside of the loop. /// -void LICM::sink(Instruction &I) { +static bool sink(Instruction &I, LoopInfo *LI, DominatorTree *DT, + Loop *CurLoop, AliasSetTracker *CurAST ) { DEBUG(dbgs() << "LICM sinking instruction: " << I << "\n"); - + bool Changed = false; if (isa<LoadInst>(I)) ++NumMovedLoads; else if (isa<CallInst>(I)) ++NumMovedCalls; ++NumSunk; @@ -590,7 +584,8 @@ void LICM::sink(Instruction &I) { #ifndef NDEBUG SmallVector<BasicBlock *, 32> ExitBlocks; CurLoop->getUniqueExitBlocks(ExitBlocks); - SmallPtrSet<BasicBlock *, 32> ExitBlockSet(ExitBlocks.begin(), ExitBlocks.end()); + SmallPtrSet<BasicBlock *, 32> ExitBlockSet(ExitBlocks.begin(), + ExitBlocks.end()); #endif // Clones of this instruction. Don't create more than one per exit block! @@ -618,7 +613,7 @@ void LICM::sink(Instruction &I) { New = It->second; else New = SunkCopies[ExitBlock] = - CloneInstructionInExitBlock(I, *ExitBlock, *PN); + CloneInstructionInExitBlock(I, *ExitBlock, *PN, LI); PN->replaceAllUsesWith(New); PN->eraseFromParent(); @@ -626,44 +621,41 @@ void LICM::sink(Instruction &I) { CurAST->deleteValue(&I); I.eraseFromParent(); + return Changed; } -/// hoist - When an instruction is found to only use loop invariant operands -/// that is safe to hoist, this instruction is called to do the dirty work. +/// When an instruction is found to only use loop invariant operands that +/// is safe to hoist, this instruction is called to do the dirty work. /// -void LICM::hoist(Instruction &I) { +static bool hoist(Instruction &I, BasicBlock *Preheader) { DEBUG(dbgs() << "LICM hoisting to " << Preheader->getName() << ": " << I << "\n"); - // Move the new node to the Preheader, before its terminator. I.moveBefore(Preheader->getTerminator()); if (isa<LoadInst>(I)) ++NumMovedLoads; else if (isa<CallInst>(I)) ++NumMovedCalls; ++NumHoisted; - Changed = true; + return true; } -/// isSafeToExecuteUnconditionally - Only sink or hoist an instruction if it is -/// not a trapping instruction or if it is a trapping instruction and is -/// guaranteed to execute. +/// Only sink or hoist an instruction if it is not a trapping instruction +/// or if it is a trapping instruction and is guaranteed to execute. /// -bool LICM::isSafeToExecuteUnconditionally(Instruction &Inst) { +static bool isSafeToExecuteUnconditionally(Instruction &Inst, DominatorTree *DT, + const DataLayout *DL, Loop *CurLoop, + LICMSafetyInfo * SafetyInfo) { // If it is not a trapping instruction, it is always safe to hoist. if (isSafeToSpeculativelyExecute(&Inst, DL)) return true; - return isGuaranteedToExecute(Inst); + return isGuaranteedToExecute(Inst, DT, CurLoop, SafetyInfo); } -bool LICM::isGuaranteedToExecute(Instruction &Inst) { - - // Somewhere in this loop there is an instruction which may throw and make us - // exit the loop. - if (MayThrow) - return false; +static bool isGuaranteedToExecute(Instruction &Inst, DominatorTree *DT, + Loop *CurLoop, LICMSafetyInfo * SafetyInfo) { - // Otherwise we have to check to make sure that the instruction dominates all + // We have to check to make sure that the instruction dominates all // of the exit blocks. If it doesn't, then there is a path out of the loop // which does not execute this instruction, so we can't hoist it. @@ -671,7 +663,14 @@ bool LICM::isGuaranteedToExecute(Instruction &Inst) { // common), it is always guaranteed to dominate the exit blocks. Since this // is a common case, and can save some work, check it now. if (Inst.getParent() == CurLoop->getHeader()) - return true; + // If there's a throw in the header block, we can't guarantee we'll reach + // Inst. + return !SafetyInfo->HeaderMayThrow; + + // Somewhere in this loop there is an instruction which may throw and make us + // exit the loop. + if (SafetyInfo->MayThrow) + return false; // Get the exit blocks for the current loop. SmallVector<BasicBlock*, 8> ExitBlocks; @@ -768,25 +767,37 @@ namespace { }; } // end anon namespace -/// PromoteAliasSet - Try to promote memory values to scalars by sinking -/// stores out of the loop and moving loads to before the loop. We do this by -/// looping over the stores in the loop, looking for stores to Must pointers -/// which are loop invariant. +/// Try to promote memory values to scalars by sinking stores out of the +/// loop and moving loads to before the loop. We do this by looping over +/// the stores in the loop, looking for stores to Must pointers which are +/// loop invariant. /// -void LICM::PromoteAliasSet(AliasSet &AS, - SmallVectorImpl<BasicBlock*> &ExitBlocks, - SmallVectorImpl<Instruction*> &InsertPts, - PredIteratorCache &PIC) { +bool llvm::promoteLoopAccessesToScalars(AliasSet &AS, + SmallVectorImpl<BasicBlock*>&ExitBlocks, + SmallVectorImpl<Instruction*>&InsertPts, + PredIteratorCache &PIC, LoopInfo *LI, + DominatorTree *DT, Loop *CurLoop, + AliasSetTracker *CurAST, + LICMSafetyInfo * SafetyInfo) { + // Verify inputs. + assert(LI != nullptr && DT != nullptr && + CurLoop != nullptr && CurAST != nullptr && + SafetyInfo != nullptr && + "Unexpected Input to promoteLoopAccessesToScalars"); + // Initially set Changed status to false. + bool Changed = false; // We can promote this alias set if it has a store, if it is a "Must" alias // set, if the pointer is loop invariant, and if we are not eliminating any // volatile loads or stores. if (AS.isForwardingAliasSet() || !AS.isMod() || !AS.isMustAlias() || AS.isVolatile() || !CurLoop->isLoopInvariant(AS.begin()->getValue())) - return; + return Changed; assert(!AS.empty() && "Must alias set should have at least one pointer element in it!"); + Value *SomePtr = AS.begin()->getValue(); + BasicBlock * Preheader = CurLoop->getLoopPreheader(); // It isn't safe to promote a load/store from the loop if the load/store is // conditional. For example, turning: @@ -810,6 +821,7 @@ void LICM::PromoteAliasSet(AliasSet &AS, // us to prove better alignment. unsigned Alignment = 1; AAMDNodes AATags; + bool HasDedicatedExits = CurLoop->hasDedicatedExits(); // Check that all of the pointers in the alias set have the same type. We // cannot (yet) promote a memory location that is loaded and stored in @@ -822,7 +834,7 @@ void LICM::PromoteAliasSet(AliasSet &AS, // cannot (yet) promote a memory location that is loaded and stored in // different sizes. if (SomePtr->getType() != ASIV->getType()) - return; + return Changed; for (User *U : ASIV->users()) { // Ignore instructions that are outside the loop. @@ -835,7 +847,7 @@ void LICM::PromoteAliasSet(AliasSet &AS, if (LoadInst *load = dyn_cast<LoadInst>(UI)) { assert(!load->isVolatile() && "AST broken"); if (!load->isSimple()) - return; + return Changed; } else if (StoreInst *store = dyn_cast<StoreInst>(UI)) { // Stores *of* the pointer are not interesting, only stores *to* the // pointer. @@ -843,7 +855,14 @@ void LICM::PromoteAliasSet(AliasSet &AS, continue; assert(!store->isVolatile() && "AST broken"); if (!store->isSimple()) - return; + return Changed; + // Don't sink stores from loops without dedicated block exits. Exits + // containing indirect branches are not transformed by loop simplify, + // make sure we catch that. An additional load may be generated in the + // preheader for SSA updater, so also avoid sinking when no preheader + // is available. + if (!HasDedicatedExits || !Preheader) + return Changed; // Note that we only check GuaranteedToExecute inside the store case // so that we do not introduce stores where they did not exist before @@ -855,16 +874,17 @@ void LICM::PromoteAliasSet(AliasSet &AS, // Larger is better, with the exception of 0 being the best alignment. unsigned InstAlignment = store->getAlignment(); if ((InstAlignment > Alignment || InstAlignment == 0) && Alignment != 0) - if (isGuaranteedToExecute(*UI)) { + if (isGuaranteedToExecute(*UI, DT, CurLoop, SafetyInfo)) { GuaranteedToExecute = true; Alignment = InstAlignment; } if (!GuaranteedToExecute) - GuaranteedToExecute = isGuaranteedToExecute(*UI); + GuaranteedToExecute = isGuaranteedToExecute(*UI, DT, + CurLoop, SafetyInfo); } else - return; // Not a load or store. + return Changed; // Not a load or store. // Merge the AA tags. if (LoopUses.empty()) { @@ -880,7 +900,7 @@ void LICM::PromoteAliasSet(AliasSet &AS, // If there isn't a guaranteed-to-execute instruction, we can't promote. if (!GuaranteedToExecute) - return; + return Changed; // Otherwise, this is safe to promote, lets do it! DEBUG(dbgs() << "LICM: Promoting value stored to in loop: " <<*SomePtr<<'\n'); @@ -925,10 +945,12 @@ void LICM::PromoteAliasSet(AliasSet &AS, // If the SSAUpdater didn't use the load in the preheader, just zap it now. if (PreheaderLoad->use_empty()) PreheaderLoad->eraseFromParent(); -} + return Changed; +} -/// cloneBasicBlockAnalysis - Simple Analysis hook. Clone alias set info. +/// Simple Analysis hook. Clone alias set info. +/// void LICM::cloneBasicBlockAnalysis(BasicBlock *From, BasicBlock *To, Loop *L) { AliasSetTracker *AST = LoopToAliasSetMap.lookup(L); if (!AST) @@ -937,8 +959,8 @@ void LICM::cloneBasicBlockAnalysis(BasicBlock *From, BasicBlock *To, Loop *L) { AST->copyValue(From, To); } -/// deleteAnalysisValue - Simple Analysis hook. Delete value V from alias -/// set. +/// Simple Analysis hook. Delete value V from alias set +/// void LICM::deleteAnalysisValue(Value *V, Loop *L) { AliasSetTracker *AST = LoopToAliasSetMap.lookup(L); if (!AST) @@ -948,6 +970,7 @@ void LICM::deleteAnalysisValue(Value *V, Loop *L) { } /// Simple Analysis hook. Delete value L from alias set map. +/// void LICM::deleteAnalysisLoop(Loop *L) { AliasSetTracker *AST = LoopToAliasSetMap.lookup(L); if (!AST) @@ -956,3 +979,23 @@ void LICM::deleteAnalysisLoop(Loop *L) { delete AST; LoopToAliasSetMap.erase(L); } + + +/// Return true if the body of this loop may store into the memory +/// location pointed to by V. +/// +static bool pointerInvalidatedByLoop(Value *V, uint64_t Size, + const AAMDNodes &AAInfo, + AliasSetTracker *CurAST) { + // Check to see if any of the basic blocks in CurLoop invalidate *V. + return CurAST->getAliasSetForPointer(V, Size, AAInfo).isMod(); +} + +/// Little predicate that returns true if the specified basic block is in +/// a subloop of the current one, not the current one itself. +/// +static bool inSubLoop(BasicBlock *BB, Loop *CurLoop, LoopInfo *LI) { + assert(CurLoop->contains(BB) && "Only valid if BB is IN the loop"); + return LI->getLoopFor(BB) != CurLoop; +} + |