X-Git-Url: http://plrg.eecs.uci.edu/git/?p=oota-llvm.git;a=blobdiff_plain;f=lib%2FTransforms%2FScalar%2FLoopIdiomRecognize.cpp;h=ee5203105201f791815302dafe72402785f30867;hp=08d96edce0ac68ea8e7a709c430374264baa8367;hb=62b7c9cb848c8f48a40d2697015bdaba0c789fe7;hpb=af35841f2e346f9259606886698c188280406cdb diff --git a/lib/Transforms/Scalar/LoopIdiomRecognize.cpp b/lib/Transforms/Scalar/LoopIdiomRecognize.cpp index 08d96edce0a..ee520310520 100644 --- a/lib/Transforms/Scalar/LoopIdiomRecognize.cpp +++ b/lib/Transforms/Scalar/LoopIdiomRecognize.cpp @@ -41,136 +41,173 @@ // //===----------------------------------------------------------------------===// -#define DEBUG_TYPE "loop-idiom" #include "llvm/Transforms/Scalar.h" -#include "llvm/IntrinsicInst.h" -#include "llvm/Module.h" +#include "llvm/ADT/Statistic.h" #include "llvm/Analysis/AliasAnalysis.h" #include "llvm/Analysis/LoopPass.h" -#include "llvm/Analysis/ScalarEvolutionExpressions.h" #include "llvm/Analysis/ScalarEvolutionExpander.h" +#include "llvm/Analysis/ScalarEvolutionExpressions.h" +#include "llvm/Analysis/TargetLibraryInfo.h" +#include "llvm/Analysis/TargetTransformInfo.h" #include "llvm/Analysis/ValueTracking.h" -#include "llvm/Target/TargetData.h" -#include "llvm/Target/TargetLibraryInfo.h" -#include "llvm/Transforms/Utils/Local.h" +#include "llvm/IR/DataLayout.h" +#include "llvm/IR/Dominators.h" +#include "llvm/IR/IRBuilder.h" +#include "llvm/IR/IntrinsicInst.h" +#include "llvm/IR/Module.h" #include "llvm/Support/Debug.h" -#include "llvm/Support/IRBuilder.h" #include "llvm/Support/raw_ostream.h" -#include "llvm/ADT/Statistic.h" +#include "llvm/Transforms/Utils/Local.h" using namespace llvm; +#define DEBUG_TYPE "loop-idiom" + STATISTIC(NumMemSet, "Number of memset's formed from loop stores"); STATISTIC(NumMemCpy, "Number of memcpy's formed from loop load+stores"); namespace { - class LoopIdiomRecognize : public LoopPass { - Loop *CurLoop; - const TargetData *TD; - DominatorTree *DT; - ScalarEvolution *SE; - TargetLibraryInfo *TLI; - public: - static char ID; - explicit LoopIdiomRecognize() : LoopPass(ID) { - initializeLoopIdiomRecognizePass(*PassRegistry::getPassRegistry()); - } - bool runOnLoop(Loop *L, LPPassManager &LPM); - bool runOnLoopBlock(BasicBlock *BB, const SCEV *BECount, - SmallVectorImpl &ExitBlocks); - - bool processLoopStore(StoreInst *SI, const SCEV *BECount); - bool processLoopMemSet(MemSetInst *MSI, const SCEV *BECount); - - bool processLoopStridedStore(Value *DestPtr, unsigned StoreSize, - unsigned StoreAlignment, - Value *SplatValue, Instruction *TheStore, - const SCEVAddRecExpr *Ev, - const SCEV *BECount); - bool processLoopStoreOfLoopLoad(StoreInst *SI, unsigned StoreSize, - const SCEVAddRecExpr *StoreEv, - const SCEVAddRecExpr *LoadEv, - const SCEV *BECount); - - /// This transformation requires natural loop information & requires that - /// loop preheaders be inserted into the CFG. - /// - virtual void getAnalysisUsage(AnalysisUsage &AU) const { - AU.addRequired(); - AU.addPreserved(); - AU.addRequiredID(LoopSimplifyID); - AU.addPreservedID(LoopSimplifyID); - AU.addRequiredID(LCSSAID); - AU.addPreservedID(LCSSAID); - AU.addRequired(); - AU.addPreserved(); - AU.addRequired(); - AU.addPreserved(); - AU.addPreserved(); - AU.addRequired(); - AU.addRequired(); - } - }; -} +class LoopIdiomRecognize : public LoopPass { + Loop *CurLoop; + AliasAnalysis *AA; + DominatorTree *DT; + LoopInfo *LI; + ScalarEvolution *SE; + TargetLibraryInfo *TLI; + const TargetTransformInfo *TTI; + +public: + static char ID; + explicit LoopIdiomRecognize() : LoopPass(ID) { + initializeLoopIdiomRecognizePass(*PassRegistry::getPassRegistry()); + } + + bool runOnLoop(Loop *L, LPPassManager &LPM) override; + + /// This transformation requires natural loop information & requires that + /// loop preheaders be inserted into the CFG. + /// + void getAnalysisUsage(AnalysisUsage &AU) const override { + AU.addRequired(); + AU.addPreserved(); + AU.addRequiredID(LoopSimplifyID); + AU.addPreservedID(LoopSimplifyID); + AU.addRequiredID(LCSSAID); + AU.addPreservedID(LCSSAID); + AU.addRequired(); + AU.addPreserved(); + AU.addRequired(); + AU.addPreserved(); + AU.addPreserved(); + AU.addRequired(); + AU.addRequired(); + AU.addRequired(); + } + +private: + /// \name Countable Loop Idiom Handling + /// @{ + + bool runOnCountableLoop(); + bool runOnLoopBlock(BasicBlock *BB, const SCEV *BECount, + SmallVectorImpl &ExitBlocks); + + bool processLoopStore(StoreInst *SI, const SCEV *BECount); + bool processLoopMemSet(MemSetInst *MSI, const SCEV *BECount); + + bool processLoopStridedStore(Value *DestPtr, unsigned StoreSize, + unsigned StoreAlignment, Value *SplatValue, + Instruction *TheStore, const SCEVAddRecExpr *Ev, + const SCEV *BECount); + bool processLoopStoreOfLoopLoad(StoreInst *SI, unsigned StoreSize, + const SCEVAddRecExpr *StoreEv, + const SCEVAddRecExpr *LoadEv, + const SCEV *BECount); + + /// @} + /// \name Noncountable Loop Idiom Handling + /// @{ + + bool runOnNoncountableLoop(); + + bool recognizePopcount(); + void transformLoopToPopcount(BasicBlock *PreCondBB, Instruction *CntInst, + PHINode *CntPhi, Value *Var); + + /// @} +}; + +} // End anonymous namespace. char LoopIdiomRecognize::ID = 0; INITIALIZE_PASS_BEGIN(LoopIdiomRecognize, "loop-idiom", "Recognize loop idioms", false, false) -INITIALIZE_PASS_DEPENDENCY(LoopInfo) -INITIALIZE_PASS_DEPENDENCY(DominatorTree) +INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass) +INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) 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_DEPENDENCY(TargetTransformInfoWrapperPass) INITIALIZE_PASS_END(LoopIdiomRecognize, "loop-idiom", "Recognize loop idioms", false, false) Pass *llvm::createLoopIdiomPass() { return new LoopIdiomRecognize(); } -/// DeleteDeadInstruction - Delete this instruction. Before we do, go through +/// deleteDeadInstruction - Delete this instruction. Before we do, go through /// and zero out all the operands of this instruction. If any of them become /// dead, delete them and the computation tree that feeds them. /// -static void DeleteDeadInstruction(Instruction *I, ScalarEvolution &SE) { - SmallVector NowDeadInsts; - - NowDeadInsts.push_back(I); +static void deleteDeadInstruction(Instruction *I, + const TargetLibraryInfo *TLI) { + SmallVector Operands(I->value_op_begin(), I->value_op_end()); + I->replaceAllUsesWith(UndefValue::get(I->getType())); + I->eraseFromParent(); + for (Value *Op : Operands) + RecursivelyDeleteTriviallyDeadInstructions(Op, TLI); +} - // Before we touch this instruction, remove it from SE! - do { - Instruction *DeadInst = NowDeadInsts.pop_back_val(); +//===----------------------------------------------------------------------===// +// +// Implementation of LoopIdiomRecognize +// +//===----------------------------------------------------------------------===// - // This instruction is dead, zap it, in stages. Start by removing it from - // SCEV. - SE.forgetValue(DeadInst); +bool LoopIdiomRecognize::runOnLoop(Loop *L, LPPassManager &LPM) { + if (skipOptnoneFunction(L)) + return false; - for (unsigned op = 0, e = DeadInst->getNumOperands(); op != e; ++op) { - Value *Op = DeadInst->getOperand(op); - DeadInst->setOperand(op, 0); + CurLoop = L; + // If the loop could not be converted to canonical form, it must have an + // indirectbr in it, just give up. + if (!L->getLoopPreheader()) + return false; - // If this operand just became dead, add it to the NowDeadInsts list. - if (!Op->use_empty()) continue; + // Disable loop idiom recognition if the function's name is a common idiom. + StringRef Name = L->getHeader()->getParent()->getName(); + if (Name == "memset" || Name == "memcpy") + return false; - if (Instruction *OpI = dyn_cast(Op)) - if (isInstructionTriviallyDead(OpI)) - NowDeadInsts.push_back(OpI); - } + AA = &getAnalysis(); + DT = &getAnalysis().getDomTree(); + LI = &getAnalysis().getLoopInfo(); + SE = &getAnalysis(); + TLI = &getAnalysis().getTLI(); + TTI = &getAnalysis().getTTI( + *CurLoop->getHeader()->getParent()); - DeadInst->eraseFromParent(); + if (SE->hasLoopInvariantBackedgeTakenCount(L)) + return runOnCountableLoop(); - } while (!NowDeadInsts.empty()); + return runOnNoncountableLoop(); } -bool LoopIdiomRecognize::runOnLoop(Loop *L, LPPassManager &LPM) { - CurLoop = L; - - // The trip count of the loop must be analyzable. - SE = &getAnalysis(); - if (!SE->hasLoopInvariantBackedgeTakenCount(L)) - return false; - const SCEV *BECount = SE->getBackedgeTakenCount(L); - if (isa(BECount)) return false; +bool LoopIdiomRecognize::runOnCountableLoop() { + const SCEV *BECount = SE->getBackedgeTakenCount(CurLoop); + assert(!isa(BECount) && + "runOnCountableLoop() called on a loop without a predictable" + "backedge-taken count"); // If this loop executes exactly one time, then it should be peeled, not // optimized by this pass. @@ -178,30 +215,21 @@ bool LoopIdiomRecognize::runOnLoop(Loop *L, LPPassManager &LPM) { if (BECst->getValue()->getValue() == 0) return false; - // We require target data for now. - TD = getAnalysisIfAvailable(); - if (TD == 0) return false; - - DT = &getAnalysis(); - LoopInfo &LI = getAnalysis(); - TLI = &getAnalysis(); - - SmallVector ExitBlocks; + SmallVector ExitBlocks; CurLoop->getUniqueExitBlocks(ExitBlocks); DEBUG(dbgs() << "loop-idiom Scanning: F[" - << L->getHeader()->getParent()->getName() - << "] Loop %" << L->getHeader()->getName() << "\n"); + << CurLoop->getHeader()->getParent()->getName() << "] Loop %" + << CurLoop->getHeader()->getName() << "\n"); bool MadeChange = false; // Scan all the blocks in the loop that are not in subloops. - for (Loop::block_iterator BI = L->block_begin(), E = L->block_end(); BI != E; - ++BI) { + for (auto *BB : CurLoop->getBlocks()) { // Ignore blocks in subloops. - if (LI.getLoopFor(*BI) != CurLoop) + if (LI->getLoopFor(BB) != CurLoop) continue; - MadeChange |= runOnLoopBlock(*BI, BECount, ExitBlocks); + MadeChange |= runOnLoopBlock(BB, BECount, ExitBlocks); } return MadeChange; } @@ -209,8 +237,9 @@ bool LoopIdiomRecognize::runOnLoop(Loop *L, LPPassManager &LPM) { /// runOnLoopBlock - Process the specified block, which lives in a counted loop /// with the specified backedge count. This block is known to be in the current /// loop and not in any subloops. -bool LoopIdiomRecognize::runOnLoopBlock(BasicBlock *BB, const SCEV *BECount, - SmallVectorImpl &ExitBlocks) { +bool LoopIdiomRecognize::runOnLoopBlock( + BasicBlock *BB, const SCEV *BECount, + SmallVectorImpl &ExitBlocks) { // We can only promote stores in this block if they are unconditionally // executed in the loop. For a block to be unconditionally executed, it has // to dominate all the exit blocks of the loop. Verify this now. @@ -219,30 +248,32 @@ bool LoopIdiomRecognize::runOnLoopBlock(BasicBlock *BB, const SCEV *BECount, return false; bool MadeChange = false; - for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) { + for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;) { Instruction *Inst = I++; // Look for store instructions, which may be optimized to memset/memcpy. - if (StoreInst *SI = dyn_cast(Inst)) { + if (StoreInst *SI = dyn_cast(Inst)) { WeakVH InstPtr(I); - if (!processLoopStore(SI, BECount)) continue; + if (!processLoopStore(SI, BECount)) + continue; MadeChange = true; // If processing the store invalidated our iterator, start over from the // top of the block. - if (InstPtr == 0) + if (!InstPtr) I = BB->begin(); continue; } // Look for memset instructions, which may be optimized to a larger memset. - if (MemSetInst *MSI = dyn_cast(Inst)) { + if (MemSetInst *MSI = dyn_cast(Inst)) { WeakVH InstPtr(I); - if (!processLoopMemSet(MSI, BECount)) continue; + if (!processLoopMemSet(MSI, BECount)) + continue; MadeChange = true; // If processing the memset invalidated our iterator, start over from the // top of the block. - if (InstPtr == 0) + if (!InstPtr) I = BB->begin(); continue; } @@ -251,16 +282,17 @@ bool LoopIdiomRecognize::runOnLoopBlock(BasicBlock *BB, const SCEV *BECount, return MadeChange; } - /// processLoopStore - See if this store can be promoted to a memset or memcpy. bool LoopIdiomRecognize::processLoopStore(StoreInst *SI, const SCEV *BECount) { - if (SI->isVolatile()) return false; + if (!SI->isSimple()) + return false; Value *StoredVal = SI->getValueOperand(); Value *StorePtr = SI->getPointerOperand(); // Reject stores that are so large that they overflow an unsigned. - uint64_t SizeInBits = TD->getTypeSizeInBits(StoredVal->getType()); + auto &DL = CurLoop->getHeader()->getModule()->getDataLayout(); + uint64_t SizeInBits = DL.getTypeSizeInBits(StoredVal->getType()); if ((SizeInBits & 7) || (SizeInBits >> 32) != 0) return false; @@ -268,8 +300,8 @@ bool LoopIdiomRecognize::processLoopStore(StoreInst *SI, const SCEV *BECount) { // loop, which indicates a strided store. If we have something else, it's a // random store we can't handle. const SCEVAddRecExpr *StoreEv = - dyn_cast(SE->getSCEV(StorePtr)); - if (StoreEv == 0 || StoreEv->getLoop() != CurLoop || !StoreEv->isAffine()) + dyn_cast(SE->getSCEV(StorePtr)); + if (!StoreEv || StoreEv->getLoop() != CurLoop || !StoreEv->isAffine()) return false; // Check to see if the stride matches the size of the store. If so, then we @@ -277,7 +309,7 @@ bool LoopIdiomRecognize::processLoopStore(StoreInst *SI, const SCEV *BECount) { unsigned StoreSize = (unsigned)SizeInBits >> 3; const SCEVConstant *Stride = dyn_cast(StoreEv->getOperand(1)); - if (Stride == 0 || StoreSize != Stride->getValue()->getValue()) { + if (!Stride || StoreSize != Stride->getValue()->getValue()) { // TODO: Could also handle negative stride here someday, that will require // the validity check in mayLoopAccessLocation to be updated though. // Enable this to print exact negative strides. @@ -299,22 +331,23 @@ bool LoopIdiomRecognize::processLoopStore(StoreInst *SI, const SCEV *BECount) { // for (i) A[i] = B[i]; if (LoadInst *LI = dyn_cast(StoredVal)) { const SCEVAddRecExpr *LoadEv = - dyn_cast(SE->getSCEV(LI->getOperand(0))); + dyn_cast(SE->getSCEV(LI->getOperand(0))); if (LoadEv && LoadEv->getLoop() == CurLoop && LoadEv->isAffine() && - StoreEv->getOperand(1) == LoadEv->getOperand(1) && !LI->isVolatile()) + StoreEv->getOperand(1) == LoadEv->getOperand(1) && LI->isSimple()) if (processLoopStoreOfLoopLoad(SI, StoreSize, StoreEv, LoadEv, BECount)) return true; } - //errs() << "UNHANDLED strided store: " << *StoreEv << " - " << *SI << "\n"; + // errs() << "UNHANDLED strided store: " << *StoreEv << " - " << *SI << "\n"; return false; } /// processLoopMemSet - See if this memset can be promoted to a large memset. -bool LoopIdiomRecognize:: -processLoopMemSet(MemSetInst *MSI, const SCEV *BECount) { +bool LoopIdiomRecognize::processLoopMemSet(MemSetInst *MSI, + const SCEV *BECount) { // We can only handle non-volatile memsets with a constant size. - if (MSI->isVolatile() || !isa(MSI->getLength())) return false; + if (MSI->isVolatile() || !isa(MSI->getLength())) + return false; // If we're not allowed to hack on memset, we fail. if (!TLI->has(LibFunc::memset)) @@ -326,7 +359,7 @@ processLoopMemSet(MemSetInst *MSI, const SCEV *BECount) { // loop, which indicates a strided store. If we have something else, it's a // random store we can't handle. const SCEVAddRecExpr *Ev = dyn_cast(SE->getSCEV(Pointer)); - if (Ev == 0 || Ev->getLoop() != CurLoop || !Ev->isAffine()) + if (!Ev || Ev->getLoop() != CurLoop || !Ev->isAffine()) return false; // Reject memsets that are so large that they overflow an unsigned. @@ -340,43 +373,41 @@ processLoopMemSet(MemSetInst *MSI, const SCEV *BECount) { // TODO: Could also handle negative stride here someday, that will require the // validity check in mayLoopAccessLocation to be updated though. - if (Stride == 0 || MSI->getLength() != Stride->getValue()) + if (!Stride || MSI->getLength() != Stride->getValue()) return false; return processLoopStridedStore(Pointer, (unsigned)SizeInBytes, - MSI->getAlignment(), MSI->getValue(), - MSI, Ev, BECount); + MSI->getAlignment(), MSI->getValue(), MSI, Ev, + BECount); } - /// mayLoopAccessLocation - Return true if the specified loop might access the /// specified pointer location, which is a loop-strided access. The 'Access' /// argument specifies what the verboten forms of access are (read or write). -static bool mayLoopAccessLocation(Value *Ptr,AliasAnalysis::ModRefResult Access, - Loop *L, const SCEV *BECount, - unsigned StoreSize, AliasAnalysis &AA, +static bool mayLoopAccessLocation(Value *Ptr, ModRefInfo Access, Loop *L, + const SCEV *BECount, unsigned StoreSize, + AliasAnalysis &AA, Instruction *IgnoredStore) { // Get the location that may be stored across the loop. Since the access is // strided positively through memory, we say that the modified location starts // at the pointer and has infinite size. - uint64_t AccessSize = AliasAnalysis::UnknownSize; + uint64_t AccessSize = MemoryLocation::UnknownSize; // If the loop iterates a fixed number of times, we can refine the access size // to be exactly the size of the memset, which is (BECount+1)*StoreSize if (const SCEVConstant *BECst = dyn_cast(BECount)) - AccessSize = (BECst->getValue()->getZExtValue()+1)*StoreSize; + AccessSize = (BECst->getValue()->getZExtValue() + 1) * StoreSize; // TODO: For this to be really effective, we have to dive into the pointer // operand in the store. Store to &A[i] of 100 will always return may alias // with store of &A[100], we need to StoreLoc to be "A" with size of 100, // which will then no-alias a store to &A[100]. - AliasAnalysis::Location StoreLoc(Ptr, AccessSize); + MemoryLocation StoreLoc(Ptr, AccessSize); for (Loop::block_iterator BI = L->block_begin(), E = L->block_end(); BI != E; ++BI) for (BasicBlock::iterator I = (*BI)->begin(), E = (*BI)->end(); I != E; ++I) - if (&*I != IgnoredStore && - (AA.getModRefInfo(I, StoreLoc) & Access)) + if (&*I != IgnoredStore && (AA.getModRefInfo(I, StoreLoc) & Access)) return true; return false; @@ -388,53 +419,56 @@ static bool mayLoopAccessLocation(Value *Ptr,AliasAnalysis::ModRefResult Access, /// /// Note that we don't ever attempt to use memset_pattern8 or 4, because these /// just replicate their input array and then pass on to memset_pattern16. -static Constant *getMemSetPatternValue(Value *V, const TargetData &TD) { +static Constant *getMemSetPatternValue(Value *V, const DataLayout &DL) { // If the value isn't a constant, we can't promote it to being in a constant // array. We could theoretically do a store to an alloca or something, but // that doesn't seem worthwhile. Constant *C = dyn_cast(V); - if (C == 0) return 0; + if (!C) + return nullptr; // Only handle simple values that are a power of two bytes in size. - uint64_t Size = TD.getTypeSizeInBits(V->getType()); - if (Size == 0 || (Size & 7) || (Size & (Size-1))) - return 0; + uint64_t Size = DL.getTypeSizeInBits(V->getType()); + if (Size == 0 || (Size & 7) || (Size & (Size - 1))) + return nullptr; // Don't care enough about darwin/ppc to implement this. - if (TD.isBigEndian()) - return 0; + if (DL.isBigEndian()) + return nullptr; // Convert to size in bytes. Size /= 8; // TODO: If CI is larger than 16-bytes, we can try slicing it in half to see // if the top and bottom are the same (e.g. for vectors and large integers). - if (Size > 16) return 0; + if (Size > 16) + return nullptr; // If the constant is exactly 16 bytes, just use it. - if (Size == 16) return C; + if (Size == 16) + return C; // Otherwise, we'll use an array of the constants. - unsigned ArraySize = 16/Size; + unsigned ArraySize = 16 / Size; ArrayType *AT = ArrayType::get(V->getType(), ArraySize); - return ConstantArray::get(AT, std::vector(ArraySize, C)); + return ConstantArray::get(AT, std::vector(ArraySize, C)); } - /// processLoopStridedStore - We see a strided store of some value. If we can /// transform this into a memset or memset_pattern in the loop preheader, do so. -bool LoopIdiomRecognize:: -processLoopStridedStore(Value *DestPtr, unsigned StoreSize, - unsigned StoreAlignment, Value *StoredVal, - Instruction *TheStore, const SCEVAddRecExpr *Ev, - const SCEV *BECount) { +bool LoopIdiomRecognize::processLoopStridedStore( + Value *DestPtr, unsigned StoreSize, unsigned StoreAlignment, + Value *StoredVal, Instruction *TheStore, const SCEVAddRecExpr *Ev, + const SCEV *BECount) { // If the stored value is a byte-wise value (like i32 -1), then it may be // turned into a memset of i8 -1, assuming that all the consecutive bytes // are stored. A store of i32 0x01020304 can never be turned into a memset, // but it can be turned into memset_pattern if the target supports it. Value *SplatValue = isBytewiseValue(StoredVal); - Constant *PatternValue = 0; + Constant *PatternValue = nullptr; + auto &DL = CurLoop->getHeader()->getModule()->getDataLayout(); + unsigned DestAS = DestPtr->getType()->getPointerAddressSpace(); // If we're allowed to form a memset, and the stored value would be acceptable // for memset, use it. @@ -443,76 +477,82 @@ processLoopStridedStore(Value *DestPtr, unsigned StoreSize, // promote the memset. CurLoop->isLoopInvariant(SplatValue)) { // Keep and use SplatValue. - PatternValue = 0; - } else if (TLI->has(LibFunc::memset_pattern16) && - (PatternValue = getMemSetPatternValue(StoredVal, *TD))) { + PatternValue = nullptr; + } else if (DestAS == 0 && TLI->has(LibFunc::memset_pattern16) && + (PatternValue = getMemSetPatternValue(StoredVal, DL))) { + // Don't create memset_pattern16s with address spaces. // It looks like we can use PatternValue! - SplatValue = 0; + SplatValue = nullptr; } else { // Otherwise, this isn't an idiom we can transform. For example, we can't - // do anything with a 3-byte store, for example. + // do anything with a 3-byte store. return false; } + // The trip count of the loop and the base pointer of the addrec SCEV is + // guaranteed to be loop invariant, which means that it should dominate the + // header. This allows us to insert code for it in the preheader. + BasicBlock *Preheader = CurLoop->getLoopPreheader(); + IRBuilder<> Builder(Preheader->getTerminator()); + SCEVExpander Expander(*SE, DL, "loop-idiom"); + + Type *DestInt8PtrTy = Builder.getInt8PtrTy(DestAS); // Okay, we have a strided store "p[i]" of a splattable value. We can turn // this into a memset in the loop preheader now if we want. However, this // would be unsafe to do if there is anything else in the loop that may read - // or write to the aliased location. Check for an alias. - if (mayLoopAccessLocation(DestPtr, AliasAnalysis::ModRef, - CurLoop, BECount, - StoreSize, getAnalysis(), TheStore)) + // or write to the aliased location. Check for any overlap by generating the + // base pointer and checking the region. + Value *BasePtr = Expander.expandCodeFor(Ev->getStart(), DestInt8PtrTy, + Preheader->getTerminator()); + + if (mayLoopAccessLocation(BasePtr, MRI_ModRef, CurLoop, BECount, StoreSize, + *AA, TheStore)) { + Expander.clear(); + // If we generated new code for the base pointer, clean up. + RecursivelyDeleteTriviallyDeadInstructions(BasePtr, TLI); return false; + } // Okay, everything looks good, insert the memset. - BasicBlock *Preheader = CurLoop->getLoopPreheader(); - - IRBuilder<> Builder(Preheader->getTerminator()); - - // The trip count of the loop and the base pointer of the addrec SCEV is - // guaranteed to be loop invariant, which means that it should dominate the - // header. Just insert code for it in the preheader. - SCEVExpander Expander(*SE); - - unsigned AddrSpace = cast(DestPtr->getType())->getAddressSpace(); - Value *BasePtr = - Expander.expandCodeFor(Ev->getStart(), Builder.getInt8PtrTy(AddrSpace), - Preheader->getTerminator()); // The # stored bytes is (BECount+1)*Size. Expand the trip count out to // pointer size if it isn't already. - const Type *IntPtr = TD->getIntPtrType(DestPtr->getContext()); + Type *IntPtr = Builder.getIntPtrTy(DL, DestAS); BECount = SE->getTruncateOrZeroExtend(BECount, IntPtr); - const SCEV *NumBytesS = SE->getAddExpr(BECount, SE->getConstant(IntPtr, 1), - SCEV::FlagNUW); - if (StoreSize != 1) + const SCEV *NumBytesS = + SE->getAddExpr(BECount, SE->getConstant(IntPtr, 1), SCEV::FlagNUW); + if (StoreSize != 1) { NumBytesS = SE->getMulExpr(NumBytesS, SE->getConstant(IntPtr, StoreSize), SCEV::FlagNUW); + } Value *NumBytes = - Expander.expandCodeFor(NumBytesS, IntPtr, Preheader->getTerminator()); + Expander.expandCodeFor(NumBytesS, IntPtr, Preheader->getTerminator()); CallInst *NewCall; - if (SplatValue) - NewCall = Builder.CreateMemSet(BasePtr, SplatValue,NumBytes,StoreAlignment); - else { + if (SplatValue) { + NewCall = + Builder.CreateMemSet(BasePtr, SplatValue, NumBytes, StoreAlignment); + } else { + // Everything is emitted in default address space + Type *Int8PtrTy = DestInt8PtrTy; + Module *M = TheStore->getParent()->getParent()->getParent(); - Value *MSP = M->getOrInsertFunction("memset_pattern16", - Builder.getVoidTy(), - Builder.getInt8PtrTy(), - Builder.getInt8PtrTy(), IntPtr, - (void*)0); + Value *MSP = + M->getOrInsertFunction("memset_pattern16", Builder.getVoidTy(), + Int8PtrTy, Int8PtrTy, IntPtr, (void *)nullptr); // Otherwise we should form a memset_pattern16. PatternValue is known to be // an constant array of 16-bytes. Plop the value into a mergable global. GlobalVariable *GV = new GlobalVariable(*M, PatternValue->getType(), true, - GlobalValue::InternalLinkage, + GlobalValue::PrivateLinkage, PatternValue, ".memset_pattern"); GV->setUnnamedAddr(true); // Ok to merge these. GV->setAlignment(16); - Value *PatternPtr = ConstantExpr::getBitCast(GV, Builder.getInt8PtrTy()); - NewCall = Builder.CreateCall3(MSP, BasePtr, PatternPtr, NumBytes); + Value *PatternPtr = ConstantExpr::getBitCast(GV, Int8PtrTy); + NewCall = Builder.CreateCall(MSP, {BasePtr, PatternPtr, NumBytes}); } DEBUG(dbgs() << " Formed memset: " << *NewCall << "\n" @@ -521,87 +561,432 @@ processLoopStridedStore(Value *DestPtr, unsigned StoreSize, // Okay, the memset has been formed. Zap the original store and anything that // feeds into it. - DeleteDeadInstruction(TheStore, *SE); + deleteDeadInstruction(TheStore, TLI); ++NumMemSet; return true; } /// processLoopStoreOfLoopLoad - We see a strided store whose value is a /// same-strided load. -bool LoopIdiomRecognize:: -processLoopStoreOfLoopLoad(StoreInst *SI, unsigned StoreSize, - const SCEVAddRecExpr *StoreEv, - const SCEVAddRecExpr *LoadEv, - const SCEV *BECount) { +bool LoopIdiomRecognize::processLoopStoreOfLoopLoad( + StoreInst *SI, unsigned StoreSize, const SCEVAddRecExpr *StoreEv, + const SCEVAddRecExpr *LoadEv, const SCEV *BECount) { // If we're not allowed to form memcpy, we fail. if (!TLI->has(LibFunc::memcpy)) return false; LoadInst *LI = cast(SI->getValueOperand()); + // The trip count of the loop and the base pointer of the addrec SCEV is + // guaranteed to be loop invariant, which means that it should dominate the + // header. This allows us to insert code for it in the preheader. + BasicBlock *Preheader = CurLoop->getLoopPreheader(); + IRBuilder<> Builder(Preheader->getTerminator()); + const DataLayout &DL = Preheader->getModule()->getDataLayout(); + SCEVExpander Expander(*SE, DL, "loop-idiom"); + // Okay, we have a strided store "p[i]" of a loaded value. We can turn // this into a memcpy in the loop preheader now if we want. However, this // would be unsafe to do if there is anything else in the loop that may read - // or write to the stored location (including the load feeding the stores). - // Check for an alias. - if (mayLoopAccessLocation(SI->getPointerOperand(), AliasAnalysis::ModRef, - CurLoop, BECount, StoreSize, - getAnalysis(), SI)) + // or write the memory region we're storing to. This includes the load that + // feeds the stores. Check for an alias by generating the base address and + // checking everything. + Value *StoreBasePtr = Expander.expandCodeFor( + StoreEv->getStart(), Builder.getInt8PtrTy(SI->getPointerAddressSpace()), + Preheader->getTerminator()); + + if (mayLoopAccessLocation(StoreBasePtr, MRI_ModRef, CurLoop, BECount, + StoreSize, *AA, SI)) { + Expander.clear(); + // If we generated new code for the base pointer, clean up. + RecursivelyDeleteTriviallyDeadInstructions(StoreBasePtr, TLI); return false; + } // For a memcpy, we have to make sure that the input array is not being // mutated by the loop. - if (mayLoopAccessLocation(LI->getPointerOperand(), AliasAnalysis::Mod, - CurLoop, BECount, StoreSize, - getAnalysis(), SI)) + Value *LoadBasePtr = Expander.expandCodeFor( + LoadEv->getStart(), Builder.getInt8PtrTy(LI->getPointerAddressSpace()), + Preheader->getTerminator()); + + if (mayLoopAccessLocation(LoadBasePtr, MRI_Mod, CurLoop, BECount, StoreSize, + *AA, SI)) { + Expander.clear(); + // If we generated new code for the base pointer, clean up. + RecursivelyDeleteTriviallyDeadInstructions(LoadBasePtr, TLI); + RecursivelyDeleteTriviallyDeadInstructions(StoreBasePtr, TLI); return false; + } - // Okay, everything looks good, insert the memcpy. - BasicBlock *Preheader = CurLoop->getLoopPreheader(); - - IRBuilder<> Builder(Preheader->getTerminator()); - - // The trip count of the loop and the base pointer of the addrec SCEV is - // guaranteed to be loop invariant, which means that it should dominate the - // header. Just insert code for it in the preheader. - SCEVExpander Expander(*SE); - - Value *LoadBasePtr = - Expander.expandCodeFor(LoadEv->getStart(), - Builder.getInt8PtrTy(LI->getPointerAddressSpace()), - Preheader->getTerminator()); - Value *StoreBasePtr = - Expander.expandCodeFor(StoreEv->getStart(), - Builder.getInt8PtrTy(SI->getPointerAddressSpace()), - Preheader->getTerminator()); + // Okay, everything is safe, we can transform this! // The # stored bytes is (BECount+1)*Size. Expand the trip count out to // pointer size if it isn't already. - const Type *IntPtr = TD->getIntPtrType(SI->getContext()); - BECount = SE->getTruncateOrZeroExtend(BECount, IntPtr); + Type *IntPtrTy = Builder.getIntPtrTy(DL, SI->getPointerAddressSpace()); + BECount = SE->getTruncateOrZeroExtend(BECount, IntPtrTy); - const SCEV *NumBytesS = SE->getAddExpr(BECount, SE->getConstant(IntPtr, 1), - SCEV::FlagNUW); + const SCEV *NumBytesS = + SE->getAddExpr(BECount, SE->getConstant(IntPtrTy, 1), SCEV::FlagNUW); if (StoreSize != 1) - NumBytesS = SE->getMulExpr(NumBytesS, SE->getConstant(IntPtr, StoreSize), + NumBytesS = SE->getMulExpr(NumBytesS, SE->getConstant(IntPtrTy, StoreSize), SCEV::FlagNUW); Value *NumBytes = - Expander.expandCodeFor(NumBytesS, IntPtr, Preheader->getTerminator()); + Expander.expandCodeFor(NumBytesS, IntPtrTy, Preheader->getTerminator()); CallInst *NewCall = - Builder.CreateMemCpy(StoreBasePtr, LoadBasePtr, NumBytes, - std::min(SI->getAlignment(), LI->getAlignment())); + Builder.CreateMemCpy(StoreBasePtr, LoadBasePtr, NumBytes, + std::min(SI->getAlignment(), LI->getAlignment())); NewCall->setDebugLoc(SI->getDebugLoc()); DEBUG(dbgs() << " Formed memcpy: " << *NewCall << "\n" << " from load ptr=" << *LoadEv << " at: " << *LI << "\n" << " from store ptr=" << *StoreEv << " at: " << *SI << "\n"); - // Okay, the memset has been formed. Zap the original store and anything that // feeds into it. - DeleteDeadInstruction(SI, *SE); + deleteDeadInstruction(SI, TLI); ++NumMemCpy; return true; } + +bool LoopIdiomRecognize::runOnNoncountableLoop() { + if (recognizePopcount()) + return true; + + return false; +} + +/// Check if the given conditional branch is based on the comparison between +/// a variable and zero, and if the variable is non-zero, the control yields to +/// the loop entry. If the branch matches the behavior, the variable involved +/// in the comparion is returned. This function will be called to see if the +/// precondition and postcondition of the loop are in desirable form. +static Value *matchCondition(BranchInst *BI, BasicBlock *LoopEntry) { + if (!BI || !BI->isConditional()) + return nullptr; + + ICmpInst *Cond = dyn_cast(BI->getCondition()); + if (!Cond) + return nullptr; + + ConstantInt *CmpZero = dyn_cast(Cond->getOperand(1)); + if (!CmpZero || !CmpZero->isZero()) + return nullptr; + + ICmpInst::Predicate Pred = Cond->getPredicate(); + if ((Pred == ICmpInst::ICMP_NE && BI->getSuccessor(0) == LoopEntry) || + (Pred == ICmpInst::ICMP_EQ && BI->getSuccessor(1) == LoopEntry)) + return Cond->getOperand(0); + + return nullptr; +} + +/// Return true iff the idiom is detected in the loop. +/// +/// Additionally: +/// 1) \p CntInst is set to the instruction counting the population bit. +/// 2) \p CntPhi is set to the corresponding phi node. +/// 3) \p Var is set to the value whose population bits are being counted. +/// +/// The core idiom we are trying to detect is: +/// \code +/// if (x0 != 0) +/// goto loop-exit // the precondition of the loop +/// cnt0 = init-val; +/// do { +/// x1 = phi (x0, x2); +/// cnt1 = phi(cnt0, cnt2); +/// +/// cnt2 = cnt1 + 1; +/// ... +/// x2 = x1 & (x1 - 1); +/// ... +/// } while(x != 0); +/// +/// loop-exit: +/// \endcode +static bool detectPopcountIdiom(Loop *CurLoop, BasicBlock *PreCondBB, + Instruction *&CntInst, PHINode *&CntPhi, + Value *&Var) { + // step 1: Check to see if the look-back branch match this pattern: + // "if (a!=0) goto loop-entry". + BasicBlock *LoopEntry; + Instruction *DefX2, *CountInst; + Value *VarX1, *VarX0; + PHINode *PhiX, *CountPhi; + + DefX2 = CountInst = nullptr; + VarX1 = VarX0 = nullptr; + PhiX = CountPhi = nullptr; + LoopEntry = *(CurLoop->block_begin()); + + // step 1: Check if the loop-back branch is in desirable form. + { + if (Value *T = matchCondition( + dyn_cast(LoopEntry->getTerminator()), LoopEntry)) + DefX2 = dyn_cast(T); + else + return false; + } + + // step 2: detect instructions corresponding to "x2 = x1 & (x1 - 1)" + { + if (!DefX2 || DefX2->getOpcode() != Instruction::And) + return false; + + BinaryOperator *SubOneOp; + + if ((SubOneOp = dyn_cast(DefX2->getOperand(0)))) + VarX1 = DefX2->getOperand(1); + else { + VarX1 = DefX2->getOperand(0); + SubOneOp = dyn_cast(DefX2->getOperand(1)); + } + if (!SubOneOp) + return false; + + Instruction *SubInst = cast(SubOneOp); + ConstantInt *Dec = dyn_cast(SubInst->getOperand(1)); + if (!Dec || + !((SubInst->getOpcode() == Instruction::Sub && Dec->isOne()) || + (SubInst->getOpcode() == Instruction::Add && + Dec->isAllOnesValue()))) { + return false; + } + } + + // step 3: Check the recurrence of variable X + { + PhiX = dyn_cast(VarX1); + if (!PhiX || + (PhiX->getOperand(0) != DefX2 && PhiX->getOperand(1) != DefX2)) { + return false; + } + } + + // step 4: Find the instruction which count the population: cnt2 = cnt1 + 1 + { + CountInst = nullptr; + for (BasicBlock::iterator Iter = LoopEntry->getFirstNonPHI(), + IterE = LoopEntry->end(); + Iter != IterE; Iter++) { + Instruction *Inst = Iter; + if (Inst->getOpcode() != Instruction::Add) + continue; + + ConstantInt *Inc = dyn_cast(Inst->getOperand(1)); + if (!Inc || !Inc->isOne()) + continue; + + PHINode *Phi = dyn_cast(Inst->getOperand(0)); + if (!Phi || Phi->getParent() != LoopEntry) + continue; + + // Check if the result of the instruction is live of the loop. + bool LiveOutLoop = false; + for (User *U : Inst->users()) { + if ((cast(U))->getParent() != LoopEntry) { + LiveOutLoop = true; + break; + } + } + + if (LiveOutLoop) { + CountInst = Inst; + CountPhi = Phi; + break; + } + } + + if (!CountInst) + return false; + } + + // step 5: check if the precondition is in this form: + // "if (x != 0) goto loop-head ; else goto somewhere-we-don't-care;" + { + auto *PreCondBr = dyn_cast(PreCondBB->getTerminator()); + Value *T = matchCondition(PreCondBr, CurLoop->getLoopPreheader()); + if (T != PhiX->getOperand(0) && T != PhiX->getOperand(1)) + return false; + + CntInst = CountInst; + CntPhi = CountPhi; + Var = T; + } + + return true; +} + +/// Recognizes a population count idiom in a non-countable loop. +/// +/// If detected, transforms the relevant code to issue the popcount intrinsic +/// function call, and returns true; otherwise, returns false. +bool LoopIdiomRecognize::recognizePopcount() { + if (TTI->getPopcntSupport(32) != TargetTransformInfo::PSK_FastHardware) + return false; + + // Counting population are usually conducted by few arithmetic instructions. + // Such instructions can be easilly "absorbed" by vacant slots in a + // non-compact loop. Therefore, recognizing popcount idiom only makes sense + // in a compact loop. + + // Give up if the loop has multiple blocks or multiple backedges. + if (CurLoop->getNumBackEdges() != 1 || CurLoop->getNumBlocks() != 1) + return false; + + BasicBlock *LoopBody = *(CurLoop->block_begin()); + if (LoopBody->size() >= 20) { + // The loop is too big, bail out. + return false; + } + + // It should have a preheader containing nothing but an unconditional branch. + BasicBlock *PH = CurLoop->getLoopPreheader(); + if (!PH) + return false; + if (&PH->front() != PH->getTerminator()) + return false; + auto *EntryBI = dyn_cast(PH->getTerminator()); + if (!EntryBI || EntryBI->isConditional()) + return false; + + // It should have a precondition block where the generated popcount instrinsic + // function can be inserted. + auto *PreCondBB = PH->getSinglePredecessor(); + if (!PreCondBB) + return false; + auto *PreCondBI = dyn_cast(PreCondBB->getTerminator()); + if (!PreCondBI || PreCondBI->isUnconditional()) + return false; + + Instruction *CntInst; + PHINode *CntPhi; + Value *Val; + if (!detectPopcountIdiom(CurLoop, PreCondBB, CntInst, CntPhi, Val)) + return false; + + transformLoopToPopcount(PreCondBB, CntInst, CntPhi, Val); + return true; +} + +static CallInst *createPopcntIntrinsic(IRBuilder<> &IRBuilder, Value *Val, + DebugLoc DL) { + Value *Ops[] = {Val}; + Type *Tys[] = {Val->getType()}; + + Module *M = IRBuilder.GetInsertBlock()->getParent()->getParent(); + Value *Func = Intrinsic::getDeclaration(M, Intrinsic::ctpop, Tys); + CallInst *CI = IRBuilder.CreateCall(Func, Ops); + CI->setDebugLoc(DL); + + return CI; +} + +void LoopIdiomRecognize::transformLoopToPopcount(BasicBlock *PreCondBB, + Instruction *CntInst, + PHINode *CntPhi, Value *Var) { + BasicBlock *PreHead = CurLoop->getLoopPreheader(); + auto *PreCondBr = dyn_cast(PreCondBB->getTerminator()); + const DebugLoc DL = CntInst->getDebugLoc(); + + // Assuming before transformation, the loop is following: + // if (x) // the precondition + // do { cnt++; x &= x - 1; } while(x); + + // Step 1: Insert the ctpop instruction at the end of the precondition block + IRBuilder<> Builder(PreCondBr); + Value *PopCnt, *PopCntZext, *NewCount, *TripCnt; + { + PopCnt = createPopcntIntrinsic(Builder, Var, DL); + NewCount = PopCntZext = + Builder.CreateZExtOrTrunc(PopCnt, cast(CntPhi->getType())); + + if (NewCount != PopCnt) + (cast(NewCount))->setDebugLoc(DL); + + // TripCnt is exactly the number of iterations the loop has + TripCnt = NewCount; + + // If the population counter's initial value is not zero, insert Add Inst. + Value *CntInitVal = CntPhi->getIncomingValueForBlock(PreHead); + ConstantInt *InitConst = dyn_cast(CntInitVal); + if (!InitConst || !InitConst->isZero()) { + NewCount = Builder.CreateAdd(NewCount, CntInitVal); + (cast(NewCount))->setDebugLoc(DL); + } + } + + // Step 2: Replace the precondition from "if(x == 0) goto loop-exit" to + // "if(NewCount == 0) loop-exit". Withtout this change, the intrinsic + // function would be partial dead code, and downstream passes will drag + // it back from the precondition block to the preheader. + { + ICmpInst *PreCond = cast(PreCondBr->getCondition()); + + Value *Opnd0 = PopCntZext; + Value *Opnd1 = ConstantInt::get(PopCntZext->getType(), 0); + if (PreCond->getOperand(0) != Var) + std::swap(Opnd0, Opnd1); + + ICmpInst *NewPreCond = cast( + Builder.CreateICmp(PreCond->getPredicate(), Opnd0, Opnd1)); + PreCondBr->setCondition(NewPreCond); + + RecursivelyDeleteTriviallyDeadInstructions(PreCond, TLI); + } + + // Step 3: Note that the population count is exactly the trip count of the + // loop in question, which enble us to to convert the loop from noncountable + // loop into a countable one. The benefit is twofold: + // + // - If the loop only counts population, the entire loop become dead after + // the transformation. It is lots easier to prove a countable loop dead + // than to prove a noncountable one. (In some C dialects, a infite loop + // isn't dead even if it computes nothing useful. In general, DCE needs + // to prove a noncountable loop finite before safely delete it.) + // + // - If the loop also performs something else, it remains alive. + // Since it is transformed to countable form, it can be aggressively + // optimized by some optimizations which are in general not applicable + // to a noncountable loop. + // + // After this step, this loop (conceptually) would look like following: + // newcnt = __builtin_ctpop(x); + // t = newcnt; + // if (x) + // do { cnt++; x &= x-1; t--) } while (t > 0); + BasicBlock *Body = *(CurLoop->block_begin()); + { + auto *LbBr = dyn_cast(Body->getTerminator()); + ICmpInst *LbCond = cast(LbBr->getCondition()); + Type *Ty = TripCnt->getType(); + + PHINode *TcPhi = PHINode::Create(Ty, 2, "tcphi", Body->begin()); + + Builder.SetInsertPoint(LbCond); + Value *Opnd1 = cast(TcPhi); + Value *Opnd2 = cast(ConstantInt::get(Ty, 1)); + Instruction *TcDec = cast( + Builder.CreateSub(Opnd1, Opnd2, "tcdec", false, true)); + + TcPhi->addIncoming(TripCnt, PreHead); + TcPhi->addIncoming(TcDec, Body); + + CmpInst::Predicate Pred = + (LbBr->getSuccessor(0) == Body) ? CmpInst::ICMP_UGT : CmpInst::ICMP_SLE; + LbCond->setPredicate(Pred); + LbCond->setOperand(0, TcDec); + LbCond->setOperand(1, cast(ConstantInt::get(Ty, 0))); + } + + // Step 4: All the references to the original population counter outside + // the loop are replaced with the NewCount -- the value returned from + // __builtin_ctpop(). + CntInst->replaceUsesOutsideBlock(NewCount, Body); + + // step 5: Forget the "non-computable" trip-count SCEV associated with the + // loop. The loop would otherwise not be deleted even if it becomes empty. + SE->forgetLoop(CurLoop); +}