LoopIdiomRecognize.cpp revision e2c43920919c6fe376613d1d8331897dc1ba3d57
1e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner//===-- LoopIdiomRecognize.cpp - Loop idiom recognition -------------------===// 2e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner// 3e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner// The LLVM Compiler Infrastructure 4e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner// 5e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner// This file is distributed under the University of Illinois Open Source 6e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner// License. See LICENSE.TXT for details. 7e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner// 8e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner//===----------------------------------------------------------------------===// 9e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner// 10e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner// This pass implements an idiom recognizer that transforms simple loops into a 11e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner// non-loop form. In cases that this kicks in, it can be a significant 12e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner// performance win. 13e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner// 14e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner//===----------------------------------------------------------------------===// 15e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner 16e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner#define DEBUG_TYPE "loop-idiom" 17e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner#include "llvm/Transforms/Scalar.h" 182e12f1ac6ebd49e5c41b7e9dcd802f3df40a1bc7Chris Lattner#include "llvm/Analysis/AliasAnalysis.h" 19e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner#include "llvm/Analysis/LoopPass.h" 20e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner#include "llvm/Analysis/ScalarEvolutionExpressions.h" 21a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner#include "llvm/Analysis/ScalarEvolutionExpander.h" 2222920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner#include "llvm/Analysis/ValueTracking.h" 2322920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner#include "llvm/Target/TargetData.h" 249f39188def2b4102817945522fac1209083efa06Chris Lattner#include "llvm/Transforms/Utils/Local.h" 25e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner#include "llvm/Support/Debug.h" 26a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner#include "llvm/Support/IRBuilder.h" 27e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner#include "llvm/Support/raw_ostream.h" 28e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattnerusing namespace llvm; 29e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner 30e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner// TODO: Recognize "N" size array multiplies: replace with call to blas or 31e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner// something. 32e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner 33e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattnernamespace { 34e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner class LoopIdiomRecognize : public LoopPass { 3522920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner Loop *CurLoop; 3622920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner const TargetData *TD; 3722920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner ScalarEvolution *SE; 38e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner public: 39e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner static char ID; 40e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner explicit LoopIdiomRecognize() : LoopPass(ID) { 41e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner initializeLoopIdiomRecognizePass(*PassRegistry::getPassRegistry()); 42e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner } 43e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner 44e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner bool runOnLoop(Loop *L, LPPassManager &LPM); 45e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner 4622920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner bool processLoopStore(StoreInst *SI, const SCEV *BECount); 47e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner 48a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner bool processLoopStoreOfSplatValue(StoreInst *SI, unsigned StoreSize, 49a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner Value *SplatValue, 50a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner const SCEVAddRecExpr *Ev, 51a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner const SCEV *BECount); 52e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner bool processLoopStoreOfLoopLoad(StoreInst *SI, unsigned StoreSize, 53e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner const SCEVAddRecExpr *StoreEv, 54e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner const SCEVAddRecExpr *LoadEv, 55e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner const SCEV *BECount); 56e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner 57e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner /// This transformation requires natural loop information & requires that 58e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner /// loop preheaders be inserted into the CFG. 59e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner /// 60e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner virtual void getAnalysisUsage(AnalysisUsage &AU) const { 61e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner AU.addRequired<LoopInfo>(); 62e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner AU.addPreserved<LoopInfo>(); 63e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner AU.addRequiredID(LoopSimplifyID); 64e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner AU.addPreservedID(LoopSimplifyID); 65e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner AU.addRequiredID(LCSSAID); 66e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner AU.addPreservedID(LCSSAID); 672e12f1ac6ebd49e5c41b7e9dcd802f3df40a1bc7Chris Lattner AU.addRequired<AliasAnalysis>(); 682e12f1ac6ebd49e5c41b7e9dcd802f3df40a1bc7Chris Lattner AU.addPreserved<AliasAnalysis>(); 69e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner AU.addRequired<ScalarEvolution>(); 70e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner AU.addPreserved<ScalarEvolution>(); 71e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner AU.addPreserved<DominatorTree>(); 72e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner } 73e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner }; 74e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner} 75e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner 76e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattnerchar LoopIdiomRecognize::ID = 0; 77e6bb649ec63059d795a31198c3c569c137e7ad59Chris LattnerINITIALIZE_PASS_BEGIN(LoopIdiomRecognize, "loop-idiom", "Recognize loop idioms", 78e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner false, false) 79e6bb649ec63059d795a31198c3c569c137e7ad59Chris LattnerINITIALIZE_PASS_DEPENDENCY(LoopInfo) 80e6bb649ec63059d795a31198c3c569c137e7ad59Chris LattnerINITIALIZE_PASS_DEPENDENCY(LoopSimplify) 81e6bb649ec63059d795a31198c3c569c137e7ad59Chris LattnerINITIALIZE_PASS_DEPENDENCY(LCSSA) 82e6bb649ec63059d795a31198c3c569c137e7ad59Chris LattnerINITIALIZE_PASS_DEPENDENCY(ScalarEvolution) 832e12f1ac6ebd49e5c41b7e9dcd802f3df40a1bc7Chris LattnerINITIALIZE_AG_DEPENDENCY(AliasAnalysis) 84e6bb649ec63059d795a31198c3c569c137e7ad59Chris LattnerINITIALIZE_PASS_END(LoopIdiomRecognize, "loop-idiom", "Recognize loop idioms", 85e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner false, false) 86e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner 87e6bb649ec63059d795a31198c3c569c137e7ad59Chris LattnerPass *llvm::createLoopIdiomPass() { return new LoopIdiomRecognize(); } 88e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner 899f39188def2b4102817945522fac1209083efa06Chris Lattner/// DeleteDeadInstruction - Delete this instruction. Before we do, go through 909f39188def2b4102817945522fac1209083efa06Chris Lattner/// and zero out all the operands of this instruction. If any of them become 919f39188def2b4102817945522fac1209083efa06Chris Lattner/// dead, delete them and the computation tree that feeds them. 929f39188def2b4102817945522fac1209083efa06Chris Lattner/// 939f39188def2b4102817945522fac1209083efa06Chris Lattnerstatic void DeleteDeadInstruction(Instruction *I, ScalarEvolution &SE) { 949f39188def2b4102817945522fac1209083efa06Chris Lattner SmallVector<Instruction*, 32> NowDeadInsts; 959f39188def2b4102817945522fac1209083efa06Chris Lattner 969f39188def2b4102817945522fac1209083efa06Chris Lattner NowDeadInsts.push_back(I); 979f39188def2b4102817945522fac1209083efa06Chris Lattner 989f39188def2b4102817945522fac1209083efa06Chris Lattner // Before we touch this instruction, remove it from SE! 999f39188def2b4102817945522fac1209083efa06Chris Lattner do { 1009f39188def2b4102817945522fac1209083efa06Chris Lattner Instruction *DeadInst = NowDeadInsts.pop_back_val(); 1019f39188def2b4102817945522fac1209083efa06Chris Lattner 1029f39188def2b4102817945522fac1209083efa06Chris Lattner // This instruction is dead, zap it, in stages. Start by removing it from 1039f39188def2b4102817945522fac1209083efa06Chris Lattner // SCEV. 1049f39188def2b4102817945522fac1209083efa06Chris Lattner SE.forgetValue(DeadInst); 1059f39188def2b4102817945522fac1209083efa06Chris Lattner 1069f39188def2b4102817945522fac1209083efa06Chris Lattner for (unsigned op = 0, e = DeadInst->getNumOperands(); op != e; ++op) { 1079f39188def2b4102817945522fac1209083efa06Chris Lattner Value *Op = DeadInst->getOperand(op); 1089f39188def2b4102817945522fac1209083efa06Chris Lattner DeadInst->setOperand(op, 0); 1099f39188def2b4102817945522fac1209083efa06Chris Lattner 1109f39188def2b4102817945522fac1209083efa06Chris Lattner // If this operand just became dead, add it to the NowDeadInsts list. 1119f39188def2b4102817945522fac1209083efa06Chris Lattner if (!Op->use_empty()) continue; 1129f39188def2b4102817945522fac1209083efa06Chris Lattner 1139f39188def2b4102817945522fac1209083efa06Chris Lattner if (Instruction *OpI = dyn_cast<Instruction>(Op)) 1149f39188def2b4102817945522fac1209083efa06Chris Lattner if (isInstructionTriviallyDead(OpI)) 1159f39188def2b4102817945522fac1209083efa06Chris Lattner NowDeadInsts.push_back(OpI); 1169f39188def2b4102817945522fac1209083efa06Chris Lattner } 1179f39188def2b4102817945522fac1209083efa06Chris Lattner 1189f39188def2b4102817945522fac1209083efa06Chris Lattner DeadInst->eraseFromParent(); 1199f39188def2b4102817945522fac1209083efa06Chris Lattner 1209f39188def2b4102817945522fac1209083efa06Chris Lattner } while (!NowDeadInsts.empty()); 1219f39188def2b4102817945522fac1209083efa06Chris Lattner} 1229f39188def2b4102817945522fac1209083efa06Chris Lattner 123e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattnerbool LoopIdiomRecognize::runOnLoop(Loop *L, LPPassManager &LPM) { 12422920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner CurLoop = L; 12522920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner 126e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner // We only look at trivial single basic block loops. 127e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner // TODO: eventually support more complex loops, scanning the header. 128e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner if (L->getBlocks().size() != 1) 129e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner return false; 130e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner 13122920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner // The trip count of the loop must be analyzable. 13222920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner SE = &getAnalysis<ScalarEvolution>(); 13322920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner if (!SE->hasLoopInvariantBackedgeTakenCount(L)) 13422920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner return false; 13522920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner const SCEV *BECount = SE->getBackedgeTakenCount(L); 13622920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner if (isa<SCEVCouldNotCompute>(BECount)) return false; 13722920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner 13822920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner // We require target data for now. 13922920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner TD = getAnalysisIfAvailable<TargetData>(); 14022920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner if (TD == 0) return false; 14122920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner 142e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner BasicBlock *BB = L->getHeader(); 14322920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner DEBUG(dbgs() << "loop-idiom Scanning: F[" << BB->getParent()->getName() 144e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner << "] Loop %" << BB->getName() << "\n"); 145e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner 14622920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner bool MadeChange = false; 14722920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) { 14822920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner // Look for store instructions, which may be memsets. 149a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner StoreInst *SI = dyn_cast<StoreInst>(I++); 150a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner if (SI == 0 || SI->isVolatile()) continue; 151a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner 1522e12f1ac6ebd49e5c41b7e9dcd802f3df40a1bc7Chris Lattner WeakVH InstPtr(SI); 1532e12f1ac6ebd49e5c41b7e9dcd802f3df40a1bc7Chris Lattner if (!processLoopStore(SI, BECount)) continue; 1542e12f1ac6ebd49e5c41b7e9dcd802f3df40a1bc7Chris Lattner 1552e12f1ac6ebd49e5c41b7e9dcd802f3df40a1bc7Chris Lattner MadeChange = true; 1562e12f1ac6ebd49e5c41b7e9dcd802f3df40a1bc7Chris Lattner 1572e12f1ac6ebd49e5c41b7e9dcd802f3df40a1bc7Chris Lattner // If processing the store invalidated our iterator, start over from the 1582e12f1ac6ebd49e5c41b7e9dcd802f3df40a1bc7Chris Lattner // head of the loop. 1592e12f1ac6ebd49e5c41b7e9dcd802f3df40a1bc7Chris Lattner if (InstPtr == 0) 1602e12f1ac6ebd49e5c41b7e9dcd802f3df40a1bc7Chris Lattner I = BB->begin(); 16122920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner } 16222920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner 16322920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner return MadeChange; 164e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner} 165e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner 166e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner/// scanBlock - Look over a block to see if we can promote anything out of it. 16722920b59864cac3b62d158fd4111cfda3c09c67aChris Lattnerbool LoopIdiomRecognize::processLoopStore(StoreInst *SI, const SCEV *BECount) { 16822920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner Value *StoredVal = SI->getValueOperand(); 169a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner Value *StorePtr = SI->getPointerOperand(); 170e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner 17195ae676bc89b4cb9166576b74f1220ab5b0ff0adChris Lattner // Reject stores that are so large that they overflow an unsigned. 17222920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner uint64_t SizeInBits = TD->getTypeSizeInBits(StoredVal->getType()); 17395ae676bc89b4cb9166576b74f1220ab5b0ff0adChris Lattner if ((SizeInBits & 7) || (SizeInBits >> 32) != 0) 17422920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner return false; 17522920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner 17622920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner // See if the pointer expression is an AddRec like {base,+,1} on the current 17722920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner // loop, which indicates a strided store. If we have something else, it's a 17822920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner // random store we can't handle. 179e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner const SCEVAddRecExpr *StoreEv = 180e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner dyn_cast<SCEVAddRecExpr>(SE->getSCEV(StorePtr)); 181e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner if (StoreEv == 0 || StoreEv->getLoop() != CurLoop || !StoreEv->isAffine()) 18222920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner return false; 18322920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner 18422920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner // Check to see if the stride matches the size of the store. If so, then we 18522920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner // know that every byte is touched in the loop. 18622920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner unsigned StoreSize = (unsigned)SizeInBits >> 3; 187e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner const SCEVConstant *Stride = dyn_cast<SCEVConstant>(StoreEv->getOperand(1)); 18830980b68151a1c1527306aa0f39e3b297af05583Chris Lattner 18930980b68151a1c1527306aa0f39e3b297af05583Chris Lattner // TODO: Could also handle negative stride here someday, that will require the 19030980b68151a1c1527306aa0f39e3b297af05583Chris Lattner // validity check in mayLoopModRefLocation to be updated though. 19122920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner if (Stride == 0 || StoreSize != Stride->getValue()->getValue()) 19222920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner return false; 193e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner 19422920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner // If the stored value is a byte-wise value (like i32 -1), then it may be 19522920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner // turned into a memset of i8 -1, assuming that all the consequtive bytes 19622920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner // are stored. A store of i32 0x01020304 can never be turned into a memset. 197a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner if (Value *SplatValue = isBytewiseValue(StoredVal)) 198e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner if (processLoopStoreOfSplatValue(SI, StoreSize, SplatValue, StoreEv, 199e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner BECount)) 200e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner return true; 201a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner 202e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner // If the stored value is a strided load in the same loop with the same stride 203e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner // this this may be transformable into a memcpy. This kicks in for stuff like 204e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner // for (i) A[i] = B[i]; 205e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) { 206e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner const SCEVAddRecExpr *LoadEv = 207e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner dyn_cast<SCEVAddRecExpr>(SE->getSCEV(LI->getOperand(0))); 208e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner if (LoadEv && LoadEv->getLoop() == CurLoop && LoadEv->isAffine() && 209e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner StoreEv->getOperand(1) == LoadEv->getOperand(1) && !LI->isVolatile()) 210e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner if (processLoopStoreOfLoopLoad(SI, StoreSize, StoreEv, LoadEv, BECount)) 211e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner return true; 212e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner } 213e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner // errs() << "UNHANDLED strided store: " << *Ev << " - " << *SI << "\n"; 21422920b59864cac3b62d158fd4111cfda3c09c67aChris Lattner 215e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner return false; 216e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner} 217e6bb649ec63059d795a31198c3c569c137e7ad59Chris Lattner 21830980b68151a1c1527306aa0f39e3b297af05583Chris Lattner/// mayLoopModRefLocation - Return true if the specified loop might do a load or 21930980b68151a1c1527306aa0f39e3b297af05583Chris Lattner/// store to the same location that the specified store could store to, which is 22030980b68151a1c1527306aa0f39e3b297af05583Chris Lattner/// a loop-strided access. 221e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattnerstatic bool mayLoopModRefLocation(Value *Ptr, Loop *L, const SCEV *BECount, 222e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner unsigned StoreSize, AliasAnalysis &AA, 223e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner StoreInst *IgnoredStore) { 22430980b68151a1c1527306aa0f39e3b297af05583Chris Lattner // Get the location that may be stored across the loop. Since the access is 22530980b68151a1c1527306aa0f39e3b297af05583Chris Lattner // strided positively through memory, we say that the modified location starts 22630980b68151a1c1527306aa0f39e3b297af05583Chris Lattner // at the pointer and has infinite size. 227a64cbf067d6315522d13b606774bbadb4e328d1bChris Lattner uint64_t AccessSize = AliasAnalysis::UnknownSize; 228a64cbf067d6315522d13b606774bbadb4e328d1bChris Lattner 229a64cbf067d6315522d13b606774bbadb4e328d1bChris Lattner // If the loop iterates a fixed number of times, we can refine the access size 230a64cbf067d6315522d13b606774bbadb4e328d1bChris Lattner // to be exactly the size of the memset, which is (BECount+1)*StoreSize 231a64cbf067d6315522d13b606774bbadb4e328d1bChris Lattner if (const SCEVConstant *BECst = dyn_cast<SCEVConstant>(BECount)) 232a64cbf067d6315522d13b606774bbadb4e328d1bChris Lattner AccessSize = (BECst->getValue()->getZExtValue()+1)*StoreSize; 233a64cbf067d6315522d13b606774bbadb4e328d1bChris Lattner 234a64cbf067d6315522d13b606774bbadb4e328d1bChris Lattner // TODO: For this to be really effective, we have to dive into the pointer 235a64cbf067d6315522d13b606774bbadb4e328d1bChris Lattner // operand in the store. Store to &A[i] of 100 will always return may alias 236a64cbf067d6315522d13b606774bbadb4e328d1bChris Lattner // with store of &A[100], we need to StoreLoc to be "A" with size of 100, 237a64cbf067d6315522d13b606774bbadb4e328d1bChris Lattner // which will then no-alias a store to &A[100]. 238e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner AliasAnalysis::Location StoreLoc(Ptr, AccessSize); 23930980b68151a1c1527306aa0f39e3b297af05583Chris Lattner 24030980b68151a1c1527306aa0f39e3b297af05583Chris Lattner for (Loop::block_iterator BI = L->block_begin(), E = L->block_end(); BI != E; 24130980b68151a1c1527306aa0f39e3b297af05583Chris Lattner ++BI) 24230980b68151a1c1527306aa0f39e3b297af05583Chris Lattner for (BasicBlock::iterator I = (*BI)->begin(), E = (*BI)->end(); I != E; ++I) 243e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner if (&*I != IgnoredStore && 244e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner AA.getModRefInfo(I, StoreLoc) != AliasAnalysis::NoModRef) 24530980b68151a1c1527306aa0f39e3b297af05583Chris Lattner return true; 24630980b68151a1c1527306aa0f39e3b297af05583Chris Lattner 24730980b68151a1c1527306aa0f39e3b297af05583Chris Lattner return false; 24830980b68151a1c1527306aa0f39e3b297af05583Chris Lattner} 24930980b68151a1c1527306aa0f39e3b297af05583Chris Lattner 250a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner/// processLoopStoreOfSplatValue - We see a strided store of a memsetable value. 251a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner/// If we can transform this into a memset in the loop preheader, do so. 252a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattnerbool LoopIdiomRecognize:: 253a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris LattnerprocessLoopStoreOfSplatValue(StoreInst *SI, unsigned StoreSize, 254a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner Value *SplatValue, 255a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner const SCEVAddRecExpr *Ev, const SCEV *BECount) { 256bafa117e8f2e3532f391227ebc9d4513b17edbadChris Lattner // Verify that the stored value is loop invariant. If not, we can't promote 257bafa117e8f2e3532f391227ebc9d4513b17edbadChris Lattner // the memset. 258bafa117e8f2e3532f391227ebc9d4513b17edbadChris Lattner if (!CurLoop->isLoopInvariant(SplatValue)) 259bafa117e8f2e3532f391227ebc9d4513b17edbadChris Lattner return false; 260bafa117e8f2e3532f391227ebc9d4513b17edbadChris Lattner 261a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner // Okay, we have a strided store "p[i]" of a splattable value. We can turn 262a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner // this into a memset in the loop preheader now if we want. However, this 263a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner // would be unsafe to do if there is anything else in the loop that may read 264a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner // or write to the aliased location. Check for an alias. 265e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner if (mayLoopModRefLocation(SI->getPointerOperand(), CurLoop, BECount, 266e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner StoreSize, getAnalysis<AliasAnalysis>(), SI)) 267e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner return false; 268a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner 269a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner // Okay, everything looks good, insert the memset. 270a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner BasicBlock *Preheader = CurLoop->getLoopPreheader(); 271a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner 272a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner IRBuilder<> Builder(Preheader->getTerminator()); 273a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner 274a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner // The trip count of the loop and the base pointer of the addrec SCEV is 275a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner // guaranteed to be loop invariant, which means that it should dominate the 276a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner // header. Just insert code for it in the preheader. 277a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner SCEVExpander Expander(*SE); 278a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner 279a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner unsigned AddrSpace = SI->getPointerAddressSpace(); 280a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner Value *BasePtr = 281a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner Expander.expandCodeFor(Ev->getStart(), Builder.getInt8PtrTy(AddrSpace), 282a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner Preheader->getTerminator()); 283a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner 284a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner // The # stored bytes is (BECount+1)*Size. Expand the trip count out to 285a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner // pointer size if it isn't already. 286a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner const Type *IntPtr = TD->getIntPtrType(SI->getContext()); 287a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner unsigned BESize = SE->getTypeSizeInBits(BECount->getType()); 288a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner if (BESize < TD->getPointerSizeInBits()) 289a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner BECount = SE->getZeroExtendExpr(BECount, IntPtr); 290a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner else if (BESize > TD->getPointerSizeInBits()) 291a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner BECount = SE->getTruncateExpr(BECount, IntPtr); 292a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner 293a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner const SCEV *NumBytesS = SE->getAddExpr(BECount, SE->getConstant(IntPtr, 1), 294a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner true, true /*nooverflow*/); 295a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner if (StoreSize != 1) 296a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner NumBytesS = SE->getMulExpr(NumBytesS, SE->getConstant(IntPtr, StoreSize), 297a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner true, true /*nooverflow*/); 298a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner 299a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner Value *NumBytes = 300a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner Expander.expandCodeFor(NumBytesS, IntPtr, Preheader->getTerminator()); 301a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner 302a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner Value *NewCall = 303a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner Builder.CreateMemSet(BasePtr, SplatValue, NumBytes, SI->getAlignment()); 304a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner 305a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner DEBUG(dbgs() << " Formed memset: " << *NewCall << "\n" 306a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner << " from store to: " << *Ev << " at: " << *SI << "\n"); 3077922d34b6073712cb62f7d4d74810509c19a84dfDuncan Sands (void)NewCall; 308a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner 3099f39188def2b4102817945522fac1209083efa06Chris Lattner // Okay, the memset has been formed. Zap the original store and anything that 3109f39188def2b4102817945522fac1209083efa06Chris Lattner // feeds into it. 3119f39188def2b4102817945522fac1209083efa06Chris Lattner DeleteDeadInstruction(SI, *SE); 312a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner return true; 313a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner} 314a92ff91a967c63a2395a34c9e8331a7d50d6ab10Chris Lattner 315e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner/// processLoopStoreOfLoopLoad - We see a strided store whose value is a 316e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner/// same-strided load. 317e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattnerbool LoopIdiomRecognize:: 318e2c43920919c6fe376613d1d8331897dc1ba3d57Chris LattnerprocessLoopStoreOfLoopLoad(StoreInst *SI, unsigned StoreSize, 319e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner const SCEVAddRecExpr *StoreEv, 320e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner const SCEVAddRecExpr *LoadEv, 321e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner const SCEV *BECount) { 322e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner LoadInst *LI = cast<LoadInst>(SI->getValueOperand()); 323e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner 324e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner // Okay, we have a strided store "p[i]" of a loaded value. We can turn 325e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner // this into a memcmp in the loop preheader now if we want. However, this 326e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner // would be unsafe to do if there is anything else in the loop that may read 327e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner // or write to the aliased location (including the load feeding the stores). 328e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner // Check for an alias. 329e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner if (mayLoopModRefLocation(SI->getPointerOperand(), CurLoop, BECount, 330e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner StoreSize, getAnalysis<AliasAnalysis>(), SI)) 331e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner return false; 332e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner 333e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner // Okay, everything looks good, insert the memcpy. 334e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner BasicBlock *Preheader = CurLoop->getLoopPreheader(); 335e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner 336e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner IRBuilder<> Builder(Preheader->getTerminator()); 337e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner 338e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner // The trip count of the loop and the base pointer of the addrec SCEV is 339e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner // guaranteed to be loop invariant, which means that it should dominate the 340e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner // header. Just insert code for it in the preheader. 341e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner SCEVExpander Expander(*SE); 342e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner 343e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner Value *LoadBasePtr = 344e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner Expander.expandCodeFor(LoadEv->getStart(), 345e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner Builder.getInt8PtrTy(LI->getPointerAddressSpace()), 346e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner Preheader->getTerminator()); 347e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner Value *StoreBasePtr = 348e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner Expander.expandCodeFor(StoreEv->getStart(), 349e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner Builder.getInt8PtrTy(SI->getPointerAddressSpace()), 350e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner Preheader->getTerminator()); 351e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner 352e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner // The # stored bytes is (BECount+1)*Size. Expand the trip count out to 353e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner // pointer size if it isn't already. 354e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner const Type *IntPtr = TD->getIntPtrType(SI->getContext()); 355e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner unsigned BESize = SE->getTypeSizeInBits(BECount->getType()); 356e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner if (BESize < TD->getPointerSizeInBits()) 357e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner BECount = SE->getZeroExtendExpr(BECount, IntPtr); 358e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner else if (BESize > TD->getPointerSizeInBits()) 359e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner BECount = SE->getTruncateExpr(BECount, IntPtr); 360e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner 361e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner const SCEV *NumBytesS = SE->getAddExpr(BECount, SE->getConstant(IntPtr, 1), 362e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner true, true /*nooverflow*/); 363e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner if (StoreSize != 1) 364e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner NumBytesS = SE->getMulExpr(NumBytesS, SE->getConstant(IntPtr, StoreSize), 365e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner true, true /*nooverflow*/); 366e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner 367e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner Value *NumBytes = 368e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner Expander.expandCodeFor(NumBytesS, IntPtr, Preheader->getTerminator()); 369e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner 370e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner Value *NewCall = 371e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner Builder.CreateMemCpy(StoreBasePtr, LoadBasePtr, NumBytes, 372e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner std::min(SI->getAlignment(), LI->getAlignment())); 373e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner 374e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner DEBUG(dbgs() << " Formed memcpy: " << *NewCall << "\n" 375e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner << " from load ptr=" << *LoadEv << " at: " << *LI << "\n" 376e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner << " from store ptr=" << *StoreEv << " at: " << *SI << "\n"); 377e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner (void)NewCall; 378e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner 379e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner // Okay, the memset has been formed. Zap the original store and anything that 380e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner // feeds into it. 381e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner DeleteDeadInstruction(SI, *SE); 382e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner return true; 383e2c43920919c6fe376613d1d8331897dc1ba3d57Chris Lattner} 384