LoopVectorize.cpp revision 655d2c5354fcd44c329d99428c7d9196bc78dbad
1//===- LoopVectorize.cpp - A Loop Vectorizer ------------------------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9#include "LoopVectorize.h" 10#include "llvm/ADT/StringExtras.h" 11#include "llvm/Analysis/AliasAnalysis.h" 12#include "llvm/Analysis/AliasSetTracker.h" 13#include "llvm/Analysis/Dominators.h" 14#include "llvm/Analysis/LoopInfo.h" 15#include "llvm/Analysis/LoopIterator.h" 16#include "llvm/Analysis/LoopPass.h" 17#include "llvm/Analysis/ScalarEvolutionExpander.h" 18#include "llvm/Analysis/ScalarEvolutionExpander.h" 19#include "llvm/Analysis/ScalarEvolutionExpressions.h" 20#include "llvm/Analysis/ValueTracking.h" 21#include "llvm/Analysis/Verifier.h" 22#include "llvm/Constants.h" 23#include "llvm/DataLayout.h" 24#include "llvm/DerivedTypes.h" 25#include "llvm/Function.h" 26#include "llvm/Instructions.h" 27#include "llvm/IntrinsicInst.h" 28#include "llvm/LLVMContext.h" 29#include "llvm/Module.h" 30#include "llvm/Pass.h" 31#include "llvm/Support/CommandLine.h" 32#include "llvm/Support/Debug.h" 33#include "llvm/Support/raw_ostream.h" 34#include "llvm/TargetTransformInfo.h" 35#include "llvm/Transforms/Scalar.h" 36#include "llvm/Transforms/Utils/BasicBlockUtils.h" 37#include "llvm/Transforms/Utils/Local.h" 38#include "llvm/Transforms/Vectorize.h" 39#include "llvm/Type.h" 40#include "llvm/Value.h" 41 42static cl::opt<unsigned> 43VectorizationFactor("force-vector-width", cl::init(0), cl::Hidden, 44 cl::desc("Sets the SIMD width. Zero is autoselect.")); 45 46static cl::opt<bool> 47EnableIfConversion("enable-if-conversion", cl::init(true), cl::Hidden, 48 cl::desc("Enable if-conversion during vectorization.")); 49 50namespace { 51 52/// The LoopVectorize Pass. 53struct LoopVectorize : public LoopPass { 54 static char ID; // Pass identification, replacement for typeid 55 56 LoopVectorize() : LoopPass(ID) { 57 initializeLoopVectorizePass(*PassRegistry::getPassRegistry()); 58 } 59 60 ScalarEvolution *SE; 61 DataLayout *DL; 62 LoopInfo *LI; 63 TargetTransformInfo *TTI; 64 DominatorTree *DT; 65 66 virtual bool runOnLoop(Loop *L, LPPassManager &LPM) { 67 // We only vectorize innermost loops. 68 if (!L->empty()) 69 return false; 70 71 SE = &getAnalysis<ScalarEvolution>(); 72 DL = getAnalysisIfAvailable<DataLayout>(); 73 LI = &getAnalysis<LoopInfo>(); 74 TTI = getAnalysisIfAvailable<TargetTransformInfo>(); 75 DT = &getAnalysis<DominatorTree>(); 76 77 DEBUG(dbgs() << "LV: Checking a loop in \"" << 78 L->getHeader()->getParent()->getName() << "\"\n"); 79 80 // Check if it is legal to vectorize the loop. 81 LoopVectorizationLegality LVL(L, SE, DL, DT); 82 if (!LVL.canVectorize()) { 83 DEBUG(dbgs() << "LV: Not vectorizing.\n"); 84 return false; 85 } 86 87 // Select the preffered vectorization factor. 88 unsigned VF = 1; 89 if (VectorizationFactor == 0) { 90 const VectorTargetTransformInfo *VTTI = 0; 91 if (TTI) 92 VTTI = TTI->getVectorTargetTransformInfo(); 93 // Use the cost model. 94 LoopVectorizationCostModel CM(L, SE, &LVL, VTTI); 95 VF = CM.findBestVectorizationFactor(); 96 97 if (VF == 1) { 98 DEBUG(dbgs() << "LV: Vectorization is possible but not beneficial.\n"); 99 return false; 100 } 101 102 } else { 103 // Use the user command flag. 104 VF = VectorizationFactor; 105 } 106 107 DEBUG(dbgs() << "LV: Found a vectorizable loop ("<< VF << ") in "<< 108 L->getHeader()->getParent()->getParent()->getModuleIdentifier()<< 109 "\n"); 110 111 // If we decided that it is *legal* to vectorizer the loop then do it. 112 InnerLoopVectorizer LB(L, SE, LI, DT, DL, VF); 113 LB.vectorize(&LVL); 114 115 DEBUG(verifyFunction(*L->getHeader()->getParent())); 116 return true; 117 } 118 119 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 120 LoopPass::getAnalysisUsage(AU); 121 AU.addRequiredID(LoopSimplifyID); 122 AU.addRequiredID(LCSSAID); 123 AU.addRequired<LoopInfo>(); 124 AU.addRequired<ScalarEvolution>(); 125 AU.addRequired<DominatorTree>(); 126 AU.addPreserved<LoopInfo>(); 127 AU.addPreserved<DominatorTree>(); 128 } 129 130}; 131 132}// namespace 133 134//===----------------------------------------------------------------------===// 135// Implementation of LoopVectorizationLegality, InnerLoopVectorizer and 136// LoopVectorizationCostModel. 137//===----------------------------------------------------------------------===// 138 139void 140LoopVectorizationLegality::RuntimePointerCheck::insert(ScalarEvolution *SE, 141 Loop *Lp, Value *Ptr) { 142 const SCEV *Sc = SE->getSCEV(Ptr); 143 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Sc); 144 assert(AR && "Invalid addrec expression"); 145 const SCEV *Ex = SE->getExitCount(Lp, Lp->getLoopLatch()); 146 const SCEV *ScEnd = AR->evaluateAtIteration(Ex, *SE); 147 Pointers.push_back(Ptr); 148 Starts.push_back(AR->getStart()); 149 Ends.push_back(ScEnd); 150} 151 152Value *InnerLoopVectorizer::getBroadcastInstrs(Value *V) { 153 // Create the types. 154 LLVMContext &C = V->getContext(); 155 Type *VTy = VectorType::get(V->getType(), VF); 156 Type *I32 = IntegerType::getInt32Ty(C); 157 158 // Save the current insertion location. 159 Instruction *Loc = Builder.GetInsertPoint(); 160 161 // We need to place the broadcast of invariant variables outside the loop. 162 Instruction *Instr = dyn_cast<Instruction>(V); 163 bool NewInstr = (Instr && Instr->getParent() == LoopVectorBody); 164 bool Invariant = OrigLoop->isLoopInvariant(V) && !NewInstr; 165 166 // Place the code for broadcasting invariant variables in the new preheader. 167 if (Invariant) 168 Builder.SetInsertPoint(LoopVectorPreHeader->getTerminator()); 169 170 Constant *Zero = ConstantInt::get(I32, 0); 171 Value *Zeros = ConstantAggregateZero::get(VectorType::get(I32, VF)); 172 Value *UndefVal = UndefValue::get(VTy); 173 // Insert the value into a new vector. 174 Value *SingleElem = Builder.CreateInsertElement(UndefVal, V, Zero); 175 // Broadcast the scalar into all locations in the vector. 176 Value *Shuf = Builder.CreateShuffleVector(SingleElem, UndefVal, Zeros, 177 "broadcast"); 178 179 // Restore the builder insertion point. 180 if (Invariant) 181 Builder.SetInsertPoint(Loc); 182 183 return Shuf; 184} 185 186Value *InnerLoopVectorizer::getConsecutiveVector(Value* Val, bool Negate) { 187 assert(Val->getType()->isVectorTy() && "Must be a vector"); 188 assert(Val->getType()->getScalarType()->isIntegerTy() && 189 "Elem must be an integer"); 190 // Create the types. 191 Type *ITy = Val->getType()->getScalarType(); 192 VectorType *Ty = cast<VectorType>(Val->getType()); 193 int VLen = Ty->getNumElements(); 194 SmallVector<Constant*, 8> Indices; 195 196 // Create a vector of consecutive numbers from zero to VF. 197 for (int i = 0; i < VLen; ++i) 198 Indices.push_back(ConstantInt::get(ITy, Negate ? (-i): i )); 199 200 // Add the consecutive indices to the vector value. 201 Constant *Cv = ConstantVector::get(Indices); 202 assert(Cv->getType() == Val->getType() && "Invalid consecutive vec"); 203 return Builder.CreateAdd(Val, Cv, "induction"); 204} 205 206bool LoopVectorizationLegality::isConsecutivePtr(Value *Ptr) { 207 assert(Ptr->getType()->isPointerTy() && "Unexpected non ptr"); 208 209 // If this value is a pointer induction variable we know it is consecutive. 210 PHINode *Phi = dyn_cast_or_null<PHINode>(Ptr); 211 if (Phi && Inductions.count(Phi)) { 212 InductionInfo II = Inductions[Phi]; 213 if (PtrInduction == II.IK) 214 return true; 215 } 216 217 GetElementPtrInst *Gep = dyn_cast_or_null<GetElementPtrInst>(Ptr); 218 if (!Gep) 219 return false; 220 221 unsigned NumOperands = Gep->getNumOperands(); 222 Value *LastIndex = Gep->getOperand(NumOperands - 1); 223 224 // Check that all of the gep indices are uniform except for the last. 225 for (unsigned i = 0; i < NumOperands - 1; ++i) 226 if (!SE->isLoopInvariant(SE->getSCEV(Gep->getOperand(i)), TheLoop)) 227 return false; 228 229 // We can emit wide load/stores only if the last index is the induction 230 // variable. 231 const SCEV *Last = SE->getSCEV(LastIndex); 232 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Last)) { 233 const SCEV *Step = AR->getStepRecurrence(*SE); 234 235 // The memory is consecutive because the last index is consecutive 236 // and all other indices are loop invariant. 237 if (Step->isOne()) 238 return true; 239 } 240 241 return false; 242} 243 244bool LoopVectorizationLegality::isUniform(Value *V) { 245 return (SE->isLoopInvariant(SE->getSCEV(V), TheLoop)); 246} 247 248Value *InnerLoopVectorizer::getVectorValue(Value *V) { 249 assert(V != Induction && "The new induction variable should not be used."); 250 assert(!V->getType()->isVectorTy() && "Can't widen a vector"); 251 // If we saved a vectorized copy of V, use it. 252 Value *&MapEntry = WidenMap[V]; 253 if (MapEntry) 254 return MapEntry; 255 256 // Broadcast V and save the value for future uses. 257 Value *B = getBroadcastInstrs(V); 258 MapEntry = B; 259 return B; 260} 261 262Constant* 263InnerLoopVectorizer::getUniformVector(unsigned Val, Type* ScalarTy) { 264 return ConstantVector::getSplat(VF, ConstantInt::get(ScalarTy, Val, true)); 265} 266 267void InnerLoopVectorizer::scalarizeInstruction(Instruction *Instr) { 268 assert(!Instr->getType()->isAggregateType() && "Can't handle vectors"); 269 // Holds vector parameters or scalars, in case of uniform vals. 270 SmallVector<Value*, 8> Params; 271 272 // Find all of the vectorized parameters. 273 for (unsigned op = 0, e = Instr->getNumOperands(); op != e; ++op) { 274 Value *SrcOp = Instr->getOperand(op); 275 276 // If we are accessing the old induction variable, use the new one. 277 if (SrcOp == OldInduction) { 278 Params.push_back(getVectorValue(SrcOp)); 279 continue; 280 } 281 282 // Try using previously calculated values. 283 Instruction *SrcInst = dyn_cast<Instruction>(SrcOp); 284 285 // If the src is an instruction that appeared earlier in the basic block 286 // then it should already be vectorized. 287 if (SrcInst && SrcInst->getParent() == Instr->getParent()) { 288 assert(WidenMap.count(SrcInst) && "Source operand is unavailable"); 289 // The parameter is a vector value from earlier. 290 Params.push_back(WidenMap[SrcInst]); 291 } else { 292 // The parameter is a scalar from outside the loop. Maybe even a constant. 293 Params.push_back(SrcOp); 294 } 295 } 296 297 assert(Params.size() == Instr->getNumOperands() && 298 "Invalid number of operands"); 299 300 // Does this instruction return a value ? 301 bool IsVoidRetTy = Instr->getType()->isVoidTy(); 302 Value *VecResults = 0; 303 304 // If we have a return value, create an empty vector. We place the scalarized 305 // instructions in this vector. 306 if (!IsVoidRetTy) 307 VecResults = UndefValue::get(VectorType::get(Instr->getType(), VF)); 308 309 // For each scalar that we create: 310 for (unsigned i = 0; i < VF; ++i) { 311 Instruction *Cloned = Instr->clone(); 312 if (!IsVoidRetTy) 313 Cloned->setName(Instr->getName() + ".cloned"); 314 // Replace the operands of the cloned instrucions with extracted scalars. 315 for (unsigned op = 0, e = Instr->getNumOperands(); op != e; ++op) { 316 Value *Op = Params[op]; 317 // Param is a vector. Need to extract the right lane. 318 if (Op->getType()->isVectorTy()) 319 Op = Builder.CreateExtractElement(Op, Builder.getInt32(i)); 320 Cloned->setOperand(op, Op); 321 } 322 323 // Place the cloned scalar in the new loop. 324 Builder.Insert(Cloned); 325 326 // If the original scalar returns a value we need to place it in a vector 327 // so that future users will be able to use it. 328 if (!IsVoidRetTy) 329 VecResults = Builder.CreateInsertElement(VecResults, Cloned, 330 Builder.getInt32(i)); 331 } 332 333 if (!IsVoidRetTy) 334 WidenMap[Instr] = VecResults; 335} 336 337Value* 338InnerLoopVectorizer::addRuntimeCheck(LoopVectorizationLegality *Legal, 339 Instruction *Loc) { 340 LoopVectorizationLegality::RuntimePointerCheck *PtrRtCheck = 341 Legal->getRuntimePointerCheck(); 342 343 if (!PtrRtCheck->Need) 344 return NULL; 345 346 Value *MemoryRuntimeCheck = 0; 347 unsigned NumPointers = PtrRtCheck->Pointers.size(); 348 SmallVector<Value* , 2> Starts; 349 SmallVector<Value* , 2> Ends; 350 351 SCEVExpander Exp(*SE, "induction"); 352 353 // Use this type for pointer arithmetic. 354 Type* PtrArithTy = Type::getInt8PtrTy(Loc->getContext(), 0); 355 356 for (unsigned i = 0; i < NumPointers; ++i) { 357 Value *Ptr = PtrRtCheck->Pointers[i]; 358 const SCEV *Sc = SE->getSCEV(Ptr); 359 360 if (SE->isLoopInvariant(Sc, OrigLoop)) { 361 DEBUG(dbgs() << "LV: Adding RT check for a loop invariant ptr:" << 362 *Ptr <<"\n"); 363 Starts.push_back(Ptr); 364 Ends.push_back(Ptr); 365 } else { 366 DEBUG(dbgs() << "LV: Adding RT check for range:" << *Ptr <<"\n"); 367 368 Value *Start = Exp.expandCodeFor(PtrRtCheck->Starts[i], PtrArithTy, Loc); 369 Value *End = Exp.expandCodeFor(PtrRtCheck->Ends[i], PtrArithTy, Loc); 370 Starts.push_back(Start); 371 Ends.push_back(End); 372 } 373 } 374 375 for (unsigned i = 0; i < NumPointers; ++i) { 376 for (unsigned j = i+1; j < NumPointers; ++j) { 377 Instruction::CastOps Op = Instruction::BitCast; 378 Value *Start0 = CastInst::Create(Op, Starts[i], PtrArithTy, "bc", Loc); 379 Value *Start1 = CastInst::Create(Op, Starts[j], PtrArithTy, "bc", Loc); 380 Value *End0 = CastInst::Create(Op, Ends[i], PtrArithTy, "bc", Loc); 381 Value *End1 = CastInst::Create(Op, Ends[j], PtrArithTy, "bc", Loc); 382 383 Value *Cmp0 = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_ULE, 384 Start0, End1, "bound0", Loc); 385 Value *Cmp1 = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_ULE, 386 Start1, End0, "bound1", Loc); 387 Value *IsConflict = BinaryOperator::Create(Instruction::And, Cmp0, Cmp1, 388 "found.conflict", Loc); 389 if (MemoryRuntimeCheck) 390 MemoryRuntimeCheck = BinaryOperator::Create(Instruction::Or, 391 MemoryRuntimeCheck, 392 IsConflict, 393 "conflict.rdx", Loc); 394 else 395 MemoryRuntimeCheck = IsConflict; 396 397 } 398 } 399 400 return MemoryRuntimeCheck; 401} 402 403void 404InnerLoopVectorizer::createEmptyLoop(LoopVectorizationLegality *Legal) { 405 /* 406 In this function we generate a new loop. The new loop will contain 407 the vectorized instructions while the old loop will continue to run the 408 scalar remainder. 409 410 [ ] <-- vector loop bypass. 411 / | 412 / v 413 | [ ] <-- vector pre header. 414 | | 415 | v 416 | [ ] \ 417 | [ ]_| <-- vector loop. 418 | | 419 \ v 420 >[ ] <--- middle-block. 421 / | 422 / v 423 | [ ] <--- new preheader. 424 | | 425 | v 426 | [ ] \ 427 | [ ]_| <-- old scalar loop to handle remainder. 428 \ | 429 \ v 430 >[ ] <-- exit block. 431 ... 432 */ 433 434 BasicBlock *OldBasicBlock = OrigLoop->getHeader(); 435 BasicBlock *BypassBlock = OrigLoop->getLoopPreheader(); 436 BasicBlock *ExitBlock = OrigLoop->getExitBlock(); 437 assert(ExitBlock && "Must have an exit block"); 438 439 // Some loops have a single integer induction variable, while other loops 440 // don't. One example is c++ iterators that often have multiple pointer 441 // induction variables. In the code below we also support a case where we 442 // don't have a single induction variable. 443 OldInduction = Legal->getInduction(); 444 Type *IdxTy = OldInduction ? OldInduction->getType() : 445 DL->getIntPtrType(SE->getContext()); 446 447 // Find the loop boundaries. 448 const SCEV *ExitCount = SE->getExitCount(OrigLoop, OrigLoop->getLoopLatch()); 449 assert(ExitCount != SE->getCouldNotCompute() && "Invalid loop count"); 450 451 // Get the total trip count from the count by adding 1. 452 ExitCount = SE->getAddExpr(ExitCount, 453 SE->getConstant(ExitCount->getType(), 1)); 454 455 // Expand the trip count and place the new instructions in the preheader. 456 // Notice that the pre-header does not change, only the loop body. 457 SCEVExpander Exp(*SE, "induction"); 458 459 // Count holds the overall loop count (N). 460 Value *Count = Exp.expandCodeFor(ExitCount, ExitCount->getType(), 461 BypassBlock->getTerminator()); 462 463 // The loop index does not have to start at Zero. Find the original start 464 // value from the induction PHI node. If we don't have an induction variable 465 // then we know that it starts at zero. 466 Value *StartIdx = OldInduction ? 467 OldInduction->getIncomingValueForBlock(BypassBlock): 468 ConstantInt::get(IdxTy, 0); 469 470 assert(BypassBlock && "Invalid loop structure"); 471 472 // Generate the code that checks in runtime if arrays overlap. 473 Value *MemoryRuntimeCheck = addRuntimeCheck(Legal, 474 BypassBlock->getTerminator()); 475 476 // Split the single block loop into the two loop structure described above. 477 BasicBlock *VectorPH = 478 BypassBlock->splitBasicBlock(BypassBlock->getTerminator(), "vector.ph"); 479 BasicBlock *VecBody = 480 VectorPH->splitBasicBlock(VectorPH->getTerminator(), "vector.body"); 481 BasicBlock *MiddleBlock = 482 VecBody->splitBasicBlock(VecBody->getTerminator(), "middle.block"); 483 BasicBlock *ScalarPH = 484 MiddleBlock->splitBasicBlock(MiddleBlock->getTerminator(), "scalar.ph"); 485 486 // This is the location in which we add all of the logic for bypassing 487 // the new vector loop. 488 Instruction *Loc = BypassBlock->getTerminator(); 489 490 // Use this IR builder to create the loop instructions (Phi, Br, Cmp) 491 // inside the loop. 492 Builder.SetInsertPoint(VecBody->getFirstInsertionPt()); 493 494 // Generate the induction variable. 495 Induction = Builder.CreatePHI(IdxTy, 2, "index"); 496 Constant *Step = ConstantInt::get(IdxTy, VF); 497 498 // We may need to extend the index in case there is a type mismatch. 499 // We know that the count starts at zero and does not overflow. 500 if (Count->getType() != IdxTy) { 501 // The exit count can be of pointer type. Convert it to the correct 502 // integer type. 503 if (ExitCount->getType()->isPointerTy()) 504 Count = CastInst::CreatePointerCast(Count, IdxTy, "ptrcnt.to.int", Loc); 505 else 506 Count = CastInst::CreateZExtOrBitCast(Count, IdxTy, "zext.cnt", Loc); 507 } 508 509 // Add the start index to the loop count to get the new end index. 510 Value *IdxEnd = BinaryOperator::CreateAdd(Count, StartIdx, "end.idx", Loc); 511 512 // Now we need to generate the expression for N - (N % VF), which is 513 // the part that the vectorized body will execute. 514 Constant *CIVF = ConstantInt::get(IdxTy, VF); 515 Value *R = BinaryOperator::CreateURem(Count, CIVF, "n.mod.vf", Loc); 516 Value *CountRoundDown = BinaryOperator::CreateSub(Count, R, "n.vec", Loc); 517 Value *IdxEndRoundDown = BinaryOperator::CreateAdd(CountRoundDown, StartIdx, 518 "end.idx.rnd.down", Loc); 519 520 // Now, compare the new count to zero. If it is zero skip the vector loop and 521 // jump to the scalar loop. 522 Value *Cmp = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ, 523 IdxEndRoundDown, 524 StartIdx, 525 "cmp.zero", Loc); 526 527 // If we are using memory runtime checks, include them in. 528 if (MemoryRuntimeCheck) 529 Cmp = BinaryOperator::Create(Instruction::Or, Cmp, MemoryRuntimeCheck, 530 "CntOrMem", Loc); 531 532 BranchInst::Create(MiddleBlock, VectorPH, Cmp, Loc); 533 // Remove the old terminator. 534 Loc->eraseFromParent(); 535 536 // We are going to resume the execution of the scalar loop. 537 // Go over all of the induction variables that we found and fix the 538 // PHIs that are left in the scalar version of the loop. 539 // The starting values of PHI nodes depend on the counter of the last 540 // iteration in the vectorized loop. 541 // If we come from a bypass edge then we need to start from the original 542 // start value. 543 544 // This variable saves the new starting index for the scalar loop. 545 PHINode *ResumeIndex = 0; 546 LoopVectorizationLegality::InductionList::iterator I, E; 547 LoopVectorizationLegality::InductionList *List = Legal->getInductionVars(); 548 for (I = List->begin(), E = List->end(); I != E; ++I) { 549 PHINode *OrigPhi = I->first; 550 LoopVectorizationLegality::InductionInfo II = I->second; 551 PHINode *ResumeVal = PHINode::Create(OrigPhi->getType(), 2, "resume.val", 552 MiddleBlock->getTerminator()); 553 Value *EndValue = 0; 554 switch (II.IK) { 555 case LoopVectorizationLegality::NoInduction: 556 llvm_unreachable("Unknown induction"); 557 case LoopVectorizationLegality::IntInduction: { 558 // Handle the integer induction counter: 559 assert(OrigPhi->getType()->isIntegerTy() && "Invalid type"); 560 assert(OrigPhi == OldInduction && "Unknown integer PHI"); 561 // We know what the end value is. 562 EndValue = IdxEndRoundDown; 563 // We also know which PHI node holds it. 564 ResumeIndex = ResumeVal; 565 break; 566 } 567 case LoopVectorizationLegality::ReverseIntInduction: { 568 // Convert the CountRoundDown variable to the PHI size. 569 unsigned CRDSize = CountRoundDown->getType()->getScalarSizeInBits(); 570 unsigned IISize = II.StartValue->getType()->getScalarSizeInBits(); 571 Value *CRD = CountRoundDown; 572 if (CRDSize > IISize) 573 CRD = CastInst::Create(Instruction::Trunc, CountRoundDown, 574 II.StartValue->getType(), 575 "tr.crd", BypassBlock->getTerminator()); 576 else if (CRDSize < IISize) 577 CRD = CastInst::Create(Instruction::SExt, CountRoundDown, 578 II.StartValue->getType(), 579 "sext.crd", BypassBlock->getTerminator()); 580 // Handle reverse integer induction counter: 581 EndValue = BinaryOperator::CreateSub(II.StartValue, CRD, "rev.ind.end", 582 BypassBlock->getTerminator()); 583 break; 584 } 585 case LoopVectorizationLegality::PtrInduction: { 586 // For pointer induction variables, calculate the offset using 587 // the end index. 588 EndValue = GetElementPtrInst::Create(II.StartValue, CountRoundDown, 589 "ptr.ind.end", 590 BypassBlock->getTerminator()); 591 break; 592 } 593 }// end of case 594 595 // The new PHI merges the original incoming value, in case of a bypass, 596 // or the value at the end of the vectorized loop. 597 ResumeVal->addIncoming(II.StartValue, BypassBlock); 598 ResumeVal->addIncoming(EndValue, VecBody); 599 600 // Fix the scalar body counter (PHI node). 601 unsigned BlockIdx = OrigPhi->getBasicBlockIndex(ScalarPH); 602 OrigPhi->setIncomingValue(BlockIdx, ResumeVal); 603 } 604 605 // If we are generating a new induction variable then we also need to 606 // generate the code that calculates the exit value. This value is not 607 // simply the end of the counter because we may skip the vectorized body 608 // in case of a runtime check. 609 if (!OldInduction){ 610 assert(!ResumeIndex && "Unexpected resume value found"); 611 ResumeIndex = PHINode::Create(IdxTy, 2, "new.indc.resume.val", 612 MiddleBlock->getTerminator()); 613 ResumeIndex->addIncoming(StartIdx, BypassBlock); 614 ResumeIndex->addIncoming(IdxEndRoundDown, VecBody); 615 } 616 617 // Make sure that we found the index where scalar loop needs to continue. 618 assert(ResumeIndex && ResumeIndex->getType()->isIntegerTy() && 619 "Invalid resume Index"); 620 621 // Add a check in the middle block to see if we have completed 622 // all of the iterations in the first vector loop. 623 // If (N - N%VF) == N, then we *don't* need to run the remainder. 624 Value *CmpN = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ, IdxEnd, 625 ResumeIndex, "cmp.n", 626 MiddleBlock->getTerminator()); 627 628 BranchInst::Create(ExitBlock, ScalarPH, CmpN, MiddleBlock->getTerminator()); 629 // Remove the old terminator. 630 MiddleBlock->getTerminator()->eraseFromParent(); 631 632 // Create i+1 and fill the PHINode. 633 Value *NextIdx = Builder.CreateAdd(Induction, Step, "index.next"); 634 Induction->addIncoming(StartIdx, VectorPH); 635 Induction->addIncoming(NextIdx, VecBody); 636 // Create the compare. 637 Value *ICmp = Builder.CreateICmpEQ(NextIdx, IdxEndRoundDown); 638 Builder.CreateCondBr(ICmp, MiddleBlock, VecBody); 639 640 // Now we have two terminators. Remove the old one from the block. 641 VecBody->getTerminator()->eraseFromParent(); 642 643 // Get ready to start creating new instructions into the vectorized body. 644 Builder.SetInsertPoint(VecBody->getFirstInsertionPt()); 645 646 // Create and register the new vector loop. 647 Loop* Lp = new Loop(); 648 Loop *ParentLoop = OrigLoop->getParentLoop(); 649 650 // Insert the new loop into the loop nest and register the new basic blocks. 651 if (ParentLoop) { 652 ParentLoop->addChildLoop(Lp); 653 ParentLoop->addBasicBlockToLoop(ScalarPH, LI->getBase()); 654 ParentLoop->addBasicBlockToLoop(VectorPH, LI->getBase()); 655 ParentLoop->addBasicBlockToLoop(MiddleBlock, LI->getBase()); 656 } else { 657 LI->addTopLevelLoop(Lp); 658 } 659 660 Lp->addBasicBlockToLoop(VecBody, LI->getBase()); 661 662 // Save the state. 663 LoopVectorPreHeader = VectorPH; 664 LoopScalarPreHeader = ScalarPH; 665 LoopMiddleBlock = MiddleBlock; 666 LoopExitBlock = ExitBlock; 667 LoopVectorBody = VecBody; 668 LoopScalarBody = OldBasicBlock; 669 LoopBypassBlock = BypassBlock; 670} 671 672/// This function returns the identity element (or neutral element) for 673/// the operation K. 674static unsigned 675getReductionIdentity(LoopVectorizationLegality::ReductionKind K) { 676 switch (K) { 677 case LoopVectorizationLegality::IntegerXor: 678 case LoopVectorizationLegality::IntegerAdd: 679 case LoopVectorizationLegality::IntegerOr: 680 // Adding, Xoring, Oring zero to a number does not change it. 681 return 0; 682 case LoopVectorizationLegality::IntegerMult: 683 // Multiplying a number by 1 does not change it. 684 return 1; 685 case LoopVectorizationLegality::IntegerAnd: 686 // AND-ing a number with an all-1 value does not change it. 687 return -1; 688 default: 689 llvm_unreachable("Unknown reduction kind"); 690 } 691} 692 693static bool 694isTriviallyVectorizableIntrinsic(Instruction *Inst) { 695 IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst); 696 if (!II) 697 return false; 698 switch (II->getIntrinsicID()) { 699 case Intrinsic::sqrt: 700 case Intrinsic::sin: 701 case Intrinsic::cos: 702 case Intrinsic::exp: 703 case Intrinsic::exp2: 704 case Intrinsic::log: 705 case Intrinsic::log10: 706 case Intrinsic::log2: 707 case Intrinsic::fabs: 708 case Intrinsic::floor: 709 case Intrinsic::ceil: 710 case Intrinsic::trunc: 711 case Intrinsic::rint: 712 case Intrinsic::nearbyint: 713 case Intrinsic::pow: 714 case Intrinsic::fma: 715 return true; 716 default: 717 return false; 718 } 719 return false; 720} 721 722void 723InnerLoopVectorizer::vectorizeLoop(LoopVectorizationLegality *Legal) { 724 //===------------------------------------------------===// 725 // 726 // Notice: any optimization or new instruction that go 727 // into the code below should be also be implemented in 728 // the cost-model. 729 // 730 //===------------------------------------------------===// 731 BasicBlock &BB = *OrigLoop->getHeader(); 732 Constant *Zero = 733 ConstantInt::get(IntegerType::getInt32Ty(BB.getContext()), 0); 734 735 // In order to support reduction variables we need to be able to vectorize 736 // Phi nodes. Phi nodes have cycles, so we need to vectorize them in two 737 // stages. First, we create a new vector PHI node with no incoming edges. 738 // We use this value when we vectorize all of the instructions that use the 739 // PHI. Next, after all of the instructions in the block are complete we 740 // add the new incoming edges to the PHI. At this point all of the 741 // instructions in the basic block are vectorized, so we can use them to 742 // construct the PHI. 743 PhiVector RdxPHIsToFix; 744 745 // Scan the loop in a topological order to ensure that defs are vectorized 746 // before users. 747 LoopBlocksDFS DFS(OrigLoop); 748 DFS.perform(LI); 749 750 // Vectorize all of the blocks in the original loop. 751 for (LoopBlocksDFS::RPOIterator bb = DFS.beginRPO(), 752 be = DFS.endRPO(); bb != be; ++bb) 753 vectorizeBlockInLoop(Legal, *bb, &RdxPHIsToFix); 754 755 // At this point every instruction in the original loop is widened to 756 // a vector form. We are almost done. Now, we need to fix the PHI nodes 757 // that we vectorized. The PHI nodes are currently empty because we did 758 // not want to introduce cycles. Notice that the remaining PHI nodes 759 // that we need to fix are reduction variables. 760 761 // Create the 'reduced' values for each of the induction vars. 762 // The reduced values are the vector values that we scalarize and combine 763 // after the loop is finished. 764 for (PhiVector::iterator it = RdxPHIsToFix.begin(), e = RdxPHIsToFix.end(); 765 it != e; ++it) { 766 PHINode *RdxPhi = *it; 767 PHINode *VecRdxPhi = dyn_cast<PHINode>(WidenMap[RdxPhi]); 768 assert(RdxPhi && "Unable to recover vectorized PHI"); 769 770 // Find the reduction variable descriptor. 771 assert(Legal->getReductionVars()->count(RdxPhi) && 772 "Unable to find the reduction variable"); 773 LoopVectorizationLegality::ReductionDescriptor RdxDesc = 774 (*Legal->getReductionVars())[RdxPhi]; 775 776 // We need to generate a reduction vector from the incoming scalar. 777 // To do so, we need to generate the 'identity' vector and overide 778 // one of the elements with the incoming scalar reduction. We need 779 // to do it in the vector-loop preheader. 780 Builder.SetInsertPoint(LoopBypassBlock->getTerminator()); 781 782 // This is the vector-clone of the value that leaves the loop. 783 Value *VectorExit = getVectorValue(RdxDesc.LoopExitInstr); 784 Type *VecTy = VectorExit->getType(); 785 786 // Find the reduction identity variable. Zero for addition, or, xor, 787 // one for multiplication, -1 for And. 788 Constant *Identity = getUniformVector(getReductionIdentity(RdxDesc.Kind), 789 VecTy->getScalarType()); 790 791 // This vector is the Identity vector where the first element is the 792 // incoming scalar reduction. 793 Value *VectorStart = Builder.CreateInsertElement(Identity, 794 RdxDesc.StartValue, Zero); 795 796 // Fix the vector-loop phi. 797 // We created the induction variable so we know that the 798 // preheader is the first entry. 799 BasicBlock *VecPreheader = Induction->getIncomingBlock(0); 800 801 // Reductions do not have to start at zero. They can start with 802 // any loop invariant values. 803 VecRdxPhi->addIncoming(VectorStart, VecPreheader); 804 Value *Val = 805 getVectorValue(RdxPhi->getIncomingValueForBlock(OrigLoop->getLoopLatch())); 806 VecRdxPhi->addIncoming(Val, LoopVectorBody); 807 808 // Before each round, move the insertion point right between 809 // the PHIs and the values we are going to write. 810 // This allows us to write both PHINodes and the extractelement 811 // instructions. 812 Builder.SetInsertPoint(LoopMiddleBlock->getFirstInsertionPt()); 813 814 // This PHINode contains the vectorized reduction variable, or 815 // the initial value vector, if we bypass the vector loop. 816 PHINode *NewPhi = Builder.CreatePHI(VecTy, 2, "rdx.vec.exit.phi"); 817 NewPhi->addIncoming(VectorStart, LoopBypassBlock); 818 NewPhi->addIncoming(getVectorValue(RdxDesc.LoopExitInstr), LoopVectorBody); 819 820 // Extract the first scalar. 821 Value *Scalar0 = 822 Builder.CreateExtractElement(NewPhi, Builder.getInt32(0)); 823 // Extract and reduce the remaining vector elements. 824 for (unsigned i=1; i < VF; ++i) { 825 Value *Scalar1 = 826 Builder.CreateExtractElement(NewPhi, Builder.getInt32(i)); 827 switch (RdxDesc.Kind) { 828 case LoopVectorizationLegality::IntegerAdd: 829 Scalar0 = Builder.CreateAdd(Scalar0, Scalar1, "add.rdx"); 830 break; 831 case LoopVectorizationLegality::IntegerMult: 832 Scalar0 = Builder.CreateMul(Scalar0, Scalar1, "mul.rdx"); 833 break; 834 case LoopVectorizationLegality::IntegerOr: 835 Scalar0 = Builder.CreateOr(Scalar0, Scalar1, "or.rdx"); 836 break; 837 case LoopVectorizationLegality::IntegerAnd: 838 Scalar0 = Builder.CreateAnd(Scalar0, Scalar1, "and.rdx"); 839 break; 840 case LoopVectorizationLegality::IntegerXor: 841 Scalar0 = Builder.CreateXor(Scalar0, Scalar1, "xor.rdx"); 842 break; 843 default: 844 llvm_unreachable("Unknown reduction operation"); 845 } 846 } 847 848 // Now, we need to fix the users of the reduction variable 849 // inside and outside of the scalar remainder loop. 850 // We know that the loop is in LCSSA form. We need to update the 851 // PHI nodes in the exit blocks. 852 for (BasicBlock::iterator LEI = LoopExitBlock->begin(), 853 LEE = LoopExitBlock->end(); LEI != LEE; ++LEI) { 854 PHINode *LCSSAPhi = dyn_cast<PHINode>(LEI); 855 if (!LCSSAPhi) continue; 856 857 // All PHINodes need to have a single entry edge, or two if 858 // we already fixed them. 859 assert(LCSSAPhi->getNumIncomingValues() < 3 && "Invalid LCSSA PHI"); 860 861 // We found our reduction value exit-PHI. Update it with the 862 // incoming bypass edge. 863 if (LCSSAPhi->getIncomingValue(0) == RdxDesc.LoopExitInstr) { 864 // Add an edge coming from the bypass. 865 LCSSAPhi->addIncoming(Scalar0, LoopMiddleBlock); 866 break; 867 } 868 }// end of the LCSSA phi scan. 869 870 // Fix the scalar loop reduction variable with the incoming reduction sum 871 // from the vector body and from the backedge value. 872 int IncomingEdgeBlockIdx = 873 (RdxPhi)->getBasicBlockIndex(OrigLoop->getLoopLatch()); 874 assert(IncomingEdgeBlockIdx >= 0 && "Invalid block index"); 875 // Pick the other block. 876 int SelfEdgeBlockIdx = (IncomingEdgeBlockIdx ? 0 : 1); 877 (RdxPhi)->setIncomingValue(SelfEdgeBlockIdx, Scalar0); 878 (RdxPhi)->setIncomingValue(IncomingEdgeBlockIdx, RdxDesc.LoopExitInstr); 879 }// end of for each redux variable. 880} 881 882Value *InnerLoopVectorizer::createEdgeMask(BasicBlock *Src, BasicBlock *Dst) { 883 assert(std::find(pred_begin(Dst), pred_end(Dst), Src) != pred_end(Dst) && 884 "Invalid edge"); 885 886 Value *SrcMask = createBlockInMask(Src); 887 888 // The terminator has to be a branch inst! 889 BranchInst *BI = dyn_cast<BranchInst>(Src->getTerminator()); 890 assert(BI && "Unexpected terminator found"); 891 892 Value *EdgeMask = SrcMask; 893 if (BI->isConditional()) { 894 EdgeMask = getVectorValue(BI->getCondition()); 895 if (BI->getSuccessor(0) != Dst) 896 EdgeMask = Builder.CreateNot(EdgeMask); 897 } 898 899 return Builder.CreateAnd(EdgeMask, SrcMask); 900} 901 902Value *InnerLoopVectorizer::createBlockInMask(BasicBlock *BB) { 903 assert(OrigLoop->contains(BB) && "Block is not a part of a loop"); 904 905 // Loop incoming mask is all-one. 906 if (OrigLoop->getHeader() == BB) { 907 Value *C = ConstantInt::get(IntegerType::getInt1Ty(BB->getContext()), 1); 908 return getVectorValue(C); 909 } 910 911 // This is the block mask. We OR all incoming edges, and with zero. 912 Value *Zero = ConstantInt::get(IntegerType::getInt1Ty(BB->getContext()), 0); 913 Value *BlockMask = getVectorValue(Zero); 914 915 // For each pred: 916 for (pred_iterator it = pred_begin(BB), e = pred_end(BB); it != e; ++it) 917 BlockMask = Builder.CreateOr(BlockMask, createEdgeMask(*it, BB)); 918 919 return BlockMask; 920} 921 922void 923InnerLoopVectorizer::vectorizeBlockInLoop(LoopVectorizationLegality *Legal, 924 BasicBlock *BB, PhiVector *PV) { 925 Constant *Zero = 926 ConstantInt::get(IntegerType::getInt32Ty(BB->getContext()), 0); 927 928 // For each instruction in the old loop. 929 for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e; ++it) { 930 switch (it->getOpcode()) { 931 case Instruction::Br: 932 // Nothing to do for PHIs and BR, since we already took care of the 933 // loop control flow instructions. 934 continue; 935 case Instruction::PHI:{ 936 PHINode* P = cast<PHINode>(it); 937 // Handle reduction variables: 938 if (Legal->getReductionVars()->count(P)) { 939 // This is phase one of vectorizing PHIs. 940 Type *VecTy = VectorType::get(it->getType(), VF); 941 WidenMap[it] = 942 PHINode::Create(VecTy, 2, "vec.phi", 943 LoopVectorBody->getFirstInsertionPt()); 944 PV->push_back(P); 945 continue; 946 } 947 948 // Check for PHI nodes that are lowered to vector selects. 949 if (P->getParent() != OrigLoop->getHeader()) { 950 // We know that all PHIs in non header blocks are converted into 951 // selects, so we don't have to worry about the insertion order and we 952 // can just use the builder. 953 954 // At this point we generate the predication tree. There may be 955 // duplications since this is a simple recursive scan, but future 956 // optimizations will clean it up. 957 Value *Cond = createEdgeMask(P->getIncomingBlock(0), P->getParent()); 958 WidenMap[P] = 959 Builder.CreateSelect(Cond, 960 getVectorValue(P->getIncomingValue(0)), 961 getVectorValue(P->getIncomingValue(1)), 962 "predphi"); 963 continue; 964 } 965 966 // This PHINode must be an induction variable. 967 // Make sure that we know about it. 968 assert(Legal->getInductionVars()->count(P) && 969 "Not an induction variable"); 970 971 LoopVectorizationLegality::InductionInfo II = 972 Legal->getInductionVars()->lookup(P); 973 974 switch (II.IK) { 975 case LoopVectorizationLegality::NoInduction: 976 llvm_unreachable("Unknown induction"); 977 case LoopVectorizationLegality::IntInduction: { 978 assert(P == OldInduction && "Unexpected PHI"); 979 Value *Broadcasted = getBroadcastInstrs(Induction); 980 // After broadcasting the induction variable we need to make the 981 // vector consecutive by adding 0, 1, 2 ... 982 Value *ConsecutiveInduction = getConsecutiveVector(Broadcasted); 983 WidenMap[OldInduction] = ConsecutiveInduction; 984 continue; 985 } 986 case LoopVectorizationLegality::ReverseIntInduction: 987 case LoopVectorizationLegality::PtrInduction: 988 // Handle reverse integer and pointer inductions. 989 Value *StartIdx = 0; 990 // If we have a single integer induction variable then use it. 991 // Otherwise, start counting at zero. 992 if (OldInduction) { 993 LoopVectorizationLegality::InductionInfo OldII = 994 Legal->getInductionVars()->lookup(OldInduction); 995 StartIdx = OldII.StartValue; 996 } else { 997 StartIdx = ConstantInt::get(Induction->getType(), 0); 998 } 999 // This is the normalized GEP that starts counting at zero. 1000 Value *NormalizedIdx = Builder.CreateSub(Induction, StartIdx, 1001 "normalized.idx"); 1002 1003 // Handle the reverse integer induction variable case. 1004 if (LoopVectorizationLegality::ReverseIntInduction == II.IK) { 1005 IntegerType *DstTy = cast<IntegerType>(II.StartValue->getType()); 1006 Value *CNI = Builder.CreateSExtOrTrunc(NormalizedIdx, DstTy, 1007 "resize.norm.idx"); 1008 Value *ReverseInd = Builder.CreateSub(II.StartValue, CNI, 1009 "reverse.idx"); 1010 1011 // This is a new value so do not hoist it out. 1012 Value *Broadcasted = getBroadcastInstrs(ReverseInd); 1013 // After broadcasting the induction variable we need to make the 1014 // vector consecutive by adding ... -3, -2, -1, 0. 1015 Value *ConsecutiveInduction = getConsecutiveVector(Broadcasted, 1016 true); 1017 WidenMap[it] = ConsecutiveInduction; 1018 continue; 1019 } 1020 1021 // Handle the pointer induction variable case. 1022 assert(P->getType()->isPointerTy() && "Unexpected type."); 1023 1024 // This is the vector of results. Notice that we don't generate 1025 // vector geps because scalar geps result in better code. 1026 Value *VecVal = UndefValue::get(VectorType::get(P->getType(), VF)); 1027 for (unsigned int i = 0; i < VF; ++i) { 1028 Constant *Idx = ConstantInt::get(Induction->getType(), i); 1029 Value *GlobalIdx = Builder.CreateAdd(NormalizedIdx, Idx, 1030 "gep.idx"); 1031 Value *SclrGep = Builder.CreateGEP(II.StartValue, GlobalIdx, 1032 "next.gep"); 1033 VecVal = Builder.CreateInsertElement(VecVal, SclrGep, 1034 Builder.getInt32(i), 1035 "insert.gep"); 1036 } 1037 1038 WidenMap[it] = VecVal; 1039 continue; 1040 } 1041 1042 }// End of PHI. 1043 1044 case Instruction::Add: 1045 case Instruction::FAdd: 1046 case Instruction::Sub: 1047 case Instruction::FSub: 1048 case Instruction::Mul: 1049 case Instruction::FMul: 1050 case Instruction::UDiv: 1051 case Instruction::SDiv: 1052 case Instruction::FDiv: 1053 case Instruction::URem: 1054 case Instruction::SRem: 1055 case Instruction::FRem: 1056 case Instruction::Shl: 1057 case Instruction::LShr: 1058 case Instruction::AShr: 1059 case Instruction::And: 1060 case Instruction::Or: 1061 case Instruction::Xor: { 1062 // Just widen binops. 1063 BinaryOperator *BinOp = dyn_cast<BinaryOperator>(it); 1064 Value *A = getVectorValue(it->getOperand(0)); 1065 Value *B = getVectorValue(it->getOperand(1)); 1066 1067 // Use this vector value for all users of the original instruction. 1068 Value *V = Builder.CreateBinOp(BinOp->getOpcode(), A, B); 1069 WidenMap[it] = V; 1070 1071 // Update the NSW, NUW and Exact flags. 1072 BinaryOperator *VecOp = cast<BinaryOperator>(V); 1073 if (isa<OverflowingBinaryOperator>(BinOp)) { 1074 VecOp->setHasNoSignedWrap(BinOp->hasNoSignedWrap()); 1075 VecOp->setHasNoUnsignedWrap(BinOp->hasNoUnsignedWrap()); 1076 } 1077 if (isa<PossiblyExactOperator>(VecOp)) 1078 VecOp->setIsExact(BinOp->isExact()); 1079 break; 1080 } 1081 case Instruction::Select: { 1082 // Widen selects. 1083 // If the selector is loop invariant we can create a select 1084 // instruction with a scalar condition. Otherwise, use vector-select. 1085 Value *Cond = it->getOperand(0); 1086 bool InvariantCond = SE->isLoopInvariant(SE->getSCEV(Cond), OrigLoop); 1087 1088 // The condition can be loop invariant but still defined inside the 1089 // loop. This means that we can't just use the original 'cond' value. 1090 // We have to take the 'vectorized' value and pick the first lane. 1091 // Instcombine will make this a no-op. 1092 Cond = getVectorValue(Cond); 1093 if (InvariantCond) 1094 Cond = Builder.CreateExtractElement(Cond, Builder.getInt32(0)); 1095 1096 Value *Op0 = getVectorValue(it->getOperand(1)); 1097 Value *Op1 = getVectorValue(it->getOperand(2)); 1098 WidenMap[it] = Builder.CreateSelect(Cond, Op0, Op1); 1099 break; 1100 } 1101 1102 case Instruction::ICmp: 1103 case Instruction::FCmp: { 1104 // Widen compares. Generate vector compares. 1105 bool FCmp = (it->getOpcode() == Instruction::FCmp); 1106 CmpInst *Cmp = dyn_cast<CmpInst>(it); 1107 Value *A = getVectorValue(it->getOperand(0)); 1108 Value *B = getVectorValue(it->getOperand(1)); 1109 if (FCmp) 1110 WidenMap[it] = Builder.CreateFCmp(Cmp->getPredicate(), A, B); 1111 else 1112 WidenMap[it] = Builder.CreateICmp(Cmp->getPredicate(), A, B); 1113 break; 1114 } 1115 1116 case Instruction::Store: { 1117 // Attempt to issue a wide store. 1118 StoreInst *SI = dyn_cast<StoreInst>(it); 1119 Type *StTy = VectorType::get(SI->getValueOperand()->getType(), VF); 1120 Value *Ptr = SI->getPointerOperand(); 1121 unsigned Alignment = SI->getAlignment(); 1122 1123 assert(!Legal->isUniform(Ptr) && 1124 "We do not allow storing to uniform addresses"); 1125 1126 GetElementPtrInst *Gep = dyn_cast<GetElementPtrInst>(Ptr); 1127 1128 // This store does not use GEPs. 1129 if (!Legal->isConsecutivePtr(Ptr)) { 1130 scalarizeInstruction(it); 1131 break; 1132 } 1133 1134 if (Gep) { 1135 // The last index does not have to be the induction. It can be 1136 // consecutive and be a function of the index. For example A[I+1]; 1137 unsigned NumOperands = Gep->getNumOperands(); 1138 Value *LastIndex = getVectorValue(Gep->getOperand(NumOperands - 1)); 1139 LastIndex = Builder.CreateExtractElement(LastIndex, Zero); 1140 1141 // Create the new GEP with the new induction variable. 1142 GetElementPtrInst *Gep2 = cast<GetElementPtrInst>(Gep->clone()); 1143 Gep2->setOperand(NumOperands - 1, LastIndex); 1144 Ptr = Builder.Insert(Gep2); 1145 } else { 1146 // Use the induction element ptr. 1147 assert(isa<PHINode>(Ptr) && "Invalid induction ptr"); 1148 Ptr = Builder.CreateExtractElement(getVectorValue(Ptr), Zero); 1149 } 1150 Ptr = Builder.CreateBitCast(Ptr, StTy->getPointerTo()); 1151 Value *Val = getVectorValue(SI->getValueOperand()); 1152 Builder.CreateStore(Val, Ptr)->setAlignment(Alignment); 1153 break; 1154 } 1155 case Instruction::Load: { 1156 // Attempt to issue a wide load. 1157 LoadInst *LI = dyn_cast<LoadInst>(it); 1158 Type *RetTy = VectorType::get(LI->getType(), VF); 1159 Value *Ptr = LI->getPointerOperand(); 1160 unsigned Alignment = LI->getAlignment(); 1161 GetElementPtrInst *Gep = dyn_cast<GetElementPtrInst>(Ptr); 1162 1163 // If the pointer is loop invariant or if it is non consecutive, 1164 // scalarize the load. 1165 bool Con = Legal->isConsecutivePtr(Ptr); 1166 if (Legal->isUniform(Ptr) || !Con) { 1167 scalarizeInstruction(it); 1168 break; 1169 } 1170 1171 if (Gep) { 1172 // The last index does not have to be the induction. It can be 1173 // consecutive and be a function of the index. For example A[I+1]; 1174 unsigned NumOperands = Gep->getNumOperands(); 1175 Value *LastIndex = getVectorValue(Gep->getOperand(NumOperands -1)); 1176 LastIndex = Builder.CreateExtractElement(LastIndex, Zero); 1177 1178 // Create the new GEP with the new induction variable. 1179 GetElementPtrInst *Gep2 = cast<GetElementPtrInst>(Gep->clone()); 1180 Gep2->setOperand(NumOperands - 1, LastIndex); 1181 Ptr = Builder.Insert(Gep2); 1182 } else { 1183 // Use the induction element ptr. 1184 assert(isa<PHINode>(Ptr) && "Invalid induction ptr"); 1185 Ptr = Builder.CreateExtractElement(getVectorValue(Ptr), Zero); 1186 } 1187 1188 Ptr = Builder.CreateBitCast(Ptr, RetTy->getPointerTo()); 1189 LI = Builder.CreateLoad(Ptr); 1190 LI->setAlignment(Alignment); 1191 // Use this vector value for all users of the load. 1192 WidenMap[it] = LI; 1193 break; 1194 } 1195 case Instruction::ZExt: 1196 case Instruction::SExt: 1197 case Instruction::FPToUI: 1198 case Instruction::FPToSI: 1199 case Instruction::FPExt: 1200 case Instruction::PtrToInt: 1201 case Instruction::IntToPtr: 1202 case Instruction::SIToFP: 1203 case Instruction::UIToFP: 1204 case Instruction::Trunc: 1205 case Instruction::FPTrunc: 1206 case Instruction::BitCast: { 1207 CastInst *CI = dyn_cast<CastInst>(it); 1208 /// Optimize the special case where the source is the induction 1209 /// variable. Notice that we can only optimize the 'trunc' case 1210 /// because: a. FP conversions lose precision, b. sext/zext may wrap, 1211 /// c. other casts depend on pointer size. 1212 if (CI->getOperand(0) == OldInduction && 1213 it->getOpcode() == Instruction::Trunc) { 1214 Value *ScalarCast = Builder.CreateCast(CI->getOpcode(), Induction, 1215 CI->getType()); 1216 Value *Broadcasted = getBroadcastInstrs(ScalarCast); 1217 WidenMap[it] = getConsecutiveVector(Broadcasted); 1218 break; 1219 } 1220 /// Vectorize casts. 1221 Value *A = getVectorValue(it->getOperand(0)); 1222 Type *DestTy = VectorType::get(CI->getType()->getScalarType(), VF); 1223 WidenMap[it] = Builder.CreateCast(CI->getOpcode(), A, DestTy); 1224 break; 1225 } 1226 1227 case Instruction::Call: { 1228 assert(isTriviallyVectorizableIntrinsic(it)); 1229 Module *M = BB->getParent()->getParent(); 1230 IntrinsicInst *II = cast<IntrinsicInst>(it); 1231 Intrinsic::ID ID = II->getIntrinsicID(); 1232 SmallVector<Value*, 4> Args; 1233 for (unsigned i = 0, ie = II->getNumArgOperands(); i != ie; ++i) 1234 Args.push_back(getVectorValue(II->getArgOperand(i))); 1235 Type *Tys[] = { VectorType::get(II->getType()->getScalarType(), VF) }; 1236 Function *F = Intrinsic::getDeclaration(M, ID, Tys); 1237 WidenMap[it] = Builder.CreateCall(F, Args); 1238 break; 1239 } 1240 1241 default: 1242 // All other instructions are unsupported. Scalarize them. 1243 scalarizeInstruction(it); 1244 break; 1245 }// end of switch. 1246 }// end of for_each instr. 1247} 1248 1249void InnerLoopVectorizer::updateAnalysis() { 1250 // Forget the original basic block. 1251 SE->forgetLoop(OrigLoop); 1252 1253 // Update the dominator tree information. 1254 assert(DT->properlyDominates(LoopBypassBlock, LoopExitBlock) && 1255 "Entry does not dominate exit."); 1256 1257 DT->addNewBlock(LoopVectorPreHeader, LoopBypassBlock); 1258 DT->addNewBlock(LoopVectorBody, LoopVectorPreHeader); 1259 DT->addNewBlock(LoopMiddleBlock, LoopBypassBlock); 1260 DT->addNewBlock(LoopScalarPreHeader, LoopMiddleBlock); 1261 DT->changeImmediateDominator(LoopScalarBody, LoopScalarPreHeader); 1262 DT->changeImmediateDominator(LoopExitBlock, LoopMiddleBlock); 1263 1264 DEBUG(DT->verifyAnalysis()); 1265} 1266 1267bool LoopVectorizationLegality::canVectorizeWithIfConvert() { 1268 if (!EnableIfConversion) 1269 return false; 1270 1271 assert(TheLoop->getNumBlocks() > 1 && "Single block loops are vectorizable"); 1272 std::vector<BasicBlock*> &LoopBlocks = TheLoop->getBlocksVector(); 1273 1274 // Collect the blocks that need predication. 1275 for (unsigned i = 0, e = LoopBlocks.size(); i < e; ++i) { 1276 BasicBlock *BB = LoopBlocks[i]; 1277 1278 // We don't support switch statements inside loops. 1279 if (!isa<BranchInst>(BB->getTerminator())) 1280 return false; 1281 1282 // We must have at most two predecessors because we need to convert 1283 // all PHIs to selects. 1284 unsigned Preds = std::distance(pred_begin(BB), pred_end(BB)); 1285 if (Preds > 2) 1286 return false; 1287 1288 // We must be able to predicate all blocks that need to be predicated. 1289 if (blockNeedsPredication(BB) && !blockCanBePredicated(BB)) 1290 return false; 1291 } 1292 1293 // We can if-convert this loop. 1294 return true; 1295} 1296 1297bool LoopVectorizationLegality::canVectorize() { 1298 assert(TheLoop->getLoopPreheader() && "No preheader!!"); 1299 1300 // We can only vectorize innermost loops. 1301 if (TheLoop->getSubLoopsVector().size()) 1302 return false; 1303 1304 // We must have a single backedge. 1305 if (TheLoop->getNumBackEdges() != 1) 1306 return false; 1307 1308 // We must have a single exiting block. 1309 if (!TheLoop->getExitingBlock()) 1310 return false; 1311 1312 unsigned NumBlocks = TheLoop->getNumBlocks(); 1313 1314 // Check if we can if-convert non single-bb loops. 1315 if (NumBlocks != 1 && !canVectorizeWithIfConvert()) { 1316 DEBUG(dbgs() << "LV: Can't if-convert the loop.\n"); 1317 return false; 1318 } 1319 1320 // We need to have a loop header. 1321 BasicBlock *Latch = TheLoop->getLoopLatch(); 1322 DEBUG(dbgs() << "LV: Found a loop: " << 1323 TheLoop->getHeader()->getName() << "\n"); 1324 1325 // ScalarEvolution needs to be able to find the exit count. 1326 const SCEV *ExitCount = SE->getExitCount(TheLoop, Latch); 1327 if (ExitCount == SE->getCouldNotCompute()) { 1328 DEBUG(dbgs() << "LV: SCEV could not compute the loop exit count.\n"); 1329 return false; 1330 } 1331 1332 // Do not loop-vectorize loops with a tiny trip count. 1333 unsigned TC = SE->getSmallConstantTripCount(TheLoop, Latch); 1334 if (TC > 0u && TC < TinyTripCountThreshold) { 1335 DEBUG(dbgs() << "LV: Found a loop with a very small trip count. " << 1336 "This loop is not worth vectorizing.\n"); 1337 return false; 1338 } 1339 1340 // Check if we can vectorize the instructions and CFG in this loop. 1341 if (!canVectorizeInstrs()) { 1342 DEBUG(dbgs() << "LV: Can't vectorize the instructions or CFG\n"); 1343 return false; 1344 } 1345 1346 // Go over each instruction and look at memory deps. 1347 if (!canVectorizeMemory()) { 1348 DEBUG(dbgs() << "LV: Can't vectorize due to memory conflicts\n"); 1349 return false; 1350 } 1351 1352 // Collect all of the variables that remain uniform after vectorization. 1353 collectLoopUniforms(); 1354 1355 DEBUG(dbgs() << "LV: We can vectorize this loop" << 1356 (PtrRtCheck.Need ? " (with a runtime bound check)" : "") 1357 <<"!\n"); 1358 1359 // Okay! We can vectorize. At this point we don't have any other mem analysis 1360 // which may limit our maximum vectorization factor, so just return true with 1361 // no restrictions. 1362 return true; 1363} 1364 1365bool LoopVectorizationLegality::canVectorizeInstrs() { 1366 BasicBlock *PreHeader = TheLoop->getLoopPreheader(); 1367 BasicBlock *Header = TheLoop->getHeader(); 1368 1369 // For each block in the loop. 1370 for (Loop::block_iterator bb = TheLoop->block_begin(), 1371 be = TheLoop->block_end(); bb != be; ++bb) { 1372 1373 // Scan the instructions in the block and look for hazards. 1374 for (BasicBlock::iterator it = (*bb)->begin(), e = (*bb)->end(); it != e; 1375 ++it) { 1376 1377 if (PHINode *Phi = dyn_cast<PHINode>(it)) { 1378 // This should not happen because the loop should be normalized. 1379 if (Phi->getNumIncomingValues() != 2) { 1380 DEBUG(dbgs() << "LV: Found an invalid PHI.\n"); 1381 return false; 1382 } 1383 1384 // Check that this PHI type is allowed. 1385 if (!Phi->getType()->isIntegerTy() && 1386 !Phi->getType()->isPointerTy()) { 1387 DEBUG(dbgs() << "LV: Found an non-int non-pointer PHI.\n"); 1388 return false; 1389 } 1390 1391 // If this PHINode is not in the header block, then we know that we 1392 // can convert it to select during if-conversion. No need to check if 1393 // the PHIs in this block are induction or reduction variables. 1394 if (*bb != Header) 1395 continue; 1396 1397 // This is the value coming from the preheader. 1398 Value *StartValue = Phi->getIncomingValueForBlock(PreHeader); 1399 // Check if this is an induction variable. 1400 InductionKind IK = isInductionVariable(Phi); 1401 1402 if (NoInduction != IK) { 1403 // Int inductions are special because we only allow one IV. 1404 if (IK == IntInduction) { 1405 if (Induction) { 1406 DEBUG(dbgs() << "LV: Found too many inductions."<< *Phi <<"\n"); 1407 return false; 1408 } 1409 Induction = Phi; 1410 } 1411 1412 DEBUG(dbgs() << "LV: Found an induction variable.\n"); 1413 Inductions[Phi] = InductionInfo(StartValue, IK); 1414 continue; 1415 } 1416 1417 if (AddReductionVar(Phi, IntegerAdd)) { 1418 DEBUG(dbgs() << "LV: Found an ADD reduction PHI."<< *Phi <<"\n"); 1419 continue; 1420 } 1421 if (AddReductionVar(Phi, IntegerMult)) { 1422 DEBUG(dbgs() << "LV: Found a MUL reduction PHI."<< *Phi <<"\n"); 1423 continue; 1424 } 1425 if (AddReductionVar(Phi, IntegerOr)) { 1426 DEBUG(dbgs() << "LV: Found an OR reduction PHI."<< *Phi <<"\n"); 1427 continue; 1428 } 1429 if (AddReductionVar(Phi, IntegerAnd)) { 1430 DEBUG(dbgs() << "LV: Found an AND reduction PHI."<< *Phi <<"\n"); 1431 continue; 1432 } 1433 if (AddReductionVar(Phi, IntegerXor)) { 1434 DEBUG(dbgs() << "LV: Found a XOR reduction PHI."<< *Phi <<"\n"); 1435 continue; 1436 } 1437 1438 DEBUG(dbgs() << "LV: Found an unidentified PHI."<< *Phi <<"\n"); 1439 return false; 1440 }// end of PHI handling 1441 1442 // We still don't handle functions. 1443 CallInst *CI = dyn_cast<CallInst>(it); 1444 if (CI && !isTriviallyVectorizableIntrinsic(it)) { 1445 DEBUG(dbgs() << "LV: Found a call site.\n"); 1446 return false; 1447 } 1448 1449 // We do not re-vectorize vectors. 1450 if (!VectorType::isValidElementType(it->getType()) && 1451 !it->getType()->isVoidTy()) { 1452 DEBUG(dbgs() << "LV: Found unvectorizable type." << "\n"); 1453 return false; 1454 } 1455 1456 // Reduction instructions are allowed to have exit users. 1457 // All other instructions must not have external users. 1458 if (!AllowedExit.count(it)) 1459 //Check that all of the users of the loop are inside the BB. 1460 for (Value::use_iterator I = it->use_begin(), E = it->use_end(); 1461 I != E; ++I) { 1462 Instruction *U = cast<Instruction>(*I); 1463 // This user may be a reduction exit value. 1464 if (!TheLoop->contains(U)) { 1465 DEBUG(dbgs() << "LV: Found an outside user for : "<< *U << "\n"); 1466 return false; 1467 } 1468 } 1469 } // next instr. 1470 1471 } 1472 1473 if (!Induction) { 1474 DEBUG(dbgs() << "LV: Did not find one integer induction var.\n"); 1475 assert(getInductionVars()->size() && "No induction variables"); 1476 } 1477 1478 return true; 1479} 1480 1481void LoopVectorizationLegality::collectLoopUniforms() { 1482 // We now know that the loop is vectorizable! 1483 // Collect variables that will remain uniform after vectorization. 1484 std::vector<Value*> Worklist; 1485 BasicBlock *Latch = TheLoop->getLoopLatch(); 1486 1487 // Start with the conditional branch and walk up the block. 1488 Worklist.push_back(Latch->getTerminator()->getOperand(0)); 1489 1490 while (Worklist.size()) { 1491 Instruction *I = dyn_cast<Instruction>(Worklist.back()); 1492 Worklist.pop_back(); 1493 1494 // Look at instructions inside this loop. 1495 // Stop when reaching PHI nodes. 1496 // TODO: we need to follow values all over the loop, not only in this block. 1497 if (!I || !TheLoop->contains(I) || isa<PHINode>(I)) 1498 continue; 1499 1500 // This is a known uniform. 1501 Uniforms.insert(I); 1502 1503 // Insert all operands. 1504 for (int i = 0, Op = I->getNumOperands(); i < Op; ++i) { 1505 Worklist.push_back(I->getOperand(i)); 1506 } 1507 } 1508} 1509 1510bool LoopVectorizationLegality::canVectorizeMemory() { 1511 typedef SmallVector<Value*, 16> ValueVector; 1512 typedef SmallPtrSet<Value*, 16> ValueSet; 1513 // Holds the Load and Store *instructions*. 1514 ValueVector Loads; 1515 ValueVector Stores; 1516 PtrRtCheck.Pointers.clear(); 1517 PtrRtCheck.Need = false; 1518 1519 // For each block. 1520 for (Loop::block_iterator bb = TheLoop->block_begin(), 1521 be = TheLoop->block_end(); bb != be; ++bb) { 1522 1523 // Scan the BB and collect legal loads and stores. 1524 for (BasicBlock::iterator it = (*bb)->begin(), e = (*bb)->end(); it != e; 1525 ++it) { 1526 1527 // If this is a load, save it. If this instruction can read from memory 1528 // but is not a load, then we quit. Notice that we don't handle function 1529 // calls that read or write. 1530 if (it->mayReadFromMemory()) { 1531 LoadInst *Ld = dyn_cast<LoadInst>(it); 1532 if (!Ld) return false; 1533 if (!Ld->isSimple()) { 1534 DEBUG(dbgs() << "LV: Found a non-simple load.\n"); 1535 return false; 1536 } 1537 Loads.push_back(Ld); 1538 continue; 1539 } 1540 1541 // Save 'store' instructions. Abort if other instructions write to memory. 1542 if (it->mayWriteToMemory()) { 1543 StoreInst *St = dyn_cast<StoreInst>(it); 1544 if (!St) return false; 1545 if (!St->isSimple()) { 1546 DEBUG(dbgs() << "LV: Found a non-simple store.\n"); 1547 return false; 1548 } 1549 Stores.push_back(St); 1550 } 1551 } // next instr. 1552 } // next block. 1553 1554 // Now we have two lists that hold the loads and the stores. 1555 // Next, we find the pointers that they use. 1556 1557 // Check if we see any stores. If there are no stores, then we don't 1558 // care if the pointers are *restrict*. 1559 if (!Stores.size()) { 1560 DEBUG(dbgs() << "LV: Found a read-only loop!\n"); 1561 return true; 1562 } 1563 1564 // Holds the read and read-write *pointers* that we find. 1565 ValueVector Reads; 1566 ValueVector ReadWrites; 1567 1568 // Holds the analyzed pointers. We don't want to call GetUnderlyingObjects 1569 // multiple times on the same object. If the ptr is accessed twice, once 1570 // for read and once for write, it will only appear once (on the write 1571 // list). This is okay, since we are going to check for conflicts between 1572 // writes and between reads and writes, but not between reads and reads. 1573 ValueSet Seen; 1574 1575 ValueVector::iterator I, IE; 1576 for (I = Stores.begin(), IE = Stores.end(); I != IE; ++I) { 1577 StoreInst *ST = dyn_cast<StoreInst>(*I); 1578 assert(ST && "Bad StoreInst"); 1579 Value* Ptr = ST->getPointerOperand(); 1580 1581 if (isUniform(Ptr)) { 1582 DEBUG(dbgs() << "LV: We don't allow storing to uniform addresses\n"); 1583 return false; 1584 } 1585 1586 // If we did *not* see this pointer before, insert it to 1587 // the read-write list. At this phase it is only a 'write' list. 1588 if (Seen.insert(Ptr)) 1589 ReadWrites.push_back(Ptr); 1590 } 1591 1592 for (I = Loads.begin(), IE = Loads.end(); I != IE; ++I) { 1593 LoadInst *LD = dyn_cast<LoadInst>(*I); 1594 assert(LD && "Bad LoadInst"); 1595 Value* Ptr = LD->getPointerOperand(); 1596 // If we did *not* see this pointer before, insert it to the 1597 // read list. If we *did* see it before, then it is already in 1598 // the read-write list. This allows us to vectorize expressions 1599 // such as A[i] += x; Because the address of A[i] is a read-write 1600 // pointer. This only works if the index of A[i] is consecutive. 1601 // If the address of i is unknown (for example A[B[i]]) then we may 1602 // read a few words, modify, and write a few words, and some of the 1603 // words may be written to the same address. 1604 if (Seen.insert(Ptr) || !isConsecutivePtr(Ptr)) 1605 Reads.push_back(Ptr); 1606 } 1607 1608 // If we write (or read-write) to a single destination and there are no 1609 // other reads in this loop then is it safe to vectorize. 1610 if (ReadWrites.size() == 1 && Reads.size() == 0) { 1611 DEBUG(dbgs() << "LV: Found a write-only loop!\n"); 1612 return true; 1613 } 1614 1615 // Find pointers with computable bounds. We are going to use this information 1616 // to place a runtime bound check. 1617 bool RT = true; 1618 for (I = ReadWrites.begin(), IE = ReadWrites.end(); I != IE; ++I) 1619 if (hasComputableBounds(*I)) { 1620 PtrRtCheck.insert(SE, TheLoop, *I); 1621 DEBUG(dbgs() << "LV: Found a runtime check ptr:" << **I <<"\n"); 1622 } else { 1623 RT = false; 1624 break; 1625 } 1626 for (I = Reads.begin(), IE = Reads.end(); I != IE; ++I) 1627 if (hasComputableBounds(*I)) { 1628 PtrRtCheck.insert(SE, TheLoop, *I); 1629 DEBUG(dbgs() << "LV: Found a runtime check ptr:" << **I <<"\n"); 1630 } else { 1631 RT = false; 1632 break; 1633 } 1634 1635 // Check that we did not collect too many pointers or found a 1636 // unsizeable pointer. 1637 if (!RT || PtrRtCheck.Pointers.size() > RuntimeMemoryCheckThreshold) { 1638 PtrRtCheck.reset(); 1639 RT = false; 1640 } 1641 1642 PtrRtCheck.Need = RT; 1643 1644 if (RT) { 1645 DEBUG(dbgs() << "LV: We can perform a memory runtime check if needed.\n"); 1646 } 1647 1648 // Now that the pointers are in two lists (Reads and ReadWrites), we 1649 // can check that there are no conflicts between each of the writes and 1650 // between the writes to the reads. 1651 ValueSet WriteObjects; 1652 ValueVector TempObjects; 1653 1654 // Check that the read-writes do not conflict with other read-write 1655 // pointers. 1656 for (I = ReadWrites.begin(), IE = ReadWrites.end(); I != IE; ++I) { 1657 GetUnderlyingObjects(*I, TempObjects, DL); 1658 for (ValueVector::iterator it=TempObjects.begin(), e=TempObjects.end(); 1659 it != e; ++it) { 1660 if (!isIdentifiedObject(*it)) { 1661 DEBUG(dbgs() << "LV: Found an unidentified write ptr:"<< **it <<"\n"); 1662 return RT; 1663 } 1664 if (!WriteObjects.insert(*it)) { 1665 DEBUG(dbgs() << "LV: Found a possible write-write reorder:" 1666 << **it <<"\n"); 1667 return RT; 1668 } 1669 } 1670 TempObjects.clear(); 1671 } 1672 1673 /// Check that the reads don't conflict with the read-writes. 1674 for (I = Reads.begin(), IE = Reads.end(); I != IE; ++I) { 1675 GetUnderlyingObjects(*I, TempObjects, DL); 1676 for (ValueVector::iterator it=TempObjects.begin(), e=TempObjects.end(); 1677 it != e; ++it) { 1678 if (!isIdentifiedObject(*it)) { 1679 DEBUG(dbgs() << "LV: Found an unidentified read ptr:"<< **it <<"\n"); 1680 return RT; 1681 } 1682 if (WriteObjects.count(*it)) { 1683 DEBUG(dbgs() << "LV: Found a possible read/write reorder:" 1684 << **it <<"\n"); 1685 return RT; 1686 } 1687 } 1688 TempObjects.clear(); 1689 } 1690 1691 // It is safe to vectorize and we don't need any runtime checks. 1692 DEBUG(dbgs() << "LV: We don't need a runtime memory check.\n"); 1693 PtrRtCheck.reset(); 1694 return true; 1695} 1696 1697bool LoopVectorizationLegality::AddReductionVar(PHINode *Phi, 1698 ReductionKind Kind) { 1699 if (Phi->getNumIncomingValues() != 2) 1700 return false; 1701 1702 // Reduction variables are only found in the loop header block. 1703 if (Phi->getParent() != TheLoop->getHeader()) 1704 return false; 1705 1706 // Obtain the reduction start value from the value that comes from the loop 1707 // preheader. 1708 Value *RdxStart = Phi->getIncomingValueForBlock(TheLoop->getLoopPreheader()); 1709 1710 // ExitInstruction is the single value which is used outside the loop. 1711 // We only allow for a single reduction value to be used outside the loop. 1712 // This includes users of the reduction, variables (which form a cycle 1713 // which ends in the phi node). 1714 Instruction *ExitInstruction = 0; 1715 1716 // Iter is our iterator. We start with the PHI node and scan for all of the 1717 // users of this instruction. All users must be instructions which can be 1718 // used as reduction variables (such as ADD). We may have a single 1719 // out-of-block user. They cycle must end with the original PHI. 1720 // Also, we can't have multiple block-local users. 1721 Instruction *Iter = Phi; 1722 while (true) { 1723 // If the instruction has no users then this is a broken 1724 // chain and can't be a reduction variable. 1725 if (Iter->use_empty()) 1726 return false; 1727 1728 // Any reduction instr must be of one of the allowed kinds. 1729 if (!isReductionInstr(Iter, Kind)) 1730 return false; 1731 1732 // Did we find a user inside this block ? 1733 bool FoundInBlockUser = false; 1734 // Did we reach the initial PHI node ? 1735 bool FoundStartPHI = false; 1736 1737 // For each of the *users* of iter. 1738 for (Value::use_iterator it = Iter->use_begin(), e = Iter->use_end(); 1739 it != e; ++it) { 1740 Instruction *U = cast<Instruction>(*it); 1741 // We already know that the PHI is a user. 1742 if (U == Phi) { 1743 FoundStartPHI = true; 1744 continue; 1745 } 1746 1747 // Check if we found the exit user. 1748 BasicBlock *Parent = U->getParent(); 1749 if (!TheLoop->contains(Parent)) { 1750 // Exit if you find multiple outside users. 1751 if (ExitInstruction != 0) 1752 return false; 1753 ExitInstruction = Iter; 1754 } 1755 1756 // We allow in-loop PHINodes which are not the original reduction PHI 1757 // node. If this PHI is the only user of Iter (happens in IF w/ no ELSE 1758 // structure) then don't skip this PHI. 1759 if (isa<PHINode>(U) && U->getParent() != TheLoop->getHeader() && 1760 TheLoop->contains(U) && Iter->getNumUses() > 1) 1761 continue; 1762 1763 // We can't have multiple inside users. 1764 if (FoundInBlockUser) 1765 return false; 1766 FoundInBlockUser = true; 1767 Iter = U; 1768 } 1769 1770 // We found a reduction var if we have reached the original 1771 // phi node and we only have a single instruction with out-of-loop 1772 // users. 1773 if (FoundStartPHI && ExitInstruction) { 1774 // This instruction is allowed to have out-of-loop users. 1775 AllowedExit.insert(ExitInstruction); 1776 1777 // Save the description of this reduction variable. 1778 ReductionDescriptor RD(RdxStart, ExitInstruction, Kind); 1779 Reductions[Phi] = RD; 1780 return true; 1781 } 1782 1783 // If we've reached the start PHI but did not find an outside user then 1784 // this is dead code. Abort. 1785 if (FoundStartPHI) 1786 return false; 1787 } 1788} 1789 1790bool 1791LoopVectorizationLegality::isReductionInstr(Instruction *I, 1792 ReductionKind Kind) { 1793 switch (I->getOpcode()) { 1794 default: 1795 return false; 1796 case Instruction::PHI: 1797 // possibly. 1798 return true; 1799 case Instruction::Add: 1800 case Instruction::Sub: 1801 return Kind == IntegerAdd; 1802 case Instruction::Mul: 1803 return Kind == IntegerMult; 1804 case Instruction::And: 1805 return Kind == IntegerAnd; 1806 case Instruction::Or: 1807 return Kind == IntegerOr; 1808 case Instruction::Xor: 1809 return Kind == IntegerXor; 1810 } 1811} 1812 1813LoopVectorizationLegality::InductionKind 1814LoopVectorizationLegality::isInductionVariable(PHINode *Phi) { 1815 Type *PhiTy = Phi->getType(); 1816 // We only handle integer and pointer inductions variables. 1817 if (!PhiTy->isIntegerTy() && !PhiTy->isPointerTy()) 1818 return NoInduction; 1819 1820 // Check that the PHI is consecutive and starts at zero. 1821 const SCEV *PhiScev = SE->getSCEV(Phi); 1822 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(PhiScev); 1823 if (!AR) { 1824 DEBUG(dbgs() << "LV: PHI is not a poly recurrence.\n"); 1825 return NoInduction; 1826 } 1827 const SCEV *Step = AR->getStepRecurrence(*SE); 1828 1829 // Integer inductions need to have a stride of one. 1830 if (PhiTy->isIntegerTy()) { 1831 if (Step->isOne()) 1832 return IntInduction; 1833 if (Step->isAllOnesValue()) 1834 return ReverseIntInduction; 1835 return NoInduction; 1836 } 1837 1838 // Calculate the pointer stride and check if it is consecutive. 1839 const SCEVConstant *C = dyn_cast<SCEVConstant>(Step); 1840 if (!C) 1841 return NoInduction; 1842 1843 assert(PhiTy->isPointerTy() && "The PHI must be a pointer"); 1844 uint64_t Size = DL->getTypeAllocSize(PhiTy->getPointerElementType()); 1845 if (C->getValue()->equalsInt(Size)) 1846 return PtrInduction; 1847 1848 return NoInduction; 1849} 1850 1851bool LoopVectorizationLegality::blockNeedsPredication(BasicBlock *BB) { 1852 assert(TheLoop->contains(BB) && "Unknown block used"); 1853 1854 // Blocks that do not dominate the latch need predication. 1855 BasicBlock* Latch = TheLoop->getLoopLatch(); 1856 return !DT->dominates(BB, Latch); 1857} 1858 1859bool LoopVectorizationLegality::blockCanBePredicated(BasicBlock *BB) { 1860 for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e; ++it) { 1861 // We don't predicate loads/stores at the moment. 1862 if (it->mayReadFromMemory() || it->mayWriteToMemory() || it->mayThrow()) 1863 return false; 1864 1865 // The isntructions below can trap. 1866 switch (it->getOpcode()) { 1867 default: continue; 1868 case Instruction::UDiv: 1869 case Instruction::SDiv: 1870 case Instruction::URem: 1871 case Instruction::SRem: 1872 return false; 1873 } 1874 } 1875 1876 return true; 1877} 1878 1879bool LoopVectorizationLegality::hasComputableBounds(Value *Ptr) { 1880 const SCEV *PhiScev = SE->getSCEV(Ptr); 1881 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(PhiScev); 1882 if (!AR) 1883 return false; 1884 1885 return AR->isAffine(); 1886} 1887 1888unsigned 1889LoopVectorizationCostModel::findBestVectorizationFactor(unsigned VF) { 1890 if (!VTTI) { 1891 DEBUG(dbgs() << "LV: No vector target information. Not vectorizing. \n"); 1892 return 1; 1893 } 1894 1895 float Cost = expectedCost(1); 1896 unsigned Width = 1; 1897 DEBUG(dbgs() << "LV: Scalar loop costs: "<< (int)Cost << ".\n"); 1898 for (unsigned i=2; i <= VF; i*=2) { 1899 // Notice that the vector loop needs to be executed less times, so 1900 // we need to divide the cost of the vector loops by the width of 1901 // the vector elements. 1902 float VectorCost = expectedCost(i) / (float)i; 1903 DEBUG(dbgs() << "LV: Vector loop of width "<< i << " costs: " << 1904 (int)VectorCost << ".\n"); 1905 if (VectorCost < Cost) { 1906 Cost = VectorCost; 1907 Width = i; 1908 } 1909 } 1910 1911 DEBUG(dbgs() << "LV: Selecting VF = : "<< Width << ".\n"); 1912 return Width; 1913} 1914 1915unsigned LoopVectorizationCostModel::expectedCost(unsigned VF) { 1916 unsigned Cost = 0; 1917 1918 // For each block. 1919 for (Loop::block_iterator bb = TheLoop->block_begin(), 1920 be = TheLoop->block_end(); bb != be; ++bb) { 1921 unsigned BlockCost = 0; 1922 BasicBlock *BB = *bb; 1923 1924 // For each instruction in the old loop. 1925 for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e; ++it) { 1926 unsigned C = getInstructionCost(it, VF); 1927 Cost += C; 1928 DEBUG(dbgs() << "LV: Found an estimated cost of "<< C <<" for VF " << 1929 VF << " For instruction: "<< *it << "\n"); 1930 } 1931 1932 // We assume that if-converted blocks have a 50% chance of being executed. 1933 // When the code is scalar then some of the blocks are avoided due to CF. 1934 // When the code is vectorized we execute all code paths. 1935 if (Legal->blockNeedsPredication(*bb) && VF == 1) 1936 BlockCost /= 2; 1937 1938 Cost += BlockCost; 1939 } 1940 1941 return Cost; 1942} 1943 1944unsigned 1945LoopVectorizationCostModel::getInstructionCost(Instruction *I, unsigned VF) { 1946 assert(VTTI && "Invalid vector target transformation info"); 1947 1948 // If we know that this instruction will remain uniform, check the cost of 1949 // the scalar version. 1950 if (Legal->isUniformAfterVectorization(I)) 1951 VF = 1; 1952 1953 Type *RetTy = I->getType(); 1954 Type *VectorTy = ToVectorTy(RetTy, VF); 1955 1956 // TODO: We need to estimate the cost of intrinsic calls. 1957 switch (I->getOpcode()) { 1958 case Instruction::GetElementPtr: 1959 // We mark this instruction as zero-cost because scalar GEPs are usually 1960 // lowered to the intruction addressing mode. At the moment we don't 1961 // generate vector geps. 1962 return 0; 1963 case Instruction::Br: { 1964 return VTTI->getCFInstrCost(I->getOpcode()); 1965 } 1966 case Instruction::PHI: 1967 //TODO: IF-converted IFs become selects. 1968 return 0; 1969 case Instruction::Add: 1970 case Instruction::FAdd: 1971 case Instruction::Sub: 1972 case Instruction::FSub: 1973 case Instruction::Mul: 1974 case Instruction::FMul: 1975 case Instruction::UDiv: 1976 case Instruction::SDiv: 1977 case Instruction::FDiv: 1978 case Instruction::URem: 1979 case Instruction::SRem: 1980 case Instruction::FRem: 1981 case Instruction::Shl: 1982 case Instruction::LShr: 1983 case Instruction::AShr: 1984 case Instruction::And: 1985 case Instruction::Or: 1986 case Instruction::Xor: 1987 return VTTI->getArithmeticInstrCost(I->getOpcode(), VectorTy); 1988 case Instruction::Select: { 1989 SelectInst *SI = cast<SelectInst>(I); 1990 const SCEV *CondSCEV = SE->getSCEV(SI->getCondition()); 1991 bool ScalarCond = (SE->isLoopInvariant(CondSCEV, TheLoop)); 1992 Type *CondTy = SI->getCondition()->getType(); 1993 if (ScalarCond) 1994 CondTy = VectorType::get(CondTy, VF); 1995 1996 return VTTI->getCmpSelInstrCost(I->getOpcode(), VectorTy, CondTy); 1997 } 1998 case Instruction::ICmp: 1999 case Instruction::FCmp: { 2000 Type *ValTy = I->getOperand(0)->getType(); 2001 VectorTy = ToVectorTy(ValTy, VF); 2002 return VTTI->getCmpSelInstrCost(I->getOpcode(), VectorTy); 2003 } 2004 case Instruction::Store: { 2005 StoreInst *SI = cast<StoreInst>(I); 2006 Type *ValTy = SI->getValueOperand()->getType(); 2007 VectorTy = ToVectorTy(ValTy, VF); 2008 2009 if (VF == 1) 2010 return VTTI->getMemoryOpCost(I->getOpcode(), ValTy, 2011 SI->getAlignment(), 2012 SI->getPointerAddressSpace()); 2013 2014 // Scalarized stores. 2015 if (!Legal->isConsecutivePtr(SI->getPointerOperand())) { 2016 unsigned Cost = 0; 2017 unsigned ExtCost = VTTI->getInstrCost(Instruction::ExtractElement, 2018 ValTy); 2019 // The cost of extracting from the value vector. 2020 Cost += VF * (ExtCost); 2021 // The cost of the scalar stores. 2022 Cost += VF * VTTI->getMemoryOpCost(I->getOpcode(), 2023 ValTy->getScalarType(), 2024 SI->getAlignment(), 2025 SI->getPointerAddressSpace()); 2026 return Cost; 2027 } 2028 2029 // Wide stores. 2030 return VTTI->getMemoryOpCost(I->getOpcode(), VectorTy, SI->getAlignment(), 2031 SI->getPointerAddressSpace()); 2032 } 2033 case Instruction::Load: { 2034 LoadInst *LI = cast<LoadInst>(I); 2035 2036 if (VF == 1) 2037 return VTTI->getMemoryOpCost(I->getOpcode(), RetTy, 2038 LI->getAlignment(), 2039 LI->getPointerAddressSpace()); 2040 2041 // Scalarized loads. 2042 if (!Legal->isConsecutivePtr(LI->getPointerOperand())) { 2043 unsigned Cost = 0; 2044 unsigned InCost = VTTI->getInstrCost(Instruction::InsertElement, RetTy); 2045 // The cost of inserting the loaded value into the result vector. 2046 Cost += VF * (InCost); 2047 // The cost of the scalar stores. 2048 Cost += VF * VTTI->getMemoryOpCost(I->getOpcode(), 2049 RetTy->getScalarType(), 2050 LI->getAlignment(), 2051 LI->getPointerAddressSpace()); 2052 return Cost; 2053 } 2054 2055 // Wide loads. 2056 return VTTI->getMemoryOpCost(I->getOpcode(), VectorTy, LI->getAlignment(), 2057 LI->getPointerAddressSpace()); 2058 } 2059 case Instruction::ZExt: 2060 case Instruction::SExt: 2061 case Instruction::FPToUI: 2062 case Instruction::FPToSI: 2063 case Instruction::FPExt: 2064 case Instruction::PtrToInt: 2065 case Instruction::IntToPtr: 2066 case Instruction::SIToFP: 2067 case Instruction::UIToFP: 2068 case Instruction::Trunc: 2069 case Instruction::FPTrunc: 2070 case Instruction::BitCast: { 2071 Type *SrcVecTy = ToVectorTy(I->getOperand(0)->getType(), VF); 2072 return VTTI->getCastInstrCost(I->getOpcode(), VectorTy, SrcVecTy); 2073 } 2074 case Instruction::Call: { 2075 assert(isTriviallyVectorizableIntrinsic(I)); 2076 IntrinsicInst *II = cast<IntrinsicInst>(I); 2077 Type *RetTy = ToVectorTy(II->getType(), VF); 2078 SmallVector<Type*, 4> Tys; 2079 for (unsigned i = 0, ie = II->getNumArgOperands(); i != ie; ++i) 2080 Tys.push_back(ToVectorTy(II->getArgOperand(i)->getType(), VF)); 2081 return VTTI->getIntrinsicInstrCost(II->getIntrinsicID(), RetTy, Tys); 2082 } 2083 default: { 2084 // We are scalarizing the instruction. Return the cost of the scalar 2085 // instruction, plus the cost of insert and extract into vector 2086 // elements, times the vector width. 2087 unsigned Cost = 0; 2088 2089 bool IsVoid = RetTy->isVoidTy(); 2090 2091 unsigned InsCost = (IsVoid ? 0 : 2092 VTTI->getInstrCost(Instruction::InsertElement, 2093 VectorTy)); 2094 2095 unsigned ExtCost = VTTI->getInstrCost(Instruction::ExtractElement, 2096 VectorTy); 2097 2098 // The cost of inserting the results plus extracting each one of the 2099 // operands. 2100 Cost += VF * (InsCost + ExtCost * I->getNumOperands()); 2101 2102 // The cost of executing VF copies of the scalar instruction. 2103 Cost += VF * VTTI->getInstrCost(I->getOpcode(), RetTy); 2104 return Cost; 2105 } 2106 }// end of switch. 2107} 2108 2109Type* LoopVectorizationCostModel::ToVectorTy(Type *Scalar, unsigned VF) { 2110 if (Scalar->isVoidTy() || VF == 1) 2111 return Scalar; 2112 return VectorType::get(Scalar, VF); 2113} 2114 2115char LoopVectorize::ID = 0; 2116static const char lv_name[] = "Loop Vectorization"; 2117INITIALIZE_PASS_BEGIN(LoopVectorize, LV_NAME, lv_name, false, false) 2118INITIALIZE_AG_DEPENDENCY(AliasAnalysis) 2119INITIALIZE_PASS_DEPENDENCY(ScalarEvolution) 2120INITIALIZE_PASS_DEPENDENCY(LoopSimplify) 2121INITIALIZE_PASS_END(LoopVectorize, LV_NAME, lv_name, false, false) 2122 2123namespace llvm { 2124 Pass *createLoopVectorizePass() { 2125 return new LoopVectorize(); 2126 } 2127} 2128 2129 2130