BBVectorize.cpp revision 35564dc3ae1c377abad425cb09928eaf676dcb3c
1//===- BBVectorize.cpp - A Basic-Block 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// 10// This file implements a basic-block vectorization pass. The algorithm was 11// inspired by that used by the Vienna MAP Vectorizor by Franchetti and Kral, 12// et al. It works by looking for chains of pairable operations and then 13// pairing them. 14// 15//===----------------------------------------------------------------------===// 16 17#define BBV_NAME "bb-vectorize" 18#define DEBUG_TYPE BBV_NAME 19#include "llvm/Constants.h" 20#include "llvm/DerivedTypes.h" 21#include "llvm/Function.h" 22#include "llvm/Instructions.h" 23#include "llvm/IntrinsicInst.h" 24#include "llvm/Intrinsics.h" 25#include "llvm/LLVMContext.h" 26#include "llvm/Pass.h" 27#include "llvm/Type.h" 28#include "llvm/ADT/DenseMap.h" 29#include "llvm/ADT/DenseSet.h" 30#include "llvm/ADT/SmallVector.h" 31#include "llvm/ADT/Statistic.h" 32#include "llvm/ADT/STLExtras.h" 33#include "llvm/ADT/StringExtras.h" 34#include "llvm/Analysis/AliasAnalysis.h" 35#include "llvm/Analysis/AliasSetTracker.h" 36#include "llvm/Analysis/ScalarEvolution.h" 37#include "llvm/Analysis/ScalarEvolutionExpressions.h" 38#include "llvm/Analysis/ValueTracking.h" 39#include "llvm/Support/CommandLine.h" 40#include "llvm/Support/Debug.h" 41#include "llvm/Support/raw_ostream.h" 42#include "llvm/Support/ValueHandle.h" 43#include "llvm/Target/TargetData.h" 44#include "llvm/Transforms/Vectorize.h" 45#include <algorithm> 46#include <map> 47using namespace llvm; 48 49static cl::opt<unsigned> 50ReqChainDepth("bb-vectorize-req-chain-depth", cl::init(6), cl::Hidden, 51 cl::desc("The required chain depth for vectorization")); 52 53static cl::opt<unsigned> 54SearchLimit("bb-vectorize-search-limit", cl::init(400), cl::Hidden, 55 cl::desc("The maximum search distance for instruction pairs")); 56 57static cl::opt<bool> 58SplatBreaksChain("bb-vectorize-splat-breaks-chain", cl::init(false), cl::Hidden, 59 cl::desc("Replicating one element to a pair breaks the chain")); 60 61static cl::opt<unsigned> 62VectorBits("bb-vectorize-vector-bits", cl::init(128), cl::Hidden, 63 cl::desc("The size of the native vector registers")); 64 65static cl::opt<unsigned> 66MaxIter("bb-vectorize-max-iter", cl::init(0), cl::Hidden, 67 cl::desc("The maximum number of pairing iterations")); 68 69static cl::opt<unsigned> 70MaxInsts("bb-vectorize-max-instr-per-group", cl::init(500), cl::Hidden, 71 cl::desc("The maximum number of pairable instructions per group")); 72 73static cl::opt<unsigned> 74MaxCandPairsForCycleCheck("bb-vectorize-max-cycle-check-pairs", cl::init(200), 75 cl::Hidden, cl::desc("The maximum number of candidate pairs with which to use" 76 " a full cycle check")); 77 78static cl::opt<bool> 79NoInts("bb-vectorize-no-ints", cl::init(false), cl::Hidden, 80 cl::desc("Don't try to vectorize integer values")); 81 82static cl::opt<bool> 83NoFloats("bb-vectorize-no-floats", cl::init(false), cl::Hidden, 84 cl::desc("Don't try to vectorize floating-point values")); 85 86static cl::opt<bool> 87NoCasts("bb-vectorize-no-casts", cl::init(false), cl::Hidden, 88 cl::desc("Don't try to vectorize casting (conversion) operations")); 89 90static cl::opt<bool> 91NoMath("bb-vectorize-no-math", cl::init(false), cl::Hidden, 92 cl::desc("Don't try to vectorize floating-point math intrinsics")); 93 94static cl::opt<bool> 95NoFMA("bb-vectorize-no-fma", cl::init(false), cl::Hidden, 96 cl::desc("Don't try to vectorize the fused-multiply-add intrinsic")); 97 98static cl::opt<bool> 99NoMemOps("bb-vectorize-no-mem-ops", cl::init(false), cl::Hidden, 100 cl::desc("Don't try to vectorize loads and stores")); 101 102static cl::opt<bool> 103AlignedOnly("bb-vectorize-aligned-only", cl::init(false), cl::Hidden, 104 cl::desc("Only generate aligned loads and stores")); 105 106static cl::opt<bool> 107FastDep("bb-vectorize-fast-dep", cl::init(false), cl::Hidden, 108 cl::desc("Use a fast instruction dependency analysis")); 109 110#ifndef NDEBUG 111static cl::opt<bool> 112DebugInstructionExamination("bb-vectorize-debug-instruction-examination", 113 cl::init(false), cl::Hidden, 114 cl::desc("When debugging is enabled, output information on the" 115 " instruction-examination process")); 116static cl::opt<bool> 117DebugCandidateSelection("bb-vectorize-debug-candidate-selection", 118 cl::init(false), cl::Hidden, 119 cl::desc("When debugging is enabled, output information on the" 120 " candidate-selection process")); 121static cl::opt<bool> 122DebugPairSelection("bb-vectorize-debug-pair-selection", 123 cl::init(false), cl::Hidden, 124 cl::desc("When debugging is enabled, output information on the" 125 " pair-selection process")); 126static cl::opt<bool> 127DebugCycleCheck("bb-vectorize-debug-cycle-check", 128 cl::init(false), cl::Hidden, 129 cl::desc("When debugging is enabled, output information on the" 130 " cycle-checking process")); 131#endif 132 133STATISTIC(NumFusedOps, "Number of operations fused by bb-vectorize"); 134 135namespace { 136 struct BBVectorize : public BasicBlockPass { 137 static char ID; // Pass identification, replacement for typeid 138 BBVectorize() : BasicBlockPass(ID) { 139 initializeBBVectorizePass(*PassRegistry::getPassRegistry()); 140 } 141 142 typedef std::pair<Value *, Value *> ValuePair; 143 typedef std::pair<ValuePair, size_t> ValuePairWithDepth; 144 typedef std::pair<ValuePair, ValuePair> VPPair; // A ValuePair pair 145 typedef std::pair<std::multimap<Value *, Value *>::iterator, 146 std::multimap<Value *, Value *>::iterator> VPIteratorPair; 147 typedef std::pair<std::multimap<ValuePair, ValuePair>::iterator, 148 std::multimap<ValuePair, ValuePair>::iterator> 149 VPPIteratorPair; 150 151 AliasAnalysis *AA; 152 ScalarEvolution *SE; 153 TargetData *TD; 154 155 // FIXME: const correct? 156 157 bool vectorizePairs(BasicBlock &BB); 158 159 bool getCandidatePairs(BasicBlock &BB, 160 BasicBlock::iterator &Start, 161 std::multimap<Value *, Value *> &CandidatePairs, 162 std::vector<Value *> &PairableInsts); 163 164 void computeConnectedPairs(std::multimap<Value *, Value *> &CandidatePairs, 165 std::vector<Value *> &PairableInsts, 166 std::multimap<ValuePair, ValuePair> &ConnectedPairs); 167 168 void buildDepMap(BasicBlock &BB, 169 std::multimap<Value *, Value *> &CandidatePairs, 170 std::vector<Value *> &PairableInsts, 171 DenseSet<ValuePair> &PairableInstUsers); 172 173 void choosePairs(std::multimap<Value *, Value *> &CandidatePairs, 174 std::vector<Value *> &PairableInsts, 175 std::multimap<ValuePair, ValuePair> &ConnectedPairs, 176 DenseSet<ValuePair> &PairableInstUsers, 177 DenseMap<Value *, Value *>& ChosenPairs); 178 179 void fuseChosenPairs(BasicBlock &BB, 180 std::vector<Value *> &PairableInsts, 181 DenseMap<Value *, Value *>& ChosenPairs); 182 183 bool isInstVectorizable(Instruction *I, bool &IsSimpleLoadStore); 184 185 bool areInstsCompatible(Instruction *I, Instruction *J, 186 bool IsSimpleLoadStore); 187 188 bool trackUsesOfI(DenseSet<Value *> &Users, 189 AliasSetTracker &WriteSet, Instruction *I, 190 Instruction *J, bool UpdateUsers = true, 191 std::multimap<Value *, Value *> *LoadMoveSet = 0); 192 193 void computePairsConnectedTo( 194 std::multimap<Value *, Value *> &CandidatePairs, 195 std::vector<Value *> &PairableInsts, 196 std::multimap<ValuePair, ValuePair> &ConnectedPairs, 197 ValuePair P); 198 199 bool pairsConflict(ValuePair P, ValuePair Q, 200 DenseSet<ValuePair> &PairableInstUsers, 201 std::multimap<ValuePair, ValuePair> *PairableInstUserMap = 0); 202 203 bool pairWillFormCycle(ValuePair P, 204 std::multimap<ValuePair, ValuePair> &PairableInstUsers, 205 DenseSet<ValuePair> &CurrentPairs); 206 207 void pruneTreeFor( 208 std::multimap<Value *, Value *> &CandidatePairs, 209 std::vector<Value *> &PairableInsts, 210 std::multimap<ValuePair, ValuePair> &ConnectedPairs, 211 DenseSet<ValuePair> &PairableInstUsers, 212 std::multimap<ValuePair, ValuePair> &PairableInstUserMap, 213 DenseMap<Value *, Value *> &ChosenPairs, 214 DenseMap<ValuePair, size_t> &Tree, 215 DenseSet<ValuePair> &PrunedTree, ValuePair J, 216 bool UseCycleCheck); 217 218 void buildInitialTreeFor( 219 std::multimap<Value *, Value *> &CandidatePairs, 220 std::vector<Value *> &PairableInsts, 221 std::multimap<ValuePair, ValuePair> &ConnectedPairs, 222 DenseSet<ValuePair> &PairableInstUsers, 223 DenseMap<Value *, Value *> &ChosenPairs, 224 DenseMap<ValuePair, size_t> &Tree, ValuePair J); 225 226 void findBestTreeFor( 227 std::multimap<Value *, Value *> &CandidatePairs, 228 std::vector<Value *> &PairableInsts, 229 std::multimap<ValuePair, ValuePair> &ConnectedPairs, 230 DenseSet<ValuePair> &PairableInstUsers, 231 std::multimap<ValuePair, ValuePair> &PairableInstUserMap, 232 DenseMap<Value *, Value *> &ChosenPairs, 233 DenseSet<ValuePair> &BestTree, size_t &BestMaxDepth, 234 size_t &BestEffSize, VPIteratorPair ChoiceRange, 235 bool UseCycleCheck); 236 237 Value *getReplacementPointerInput(LLVMContext& Context, Instruction *I, 238 Instruction *J, unsigned o, bool &FlipMemInputs); 239 240 void fillNewShuffleMask(LLVMContext& Context, Instruction *J, 241 unsigned NumElem, unsigned MaskOffset, unsigned NumInElem, 242 unsigned IdxOffset, std::vector<Constant*> &Mask); 243 244 Value *getReplacementShuffleMask(LLVMContext& Context, Instruction *I, 245 Instruction *J); 246 247 Value *getReplacementInput(LLVMContext& Context, Instruction *I, 248 Instruction *J, unsigned o, bool FlipMemInputs); 249 250 void getReplacementInputsForPair(LLVMContext& Context, Instruction *I, 251 Instruction *J, SmallVector<Value *, 3> &ReplacedOperands, 252 bool &FlipMemInputs); 253 254 void replaceOutputsOfPair(LLVMContext& Context, Instruction *I, 255 Instruction *J, Instruction *K, 256 Instruction *&InsertionPt, Instruction *&K1, 257 Instruction *&K2, bool &FlipMemInputs); 258 259 void collectPairLoadMoveSet(BasicBlock &BB, 260 DenseMap<Value *, Value *> &ChosenPairs, 261 std::multimap<Value *, Value *> &LoadMoveSet, 262 Instruction *I); 263 264 void collectLoadMoveSet(BasicBlock &BB, 265 std::vector<Value *> &PairableInsts, 266 DenseMap<Value *, Value *> &ChosenPairs, 267 std::multimap<Value *, Value *> &LoadMoveSet); 268 269 bool canMoveUsesOfIAfterJ(BasicBlock &BB, 270 std::multimap<Value *, Value *> &LoadMoveSet, 271 Instruction *I, Instruction *J); 272 273 void moveUsesOfIAfterJ(BasicBlock &BB, 274 std::multimap<Value *, Value *> &LoadMoveSet, 275 Instruction *&InsertionPt, 276 Instruction *I, Instruction *J); 277 278 virtual bool runOnBasicBlock(BasicBlock &BB) { 279 AA = &getAnalysis<AliasAnalysis>(); 280 SE = &getAnalysis<ScalarEvolution>(); 281 TD = getAnalysisIfAvailable<TargetData>(); 282 283 bool changed = false; 284 // Iterate a sufficient number of times to merge types of size 1 bit, 285 // then 2 bits, then 4, etc. up to half of the target vector width of the 286 // target vector register. 287 for (unsigned v = 2, n = 1; v <= VectorBits && (!MaxIter || n <= MaxIter); 288 v *= 2, ++n) { 289 DEBUG(dbgs() << "BBV: fusing loop #" << n << 290 " for " << BB.getName() << " in " << 291 BB.getParent()->getName() << "...\n"); 292 if (vectorizePairs(BB)) 293 changed = true; 294 else 295 break; 296 } 297 298 DEBUG(dbgs() << "BBV: done!\n"); 299 return changed; 300 } 301 302 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 303 BasicBlockPass::getAnalysisUsage(AU); 304 AU.addRequired<AliasAnalysis>(); 305 AU.addRequired<ScalarEvolution>(); 306 AU.addPreserved<AliasAnalysis>(); 307 AU.addPreserved<ScalarEvolution>(); 308 AU.setPreservesCFG(); 309 } 310 311 // This returns the vector type that holds a pair of the provided type. 312 // If the provided type is already a vector, then its length is doubled. 313 static inline VectorType *getVecTypeForPair(Type *ElemTy) { 314 if (VectorType *VTy = dyn_cast<VectorType>(ElemTy)) { 315 unsigned numElem = VTy->getNumElements(); 316 return VectorType::get(ElemTy->getScalarType(), numElem*2); 317 } 318 319 return VectorType::get(ElemTy, 2); 320 } 321 322 // Returns the weight associated with the provided value. A chain of 323 // candidate pairs has a length given by the sum of the weights of its 324 // members (one weight per pair; the weight of each member of the pair 325 // is assumed to be the same). This length is then compared to the 326 // chain-length threshold to determine if a given chain is significant 327 // enough to be vectorized. The length is also used in comparing 328 // candidate chains where longer chains are considered to be better. 329 // Note: when this function returns 0, the resulting instructions are 330 // not actually fused. 331 static inline size_t getDepthFactor(Value *V) { 332 // InsertElement and ExtractElement have a depth factor of zero. This is 333 // for two reasons: First, they cannot be usefully fused. Second, because 334 // the pass generates a lot of these, they can confuse the simple metric 335 // used to compare the trees in the next iteration. Thus, giving them a 336 // weight of zero allows the pass to essentially ignore them in 337 // subsequent iterations when looking for vectorization opportunities 338 // while still tracking dependency chains that flow through those 339 // instructions. 340 if (isa<InsertElementInst>(V) || isa<ExtractElementInst>(V)) 341 return 0; 342 343 return 1; 344 } 345 346 // This determines the relative offset of two loads or stores, returning 347 // true if the offset could be determined to be some constant value. 348 // For example, if OffsetInElmts == 1, then J accesses the memory directly 349 // after I; if OffsetInElmts == -1 then I accesses the memory 350 // directly after J. This function assumes that both instructions 351 // have the same type. 352 bool getPairPtrInfo(Instruction *I, Instruction *J, 353 Value *&IPtr, Value *&JPtr, unsigned &IAlignment, unsigned &JAlignment, 354 int64_t &OffsetInElmts) { 355 OffsetInElmts = 0; 356 if (isa<LoadInst>(I)) { 357 IPtr = cast<LoadInst>(I)->getPointerOperand(); 358 JPtr = cast<LoadInst>(J)->getPointerOperand(); 359 IAlignment = cast<LoadInst>(I)->getAlignment(); 360 JAlignment = cast<LoadInst>(J)->getAlignment(); 361 } else { 362 IPtr = cast<StoreInst>(I)->getPointerOperand(); 363 JPtr = cast<StoreInst>(J)->getPointerOperand(); 364 IAlignment = cast<StoreInst>(I)->getAlignment(); 365 JAlignment = cast<StoreInst>(J)->getAlignment(); 366 } 367 368 const SCEV *IPtrSCEV = SE->getSCEV(IPtr); 369 const SCEV *JPtrSCEV = SE->getSCEV(JPtr); 370 371 // If this is a trivial offset, then we'll get something like 372 // 1*sizeof(type). With target data, which we need anyway, this will get 373 // constant folded into a number. 374 const SCEV *OffsetSCEV = SE->getMinusSCEV(JPtrSCEV, IPtrSCEV); 375 if (const SCEVConstant *ConstOffSCEV = 376 dyn_cast<SCEVConstant>(OffsetSCEV)) { 377 ConstantInt *IntOff = ConstOffSCEV->getValue(); 378 int64_t Offset = IntOff->getSExtValue(); 379 380 Type *VTy = cast<PointerType>(IPtr->getType())->getElementType(); 381 int64_t VTyTSS = (int64_t) TD->getTypeStoreSize(VTy); 382 383 assert(VTy == cast<PointerType>(JPtr->getType())->getElementType()); 384 385 OffsetInElmts = Offset/VTyTSS; 386 return (abs64(Offset) % VTyTSS) == 0; 387 } 388 389 return false; 390 } 391 392 // Returns true if the provided CallInst represents an intrinsic that can 393 // be vectorized. 394 bool isVectorizableIntrinsic(CallInst* I) { 395 Function *F = I->getCalledFunction(); 396 if (!F) return false; 397 398 unsigned IID = F->getIntrinsicID(); 399 if (!IID) return false; 400 401 switch(IID) { 402 default: 403 return false; 404 case Intrinsic::sqrt: 405 case Intrinsic::powi: 406 case Intrinsic::sin: 407 case Intrinsic::cos: 408 case Intrinsic::log: 409 case Intrinsic::log2: 410 case Intrinsic::log10: 411 case Intrinsic::exp: 412 case Intrinsic::exp2: 413 case Intrinsic::pow: 414 return !NoMath; 415 case Intrinsic::fma: 416 return !NoFMA; 417 } 418 } 419 420 // Returns true if J is the second element in some pair referenced by 421 // some multimap pair iterator pair. 422 template <typename V> 423 bool isSecondInIteratorPair(V J, std::pair< 424 typename std::multimap<V, V>::iterator, 425 typename std::multimap<V, V>::iterator> PairRange) { 426 for (typename std::multimap<V, V>::iterator K = PairRange.first; 427 K != PairRange.second; ++K) 428 if (K->second == J) return true; 429 430 return false; 431 } 432 }; 433 434 // This function implements one vectorization iteration on the provided 435 // basic block. It returns true if the block is changed. 436 bool BBVectorize::vectorizePairs(BasicBlock &BB) { 437 bool ShouldContinue; 438 BasicBlock::iterator Start = BB.getFirstInsertionPt(); 439 440 std::vector<Value *> AllPairableInsts; 441 DenseMap<Value *, Value *> AllChosenPairs; 442 443 do { 444 std::vector<Value *> PairableInsts; 445 std::multimap<Value *, Value *> CandidatePairs; 446 ShouldContinue = getCandidatePairs(BB, Start, CandidatePairs, 447 PairableInsts); 448 if (PairableInsts.empty()) continue; 449 450 // Now we have a map of all of the pairable instructions and we need to 451 // select the best possible pairing. A good pairing is one such that the 452 // users of the pair are also paired. This defines a (directed) forest 453 // over the pairs such that two pairs are connected iff the second pair 454 // uses the first. 455 456 // Note that it only matters that both members of the second pair use some 457 // element of the first pair (to allow for splatting). 458 459 std::multimap<ValuePair, ValuePair> ConnectedPairs; 460 computeConnectedPairs(CandidatePairs, PairableInsts, ConnectedPairs); 461 if (ConnectedPairs.empty()) continue; 462 463 // Build the pairable-instruction dependency map 464 DenseSet<ValuePair> PairableInstUsers; 465 buildDepMap(BB, CandidatePairs, PairableInsts, PairableInstUsers); 466 467 // There is now a graph of the connected pairs. For each variable, pick 468 // the pairing with the largest tree meeting the depth requirement on at 469 // least one branch. Then select all pairings that are part of that tree 470 // and remove them from the list of available pairings and pairable 471 // variables. 472 473 DenseMap<Value *, Value *> ChosenPairs; 474 choosePairs(CandidatePairs, PairableInsts, ConnectedPairs, 475 PairableInstUsers, ChosenPairs); 476 477 if (ChosenPairs.empty()) continue; 478 AllPairableInsts.insert(AllPairableInsts.end(), PairableInsts.begin(), 479 PairableInsts.end()); 480 AllChosenPairs.insert(ChosenPairs.begin(), ChosenPairs.end()); 481 } while (ShouldContinue); 482 483 if (AllChosenPairs.empty()) return false; 484 NumFusedOps += AllChosenPairs.size(); 485 486 // A set of pairs has now been selected. It is now necessary to replace the 487 // paired instructions with vector instructions. For this procedure each 488 // operand much be replaced with a vector operand. This vector is formed 489 // by using build_vector on the old operands. The replaced values are then 490 // replaced with a vector_extract on the result. Subsequent optimization 491 // passes should coalesce the build/extract combinations. 492 493 fuseChosenPairs(BB, AllPairableInsts, AllChosenPairs); 494 return true; 495 } 496 497 // This function returns true if the provided instruction is capable of being 498 // fused into a vector instruction. This determination is based only on the 499 // type and other attributes of the instruction. 500 bool BBVectorize::isInstVectorizable(Instruction *I, 501 bool &IsSimpleLoadStore) { 502 IsSimpleLoadStore = false; 503 504 if (CallInst *C = dyn_cast<CallInst>(I)) { 505 if (!isVectorizableIntrinsic(C)) 506 return false; 507 } else if (LoadInst *L = dyn_cast<LoadInst>(I)) { 508 // Vectorize simple loads if possbile: 509 IsSimpleLoadStore = L->isSimple(); 510 if (!IsSimpleLoadStore || NoMemOps) 511 return false; 512 } else if (StoreInst *S = dyn_cast<StoreInst>(I)) { 513 // Vectorize simple stores if possbile: 514 IsSimpleLoadStore = S->isSimple(); 515 if (!IsSimpleLoadStore || NoMemOps) 516 return false; 517 } else if (CastInst *C = dyn_cast<CastInst>(I)) { 518 // We can vectorize casts, but not casts of pointer types, etc. 519 if (NoCasts) 520 return false; 521 522 Type *SrcTy = C->getSrcTy(); 523 if (!SrcTy->isSingleValueType() || SrcTy->isPointerTy()) 524 return false; 525 526 Type *DestTy = C->getDestTy(); 527 if (!DestTy->isSingleValueType() || DestTy->isPointerTy()) 528 return false; 529 } else if (!(I->isBinaryOp() || isa<ShuffleVectorInst>(I) || 530 isa<ExtractElementInst>(I) || isa<InsertElementInst>(I))) { 531 return false; 532 } 533 534 // We can't vectorize memory operations without target data 535 if (TD == 0 && IsSimpleLoadStore) 536 return false; 537 538 Type *T1, *T2; 539 if (isa<StoreInst>(I)) { 540 // For stores, it is the value type, not the pointer type that matters 541 // because the value is what will come from a vector register. 542 543 Value *IVal = cast<StoreInst>(I)->getValueOperand(); 544 T1 = IVal->getType(); 545 } else { 546 T1 = I->getType(); 547 } 548 549 if (I->isCast()) 550 T2 = cast<CastInst>(I)->getSrcTy(); 551 else 552 T2 = T1; 553 554 // Not every type can be vectorized... 555 if (!(VectorType::isValidElementType(T1) || T1->isVectorTy()) || 556 !(VectorType::isValidElementType(T2) || T2->isVectorTy())) 557 return false; 558 559 if (NoInts && (T1->isIntOrIntVectorTy() || T2->isIntOrIntVectorTy())) 560 return false; 561 562 if (NoFloats && (T1->isFPOrFPVectorTy() || T2->isFPOrFPVectorTy())) 563 return false; 564 565 if (T1->getPrimitiveSizeInBits() > VectorBits/2 || 566 T2->getPrimitiveSizeInBits() > VectorBits/2) 567 return false; 568 569 return true; 570 } 571 572 // This function returns true if the two provided instructions are compatible 573 // (meaning that they can be fused into a vector instruction). This assumes 574 // that I has already been determined to be vectorizable and that J is not 575 // in the use tree of I. 576 bool BBVectorize::areInstsCompatible(Instruction *I, Instruction *J, 577 bool IsSimpleLoadStore) { 578 DEBUG(if (DebugInstructionExamination) dbgs() << "BBV: looking at " << *I << 579 " <-> " << *J << "\n"); 580 581 // Loads and stores can be merged if they have different alignments, 582 // but are otherwise the same. 583 LoadInst *LI, *LJ; 584 StoreInst *SI, *SJ; 585 if ((LI = dyn_cast<LoadInst>(I)) && (LJ = dyn_cast<LoadInst>(J))) { 586 if (I->getType() != J->getType()) 587 return false; 588 589 if (LI->getPointerOperand()->getType() != 590 LJ->getPointerOperand()->getType() || 591 LI->isVolatile() != LJ->isVolatile() || 592 LI->getOrdering() != LJ->getOrdering() || 593 LI->getSynchScope() != LJ->getSynchScope()) 594 return false; 595 } else if ((SI = dyn_cast<StoreInst>(I)) && (SJ = dyn_cast<StoreInst>(J))) { 596 if (SI->getValueOperand()->getType() != 597 SJ->getValueOperand()->getType() || 598 SI->getPointerOperand()->getType() != 599 SJ->getPointerOperand()->getType() || 600 SI->isVolatile() != SJ->isVolatile() || 601 SI->getOrdering() != SJ->getOrdering() || 602 SI->getSynchScope() != SJ->getSynchScope()) 603 return false; 604 } else if (!J->isSameOperationAs(I)) { 605 return false; 606 } 607 // FIXME: handle addsub-type operations! 608 609 if (IsSimpleLoadStore) { 610 Value *IPtr, *JPtr; 611 unsigned IAlignment, JAlignment; 612 int64_t OffsetInElmts = 0; 613 if (getPairPtrInfo(I, J, IPtr, JPtr, IAlignment, JAlignment, 614 OffsetInElmts) && abs64(OffsetInElmts) == 1) { 615 if (AlignedOnly) { 616 Type *aType = isa<StoreInst>(I) ? 617 cast<StoreInst>(I)->getValueOperand()->getType() : I->getType(); 618 // An aligned load or store is possible only if the instruction 619 // with the lower offset has an alignment suitable for the 620 // vector type. 621 622 unsigned BottomAlignment = IAlignment; 623 if (OffsetInElmts < 0) BottomAlignment = JAlignment; 624 625 Type *VType = getVecTypeForPair(aType); 626 unsigned VecAlignment = TD->getPrefTypeAlignment(VType); 627 if (BottomAlignment < VecAlignment) 628 return false; 629 } 630 } else { 631 return false; 632 } 633 } else if (isa<ShuffleVectorInst>(I)) { 634 // Only merge two shuffles if they're both constant 635 return isa<Constant>(I->getOperand(2)) && 636 isa<Constant>(J->getOperand(2)); 637 // FIXME: We may want to vectorize non-constant shuffles also. 638 } 639 640 return true; 641 } 642 643 // Figure out whether or not J uses I and update the users and write-set 644 // structures associated with I. Specifically, Users represents the set of 645 // instructions that depend on I. WriteSet represents the set 646 // of memory locations that are dependent on I. If UpdateUsers is true, 647 // and J uses I, then Users is updated to contain J and WriteSet is updated 648 // to contain any memory locations to which J writes. The function returns 649 // true if J uses I. By default, alias analysis is used to determine 650 // whether J reads from memory that overlaps with a location in WriteSet. 651 // If LoadMoveSet is not null, then it is a previously-computed multimap 652 // where the key is the memory-based user instruction and the value is 653 // the instruction to be compared with I. So, if LoadMoveSet is provided, 654 // then the alias analysis is not used. This is necessary because this 655 // function is called during the process of moving instructions during 656 // vectorization and the results of the alias analysis are not stable during 657 // that process. 658 bool BBVectorize::trackUsesOfI(DenseSet<Value *> &Users, 659 AliasSetTracker &WriteSet, Instruction *I, 660 Instruction *J, bool UpdateUsers, 661 std::multimap<Value *, Value *> *LoadMoveSet) { 662 bool UsesI = false; 663 664 // This instruction may already be marked as a user due, for example, to 665 // being a member of a selected pair. 666 if (Users.count(J)) 667 UsesI = true; 668 669 if (!UsesI) 670 for (User::op_iterator JU = J->op_begin(), JE = J->op_end(); 671 JU != JE; ++JU) { 672 Value *V = *JU; 673 if (I == V || Users.count(V)) { 674 UsesI = true; 675 break; 676 } 677 } 678 if (!UsesI && J->mayReadFromMemory()) { 679 if (LoadMoveSet) { 680 VPIteratorPair JPairRange = LoadMoveSet->equal_range(J); 681 UsesI = isSecondInIteratorPair<Value*>(I, JPairRange); 682 } else { 683 for (AliasSetTracker::iterator W = WriteSet.begin(), 684 WE = WriteSet.end(); W != WE; ++W) { 685 for (AliasSet::iterator A = W->begin(), AE = W->end(); 686 A != AE; ++A) { 687 AliasAnalysis::Location ptrLoc(A->getValue(), A->getSize(), 688 A->getTBAAInfo()); 689 if (AA->getModRefInfo(J, ptrLoc) != AliasAnalysis::NoModRef) { 690 UsesI = true; 691 break; 692 } 693 } 694 if (UsesI) break; 695 } 696 } 697 } 698 699 if (UsesI && UpdateUsers) { 700 if (J->mayWriteToMemory()) WriteSet.add(J); 701 Users.insert(J); 702 } 703 704 return UsesI; 705 } 706 707 // This function iterates over all instruction pairs in the provided 708 // basic block and collects all candidate pairs for vectorization. 709 bool BBVectorize::getCandidatePairs(BasicBlock &BB, 710 BasicBlock::iterator &Start, 711 std::multimap<Value *, Value *> &CandidatePairs, 712 std::vector<Value *> &PairableInsts) { 713 BasicBlock::iterator E = BB.end(); 714 if (Start == E) return false; 715 716 bool ShouldContinue = false, IAfterStart = false; 717 for (BasicBlock::iterator I = Start++; I != E; ++I) { 718 if (I == Start) IAfterStart = true; 719 720 bool IsSimpleLoadStore; 721 if (!isInstVectorizable(I, IsSimpleLoadStore)) continue; 722 723 // Look for an instruction with which to pair instruction *I... 724 DenseSet<Value *> Users; 725 AliasSetTracker WriteSet(*AA); 726 bool JAfterStart = IAfterStart; 727 BasicBlock::iterator J = llvm::next(I); 728 for (unsigned ss = 0; J != E && ss <= SearchLimit; ++J, ++ss) { 729 if (J == Start) JAfterStart = true; 730 731 // Determine if J uses I, if so, exit the loop. 732 bool UsesI = trackUsesOfI(Users, WriteSet, I, J, !FastDep); 733 if (FastDep) { 734 // Note: For this heuristic to be effective, independent operations 735 // must tend to be intermixed. This is likely to be true from some 736 // kinds of grouped loop unrolling (but not the generic LLVM pass), 737 // but otherwise may require some kind of reordering pass. 738 739 // When using fast dependency analysis, 740 // stop searching after first use: 741 if (UsesI) break; 742 } else { 743 if (UsesI) continue; 744 } 745 746 // J does not use I, and comes before the first use of I, so it can be 747 // merged with I if the instructions are compatible. 748 if (!areInstsCompatible(I, J, IsSimpleLoadStore)) continue; 749 750 // J is a candidate for merging with I. 751 if (!PairableInsts.size() || 752 PairableInsts[PairableInsts.size()-1] != I) { 753 PairableInsts.push_back(I); 754 } 755 756 CandidatePairs.insert(ValuePair(I, J)); 757 758 // The next call to this function must start after the last instruction 759 // selected during this invocation. 760 if (JAfterStart) { 761 Start = llvm::next(J); 762 IAfterStart = JAfterStart = false; 763 } 764 765 DEBUG(if (DebugCandidateSelection) dbgs() << "BBV: candidate pair " 766 << *I << " <-> " << *J << "\n"); 767 768 // If we have already found too many pairs, break here and this function 769 // will be called again starting after the last instruction selected 770 // during this invocation. 771 if (PairableInsts.size() >= MaxInsts) { 772 ShouldContinue = true; 773 break; 774 } 775 } 776 777 if (ShouldContinue) 778 break; 779 } 780 781 DEBUG(dbgs() << "BBV: found " << PairableInsts.size() 782 << " instructions with candidate pairs\n"); 783 784 return ShouldContinue; 785 } 786 787 // Finds candidate pairs connected to the pair P = <PI, PJ>. This means that 788 // it looks for pairs such that both members have an input which is an 789 // output of PI or PJ. 790 void BBVectorize::computePairsConnectedTo( 791 std::multimap<Value *, Value *> &CandidatePairs, 792 std::vector<Value *> &PairableInsts, 793 std::multimap<ValuePair, ValuePair> &ConnectedPairs, 794 ValuePair P) { 795 // For each possible pairing for this variable, look at the uses of 796 // the first value... 797 for (Value::use_iterator I = P.first->use_begin(), 798 E = P.first->use_end(); I != E; ++I) { 799 VPIteratorPair IPairRange = CandidatePairs.equal_range(*I); 800 801 // For each use of the first variable, look for uses of the second 802 // variable... 803 for (Value::use_iterator J = P.second->use_begin(), 804 E2 = P.second->use_end(); J != E2; ++J) { 805 VPIteratorPair JPairRange = CandidatePairs.equal_range(*J); 806 807 // Look for <I, J>: 808 if (isSecondInIteratorPair<Value*>(*J, IPairRange)) 809 ConnectedPairs.insert(VPPair(P, ValuePair(*I, *J))); 810 811 // Look for <J, I>: 812 if (isSecondInIteratorPair<Value*>(*I, JPairRange)) 813 ConnectedPairs.insert(VPPair(P, ValuePair(*J, *I))); 814 } 815 816 if (SplatBreaksChain) continue; 817 // Look for cases where just the first value in the pair is used by 818 // both members of another pair (splatting). 819 for (Value::use_iterator J = P.first->use_begin(); J != E; ++J) { 820 if (isSecondInIteratorPair<Value*>(*J, IPairRange)) 821 ConnectedPairs.insert(VPPair(P, ValuePair(*I, *J))); 822 } 823 } 824 825 if (SplatBreaksChain) return; 826 // Look for cases where just the second value in the pair is used by 827 // both members of another pair (splatting). 828 for (Value::use_iterator I = P.second->use_begin(), 829 E = P.second->use_end(); I != E; ++I) { 830 VPIteratorPair IPairRange = CandidatePairs.equal_range(*I); 831 832 for (Value::use_iterator J = P.second->use_begin(); J != E; ++J) { 833 if (isSecondInIteratorPair<Value*>(*J, IPairRange)) 834 ConnectedPairs.insert(VPPair(P, ValuePair(*I, *J))); 835 } 836 } 837 } 838 839 // This function figures out which pairs are connected. Two pairs are 840 // connected if some output of the first pair forms an input to both members 841 // of the second pair. 842 void BBVectorize::computeConnectedPairs( 843 std::multimap<Value *, Value *> &CandidatePairs, 844 std::vector<Value *> &PairableInsts, 845 std::multimap<ValuePair, ValuePair> &ConnectedPairs) { 846 847 for (std::vector<Value *>::iterator PI = PairableInsts.begin(), 848 PE = PairableInsts.end(); PI != PE; ++PI) { 849 VPIteratorPair choiceRange = CandidatePairs.equal_range(*PI); 850 851 for (std::multimap<Value *, Value *>::iterator P = choiceRange.first; 852 P != choiceRange.second; ++P) 853 computePairsConnectedTo(CandidatePairs, PairableInsts, 854 ConnectedPairs, *P); 855 } 856 857 DEBUG(dbgs() << "BBV: found " << ConnectedPairs.size() 858 << " pair connections.\n"); 859 } 860 861 // This function builds a set of use tuples such that <A, B> is in the set 862 // if B is in the use tree of A. If B is in the use tree of A, then B 863 // depends on the output of A. 864 void BBVectorize::buildDepMap( 865 BasicBlock &BB, 866 std::multimap<Value *, Value *> &CandidatePairs, 867 std::vector<Value *> &PairableInsts, 868 DenseSet<ValuePair> &PairableInstUsers) { 869 DenseSet<Value *> IsInPair; 870 for (std::multimap<Value *, Value *>::iterator C = CandidatePairs.begin(), 871 E = CandidatePairs.end(); C != E; ++C) { 872 IsInPair.insert(C->first); 873 IsInPair.insert(C->second); 874 } 875 876 // Iterate through the basic block, recording all Users of each 877 // pairable instruction. 878 879 BasicBlock::iterator E = BB.end(); 880 for (BasicBlock::iterator I = BB.getFirstInsertionPt(); I != E; ++I) { 881 if (IsInPair.find(I) == IsInPair.end()) continue; 882 883 DenseSet<Value *> Users; 884 AliasSetTracker WriteSet(*AA); 885 for (BasicBlock::iterator J = llvm::next(I); J != E; ++J) 886 (void) trackUsesOfI(Users, WriteSet, I, J); 887 888 for (DenseSet<Value *>::iterator U = Users.begin(), E = Users.end(); 889 U != E; ++U) 890 PairableInstUsers.insert(ValuePair(I, *U)); 891 } 892 } 893 894 // Returns true if an input to pair P is an output of pair Q and also an 895 // input of pair Q is an output of pair P. If this is the case, then these 896 // two pairs cannot be simultaneously fused. 897 bool BBVectorize::pairsConflict(ValuePair P, ValuePair Q, 898 DenseSet<ValuePair> &PairableInstUsers, 899 std::multimap<ValuePair, ValuePair> *PairableInstUserMap) { 900 // Two pairs are in conflict if they are mutual Users of eachother. 901 bool QUsesP = PairableInstUsers.count(ValuePair(P.first, Q.first)) || 902 PairableInstUsers.count(ValuePair(P.first, Q.second)) || 903 PairableInstUsers.count(ValuePair(P.second, Q.first)) || 904 PairableInstUsers.count(ValuePair(P.second, Q.second)); 905 bool PUsesQ = PairableInstUsers.count(ValuePair(Q.first, P.first)) || 906 PairableInstUsers.count(ValuePair(Q.first, P.second)) || 907 PairableInstUsers.count(ValuePair(Q.second, P.first)) || 908 PairableInstUsers.count(ValuePair(Q.second, P.second)); 909 if (PairableInstUserMap) { 910 // FIXME: The expensive part of the cycle check is not so much the cycle 911 // check itself but this edge insertion procedure. This needs some 912 // profiling and probably a different data structure (same is true of 913 // most uses of std::multimap). 914 if (PUsesQ) { 915 VPPIteratorPair QPairRange = PairableInstUserMap->equal_range(Q); 916 if (!isSecondInIteratorPair(P, QPairRange)) 917 PairableInstUserMap->insert(VPPair(Q, P)); 918 } 919 if (QUsesP) { 920 VPPIteratorPair PPairRange = PairableInstUserMap->equal_range(P); 921 if (!isSecondInIteratorPair(Q, PPairRange)) 922 PairableInstUserMap->insert(VPPair(P, Q)); 923 } 924 } 925 926 return (QUsesP && PUsesQ); 927 } 928 929 // This function walks the use graph of current pairs to see if, starting 930 // from P, the walk returns to P. 931 bool BBVectorize::pairWillFormCycle(ValuePair P, 932 std::multimap<ValuePair, ValuePair> &PairableInstUserMap, 933 DenseSet<ValuePair> &CurrentPairs) { 934 DEBUG(if (DebugCycleCheck) 935 dbgs() << "BBV: starting cycle check for : " << *P.first << " <-> " 936 << *P.second << "\n"); 937 // A lookup table of visisted pairs is kept because the PairableInstUserMap 938 // contains non-direct associations. 939 DenseSet<ValuePair> Visited; 940 SmallVector<ValuePair, 32> Q; 941 // General depth-first post-order traversal: 942 Q.push_back(P); 943 do { 944 ValuePair QTop = Q.pop_back_val(); 945 Visited.insert(QTop); 946 947 DEBUG(if (DebugCycleCheck) 948 dbgs() << "BBV: cycle check visiting: " << *QTop.first << " <-> " 949 << *QTop.second << "\n"); 950 VPPIteratorPair QPairRange = PairableInstUserMap.equal_range(QTop); 951 for (std::multimap<ValuePair, ValuePair>::iterator C = QPairRange.first; 952 C != QPairRange.second; ++C) { 953 if (C->second == P) { 954 DEBUG(dbgs() 955 << "BBV: rejected to prevent non-trivial cycle formation: " 956 << *C->first.first << " <-> " << *C->first.second << "\n"); 957 return true; 958 } 959 960 if (CurrentPairs.count(C->second) > 0 && 961 Visited.count(C->second) == 0) 962 Q.push_back(C->second); 963 } 964 } while (!Q.empty()); 965 966 return false; 967 } 968 969 // This function builds the initial tree of connected pairs with the 970 // pair J at the root. 971 void BBVectorize::buildInitialTreeFor( 972 std::multimap<Value *, Value *> &CandidatePairs, 973 std::vector<Value *> &PairableInsts, 974 std::multimap<ValuePair, ValuePair> &ConnectedPairs, 975 DenseSet<ValuePair> &PairableInstUsers, 976 DenseMap<Value *, Value *> &ChosenPairs, 977 DenseMap<ValuePair, size_t> &Tree, ValuePair J) { 978 // Each of these pairs is viewed as the root node of a Tree. The Tree 979 // is then walked (depth-first). As this happens, we keep track of 980 // the pairs that compose the Tree and the maximum depth of the Tree. 981 SmallVector<ValuePairWithDepth, 32> Q; 982 // General depth-first post-order traversal: 983 Q.push_back(ValuePairWithDepth(J, getDepthFactor(J.first))); 984 do { 985 ValuePairWithDepth QTop = Q.back(); 986 987 // Push each child onto the queue: 988 bool MoreChildren = false; 989 size_t MaxChildDepth = QTop.second; 990 VPPIteratorPair qtRange = ConnectedPairs.equal_range(QTop.first); 991 for (std::multimap<ValuePair, ValuePair>::iterator k = qtRange.first; 992 k != qtRange.second; ++k) { 993 // Make sure that this child pair is still a candidate: 994 bool IsStillCand = false; 995 VPIteratorPair checkRange = 996 CandidatePairs.equal_range(k->second.first); 997 for (std::multimap<Value *, Value *>::iterator m = checkRange.first; 998 m != checkRange.second; ++m) { 999 if (m->second == k->second.second) { 1000 IsStillCand = true; 1001 break; 1002 } 1003 } 1004 1005 if (IsStillCand) { 1006 DenseMap<ValuePair, size_t>::iterator C = Tree.find(k->second); 1007 if (C == Tree.end()) { 1008 size_t d = getDepthFactor(k->second.first); 1009 Q.push_back(ValuePairWithDepth(k->second, QTop.second+d)); 1010 MoreChildren = true; 1011 } else { 1012 MaxChildDepth = std::max(MaxChildDepth, C->second); 1013 } 1014 } 1015 } 1016 1017 if (!MoreChildren) { 1018 // Record the current pair as part of the Tree: 1019 Tree.insert(ValuePairWithDepth(QTop.first, MaxChildDepth)); 1020 Q.pop_back(); 1021 } 1022 } while (!Q.empty()); 1023 } 1024 1025 // Given some initial tree, prune it by removing conflicting pairs (pairs 1026 // that cannot be simultaneously chosen for vectorization). 1027 void BBVectorize::pruneTreeFor( 1028 std::multimap<Value *, Value *> &CandidatePairs, 1029 std::vector<Value *> &PairableInsts, 1030 std::multimap<ValuePair, ValuePair> &ConnectedPairs, 1031 DenseSet<ValuePair> &PairableInstUsers, 1032 std::multimap<ValuePair, ValuePair> &PairableInstUserMap, 1033 DenseMap<Value *, Value *> &ChosenPairs, 1034 DenseMap<ValuePair, size_t> &Tree, 1035 DenseSet<ValuePair> &PrunedTree, ValuePair J, 1036 bool UseCycleCheck) { 1037 SmallVector<ValuePairWithDepth, 32> Q; 1038 // General depth-first post-order traversal: 1039 Q.push_back(ValuePairWithDepth(J, getDepthFactor(J.first))); 1040 do { 1041 ValuePairWithDepth QTop = Q.pop_back_val(); 1042 PrunedTree.insert(QTop.first); 1043 1044 // Visit each child, pruning as necessary... 1045 DenseMap<ValuePair, size_t> BestChilden; 1046 VPPIteratorPair QTopRange = ConnectedPairs.equal_range(QTop.first); 1047 for (std::multimap<ValuePair, ValuePair>::iterator K = QTopRange.first; 1048 K != QTopRange.second; ++K) { 1049 DenseMap<ValuePair, size_t>::iterator C = Tree.find(K->second); 1050 if (C == Tree.end()) continue; 1051 1052 // This child is in the Tree, now we need to make sure it is the 1053 // best of any conflicting children. There could be multiple 1054 // conflicting children, so first, determine if we're keeping 1055 // this child, then delete conflicting children as necessary. 1056 1057 // It is also necessary to guard against pairing-induced 1058 // dependencies. Consider instructions a .. x .. y .. b 1059 // such that (a,b) are to be fused and (x,y) are to be fused 1060 // but a is an input to x and b is an output from y. This 1061 // means that y cannot be moved after b but x must be moved 1062 // after b for (a,b) to be fused. In other words, after 1063 // fusing (a,b) we have y .. a/b .. x where y is an input 1064 // to a/b and x is an output to a/b: x and y can no longer 1065 // be legally fused. To prevent this condition, we must 1066 // make sure that a child pair added to the Tree is not 1067 // both an input and output of an already-selected pair. 1068 1069 // Pairing-induced dependencies can also form from more complicated 1070 // cycles. The pair vs. pair conflicts are easy to check, and so 1071 // that is done explicitly for "fast rejection", and because for 1072 // child vs. child conflicts, we may prefer to keep the current 1073 // pair in preference to the already-selected child. 1074 DenseSet<ValuePair> CurrentPairs; 1075 1076 bool CanAdd = true; 1077 for (DenseMap<ValuePair, size_t>::iterator C2 1078 = BestChilden.begin(), E2 = BestChilden.end(); 1079 C2 != E2; ++C2) { 1080 if (C2->first.first == C->first.first || 1081 C2->first.first == C->first.second || 1082 C2->first.second == C->first.first || 1083 C2->first.second == C->first.second || 1084 pairsConflict(C2->first, C->first, PairableInstUsers, 1085 UseCycleCheck ? &PairableInstUserMap : 0)) { 1086 if (C2->second >= C->second) { 1087 CanAdd = false; 1088 break; 1089 } 1090 1091 CurrentPairs.insert(C2->first); 1092 } 1093 } 1094 if (!CanAdd) continue; 1095 1096 // Even worse, this child could conflict with another node already 1097 // selected for the Tree. If that is the case, ignore this child. 1098 for (DenseSet<ValuePair>::iterator T = PrunedTree.begin(), 1099 E2 = PrunedTree.end(); T != E2; ++T) { 1100 if (T->first == C->first.first || 1101 T->first == C->first.second || 1102 T->second == C->first.first || 1103 T->second == C->first.second || 1104 pairsConflict(*T, C->first, PairableInstUsers, 1105 UseCycleCheck ? &PairableInstUserMap : 0)) { 1106 CanAdd = false; 1107 break; 1108 } 1109 1110 CurrentPairs.insert(*T); 1111 } 1112 if (!CanAdd) continue; 1113 1114 // And check the queue too... 1115 for (SmallVector<ValuePairWithDepth, 32>::iterator C2 = Q.begin(), 1116 E2 = Q.end(); C2 != E2; ++C2) { 1117 if (C2->first.first == C->first.first || 1118 C2->first.first == C->first.second || 1119 C2->first.second == C->first.first || 1120 C2->first.second == C->first.second || 1121 pairsConflict(C2->first, C->first, PairableInstUsers, 1122 UseCycleCheck ? &PairableInstUserMap : 0)) { 1123 CanAdd = false; 1124 break; 1125 } 1126 1127 CurrentPairs.insert(C2->first); 1128 } 1129 if (!CanAdd) continue; 1130 1131 // Last but not least, check for a conflict with any of the 1132 // already-chosen pairs. 1133 for (DenseMap<Value *, Value *>::iterator C2 = 1134 ChosenPairs.begin(), E2 = ChosenPairs.end(); 1135 C2 != E2; ++C2) { 1136 if (pairsConflict(*C2, C->first, PairableInstUsers, 1137 UseCycleCheck ? &PairableInstUserMap : 0)) { 1138 CanAdd = false; 1139 break; 1140 } 1141 1142 CurrentPairs.insert(*C2); 1143 } 1144 if (!CanAdd) continue; 1145 1146 // To check for non-trivial cycles formed by the addition of the 1147 // current pair we've formed a list of all relevant pairs, now use a 1148 // graph walk to check for a cycle. We start from the current pair and 1149 // walk the use tree to see if we again reach the current pair. If we 1150 // do, then the current pair is rejected. 1151 1152 // FIXME: It may be more efficient to use a topological-ordering 1153 // algorithm to improve the cycle check. This should be investigated. 1154 if (UseCycleCheck && 1155 pairWillFormCycle(C->first, PairableInstUserMap, CurrentPairs)) 1156 continue; 1157 1158 // This child can be added, but we may have chosen it in preference 1159 // to an already-selected child. Check for this here, and if a 1160 // conflict is found, then remove the previously-selected child 1161 // before adding this one in its place. 1162 for (DenseMap<ValuePair, size_t>::iterator C2 1163 = BestChilden.begin(); C2 != BestChilden.end();) { 1164 if (C2->first.first == C->first.first || 1165 C2->first.first == C->first.second || 1166 C2->first.second == C->first.first || 1167 C2->first.second == C->first.second || 1168 pairsConflict(C2->first, C->first, PairableInstUsers)) 1169 BestChilden.erase(C2++); 1170 else 1171 ++C2; 1172 } 1173 1174 BestChilden.insert(ValuePairWithDepth(C->first, C->second)); 1175 } 1176 1177 for (DenseMap<ValuePair, size_t>::iterator C 1178 = BestChilden.begin(), E2 = BestChilden.end(); 1179 C != E2; ++C) { 1180 size_t DepthF = getDepthFactor(C->first.first); 1181 Q.push_back(ValuePairWithDepth(C->first, QTop.second+DepthF)); 1182 } 1183 } while (!Q.empty()); 1184 } 1185 1186 // This function finds the best tree of mututally-compatible connected 1187 // pairs, given the choice of root pairs as an iterator range. 1188 void BBVectorize::findBestTreeFor( 1189 std::multimap<Value *, Value *> &CandidatePairs, 1190 std::vector<Value *> &PairableInsts, 1191 std::multimap<ValuePair, ValuePair> &ConnectedPairs, 1192 DenseSet<ValuePair> &PairableInstUsers, 1193 std::multimap<ValuePair, ValuePair> &PairableInstUserMap, 1194 DenseMap<Value *, Value *> &ChosenPairs, 1195 DenseSet<ValuePair> &BestTree, size_t &BestMaxDepth, 1196 size_t &BestEffSize, VPIteratorPair ChoiceRange, 1197 bool UseCycleCheck) { 1198 for (std::multimap<Value *, Value *>::iterator J = ChoiceRange.first; 1199 J != ChoiceRange.second; ++J) { 1200 1201 // Before going any further, make sure that this pair does not 1202 // conflict with any already-selected pairs (see comment below 1203 // near the Tree pruning for more details). 1204 DenseSet<ValuePair> ChosenPairSet; 1205 bool DoesConflict = false; 1206 for (DenseMap<Value *, Value *>::iterator C = ChosenPairs.begin(), 1207 E = ChosenPairs.end(); C != E; ++C) { 1208 if (pairsConflict(*C, *J, PairableInstUsers, 1209 UseCycleCheck ? &PairableInstUserMap : 0)) { 1210 DoesConflict = true; 1211 break; 1212 } 1213 1214 ChosenPairSet.insert(*C); 1215 } 1216 if (DoesConflict) continue; 1217 1218 if (UseCycleCheck && 1219 pairWillFormCycle(*J, PairableInstUserMap, ChosenPairSet)) 1220 continue; 1221 1222 DenseMap<ValuePair, size_t> Tree; 1223 buildInitialTreeFor(CandidatePairs, PairableInsts, ConnectedPairs, 1224 PairableInstUsers, ChosenPairs, Tree, *J); 1225 1226 // Because we'll keep the child with the largest depth, the largest 1227 // depth is still the same in the unpruned Tree. 1228 size_t MaxDepth = Tree.lookup(*J); 1229 1230 DEBUG(if (DebugPairSelection) dbgs() << "BBV: found Tree for pair {" 1231 << *J->first << " <-> " << *J->second << "} of depth " << 1232 MaxDepth << " and size " << Tree.size() << "\n"); 1233 1234 // At this point the Tree has been constructed, but, may contain 1235 // contradictory children (meaning that different children of 1236 // some tree node may be attempting to fuse the same instruction). 1237 // So now we walk the tree again, in the case of a conflict, 1238 // keep only the child with the largest depth. To break a tie, 1239 // favor the first child. 1240 1241 DenseSet<ValuePair> PrunedTree; 1242 pruneTreeFor(CandidatePairs, PairableInsts, ConnectedPairs, 1243 PairableInstUsers, PairableInstUserMap, ChosenPairs, Tree, 1244 PrunedTree, *J, UseCycleCheck); 1245 1246 size_t EffSize = 0; 1247 for (DenseSet<ValuePair>::iterator S = PrunedTree.begin(), 1248 E = PrunedTree.end(); S != E; ++S) 1249 EffSize += getDepthFactor(S->first); 1250 1251 DEBUG(if (DebugPairSelection) 1252 dbgs() << "BBV: found pruned Tree for pair {" 1253 << *J->first << " <-> " << *J->second << "} of depth " << 1254 MaxDepth << " and size " << PrunedTree.size() << 1255 " (effective size: " << EffSize << ")\n"); 1256 if (MaxDepth >= ReqChainDepth && EffSize > BestEffSize) { 1257 BestMaxDepth = MaxDepth; 1258 BestEffSize = EffSize; 1259 BestTree = PrunedTree; 1260 } 1261 } 1262 } 1263 1264 // Given the list of candidate pairs, this function selects those 1265 // that will be fused into vector instructions. 1266 void BBVectorize::choosePairs( 1267 std::multimap<Value *, Value *> &CandidatePairs, 1268 std::vector<Value *> &PairableInsts, 1269 std::multimap<ValuePair, ValuePair> &ConnectedPairs, 1270 DenseSet<ValuePair> &PairableInstUsers, 1271 DenseMap<Value *, Value *>& ChosenPairs) { 1272 bool UseCycleCheck = CandidatePairs.size() <= MaxCandPairsForCycleCheck; 1273 std::multimap<ValuePair, ValuePair> PairableInstUserMap; 1274 for (std::vector<Value *>::iterator I = PairableInsts.begin(), 1275 E = PairableInsts.end(); I != E; ++I) { 1276 // The number of possible pairings for this variable: 1277 size_t NumChoices = CandidatePairs.count(*I); 1278 if (!NumChoices) continue; 1279 1280 VPIteratorPair ChoiceRange = CandidatePairs.equal_range(*I); 1281 1282 // The best pair to choose and its tree: 1283 size_t BestMaxDepth = 0, BestEffSize = 0; 1284 DenseSet<ValuePair> BestTree; 1285 findBestTreeFor(CandidatePairs, PairableInsts, ConnectedPairs, 1286 PairableInstUsers, PairableInstUserMap, ChosenPairs, 1287 BestTree, BestMaxDepth, BestEffSize, ChoiceRange, 1288 UseCycleCheck); 1289 1290 // A tree has been chosen (or not) at this point. If no tree was 1291 // chosen, then this instruction, I, cannot be paired (and is no longer 1292 // considered). 1293 1294 DEBUG(if (BestTree.size() > 0) 1295 dbgs() << "BBV: selected pairs in the best tree for: " 1296 << *cast<Instruction>(*I) << "\n"); 1297 1298 for (DenseSet<ValuePair>::iterator S = BestTree.begin(), 1299 SE2 = BestTree.end(); S != SE2; ++S) { 1300 // Insert the members of this tree into the list of chosen pairs. 1301 ChosenPairs.insert(ValuePair(S->first, S->second)); 1302 DEBUG(dbgs() << "BBV: selected pair: " << *S->first << " <-> " << 1303 *S->second << "\n"); 1304 1305 // Remove all candidate pairs that have values in the chosen tree. 1306 for (std::multimap<Value *, Value *>::iterator K = 1307 CandidatePairs.begin(); K != CandidatePairs.end();) { 1308 if (K->first == S->first || K->second == S->first || 1309 K->second == S->second || K->first == S->second) { 1310 // Don't remove the actual pair chosen so that it can be used 1311 // in subsequent tree selections. 1312 if (!(K->first == S->first && K->second == S->second)) 1313 CandidatePairs.erase(K++); 1314 else 1315 ++K; 1316 } else { 1317 ++K; 1318 } 1319 } 1320 } 1321 } 1322 1323 DEBUG(dbgs() << "BBV: selected " << ChosenPairs.size() << " pairs.\n"); 1324 } 1325 1326 std::string getReplacementName(Instruction *I, bool IsInput, unsigned o, 1327 unsigned n = 0) { 1328 if (!I->hasName()) 1329 return ""; 1330 1331 return (I->getName() + (IsInput ? ".v.i" : ".v.r") + utostr(o) + 1332 (n > 0 ? "." + utostr(n) : "")).str(); 1333 } 1334 1335 // Returns the value that is to be used as the pointer input to the vector 1336 // instruction that fuses I with J. 1337 Value *BBVectorize::getReplacementPointerInput(LLVMContext& Context, 1338 Instruction *I, Instruction *J, unsigned o, 1339 bool &FlipMemInputs) { 1340 Value *IPtr, *JPtr; 1341 unsigned IAlignment, JAlignment; 1342 int64_t OffsetInElmts; 1343 (void) getPairPtrInfo(I, J, IPtr, JPtr, IAlignment, JAlignment, 1344 OffsetInElmts); 1345 1346 // The pointer value is taken to be the one with the lowest offset. 1347 Value *VPtr; 1348 if (OffsetInElmts > 0) { 1349 VPtr = IPtr; 1350 } else { 1351 FlipMemInputs = true; 1352 VPtr = JPtr; 1353 } 1354 1355 Type *ArgType = cast<PointerType>(IPtr->getType())->getElementType(); 1356 Type *VArgType = getVecTypeForPair(ArgType); 1357 Type *VArgPtrType = PointerType::get(VArgType, 1358 cast<PointerType>(IPtr->getType())->getAddressSpace()); 1359 return new BitCastInst(VPtr, VArgPtrType, getReplacementName(I, true, o), 1360 /* insert before */ FlipMemInputs ? J : I); 1361 } 1362 1363 void BBVectorize::fillNewShuffleMask(LLVMContext& Context, Instruction *J, 1364 unsigned NumElem, unsigned MaskOffset, unsigned NumInElem, 1365 unsigned IdxOffset, std::vector<Constant*> &Mask) { 1366 for (unsigned v = 0; v < NumElem/2; ++v) { 1367 int m = cast<ShuffleVectorInst>(J)->getMaskValue(v); 1368 if (m < 0) { 1369 Mask[v+MaskOffset] = UndefValue::get(Type::getInt32Ty(Context)); 1370 } else { 1371 unsigned mm = m + (int) IdxOffset; 1372 if (m >= (int) NumInElem) 1373 mm += (int) NumInElem; 1374 1375 Mask[v+MaskOffset] = 1376 ConstantInt::get(Type::getInt32Ty(Context), mm); 1377 } 1378 } 1379 } 1380 1381 // Returns the value that is to be used as the vector-shuffle mask to the 1382 // vector instruction that fuses I with J. 1383 Value *BBVectorize::getReplacementShuffleMask(LLVMContext& Context, 1384 Instruction *I, Instruction *J) { 1385 // This is the shuffle mask. We need to append the second 1386 // mask to the first, and the numbers need to be adjusted. 1387 1388 Type *ArgType = I->getType(); 1389 Type *VArgType = getVecTypeForPair(ArgType); 1390 1391 // Get the total number of elements in the fused vector type. 1392 // By definition, this must equal the number of elements in 1393 // the final mask. 1394 unsigned NumElem = cast<VectorType>(VArgType)->getNumElements(); 1395 std::vector<Constant*> Mask(NumElem); 1396 1397 Type *OpType = I->getOperand(0)->getType(); 1398 unsigned NumInElem = cast<VectorType>(OpType)->getNumElements(); 1399 1400 // For the mask from the first pair... 1401 fillNewShuffleMask(Context, I, NumElem, 0, NumInElem, 0, Mask); 1402 1403 // For the mask from the second pair... 1404 fillNewShuffleMask(Context, J, NumElem, NumElem/2, NumInElem, NumInElem, 1405 Mask); 1406 1407 return ConstantVector::get(Mask); 1408 } 1409 1410 // Returns the value to be used as the specified operand of the vector 1411 // instruction that fuses I with J. 1412 Value *BBVectorize::getReplacementInput(LLVMContext& Context, Instruction *I, 1413 Instruction *J, unsigned o, bool FlipMemInputs) { 1414 Value *CV0 = ConstantInt::get(Type::getInt32Ty(Context), 0); 1415 Value *CV1 = ConstantInt::get(Type::getInt32Ty(Context), 1); 1416 1417 // Compute the fused vector type for this operand 1418 Type *ArgType = I->getOperand(o)->getType(); 1419 VectorType *VArgType = getVecTypeForPair(ArgType); 1420 1421 Instruction *L = I, *H = J; 1422 if (FlipMemInputs) { 1423 L = J; 1424 H = I; 1425 } 1426 1427 if (ArgType->isVectorTy()) { 1428 unsigned numElem = cast<VectorType>(VArgType)->getNumElements(); 1429 std::vector<Constant*> Mask(numElem); 1430 for (unsigned v = 0; v < numElem; ++v) 1431 Mask[v] = ConstantInt::get(Type::getInt32Ty(Context), v); 1432 1433 Instruction *BV = new ShuffleVectorInst(L->getOperand(o), 1434 H->getOperand(o), 1435 ConstantVector::get(Mask), 1436 getReplacementName(I, true, o)); 1437 BV->insertBefore(J); 1438 return BV; 1439 } 1440 1441 // If these two inputs are the output of another vector instruction, 1442 // then we should use that output directly. It might be necessary to 1443 // permute it first. [When pairings are fused recursively, you can 1444 // end up with cases where a large vector is decomposed into scalars 1445 // using extractelement instructions, then built into size-2 1446 // vectors using insertelement and the into larger vectors using 1447 // shuffles. InstCombine does not simplify all of these cases well, 1448 // and so we make sure that shuffles are generated here when possible. 1449 ExtractElementInst *LEE 1450 = dyn_cast<ExtractElementInst>(L->getOperand(o)); 1451 ExtractElementInst *HEE 1452 = dyn_cast<ExtractElementInst>(H->getOperand(o)); 1453 1454 if (LEE && HEE && 1455 LEE->getOperand(0)->getType() == HEE->getOperand(0)->getType()) { 1456 VectorType *EEType = cast<VectorType>(LEE->getOperand(0)->getType()); 1457 unsigned LowIndx = cast<ConstantInt>(LEE->getOperand(1))->getZExtValue(); 1458 unsigned HighIndx = cast<ConstantInt>(HEE->getOperand(1))->getZExtValue(); 1459 if (LEE->getOperand(0) == HEE->getOperand(0)) { 1460 if (LowIndx == 0 && HighIndx == 1) 1461 return LEE->getOperand(0); 1462 1463 std::vector<Constant*> Mask(2); 1464 Mask[0] = ConstantInt::get(Type::getInt32Ty(Context), LowIndx); 1465 Mask[1] = ConstantInt::get(Type::getInt32Ty(Context), HighIndx); 1466 1467 Instruction *BV = new ShuffleVectorInst(LEE->getOperand(0), 1468 UndefValue::get(EEType), 1469 ConstantVector::get(Mask), 1470 getReplacementName(I, true, o)); 1471 BV->insertBefore(J); 1472 return BV; 1473 } 1474 1475 std::vector<Constant*> Mask(2); 1476 HighIndx += EEType->getNumElements(); 1477 Mask[0] = ConstantInt::get(Type::getInt32Ty(Context), LowIndx); 1478 Mask[1] = ConstantInt::get(Type::getInt32Ty(Context), HighIndx); 1479 1480 Instruction *BV = new ShuffleVectorInst(LEE->getOperand(0), 1481 HEE->getOperand(0), 1482 ConstantVector::get(Mask), 1483 getReplacementName(I, true, o)); 1484 BV->insertBefore(J); 1485 return BV; 1486 } 1487 1488 Instruction *BV1 = InsertElementInst::Create( 1489 UndefValue::get(VArgType), 1490 L->getOperand(o), CV0, 1491 getReplacementName(I, true, o, 1)); 1492 BV1->insertBefore(I); 1493 Instruction *BV2 = InsertElementInst::Create(BV1, H->getOperand(o), 1494 CV1, 1495 getReplacementName(I, true, o, 2)); 1496 BV2->insertBefore(J); 1497 return BV2; 1498 } 1499 1500 // This function creates an array of values that will be used as the inputs 1501 // to the vector instruction that fuses I with J. 1502 void BBVectorize::getReplacementInputsForPair(LLVMContext& Context, 1503 Instruction *I, Instruction *J, 1504 SmallVector<Value *, 3> &ReplacedOperands, 1505 bool &FlipMemInputs) { 1506 FlipMemInputs = false; 1507 unsigned NumOperands = I->getNumOperands(); 1508 1509 for (unsigned p = 0, o = NumOperands-1; p < NumOperands; ++p, --o) { 1510 // Iterate backward so that we look at the store pointer 1511 // first and know whether or not we need to flip the inputs. 1512 1513 if (isa<LoadInst>(I) || (o == 1 && isa<StoreInst>(I))) { 1514 // This is the pointer for a load/store instruction. 1515 ReplacedOperands[o] = getReplacementPointerInput(Context, I, J, o, 1516 FlipMemInputs); 1517 continue; 1518 } else if (isa<CallInst>(I) && o == NumOperands-1) { 1519 Function *F = cast<CallInst>(I)->getCalledFunction(); 1520 unsigned IID = F->getIntrinsicID(); 1521 BasicBlock &BB = *I->getParent(); 1522 1523 Module *M = BB.getParent()->getParent(); 1524 Type *ArgType = I->getType(); 1525 Type *VArgType = getVecTypeForPair(ArgType); 1526 1527 // FIXME: is it safe to do this here? 1528 ReplacedOperands[o] = Intrinsic::getDeclaration(M, 1529 (Intrinsic::ID) IID, VArgType); 1530 continue; 1531 } else if (isa<ShuffleVectorInst>(I) && o == NumOperands-1) { 1532 ReplacedOperands[o] = getReplacementShuffleMask(Context, I, J); 1533 continue; 1534 } 1535 1536 ReplacedOperands[o] = 1537 getReplacementInput(Context, I, J, o, FlipMemInputs); 1538 } 1539 } 1540 1541 // This function creates two values that represent the outputs of the 1542 // original I and J instructions. These are generally vector shuffles 1543 // or extracts. In many cases, these will end up being unused and, thus, 1544 // eliminated by later passes. 1545 void BBVectorize::replaceOutputsOfPair(LLVMContext& Context, Instruction *I, 1546 Instruction *J, Instruction *K, 1547 Instruction *&InsertionPt, 1548 Instruction *&K1, Instruction *&K2, 1549 bool &FlipMemInputs) { 1550 Value *CV0 = ConstantInt::get(Type::getInt32Ty(Context), 0); 1551 Value *CV1 = ConstantInt::get(Type::getInt32Ty(Context), 1); 1552 1553 if (isa<StoreInst>(I)) { 1554 AA->replaceWithNewValue(I, K); 1555 AA->replaceWithNewValue(J, K); 1556 } else { 1557 Type *IType = I->getType(); 1558 Type *VType = getVecTypeForPair(IType); 1559 1560 if (IType->isVectorTy()) { 1561 unsigned numElem = cast<VectorType>(IType)->getNumElements(); 1562 std::vector<Constant*> Mask1(numElem), Mask2(numElem); 1563 for (unsigned v = 0; v < numElem; ++v) { 1564 Mask1[v] = ConstantInt::get(Type::getInt32Ty(Context), v); 1565 Mask2[v] = ConstantInt::get(Type::getInt32Ty(Context), numElem+v); 1566 } 1567 1568 K1 = new ShuffleVectorInst(K, UndefValue::get(VType), 1569 ConstantVector::get( 1570 FlipMemInputs ? Mask2 : Mask1), 1571 getReplacementName(K, false, 1)); 1572 K2 = new ShuffleVectorInst(K, UndefValue::get(VType), 1573 ConstantVector::get( 1574 FlipMemInputs ? Mask1 : Mask2), 1575 getReplacementName(K, false, 2)); 1576 } else { 1577 K1 = ExtractElementInst::Create(K, FlipMemInputs ? CV1 : CV0, 1578 getReplacementName(K, false, 1)); 1579 K2 = ExtractElementInst::Create(K, FlipMemInputs ? CV0 : CV1, 1580 getReplacementName(K, false, 2)); 1581 } 1582 1583 K1->insertAfter(K); 1584 K2->insertAfter(K1); 1585 InsertionPt = K2; 1586 } 1587 } 1588 1589 // Move all uses of the function I (including pairing-induced uses) after J. 1590 bool BBVectorize::canMoveUsesOfIAfterJ(BasicBlock &BB, 1591 std::multimap<Value *, Value *> &LoadMoveSet, 1592 Instruction *I, Instruction *J) { 1593 // Skip to the first instruction past I. 1594 BasicBlock::iterator L = BB.begin(); 1595 for (; cast<Instruction>(L) != I; ++L); 1596 ++L; 1597 1598 DenseSet<Value *> Users; 1599 AliasSetTracker WriteSet(*AA); 1600 for (; cast<Instruction>(L) != J; ++L) 1601 (void) trackUsesOfI(Users, WriteSet, I, L, true, &LoadMoveSet); 1602 1603 assert(cast<Instruction>(L) == J && 1604 "Tracking has not proceeded far enough to check for dependencies"); 1605 // If J is now in the use set of I, then trackUsesOfI will return true 1606 // and we have a dependency cycle (and the fusing operation must abort). 1607 return !trackUsesOfI(Users, WriteSet, I, J, true, &LoadMoveSet); 1608 } 1609 1610 // Move all uses of the function I (including pairing-induced uses) after J. 1611 void BBVectorize::moveUsesOfIAfterJ(BasicBlock &BB, 1612 std::multimap<Value *, Value *> &LoadMoveSet, 1613 Instruction *&InsertionPt, 1614 Instruction *I, Instruction *J) { 1615 // Skip to the first instruction past I. 1616 BasicBlock::iterator L = BB.begin(); 1617 for (; cast<Instruction>(L) != I; ++L); 1618 ++L; 1619 1620 DenseSet<Value *> Users; 1621 AliasSetTracker WriteSet(*AA); 1622 for (; cast<Instruction>(L) != J;) { 1623 if (trackUsesOfI(Users, WriteSet, I, L, true, &LoadMoveSet)) { 1624 // Move this instruction 1625 Instruction *InstToMove = L; ++L; 1626 1627 DEBUG(dbgs() << "BBV: moving: " << *InstToMove << 1628 " to after " << *InsertionPt << "\n"); 1629 InstToMove->removeFromParent(); 1630 InstToMove->insertAfter(InsertionPt); 1631 InsertionPt = InstToMove; 1632 } else { 1633 ++L; 1634 } 1635 } 1636 } 1637 1638 // Collect all load instruction that are in the move set of a given first 1639 // pair member. These loads depend on the first instruction, I, and so need 1640 // to be moved after J (the second instruction) when the pair is fused. 1641 void BBVectorize::collectPairLoadMoveSet(BasicBlock &BB, 1642 DenseMap<Value *, Value *> &ChosenPairs, 1643 std::multimap<Value *, Value *> &LoadMoveSet, 1644 Instruction *I) { 1645 // Skip to the first instruction past I. 1646 BasicBlock::iterator L = BB.begin(); 1647 for (; cast<Instruction>(L) != I; ++L); 1648 ++L; 1649 1650 DenseSet<Value *> Users; 1651 AliasSetTracker WriteSet(*AA); 1652 1653 // Note: We cannot end the loop when we reach J because J could be moved 1654 // farther down the use chain by another instruction pairing. Also, J 1655 // could be before I if this is an inverted input. 1656 for (BasicBlock::iterator E = BB.end(); cast<Instruction>(L) != E; ++L) { 1657 if (trackUsesOfI(Users, WriteSet, I, L)) { 1658 if (L->mayReadFromMemory()) 1659 LoadMoveSet.insert(ValuePair(L, I)); 1660 } 1661 } 1662 } 1663 1664 // In cases where both load/stores and the computation of their pointers 1665 // are chosen for vectorization, we can end up in a situation where the 1666 // aliasing analysis starts returning different query results as the 1667 // process of fusing instruction pairs continues. Because the algorithm 1668 // relies on finding the same use trees here as were found earlier, we'll 1669 // need to precompute the necessary aliasing information here and then 1670 // manually update it during the fusion process. 1671 void BBVectorize::collectLoadMoveSet(BasicBlock &BB, 1672 std::vector<Value *> &PairableInsts, 1673 DenseMap<Value *, Value *> &ChosenPairs, 1674 std::multimap<Value *, Value *> &LoadMoveSet) { 1675 for (std::vector<Value *>::iterator PI = PairableInsts.begin(), 1676 PIE = PairableInsts.end(); PI != PIE; ++PI) { 1677 DenseMap<Value *, Value *>::iterator P = ChosenPairs.find(*PI); 1678 if (P == ChosenPairs.end()) continue; 1679 1680 Instruction *I = cast<Instruction>(P->first); 1681 collectPairLoadMoveSet(BB, ChosenPairs, LoadMoveSet, I); 1682 } 1683 } 1684 1685 // This function fuses the chosen instruction pairs into vector instructions, 1686 // taking care preserve any needed scalar outputs and, then, it reorders the 1687 // remaining instructions as needed (users of the first member of the pair 1688 // need to be moved to after the location of the second member of the pair 1689 // because the vector instruction is inserted in the location of the pair's 1690 // second member). 1691 void BBVectorize::fuseChosenPairs(BasicBlock &BB, 1692 std::vector<Value *> &PairableInsts, 1693 DenseMap<Value *, Value *> &ChosenPairs) { 1694 LLVMContext& Context = BB.getContext(); 1695 1696 // During the vectorization process, the order of the pairs to be fused 1697 // could be flipped. So we'll add each pair, flipped, into the ChosenPairs 1698 // list. After a pair is fused, the flipped pair is removed from the list. 1699 std::vector<ValuePair> FlippedPairs; 1700 FlippedPairs.reserve(ChosenPairs.size()); 1701 for (DenseMap<Value *, Value *>::iterator P = ChosenPairs.begin(), 1702 E = ChosenPairs.end(); P != E; ++P) 1703 FlippedPairs.push_back(ValuePair(P->second, P->first)); 1704 for (std::vector<ValuePair>::iterator P = FlippedPairs.begin(), 1705 E = FlippedPairs.end(); P != E; ++P) 1706 ChosenPairs.insert(*P); 1707 1708 std::multimap<Value *, Value *> LoadMoveSet; 1709 collectLoadMoveSet(BB, PairableInsts, ChosenPairs, LoadMoveSet); 1710 1711 DEBUG(dbgs() << "BBV: initial: \n" << BB << "\n"); 1712 1713 for (BasicBlock::iterator PI = BB.getFirstInsertionPt(); PI != BB.end();) { 1714 DenseMap<Value *, Value *>::iterator P = ChosenPairs.find(PI); 1715 if (P == ChosenPairs.end()) { 1716 ++PI; 1717 continue; 1718 } 1719 1720 if (getDepthFactor(P->first) == 0) { 1721 // These instructions are not really fused, but are tracked as though 1722 // they are. Any case in which it would be interesting to fuse them 1723 // will be taken care of by InstCombine. 1724 --NumFusedOps; 1725 ++PI; 1726 continue; 1727 } 1728 1729 Instruction *I = cast<Instruction>(P->first), 1730 *J = cast<Instruction>(P->second); 1731 1732 DEBUG(dbgs() << "BBV: fusing: " << *I << 1733 " <-> " << *J << "\n"); 1734 1735 // Remove the pair and flipped pair from the list. 1736 DenseMap<Value *, Value *>::iterator FP = ChosenPairs.find(P->second); 1737 assert(FP != ChosenPairs.end() && "Flipped pair not found in list"); 1738 ChosenPairs.erase(FP); 1739 ChosenPairs.erase(P); 1740 1741 if (!canMoveUsesOfIAfterJ(BB, LoadMoveSet, I, J)) { 1742 DEBUG(dbgs() << "BBV: fusion of: " << *I << 1743 " <-> " << *J << 1744 " aborted because of non-trivial dependency cycle\n"); 1745 --NumFusedOps; 1746 ++PI; 1747 continue; 1748 } 1749 1750 bool FlipMemInputs; 1751 unsigned NumOperands = I->getNumOperands(); 1752 SmallVector<Value *, 3> ReplacedOperands(NumOperands); 1753 getReplacementInputsForPair(Context, I, J, ReplacedOperands, 1754 FlipMemInputs); 1755 1756 // Make a copy of the original operation, change its type to the vector 1757 // type and replace its operands with the vector operands. 1758 Instruction *K = I->clone(); 1759 if (I->hasName()) K->takeName(I); 1760 1761 if (!isa<StoreInst>(K)) 1762 K->mutateType(getVecTypeForPair(I->getType())); 1763 1764 for (unsigned o = 0; o < NumOperands; ++o) 1765 K->setOperand(o, ReplacedOperands[o]); 1766 1767 // If we've flipped the memory inputs, make sure that we take the correct 1768 // alignment. 1769 if (FlipMemInputs) { 1770 if (isa<StoreInst>(K)) 1771 cast<StoreInst>(K)->setAlignment(cast<StoreInst>(J)->getAlignment()); 1772 else 1773 cast<LoadInst>(K)->setAlignment(cast<LoadInst>(J)->getAlignment()); 1774 } 1775 1776 K->insertAfter(J); 1777 1778 // Instruction insertion point: 1779 Instruction *InsertionPt = K; 1780 Instruction *K1 = 0, *K2 = 0; 1781 replaceOutputsOfPair(Context, I, J, K, InsertionPt, K1, K2, 1782 FlipMemInputs); 1783 1784 // The use tree of the first original instruction must be moved to after 1785 // the location of the second instruction. The entire use tree of the 1786 // first instruction is disjoint from the input tree of the second 1787 // (by definition), and so commutes with it. 1788 1789 moveUsesOfIAfterJ(BB, LoadMoveSet, InsertionPt, I, J); 1790 1791 if (!isa<StoreInst>(I)) { 1792 I->replaceAllUsesWith(K1); 1793 J->replaceAllUsesWith(K2); 1794 AA->replaceWithNewValue(I, K1); 1795 AA->replaceWithNewValue(J, K2); 1796 } 1797 1798 // Instructions that may read from memory may be in the load move set. 1799 // Once an instruction is fused, we no longer need its move set, and so 1800 // the values of the map never need to be updated. However, when a load 1801 // is fused, we need to merge the entries from both instructions in the 1802 // pair in case those instructions were in the move set of some other 1803 // yet-to-be-fused pair. The loads in question are the keys of the map. 1804 if (I->mayReadFromMemory()) { 1805 std::vector<ValuePair> NewSetMembers; 1806 VPIteratorPair IPairRange = LoadMoveSet.equal_range(I); 1807 VPIteratorPair JPairRange = LoadMoveSet.equal_range(J); 1808 for (std::multimap<Value *, Value *>::iterator N = IPairRange.first; 1809 N != IPairRange.second; ++N) 1810 NewSetMembers.push_back(ValuePair(K, N->second)); 1811 for (std::multimap<Value *, Value *>::iterator N = JPairRange.first; 1812 N != JPairRange.second; ++N) 1813 NewSetMembers.push_back(ValuePair(K, N->second)); 1814 for (std::vector<ValuePair>::iterator A = NewSetMembers.begin(), 1815 AE = NewSetMembers.end(); A != AE; ++A) 1816 LoadMoveSet.insert(*A); 1817 } 1818 1819 // Before removing I, set the iterator to the next instruction. 1820 PI = llvm::next(BasicBlock::iterator(I)); 1821 if (cast<Instruction>(PI) == J) 1822 ++PI; 1823 1824 SE->forgetValue(I); 1825 SE->forgetValue(J); 1826 I->eraseFromParent(); 1827 J->eraseFromParent(); 1828 } 1829 1830 DEBUG(dbgs() << "BBV: final: \n" << BB << "\n"); 1831 } 1832} 1833 1834char BBVectorize::ID = 0; 1835static const char bb_vectorize_name[] = "Basic-Block Vectorization"; 1836INITIALIZE_PASS_BEGIN(BBVectorize, BBV_NAME, bb_vectorize_name, false, false) 1837INITIALIZE_AG_DEPENDENCY(AliasAnalysis) 1838INITIALIZE_PASS_DEPENDENCY(ScalarEvolution) 1839INITIALIZE_PASS_END(BBVectorize, BBV_NAME, bb_vectorize_name, false, false) 1840 1841BasicBlockPass *llvm::createBBVectorizePass() { 1842 return new BBVectorize(); 1843} 1844 1845