1 //===- llvm/Analysis/LoopAccessAnalysis.h -----------------------*- C++ -*-===// 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 defines the interface for the loop memory dependence framework that 11 // was originally developed for the Loop Vectorizer. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #ifndef LLVM_ANALYSIS_LOOPACCESSANALYSIS_H 16 #define LLVM_ANALYSIS_LOOPACCESSANALYSIS_H 17 18 #include "llvm/ADT/EquivalenceClasses.h" 19 #include "llvm/ADT/Optional.h" 20 #include "llvm/ADT/SetVector.h" 21 #include "llvm/Analysis/AliasAnalysis.h" 22 #include "llvm/Analysis/AliasSetTracker.h" 23 #include "llvm/Analysis/ScalarEvolutionExpressions.h" 24 #include "llvm/IR/ValueHandle.h" 25 #include "llvm/Pass.h" 26 #include "llvm/Support/raw_ostream.h" 27 28 namespace llvm { 29 30 class Value; 31 class DataLayout; 32 class ScalarEvolution; 33 class Loop; 34 class SCEV; 35 class SCEVUnionPredicate; 36 class LoopAccessInfo; 37 38 /// Optimization analysis message produced during vectorization. Messages inform 39 /// the user why vectorization did not occur. 40 class LoopAccessReport { 41 std::string Message; 42 const Instruction *Instr; 43 44 protected: 45 LoopAccessReport(const Twine &Message, const Instruction *I) 46 : Message(Message.str()), Instr(I) {} 47 48 public: 49 LoopAccessReport(const Instruction *I = nullptr) : Instr(I) {} 50 51 template <typename A> LoopAccessReport &operator<<(const A &Value) { 52 raw_string_ostream Out(Message); 53 Out << Value; 54 return *this; 55 } 56 57 const Instruction *getInstr() const { return Instr; } 58 59 std::string &str() { return Message; } 60 const std::string &str() const { return Message; } 61 operator Twine() { return Message; } 62 63 /// \brief Emit an analysis note for \p PassName with the debug location from 64 /// the instruction in \p Message if available. Otherwise use the location of 65 /// \p TheLoop. 66 static void emitAnalysis(const LoopAccessReport &Message, 67 const Function *TheFunction, 68 const Loop *TheLoop, 69 const char *PassName); 70 }; 71 72 /// \brief Collection of parameters shared beetween the Loop Vectorizer and the 73 /// Loop Access Analysis. 74 struct VectorizerParams { 75 /// \brief Maximum SIMD width. 76 static const unsigned MaxVectorWidth; 77 78 /// \brief VF as overridden by the user. 79 static unsigned VectorizationFactor; 80 /// \brief Interleave factor as overridden by the user. 81 static unsigned VectorizationInterleave; 82 /// \brief True if force-vector-interleave was specified by the user. 83 static bool isInterleaveForced(); 84 85 /// \\brief When performing memory disambiguation checks at runtime do not 86 /// make more than this number of comparisons. 87 static unsigned RuntimeMemoryCheckThreshold; 88 }; 89 90 /// \brief Checks memory dependences among accesses to the same underlying 91 /// object to determine whether there vectorization is legal or not (and at 92 /// which vectorization factor). 93 /// 94 /// Note: This class will compute a conservative dependence for access to 95 /// different underlying pointers. Clients, such as the loop vectorizer, will 96 /// sometimes deal these potential dependencies by emitting runtime checks. 97 /// 98 /// We use the ScalarEvolution framework to symbolically evalutate access 99 /// functions pairs. Since we currently don't restructure the loop we can rely 100 /// on the program order of memory accesses to determine their safety. 101 /// At the moment we will only deem accesses as safe for: 102 /// * A negative constant distance assuming program order. 103 /// 104 /// Safe: tmp = a[i + 1]; OR a[i + 1] = x; 105 /// a[i] = tmp; y = a[i]; 106 /// 107 /// The latter case is safe because later checks guarantuee that there can't 108 /// be a cycle through a phi node (that is, we check that "x" and "y" is not 109 /// the same variable: a header phi can only be an induction or a reduction, a 110 /// reduction can't have a memory sink, an induction can't have a memory 111 /// source). This is important and must not be violated (or we have to 112 /// resort to checking for cycles through memory). 113 /// 114 /// * A positive constant distance assuming program order that is bigger 115 /// than the biggest memory access. 116 /// 117 /// tmp = a[i] OR b[i] = x 118 /// a[i+2] = tmp y = b[i+2]; 119 /// 120 /// Safe distance: 2 x sizeof(a[0]), and 2 x sizeof(b[0]), respectively. 121 /// 122 /// * Zero distances and all accesses have the same size. 123 /// 124 class MemoryDepChecker { 125 public: 126 typedef PointerIntPair<Value *, 1, bool> MemAccessInfo; 127 typedef SmallPtrSet<MemAccessInfo, 8> MemAccessInfoSet; 128 /// \brief Set of potential dependent memory accesses. 129 typedef EquivalenceClasses<MemAccessInfo> DepCandidates; 130 131 /// \brief Dependece between memory access instructions. 132 struct Dependence { 133 /// \brief The type of the dependence. 134 enum DepType { 135 // No dependence. 136 NoDep, 137 // We couldn't determine the direction or the distance. 138 Unknown, 139 // Lexically forward. 140 // 141 // FIXME: If we only have loop-independent forward dependences (e.g. a 142 // read and write of A[i]), LAA will locally deem the dependence "safe" 143 // without querying the MemoryDepChecker. Therefore we can miss 144 // enumerating loop-independent forward dependences in 145 // getDependences. Note that as soon as there are different 146 // indices used to access the same array, the MemoryDepChecker *is* 147 // queried and the dependence list is complete. 148 Forward, 149 // Forward, but if vectorized, is likely to prevent store-to-load 150 // forwarding. 151 ForwardButPreventsForwarding, 152 // Lexically backward. 153 Backward, 154 // Backward, but the distance allows a vectorization factor of 155 // MaxSafeDepDistBytes. 156 BackwardVectorizable, 157 // Same, but may prevent store-to-load forwarding. 158 BackwardVectorizableButPreventsForwarding 159 }; 160 161 /// \brief String version of the types. 162 static const char *DepName[]; 163 164 /// \brief Index of the source of the dependence in the InstMap vector. 165 unsigned Source; 166 /// \brief Index of the destination of the dependence in the InstMap vector. 167 unsigned Destination; 168 /// \brief The type of the dependence. 169 DepType Type; 170 171 Dependence(unsigned Source, unsigned Destination, DepType Type) 172 : Source(Source), Destination(Destination), Type(Type) {} 173 174 /// \brief Return the source instruction of the dependence. 175 Instruction *getSource(const LoopAccessInfo &LAI) const; 176 /// \brief Return the destination instruction of the dependence. 177 Instruction *getDestination(const LoopAccessInfo &LAI) const; 178 179 /// \brief Dependence types that don't prevent vectorization. 180 static bool isSafeForVectorization(DepType Type); 181 182 /// \brief Lexically forward dependence. 183 bool isForward() const; 184 /// \brief Lexically backward dependence. 185 bool isBackward() const; 186 187 /// \brief May be a lexically backward dependence type (includes Unknown). 188 bool isPossiblyBackward() const; 189 190 /// \brief Print the dependence. \p Instr is used to map the instruction 191 /// indices to instructions. 192 void print(raw_ostream &OS, unsigned Depth, 193 const SmallVectorImpl<Instruction *> &Instrs) const; 194 }; 195 196 MemoryDepChecker(PredicatedScalarEvolution &PSE, const Loop *L) 197 : PSE(PSE), InnermostLoop(L), AccessIdx(0), 198 ShouldRetryWithRuntimeCheck(false), SafeForVectorization(true), 199 RecordDependences(true) {} 200 201 /// \brief Register the location (instructions are given increasing numbers) 202 /// of a write access. 203 void addAccess(StoreInst *SI) { 204 Value *Ptr = SI->getPointerOperand(); 205 Accesses[MemAccessInfo(Ptr, true)].push_back(AccessIdx); 206 InstMap.push_back(SI); 207 ++AccessIdx; 208 } 209 210 /// \brief Register the location (instructions are given increasing numbers) 211 /// of a write access. 212 void addAccess(LoadInst *LI) { 213 Value *Ptr = LI->getPointerOperand(); 214 Accesses[MemAccessInfo(Ptr, false)].push_back(AccessIdx); 215 InstMap.push_back(LI); 216 ++AccessIdx; 217 } 218 219 /// \brief Check whether the dependencies between the accesses are safe. 220 /// 221 /// Only checks sets with elements in \p CheckDeps. 222 bool areDepsSafe(DepCandidates &AccessSets, MemAccessInfoSet &CheckDeps, 223 const ValueToValueMap &Strides); 224 225 /// \brief No memory dependence was encountered that would inhibit 226 /// vectorization. 227 bool isSafeForVectorization() const { return SafeForVectorization; } 228 229 /// \brief The maximum number of bytes of a vector register we can vectorize 230 /// the accesses safely with. 231 unsigned getMaxSafeDepDistBytes() { return MaxSafeDepDistBytes; } 232 233 /// \brief In same cases when the dependency check fails we can still 234 /// vectorize the loop with a dynamic array access check. 235 bool shouldRetryWithRuntimeCheck() { return ShouldRetryWithRuntimeCheck; } 236 237 /// \brief Returns the memory dependences. If null is returned we exceeded 238 /// the MaxDependences threshold and this information is not 239 /// available. 240 const SmallVectorImpl<Dependence> *getDependences() const { 241 return RecordDependences ? &Dependences : nullptr; 242 } 243 244 void clearDependences() { Dependences.clear(); } 245 246 /// \brief The vector of memory access instructions. The indices are used as 247 /// instruction identifiers in the Dependence class. 248 const SmallVectorImpl<Instruction *> &getMemoryInstructions() const { 249 return InstMap; 250 } 251 252 /// \brief Generate a mapping between the memory instructions and their 253 /// indices according to program order. 254 DenseMap<Instruction *, unsigned> generateInstructionOrderMap() const { 255 DenseMap<Instruction *, unsigned> OrderMap; 256 257 for (unsigned I = 0; I < InstMap.size(); ++I) 258 OrderMap[InstMap[I]] = I; 259 260 return OrderMap; 261 } 262 263 /// \brief Find the set of instructions that read or write via \p Ptr. 264 SmallVector<Instruction *, 4> getInstructionsForAccess(Value *Ptr, 265 bool isWrite) const; 266 267 private: 268 /// A wrapper around ScalarEvolution, used to add runtime SCEV checks, and 269 /// applies dynamic knowledge to simplify SCEV expressions and convert them 270 /// to a more usable form. We need this in case assumptions about SCEV 271 /// expressions need to be made in order to avoid unknown dependences. For 272 /// example we might assume a unit stride for a pointer in order to prove 273 /// that a memory access is strided and doesn't wrap. 274 PredicatedScalarEvolution &PSE; 275 const Loop *InnermostLoop; 276 277 /// \brief Maps access locations (ptr, read/write) to program order. 278 DenseMap<MemAccessInfo, std::vector<unsigned> > Accesses; 279 280 /// \brief Memory access instructions in program order. 281 SmallVector<Instruction *, 16> InstMap; 282 283 /// \brief The program order index to be used for the next instruction. 284 unsigned AccessIdx; 285 286 // We can access this many bytes in parallel safely. 287 unsigned MaxSafeDepDistBytes; 288 289 /// \brief If we see a non-constant dependence distance we can still try to 290 /// vectorize this loop with runtime checks. 291 bool ShouldRetryWithRuntimeCheck; 292 293 /// \brief No memory dependence was encountered that would inhibit 294 /// vectorization. 295 bool SafeForVectorization; 296 297 //// \brief True if Dependences reflects the dependences in the 298 //// loop. If false we exceeded MaxDependences and 299 //// Dependences is invalid. 300 bool RecordDependences; 301 302 /// \brief Memory dependences collected during the analysis. Only valid if 303 /// RecordDependences is true. 304 SmallVector<Dependence, 8> Dependences; 305 306 /// \brief Check whether there is a plausible dependence between the two 307 /// accesses. 308 /// 309 /// Access \p A must happen before \p B in program order. The two indices 310 /// identify the index into the program order map. 311 /// 312 /// This function checks whether there is a plausible dependence (or the 313 /// absence of such can't be proved) between the two accesses. If there is a 314 /// plausible dependence but the dependence distance is bigger than one 315 /// element access it records this distance in \p MaxSafeDepDistBytes (if this 316 /// distance is smaller than any other distance encountered so far). 317 /// Otherwise, this function returns true signaling a possible dependence. 318 Dependence::DepType isDependent(const MemAccessInfo &A, unsigned AIdx, 319 const MemAccessInfo &B, unsigned BIdx, 320 const ValueToValueMap &Strides); 321 322 /// \brief Check whether the data dependence could prevent store-load 323 /// forwarding. 324 bool couldPreventStoreLoadForward(unsigned Distance, unsigned TypeByteSize); 325 }; 326 327 /// \brief Holds information about the memory runtime legality checks to verify 328 /// that a group of pointers do not overlap. 329 class RuntimePointerChecking { 330 public: 331 struct PointerInfo { 332 /// Holds the pointer value that we need to check. 333 TrackingVH<Value> PointerValue; 334 /// Holds the pointer value at the beginning of the loop. 335 const SCEV *Start; 336 /// Holds the pointer value at the end of the loop. 337 const SCEV *End; 338 /// Holds the information if this pointer is used for writing to memory. 339 bool IsWritePtr; 340 /// Holds the id of the set of pointers that could be dependent because of a 341 /// shared underlying object. 342 unsigned DependencySetId; 343 /// Holds the id of the disjoint alias set to which this pointer belongs. 344 unsigned AliasSetId; 345 /// SCEV for the access. 346 const SCEV *Expr; 347 348 PointerInfo(Value *PointerValue, const SCEV *Start, const SCEV *End, 349 bool IsWritePtr, unsigned DependencySetId, unsigned AliasSetId, 350 const SCEV *Expr) 351 : PointerValue(PointerValue), Start(Start), End(End), 352 IsWritePtr(IsWritePtr), DependencySetId(DependencySetId), 353 AliasSetId(AliasSetId), Expr(Expr) {} 354 }; 355 356 RuntimePointerChecking(ScalarEvolution *SE) : Need(false), SE(SE) {} 357 358 /// Reset the state of the pointer runtime information. 359 void reset() { 360 Need = false; 361 Pointers.clear(); 362 Checks.clear(); 363 } 364 365 /// Insert a pointer and calculate the start and end SCEVs. 366 /// \p We need Preds in order to compute the SCEV expression of the pointer 367 /// according to the assumptions that we've made during the analysis. 368 /// The method might also version the pointer stride according to \p Strides, 369 /// and change \p Preds. 370 void insert(Loop *Lp, Value *Ptr, bool WritePtr, unsigned DepSetId, 371 unsigned ASId, const ValueToValueMap &Strides, 372 PredicatedScalarEvolution &PSE); 373 374 /// \brief No run-time memory checking is necessary. 375 bool empty() const { return Pointers.empty(); } 376 377 /// A grouping of pointers. A single memcheck is required between 378 /// two groups. 379 struct CheckingPtrGroup { 380 /// \brief Create a new pointer checking group containing a single 381 /// pointer, with index \p Index in RtCheck. 382 CheckingPtrGroup(unsigned Index, RuntimePointerChecking &RtCheck) 383 : RtCheck(RtCheck), High(RtCheck.Pointers[Index].End), 384 Low(RtCheck.Pointers[Index].Start) { 385 Members.push_back(Index); 386 } 387 388 /// \brief Tries to add the pointer recorded in RtCheck at index 389 /// \p Index to this pointer checking group. We can only add a pointer 390 /// to a checking group if we will still be able to get 391 /// the upper and lower bounds of the check. Returns true in case 392 /// of success, false otherwise. 393 bool addPointer(unsigned Index); 394 395 /// Constitutes the context of this pointer checking group. For each 396 /// pointer that is a member of this group we will retain the index 397 /// at which it appears in RtCheck. 398 RuntimePointerChecking &RtCheck; 399 /// The SCEV expression which represents the upper bound of all the 400 /// pointers in this group. 401 const SCEV *High; 402 /// The SCEV expression which represents the lower bound of all the 403 /// pointers in this group. 404 const SCEV *Low; 405 /// Indices of all the pointers that constitute this grouping. 406 SmallVector<unsigned, 2> Members; 407 }; 408 409 /// \brief A memcheck which made up of a pair of grouped pointers. 410 /// 411 /// These *have* to be const for now, since checks are generated from 412 /// CheckingPtrGroups in LAI::addRuntimeChecks which is a const member 413 /// function. FIXME: once check-generation is moved inside this class (after 414 /// the PtrPartition hack is removed), we could drop const. 415 typedef std::pair<const CheckingPtrGroup *, const CheckingPtrGroup *> 416 PointerCheck; 417 418 /// \brief Generate the checks and store it. This also performs the grouping 419 /// of pointers to reduce the number of memchecks necessary. 420 void generateChecks(MemoryDepChecker::DepCandidates &DepCands, 421 bool UseDependencies); 422 423 /// \brief Returns the checks that generateChecks created. 424 const SmallVector<PointerCheck, 4> &getChecks() const { return Checks; } 425 426 /// \brief Decide if we need to add a check between two groups of pointers, 427 /// according to needsChecking. 428 bool needsChecking(const CheckingPtrGroup &M, 429 const CheckingPtrGroup &N) const; 430 431 /// \brief Returns the number of run-time checks required according to 432 /// needsChecking. 433 unsigned getNumberOfChecks() const { return Checks.size(); } 434 435 /// \brief Print the list run-time memory checks necessary. 436 void print(raw_ostream &OS, unsigned Depth = 0) const; 437 438 /// Print \p Checks. 439 void printChecks(raw_ostream &OS, const SmallVectorImpl<PointerCheck> &Checks, 440 unsigned Depth = 0) const; 441 442 /// This flag indicates if we need to add the runtime check. 443 bool Need; 444 445 /// Information about the pointers that may require checking. 446 SmallVector<PointerInfo, 2> Pointers; 447 448 /// Holds a partitioning of pointers into "check groups". 449 SmallVector<CheckingPtrGroup, 2> CheckingGroups; 450 451 /// \brief Check if pointers are in the same partition 452 /// 453 /// \p PtrToPartition contains the partition number for pointers (-1 if the 454 /// pointer belongs to multiple partitions). 455 static bool 456 arePointersInSamePartition(const SmallVectorImpl<int> &PtrToPartition, 457 unsigned PtrIdx1, unsigned PtrIdx2); 458 459 /// \brief Decide whether we need to issue a run-time check for pointer at 460 /// index \p I and \p J to prove their independence. 461 bool needsChecking(unsigned I, unsigned J) const; 462 463 /// \brief Return PointerInfo for pointer at index \p PtrIdx. 464 const PointerInfo &getPointerInfo(unsigned PtrIdx) const { 465 return Pointers[PtrIdx]; 466 } 467 468 private: 469 /// \brief Groups pointers such that a single memcheck is required 470 /// between two different groups. This will clear the CheckingGroups vector 471 /// and re-compute it. We will only group dependecies if \p UseDependencies 472 /// is true, otherwise we will create a separate group for each pointer. 473 void groupChecks(MemoryDepChecker::DepCandidates &DepCands, 474 bool UseDependencies); 475 476 /// Generate the checks and return them. 477 SmallVector<PointerCheck, 4> 478 generateChecks() const; 479 480 /// Holds a pointer to the ScalarEvolution analysis. 481 ScalarEvolution *SE; 482 483 /// \brief Set of run-time checks required to establish independence of 484 /// otherwise may-aliasing pointers in the loop. 485 SmallVector<PointerCheck, 4> Checks; 486 }; 487 488 /// \brief Drive the analysis of memory accesses in the loop 489 /// 490 /// This class is responsible for analyzing the memory accesses of a loop. It 491 /// collects the accesses and then its main helper the AccessAnalysis class 492 /// finds and categorizes the dependences in buildDependenceSets. 493 /// 494 /// For memory dependences that can be analyzed at compile time, it determines 495 /// whether the dependence is part of cycle inhibiting vectorization. This work 496 /// is delegated to the MemoryDepChecker class. 497 /// 498 /// For memory dependences that cannot be determined at compile time, it 499 /// generates run-time checks to prove independence. This is done by 500 /// AccessAnalysis::canCheckPtrAtRT and the checks are maintained by the 501 /// RuntimePointerCheck class. 502 /// 503 /// If pointers can wrap or can't be expressed as affine AddRec expressions by 504 /// ScalarEvolution, we will generate run-time checks by emitting a 505 /// SCEVUnionPredicate. 506 /// 507 /// Checks for both memory dependences and the SCEV predicates contained in the 508 /// PSE must be emitted in order for the results of this analysis to be valid. 509 class LoopAccessInfo { 510 public: 511 LoopAccessInfo(Loop *L, ScalarEvolution *SE, const DataLayout &DL, 512 const TargetLibraryInfo *TLI, AliasAnalysis *AA, 513 DominatorTree *DT, LoopInfo *LI, 514 const ValueToValueMap &Strides); 515 516 /// Return true we can analyze the memory accesses in the loop and there are 517 /// no memory dependence cycles. 518 bool canVectorizeMemory() const { return CanVecMem; } 519 520 const RuntimePointerChecking *getRuntimePointerChecking() const { 521 return &PtrRtChecking; 522 } 523 524 /// \brief Number of memchecks required to prove independence of otherwise 525 /// may-alias pointers. 526 unsigned getNumRuntimePointerChecks() const { 527 return PtrRtChecking.getNumberOfChecks(); 528 } 529 530 /// Return true if the block BB needs to be predicated in order for the loop 531 /// to be vectorized. 532 static bool blockNeedsPredication(BasicBlock *BB, Loop *TheLoop, 533 DominatorTree *DT); 534 535 /// Returns true if the value V is uniform within the loop. 536 bool isUniform(Value *V) const; 537 538 unsigned getMaxSafeDepDistBytes() const { return MaxSafeDepDistBytes; } 539 unsigned getNumStores() const { return NumStores; } 540 unsigned getNumLoads() const { return NumLoads;} 541 542 /// \brief Add code that checks at runtime if the accessed arrays overlap. 543 /// 544 /// Returns a pair of instructions where the first element is the first 545 /// instruction generated in possibly a sequence of instructions and the 546 /// second value is the final comparator value or NULL if no check is needed. 547 std::pair<Instruction *, Instruction *> 548 addRuntimeChecks(Instruction *Loc) const; 549 550 /// \brief Generete the instructions for the checks in \p PointerChecks. 551 /// 552 /// Returns a pair of instructions where the first element is the first 553 /// instruction generated in possibly a sequence of instructions and the 554 /// second value is the final comparator value or NULL if no check is needed. 555 std::pair<Instruction *, Instruction *> 556 addRuntimeChecks(Instruction *Loc, 557 const SmallVectorImpl<RuntimePointerChecking::PointerCheck> 558 &PointerChecks) const; 559 560 /// \brief The diagnostics report generated for the analysis. E.g. why we 561 /// couldn't analyze the loop. 562 const Optional<LoopAccessReport> &getReport() const { return Report; } 563 564 /// \brief the Memory Dependence Checker which can determine the 565 /// loop-independent and loop-carried dependences between memory accesses. 566 const MemoryDepChecker &getDepChecker() const { return DepChecker; } 567 568 /// \brief Return the list of instructions that use \p Ptr to read or write 569 /// memory. 570 SmallVector<Instruction *, 4> getInstructionsForAccess(Value *Ptr, 571 bool isWrite) const { 572 return DepChecker.getInstructionsForAccess(Ptr, isWrite); 573 } 574 575 /// \brief Print the information about the memory accesses in the loop. 576 void print(raw_ostream &OS, unsigned Depth = 0) const; 577 578 /// \brief Used to ensure that if the analysis was run with speculating the 579 /// value of symbolic strides, the client queries it with the same assumption. 580 /// Only used in DEBUG build but we don't want NDEBUG-dependent ABI. 581 unsigned NumSymbolicStrides; 582 583 /// \brief Checks existence of store to invariant address inside loop. 584 /// If the loop has any store to invariant address, then it returns true, 585 /// else returns false. 586 bool hasStoreToLoopInvariantAddress() const { 587 return StoreToLoopInvariantAddress; 588 } 589 590 /// Used to add runtime SCEV checks. Simplifies SCEV expressions and converts 591 /// them to a more usable form. All SCEV expressions during the analysis 592 /// should be re-written (and therefore simplified) according to PSE. 593 /// A user of LoopAccessAnalysis will need to emit the runtime checks 594 /// associated with this predicate. 595 PredicatedScalarEvolution PSE; 596 597 private: 598 /// \brief Analyze the loop. Substitute symbolic strides using Strides. 599 void analyzeLoop(const ValueToValueMap &Strides); 600 601 /// \brief Check if the structure of the loop allows it to be analyzed by this 602 /// pass. 603 bool canAnalyzeLoop(); 604 605 void emitAnalysis(LoopAccessReport &Message); 606 607 /// We need to check that all of the pointers in this list are disjoint 608 /// at runtime. 609 RuntimePointerChecking PtrRtChecking; 610 611 /// \brief the Memory Dependence Checker which can determine the 612 /// loop-independent and loop-carried dependences between memory accesses. 613 MemoryDepChecker DepChecker; 614 615 Loop *TheLoop; 616 const DataLayout &DL; 617 const TargetLibraryInfo *TLI; 618 AliasAnalysis *AA; 619 DominatorTree *DT; 620 LoopInfo *LI; 621 622 unsigned NumLoads; 623 unsigned NumStores; 624 625 unsigned MaxSafeDepDistBytes; 626 627 /// \brief Cache the result of analyzeLoop. 628 bool CanVecMem; 629 630 /// \brief Indicator for storing to uniform addresses. 631 /// If a loop has write to a loop invariant address then it should be true. 632 bool StoreToLoopInvariantAddress; 633 634 /// \brief The diagnostics report generated for the analysis. E.g. why we 635 /// couldn't analyze the loop. 636 Optional<LoopAccessReport> Report; 637 }; 638 639 Value *stripIntegerCast(Value *V); 640 641 ///\brief Return the SCEV corresponding to a pointer with the symbolic stride 642 /// replaced with constant one, assuming \p Preds is true. 643 /// 644 /// If necessary this method will version the stride of the pointer according 645 /// to \p PtrToStride and therefore add a new predicate to \p Preds. 646 /// 647 /// If \p OrigPtr is not null, use it to look up the stride value instead of \p 648 /// Ptr. \p PtrToStride provides the mapping between the pointer value and its 649 /// stride as collected by LoopVectorizationLegality::collectStridedAccess. 650 const SCEV *replaceSymbolicStrideSCEV(PredicatedScalarEvolution &PSE, 651 const ValueToValueMap &PtrToStride, 652 Value *Ptr, Value *OrigPtr = nullptr); 653 654 /// \brief Check the stride of the pointer and ensure that it does not wrap in 655 /// the address space, assuming \p Preds is true. 656 /// 657 /// If necessary this method will version the stride of the pointer according 658 /// to \p PtrToStride and therefore add a new predicate to \p Preds. 659 int isStridedPtr(PredicatedScalarEvolution &PSE, Value *Ptr, const Loop *Lp, 660 const ValueToValueMap &StridesMap); 661 662 /// \brief This analysis provides dependence information for the memory accesses 663 /// of a loop. 664 /// 665 /// It runs the analysis for a loop on demand. This can be initiated by 666 /// querying the loop access info via LAA::getInfo. getInfo return a 667 /// LoopAccessInfo object. See this class for the specifics of what information 668 /// is provided. 669 class LoopAccessAnalysis : public FunctionPass { 670 public: 671 static char ID; 672 673 LoopAccessAnalysis() : FunctionPass(ID) { 674 initializeLoopAccessAnalysisPass(*PassRegistry::getPassRegistry()); 675 } 676 677 bool runOnFunction(Function &F) override; 678 679 void getAnalysisUsage(AnalysisUsage &AU) const override; 680 681 /// \brief Query the result of the loop access information for the loop \p L. 682 /// 683 /// If the client speculates (and then issues run-time checks) for the values 684 /// of symbolic strides, \p Strides provides the mapping (see 685 /// replaceSymbolicStrideSCEV). If there is no cached result available run 686 /// the analysis. 687 const LoopAccessInfo &getInfo(Loop *L, const ValueToValueMap &Strides); 688 689 void releaseMemory() override { 690 // Invalidate the cache when the pass is freed. 691 LoopAccessInfoMap.clear(); 692 } 693 694 /// \brief Print the result of the analysis when invoked with -analyze. 695 void print(raw_ostream &OS, const Module *M = nullptr) const override; 696 697 private: 698 /// \brief The cache. 699 DenseMap<Loop *, std::unique_ptr<LoopAccessInfo>> LoopAccessInfoMap; 700 701 // The used analysis passes. 702 ScalarEvolution *SE; 703 const TargetLibraryInfo *TLI; 704 AliasAnalysis *AA; 705 DominatorTree *DT; 706 LoopInfo *LI; 707 }; 708 709 inline Instruction *MemoryDepChecker::Dependence::getSource( 710 const LoopAccessInfo &LAI) const { 711 return LAI.getDepChecker().getMemoryInstructions()[Source]; 712 } 713 714 inline Instruction *MemoryDepChecker::Dependence::getDestination( 715 const LoopAccessInfo &LAI) const { 716 return LAI.getDepChecker().getMemoryInstructions()[Destination]; 717 } 718 719 } // End llvm namespace 720 721 #endif 722