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/LoopAnalysisManager.h" 24#include "llvm/Analysis/ScalarEvolutionExpressions.h" 25#include "llvm/IR/DiagnosticInfo.h" 26#include "llvm/IR/ValueHandle.h" 27#include "llvm/Pass.h" 28#include "llvm/Support/raw_ostream.h" 29 30namespace llvm { 31 32class Value; 33class DataLayout; 34class ScalarEvolution; 35class Loop; 36class SCEV; 37class SCEVUnionPredicate; 38class LoopAccessInfo; 39class OptimizationRemarkEmitter; 40 41/// \brief Collection of parameters shared beetween the Loop Vectorizer and the 42/// Loop Access Analysis. 43struct VectorizerParams { 44 /// \brief Maximum SIMD width. 45 static const unsigned MaxVectorWidth; 46 47 /// \brief VF as overridden by the user. 48 static unsigned VectorizationFactor; 49 /// \brief Interleave factor as overridden by the user. 50 static unsigned VectorizationInterleave; 51 /// \brief True if force-vector-interleave was specified by the user. 52 static bool isInterleaveForced(); 53 54 /// \\brief When performing memory disambiguation checks at runtime do not 55 /// make more than this number of comparisons. 56 static unsigned RuntimeMemoryCheckThreshold; 57}; 58 59/// \brief Checks memory dependences among accesses to the same underlying 60/// object to determine whether there vectorization is legal or not (and at 61/// which vectorization factor). 62/// 63/// Note: This class will compute a conservative dependence for access to 64/// different underlying pointers. Clients, such as the loop vectorizer, will 65/// sometimes deal these potential dependencies by emitting runtime checks. 66/// 67/// We use the ScalarEvolution framework to symbolically evalutate access 68/// functions pairs. Since we currently don't restructure the loop we can rely 69/// on the program order of memory accesses to determine their safety. 70/// At the moment we will only deem accesses as safe for: 71/// * A negative constant distance assuming program order. 72/// 73/// Safe: tmp = a[i + 1]; OR a[i + 1] = x; 74/// a[i] = tmp; y = a[i]; 75/// 76/// The latter case is safe because later checks guarantuee that there can't 77/// be a cycle through a phi node (that is, we check that "x" and "y" is not 78/// the same variable: a header phi can only be an induction or a reduction, a 79/// reduction can't have a memory sink, an induction can't have a memory 80/// source). This is important and must not be violated (or we have to 81/// resort to checking for cycles through memory). 82/// 83/// * A positive constant distance assuming program order that is bigger 84/// than the biggest memory access. 85/// 86/// tmp = a[i] OR b[i] = x 87/// a[i+2] = tmp y = b[i+2]; 88/// 89/// Safe distance: 2 x sizeof(a[0]), and 2 x sizeof(b[0]), respectively. 90/// 91/// * Zero distances and all accesses have the same size. 92/// 93class MemoryDepChecker { 94public: 95 typedef PointerIntPair<Value *, 1, bool> MemAccessInfo; 96 typedef SmallVector<MemAccessInfo, 8> MemAccessInfoList; 97 /// \brief Set of potential dependent memory accesses. 98 typedef EquivalenceClasses<MemAccessInfo> DepCandidates; 99 100 /// \brief Dependece between memory access instructions. 101 struct Dependence { 102 /// \brief The type of the dependence. 103 enum DepType { 104 // No dependence. 105 NoDep, 106 // We couldn't determine the direction or the distance. 107 Unknown, 108 // Lexically forward. 109 // 110 // FIXME: If we only have loop-independent forward dependences (e.g. a 111 // read and write of A[i]), LAA will locally deem the dependence "safe" 112 // without querying the MemoryDepChecker. Therefore we can miss 113 // enumerating loop-independent forward dependences in 114 // getDependences. Note that as soon as there are different 115 // indices used to access the same array, the MemoryDepChecker *is* 116 // queried and the dependence list is complete. 117 Forward, 118 // Forward, but if vectorized, is likely to prevent store-to-load 119 // forwarding. 120 ForwardButPreventsForwarding, 121 // Lexically backward. 122 Backward, 123 // Backward, but the distance allows a vectorization factor of 124 // MaxSafeDepDistBytes. 125 BackwardVectorizable, 126 // Same, but may prevent store-to-load forwarding. 127 BackwardVectorizableButPreventsForwarding 128 }; 129 130 /// \brief String version of the types. 131 static const char *DepName[]; 132 133 /// \brief Index of the source of the dependence in the InstMap vector. 134 unsigned Source; 135 /// \brief Index of the destination of the dependence in the InstMap vector. 136 unsigned Destination; 137 /// \brief The type of the dependence. 138 DepType Type; 139 140 Dependence(unsigned Source, unsigned Destination, DepType Type) 141 : Source(Source), Destination(Destination), Type(Type) {} 142 143 /// \brief Return the source instruction of the dependence. 144 Instruction *getSource(const LoopAccessInfo &LAI) const; 145 /// \brief Return the destination instruction of the dependence. 146 Instruction *getDestination(const LoopAccessInfo &LAI) const; 147 148 /// \brief Dependence types that don't prevent vectorization. 149 static bool isSafeForVectorization(DepType Type); 150 151 /// \brief Lexically forward dependence. 152 bool isForward() const; 153 /// \brief Lexically backward dependence. 154 bool isBackward() const; 155 156 /// \brief May be a lexically backward dependence type (includes Unknown). 157 bool isPossiblyBackward() const; 158 159 /// \brief Print the dependence. \p Instr is used to map the instruction 160 /// indices to instructions. 161 void print(raw_ostream &OS, unsigned Depth, 162 const SmallVectorImpl<Instruction *> &Instrs) const; 163 }; 164 165 MemoryDepChecker(PredicatedScalarEvolution &PSE, const Loop *L) 166 : PSE(PSE), InnermostLoop(L), AccessIdx(0), MaxSafeRegisterWidth(-1U), 167 ShouldRetryWithRuntimeCheck(false), SafeForVectorization(true), 168 RecordDependences(true) {} 169 170 /// \brief Register the location (instructions are given increasing numbers) 171 /// of a write access. 172 void addAccess(StoreInst *SI) { 173 Value *Ptr = SI->getPointerOperand(); 174 Accesses[MemAccessInfo(Ptr, true)].push_back(AccessIdx); 175 InstMap.push_back(SI); 176 ++AccessIdx; 177 } 178 179 /// \brief Register the location (instructions are given increasing numbers) 180 /// of a write access. 181 void addAccess(LoadInst *LI) { 182 Value *Ptr = LI->getPointerOperand(); 183 Accesses[MemAccessInfo(Ptr, false)].push_back(AccessIdx); 184 InstMap.push_back(LI); 185 ++AccessIdx; 186 } 187 188 /// \brief Check whether the dependencies between the accesses are safe. 189 /// 190 /// Only checks sets with elements in \p CheckDeps. 191 bool areDepsSafe(DepCandidates &AccessSets, MemAccessInfoList &CheckDeps, 192 const ValueToValueMap &Strides); 193 194 /// \brief No memory dependence was encountered that would inhibit 195 /// vectorization. 196 bool isSafeForVectorization() const { return SafeForVectorization; } 197 198 /// \brief The maximum number of bytes of a vector register we can vectorize 199 /// the accesses safely with. 200 uint64_t getMaxSafeDepDistBytes() { return MaxSafeDepDistBytes; } 201 202 /// \brief Return the number of elements that are safe to operate on 203 /// simultaneously, multiplied by the size of the element in bits. 204 uint64_t getMaxSafeRegisterWidth() const { return MaxSafeRegisterWidth; } 205 206 /// \brief In same cases when the dependency check fails we can still 207 /// vectorize the loop with a dynamic array access check. 208 bool shouldRetryWithRuntimeCheck() { return ShouldRetryWithRuntimeCheck; } 209 210 /// \brief Returns the memory dependences. If null is returned we exceeded 211 /// the MaxDependences threshold and this information is not 212 /// available. 213 const SmallVectorImpl<Dependence> *getDependences() const { 214 return RecordDependences ? &Dependences : nullptr; 215 } 216 217 void clearDependences() { Dependences.clear(); } 218 219 /// \brief The vector of memory access instructions. The indices are used as 220 /// instruction identifiers in the Dependence class. 221 const SmallVectorImpl<Instruction *> &getMemoryInstructions() const { 222 return InstMap; 223 } 224 225 /// \brief Generate a mapping between the memory instructions and their 226 /// indices according to program order. 227 DenseMap<Instruction *, unsigned> generateInstructionOrderMap() const { 228 DenseMap<Instruction *, unsigned> OrderMap; 229 230 for (unsigned I = 0; I < InstMap.size(); ++I) 231 OrderMap[InstMap[I]] = I; 232 233 return OrderMap; 234 } 235 236 /// \brief Find the set of instructions that read or write via \p Ptr. 237 SmallVector<Instruction *, 4> getInstructionsForAccess(Value *Ptr, 238 bool isWrite) const; 239 240private: 241 /// A wrapper around ScalarEvolution, used to add runtime SCEV checks, and 242 /// applies dynamic knowledge to simplify SCEV expressions and convert them 243 /// to a more usable form. We need this in case assumptions about SCEV 244 /// expressions need to be made in order to avoid unknown dependences. For 245 /// example we might assume a unit stride for a pointer in order to prove 246 /// that a memory access is strided and doesn't wrap. 247 PredicatedScalarEvolution &PSE; 248 const Loop *InnermostLoop; 249 250 /// \brief Maps access locations (ptr, read/write) to program order. 251 DenseMap<MemAccessInfo, std::vector<unsigned> > Accesses; 252 253 /// \brief Memory access instructions in program order. 254 SmallVector<Instruction *, 16> InstMap; 255 256 /// \brief The program order index to be used for the next instruction. 257 unsigned AccessIdx; 258 259 // We can access this many bytes in parallel safely. 260 uint64_t MaxSafeDepDistBytes; 261 262 /// \brief Number of elements (from consecutive iterations) that are safe to 263 /// operate on simultaneously, multiplied by the size of the element in bits. 264 /// The size of the element is taken from the memory access that is most 265 /// restrictive. 266 uint64_t MaxSafeRegisterWidth; 267 268 /// \brief If we see a non-constant dependence distance we can still try to 269 /// vectorize this loop with runtime checks. 270 bool ShouldRetryWithRuntimeCheck; 271 272 /// \brief No memory dependence was encountered that would inhibit 273 /// vectorization. 274 bool SafeForVectorization; 275 276 //// \brief True if Dependences reflects the dependences in the 277 //// loop. If false we exceeded MaxDependences and 278 //// Dependences is invalid. 279 bool RecordDependences; 280 281 /// \brief Memory dependences collected during the analysis. Only valid if 282 /// RecordDependences is true. 283 SmallVector<Dependence, 8> Dependences; 284 285 /// \brief Check whether there is a plausible dependence between the two 286 /// accesses. 287 /// 288 /// Access \p A must happen before \p B in program order. The two indices 289 /// identify the index into the program order map. 290 /// 291 /// This function checks whether there is a plausible dependence (or the 292 /// absence of such can't be proved) between the two accesses. If there is a 293 /// plausible dependence but the dependence distance is bigger than one 294 /// element access it records this distance in \p MaxSafeDepDistBytes (if this 295 /// distance is smaller than any other distance encountered so far). 296 /// Otherwise, this function returns true signaling a possible dependence. 297 Dependence::DepType isDependent(const MemAccessInfo &A, unsigned AIdx, 298 const MemAccessInfo &B, unsigned BIdx, 299 const ValueToValueMap &Strides); 300 301 /// \brief Check whether the data dependence could prevent store-load 302 /// forwarding. 303 /// 304 /// \return false if we shouldn't vectorize at all or avoid larger 305 /// vectorization factors by limiting MaxSafeDepDistBytes. 306 bool couldPreventStoreLoadForward(uint64_t Distance, uint64_t TypeByteSize); 307}; 308 309/// \brief Holds information about the memory runtime legality checks to verify 310/// that a group of pointers do not overlap. 311class RuntimePointerChecking { 312public: 313 struct PointerInfo { 314 /// Holds the pointer value that we need to check. 315 TrackingVH<Value> PointerValue; 316 /// Holds the smallest byte address accessed by the pointer throughout all 317 /// iterations of the loop. 318 const SCEV *Start; 319 /// Holds the largest byte address accessed by the pointer throughout all 320 /// iterations of the loop, plus 1. 321 const SCEV *End; 322 /// Holds the information if this pointer is used for writing to memory. 323 bool IsWritePtr; 324 /// Holds the id of the set of pointers that could be dependent because of a 325 /// shared underlying object. 326 unsigned DependencySetId; 327 /// Holds the id of the disjoint alias set to which this pointer belongs. 328 unsigned AliasSetId; 329 /// SCEV for the access. 330 const SCEV *Expr; 331 332 PointerInfo(Value *PointerValue, const SCEV *Start, const SCEV *End, 333 bool IsWritePtr, unsigned DependencySetId, unsigned AliasSetId, 334 const SCEV *Expr) 335 : PointerValue(PointerValue), Start(Start), End(End), 336 IsWritePtr(IsWritePtr), DependencySetId(DependencySetId), 337 AliasSetId(AliasSetId), Expr(Expr) {} 338 }; 339 340 RuntimePointerChecking(ScalarEvolution *SE) : Need(false), SE(SE) {} 341 342 /// Reset the state of the pointer runtime information. 343 void reset() { 344 Need = false; 345 Pointers.clear(); 346 Checks.clear(); 347 } 348 349 /// Insert a pointer and calculate the start and end SCEVs. 350 /// We need \p PSE in order to compute the SCEV expression of the pointer 351 /// according to the assumptions that we've made during the analysis. 352 /// The method might also version the pointer stride according to \p Strides, 353 /// and add new predicates to \p PSE. 354 void insert(Loop *Lp, Value *Ptr, bool WritePtr, unsigned DepSetId, 355 unsigned ASId, const ValueToValueMap &Strides, 356 PredicatedScalarEvolution &PSE); 357 358 /// \brief No run-time memory checking is necessary. 359 bool empty() const { return Pointers.empty(); } 360 361 /// A grouping of pointers. A single memcheck is required between 362 /// two groups. 363 struct CheckingPtrGroup { 364 /// \brief Create a new pointer checking group containing a single 365 /// pointer, with index \p Index in RtCheck. 366 CheckingPtrGroup(unsigned Index, RuntimePointerChecking &RtCheck) 367 : RtCheck(RtCheck), High(RtCheck.Pointers[Index].End), 368 Low(RtCheck.Pointers[Index].Start) { 369 Members.push_back(Index); 370 } 371 372 /// \brief Tries to add the pointer recorded in RtCheck at index 373 /// \p Index to this pointer checking group. We can only add a pointer 374 /// to a checking group if we will still be able to get 375 /// the upper and lower bounds of the check. Returns true in case 376 /// of success, false otherwise. 377 bool addPointer(unsigned Index); 378 379 /// Constitutes the context of this pointer checking group. For each 380 /// pointer that is a member of this group we will retain the index 381 /// at which it appears in RtCheck. 382 RuntimePointerChecking &RtCheck; 383 /// The SCEV expression which represents the upper bound of all the 384 /// pointers in this group. 385 const SCEV *High; 386 /// The SCEV expression which represents the lower bound of all the 387 /// pointers in this group. 388 const SCEV *Low; 389 /// Indices of all the pointers that constitute this grouping. 390 SmallVector<unsigned, 2> Members; 391 }; 392 393 /// \brief A memcheck which made up of a pair of grouped pointers. 394 /// 395 /// These *have* to be const for now, since checks are generated from 396 /// CheckingPtrGroups in LAI::addRuntimeChecks which is a const member 397 /// function. FIXME: once check-generation is moved inside this class (after 398 /// the PtrPartition hack is removed), we could drop const. 399 typedef std::pair<const CheckingPtrGroup *, const CheckingPtrGroup *> 400 PointerCheck; 401 402 /// \brief Generate the checks and store it. This also performs the grouping 403 /// of pointers to reduce the number of memchecks necessary. 404 void generateChecks(MemoryDepChecker::DepCandidates &DepCands, 405 bool UseDependencies); 406 407 /// \brief Returns the checks that generateChecks created. 408 const SmallVector<PointerCheck, 4> &getChecks() const { return Checks; } 409 410 /// \brief Decide if we need to add a check between two groups of pointers, 411 /// according to needsChecking. 412 bool needsChecking(const CheckingPtrGroup &M, 413 const CheckingPtrGroup &N) const; 414 415 /// \brief Returns the number of run-time checks required according to 416 /// needsChecking. 417 unsigned getNumberOfChecks() const { return Checks.size(); } 418 419 /// \brief Print the list run-time memory checks necessary. 420 void print(raw_ostream &OS, unsigned Depth = 0) const; 421 422 /// Print \p Checks. 423 void printChecks(raw_ostream &OS, const SmallVectorImpl<PointerCheck> &Checks, 424 unsigned Depth = 0) const; 425 426 /// This flag indicates if we need to add the runtime check. 427 bool Need; 428 429 /// Information about the pointers that may require checking. 430 SmallVector<PointerInfo, 2> Pointers; 431 432 /// Holds a partitioning of pointers into "check groups". 433 SmallVector<CheckingPtrGroup, 2> CheckingGroups; 434 435 /// \brief Check if pointers are in the same partition 436 /// 437 /// \p PtrToPartition contains the partition number for pointers (-1 if the 438 /// pointer belongs to multiple partitions). 439 static bool 440 arePointersInSamePartition(const SmallVectorImpl<int> &PtrToPartition, 441 unsigned PtrIdx1, unsigned PtrIdx2); 442 443 /// \brief Decide whether we need to issue a run-time check for pointer at 444 /// index \p I and \p J to prove their independence. 445 bool needsChecking(unsigned I, unsigned J) const; 446 447 /// \brief Return PointerInfo for pointer at index \p PtrIdx. 448 const PointerInfo &getPointerInfo(unsigned PtrIdx) const { 449 return Pointers[PtrIdx]; 450 } 451 452private: 453 /// \brief Groups pointers such that a single memcheck is required 454 /// between two different groups. This will clear the CheckingGroups vector 455 /// and re-compute it. We will only group dependecies if \p UseDependencies 456 /// is true, otherwise we will create a separate group for each pointer. 457 void groupChecks(MemoryDepChecker::DepCandidates &DepCands, 458 bool UseDependencies); 459 460 /// Generate the checks and return them. 461 SmallVector<PointerCheck, 4> 462 generateChecks() const; 463 464 /// Holds a pointer to the ScalarEvolution analysis. 465 ScalarEvolution *SE; 466 467 /// \brief Set of run-time checks required to establish independence of 468 /// otherwise may-aliasing pointers in the loop. 469 SmallVector<PointerCheck, 4> Checks; 470}; 471 472/// \brief Drive the analysis of memory accesses in the loop 473/// 474/// This class is responsible for analyzing the memory accesses of a loop. It 475/// collects the accesses and then its main helper the AccessAnalysis class 476/// finds and categorizes the dependences in buildDependenceSets. 477/// 478/// For memory dependences that can be analyzed at compile time, it determines 479/// whether the dependence is part of cycle inhibiting vectorization. This work 480/// is delegated to the MemoryDepChecker class. 481/// 482/// For memory dependences that cannot be determined at compile time, it 483/// generates run-time checks to prove independence. This is done by 484/// AccessAnalysis::canCheckPtrAtRT and the checks are maintained by the 485/// RuntimePointerCheck class. 486/// 487/// If pointers can wrap or can't be expressed as affine AddRec expressions by 488/// ScalarEvolution, we will generate run-time checks by emitting a 489/// SCEVUnionPredicate. 490/// 491/// Checks for both memory dependences and the SCEV predicates contained in the 492/// PSE must be emitted in order for the results of this analysis to be valid. 493class LoopAccessInfo { 494public: 495 LoopAccessInfo(Loop *L, ScalarEvolution *SE, const TargetLibraryInfo *TLI, 496 AliasAnalysis *AA, DominatorTree *DT, LoopInfo *LI); 497 498 /// Return true we can analyze the memory accesses in the loop and there are 499 /// no memory dependence cycles. 500 bool canVectorizeMemory() const { return CanVecMem; } 501 502 const RuntimePointerChecking *getRuntimePointerChecking() const { 503 return PtrRtChecking.get(); 504 } 505 506 /// \brief Number of memchecks required to prove independence of otherwise 507 /// may-alias pointers. 508 unsigned getNumRuntimePointerChecks() const { 509 return PtrRtChecking->getNumberOfChecks(); 510 } 511 512 /// Return true if the block BB needs to be predicated in order for the loop 513 /// to be vectorized. 514 static bool blockNeedsPredication(BasicBlock *BB, Loop *TheLoop, 515 DominatorTree *DT); 516 517 /// Returns true if the value V is uniform within the loop. 518 bool isUniform(Value *V) const; 519 520 uint64_t getMaxSafeDepDistBytes() const { return MaxSafeDepDistBytes; } 521 unsigned getNumStores() const { return NumStores; } 522 unsigned getNumLoads() const { return NumLoads;} 523 524 /// \brief Add code that checks at runtime if the accessed arrays overlap. 525 /// 526 /// Returns a pair of instructions where the first element is the first 527 /// instruction generated in possibly a sequence of instructions and the 528 /// second value is the final comparator value or NULL if no check is needed. 529 std::pair<Instruction *, Instruction *> 530 addRuntimeChecks(Instruction *Loc) const; 531 532 /// \brief Generete the instructions for the checks in \p PointerChecks. 533 /// 534 /// Returns a pair of instructions where the first element is the first 535 /// instruction generated in possibly a sequence of instructions and the 536 /// second value is the final comparator value or NULL if no check is needed. 537 std::pair<Instruction *, Instruction *> 538 addRuntimeChecks(Instruction *Loc, 539 const SmallVectorImpl<RuntimePointerChecking::PointerCheck> 540 &PointerChecks) const; 541 542 /// \brief The diagnostics report generated for the analysis. E.g. why we 543 /// couldn't analyze the loop. 544 const OptimizationRemarkAnalysis *getReport() const { return Report.get(); } 545 546 /// \brief the Memory Dependence Checker which can determine the 547 /// loop-independent and loop-carried dependences between memory accesses. 548 const MemoryDepChecker &getDepChecker() const { return *DepChecker; } 549 550 /// \brief Return the list of instructions that use \p Ptr to read or write 551 /// memory. 552 SmallVector<Instruction *, 4> getInstructionsForAccess(Value *Ptr, 553 bool isWrite) const { 554 return DepChecker->getInstructionsForAccess(Ptr, isWrite); 555 } 556 557 /// \brief If an access has a symbolic strides, this maps the pointer value to 558 /// the stride symbol. 559 const ValueToValueMap &getSymbolicStrides() const { return SymbolicStrides; } 560 561 /// \brief Pointer has a symbolic stride. 562 bool hasStride(Value *V) const { return StrideSet.count(V); } 563 564 /// \brief Print the information about the memory accesses in the loop. 565 void print(raw_ostream &OS, unsigned Depth = 0) const; 566 567 /// \brief Checks existence of store to invariant address inside loop. 568 /// If the loop has any store to invariant address, then it returns true, 569 /// else returns false. 570 bool hasStoreToLoopInvariantAddress() const { 571 return StoreToLoopInvariantAddress; 572 } 573 574 /// Used to add runtime SCEV checks. Simplifies SCEV expressions and converts 575 /// them to a more usable form. All SCEV expressions during the analysis 576 /// should be re-written (and therefore simplified) according to PSE. 577 /// A user of LoopAccessAnalysis will need to emit the runtime checks 578 /// associated with this predicate. 579 const PredicatedScalarEvolution &getPSE() const { return *PSE; } 580 581private: 582 /// \brief Analyze the loop. 583 void analyzeLoop(AliasAnalysis *AA, LoopInfo *LI, 584 const TargetLibraryInfo *TLI, DominatorTree *DT); 585 586 /// \brief Check if the structure of the loop allows it to be analyzed by this 587 /// pass. 588 bool canAnalyzeLoop(); 589 590 /// \brief Save the analysis remark. 591 /// 592 /// LAA does not directly emits the remarks. Instead it stores it which the 593 /// client can retrieve and presents as its own analysis 594 /// (e.g. -Rpass-analysis=loop-vectorize). 595 OptimizationRemarkAnalysis &recordAnalysis(StringRef RemarkName, 596 Instruction *Instr = nullptr); 597 598 /// \brief Collect memory access with loop invariant strides. 599 /// 600 /// Looks for accesses like "a[i * StrideA]" where "StrideA" is loop 601 /// invariant. 602 void collectStridedAccess(Value *LoadOrStoreInst); 603 604 std::unique_ptr<PredicatedScalarEvolution> PSE; 605 606 /// We need to check that all of the pointers in this list are disjoint 607 /// at runtime. Using std::unique_ptr to make using move ctor simpler. 608 std::unique_ptr<RuntimePointerChecking> PtrRtChecking; 609 610 /// \brief the Memory Dependence Checker which can determine the 611 /// loop-independent and loop-carried dependences between memory accesses. 612 std::unique_ptr<MemoryDepChecker> DepChecker; 613 614 Loop *TheLoop; 615 616 unsigned NumLoads; 617 unsigned NumStores; 618 619 uint64_t MaxSafeDepDistBytes; 620 621 /// \brief Cache the result of analyzeLoop. 622 bool CanVecMem; 623 624 /// \brief Indicator for storing to uniform addresses. 625 /// If a loop has write to a loop invariant address then it should be true. 626 bool StoreToLoopInvariantAddress; 627 628 /// \brief The diagnostics report generated for the analysis. E.g. why we 629 /// couldn't analyze the loop. 630 std::unique_ptr<OptimizationRemarkAnalysis> Report; 631 632 /// \brief If an access has a symbolic strides, this maps the pointer value to 633 /// the stride symbol. 634 ValueToValueMap SymbolicStrides; 635 636 /// \brief Set of symbolic strides values. 637 SmallPtrSet<Value *, 8> StrideSet; 638}; 639 640Value *stripIntegerCast(Value *V); 641 642/// \brief Return the SCEV corresponding to a pointer with the symbolic stride 643/// replaced with constant one, assuming the SCEV predicate associated with 644/// \p PSE is true. 645/// 646/// If necessary this method will version the stride of the pointer according 647/// to \p PtrToStride and therefore add further predicates to \p PSE. 648/// 649/// If \p OrigPtr is not null, use it to look up the stride value instead of \p 650/// Ptr. \p PtrToStride provides the mapping between the pointer value and its 651/// stride as collected by LoopVectorizationLegality::collectStridedAccess. 652const SCEV *replaceSymbolicStrideSCEV(PredicatedScalarEvolution &PSE, 653 const ValueToValueMap &PtrToStride, 654 Value *Ptr, Value *OrigPtr = nullptr); 655 656/// \brief If the pointer has a constant stride return it in units of its 657/// element size. Otherwise return zero. 658/// 659/// Ensure that it does not wrap in the address space, assuming the predicate 660/// associated with \p PSE is true. 661/// 662/// If necessary this method will version the stride of the pointer according 663/// to \p PtrToStride and therefore add further predicates to \p PSE. 664/// The \p Assume parameter indicates if we are allowed to make additional 665/// run-time assumptions. 666int64_t getPtrStride(PredicatedScalarEvolution &PSE, Value *Ptr, const Loop *Lp, 667 const ValueToValueMap &StridesMap = ValueToValueMap(), 668 bool Assume = false, bool ShouldCheckWrap = true); 669 670/// \brief Returns true if the memory operations \p A and \p B are consecutive. 671/// This is a simple API that does not depend on the analysis pass. 672bool isConsecutiveAccess(Value *A, Value *B, const DataLayout &DL, 673 ScalarEvolution &SE, bool CheckType = true); 674 675/// \brief This analysis provides dependence information for the memory accesses 676/// of a loop. 677/// 678/// It runs the analysis for a loop on demand. This can be initiated by 679/// querying the loop access info via LAA::getInfo. getInfo return a 680/// LoopAccessInfo object. See this class for the specifics of what information 681/// is provided. 682class LoopAccessLegacyAnalysis : public FunctionPass { 683public: 684 static char ID; 685 686 LoopAccessLegacyAnalysis() : FunctionPass(ID) { 687 initializeLoopAccessLegacyAnalysisPass(*PassRegistry::getPassRegistry()); 688 } 689 690 bool runOnFunction(Function &F) override; 691 692 void getAnalysisUsage(AnalysisUsage &AU) const override; 693 694 /// \brief Query the result of the loop access information for the loop \p L. 695 /// 696 /// If there is no cached result available run the analysis. 697 const LoopAccessInfo &getInfo(Loop *L); 698 699 void releaseMemory() override { 700 // Invalidate the cache when the pass is freed. 701 LoopAccessInfoMap.clear(); 702 } 703 704 /// \brief Print the result of the analysis when invoked with -analyze. 705 void print(raw_ostream &OS, const Module *M = nullptr) const override; 706 707private: 708 /// \brief The cache. 709 DenseMap<Loop *, std::unique_ptr<LoopAccessInfo>> LoopAccessInfoMap; 710 711 // The used analysis passes. 712 ScalarEvolution *SE; 713 const TargetLibraryInfo *TLI; 714 AliasAnalysis *AA; 715 DominatorTree *DT; 716 LoopInfo *LI; 717}; 718 719/// \brief This analysis provides dependence information for the memory 720/// accesses of a loop. 721/// 722/// It runs the analysis for a loop on demand. This can be initiated by 723/// querying the loop access info via AM.getResult<LoopAccessAnalysis>. 724/// getResult return a LoopAccessInfo object. See this class for the 725/// specifics of what information is provided. 726class LoopAccessAnalysis 727 : public AnalysisInfoMixin<LoopAccessAnalysis> { 728 friend AnalysisInfoMixin<LoopAccessAnalysis>; 729 static AnalysisKey Key; 730 731public: 732 typedef LoopAccessInfo Result; 733 734 Result run(Loop &L, LoopAnalysisManager &AM, LoopStandardAnalysisResults &AR); 735}; 736 737inline Instruction *MemoryDepChecker::Dependence::getSource( 738 const LoopAccessInfo &LAI) const { 739 return LAI.getDepChecker().getMemoryInstructions()[Source]; 740} 741 742inline Instruction *MemoryDepChecker::Dependence::getDestination( 743 const LoopAccessInfo &LAI) const { 744 return LAI.getDepChecker().getMemoryInstructions()[Destination]; 745} 746 747} // End llvm namespace 748 749#endif 750