1 //===- llvm/Analysis/LoopAccessAnalysis.h -----------------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the interface for the loop memory dependence framework that
11 // was originally developed for the Loop Vectorizer.
13 //===----------------------------------------------------------------------===//
15 #ifndef LLVM_ANALYSIS_LOOPACCESSANALYSIS_H
16 #define LLVM_ANALYSIS_LOOPACCESSANALYSIS_H
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"
32 class ScalarEvolution;
35 class SCEVUnionPredicate;
38 /// Optimization analysis message produced during vectorization. Messages inform
39 /// the user why vectorization did not occur.
40 class LoopAccessReport {
42 const Instruction *Instr;
45 LoopAccessReport(const Twine &Message, const Instruction *I)
46 : Message(Message.str()), Instr(I) {}
49 LoopAccessReport(const Instruction *I = nullptr) : Instr(I) {}
51 template <typename A> LoopAccessReport &operator<<(const A &Value) {
52 raw_string_ostream Out(Message);
57 const Instruction *getInstr() const { return Instr; }
59 std::string &str() { return Message; }
60 const std::string &str() const { return Message; }
61 operator Twine() { return Message; }
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
66 static void emitAnalysis(const LoopAccessReport &Message,
67 const Function *TheFunction,
69 const char *PassName);
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;
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();
85 /// \\brief When performing memory disambiguation checks at runtime do not
86 /// make more than this number of comparisons.
87 static unsigned RuntimeMemoryCheckThreshold;
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).
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.
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.
104 /// Safe: tmp = a[i + 1]; OR a[i + 1] = x;
105 /// a[i] = tmp; y = a[i];
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).
114 /// * A positive constant distance assuming program order that is bigger
115 /// than the biggest memory access.
117 /// tmp = a[i] OR b[i] = x
118 /// a[i+2] = tmp y = b[i+2];
120 /// Safe distance: 2 x sizeof(a[0]), and 2 x sizeof(b[0]), respectively.
122 /// * Zero distances and all accesses have the same size.
124 class MemoryDepChecker {
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;
131 /// \brief Dependece between memory access instructions.
133 /// \brief The type of the dependence.
137 // We couldn't determine the direction or the distance.
139 // Lexically forward.
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.
149 // Forward, but if vectorized, is likely to prevent store-to-load
151 ForwardButPreventsForwarding,
152 // Lexically 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
161 /// \brief String version of the types.
162 static const char *DepName[];
164 /// \brief Index of the source of the dependence in the InstMap vector.
166 /// \brief Index of the destination of the dependence in the InstMap vector.
167 unsigned Destination;
168 /// \brief The type of the dependence.
171 Dependence(unsigned Source, unsigned Destination, DepType Type)
172 : Source(Source), Destination(Destination), Type(Type) {}
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;
179 /// \brief Dependence types that don't prevent vectorization.
180 static bool isSafeForVectorization(DepType Type);
182 /// \brief Lexically forward dependence.
183 bool isForward() const;
184 /// \brief Lexically backward dependence.
185 bool isBackward() const;
187 /// \brief May be a lexically backward dependence type (includes Unknown).
188 bool isPossiblyBackward() const;
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;
196 MemoryDepChecker(PredicatedScalarEvolution &PSE, const Loop *L)
197 : PSE(PSE), InnermostLoop(L), AccessIdx(0),
198 ShouldRetryWithRuntimeCheck(false), SafeForVectorization(true),
199 RecordDependences(true) {}
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);
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);
219 /// \brief Check whether the dependencies between the accesses are safe.
221 /// Only checks sets with elements in \p CheckDeps.
222 bool areDepsSafe(DepCandidates &AccessSets, MemAccessInfoSet &CheckDeps,
223 const ValueToValueMap &Strides);
225 /// \brief No memory dependence was encountered that would inhibit
227 bool isSafeForVectorization() const { return SafeForVectorization; }
229 /// \brief The maximum number of bytes of a vector register we can vectorize
230 /// the accesses safely with.
231 uint64_t getMaxSafeDepDistBytes() { return MaxSafeDepDistBytes; }
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; }
237 /// \brief Returns the memory dependences. If null is returned we exceeded
238 /// the MaxDependences threshold and this information is not
240 const SmallVectorImpl<Dependence> *getDependences() const {
241 return RecordDependences ? &Dependences : nullptr;
244 void clearDependences() { Dependences.clear(); }
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 {
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;
257 for (unsigned I = 0; I < InstMap.size(); ++I)
258 OrderMap[InstMap[I]] = I;
263 /// \brief Find the set of instructions that read or write via \p Ptr.
264 SmallVector<Instruction *, 4> getInstructionsForAccess(Value *Ptr,
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;
277 /// \brief Maps access locations (ptr, read/write) to program order.
278 DenseMap<MemAccessInfo, std::vector<unsigned> > Accesses;
280 /// \brief Memory access instructions in program order.
281 SmallVector<Instruction *, 16> InstMap;
283 /// \brief The program order index to be used for the next instruction.
286 // We can access this many bytes in parallel safely.
287 uint64_t MaxSafeDepDistBytes;
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;
293 /// \brief No memory dependence was encountered that would inhibit
295 bool SafeForVectorization;
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;
302 /// \brief Memory dependences collected during the analysis. Only valid if
303 /// RecordDependences is true.
304 SmallVector<Dependence, 8> Dependences;
306 /// \brief Check whether there is a plausible dependence between the two
309 /// Access \p A must happen before \p B in program order. The two indices
310 /// identify the index into the program order map.
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);
322 /// \brief Check whether the data dependence could prevent store-load
325 /// \return false if we shouldn't vectorize at all or avoid larger
326 /// vectorization factors by limiting MaxSafeDepDistBytes.
327 bool couldPreventStoreLoadForward(uint64_t Distance, uint64_t TypeByteSize);
330 /// \brief Holds information about the memory runtime legality checks to verify
331 /// that a group of pointers do not overlap.
332 class RuntimePointerChecking {
335 /// Holds the pointer value that we need to check.
336 TrackingVH<Value> PointerValue;
337 /// Holds the smallest byte address accessed by the pointer throughout all
338 /// iterations of the loop.
340 /// Holds the largest byte address accessed by the pointer throughout all
341 /// iterations of the loop, plus 1.
343 /// Holds the information if this pointer is used for writing to memory.
345 /// Holds the id of the set of pointers that could be dependent because of a
346 /// shared underlying object.
347 unsigned DependencySetId;
348 /// Holds the id of the disjoint alias set to which this pointer belongs.
350 /// SCEV for the access.
353 PointerInfo(Value *PointerValue, const SCEV *Start, const SCEV *End,
354 bool IsWritePtr, unsigned DependencySetId, unsigned AliasSetId,
356 : PointerValue(PointerValue), Start(Start), End(End),
357 IsWritePtr(IsWritePtr), DependencySetId(DependencySetId),
358 AliasSetId(AliasSetId), Expr(Expr) {}
361 RuntimePointerChecking(ScalarEvolution *SE) : Need(false), SE(SE) {}
363 /// Reset the state of the pointer runtime information.
370 /// Insert a pointer and calculate the start and end SCEVs.
371 /// We need \p PSE in order to compute the SCEV expression of the pointer
372 /// according to the assumptions that we've made during the analysis.
373 /// The method might also version the pointer stride according to \p Strides,
374 /// and add new predicates to \p PSE.
375 void insert(Loop *Lp, Value *Ptr, bool WritePtr, unsigned DepSetId,
376 unsigned ASId, const ValueToValueMap &Strides,
377 PredicatedScalarEvolution &PSE);
379 /// \brief No run-time memory checking is necessary.
380 bool empty() const { return Pointers.empty(); }
382 /// A grouping of pointers. A single memcheck is required between
384 struct CheckingPtrGroup {
385 /// \brief Create a new pointer checking group containing a single
386 /// pointer, with index \p Index in RtCheck.
387 CheckingPtrGroup(unsigned Index, RuntimePointerChecking &RtCheck)
388 : RtCheck(RtCheck), High(RtCheck.Pointers[Index].End),
389 Low(RtCheck.Pointers[Index].Start) {
390 Members.push_back(Index);
393 /// \brief Tries to add the pointer recorded in RtCheck at index
394 /// \p Index to this pointer checking group. We can only add a pointer
395 /// to a checking group if we will still be able to get
396 /// the upper and lower bounds of the check. Returns true in case
397 /// of success, false otherwise.
398 bool addPointer(unsigned Index);
400 /// Constitutes the context of this pointer checking group. For each
401 /// pointer that is a member of this group we will retain the index
402 /// at which it appears in RtCheck.
403 RuntimePointerChecking &RtCheck;
404 /// The SCEV expression which represents the upper bound of all the
405 /// pointers in this group.
407 /// The SCEV expression which represents the lower bound of all the
408 /// pointers in this group.
410 /// Indices of all the pointers that constitute this grouping.
411 SmallVector<unsigned, 2> Members;
414 /// \brief A memcheck which made up of a pair of grouped pointers.
416 /// These *have* to be const for now, since checks are generated from
417 /// CheckingPtrGroups in LAI::addRuntimeChecks which is a const member
418 /// function. FIXME: once check-generation is moved inside this class (after
419 /// the PtrPartition hack is removed), we could drop const.
420 typedef std::pair<const CheckingPtrGroup *, const CheckingPtrGroup *>
423 /// \brief Generate the checks and store it. This also performs the grouping
424 /// of pointers to reduce the number of memchecks necessary.
425 void generateChecks(MemoryDepChecker::DepCandidates &DepCands,
426 bool UseDependencies);
428 /// \brief Returns the checks that generateChecks created.
429 const SmallVector<PointerCheck, 4> &getChecks() const { return Checks; }
431 /// \brief Decide if we need to add a check between two groups of pointers,
432 /// according to needsChecking.
433 bool needsChecking(const CheckingPtrGroup &M,
434 const CheckingPtrGroup &N) const;
436 /// \brief Returns the number of run-time checks required according to
438 unsigned getNumberOfChecks() const { return Checks.size(); }
440 /// \brief Print the list run-time memory checks necessary.
441 void print(raw_ostream &OS, unsigned Depth = 0) const;
444 void printChecks(raw_ostream &OS, const SmallVectorImpl<PointerCheck> &Checks,
445 unsigned Depth = 0) const;
447 /// This flag indicates if we need to add the runtime check.
450 /// Information about the pointers that may require checking.
451 SmallVector<PointerInfo, 2> Pointers;
453 /// Holds a partitioning of pointers into "check groups".
454 SmallVector<CheckingPtrGroup, 2> CheckingGroups;
456 /// \brief Check if pointers are in the same partition
458 /// \p PtrToPartition contains the partition number for pointers (-1 if the
459 /// pointer belongs to multiple partitions).
461 arePointersInSamePartition(const SmallVectorImpl<int> &PtrToPartition,
462 unsigned PtrIdx1, unsigned PtrIdx2);
464 /// \brief Decide whether we need to issue a run-time check for pointer at
465 /// index \p I and \p J to prove their independence.
466 bool needsChecking(unsigned I, unsigned J) const;
468 /// \brief Return PointerInfo for pointer at index \p PtrIdx.
469 const PointerInfo &getPointerInfo(unsigned PtrIdx) const {
470 return Pointers[PtrIdx];
474 /// \brief Groups pointers such that a single memcheck is required
475 /// between two different groups. This will clear the CheckingGroups vector
476 /// and re-compute it. We will only group dependecies if \p UseDependencies
477 /// is true, otherwise we will create a separate group for each pointer.
478 void groupChecks(MemoryDepChecker::DepCandidates &DepCands,
479 bool UseDependencies);
481 /// Generate the checks and return them.
482 SmallVector<PointerCheck, 4>
483 generateChecks() const;
485 /// Holds a pointer to the ScalarEvolution analysis.
488 /// \brief Set of run-time checks required to establish independence of
489 /// otherwise may-aliasing pointers in the loop.
490 SmallVector<PointerCheck, 4> Checks;
493 /// \brief Drive the analysis of memory accesses in the loop
495 /// This class is responsible for analyzing the memory accesses of a loop. It
496 /// collects the accesses and then its main helper the AccessAnalysis class
497 /// finds and categorizes the dependences in buildDependenceSets.
499 /// For memory dependences that can be analyzed at compile time, it determines
500 /// whether the dependence is part of cycle inhibiting vectorization. This work
501 /// is delegated to the MemoryDepChecker class.
503 /// For memory dependences that cannot be determined at compile time, it
504 /// generates run-time checks to prove independence. This is done by
505 /// AccessAnalysis::canCheckPtrAtRT and the checks are maintained by the
506 /// RuntimePointerCheck class.
508 /// If pointers can wrap or can't be expressed as affine AddRec expressions by
509 /// ScalarEvolution, we will generate run-time checks by emitting a
510 /// SCEVUnionPredicate.
512 /// Checks for both memory dependences and the SCEV predicates contained in the
513 /// PSE must be emitted in order for the results of this analysis to be valid.
514 class LoopAccessInfo {
516 LoopAccessInfo(Loop *L, ScalarEvolution *SE, const TargetLibraryInfo *TLI,
517 AliasAnalysis *AA, DominatorTree *DT, LoopInfo *LI);
520 // Hack for MSVC 2013 which sems like it can't synthesize this even
521 // with default keyword:
522 // LoopAccessInfo(LoopAccessInfo &&LAI) = default;
523 LoopAccessInfo(LoopAccessInfo &&LAI)
524 : PSE(std::move(LAI.PSE)), PtrRtChecking(std::move(LAI.PtrRtChecking)),
525 DepChecker(std::move(LAI.DepChecker)), TheLoop(LAI.TheLoop),
526 NumLoads(LAI.NumLoads), NumStores(LAI.NumStores),
527 MaxSafeDepDistBytes(LAI.MaxSafeDepDistBytes), CanVecMem(LAI.CanVecMem),
528 StoreToLoopInvariantAddress(LAI.StoreToLoopInvariantAddress),
529 Report(std::move(LAI.Report)),
530 SymbolicStrides(std::move(LAI.SymbolicStrides)),
531 StrideSet(std::move(LAI.StrideSet)) {}
532 // LoopAccessInfo &operator=(LoopAccessInfo &&LAI) = default;
533 LoopAccessInfo &operator=(LoopAccessInfo &&LAI) {
534 assert(this != &LAI);
536 PSE = std::move(LAI.PSE);
537 PtrRtChecking = std::move(LAI.PtrRtChecking);
538 DepChecker = std::move(LAI.DepChecker);
539 TheLoop = LAI.TheLoop;
540 NumLoads = LAI.NumLoads;
541 NumStores = LAI.NumStores;
542 MaxSafeDepDistBytes = LAI.MaxSafeDepDistBytes;
543 CanVecMem = LAI.CanVecMem;
544 StoreToLoopInvariantAddress = LAI.StoreToLoopInvariantAddress;
545 Report = std::move(LAI.Report);
546 SymbolicStrides = std::move(LAI.SymbolicStrides);
547 StrideSet = std::move(LAI.StrideSet);
551 /// Return true we can analyze the memory accesses in the loop and there are
552 /// no memory dependence cycles.
553 bool canVectorizeMemory() const { return CanVecMem; }
555 const RuntimePointerChecking *getRuntimePointerChecking() const {
556 return PtrRtChecking.get();
559 /// \brief Number of memchecks required to prove independence of otherwise
560 /// may-alias pointers.
561 unsigned getNumRuntimePointerChecks() const {
562 return PtrRtChecking->getNumberOfChecks();
565 /// Return true if the block BB needs to be predicated in order for the loop
566 /// to be vectorized.
567 static bool blockNeedsPredication(BasicBlock *BB, Loop *TheLoop,
570 /// Returns true if the value V is uniform within the loop.
571 bool isUniform(Value *V) const;
573 uint64_t getMaxSafeDepDistBytes() const { return MaxSafeDepDistBytes; }
574 unsigned getNumStores() const { return NumStores; }
575 unsigned getNumLoads() const { return NumLoads;}
577 /// \brief Add code that checks at runtime if the accessed arrays overlap.
579 /// Returns a pair of instructions where the first element is the first
580 /// instruction generated in possibly a sequence of instructions and the
581 /// second value is the final comparator value or NULL if no check is needed.
582 std::pair<Instruction *, Instruction *>
583 addRuntimeChecks(Instruction *Loc) const;
585 /// \brief Generete the instructions for the checks in \p PointerChecks.
587 /// Returns a pair of instructions where the first element is the first
588 /// instruction generated in possibly a sequence of instructions and the
589 /// second value is the final comparator value or NULL if no check is needed.
590 std::pair<Instruction *, Instruction *>
591 addRuntimeChecks(Instruction *Loc,
592 const SmallVectorImpl<RuntimePointerChecking::PointerCheck>
593 &PointerChecks) const;
595 /// \brief The diagnostics report generated for the analysis. E.g. why we
596 /// couldn't analyze the loop.
597 const Optional<LoopAccessReport> &getReport() const { return Report; }
599 /// \brief the Memory Dependence Checker which can determine the
600 /// loop-independent and loop-carried dependences between memory accesses.
601 const MemoryDepChecker &getDepChecker() const { return *DepChecker; }
603 /// \brief Return the list of instructions that use \p Ptr to read or write
605 SmallVector<Instruction *, 4> getInstructionsForAccess(Value *Ptr,
606 bool isWrite) const {
607 return DepChecker->getInstructionsForAccess(Ptr, isWrite);
610 /// \brief If an access has a symbolic strides, this maps the pointer value to
611 /// the stride symbol.
612 const ValueToValueMap &getSymbolicStrides() const { return SymbolicStrides; }
614 /// \brief Pointer has a symbolic stride.
615 bool hasStride(Value *V) const { return StrideSet.count(V); }
617 /// \brief Print the information about the memory accesses in the loop.
618 void print(raw_ostream &OS, unsigned Depth = 0) const;
620 /// \brief Checks existence of store to invariant address inside loop.
621 /// If the loop has any store to invariant address, then it returns true,
622 /// else returns false.
623 bool hasStoreToLoopInvariantAddress() const {
624 return StoreToLoopInvariantAddress;
627 /// Used to add runtime SCEV checks. Simplifies SCEV expressions and converts
628 /// them to a more usable form. All SCEV expressions during the analysis
629 /// should be re-written (and therefore simplified) according to PSE.
630 /// A user of LoopAccessAnalysis will need to emit the runtime checks
631 /// associated with this predicate.
632 const PredicatedScalarEvolution &getPSE() const { return *PSE; }
635 /// \brief Analyze the loop.
636 void analyzeLoop(AliasAnalysis *AA, LoopInfo *LI,
637 const TargetLibraryInfo *TLI, DominatorTree *DT);
639 /// \brief Check if the structure of the loop allows it to be analyzed by this
641 bool canAnalyzeLoop();
643 void emitAnalysis(LoopAccessReport &Message);
645 /// \brief Collect memory access with loop invariant strides.
647 /// Looks for accesses like "a[i * StrideA]" where "StrideA" is loop
649 void collectStridedAccess(Value *LoadOrStoreInst);
651 std::unique_ptr<PredicatedScalarEvolution> PSE;
653 /// We need to check that all of the pointers in this list are disjoint
654 /// at runtime. Using std::unique_ptr to make using move ctor simpler.
655 std::unique_ptr<RuntimePointerChecking> PtrRtChecking;
657 /// \brief the Memory Dependence Checker which can determine the
658 /// loop-independent and loop-carried dependences between memory accesses.
659 std::unique_ptr<MemoryDepChecker> DepChecker;
666 uint64_t MaxSafeDepDistBytes;
668 /// \brief Cache the result of analyzeLoop.
671 /// \brief Indicator for storing to uniform addresses.
672 /// If a loop has write to a loop invariant address then it should be true.
673 bool StoreToLoopInvariantAddress;
675 /// \brief The diagnostics report generated for the analysis. E.g. why we
676 /// couldn't analyze the loop.
677 Optional<LoopAccessReport> Report;
679 /// \brief If an access has a symbolic strides, this maps the pointer value to
680 /// the stride symbol.
681 ValueToValueMap SymbolicStrides;
683 /// \brief Set of symbolic strides values.
684 SmallPtrSet<Value *, 8> StrideSet;
687 Value *stripIntegerCast(Value *V);
689 /// \brief Return the SCEV corresponding to a pointer with the symbolic stride
690 /// replaced with constant one, assuming the SCEV predicate associated with
693 /// If necessary this method will version the stride of the pointer according
694 /// to \p PtrToStride and therefore add further predicates to \p PSE.
696 /// If \p OrigPtr is not null, use it to look up the stride value instead of \p
697 /// Ptr. \p PtrToStride provides the mapping between the pointer value and its
698 /// stride as collected by LoopVectorizationLegality::collectStridedAccess.
699 const SCEV *replaceSymbolicStrideSCEV(PredicatedScalarEvolution &PSE,
700 const ValueToValueMap &PtrToStride,
701 Value *Ptr, Value *OrigPtr = nullptr);
703 /// \brief If the pointer has a constant stride return it in units of its
704 /// element size. Otherwise return zero.
706 /// Ensure that it does not wrap in the address space, assuming the predicate
707 /// associated with \p PSE is true.
709 /// If necessary this method will version the stride of the pointer according
710 /// to \p PtrToStride and therefore add further predicates to \p PSE.
711 /// The \p Assume parameter indicates if we are allowed to make additional
712 /// run-time assumptions.
713 int64_t getPtrStride(PredicatedScalarEvolution &PSE, Value *Ptr, const Loop *Lp,
714 const ValueToValueMap &StridesMap = ValueToValueMap(),
715 bool Assume = false);
717 /// \brief Returns true if the memory operations \p A and \p B are consecutive.
718 /// This is a simple API that does not depend on the analysis pass.
719 bool isConsecutiveAccess(Value *A, Value *B, const DataLayout &DL,
720 ScalarEvolution &SE, bool CheckType = true);
722 /// \brief This analysis provides dependence information for the memory accesses
725 /// It runs the analysis for a loop on demand. This can be initiated by
726 /// querying the loop access info via LAA::getInfo. getInfo return a
727 /// LoopAccessInfo object. See this class for the specifics of what information
729 class LoopAccessLegacyAnalysis : public FunctionPass {
733 LoopAccessLegacyAnalysis() : FunctionPass(ID) {
734 initializeLoopAccessLegacyAnalysisPass(*PassRegistry::getPassRegistry());
737 bool runOnFunction(Function &F) override;
739 void getAnalysisUsage(AnalysisUsage &AU) const override;
741 /// \brief Query the result of the loop access information for the loop \p L.
743 /// If there is no cached result available run the analysis.
744 const LoopAccessInfo &getInfo(Loop *L);
746 void releaseMemory() override {
747 // Invalidate the cache when the pass is freed.
748 LoopAccessInfoMap.clear();
751 /// \brief Print the result of the analysis when invoked with -analyze.
752 void print(raw_ostream &OS, const Module *M = nullptr) const override;
755 /// \brief The cache.
756 DenseMap<Loop *, std::unique_ptr<LoopAccessInfo>> LoopAccessInfoMap;
758 // The used analysis passes.
760 const TargetLibraryInfo *TLI;
766 /// \brief This analysis provides dependence information for the memory
767 /// accesses of a loop.
769 /// It runs the analysis for a loop on demand. This can be initiated by
770 /// querying the loop access info via AM.getResult<LoopAccessAnalysis>.
771 /// getResult return a LoopAccessInfo object. See this class for the
772 /// specifics of what information is provided.
773 class LoopAccessAnalysis
774 : public AnalysisInfoMixin<LoopAccessAnalysis> {
775 friend AnalysisInfoMixin<LoopAccessAnalysis>;
779 typedef LoopAccessInfo Result;
780 Result run(Loop &, AnalysisManager<Loop> &);
781 static StringRef name() { return "LoopAccessAnalysis"; }
784 /// \brief Printer pass for the \c LoopAccessInfo results.
785 class LoopAccessInfoPrinterPass
786 : public PassInfoMixin<LoopAccessInfoPrinterPass> {
790 explicit LoopAccessInfoPrinterPass(raw_ostream &OS) : OS(OS) {}
791 PreservedAnalyses run(Loop &L, AnalysisManager<Loop> &AM);
794 inline Instruction *MemoryDepChecker::Dependence::getSource(
795 const LoopAccessInfo &LAI) const {
796 return LAI.getDepChecker().getMemoryInstructions()[Source];
799 inline Instruction *MemoryDepChecker::Dependence::getDestination(
800 const LoopAccessInfo &LAI) const {
801 return LAI.getDepChecker().getMemoryInstructions()[Destination];
804 } // End llvm namespace