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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 :
30 : namespace llvm {
31 :
32 : class Value;
33 : class DataLayout;
34 : class ScalarEvolution;
35 : class Loop;
36 : class SCEV;
37 : class SCEVUnionPredicate;
38 : class LoopAccessInfo;
39 : class OptimizationRemarkEmitter;
40 :
41 : /// Collection of parameters shared beetween the Loop Vectorizer and the
42 : /// Loop Access Analysis.
43 : struct VectorizerParams {
44 : /// Maximum SIMD width.
45 : static const unsigned MaxVectorWidth;
46 :
47 : /// VF as overridden by the user.
48 : static unsigned VectorizationFactor;
49 : /// Interleave factor as overridden by the user.
50 : static unsigned VectorizationInterleave;
51 : /// True if force-vector-interleave was specified by the user.
52 : static bool isInterleaveForced();
53 :
54 : /// \When performing memory disambiguation checks at runtime do not
55 : /// make more than this number of comparisons.
56 : static unsigned RuntimeMemoryCheckThreshold;
57 : };
58 :
59 : /// 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 : ///
93 : class MemoryDepChecker {
94 : public:
95 : typedef PointerIntPair<Value *, 1, bool> MemAccessInfo;
96 : typedef SmallVector<MemAccessInfo, 8> MemAccessInfoList;
97 : /// Set of potential dependent memory accesses.
98 : typedef EquivalenceClasses<MemAccessInfo> DepCandidates;
99 :
100 : /// Dependece between memory access instructions.
101 : struct Dependence {
102 : /// 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 : /// String version of the types.
131 : static const char *DepName[];
132 :
133 : /// Index of the source of the dependence in the InstMap vector.
134 : unsigned Source;
135 : /// Index of the destination of the dependence in the InstMap vector.
136 : unsigned Destination;
137 : /// The type of the dependence.
138 : DepType Type;
139 :
140 : Dependence(unsigned Source, unsigned Destination, DepType Type)
141 3651 : : Source(Source), Destination(Destination), Type(Type) {}
142 :
143 : /// Return the source instruction of the dependence.
144 : Instruction *getSource(const LoopAccessInfo &LAI) const;
145 : /// Return the destination instruction of the dependence.
146 : Instruction *getDestination(const LoopAccessInfo &LAI) const;
147 :
148 : /// Dependence types that don't prevent vectorization.
149 : static bool isSafeForVectorization(DepType Type);
150 :
151 : /// Lexically forward dependence.
152 : bool isForward() const;
153 : /// Lexically backward dependence.
154 : bool isBackward() const;
155 :
156 : /// May be a lexically backward dependence type (includes Unknown).
157 : bool isPossiblyBackward() const;
158 :
159 : /// 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 0 : : PSE(PSE), InnermostLoop(L), AccessIdx(0), MaxSafeRegisterWidth(-1U),
167 : ShouldRetryWithRuntimeCheck(false), SafeForVectorization(true),
168 0 : RecordDependences(true) {}
169 :
170 : /// Register the location (instructions are given increasing numbers)
171 : /// of a write access.
172 4260 : void addAccess(StoreInst *SI) {
173 : Value *Ptr = SI->getPointerOperand();
174 4260 : Accesses[MemAccessInfo(Ptr, true)].push_back(AccessIdx);
175 4260 : InstMap.push_back(SI);
176 4260 : ++AccessIdx;
177 4260 : }
178 :
179 : /// Register the location (instructions are given increasing numbers)
180 : /// of a write access.
181 5206 : void addAccess(LoadInst *LI) {
182 : Value *Ptr = LI->getPointerOperand();
183 5206 : Accesses[MemAccessInfo(Ptr, false)].push_back(AccessIdx);
184 5206 : InstMap.push_back(LI);
185 5206 : ++AccessIdx;
186 5206 : }
187 :
188 : /// 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 : /// No memory dependence was encountered that would inhibit
195 : /// vectorization.
196 : bool isSafeForVectorization() const { return SafeForVectorization; }
197 :
198 : /// The maximum number of bytes of a vector register we can vectorize
199 : /// the accesses safely with.
200 0 : uint64_t getMaxSafeDepDistBytes() { return MaxSafeDepDistBytes; }
201 :
202 : /// Return the number of elements that are safe to operate on
203 : /// simultaneously, multiplied by the size of the element in bits.
204 0 : uint64_t getMaxSafeRegisterWidth() const { return MaxSafeRegisterWidth; }
205 :
206 : /// In same cases when the dependency check fails we can still
207 : /// vectorize the loop with a dynamic array access check.
208 0 : bool shouldRetryWithRuntimeCheck() { return ShouldRetryWithRuntimeCheck; }
209 :
210 : /// 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 {
214 658 : return RecordDependences ? &Dependences : nullptr;
215 : }
216 :
217 : void clearDependences() { Dependences.clear(); }
218 :
219 : /// 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 99 : return InstMap;
223 : }
224 :
225 : /// Generate a mapping between the memory instructions and their
226 : /// indices according to program order.
227 34 : DenseMap<Instruction *, unsigned> generateInstructionOrderMap() const {
228 : DenseMap<Instruction *, unsigned> OrderMap;
229 :
230 239 : for (unsigned I = 0; I < InstMap.size(); ++I)
231 205 : OrderMap[InstMap[I]] = I;
232 :
233 34 : return OrderMap;
234 : }
235 :
236 : /// Find the set of instructions that read or write via \p Ptr.
237 : SmallVector<Instruction *, 4> getInstructionsForAccess(Value *Ptr,
238 : bool isWrite) const;
239 :
240 : private:
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 : /// Maps access locations (ptr, read/write) to program order.
251 : DenseMap<MemAccessInfo, std::vector<unsigned> > Accesses;
252 :
253 : /// Memory access instructions in program order.
254 : SmallVector<Instruction *, 16> InstMap;
255 :
256 : /// 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 : /// 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 : /// 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 : /// No memory dependence was encountered that would inhibit
273 : /// vectorization.
274 : bool SafeForVectorization;
275 :
276 : //// 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 : /// Memory dependences collected during the analysis. Only valid if
282 : /// RecordDependences is true.
283 : SmallVector<Dependence, 8> Dependences;
284 :
285 : /// 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 : /// 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 : /// Holds information about the memory runtime legality checks to verify
310 : /// that a group of pointers do not overlap.
311 : class RuntimePointerChecking {
312 : public:
313 8883 : 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 4271 : : PointerValue(PointerValue), Start(Start), End(End),
336 : IsWritePtr(IsWritePtr), DependencySetId(DependencySetId),
337 4271 : AliasSetId(AliasSetId), Expr(Expr) {}
338 : };
339 :
340 0 : RuntimePointerChecking(ScalarEvolution *SE) : Need(false), SE(SE) {}
341 :
342 : /// Reset the state of the pointer runtime information.
343 : void reset() {
344 148 : 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 : /// 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 8938 : struct CheckingPtrGroup {
364 : /// Create a new pointer checking group containing a single
365 : /// pointer, with index \p Index in RtCheck.
366 1945 : CheckingPtrGroup(unsigned Index, RuntimePointerChecking &RtCheck)
367 5835 : : RtCheck(RtCheck), High(RtCheck.Pointers[Index].End),
368 5835 : Low(RtCheck.Pointers[Index].Start) {
369 1945 : Members.push_back(Index);
370 1945 : }
371 :
372 : /// 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 : /// 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 : /// 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 : /// Returns the checks that generateChecks created.
408 : const SmallVector<PointerCheck, 4> &getChecks() const { return Checks; }
409 :
410 : /// 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 : /// Returns the number of run-time checks required according to
416 : /// needsChecking.
417 1010 : unsigned getNumberOfChecks() const { return Checks.size(); }
418 :
419 : /// 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 : /// 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 : /// 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 : /// Return PointerInfo for pointer at index \p PtrIdx.
448 : const PointerInfo &getPointerInfo(unsigned PtrIdx) const {
449 591 : return Pointers[PtrIdx];
450 : }
451 :
452 : private:
453 : /// 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 : /// 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 : /// 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.
493 : class LoopAccessInfo {
494 : public:
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 0 : bool canVectorizeMemory() const { return CanVecMem; }
501 :
502 : const RuntimePointerChecking *getRuntimePointerChecking() const {
503 : return PtrRtChecking.get();
504 : }
505 :
506 : /// 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 0 : uint64_t getMaxSafeDepDistBytes() const { return MaxSafeDepDistBytes; }
521 0 : unsigned getNumStores() const { return NumStores; }
522 0 : unsigned getNumLoads() const { return NumLoads;}
523 :
524 : /// 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 : /// 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 : /// 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 : /// 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 : /// 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 {
554 112 : return DepChecker->getInstructionsForAccess(Ptr, isWrite);
555 : }
556 :
557 : /// If an access has a symbolic strides, this maps the pointer value to
558 : /// the stride symbol.
559 9123 : const ValueToValueMap &getSymbolicStrides() const { return SymbolicStrides; }
560 :
561 : /// Pointer has a symbolic stride.
562 8452 : bool hasStride(Value *V) const { return StrideSet.count(V); }
563 :
564 : /// Print the information about the memory accesses in the loop.
565 : void print(raw_ostream &OS, unsigned Depth = 0) const;
566 :
567 : /// If the loop has multiple stores to an invariant address, then
568 : /// return true, else return false.
569 0 : bool hasMultipleStoresToLoopInvariantAddress() const {
570 0 : return HasMultipleStoresToLoopInvariantAddress;
571 : }
572 :
573 : /// Used to add runtime SCEV checks. Simplifies SCEV expressions and converts
574 : /// them to a more usable form. All SCEV expressions during the analysis
575 : /// should be re-written (and therefore simplified) according to PSE.
576 : /// A user of LoopAccessAnalysis will need to emit the runtime checks
577 : /// associated with this predicate.
578 : const PredicatedScalarEvolution &getPSE() const { return *PSE; }
579 :
580 : private:
581 : /// Analyze the loop.
582 : void analyzeLoop(AliasAnalysis *AA, LoopInfo *LI,
583 : const TargetLibraryInfo *TLI, DominatorTree *DT);
584 :
585 : /// Check if the structure of the loop allows it to be analyzed by this
586 : /// pass.
587 : bool canAnalyzeLoop();
588 :
589 : /// Save the analysis remark.
590 : ///
591 : /// LAA does not directly emits the remarks. Instead it stores it which the
592 : /// client can retrieve and presents as its own analysis
593 : /// (e.g. -Rpass-analysis=loop-vectorize).
594 : OptimizationRemarkAnalysis &recordAnalysis(StringRef RemarkName,
595 : Instruction *Instr = nullptr);
596 :
597 : /// Collect memory access with loop invariant strides.
598 : ///
599 : /// Looks for accesses like "a[i * StrideA]" where "StrideA" is loop
600 : /// invariant.
601 : void collectStridedAccess(Value *LoadOrStoreInst);
602 :
603 : std::unique_ptr<PredicatedScalarEvolution> PSE;
604 :
605 : /// We need to check that all of the pointers in this list are disjoint
606 : /// at runtime. Using std::unique_ptr to make using move ctor simpler.
607 : std::unique_ptr<RuntimePointerChecking> PtrRtChecking;
608 :
609 : /// the Memory Dependence Checker which can determine the
610 : /// loop-independent and loop-carried dependences between memory accesses.
611 : std::unique_ptr<MemoryDepChecker> DepChecker;
612 :
613 : Loop *TheLoop;
614 :
615 : unsigned NumLoads;
616 : unsigned NumStores;
617 :
618 : uint64_t MaxSafeDepDistBytes;
619 :
620 : /// Cache the result of analyzeLoop.
621 : bool CanVecMem;
622 :
623 : /// Indicator that there are multiple stores to a uniform address.
624 : bool HasMultipleStoresToLoopInvariantAddress;
625 :
626 : /// The diagnostics report generated for the analysis. E.g. why we
627 : /// couldn't analyze the loop.
628 : std::unique_ptr<OptimizationRemarkAnalysis> Report;
629 :
630 : /// If an access has a symbolic strides, this maps the pointer value to
631 : /// the stride symbol.
632 : ValueToValueMap SymbolicStrides;
633 :
634 : /// Set of symbolic strides values.
635 : SmallPtrSet<Value *, 8> StrideSet;
636 : };
637 :
638 : Value *stripIntegerCast(Value *V);
639 :
640 : /// Return the SCEV corresponding to a pointer with the symbolic stride
641 : /// replaced with constant one, assuming the SCEV predicate associated with
642 : /// \p PSE is true.
643 : ///
644 : /// If necessary this method will version the stride of the pointer according
645 : /// to \p PtrToStride and therefore add further predicates to \p PSE.
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 : /// If the pointer has a constant stride return it in units of its
655 : /// element size. Otherwise return zero.
656 : ///
657 : /// Ensure that it does not wrap in the address space, assuming the predicate
658 : /// associated with \p PSE is true.
659 : ///
660 : /// If necessary this method will version the stride of the pointer according
661 : /// to \p PtrToStride and therefore add further predicates to \p PSE.
662 : /// The \p Assume parameter indicates if we are allowed to make additional
663 : /// run-time assumptions.
664 : int64_t getPtrStride(PredicatedScalarEvolution &PSE, Value *Ptr, const Loop *Lp,
665 : const ValueToValueMap &StridesMap = ValueToValueMap(),
666 : bool Assume = false, bool ShouldCheckWrap = true);
667 :
668 : /// Attempt to sort the pointers in \p VL and return the sorted indices
669 : /// in \p SortedIndices, if reordering is required.
670 : ///
671 : /// Returns 'true' if sorting is legal, otherwise returns 'false'.
672 : ///
673 : /// For example, for a given \p VL of memory accesses in program order, a[i+4],
674 : /// a[i+0], a[i+1] and a[i+7], this function will sort the \p VL and save the
675 : /// sorted indices in \p SortedIndices as a[i+0], a[i+1], a[i+4], a[i+7] and
676 : /// saves the mask for actual memory accesses in program order in
677 : /// \p SortedIndices as <1,2,0,3>
678 : bool sortPtrAccesses(ArrayRef<Value *> VL, const DataLayout &DL,
679 : ScalarEvolution &SE,
680 : SmallVectorImpl<unsigned> &SortedIndices);
681 :
682 : /// Returns true if the memory operations \p A and \p B are consecutive.
683 : /// This is a simple API that does not depend on the analysis pass.
684 : bool isConsecutiveAccess(Value *A, Value *B, const DataLayout &DL,
685 : ScalarEvolution &SE, bool CheckType = true);
686 :
687 : /// This analysis provides dependence information for the memory accesses
688 : /// of a loop.
689 : ///
690 : /// It runs the analysis for a loop on demand. This can be initiated by
691 : /// querying the loop access info via LAA::getInfo. getInfo return a
692 : /// LoopAccessInfo object. See this class for the specifics of what information
693 : /// is provided.
694 : class LoopAccessLegacyAnalysis : public FunctionPass {
695 : public:
696 : static char ID;
697 :
698 9096 : LoopAccessLegacyAnalysis() : FunctionPass(ID) {
699 4548 : initializeLoopAccessLegacyAnalysisPass(*PassRegistry::getPassRegistry());
700 4548 : }
701 :
702 : bool runOnFunction(Function &F) override;
703 :
704 : void getAnalysisUsage(AnalysisUsage &AU) const override;
705 :
706 : /// Query the result of the loop access information for the loop \p L.
707 : ///
708 : /// If there is no cached result available run the analysis.
709 : const LoopAccessInfo &getInfo(Loop *L);
710 :
711 41254 : void releaseMemory() override {
712 : // Invalidate the cache when the pass is freed.
713 41254 : LoopAccessInfoMap.clear();
714 41254 : }
715 :
716 : /// Print the result of the analysis when invoked with -analyze.
717 : void print(raw_ostream &OS, const Module *M = nullptr) const override;
718 :
719 : private:
720 : /// The cache.
721 : DenseMap<Loop *, std::unique_ptr<LoopAccessInfo>> LoopAccessInfoMap;
722 :
723 : // The used analysis passes.
724 : ScalarEvolution *SE;
725 : const TargetLibraryInfo *TLI;
726 : AliasAnalysis *AA;
727 : DominatorTree *DT;
728 : LoopInfo *LI;
729 : };
730 :
731 : /// This analysis provides dependence information for the memory
732 : /// accesses of a loop.
733 : ///
734 : /// It runs the analysis for a loop on demand. This can be initiated by
735 : /// querying the loop access info via AM.getResult<LoopAccessAnalysis>.
736 : /// getResult return a LoopAccessInfo object. See this class for the
737 : /// specifics of what information is provided.
738 : class LoopAccessAnalysis
739 : : public AnalysisInfoMixin<LoopAccessAnalysis> {
740 : friend AnalysisInfoMixin<LoopAccessAnalysis>;
741 : static AnalysisKey Key;
742 :
743 : public:
744 : typedef LoopAccessInfo Result;
745 :
746 : Result run(Loop &L, LoopAnalysisManager &AM, LoopStandardAnalysisResults &AR);
747 : };
748 :
749 0 : inline Instruction *MemoryDepChecker::Dependence::getSource(
750 : const LoopAccessInfo &LAI) const {
751 52 : return LAI.getDepChecker().getMemoryInstructions()[Source];
752 : }
753 :
754 0 : inline Instruction *MemoryDepChecker::Dependence::getDestination(
755 : const LoopAccessInfo &LAI) const {
756 52 : return LAI.getDepChecker().getMemoryInstructions()[Destination];
757 : }
758 :
759 : } // End llvm namespace
760 :
761 : #endif
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