Coverage Report

Created: 2018-09-19 08:35

/Users/buildslave/jenkins/workspace/clang-stage2-coverage-R/llvm/include/llvm/Analysis/LoopAccessAnalysis.h
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//===- llvm/Analysis/LoopAccessAnalysis.h -----------------------*- C++ -*-===//
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//
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//                     The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the interface for the loop memory dependence framework that
11
// was originally developed for the Loop Vectorizer.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_LOOPACCESSANALYSIS_H
16
#define LLVM_ANALYSIS_LOOPACCESSANALYSIS_H
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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"
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#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,
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      // 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
29.3k
        : 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
      : PSE(PSE), InnermostLoop(L), AccessIdx(0), MaxSafeRegisterWidth(-1U),
167
        ShouldRetryWithRuntimeCheck(false), SafeForVectorization(true),
168
190k
        RecordDependences(true) {}
169
170
  /// Register the location (instructions are given increasing numbers)
171
  /// of a write access.
172
108k
  void addAccess(StoreInst *SI) {
173
108k
    Value *Ptr = SI->getPointerOperand();
174
108k
    Accesses[MemAccessInfo(Ptr, true)].push_back(AccessIdx);
175
108k
    InstMap.push_back(SI);
176
108k
    ++AccessIdx;
177
108k
  }
178
179
  /// Register the location (instructions are given increasing numbers)
180
  /// of a write access.
181
116k
  void addAccess(LoadInst *LI) {
182
116k
    Value *Ptr = LI->getPointerOperand();
183
116k
    Accesses[MemAccessInfo(Ptr, false)].push_back(AccessIdx);
184
116k
    InstMap.push_back(LI);
185
116k
    ++AccessIdx;
186
116k
  }
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
21.8k
  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
19.3k
  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
1.65k
  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
203k
  const SmallVectorImpl<Dependence> *getDependences() const {
214
203k
    return RecordDependences ? 
&Dependences203k
:
nullptr118
;
215
203k
  }
216
217
587
  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
21.4k
  const SmallVectorImpl<Instruction *> &getMemoryInstructions() const {
222
21.4k
    return InstMap;
223
21.4k
  }
224
225
  /// Generate a mapping between the memory instructions and their
226
  /// indices according to program order.
227
239
  DenseMap<Instruction *, unsigned> generateInstructionOrderMap() const {
228
239
    DenseMap<Instruction *, unsigned> OrderMap;
229
239
230
1.66k
    for (unsigned I = 0; I < InstMap.size(); 
++I1.43k
)
231
1.43k
      OrderMap[InstMap[I]] = I;
232
239
233
239
    return OrderMap;
234
239
  }
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
  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
97.4k
          AliasSetId(AliasSetId), Expr(Expr) {}
338
  };
339
340
190k
  RuntimePointerChecking(ScalarEvolution *SE) : Need(false), SE(SE) {}
341
342
  /// Reset the state of the pointer runtime information.
343
4.67k
  void reset() {
344
4.67k
    Need = false;
345
4.67k
    Pointers.clear();
346
4.67k
    Checks.clear();
347
4.67k
  }
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
  struct CheckingPtrGroup {
364
    /// 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
27.6k
          Low(RtCheck.Pointers[Index].Start) {
369
27.6k
      Members.push_back(Index);
370
27.6k
    }
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
5.27k
  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
19.4k
  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
7.16k
  const PointerInfo &getPointerInfo(unsigned PtrIdx) const {
449
7.16k
    return Pointers[PtrIdx];
450
7.16k
  }
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
27.0k
  bool canVectorizeMemory() const { return CanVecMem; }
501
502
27.4k
  const RuntimePointerChecking *getRuntimePointerChecking() const {
503
27.4k
    return PtrRtChecking.get();
504
27.4k
  }
505
506
  /// Number of memchecks required to prove independence of otherwise
507
  /// may-alias pointers.
508
19.4k
  unsigned getNumRuntimePointerChecks() const {
509
19.4k
    return PtrRtChecking->getNumberOfChecks();
510
19.4k
  }
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
37.9k
  uint64_t getMaxSafeDepDistBytes() const { return MaxSafeDepDistBytes; }
521
15.4k
  unsigned getNumStores() const { return NumStores; }
522
15.4k
  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
27.0k
  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
244k
  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
112
                                                         bool isWrite) const {
554
112
    return DepChecker->getInstructionsForAccess(Ptr, isWrite);
555
112
  }
556
557
  /// If an access has a symbolic strides, this maps the pointer value to
558
  /// the stride symbol.
559
330k
  const ValueToValueMap &getSymbolicStrides() const { return SymbolicStrides; }
560
561
  /// Pointer has a symbolic stride.
562
213k
  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
  /// 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
19.4k
  bool hasStoreToLoopInvariantAddress() const {
571
19.4k
    return StoreToLoopInvariantAddress;
572
19.4k
  }
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
183k
  const PredicatedScalarEvolution &getPSE() const { return *PSE; }
580
581
private:
582
  /// Analyze the loop.
583
  void analyzeLoop(AliasAnalysis *AA, LoopInfo *LI,
584
                   const TargetLibraryInfo *TLI, DominatorTree *DT);
585
586
  /// Check if the structure of the loop allows it to be analyzed by this
587
  /// pass.
588
  bool canAnalyzeLoop();
589
590
  /// 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
  /// 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
  /// 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
  /// Cache the result of analyzeLoop.
622
  bool CanVecMem;
623
624
  /// 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
  /// 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
  /// If an access has a symbolic strides, this maps the pointer value to
633
  /// the stride symbol.
634
  ValueToValueMap SymbolicStrides;
635
636
  /// Set of symbolic strides values.
637
  SmallPtrSet<Value *, 8> StrideSet;
638
};
639
640
Value *stripIntegerCast(Value *V);
641
642
/// 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.
652
const SCEV *replaceSymbolicStrideSCEV(PredicatedScalarEvolution &PSE,
653
                                      const ValueToValueMap &PtrToStride,
654
                                      Value *Ptr, Value *OrigPtr = nullptr);
655
656
/// 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.
666
int64_t getPtrStride(PredicatedScalarEvolution &PSE, Value *Ptr, const Loop *Lp,
667
                     const ValueToValueMap &StridesMap = ValueToValueMap(),
668
                     bool Assume = false, bool ShouldCheckWrap = true);
669
670
/// Attempt to sort the pointers in \p VL and return the sorted indices
671
/// in \p SortedIndices, if reordering is required.
672
///
673
/// Returns 'true' if sorting is legal, otherwise returns 'false'.
674
///
675
/// For example, for a given \p VL of memory accesses in program order, a[i+4],
676
/// a[i+0], a[i+1] and a[i+7], this function will sort the \p VL and save the
677
/// sorted indices in \p SortedIndices as a[i+0], a[i+1], a[i+4], a[i+7] and
678
/// saves the mask for actual memory accesses in program order in
679
/// \p SortedIndices as <1,2,0,3>
680
bool sortPtrAccesses(ArrayRef<Value *> VL, const DataLayout &DL,
681
                     ScalarEvolution &SE,
682
                     SmallVectorImpl<unsigned> &SortedIndices);
683
684
/// Returns true if the memory operations \p A and \p B are consecutive.
685
/// This is a simple API that does not depend on the analysis pass.
686
bool isConsecutiveAccess(Value *A, Value *B, const DataLayout &DL,
687
                         ScalarEvolution &SE, bool CheckType = true);
688
689
/// This analysis provides dependence information for the memory accesses
690
/// of a loop.
691
///
692
/// It runs the analysis for a loop on demand.  This can be initiated by
693
/// querying the loop access info via LAA::getInfo.  getInfo return a
694
/// LoopAccessInfo object.  See this class for the specifics of what information
695
/// is provided.
696
class LoopAccessLegacyAnalysis : public FunctionPass {
697
public:
698
  static char ID;
699
700
39.6k
  LoopAccessLegacyAnalysis() : FunctionPass(ID) {
701
39.6k
    initializeLoopAccessLegacyAnalysisPass(*PassRegistry::getPassRegistry());
702
39.6k
  }
703
704
  bool runOnFunction(Function &F) override;
705
706
  void getAnalysisUsage(AnalysisUsage &AU) const override;
707
708
  /// Query the result of the loop access information for the loop \p L.
709
  ///
710
  /// If there is no cached result available run the analysis.
711
  const LoopAccessInfo &getInfo(Loop *L);
712
713
836k
  void releaseMemory() override {
714
836k
    // Invalidate the cache when the pass is freed.
715
836k
    LoopAccessInfoMap.clear();
716
836k
  }
717
718
  /// Print the result of the analysis when invoked with -analyze.
719
  void print(raw_ostream &OS, const Module *M = nullptr) const override;
720
721
private:
722
  /// The cache.
723
  DenseMap<Loop *, std::unique_ptr<LoopAccessInfo>> LoopAccessInfoMap;
724
725
  // The used analysis passes.
726
  ScalarEvolution *SE;
727
  const TargetLibraryInfo *TLI;
728
  AliasAnalysis *AA;
729
  DominatorTree *DT;
730
  LoopInfo *LI;
731
};
732
733
/// This analysis provides dependence information for the memory
734
/// accesses of a loop.
735
///
736
/// It runs the analysis for a loop on demand.  This can be initiated by
737
/// querying the loop access info via AM.getResult<LoopAccessAnalysis>.
738
/// getResult return a LoopAccessInfo object.  See this class for the
739
/// specifics of what information is provided.
740
class LoopAccessAnalysis
741
    : public AnalysisInfoMixin<LoopAccessAnalysis> {
742
  friend AnalysisInfoMixin<LoopAccessAnalysis>;
743
  static AnalysisKey Key;
744
745
public:
746
  typedef LoopAccessInfo Result;
747
748
  Result run(Loop &L, LoopAnalysisManager &AM, LoopStandardAnalysisResults &AR);
749
};
750
751
inline Instruction *MemoryDepChecker::Dependence::getSource(
752
10.6k
    const LoopAccessInfo &LAI) const {
753
10.6k
  return LAI.getDepChecker().getMemoryInstructions()[Source];
754
10.6k
}
755
756
inline Instruction *MemoryDepChecker::Dependence::getDestination(
757
10.6k
    const LoopAccessInfo &LAI) const {
758
10.6k
  return LAI.getDepChecker().getMemoryInstructions()[Destination];
759
10.6k
}
760
761
} // End llvm namespace
762
763
#endif