aboutsummaryrefslogtreecommitdiffstats
path: root/contrib/libs/llvm14/include/llvm/Analysis/AliasSetTracker.h
blob: d233cc2fc6aea91ed12466677f5155995f4c7290 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
#pragma once

#ifdef __GNUC__
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-parameter"
#endif

//===- llvm/Analysis/AliasSetTracker.h - Build Alias Sets -------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines two classes: AliasSetTracker and AliasSet. These interfaces
// are used to classify a collection of pointer references into a maximal number
// of disjoint sets. Each AliasSet object constructed by the AliasSetTracker
// object refers to memory disjoint from the other sets.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_ANALYSIS_ALIASSETTRACKER_H
#define LLVM_ANALYSIS_ALIASSETTRACKER_H

#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseMapInfo.h"
#include "llvm/ADT/ilist.h"
#include "llvm/ADT/ilist_node.h"
#include "llvm/Analysis/MemoryLocation.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/PassManager.h"
#include "llvm/IR/ValueHandle.h"
#include "llvm/Support/Casting.h"
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <iterator>
#include <vector>

namespace llvm {

class AAResults;
class AliasResult;
class AliasSetTracker;
class AnyMemSetInst;
class AnyMemTransferInst;
class BasicBlock;
class LoadInst;
class raw_ostream;
class StoreInst;
class VAArgInst;
class Value;

class AliasSet : public ilist_node<AliasSet> {
  friend class AliasSetTracker;

  class PointerRec {
    Value *Val;  // The pointer this record corresponds to.
    PointerRec **PrevInList = nullptr;
    PointerRec *NextInList = nullptr;
    AliasSet *AS = nullptr;
    LocationSize Size = LocationSize::mapEmpty();
    AAMDNodes AAInfo;

    // Whether the size for this record has been set at all. This makes no
    // guarantees about the size being known.
    bool isSizeSet() const { return Size != LocationSize::mapEmpty(); }

  public:
    PointerRec(Value *V)
      : Val(V), AAInfo(DenseMapInfo<AAMDNodes>::getEmptyKey()) {}

    Value *getValue() const { return Val; }

    PointerRec *getNext() const { return NextInList; }
    bool hasAliasSet() const { return AS != nullptr; }

    PointerRec** setPrevInList(PointerRec **PIL) {
      PrevInList = PIL;
      return &NextInList;
    }

    bool updateSizeAndAAInfo(LocationSize NewSize, const AAMDNodes &NewAAInfo) {
      bool SizeChanged = false;
      if (NewSize != Size) {
        LocationSize OldSize = Size;
        Size = isSizeSet() ? Size.unionWith(NewSize) : NewSize;
        SizeChanged = OldSize != Size;
      }

      if (AAInfo == DenseMapInfo<AAMDNodes>::getEmptyKey())
        // We don't have a AAInfo yet. Set it to NewAAInfo.
        AAInfo = NewAAInfo;
      else {
        AAMDNodes Intersection(AAInfo.intersect(NewAAInfo));
        SizeChanged |= Intersection != AAInfo;
        AAInfo = Intersection;
      }
      return SizeChanged;
    }

    LocationSize getSize() const {
      assert(isSizeSet() && "Getting an unset size!");
      return Size;
    }

    /// Return the AAInfo, or null if there is no information or conflicting
    /// information.
    AAMDNodes getAAInfo() const {
      // If we have missing or conflicting AAInfo, return null.
      if (AAInfo == DenseMapInfo<AAMDNodes>::getEmptyKey() ||
          AAInfo == DenseMapInfo<AAMDNodes>::getTombstoneKey())
        return AAMDNodes();
      return AAInfo;
    }

    AliasSet *getAliasSet(AliasSetTracker &AST) {
      assert(AS && "No AliasSet yet!");
      if (AS->Forward) {
        AliasSet *OldAS = AS;
        AS = OldAS->getForwardedTarget(AST);
        AS->addRef();
        OldAS->dropRef(AST);
      }
      return AS;
    }

    void setAliasSet(AliasSet *as) {
      assert(!AS && "Already have an alias set!");
      AS = as;
    }

    void eraseFromList() {
      if (NextInList) NextInList->PrevInList = PrevInList;
      *PrevInList = NextInList;
      if (AS->PtrListEnd == &NextInList) {
        AS->PtrListEnd = PrevInList;
        assert(*AS->PtrListEnd == nullptr && "List not terminated right!");
      }
      delete this;
    }
  };

  // Doubly linked list of nodes.
  PointerRec *PtrList = nullptr;
  PointerRec **PtrListEnd;
  // Forwarding pointer.
  AliasSet *Forward = nullptr;

  /// All instructions without a specific address in this alias set.
  /// In rare cases this vector can have a null'ed out WeakVH
  /// instances (can happen if some other loop pass deletes an
  /// instruction in this list).
  std::vector<WeakVH> UnknownInsts;

  /// Number of nodes pointing to this AliasSet plus the number of AliasSets
  /// forwarding to it.
  unsigned RefCount : 27;

  // Signifies that this set should be considered to alias any pointer.
  // Use when the tracker holding this set is saturated.
  unsigned AliasAny : 1;

  /// The kinds of access this alias set models.
  ///
  /// We keep track of whether this alias set merely refers to the locations of
  /// memory (and not any particular access), whether it modifies or references
  /// the memory, or whether it does both. The lattice goes from "NoAccess" to
  /// either RefAccess or ModAccess, then to ModRefAccess as necessary.
  enum AccessLattice {
    NoAccess = 0,
    RefAccess = 1,
    ModAccess = 2,
    ModRefAccess = RefAccess | ModAccess
  };
  unsigned Access : 2;

  /// The kind of alias relationship between pointers of the set.
  ///
  /// These represent conservatively correct alias results between any members
  /// of the set. We represent these independently of the values of alias
  /// results in order to pack it into a single bit. Lattice goes from
  /// MustAlias to MayAlias.
  enum AliasLattice {
    SetMustAlias = 0, SetMayAlias = 1
  };
  unsigned Alias : 1;

  unsigned SetSize = 0;

  void addRef() { ++RefCount; }

  void dropRef(AliasSetTracker &AST) {
    assert(RefCount >= 1 && "Invalid reference count detected!");
    if (--RefCount == 0)
      removeFromTracker(AST);
  }

  Instruction *getUnknownInst(unsigned i) const {
    assert(i < UnknownInsts.size());
    return cast_or_null<Instruction>(UnknownInsts[i]);
  }

public:
  AliasSet(const AliasSet &) = delete;
  AliasSet &operator=(const AliasSet &) = delete;

  /// Accessors...
  bool isRef() const { return Access & RefAccess; }
  bool isMod() const { return Access & ModAccess; }
  bool isMustAlias() const { return Alias == SetMustAlias; }
  bool isMayAlias()  const { return Alias == SetMayAlias; }

  /// Return true if this alias set should be ignored as part of the
  /// AliasSetTracker object.
  bool isForwardingAliasSet() const { return Forward; }

  /// Merge the specified alias set into this alias set.
  void mergeSetIn(AliasSet &AS, AliasSetTracker &AST);

  // Alias Set iteration - Allow access to all of the pointers which are part of
  // this alias set.
  class iterator;
  iterator begin() const { return iterator(PtrList); }
  iterator end()   const { return iterator(); }
  bool empty() const { return PtrList == nullptr; }

  // Unfortunately, ilist::size() is linear, so we have to add code to keep
  // track of the list's exact size.
  unsigned size() { return SetSize; }

  /// If this alias set is known to contain a single instruction and *only* a
  /// single unique instruction, return it.  Otherwise, return nullptr.
  Instruction* getUniqueInstruction();

  void print(raw_ostream &OS) const;
  void dump() const;

  /// Define an iterator for alias sets... this is just a forward iterator.
  class iterator {
    PointerRec *CurNode;

  public:
    using iterator_category = std::forward_iterator_tag;
    using value_type = PointerRec;
    using difference_type = std::ptrdiff_t;
    using pointer = value_type *;
    using reference = value_type &;

    explicit iterator(PointerRec *CN = nullptr) : CurNode(CN) {}

    bool operator==(const iterator& x) const {
      return CurNode == x.CurNode;
    }
    bool operator!=(const iterator& x) const { return !operator==(x); }

    value_type &operator*() const {
      assert(CurNode && "Dereferencing AliasSet.end()!");
      return *CurNode;
    }
    value_type *operator->() const { return &operator*(); }

    Value *getPointer() const { return CurNode->getValue(); }
    LocationSize getSize() const { return CurNode->getSize(); }
    AAMDNodes getAAInfo() const { return CurNode->getAAInfo(); }

    iterator& operator++() {                // Preincrement
      assert(CurNode && "Advancing past AliasSet.end()!");
      CurNode = CurNode->getNext();
      return *this;
    }
    iterator operator++(int) { // Postincrement
      iterator tmp = *this; ++*this; return tmp;
    }
  };

private:
  // Can only be created by AliasSetTracker.
  AliasSet()
      : PtrListEnd(&PtrList), RefCount(0),  AliasAny(false), Access(NoAccess),
        Alias(SetMustAlias) {}

  PointerRec *getSomePointer() const {
    return PtrList;
  }

  /// Return the real alias set this represents. If this has been merged with
  /// another set and is forwarding, return the ultimate destination set. This
  /// also implements the union-find collapsing as well.
  AliasSet *getForwardedTarget(AliasSetTracker &AST) {
    if (!Forward) return this;

    AliasSet *Dest = Forward->getForwardedTarget(AST);
    if (Dest != Forward) {
      Dest->addRef();
      Forward->dropRef(AST);
      Forward = Dest;
    }
    return Dest;
  }

  void removeFromTracker(AliasSetTracker &AST);

  void addPointer(AliasSetTracker &AST, PointerRec &Entry, LocationSize Size,
                  const AAMDNodes &AAInfo, bool KnownMustAlias = false,
                  bool SkipSizeUpdate = false);
  void addUnknownInst(Instruction *I, AAResults &AA);

  void removeUnknownInst(AliasSetTracker &AST, Instruction *I) {
    bool WasEmpty = UnknownInsts.empty();
    for (size_t i = 0, e = UnknownInsts.size(); i != e; ++i)
      if (UnknownInsts[i] == I) {
        UnknownInsts[i] = UnknownInsts.back();
        UnknownInsts.pop_back();
        --i; --e;  // Revisit the moved entry.
      }
    if (!WasEmpty && UnknownInsts.empty())
      dropRef(AST);
  }

public:
  /// If the specified pointer "may" (or must) alias one of the members in the
  /// set return the appropriate AliasResult. Otherwise return NoAlias.
  AliasResult aliasesPointer(const Value *Ptr, LocationSize Size,
                             const AAMDNodes &AAInfo, AAResults &AA) const;
  bool aliasesUnknownInst(const Instruction *Inst, AAResults &AA) const;
};

inline raw_ostream& operator<<(raw_ostream &OS, const AliasSet &AS) {
  AS.print(OS);
  return OS;
}

class AliasSetTracker {
  /// A CallbackVH to arrange for AliasSetTracker to be notified whenever a
  /// Value is deleted.
  class ASTCallbackVH final : public CallbackVH {
    AliasSetTracker *AST;

    void deleted() override;
    void allUsesReplacedWith(Value *) override;

  public:
    ASTCallbackVH(Value *V, AliasSetTracker *AST = nullptr);

    ASTCallbackVH &operator=(Value *V);
  };
  /// Traits to tell DenseMap that tell us how to compare and hash the value
  /// handle.
  struct ASTCallbackVHDenseMapInfo : public DenseMapInfo<Value *> {};

  AAResults &AA;
  ilist<AliasSet> AliasSets;

  using PointerMapType = DenseMap<ASTCallbackVH, AliasSet::PointerRec *,
                                  ASTCallbackVHDenseMapInfo>;

  // Map from pointers to their node
  PointerMapType PointerMap;

public:
  /// Create an empty collection of AliasSets, and use the specified alias
  /// analysis object to disambiguate load and store addresses.
  explicit AliasSetTracker(AAResults &AA) : AA(AA) {}
  ~AliasSetTracker() { clear(); }

  /// These methods are used to add different types of instructions to the alias
  /// sets. Adding a new instruction can result in one of three actions
  /// happening:
  ///
  ///   1. If the instruction doesn't alias any other sets, create a new set.
  ///   2. If the instruction aliases exactly one set, add it to the set
  ///   3. If the instruction aliases multiple sets, merge the sets, and add
  ///      the instruction to the result.
  ///
  /// These methods return true if inserting the instruction resulted in the
  /// addition of a new alias set (i.e., the pointer did not alias anything).
  ///
  void add(Value *Ptr, LocationSize Size, const AAMDNodes &AAInfo); // Add a loc
  void add(LoadInst *LI);
  void add(StoreInst *SI);
  void add(VAArgInst *VAAI);
  void add(AnyMemSetInst *MSI);
  void add(AnyMemTransferInst *MTI);
  void add(Instruction *I);       // Dispatch to one of the other add methods...
  void add(BasicBlock &BB);       // Add all instructions in basic block
  void add(const AliasSetTracker &AST); // Add alias relations from another AST
  void addUnknown(Instruction *I);

  void clear();

  /// Return the alias sets that are active.
  const ilist<AliasSet> &getAliasSets() const { return AliasSets; }

  /// Return the alias set which contains the specified memory location.  If
  /// the memory location aliases two or more existing alias sets, will have
  /// the effect of merging those alias sets before the single resulting alias
  /// set is returned.
  AliasSet &getAliasSetFor(const MemoryLocation &MemLoc);

  /// Return the underlying alias analysis object used by this tracker.
  AAResults &getAliasAnalysis() const { return AA; }

  /// This method is used to remove a pointer value from the AliasSetTracker
  /// entirely. It should be used when an instruction is deleted from the
  /// program to update the AST. If you don't use this, you would have dangling
  /// pointers to deleted instructions.
  void deleteValue(Value *PtrVal);

  /// This method should be used whenever a preexisting value in the program is
  /// copied or cloned, introducing a new value.  Note that it is ok for clients
  /// that use this method to introduce the same value multiple times: if the
  /// tracker already knows about a value, it will ignore the request.
  void copyValue(Value *From, Value *To);

  using iterator = ilist<AliasSet>::iterator;
  using const_iterator = ilist<AliasSet>::const_iterator;

  const_iterator begin() const { return AliasSets.begin(); }
  const_iterator end()   const { return AliasSets.end(); }

  iterator begin() { return AliasSets.begin(); }
  iterator end()   { return AliasSets.end(); }

  void print(raw_ostream &OS) const;
  void dump() const;

private:
  friend class AliasSet;

  // The total number of pointers contained in all "may" alias sets.
  unsigned TotalMayAliasSetSize = 0;

  // A non-null value signifies this AST is saturated. A saturated AST lumps
  // all pointers into a single "May" set.
  AliasSet *AliasAnyAS = nullptr;

  void removeAliasSet(AliasSet *AS);

  /// Just like operator[] on the map, except that it creates an entry for the
  /// pointer if it doesn't already exist.
  AliasSet::PointerRec &getEntryFor(Value *V) {
    AliasSet::PointerRec *&Entry = PointerMap[ASTCallbackVH(V, this)];
    if (!Entry)
      Entry = new AliasSet::PointerRec(V);
    return *Entry;
  }

  AliasSet &addPointer(MemoryLocation Loc, AliasSet::AccessLattice E);
  AliasSet *mergeAliasSetsForPointer(const Value *Ptr, LocationSize Size,
                                     const AAMDNodes &AAInfo,
                                     bool &MustAliasAll);

  /// Merge all alias sets into a single set that is considered to alias any
  /// pointer.
  AliasSet &mergeAllAliasSets();

  AliasSet *findAliasSetForUnknownInst(Instruction *Inst);
};

inline raw_ostream& operator<<(raw_ostream &OS, const AliasSetTracker &AST) {
  AST.print(OS);
  return OS;
}

class AliasSetsPrinterPass : public PassInfoMixin<AliasSetsPrinterPass> {
  raw_ostream &OS;

public:
  explicit AliasSetsPrinterPass(raw_ostream &OS);
  PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
};

} // end namespace llvm

#endif // LLVM_ANALYSIS_ALIASSETTRACKER_H

#ifdef __GNUC__
#pragma GCC diagnostic pop
#endif