llvm.org GIT mirror llvm / 5864ac7 include / llvm / Analysis / AliasAnalysis.h
5864ac7

Tree @5864ac7 (Download .tar.gz)

AliasAnalysis.h @5864ac7raw · history · 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
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
//===- llvm/Analysis/AliasAnalysis.h - Alias Analysis Interface -*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the generic AliasAnalysis interface, which is used as the
// common interface used by all clients of alias analysis information, and
// implemented by all alias analysis implementations.  Mod/Ref information is
// also captured by this interface.
//
// Implementations of this interface must implement the various virtual methods,
// which automatically provides functionality for the entire suite of client
// APIs.
//
// This API identifies memory regions with the MemoryLocation class. The pointer
// component specifies the base memory address of the region. The Size specifies
// the maximum size (in address units) of the memory region, or
// MemoryLocation::UnknownSize if the size is not known. The TBAA tag
// identifies the "type" of the memory reference; see the
// TypeBasedAliasAnalysis class for details.
//
// Some non-obvious details include:
//  - Pointers that point to two completely different objects in memory never
//    alias, regardless of the value of the Size component.
//  - NoAlias doesn't imply inequal pointers. The most obvious example of this
//    is two pointers to constant memory. Even if they are equal, constant
//    memory is never stored to, so there will never be any dependencies.
//    In this and other situations, the pointers may be both NoAlias and
//    MustAlias at the same time. The current API can only return one result,
//    though this is rarely a problem in practice.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_ANALYSIS_ALIASANALYSIS_H
#define LLVM_ANALYSIS_ALIASANALYSIS_H

#include "llvm/ADT/DenseMap.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/Metadata.h"
#include "llvm/Analysis/MemoryLocation.h"

namespace llvm {

class LoadInst;
class StoreInst;
class VAArgInst;
class DataLayout;
class TargetLibraryInfo;
class Pass;
class AnalysisUsage;
class MemTransferInst;
class MemIntrinsic;
class DominatorTree;
class OrderedBasicBlock;

/// The possible results of an alias query.
///
/// These results are always computed between two MemoryLocation objects as
/// a query to some alias analysis.
///
/// Note that these are unscoped enumerations because we would like to support
/// implicitly testing a result for the existence of any possible aliasing with
/// a conversion to bool, but an "enum class" doesn't support this. The
/// canonical names from the literature are suffixed and unique anyways, and so
/// they serve as global constants in LLVM for these results.
///
/// See docs/AliasAnalysis.html for more information on the specific meanings
/// of these values.
enum AliasResult {
  /// The two locations do not alias at all.
  ///
  /// This value is arranged to convert to false, while all other values
  /// convert to true. This allows a boolean context to convert the result to
  /// a binary flag indicating whether there is the possibility of aliasing.
  NoAlias = 0,
  /// The two locations may or may not alias. This is the least precise result.
  MayAlias,
  /// The two locations alias, but only due to a partial overlap.
  PartialAlias,
  /// The two locations precisely alias each other.
  MustAlias,
};

/// Flags indicating whether a memory access modifies or references memory.
///
/// This is no access at all, a modification, a reference, or both
/// a modification and a reference. These are specifically structured such that
/// they form a two bit matrix and bit-tests for 'mod' or 'ref' work with any
/// of the possible values.
enum ModRefInfo {
  /// The access neither references nor modifies the value stored in memory.
  MRI_NoModRef = 0,
  /// The access references the value stored in memory.
  MRI_Ref = 1,
  /// The access modifies the value stored in memory.
  MRI_Mod = 2,
  /// The access both references and modifies the value stored in memory.
  MRI_ModRef = MRI_Ref | MRI_Mod
};

/// The locations at which a function might access memory.
///
/// These are primarily used in conjunction with the \c AccessKind bits to
/// describe both the nature of access and the locations of access for a
/// function call.
enum FunctionModRefLocation {
  /// Base case is no access to memory.
  FMRL_Nowhere = 0,
  /// Access to memory via argument pointers.
  FMRL_ArgumentPointees = 4,
  /// Access to any memory.
  FMRL_Anywhere = 8 | FMRL_ArgumentPointees
};

/// Summary of how a function affects memory in the program.
///
/// Loads from constant globals are not considered memory accesses for this
/// interface. Also, functions may freely modify stack space local to their
/// invocation without having to report it through these interfaces.
enum FunctionModRefBehavior {
  /// This function does not perform any non-local loads or stores to memory.
  ///
  /// This property corresponds to the GCC 'const' attribute.
  /// This property corresponds to the LLVM IR 'readnone' attribute.
  /// This property corresponds to the IntrNoMem LLVM intrinsic flag.
  FMRB_DoesNotAccessMemory = FMRL_Nowhere | MRI_NoModRef,

  /// The only memory references in this function (if it has any) are
  /// non-volatile loads from objects pointed to by its pointer-typed
  /// arguments, with arbitrary offsets.
  ///
  /// This property corresponds to the IntrReadArgMem LLVM intrinsic flag.
  FMRB_OnlyReadsArgumentPointees = FMRL_ArgumentPointees | MRI_Ref,

  /// The only memory references in this function (if it has any) are
  /// non-volatile loads and stores from objects pointed to by its
  /// pointer-typed arguments, with arbitrary offsets.
  ///
  /// This property corresponds to the IntrReadWriteArgMem LLVM intrinsic flag.
  FMRB_OnlyAccessesArgumentPointees = FMRL_ArgumentPointees | MRI_ModRef,

  /// This function does not perform any non-local stores or volatile loads,
  /// but may read from any memory location.
  ///
  /// This property corresponds to the GCC 'pure' attribute.
  /// This property corresponds to the LLVM IR 'readonly' attribute.
  /// This property corresponds to the IntrReadMem LLVM intrinsic flag.
  FMRB_OnlyReadsMemory = FMRL_Anywhere | MRI_Ref,

  /// This indicates that the function could not be classified into one of the
  /// behaviors above.
  FMRB_UnknownModRefBehavior = FMRL_Anywhere | MRI_ModRef
};

class AliasAnalysis {
protected:
  const DataLayout *DL;
  const TargetLibraryInfo *TLI;

private:
  AliasAnalysis *AA;       // Previous Alias Analysis to chain to.

protected:
  /// InitializeAliasAnalysis - Subclasses must call this method to initialize
  /// the AliasAnalysis interface before any other methods are called.  This is
  /// typically called by the run* methods of these subclasses.  This may be
  /// called multiple times.
  ///
  void InitializeAliasAnalysis(Pass *P, const DataLayout *DL);

  /// getAnalysisUsage - All alias analysis implementations should invoke this
  /// directly (using AliasAnalysis::getAnalysisUsage(AU)).
  virtual void getAnalysisUsage(AnalysisUsage &AU) const;

public:
  static char ID; // Class identification, replacement for typeinfo
  AliasAnalysis() : DL(nullptr), TLI(nullptr), AA(nullptr) {}
  virtual ~AliasAnalysis();  // We want to be subclassed

  /// getTargetLibraryInfo - Return a pointer to the current TargetLibraryInfo
  /// object, or null if no TargetLibraryInfo object is available.
  ///
  const TargetLibraryInfo *getTargetLibraryInfo() const { return TLI; }

  //===--------------------------------------------------------------------===//
  /// \name Alias Queries
  /// @{

  /// The main low level interface to the alias analysis implementation.
  /// Returns an AliasResult indicating whether the two pointers are aliased to
  /// each other. This is the interface that must be implemented by specific
  /// alias analysis implementations.
  virtual AliasResult alias(const MemoryLocation &LocA,
                            const MemoryLocation &LocB);

  /// A convenience wrapper around the primary \c alias interface.
  AliasResult alias(const Value *V1, uint64_t V1Size, const Value *V2,
                    uint64_t V2Size) {
    return alias(MemoryLocation(V1, V1Size), MemoryLocation(V2, V2Size));
  }

  /// A convenience wrapper around the primary \c alias interface.
  AliasResult alias(const Value *V1, const Value *V2) {
    return alias(V1, MemoryLocation::UnknownSize, V2,
                 MemoryLocation::UnknownSize);
  }

  /// A trivial helper function to check to see if the specified pointers are
  /// no-alias.
  bool isNoAlias(const MemoryLocation &LocA, const MemoryLocation &LocB) {
    return alias(LocA, LocB) == NoAlias;
  }

  /// A convenience wrapper around the \c isNoAlias helper interface.
  bool isNoAlias(const Value *V1, uint64_t V1Size, const Value *V2,
                 uint64_t V2Size) {
    return isNoAlias(MemoryLocation(V1, V1Size), MemoryLocation(V2, V2Size));
  }

  /// A convenience wrapper around the \c isNoAlias helper interface.
  bool isNoAlias(const Value *V1, const Value *V2) {
    return isNoAlias(MemoryLocation(V1), MemoryLocation(V2));
  }

  /// A trivial helper function to check to see if the specified pointers are
  /// must-alias.
  bool isMustAlias(const MemoryLocation &LocA, const MemoryLocation &LocB) {
    return alias(LocA, LocB) == MustAlias;
  }

  /// A convenience wrapper around the \c isMustAlias helper interface.
  bool isMustAlias(const Value *V1, const Value *V2) {
    return alias(V1, 1, V2, 1) == MustAlias;
  }

  /// Checks whether the given location points to constant memory, or if
  /// \p OrLocal is true whether it points to a local alloca.
  virtual bool pointsToConstantMemory(const MemoryLocation &Loc,
                                      bool OrLocal = false);

  /// A convenience wrapper around the primary \c pointsToConstantMemory
  /// interface.
  bool pointsToConstantMemory(const Value *P, bool OrLocal = false) {
    return pointsToConstantMemory(MemoryLocation(P), OrLocal);
  }

  /// @}
  //===--------------------------------------------------------------------===//
  /// \name Simple mod/ref information
  /// @{

  /// Get the ModRef info associated with a pointer argument of a callsite. The
  /// result's bits are set to indicate the allowed aliasing ModRef kinds. Note
  /// that these bits do not necessarily account for the overall behavior of
  /// the function, but rather only provide additional per-argument
  /// information.
  virtual ModRefInfo getArgModRefInfo(ImmutableCallSite CS, unsigned ArgIdx);

  /// Return the behavior of the given call site.
  virtual FunctionModRefBehavior getModRefBehavior(ImmutableCallSite CS);

  /// Return the behavior when calling the given function.
  virtual FunctionModRefBehavior getModRefBehavior(const Function *F);

  /// Checks if the specified call is known to never read or write memory.
  ///
  /// Note that if the call only reads from known-constant memory, it is also
  /// legal to return true. Also, calls that unwind the stack are legal for
  /// this predicate.
  ///
  /// Many optimizations (such as CSE and LICM) can be performed on such calls
  /// without worrying about aliasing properties, and many calls have this
  /// property (e.g. calls to 'sin' and 'cos').
  ///
  /// This property corresponds to the GCC 'const' attribute.
  bool doesNotAccessMemory(ImmutableCallSite CS) {
    return getModRefBehavior(CS) == FMRB_DoesNotAccessMemory;
  }

  /// Checks if the specified function is known to never read or write memory.
  ///
  /// Note that if the function only reads from known-constant memory, it is
  /// also legal to return true. Also, function that unwind the stack are legal
  /// for this predicate.
  ///
  /// Many optimizations (such as CSE and LICM) can be performed on such calls
  /// to such functions without worrying about aliasing properties, and many
  /// functions have this property (e.g. 'sin' and 'cos').
  ///
  /// This property corresponds to the GCC 'const' attribute.
  bool doesNotAccessMemory(const Function *F) {
    return getModRefBehavior(F) == FMRB_DoesNotAccessMemory;
  }

  /// Checks if the specified call is known to only read from non-volatile
  /// memory (or not access memory at all).
  ///
  /// Calls that unwind the stack are legal for this predicate.
  ///
  /// This property allows many common optimizations to be performed in the
  /// absence of interfering store instructions, such as CSE of strlen calls.
  ///
  /// This property corresponds to the GCC 'pure' attribute.
  bool onlyReadsMemory(ImmutableCallSite CS) {
    return onlyReadsMemory(getModRefBehavior(CS));
  }

  /// Checks if the specified function is known to only read from non-volatile
  /// memory (or not access memory at all).
  ///
  /// Functions that unwind the stack are legal for this predicate.
  ///
  /// This property allows many common optimizations to be performed in the
  /// absence of interfering store instructions, such as CSE of strlen calls.
  ///
  /// This property corresponds to the GCC 'pure' attribute.
  bool onlyReadsMemory(const Function *F) {
    return onlyReadsMemory(getModRefBehavior(F));
  }

  /// Checks if functions with the specified behavior are known to only read
  /// from non-volatile memory (or not access memory at all).
  static bool onlyReadsMemory(FunctionModRefBehavior MRB) {
    return !(MRB & MRI_Mod);
  }

  /// Checks if functions with the specified behavior are known to read and
  /// write at most from objects pointed to by their pointer-typed arguments
  /// (with arbitrary offsets).
  static bool onlyAccessesArgPointees(FunctionModRefBehavior MRB) {
    return !(MRB & FMRL_Anywhere & ~FMRL_ArgumentPointees);
  }

  /// Checks if functions with the specified behavior are known to potentially
  /// read or write from objects pointed to be their pointer-typed arguments
  /// (with arbitrary offsets).
  static bool doesAccessArgPointees(FunctionModRefBehavior MRB) {
    return (MRB & MRI_ModRef) && (MRB & FMRL_ArgumentPointees);
  }

  /// getModRefInfo (for call sites) - Return information about whether
  /// a particular call site modifies or reads the specified memory location.
  virtual ModRefInfo getModRefInfo(ImmutableCallSite CS,
                                   const MemoryLocation &Loc);

  /// getModRefInfo (for call sites) - A convenience wrapper.
  ModRefInfo getModRefInfo(ImmutableCallSite CS, const Value *P,
                           uint64_t Size) {
    return getModRefInfo(CS, MemoryLocation(P, Size));
  }

  /// getModRefInfo (for calls) - Return information about whether
  /// a particular call modifies or reads the specified memory location.
  ModRefInfo getModRefInfo(const CallInst *C, const MemoryLocation &Loc) {
    return getModRefInfo(ImmutableCallSite(C), Loc);
  }

  /// getModRefInfo (for calls) - A convenience wrapper.
  ModRefInfo getModRefInfo(const CallInst *C, const Value *P, uint64_t Size) {
    return getModRefInfo(C, MemoryLocation(P, Size));
  }

  /// getModRefInfo (for invokes) - Return information about whether
  /// a particular invoke modifies or reads the specified memory location.
  ModRefInfo getModRefInfo(const InvokeInst *I, const MemoryLocation &Loc) {
    return getModRefInfo(ImmutableCallSite(I), Loc);
  }

  /// getModRefInfo (for invokes) - A convenience wrapper.
  ModRefInfo getModRefInfo(const InvokeInst *I, const Value *P, uint64_t Size) {
    return getModRefInfo(I, MemoryLocation(P, Size));
  }

  /// getModRefInfo (for loads) - Return information about whether
  /// a particular load modifies or reads the specified memory location.
  ModRefInfo getModRefInfo(const LoadInst *L, const MemoryLocation &Loc);

  /// getModRefInfo (for loads) - A convenience wrapper.
  ModRefInfo getModRefInfo(const LoadInst *L, const Value *P, uint64_t Size) {
    return getModRefInfo(L, MemoryLocation(P, Size));
  }

  /// getModRefInfo (for stores) - Return information about whether
  /// a particular store modifies or reads the specified memory location.
  ModRefInfo getModRefInfo(const StoreInst *S, const MemoryLocation &Loc);

  /// getModRefInfo (for stores) - A convenience wrapper.
  ModRefInfo getModRefInfo(const StoreInst *S, const Value *P, uint64_t Size) {
    return getModRefInfo(S, MemoryLocation(P, Size));
  }

  /// getModRefInfo (for fences) - Return information about whether
  /// a particular store modifies or reads the specified memory location.
  ModRefInfo getModRefInfo(const FenceInst *S, const MemoryLocation &Loc) {
    // Conservatively correct.  (We could possibly be a bit smarter if
    // Loc is a alloca that doesn't escape.)
    return MRI_ModRef;
  }

  /// getModRefInfo (for fences) - A convenience wrapper.
  ModRefInfo getModRefInfo(const FenceInst *S, const Value *P, uint64_t Size) {
    return getModRefInfo(S, MemoryLocation(P, Size));
  }

  /// getModRefInfo (for cmpxchges) - Return information about whether
  /// a particular cmpxchg modifies or reads the specified memory location.
  ModRefInfo getModRefInfo(const AtomicCmpXchgInst *CX,
                           const MemoryLocation &Loc);

  /// getModRefInfo (for cmpxchges) - A convenience wrapper.
  ModRefInfo getModRefInfo(const AtomicCmpXchgInst *CX, const Value *P,
                           unsigned Size) {
    return getModRefInfo(CX, MemoryLocation(P, Size));
  }

  /// getModRefInfo (for atomicrmws) - Return information about whether
  /// a particular atomicrmw modifies or reads the specified memory location.
  ModRefInfo getModRefInfo(const AtomicRMWInst *RMW, const MemoryLocation &Loc);

  /// getModRefInfo (for atomicrmws) - A convenience wrapper.
  ModRefInfo getModRefInfo(const AtomicRMWInst *RMW, const Value *P,
                           unsigned Size) {
    return getModRefInfo(RMW, MemoryLocation(P, Size));
  }

  /// getModRefInfo (for va_args) - Return information about whether
  /// a particular va_arg modifies or reads the specified memory location.
  ModRefInfo getModRefInfo(const VAArgInst *I, const MemoryLocation &Loc);

  /// getModRefInfo (for va_args) - A convenience wrapper.
  ModRefInfo getModRefInfo(const VAArgInst *I, const Value *P, uint64_t Size) {
    return getModRefInfo(I, MemoryLocation(P, Size));
  }

  /// Check whether or not an instruction may read or write memory (without
  /// regard to a specific location).
  ///
  /// For function calls, this delegates to the alias-analysis specific
  /// call-site mod-ref behavior queries. Otherwise it delegates to the generic
  /// mod ref information query without a location.
  ModRefInfo getModRefInfo(const Instruction *I) {
    if (auto CS = ImmutableCallSite(I)) {
      auto MRB = getModRefBehavior(CS);
      if (MRB & MRI_ModRef)
        return MRI_ModRef;
      else if (MRB & MRI_Ref)
        return MRI_Ref;
      else if (MRB & MRI_Mod)
        return MRI_Mod;
      return MRI_NoModRef;
    }

    return getModRefInfo(I, MemoryLocation());
  }

  /// Check whether or not an instruction may read or write the specified
  /// memory location.
  ///
  /// An instruction that doesn't read or write memory may be trivially LICM'd
  /// for example.
  ///
  /// This primarily delegates to specific helpers above.
  ModRefInfo getModRefInfo(const Instruction *I, const MemoryLocation &Loc) {
    switch (I->getOpcode()) {
    case Instruction::VAArg:  return getModRefInfo((const VAArgInst*)I, Loc);
    case Instruction::Load:   return getModRefInfo((const LoadInst*)I,  Loc);
    case Instruction::Store:  return getModRefInfo((const StoreInst*)I, Loc);
    case Instruction::Fence:  return getModRefInfo((const FenceInst*)I, Loc);
    case Instruction::AtomicCmpXchg:
      return getModRefInfo((const AtomicCmpXchgInst*)I, Loc);
    case Instruction::AtomicRMW:
      return getModRefInfo((const AtomicRMWInst*)I, Loc);
    case Instruction::Call:   return getModRefInfo((const CallInst*)I,  Loc);
    case Instruction::Invoke: return getModRefInfo((const InvokeInst*)I,Loc);
    default:
      return MRI_NoModRef;
    }
  }

  /// A convenience wrapper for constructing the memory location.
  ModRefInfo getModRefInfo(const Instruction *I, const Value *P,
                           uint64_t Size) {
    return getModRefInfo(I, MemoryLocation(P, Size));
  }

  /// Return information about whether a call and an instruction may refer to
  /// the same memory locations.
  ModRefInfo getModRefInfo(Instruction *I, ImmutableCallSite Call);

  /// Return information about whether two call sites may refer to the same set
  /// of memory locations. See the AA documentation for details:
  ///   http://llvm.org/docs/AliasAnalysis.html#ModRefInfo
  virtual ModRefInfo getModRefInfo(ImmutableCallSite CS1,
                                   ImmutableCallSite CS2);

  /// \brief Return information about whether a particular call site modifies
  /// or reads the specified memory location \p MemLoc before instruction \p I
  /// in a BasicBlock. A ordered basic block \p OBB can be used to speed up
  /// instruction ordering queries inside the BasicBlock containing \p I.
  ModRefInfo callCapturesBefore(const Instruction *I,
                                const MemoryLocation &MemLoc, DominatorTree *DT,
                                OrderedBasicBlock *OBB = nullptr);

  /// \brief A convenience wrapper to synthesize a memory location.
  ModRefInfo callCapturesBefore(const Instruction *I, const Value *P,
                                uint64_t Size, DominatorTree *DT,
                                OrderedBasicBlock *OBB = nullptr) {
    return callCapturesBefore(I, MemoryLocation(P, Size), DT, OBB);
  }

  /// @}
  //===--------------------------------------------------------------------===//
  /// \name Higher level methods for querying mod/ref information.
  /// @{

  /// Check if it is possible for execution of the specified basic block to
  /// modify the location Loc.
  bool canBasicBlockModify(const BasicBlock &BB, const MemoryLocation &Loc);

  /// A convenience wrapper synthesizing a memory location.
  bool canBasicBlockModify(const BasicBlock &BB, const Value *P,
                           uint64_t Size) {
    return canBasicBlockModify(BB, MemoryLocation(P, Size));
  }

  /// Check if it is possible for the execution of the specified instructions
  /// to mod\ref (according to the mode) the location Loc.
  ///
  /// The instructions to consider are all of the instructions in the range of
  /// [I1,I2] INCLUSIVE. I1 and I2 must be in the same basic block.
  bool canInstructionRangeModRef(const Instruction &I1, const Instruction &I2,
                                 const MemoryLocation &Loc,
                                 const ModRefInfo Mode);

  /// A convenience wrapper synthesizing a memory location.
  bool canInstructionRangeModRef(const Instruction &I1, const Instruction &I2,
                                 const Value *Ptr, uint64_t Size,
                                 const ModRefInfo Mode) {
    return canInstructionRangeModRef(I1, I2, MemoryLocation(Ptr, Size), Mode);
  }
};

/// isNoAliasCall - Return true if this pointer is returned by a noalias
/// function.
bool isNoAliasCall(const Value *V);

/// isNoAliasArgument - Return true if this is an argument with the noalias
/// attribute.
bool isNoAliasArgument(const Value *V);

/// isIdentifiedObject - Return true if this pointer refers to a distinct and
/// identifiable object.  This returns true for:
///    Global Variables and Functions (but not Global Aliases)
///    Allocas
///    ByVal and NoAlias Arguments
///    NoAlias returns (e.g. calls to malloc)
///
bool isIdentifiedObject(const Value *V);

/// isIdentifiedFunctionLocal - Return true if V is umabigously identified
/// at the function-level. Different IdentifiedFunctionLocals can't alias.
/// Further, an IdentifiedFunctionLocal can not alias with any function
/// arguments other than itself, which is not necessarily true for
/// IdentifiedObjects.
bool isIdentifiedFunctionLocal(const Value *V);

} // End llvm namespace

#endif