src/llvm/include/llvm/Analysis/AliasAnalysis.h

   1 //===- llvm/Analysis/AliasAnalysis.h - Alias Analysis Interface -*- 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 generic AliasAnalysis interface, which is used as the
  11 // common interface used by all clients of alias analysis information, and
  12 // implemented by all alias analysis implementations.  Mod/Ref information is
  13 // also captured by this interface.
  14 //
  15 // Implementations of this interface must implement the various virtual methods,
  16 // which automatically provides functionality for the entire suite of client
  17 // APIs.
  18 //
  19 // This API identifies memory regions with the Location class. The pointer
  20 // component specifies the base memory address of the region. The Size specifies
  21 // the maximum size (in address units) of the memory region, or UnknownSize if
  22 // the size is not known. The TBAA tag identifies the "type" of the memory
  23 // reference; see the TypeBasedAliasAnalysis class for details.
  24 //
  25 // Some non-obvious details include:
  26 //  - Pointers that point to two completely different objects in memory never
  27 //    alias, regardless of the value of the Size component.
  28 //  - NoAlias doesn't imply inequal pointers. The most obvious example of this
  29 //    is two pointers to constant memory. Even if they are equal, constant
  30 //    memory is never stored to, so there will never be any dependencies.
  31 //    In this and other situations, the pointers may be both NoAlias and
  32 //    MustAlias at the same time. The current API can only return one result,
  33 //    though this is rarely a problem in practice.
  34 //
  35 //===----------------------------------------------------------------------===//
  36
  37 #ifndef LLVM_ANALYSIS_ALIAS_ANALYSIS_H
  38 #define LLVM_ANALYSIS_ALIAS_ANALYSIS_H
  39
  40 #include "llvm/Support/CallSite.h"
  41 #include "llvm/ADT/DenseMap.h"
  42
  43 namespace llvm {
  44
  45 class LoadInst;
  46 class StoreInst;
  47 class VAArgInst;
  48 class TargetData;
  49 class TargetLibraryInfo;
  50 class Pass;
  51 class AnalysisUsage;
  52 class MemTransferInst;
  53 class MemIntrinsic;
  54 class DominatorTree;
  55
  56 class AliasAnalysis {
  57 protected:
  58   const TargetData *TD;
  59   const TargetLibraryInfo *TLI;
  60
  61 private:
  62   AliasAnalysis *AA;       // Previous Alias Analysis to chain to.
  63
  64 protected:
  65   /// InitializeAliasAnalysis - Subclasses must call this method to initialize
  66   /// the AliasAnalysis interface before any other methods are called.  This is
  67   /// typically called by the run* methods of these subclasses.  This may be
  68   /// called multiple times.
  69   ///
  70   void InitializeAliasAnalysis(Pass *P);
  71
  72   /// getAnalysisUsage - All alias analysis implementations should invoke this
  73   /// directly (using AliasAnalysis::getAnalysisUsage(AU)).
  74   virtual void getAnalysisUsage(AnalysisUsage &AU) const;
  75
  76 public:
  77   static char ID; // Class identification, replacement for typeinfo
  78   AliasAnalysis() : TD(0), TLI(0), AA(0) {}
  79   virtual ~AliasAnalysis();  // We want to be subclassed
  80
  81   /// UnknownSize - This is a special value which can be used with the
  82   /// size arguments in alias queries to indicate that the caller does not
  83   /// know the sizes of the potential memory references.
  84   static uint64_t const UnknownSize = ~UINT64_C(0);
  85
  86   /// getTargetData - Return a pointer to the current TargetData object, or
  87   /// null if no TargetData object is available.
  88   ///
  89   const TargetData *getTargetData() const { return TD; }
  90
  91   /// getTargetLibraryInfo - Return a pointer to the current TargetLibraryInfo
  92   /// object, or null if no TargetLibraryInfo object is available.
  93   ///
  94   const TargetLibraryInfo *getTargetLibraryInfo() const { return TLI; }
  95
  96   /// getTypeStoreSize - Return the TargetData store size for the given type,
  97   /// if known, or a conservative value otherwise.
  98   ///
  99   uint64_t getTypeStoreSize(Type *Ty);
 100
 101   //===--------------------------------------------------------------------===//
 102   /// Alias Queries...
 103   ///
 104
 105   /// Location - A description of a memory location.
 106   struct Location {
 107     /// Ptr - The address of the start of the location.
 108     const Value *Ptr;
 109     /// Size - The maximum size of the location, in address-units, or
 110     /// UnknownSize if the size is not known.  Note that an unknown size does
 111     /// not mean the pointer aliases the entire virtual address space, because
 112     /// there are restrictions on stepping out of one object and into another.
 113     /// See http://llvm.org/docs/LangRef.html#pointeraliasing
 114     uint64_t Size;
 115     /// TBAATag - The metadata node which describes the TBAA type of
 116     /// the location, or null if there is no known unique tag.
 117     const MDNode *TBAATag;
 118
 119     explicit Location(const Value *P = 0, uint64_t S = UnknownSize,
 120                       const MDNode *N = 0)
 121       : Ptr(P), Size(S), TBAATag(N) {}
 122
 123     Location getWithNewPtr(const Value *NewPtr) const {
 124       Location Copy(*this);
 125       Copy.Ptr = NewPtr;
 126       return Copy;
 127     }
 128
 129     Location getWithNewSize(uint64_t NewSize) const {
 130       Location Copy(*this);
 131       Copy.Size = NewSize;
 132       return Copy;
 133     }
 134
 135     Location getWithoutTBAATag() const {
 136       Location Copy(*this);
 137       Copy.TBAATag = 0;
 138       return Copy;
 139     }
 140   };
 141
 142   /// getLocation - Fill in Loc with information about the memory reference by
 143   /// the given instruction.
 144   Location getLocation(const LoadInst *LI);
 145   Location getLocation(const StoreInst *SI);
 146   Location getLocation(const VAArgInst *VI);
 147   Location getLocation(const AtomicCmpXchgInst *CXI);
 148   Location getLocation(const AtomicRMWInst *RMWI);
 149   static Location getLocationForSource(const MemTransferInst *MTI);
 150   static Location getLocationForDest(const MemIntrinsic *MI);
 151
 152   /// Alias analysis result - Either we know for sure that it does not alias, we
 153   /// know for sure it must alias, or we don't know anything: The two pointers
 154   /// _might_ alias.  This enum is designed so you can do things like:
 155   ///     if (AA.alias(P1, P2)) { ... }
 156   /// to check to see if two pointers might alias.
 157   ///
 158   /// See docs/AliasAnalysis.html for more information on the specific meanings
 159   /// of these values.
 160   ///
 161   enum AliasResult {
 162     NoAlias = 0,        ///< No dependencies.
 163     MayAlias,           ///< Anything goes.
 164     PartialAlias,       ///< Pointers differ, but pointees overlap.
 165     MustAlias           ///< Pointers are equal.
 166   };
 167
 168   /// alias - The main low level interface to the alias analysis implementation.
 169   /// Returns an AliasResult indicating whether the two pointers are aliased to
 170   /// each other.  This is the interface that must be implemented by specific
 171   /// alias analysis implementations.
 172   virtual AliasResult alias(const Location &LocA, const Location &LocB);
 173
 174   /// alias - A convenience wrapper.
 175   AliasResult alias(const Value *V1, uint64_t V1Size,
 176                     const Value *V2, uint64_t V2Size) {
 177     return alias(Location(V1, V1Size), Location(V2, V2Size));
 178   }
 179
 180   /// alias - A convenience wrapper.
 181   AliasResult alias(const Value *V1, const Value *V2) {
 182     return alias(V1, UnknownSize, V2, UnknownSize);
 183   }
 184
 185   /// isNoAlias - A trivial helper function to check to see if the specified
 186   /// pointers are no-alias.
 187   bool isNoAlias(const Location &LocA, const Location &LocB) {
 188     return alias(LocA, LocB) == NoAlias;
 189   }
 190
 191   /// isNoAlias - A convenience wrapper.
 192   bool isNoAlias(const Value *V1, uint64_t V1Size,
 193                  const Value *V2, uint64_t V2Size) {
 194     return isNoAlias(Location(V1, V1Size), Location(V2, V2Size));
 195   }
 196
 197   /// isNoAlias - A convenience wrapper.
 198   bool isNoAlias(const Value *V1, const Value *V2) {
 199     return isNoAlias(Location(V1), Location(V2));
 200   }
 201
 202   /// isMustAlias - A convenience wrapper.
 203   bool isMustAlias(const Location &LocA, const Location &LocB) {
 204     return alias(LocA, LocB) == MustAlias;
 205   }
 206
 207   /// isMustAlias - A convenience wrapper.
 208   bool isMustAlias(const Value *V1, const Value *V2) {
 209     return alias(V1, 1, V2, 1) == MustAlias;
 210   }
 211
 212   /// pointsToConstantMemory - If the specified memory location is
 213   /// known to be constant, return true. If OrLocal is true and the
 214   /// specified memory location is known to be "local" (derived from
 215   /// an alloca), return true. Otherwise return false.
 216   virtual bool pointsToConstantMemory(const Location &Loc,
 217                                       bool OrLocal = false);
 218
 219   /// pointsToConstantMemory - A convenient wrapper.
 220   bool pointsToConstantMemory(const Value *P, bool OrLocal = false) {
 221     return pointsToConstantMemory(Location(P), OrLocal);
 222   }
 223
 224   //===--------------------------------------------------------------------===//
 225   /// Simple mod/ref information...
 226   ///
 227
 228   /// ModRefResult - Represent the result of a mod/ref query.  Mod and Ref are
 229   /// bits which may be or'd together.
 230   ///
 231   enum ModRefResult { NoModRef = 0, Ref = 1, Mod = 2, ModRef = 3 };
 232
 233   /// These values define additional bits used to define the
 234   /// ModRefBehavior values.
 235   enum { Nowhere = 0, ArgumentPointees = 4, Anywhere = 8 | ArgumentPointees };
 236
 237   /// ModRefBehavior - Summary of how a function affects memory in the program.
 238   /// Loads from constant globals are not considered memory accesses for this
 239   /// interface.  Also, functions may freely modify stack space local to their
 240   /// invocation without having to report it through these interfaces.
 241   enum ModRefBehavior {
 242     /// DoesNotAccessMemory - This function does not perform any non-local loads
 243     /// or stores to memory.
 244     ///
 245     /// This property corresponds to the GCC 'const' attribute.
 246     /// This property corresponds to the LLVM IR 'readnone' attribute.
 247     /// This property corresponds to the IntrNoMem LLVM intrinsic flag.
 248     DoesNotAccessMemory = Nowhere | NoModRef,
 249
 250     /// OnlyReadsArgumentPointees - The only memory references in this function
 251     /// (if it has any) are non-volatile loads from objects pointed to by its
 252     /// pointer-typed arguments, with arbitrary offsets.
 253     ///
 254     /// This property corresponds to the IntrReadArgMem LLVM intrinsic flag.
 255     OnlyReadsArgumentPointees = ArgumentPointees | Ref,
 256
 257     /// OnlyAccessesArgumentPointees - The only memory references in this
 258     /// function (if it has any) are non-volatile loads and stores from objects
 259     /// pointed to by its pointer-typed arguments, with arbitrary offsets.
 260     ///
 261     /// This property corresponds to the IntrReadWriteArgMem LLVM intrinsic flag.
 262     OnlyAccessesArgumentPointees = ArgumentPointees | ModRef,
 263
 264     /// OnlyReadsMemory - This function does not perform any non-local stores or
 265     /// volatile loads, but may read from any memory location.
 266     ///
 267     /// This property corresponds to the GCC 'pure' attribute.
 268     /// This property corresponds to the LLVM IR 'readonly' attribute.
 269     /// This property corresponds to the IntrReadMem LLVM intrinsic flag.
 270     OnlyReadsMemory = Anywhere | Ref,
 271
 272     /// UnknownModRefBehavior - This indicates that the function could not be
 273     /// classified into one of the behaviors above.
 274     UnknownModRefBehavior = Anywhere | ModRef
 275   };
 276
 277   /// getModRefBehavior - Return the behavior when calling the given call site.
 278   virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS);
 279
 280   /// getModRefBehavior - Return the behavior when calling the given function.
 281   /// For use when the call site is not known.
 282   virtual ModRefBehavior getModRefBehavior(const Function *F);
 283
 284   /// doesNotAccessMemory - If the specified call is known to never read or
 285   /// write memory, return true.  If the call only reads from known-constant
 286   /// memory, it is also legal to return true.  Calls that unwind the stack
 287   /// are legal for this predicate.
 288   ///
 289   /// Many optimizations (such as CSE and LICM) can be performed on such calls
 290   /// without worrying about aliasing properties, and many calls have this
 291   /// property (e.g. calls to 'sin' and 'cos').
 292   ///
 293   /// This property corresponds to the GCC 'const' attribute.
 294   ///
 295   bool doesNotAccessMemory(ImmutableCallSite CS) {
 296     return getModRefBehavior(CS) == DoesNotAccessMemory;
 297   }
 298
 299   /// doesNotAccessMemory - If the specified function is known to never read or
 300   /// write memory, return true.  For use when the call site is not known.
 301   ///
 302   bool doesNotAccessMemory(const Function *F) {
 303     return getModRefBehavior(F) == DoesNotAccessMemory;
 304   }
 305
 306   /// onlyReadsMemory - If the specified call is known to only read from
 307   /// non-volatile memory (or not access memory at all), return true.  Calls
 308   /// that unwind the stack are legal for this predicate.
 309   ///
 310   /// This property allows many common optimizations to be performed in the
 311   /// absence of interfering store instructions, such as CSE of strlen calls.
 312   ///
 313   /// This property corresponds to the GCC 'pure' attribute.
 314   ///
 315   bool onlyReadsMemory(ImmutableCallSite CS) {
 316     return onlyReadsMemory(getModRefBehavior(CS));
 317   }
 318
 319   /// onlyReadsMemory - If the specified function is known to only read from
 320   /// non-volatile memory (or not access memory at all), return true.  For use
 321   /// when the call site is not known.
 322   ///
 323   bool onlyReadsMemory(const Function *F) {
 324     return onlyReadsMemory(getModRefBehavior(F));
 325   }
 326
 327   /// onlyReadsMemory - Return true if functions with the specified behavior are
 328   /// known to only read from non-volatile memory (or not access memory at all).
 329   ///
 330   static bool onlyReadsMemory(ModRefBehavior MRB) {
 331     return !(MRB & Mod);
 332   }
 333
 334   /// onlyAccessesArgPointees - Return true if functions with the specified
 335   /// behavior are known to read and write at most from objects pointed to by
 336   /// their pointer-typed arguments (with arbitrary offsets).
 337   ///
 338   static bool onlyAccessesArgPointees(ModRefBehavior MRB) {
 339     return !(MRB & Anywhere & ~ArgumentPointees);
 340   }
 341
 342   /// doesAccessArgPointees - Return true if functions with the specified
 343   /// behavior are known to potentially read or write from objects pointed
 344   /// to be their pointer-typed arguments (with arbitrary offsets).
 345   ///
 346   static bool doesAccessArgPointees(ModRefBehavior MRB) {
 347     return (MRB & ModRef) && (MRB & ArgumentPointees);
 348   }
 349
 350   /// getModRefInfo - Return information about whether or not an instruction may
 351   /// read or write the specified memory location.  An instruction
 352   /// that doesn't read or write memory may be trivially LICM'd for example.
 353   ModRefResult getModRefInfo(const Instruction *I,
 354                              const Location &Loc) {
 355     switch (I->getOpcode()) {
 356     case Instruction::VAArg:  return getModRefInfo((const VAArgInst*)I, Loc);
 357     case Instruction::Load:   return getModRefInfo((const LoadInst*)I,  Loc);
 358     case Instruction::Store:  return getModRefInfo((const StoreInst*)I, Loc);
 359     case Instruction::Fence:  return getModRefInfo((const FenceInst*)I, Loc);
 360     case Instruction::AtomicCmpXchg:
 361       return getModRefInfo((const AtomicCmpXchgInst*)I, Loc);
 362     case Instruction::AtomicRMW:
 363       return getModRefInfo((const AtomicRMWInst*)I, Loc);
 364     case Instruction::Call:   return getModRefInfo((const CallInst*)I,  Loc);
 365     case Instruction::Invoke: return getModRefInfo((const InvokeInst*)I,Loc);
 366     default:                  return NoModRef;
 367     }
 368   }
 369
 370   /// getModRefInfo - A convenience wrapper.
 371   ModRefResult getModRefInfo(const Instruction *I,
 372                              const Value *P, uint64_t Size) {
 373     return getModRefInfo(I, Location(P, Size));
 374   }
 375
 376   /// getModRefInfo (for call sites) - Return whether information about whether
 377   /// a particular call site modifies or reads the specified memory location.
 378   virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
 379                                      const Location &Loc);
 380
 381   /// getModRefInfo (for call sites) - A convenience wrapper.
 382   ModRefResult getModRefInfo(ImmutableCallSite CS,
 383                              const Value *P, uint64_t Size) {
 384     return getModRefInfo(CS, Location(P, Size));
 385   }
 386
 387   /// getModRefInfo (for calls) - Return whether information about whether
 388   /// a particular call modifies or reads the specified memory location.
 389   ModRefResult getModRefInfo(const CallInst *C, const Location &Loc) {
 390     return getModRefInfo(ImmutableCallSite(C), Loc);
 391   }
 392
 393   /// getModRefInfo (for calls) - A convenience wrapper.
 394   ModRefResult getModRefInfo(const CallInst *C, const Value *P, uint64_t Size) {
 395     return getModRefInfo(C, Location(P, Size));
 396   }
 397
 398   /// getModRefInfo (for invokes) - Return whether information about whether
 399   /// a particular invoke modifies or reads the specified memory location.
 400   ModRefResult getModRefInfo(const InvokeInst *I,
 401                              const Location &Loc) {
 402     return getModRefInfo(ImmutableCallSite(I), Loc);
 403   }
 404
 405   /// getModRefInfo (for invokes) - A convenience wrapper.
 406   ModRefResult getModRefInfo(const InvokeInst *I,
 407                              const Value *P, uint64_t Size) {
 408     return getModRefInfo(I, Location(P, Size));
 409   }
 410
 411   /// getModRefInfo (for loads) - Return whether information about whether
 412   /// a particular load modifies or reads the specified memory location.
 413   ModRefResult getModRefInfo(const LoadInst *L, const Location &Loc);
 414
 415   /// getModRefInfo (for loads) - A convenience wrapper.
 416   ModRefResult getModRefInfo(const LoadInst *L, const Value *P, uint64_t Size) {
 417     return getModRefInfo(L, Location(P, Size));
 418   }
 419
 420   /// getModRefInfo (for stores) - Return whether information about whether
 421   /// a particular store modifies or reads the specified memory location.
 422   ModRefResult getModRefInfo(const StoreInst *S, const Location &Loc);
 423
 424   /// getModRefInfo (for stores) - A convenience wrapper.
 425   ModRefResult getModRefInfo(const StoreInst *S, const Value *P, uint64_t Size){
 426     return getModRefInfo(S, Location(P, Size));
 427   }
 428
 429   /// getModRefInfo (for fences) - Return whether information about whether
 430   /// a particular store modifies or reads the specified memory location.
 431   ModRefResult getModRefInfo(const FenceInst *S, const Location &Loc) {
 432     // Conservatively correct.  (We could possibly be a bit smarter if
 433     // Loc is a alloca that doesn't escape.)
 434     return ModRef;
 435   }
 436
 437   /// getModRefInfo (for fences) - A convenience wrapper.
 438   ModRefResult getModRefInfo(const FenceInst *S, const Value *P, uint64_t Size){
 439     return getModRefInfo(S, Location(P, Size));
 440   }
 441
 442   /// getModRefInfo (for cmpxchges) - Return whether information about whether
 443   /// a particular cmpxchg modifies or reads the specified memory location.
 444   ModRefResult getModRefInfo(const AtomicCmpXchgInst *CX, const Location &Loc);
 445
 446   /// getModRefInfo (for cmpxchges) - A convenience wrapper.
 447   ModRefResult getModRefInfo(const AtomicCmpXchgInst *CX,
 448                              const Value *P, unsigned Size) {
 449     return getModRefInfo(CX, Location(P, Size));
 450   }
 451
 452   /// getModRefInfo (for atomicrmws) - Return whether information about whether
 453   /// a particular atomicrmw modifies or reads the specified memory location.
 454   ModRefResult getModRefInfo(const AtomicRMWInst *RMW, const Location &Loc);
 455
 456   /// getModRefInfo (for atomicrmws) - A convenience wrapper.
 457   ModRefResult getModRefInfo(const AtomicRMWInst *RMW,
 458                              const Value *P, unsigned Size) {
 459     return getModRefInfo(RMW, Location(P, Size));
 460   }
 461
 462   /// getModRefInfo (for va_args) - Return whether information about whether
 463   /// a particular va_arg modifies or reads the specified memory location.
 464   ModRefResult getModRefInfo(const VAArgInst* I, const Location &Loc);
 465
 466   /// getModRefInfo (for va_args) - A convenience wrapper.
 467   ModRefResult getModRefInfo(const VAArgInst* I, const Value* P, uint64_t Size){
 468     return getModRefInfo(I, Location(P, Size));
 469   }
 470
 471   /// getModRefInfo - Return information about whether two call sites may refer
 472   /// to the same set of memory locations.  See
 473   ///   http://llvm.org/docs/AliasAnalysis.html#ModRefInfo
 474   /// for details.
 475   virtual ModRefResult getModRefInfo(ImmutableCallSite CS1,
 476                                      ImmutableCallSite CS2);
 477
 478   /// callCapturesBefore - Return information about whether a particular call
 479   /// site modifies or reads the specified memory location.
 480   ModRefResult callCapturesBefore(const Instruction *I,
 481                                   const AliasAnalysis::Location &MemLoc,
 482                                   DominatorTree *DT);
 483
 484   /// callCapturesBefore - A convenience wrapper.
 485   ModRefResult callCapturesBefore(const Instruction *I, const Value *P,
 486                                   uint64_t Size, DominatorTree *DT) {
 487     return callCapturesBefore(I, Location(P, Size), DT);
 488   }
 489
 490   //===--------------------------------------------------------------------===//
 491   /// Higher level methods for querying mod/ref information.
 492   ///
 493
 494   /// canBasicBlockModify - Return true if it is possible for execution of the
 495   /// specified basic block to modify the value pointed to by Ptr.
 496   bool canBasicBlockModify(const BasicBlock &BB, const Location &Loc);
 497
 498   /// canBasicBlockModify - A convenience wrapper.
 499   bool canBasicBlockModify(const BasicBlock &BB, const Value *P, uint64_t Size){
 500     return canBasicBlockModify(BB, Location(P, Size));
 501   }
 502
 503   /// canInstructionRangeModify - Return true if it is possible for the
 504   /// execution of the specified instructions to modify the value pointed to by
 505   /// Ptr.  The instructions to consider are all of the instructions in the
 506   /// range of [I1,I2] INCLUSIVE.  I1 and I2 must be in the same basic block.
 507   bool canInstructionRangeModify(const Instruction &I1, const Instruction &I2,
 508                                  const Location &Loc);
 509
 510   /// canInstructionRangeModify - A convenience wrapper.
 511   bool canInstructionRangeModify(const Instruction &I1, const Instruction &I2,
 512                                  const Value *Ptr, uint64_t Size) {
 513     return canInstructionRangeModify(I1, I2, Location(Ptr, Size));
 514   }
 515
 516   //===--------------------------------------------------------------------===//
 517   /// Methods that clients should call when they transform the program to allow
 518   /// alias analyses to update their internal data structures.  Note that these
 519   /// methods may be called on any instruction, regardless of whether or not
 520   /// they have pointer-analysis implications.
 521   ///
 522
 523   /// deleteValue - This method should be called whenever an LLVM Value is
 524   /// deleted from the program, for example when an instruction is found to be
 525   /// redundant and is eliminated.
 526   ///
 527   virtual void deleteValue(Value *V);
 528
 529   /// copyValue - This method should be used whenever a preexisting value in the
 530   /// program is copied or cloned, introducing a new value.  Note that analysis
 531   /// implementations should tolerate clients that use this method to introduce
 532   /// the same value multiple times: if the analysis already knows about a
 533   /// value, it should ignore the request.
 534   ///
 535   virtual void copyValue(Value *From, Value *To);
 536
 537   /// addEscapingUse - This method should be used whenever an escaping use is
 538   /// added to a pointer value.  Analysis implementations may either return
 539   /// conservative responses for that value in the future, or may recompute
 540   /// some or all internal state to continue providing precise responses.
 541   ///
 542   /// Escaping uses are considered by anything _except_ the following:
 543   ///  - GEPs or bitcasts of the pointer
 544   ///  - Loads through the pointer
 545   ///  - Stores through (but not of) the pointer
 546   virtual void addEscapingUse(Use &U);
 547
 548   /// replaceWithNewValue - This method is the obvious combination of the two
 549   /// above, and it provided as a helper to simplify client code.
 550   ///
 551   void replaceWithNewValue(Value *Old, Value *New) {
 552     copyValue(Old, New);
 553     deleteValue(Old);
 554   }
 555 };
 556
 557 // Specialize DenseMapInfo for Location.
 558 template<>
 559 struct DenseMapInfo<AliasAnalysis::Location> {
 560   static inline AliasAnalysis::Location getEmptyKey() {
 561     return
 562       AliasAnalysis::Location(DenseMapInfo<const Value *>::getEmptyKey(),
 563                               0, 0);
 564   }
 565   static inline AliasAnalysis::Location getTombstoneKey() {
 566     return
 567       AliasAnalysis::Location(DenseMapInfo<const Value *>::getTombstoneKey(),
 568                               0, 0);
 569   }
 570   static unsigned getHashValue(const AliasAnalysis::Location &Val) {
 571     return DenseMapInfo<const Value *>::getHashValue(Val.Ptr) ^
 572            DenseMapInfo<uint64_t>::getHashValue(Val.Size) ^
 573            DenseMapInfo<const MDNode *>::getHashValue(Val.TBAATag);
 574   }
 575   static bool isEqual(const AliasAnalysis::Location &LHS,
 576                       const AliasAnalysis::Location &RHS) {
 577     return LHS.Ptr == RHS.Ptr &&
 578            LHS.Size == RHS.Size &&
 579            LHS.TBAATag == RHS.TBAATag;
 580   }
 581 };
 582
 583 /// isNoAliasCall - Return true if this pointer is returned by a noalias
 584 /// function.
 585 bool isNoAliasCall(const Value *V);
 586
 587 /// isIdentifiedObject - Return true if this pointer refers to a distinct and
 588 /// identifiable object.  This returns true for:
 589 ///    Global Variables and Functions (but not Global Aliases)
 590 ///    Allocas and Mallocs
 591 ///    ByVal and NoAlias Arguments
 592 ///    NoAlias returns
 593 ///
 594 bool isIdentifiedObject(const Value *V);
 595
 596 /// isKnownNonNull - Return true if this pointer couldn't possibly be null by
 597 /// its definition.  This returns true for allocas, non-extern-weak globals and
 598 /// byval arguments.
 599 bool isKnownNonNull(const Value *V);
 600
 601 } // End llvm namespace
 602
 603 #endif