lib/Analysis/AliasSetTracker.cpp

   1 //===- AliasSetTracker.cpp - Alias Sets Tracker implementation-------------===//
   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 implements the AliasSetTracker and AliasSet classes.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/Analysis/AliasSetTracker.h"
  15 #include "llvm/Analysis/AliasAnalysis.h"
  16 #include "llvm/Instructions.h"
  17 #include "llvm/IntrinsicInst.h"
  18 #include "llvm/Pass.h"
  19 #include "llvm/Type.h"
  20 #include "llvm/Target/TargetData.h"
  21 #include "llvm/Assembly/Writer.h"
  22 #include "llvm/Support/Compiler.h"
  23 #include "llvm/Support/ErrorHandling.h"
  24 #include "llvm/Support/InstIterator.h"
  25 #include "llvm/Support/Format.h"
  26 #include "llvm/Support/raw_ostream.h"
  27 using namespace llvm;
  28
  29 /// mergeSetIn - Merge the specified alias set into this alias set.
  30 ///
  31 void AliasSet::mergeSetIn(AliasSet &AS, AliasSetTracker &AST) {
  32   assert(!AS.Forward && "Alias set is already forwarding!");
  33   assert(!Forward && "This set is a forwarding set!!");
  34
  35   // Update the alias and access types of this set...
  36   AccessTy |= AS.AccessTy;
  37   AliasTy  |= AS.AliasTy;
  38
  39   if (AliasTy == MustAlias) {
  40     // Check that these two merged sets really are must aliases.  Since both
  41     // used to be must-alias sets, we can just check any pointer from each set
  42     // for aliasing.
  43     AliasAnalysis &AA = AST.getAliasAnalysis();
  44     PointerRec *L = getSomePointer();
  45     PointerRec *R = AS.getSomePointer();
  46
  47     // If the pointers are not a must-alias pair, this set becomes a may alias.
  48     if (AA.alias(L->getValue(), L->getSize(), R->getValue(), R->getSize())
  49         != AliasAnalysis::MustAlias)
  50       AliasTy = MayAlias;
  51   }
  52
  53   if (CallSites.empty()) {            // Merge call sites...
  54     if (!AS.CallSites.empty())
  55       std::swap(CallSites, AS.CallSites);
  56   } else if (!AS.CallSites.empty()) {
  57     CallSites.insert(CallSites.end(), AS.CallSites.begin(), AS.CallSites.end());
  58     AS.CallSites.clear();
  59   }
  60
  61   AS.Forward = this;  // Forward across AS now...
  62   addRef();           // AS is now pointing to us...
  63
  64   // Merge the list of constituent pointers...
  65   if (AS.PtrList) {
  66     *PtrListEnd = AS.PtrList;
  67     AS.PtrList->setPrevInList(PtrListEnd);
  68     PtrListEnd = AS.PtrListEnd;
  69
  70     AS.PtrList = 0;
  71     AS.PtrListEnd = &AS.PtrList;
  72     assert(*AS.PtrListEnd == 0 && "End of list is not null?");
  73   }
  74 }
  75
  76 void AliasSetTracker::removeAliasSet(AliasSet *AS) {
  77   if (AliasSet *Fwd = AS->Forward) {
  78     Fwd->dropRef(*this);
  79     AS->Forward = 0;
  80   }
  81   AliasSets.erase(AS);
  82 }
  83
  84 void AliasSet::removeFromTracker(AliasSetTracker &AST) {
  85   assert(RefCount == 0 && "Cannot remove non-dead alias set from tracker!");
  86   AST.removeAliasSet(this);
  87 }
  88
  89 void AliasSet::addPointer(AliasSetTracker &AST, PointerRec &Entry,
  90                           unsigned Size, bool KnownMustAlias) {
  91   assert(!Entry.hasAliasSet() && "Entry already in set!");
  92
  93   // Check to see if we have to downgrade to _may_ alias.
  94   if (isMustAlias() && !KnownMustAlias)
  95     if (PointerRec *P = getSomePointer()) {
  96       AliasAnalysis &AA = AST.getAliasAnalysis();
  97       AliasAnalysis::AliasResult Result =
  98         AA.alias(P->getValue(), P->getSize(), Entry.getValue(), Size);
  99       if (Result == AliasAnalysis::MayAlias)
 100         AliasTy = MayAlias;
 101       else                  // First entry of must alias must have maximum size!
 102         P->updateSize(Size);
 103       assert(Result != AliasAnalysis::NoAlias && "Cannot be part of must set!");
 104     }
 105
 106   Entry.setAliasSet(this);
 107   Entry.updateSize(Size);
 108
 109   // Add it to the end of the list...
 110   assert(*PtrListEnd == 0 && "End of list is not null?");
 111   *PtrListEnd = &Entry;
 112   PtrListEnd = Entry.setPrevInList(PtrListEnd);
 113   assert(*PtrListEnd == 0 && "End of list is not null?");
 114   addRef();               // Entry points to alias set...
 115 }
 116
 117 void AliasSet::addCallSite(CallSite CS, AliasAnalysis &AA) {
 118   CallSites.push_back(CS);
 119
 120   AliasAnalysis::ModRefBehavior Behavior = AA.getModRefBehavior(CS);
 121   if (Behavior == AliasAnalysis::DoesNotAccessMemory)
 122     return;
 123   else if (Behavior == AliasAnalysis::OnlyReadsMemory) {
 124     AliasTy = MayAlias;
 125     AccessTy |= Refs;
 126     return;
 127   }
 128
 129   // FIXME: This should use mod/ref information to make this not suck so bad
 130   AliasTy = MayAlias;
 131   AccessTy = ModRef;
 132 }
 133
 134 /// aliasesPointer - Return true if the specified pointer "may" (or must)
 135 /// alias one of the members in the set.
 136 ///
 137 bool AliasSet::aliasesPointer(const Value *Ptr, unsigned Size,
 138                               AliasAnalysis &AA) const {
 139   if (AliasTy == MustAlias) {
 140     assert(CallSites.empty() && "Illegal must alias set!");
 141
 142     // If this is a set of MustAliases, only check to see if the pointer aliases
 143     // SOME value in the set...
 144     PointerRec *SomePtr = getSomePointer();
 145     assert(SomePtr && "Empty must-alias set??");
 146     return AA.alias(SomePtr->getValue(), SomePtr->getSize(), Ptr, Size);
 147   }
 148
 149   // If this is a may-alias set, we have to check all of the pointers in the set
 150   // to be sure it doesn't alias the set...
 151   for (iterator I = begin(), E = end(); I != E; ++I)
 152     if (AA.alias(Ptr, Size, I.getPointer(), I.getSize()))
 153       return true;
 154
 155   // Check the call sites list and invoke list...
 156   if (!CallSites.empty()) {
 157     if (AA.hasNoModRefInfoForCalls())
 158       return true;
 159
 160     for (unsigned i = 0, e = CallSites.size(); i != e; ++i)
 161       if (AA.getModRefInfo(CallSites[i], const_cast<Value*>(Ptr), Size)
 162                    != AliasAnalysis::NoModRef)
 163         return true;
 164   }
 165
 166   return false;
 167 }
 168
 169 bool AliasSet::aliasesCallSite(CallSite CS, AliasAnalysis &AA) const {
 170   if (AA.doesNotAccessMemory(CS))
 171     return false;
 172
 173   if (AA.hasNoModRefInfoForCalls())
 174     return true;
 175
 176   for (unsigned i = 0, e = CallSites.size(); i != e; ++i)
 177     if (AA.getModRefInfo(CallSites[i], CS) != AliasAnalysis::NoModRef ||
 178         AA.getModRefInfo(CS, CallSites[i]) != AliasAnalysis::NoModRef)
 179       return true;
 180
 181   for (iterator I = begin(), E = end(); I != E; ++I)
 182     if (AA.getModRefInfo(CS, I.getPointer(), I.getSize()) !=
 183            AliasAnalysis::NoModRef)
 184       return true;
 185
 186   return false;
 187 }
 188
 189 void AliasSetTracker::clear() {
 190   // Delete all the PointerRec entries.
 191   for (PointerMapType::iterator I = PointerMap.begin(), E = PointerMap.end();
 192        I != E; ++I)
 193     I->second->eraseFromList();
 194
 195   PointerMap.clear();
 196
 197   // The alias sets should all be clear now.
 198   AliasSets.clear();
 199 }
 200
 201
 202 /// findAliasSetForPointer - Given a pointer, find the one alias set to put the
 203 /// instruction referring to the pointer into.  If there are multiple alias sets
 204 /// that may alias the pointer, merge them together and return the unified set.
 205 ///
 206 AliasSet *AliasSetTracker::findAliasSetForPointer(const Value *Ptr,
 207                                                   unsigned Size) {
 208   AliasSet *FoundSet = 0;
 209   for (iterator I = begin(), E = end(); I != E; ++I)
 210     if (!I->Forward && I->aliasesPointer(Ptr, Size, AA)) {
 211       if (FoundSet == 0) {  // If this is the first alias set ptr can go into.
 212         FoundSet = I;       // Remember it.
 213       } else {              // Otherwise, we must merge the sets.
 214         FoundSet->mergeSetIn(*I, *this);     // Merge in contents.
 215       }
 216     }
 217
 218   return FoundSet;
 219 }
 220
 221 /// containsPointer - Return true if the specified location is represented by
 222 /// this alias set, false otherwise.  This does not modify the AST object or
 223 /// alias sets.
 224 bool AliasSetTracker::containsPointer(Value *Ptr, unsigned Size) const {
 225   for (const_iterator I = begin(), E = end(); I != E; ++I)
 226     if (!I->Forward && I->aliasesPointer(Ptr, Size, AA))
 227       return true;
 228   return false;
 229 }
 230
 231
 232
 233 AliasSet *AliasSetTracker::findAliasSetForCallSite(CallSite CS) {
 234   AliasSet *FoundSet = 0;
 235   for (iterator I = begin(), E = end(); I != E; ++I)
 236     if (!I->Forward && I->aliasesCallSite(CS, AA)) {
 237       if (FoundSet == 0) {  // If this is the first alias set ptr can go into.
 238         FoundSet = I;       // Remember it.
 239       } else if (!I->Forward) {     // Otherwise, we must merge the sets.
 240         FoundSet->mergeSetIn(*I, *this);     // Merge in contents.
 241       }
 242     }
 243
 244   return FoundSet;
 245 }
 246
 247
 248
 249
 250 /// getAliasSetForPointer - Return the alias set that the specified pointer
 251 /// lives in.
 252 AliasSet &AliasSetTracker::getAliasSetForPointer(Value *Pointer, unsigned Size,
 253                                                  bool *New) {
 254   AliasSet::PointerRec &Entry = getEntryFor(Pointer);
 255
 256   // Check to see if the pointer is already known...
 257   if (Entry.hasAliasSet()) {
 258     Entry.updateSize(Size);
 259     // Return the set!
 260     return *Entry.getAliasSet(*this)->getForwardedTarget(*this);
 261   } else if (AliasSet *AS = findAliasSetForPointer(Pointer, Size)) {
 262     // Add it to the alias set it aliases...
 263     AS->addPointer(*this, Entry, Size);
 264     return *AS;
 265   } else {
 266     if (New) *New = true;
 267     // Otherwise create a new alias set to hold the loaded pointer...
 268     AliasSets.push_back(new AliasSet());
 269     AliasSets.back().addPointer(*this, Entry, Size);
 270     return AliasSets.back();
 271   }
 272 }
 273
 274 bool AliasSetTracker::add(Value *Ptr, unsigned Size) {
 275   bool NewPtr;
 276   addPointer(Ptr, Size, AliasSet::NoModRef, NewPtr);
 277   return NewPtr;
 278 }
 279
 280
 281 bool AliasSetTracker::add(LoadInst *LI) {
 282   bool NewPtr;
 283   AliasSet &AS = addPointer(LI->getOperand(0),
 284                             AA.getTypeStoreSize(LI->getType()),
 285                             AliasSet::Refs, NewPtr);
 286   if (LI->isVolatile()) AS.setVolatile();
 287   return NewPtr;
 288 }
 289
 290 bool AliasSetTracker::add(StoreInst *SI) {
 291   bool NewPtr;
 292   Value *Val = SI->getOperand(0);
 293   AliasSet &AS = addPointer(SI->getOperand(1),
 294                             AA.getTypeStoreSize(Val->getType()),
 295                             AliasSet::Mods, NewPtr);
 296   if (SI->isVolatile()) AS.setVolatile();
 297   return NewPtr;
 298 }
 299
 300 bool AliasSetTracker::add(FreeInst *FI) {
 301   bool NewPtr;
 302   addPointer(FI->getOperand(0), ~0, AliasSet::Mods, NewPtr);
 303   return NewPtr;
 304 }
 305
 306 bool AliasSetTracker::add(VAArgInst *VAAI) {
 307   bool NewPtr;
 308   addPointer(VAAI->getOperand(0), ~0, AliasSet::ModRef, NewPtr);
 309   return NewPtr;
 310 }
 311
 312
 313 bool AliasSetTracker::add(CallSite CS) {
 314   if (isa<DbgInfoIntrinsic>(CS.getInstruction()))
 315     return true; // Ignore DbgInfo Intrinsics.
 316   if (AA.doesNotAccessMemory(CS))
 317     return true; // doesn't alias anything
 318
 319   AliasSet *AS = findAliasSetForCallSite(CS);
 320   if (!AS) {
 321     AliasSets.push_back(new AliasSet());
 322     AS = &AliasSets.back();
 323     AS->addCallSite(CS, AA);
 324     return true;
 325   } else {
 326     AS->addCallSite(CS, AA);
 327     return false;
 328   }
 329 }
 330
 331 bool AliasSetTracker::add(Instruction *I) {
 332   // Dispatch to one of the other add methods...
 333   if (LoadInst *LI = dyn_cast<LoadInst>(I))
 334     return add(LI);
 335   else if (StoreInst *SI = dyn_cast<StoreInst>(I))
 336     return add(SI);
 337   else if (CallInst *CI = dyn_cast<CallInst>(I))
 338     return add(CI);
 339   else if (InvokeInst *II = dyn_cast<InvokeInst>(I))
 340     return add(II);
 341   else if (FreeInst *FI = dyn_cast<FreeInst>(I))
 342     return add(FI);
 343   else if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I))
 344     return add(VAAI);
 345   return true;
 346 }
 347
 348 void AliasSetTracker::add(BasicBlock &BB) {
 349   for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
 350     add(I);
 351 }
 352
 353 void AliasSetTracker::add(const AliasSetTracker &AST) {
 354   assert(&AA == &AST.AA &&
 355          "Merging AliasSetTracker objects with different Alias Analyses!");
 356
 357   // Loop over all of the alias sets in AST, adding the pointers contained
 358   // therein into the current alias sets.  This can cause alias sets to be
 359   // merged together in the current AST.
 360   for (const_iterator I = AST.begin(), E = AST.end(); I != E; ++I)
 361     if (!I->Forward) {   // Ignore forwarding alias sets
 362       AliasSet &AS = const_cast<AliasSet&>(*I);
 363
 364       // If there are any call sites in the alias set, add them to this AST.
 365       for (unsigned i = 0, e = AS.CallSites.size(); i != e; ++i)
 366         add(AS.CallSites[i]);
 367
 368       // Loop over all of the pointers in this alias set...
 369       AliasSet::iterator I = AS.begin(), E = AS.end();
 370       bool X;
 371       for (; I != E; ++I) {
 372         AliasSet &NewAS = addPointer(I.getPointer(), I.getSize(),
 373                                      (AliasSet::AccessType)AS.AccessTy, X);
 374         if (AS.isVolatile()) NewAS.setVolatile();
 375       }
 376     }
 377 }
 378
 379 /// remove - Remove the specified (potentially non-empty) alias set from the
 380 /// tracker.
 381 void AliasSetTracker::remove(AliasSet &AS) {
 382   // Drop all call sites.
 383   AS.CallSites.clear();
 384
 385   // Clear the alias set.
 386   unsigned NumRefs = 0;
 387   while (!AS.empty()) {
 388     AliasSet::PointerRec *P = AS.PtrList;
 389
 390     Value *ValToRemove = P->getValue();
 391
 392     // Unlink and delete entry from the list of values.
 393     P->eraseFromList();
 394
 395     // Remember how many references need to be dropped.
 396     ++NumRefs;
 397
 398     // Finally, remove the entry.
 399     PointerMap.erase(ValToRemove);
 400   }
 401
 402   // Stop using the alias set, removing it.
 403   AS.RefCount -= NumRefs;
 404   if (AS.RefCount == 0)
 405     AS.removeFromTracker(*this);
 406 }
 407
 408 bool AliasSetTracker::remove(Value *Ptr, unsigned Size) {
 409   AliasSet *AS = findAliasSetForPointer(Ptr, Size);
 410   if (!AS) return false;
 411   remove(*AS);
 412   return true;
 413 }
 414
 415 bool AliasSetTracker::remove(LoadInst *LI) {
 416   unsigned Size = AA.getTypeStoreSize(LI->getType());
 417   AliasSet *AS = findAliasSetForPointer(LI->getOperand(0), Size);
 418   if (!AS) return false;
 419   remove(*AS);
 420   return true;
 421 }
 422
 423 bool AliasSetTracker::remove(StoreInst *SI) {
 424   unsigned Size = AA.getTypeStoreSize(SI->getOperand(0)->getType());
 425   AliasSet *AS = findAliasSetForPointer(SI->getOperand(1), Size);
 426   if (!AS) return false;
 427   remove(*AS);
 428   return true;
 429 }
 430
 431 bool AliasSetTracker::remove(FreeInst *FI) {
 432   AliasSet *AS = findAliasSetForPointer(FI->getOperand(0), ~0);
 433   if (!AS) return false;
 434   remove(*AS);
 435   return true;
 436 }
 437
 438 bool AliasSetTracker::remove(VAArgInst *VAAI) {
 439   AliasSet *AS = findAliasSetForPointer(VAAI->getOperand(0), ~0);
 440   if (!AS) return false;
 441   remove(*AS);
 442   return true;
 443 }
 444
 445 bool AliasSetTracker::remove(CallSite CS) {
 446   if (AA.doesNotAccessMemory(CS))
 447     return false; // doesn't alias anything
 448
 449   AliasSet *AS = findAliasSetForCallSite(CS);
 450   if (!AS) return false;
 451   remove(*AS);
 452   return true;
 453 }
 454
 455 bool AliasSetTracker::remove(Instruction *I) {
 456   // Dispatch to one of the other remove methods...
 457   if (LoadInst *LI = dyn_cast<LoadInst>(I))
 458     return remove(LI);
 459   else if (StoreInst *SI = dyn_cast<StoreInst>(I))
 460     return remove(SI);
 461   else if (CallInst *CI = dyn_cast<CallInst>(I))
 462     return remove(CI);
 463   else if (FreeInst *FI = dyn_cast<FreeInst>(I))
 464     return remove(FI);
 465   else if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I))
 466     return remove(VAAI);
 467   return true;
 468 }
 469
 470
 471 // deleteValue method - This method is used to remove a pointer value from the
 472 // AliasSetTracker entirely.  It should be used when an instruction is deleted
 473 // from the program to update the AST.  If you don't use this, you would have
 474 // dangling pointers to deleted instructions.
 475 //
 476 void AliasSetTracker::deleteValue(Value *PtrVal) {
 477   // Notify the alias analysis implementation that this value is gone.
 478   AA.deleteValue(PtrVal);
 479
 480   // If this is a call instruction, remove the callsite from the appropriate
 481   // AliasSet.
 482   CallSite CS = CallSite::get(PtrVal);
 483   if (CS.getInstruction())
 484     if (!AA.doesNotAccessMemory(CS))
 485       if (AliasSet *AS = findAliasSetForCallSite(CS))
 486         AS->removeCallSite(CS);
 487
 488   // First, look up the PointerRec for this pointer.
 489   PointerMapType::iterator I = PointerMap.find(PtrVal);
 490   if (I == PointerMap.end()) return;  // Noop
 491
 492   // If we found one, remove the pointer from the alias set it is in.
 493   AliasSet::PointerRec *PtrValEnt = I->second;
 494   AliasSet *AS = PtrValEnt->getAliasSet(*this);
 495
 496   // Unlink and delete from the list of values.
 497   PtrValEnt->eraseFromList();
 498
 499   // Stop using the alias set.
 500   AS->dropRef(*this);
 501
 502   PointerMap.erase(I);
 503 }
 504
 505 // copyValue - This method should be used whenever a preexisting value in the
 506 // program is copied or cloned, introducing a new value.  Note that it is ok for
 507 // clients that use this method to introduce the same value multiple times: if
 508 // the tracker already knows about a value, it will ignore the request.
 509 //
 510 void AliasSetTracker::copyValue(Value *From, Value *To) {
 511   // Notify the alias analysis implementation that this value is copied.
 512   AA.copyValue(From, To);
 513
 514   // First, look up the PointerRec for this pointer.
 515   PointerMapType::iterator I = PointerMap.find(From);
 516   if (I == PointerMap.end())
 517     return;  // Noop
 518   assert(I->second->hasAliasSet() && "Dead entry?");
 519
 520   AliasSet::PointerRec &Entry = getEntryFor(To);
 521   if (Entry.hasAliasSet()) return;    // Already in the tracker!
 522
 523   // Add it to the alias set it aliases...
 524   I = PointerMap.find(From);
 525   AliasSet *AS = I->second->getAliasSet(*this);
 526   AS->addPointer(*this, Entry, I->second->getSize(), true);
 527 }
 528
 529
 530
 531 //===----------------------------------------------------------------------===//
 532 //               AliasSet/AliasSetTracker Printing Support
 533 //===----------------------------------------------------------------------===//
 534
 535 void AliasSet::print(raw_ostream &OS) const {
 536   OS << "  AliasSet[" << format("0x%p", (void*)this) << "," << RefCount << "] ";
 537   OS << (AliasTy == MustAlias ? "must" : "may") << " alias, ";
 538   switch (AccessTy) {
 539   case NoModRef: OS << "No access "; break;
 540   case Refs    : OS << "Ref       "; break;
 541   case Mods    : OS << "Mod       "; break;
 542   case ModRef  : OS << "Mod/Ref   "; break;
 543   default: llvm_unreachable("Bad value for AccessTy!");
 544   }
 545   if (isVolatile()) OS << "[volatile] ";
 546   if (Forward)
 547     OS << " forwarding to " << (void*)Forward;
 548
 549
 550   if (!empty()) {
 551     OS << "Pointers: ";
 552     for (iterator I = begin(), E = end(); I != E; ++I) {
 553       if (I != begin()) OS << ", ";
 554       WriteAsOperand(OS << "(", I.getPointer());
 555       OS << ", " << I.getSize() << ")";
 556     }
 557   }
 558   if (!CallSites.empty()) {
 559     OS << "\n    " << CallSites.size() << " Call Sites: ";
 560     for (unsigned i = 0, e = CallSites.size(); i != e; ++i) {
 561       if (i) OS << ", ";
 562       WriteAsOperand(OS, CallSites[i].getCalledValue());
 563     }
 564   }
 565   OS << "\n";
 566 }
 567
 568 void AliasSetTracker::print(raw_ostream &OS) const {
 569   OS << "Alias Set Tracker: " << AliasSets.size() << " alias sets for "
 570      << PointerMap.size() << " pointer values.\n";
 571   for (const_iterator I = begin(), E = end(); I != E; ++I)
 572     I->print(OS);
 573   OS << "\n";
 574 }
 575
 576 void AliasSet::dump() const { print(errs()); }
 577 void AliasSetTracker::dump() const { print(errs()); }
 578
 579 //===----------------------------------------------------------------------===//
 580 //                     ASTCallbackVH Class Implementation
 581 //===----------------------------------------------------------------------===//
 582
 583 void AliasSetTracker::ASTCallbackVH::deleted() {
 584   assert(AST && "ASTCallbackVH called with a null AliasSetTracker!");
 585   AST->deleteValue(getValPtr());
 586   // this now dangles!
 587 }
 588
 589 AliasSetTracker::ASTCallbackVH::ASTCallbackVH(Value *V, AliasSetTracker *ast)
 590   : CallbackVH(V), AST(ast) {}
 591
 592 AliasSetTracker::ASTCallbackVH &
 593 AliasSetTracker::ASTCallbackVH::operator=(Value *V) {
 594   return *this = ASTCallbackVH(V, AST);
 595 }
 596
 597 //===----------------------------------------------------------------------===//
 598 //                            AliasSetPrinter Pass
 599 //===----------------------------------------------------------------------===//
 600
 601 namespace {
 602   class VISIBILITY_HIDDEN AliasSetPrinter : public FunctionPass {
 603     AliasSetTracker *Tracker;
 604   public:
 605     static char ID; // Pass identification, replacement for typeid
 606     AliasSetPrinter() : FunctionPass(&ID) {}
 607
 608     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
 609       AU.setPreservesAll();
 610       AU.addRequired<AliasAnalysis>();
 611     }
 612
 613     virtual bool runOnFunction(Function &F) {
 614       Tracker = new AliasSetTracker(getAnalysis<AliasAnalysis>());
 615
 616       for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
 617         Tracker->add(&*I);
 618       Tracker->print(errs());
 619       delete Tracker;
 620       return false;
 621     }
 622   };
 623 }
 624
 625 char AliasSetPrinter::ID = 0;
 626 static RegisterPass<AliasSetPrinter>
 627 X("print-alias-sets", "Alias Set Printer", false, true);