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