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/Analysis/GuardUtils.h"
  17 #include "llvm/Analysis/MemoryLocation.h"
  18 #include "llvm/Config/llvm-config.h"
  19 #include "llvm/IR/CallSite.h"
  20 #include "llvm/IR/Constants.h"
  21 #include "llvm/IR/DataLayout.h"
  22 #include "llvm/IR/Function.h"
  23 #include "llvm/IR/InstIterator.h"
  24 #include "llvm/IR/Instruction.h"
  25 #include "llvm/IR/Instructions.h"
  26 #include "llvm/IR/IntrinsicInst.h"
  27 #include "llvm/IR/Module.h"
  28 #include "llvm/IR/PatternMatch.h"
  29 #include "llvm/IR/Value.h"
  30 #include "llvm/Pass.h"
  31 #include "llvm/Support/AtomicOrdering.h"
  32 #include "llvm/Support/Casting.h"
  33 #include "llvm/Support/CommandLine.h"
  34 #include "llvm/Support/Compiler.h"
  35 #include "llvm/Support/Debug.h"
  36 #include "llvm/Support/ErrorHandling.h"
  37 #include "llvm/Support/raw_ostream.h"
  38 #include <cassert>
  39 #include <cstdint>
  40 #include <vector>
  41
  42 using namespace llvm;
  43
  44 static cl::opt<unsigned>
  45     SaturationThreshold("alias-set-saturation-threshold", cl::Hidden,
  46                         cl::init(250),
  47                         cl::desc("The maximum number of pointers may-alias "
  48                                  "sets may contain before degradation"));
  49
  50 /// mergeSetIn - Merge the specified alias set into this alias set.
  51 ///
  52 void AliasSet::mergeSetIn(AliasSet &AS, AliasSetTracker &AST) {
  53   assert(!AS.Forward && "Alias set is already forwarding!");
  54   assert(!Forward && "This set is a forwarding set!!");
  55
  56   bool WasMustAlias = (Alias == SetMustAlias);
  57   // Update the alias and access types of this set...
  58   Access |= AS.Access;
  59   Alias  |= AS.Alias;
  60
  61   if (Alias == SetMustAlias) {
  62     // Check that these two merged sets really are must aliases.  Since both
  63     // used to be must-alias sets, we can just check any pointer from each set
  64     // for aliasing.
  65     AliasAnalysis &AA = AST.getAliasAnalysis();
  66     PointerRec *L = getSomePointer();
  67     PointerRec *R = AS.getSomePointer();
  68
  69     // If the pointers are not a must-alias pair, this set becomes a may alias.
  70     if (AA.alias(MemoryLocation(L->getValue(), L->getSize(), L->getAAInfo()),
  71                  MemoryLocation(R->getValue(), R->getSize(), R->getAAInfo())) !=
  72         MustAlias)
  73       Alias = SetMayAlias;
  74   }
  75
  76   if (Alias == SetMayAlias) {
  77     if (WasMustAlias)
  78       AST.TotalMayAliasSetSize += size();
  79     if (AS.Alias == SetMustAlias)
  80       AST.TotalMayAliasSetSize += AS.size();
  81   }
  82
  83   bool ASHadUnknownInsts = !AS.UnknownInsts.empty();
  84   if (UnknownInsts.empty()) {            // Merge call sites...
  85     if (ASHadUnknownInsts) {
  86       std::swap(UnknownInsts, AS.UnknownInsts);
  87       addRef();
  88     }
  89   } else if (ASHadUnknownInsts) {
  90     UnknownInsts.insert(UnknownInsts.end(), AS.UnknownInsts.begin(), AS.UnknownInsts.end());
  91     AS.UnknownInsts.clear();
  92   }
  93
  94   AS.Forward = this; // Forward across AS now...
  95   addRef();          // AS is now pointing to us...
  96
  97   // Merge the list of constituent pointers...
  98   if (AS.PtrList) {
  99     SetSize += AS.size();
 100     AS.SetSize = 0;
 101     *PtrListEnd = AS.PtrList;
 102     AS.PtrList->setPrevInList(PtrListEnd);
 103     PtrListEnd = AS.PtrListEnd;
 104
 105     AS.PtrList = nullptr;
 106     AS.PtrListEnd = &AS.PtrList;
 107     assert(*AS.PtrListEnd == nullptr && "End of list is not null?");
 108   }
 109   if (ASHadUnknownInsts)
 110     AS.dropRef(AST);
 111 }
 112
 113 void AliasSetTracker::removeAliasSet(AliasSet *AS) {
 114   if (AliasSet *Fwd = AS->Forward) {
 115     Fwd->dropRef(*this);
 116     AS->Forward = nullptr;
 117   }
 118
 119   if (AS->Alias == AliasSet::SetMayAlias)
 120     TotalMayAliasSetSize -= AS->size();
 121
 122   AliasSets.erase(AS);
 123 }
 124
 125 void AliasSet::removeFromTracker(AliasSetTracker &AST) {
 126   assert(RefCount == 0 && "Cannot remove non-dead alias set from tracker!");
 127   AST.removeAliasSet(this);
 128 }
 129
 130 void AliasSet::addPointer(AliasSetTracker &AST, PointerRec &Entry,
 131                           LocationSize Size, const AAMDNodes &AAInfo,
 132                           bool KnownMustAlias) {
 133   assert(!Entry.hasAliasSet() && "Entry already in set!");
 134
 135   // Check to see if we have to downgrade to _may_ alias.
 136   if (isMustAlias() && !KnownMustAlias)
 137     if (PointerRec *P = getSomePointer()) {
 138       AliasAnalysis &AA = AST.getAliasAnalysis();
 139       AliasResult Result =
 140           AA.alias(MemoryLocation(P->getValue(), P->getSize(), P->getAAInfo()),
 141                    MemoryLocation(Entry.getValue(), Size, AAInfo));
 142       if (Result != MustAlias) {
 143         Alias = SetMayAlias;
 144         AST.TotalMayAliasSetSize += size();
 145       } else {
 146         // First entry of must alias must have maximum size!
 147         P->updateSizeAndAAInfo(Size, AAInfo);
 148       }
 149       assert(Result != NoAlias && "Cannot be part of must set!");
 150     }
 151
 152   Entry.setAliasSet(this);
 153   Entry.updateSizeAndAAInfo(Size, AAInfo);
 154
 155   // Add it to the end of the list...
 156   ++SetSize;
 157   assert(*PtrListEnd == nullptr && "End of list is not null?");
 158   *PtrListEnd = &Entry;
 159   PtrListEnd = Entry.setPrevInList(PtrListEnd);
 160   assert(*PtrListEnd == nullptr && "End of list is not null?");
 161   // Entry points to alias set.
 162   addRef();
 163
 164   if (Alias == SetMayAlias)
 165     AST.TotalMayAliasSetSize++;
 166 }
 167
 168 void AliasSet::addUnknownInst(Instruction *I, AliasAnalysis &AA) {
 169   if (UnknownInsts.empty())
 170     addRef();
 171   UnknownInsts.emplace_back(I);
 172
 173   // Guards are marked as modifying memory for control flow modelling purposes,
 174   // but don't actually modify any specific memory location.
 175   using namespace PatternMatch;
 176   bool MayWriteMemory = I->mayWriteToMemory() && !isGuard(I) &&
 177     !(I->use_empty() && match(I, m_Intrinsic<Intrinsic::invariant_start>()));
 178   if (!MayWriteMemory) {
 179     Alias = SetMayAlias;
 180     Access |= RefAccess;
 181     return;
 182   }
 183
 184   // FIXME: This should use mod/ref information to make this not suck so bad
 185   Alias = SetMayAlias;
 186   Access = ModRefAccess;
 187 }
 188
 189 /// aliasesPointer - Return true if the specified pointer "may" (or must)
 190 /// alias one of the members in the set.
 191 ///
 192 bool AliasSet::aliasesPointer(const Value *Ptr, LocationSize Size,
 193                               const AAMDNodes &AAInfo,
 194                               AliasAnalysis &AA) const {
 195   if (AliasAny)
 196     return true;
 197
 198   if (Alias == SetMustAlias) {
 199     assert(UnknownInsts.empty() && "Illegal must alias set!");
 200
 201     // If this is a set of MustAliases, only check to see if the pointer aliases
 202     // SOME value in the set.
 203     PointerRec *SomePtr = getSomePointer();
 204     assert(SomePtr && "Empty must-alias set??");
 205     return AA.alias(MemoryLocation(SomePtr->getValue(), SomePtr->getSize(),
 206                                    SomePtr->getAAInfo()),
 207                     MemoryLocation(Ptr, Size, AAInfo));
 208   }
 209
 210   // If this is a may-alias set, we have to check all of the pointers in the set
 211   // to be sure it doesn't alias the set...
 212   for (iterator I = begin(), E = end(); I != E; ++I)
 213     if (AA.alias(MemoryLocation(Ptr, Size, AAInfo),
 214                  MemoryLocation(I.getPointer(), I.getSize(), I.getAAInfo())))
 215       return true;
 216
 217   // Check the unknown instructions...
 218   if (!UnknownInsts.empty()) {
 219     for (unsigned i = 0, e = UnknownInsts.size(); i != e; ++i)
 220       if (auto *Inst = getUnknownInst(i))
 221         if (isModOrRefSet(
 222                 AA.getModRefInfo(Inst, MemoryLocation(Ptr, Size, AAInfo))))
 223           return true;
 224   }
 225
 226   return false;
 227 }
 228
 229 bool AliasSet::aliasesUnknownInst(const Instruction *Inst,
 230                                   AliasAnalysis &AA) const {
 231
 232   if (AliasAny)
 233     return true;
 234
 235   if (!Inst->mayReadOrWriteMemory())
 236     return false;
 237
 238   for (unsigned i = 0, e = UnknownInsts.size(); i != e; ++i) {
 239     if (auto *UnknownInst = getUnknownInst(i)) {
 240       ImmutableCallSite C1(UnknownInst), C2(Inst);
 241       if (!C1 || !C2 || isModOrRefSet(AA.getModRefInfo(C1, C2)) ||
 242           isModOrRefSet(AA.getModRefInfo(C2, C1)))
 243         return true;
 244     }
 245   }
 246
 247   for (iterator I = begin(), E = end(); I != E; ++I)
 248     if (isModOrRefSet(AA.getModRefInfo(
 249             Inst, MemoryLocation(I.getPointer(), I.getSize(), I.getAAInfo()))))
 250       return true;
 251
 252   return false;
 253 }
 254
 255 Instruction* AliasSet::getUniqueInstruction() {
 256   if (AliasAny)
 257     // May have collapses alias set
 258     return nullptr;
 259   if (begin() != end()) {
 260     if (!UnknownInsts.empty())
 261       // Another instruction found
 262       return nullptr;
 263     if (std::next(begin()) != end())
 264       // Another instruction found
 265       return nullptr;
 266     Value *Addr = begin()->getValue();
 267     assert(!Addr->user_empty() &&
 268            "where's the instruction which added this pointer?");
 269     if (std::next(Addr->user_begin()) != Addr->user_end())
 270       // Another instruction found -- this is really restrictive
 271       // TODO: generalize!
 272       return nullptr;
 273     return cast<Instruction>(*(Addr->user_begin()));
 274   }
 275   if (1 != UnknownInsts.size())
 276     return nullptr;
 277   return cast<Instruction>(UnknownInsts[0]);
 278 }
 279
 280 void AliasSetTracker::clear() {
 281   // Delete all the PointerRec entries.
 282   for (PointerMapType::iterator I = PointerMap.begin(), E = PointerMap.end();
 283        I != E; ++I)
 284     I->second->eraseFromList();
 285
 286   PointerMap.clear();
 287
 288   // The alias sets should all be clear now.
 289   AliasSets.clear();
 290 }
 291
 292
 293 /// mergeAliasSetsForPointer - Given a pointer, merge all alias sets that may
 294 /// alias the pointer. Return the unified set, or nullptr if no set that aliases
 295 /// the pointer was found.
 296 AliasSet *AliasSetTracker::mergeAliasSetsForPointer(const Value *Ptr,
 297                                                     LocationSize Size,
 298                                                     const AAMDNodes &AAInfo) {
 299   AliasSet *FoundSet = nullptr;
 300   for (iterator I = begin(), E = end(); I != E;) {
 301     iterator Cur = I++;
 302     if (Cur->Forward || !Cur->aliasesPointer(Ptr, Size, AAInfo, AA)) continue;
 303
 304     if (!FoundSet) {      // If this is the first alias set ptr can go into.
 305       FoundSet = &*Cur;   // Remember it.
 306     } else {              // Otherwise, we must merge the sets.
 307       FoundSet->mergeSetIn(*Cur, *this);     // Merge in contents.
 308     }
 309   }
 310
 311   return FoundSet;
 312 }
 313
 314 bool AliasSetTracker::containsUnknown(const Instruction *Inst) const {
 315   for (const AliasSet &AS : *this)
 316     if (!AS.Forward && AS.aliasesUnknownInst(Inst, AA))
 317       return true;
 318   return false;
 319 }
 320
 321 AliasSet *AliasSetTracker::findAliasSetForUnknownInst(Instruction *Inst) {
 322   AliasSet *FoundSet = nullptr;
 323   for (iterator I = begin(), E = end(); I != E;) {
 324     iterator Cur = I++;
 325     if (Cur->Forward || !Cur->aliasesUnknownInst(Inst, AA))
 326       continue;
 327     if (!FoundSet)            // If this is the first alias set ptr can go into.
 328       FoundSet = &*Cur;       // Remember it.
 329     else if (!Cur->Forward)   // Otherwise, we must merge the sets.
 330       FoundSet->mergeSetIn(*Cur, *this);     // Merge in contents.
 331   }
 332   return FoundSet;
 333 }
 334
 335 AliasSet &AliasSetTracker::getAliasSetFor(const MemoryLocation &MemLoc) {
 336
 337   Value * const Pointer = const_cast<Value*>(MemLoc.Ptr);
 338   const LocationSize Size = MemLoc.Size;
 339   const AAMDNodes &AAInfo = MemLoc.AATags;
 340
 341   AliasSet::PointerRec &Entry = getEntryFor(Pointer);
 342
 343   if (AliasAnyAS) {
 344     // At this point, the AST is saturated, so we only have one active alias
 345     // set. That means we already know which alias set we want to return, and
 346     // just need to add the pointer to that set to keep the data structure
 347     // consistent.
 348     // This, of course, means that we will never need a merge here.
 349     if (Entry.hasAliasSet()) {
 350       Entry.updateSizeAndAAInfo(Size, AAInfo);
 351       assert(Entry.getAliasSet(*this) == AliasAnyAS &&
 352              "Entry in saturated AST must belong to only alias set");
 353     } else {
 354       AliasAnyAS->addPointer(*this, Entry, Size, AAInfo);
 355     }
 356     return *AliasAnyAS;
 357   }
 358
 359   // Check to see if the pointer is already known.
 360   if (Entry.hasAliasSet()) {
 361     // If the size changed, we may need to merge several alias sets.
 362     // Note that we can *not* return the result of mergeAliasSetsForPointer
 363     // due to a quirk of alias analysis behavior. Since alias(undef, undef)
 364     // is NoAlias, mergeAliasSetsForPointer(undef, ...) will not find the
 365     // the right set for undef, even if it exists.
 366     if (Entry.updateSizeAndAAInfo(Size, AAInfo))
 367       mergeAliasSetsForPointer(Pointer, Size, AAInfo);
 368     // Return the set!
 369     return *Entry.getAliasSet(*this)->getForwardedTarget(*this);
 370   }
 371
 372   if (AliasSet *AS = mergeAliasSetsForPointer(Pointer, Size, AAInfo)) {
 373     // Add it to the alias set it aliases.
 374     AS->addPointer(*this, Entry, Size, AAInfo);
 375     return *AS;
 376   }
 377
 378   // Otherwise create a new alias set to hold the loaded pointer.
 379   AliasSets.push_back(new AliasSet());
 380   AliasSets.back().addPointer(*this, Entry, Size, AAInfo);
 381   return AliasSets.back();
 382 }
 383
 384 void AliasSetTracker::add(Value *Ptr, LocationSize Size,
 385                           const AAMDNodes &AAInfo) {
 386   addPointer(Ptr, Size, AAInfo, AliasSet::NoAccess);
 387 }
 388
 389 void AliasSetTracker::add(LoadInst *LI) {
 390   if (isStrongerThanMonotonic(LI->getOrdering()))
 391     return addUnknown(LI);
 392   addPointer(MemoryLocation::get(LI), AliasSet::RefAccess);
 393 }
 394
 395 void AliasSetTracker::add(StoreInst *SI) {
 396   if (isStrongerThanMonotonic(SI->getOrdering()))
 397     return addUnknown(SI);
 398   addPointer(MemoryLocation::get(SI), AliasSet::ModAccess);
 399 }
 400
 401 void AliasSetTracker::add(VAArgInst *VAAI) {
 402   addPointer(MemoryLocation::get(VAAI), AliasSet::ModRefAccess);
 403 }
 404
 405 void AliasSetTracker::add(AnyMemSetInst *MSI) {
 406   addPointer(MemoryLocation::getForDest(MSI), AliasSet::ModAccess);
 407 }
 408
 409 void AliasSetTracker::add(AnyMemTransferInst *MTI) {
 410   addPointer(MemoryLocation::getForDest(MTI), AliasSet::ModAccess);
 411   addPointer(MemoryLocation::getForSource(MTI), AliasSet::RefAccess);
 412 }
 413
 414 void AliasSetTracker::addUnknown(Instruction *Inst) {
 415   if (isa<DbgInfoIntrinsic>(Inst))
 416     return; // Ignore DbgInfo Intrinsics.
 417
 418   if (auto *II = dyn_cast<IntrinsicInst>(Inst)) {
 419     // These intrinsics will show up as affecting memory, but they are just
 420     // markers.
 421     switch (II->getIntrinsicID()) {
 422     default:
 423       break;
 424       // FIXME: Add lifetime/invariant intrinsics (See: PR30807).
 425     case Intrinsic::assume:
 426     case Intrinsic::sideeffect:
 427       return;
 428     }
 429   }
 430   if (!Inst->mayReadOrWriteMemory())
 431     return; // doesn't alias anything
 432
 433   AliasSet *AS = findAliasSetForUnknownInst(Inst);
 434   if (AS) {
 435     AS->addUnknownInst(Inst, AA);
 436     return;
 437   }
 438   AliasSets.push_back(new AliasSet());
 439   AS = &AliasSets.back();
 440   AS->addUnknownInst(Inst, AA);
 441 }
 442
 443 void AliasSetTracker::add(Instruction *I) {
 444   // Dispatch to one of the other add methods.
 445   if (LoadInst *LI = dyn_cast<LoadInst>(I))
 446     return add(LI);
 447   if (StoreInst *SI = dyn_cast<StoreInst>(I))
 448     return add(SI);
 449   if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I))
 450     return add(VAAI);
 451   if (AnyMemSetInst *MSI = dyn_cast<AnyMemSetInst>(I))
 452     return add(MSI);
 453   if (AnyMemTransferInst *MTI = dyn_cast<AnyMemTransferInst>(I))
 454     return add(MTI);
 455
 456   // Handle all calls with known mod/ref sets genericall
 457   CallSite CS(I);
 458   if (CS && CS.onlyAccessesArgMemory()) {
 459     auto getAccessFromModRef = [](ModRefInfo MRI) {
 460       if (isRefSet(MRI) && isModSet(MRI))
 461         return AliasSet::ModRefAccess;
 462       else if (isModSet(MRI))
 463         return AliasSet::ModAccess;
 464       else if (isRefSet(MRI))
 465         return AliasSet::RefAccess;
 466       else
 467         return AliasSet::NoAccess;
 468
 469     };
 470
 471     ModRefInfo CallMask = createModRefInfo(AA.getModRefBehavior(CS));
 472
 473     // Some intrinsics are marked as modifying memory for control flow
 474     // modelling purposes, but don't actually modify any specific memory
 475     // location.
 476     using namespace PatternMatch;
 477     if (I->use_empty() && match(I, m_Intrinsic<Intrinsic::invariant_start>()))
 478       CallMask = clearMod(CallMask);
 479
 480     for (auto AI = CS.arg_begin(), AE = CS.arg_end(); AI != AE; ++AI) {
 481       const Value *Arg = *AI;
 482       if (!Arg->getType()->isPointerTy())
 483         continue;
 484       unsigned ArgIdx = std::distance(CS.arg_begin(), AI);
 485       MemoryLocation ArgLoc = MemoryLocation::getForArgument(CS, ArgIdx,
 486                                                              nullptr);
 487       ModRefInfo ArgMask = AA.getArgModRefInfo(CS, ArgIdx);
 488       ArgMask = intersectModRef(CallMask, ArgMask);
 489       if (!isNoModRef(ArgMask))
 490         addPointer(ArgLoc, getAccessFromModRef(ArgMask));
 491     }
 492     return;
 493   }
 494
 495   return addUnknown(I);
 496 }
 497
 498 void AliasSetTracker::add(BasicBlock &BB) {
 499   for (auto &I : BB)
 500     add(&I);
 501 }
 502
 503 void AliasSetTracker::add(const AliasSetTracker &AST) {
 504   assert(&AA == &AST.AA &&
 505          "Merging AliasSetTracker objects with different Alias Analyses!");
 506
 507   // Loop over all of the alias sets in AST, adding the pointers contained
 508   // therein into the current alias sets.  This can cause alias sets to be
 509   // merged together in the current AST.
 510   for (const AliasSet &AS : AST) {
 511     if (AS.Forward)
 512       continue; // Ignore forwarding alias sets
 513
 514     // If there are any call sites in the alias set, add them to this AST.
 515     for (unsigned i = 0, e = AS.UnknownInsts.size(); i != e; ++i)
 516       if (auto *Inst = AS.getUnknownInst(i))
 517         add(Inst);
 518
 519     // Loop over all of the pointers in this alias set.
 520     for (AliasSet::iterator ASI = AS.begin(), E = AS.end(); ASI != E; ++ASI)
 521       addPointer(ASI.getPointer(), ASI.getSize(), ASI.getAAInfo(),
 522                  (AliasSet::AccessLattice)AS.Access);
 523   }
 524 }
 525
 526 // deleteValue method - This method is used to remove a pointer value from the
 527 // AliasSetTracker entirely.  It should be used when an instruction is deleted
 528 // from the program to update the AST.  If you don't use this, you would have
 529 // dangling pointers to deleted instructions.
 530 //
 531 void AliasSetTracker::deleteValue(Value *PtrVal) {
 532   // First, look up the PointerRec for this pointer.
 533   PointerMapType::iterator I = PointerMap.find_as(PtrVal);
 534   if (I == PointerMap.end()) return;  // Noop
 535
 536   // If we found one, remove the pointer from the alias set it is in.
 537   AliasSet::PointerRec *PtrValEnt = I->second;
 538   AliasSet *AS = PtrValEnt->getAliasSet(*this);
 539
 540   // Unlink and delete from the list of values.
 541   PtrValEnt->eraseFromList();
 542
 543   if (AS->Alias == AliasSet::SetMayAlias) {
 544     AS->SetSize--;
 545     TotalMayAliasSetSize--;
 546   }
 547
 548   // Stop using the alias set.
 549   AS->dropRef(*this);
 550
 551   PointerMap.erase(I);
 552 }
 553
 554 // copyValue - This method should be used whenever a preexisting value in the
 555 // program is copied or cloned, introducing a new value.  Note that it is ok for
 556 // clients that use this method to introduce the same value multiple times: if
 557 // the tracker already knows about a value, it will ignore the request.
 558 //
 559 void AliasSetTracker::copyValue(Value *From, Value *To) {
 560   // First, look up the PointerRec for this pointer.
 561   PointerMapType::iterator I = PointerMap.find_as(From);
 562   if (I == PointerMap.end())
 563     return;  // Noop
 564   assert(I->second->hasAliasSet() && "Dead entry?");
 565
 566   AliasSet::PointerRec &Entry = getEntryFor(To);
 567   if (Entry.hasAliasSet()) return;    // Already in the tracker!
 568
 569   // getEntryFor above may invalidate iterator \c I, so reinitialize it.
 570   I = PointerMap.find_as(From);
 571   // Add it to the alias set it aliases...
 572   AliasSet *AS = I->second->getAliasSet(*this);
 573   AS->addPointer(*this, Entry, I->second->getSize(),
 574                  I->second->getAAInfo(),
 575                  true);
 576 }
 577
 578 AliasSet &AliasSetTracker::mergeAllAliasSets() {
 579   assert(!AliasAnyAS && (TotalMayAliasSetSize > SaturationThreshold) &&
 580          "Full merge should happen once, when the saturation threshold is "
 581          "reached");
 582
 583   // Collect all alias sets, so that we can drop references with impunity
 584   // without worrying about iterator invalidation.
 585   std::vector<AliasSet *> ASVector;
 586   ASVector.reserve(SaturationThreshold);
 587   for (iterator I = begin(), E = end(); I != E; I++)
 588     ASVector.push_back(&*I);
 589
 590   // Copy all instructions and pointers into a new set, and forward all other
 591   // sets to it.
 592   AliasSets.push_back(new AliasSet());
 593   AliasAnyAS = &AliasSets.back();
 594   AliasAnyAS->Alias = AliasSet::SetMayAlias;
 595   AliasAnyAS->Access = AliasSet::ModRefAccess;
 596   AliasAnyAS->AliasAny = true;
 597
 598   for (auto Cur : ASVector) {
 599     // If Cur was already forwarding, just forward to the new AS instead.
 600     AliasSet *FwdTo = Cur->Forward;
 601     if (FwdTo) {
 602       Cur->Forward = AliasAnyAS;
 603       AliasAnyAS->addRef();
 604       FwdTo->dropRef(*this);
 605       continue;
 606     }
 607
 608     // Otherwise, perform the actual merge.
 609     AliasAnyAS->mergeSetIn(*Cur, *this);
 610   }
 611
 612   return *AliasAnyAS;
 613 }
 614
 615 AliasSet &AliasSetTracker::addPointer(Value *P, LocationSize Size,
 616                                       const AAMDNodes &AAInfo,
 617                                       AliasSet::AccessLattice E) {
 618   AliasSet &AS = getAliasSetFor(MemoryLocation(P, Size, AAInfo));
 619   AS.Access |= E;
 620
 621   if (!AliasAnyAS && (TotalMayAliasSetSize > SaturationThreshold)) {
 622     // The AST is now saturated. From here on, we conservatively consider all
 623     // pointers to alias each-other.
 624     return mergeAllAliasSets();
 625   }
 626
 627   return AS;
 628 }
 629
 630 //===----------------------------------------------------------------------===//
 631 //               AliasSet/AliasSetTracker Printing Support
 632 //===----------------------------------------------------------------------===//
 633
 634 void AliasSet::print(raw_ostream &OS) const {
 635   OS << "  AliasSet[" << (const void*)this << ", " << RefCount << "] ";
 636   OS << (Alias == SetMustAlias ? "must" : "may") << " alias, ";
 637   switch (Access) {
 638   case NoAccess:     OS << "No access "; break;
 639   case RefAccess:    OS << "Ref       "; break;
 640   case ModAccess:    OS << "Mod       "; break;
 641   case ModRefAccess: OS << "Mod/Ref   "; break;
 642   default: llvm_unreachable("Bad value for Access!");
 643   }
 644   if (Forward)
 645     OS << " forwarding to " << (void*)Forward;
 646
 647   if (!empty()) {
 648     OS << "Pointers: ";
 649     for (iterator I = begin(), E = end(); I != E; ++I) {
 650       if (I != begin()) OS << ", ";
 651       I.getPointer()->printAsOperand(OS << "(");
 652       if (I.getSize() == LocationSize::unknown())
 653         OS << ", unknown)";
 654       else
 655         OS << ", " << I.getSize() << ")";
 656     }
 657   }
 658   if (!UnknownInsts.empty()) {
 659     OS << "\n    " << UnknownInsts.size() << " Unknown instructions: ";
 660     for (unsigned i = 0, e = UnknownInsts.size(); i != e; ++i) {
 661       if (i) OS << ", ";
 662       if (auto *I = getUnknownInst(i)) {
 663         if (I->hasName())
 664           I->printAsOperand(OS);
 665         else
 666           I->print(OS);
 667       }
 668     }
 669   }
 670   OS << "\n";
 671 }
 672
 673 void AliasSetTracker::print(raw_ostream &OS) const {
 674   OS << "Alias Set Tracker: " << AliasSets.size() << " alias sets for "
 675      << PointerMap.size() << " pointer values.\n";
 676   for (const AliasSet &AS : *this)
 677     AS.print(OS);
 678   OS << "\n";
 679 }
 680
 681 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 682 LLVM_DUMP_METHOD void AliasSet::dump() const { print(dbgs()); }
 683 LLVM_DUMP_METHOD void AliasSetTracker::dump() const { print(dbgs()); }
 684 #endif
 685
 686 //===----------------------------------------------------------------------===//
 687 //                     ASTCallbackVH Class Implementation
 688 //===----------------------------------------------------------------------===//
 689
 690 void AliasSetTracker::ASTCallbackVH::deleted() {
 691   assert(AST && "ASTCallbackVH called with a null AliasSetTracker!");
 692   AST->deleteValue(getValPtr());
 693   // this now dangles!
 694 }
 695
 696 void AliasSetTracker::ASTCallbackVH::allUsesReplacedWith(Value *V) {
 697   AST->copyValue(getValPtr(), V);
 698 }
 699
 700 AliasSetTracker::ASTCallbackVH::ASTCallbackVH(Value *V, AliasSetTracker *ast)
 701   : CallbackVH(V), AST(ast) {}
 702
 703 AliasSetTracker::ASTCallbackVH &
 704 AliasSetTracker::ASTCallbackVH::operator=(Value *V) {
 705   return *this = ASTCallbackVH(V, AST);
 706 }
 707
 708 //===----------------------------------------------------------------------===//
 709 //                            AliasSetPrinter Pass
 710 //===----------------------------------------------------------------------===//
 711
 712 namespace {
 713
 714   class AliasSetPrinter : public FunctionPass {
 715     AliasSetTracker *Tracker;
 716
 717   public:
 718     static char ID; // Pass identification, replacement for typeid
 719
 720     AliasSetPrinter() : FunctionPass(ID) {
 721       initializeAliasSetPrinterPass(*PassRegistry::getPassRegistry());
 722     }
 723
 724     void getAnalysisUsage(AnalysisUsage &AU) const override {
 725       AU.setPreservesAll();
 726       AU.addRequired<AAResultsWrapperPass>();
 727     }
 728
 729     bool runOnFunction(Function &F) override {
 730       auto &AAWP = getAnalysis<AAResultsWrapperPass>();
 731       Tracker = new AliasSetTracker(AAWP.getAAResults());
 732       errs() << "Alias sets for function '" << F.getName() << "':\n";
 733       for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
 734         Tracker->add(&*I);
 735       Tracker->print(errs());
 736       delete Tracker;
 737       return false;
 738     }
 739   };
 740
 741 } // end anonymous namespace
 742
 743 char AliasSetPrinter::ID = 0;
 744
 745 INITIALIZE_PASS_BEGIN(AliasSetPrinter, "print-alias-sets",
 746                 "Alias Set Printer", false, true)
 747 INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
 748 INITIALIZE_PASS_END(AliasSetPrinter, "print-alias-sets",
 749                 "Alias Set Printer", false, true)