lib/Analysis/AliasAnalysis.cpp

   1 //==- AliasAnalysis.cpp - Generic Alias Analysis Interface 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 generic AliasAnalysis interface which is used as the
  11 // common interface used by all clients and implementations of alias analysis.
  12 //
  13 // This file also implements the default version of the AliasAnalysis interface
  14 // that is to be used when no other implementation is specified.  This does some
  15 // simple tests that detect obvious cases: two different global pointers cannot
  16 // alias, a global cannot alias a malloc, two different mallocs cannot alias,
  17 // etc.
  18 //
  19 // This alias analysis implementation really isn't very good for anything, but
  20 // it is very fast, and makes a nice clean default implementation.  Because it
  21 // handles lots of little corner cases, other, more complex, alias analysis
  22 // implementations may choose to rely on this pass to resolve these simple and
  23 // easy cases.
  24 //
  25 //===----------------------------------------------------------------------===//
  26
  27 #include "llvm/Analysis/AliasAnalysis.h"
  28 #include "llvm/Analysis/BasicAliasAnalysis.h"
  29 #include "llvm/Analysis/CFLAndersAliasAnalysis.h"
  30 #include "llvm/Analysis/CFLSteensAliasAnalysis.h"
  31 #include "llvm/Analysis/CaptureTracking.h"
  32 #include "llvm/Analysis/GlobalsModRef.h"
  33 #include "llvm/Analysis/MemoryLocation.h"
  34 #include "llvm/Analysis/ObjCARCAliasAnalysis.h"
  35 #include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h"
  36 #include "llvm/Analysis/ScopedNoAliasAA.h"
  37 #include "llvm/Analysis/TargetLibraryInfo.h"
  38 #include "llvm/Analysis/TypeBasedAliasAnalysis.h"
  39 #include "llvm/Analysis/ValueTracking.h"
  40 #include "llvm/IR/Argument.h"
  41 #include "llvm/IR/Attributes.h"
  42 #include "llvm/IR/BasicBlock.h"
  43 #include "llvm/IR/CallSite.h"
  44 #include "llvm/IR/Instruction.h"
  45 #include "llvm/IR/Instructions.h"
  46 #include "llvm/IR/Module.h"
  47 #include "llvm/IR/Type.h"
  48 #include "llvm/IR/Value.h"
  49 #include "llvm/Pass.h"
  50 #include "llvm/Support/AtomicOrdering.h"
  51 #include "llvm/Support/Casting.h"
  52 #include "llvm/Support/CommandLine.h"
  53 #include <algorithm>
  54 #include <cassert>
  55 #include <functional>
  56 #include <iterator>
  57
  58 using namespace llvm;
  59
  60 /// Allow disabling BasicAA from the AA results. This is particularly useful
  61 /// when testing to isolate a single AA implementation.
  62 static cl::opt<bool> DisableBasicAA("disable-basicaa", cl::Hidden,
  63                                     cl::init(false));
  64
  65 AAResults::AAResults(AAResults &&Arg)
  66     : TLI(Arg.TLI), AAs(std::move(Arg.AAs)), AADeps(std::move(Arg.AADeps)) {
  67   for (auto &AA : AAs)
  68     AA->setAAResults(this);
  69 }
  70
  71 AAResults::~AAResults() {
  72 // FIXME; It would be nice to at least clear out the pointers back to this
  73 // aggregation here, but we end up with non-nesting lifetimes in the legacy
  74 // pass manager that prevent this from working. In the legacy pass manager
  75 // we'll end up with dangling references here in some cases.
  76 #if 0
  77   for (auto &AA : AAs)
  78     AA->setAAResults(nullptr);
  79 #endif
  80 }
  81
  82 bool AAResults::invalidate(Function &F, const PreservedAnalyses &PA,
  83                            FunctionAnalysisManager::Invalidator &Inv) {
  84   // Check if the AA manager itself has been invalidated.
  85   auto PAC = PA.getChecker<AAManager>();
  86   if (!PAC.preserved() && !PAC.preservedSet<AllAnalysesOn<Function>>())
  87     return true; // The manager needs to be blown away, clear everything.
  88
  89   // Check all of the dependencies registered.
  90   for (AnalysisKey *ID : AADeps)
  91     if (Inv.invalidate(ID, F, PA))
  92       return true;
  93
  94   // Everything we depend on is still fine, so are we. Nothing to invalidate.
  95   return false;
  96 }
  97
  98 //===----------------------------------------------------------------------===//
  99 // Default chaining methods
 100 //===----------------------------------------------------------------------===//
 101
 102 AliasResult AAResults::alias(const MemoryLocation &LocA,
 103                              const MemoryLocation &LocB) {
 104   for (const auto &AA : AAs) {
 105     auto Result = AA->alias(LocA, LocB);
 106     if (Result != MayAlias)
 107       return Result;
 108   }
 109   return MayAlias;
 110 }
 111
 112 bool AAResults::pointsToConstantMemory(const MemoryLocation &Loc,
 113                                        bool OrLocal) {
 114   for (const auto &AA : AAs)
 115     if (AA->pointsToConstantMemory(Loc, OrLocal))
 116       return true;
 117
 118   return false;
 119 }
 120
 121 ModRefInfo AAResults::getArgModRefInfo(ImmutableCallSite CS, unsigned ArgIdx) {
 122   ModRefInfo Result = MRI_ModRef;
 123
 124   for (const auto &AA : AAs) {
 125     Result = ModRefInfo(Result & AA->getArgModRefInfo(CS, ArgIdx));
 126
 127     // Early-exit the moment we reach the bottom of the lattice.
 128     if (Result == MRI_NoModRef)
 129       return Result;
 130   }
 131
 132   return Result;
 133 }
 134
 135 ModRefInfo AAResults::getModRefInfo(Instruction *I, ImmutableCallSite Call) {
 136   // We may have two calls
 137   if (auto CS = ImmutableCallSite(I)) {
 138     // Check if the two calls modify the same memory
 139     return getModRefInfo(CS, Call);
 140   } else if (I->isFenceLike()) {
 141     // If this is a fence, just return MRI_ModRef.
 142     return MRI_ModRef;
 143   } else {
 144     // Otherwise, check if the call modifies or references the
 145     // location this memory access defines.  The best we can say
 146     // is that if the call references what this instruction
 147     // defines, it must be clobbered by this location.
 148     const MemoryLocation DefLoc = MemoryLocation::get(I);
 149     if (getModRefInfo(Call, DefLoc) != MRI_NoModRef)
 150       return MRI_ModRef;
 151   }
 152   return MRI_NoModRef;
 153 }
 154
 155 ModRefInfo AAResults::getModRefInfo(ImmutableCallSite CS,
 156                                     const MemoryLocation &Loc) {
 157   ModRefInfo Result = MRI_ModRef;
 158
 159   for (const auto &AA : AAs) {
 160     Result = ModRefInfo(Result & AA->getModRefInfo(CS, Loc));
 161
 162     // Early-exit the moment we reach the bottom of the lattice.
 163     if (Result == MRI_NoModRef)
 164       return Result;
 165   }
 166
 167   // Try to refine the mod-ref info further using other API entry points to the
 168   // aggregate set of AA results.
 169   auto MRB = getModRefBehavior(CS);
 170   if (MRB == FMRB_DoesNotAccessMemory ||
 171       MRB == FMRB_OnlyAccessesInaccessibleMem)
 172     return MRI_NoModRef;
 173
 174   if (onlyReadsMemory(MRB))
 175     Result = ModRefInfo(Result & MRI_Ref);
 176   else if (doesNotReadMemory(MRB))
 177     Result = ModRefInfo(Result & MRI_Mod);
 178
 179   if (onlyAccessesArgPointees(MRB) || onlyAccessesInaccessibleOrArgMem(MRB)) {
 180     bool DoesAlias = false;
 181     ModRefInfo AllArgsMask = MRI_NoModRef;
 182     if (doesAccessArgPointees(MRB)) {
 183       for (auto AI = CS.arg_begin(), AE = CS.arg_end(); AI != AE; ++AI) {
 184         const Value *Arg = *AI;
 185         if (!Arg->getType()->isPointerTy())
 186           continue;
 187         unsigned ArgIdx = std::distance(CS.arg_begin(), AI);
 188         MemoryLocation ArgLoc = MemoryLocation::getForArgument(CS, ArgIdx, TLI);
 189         AliasResult ArgAlias = alias(ArgLoc, Loc);
 190         if (ArgAlias != NoAlias) {
 191           ModRefInfo ArgMask = getArgModRefInfo(CS, ArgIdx);
 192           DoesAlias = true;
 193           AllArgsMask = ModRefInfo(AllArgsMask | ArgMask);
 194         }
 195       }
 196     }
 197     if (!DoesAlias)
 198       return MRI_NoModRef;
 199     Result = ModRefInfo(Result & AllArgsMask);
 200   }
 201
 202   // If Loc is a constant memory location, the call definitely could not
 203   // modify the memory location.
 204   if ((Result & MRI_Mod) &&
 205       pointsToConstantMemory(Loc, /*OrLocal*/ false))
 206     Result = ModRefInfo(Result & ~MRI_Mod);
 207
 208   return Result;
 209 }
 210
 211 ModRefInfo AAResults::getModRefInfo(ImmutableCallSite CS1,
 212                                     ImmutableCallSite CS2) {
 213   ModRefInfo Result = MRI_ModRef;
 214
 215   for (const auto &AA : AAs) {
 216     Result = ModRefInfo(Result & AA->getModRefInfo(CS1, CS2));
 217
 218     // Early-exit the moment we reach the bottom of the lattice.
 219     if (Result == MRI_NoModRef)
 220       return Result;
 221   }
 222
 223   // Try to refine the mod-ref info further using other API entry points to the
 224   // aggregate set of AA results.
 225
 226   // If CS1 or CS2 are readnone, they don't interact.
 227   auto CS1B = getModRefBehavior(CS1);
 228   if (CS1B == FMRB_DoesNotAccessMemory)
 229     return MRI_NoModRef;
 230
 231   auto CS2B = getModRefBehavior(CS2);
 232   if (CS2B == FMRB_DoesNotAccessMemory)
 233     return MRI_NoModRef;
 234
 235   // If they both only read from memory, there is no dependence.
 236   if (onlyReadsMemory(CS1B) && onlyReadsMemory(CS2B))
 237     return MRI_NoModRef;
 238
 239   // If CS1 only reads memory, the only dependence on CS2 can be
 240   // from CS1 reading memory written by CS2.
 241   if (onlyReadsMemory(CS1B))
 242     Result = ModRefInfo(Result & MRI_Ref);
 243   else if (doesNotReadMemory(CS1B))
 244     Result = ModRefInfo(Result & MRI_Mod);
 245
 246   // If CS2 only access memory through arguments, accumulate the mod/ref
 247   // information from CS1's references to the memory referenced by
 248   // CS2's arguments.
 249   if (onlyAccessesArgPointees(CS2B)) {
 250     ModRefInfo R = MRI_NoModRef;
 251     if (doesAccessArgPointees(CS2B)) {
 252       for (auto I = CS2.arg_begin(), E = CS2.arg_end(); I != E; ++I) {
 253         const Value *Arg = *I;
 254         if (!Arg->getType()->isPointerTy())
 255           continue;
 256         unsigned CS2ArgIdx = std::distance(CS2.arg_begin(), I);
 257         auto CS2ArgLoc = MemoryLocation::getForArgument(CS2, CS2ArgIdx, TLI);
 258
 259         // ArgMask indicates what CS2 might do to CS2ArgLoc, and the dependence
 260         // of CS1 on that location is the inverse.
 261         ModRefInfo ArgMask = getArgModRefInfo(CS2, CS2ArgIdx);
 262         if (ArgMask == MRI_Mod)
 263           ArgMask = MRI_ModRef;
 264         else if (ArgMask == MRI_Ref)
 265           ArgMask = MRI_Mod;
 266
 267         ArgMask = ModRefInfo(ArgMask & getModRefInfo(CS1, CS2ArgLoc));
 268
 269         R = ModRefInfo((R | ArgMask) & Result);
 270         if (R == Result)
 271           break;
 272       }
 273     }
 274     return R;
 275   }
 276
 277   // If CS1 only accesses memory through arguments, check if CS2 references
 278   // any of the memory referenced by CS1's arguments. If not, return NoModRef.
 279   if (onlyAccessesArgPointees(CS1B)) {
 280     ModRefInfo R = MRI_NoModRef;
 281     if (doesAccessArgPointees(CS1B)) {
 282       for (auto I = CS1.arg_begin(), E = CS1.arg_end(); I != E; ++I) {
 283         const Value *Arg = *I;
 284         if (!Arg->getType()->isPointerTy())
 285           continue;
 286         unsigned CS1ArgIdx = std::distance(CS1.arg_begin(), I);
 287         auto CS1ArgLoc = MemoryLocation::getForArgument(CS1, CS1ArgIdx, TLI);
 288
 289         // ArgMask indicates what CS1 might do to CS1ArgLoc; if CS1 might Mod
 290         // CS1ArgLoc, then we care about either a Mod or a Ref by CS2. If CS1
 291         // might Ref, then we care only about a Mod by CS2.
 292         ModRefInfo ArgMask = getArgModRefInfo(CS1, CS1ArgIdx);
 293         ModRefInfo ArgR = getModRefInfo(CS2, CS1ArgLoc);
 294         if (((ArgMask & MRI_Mod) != MRI_NoModRef &&
 295              (ArgR & MRI_ModRef) != MRI_NoModRef) ||
 296             ((ArgMask & MRI_Ref) != MRI_NoModRef &&
 297              (ArgR & MRI_Mod) != MRI_NoModRef))
 298           R = ModRefInfo((R | ArgMask) & Result);
 299
 300         if (R == Result)
 301           break;
 302       }
 303     }
 304     return R;
 305   }
 306
 307   return Result;
 308 }
 309
 310 FunctionModRefBehavior AAResults::getModRefBehavior(ImmutableCallSite CS) {
 311   FunctionModRefBehavior Result = FMRB_UnknownModRefBehavior;
 312
 313   for (const auto &AA : AAs) {
 314     Result = FunctionModRefBehavior(Result & AA->getModRefBehavior(CS));
 315
 316     // Early-exit the moment we reach the bottom of the lattice.
 317     if (Result == FMRB_DoesNotAccessMemory)
 318       return Result;
 319   }
 320
 321   return Result;
 322 }
 323
 324 FunctionModRefBehavior AAResults::getModRefBehavior(const Function *F) {
 325   FunctionModRefBehavior Result = FMRB_UnknownModRefBehavior;
 326
 327   for (const auto &AA : AAs) {
 328     Result = FunctionModRefBehavior(Result & AA->getModRefBehavior(F));
 329
 330     // Early-exit the moment we reach the bottom of the lattice.
 331     if (Result == FMRB_DoesNotAccessMemory)
 332       return Result;
 333   }
 334
 335   return Result;
 336 }
 337
 338 //===----------------------------------------------------------------------===//
 339 // Helper method implementation
 340 //===----------------------------------------------------------------------===//
 341
 342 ModRefInfo AAResults::getModRefInfo(const LoadInst *L,
 343                                     const MemoryLocation &Loc) {
 344   // Be conservative in the face of atomic.
 345   if (isStrongerThan(L->getOrdering(), AtomicOrdering::Unordered))
 346     return MRI_ModRef;
 347
 348   // If the load address doesn't alias the given address, it doesn't read
 349   // or write the specified memory.
 350   if (Loc.Ptr && !alias(MemoryLocation::get(L), Loc))
 351     return MRI_NoModRef;
 352
 353   // Otherwise, a load just reads.
 354   return MRI_Ref;
 355 }
 356
 357 ModRefInfo AAResults::getModRefInfo(const StoreInst *S,
 358                                     const MemoryLocation &Loc) {
 359   // Be conservative in the face of atomic.
 360   if (isStrongerThan(S->getOrdering(), AtomicOrdering::Unordered))
 361     return MRI_ModRef;
 362
 363   if (Loc.Ptr) {
 364     // If the store address cannot alias the pointer in question, then the
 365     // specified memory cannot be modified by the store.
 366     if (!alias(MemoryLocation::get(S), Loc))
 367       return MRI_NoModRef;
 368
 369     // If the pointer is a pointer to constant memory, then it could not have
 370     // been modified by this store.
 371     if (pointsToConstantMemory(Loc))
 372       return MRI_NoModRef;
 373   }
 374
 375   // Otherwise, a store just writes.
 376   return MRI_Mod;
 377 }
 378
 379 ModRefInfo AAResults::getModRefInfo(const FenceInst *S, const MemoryLocation &Loc) {
 380   // If we know that the location is a constant memory location, the fence
 381   // cannot modify this location.
 382   if (Loc.Ptr && pointsToConstantMemory(Loc))
 383     return MRI_Ref;
 384   return MRI_ModRef;
 385 }
 386
 387 ModRefInfo AAResults::getModRefInfo(const VAArgInst *V,
 388                                     const MemoryLocation &Loc) {
 389   if (Loc.Ptr) {
 390     // If the va_arg address cannot alias the pointer in question, then the
 391     // specified memory cannot be accessed by the va_arg.
 392     if (!alias(MemoryLocation::get(V), Loc))
 393       return MRI_NoModRef;
 394
 395     // If the pointer is a pointer to constant memory, then it could not have
 396     // been modified by this va_arg.
 397     if (pointsToConstantMemory(Loc))
 398       return MRI_NoModRef;
 399   }
 400
 401   // Otherwise, a va_arg reads and writes.
 402   return MRI_ModRef;
 403 }
 404
 405 ModRefInfo AAResults::getModRefInfo(const CatchPadInst *CatchPad,
 406                                     const MemoryLocation &Loc) {
 407   if (Loc.Ptr) {
 408     // If the pointer is a pointer to constant memory,
 409     // then it could not have been modified by this catchpad.
 410     if (pointsToConstantMemory(Loc))
 411       return MRI_NoModRef;
 412   }
 413
 414   // Otherwise, a catchpad reads and writes.
 415   return MRI_ModRef;
 416 }
 417
 418 ModRefInfo AAResults::getModRefInfo(const CatchReturnInst *CatchRet,
 419                                     const MemoryLocation &Loc) {
 420   if (Loc.Ptr) {
 421     // If the pointer is a pointer to constant memory,
 422     // then it could not have been modified by this catchpad.
 423     if (pointsToConstantMemory(Loc))
 424       return MRI_NoModRef;
 425   }
 426
 427   // Otherwise, a catchret reads and writes.
 428   return MRI_ModRef;
 429 }
 430
 431 ModRefInfo AAResults::getModRefInfo(const AtomicCmpXchgInst *CX,
 432                                     const MemoryLocation &Loc) {
 433   // Acquire/Release cmpxchg has properties that matter for arbitrary addresses.
 434   if (isStrongerThanMonotonic(CX->getSuccessOrdering()))
 435     return MRI_ModRef;
 436
 437   // If the cmpxchg address does not alias the location, it does not access it.
 438   if (Loc.Ptr && !alias(MemoryLocation::get(CX), Loc))
 439     return MRI_NoModRef;
 440
 441   return MRI_ModRef;
 442 }
 443
 444 ModRefInfo AAResults::getModRefInfo(const AtomicRMWInst *RMW,
 445                                     const MemoryLocation &Loc) {
 446   // Acquire/Release atomicrmw has properties that matter for arbitrary addresses.
 447   if (isStrongerThanMonotonic(RMW->getOrdering()))
 448     return MRI_ModRef;
 449
 450   // If the atomicrmw address does not alias the location, it does not access it.
 451   if (Loc.Ptr && !alias(MemoryLocation::get(RMW), Loc))
 452     return MRI_NoModRef;
 453
 454   return MRI_ModRef;
 455 }
 456
 457 /// \brief Return information about whether a particular call site modifies
 458 /// or reads the specified memory location \p MemLoc before instruction \p I
 459 /// in a BasicBlock. A ordered basic block \p OBB can be used to speed up
 460 /// instruction-ordering queries inside the BasicBlock containing \p I.
 461 /// FIXME: this is really just shoring-up a deficiency in alias analysis.
 462 /// BasicAA isn't willing to spend linear time determining whether an alloca
 463 /// was captured before or after this particular call, while we are. However,
 464 /// with a smarter AA in place, this test is just wasting compile time.
 465 ModRefInfo AAResults::callCapturesBefore(const Instruction *I,
 466                                          const MemoryLocation &MemLoc,
 467                                          DominatorTree *DT,
 468                                          OrderedBasicBlock *OBB) {
 469   if (!DT)
 470     return MRI_ModRef;
 471
 472   const Value *Object =
 473       GetUnderlyingObject(MemLoc.Ptr, I->getModule()->getDataLayout());
 474   if (!isIdentifiedObject(Object) || isa<GlobalValue>(Object) ||
 475       isa<Constant>(Object))
 476     return MRI_ModRef;
 477
 478   ImmutableCallSite CS(I);
 479   if (!CS.getInstruction() || CS.getInstruction() == Object)
 480     return MRI_ModRef;
 481
 482   if (PointerMayBeCapturedBefore(Object, /* ReturnCaptures */ true,
 483                                  /* StoreCaptures */ true, I, DT,
 484                                  /* include Object */ true,
 485                                  /* OrderedBasicBlock */ OBB))
 486     return MRI_ModRef;
 487
 488   unsigned ArgNo = 0;
 489   ModRefInfo R = MRI_NoModRef;
 490   for (auto CI = CS.data_operands_begin(), CE = CS.data_operands_end();
 491        CI != CE; ++CI, ++ArgNo) {
 492     // Only look at the no-capture or byval pointer arguments.  If this
 493     // pointer were passed to arguments that were neither of these, then it
 494     // couldn't be no-capture.
 495     if (!(*CI)->getType()->isPointerTy() ||
 496         (!CS.doesNotCapture(ArgNo) &&
 497          ArgNo < CS.getNumArgOperands() && !CS.isByValArgument(ArgNo)))
 498       continue;
 499
 500     // If this is a no-capture pointer argument, see if we can tell that it
 501     // is impossible to alias the pointer we're checking.  If not, we have to
 502     // assume that the call could touch the pointer, even though it doesn't
 503     // escape.
 504     if (isNoAlias(MemoryLocation(*CI), MemoryLocation(Object)))
 505       continue;
 506     if (CS.doesNotAccessMemory(ArgNo))
 507       continue;
 508     if (CS.onlyReadsMemory(ArgNo)) {
 509       R = MRI_Ref;
 510       continue;
 511     }
 512     return MRI_ModRef;
 513   }
 514   return R;
 515 }
 516
 517 /// canBasicBlockModify - Return true if it is possible for execution of the
 518 /// specified basic block to modify the location Loc.
 519 ///
 520 bool AAResults::canBasicBlockModify(const BasicBlock &BB,
 521                                     const MemoryLocation &Loc) {
 522   return canInstructionRangeModRef(BB.front(), BB.back(), Loc, MRI_Mod);
 523 }
 524
 525 /// canInstructionRangeModRef - Return true if it is possible for the
 526 /// execution of the specified instructions to mod\ref (according to the
 527 /// mode) the location Loc. The instructions to consider are all
 528 /// of the instructions in the range of [I1,I2] INCLUSIVE.
 529 /// I1 and I2 must be in the same basic block.
 530 bool AAResults::canInstructionRangeModRef(const Instruction &I1,
 531                                           const Instruction &I2,
 532                                           const MemoryLocation &Loc,
 533                                           const ModRefInfo Mode) {
 534   assert(I1.getParent() == I2.getParent() &&
 535          "Instructions not in same basic block!");
 536   BasicBlock::const_iterator I = I1.getIterator();
 537   BasicBlock::const_iterator E = I2.getIterator();
 538   ++E;  // Convert from inclusive to exclusive range.
 539
 540   for (; I != E; ++I) // Check every instruction in range
 541     if (getModRefInfo(&*I, Loc) & Mode)
 542       return true;
 543   return false;
 544 }
 545
 546 // Provide a definition for the root virtual destructor.
 547 AAResults::Concept::~Concept() = default;
 548
 549 // Provide a definition for the static object used to identify passes.
 550 AnalysisKey AAManager::Key;
 551
 552 namespace {
 553
 554 /// A wrapper pass for external alias analyses. This just squirrels away the
 555 /// callback used to run any analyses and register their results.
 556 struct ExternalAAWrapperPass : ImmutablePass {
 557   using CallbackT = std::function<void(Pass &, Function &, AAResults &)>;
 558
 559   CallbackT CB;
 560
 561   static char ID;
 562
 563   ExternalAAWrapperPass() : ImmutablePass(ID) {
 564     initializeExternalAAWrapperPassPass(*PassRegistry::getPassRegistry());
 565   }
 566
 567   explicit ExternalAAWrapperPass(CallbackT CB)
 568       : ImmutablePass(ID), CB(std::move(CB)) {
 569     initializeExternalAAWrapperPassPass(*PassRegistry::getPassRegistry());
 570   }
 571
 572   void getAnalysisUsage(AnalysisUsage &AU) const override {
 573     AU.setPreservesAll();
 574   }
 575 };
 576
 577 } // end anonymous namespace
 578
 579 char ExternalAAWrapperPass::ID = 0;
 580
 581 INITIALIZE_PASS(ExternalAAWrapperPass, "external-aa", "External Alias Analysis",
 582                 false, true)
 583
 584 ImmutablePass *
 585 llvm::createExternalAAWrapperPass(ExternalAAWrapperPass::CallbackT Callback) {
 586   return new ExternalAAWrapperPass(std::move(Callback));
 587 }
 588
 589 AAResultsWrapperPass::AAResultsWrapperPass() : FunctionPass(ID) {
 590   initializeAAResultsWrapperPassPass(*PassRegistry::getPassRegistry());
 591 }
 592
 593 char AAResultsWrapperPass::ID = 0;
 594
 595 INITIALIZE_PASS_BEGIN(AAResultsWrapperPass, "aa",
 596                       "Function Alias Analysis Results", false, true)
 597 INITIALIZE_PASS_DEPENDENCY(BasicAAWrapperPass)
 598 INITIALIZE_PASS_DEPENDENCY(CFLAndersAAWrapperPass)
 599 INITIALIZE_PASS_DEPENDENCY(CFLSteensAAWrapperPass)
 600 INITIALIZE_PASS_DEPENDENCY(ExternalAAWrapperPass)
 601 INITIALIZE_PASS_DEPENDENCY(GlobalsAAWrapperPass)
 602 INITIALIZE_PASS_DEPENDENCY(ObjCARCAAWrapperPass)
 603 INITIALIZE_PASS_DEPENDENCY(SCEVAAWrapperPass)
 604 INITIALIZE_PASS_DEPENDENCY(ScopedNoAliasAAWrapperPass)
 605 INITIALIZE_PASS_DEPENDENCY(TypeBasedAAWrapperPass)
 606 INITIALIZE_PASS_END(AAResultsWrapperPass, "aa",
 607                     "Function Alias Analysis Results", false, true)
 608
 609 FunctionPass *llvm::createAAResultsWrapperPass() {
 610   return new AAResultsWrapperPass();
 611 }
 612
 613 /// Run the wrapper pass to rebuild an aggregation over known AA passes.
 614 ///
 615 /// This is the legacy pass manager's interface to the new-style AA results
 616 /// aggregation object. Because this is somewhat shoe-horned into the legacy
 617 /// pass manager, we hard code all the specific alias analyses available into
 618 /// it. While the particular set enabled is configured via commandline flags,
 619 /// adding a new alias analysis to LLVM will require adding support for it to
 620 /// this list.
 621 bool AAResultsWrapperPass::runOnFunction(Function &F) {
 622   // NB! This *must* be reset before adding new AA results to the new
 623   // AAResults object because in the legacy pass manager, each instance
 624   // of these will refer to the *same* immutable analyses, registering and
 625   // unregistering themselves with them. We need to carefully tear down the
 626   // previous object first, in this case replacing it with an empty one, before
 627   // registering new results.
 628   AAR.reset(
 629       new AAResults(getAnalysis<TargetLibraryInfoWrapperPass>().getTLI()));
 630
 631   // BasicAA is always available for function analyses. Also, we add it first
 632   // so that it can trump TBAA results when it proves MustAlias.
 633   // FIXME: TBAA should have an explicit mode to support this and then we
 634   // should reconsider the ordering here.
 635   if (!DisableBasicAA)
 636     AAR->addAAResult(getAnalysis<BasicAAWrapperPass>().getResult());
 637
 638   // Populate the results with the currently available AAs.
 639   if (auto *WrapperPass = getAnalysisIfAvailable<ScopedNoAliasAAWrapperPass>())
 640     AAR->addAAResult(WrapperPass->getResult());
 641   if (auto *WrapperPass = getAnalysisIfAvailable<TypeBasedAAWrapperPass>())
 642     AAR->addAAResult(WrapperPass->getResult());
 643   if (auto *WrapperPass =
 644           getAnalysisIfAvailable<objcarc::ObjCARCAAWrapperPass>())
 645     AAR->addAAResult(WrapperPass->getResult());
 646   if (auto *WrapperPass = getAnalysisIfAvailable<GlobalsAAWrapperPass>())
 647     AAR->addAAResult(WrapperPass->getResult());
 648   if (auto *WrapperPass = getAnalysisIfAvailable<SCEVAAWrapperPass>())
 649     AAR->addAAResult(WrapperPass->getResult());
 650   if (auto *WrapperPass = getAnalysisIfAvailable<CFLAndersAAWrapperPass>())
 651     AAR->addAAResult(WrapperPass->getResult());
 652   if (auto *WrapperPass = getAnalysisIfAvailable<CFLSteensAAWrapperPass>())
 653     AAR->addAAResult(WrapperPass->getResult());
 654
 655   // If available, run an external AA providing callback over the results as
 656   // well.
 657   if (auto *WrapperPass = getAnalysisIfAvailable<ExternalAAWrapperPass>())
 658     if (WrapperPass->CB)
 659       WrapperPass->CB(*this, F, *AAR);
 660
 661   // Analyses don't mutate the IR, so return false.
 662   return false;
 663 }
 664
 665 void AAResultsWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
 666   AU.setPreservesAll();
 667   AU.addRequired<BasicAAWrapperPass>();
 668   AU.addRequired<TargetLibraryInfoWrapperPass>();
 669
 670   // We also need to mark all the alias analysis passes we will potentially
 671   // probe in runOnFunction as used here to ensure the legacy pass manager
 672   // preserves them. This hard coding of lists of alias analyses is specific to
 673   // the legacy pass manager.
 674   AU.addUsedIfAvailable<ScopedNoAliasAAWrapperPass>();
 675   AU.addUsedIfAvailable<TypeBasedAAWrapperPass>();
 676   AU.addUsedIfAvailable<objcarc::ObjCARCAAWrapperPass>();
 677   AU.addUsedIfAvailable<GlobalsAAWrapperPass>();
 678   AU.addUsedIfAvailable<SCEVAAWrapperPass>();
 679   AU.addUsedIfAvailable<CFLAndersAAWrapperPass>();
 680   AU.addUsedIfAvailable<CFLSteensAAWrapperPass>();
 681 }
 682
 683 AAResults llvm::createLegacyPMAAResults(Pass &P, Function &F,
 684                                         BasicAAResult &BAR) {
 685   AAResults AAR(P.getAnalysis<TargetLibraryInfoWrapperPass>().getTLI());
 686
 687   // Add in our explicitly constructed BasicAA results.
 688   if (!DisableBasicAA)
 689     AAR.addAAResult(BAR);
 690
 691   // Populate the results with the other currently available AAs.
 692   if (auto *WrapperPass =
 693           P.getAnalysisIfAvailable<ScopedNoAliasAAWrapperPass>())
 694     AAR.addAAResult(WrapperPass->getResult());
 695   if (auto *WrapperPass = P.getAnalysisIfAvailable<TypeBasedAAWrapperPass>())
 696     AAR.addAAResult(WrapperPass->getResult());
 697   if (auto *WrapperPass =
 698           P.getAnalysisIfAvailable<objcarc::ObjCARCAAWrapperPass>())
 699     AAR.addAAResult(WrapperPass->getResult());
 700   if (auto *WrapperPass = P.getAnalysisIfAvailable<GlobalsAAWrapperPass>())
 701     AAR.addAAResult(WrapperPass->getResult());
 702   if (auto *WrapperPass = P.getAnalysisIfAvailable<CFLAndersAAWrapperPass>())
 703     AAR.addAAResult(WrapperPass->getResult());
 704   if (auto *WrapperPass = P.getAnalysisIfAvailable<CFLSteensAAWrapperPass>())
 705     AAR.addAAResult(WrapperPass->getResult());
 706
 707   return AAR;
 708 }
 709
 710 bool llvm::isNoAliasCall(const Value *V) {
 711   if (auto CS = ImmutableCallSite(V))
 712     return CS.hasRetAttr(Attribute::NoAlias);
 713   return false;
 714 }
 715
 716 bool llvm::isNoAliasArgument(const Value *V) {
 717   if (const Argument *A = dyn_cast<Argument>(V))
 718     return A->hasNoAliasAttr();
 719   return false;
 720 }
 721
 722 bool llvm::isIdentifiedObject(const Value *V) {
 723   if (isa<AllocaInst>(V))
 724     return true;
 725   if (isa<GlobalValue>(V) && !isa<GlobalAlias>(V))
 726     return true;
 727   if (isNoAliasCall(V))
 728     return true;
 729   if (const Argument *A = dyn_cast<Argument>(V))
 730     return A->hasNoAliasAttr() || A->hasByValAttr();
 731   return false;
 732 }
 733
 734 bool llvm::isIdentifiedFunctionLocal(const Value *V) {
 735   return isa<AllocaInst>(V) || isNoAliasCall(V) || isNoAliasArgument(V);
 736 }
 737
 738 void llvm::getAAResultsAnalysisUsage(AnalysisUsage &AU) {
 739   // This function needs to be in sync with llvm::createLegacyPMAAResults -- if
 740   // more alias analyses are added to llvm::createLegacyPMAAResults, they need
 741   // to be added here also.
 742   AU.addRequired<TargetLibraryInfoWrapperPass>();
 743   AU.addUsedIfAvailable<ScopedNoAliasAAWrapperPass>();
 744   AU.addUsedIfAvailable<TypeBasedAAWrapperPass>();
 745   AU.addUsedIfAvailable<objcarc::ObjCARCAAWrapperPass>();
 746   AU.addUsedIfAvailable<GlobalsAAWrapperPass>();
 747   AU.addUsedIfAvailable<CFLAndersAAWrapperPass>();
 748   AU.addUsedIfAvailable<CFLSteensAAWrapperPass>();
 749 }