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 = ModRefInfo::ModRef;
 123
 124   for (const auto &AA : AAs) {
 125     Result = intersectModRef(Result, AA->getArgModRefInfo(CS, ArgIdx));
 126
 127     // Early-exit the moment we reach the bottom of the lattice.
 128     if (isNoModRef(Result))
 129       return ModRefInfo::NoModRef;
 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 ModRef.
 142     return ModRefInfo::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     ModRefInfo MR = getModRefInfo(Call, DefLoc);
 150     if (isModOrRefSet(MR))
 151       return setModAndRef(MR);
 152   }
 153   return ModRefInfo::NoModRef;
 154 }
 155
 156 ModRefInfo AAResults::getModRefInfo(ImmutableCallSite CS,
 157                                     const MemoryLocation &Loc) {
 158   ModRefInfo Result = ModRefInfo::ModRef;
 159
 160   for (const auto &AA : AAs) {
 161     Result = intersectModRef(Result, AA->getModRefInfo(CS, Loc));
 162
 163     // Early-exit the moment we reach the bottom of the lattice.
 164     if (isNoModRef(Result))
 165       return ModRefInfo::NoModRef;
 166   }
 167
 168   // Try to refine the mod-ref info further using other API entry points to the
 169   // aggregate set of AA results.
 170   auto MRB = getModRefBehavior(CS);
 171   if (MRB == FMRB_DoesNotAccessMemory ||
 172       MRB == FMRB_OnlyAccessesInaccessibleMem)
 173     return ModRefInfo::NoModRef;
 174
 175   if (onlyReadsMemory(MRB))
 176     Result = clearMod(Result);
 177   else if (doesNotReadMemory(MRB))
 178     Result = clearRef(Result);
 179
 180   if (onlyAccessesArgPointees(MRB) || onlyAccessesInaccessibleOrArgMem(MRB)) {
 181     bool DoesAlias = false;
 182     bool IsMustAlias = true;
 183     ModRefInfo AllArgsMask = ModRefInfo::NoModRef;
 184     if (doesAccessArgPointees(MRB)) {
 185       for (auto AI = CS.arg_begin(), AE = CS.arg_end(); AI != AE; ++AI) {
 186         const Value *Arg = *AI;
 187         if (!Arg->getType()->isPointerTy())
 188           continue;
 189         unsigned ArgIdx = std::distance(CS.arg_begin(), AI);
 190         MemoryLocation ArgLoc = MemoryLocation::getForArgument(CS, ArgIdx, TLI);
 191         AliasResult ArgAlias = alias(ArgLoc, Loc);
 192         if (ArgAlias != NoAlias) {
 193           ModRefInfo ArgMask = getArgModRefInfo(CS, ArgIdx);
 194           DoesAlias = true;
 195           AllArgsMask = unionModRef(AllArgsMask, ArgMask);
 196         }
 197         // Conservatively clear IsMustAlias unless only MustAlias is found.
 198         IsMustAlias &= (ArgAlias == MustAlias);
 199       }
 200     }
 201     // Return NoModRef if no alias found with any argument.
 202     if (!DoesAlias)
 203       return ModRefInfo::NoModRef;
 204     // Logical & between other AA analyses and argument analysis.
 205     Result = intersectModRef(Result, AllArgsMask);
 206     // If only MustAlias found above, set Must bit.
 207     Result = IsMustAlias ? setMust(Result) : clearMust(Result);
 208   }
 209
 210   // If Loc is a constant memory location, the call definitely could not
 211   // modify the memory location.
 212   if (isModSet(Result) && pointsToConstantMemory(Loc, /*OrLocal*/ false))
 213     Result = clearMod(Result);
 214
 215   return Result;
 216 }
 217
 218 ModRefInfo AAResults::getModRefInfo(ImmutableCallSite CS1,
 219                                     ImmutableCallSite CS2) {
 220   ModRefInfo Result = ModRefInfo::ModRef;
 221
 222   for (const auto &AA : AAs) {
 223     Result = intersectModRef(Result, AA->getModRefInfo(CS1, CS2));
 224
 225     // Early-exit the moment we reach the bottom of the lattice.
 226     if (isNoModRef(Result))
 227       return ModRefInfo::NoModRef;
 228   }
 229
 230   // Try to refine the mod-ref info further using other API entry points to the
 231   // aggregate set of AA results.
 232
 233   // If CS1 or CS2 are readnone, they don't interact.
 234   auto CS1B = getModRefBehavior(CS1);
 235   if (CS1B == FMRB_DoesNotAccessMemory)
 236     return ModRefInfo::NoModRef;
 237
 238   auto CS2B = getModRefBehavior(CS2);
 239   if (CS2B == FMRB_DoesNotAccessMemory)
 240     return ModRefInfo::NoModRef;
 241
 242   // If they both only read from memory, there is no dependence.
 243   if (onlyReadsMemory(CS1B) && onlyReadsMemory(CS2B))
 244     return ModRefInfo::NoModRef;
 245
 246   // If CS1 only reads memory, the only dependence on CS2 can be
 247   // from CS1 reading memory written by CS2.
 248   if (onlyReadsMemory(CS1B))
 249     Result = clearMod(Result);
 250   else if (doesNotReadMemory(CS1B))
 251     Result = clearRef(Result);
 252
 253   // If CS2 only access memory through arguments, accumulate the mod/ref
 254   // information from CS1's references to the memory referenced by
 255   // CS2's arguments.
 256   if (onlyAccessesArgPointees(CS2B)) {
 257     if (!doesAccessArgPointees(CS2B))
 258       return ModRefInfo::NoModRef;
 259     ModRefInfo R = ModRefInfo::NoModRef;
 260     bool IsMustAlias = true;
 261     for (auto I = CS2.arg_begin(), E = CS2.arg_end(); I != E; ++I) {
 262       const Value *Arg = *I;
 263       if (!Arg->getType()->isPointerTy())
 264         continue;
 265       unsigned CS2ArgIdx = std::distance(CS2.arg_begin(), I);
 266       auto CS2ArgLoc = MemoryLocation::getForArgument(CS2, CS2ArgIdx, TLI);
 267
 268       // ArgModRefCS2 indicates what CS2 might do to CS2ArgLoc, and the
 269       // dependence of CS1 on that location is the inverse:
 270       // - If CS2 modifies location, dependence exists if CS1 reads or writes.
 271       // - If CS2 only reads location, dependence exists if CS1 writes.
 272       ModRefInfo ArgModRefCS2 = getArgModRefInfo(CS2, CS2ArgIdx);
 273       ModRefInfo ArgMask = ModRefInfo::NoModRef;
 274       if (isModSet(ArgModRefCS2))
 275         ArgMask = ModRefInfo::ModRef;
 276       else if (isRefSet(ArgModRefCS2))
 277         ArgMask = ModRefInfo::Mod;
 278
 279       // ModRefCS1 indicates what CS1 might do to CS2ArgLoc, and we use
 280       // above ArgMask to update dependence info.
 281       ModRefInfo ModRefCS1 = getModRefInfo(CS1, CS2ArgLoc);
 282       ArgMask = intersectModRef(ArgMask, ModRefCS1);
 283
 284       // Conservatively clear IsMustAlias unless only MustAlias is found.
 285       IsMustAlias &= isMustSet(ModRefCS1);
 286
 287       R = intersectModRef(unionModRef(R, ArgMask), Result);
 288       if (R == Result) {
 289         // On early exit, not all args were checked, cannot set Must.
 290         if (I + 1 != E)
 291           IsMustAlias = false;
 292         break;
 293       }
 294     }
 295
 296     if (isNoModRef(R))
 297       return ModRefInfo::NoModRef;
 298
 299     // If MustAlias found above, set Must bit.
 300     return IsMustAlias ? setMust(R) : clearMust(R);
 301   }
 302
 303   // If CS1 only accesses memory through arguments, check if CS2 references
 304   // any of the memory referenced by CS1's arguments. If not, return NoModRef.
 305   if (onlyAccessesArgPointees(CS1B)) {
 306     if (!doesAccessArgPointees(CS1B))
 307       return ModRefInfo::NoModRef;
 308     ModRefInfo R = ModRefInfo::NoModRef;
 309     bool IsMustAlias = true;
 310     for (auto I = CS1.arg_begin(), E = CS1.arg_end(); I != E; ++I) {
 311       const Value *Arg = *I;
 312       if (!Arg->getType()->isPointerTy())
 313         continue;
 314       unsigned CS1ArgIdx = std::distance(CS1.arg_begin(), I);
 315       auto CS1ArgLoc = MemoryLocation::getForArgument(CS1, CS1ArgIdx, TLI);
 316
 317       // ArgModRefCS1 indicates what CS1 might do to CS1ArgLoc; if CS1 might
 318       // Mod CS1ArgLoc, then we care about either a Mod or a Ref by CS2. If
 319       // CS1 might Ref, then we care only about a Mod by CS2.
 320       ModRefInfo ArgModRefCS1 = getArgModRefInfo(CS1, CS1ArgIdx);
 321       ModRefInfo ModRefCS2 = getModRefInfo(CS2, CS1ArgLoc);
 322       if ((isModSet(ArgModRefCS1) && isModOrRefSet(ModRefCS2)) ||
 323           (isRefSet(ArgModRefCS1) && isModSet(ModRefCS2)))
 324         R = intersectModRef(unionModRef(R, ArgModRefCS1), Result);
 325
 326       // Conservatively clear IsMustAlias unless only MustAlias is found.
 327       IsMustAlias &= isMustSet(ModRefCS2);
 328
 329       if (R == Result) {
 330         // On early exit, not all args were checked, cannot set Must.
 331         if (I + 1 != E)
 332           IsMustAlias = false;
 333         break;
 334       }
 335     }
 336
 337     if (isNoModRef(R))
 338       return ModRefInfo::NoModRef;
 339
 340     // If MustAlias found above, set Must bit.
 341     return IsMustAlias ? setMust(R) : clearMust(R);
 342   }
 343
 344   return Result;
 345 }
 346
 347 FunctionModRefBehavior AAResults::getModRefBehavior(ImmutableCallSite CS) {
 348   FunctionModRefBehavior Result = FMRB_UnknownModRefBehavior;
 349
 350   for (const auto &AA : AAs) {
 351     Result = FunctionModRefBehavior(Result & AA->getModRefBehavior(CS));
 352
 353     // Early-exit the moment we reach the bottom of the lattice.
 354     if (Result == FMRB_DoesNotAccessMemory)
 355       return Result;
 356   }
 357
 358   return Result;
 359 }
 360
 361 FunctionModRefBehavior AAResults::getModRefBehavior(const Function *F) {
 362   FunctionModRefBehavior Result = FMRB_UnknownModRefBehavior;
 363
 364   for (const auto &AA : AAs) {
 365     Result = FunctionModRefBehavior(Result & AA->getModRefBehavior(F));
 366
 367     // Early-exit the moment we reach the bottom of the lattice.
 368     if (Result == FMRB_DoesNotAccessMemory)
 369       return Result;
 370   }
 371
 372   return Result;
 373 }
 374
 375 raw_ostream &llvm::operator<<(raw_ostream &OS, AliasResult AR) {
 376   switch (AR) {
 377   case NoAlias:
 378     OS << "NoAlias";
 379     break;
 380   case MustAlias:
 381     OS << "MustAlias";
 382     break;
 383   case MayAlias:
 384     OS << "MayAlias";
 385     break;
 386   case PartialAlias:
 387     OS << "PartialAlias";
 388     break;
 389   }
 390   return OS;
 391 }
 392
 393 //===----------------------------------------------------------------------===//
 394 // Helper method implementation
 395 //===----------------------------------------------------------------------===//
 396
 397 ModRefInfo AAResults::getModRefInfo(const LoadInst *L,
 398                                     const MemoryLocation &Loc) {
 399   // Be conservative in the face of atomic.
 400   if (isStrongerThan(L->getOrdering(), AtomicOrdering::Unordered))
 401     return ModRefInfo::ModRef;
 402
 403   // If the load address doesn't alias the given address, it doesn't read
 404   // or write the specified memory.
 405   if (Loc.Ptr) {
 406     AliasResult AR = alias(MemoryLocation::get(L), Loc);
 407     if (AR == NoAlias)
 408       return ModRefInfo::NoModRef;
 409     if (AR == MustAlias)
 410       return ModRefInfo::MustRef;
 411   }
 412   // Otherwise, a load just reads.
 413   return ModRefInfo::Ref;
 414 }
 415
 416 ModRefInfo AAResults::getModRefInfo(const StoreInst *S,
 417                                     const MemoryLocation &Loc) {
 418   // Be conservative in the face of atomic.
 419   if (isStrongerThan(S->getOrdering(), AtomicOrdering::Unordered))
 420     return ModRefInfo::ModRef;
 421
 422   if (Loc.Ptr) {
 423     AliasResult AR = alias(MemoryLocation::get(S), Loc);
 424     // If the store address cannot alias the pointer in question, then the
 425     // specified memory cannot be modified by the store.
 426     if (AR == NoAlias)
 427       return ModRefInfo::NoModRef;
 428
 429     // If the pointer is a pointer to constant memory, then it could not have
 430     // been modified by this store.
 431     if (pointsToConstantMemory(Loc))
 432       return ModRefInfo::NoModRef;
 433
 434     // If the store address aliases the pointer as must alias, set Must.
 435     if (AR == MustAlias)
 436       return ModRefInfo::MustMod;
 437   }
 438
 439   // Otherwise, a store just writes.
 440   return ModRefInfo::Mod;
 441 }
 442
 443 ModRefInfo AAResults::getModRefInfo(const FenceInst *S, const MemoryLocation &Loc) {
 444   // If we know that the location is a constant memory location, the fence
 445   // cannot modify this location.
 446   if (Loc.Ptr && pointsToConstantMemory(Loc))
 447     return ModRefInfo::Ref;
 448   return ModRefInfo::ModRef;
 449 }
 450
 451 ModRefInfo AAResults::getModRefInfo(const VAArgInst *V,
 452                                     const MemoryLocation &Loc) {
 453   if (Loc.Ptr) {
 454     AliasResult AR = alias(MemoryLocation::get(V), Loc);
 455     // If the va_arg address cannot alias the pointer in question, then the
 456     // specified memory cannot be accessed by the va_arg.
 457     if (AR == NoAlias)
 458       return ModRefInfo::NoModRef;
 459
 460     // If the pointer is a pointer to constant memory, then it could not have
 461     // been modified by this va_arg.
 462     if (pointsToConstantMemory(Loc))
 463       return ModRefInfo::NoModRef;
 464
 465     // If the va_arg aliases the pointer as must alias, set Must.
 466     if (AR == MustAlias)
 467       return ModRefInfo::MustModRef;
 468   }
 469
 470   // Otherwise, a va_arg reads and writes.
 471   return ModRefInfo::ModRef;
 472 }
 473
 474 ModRefInfo AAResults::getModRefInfo(const CatchPadInst *CatchPad,
 475                                     const MemoryLocation &Loc) {
 476   if (Loc.Ptr) {
 477     // If the pointer is a pointer to constant memory,
 478     // then it could not have been modified by this catchpad.
 479     if (pointsToConstantMemory(Loc))
 480       return ModRefInfo::NoModRef;
 481   }
 482
 483   // Otherwise, a catchpad reads and writes.
 484   return ModRefInfo::ModRef;
 485 }
 486
 487 ModRefInfo AAResults::getModRefInfo(const CatchReturnInst *CatchRet,
 488                                     const MemoryLocation &Loc) {
 489   if (Loc.Ptr) {
 490     // If the pointer is a pointer to constant memory,
 491     // then it could not have been modified by this catchpad.
 492     if (pointsToConstantMemory(Loc))
 493       return ModRefInfo::NoModRef;
 494   }
 495
 496   // Otherwise, a catchret reads and writes.
 497   return ModRefInfo::ModRef;
 498 }
 499
 500 ModRefInfo AAResults::getModRefInfo(const AtomicCmpXchgInst *CX,
 501                                     const MemoryLocation &Loc) {
 502   // Acquire/Release cmpxchg has properties that matter for arbitrary addresses.
 503   if (isStrongerThanMonotonic(CX->getSuccessOrdering()))
 504     return ModRefInfo::ModRef;
 505
 506   if (Loc.Ptr) {
 507     AliasResult AR = alias(MemoryLocation::get(CX), Loc);
 508     // If the cmpxchg address does not alias the location, it does not access
 509     // it.
 510     if (AR == NoAlias)
 511       return ModRefInfo::NoModRef;
 512
 513     // If the cmpxchg address aliases the pointer as must alias, set Must.
 514     if (AR == MustAlias)
 515       return ModRefInfo::MustModRef;
 516   }
 517
 518   return ModRefInfo::ModRef;
 519 }
 520
 521 ModRefInfo AAResults::getModRefInfo(const AtomicRMWInst *RMW,
 522                                     const MemoryLocation &Loc) {
 523   // Acquire/Release atomicrmw has properties that matter for arbitrary addresses.
 524   if (isStrongerThanMonotonic(RMW->getOrdering()))
 525     return ModRefInfo::ModRef;
 526
 527   if (Loc.Ptr) {
 528     AliasResult AR = alias(MemoryLocation::get(RMW), Loc);
 529     // If the atomicrmw address does not alias the location, it does not access
 530     // it.
 531     if (AR == NoAlias)
 532       return ModRefInfo::NoModRef;
 533
 534     // If the atomicrmw address aliases the pointer as must alias, set Must.
 535     if (AR == MustAlias)
 536       return ModRefInfo::MustModRef;
 537   }
 538
 539   return ModRefInfo::ModRef;
 540 }
 541
 542 /// Return information about whether a particular call site modifies
 543 /// or reads the specified memory location \p MemLoc before instruction \p I
 544 /// in a BasicBlock. An ordered basic block \p OBB can be used to speed up
 545 /// instruction-ordering queries inside the BasicBlock containing \p I.
 546 /// FIXME: this is really just shoring-up a deficiency in alias analysis.
 547 /// BasicAA isn't willing to spend linear time determining whether an alloca
 548 /// was captured before or after this particular call, while we are. However,
 549 /// with a smarter AA in place, this test is just wasting compile time.
 550 ModRefInfo AAResults::callCapturesBefore(const Instruction *I,
 551                                          const MemoryLocation &MemLoc,
 552                                          DominatorTree *DT,
 553                                          OrderedBasicBlock *OBB) {
 554   if (!DT)
 555     return ModRefInfo::ModRef;
 556
 557   const Value *Object =
 558       GetUnderlyingObject(MemLoc.Ptr, I->getModule()->getDataLayout());
 559   if (!isIdentifiedObject(Object) || isa<GlobalValue>(Object) ||
 560       isa<Constant>(Object))
 561     return ModRefInfo::ModRef;
 562
 563   ImmutableCallSite CS(I);
 564   if (!CS.getInstruction() || CS.getInstruction() == Object)
 565     return ModRefInfo::ModRef;
 566
 567   if (PointerMayBeCapturedBefore(Object, /* ReturnCaptures */ true,
 568                                  /* StoreCaptures */ true, I, DT,
 569                                  /* include Object */ true,
 570                                  /* OrderedBasicBlock */ OBB))
 571     return ModRefInfo::ModRef;
 572
 573   unsigned ArgNo = 0;
 574   ModRefInfo R = ModRefInfo::NoModRef;
 575   bool IsMustAlias = true;
 576   // Set flag only if no May found and all operands processed.
 577   for (auto CI = CS.data_operands_begin(), CE = CS.data_operands_end();
 578        CI != CE; ++CI, ++ArgNo) {
 579     // Only look at the no-capture or byval pointer arguments.  If this
 580     // pointer were passed to arguments that were neither of these, then it
 581     // couldn't be no-capture.
 582     if (!(*CI)->getType()->isPointerTy() ||
 583         (!CS.doesNotCapture(ArgNo) &&
 584          ArgNo < CS.getNumArgOperands() && !CS.isByValArgument(ArgNo)))
 585       continue;
 586
 587     AliasResult AR = alias(MemoryLocation(*CI), MemoryLocation(Object));
 588     // If this is a no-capture pointer argument, see if we can tell that it
 589     // is impossible to alias the pointer we're checking.  If not, we have to
 590     // assume that the call could touch the pointer, even though it doesn't
 591     // escape.
 592     if (AR != MustAlias)
 593       IsMustAlias = false;
 594     if (AR == NoAlias)
 595       continue;
 596     if (CS.doesNotAccessMemory(ArgNo))
 597       continue;
 598     if (CS.onlyReadsMemory(ArgNo)) {
 599       R = ModRefInfo::Ref;
 600       continue;
 601     }
 602     // Not returning MustModRef since we have not seen all the arguments.
 603     return ModRefInfo::ModRef;
 604   }
 605   return IsMustAlias ? setMust(R) : clearMust(R);
 606 }
 607
 608 /// canBasicBlockModify - Return true if it is possible for execution of the
 609 /// specified basic block to modify the location Loc.
 610 ///
 611 bool AAResults::canBasicBlockModify(const BasicBlock &BB,
 612                                     const MemoryLocation &Loc) {
 613   return canInstructionRangeModRef(BB.front(), BB.back(), Loc, ModRefInfo::Mod);
 614 }
 615
 616 /// canInstructionRangeModRef - Return true if it is possible for the
 617 /// execution of the specified instructions to mod\ref (according to the
 618 /// mode) the location Loc. The instructions to consider are all
 619 /// of the instructions in the range of [I1,I2] INCLUSIVE.
 620 /// I1 and I2 must be in the same basic block.
 621 bool AAResults::canInstructionRangeModRef(const Instruction &I1,
 622                                           const Instruction &I2,
 623                                           const MemoryLocation &Loc,
 624                                           const ModRefInfo Mode) {
 625   assert(I1.getParent() == I2.getParent() &&
 626          "Instructions not in same basic block!");
 627   BasicBlock::const_iterator I = I1.getIterator();
 628   BasicBlock::const_iterator E = I2.getIterator();
 629   ++E;  // Convert from inclusive to exclusive range.
 630
 631   for (; I != E; ++I) // Check every instruction in range
 632     if (isModOrRefSet(intersectModRef(getModRefInfo(&*I, Loc), Mode)))
 633       return true;
 634   return false;
 635 }
 636
 637 // Provide a definition for the root virtual destructor.
 638 AAResults::Concept::~Concept() = default;
 639
 640 // Provide a definition for the static object used to identify passes.
 641 AnalysisKey AAManager::Key;
 642
 643 namespace {
 644
 645 /// A wrapper pass for external alias analyses. This just squirrels away the
 646 /// callback used to run any analyses and register their results.
 647 struct ExternalAAWrapperPass : ImmutablePass {
 648   using CallbackT = std::function<void(Pass &, Function &, AAResults &)>;
 649
 650   CallbackT CB;
 651
 652   static char ID;
 653
 654   ExternalAAWrapperPass() : ImmutablePass(ID) {
 655     initializeExternalAAWrapperPassPass(*PassRegistry::getPassRegistry());
 656   }
 657
 658   explicit ExternalAAWrapperPass(CallbackT CB)
 659       : ImmutablePass(ID), CB(std::move(CB)) {
 660     initializeExternalAAWrapperPassPass(*PassRegistry::getPassRegistry());
 661   }
 662
 663   void getAnalysisUsage(AnalysisUsage &AU) const override {
 664     AU.setPreservesAll();
 665   }
 666 };
 667
 668 } // end anonymous namespace
 669
 670 char ExternalAAWrapperPass::ID = 0;
 671
 672 INITIALIZE_PASS(ExternalAAWrapperPass, "external-aa", "External Alias Analysis",
 673                 false, true)
 674
 675 ImmutablePass *
 676 llvm::createExternalAAWrapperPass(ExternalAAWrapperPass::CallbackT Callback) {
 677   return new ExternalAAWrapperPass(std::move(Callback));
 678 }
 679
 680 AAResultsWrapperPass::AAResultsWrapperPass() : FunctionPass(ID) {
 681   initializeAAResultsWrapperPassPass(*PassRegistry::getPassRegistry());
 682 }
 683
 684 char AAResultsWrapperPass::ID = 0;
 685
 686 INITIALIZE_PASS_BEGIN(AAResultsWrapperPass, "aa",
 687                       "Function Alias Analysis Results", false, true)
 688 INITIALIZE_PASS_DEPENDENCY(BasicAAWrapperPass)
 689 INITIALIZE_PASS_DEPENDENCY(CFLAndersAAWrapperPass)
 690 INITIALIZE_PASS_DEPENDENCY(CFLSteensAAWrapperPass)
 691 INITIALIZE_PASS_DEPENDENCY(ExternalAAWrapperPass)
 692 INITIALIZE_PASS_DEPENDENCY(GlobalsAAWrapperPass)
 693 INITIALIZE_PASS_DEPENDENCY(ObjCARCAAWrapperPass)
 694 INITIALIZE_PASS_DEPENDENCY(SCEVAAWrapperPass)
 695 INITIALIZE_PASS_DEPENDENCY(ScopedNoAliasAAWrapperPass)
 696 INITIALIZE_PASS_DEPENDENCY(TypeBasedAAWrapperPass)
 697 INITIALIZE_PASS_END(AAResultsWrapperPass, "aa",
 698                     "Function Alias Analysis Results", false, true)
 699
 700 FunctionPass *llvm::createAAResultsWrapperPass() {
 701   return new AAResultsWrapperPass();
 702 }
 703
 704 /// Run the wrapper pass to rebuild an aggregation over known AA passes.
 705 ///
 706 /// This is the legacy pass manager's interface to the new-style AA results
 707 /// aggregation object. Because this is somewhat shoe-horned into the legacy
 708 /// pass manager, we hard code all the specific alias analyses available into
 709 /// it. While the particular set enabled is configured via commandline flags,
 710 /// adding a new alias analysis to LLVM will require adding support for it to
 711 /// this list.
 712 bool AAResultsWrapperPass::runOnFunction(Function &F) {
 713   // NB! This *must* be reset before adding new AA results to the new
 714   // AAResults object because in the legacy pass manager, each instance
 715   // of these will refer to the *same* immutable analyses, registering and
 716   // unregistering themselves with them. We need to carefully tear down the
 717   // previous object first, in this case replacing it with an empty one, before
 718   // registering new results.
 719   AAR.reset(
 720       new AAResults(getAnalysis<TargetLibraryInfoWrapperPass>().getTLI()));
 721
 722   // BasicAA is always available for function analyses. Also, we add it first
 723   // so that it can trump TBAA results when it proves MustAlias.
 724   // FIXME: TBAA should have an explicit mode to support this and then we
 725   // should reconsider the ordering here.
 726   if (!DisableBasicAA)
 727     AAR->addAAResult(getAnalysis<BasicAAWrapperPass>().getResult());
 728
 729   // Populate the results with the currently available AAs.
 730   if (auto *WrapperPass = getAnalysisIfAvailable<ScopedNoAliasAAWrapperPass>())
 731     AAR->addAAResult(WrapperPass->getResult());
 732   if (auto *WrapperPass = getAnalysisIfAvailable<TypeBasedAAWrapperPass>())
 733     AAR->addAAResult(WrapperPass->getResult());
 734   if (auto *WrapperPass =
 735           getAnalysisIfAvailable<objcarc::ObjCARCAAWrapperPass>())
 736     AAR->addAAResult(WrapperPass->getResult());
 737   if (auto *WrapperPass = getAnalysisIfAvailable<GlobalsAAWrapperPass>())
 738     AAR->addAAResult(WrapperPass->getResult());
 739   if (auto *WrapperPass = getAnalysisIfAvailable<SCEVAAWrapperPass>())
 740     AAR->addAAResult(WrapperPass->getResult());
 741   if (auto *WrapperPass = getAnalysisIfAvailable<CFLAndersAAWrapperPass>())
 742     AAR->addAAResult(WrapperPass->getResult());
 743   if (auto *WrapperPass = getAnalysisIfAvailable<CFLSteensAAWrapperPass>())
 744     AAR->addAAResult(WrapperPass->getResult());
 745
 746   // If available, run an external AA providing callback over the results as
 747   // well.
 748   if (auto *WrapperPass = getAnalysisIfAvailable<ExternalAAWrapperPass>())
 749     if (WrapperPass->CB)
 750       WrapperPass->CB(*this, F, *AAR);
 751
 752   // Analyses don't mutate the IR, so return false.
 753   return false;
 754 }
 755
 756 void AAResultsWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
 757   AU.setPreservesAll();
 758   AU.addRequired<BasicAAWrapperPass>();
 759   AU.addRequired<TargetLibraryInfoWrapperPass>();
 760
 761   // We also need to mark all the alias analysis passes we will potentially
 762   // probe in runOnFunction as used here to ensure the legacy pass manager
 763   // preserves them. This hard coding of lists of alias analyses is specific to
 764   // the legacy pass manager.
 765   AU.addUsedIfAvailable<ScopedNoAliasAAWrapperPass>();
 766   AU.addUsedIfAvailable<TypeBasedAAWrapperPass>();
 767   AU.addUsedIfAvailable<objcarc::ObjCARCAAWrapperPass>();
 768   AU.addUsedIfAvailable<GlobalsAAWrapperPass>();
 769   AU.addUsedIfAvailable<SCEVAAWrapperPass>();
 770   AU.addUsedIfAvailable<CFLAndersAAWrapperPass>();
 771   AU.addUsedIfAvailable<CFLSteensAAWrapperPass>();
 772 }
 773
 774 AAResults llvm::createLegacyPMAAResults(Pass &P, Function &F,
 775                                         BasicAAResult &BAR) {
 776   AAResults AAR(P.getAnalysis<TargetLibraryInfoWrapperPass>().getTLI());
 777
 778   // Add in our explicitly constructed BasicAA results.
 779   if (!DisableBasicAA)
 780     AAR.addAAResult(BAR);
 781
 782   // Populate the results with the other currently available AAs.
 783   if (auto *WrapperPass =
 784           P.getAnalysisIfAvailable<ScopedNoAliasAAWrapperPass>())
 785     AAR.addAAResult(WrapperPass->getResult());
 786   if (auto *WrapperPass = P.getAnalysisIfAvailable<TypeBasedAAWrapperPass>())
 787     AAR.addAAResult(WrapperPass->getResult());
 788   if (auto *WrapperPass =
 789           P.getAnalysisIfAvailable<objcarc::ObjCARCAAWrapperPass>())
 790     AAR.addAAResult(WrapperPass->getResult());
 791   if (auto *WrapperPass = P.getAnalysisIfAvailable<GlobalsAAWrapperPass>())
 792     AAR.addAAResult(WrapperPass->getResult());
 793   if (auto *WrapperPass = P.getAnalysisIfAvailable<CFLAndersAAWrapperPass>())
 794     AAR.addAAResult(WrapperPass->getResult());
 795   if (auto *WrapperPass = P.getAnalysisIfAvailable<CFLSteensAAWrapperPass>())
 796     AAR.addAAResult(WrapperPass->getResult());
 797
 798   return AAR;
 799 }
 800
 801 bool llvm::isNoAliasCall(const Value *V) {
 802   if (auto CS = ImmutableCallSite(V))
 803     return CS.hasRetAttr(Attribute::NoAlias);
 804   return false;
 805 }
 806
 807 bool llvm::isNoAliasArgument(const Value *V) {
 808   if (const Argument *A = dyn_cast<Argument>(V))
 809     return A->hasNoAliasAttr();
 810   return false;
 811 }
 812
 813 bool llvm::isIdentifiedObject(const Value *V) {
 814   if (isa<AllocaInst>(V))
 815     return true;
 816   if (isa<GlobalValue>(V) && !isa<GlobalAlias>(V))
 817     return true;
 818   if (isNoAliasCall(V))
 819     return true;
 820   if (const Argument *A = dyn_cast<Argument>(V))
 821     return A->hasNoAliasAttr() || A->hasByValAttr();
 822   return false;
 823 }
 824
 825 bool llvm::isIdentifiedFunctionLocal(const Value *V) {
 826   return isa<AllocaInst>(V) || isNoAliasCall(V) || isNoAliasArgument(V);
 827 }
 828
 829 void llvm::getAAResultsAnalysisUsage(AnalysisUsage &AU) {
 830   // This function needs to be in sync with llvm::createLegacyPMAAResults -- if
 831   // more alias analyses are added to llvm::createLegacyPMAAResults, they need
 832   // to be added here also.
 833   AU.addRequired<TargetLibraryInfoWrapperPass>();
 834   AU.addUsedIfAvailable<ScopedNoAliasAAWrapperPass>();
 835   AU.addUsedIfAvailable<TypeBasedAAWrapperPass>();
 836   AU.addUsedIfAvailable<objcarc::ObjCARCAAWrapperPass>();
 837   AU.addUsedIfAvailable<GlobalsAAWrapperPass>();
 838   AU.addUsedIfAvailable<CFLAndersAAWrapperPass>();
 839   AU.addUsedIfAvailable<CFLSteensAAWrapperPass>();
 840 }