AliasSetTracker.cpp revision 198892
1//===- AliasSetTracker.cpp - Alias Sets Tracker implementation-------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file implements the AliasSetTracker and AliasSet classes. 11// 12//===----------------------------------------------------------------------===// 13 14#include "llvm/Analysis/AliasSetTracker.h" 15#include "llvm/Analysis/AliasAnalysis.h" 16#include "llvm/Instructions.h" 17#include "llvm/IntrinsicInst.h" 18#include "llvm/Pass.h" 19#include "llvm/Type.h" 20#include "llvm/Target/TargetData.h" 21#include "llvm/Assembly/Writer.h" 22#include "llvm/Support/ErrorHandling.h" 23#include "llvm/Support/InstIterator.h" 24#include "llvm/Support/Format.h" 25#include "llvm/Support/raw_ostream.h" 26using namespace llvm; 27 28/// mergeSetIn - Merge the specified alias set into this alias set. 29/// 30void AliasSet::mergeSetIn(AliasSet &AS, AliasSetTracker &AST) { 31 assert(!AS.Forward && "Alias set is already forwarding!"); 32 assert(!Forward && "This set is a forwarding set!!"); 33 34 // Update the alias and access types of this set... 35 AccessTy |= AS.AccessTy; 36 AliasTy |= AS.AliasTy; 37 38 if (AliasTy == MustAlias) { 39 // Check that these two merged sets really are must aliases. Since both 40 // used to be must-alias sets, we can just check any pointer from each set 41 // for aliasing. 42 AliasAnalysis &AA = AST.getAliasAnalysis(); 43 PointerRec *L = getSomePointer(); 44 PointerRec *R = AS.getSomePointer(); 45 46 // If the pointers are not a must-alias pair, this set becomes a may alias. 47 if (AA.alias(L->getValue(), L->getSize(), R->getValue(), R->getSize()) 48 != AliasAnalysis::MustAlias) 49 AliasTy = MayAlias; 50 } 51 52 if (CallSites.empty()) { // Merge call sites... 53 if (!AS.CallSites.empty()) 54 std::swap(CallSites, AS.CallSites); 55 } else if (!AS.CallSites.empty()) { 56 CallSites.insert(CallSites.end(), AS.CallSites.begin(), AS.CallSites.end()); 57 AS.CallSites.clear(); 58 } 59 60 AS.Forward = this; // Forward across AS now... 61 addRef(); // AS is now pointing to us... 62 63 // Merge the list of constituent pointers... 64 if (AS.PtrList) { 65 *PtrListEnd = AS.PtrList; 66 AS.PtrList->setPrevInList(PtrListEnd); 67 PtrListEnd = AS.PtrListEnd; 68 69 AS.PtrList = 0; 70 AS.PtrListEnd = &AS.PtrList; 71 assert(*AS.PtrListEnd == 0 && "End of list is not null?"); 72 } 73} 74 75void AliasSetTracker::removeAliasSet(AliasSet *AS) { 76 if (AliasSet *Fwd = AS->Forward) { 77 Fwd->dropRef(*this); 78 AS->Forward = 0; 79 } 80 AliasSets.erase(AS); 81} 82 83void AliasSet::removeFromTracker(AliasSetTracker &AST) { 84 assert(RefCount == 0 && "Cannot remove non-dead alias set from tracker!"); 85 AST.removeAliasSet(this); 86} 87 88void AliasSet::addPointer(AliasSetTracker &AST, PointerRec &Entry, 89 unsigned Size, bool KnownMustAlias) { 90 assert(!Entry.hasAliasSet() && "Entry already in set!"); 91 92 // Check to see if we have to downgrade to _may_ alias. 93 if (isMustAlias() && !KnownMustAlias) 94 if (PointerRec *P = getSomePointer()) { 95 AliasAnalysis &AA = AST.getAliasAnalysis(); 96 AliasAnalysis::AliasResult Result = 97 AA.alias(P->getValue(), P->getSize(), Entry.getValue(), Size); 98 if (Result == AliasAnalysis::MayAlias) 99 AliasTy = MayAlias; 100 else // First entry of must alias must have maximum size! 101 P->updateSize(Size); 102 assert(Result != AliasAnalysis::NoAlias && "Cannot be part of must set!"); 103 } 104 105 Entry.setAliasSet(this); 106 Entry.updateSize(Size); 107 108 // Add it to the end of the list... 109 assert(*PtrListEnd == 0 && "End of list is not null?"); 110 *PtrListEnd = &Entry; 111 PtrListEnd = Entry.setPrevInList(PtrListEnd); 112 assert(*PtrListEnd == 0 && "End of list is not null?"); 113 addRef(); // Entry points to alias set... 114} 115 116void AliasSet::addCallSite(CallSite CS, AliasAnalysis &AA) { 117 CallSites.push_back(CS); 118 119 AliasAnalysis::ModRefBehavior Behavior = AA.getModRefBehavior(CS); 120 if (Behavior == AliasAnalysis::DoesNotAccessMemory) 121 return; 122 else if (Behavior == AliasAnalysis::OnlyReadsMemory) { 123 AliasTy = MayAlias; 124 AccessTy |= Refs; 125 return; 126 } 127 128 // FIXME: This should use mod/ref information to make this not suck so bad 129 AliasTy = MayAlias; 130 AccessTy = ModRef; 131} 132 133/// aliasesPointer - Return true if the specified pointer "may" (or must) 134/// alias one of the members in the set. 135/// 136bool AliasSet::aliasesPointer(const Value *Ptr, unsigned Size, 137 AliasAnalysis &AA) const { 138 if (AliasTy == MustAlias) { 139 assert(CallSites.empty() && "Illegal must alias set!"); 140 141 // If this is a set of MustAliases, only check to see if the pointer aliases 142 // SOME value in the set... 143 PointerRec *SomePtr = getSomePointer(); 144 assert(SomePtr && "Empty must-alias set??"); 145 return AA.alias(SomePtr->getValue(), SomePtr->getSize(), Ptr, Size); 146 } 147 148 // If this is a may-alias set, we have to check all of the pointers in the set 149 // to be sure it doesn't alias the set... 150 for (iterator I = begin(), E = end(); I != E; ++I) 151 if (AA.alias(Ptr, Size, I.getPointer(), I.getSize())) 152 return true; 153 154 // Check the call sites list and invoke list... 155 if (!CallSites.empty()) { 156 if (AA.hasNoModRefInfoForCalls()) 157 return true; 158 159 for (unsigned i = 0, e = CallSites.size(); i != e; ++i) 160 if (AA.getModRefInfo(CallSites[i], const_cast<Value*>(Ptr), Size) 161 != AliasAnalysis::NoModRef) 162 return true; 163 } 164 165 return false; 166} 167 168bool AliasSet::aliasesCallSite(CallSite CS, AliasAnalysis &AA) const { 169 if (AA.doesNotAccessMemory(CS)) 170 return false; 171 172 if (AA.hasNoModRefInfoForCalls()) 173 return true; 174 175 for (unsigned i = 0, e = CallSites.size(); i != e; ++i) 176 if (AA.getModRefInfo(CallSites[i], CS) != AliasAnalysis::NoModRef || 177 AA.getModRefInfo(CS, CallSites[i]) != AliasAnalysis::NoModRef) 178 return true; 179 180 for (iterator I = begin(), E = end(); I != E; ++I) 181 if (AA.getModRefInfo(CS, I.getPointer(), I.getSize()) != 182 AliasAnalysis::NoModRef) 183 return true; 184 185 return false; 186} 187 188void AliasSetTracker::clear() { 189 // Delete all the PointerRec entries. 190 for (PointerMapType::iterator I = PointerMap.begin(), E = PointerMap.end(); 191 I != E; ++I) 192 I->second->eraseFromList(); 193 194 PointerMap.clear(); 195 196 // The alias sets should all be clear now. 197 AliasSets.clear(); 198} 199 200 201/// findAliasSetForPointer - Given a pointer, find the one alias set to put the 202/// instruction referring to the pointer into. If there are multiple alias sets 203/// that may alias the pointer, merge them together and return the unified set. 204/// 205AliasSet *AliasSetTracker::findAliasSetForPointer(const Value *Ptr, 206 unsigned Size) { 207 AliasSet *FoundSet = 0; 208 for (iterator I = begin(), E = end(); I != E; ++I) 209 if (!I->Forward && I->aliasesPointer(Ptr, Size, AA)) { 210 if (FoundSet == 0) { // If this is the first alias set ptr can go into. 211 FoundSet = I; // Remember it. 212 } else { // Otherwise, we must merge the sets. 213 FoundSet->mergeSetIn(*I, *this); // Merge in contents. 214 } 215 } 216 217 return FoundSet; 218} 219 220/// containsPointer - Return true if the specified location is represented by 221/// this alias set, false otherwise. This does not modify the AST object or 222/// alias sets. 223bool AliasSetTracker::containsPointer(Value *Ptr, unsigned Size) const { 224 for (const_iterator I = begin(), E = end(); I != E; ++I) 225 if (!I->Forward && I->aliasesPointer(Ptr, Size, AA)) 226 return true; 227 return false; 228} 229 230 231 232AliasSet *AliasSetTracker::findAliasSetForCallSite(CallSite CS) { 233 AliasSet *FoundSet = 0; 234 for (iterator I = begin(), E = end(); I != E; ++I) 235 if (!I->Forward && I->aliasesCallSite(CS, AA)) { 236 if (FoundSet == 0) { // If this is the first alias set ptr can go into. 237 FoundSet = I; // Remember it. 238 } else if (!I->Forward) { // Otherwise, we must merge the sets. 239 FoundSet->mergeSetIn(*I, *this); // Merge in contents. 240 } 241 } 242 243 return FoundSet; 244} 245 246 247 248 249/// getAliasSetForPointer - Return the alias set that the specified pointer 250/// lives in. 251AliasSet &AliasSetTracker::getAliasSetForPointer(Value *Pointer, unsigned Size, 252 bool *New) { 253 AliasSet::PointerRec &Entry = getEntryFor(Pointer); 254 255 // Check to see if the pointer is already known... 256 if (Entry.hasAliasSet()) { 257 Entry.updateSize(Size); 258 // Return the set! 259 return *Entry.getAliasSet(*this)->getForwardedTarget(*this); 260 } else if (AliasSet *AS = findAliasSetForPointer(Pointer, Size)) { 261 // Add it to the alias set it aliases... 262 AS->addPointer(*this, Entry, Size); 263 return *AS; 264 } else { 265 if (New) *New = true; 266 // Otherwise create a new alias set to hold the loaded pointer... 267 AliasSets.push_back(new AliasSet()); 268 AliasSets.back().addPointer(*this, Entry, Size); 269 return AliasSets.back(); 270 } 271} 272 273bool AliasSetTracker::add(Value *Ptr, unsigned Size) { 274 bool NewPtr; 275 addPointer(Ptr, Size, AliasSet::NoModRef, NewPtr); 276 return NewPtr; 277} 278 279 280bool AliasSetTracker::add(LoadInst *LI) { 281 bool NewPtr; 282 AliasSet &AS = addPointer(LI->getOperand(0), 283 AA.getTypeStoreSize(LI->getType()), 284 AliasSet::Refs, NewPtr); 285 if (LI->isVolatile()) AS.setVolatile(); 286 return NewPtr; 287} 288 289bool AliasSetTracker::add(StoreInst *SI) { 290 bool NewPtr; 291 Value *Val = SI->getOperand(0); 292 AliasSet &AS = addPointer(SI->getOperand(1), 293 AA.getTypeStoreSize(Val->getType()), 294 AliasSet::Mods, NewPtr); 295 if (SI->isVolatile()) AS.setVolatile(); 296 return NewPtr; 297} 298 299bool AliasSetTracker::add(VAArgInst *VAAI) { 300 bool NewPtr; 301 addPointer(VAAI->getOperand(0), ~0, AliasSet::ModRef, NewPtr); 302 return NewPtr; 303} 304 305 306bool AliasSetTracker::add(CallSite CS) { 307 if (isa<DbgInfoIntrinsic>(CS.getInstruction())) 308 return true; // Ignore DbgInfo Intrinsics. 309 if (AA.doesNotAccessMemory(CS)) 310 return true; // doesn't alias anything 311 312 AliasSet *AS = findAliasSetForCallSite(CS); 313 if (!AS) { 314 AliasSets.push_back(new AliasSet()); 315 AS = &AliasSets.back(); 316 AS->addCallSite(CS, AA); 317 return true; 318 } else { 319 AS->addCallSite(CS, AA); 320 return false; 321 } 322} 323 324bool AliasSetTracker::add(Instruction *I) { 325 // Dispatch to one of the other add methods... 326 if (LoadInst *LI = dyn_cast<LoadInst>(I)) 327 return add(LI); 328 else if (StoreInst *SI = dyn_cast<StoreInst>(I)) 329 return add(SI); 330 else if (CallInst *CI = dyn_cast<CallInst>(I)) 331 return add(CI); 332 else if (InvokeInst *II = dyn_cast<InvokeInst>(I)) 333 return add(II); 334 else if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I)) 335 return add(VAAI); 336 return true; 337} 338 339void AliasSetTracker::add(BasicBlock &BB) { 340 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) 341 add(I); 342} 343 344void AliasSetTracker::add(const AliasSetTracker &AST) { 345 assert(&AA == &AST.AA && 346 "Merging AliasSetTracker objects with different Alias Analyses!"); 347 348 // Loop over all of the alias sets in AST, adding the pointers contained 349 // therein into the current alias sets. This can cause alias sets to be 350 // merged together in the current AST. 351 for (const_iterator I = AST.begin(), E = AST.end(); I != E; ++I) 352 if (!I->Forward) { // Ignore forwarding alias sets 353 AliasSet &AS = const_cast<AliasSet&>(*I); 354 355 // If there are any call sites in the alias set, add them to this AST. 356 for (unsigned i = 0, e = AS.CallSites.size(); i != e; ++i) 357 add(AS.CallSites[i]); 358 359 // Loop over all of the pointers in this alias set... 360 AliasSet::iterator I = AS.begin(), E = AS.end(); 361 bool X; 362 for (; I != E; ++I) { 363 AliasSet &NewAS = addPointer(I.getPointer(), I.getSize(), 364 (AliasSet::AccessType)AS.AccessTy, X); 365 if (AS.isVolatile()) NewAS.setVolatile(); 366 } 367 } 368} 369 370/// remove - Remove the specified (potentially non-empty) alias set from the 371/// tracker. 372void AliasSetTracker::remove(AliasSet &AS) { 373 // Drop all call sites. 374 AS.CallSites.clear(); 375 376 // Clear the alias set. 377 unsigned NumRefs = 0; 378 while (!AS.empty()) { 379 AliasSet::PointerRec *P = AS.PtrList; 380 381 Value *ValToRemove = P->getValue(); 382 383 // Unlink and delete entry from the list of values. 384 P->eraseFromList(); 385 386 // Remember how many references need to be dropped. 387 ++NumRefs; 388 389 // Finally, remove the entry. 390 PointerMap.erase(ValToRemove); 391 } 392 393 // Stop using the alias set, removing it. 394 AS.RefCount -= NumRefs; 395 if (AS.RefCount == 0) 396 AS.removeFromTracker(*this); 397} 398 399bool AliasSetTracker::remove(Value *Ptr, unsigned Size) { 400 AliasSet *AS = findAliasSetForPointer(Ptr, Size); 401 if (!AS) return false; 402 remove(*AS); 403 return true; 404} 405 406bool AliasSetTracker::remove(LoadInst *LI) { 407 unsigned Size = AA.getTypeStoreSize(LI->getType()); 408 AliasSet *AS = findAliasSetForPointer(LI->getOperand(0), Size); 409 if (!AS) return false; 410 remove(*AS); 411 return true; 412} 413 414bool AliasSetTracker::remove(StoreInst *SI) { 415 unsigned Size = AA.getTypeStoreSize(SI->getOperand(0)->getType()); 416 AliasSet *AS = findAliasSetForPointer(SI->getOperand(1), Size); 417 if (!AS) return false; 418 remove(*AS); 419 return true; 420} 421 422bool AliasSetTracker::remove(VAArgInst *VAAI) { 423 AliasSet *AS = findAliasSetForPointer(VAAI->getOperand(0), ~0); 424 if (!AS) return false; 425 remove(*AS); 426 return true; 427} 428 429bool AliasSetTracker::remove(CallSite CS) { 430 if (AA.doesNotAccessMemory(CS)) 431 return false; // doesn't alias anything 432 433 AliasSet *AS = findAliasSetForCallSite(CS); 434 if (!AS) return false; 435 remove(*AS); 436 return true; 437} 438 439bool AliasSetTracker::remove(Instruction *I) { 440 // Dispatch to one of the other remove methods... 441 if (LoadInst *LI = dyn_cast<LoadInst>(I)) 442 return remove(LI); 443 else if (StoreInst *SI = dyn_cast<StoreInst>(I)) 444 return remove(SI); 445 else if (CallInst *CI = dyn_cast<CallInst>(I)) 446 return remove(CI); 447 else if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I)) 448 return remove(VAAI); 449 return true; 450} 451 452 453// deleteValue method - This method is used to remove a pointer value from the 454// AliasSetTracker entirely. It should be used when an instruction is deleted 455// from the program to update the AST. If you don't use this, you would have 456// dangling pointers to deleted instructions. 457// 458void AliasSetTracker::deleteValue(Value *PtrVal) { 459 // Notify the alias analysis implementation that this value is gone. 460 AA.deleteValue(PtrVal); 461 462 // If this is a call instruction, remove the callsite from the appropriate 463 // AliasSet. 464 CallSite CS = CallSite::get(PtrVal); 465 if (CS.getInstruction()) 466 if (!AA.doesNotAccessMemory(CS)) 467 if (AliasSet *AS = findAliasSetForCallSite(CS)) 468 AS->removeCallSite(CS); 469 470 // First, look up the PointerRec for this pointer. 471 PointerMapType::iterator I = PointerMap.find(PtrVal); 472 if (I == PointerMap.end()) return; // Noop 473 474 // If we found one, remove the pointer from the alias set it is in. 475 AliasSet::PointerRec *PtrValEnt = I->second; 476 AliasSet *AS = PtrValEnt->getAliasSet(*this); 477 478 // Unlink and delete from the list of values. 479 PtrValEnt->eraseFromList(); 480 481 // Stop using the alias set. 482 AS->dropRef(*this); 483 484 PointerMap.erase(I); 485} 486 487// copyValue - This method should be used whenever a preexisting value in the 488// program is copied or cloned, introducing a new value. Note that it is ok for 489// clients that use this method to introduce the same value multiple times: if 490// the tracker already knows about a value, it will ignore the request. 491// 492void AliasSetTracker::copyValue(Value *From, Value *To) { 493 // Notify the alias analysis implementation that this value is copied. 494 AA.copyValue(From, To); 495 496 // First, look up the PointerRec for this pointer. 497 PointerMapType::iterator I = PointerMap.find(From); 498 if (I == PointerMap.end()) 499 return; // Noop 500 assert(I->second->hasAliasSet() && "Dead entry?"); 501 502 AliasSet::PointerRec &Entry = getEntryFor(To); 503 if (Entry.hasAliasSet()) return; // Already in the tracker! 504 505 // Add it to the alias set it aliases... 506 I = PointerMap.find(From); 507 AliasSet *AS = I->second->getAliasSet(*this); 508 AS->addPointer(*this, Entry, I->second->getSize(), true); 509} 510 511 512 513//===----------------------------------------------------------------------===// 514// AliasSet/AliasSetTracker Printing Support 515//===----------------------------------------------------------------------===// 516 517void AliasSet::print(raw_ostream &OS) const { 518 OS << " AliasSet[" << format("0x%p", (void*)this) << "," << RefCount << "] "; 519 OS << (AliasTy == MustAlias ? "must" : "may") << " alias, "; 520 switch (AccessTy) { 521 case NoModRef: OS << "No access "; break; 522 case Refs : OS << "Ref "; break; 523 case Mods : OS << "Mod "; break; 524 case ModRef : OS << "Mod/Ref "; break; 525 default: llvm_unreachable("Bad value for AccessTy!"); 526 } 527 if (isVolatile()) OS << "[volatile] "; 528 if (Forward) 529 OS << " forwarding to " << (void*)Forward; 530 531 532 if (!empty()) { 533 OS << "Pointers: "; 534 for (iterator I = begin(), E = end(); I != E; ++I) { 535 if (I != begin()) OS << ", "; 536 WriteAsOperand(OS << "(", I.getPointer()); 537 OS << ", " << I.getSize() << ")"; 538 } 539 } 540 if (!CallSites.empty()) { 541 OS << "\n " << CallSites.size() << " Call Sites: "; 542 for (unsigned i = 0, e = CallSites.size(); i != e; ++i) { 543 if (i) OS << ", "; 544 WriteAsOperand(OS, CallSites[i].getCalledValue()); 545 } 546 } 547 OS << "\n"; 548} 549 550void AliasSetTracker::print(raw_ostream &OS) const { 551 OS << "Alias Set Tracker: " << AliasSets.size() << " alias sets for " 552 << PointerMap.size() << " pointer values.\n"; 553 for (const_iterator I = begin(), E = end(); I != E; ++I) 554 I->print(OS); 555 OS << "\n"; 556} 557 558void AliasSet::dump() const { print(errs()); } 559void AliasSetTracker::dump() const { print(errs()); } 560 561//===----------------------------------------------------------------------===// 562// ASTCallbackVH Class Implementation 563//===----------------------------------------------------------------------===// 564 565void AliasSetTracker::ASTCallbackVH::deleted() { 566 assert(AST && "ASTCallbackVH called with a null AliasSetTracker!"); 567 AST->deleteValue(getValPtr()); 568 // this now dangles! 569} 570 571AliasSetTracker::ASTCallbackVH::ASTCallbackVH(Value *V, AliasSetTracker *ast) 572 : CallbackVH(V), AST(ast) {} 573 574AliasSetTracker::ASTCallbackVH & 575AliasSetTracker::ASTCallbackVH::operator=(Value *V) { 576 return *this = ASTCallbackVH(V, AST); 577} 578 579//===----------------------------------------------------------------------===// 580// AliasSetPrinter Pass 581//===----------------------------------------------------------------------===// 582 583namespace { 584 class AliasSetPrinter : public FunctionPass { 585 AliasSetTracker *Tracker; 586 public: 587 static char ID; // Pass identification, replacement for typeid 588 AliasSetPrinter() : FunctionPass(&ID) {} 589 590 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 591 AU.setPreservesAll(); 592 AU.addRequired<AliasAnalysis>(); 593 } 594 595 virtual bool runOnFunction(Function &F) { 596 Tracker = new AliasSetTracker(getAnalysis<AliasAnalysis>()); 597 598 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) 599 Tracker->add(&*I); 600 Tracker->print(errs()); 601 delete Tracker; 602 return false; 603 } 604 }; 605} 606 607char AliasSetPrinter::ID = 0; 608static RegisterPass<AliasSetPrinter> 609X("print-alias-sets", "Alias Set Printer", false, true); 610