AliasSetTracker.cpp revision 193323
1//===- AliasSetTracker.cpp - Alias Sets Tracker implementation-------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file implements the AliasSetTracker and AliasSet classes. 11// 12//===----------------------------------------------------------------------===// 13 14#include "llvm/Analysis/AliasSetTracker.h" 15#include "llvm/Analysis/AliasAnalysis.h" 16#include "llvm/Instructions.h" 17#include "llvm/IntrinsicInst.h" 18#include "llvm/Pass.h" 19#include "llvm/Type.h" 20#include "llvm/Target/TargetData.h" 21#include "llvm/Assembly/Writer.h" 22#include "llvm/Support/Compiler.h" 23#include "llvm/Support/InstIterator.h" 24#include "llvm/Support/Streams.h" 25using namespace llvm; 26 27/// mergeSetIn - Merge the specified alias set into this alias set. 28/// 29void AliasSet::mergeSetIn(AliasSet &AS, AliasSetTracker &AST) { 30 assert(!AS.Forward && "Alias set is already forwarding!"); 31 assert(!Forward && "This set is a forwarding set!!"); 32 33 // Update the alias and access types of this set... 34 AccessTy |= AS.AccessTy; 35 AliasTy |= AS.AliasTy; 36 37 if (AliasTy == MustAlias) { 38 // Check that these two merged sets really are must aliases. Since both 39 // used to be must-alias sets, we can just check any pointer from each set 40 // for aliasing. 41 AliasAnalysis &AA = AST.getAliasAnalysis(); 42 PointerRec *L = getSomePointer(); 43 PointerRec *R = AS.getSomePointer(); 44 45 // If the pointers are not a must-alias pair, this set becomes a may alias. 46 if (AA.alias(L->getValue(), L->getSize(), R->getValue(), R->getSize()) 47 != AliasAnalysis::MustAlias) 48 AliasTy = MayAlias; 49 } 50 51 if (CallSites.empty()) { // Merge call sites... 52 if (!AS.CallSites.empty()) 53 std::swap(CallSites, AS.CallSites); 54 } else if (!AS.CallSites.empty()) { 55 CallSites.insert(CallSites.end(), AS.CallSites.begin(), AS.CallSites.end()); 56 AS.CallSites.clear(); 57 } 58 59 AS.Forward = this; // Forward across AS now... 60 addRef(); // AS is now pointing to us... 61 62 // Merge the list of constituent pointers... 63 if (AS.PtrList) { 64 *PtrListEnd = AS.PtrList; 65 AS.PtrList->setPrevInList(PtrListEnd); 66 PtrListEnd = AS.PtrListEnd; 67 68 AS.PtrList = 0; 69 AS.PtrListEnd = &AS.PtrList; 70 assert(*AS.PtrListEnd == 0 && "End of list is not null?"); 71 } 72} 73 74void AliasSetTracker::removeAliasSet(AliasSet *AS) { 75 if (AliasSet *Fwd = AS->Forward) { 76 Fwd->dropRef(*this); 77 AS->Forward = 0; 78 } 79 AliasSets.erase(AS); 80} 81 82void AliasSet::removeFromTracker(AliasSetTracker &AST) { 83 assert(RefCount == 0 && "Cannot remove non-dead alias set from tracker!"); 84 AST.removeAliasSet(this); 85} 86 87void AliasSet::addPointer(AliasSetTracker &AST, PointerRec &Entry, 88 unsigned Size, bool KnownMustAlias) { 89 assert(!Entry.hasAliasSet() && "Entry already in set!"); 90 91 // Check to see if we have to downgrade to _may_ alias. 92 if (isMustAlias() && !KnownMustAlias) 93 if (PointerRec *P = getSomePointer()) { 94 AliasAnalysis &AA = AST.getAliasAnalysis(); 95 AliasAnalysis::AliasResult Result = 96 AA.alias(P->getValue(), P->getSize(), Entry.getValue(), Size); 97 if (Result == AliasAnalysis::MayAlias) 98 AliasTy = MayAlias; 99 else // First entry of must alias must have maximum size! 100 P->updateSize(Size); 101 assert(Result != AliasAnalysis::NoAlias && "Cannot be part of must set!"); 102 } 103 104 Entry.setAliasSet(this); 105 Entry.updateSize(Size); 106 107 // Add it to the end of the list... 108 assert(*PtrListEnd == 0 && "End of list is not null?"); 109 *PtrListEnd = &Entry; 110 PtrListEnd = Entry.setPrevInList(PtrListEnd); 111 assert(*PtrListEnd == 0 && "End of list is not null?"); 112 addRef(); // Entry points to alias set... 113} 114 115void AliasSet::addCallSite(CallSite CS, AliasAnalysis &AA) { 116 CallSites.push_back(CS); 117 118 AliasAnalysis::ModRefBehavior Behavior = AA.getModRefBehavior(CS); 119 if (Behavior == AliasAnalysis::DoesNotAccessMemory) 120 return; 121 else if (Behavior == AliasAnalysis::OnlyReadsMemory) { 122 AliasTy = MayAlias; 123 AccessTy |= Refs; 124 return; 125 } 126 127 // FIXME: This should use mod/ref information to make this not suck so bad 128 AliasTy = MayAlias; 129 AccessTy = ModRef; 130} 131 132/// aliasesPointer - Return true if the specified pointer "may" (or must) 133/// alias one of the members in the set. 134/// 135bool AliasSet::aliasesPointer(const Value *Ptr, unsigned Size, 136 AliasAnalysis &AA) const { 137 if (AliasTy == MustAlias) { 138 assert(CallSites.empty() && "Illegal must alias set!"); 139 140 // If this is a set of MustAliases, only check to see if the pointer aliases 141 // SOME value in the set... 142 PointerRec *SomePtr = getSomePointer(); 143 assert(SomePtr && "Empty must-alias set??"); 144 return AA.alias(SomePtr->getValue(), SomePtr->getSize(), Ptr, Size); 145 } 146 147 // If this is a may-alias set, we have to check all of the pointers in the set 148 // to be sure it doesn't alias the set... 149 for (iterator I = begin(), E = end(); I != E; ++I) 150 if (AA.alias(Ptr, Size, I.getPointer(), I.getSize())) 151 return true; 152 153 // Check the call sites list and invoke list... 154 if (!CallSites.empty()) { 155 if (AA.hasNoModRefInfoForCalls()) 156 return true; 157 158 for (unsigned i = 0, e = CallSites.size(); i != e; ++i) 159 if (AA.getModRefInfo(CallSites[i], const_cast<Value*>(Ptr), Size) 160 != AliasAnalysis::NoModRef) 161 return true; 162 } 163 164 return false; 165} 166 167bool AliasSet::aliasesCallSite(CallSite CS, AliasAnalysis &AA) const { 168 if (AA.doesNotAccessMemory(CS)) 169 return false; 170 171 if (AA.hasNoModRefInfoForCalls()) 172 return true; 173 174 for (unsigned i = 0, e = CallSites.size(); i != e; ++i) 175 if (AA.getModRefInfo(CallSites[i], CS) != AliasAnalysis::NoModRef || 176 AA.getModRefInfo(CS, CallSites[i]) != AliasAnalysis::NoModRef) 177 return true; 178 179 for (iterator I = begin(), E = end(); I != E; ++I) 180 if (AA.getModRefInfo(CS, I.getPointer(), I.getSize()) != 181 AliasAnalysis::NoModRef) 182 return true; 183 184 return false; 185} 186 187void AliasSetTracker::clear() { 188 // Delete all the PointerRec entries. 189 for (DenseMap<Value*, AliasSet::PointerRec*>::iterator I = PointerMap.begin(), 190 E = PointerMap.end(); I != E; ++I) 191 I->second->eraseFromList(); 192 193 PointerMap.clear(); 194 195 // The alias sets should all be clear now. 196 AliasSets.clear(); 197} 198 199 200/// findAliasSetForPointer - Given a pointer, find the one alias set to put the 201/// instruction referring to the pointer into. If there are multiple alias sets 202/// that may alias the pointer, merge them together and return the unified set. 203/// 204AliasSet *AliasSetTracker::findAliasSetForPointer(const Value *Ptr, 205 unsigned Size) { 206 AliasSet *FoundSet = 0; 207 for (iterator I = begin(), E = end(); I != E; ++I) 208 if (!I->Forward && I->aliasesPointer(Ptr, Size, AA)) { 209 if (FoundSet == 0) { // If this is the first alias set ptr can go into. 210 FoundSet = I; // Remember it. 211 } else { // Otherwise, we must merge the sets. 212 FoundSet->mergeSetIn(*I, *this); // Merge in contents. 213 } 214 } 215 216 return FoundSet; 217} 218 219/// containsPointer - Return true if the specified location is represented by 220/// this alias set, false otherwise. This does not modify the AST object or 221/// alias sets. 222bool AliasSetTracker::containsPointer(Value *Ptr, unsigned Size) const { 223 for (const_iterator I = begin(), E = end(); I != E; ++I) 224 if (!I->Forward && I->aliasesPointer(Ptr, Size, AA)) 225 return true; 226 return false; 227} 228 229 230 231AliasSet *AliasSetTracker::findAliasSetForCallSite(CallSite CS) { 232 AliasSet *FoundSet = 0; 233 for (iterator I = begin(), E = end(); I != E; ++I) 234 if (!I->Forward && I->aliasesCallSite(CS, AA)) { 235 if (FoundSet == 0) { // If this is the first alias set ptr can go into. 236 FoundSet = I; // Remember it. 237 } else if (!I->Forward) { // Otherwise, we must merge the sets. 238 FoundSet->mergeSetIn(*I, *this); // Merge in contents. 239 } 240 } 241 242 return FoundSet; 243} 244 245 246 247 248/// getAliasSetForPointer - Return the alias set that the specified pointer 249/// lives in. 250AliasSet &AliasSetTracker::getAliasSetForPointer(Value *Pointer, unsigned Size, 251 bool *New) { 252 AliasSet::PointerRec &Entry = getEntryFor(Pointer); 253 254 // Check to see if the pointer is already known... 255 if (Entry.hasAliasSet()) { 256 Entry.updateSize(Size); 257 // Return the set! 258 return *Entry.getAliasSet(*this)->getForwardedTarget(*this); 259 } else if (AliasSet *AS = findAliasSetForPointer(Pointer, Size)) { 260 // Add it to the alias set it aliases... 261 AS->addPointer(*this, Entry, Size); 262 return *AS; 263 } else { 264 if (New) *New = true; 265 // Otherwise create a new alias set to hold the loaded pointer... 266 AliasSets.push_back(new AliasSet()); 267 AliasSets.back().addPointer(*this, Entry, Size); 268 return AliasSets.back(); 269 } 270} 271 272bool AliasSetTracker::add(Value *Ptr, unsigned Size) { 273 bool NewPtr; 274 addPointer(Ptr, Size, AliasSet::NoModRef, NewPtr); 275 return NewPtr; 276} 277 278 279bool AliasSetTracker::add(LoadInst *LI) { 280 bool NewPtr; 281 AliasSet &AS = addPointer(LI->getOperand(0), 282 AA.getTargetData().getTypeStoreSize(LI->getType()), 283 AliasSet::Refs, NewPtr); 284 if (LI->isVolatile()) AS.setVolatile(); 285 return NewPtr; 286} 287 288bool AliasSetTracker::add(StoreInst *SI) { 289 bool NewPtr; 290 Value *Val = SI->getOperand(0); 291 AliasSet &AS = addPointer(SI->getOperand(1), 292 AA.getTargetData().getTypeStoreSize(Val->getType()), 293 AliasSet::Mods, NewPtr); 294 if (SI->isVolatile()) AS.setVolatile(); 295 return NewPtr; 296} 297 298bool AliasSetTracker::add(FreeInst *FI) { 299 bool NewPtr; 300 addPointer(FI->getOperand(0), ~0, AliasSet::Mods, NewPtr); 301 return NewPtr; 302} 303 304bool AliasSetTracker::add(VAArgInst *VAAI) { 305 bool NewPtr; 306 addPointer(VAAI->getOperand(0), ~0, AliasSet::ModRef, NewPtr); 307 return NewPtr; 308} 309 310 311bool AliasSetTracker::add(CallSite CS) { 312 if (isa<DbgInfoIntrinsic>(CS.getInstruction())) 313 return true; // Ignore DbgInfo Intrinsics. 314 if (AA.doesNotAccessMemory(CS)) 315 return true; // doesn't alias anything 316 317 AliasSet *AS = findAliasSetForCallSite(CS); 318 if (!AS) { 319 AliasSets.push_back(new AliasSet()); 320 AS = &AliasSets.back(); 321 AS->addCallSite(CS, AA); 322 return true; 323 } else { 324 AS->addCallSite(CS, AA); 325 return false; 326 } 327} 328 329bool AliasSetTracker::add(Instruction *I) { 330 // Dispatch to one of the other add methods... 331 if (LoadInst *LI = dyn_cast<LoadInst>(I)) 332 return add(LI); 333 else if (StoreInst *SI = dyn_cast<StoreInst>(I)) 334 return add(SI); 335 else if (CallInst *CI = dyn_cast<CallInst>(I)) 336 return add(CI); 337 else if (InvokeInst *II = dyn_cast<InvokeInst>(I)) 338 return add(II); 339 else if (FreeInst *FI = dyn_cast<FreeInst>(I)) 340 return add(FI); 341 else if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I)) 342 return add(VAAI); 343 return true; 344} 345 346void AliasSetTracker::add(BasicBlock &BB) { 347 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) 348 add(I); 349} 350 351void AliasSetTracker::add(const AliasSetTracker &AST) { 352 assert(&AA == &AST.AA && 353 "Merging AliasSetTracker objects with different Alias Analyses!"); 354 355 // Loop over all of the alias sets in AST, adding the pointers contained 356 // therein into the current alias sets. This can cause alias sets to be 357 // merged together in the current AST. 358 for (const_iterator I = AST.begin(), E = AST.end(); I != E; ++I) 359 if (!I->Forward) { // Ignore forwarding alias sets 360 AliasSet &AS = const_cast<AliasSet&>(*I); 361 362 // If there are any call sites in the alias set, add them to this AST. 363 for (unsigned i = 0, e = AS.CallSites.size(); i != e; ++i) 364 add(AS.CallSites[i]); 365 366 // Loop over all of the pointers in this alias set... 367 AliasSet::iterator I = AS.begin(), E = AS.end(); 368 bool X; 369 for (; I != E; ++I) { 370 AliasSet &NewAS = addPointer(I.getPointer(), I.getSize(), 371 (AliasSet::AccessType)AS.AccessTy, X); 372 if (AS.isVolatile()) NewAS.setVolatile(); 373 } 374 } 375} 376 377/// remove - Remove the specified (potentially non-empty) alias set from the 378/// tracker. 379void AliasSetTracker::remove(AliasSet &AS) { 380 // Drop all call sites. 381 AS.CallSites.clear(); 382 383 // Clear the alias set. 384 unsigned NumRefs = 0; 385 while (!AS.empty()) { 386 AliasSet::PointerRec *P = AS.PtrList; 387 388 Value *ValToRemove = P->getValue(); 389 390 // Unlink and delete entry from the list of values. 391 P->eraseFromList(); 392 393 // Remember how many references need to be dropped. 394 ++NumRefs; 395 396 // Finally, remove the entry. 397 PointerMap.erase(ValToRemove); 398 } 399 400 // Stop using the alias set, removing it. 401 AS.RefCount -= NumRefs; 402 if (AS.RefCount == 0) 403 AS.removeFromTracker(*this); 404} 405 406bool AliasSetTracker::remove(Value *Ptr, unsigned Size) { 407 AliasSet *AS = findAliasSetForPointer(Ptr, Size); 408 if (!AS) return false; 409 remove(*AS); 410 return true; 411} 412 413bool AliasSetTracker::remove(LoadInst *LI) { 414 unsigned Size = AA.getTargetData().getTypeStoreSize(LI->getType()); 415 AliasSet *AS = findAliasSetForPointer(LI->getOperand(0), Size); 416 if (!AS) return false; 417 remove(*AS); 418 return true; 419} 420 421bool AliasSetTracker::remove(StoreInst *SI) { 422 unsigned Size = 423 AA.getTargetData().getTypeStoreSize(SI->getOperand(0)->getType()); 424 AliasSet *AS = findAliasSetForPointer(SI->getOperand(1), Size); 425 if (!AS) return false; 426 remove(*AS); 427 return true; 428} 429 430bool AliasSetTracker::remove(FreeInst *FI) { 431 AliasSet *AS = findAliasSetForPointer(FI->getOperand(0), ~0); 432 if (!AS) return false; 433 remove(*AS); 434 return true; 435} 436 437bool AliasSetTracker::remove(VAArgInst *VAAI) { 438 AliasSet *AS = findAliasSetForPointer(VAAI->getOperand(0), ~0); 439 if (!AS) return false; 440 remove(*AS); 441 return true; 442} 443 444bool AliasSetTracker::remove(CallSite CS) { 445 if (AA.doesNotAccessMemory(CS)) 446 return false; // doesn't alias anything 447 448 AliasSet *AS = findAliasSetForCallSite(CS); 449 if (!AS) return false; 450 remove(*AS); 451 return true; 452} 453 454bool AliasSetTracker::remove(Instruction *I) { 455 // Dispatch to one of the other remove methods... 456 if (LoadInst *LI = dyn_cast<LoadInst>(I)) 457 return remove(LI); 458 else if (StoreInst *SI = dyn_cast<StoreInst>(I)) 459 return remove(SI); 460 else if (CallInst *CI = dyn_cast<CallInst>(I)) 461 return remove(CI); 462 else if (FreeInst *FI = dyn_cast<FreeInst>(I)) 463 return remove(FI); 464 else if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I)) 465 return remove(VAAI); 466 return true; 467} 468 469 470// deleteValue method - This method is used to remove a pointer value from the 471// AliasSetTracker entirely. It should be used when an instruction is deleted 472// from the program to update the AST. If you don't use this, you would have 473// dangling pointers to deleted instructions. 474// 475void AliasSetTracker::deleteValue(Value *PtrVal) { 476 // Notify the alias analysis implementation that this value is gone. 477 AA.deleteValue(PtrVal); 478 479 // If this is a call instruction, remove the callsite from the appropriate 480 // AliasSet. 481 CallSite CS = CallSite::get(PtrVal); 482 if (CS.getInstruction()) 483 if (!AA.doesNotAccessMemory(CS)) 484 if (AliasSet *AS = findAliasSetForCallSite(CS)) 485 AS->removeCallSite(CS); 486 487 // First, look up the PointerRec for this pointer. 488 DenseMap<Value*, AliasSet::PointerRec*>::iterator I = PointerMap.find(PtrVal); 489 if (I == PointerMap.end()) return; // Noop 490 491 // If we found one, remove the pointer from the alias set it is in. 492 AliasSet::PointerRec *PtrValEnt = I->second; 493 AliasSet *AS = PtrValEnt->getAliasSet(*this); 494 495 // Unlink and delete from the list of values. 496 PtrValEnt->eraseFromList(); 497 498 // Stop using the alias set. 499 AS->dropRef(*this); 500 501 PointerMap.erase(I); 502} 503 504// copyValue - This method should be used whenever a preexisting value in the 505// program is copied or cloned, introducing a new value. Note that it is ok for 506// clients that use this method to introduce the same value multiple times: if 507// the tracker already knows about a value, it will ignore the request. 508// 509void AliasSetTracker::copyValue(Value *From, Value *To) { 510 // Notify the alias analysis implementation that this value is copied. 511 AA.copyValue(From, To); 512 513 // First, look up the PointerRec for this pointer. 514 DenseMap<Value*, AliasSet::PointerRec*>::iterator I = PointerMap.find(From); 515 if (I == PointerMap.end()) 516 return; // Noop 517 assert(I->second->hasAliasSet() && "Dead entry?"); 518 519 AliasSet::PointerRec &Entry = getEntryFor(To); 520 if (Entry.hasAliasSet()) return; // Already in the tracker! 521 522 // Add it to the alias set it aliases... 523 I = PointerMap.find(From); 524 AliasSet *AS = I->second->getAliasSet(*this); 525 AS->addPointer(*this, Entry, I->second->getSize(), true); 526} 527 528 529 530//===----------------------------------------------------------------------===// 531// AliasSet/AliasSetTracker Printing Support 532//===----------------------------------------------------------------------===// 533 534void AliasSet::print(std::ostream &OS) const { 535 OS << " AliasSet[" << (void*)this << "," << RefCount << "] "; 536 OS << (AliasTy == MustAlias ? "must" : "may") << " alias, "; 537 switch (AccessTy) { 538 case NoModRef: OS << "No access "; break; 539 case Refs : OS << "Ref "; break; 540 case Mods : OS << "Mod "; break; 541 case ModRef : OS << "Mod/Ref "; break; 542 default: assert(0 && "Bad value for AccessTy!"); 543 } 544 if (isVolatile()) OS << "[volatile] "; 545 if (Forward) 546 OS << " forwarding to " << (void*)Forward; 547 548 549 if (!empty()) { 550 OS << "Pointers: "; 551 for (iterator I = begin(), E = end(); I != E; ++I) { 552 if (I != begin()) OS << ", "; 553 WriteAsOperand(OS << "(", I.getPointer()); 554 OS << ", " << I.getSize() << ")"; 555 } 556 } 557 if (!CallSites.empty()) { 558 OS << "\n " << CallSites.size() << " Call Sites: "; 559 for (unsigned i = 0, e = CallSites.size(); i != e; ++i) { 560 if (i) OS << ", "; 561 WriteAsOperand(OS, CallSites[i].getCalledValue()); 562 } 563 } 564 OS << "\n"; 565} 566 567void AliasSetTracker::print(std::ostream &OS) const { 568 OS << "Alias Set Tracker: " << AliasSets.size() << " alias sets for " 569 << PointerMap.size() << " pointer values.\n"; 570 for (const_iterator I = begin(), E = end(); I != E; ++I) 571 I->print(OS); 572 OS << "\n"; 573} 574 575void AliasSet::dump() const { print (cerr); } 576void AliasSetTracker::dump() const { print(cerr); } 577 578//===----------------------------------------------------------------------===// 579// AliasSetPrinter Pass 580//===----------------------------------------------------------------------===// 581 582namespace { 583 class VISIBILITY_HIDDEN AliasSetPrinter : public FunctionPass { 584 AliasSetTracker *Tracker; 585 public: 586 static char ID; // Pass identification, replacement for typeid 587 AliasSetPrinter() : FunctionPass(&ID) {} 588 589 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 590 AU.setPreservesAll(); 591 AU.addRequired<AliasAnalysis>(); 592 } 593 594 virtual bool runOnFunction(Function &F) { 595 Tracker = new AliasSetTracker(getAnalysis<AliasAnalysis>()); 596 597 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) 598 Tracker->add(&*I); 599 Tracker->print(cerr); 600 delete Tracker; 601 return false; 602 } 603 }; 604} 605 606char AliasSetPrinter::ID = 0; 607static RegisterPass<AliasSetPrinter> 608X("print-alias-sets", "Alias Set Printer", false, true); 609