AliasSetTracker.cpp revision b5b56ba9d4df47e618d4e0f9e1e09bf216733ee8
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/ErrorHandling.h" 24#include "llvm/Support/InstIterator.h" 25#include "llvm/Support/Streams.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(FreeInst *FI) { 300 bool NewPtr; 301 addPointer(FI->getOperand(0), ~0, AliasSet::Mods, NewPtr); 302 return NewPtr; 303} 304 305bool AliasSetTracker::add(VAArgInst *VAAI) { 306 bool NewPtr; 307 addPointer(VAAI->getOperand(0), ~0, AliasSet::ModRef, NewPtr); 308 return NewPtr; 309} 310 311 312bool AliasSetTracker::add(CallSite CS) { 313 if (isa<DbgInfoIntrinsic>(CS.getInstruction())) 314 return true; // Ignore DbgInfo Intrinsics. 315 if (AA.doesNotAccessMemory(CS)) 316 return true; // doesn't alias anything 317 318 AliasSet *AS = findAliasSetForCallSite(CS); 319 if (!AS) { 320 AliasSets.push_back(new AliasSet()); 321 AS = &AliasSets.back(); 322 AS->addCallSite(CS, AA); 323 return true; 324 } else { 325 AS->addCallSite(CS, AA); 326 return false; 327 } 328} 329 330bool AliasSetTracker::add(Instruction *I) { 331 // Dispatch to one of the other add methods... 332 if (LoadInst *LI = dyn_cast<LoadInst>(I)) 333 return add(LI); 334 else if (StoreInst *SI = dyn_cast<StoreInst>(I)) 335 return add(SI); 336 else if (CallInst *CI = dyn_cast<CallInst>(I)) 337 return add(CI); 338 else if (InvokeInst *II = dyn_cast<InvokeInst>(I)) 339 return add(II); 340 else if (FreeInst *FI = dyn_cast<FreeInst>(I)) 341 return add(FI); 342 else if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I)) 343 return add(VAAI); 344 return true; 345} 346 347void AliasSetTracker::add(BasicBlock &BB) { 348 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) 349 add(I); 350} 351 352void AliasSetTracker::add(const AliasSetTracker &AST) { 353 assert(&AA == &AST.AA && 354 "Merging AliasSetTracker objects with different Alias Analyses!"); 355 356 // Loop over all of the alias sets in AST, adding the pointers contained 357 // therein into the current alias sets. This can cause alias sets to be 358 // merged together in the current AST. 359 for (const_iterator I = AST.begin(), E = AST.end(); I != E; ++I) 360 if (!I->Forward) { // Ignore forwarding alias sets 361 AliasSet &AS = const_cast<AliasSet&>(*I); 362 363 // If there are any call sites in the alias set, add them to this AST. 364 for (unsigned i = 0, e = AS.CallSites.size(); i != e; ++i) 365 add(AS.CallSites[i]); 366 367 // Loop over all of the pointers in this alias set... 368 AliasSet::iterator I = AS.begin(), E = AS.end(); 369 bool X; 370 for (; I != E; ++I) { 371 AliasSet &NewAS = addPointer(I.getPointer(), I.getSize(), 372 (AliasSet::AccessType)AS.AccessTy, X); 373 if (AS.isVolatile()) NewAS.setVolatile(); 374 } 375 } 376} 377 378/// remove - Remove the specified (potentially non-empty) alias set from the 379/// tracker. 380void AliasSetTracker::remove(AliasSet &AS) { 381 // Drop all call sites. 382 AS.CallSites.clear(); 383 384 // Clear the alias set. 385 unsigned NumRefs = 0; 386 while (!AS.empty()) { 387 AliasSet::PointerRec *P = AS.PtrList; 388 389 Value *ValToRemove = P->getValue(); 390 391 // Unlink and delete entry from the list of values. 392 P->eraseFromList(); 393 394 // Remember how many references need to be dropped. 395 ++NumRefs; 396 397 // Finally, remove the entry. 398 PointerMap.erase(ValToRemove); 399 } 400 401 // Stop using the alias set, removing it. 402 AS.RefCount -= NumRefs; 403 if (AS.RefCount == 0) 404 AS.removeFromTracker(*this); 405} 406 407bool AliasSetTracker::remove(Value *Ptr, unsigned Size) { 408 AliasSet *AS = findAliasSetForPointer(Ptr, Size); 409 if (!AS) return false; 410 remove(*AS); 411 return true; 412} 413 414bool AliasSetTracker::remove(LoadInst *LI) { 415 unsigned Size = AA.getTypeStoreSize(LI->getType()); 416 AliasSet *AS = findAliasSetForPointer(LI->getOperand(0), Size); 417 if (!AS) return false; 418 remove(*AS); 419 return true; 420} 421 422bool AliasSetTracker::remove(StoreInst *SI) { 423 unsigned Size = AA.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 PointerMapType::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 PointerMapType::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: llvm_unreachable("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// ASTCallbackVH Class Implementation 580//===----------------------------------------------------------------------===// 581 582void AliasSetTracker::ASTCallbackVH::deleted() { 583 assert(AST && "ASTCallbackVH called with a null AliasSetTracker!"); 584 AST->deleteValue(getValPtr()); 585 // this now dangles! 586} 587 588AliasSetTracker::ASTCallbackVH::ASTCallbackVH(Value *V, AliasSetTracker *ast) 589 : CallbackVH(V == DenseMapInfo<Value *>::getEmptyKey() ? 0 : 590 V == DenseMapInfo<Value *>::getTombstoneKey() ? 0 : 591 V), 592 AST(ast) {} 593 594//===----------------------------------------------------------------------===// 595// AliasSetPrinter Pass 596//===----------------------------------------------------------------------===// 597 598namespace { 599 class VISIBILITY_HIDDEN AliasSetPrinter : public FunctionPass { 600 AliasSetTracker *Tracker; 601 public: 602 static char ID; // Pass identification, replacement for typeid 603 AliasSetPrinter() : FunctionPass(&ID) {} 604 605 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 606 AU.setPreservesAll(); 607 AU.addRequired<AliasAnalysis>(); 608 } 609 610 virtual bool runOnFunction(Function &F) { 611 Tracker = new AliasSetTracker(getAnalysis<AliasAnalysis>()); 612 613 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) 614 Tracker->add(&*I); 615 Tracker->print(cerr); 616 delete Tracker; 617 return false; 618 } 619 }; 620} 621 622char AliasSetPrinter::ID = 0; 623static RegisterPass<AliasSetPrinter> 624X("print-alias-sets", "Alias Set Printer", false, true); 625