AliasSetTracker.cpp revision 046e78ce55a7c3d82b7b6758d2d77f2d99f970bf
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/Analysis/MallocHelper.h" 17#include "llvm/Instructions.h" 18#include "llvm/IntrinsicInst.h" 19#include "llvm/Pass.h" 20#include "llvm/Type.h" 21#include "llvm/Target/TargetData.h" 22#include "llvm/Assembly/Writer.h" 23#include "llvm/Support/ErrorHandling.h" 24#include "llvm/Support/InstIterator.h" 25#include "llvm/Support/Format.h" 26#include "llvm/Support/raw_ostream.h" 27using namespace llvm; 28 29/// mergeSetIn - Merge the specified alias set into this alias set. 30/// 31void AliasSet::mergeSetIn(AliasSet &AS, AliasSetTracker &AST) { 32 assert(!AS.Forward && "Alias set is already forwarding!"); 33 assert(!Forward && "This set is a forwarding set!!"); 34 35 // Update the alias and access types of this set... 36 AccessTy |= AS.AccessTy; 37 AliasTy |= AS.AliasTy; 38 39 if (AliasTy == MustAlias) { 40 // Check that these two merged sets really are must aliases. Since both 41 // used to be must-alias sets, we can just check any pointer from each set 42 // for aliasing. 43 AliasAnalysis &AA = AST.getAliasAnalysis(); 44 PointerRec *L = getSomePointer(); 45 PointerRec *R = AS.getSomePointer(); 46 47 // If the pointers are not a must-alias pair, this set becomes a may alias. 48 if (AA.alias(L->getValue(), L->getSize(), R->getValue(), R->getSize()) 49 != AliasAnalysis::MustAlias) 50 AliasTy = MayAlias; 51 } 52 53 if (CallSites.empty()) { // Merge call sites... 54 if (!AS.CallSites.empty()) 55 std::swap(CallSites, AS.CallSites); 56 } else if (!AS.CallSites.empty()) { 57 CallSites.insert(CallSites.end(), AS.CallSites.begin(), AS.CallSites.end()); 58 AS.CallSites.clear(); 59 } 60 61 AS.Forward = this; // Forward across AS now... 62 addRef(); // AS is now pointing to us... 63 64 // Merge the list of constituent pointers... 65 if (AS.PtrList) { 66 *PtrListEnd = AS.PtrList; 67 AS.PtrList->setPrevInList(PtrListEnd); 68 PtrListEnd = AS.PtrListEnd; 69 70 AS.PtrList = 0; 71 AS.PtrListEnd = &AS.PtrList; 72 assert(*AS.PtrListEnd == 0 && "End of list is not null?"); 73 } 74} 75 76void AliasSetTracker::removeAliasSet(AliasSet *AS) { 77 if (AliasSet *Fwd = AS->Forward) { 78 Fwd->dropRef(*this); 79 AS->Forward = 0; 80 } 81 AliasSets.erase(AS); 82} 83 84void AliasSet::removeFromTracker(AliasSetTracker &AST) { 85 assert(RefCount == 0 && "Cannot remove non-dead alias set from tracker!"); 86 AST.removeAliasSet(this); 87} 88 89void AliasSet::addPointer(AliasSetTracker &AST, PointerRec &Entry, 90 unsigned Size, bool KnownMustAlias) { 91 assert(!Entry.hasAliasSet() && "Entry already in set!"); 92 93 // Check to see if we have to downgrade to _may_ alias. 94 if (isMustAlias() && !KnownMustAlias) 95 if (PointerRec *P = getSomePointer()) { 96 AliasAnalysis &AA = AST.getAliasAnalysis(); 97 AliasAnalysis::AliasResult Result = 98 AA.alias(P->getValue(), P->getSize(), Entry.getValue(), Size); 99 if (Result == AliasAnalysis::MayAlias) 100 AliasTy = MayAlias; 101 else // First entry of must alias must have maximum size! 102 P->updateSize(Size); 103 assert(Result != AliasAnalysis::NoAlias && "Cannot be part of must set!"); 104 } 105 106 Entry.setAliasSet(this); 107 Entry.updateSize(Size); 108 109 // Add it to the end of the list... 110 assert(*PtrListEnd == 0 && "End of list is not null?"); 111 *PtrListEnd = &Entry; 112 PtrListEnd = Entry.setPrevInList(PtrListEnd); 113 assert(*PtrListEnd == 0 && "End of list is not null?"); 114 addRef(); // Entry points to alias set... 115} 116 117void AliasSet::addCallSite(CallSite CS, AliasAnalysis &AA) { 118 CallSites.push_back(CS); 119 120 AliasAnalysis::ModRefBehavior Behavior = AA.getModRefBehavior(CS); 121 if (Behavior == AliasAnalysis::DoesNotAccessMemory) 122 return; 123 else if (Behavior == AliasAnalysis::OnlyReadsMemory) { 124 AliasTy = MayAlias; 125 AccessTy |= Refs; 126 return; 127 } 128 129 // FIXME: This should use mod/ref information to make this not suck so bad 130 AliasTy = MayAlias; 131 AccessTy = ModRef; 132} 133 134/// aliasesPointer - Return true if the specified pointer "may" (or must) 135/// alias one of the members in the set. 136/// 137bool AliasSet::aliasesPointer(const Value *Ptr, unsigned Size, 138 AliasAnalysis &AA) const { 139 if (AliasTy == MustAlias) { 140 assert(CallSites.empty() && "Illegal must alias set!"); 141 142 // If this is a set of MustAliases, only check to see if the pointer aliases 143 // SOME value in the set... 144 PointerRec *SomePtr = getSomePointer(); 145 assert(SomePtr && "Empty must-alias set??"); 146 return AA.alias(SomePtr->getValue(), SomePtr->getSize(), Ptr, Size); 147 } 148 149 // If this is a may-alias set, we have to check all of the pointers in the set 150 // to be sure it doesn't alias the set... 151 for (iterator I = begin(), E = end(); I != E; ++I) 152 if (AA.alias(Ptr, Size, I.getPointer(), I.getSize())) 153 return true; 154 155 // Check the call sites list and invoke list... 156 if (!CallSites.empty()) { 157 if (AA.hasNoModRefInfoForCalls()) 158 return true; 159 160 for (unsigned i = 0, e = CallSites.size(); i != e; ++i) 161 if (AA.getModRefInfo(CallSites[i], const_cast<Value*>(Ptr), Size) 162 != AliasAnalysis::NoModRef) 163 return true; 164 } 165 166 return false; 167} 168 169bool AliasSet::aliasesCallSite(CallSite CS, AliasAnalysis &AA) const { 170 if (AA.doesNotAccessMemory(CS)) 171 return false; 172 173 if (AA.hasNoModRefInfoForCalls()) 174 return true; 175 176 for (unsigned i = 0, e = CallSites.size(); i != e; ++i) 177 if (AA.getModRefInfo(CallSites[i], CS) != AliasAnalysis::NoModRef || 178 AA.getModRefInfo(CS, CallSites[i]) != AliasAnalysis::NoModRef) 179 return true; 180 181 for (iterator I = begin(), E = end(); I != E; ++I) 182 if (AA.getModRefInfo(CS, I.getPointer(), I.getSize()) != 183 AliasAnalysis::NoModRef) 184 return true; 185 186 return false; 187} 188 189void AliasSetTracker::clear() { 190 // Delete all the PointerRec entries. 191 for (PointerMapType::iterator I = PointerMap.begin(), E = PointerMap.end(); 192 I != E; ++I) 193 I->second->eraseFromList(); 194 195 PointerMap.clear(); 196 197 // The alias sets should all be clear now. 198 AliasSets.clear(); 199} 200 201 202/// findAliasSetForPointer - Given a pointer, find the one alias set to put the 203/// instruction referring to the pointer into. If there are multiple alias sets 204/// that may alias the pointer, merge them together and return the unified set. 205/// 206AliasSet *AliasSetTracker::findAliasSetForPointer(const Value *Ptr, 207 unsigned Size) { 208 AliasSet *FoundSet = 0; 209 for (iterator I = begin(), E = end(); I != E; ++I) 210 if (!I->Forward && I->aliasesPointer(Ptr, Size, AA)) { 211 if (FoundSet == 0) { // If this is the first alias set ptr can go into. 212 FoundSet = I; // Remember it. 213 } else { // Otherwise, we must merge the sets. 214 FoundSet->mergeSetIn(*I, *this); // Merge in contents. 215 } 216 } 217 218 return FoundSet; 219} 220 221/// containsPointer - Return true if the specified location is represented by 222/// this alias set, false otherwise. This does not modify the AST object or 223/// alias sets. 224bool AliasSetTracker::containsPointer(Value *Ptr, unsigned Size) const { 225 for (const_iterator I = begin(), E = end(); I != E; ++I) 226 if (!I->Forward && I->aliasesPointer(Ptr, Size, AA)) 227 return true; 228 return false; 229} 230 231 232 233AliasSet *AliasSetTracker::findAliasSetForCallSite(CallSite CS) { 234 AliasSet *FoundSet = 0; 235 for (iterator I = begin(), E = end(); I != E; ++I) 236 if (!I->Forward && I->aliasesCallSite(CS, AA)) { 237 if (FoundSet == 0) { // If this is the first alias set ptr can go into. 238 FoundSet = I; // Remember it. 239 } else if (!I->Forward) { // Otherwise, we must merge the sets. 240 FoundSet->mergeSetIn(*I, *this); // Merge in contents. 241 } 242 } 243 244 return FoundSet; 245} 246 247 248 249 250/// getAliasSetForPointer - Return the alias set that the specified pointer 251/// lives in. 252AliasSet &AliasSetTracker::getAliasSetForPointer(Value *Pointer, unsigned Size, 253 bool *New) { 254 AliasSet::PointerRec &Entry = getEntryFor(Pointer); 255 256 // Check to see if the pointer is already known... 257 if (Entry.hasAliasSet()) { 258 Entry.updateSize(Size); 259 // Return the set! 260 return *Entry.getAliasSet(*this)->getForwardedTarget(*this); 261 } else if (AliasSet *AS = findAliasSetForPointer(Pointer, Size)) { 262 // Add it to the alias set it aliases... 263 AS->addPointer(*this, Entry, Size); 264 return *AS; 265 } else { 266 if (New) *New = true; 267 // Otherwise create a new alias set to hold the loaded pointer... 268 AliasSets.push_back(new AliasSet()); 269 AliasSets.back().addPointer(*this, Entry, Size); 270 return AliasSets.back(); 271 } 272} 273 274bool AliasSetTracker::add(Value *Ptr, unsigned Size) { 275 bool NewPtr; 276 addPointer(Ptr, Size, AliasSet::NoModRef, NewPtr); 277 return NewPtr; 278} 279 280 281bool AliasSetTracker::add(LoadInst *LI) { 282 bool NewPtr; 283 AliasSet &AS = addPointer(LI->getOperand(0), 284 AA.getTypeStoreSize(LI->getType()), 285 AliasSet::Refs, NewPtr); 286 if (LI->isVolatile()) AS.setVolatile(); 287 return NewPtr; 288} 289 290bool AliasSetTracker::add(StoreInst *SI) { 291 bool NewPtr; 292 Value *Val = SI->getOperand(0); 293 AliasSet &AS = addPointer(SI->getOperand(1), 294 AA.getTypeStoreSize(Val->getType()), 295 AliasSet::Mods, NewPtr); 296 if (SI->isVolatile()) AS.setVolatile(); 297 return NewPtr; 298} 299 300bool AliasSetTracker::add(VAArgInst *VAAI) { 301 bool NewPtr; 302 addPointer(VAAI->getOperand(0), ~0, AliasSet::ModRef, NewPtr); 303 return NewPtr; 304} 305 306 307bool AliasSetTracker::add(CallSite CS) { 308 Instruction* Inst = CS.getInstruction(); 309 if (isFreeCall(Inst)) { 310 bool NewPtr; 311 addPointer(Inst->getOperand(1), ~0, AliasSet::Mods, NewPtr); 312 return NewPtr; 313 } 314 315 if (isa<DbgInfoIntrinsic>(CS.getInstruction())) 316 return true; // Ignore DbgInfo Intrinsics. 317 if (AA.doesNotAccessMemory(CS)) 318 return true; // doesn't alias anything 319 320 AliasSet *AS = findAliasSetForCallSite(CS); 321 if (!AS) { 322 AliasSets.push_back(new AliasSet()); 323 AS = &AliasSets.back(); 324 AS->addCallSite(CS, AA); 325 return true; 326 } else { 327 AS->addCallSite(CS, AA); 328 return false; 329 } 330} 331 332bool AliasSetTracker::add(Instruction *I) { 333 // Dispatch to one of the other add methods... 334 if (LoadInst *LI = dyn_cast<LoadInst>(I)) 335 return add(LI); 336 else if (StoreInst *SI = dyn_cast<StoreInst>(I)) 337 return add(SI); 338 else if (CallInst *CI = dyn_cast<CallInst>(I)) 339 return add(CI); 340 else if (InvokeInst *II = dyn_cast<InvokeInst>(I)) 341 return add(II); 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(VAArgInst *VAAI) { 431 AliasSet *AS = findAliasSetForPointer(VAAI->getOperand(0), ~0); 432 if (!AS) return false; 433 remove(*AS); 434 return true; 435} 436 437bool AliasSetTracker::remove(CallSite CS) { 438 Instruction* Inst = CS.getInstruction(); 439 if (isFreeCall(Inst)) { 440 AliasSet *AS = findAliasSetForPointer(Inst->getOperand(1), ~0); 441 if (!AS) return false; 442 remove(*AS); 443 return true; 444 } 445 446 if (AA.doesNotAccessMemory(CS)) 447 return false; // doesn't alias anything 448 449 AliasSet *AS = findAliasSetForCallSite(CS); 450 if (!AS) return false; 451 remove(*AS); 452 return true; 453} 454 455bool AliasSetTracker::remove(Instruction *I) { 456 // Dispatch to one of the other remove methods... 457 if (LoadInst *LI = dyn_cast<LoadInst>(I)) 458 return remove(LI); 459 else if (StoreInst *SI = dyn_cast<StoreInst>(I)) 460 return remove(SI); 461 else if (CallInst *CI = dyn_cast<CallInst>(I)) 462 return remove(CI); 463 else if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I)) 464 return remove(VAAI); 465 return true; 466} 467 468 469// deleteValue method - This method is used to remove a pointer value from the 470// AliasSetTracker entirely. It should be used when an instruction is deleted 471// from the program to update the AST. If you don't use this, you would have 472// dangling pointers to deleted instructions. 473// 474void AliasSetTracker::deleteValue(Value *PtrVal) { 475 // Notify the alias analysis implementation that this value is gone. 476 AA.deleteValue(PtrVal); 477 478 // If this is a call instruction, remove the callsite from the appropriate 479 // AliasSet. 480 CallSite CS = CallSite::get(PtrVal); 481 if (CS.getInstruction()) 482 if (!AA.doesNotAccessMemory(CS)) 483 if (AliasSet *AS = findAliasSetForCallSite(CS)) 484 AS->removeCallSite(CS); 485 486 // First, look up the PointerRec for this pointer. 487 PointerMapType::iterator I = PointerMap.find(PtrVal); 488 if (I == PointerMap.end()) return; // Noop 489 490 // If we found one, remove the pointer from the alias set it is in. 491 AliasSet::PointerRec *PtrValEnt = I->second; 492 AliasSet *AS = PtrValEnt->getAliasSet(*this); 493 494 // Unlink and delete from the list of values. 495 PtrValEnt->eraseFromList(); 496 497 // Stop using the alias set. 498 AS->dropRef(*this); 499 500 PointerMap.erase(I); 501} 502 503// copyValue - This method should be used whenever a preexisting value in the 504// program is copied or cloned, introducing a new value. Note that it is ok for 505// clients that use this method to introduce the same value multiple times: if 506// the tracker already knows about a value, it will ignore the request. 507// 508void AliasSetTracker::copyValue(Value *From, Value *To) { 509 // Notify the alias analysis implementation that this value is copied. 510 AA.copyValue(From, To); 511 512 // First, look up the PointerRec for this pointer. 513 PointerMapType::iterator I = PointerMap.find(From); 514 if (I == PointerMap.end()) 515 return; // Noop 516 assert(I->second->hasAliasSet() && "Dead entry?"); 517 518 AliasSet::PointerRec &Entry = getEntryFor(To); 519 if (Entry.hasAliasSet()) return; // Already in the tracker! 520 521 // Add it to the alias set it aliases... 522 I = PointerMap.find(From); 523 AliasSet *AS = I->second->getAliasSet(*this); 524 AS->addPointer(*this, Entry, I->second->getSize(), true); 525} 526 527 528 529//===----------------------------------------------------------------------===// 530// AliasSet/AliasSetTracker Printing Support 531//===----------------------------------------------------------------------===// 532 533void AliasSet::print(raw_ostream &OS) const { 534 OS << " AliasSet[" << format("0x%p", (void*)this) << "," << RefCount << "] "; 535 OS << (AliasTy == MustAlias ? "must" : "may") << " alias, "; 536 switch (AccessTy) { 537 case NoModRef: OS << "No access "; break; 538 case Refs : OS << "Ref "; break; 539 case Mods : OS << "Mod "; break; 540 case ModRef : OS << "Mod/Ref "; break; 541 default: llvm_unreachable("Bad value for AccessTy!"); 542 } 543 if (isVolatile()) OS << "[volatile] "; 544 if (Forward) 545 OS << " forwarding to " << (void*)Forward; 546 547 548 if (!empty()) { 549 OS << "Pointers: "; 550 for (iterator I = begin(), E = end(); I != E; ++I) { 551 if (I != begin()) OS << ", "; 552 WriteAsOperand(OS << "(", I.getPointer()); 553 OS << ", " << I.getSize() << ")"; 554 } 555 } 556 if (!CallSites.empty()) { 557 OS << "\n " << CallSites.size() << " Call Sites: "; 558 for (unsigned i = 0, e = CallSites.size(); i != e; ++i) { 559 if (i) OS << ", "; 560 WriteAsOperand(OS, CallSites[i].getCalledValue()); 561 } 562 } 563 OS << "\n"; 564} 565 566void AliasSetTracker::print(raw_ostream &OS) const { 567 OS << "Alias Set Tracker: " << AliasSets.size() << " alias sets for " 568 << PointerMap.size() << " pointer values.\n"; 569 for (const_iterator I = begin(), E = end(); I != E; ++I) 570 I->print(OS); 571 OS << "\n"; 572} 573 574void AliasSet::dump() const { print(errs()); } 575void AliasSetTracker::dump() const { print(errs()); } 576 577//===----------------------------------------------------------------------===// 578// ASTCallbackVH Class Implementation 579//===----------------------------------------------------------------------===// 580 581void AliasSetTracker::ASTCallbackVH::deleted() { 582 assert(AST && "ASTCallbackVH called with a null AliasSetTracker!"); 583 AST->deleteValue(getValPtr()); 584 // this now dangles! 585} 586 587AliasSetTracker::ASTCallbackVH::ASTCallbackVH(Value *V, AliasSetTracker *ast) 588 : CallbackVH(V), AST(ast) {} 589 590AliasSetTracker::ASTCallbackVH & 591AliasSetTracker::ASTCallbackVH::operator=(Value *V) { 592 return *this = ASTCallbackVH(V, AST); 593} 594 595//===----------------------------------------------------------------------===// 596// AliasSetPrinter Pass 597//===----------------------------------------------------------------------===// 598 599namespace { 600 class AliasSetPrinter : public FunctionPass { 601 AliasSetTracker *Tracker; 602 public: 603 static char ID; // Pass identification, replacement for typeid 604 AliasSetPrinter() : FunctionPass(&ID) {} 605 606 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 607 AU.setPreservesAll(); 608 AU.addRequired<AliasAnalysis>(); 609 } 610 611 virtual bool runOnFunction(Function &F) { 612 Tracker = new AliasSetTracker(getAnalysis<AliasAnalysis>()); 613 614 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) 615 Tracker->add(&*I); 616 Tracker->print(errs()); 617 delete Tracker; 618 return false; 619 } 620 }; 621} 622 623char AliasSetPrinter::ID = 0; 624static RegisterPass<AliasSetPrinter> 625X("print-alias-sets", "Alias Set Printer", false, true); 626