AliasSetTracker.cpp revision fedac7d9b0c83c94f0f8cc2aaa6b4cce4a6e9a55
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/Debug.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 Volatile |= AS.Volatile; 39 40 if (AliasTy == MustAlias) { 41 // Check that these two merged sets really are must aliases. Since both 42 // used to be must-alias sets, we can just check any pointer from each set 43 // for aliasing. 44 AliasAnalysis &AA = AST.getAliasAnalysis(); 45 PointerRec *L = getSomePointer(); 46 PointerRec *R = AS.getSomePointer(); 47 48 // If the pointers are not a must-alias pair, this set becomes a may alias. 49 if (AA.alias(L->getValue(), L->getSize(), R->getValue(), R->getSize()) 50 != AliasAnalysis::MustAlias) 51 AliasTy = MayAlias; 52 } 53 54 if (CallSites.empty()) { // Merge call sites... 55 if (!AS.CallSites.empty()) 56 std::swap(CallSites, AS.CallSites); 57 } else if (!AS.CallSites.empty()) { 58 CallSites.insert(CallSites.end(), AS.CallSites.begin(), AS.CallSites.end()); 59 AS.CallSites.clear(); 60 } 61 62 AS.Forward = this; // Forward across AS now... 63 addRef(); // AS is now pointing to us... 64 65 // Merge the list of constituent pointers... 66 if (AS.PtrList) { 67 *PtrListEnd = AS.PtrList; 68 AS.PtrList->setPrevInList(PtrListEnd); 69 PtrListEnd = AS.PtrListEnd; 70 71 AS.PtrList = 0; 72 AS.PtrListEnd = &AS.PtrList; 73 assert(*AS.PtrListEnd == 0 && "End of list is not null?"); 74 } 75} 76 77void AliasSetTracker::removeAliasSet(AliasSet *AS) { 78 if (AliasSet *Fwd = AS->Forward) { 79 Fwd->dropRef(*this); 80 AS->Forward = 0; 81 } 82 AliasSets.erase(AS); 83} 84 85void AliasSet::removeFromTracker(AliasSetTracker &AST) { 86 assert(RefCount == 0 && "Cannot remove non-dead alias set from tracker!"); 87 AST.removeAliasSet(this); 88} 89 90void AliasSet::addPointer(AliasSetTracker &AST, PointerRec &Entry, 91 unsigned Size, bool KnownMustAlias) { 92 assert(!Entry.hasAliasSet() && "Entry already in set!"); 93 94 // Check to see if we have to downgrade to _may_ alias. 95 if (isMustAlias() && !KnownMustAlias) 96 if (PointerRec *P = getSomePointer()) { 97 AliasAnalysis &AA = AST.getAliasAnalysis(); 98 AliasAnalysis::AliasResult Result = 99 AA.alias(P->getValue(), P->getSize(), Entry.getValue(), Size); 100 if (Result == AliasAnalysis::MayAlias) 101 AliasTy = MayAlias; 102 else // First entry of must alias must have maximum size! 103 P->updateSize(Size); 104 assert(Result != AliasAnalysis::NoAlias && "Cannot be part of must set!"); 105 } 106 107 Entry.setAliasSet(this); 108 Entry.updateSize(Size); 109 110 // Add it to the end of the list... 111 assert(*PtrListEnd == 0 && "End of list is not null?"); 112 *PtrListEnd = &Entry; 113 PtrListEnd = Entry.setPrevInList(PtrListEnd); 114 assert(*PtrListEnd == 0 && "End of list is not null?"); 115 addRef(); // Entry points to alias set. 116} 117 118void AliasSet::addCallSite(CallSite CS, AliasAnalysis &AA) { 119 CallSites.push_back(CS); 120 121 AliasAnalysis::ModRefBehavior Behavior = AA.getModRefBehavior(CS); 122 if (Behavior == AliasAnalysis::DoesNotAccessMemory) 123 return; 124 else if (Behavior == AliasAnalysis::OnlyReadsMemory) { 125 AliasTy = MayAlias; 126 AccessTy |= Refs; 127 return; 128 } 129 130 // FIXME: This should use mod/ref information to make this not suck so bad 131 AliasTy = MayAlias; 132 AccessTy = ModRef; 133} 134 135/// aliasesPointer - Return true if the specified pointer "may" (or must) 136/// alias one of the members in the set. 137/// 138bool AliasSet::aliasesPointer(const Value *Ptr, unsigned Size, 139 AliasAnalysis &AA) const { 140 if (AliasTy == MustAlias) { 141 assert(CallSites.empty() && "Illegal must alias set!"); 142 143 // If this is a set of MustAliases, only check to see if the pointer aliases 144 // SOME value in the set. 145 PointerRec *SomePtr = getSomePointer(); 146 assert(SomePtr && "Empty must-alias set??"); 147 return AA.alias(SomePtr->getValue(), SomePtr->getSize(), Ptr, Size); 148 } 149 150 // If this is a may-alias set, we have to check all of the pointers in the set 151 // to be sure it doesn't alias the set... 152 for (iterator I = begin(), E = end(); I != E; ++I) 153 if (AA.alias(Ptr, Size, I.getPointer(), I.getSize())) 154 return true; 155 156 // Check the call sites list and invoke list... 157 if (!CallSites.empty()) { 158 for (unsigned i = 0, e = CallSites.size(); i != e; ++i) 159 if (AA.getModRefInfo(CallSites[i], Ptr, Size) != AliasAnalysis::NoModRef) 160 return true; 161 } 162 163 return false; 164} 165 166bool AliasSet::aliasesCallSite(CallSite CS, AliasAnalysis &AA) const { 167 if (AA.doesNotAccessMemory(CS)) 168 return false; 169 170 for (unsigned i = 0, e = CallSites.size(); i != e; ++i) 171 if (AA.getModRefInfo(CallSites[i], CS) != AliasAnalysis::NoModRef || 172 AA.getModRefInfo(CS, CallSites[i]) != AliasAnalysis::NoModRef) 173 return true; 174 175 for (iterator I = begin(), E = end(); I != E; ++I) 176 if (AA.getModRefInfo(CS, I.getPointer(), I.getSize()) != 177 AliasAnalysis::NoModRef) 178 return true; 179 180 return false; 181} 182 183void AliasSetTracker::clear() { 184 // Delete all the PointerRec entries. 185 for (PointerMapType::iterator I = PointerMap.begin(), E = PointerMap.end(); 186 I != E; ++I) 187 I->second->eraseFromList(); 188 189 PointerMap.clear(); 190 191 // The alias sets should all be clear now. 192 AliasSets.clear(); 193} 194 195 196/// findAliasSetForPointer - Given a pointer, find the one alias set to put the 197/// instruction referring to the pointer into. If there are multiple alias sets 198/// that may alias the pointer, merge them together and return the unified set. 199/// 200AliasSet *AliasSetTracker::findAliasSetForPointer(const Value *Ptr, 201 unsigned Size) { 202 AliasSet *FoundSet = 0; 203 for (iterator I = begin(), E = end(); I != E; ++I) { 204 if (I->Forward || !I->aliasesPointer(Ptr, Size, AA)) continue; 205 206 if (FoundSet == 0) { // If this is the first alias set ptr can go into. 207 FoundSet = I; // Remember it. 208 } else { // Otherwise, we must merge the sets. 209 FoundSet->mergeSetIn(*I, *this); // Merge in contents. 210 } 211 } 212 213 return FoundSet; 214} 215 216/// containsPointer - Return true if the specified location is represented by 217/// this alias set, false otherwise. This does not modify the AST object or 218/// alias sets. 219bool AliasSetTracker::containsPointer(Value *Ptr, unsigned Size) const { 220 for (const_iterator I = begin(), E = end(); I != E; ++I) 221 if (!I->Forward && I->aliasesPointer(Ptr, Size, AA)) 222 return true; 223 return false; 224} 225 226 227 228AliasSet *AliasSetTracker::findAliasSetForCallSite(CallSite CS) { 229 AliasSet *FoundSet = 0; 230 for (iterator I = begin(), E = end(); I != E; ++I) { 231 if (I->Forward || !I->aliasesCallSite(CS, AA)) 232 continue; 233 234 if (FoundSet == 0) { // If this is the first alias set ptr can go into. 235 FoundSet = I; // Remember it. 236 } else if (!I->Forward) { // Otherwise, we must merge the sets. 237 FoundSet->mergeSetIn(*I, *this); // Merge in contents. 238 } 239 } 240 return FoundSet; 241} 242 243 244 245 246/// getAliasSetForPointer - Return the alias set that the specified pointer 247/// lives in. 248AliasSet &AliasSetTracker::getAliasSetForPointer(Value *Pointer, unsigned Size, 249 bool *New) { 250 AliasSet::PointerRec &Entry = getEntryFor(Pointer); 251 252 // Check to see if the pointer is already known. 253 if (Entry.hasAliasSet()) { 254 Entry.updateSize(Size); 255 // Return the set! 256 return *Entry.getAliasSet(*this)->getForwardedTarget(*this); 257 } 258 259 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 } 264 265 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 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.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.getTypeStoreSize(Val->getType()), 293 AliasSet::Mods, NewPtr); 294 if (SI->isVolatile()) AS.setVolatile(); 295 return NewPtr; 296} 297 298bool AliasSetTracker::add(VAArgInst *VAAI) { 299 bool NewPtr; 300 addPointer(VAAI->getOperand(0), ~0, AliasSet::ModRef, NewPtr); 301 return NewPtr; 302} 303 304 305bool AliasSetTracker::add(CallSite CS) { 306 if (isa<DbgInfoIntrinsic>(CS.getInstruction())) 307 return true; // Ignore DbgInfo Intrinsics. 308 if (AA.doesNotAccessMemory(CS)) 309 return true; // doesn't alias anything 310 311 AliasSet *AS = findAliasSetForCallSite(CS); 312 if (AS) { 313 AS->addCallSite(CS, AA); 314 return false; 315 } 316 AliasSets.push_back(new AliasSet()); 317 AS = &AliasSets.back(); 318 AS->addCallSite(CS, AA); 319 return true; 320} 321 322bool AliasSetTracker::add(Instruction *I) { 323 // Dispatch to one of the other add methods. 324 if (LoadInst *LI = dyn_cast<LoadInst>(I)) 325 return add(LI); 326 if (StoreInst *SI = dyn_cast<StoreInst>(I)) 327 return add(SI); 328 if (CallInst *CI = dyn_cast<CallInst>(I)) 329 return add(CI); 330 if (InvokeInst *II = dyn_cast<InvokeInst>(I)) 331 return add(II); 332 if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I)) 333 return add(VAAI); 334 return true; 335} 336 337void AliasSetTracker::add(BasicBlock &BB) { 338 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) 339 add(I); 340} 341 342void AliasSetTracker::add(const AliasSetTracker &AST) { 343 assert(&AA == &AST.AA && 344 "Merging AliasSetTracker objects with different Alias Analyses!"); 345 346 // Loop over all of the alias sets in AST, adding the pointers contained 347 // therein into the current alias sets. This can cause alias sets to be 348 // merged together in the current AST. 349 for (const_iterator I = AST.begin(), E = AST.end(); I != E; ++I) { 350 if (I->Forward) continue; // Ignore forwarding alias sets 351 352 AliasSet &AS = const_cast<AliasSet&>(*I); 353 354 // If there are any call sites in the alias set, add them to this AST. 355 for (unsigned i = 0, e = AS.CallSites.size(); i != e; ++i) 356 add(AS.CallSites[i]); 357 358 // Loop over all of the pointers in this alias set. 359 bool X; 360 for (AliasSet::iterator ASI = AS.begin(), E = AS.end(); ASI != E; ++ASI) { 361 AliasSet &NewAS = addPointer(ASI.getPointer(), ASI.getSize(), 362 (AliasSet::AccessType)AS.AccessTy, X); 363 if (AS.isVolatile()) NewAS.setVolatile(); 364 } 365 } 366} 367 368/// remove - Remove the specified (potentially non-empty) alias set from the 369/// tracker. 370void AliasSetTracker::remove(AliasSet &AS) { 371 // Drop all call sites. 372 AS.CallSites.clear(); 373 374 // Clear the alias set. 375 unsigned NumRefs = 0; 376 while (!AS.empty()) { 377 AliasSet::PointerRec *P = AS.PtrList; 378 379 Value *ValToRemove = P->getValue(); 380 381 // Unlink and delete entry from the list of values. 382 P->eraseFromList(); 383 384 // Remember how many references need to be dropped. 385 ++NumRefs; 386 387 // Finally, remove the entry. 388 PointerMap.erase(ValToRemove); 389 } 390 391 // Stop using the alias set, removing it. 392 AS.RefCount -= NumRefs; 393 if (AS.RefCount == 0) 394 AS.removeFromTracker(*this); 395} 396 397bool AliasSetTracker::remove(Value *Ptr, unsigned Size) { 398 AliasSet *AS = findAliasSetForPointer(Ptr, Size); 399 if (!AS) return false; 400 remove(*AS); 401 return true; 402} 403 404bool AliasSetTracker::remove(LoadInst *LI) { 405 unsigned Size = AA.getTypeStoreSize(LI->getType()); 406 AliasSet *AS = findAliasSetForPointer(LI->getOperand(0), Size); 407 if (!AS) return false; 408 remove(*AS); 409 return true; 410} 411 412bool AliasSetTracker::remove(StoreInst *SI) { 413 unsigned Size = AA.getTypeStoreSize(SI->getOperand(0)->getType()); 414 AliasSet *AS = findAliasSetForPointer(SI->getOperand(1), Size); 415 if (!AS) return false; 416 remove(*AS); 417 return true; 418} 419 420bool AliasSetTracker::remove(VAArgInst *VAAI) { 421 AliasSet *AS = findAliasSetForPointer(VAAI->getOperand(0), ~0); 422 if (!AS) return false; 423 remove(*AS); 424 return true; 425} 426 427bool AliasSetTracker::remove(CallSite CS) { 428 if (AA.doesNotAccessMemory(CS)) 429 return false; // doesn't alias anything 430 431 AliasSet *AS = findAliasSetForCallSite(CS); 432 if (!AS) return false; 433 remove(*AS); 434 return true; 435} 436 437bool AliasSetTracker::remove(Instruction *I) { 438 // Dispatch to one of the other remove methods... 439 if (LoadInst *LI = dyn_cast<LoadInst>(I)) 440 return remove(LI); 441 if (StoreInst *SI = dyn_cast<StoreInst>(I)) 442 return remove(SI); 443 if (CallInst *CI = dyn_cast<CallInst>(I)) 444 return remove(CI); 445 if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I)) 446 return remove(VAAI); 447 return true; 448} 449 450 451// deleteValue method - This method is used to remove a pointer value from the 452// AliasSetTracker entirely. It should be used when an instruction is deleted 453// from the program to update the AST. If you don't use this, you would have 454// dangling pointers to deleted instructions. 455// 456void AliasSetTracker::deleteValue(Value *PtrVal) { 457 // Notify the alias analysis implementation that this value is gone. 458 AA.deleteValue(PtrVal); 459 460 // If this is a call instruction, remove the callsite from the appropriate 461 // AliasSet. 462 if (CallSite CS = PtrVal) 463 if (!AA.doesNotAccessMemory(CS)) 464 if (AliasSet *AS = findAliasSetForCallSite(CS)) 465 AS->removeCallSite(CS); 466 467 // First, look up the PointerRec for this pointer. 468 PointerMapType::iterator I = PointerMap.find(PtrVal); 469 if (I == PointerMap.end()) return; // Noop 470 471 // If we found one, remove the pointer from the alias set it is in. 472 AliasSet::PointerRec *PtrValEnt = I->second; 473 AliasSet *AS = PtrValEnt->getAliasSet(*this); 474 475 // Unlink and delete from the list of values. 476 PtrValEnt->eraseFromList(); 477 478 // Stop using the alias set. 479 AS->dropRef(*this); 480 481 PointerMap.erase(I); 482} 483 484// copyValue - This method should be used whenever a preexisting value in the 485// program is copied or cloned, introducing a new value. Note that it is ok for 486// clients that use this method to introduce the same value multiple times: if 487// the tracker already knows about a value, it will ignore the request. 488// 489void AliasSetTracker::copyValue(Value *From, Value *To) { 490 // Notify the alias analysis implementation that this value is copied. 491 AA.copyValue(From, To); 492 493 // First, look up the PointerRec for this pointer. 494 PointerMapType::iterator I = PointerMap.find(From); 495 if (I == PointerMap.end()) 496 return; // Noop 497 assert(I->second->hasAliasSet() && "Dead entry?"); 498 499 AliasSet::PointerRec &Entry = getEntryFor(To); 500 if (Entry.hasAliasSet()) return; // Already in the tracker! 501 502 // Add it to the alias set it aliases... 503 I = PointerMap.find(From); 504 AliasSet *AS = I->second->getAliasSet(*this); 505 AS->addPointer(*this, Entry, I->second->getSize(), true); 506} 507 508 509 510//===----------------------------------------------------------------------===// 511// AliasSet/AliasSetTracker Printing Support 512//===----------------------------------------------------------------------===// 513 514void AliasSet::print(raw_ostream &OS) const { 515 OS << " AliasSet[" << format("0x%p", (void*)this) << "," << RefCount << "] "; 516 OS << (AliasTy == MustAlias ? "must" : "may") << " alias, "; 517 switch (AccessTy) { 518 case NoModRef: OS << "No access "; break; 519 case Refs : OS << "Ref "; break; 520 case Mods : OS << "Mod "; break; 521 case ModRef : OS << "Mod/Ref "; break; 522 default: llvm_unreachable("Bad value for AccessTy!"); 523 } 524 if (isVolatile()) OS << "[volatile] "; 525 if (Forward) 526 OS << " forwarding to " << (void*)Forward; 527 528 529 if (!empty()) { 530 OS << "Pointers: "; 531 for (iterator I = begin(), E = end(); I != E; ++I) { 532 if (I != begin()) OS << ", "; 533 WriteAsOperand(OS << "(", I.getPointer()); 534 OS << ", " << I.getSize() << ")"; 535 } 536 } 537 if (!CallSites.empty()) { 538 OS << "\n " << CallSites.size() << " Call Sites: "; 539 for (unsigned i = 0, e = CallSites.size(); i != e; ++i) { 540 if (i) OS << ", "; 541 WriteAsOperand(OS, CallSites[i].getCalledValue()); 542 } 543 } 544 OS << "\n"; 545} 546 547void AliasSetTracker::print(raw_ostream &OS) const { 548 OS << "Alias Set Tracker: " << AliasSets.size() << " alias sets for " 549 << PointerMap.size() << " pointer values.\n"; 550 for (const_iterator I = begin(), E = end(); I != E; ++I) 551 I->print(OS); 552 OS << "\n"; 553} 554 555void AliasSet::dump() const { print(dbgs()); } 556void AliasSetTracker::dump() const { print(dbgs()); } 557 558//===----------------------------------------------------------------------===// 559// ASTCallbackVH Class Implementation 560//===----------------------------------------------------------------------===// 561 562void AliasSetTracker::ASTCallbackVH::deleted() { 563 assert(AST && "ASTCallbackVH called with a null AliasSetTracker!"); 564 AST->deleteValue(getValPtr()); 565 // this now dangles! 566} 567 568AliasSetTracker::ASTCallbackVH::ASTCallbackVH(Value *V, AliasSetTracker *ast) 569 : CallbackVH(V), AST(ast) {} 570 571AliasSetTracker::ASTCallbackVH & 572AliasSetTracker::ASTCallbackVH::operator=(Value *V) { 573 return *this = ASTCallbackVH(V, AST); 574} 575 576//===----------------------------------------------------------------------===// 577// AliasSetPrinter Pass 578//===----------------------------------------------------------------------===// 579 580namespace { 581 class AliasSetPrinter : public FunctionPass { 582 AliasSetTracker *Tracker; 583 public: 584 static char ID; // Pass identification, replacement for typeid 585 AliasSetPrinter() : FunctionPass(ID) {} 586 587 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 588 AU.setPreservesAll(); 589 AU.addRequired<AliasAnalysis>(); 590 } 591 592 virtual bool runOnFunction(Function &F) { 593 Tracker = new AliasSetTracker(getAnalysis<AliasAnalysis>()); 594 595 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) 596 Tracker->add(&*I); 597 Tracker->print(errs()); 598 delete Tracker; 599 return false; 600 } 601 }; 602} 603 604char AliasSetPrinter::ID = 0; 605INITIALIZE_PASS(AliasSetPrinter, "print-alias-sets", 606 "Alias Set Printer", false, true); 607