AliasSetTracker.cpp revision dff6710717b159f089c76a07eda074eb6347eb92
1//===- AliasSetTracker.cpp - Alias Sets Tracker implementation-------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file was developed by the LLVM research group and is distributed under 6// the University of Illinois Open Source 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/Pass.h" 18#include "llvm/Type.h" 19#include "llvm/Target/TargetData.h" 20#include "llvm/Assembly/Writer.h" 21#include "llvm/Support/Compiler.h" 22#include "llvm/Support/InstIterator.h" 23#include "llvm/Support/Streams.h" 24using namespace llvm; 25 26/// mergeSetIn - Merge the specified alias set into this alias set. 27/// 28void AliasSet::mergeSetIn(AliasSet &AS, AliasSetTracker &AST) { 29 assert(!AS.Forward && "Alias set is already forwarding!"); 30 assert(!Forward && "This set is a forwarding set!!"); 31 32 // Update the alias and access types of this set... 33 AccessTy |= AS.AccessTy; 34 AliasTy |= AS.AliasTy; 35 36 if (AliasTy == MustAlias) { 37 // Check that these two merged sets really are must aliases. Since both 38 // used to be must-alias sets, we can just check any pointer from each set 39 // for aliasing. 40 AliasAnalysis &AA = AST.getAliasAnalysis(); 41 HashNodePair *L = getSomePointer(); 42 HashNodePair *R = AS.getSomePointer(); 43 44 // If the pointers are not a must-alias pair, this set becomes a may alias. 45 if (AA.alias(L->first, L->second.getSize(), R->first, R->second.getSize()) 46 != AliasAnalysis::MustAlias) 47 AliasTy = MayAlias; 48 } 49 50 if (CallSites.empty()) { // Merge call sites... 51 if (!AS.CallSites.empty()) 52 std::swap(CallSites, AS.CallSites); 53 } else if (!AS.CallSites.empty()) { 54 CallSites.insert(CallSites.end(), AS.CallSites.begin(), AS.CallSites.end()); 55 AS.CallSites.clear(); 56 } 57 58 AS.Forward = this; // Forward across AS now... 59 addRef(); // AS is now pointing to us... 60 61 // Merge the list of constituent pointers... 62 if (AS.PtrList) { 63 *PtrListEnd = AS.PtrList; 64 AS.PtrList->second.setPrevInList(PtrListEnd); 65 PtrListEnd = AS.PtrListEnd; 66 67 AS.PtrList = 0; 68 AS.PtrListEnd = &AS.PtrList; 69 assert(*AS.PtrListEnd == 0 && "End of list is not null?"); 70 } 71} 72 73void AliasSetTracker::removeAliasSet(AliasSet *AS) { 74 if (AliasSet *Fwd = AS->Forward) { 75 Fwd->dropRef(*this); 76 AS->Forward = 0; 77 } 78 AliasSets.erase(AS); 79} 80 81void AliasSet::removeFromTracker(AliasSetTracker &AST) { 82 assert(RefCount == 0 && "Cannot remove non-dead alias set from tracker!"); 83 AST.removeAliasSet(this); 84} 85 86void AliasSet::addPointer(AliasSetTracker &AST, HashNodePair &Entry, 87 unsigned Size, bool KnownMustAlias) { 88 assert(!Entry.second.hasAliasSet() && "Entry already in set!"); 89 90 // Check to see if we have to downgrade to _may_ alias. 91 if (isMustAlias() && !KnownMustAlias) 92 if (HashNodePair *P = getSomePointer()) { 93 AliasAnalysis &AA = AST.getAliasAnalysis(); 94 AliasAnalysis::AliasResult Result = 95 AA.alias(P->first, P->second.getSize(), Entry.first, Size); 96 if (Result == AliasAnalysis::MayAlias) 97 AliasTy = MayAlias; 98 else // First entry of must alias must have maximum size! 99 P->second.updateSize(Size); 100 assert(Result != AliasAnalysis::NoAlias && "Cannot be part of must set!"); 101 } 102 103 Entry.second.setAliasSet(this); 104 Entry.second.updateSize(Size); 105 106 // Add it to the end of the list... 107 assert(*PtrListEnd == 0 && "End of list is not null?"); 108 *PtrListEnd = &Entry; 109 PtrListEnd = Entry.second.setPrevInList(PtrListEnd); 110 assert(*PtrListEnd == 0 && "End of list is not null?"); 111 addRef(); // Entry points to alias set... 112} 113 114void AliasSet::addCallSite(CallSite CS, AliasAnalysis &AA) { 115 CallSites.push_back(CS); 116 117 AliasAnalysis::ModRefBehavior Behavior = AA.getModRefBehavior(CS); 118 if (Behavior == AliasAnalysis::DoesNotAccessMemory) 119 return; 120 else if (Behavior == AliasAnalysis::OnlyReadsMemory) { 121 AliasTy = MayAlias; 122 AccessTy |= Refs; 123 return; 124 } 125 126 // FIXME: This should use mod/ref information to make this not suck so bad 127 AliasTy = MayAlias; 128 AccessTy = ModRef; 129} 130 131/// aliasesPointer - Return true if the specified pointer "may" (or must) 132/// alias one of the members in the set. 133/// 134bool AliasSet::aliasesPointer(const Value *Ptr, unsigned Size, 135 AliasAnalysis &AA) const { 136 if (AliasTy == MustAlias) { 137 assert(CallSites.empty() && "Illegal must alias set!"); 138 139 // If this is a set of MustAliases, only check to see if the pointer aliases 140 // SOME value in the set... 141 HashNodePair *SomePtr = getSomePointer(); 142 assert(SomePtr && "Empty must-alias set??"); 143 return AA.alias(SomePtr->first, SomePtr->second.getSize(), Ptr, Size); 144 } 145 146 // If this is a may-alias set, we have to check all of the pointers in the set 147 // to be sure it doesn't alias the set... 148 for (iterator I = begin(), E = end(); I != E; ++I) 149 if (AA.alias(Ptr, Size, I.getPointer(), I.getSize())) 150 return true; 151 152 // Check the call sites list and invoke list... 153 if (!CallSites.empty()) { 154 if (AA.hasNoModRefInfoForCalls()) 155 return true; 156 157 for (unsigned i = 0, e = CallSites.size(); i != e; ++i) 158 if (AA.getModRefInfo(CallSites[i], const_cast<Value*>(Ptr), Size) 159 != 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 if (AA.hasNoModRefInfoForCalls()) 171 return true; 172 173 for (unsigned i = 0, e = CallSites.size(); i != e; ++i) 174 if (AA.getModRefInfo(CallSites[i], CS) != AliasAnalysis::NoModRef || 175 AA.getModRefInfo(CS, CallSites[i]) != AliasAnalysis::NoModRef) 176 return true; 177 178 for (iterator I = begin(), E = end(); I != E; ++I) 179 if (AA.getModRefInfo(CS, I.getPointer(), I.getSize()) != 180 AliasAnalysis::NoModRef) 181 return true; 182 183 return false; 184} 185 186 187/// findAliasSetForPointer - Given a pointer, find the one alias set to put the 188/// instruction referring to the pointer into. If there are multiple alias sets 189/// that may alias the pointer, merge them together and return the unified set. 190/// 191AliasSet *AliasSetTracker::findAliasSetForPointer(const Value *Ptr, 192 unsigned Size) { 193 AliasSet *FoundSet = 0; 194 for (iterator I = begin(), E = end(); I != E; ++I) 195 if (!I->Forward && I->aliasesPointer(Ptr, Size, AA)) { 196 if (FoundSet == 0) { // If this is the first alias set ptr can go into. 197 FoundSet = I; // Remember it. 198 } else { // Otherwise, we must merge the sets. 199 FoundSet->mergeSetIn(*I, *this); // Merge in contents. 200 } 201 } 202 203 return FoundSet; 204} 205 206/// containsPointer - Return true if the specified location is represented by 207/// this alias set, false otherwise. This does not modify the AST object or 208/// alias sets. 209bool AliasSetTracker::containsPointer(Value *Ptr, unsigned Size) const { 210 for (const_iterator I = begin(), E = end(); I != E; ++I) 211 if (!I->Forward && I->aliasesPointer(Ptr, Size, AA)) 212 return true; 213 return false; 214} 215 216 217 218AliasSet *AliasSetTracker::findAliasSetForCallSite(CallSite CS) { 219 AliasSet *FoundSet = 0; 220 for (iterator I = begin(), E = end(); I != E; ++I) 221 if (!I->Forward && I->aliasesCallSite(CS, AA)) { 222 if (FoundSet == 0) { // If this is the first alias set ptr can go into. 223 FoundSet = I; // Remember it. 224 } else if (!I->Forward) { // Otherwise, we must merge the sets. 225 FoundSet->mergeSetIn(*I, *this); // Merge in contents. 226 } 227 } 228 229 return FoundSet; 230} 231 232 233 234 235/// getAliasSetForPointer - Return the alias set that the specified pointer 236/// lives in... 237AliasSet &AliasSetTracker::getAliasSetForPointer(Value *Pointer, unsigned Size, 238 bool *New) { 239 AliasSet::HashNodePair &Entry = getEntryFor(Pointer); 240 241 // Check to see if the pointer is already known... 242 if (Entry.second.hasAliasSet()) { 243 Entry.second.updateSize(Size); 244 // Return the set! 245 return *Entry.second.getAliasSet(*this)->getForwardedTarget(*this); 246 } else if (AliasSet *AS = findAliasSetForPointer(Pointer, Size)) { 247 // Add it to the alias set it aliases... 248 AS->addPointer(*this, Entry, Size); 249 return *AS; 250 } else { 251 if (New) *New = true; 252 // Otherwise create a new alias set to hold the loaded pointer... 253 AliasSets.push_back(new AliasSet()); 254 AliasSets.back().addPointer(*this, Entry, Size); 255 return AliasSets.back(); 256 } 257} 258 259bool AliasSetTracker::add(Value *Ptr, unsigned Size) { 260 bool NewPtr; 261 addPointer(Ptr, Size, AliasSet::NoModRef, NewPtr); 262 return NewPtr; 263} 264 265 266bool AliasSetTracker::add(LoadInst *LI) { 267 bool NewPtr; 268 AliasSet &AS = addPointer(LI->getOperand(0), 269 AA.getTargetData().getTypeStoreSize(LI->getType()), 270 AliasSet::Refs, NewPtr); 271 if (LI->isVolatile()) AS.setVolatile(); 272 return NewPtr; 273} 274 275bool AliasSetTracker::add(StoreInst *SI) { 276 bool NewPtr; 277 Value *Val = SI->getOperand(0); 278 AliasSet &AS = addPointer(SI->getOperand(1), 279 AA.getTargetData().getTypeStoreSize(Val->getType()), 280 AliasSet::Mods, NewPtr); 281 if (SI->isVolatile()) AS.setVolatile(); 282 return NewPtr; 283} 284 285bool AliasSetTracker::add(FreeInst *FI) { 286 bool NewPtr; 287 AliasSet &AS = addPointer(FI->getOperand(0), ~0, 288 AliasSet::Mods, NewPtr); 289 290 // Free operations are volatile ops (cannot be moved). 291 AS.setVolatile(); 292 return NewPtr; 293} 294 295 296bool AliasSetTracker::add(CallSite CS) { 297 if (AA.doesNotAccessMemory(CS)) 298 return true; // doesn't alias anything 299 300 AliasSet *AS = findAliasSetForCallSite(CS); 301 if (!AS) { 302 AliasSets.push_back(new AliasSet()); 303 AS = &AliasSets.back(); 304 AS->addCallSite(CS, AA); 305 return true; 306 } else { 307 AS->addCallSite(CS, AA); 308 return false; 309 } 310} 311 312bool AliasSetTracker::add(Instruction *I) { 313 // Dispatch to one of the other add methods... 314 if (LoadInst *LI = dyn_cast<LoadInst>(I)) 315 return add(LI); 316 else if (StoreInst *SI = dyn_cast<StoreInst>(I)) 317 return add(SI); 318 else if (CallInst *CI = dyn_cast<CallInst>(I)) 319 return add(CI); 320 else if (InvokeInst *II = dyn_cast<InvokeInst>(I)) 321 return add(II); 322 else if (FreeInst *FI = dyn_cast<FreeInst>(I)) 323 return add(FI); 324 return true; 325} 326 327void AliasSetTracker::add(BasicBlock &BB) { 328 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) 329 add(I); 330} 331 332void AliasSetTracker::add(const AliasSetTracker &AST) { 333 assert(&AA == &AST.AA && 334 "Merging AliasSetTracker objects with different Alias Analyses!"); 335 336 // Loop over all of the alias sets in AST, adding the pointers contained 337 // therein into the current alias sets. This can cause alias sets to be 338 // merged together in the current AST. 339 for (const_iterator I = AST.begin(), E = AST.end(); I != E; ++I) 340 if (!I->Forward) { // Ignore forwarding alias sets 341 AliasSet &AS = const_cast<AliasSet&>(*I); 342 343 // If there are any call sites in the alias set, add them to this AST. 344 for (unsigned i = 0, e = AS.CallSites.size(); i != e; ++i) 345 add(AS.CallSites[i]); 346 347 // Loop over all of the pointers in this alias set... 348 AliasSet::iterator I = AS.begin(), E = AS.end(); 349 bool X; 350 for (; I != E; ++I) { 351 AliasSet &NewAS = addPointer(I.getPointer(), I.getSize(), 352 (AliasSet::AccessType)AS.AccessTy, X); 353 if (AS.isVolatile()) NewAS.setVolatile(); 354 } 355 } 356} 357 358/// remove - Remove the specified (potentially non-empty) alias set from the 359/// tracker. 360void AliasSetTracker::remove(AliasSet &AS) { 361 // Drop all call sites. 362 AS.CallSites.clear(); 363 364 // Clear the alias set. 365 unsigned NumRefs = 0; 366 while (!AS.empty()) { 367 AliasSet::HashNodePair *P = AS.PtrList; 368 369 // Unlink from the list of values. 370 P->second.removeFromList(); 371 372 // Remember how many references need to be dropped. 373 ++NumRefs; 374 375 // Finally, remove the entry. 376 Value *Remove = P->first; // Take a copy because it is invalid to pass 377 PointerMap.erase(Remove); // a reference to the data being erased. 378 } 379 380 // Stop using the alias set, removing it. 381 AS.RefCount -= NumRefs; 382 if (AS.RefCount == 0) 383 AS.removeFromTracker(*this); 384} 385 386bool AliasSetTracker::remove(Value *Ptr, unsigned Size) { 387 AliasSet *AS = findAliasSetForPointer(Ptr, Size); 388 if (!AS) return false; 389 remove(*AS); 390 return true; 391} 392 393bool AliasSetTracker::remove(LoadInst *LI) { 394 unsigned Size = AA.getTargetData().getTypeStoreSize(LI->getType()); 395 AliasSet *AS = findAliasSetForPointer(LI->getOperand(0), Size); 396 if (!AS) return false; 397 remove(*AS); 398 return true; 399} 400 401bool AliasSetTracker::remove(StoreInst *SI) { 402 unsigned Size = 403 AA.getTargetData().getTypeStoreSize(SI->getOperand(0)->getType()); 404 AliasSet *AS = findAliasSetForPointer(SI->getOperand(1), Size); 405 if (!AS) return false; 406 remove(*AS); 407 return true; 408} 409 410bool AliasSetTracker::remove(FreeInst *FI) { 411 AliasSet *AS = findAliasSetForPointer(FI->getOperand(0), ~0); 412 if (!AS) return false; 413 remove(*AS); 414 return true; 415} 416 417bool AliasSetTracker::remove(CallSite CS) { 418 if (AA.doesNotAccessMemory(CS)) 419 return false; // doesn't alias anything 420 421 AliasSet *AS = findAliasSetForCallSite(CS); 422 if (!AS) return false; 423 remove(*AS); 424 return true; 425} 426 427bool AliasSetTracker::remove(Instruction *I) { 428 // Dispatch to one of the other remove methods... 429 if (LoadInst *LI = dyn_cast<LoadInst>(I)) 430 return remove(LI); 431 else if (StoreInst *SI = dyn_cast<StoreInst>(I)) 432 return remove(SI); 433 else if (CallInst *CI = dyn_cast<CallInst>(I)) 434 return remove(CI); 435 else if (FreeInst *FI = dyn_cast<FreeInst>(I)) 436 return remove(FI); 437 return true; 438} 439 440 441// deleteValue method - This method is used to remove a pointer value from the 442// AliasSetTracker entirely. It should be used when an instruction is deleted 443// from the program to update the AST. If you don't use this, you would have 444// dangling pointers to deleted instructions. 445// 446void AliasSetTracker::deleteValue(Value *PtrVal) { 447 // Notify the alias analysis implementation that this value is gone. 448 AA.deleteValue(PtrVal); 449 450 // If this is a call instruction, remove the callsite from the appropriate 451 // AliasSet. 452 CallSite CS = CallSite::get(PtrVal); 453 if (CS.getInstruction()) 454 if (!AA.doesNotAccessMemory(CS)) 455 if (AliasSet *AS = findAliasSetForCallSite(CS)) 456 AS->removeCallSite(CS); 457 458 // First, look up the PointerRec for this pointer. 459 hash_map<Value*, AliasSet::PointerRec>::iterator I = PointerMap.find(PtrVal); 460 if (I == PointerMap.end()) return; // Noop 461 462 // If we found one, remove the pointer from the alias set it is in. 463 AliasSet::HashNodePair &PtrValEnt = *I; 464 AliasSet *AS = PtrValEnt.second.getAliasSet(*this); 465 466 // Unlink from the list of values... 467 PtrValEnt.second.removeFromList(); 468 // Stop using the alias set 469 AS->dropRef(*this); 470 PointerMap.erase(I); 471} 472 473// copyValue - This method should be used whenever a preexisting value in the 474// program is copied or cloned, introducing a new value. Note that it is ok for 475// clients that use this method to introduce the same value multiple times: if 476// the tracker already knows about a value, it will ignore the request. 477// 478void AliasSetTracker::copyValue(Value *From, Value *To) { 479 // Notify the alias analysis implementation that this value is copied. 480 AA.copyValue(From, To); 481 482 // First, look up the PointerRec for this pointer. 483 hash_map<Value*, AliasSet::PointerRec>::iterator I = PointerMap.find(From); 484 if (I == PointerMap.end() || !I->second.hasAliasSet()) 485 return; // Noop 486 487 AliasSet::HashNodePair &Entry = getEntryFor(To); 488 if (Entry.second.hasAliasSet()) return; // Already in the tracker! 489 490 // Add it to the alias set it aliases... 491 AliasSet *AS = I->second.getAliasSet(*this); 492 AS->addPointer(*this, Entry, I->second.getSize(), true); 493} 494 495 496 497//===----------------------------------------------------------------------===// 498// AliasSet/AliasSetTracker Printing Support 499//===----------------------------------------------------------------------===// 500 501void AliasSet::print(std::ostream &OS) const { 502 OS << " AliasSet[" << (void*)this << "," << RefCount << "] "; 503 OS << (AliasTy == MustAlias ? "must" : "may ") << " alias, "; 504 switch (AccessTy) { 505 case NoModRef: OS << "No access "; break; 506 case Refs : OS << "Ref "; break; 507 case Mods : OS << "Mod "; break; 508 case ModRef : OS << "Mod/Ref "; break; 509 default: assert(0 && "Bad value for AccessTy!"); 510 } 511 if (isVolatile()) OS << "[volatile] "; 512 if (Forward) 513 OS << " forwarding to " << (void*)Forward; 514 515 516 if (!empty()) { 517 OS << "Pointers: "; 518 for (iterator I = begin(), E = end(); I != E; ++I) { 519 if (I != begin()) OS << ", "; 520 WriteAsOperand(OS << "(", I.getPointer()); 521 OS << ", " << I.getSize() << ")"; 522 } 523 } 524 if (!CallSites.empty()) { 525 OS << "\n " << CallSites.size() << " Call Sites: "; 526 for (unsigned i = 0, e = CallSites.size(); i != e; ++i) { 527 if (i) OS << ", "; 528 WriteAsOperand(OS, CallSites[i].getCalledValue()); 529 } 530 } 531 OS << "\n"; 532} 533 534void AliasSetTracker::print(std::ostream &OS) const { 535 OS << "Alias Set Tracker: " << AliasSets.size() << " alias sets for " 536 << PointerMap.size() << " pointer values.\n"; 537 for (const_iterator I = begin(), E = end(); I != E; ++I) 538 I->print(OS); 539 OS << "\n"; 540} 541 542void AliasSet::dump() const { print (cerr); } 543void AliasSetTracker::dump() const { print(cerr); } 544 545//===----------------------------------------------------------------------===// 546// AliasSetPrinter Pass 547//===----------------------------------------------------------------------===// 548 549namespace { 550 class VISIBILITY_HIDDEN AliasSetPrinter : public FunctionPass { 551 AliasSetTracker *Tracker; 552 public: 553 static char ID; // Pass identification, replacement for typeid 554 AliasSetPrinter() : FunctionPass((intptr_t)&ID) {} 555 556 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 557 AU.setPreservesAll(); 558 AU.addRequired<AliasAnalysis>(); 559 } 560 561 virtual bool runOnFunction(Function &F) { 562 Tracker = new AliasSetTracker(getAnalysis<AliasAnalysis>()); 563 564 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) 565 Tracker->add(&*I); 566 Tracker->print(cerr); 567 delete Tracker; 568 return false; 569 } 570 }; 571 char AliasSetPrinter::ID = 0; 572 RegisterPass<AliasSetPrinter> X("print-alias-sets", "Alias Set Printer"); 573} 574