AliasSetTracker.cpp revision 959e321a1b41e70cfb2c67cebb3a8c1f79cbf3d3
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/InstIterator.h" 22#include <iostream> 23using namespace llvm; 24 25/// mergeSetIn - Merge the specified alias set into this alias set. 26/// 27void AliasSet::mergeSetIn(AliasSet &AS, AliasSetTracker &AST) { 28 assert(!AS.Forward && "Alias set is already forwarding!"); 29 assert(!Forward && "This set is a forwarding set!!"); 30 31 // Update the alias and access types of this set... 32 AccessTy |= AS.AccessTy; 33 AliasTy |= AS.AliasTy; 34 35 if (AliasTy == MustAlias) { 36 // Check that these two merged sets really are must aliases. Since both 37 // used to be must-alias sets, we can just check any pointer from each set 38 // for aliasing. 39 AliasAnalysis &AA = AST.getAliasAnalysis(); 40 HashNodePair *L = getSomePointer(); 41 HashNodePair *R = AS.getSomePointer(); 42 43 // If the pointers are not a must-alias pair, this set becomes a may alias. 44 if (AA.alias(L->first, L->second.getSize(), R->first, R->second.getSize()) 45 != AliasAnalysis::MustAlias) 46 AliasTy = MayAlias; 47 } 48 49 if (CallSites.empty()) { // Merge call sites... 50 if (!AS.CallSites.empty()) 51 std::swap(CallSites, AS.CallSites); 52 } else if (!AS.CallSites.empty()) { 53 CallSites.insert(CallSites.end(), AS.CallSites.begin(), AS.CallSites.end()); 54 AS.CallSites.clear(); 55 } 56 57 AS.Forward = this; // Forward across AS now... 58 addRef(); // AS is now pointing to us... 59 60 // Merge the list of constituent pointers... 61 if (AS.PtrList) { 62 *PtrListEnd = AS.PtrList; 63 AS.PtrList->second.setPrevInList(PtrListEnd); 64 PtrListEnd = AS.PtrListEnd; 65 66 AS.PtrList = 0; 67 AS.PtrListEnd = &AS.PtrList; 68 assert(*AS.PtrListEnd == 0 && "End of list is not null?"); 69 } 70} 71 72void AliasSetTracker::removeAliasSet(AliasSet *AS) { 73 if (AliasSet *Fwd = AS->Forward) { 74 Fwd->dropRef(*this); 75 AS->Forward = 0; 76 } 77 AliasSets.erase(AS); 78} 79 80void AliasSet::removeFromTracker(AliasSetTracker &AST) { 81 assert(RefCount == 0 && "Cannot remove non-dead alias set from tracker!"); 82 AST.removeAliasSet(this); 83} 84 85void AliasSet::addPointer(AliasSetTracker &AST, HashNodePair &Entry, 86 unsigned Size, bool KnownMustAlias) { 87 assert(!Entry.second.hasAliasSet() && "Entry already in set!"); 88 89 // Check to see if we have to downgrade to _may_ alias. 90 if (isMustAlias() && !KnownMustAlias) 91 if (HashNodePair *P = getSomePointer()) { 92 AliasAnalysis &AA = AST.getAliasAnalysis(); 93 AliasAnalysis::AliasResult Result = 94 AA.alias(P->first, P->second.getSize(), Entry.first, Size); 95 if (Result == AliasAnalysis::MayAlias) 96 AliasTy = MayAlias; 97 else // First entry of must alias must have maximum size! 98 P->second.updateSize(Size); 99 assert(Result != AliasAnalysis::NoAlias && "Cannot be part of must set!"); 100 } 101 102 Entry.second.setAliasSet(this); 103 Entry.second.updateSize(Size); 104 105 // Add it to the end of the list... 106 assert(*PtrListEnd == 0 && "End of list is not null?"); 107 *PtrListEnd = &Entry; 108 PtrListEnd = Entry.second.setPrevInList(PtrListEnd); 109 assert(*PtrListEnd == 0 && "End of list is not null?"); 110 addRef(); // Entry points to alias set... 111} 112 113void AliasSet::addCallSite(CallSite CS, AliasAnalysis &AA) { 114 CallSites.push_back(CS); 115 116 if (Function *F = CS.getCalledFunction()) { 117 AliasAnalysis::ModRefBehavior Behavior = AA.getModRefBehavior(F, CS); 118 if (Behavior == AliasAnalysis::DoesNotAccessMemory) 119 return; 120 else if (Behavior == AliasAnalysis::OnlyReadsMemory) { 121 AliasTy = MayAlias; 122 AccessTy |= Refs; 123 return; 124 } 125 } 126 127 // 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 HashNodePair *SomePtr = getSomePointer(); 143 assert(SomePtr && "Empty must-alias set??"); 144 return AA.alias(SomePtr->first, SomePtr->second.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 (Function *F = CS.getCalledFunction()) 169 if (AA.doesNotAccessMemory(F)) 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} 187 188 189/// findAliasSetForPointer - Given a pointer, find the one alias set to put the 190/// instruction referring to the pointer into. If there are multiple alias sets 191/// that may alias the pointer, merge them together and return the unified set. 192/// 193AliasSet *AliasSetTracker::findAliasSetForPointer(const Value *Ptr, 194 unsigned Size) { 195 AliasSet *FoundSet = 0; 196 for (iterator I = begin(), E = end(); I != E; ++I) 197 if (!I->Forward && I->aliasesPointer(Ptr, Size, AA)) { 198 if (FoundSet == 0) { // If this is the first alias set ptr can go into. 199 FoundSet = I; // Remember it. 200 } else { // Otherwise, we must merge the sets. 201 FoundSet->mergeSetIn(*I, *this); // Merge in contents. 202 } 203 } 204 205 return FoundSet; 206} 207 208/// containsPointer - Return true if the specified location is represented by 209/// this alias set, false otherwise. This does not modify the AST object or 210/// alias sets. 211bool AliasSetTracker::containsPointer(Value *Ptr, unsigned Size) const { 212 for (const_iterator I = begin(), E = end(); I != E; ++I) 213 if (!I->Forward && I->aliasesPointer(Ptr, Size, AA)) 214 return true; 215 return false; 216} 217 218 219 220AliasSet *AliasSetTracker::findAliasSetForCallSite(CallSite CS) { 221 AliasSet *FoundSet = 0; 222 for (iterator I = begin(), E = end(); I != E; ++I) 223 if (!I->Forward && I->aliasesCallSite(CS, AA)) { 224 if (FoundSet == 0) { // If this is the first alias set ptr can go into. 225 FoundSet = I; // Remember it. 226 } else if (!I->Forward) { // Otherwise, we must merge the sets. 227 FoundSet->mergeSetIn(*I, *this); // Merge in contents. 228 } 229 } 230 231 return FoundSet; 232} 233 234 235 236 237/// getAliasSetForPointer - Return the alias set that the specified pointer 238/// lives in... 239AliasSet &AliasSetTracker::getAliasSetForPointer(Value *Pointer, unsigned Size, 240 bool *New) { 241 AliasSet::HashNodePair &Entry = getEntryFor(Pointer); 242 243 // Check to see if the pointer is already known... 244 if (Entry.second.hasAliasSet()) { 245 Entry.second.updateSize(Size); 246 // Return the set! 247 return *Entry.second.getAliasSet(*this)->getForwardedTarget(*this); 248 } else if (AliasSet *AS = findAliasSetForPointer(Pointer, Size)) { 249 // Add it to the alias set it aliases... 250 AS->addPointer(*this, Entry, Size); 251 return *AS; 252 } else { 253 if (New) *New = true; 254 // Otherwise create a new alias set to hold the loaded pointer... 255 AliasSets.push_back(new AliasSet()); 256 AliasSets.back().addPointer(*this, Entry, Size); 257 return AliasSets.back(); 258 } 259} 260 261bool AliasSetTracker::add(Value *Ptr, unsigned Size) { 262 bool NewPtr; 263 addPointer(Ptr, Size, AliasSet::NoModRef, NewPtr); 264 return NewPtr; 265} 266 267 268bool AliasSetTracker::add(LoadInst *LI) { 269 bool NewPtr; 270 AliasSet &AS = addPointer(LI->getOperand(0), 271 AA.getTargetData().getTypeSize(LI->getType()), 272 AliasSet::Refs, NewPtr); 273 if (LI->isVolatile()) AS.setVolatile(); 274 return NewPtr; 275} 276 277bool AliasSetTracker::add(StoreInst *SI) { 278 bool NewPtr; 279 Value *Val = SI->getOperand(0); 280 AliasSet &AS = addPointer(SI->getOperand(1), 281 AA.getTargetData().getTypeSize(Val->getType()), 282 AliasSet::Mods, NewPtr); 283 if (SI->isVolatile()) AS.setVolatile(); 284 return NewPtr; 285} 286 287bool AliasSetTracker::add(FreeInst *FI) { 288 bool NewPtr; 289 AliasSet &AS = addPointer(FI->getOperand(0), ~0, 290 AliasSet::Mods, NewPtr); 291 292 // Free operations are volatile ops (cannot be moved). 293 AS.setVolatile(); 294 return NewPtr; 295} 296 297 298bool AliasSetTracker::add(CallSite CS) { 299 if (Function *F = CS.getCalledFunction()) 300 if (AA.doesNotAccessMemory(F)) 301 return true; // doesn't alias anything 302 303 AliasSet *AS = findAliasSetForCallSite(CS); 304 if (!AS) { 305 AliasSets.push_back(new AliasSet()); 306 AS = &AliasSets.back(); 307 AS->addCallSite(CS, AA); 308 return true; 309 } else { 310 AS->addCallSite(CS, AA); 311 return false; 312 } 313} 314 315bool AliasSetTracker::add(Instruction *I) { 316 // Dispatch to one of the other add methods... 317 if (LoadInst *LI = dyn_cast<LoadInst>(I)) 318 return add(LI); 319 else if (StoreInst *SI = dyn_cast<StoreInst>(I)) 320 return add(SI); 321 else if (CallInst *CI = dyn_cast<CallInst>(I)) 322 return add(CI); 323 else if (InvokeInst *II = dyn_cast<InvokeInst>(I)) 324 return add(II); 325 else if (FreeInst *FI = dyn_cast<FreeInst>(I)) 326 return add(FI); 327 return true; 328} 329 330void AliasSetTracker::add(BasicBlock &BB) { 331 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) 332 add(I); 333} 334 335void AliasSetTracker::add(const AliasSetTracker &AST) { 336 assert(&AA == &AST.AA && 337 "Merging AliasSetTracker objects with different Alias Analyses!"); 338 339 // Loop over all of the alias sets in AST, adding the pointers contained 340 // therein into the current alias sets. This can cause alias sets to be 341 // merged together in the current AST. 342 for (const_iterator I = AST.begin(), E = AST.end(); I != E; ++I) 343 if (!I->Forward) { // Ignore forwarding alias sets 344 AliasSet &AS = const_cast<AliasSet&>(*I); 345 346 // If there are any call sites in the alias set, add them to this AST. 347 for (unsigned i = 0, e = AS.CallSites.size(); i != e; ++i) 348 add(AS.CallSites[i]); 349 350 // Loop over all of the pointers in this alias set... 351 AliasSet::iterator I = AS.begin(), E = AS.end(); 352 bool X; 353 for (; I != E; ++I) 354 addPointer(I.getPointer(), I.getSize(), 355 (AliasSet::AccessType)AS.AccessTy, X); 356 } 357} 358 359/// remove - Remove the specified (potentially non-empty) alias set from the 360/// tracker. 361void AliasSetTracker::remove(AliasSet &AS) { 362 bool SetDead; 363 do { 364 AliasSet::iterator I = AS.begin(); 365 Value *Ptr = I.getPointer(); ++I; 366 367 // deleteValue will delete the set automatically when the last pointer 368 // reference is destroyed. "Predict" when this will happen. 369 SetDead = I == AS.end(); 370 deleteValue(Ptr); // Delete all of the pointers from the set 371 } while (!SetDead); 372} 373 374bool AliasSetTracker::remove(Value *Ptr, unsigned Size) { 375 AliasSet *AS = findAliasSetForPointer(Ptr, Size); 376 if (!AS) return false; 377 remove(*AS); 378 return true; 379} 380 381bool AliasSetTracker::remove(LoadInst *LI) { 382 unsigned Size = AA.getTargetData().getTypeSize(LI->getType()); 383 AliasSet *AS = findAliasSetForPointer(LI->getOperand(0), Size); 384 if (!AS) return false; 385 remove(*AS); 386 return true; 387} 388 389bool AliasSetTracker::remove(StoreInst *SI) { 390 unsigned Size = AA.getTargetData().getTypeSize(SI->getOperand(0)->getType()); 391 AliasSet *AS = findAliasSetForPointer(SI->getOperand(1), Size); 392 if (!AS) return false; 393 remove(*AS); 394 return true; 395} 396 397bool AliasSetTracker::remove(FreeInst *FI) { 398 AliasSet *AS = findAliasSetForPointer(FI->getOperand(0), ~0); 399 if (!AS) return false; 400 remove(*AS); 401 return true; 402} 403 404bool AliasSetTracker::remove(CallSite CS) { 405 if (Function *F = CS.getCalledFunction()) 406 if (AA.doesNotAccessMemory(F)) 407 return false; // doesn't alias anything 408 409 AliasSet *AS = findAliasSetForCallSite(CS); 410 if (!AS) return false; 411 remove(*AS); 412 return true; 413} 414 415bool AliasSetTracker::remove(Instruction *I) { 416 // Dispatch to one of the other remove methods... 417 if (LoadInst *LI = dyn_cast<LoadInst>(I)) 418 return remove(LI); 419 else if (StoreInst *SI = dyn_cast<StoreInst>(I)) 420 return remove(SI); 421 else if (CallInst *CI = dyn_cast<CallInst>(I)) 422 return remove(CI); 423 else if (FreeInst *FI = dyn_cast<FreeInst>(I)) 424 return remove(FI); 425 return true; 426} 427 428 429// deleteValue method - This method is used to remove a pointer value from the 430// AliasSetTracker entirely. It should be used when an instruction is deleted 431// from the program to update the AST. If you don't use this, you would have 432// dangling pointers to deleted instructions. 433// 434void AliasSetTracker::deleteValue(Value *PtrVal) { 435 // Notify the alias analysis implementation that this value is gone. 436 AA.deleteValue(PtrVal); 437 438 // If this is a call instruction, remove the callsite from the appropriate 439 // AliasSet. 440 CallSite CS = CallSite::get(PtrVal); 441 if (CS.getInstruction()) { 442 Function *F = CS.getCalledFunction(); 443 if (!F || !AA.doesNotAccessMemory(F)) { 444 if (AliasSet *AS = findAliasSetForCallSite(CS)) 445 AS->removeCallSite(CS); 446 } 447 } 448 449 // First, look up the PointerRec for this pointer. 450 hash_map<Value*, AliasSet::PointerRec>::iterator I = PointerMap.find(PtrVal); 451 if (I == PointerMap.end()) return; // Noop 452 453 // If we found one, remove the pointer from the alias set it is in. 454 AliasSet::HashNodePair &PtrValEnt = *I; 455 AliasSet *AS = PtrValEnt.second.getAliasSet(*this); 456 457 // Unlink from the list of values... 458 PtrValEnt.second.removeFromList(); 459 // Stop using the alias set 460 AS->dropRef(*this); 461 PointerMap.erase(I); 462} 463 464// copyValue - This method should be used whenever a preexisting value in the 465// program is copied or cloned, introducing a new value. Note that it is ok for 466// clients that use this method to introduce the same value multiple times: if 467// the tracker already knows about a value, it will ignore the request. 468// 469void AliasSetTracker::copyValue(Value *From, Value *To) { 470 // Notify the alias analysis implementation that this value is copied. 471 AA.copyValue(From, To); 472 473 // First, look up the PointerRec for this pointer. 474 hash_map<Value*, AliasSet::PointerRec>::iterator I = PointerMap.find(From); 475 if (I == PointerMap.end() || !I->second.hasAliasSet()) 476 return; // Noop 477 478 AliasSet::HashNodePair &Entry = getEntryFor(To); 479 if (Entry.second.hasAliasSet()) return; // Already in the tracker! 480 481 // Add it to the alias set it aliases... 482 AliasSet *AS = I->second.getAliasSet(*this); 483 AS->addPointer(*this, Entry, I->second.getSize(), true); 484} 485 486 487 488//===----------------------------------------------------------------------===// 489// AliasSet/AliasSetTracker Printing Support 490//===----------------------------------------------------------------------===// 491 492void AliasSet::print(std::ostream &OS) const { 493 OS << " AliasSet[" << (void*)this << "," << RefCount << "] "; 494 OS << (AliasTy == MustAlias ? "must" : "may ") << " alias, "; 495 switch (AccessTy) { 496 case NoModRef: OS << "No access "; break; 497 case Refs : OS << "Ref "; break; 498 case Mods : OS << "Mod "; break; 499 case ModRef : OS << "Mod/Ref "; break; 500 default: assert(0 && "Bad value for AccessTy!"); 501 } 502 if (isVolatile()) OS << "[volatile] "; 503 if (Forward) 504 OS << " forwarding to " << (void*)Forward; 505 506 507 if (begin() != end()) { 508 OS << "Pointers: "; 509 for (iterator I = begin(), E = end(); I != E; ++I) { 510 if (I != begin()) OS << ", "; 511 WriteAsOperand(OS << "(", I.getPointer()); 512 OS << ", " << I.getSize() << ")"; 513 } 514 } 515 if (!CallSites.empty()) { 516 OS << "\n " << CallSites.size() << " Call Sites: "; 517 for (unsigned i = 0, e = CallSites.size(); i != e; ++i) { 518 if (i) OS << ", "; 519 WriteAsOperand(OS, CallSites[i].getCalledValue()); 520 } 521 } 522 OS << "\n"; 523} 524 525void AliasSetTracker::print(std::ostream &OS) const { 526 OS << "Alias Set Tracker: " << AliasSets.size() << " alias sets for " 527 << PointerMap.size() << " pointer values.\n"; 528 for (const_iterator I = begin(), E = end(); I != E; ++I) 529 I->print(OS); 530 OS << "\n"; 531} 532 533void AliasSet::dump() const { print (std::cerr); } 534void AliasSetTracker::dump() const { print(std::cerr); } 535 536//===----------------------------------------------------------------------===// 537// AliasSetPrinter Pass 538//===----------------------------------------------------------------------===// 539 540namespace { 541 class AliasSetPrinter : public FunctionPass { 542 AliasSetTracker *Tracker; 543 public: 544 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 545 AU.setPreservesAll(); 546 AU.addRequired<AliasAnalysis>(); 547 } 548 549 virtual bool runOnFunction(Function &F) { 550 Tracker = new AliasSetTracker(getAnalysis<AliasAnalysis>()); 551 552 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) 553 Tracker->add(&*I); 554 Tracker->print(std::cerr); 555 delete Tracker; 556 return false; 557 } 558 }; 559 RegisterOpt<AliasSetPrinter> X("print-alias-sets", "Alias Set Printer"); 560} 561