1 //===- AliasSetTracker.cpp - Alias Sets Tracker implementation-------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the AliasSetTracker and AliasSet classes.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/Analysis/AliasSetTracker.h"
15 #include "llvm/Analysis/AliasAnalysis.h"
16 #include "llvm/IR/DataLayout.h"
17 #include "llvm/IR/InstIterator.h"
18 #include "llvm/IR/Instructions.h"
19 #include "llvm/IR/IntrinsicInst.h"
20 #include "llvm/IR/LLVMContext.h"
21 #include "llvm/IR/Type.h"
22 #include "llvm/Pass.h"
23 #include "llvm/Support/Debug.h"
24 #include "llvm/Support/ErrorHandling.h"
25 #include "llvm/Support/raw_ostream.h"
28 /// mergeSetIn - Merge the specified alias set into this alias set.
30 void AliasSet::mergeSetIn(AliasSet &AS, AliasSetTracker &AST) {
31 assert(!AS.Forward && "Alias set is already forwarding!");
32 assert(!Forward && "This set is a forwarding set!!");
34 // Update the alias and access types of this set...
35 AccessTy |= AS.AccessTy;
36 AliasTy |= AS.AliasTy;
37 Volatile |= AS.Volatile;
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
43 AliasAnalysis &AA = AST.getAliasAnalysis();
44 PointerRec *L = getSomePointer();
45 PointerRec *R = AS.getSomePointer();
47 // If the pointers are not a must-alias pair, this set becomes a may alias.
48 if (AA.alias(AliasAnalysis::Location(L->getValue(),
51 AliasAnalysis::Location(R->getValue(),
54 != AliasAnalysis::MustAlias)
58 bool ASHadUnknownInsts = !AS.UnknownInsts.empty();
59 if (UnknownInsts.empty()) { // Merge call sites...
60 if (ASHadUnknownInsts) {
61 std::swap(UnknownInsts, AS.UnknownInsts);
64 } else if (ASHadUnknownInsts) {
65 UnknownInsts.insert(UnknownInsts.end(), AS.UnknownInsts.begin(), AS.UnknownInsts.end());
66 AS.UnknownInsts.clear();
69 AS.Forward = this; // Forward across AS now...
70 addRef(); // AS is now pointing to us...
72 // Merge the list of constituent pointers...
74 *PtrListEnd = AS.PtrList;
75 AS.PtrList->setPrevInList(PtrListEnd);
76 PtrListEnd = AS.PtrListEnd;
79 AS.PtrListEnd = &AS.PtrList;
80 assert(*AS.PtrListEnd == nullptr && "End of list is not null?");
82 if (ASHadUnknownInsts)
86 void AliasSetTracker::removeAliasSet(AliasSet *AS) {
87 if (AliasSet *Fwd = AS->Forward) {
89 AS->Forward = nullptr;
94 void AliasSet::removeFromTracker(AliasSetTracker &AST) {
95 assert(RefCount == 0 && "Cannot remove non-dead alias set from tracker!");
96 AST.removeAliasSet(this);
99 void AliasSet::addPointer(AliasSetTracker &AST, PointerRec &Entry,
100 uint64_t Size, const MDNode *TBAAInfo,
101 bool KnownMustAlias) {
102 assert(!Entry.hasAliasSet() && "Entry already in set!");
104 // Check to see if we have to downgrade to _may_ alias.
105 if (isMustAlias() && !KnownMustAlias)
106 if (PointerRec *P = getSomePointer()) {
107 AliasAnalysis &AA = AST.getAliasAnalysis();
108 AliasAnalysis::AliasResult Result =
109 AA.alias(AliasAnalysis::Location(P->getValue(), P->getSize(),
111 AliasAnalysis::Location(Entry.getValue(), Size, TBAAInfo));
112 if (Result != AliasAnalysis::MustAlias)
114 else // First entry of must alias must have maximum size!
115 P->updateSizeAndTBAAInfo(Size, TBAAInfo);
116 assert(Result != AliasAnalysis::NoAlias && "Cannot be part of must set!");
119 Entry.setAliasSet(this);
120 Entry.updateSizeAndTBAAInfo(Size, TBAAInfo);
122 // Add it to the end of the list...
123 assert(*PtrListEnd == nullptr && "End of list is not null?");
124 *PtrListEnd = &Entry;
125 PtrListEnd = Entry.setPrevInList(PtrListEnd);
126 assert(*PtrListEnd == nullptr && "End of list is not null?");
127 addRef(); // Entry points to alias set.
130 void AliasSet::addUnknownInst(Instruction *I, AliasAnalysis &AA) {
131 if (UnknownInsts.empty())
133 UnknownInsts.push_back(I);
135 if (!I->mayWriteToMemory()) {
141 // FIXME: This should use mod/ref information to make this not suck so bad
146 /// aliasesPointer - Return true if the specified pointer "may" (or must)
147 /// alias one of the members in the set.
149 bool AliasSet::aliasesPointer(const Value *Ptr, uint64_t Size,
150 const MDNode *TBAAInfo,
151 AliasAnalysis &AA) const {
152 if (AliasTy == MustAlias) {
153 assert(UnknownInsts.empty() && "Illegal must alias set!");
155 // If this is a set of MustAliases, only check to see if the pointer aliases
156 // SOME value in the set.
157 PointerRec *SomePtr = getSomePointer();
158 assert(SomePtr && "Empty must-alias set??");
159 return AA.alias(AliasAnalysis::Location(SomePtr->getValue(),
161 SomePtr->getTBAAInfo()),
162 AliasAnalysis::Location(Ptr, Size, TBAAInfo));
165 // If this is a may-alias set, we have to check all of the pointers in the set
166 // to be sure it doesn't alias the set...
167 for (iterator I = begin(), E = end(); I != E; ++I)
168 if (AA.alias(AliasAnalysis::Location(Ptr, Size, TBAAInfo),
169 AliasAnalysis::Location(I.getPointer(), I.getSize(),
173 // Check the unknown instructions...
174 if (!UnknownInsts.empty()) {
175 for (unsigned i = 0, e = UnknownInsts.size(); i != e; ++i)
176 if (AA.getModRefInfo(UnknownInsts[i],
177 AliasAnalysis::Location(Ptr, Size, TBAAInfo)) !=
178 AliasAnalysis::NoModRef)
185 bool AliasSet::aliasesUnknownInst(Instruction *Inst, AliasAnalysis &AA) const {
186 if (!Inst->mayReadOrWriteMemory())
189 for (unsigned i = 0, e = UnknownInsts.size(); i != e; ++i) {
190 CallSite C1 = getUnknownInst(i), C2 = Inst;
192 AA.getModRefInfo(C1, C2) != AliasAnalysis::NoModRef ||
193 AA.getModRefInfo(C2, C1) != AliasAnalysis::NoModRef)
197 for (iterator I = begin(), E = end(); I != E; ++I)
198 if (AA.getModRefInfo(Inst, AliasAnalysis::Location(I.getPointer(),
201 AliasAnalysis::NoModRef)
207 void AliasSetTracker::clear() {
208 // Delete all the PointerRec entries.
209 for (PointerMapType::iterator I = PointerMap.begin(), E = PointerMap.end();
211 I->second->eraseFromList();
215 // The alias sets should all be clear now.
220 /// findAliasSetForPointer - Given a pointer, find the one alias set to put the
221 /// instruction referring to the pointer into. If there are multiple alias sets
222 /// that may alias the pointer, merge them together and return the unified set.
224 AliasSet *AliasSetTracker::findAliasSetForPointer(const Value *Ptr,
226 const MDNode *TBAAInfo) {
227 AliasSet *FoundSet = nullptr;
228 for (iterator I = begin(), E = end(); I != E;) {
230 if (Cur->Forward || !Cur->aliasesPointer(Ptr, Size, TBAAInfo, AA)) continue;
232 if (!FoundSet) { // If this is the first alias set ptr can go into.
233 FoundSet = Cur; // Remember it.
234 } else { // Otherwise, we must merge the sets.
235 FoundSet->mergeSetIn(*Cur, *this); // Merge in contents.
242 /// containsPointer - Return true if the specified location is represented by
243 /// this alias set, false otherwise. This does not modify the AST object or
245 bool AliasSetTracker::containsPointer(Value *Ptr, uint64_t Size,
246 const MDNode *TBAAInfo) const {
247 for (const_iterator I = begin(), E = end(); I != E; ++I)
248 if (!I->Forward && I->aliasesPointer(Ptr, Size, TBAAInfo, AA))
255 AliasSet *AliasSetTracker::findAliasSetForUnknownInst(Instruction *Inst) {
256 AliasSet *FoundSet = nullptr;
257 for (iterator I = begin(), E = end(); I != E;) {
259 if (Cur->Forward || !Cur->aliasesUnknownInst(Inst, AA))
261 if (!FoundSet) // If this is the first alias set ptr can go into.
262 FoundSet = Cur; // Remember it.
263 else if (!Cur->Forward) // Otherwise, we must merge the sets.
264 FoundSet->mergeSetIn(*Cur, *this); // Merge in contents.
272 /// getAliasSetForPointer - Return the alias set that the specified pointer
274 AliasSet &AliasSetTracker::getAliasSetForPointer(Value *Pointer, uint64_t Size,
275 const MDNode *TBAAInfo,
277 AliasSet::PointerRec &Entry = getEntryFor(Pointer);
279 // Check to see if the pointer is already known.
280 if (Entry.hasAliasSet()) {
281 Entry.updateSizeAndTBAAInfo(Size, TBAAInfo);
283 return *Entry.getAliasSet(*this)->getForwardedTarget(*this);
286 if (AliasSet *AS = findAliasSetForPointer(Pointer, Size, TBAAInfo)) {
287 // Add it to the alias set it aliases.
288 AS->addPointer(*this, Entry, Size, TBAAInfo);
292 if (New) *New = true;
293 // Otherwise create a new alias set to hold the loaded pointer.
294 AliasSets.push_back(new AliasSet());
295 AliasSets.back().addPointer(*this, Entry, Size, TBAAInfo);
296 return AliasSets.back();
299 bool AliasSetTracker::add(Value *Ptr, uint64_t Size, const MDNode *TBAAInfo) {
301 addPointer(Ptr, Size, TBAAInfo, AliasSet::NoModRef, NewPtr);
306 bool AliasSetTracker::add(LoadInst *LI) {
307 if (LI->getOrdering() > Monotonic) return addUnknown(LI);
308 AliasSet::AccessType ATy = AliasSet::Refs;
310 AliasSet &AS = addPointer(LI->getOperand(0),
311 AA.getTypeStoreSize(LI->getType()),
312 LI->getMetadata(LLVMContext::MD_tbaa),
314 if (LI->isVolatile()) AS.setVolatile();
318 bool AliasSetTracker::add(StoreInst *SI) {
319 if (SI->getOrdering() > Monotonic) return addUnknown(SI);
320 AliasSet::AccessType ATy = AliasSet::Mods;
322 Value *Val = SI->getOperand(0);
323 AliasSet &AS = addPointer(SI->getOperand(1),
324 AA.getTypeStoreSize(Val->getType()),
325 SI->getMetadata(LLVMContext::MD_tbaa),
327 if (SI->isVolatile()) AS.setVolatile();
331 bool AliasSetTracker::add(VAArgInst *VAAI) {
333 addPointer(VAAI->getOperand(0), AliasAnalysis::UnknownSize,
334 VAAI->getMetadata(LLVMContext::MD_tbaa),
335 AliasSet::ModRef, NewPtr);
340 bool AliasSetTracker::addUnknown(Instruction *Inst) {
341 if (isa<DbgInfoIntrinsic>(Inst))
342 return true; // Ignore DbgInfo Intrinsics.
343 if (!Inst->mayReadOrWriteMemory())
344 return true; // doesn't alias anything
346 AliasSet *AS = findAliasSetForUnknownInst(Inst);
348 AS->addUnknownInst(Inst, AA);
351 AliasSets.push_back(new AliasSet());
352 AS = &AliasSets.back();
353 AS->addUnknownInst(Inst, AA);
357 bool AliasSetTracker::add(Instruction *I) {
358 // Dispatch to one of the other add methods.
359 if (LoadInst *LI = dyn_cast<LoadInst>(I))
361 if (StoreInst *SI = dyn_cast<StoreInst>(I))
363 if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I))
365 return addUnknown(I);
368 void AliasSetTracker::add(BasicBlock &BB) {
369 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
373 void AliasSetTracker::add(const AliasSetTracker &AST) {
374 assert(&AA == &AST.AA &&
375 "Merging AliasSetTracker objects with different Alias Analyses!");
377 // Loop over all of the alias sets in AST, adding the pointers contained
378 // therein into the current alias sets. This can cause alias sets to be
379 // merged together in the current AST.
380 for (const_iterator I = AST.begin(), E = AST.end(); I != E; ++I) {
381 if (I->Forward) continue; // Ignore forwarding alias sets
383 AliasSet &AS = const_cast<AliasSet&>(*I);
385 // If there are any call sites in the alias set, add them to this AST.
386 for (unsigned i = 0, e = AS.UnknownInsts.size(); i != e; ++i)
387 add(AS.UnknownInsts[i]);
389 // Loop over all of the pointers in this alias set.
391 for (AliasSet::iterator ASI = AS.begin(), E = AS.end(); ASI != E; ++ASI) {
392 AliasSet &NewAS = addPointer(ASI.getPointer(), ASI.getSize(),
394 (AliasSet::AccessType)AS.AccessTy, X);
395 if (AS.isVolatile()) NewAS.setVolatile();
400 /// remove - Remove the specified (potentially non-empty) alias set from the
402 void AliasSetTracker::remove(AliasSet &AS) {
403 // Drop all call sites.
404 if (!AS.UnknownInsts.empty())
406 AS.UnknownInsts.clear();
408 // Clear the alias set.
409 unsigned NumRefs = 0;
410 while (!AS.empty()) {
411 AliasSet::PointerRec *P = AS.PtrList;
413 Value *ValToRemove = P->getValue();
415 // Unlink and delete entry from the list of values.
418 // Remember how many references need to be dropped.
421 // Finally, remove the entry.
422 PointerMap.erase(ValToRemove);
425 // Stop using the alias set, removing it.
426 AS.RefCount -= NumRefs;
427 if (AS.RefCount == 0)
428 AS.removeFromTracker(*this);
432 AliasSetTracker::remove(Value *Ptr, uint64_t Size, const MDNode *TBAAInfo) {
433 AliasSet *AS = findAliasSetForPointer(Ptr, Size, TBAAInfo);
434 if (!AS) return false;
439 bool AliasSetTracker::remove(LoadInst *LI) {
440 uint64_t Size = AA.getTypeStoreSize(LI->getType());
441 const MDNode *TBAAInfo = LI->getMetadata(LLVMContext::MD_tbaa);
442 AliasSet *AS = findAliasSetForPointer(LI->getOperand(0), Size, TBAAInfo);
443 if (!AS) return false;
448 bool AliasSetTracker::remove(StoreInst *SI) {
449 uint64_t Size = AA.getTypeStoreSize(SI->getOperand(0)->getType());
450 const MDNode *TBAAInfo = SI->getMetadata(LLVMContext::MD_tbaa);
451 AliasSet *AS = findAliasSetForPointer(SI->getOperand(1), Size, TBAAInfo);
452 if (!AS) return false;
457 bool AliasSetTracker::remove(VAArgInst *VAAI) {
458 AliasSet *AS = findAliasSetForPointer(VAAI->getOperand(0),
459 AliasAnalysis::UnknownSize,
460 VAAI->getMetadata(LLVMContext::MD_tbaa));
461 if (!AS) return false;
466 bool AliasSetTracker::removeUnknown(Instruction *I) {
467 if (!I->mayReadOrWriteMemory())
468 return false; // doesn't alias anything
470 AliasSet *AS = findAliasSetForUnknownInst(I);
471 if (!AS) return false;
476 bool AliasSetTracker::remove(Instruction *I) {
477 // Dispatch to one of the other remove methods...
478 if (LoadInst *LI = dyn_cast<LoadInst>(I))
480 if (StoreInst *SI = dyn_cast<StoreInst>(I))
482 if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I))
484 return removeUnknown(I);
488 // deleteValue method - This method is used to remove a pointer value from the
489 // AliasSetTracker entirely. It should be used when an instruction is deleted
490 // from the program to update the AST. If you don't use this, you would have
491 // dangling pointers to deleted instructions.
493 void AliasSetTracker::deleteValue(Value *PtrVal) {
494 // Notify the alias analysis implementation that this value is gone.
495 AA.deleteValue(PtrVal);
497 // If this is a call instruction, remove the callsite from the appropriate
498 // AliasSet (if present).
499 if (Instruction *Inst = dyn_cast<Instruction>(PtrVal)) {
500 if (Inst->mayReadOrWriteMemory()) {
501 // Scan all the alias sets to see if this call site is contained.
502 for (iterator I = begin(), E = end(); I != E;) {
505 Cur->removeUnknownInst(*this, Inst);
510 // First, look up the PointerRec for this pointer.
511 PointerMapType::iterator I = PointerMap.find_as(PtrVal);
512 if (I == PointerMap.end()) return; // Noop
514 // If we found one, remove the pointer from the alias set it is in.
515 AliasSet::PointerRec *PtrValEnt = I->second;
516 AliasSet *AS = PtrValEnt->getAliasSet(*this);
518 // Unlink and delete from the list of values.
519 PtrValEnt->eraseFromList();
521 // Stop using the alias set.
527 // copyValue - This method should be used whenever a preexisting value in the
528 // program is copied or cloned, introducing a new value. Note that it is ok for
529 // clients that use this method to introduce the same value multiple times: if
530 // the tracker already knows about a value, it will ignore the request.
532 void AliasSetTracker::copyValue(Value *From, Value *To) {
533 // Notify the alias analysis implementation that this value is copied.
534 AA.copyValue(From, To);
536 // First, look up the PointerRec for this pointer.
537 PointerMapType::iterator I = PointerMap.find_as(From);
538 if (I == PointerMap.end())
540 assert(I->second->hasAliasSet() && "Dead entry?");
542 AliasSet::PointerRec &Entry = getEntryFor(To);
543 if (Entry.hasAliasSet()) return; // Already in the tracker!
545 // Add it to the alias set it aliases...
546 I = PointerMap.find_as(From);
547 AliasSet *AS = I->second->getAliasSet(*this);
548 AS->addPointer(*this, Entry, I->second->getSize(),
549 I->second->getTBAAInfo(),
555 //===----------------------------------------------------------------------===//
556 // AliasSet/AliasSetTracker Printing Support
557 //===----------------------------------------------------------------------===//
559 void AliasSet::print(raw_ostream &OS) const {
560 OS << " AliasSet[" << (const void*)this << ", " << RefCount << "] ";
561 OS << (AliasTy == MustAlias ? "must" : "may") << " alias, ";
563 case NoModRef: OS << "No access "; break;
564 case Refs : OS << "Ref "; break;
565 case Mods : OS << "Mod "; break;
566 case ModRef : OS << "Mod/Ref "; break;
567 default: llvm_unreachable("Bad value for AccessTy!");
569 if (isVolatile()) OS << "[volatile] ";
571 OS << " forwarding to " << (void*)Forward;
576 for (iterator I = begin(), E = end(); I != E; ++I) {
577 if (I != begin()) OS << ", ";
578 I.getPointer()->printAsOperand(OS << "(");
579 OS << ", " << I.getSize() << ")";
582 if (!UnknownInsts.empty()) {
583 OS << "\n " << UnknownInsts.size() << " Unknown instructions: ";
584 for (unsigned i = 0, e = UnknownInsts.size(); i != e; ++i) {
586 UnknownInsts[i]->printAsOperand(OS);
592 void AliasSetTracker::print(raw_ostream &OS) const {
593 OS << "Alias Set Tracker: " << AliasSets.size() << " alias sets for "
594 << PointerMap.size() << " pointer values.\n";
595 for (const_iterator I = begin(), E = end(); I != E; ++I)
600 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
601 void AliasSet::dump() const { print(dbgs()); }
602 void AliasSetTracker::dump() const { print(dbgs()); }
605 //===----------------------------------------------------------------------===//
606 // ASTCallbackVH Class Implementation
607 //===----------------------------------------------------------------------===//
609 void AliasSetTracker::ASTCallbackVH::deleted() {
610 assert(AST && "ASTCallbackVH called with a null AliasSetTracker!");
611 AST->deleteValue(getValPtr());
615 void AliasSetTracker::ASTCallbackVH::allUsesReplacedWith(Value *V) {
616 AST->copyValue(getValPtr(), V);
619 AliasSetTracker::ASTCallbackVH::ASTCallbackVH(Value *V, AliasSetTracker *ast)
620 : CallbackVH(V), AST(ast) {}
622 AliasSetTracker::ASTCallbackVH &
623 AliasSetTracker::ASTCallbackVH::operator=(Value *V) {
624 return *this = ASTCallbackVH(V, AST);
627 //===----------------------------------------------------------------------===//
628 // AliasSetPrinter Pass
629 //===----------------------------------------------------------------------===//
632 class AliasSetPrinter : public FunctionPass {
633 AliasSetTracker *Tracker;
635 static char ID; // Pass identification, replacement for typeid
636 AliasSetPrinter() : FunctionPass(ID) {
637 initializeAliasSetPrinterPass(*PassRegistry::getPassRegistry());
640 void getAnalysisUsage(AnalysisUsage &AU) const override {
641 AU.setPreservesAll();
642 AU.addRequired<AliasAnalysis>();
645 bool runOnFunction(Function &F) override {
646 Tracker = new AliasSetTracker(getAnalysis<AliasAnalysis>());
648 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
650 Tracker->print(errs());
657 char AliasSetPrinter::ID = 0;
658 INITIALIZE_PASS_BEGIN(AliasSetPrinter, "print-alias-sets",
659 "Alias Set Printer", false, true)
660 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
661 INITIALIZE_PASS_END(AliasSetPrinter, "print-alias-sets",
662 "Alias Set Printer", false, true)