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/Module.h"
21 #include "llvm/IR/LLVMContext.h"
22 #include "llvm/IR/Type.h"
23 #include "llvm/Pass.h"
24 #include "llvm/Support/Debug.h"
25 #include "llvm/Support/ErrorHandling.h"
26 #include "llvm/Support/raw_ostream.h"
29 /// mergeSetIn - Merge the specified alias set into this alias set.
31 void AliasSet::mergeSetIn(AliasSet &AS, AliasSetTracker &AST) {
32 assert(!AS.Forward && "Alias set is already forwarding!");
33 assert(!Forward && "This set is a forwarding set!!");
35 // Update the alias and access types of this set...
38 Volatile |= AS.Volatile;
40 if (Alias == SetMustAlias) {
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
44 AliasAnalysis &AA = AST.getAliasAnalysis();
45 PointerRec *L = getSomePointer();
46 PointerRec *R = AS.getSomePointer();
48 // If the pointers are not a must-alias pair, this set becomes a may alias.
49 if (AA.alias(MemoryLocation(L->getValue(), L->getSize(), L->getAAInfo()),
50 MemoryLocation(R->getValue(), R->getSize(), R->getAAInfo())) !=
55 bool ASHadUnknownInsts = !AS.UnknownInsts.empty();
56 if (UnknownInsts.empty()) { // Merge call sites...
57 if (ASHadUnknownInsts) {
58 std::swap(UnknownInsts, AS.UnknownInsts);
61 } else if (ASHadUnknownInsts) {
62 UnknownInsts.insert(UnknownInsts.end(), AS.UnknownInsts.begin(), AS.UnknownInsts.end());
63 AS.UnknownInsts.clear();
66 AS.Forward = this; // Forward across AS now...
67 addRef(); // AS is now pointing to us...
69 // Merge the list of constituent pointers...
71 *PtrListEnd = AS.PtrList;
72 AS.PtrList->setPrevInList(PtrListEnd);
73 PtrListEnd = AS.PtrListEnd;
76 AS.PtrListEnd = &AS.PtrList;
77 assert(*AS.PtrListEnd == nullptr && "End of list is not null?");
79 if (ASHadUnknownInsts)
83 void AliasSetTracker::removeAliasSet(AliasSet *AS) {
84 if (AliasSet *Fwd = AS->Forward) {
86 AS->Forward = nullptr;
91 void AliasSet::removeFromTracker(AliasSetTracker &AST) {
92 assert(RefCount == 0 && "Cannot remove non-dead alias set from tracker!");
93 AST.removeAliasSet(this);
96 void AliasSet::addPointer(AliasSetTracker &AST, PointerRec &Entry,
97 uint64_t Size, const AAMDNodes &AAInfo,
98 bool KnownMustAlias) {
99 assert(!Entry.hasAliasSet() && "Entry already in set!");
101 // Check to see if we have to downgrade to _may_ alias.
102 if (isMustAlias() && !KnownMustAlias)
103 if (PointerRec *P = getSomePointer()) {
104 AliasAnalysis &AA = AST.getAliasAnalysis();
106 AA.alias(MemoryLocation(P->getValue(), P->getSize(), P->getAAInfo()),
107 MemoryLocation(Entry.getValue(), Size, AAInfo));
108 if (Result != MustAlias)
110 else // First entry of must alias must have maximum size!
111 P->updateSizeAndAAInfo(Size, AAInfo);
112 assert(Result != NoAlias && "Cannot be part of must set!");
115 Entry.setAliasSet(this);
116 Entry.updateSizeAndAAInfo(Size, AAInfo);
118 // Add it to the end of the list...
119 assert(*PtrListEnd == nullptr && "End of list is not null?");
120 *PtrListEnd = &Entry;
121 PtrListEnd = Entry.setPrevInList(PtrListEnd);
122 assert(*PtrListEnd == nullptr && "End of list is not null?");
123 addRef(); // Entry points to alias set.
126 void AliasSet::addUnknownInst(Instruction *I, AliasAnalysis &AA) {
127 if (UnknownInsts.empty())
129 UnknownInsts.emplace_back(I);
131 if (!I->mayWriteToMemory()) {
137 // FIXME: This should use mod/ref information to make this not suck so bad
139 Access = ModRefAccess;
142 /// aliasesPointer - Return true if the specified pointer "may" (or must)
143 /// alias one of the members in the set.
145 bool AliasSet::aliasesPointer(const Value *Ptr, uint64_t Size,
146 const AAMDNodes &AAInfo,
147 AliasAnalysis &AA) const {
148 if (Alias == SetMustAlias) {
149 assert(UnknownInsts.empty() && "Illegal must alias set!");
151 // If this is a set of MustAliases, only check to see if the pointer aliases
152 // SOME value in the set.
153 PointerRec *SomePtr = getSomePointer();
154 assert(SomePtr && "Empty must-alias set??");
155 return AA.alias(MemoryLocation(SomePtr->getValue(), SomePtr->getSize(),
156 SomePtr->getAAInfo()),
157 MemoryLocation(Ptr, Size, AAInfo));
160 // If this is a may-alias set, we have to check all of the pointers in the set
161 // to be sure it doesn't alias the set...
162 for (iterator I = begin(), E = end(); I != E; ++I)
163 if (AA.alias(MemoryLocation(Ptr, Size, AAInfo),
164 MemoryLocation(I.getPointer(), I.getSize(), I.getAAInfo())))
167 // Check the unknown instructions...
168 if (!UnknownInsts.empty()) {
169 for (unsigned i = 0, e = UnknownInsts.size(); i != e; ++i)
170 if (AA.getModRefInfo(UnknownInsts[i],
171 MemoryLocation(Ptr, Size, AAInfo)) != MRI_NoModRef)
178 bool AliasSet::aliasesUnknownInst(const Instruction *Inst,
179 AliasAnalysis &AA) const {
180 if (!Inst->mayReadOrWriteMemory())
183 for (unsigned i = 0, e = UnknownInsts.size(); i != e; ++i) {
184 ImmutableCallSite C1(getUnknownInst(i)), C2(Inst);
185 if (!C1 || !C2 || AA.getModRefInfo(C1, C2) != MRI_NoModRef ||
186 AA.getModRefInfo(C2, C1) != MRI_NoModRef)
190 for (iterator I = begin(), E = end(); I != E; ++I)
191 if (AA.getModRefInfo(Inst, MemoryLocation(I.getPointer(), I.getSize(),
192 I.getAAInfo())) != MRI_NoModRef)
198 void AliasSetTracker::clear() {
199 // Delete all the PointerRec entries.
200 for (PointerMapType::iterator I = PointerMap.begin(), E = PointerMap.end();
202 I->second->eraseFromList();
206 // The alias sets should all be clear now.
211 /// mergeAliasSetsForPointer - Given a pointer, merge all alias sets that may
212 /// alias the pointer. Return the unified set, or nullptr if no set that aliases
213 /// the pointer was found.
214 AliasSet *AliasSetTracker::mergeAliasSetsForPointer(const Value *Ptr,
216 const AAMDNodes &AAInfo) {
217 AliasSet *FoundSet = nullptr;
218 for (iterator I = begin(), E = end(); I != E;) {
220 if (Cur->Forward || !Cur->aliasesPointer(Ptr, Size, AAInfo, AA)) continue;
222 if (!FoundSet) { // If this is the first alias set ptr can go into.
223 FoundSet = &*Cur; // Remember it.
224 } else { // Otherwise, we must merge the sets.
225 FoundSet->mergeSetIn(*Cur, *this); // Merge in contents.
232 /// containsPointer - Return true if the specified location is represented by
233 /// this alias set, false otherwise. This does not modify the AST object or
235 bool AliasSetTracker::containsPointer(const Value *Ptr, uint64_t Size,
236 const AAMDNodes &AAInfo) const {
237 for (const AliasSet &AS : *this)
238 if (!AS.Forward && AS.aliasesPointer(Ptr, Size, AAInfo, AA))
243 bool AliasSetTracker::containsUnknown(const Instruction *Inst) const {
244 for (const AliasSet &AS : *this)
245 if (!AS.Forward && AS.aliasesUnknownInst(Inst, AA))
250 AliasSet *AliasSetTracker::findAliasSetForUnknownInst(Instruction *Inst) {
251 AliasSet *FoundSet = nullptr;
252 for (iterator I = begin(), E = end(); I != E;) {
254 if (Cur->Forward || !Cur->aliasesUnknownInst(Inst, AA))
256 if (!FoundSet) // If this is the first alias set ptr can go into.
257 FoundSet = &*Cur; // Remember it.
258 else if (!Cur->Forward) // Otherwise, we must merge the sets.
259 FoundSet->mergeSetIn(*Cur, *this); // Merge in contents.
267 /// getAliasSetForPointer - Return the alias set that the specified pointer
269 AliasSet &AliasSetTracker::getAliasSetForPointer(Value *Pointer, uint64_t Size,
270 const AAMDNodes &AAInfo,
272 AliasSet::PointerRec &Entry = getEntryFor(Pointer);
274 // Check to see if the pointer is already known.
275 if (Entry.hasAliasSet()) {
276 // If the size changed, we may need to merge several alias sets.
277 // Note that we can *not* return the result of mergeAliasSetsForPointer
278 // due to a quirk of alias analysis behavior. Since alias(undef, undef)
279 // is NoAlias, mergeAliasSetsForPointer(undef, ...) will not find the
280 // the right set for undef, even if it exists.
281 if (Entry.updateSizeAndAAInfo(Size, AAInfo))
282 mergeAliasSetsForPointer(Pointer, Size, AAInfo);
284 return *Entry.getAliasSet(*this)->getForwardedTarget(*this);
287 if (AliasSet *AS = mergeAliasSetsForPointer(Pointer, Size, AAInfo)) {
288 // Add it to the alias set it aliases.
289 AS->addPointer(*this, Entry, Size, AAInfo);
293 if (New) *New = true;
294 // Otherwise create a new alias set to hold the loaded pointer.
295 AliasSets.push_back(new AliasSet());
296 AliasSets.back().addPointer(*this, Entry, Size, AAInfo);
297 return AliasSets.back();
300 bool AliasSetTracker::add(Value *Ptr, uint64_t Size, const AAMDNodes &AAInfo) {
302 addPointer(Ptr, Size, AAInfo, AliasSet::NoAccess, NewPtr);
307 bool AliasSetTracker::add(LoadInst *LI) {
308 if (isStrongerThanMonotonic(LI->getOrdering())) return addUnknown(LI);
311 LI->getAAMetadata(AAInfo);
313 AliasSet::AccessLattice Access = AliasSet::RefAccess;
315 const DataLayout &DL = LI->getModule()->getDataLayout();
316 AliasSet &AS = addPointer(LI->getOperand(0),
317 DL.getTypeStoreSize(LI->getType()),
318 AAInfo, Access, NewPtr);
319 if (LI->isVolatile()) AS.setVolatile();
323 bool AliasSetTracker::add(StoreInst *SI) {
324 if (isStrongerThanMonotonic(SI->getOrdering())) return addUnknown(SI);
327 SI->getAAMetadata(AAInfo);
329 AliasSet::AccessLattice Access = AliasSet::ModAccess;
331 const DataLayout &DL = SI->getModule()->getDataLayout();
332 Value *Val = SI->getOperand(0);
333 AliasSet &AS = addPointer(SI->getOperand(1),
334 DL.getTypeStoreSize(Val->getType()),
335 AAInfo, Access, NewPtr);
336 if (SI->isVolatile()) AS.setVolatile();
340 bool AliasSetTracker::add(VAArgInst *VAAI) {
342 VAAI->getAAMetadata(AAInfo);
345 addPointer(VAAI->getOperand(0), MemoryLocation::UnknownSize, AAInfo,
346 AliasSet::ModRefAccess, NewPtr);
350 bool AliasSetTracker::add(MemSetInst *MSI) {
352 MSI->getAAMetadata(AAInfo);
357 if (ConstantInt *C = dyn_cast<ConstantInt>(MSI->getLength()))
358 Len = C->getZExtValue();
360 Len = MemoryLocation::UnknownSize;
363 addPointer(MSI->getRawDest(), Len, AAInfo, AliasSet::ModAccess, NewPtr);
364 if (MSI->isVolatile())
369 bool AliasSetTracker::addUnknown(Instruction *Inst) {
370 if (isa<DbgInfoIntrinsic>(Inst))
371 return true; // Ignore DbgInfo Intrinsics.
372 if (!Inst->mayReadOrWriteMemory())
373 return true; // doesn't alias anything
375 AliasSet *AS = findAliasSetForUnknownInst(Inst);
377 AS->addUnknownInst(Inst, AA);
380 AliasSets.push_back(new AliasSet());
381 AS = &AliasSets.back();
382 AS->addUnknownInst(Inst, AA);
386 bool AliasSetTracker::add(Instruction *I) {
387 // Dispatch to one of the other add methods.
388 if (LoadInst *LI = dyn_cast<LoadInst>(I))
390 if (StoreInst *SI = dyn_cast<StoreInst>(I))
392 if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I))
394 if (MemSetInst *MSI = dyn_cast<MemSetInst>(I))
396 return addUnknown(I);
397 // FIXME: add support of memcpy and memmove.
400 void AliasSetTracker::add(BasicBlock &BB) {
405 void AliasSetTracker::add(const AliasSetTracker &AST) {
406 assert(&AA == &AST.AA &&
407 "Merging AliasSetTracker objects with different Alias Analyses!");
409 // Loop over all of the alias sets in AST, adding the pointers contained
410 // therein into the current alias sets. This can cause alias sets to be
411 // merged together in the current AST.
412 for (const AliasSet &AS : AST) {
414 continue; // Ignore forwarding alias sets
416 // If there are any call sites in the alias set, add them to this AST.
417 for (unsigned i = 0, e = AS.UnknownInsts.size(); i != e; ++i)
418 add(AS.UnknownInsts[i]);
420 // Loop over all of the pointers in this alias set.
422 for (AliasSet::iterator ASI = AS.begin(), E = AS.end(); ASI != E; ++ASI) {
423 AliasSet &NewAS = addPointer(ASI.getPointer(), ASI.getSize(),
425 (AliasSet::AccessLattice)AS.Access, X);
426 if (AS.isVolatile()) NewAS.setVolatile();
431 /// remove - Remove the specified (potentially non-empty) alias set from the
433 void AliasSetTracker::remove(AliasSet &AS) {
434 // Drop all call sites.
435 if (!AS.UnknownInsts.empty())
437 AS.UnknownInsts.clear();
439 // Clear the alias set.
440 unsigned NumRefs = 0;
441 while (!AS.empty()) {
442 AliasSet::PointerRec *P = AS.PtrList;
444 Value *ValToRemove = P->getValue();
446 // Unlink and delete entry from the list of values.
449 // Remember how many references need to be dropped.
452 // Finally, remove the entry.
453 PointerMap.erase(ValToRemove);
456 // Stop using the alias set, removing it.
457 AS.RefCount -= NumRefs;
458 if (AS.RefCount == 0)
459 AS.removeFromTracker(*this);
463 AliasSetTracker::remove(Value *Ptr, uint64_t Size, const AAMDNodes &AAInfo) {
464 AliasSet *AS = mergeAliasSetsForPointer(Ptr, Size, AAInfo);
465 if (!AS) return false;
470 bool AliasSetTracker::remove(LoadInst *LI) {
471 const DataLayout &DL = LI->getModule()->getDataLayout();
472 uint64_t Size = DL.getTypeStoreSize(LI->getType());
475 LI->getAAMetadata(AAInfo);
477 AliasSet *AS = mergeAliasSetsForPointer(LI->getOperand(0), Size, AAInfo);
478 if (!AS) return false;
483 bool AliasSetTracker::remove(StoreInst *SI) {
484 const DataLayout &DL = SI->getModule()->getDataLayout();
485 uint64_t Size = DL.getTypeStoreSize(SI->getOperand(0)->getType());
488 SI->getAAMetadata(AAInfo);
490 AliasSet *AS = mergeAliasSetsForPointer(SI->getOperand(1), Size, AAInfo);
491 if (!AS) return false;
496 bool AliasSetTracker::remove(VAArgInst *VAAI) {
498 VAAI->getAAMetadata(AAInfo);
500 AliasSet *AS = mergeAliasSetsForPointer(VAAI->getOperand(0),
501 MemoryLocation::UnknownSize, AAInfo);
502 if (!AS) return false;
507 bool AliasSetTracker::remove(MemSetInst *MSI) {
509 MSI->getAAMetadata(AAInfo);
512 if (ConstantInt *C = dyn_cast<ConstantInt>(MSI->getLength()))
513 Len = C->getZExtValue();
515 Len = MemoryLocation::UnknownSize;
517 AliasSet *AS = mergeAliasSetsForPointer(MSI->getRawDest(), Len, AAInfo);
524 bool AliasSetTracker::removeUnknown(Instruction *I) {
525 if (!I->mayReadOrWriteMemory())
526 return false; // doesn't alias anything
528 AliasSet *AS = findAliasSetForUnknownInst(I);
529 if (!AS) return false;
534 bool AliasSetTracker::remove(Instruction *I) {
535 // Dispatch to one of the other remove methods...
536 if (LoadInst *LI = dyn_cast<LoadInst>(I))
538 if (StoreInst *SI = dyn_cast<StoreInst>(I))
540 if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I))
542 if (MemSetInst *MSI = dyn_cast<MemSetInst>(I))
544 return removeUnknown(I);
545 // FIXME: add support of memcpy and memmove.
549 // deleteValue method - This method is used to remove a pointer value from the
550 // AliasSetTracker entirely. It should be used when an instruction is deleted
551 // from the program to update the AST. If you don't use this, you would have
552 // dangling pointers to deleted instructions.
554 void AliasSetTracker::deleteValue(Value *PtrVal) {
555 // If this is a call instruction, remove the callsite from the appropriate
556 // AliasSet (if present).
557 if (Instruction *Inst = dyn_cast<Instruction>(PtrVal)) {
558 if (Inst->mayReadOrWriteMemory()) {
559 // Scan all the alias sets to see if this call site is contained.
560 for (iterator I = begin(), E = end(); I != E;) {
563 Cur->removeUnknownInst(*this, Inst);
568 // First, look up the PointerRec for this pointer.
569 PointerMapType::iterator I = PointerMap.find_as(PtrVal);
570 if (I == PointerMap.end()) return; // Noop
572 // If we found one, remove the pointer from the alias set it is in.
573 AliasSet::PointerRec *PtrValEnt = I->second;
574 AliasSet *AS = PtrValEnt->getAliasSet(*this);
576 // Unlink and delete from the list of values.
577 PtrValEnt->eraseFromList();
579 // Stop using the alias set.
585 // copyValue - This method should be used whenever a preexisting value in the
586 // program is copied or cloned, introducing a new value. Note that it is ok for
587 // clients that use this method to introduce the same value multiple times: if
588 // the tracker already knows about a value, it will ignore the request.
590 void AliasSetTracker::copyValue(Value *From, Value *To) {
591 // First, look up the PointerRec for this pointer.
592 PointerMapType::iterator I = PointerMap.find_as(From);
593 if (I == PointerMap.end())
595 assert(I->second->hasAliasSet() && "Dead entry?");
597 AliasSet::PointerRec &Entry = getEntryFor(To);
598 if (Entry.hasAliasSet()) return; // Already in the tracker!
600 // Add it to the alias set it aliases...
601 I = PointerMap.find_as(From);
602 AliasSet *AS = I->second->getAliasSet(*this);
603 AS->addPointer(*this, Entry, I->second->getSize(),
604 I->second->getAAInfo(),
610 //===----------------------------------------------------------------------===//
611 // AliasSet/AliasSetTracker Printing Support
612 //===----------------------------------------------------------------------===//
614 void AliasSet::print(raw_ostream &OS) const {
615 OS << " AliasSet[" << (const void*)this << ", " << RefCount << "] ";
616 OS << (Alias == SetMustAlias ? "must" : "may") << " alias, ";
618 case NoAccess: OS << "No access "; break;
619 case RefAccess: OS << "Ref "; break;
620 case ModAccess: OS << "Mod "; break;
621 case ModRefAccess: OS << "Mod/Ref "; break;
622 default: llvm_unreachable("Bad value for Access!");
624 if (isVolatile()) OS << "[volatile] ";
626 OS << " forwarding to " << (void*)Forward;
631 for (iterator I = begin(), E = end(); I != E; ++I) {
632 if (I != begin()) OS << ", ";
633 I.getPointer()->printAsOperand(OS << "(");
634 OS << ", " << I.getSize() << ")";
637 if (!UnknownInsts.empty()) {
638 OS << "\n " << UnknownInsts.size() << " Unknown instructions: ";
639 for (unsigned i = 0, e = UnknownInsts.size(); i != e; ++i) {
641 UnknownInsts[i]->printAsOperand(OS);
647 void AliasSetTracker::print(raw_ostream &OS) const {
648 OS << "Alias Set Tracker: " << AliasSets.size() << " alias sets for "
649 << PointerMap.size() << " pointer values.\n";
650 for (const AliasSet &AS : *this)
655 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
656 LLVM_DUMP_METHOD void AliasSet::dump() const { print(dbgs()); }
657 LLVM_DUMP_METHOD void AliasSetTracker::dump() const { print(dbgs()); }
660 //===----------------------------------------------------------------------===//
661 // ASTCallbackVH Class Implementation
662 //===----------------------------------------------------------------------===//
664 void AliasSetTracker::ASTCallbackVH::deleted() {
665 assert(AST && "ASTCallbackVH called with a null AliasSetTracker!");
666 AST->deleteValue(getValPtr());
670 void AliasSetTracker::ASTCallbackVH::allUsesReplacedWith(Value *V) {
671 AST->copyValue(getValPtr(), V);
674 AliasSetTracker::ASTCallbackVH::ASTCallbackVH(Value *V, AliasSetTracker *ast)
675 : CallbackVH(V), AST(ast) {}
677 AliasSetTracker::ASTCallbackVH &
678 AliasSetTracker::ASTCallbackVH::operator=(Value *V) {
679 return *this = ASTCallbackVH(V, AST);
682 //===----------------------------------------------------------------------===//
683 // AliasSetPrinter Pass
684 //===----------------------------------------------------------------------===//
687 class AliasSetPrinter : public FunctionPass {
688 AliasSetTracker *Tracker;
690 static char ID; // Pass identification, replacement for typeid
691 AliasSetPrinter() : FunctionPass(ID) {
692 initializeAliasSetPrinterPass(*PassRegistry::getPassRegistry());
695 void getAnalysisUsage(AnalysisUsage &AU) const override {
696 AU.setPreservesAll();
697 AU.addRequired<AAResultsWrapperPass>();
700 bool runOnFunction(Function &F) override {
701 auto &AAWP = getAnalysis<AAResultsWrapperPass>();
702 Tracker = new AliasSetTracker(AAWP.getAAResults());
704 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
706 Tracker->print(errs());
713 char AliasSetPrinter::ID = 0;
714 INITIALIZE_PASS_BEGIN(AliasSetPrinter, "print-alias-sets",
715 "Alias Set Printer", false, true)
716 INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
717 INITIALIZE_PASS_END(AliasSetPrinter, "print-alias-sets",
718 "Alias Set Printer", false, true)