//===- AliasSetTracker.cpp - Alias Sets Tracker implementation-------------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file implements the AliasSetTracker and AliasSet classes. // //===----------------------------------------------------------------------===// #include "llvm/Analysis/AliasSetTracker.h" #include "llvm/Analysis/AliasAnalysis.h" #include "llvm/IR/DataLayout.h" #include "llvm/IR/InstIterator.h" #include "llvm/IR/Instructions.h" #include "llvm/IR/IntrinsicInst.h" #include "llvm/IR/LLVMContext.h" #include "llvm/IR/Type.h" #include "llvm/Pass.h" #include "llvm/Support/Debug.h" #include "llvm/Support/ErrorHandling.h" #include "llvm/Support/raw_ostream.h" using namespace llvm; /// mergeSetIn - Merge the specified alias set into this alias set. /// void AliasSet::mergeSetIn(AliasSet &AS, AliasSetTracker &AST) { assert(!AS.Forward && "Alias set is already forwarding!"); assert(!Forward && "This set is a forwarding set!!"); // Update the alias and access types of this set... AccessTy |= AS.AccessTy; AliasTy |= AS.AliasTy; Volatile |= AS.Volatile; if (AliasTy == MustAlias) { // Check that these two merged sets really are must aliases. Since both // used to be must-alias sets, we can just check any pointer from each set // for aliasing. AliasAnalysis &AA = AST.getAliasAnalysis(); PointerRec *L = getSomePointer(); PointerRec *R = AS.getSomePointer(); // If the pointers are not a must-alias pair, this set becomes a may alias. if (AA.alias(AliasAnalysis::Location(L->getValue(), L->getSize(), L->getTBAAInfo()), AliasAnalysis::Location(R->getValue(), R->getSize(), R->getTBAAInfo())) != AliasAnalysis::MustAlias) AliasTy = MayAlias; } if (UnknownInsts.empty()) { // Merge call sites... if (!AS.UnknownInsts.empty()) std::swap(UnknownInsts, AS.UnknownInsts); } else if (!AS.UnknownInsts.empty()) { UnknownInsts.insert(UnknownInsts.end(), AS.UnknownInsts.begin(), AS.UnknownInsts.end()); AS.UnknownInsts.clear(); } AS.Forward = this; // Forward across AS now... addRef(); // AS is now pointing to us... // Merge the list of constituent pointers... if (AS.PtrList) { *PtrListEnd = AS.PtrList; AS.PtrList->setPrevInList(PtrListEnd); PtrListEnd = AS.PtrListEnd; AS.PtrList = nullptr; AS.PtrListEnd = &AS.PtrList; assert(*AS.PtrListEnd == nullptr && "End of list is not null?"); } } void AliasSetTracker::removeAliasSet(AliasSet *AS) { if (AliasSet *Fwd = AS->Forward) { Fwd->dropRef(*this); AS->Forward = nullptr; } AliasSets.erase(AS); } void AliasSet::removeFromTracker(AliasSetTracker &AST) { assert(RefCount == 0 && "Cannot remove non-dead alias set from tracker!"); AST.removeAliasSet(this); } void AliasSet::addPointer(AliasSetTracker &AST, PointerRec &Entry, uint64_t Size, const MDNode *TBAAInfo, bool KnownMustAlias) { assert(!Entry.hasAliasSet() && "Entry already in set!"); // Check to see if we have to downgrade to _may_ alias. if (isMustAlias() && !KnownMustAlias) if (PointerRec *P = getSomePointer()) { AliasAnalysis &AA = AST.getAliasAnalysis(); AliasAnalysis::AliasResult Result = AA.alias(AliasAnalysis::Location(P->getValue(), P->getSize(), P->getTBAAInfo()), AliasAnalysis::Location(Entry.getValue(), Size, TBAAInfo)); if (Result != AliasAnalysis::MustAlias) AliasTy = MayAlias; else // First entry of must alias must have maximum size! P->updateSizeAndTBAAInfo(Size, TBAAInfo); assert(Result != AliasAnalysis::NoAlias && "Cannot be part of must set!"); } Entry.setAliasSet(this); Entry.updateSizeAndTBAAInfo(Size, TBAAInfo); // Add it to the end of the list... assert(*PtrListEnd == nullptr && "End of list is not null?"); *PtrListEnd = &Entry; PtrListEnd = Entry.setPrevInList(PtrListEnd); assert(*PtrListEnd == nullptr && "End of list is not null?"); addRef(); // Entry points to alias set. } void AliasSet::addUnknownInst(Instruction *I, AliasAnalysis &AA) { UnknownInsts.push_back(I); if (!I->mayWriteToMemory()) { AliasTy = MayAlias; AccessTy |= Refs; return; } // FIXME: This should use mod/ref information to make this not suck so bad AliasTy = MayAlias; AccessTy = ModRef; } /// aliasesPointer - Return true if the specified pointer "may" (or must) /// alias one of the members in the set. /// bool AliasSet::aliasesPointer(const Value *Ptr, uint64_t Size, const MDNode *TBAAInfo, AliasAnalysis &AA) const { if (AliasTy == MustAlias) { assert(UnknownInsts.empty() && "Illegal must alias set!"); // If this is a set of MustAliases, only check to see if the pointer aliases // SOME value in the set. PointerRec *SomePtr = getSomePointer(); assert(SomePtr && "Empty must-alias set??"); return AA.alias(AliasAnalysis::Location(SomePtr->getValue(), SomePtr->getSize(), SomePtr->getTBAAInfo()), AliasAnalysis::Location(Ptr, Size, TBAAInfo)); } // If this is a may-alias set, we have to check all of the pointers in the set // to be sure it doesn't alias the set... for (iterator I = begin(), E = end(); I != E; ++I) if (AA.alias(AliasAnalysis::Location(Ptr, Size, TBAAInfo), AliasAnalysis::Location(I.getPointer(), I.getSize(), I.getTBAAInfo()))) return true; // Check the unknown instructions... if (!UnknownInsts.empty()) { for (unsigned i = 0, e = UnknownInsts.size(); i != e; ++i) if (AA.getModRefInfo(UnknownInsts[i], AliasAnalysis::Location(Ptr, Size, TBAAInfo)) != AliasAnalysis::NoModRef) return true; } return false; } bool AliasSet::aliasesUnknownInst(Instruction *Inst, AliasAnalysis &AA) const { if (!Inst->mayReadOrWriteMemory()) return false; for (unsigned i = 0, e = UnknownInsts.size(); i != e; ++i) { CallSite C1 = getUnknownInst(i), C2 = Inst; if (!C1 || !C2 || AA.getModRefInfo(C1, C2) != AliasAnalysis::NoModRef || AA.getModRefInfo(C2, C1) != AliasAnalysis::NoModRef) return true; } for (iterator I = begin(), E = end(); I != E; ++I) if (AA.getModRefInfo(Inst, AliasAnalysis::Location(I.getPointer(), I.getSize(), I.getTBAAInfo())) != AliasAnalysis::NoModRef) return true; return false; } void AliasSetTracker::clear() { // Delete all the PointerRec entries. for (PointerMapType::iterator I = PointerMap.begin(), E = PointerMap.end(); I != E; ++I) I->second->eraseFromList(); PointerMap.clear(); // The alias sets should all be clear now. AliasSets.clear(); } /// findAliasSetForPointer - Given a pointer, find the one alias set to put the /// instruction referring to the pointer into. If there are multiple alias sets /// that may alias the pointer, merge them together and return the unified set. /// AliasSet *AliasSetTracker::findAliasSetForPointer(const Value *Ptr, uint64_t Size, const MDNode *TBAAInfo) { AliasSet *FoundSet = nullptr; for (iterator I = begin(), E = end(); I != E; ++I) { if (I->Forward || !I->aliasesPointer(Ptr, Size, TBAAInfo, AA)) continue; if (!FoundSet) { // If this is the first alias set ptr can go into. FoundSet = I; // Remember it. } else { // Otherwise, we must merge the sets. FoundSet->mergeSetIn(*I, *this); // Merge in contents. } } return FoundSet; } /// containsPointer - Return true if the specified location is represented by /// this alias set, false otherwise. This does not modify the AST object or /// alias sets. bool AliasSetTracker::containsPointer(Value *Ptr, uint64_t Size, const MDNode *TBAAInfo) const { for (const_iterator I = begin(), E = end(); I != E; ++I) if (!I->Forward && I->aliasesPointer(Ptr, Size, TBAAInfo, AA)) return true; return false; } AliasSet *AliasSetTracker::findAliasSetForUnknownInst(Instruction *Inst) { AliasSet *FoundSet = nullptr; for (iterator I = begin(), E = end(); I != E; ++I) { if (I->Forward || !I->aliasesUnknownInst(Inst, AA)) continue; if (!FoundSet) // If this is the first alias set ptr can go into. FoundSet = I; // Remember it. else if (!I->Forward) // Otherwise, we must merge the sets. FoundSet->mergeSetIn(*I, *this); // Merge in contents. } return FoundSet; } /// getAliasSetForPointer - Return the alias set that the specified pointer /// lives in. AliasSet &AliasSetTracker::getAliasSetForPointer(Value *Pointer, uint64_t Size, const MDNode *TBAAInfo, bool *New) { AliasSet::PointerRec &Entry = getEntryFor(Pointer); // Check to see if the pointer is already known. if (Entry.hasAliasSet()) { Entry.updateSizeAndTBAAInfo(Size, TBAAInfo); // Return the set! return *Entry.getAliasSet(*this)->getForwardedTarget(*this); } if (AliasSet *AS = findAliasSetForPointer(Pointer, Size, TBAAInfo)) { // Add it to the alias set it aliases. AS->addPointer(*this, Entry, Size, TBAAInfo); return *AS; } if (New) *New = true; // Otherwise create a new alias set to hold the loaded pointer. AliasSets.push_back(new AliasSet()); AliasSets.back().addPointer(*this, Entry, Size, TBAAInfo); return AliasSets.back(); } bool AliasSetTracker::add(Value *Ptr, uint64_t Size, const MDNode *TBAAInfo) { bool NewPtr; addPointer(Ptr, Size, TBAAInfo, AliasSet::NoModRef, NewPtr); return NewPtr; } bool AliasSetTracker::add(LoadInst *LI) { if (LI->getOrdering() > Monotonic) return addUnknown(LI); AliasSet::AccessType ATy = AliasSet::Refs; bool NewPtr; AliasSet &AS = addPointer(LI->getOperand(0), AA.getTypeStoreSize(LI->getType()), LI->getMetadata(LLVMContext::MD_tbaa), ATy, NewPtr); if (LI->isVolatile()) AS.setVolatile(); return NewPtr; } bool AliasSetTracker::add(StoreInst *SI) { if (SI->getOrdering() > Monotonic) return addUnknown(SI); AliasSet::AccessType ATy = AliasSet::Mods; bool NewPtr; Value *Val = SI->getOperand(0); AliasSet &AS = addPointer(SI->getOperand(1), AA.getTypeStoreSize(Val->getType()), SI->getMetadata(LLVMContext::MD_tbaa), ATy, NewPtr); if (SI->isVolatile()) AS.setVolatile(); return NewPtr; } bool AliasSetTracker::add(VAArgInst *VAAI) { bool NewPtr; addPointer(VAAI->getOperand(0), AliasAnalysis::UnknownSize, VAAI->getMetadata(LLVMContext::MD_tbaa), AliasSet::ModRef, NewPtr); return NewPtr; } bool AliasSetTracker::addUnknown(Instruction *Inst) { if (isa(Inst)) return true; // Ignore DbgInfo Intrinsics. if (!Inst->mayReadOrWriteMemory()) return true; // doesn't alias anything AliasSet *AS = findAliasSetForUnknownInst(Inst); if (AS) { AS->addUnknownInst(Inst, AA); return false; } AliasSets.push_back(new AliasSet()); AS = &AliasSets.back(); AS->addUnknownInst(Inst, AA); return true; } bool AliasSetTracker::add(Instruction *I) { // Dispatch to one of the other add methods. if (LoadInst *LI = dyn_cast(I)) return add(LI); if (StoreInst *SI = dyn_cast(I)) return add(SI); if (VAArgInst *VAAI = dyn_cast(I)) return add(VAAI); return addUnknown(I); } void AliasSetTracker::add(BasicBlock &BB) { for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) add(I); } void AliasSetTracker::add(const AliasSetTracker &AST) { assert(&AA == &AST.AA && "Merging AliasSetTracker objects with different Alias Analyses!"); // Loop over all of the alias sets in AST, adding the pointers contained // therein into the current alias sets. This can cause alias sets to be // merged together in the current AST. for (const_iterator I = AST.begin(), E = AST.end(); I != E; ++I) { if (I->Forward) continue; // Ignore forwarding alias sets AliasSet &AS = const_cast(*I); // If there are any call sites in the alias set, add them to this AST. for (unsigned i = 0, e = AS.UnknownInsts.size(); i != e; ++i) add(AS.UnknownInsts[i]); // Loop over all of the pointers in this alias set. bool X; for (AliasSet::iterator ASI = AS.begin(), E = AS.end(); ASI != E; ++ASI) { AliasSet &NewAS = addPointer(ASI.getPointer(), ASI.getSize(), ASI.getTBAAInfo(), (AliasSet::AccessType)AS.AccessTy, X); if (AS.isVolatile()) NewAS.setVolatile(); } } } /// remove - Remove the specified (potentially non-empty) alias set from the /// tracker. void AliasSetTracker::remove(AliasSet &AS) { // Drop all call sites. AS.UnknownInsts.clear(); // Clear the alias set. unsigned NumRefs = 0; while (!AS.empty()) { AliasSet::PointerRec *P = AS.PtrList; Value *ValToRemove = P->getValue(); // Unlink and delete entry from the list of values. P->eraseFromList(); // Remember how many references need to be dropped. ++NumRefs; // Finally, remove the entry. PointerMap.erase(ValToRemove); } // Stop using the alias set, removing it. AS.RefCount -= NumRefs; if (AS.RefCount == 0) AS.removeFromTracker(*this); } bool AliasSetTracker::remove(Value *Ptr, uint64_t Size, const MDNode *TBAAInfo) { AliasSet *AS = findAliasSetForPointer(Ptr, Size, TBAAInfo); if (!AS) return false; remove(*AS); return true; } bool AliasSetTracker::remove(LoadInst *LI) { uint64_t Size = AA.getTypeStoreSize(LI->getType()); const MDNode *TBAAInfo = LI->getMetadata(LLVMContext::MD_tbaa); AliasSet *AS = findAliasSetForPointer(LI->getOperand(0), Size, TBAAInfo); if (!AS) return false; remove(*AS); return true; } bool AliasSetTracker::remove(StoreInst *SI) { uint64_t Size = AA.getTypeStoreSize(SI->getOperand(0)->getType()); const MDNode *TBAAInfo = SI->getMetadata(LLVMContext::MD_tbaa); AliasSet *AS = findAliasSetForPointer(SI->getOperand(1), Size, TBAAInfo); if (!AS) return false; remove(*AS); return true; } bool AliasSetTracker::remove(VAArgInst *VAAI) { AliasSet *AS = findAliasSetForPointer(VAAI->getOperand(0), AliasAnalysis::UnknownSize, VAAI->getMetadata(LLVMContext::MD_tbaa)); if (!AS) return false; remove(*AS); return true; } bool AliasSetTracker::removeUnknown(Instruction *I) { if (!I->mayReadOrWriteMemory()) return false; // doesn't alias anything AliasSet *AS = findAliasSetForUnknownInst(I); if (!AS) return false; remove(*AS); return true; } bool AliasSetTracker::remove(Instruction *I) { // Dispatch to one of the other remove methods... if (LoadInst *LI = dyn_cast(I)) return remove(LI); if (StoreInst *SI = dyn_cast(I)) return remove(SI); if (VAArgInst *VAAI = dyn_cast(I)) return remove(VAAI); return removeUnknown(I); } // deleteValue method - This method is used to remove a pointer value from the // AliasSetTracker entirely. It should be used when an instruction is deleted // from the program to update the AST. If you don't use this, you would have // dangling pointers to deleted instructions. // void AliasSetTracker::deleteValue(Value *PtrVal) { // Notify the alias analysis implementation that this value is gone. AA.deleteValue(PtrVal); // If this is a call instruction, remove the callsite from the appropriate // AliasSet (if present). if (Instruction *Inst = dyn_cast(PtrVal)) { if (Inst->mayReadOrWriteMemory()) { // Scan all the alias sets to see if this call site is contained. for (iterator I = begin(), E = end(); I != E; ++I) { if (I->Forward) continue; I->removeUnknownInst(Inst); } } } // First, look up the PointerRec for this pointer. PointerMapType::iterator I = PointerMap.find_as(PtrVal); if (I == PointerMap.end()) return; // Noop // If we found one, remove the pointer from the alias set it is in. AliasSet::PointerRec *PtrValEnt = I->second; AliasSet *AS = PtrValEnt->getAliasSet(*this); // Unlink and delete from the list of values. PtrValEnt->eraseFromList(); // Stop using the alias set. AS->dropRef(*this); PointerMap.erase(I); } // copyValue - This method should be used whenever a preexisting value in the // program is copied or cloned, introducing a new value. Note that it is ok for // clients that use this method to introduce the same value multiple times: if // the tracker already knows about a value, it will ignore the request. // void AliasSetTracker::copyValue(Value *From, Value *To) { // Notify the alias analysis implementation that this value is copied. AA.copyValue(From, To); // First, look up the PointerRec for this pointer. PointerMapType::iterator I = PointerMap.find_as(From); if (I == PointerMap.end()) return; // Noop assert(I->second->hasAliasSet() && "Dead entry?"); AliasSet::PointerRec &Entry = getEntryFor(To); if (Entry.hasAliasSet()) return; // Already in the tracker! // Add it to the alias set it aliases... I = PointerMap.find_as(From); AliasSet *AS = I->second->getAliasSet(*this); AS->addPointer(*this, Entry, I->second->getSize(), I->second->getTBAAInfo(), true); } //===----------------------------------------------------------------------===// // AliasSet/AliasSetTracker Printing Support //===----------------------------------------------------------------------===// void AliasSet::print(raw_ostream &OS) const { OS << " AliasSet[" << (const void*)this << ", " << RefCount << "] "; OS << (AliasTy == MustAlias ? "must" : "may") << " alias, "; switch (AccessTy) { case NoModRef: OS << "No access "; break; case Refs : OS << "Ref "; break; case Mods : OS << "Mod "; break; case ModRef : OS << "Mod/Ref "; break; default: llvm_unreachable("Bad value for AccessTy!"); } if (isVolatile()) OS << "[volatile] "; if (Forward) OS << " forwarding to " << (void*)Forward; if (!empty()) { OS << "Pointers: "; for (iterator I = begin(), E = end(); I != E; ++I) { if (I != begin()) OS << ", "; I.getPointer()->printAsOperand(OS << "("); OS << ", " << I.getSize() << ")"; } } if (!UnknownInsts.empty()) { OS << "\n " << UnknownInsts.size() << " Unknown instructions: "; for (unsigned i = 0, e = UnknownInsts.size(); i != e; ++i) { if (i) OS << ", "; UnknownInsts[i]->printAsOperand(OS); } } OS << "\n"; } void AliasSetTracker::print(raw_ostream &OS) const { OS << "Alias Set Tracker: " << AliasSets.size() << " alias sets for " << PointerMap.size() << " pointer values.\n"; for (const_iterator I = begin(), E = end(); I != E; ++I) I->print(OS); OS << "\n"; } #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) void AliasSet::dump() const { print(dbgs()); } void AliasSetTracker::dump() const { print(dbgs()); } #endif //===----------------------------------------------------------------------===// // ASTCallbackVH Class Implementation //===----------------------------------------------------------------------===// void AliasSetTracker::ASTCallbackVH::deleted() { assert(AST && "ASTCallbackVH called with a null AliasSetTracker!"); AST->deleteValue(getValPtr()); // this now dangles! } void AliasSetTracker::ASTCallbackVH::allUsesReplacedWith(Value *V) { AST->copyValue(getValPtr(), V); } AliasSetTracker::ASTCallbackVH::ASTCallbackVH(Value *V, AliasSetTracker *ast) : CallbackVH(V), AST(ast) {} AliasSetTracker::ASTCallbackVH & AliasSetTracker::ASTCallbackVH::operator=(Value *V) { return *this = ASTCallbackVH(V, AST); } //===----------------------------------------------------------------------===// // AliasSetPrinter Pass //===----------------------------------------------------------------------===// namespace { class AliasSetPrinter : public FunctionPass { AliasSetTracker *Tracker; public: static char ID; // Pass identification, replacement for typeid AliasSetPrinter() : FunctionPass(ID) { initializeAliasSetPrinterPass(*PassRegistry::getPassRegistry()); } void getAnalysisUsage(AnalysisUsage &AU) const override { AU.setPreservesAll(); AU.addRequired(); } bool runOnFunction(Function &F) override { Tracker = new AliasSetTracker(getAnalysis()); for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) Tracker->add(&*I); Tracker->print(errs()); delete Tracker; return false; } }; } char AliasSetPrinter::ID = 0; INITIALIZE_PASS_BEGIN(AliasSetPrinter, "print-alias-sets", "Alias Set Printer", false, true) INITIALIZE_AG_DEPENDENCY(AliasAnalysis) INITIALIZE_PASS_END(AliasSetPrinter, "print-alias-sets", "Alias Set Printer", false, true)