| //===- NoAliasAnalysis.cpp - Minimal Alias Analysis Impl ------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file defines the default implementation of the Alias Analysis interface |
| // that simply returns "I don't know" for all queries. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Analysis/Passes.h" |
| #include "llvm/Analysis/AliasAnalysis.h" |
| #include "llvm/IR/DataLayout.h" |
| #include "llvm/IR/LLVMContext.h" |
| #include "llvm/IR/Module.h" |
| #include "llvm/Pass.h" |
| using namespace llvm; |
| |
| namespace { |
| /// NoAA - This class implements the -no-aa pass, which always returns "I |
| /// don't know" for alias queries. NoAA is unlike other alias analysis |
| /// implementations, in that it does not chain to a previous analysis. As |
| /// such it doesn't follow many of the rules that other alias analyses must. |
| /// |
| struct NoAA : public ImmutablePass, public AliasAnalysis { |
| static char ID; // Class identification, replacement for typeinfo |
| NoAA() : ImmutablePass(ID) { |
| initializeNoAAPass(*PassRegistry::getPassRegistry()); |
| } |
| |
| void getAnalysisUsage(AnalysisUsage &AU) const override {} |
| |
| bool doInitialization(Module &M) override { |
| // Note: NoAA does not call InitializeAliasAnalysis because it's |
| // special and does not support chaining. |
| DL = &M.getDataLayout(); |
| return true; |
| } |
| |
| AliasResult alias(const MemoryLocation &LocA, |
| const MemoryLocation &LocB) override { |
| return MayAlias; |
| } |
| |
| ModRefBehavior getModRefBehavior(ImmutableCallSite CS) override { |
| return UnknownModRefBehavior; |
| } |
| ModRefBehavior getModRefBehavior(const Function *F) override { |
| return UnknownModRefBehavior; |
| } |
| |
| bool pointsToConstantMemory(const MemoryLocation &Loc, |
| bool OrLocal) override { |
| return false; |
| } |
| ModRefResult getArgModRefInfo(ImmutableCallSite CS, |
| unsigned ArgIdx) override { |
| return ModRef; |
| } |
| |
| ModRefResult getModRefInfo(ImmutableCallSite CS, |
| const MemoryLocation &Loc) override { |
| return ModRef; |
| } |
| ModRefResult getModRefInfo(ImmutableCallSite CS1, |
| ImmutableCallSite CS2) override { |
| return ModRef; |
| } |
| |
| void deleteValue(Value *V) override {} |
| void addEscapingUse(Use &U) override {} |
| |
| /// getAdjustedAnalysisPointer - This method is used when a pass implements |
| /// an analysis interface through multiple inheritance. If needed, it |
| /// should override this to adjust the this pointer as needed for the |
| /// specified pass info. |
| void *getAdjustedAnalysisPointer(const void *ID) override { |
| if (ID == &AliasAnalysis::ID) |
| return (AliasAnalysis*)this; |
| return this; |
| } |
| }; |
| } // End of anonymous namespace |
| |
| // Register this pass... |
| char NoAA::ID = 0; |
| INITIALIZE_AG_PASS(NoAA, AliasAnalysis, "no-aa", |
| "No Alias Analysis (always returns 'may' alias)", |
| true, true, true) |
| |
| ImmutablePass *llvm::createNoAAPass() { return new NoAA(); } |