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- //===- 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(); }
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