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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/AliasAnalysis.h"
#include "llvm/Analysis/Passes.h"
#include "llvm/Pass.h"
#include "llvm/Target/TargetData.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) {
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
virtual void initializePass() {
// Note: NoAA does not call InitializeAliasAnalysis because it's
// special and does not support chaining.
TD = getAnalysisIfAvailable<TargetData>();
virtual AliasResult alias(const Location &LocA, const Location &LocB) {
return MayAlias;
virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS) {
return UnknownModRefBehavior;
virtual ModRefBehavior getModRefBehavior(const Function *F) {
return UnknownModRefBehavior;
virtual bool pointsToConstantMemory(const Location &Loc,
bool OrLocal) {
return false;
virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
const Location &Loc) {
return ModRef;
virtual ModRefResult getModRefInfo(ImmutableCallSite CS1,
ImmutableCallSite CS2) {
return ModRef;
virtual void deleteValue(Value *V) {}
virtual void copyValue(Value *From, Value *To) {}
virtual void addEscapingUse(Use &U) {}
/// 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.
virtual void *getAdjustedAnalysisPointer(const void *ID) {
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(); }