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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 Location &LocA, const Location &LocB) override {
return MayAlias;
}
ModRefBehavior getModRefBehavior(ImmutableCallSite CS) override {
return UnknownModRefBehavior;
}
ModRefBehavior getModRefBehavior(const Function *F) override {
return UnknownModRefBehavior;
}
bool pointsToConstantMemory(const Location &Loc, bool OrLocal) override {
return false;
}
Location getArgLocation(ImmutableCallSite CS, unsigned ArgIdx,
ModRefResult &Mask) override {
Mask = ModRef;
AAMDNodes AATags;
CS->getAAMetadata(AATags);
return Location(CS.getArgument(ArgIdx), UnknownSize, AATags);
}
ModRefResult getModRefInfo(ImmutableCallSite CS,
const Location &Loc) override {
return ModRef;
}
ModRefResult getModRefInfo(ImmutableCallSite CS1,
ImmutableCallSite CS2) override {
return ModRef;
}
void deleteValue(Value *V) override {}
void copyValue(Value *From, Value *To) 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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