llvm-project/llvm/lib/Analysis/NoAliasAnalysis.cpp

95 lines
3.3 KiB
C++

//===- 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 {}
/// 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(); }