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//==- CFLSteensAliasAnalysis.h - Unification-based Alias Analysis -*- C++-*-==//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
/// \file
/// This is the interface for LLVM's unification-based alias analysis
/// implemented with CFL graph reachability.
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/Optional.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/CFLAliasAnalysisUtils.h"
#include "llvm/Analysis/MemoryLocation.h"
#include "llvm/IR/PassManager.h"
#include "llvm/Pass.h"
#include "llvm/Support/Casting.h"
#include <forward_list>
#include <memory>
namespace llvm {
class Function;
class TargetLibraryInfo;
namespace cflaa {
struct AliasSummary;
} // end namespace cflaa
class CFLSteensAAResult : public AAResultBase<CFLSteensAAResult> {
friend AAResultBase<CFLSteensAAResult>;
class FunctionInfo;
explicit CFLSteensAAResult(const TargetLibraryInfo &TLI);
CFLSteensAAResult(CFLSteensAAResult &&Arg);
/// Handle invalidation events from the new pass manager.
/// By definition, this result is stateless and so remains valid.
bool invalidate(Function &, const PreservedAnalyses &,
FunctionAnalysisManager::Invalidator &) {
return false;
/// Inserts the given Function into the cache.
void scan(Function *Fn);
void evict(Function *Fn);
/// Ensures that the given function is available in the cache.
/// Returns the appropriate entry from the cache.
const Optional<FunctionInfo> &ensureCached(Function *Fn);
/// Get the alias summary for the given function
/// Return nullptr if the summary is not found or not available
const cflaa::AliasSummary *getAliasSummary(Function &Fn);
AliasResult query(const MemoryLocation &LocA, const MemoryLocation &LocB);
AliasResult alias(const MemoryLocation &LocA, const MemoryLocation &LocB,
AAQueryInfo &AAQI) {
if (LocA.Ptr == LocB.Ptr)
return MustAlias;
// Comparisons between global variables and other constants should be
// handled by BasicAA.
// CFLSteensAA may report NoAlias when comparing a GlobalValue and
// ConstantExpr, but every query needs to have at least one Value tied to a
// Function, and neither GlobalValues nor ConstantExprs are.
if (isa<Constant>(LocA.Ptr) && isa<Constant>(LocB.Ptr))
return AAResultBase::alias(LocA, LocB, AAQI);
AliasResult QueryResult = query(LocA, LocB);
if (QueryResult == MayAlias)
return AAResultBase::alias(LocA, LocB, AAQI);
return QueryResult;
const TargetLibraryInfo &TLI;
/// Cached mapping of Functions to their StratifiedSets.
/// If a function's sets are currently being built, it is marked
/// in the cache as an Optional without a value. This way, if we
/// have any kind of recursion, it is discernable from a function
/// that simply has empty sets.
DenseMap<Function *, Optional<FunctionInfo>> Cache;
std::forward_list<cflaa::FunctionHandle<CFLSteensAAResult>> Handles;
FunctionInfo buildSetsFrom(Function *F);
/// Analysis pass providing a never-invalidated alias analysis result.
/// FIXME: We really should refactor CFL to use the analysis more heavily, and
/// in particular to leverage invalidation to trigger re-computation of sets.
class CFLSteensAA : public AnalysisInfoMixin<CFLSteensAA> {
friend AnalysisInfoMixin<CFLSteensAA>;
static AnalysisKey Key;
using Result = CFLSteensAAResult;
CFLSteensAAResult run(Function &F, FunctionAnalysisManager &AM);
/// Legacy wrapper pass to provide the CFLSteensAAResult object.
class CFLSteensAAWrapperPass : public ImmutablePass {
std::unique_ptr<CFLSteensAAResult> Result;
static char ID;
CFLSteensAAResult &getResult() { return *Result; }
const CFLSteensAAResult &getResult() const { return *Result; }
void initializePass() override;
void getAnalysisUsage(AnalysisUsage &AU) const override;
// createCFLSteensAAWrapperPass - This pass implements a set-based approach to
// alias analysis.
ImmutablePass *createCFLSteensAAWrapperPass();
} // end namespace llvm