//===- BasicAliasAnalysis.h - Stateless, local Alias Analysis ---*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
/// \file
/// This is the interface for LLVM's primary stateless and local alias analysis.
///
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_BASICALIASANALYSIS_H
#define LLVM_ANALYSIS_BASICALIASANALYSIS_H
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/IR/PassManager.h"
#include "llvm/Pass.h"
#include <memory>
#include <optional>
#include <utility>
namespace llvm {
class AssumptionCache;
class DataLayout;
class DominatorTree;
class Function;
class GEPOperator;
class PHINode;
class SelectInst;
class TargetLibraryInfo;
class PhiValues;
class Value;
/// This is the AA result object for the basic, local, and stateless alias
/// analysis. It implements the AA query interface in an entirely stateless
/// manner. As one consequence, it is never invalidated due to IR changes.
/// While it does retain some storage, that is used as an optimization and not
/// to preserve information from query to query. However it does retain handles
/// to various other analyses and must be recomputed when those analyses are.
class BasicAAResult : public AAResultBase {
const DataLayout &DL;
const Function &F;
const TargetLibraryInfo &TLI;
AssumptionCache &AC;
DominatorTree *DT;
public:
BasicAAResult(const DataLayout &DL, const Function &F,
const TargetLibraryInfo &TLI, AssumptionCache &AC,
DominatorTree *DT = nullptr)
: DL(DL), F(F), TLI(TLI), AC(AC), DT(DT) {}
BasicAAResult(const BasicAAResult &Arg)
: AAResultBase(Arg), DL(Arg.DL), F(Arg.F), TLI(Arg.TLI), AC(Arg.AC),
DT(Arg.DT) {}
BasicAAResult(BasicAAResult &&Arg)
: AAResultBase(std::move(Arg)), DL(Arg.DL), F(Arg.F), TLI(Arg.TLI),
AC(Arg.AC), DT(Arg.DT) {}
/// Handle invalidation events in the new pass manager.
bool invalidate(Function &Fn, const PreservedAnalyses &PA,
FunctionAnalysisManager::Invalidator &Inv);
AliasResult alias(const MemoryLocation &LocA, const MemoryLocation &LocB,
AAQueryInfo &AAQI, const Instruction *CtxI);
ModRefInfo getModRefInfo(const CallBase *Call, const MemoryLocation &Loc,
AAQueryInfo &AAQI);
ModRefInfo getModRefInfo(const CallBase *Call1, const CallBase *Call2,
AAQueryInfo &AAQI);
/// Returns a bitmask that should be unconditionally applied to the ModRef
/// info of a memory location. This allows us to eliminate Mod and/or Ref
/// from the ModRef info based on the knowledge that the memory location
/// points to constant and/or locally-invariant memory.
///
/// If IgnoreLocals is true, then this method returns NoModRef for memory
/// that points to a local alloca.
ModRefInfo getModRefInfoMask(const MemoryLocation &Loc, AAQueryInfo &AAQI,
bool IgnoreLocals = false);
/// Get the location associated with a pointer argument of a callsite.
ModRefInfo getArgModRefInfo(const CallBase *Call, unsigned ArgIdx);
/// Returns the behavior when calling the given call site.
MemoryEffects getMemoryEffects(const CallBase *Call, AAQueryInfo &AAQI);
/// Returns the behavior when calling the given function. For use when the
/// call site is not known.
MemoryEffects getMemoryEffects(const Function *Fn);
private:
struct DecomposedGEP;
/// Tracks instructions visited by pointsToConstantMemory.
SmallPtrSet<const Value *, 16> Visited;
static DecomposedGEP
DecomposeGEPExpression(const Value *V, const DataLayout &DL,
AssumptionCache *AC, DominatorTree *DT);
/// A Heuristic for aliasGEP that searches for a constant offset
/// between the variables.
///
/// GetLinearExpression has some limitations, as generally zext(%x + 1)
/// != zext(%x) + zext(1) if the arithmetic overflows. GetLinearExpression
/// will therefore conservatively refuse to decompose these expressions.
/// However, we know that, for all %x, zext(%x) != zext(%x + 1), even if
/// the addition overflows.
bool constantOffsetHeuristic(const DecomposedGEP &GEP, LocationSize V1Size,
LocationSize V2Size, AssumptionCache *AC,
DominatorTree *DT, const AAQueryInfo &AAQI);
bool isValueEqualInPotentialCycles(const Value *V1, const Value *V2,
const AAQueryInfo &AAQI);
void subtractDecomposedGEPs(DecomposedGEP &DestGEP,
const DecomposedGEP &SrcGEP,
const AAQueryInfo &AAQI);
AliasResult aliasGEP(const GEPOperator *V1, LocationSize V1Size,
const Value *V2, LocationSize V2Size,
const Value *UnderlyingV1, const Value *UnderlyingV2,
AAQueryInfo &AAQI);
AliasResult aliasPHI(const PHINode *PN, LocationSize PNSize,
const Value *V2, LocationSize V2Size, AAQueryInfo &AAQI);
AliasResult aliasSelect(const SelectInst *SI, LocationSize SISize,
const Value *V2, LocationSize V2Size,
AAQueryInfo &AAQI);
AliasResult aliasCheck(const Value *V1, LocationSize V1Size, const Value *V2,
LocationSize V2Size, AAQueryInfo &AAQI,
const Instruction *CtxI);
AliasResult aliasCheckRecursive(const Value *V1, LocationSize V1Size,
const Value *V2, LocationSize V2Size,
AAQueryInfo &AAQI, const Value *O1,
const Value *O2);
};
/// Analysis pass providing a never-invalidated alias analysis result.
class BasicAA : public AnalysisInfoMixin<BasicAA> {
friend AnalysisInfoMixin<BasicAA>;
static AnalysisKey Key;
public:
using Result = BasicAAResult;
BasicAAResult run(Function &F, FunctionAnalysisManager &AM);
};
/// Legacy wrapper pass to provide the BasicAAResult object.
class BasicAAWrapperPass : public FunctionPass {
std::unique_ptr<BasicAAResult> Result;
virtual void anchor();
public:
static char ID;
BasicAAWrapperPass();
BasicAAResult &getResult() { return *Result; }
const BasicAAResult &getResult() const { return *Result; }
bool runOnFunction(Function &F) override;
void getAnalysisUsage(AnalysisUsage &AU) const override;
};
FunctionPass *createBasicAAWrapperPass();
/// A helper for the legacy pass manager to create a \c BasicAAResult object
/// populated to the best of our ability for a particular function when inside
/// of a \c ModulePass or a \c CallGraphSCCPass.
BasicAAResult createLegacyPMBasicAAResult(Pass &P, Function &F);
/// This class is a functor to be used in legacy module or SCC passes for
/// computing AA results for a function. We store the results in fields so that
/// they live long enough to be queried, but we re-use them each time.
class LegacyAARGetter {
Pass &P;
std::optional<BasicAAResult> BAR;
std::optional<AAResults> AAR;
public:
LegacyAARGetter(Pass &P) : P(P) {}
AAResults &operator()(Function &F) {
BAR.emplace(createLegacyPMBasicAAResult(P, F));
AAR.emplace(createLegacyPMAAResults(P, F, *BAR));
return *AAR;
}
};
} // end namespace llvm
#endif // LLVM_ANALYSIS_BASICALIASANALYSIS_H