llvm/llvm/include/llvm/Analysis/ObjCARCAnalysisUtils.h

//===- ObjCARCAnalysisUtils.h - ObjC ARC Analysis Utilities -----*- 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 file defines common analysis utilities used by the ObjC ARC Optimizer.
/// ARC stands for Automatic Reference Counting and is a system for managing
/// reference counts for objects in Objective C.
///
/// WARNING: This file knows about certain library functions. It recognizes them
/// by name, and hardwires knowledge of their semantics.
///
/// WARNING: This file knows about how certain Objective-C library functions are
/// used. Naive LLVM IR transformations which would otherwise be
/// behavior-preserving may break these assumptions.
///
//===----------------------------------------------------------------------===//

#ifndef LLVM_ANALYSIS_OBJCARCANALYSISUTILS_H
#define LLVM_ANALYSIS_OBJCARCANALYSISUTILS_H

#include "llvm/Analysis/ObjCARCInstKind.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/ValueHandle.h"
#include <optional>

namespace llvm {

class AAResults;

namespace objcarc {

/// A handy option to enable/disable all ARC Optimizations.
extern bool EnableARCOpts;

/// Test if the given module looks interesting to run ARC optimization
/// on.
inline bool ModuleHasARC(const Module &M) { … }

/// This is a wrapper around getUnderlyingObject which also knows how to
/// look through objc_retain and objc_autorelease calls, which we know to return
/// their argument verbatim.
inline const Value *GetUnderlyingObjCPtr(const Value *V) { … }

/// A wrapper for GetUnderlyingObjCPtr used for results memoization.
inline const Value *GetUnderlyingObjCPtrCached(
    const Value *V,
    DenseMap<const Value *, std::pair<WeakVH, WeakTrackingVH>> &Cache) { … }

/// The RCIdentity root of a value \p V is a dominating value U for which
/// retaining or releasing U is equivalent to retaining or releasing V. In other
/// words, ARC operations on \p V are equivalent to ARC operations on \p U.
///
/// We use this in the ARC optimizer to make it easier to match up ARC
/// operations by always mapping ARC operations to RCIdentityRoots instead of
/// pointers themselves.
///
/// The two ways that we see RCIdentical values in ObjC are via:
///
///   1. PointerCasts
///   2. Forwarding Calls that return their argument verbatim.
///
/// Thus this function strips off pointer casts and forwarding calls. *NOTE*
/// This implies that two RCIdentical values must alias.
inline const Value *GetRCIdentityRoot(const Value *V) { … }

/// Helper which calls const Value *GetRCIdentityRoot(const Value *V) and just
/// casts away the const of the result. For documentation about what an
/// RCIdentityRoot (and by extension GetRCIdentityRoot is) look at that
/// function.
inline Value *GetRCIdentityRoot(Value *V) { … }

/// Assuming the given instruction is one of the special calls such as
/// objc_retain or objc_release, return the RCIdentity root of the argument of
/// the call.
inline Value *GetArgRCIdentityRoot(Value *Inst) { … }

inline bool IsNullOrUndef(const Value *V) { … }

inline bool IsNoopInstruction(const Instruction *I) { … }

/// Test whether the given value is possible a retainable object pointer.
inline bool IsPotentialRetainableObjPtr(const Value *Op) { … }

bool IsPotentialRetainableObjPtr(const Value *Op, AAResults &AA);

/// Helper for GetARCInstKind. Determines what kind of construct CS
/// is.
inline ARCInstKind GetCallSiteClass(const CallBase &CB) { … }

/// Return true if this value refers to a distinct and identifiable
/// object.
///
/// This is similar to AliasAnalysis's isIdentifiedObject, except that it uses
/// special knowledge of ObjC conventions.
inline bool IsObjCIdentifiedObject(const Value *V) { … }

enum class ARCMDKindID { … };

/// A cache of MDKinds used by various ARC optimizations.
class ARCMDKindCache { … };

} // end namespace objcarc
} // end namespace llvm

#endif