llvm/llvm/lib/Transforms/ObjCARC/DependencyAnalysis.cpp

//===- DependencyAnalysis.cpp - ObjC ARC Optimization ---------------------===//
//
// 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 special dependency analysis routines used in Objective C
/// ARC Optimizations.
///
/// 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.
///
//===----------------------------------------------------------------------===//

#include "DependencyAnalysis.h"
#include "ObjCARC.h"
#include "ProvenanceAnalysis.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/IR/CFG.h"

usingnamespacellvm;
usingnamespacellvm::objcarc;

#define DEBUG_TYPE …

/// Test whether the given instruction can result in a reference count
/// modification (positive or negative) for the pointer's object.
bool llvm::objcarc::CanAlterRefCount(const Instruction *Inst, const Value *Ptr,
                                     ProvenanceAnalysis &PA,
                                     ARCInstKind Class) { … }

bool llvm::objcarc::CanDecrementRefCount(const Instruction *Inst,
                                         const Value *Ptr,
                                         ProvenanceAnalysis &PA,
                                         ARCInstKind Class) { … }

/// Test whether the given instruction can "use" the given pointer's object in a
/// way that requires the reference count to be positive.
bool llvm::objcarc::CanUse(const Instruction *Inst, const Value *Ptr,
                           ProvenanceAnalysis &PA, ARCInstKind Class) { … }

/// Test if there can be dependencies on Inst through Arg. This function only
/// tests dependencies relevant for removing pairs of calls.
bool
llvm::objcarc::Depends(DependenceKind Flavor, Instruction *Inst,
                       const Value *Arg, ProvenanceAnalysis &PA) { … }

/// Walk up the CFG from StartPos (which is in StartBB) and find local and
/// non-local dependencies on Arg.
///
/// TODO: Cache results?
static bool findDependencies(DependenceKind Flavor, const Value *Arg,
                             BasicBlock *StartBB, Instruction *StartInst,
                             SmallPtrSetImpl<Instruction *> &DependingInsts,
                             ProvenanceAnalysis &PA) { … }

llvm::Instruction *llvm::objcarc::findSingleDependency(DependenceKind Flavor,
                                                       const Value *Arg,
                                                       BasicBlock *StartBB,
                                                       Instruction *StartInst,
                                                       ProvenanceAnalysis &PA) { … }