1 //===- DependencyAnalysis.h - ObjC ARC Optimization ---*- C++ -*-----------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 /// \file
9 ///
10 /// This file declares special dependency analysis routines used in Objective C
11 /// ARC Optimizations.
12 ///
13 /// WARNING: This file knows about certain library functions. It recognizes them
14 /// by name, and hardwires knowledge of their semantics.
15 ///
16 /// WARNING: This file knows about how certain Objective-C library functions are
17 /// used. Naive LLVM IR transformations which would otherwise be
18 /// behavior-preserving may break these assumptions.
19 ///
20 //===----------------------------------------------------------------------===//
21 
22 #ifndef LLVM_LIB_TRANSFORMS_OBJCARC_DEPENDENCYANALYSIS_H
23 #define LLVM_LIB_TRANSFORMS_OBJCARC_DEPENDENCYANALYSIS_H
24 
25 #include "llvm/Analysis/ObjCARCInstKind.h"
26 
27 namespace llvm {
28   class BasicBlock;
29   class Instruction;
30   class Value;
31 }
32 
33 namespace llvm {
34 namespace objcarc {
35 
36 class ProvenanceAnalysis;
37 
38 /// \enum DependenceKind
39 /// Defines different dependence kinds among various ARC constructs.
40 ///
41 /// There are several kinds of dependence-like concepts in use here.
42 ///
43 enum DependenceKind {
44   NeedsPositiveRetainCount,
45   AutoreleasePoolBoundary,
46   CanChangeRetainCount,
47   RetainAutoreleaseDep,       ///< Blocks objc_retainAutorelease.
48   RetainAutoreleaseRVDep      ///< Blocks objc_retainAutoreleaseReturnValue.
49 };
50 
51 /// Find dependent instructions. If there is exactly one dependent instruction,
52 /// return it. Otherwise, return null.
53 llvm::Instruction *findSingleDependency(DependenceKind Flavor, const Value *Arg,
54                                         BasicBlock *StartBB,
55                                         Instruction *StartInst,
56                                         ProvenanceAnalysis &PA);
57 
58 bool
59 Depends(DependenceKind Flavor, Instruction *Inst, const Value *Arg,
60         ProvenanceAnalysis &PA);
61 
62 /// Test whether the given instruction can "use" the given pointer's object in a
63 /// way that requires the reference count to be positive.
64 bool CanUse(const Instruction *Inst, const Value *Ptr, ProvenanceAnalysis &PA,
65             ARCInstKind Class);
66 
67 /// Test whether the given instruction can result in a reference count
68 /// modification (positive or negative) for the pointer's object.
69 bool CanAlterRefCount(const Instruction *Inst, const Value *Ptr,
70                       ProvenanceAnalysis &PA, ARCInstKind Class);
71 
72 /// Returns true if we can not conservatively prove that Inst can not decrement
73 /// the reference count of Ptr. Returns false if we can.
74 bool CanDecrementRefCount(const Instruction *Inst, const Value *Ptr,
75                           ProvenanceAnalysis &PA, ARCInstKind Class);
76 
77 static inline bool CanDecrementRefCount(const Instruction *Inst,
78                                         const Value *Ptr,
79                                         ProvenanceAnalysis &PA) {
80   return CanDecrementRefCount(Inst, Ptr, PA, GetARCInstKind(Inst));
81 }
82 
83 } // namespace objcarc
84 } // namespace llvm
85 
86 #endif
87