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/ADT/SmallPtrSet.h"
26 #include "llvm/Analysis/ObjCARCInstKind.h"
27
28 namespace llvm {
29 class BasicBlock;
30 class Instruction;
31 class Value;
32 }
33
34 namespace llvm {
CanAlterRefCount(const Instruction * Inst,const Value * Ptr,ProvenanceAnalysis & PA,ARCInstKind Class)35 namespace objcarc {
36
37 class ProvenanceAnalysis;
38
39 /// \enum DependenceKind
40 /// Defines different dependence kinds among various ARC constructs.
41 ///
42 /// There are several kinds of dependence-like concepts in use here.
43 ///
44 enum DependenceKind {
45 NeedsPositiveRetainCount,
46 AutoreleasePoolBoundary,
47 CanChangeRetainCount,
48 RetainAutoreleaseDep, ///< Blocks objc_retainAutorelease.
49 RetainAutoreleaseRVDep, ///< Blocks objc_retainAutoreleaseReturnValue.
50 RetainRVDep ///< Blocks objc_retainAutoreleasedReturnValue.
51 };
52
53 /// Find dependent instructions. If there is exactly one dependent instruction,
54 /// return it. Otherwise, return null.
55 llvm::Instruction *findSingleDependency(DependenceKind Flavor, const Value *Arg,
56 BasicBlock *StartBB,
57 Instruction *StartInst,
58 ProvenanceAnalysis &PA);
59
60 bool
61 Depends(DependenceKind Flavor, Instruction *Inst, const Value *Arg,
62 ProvenanceAnalysis &PA);
63
64 /// Test whether the given instruction can "use" the given pointer's object in a
65 /// way that requires the reference count to be positive.
66 bool CanUse(const Instruction *Inst, const Value *Ptr, ProvenanceAnalysis &PA,
67 ARCInstKind Class);
68
69 /// Test whether the given instruction can result in a reference count
70 /// modification (positive or negative) for the pointer's object.
71 bool CanAlterRefCount(const Instruction *Inst, const Value *Ptr,
72 ProvenanceAnalysis &PA, ARCInstKind Class);
73
74 /// Returns true if we can not conservatively prove that Inst can not decrement
75 /// the reference count of Ptr. Returns false if we can.
76 bool CanDecrementRefCount(const Instruction *Inst, const Value *Ptr,
77 ProvenanceAnalysis &PA, ARCInstKind Class);
78
79 static inline bool CanDecrementRefCount(const Instruction *Inst,
80 const Value *Ptr,
81 ProvenanceAnalysis &PA) {
82 return CanDecrementRefCount(Inst, Ptr, PA, GetARCInstKind(Inst));
83 }
84
85 } // namespace objcarc
86 } // namespace llvm
87
88 #endif
89