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