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 { 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 }; 51 52 /// Find dependent instructions. If there is exactly one dependent instruction, 53 /// return it. Otherwise, return null. 54 llvm::Instruction *findSingleDependency(DependenceKind Flavor, const Value *Arg, 55 BasicBlock *StartBB, 56 Instruction *StartInst, 57 ProvenanceAnalysis &PA); 58 59 bool 60 Depends(DependenceKind Flavor, Instruction *Inst, const Value *Arg, 61 ProvenanceAnalysis &PA); 62 63 /// Test whether the given instruction can "use" the given pointer's object in a 64 /// way that requires the reference count to be positive. 65 bool CanUse(const Instruction *Inst, const Value *Ptr, ProvenanceAnalysis &PA, 66 ARCInstKind Class); 67 68 /// Test whether the given instruction can result in a reference count 69 /// modification (positive or negative) for the pointer's object. 70 bool CanAlterRefCount(const Instruction *Inst, const Value *Ptr, 71 ProvenanceAnalysis &PA, ARCInstKind Class); 72 73 /// Returns true if we can not conservatively prove that Inst can not decrement 74 /// the reference count of Ptr. Returns false if we can. 75 bool CanDecrementRefCount(const Instruction *Inst, const Value *Ptr, 76 ProvenanceAnalysis &PA, ARCInstKind Class); 77 78 static inline bool CanDecrementRefCount(const Instruction *Inst, 79 const Value *Ptr, 80 ProvenanceAnalysis &PA) { 81 return CanDecrementRefCount(Inst, Ptr, PA, GetARCInstKind(Inst)); 82 } 83 84 } // namespace objcarc 85 } // namespace llvm 86 87 #endif 88