1 //===- ProvenanceAnalysis.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 // 9 /// \file 10 /// 11 /// This file declares a special form of Alias Analysis called ``Provenance 12 /// Analysis''. The word ``provenance'' refers to the history of the ownership 13 /// of an object. Thus ``Provenance Analysis'' is an analysis which attempts to 14 /// use various techniques to determine if locally 15 /// 16 /// WARNING: This file knows about certain library functions. It recognizes them 17 /// by name, and hardwires knowledge of their semantics. 18 /// 19 /// WARNING: This file knows about how certain Objective-C library functions are 20 /// used. Naive LLVM IR transformations which would otherwise be 21 /// behavior-preserving may break these assumptions. 22 // 23 //===----------------------------------------------------------------------===// 24 25 #ifndef LLVM_LIB_TRANSFORMS_OBJCARC_PROVENANCEANALYSIS_H 26 #define LLVM_LIB_TRANSFORMS_OBJCARC_PROVENANCEANALYSIS_H 27 28 #include "llvm/ADT/DenseMap.h" 29 #include "llvm/IR/ValueHandle.h" 30 #include <utility> 31 32 namespace llvm { 33 34 class AAResults; 35 class DataLayout; 36 class PHINode; 37 class SelectInst; 38 class Value; 39 40 namespace objcarc { 41 42 /// This is similar to BasicAliasAnalysis, and it uses many of the same 43 /// techniques, except it uses special ObjC-specific reasoning about pointer 44 /// relationships. 45 /// 46 /// In this context ``Provenance'' is defined as the history of an object's 47 /// ownership. Thus ``Provenance Analysis'' is defined by using the notion of 48 /// an ``independent provenance source'' of a pointer to determine whether or 49 /// not two pointers have the same provenance source and thus could 50 /// potentially be related. 51 class ProvenanceAnalysis { 52 AAResults *AA; 53 54 using ValuePairTy = std::pair<const Value *, const Value *>; 55 using CachedResultsTy = DenseMap<ValuePairTy, bool>; 56 57 CachedResultsTy CachedResults; 58 59 DenseMap<const Value *, WeakTrackingVH> UnderlyingObjCPtrCache; 60 61 bool relatedCheck(const Value *A, const Value *B); 62 bool relatedSelect(const SelectInst *A, const Value *B); 63 bool relatedPHI(const PHINode *A, const Value *B); 64 65 public: 66 ProvenanceAnalysis() = default; 67 ProvenanceAnalysis(const ProvenanceAnalysis &) = delete; 68 ProvenanceAnalysis &operator=(const ProvenanceAnalysis &) = delete; 69 70 void setAA(AAResults *aa) { AA = aa; } 71 72 AAResults *getAA() const { return AA; } 73 74 bool related(const Value *A, const Value *B); 75 76 void clear() { 77 CachedResults.clear(); 78 UnderlyingObjCPtrCache.clear(); 79 } 80 }; 81 82 } // end namespace objcarc 83 84 } // end namespace llvm 85 86 #endif // LLVM_LIB_TRANSFORMS_OBJCARC_PROVENANCEANALYSIS_H 87