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 PHINode;
36 class SelectInst;
37 class Value;
38 
39 namespace objcarc {
40 
41 /// This is similar to BasicAliasAnalysis, and it uses many of the same
42 /// techniques, except it uses special ObjC-specific reasoning about pointer
43 /// relationships.
44 ///
45 /// In this context ``Provenance'' is defined as the history of an object's
46 /// ownership. Thus ``Provenance Analysis'' is defined by using the notion of
47 /// an ``independent provenance source'' of a pointer to determine whether or
48 /// not two pointers have the same provenance source and thus could
49 /// potentially be related.
50 class ProvenanceAnalysis {
51   AAResults *AA;
52 
53   using ValuePairTy = std::pair<const Value *, const Value *>;
54   using CachedResultsTy = DenseMap<ValuePairTy, bool>;
55 
56   CachedResultsTy CachedResults;
57 
58   DenseMap<const Value *, std::pair<WeakVH, WeakTrackingVH>>
59       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