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/PassManager.h"
30 #include "llvm/IR/ValueHandle.h"
31 #include <utility>
32 
33 namespace llvm {
34 
35 class AAResults;
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 *, std::pair<WeakVH, WeakTrackingVH>>
60       UnderlyingObjCPtrCache;
61 
62   bool relatedCheck(const Value *A, const Value *B);
63   bool relatedSelect(const SelectInst *A, const Value *B);
64   bool relatedPHI(const PHINode *A, const Value *B);
65 
66 public:
67   ProvenanceAnalysis() = default;
68   ProvenanceAnalysis(const ProvenanceAnalysis &) = delete;
69   ProvenanceAnalysis &operator=(const ProvenanceAnalysis &) = delete;
70 
71   void setAA(AAResults *aa) { AA = aa; }
72 
73   AAResults *getAA() const { return AA; }
74 
75   bool related(const Value *A, const Value *B);
76 
77   void clear() {
78     CachedResults.clear();
79     UnderlyingObjCPtrCache.clear();
80   }
81 };
82 
83 } // end namespace objcarc
84 
85 } // end namespace llvm
86 
87 #endif // LLVM_LIB_TRANSFORMS_OBJCARC_PROVENANCEANALYSIS_H
88