1//===------------------------ MapLattice.h ----------------------*- 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//  This file defines a parameterized lattice that maps keys to individual
10//  lattice elements (of the parameter lattice type). A typical usage is lifting
11//  a particular lattice to all variables in a lexical scope.
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_CLANG_ANALYSIS_FLOWSENSITIVE__MAPLATTICE_H
16#define LLVM_CLANG_ANALYSIS_FLOWSENSITIVE__MAPLATTICE_H
17
18#include <ostream>
19#include <string>
20#include <utility>
21
22#include "DataflowAnalysis.h"
23#include "clang/AST/Decl.h"
24#include "clang/Analysis/FlowSensitive/DataflowLattice.h"
25#include "llvm/ADT/DenseMap.h"
26#include "llvm/ADT/StringRef.h"
27
28namespace clang {
29namespace dataflow {
30
31/// A lattice that maps keys to individual lattice elements. When instantiated
32/// with an `ElementLattice` that is a bounded semi-lattice, `MapLattice` is
33/// itself a bounded semi-lattice, so long as the user limits themselves to a
34/// finite number of keys. In that case, `top` is (implicitly), the map
35/// containing all valid keys mapped to `top` of `ElementLattice`.
36///
37/// Requirements on `ElementLattice`:
38/// * Provides standard declarations of a bounded semi-lattice.
39template <typename Key, typename ElementLattice> class MapLattice {
40  using Container = llvm::DenseMap<Key, ElementLattice>;
41  Container C;
42
43public:
44  using key_type = Key;
45  using mapped_type = ElementLattice;
46  using value_type = typename Container::value_type;
47  using iterator = typename Container::iterator;
48  using const_iterator = typename Container::const_iterator;
49
50  MapLattice() = default;
51
52  explicit MapLattice(Container C) { C = std::move(C); }
53
54  // The `bottom` element is the empty map.
55  static MapLattice bottom() { return MapLattice(); }
56
57  std::pair<iterator, bool>
58  insert(const std::pair<const key_type, mapped_type> &P) {
59    return C.insert(P);
60  }
61
62  std::pair<iterator, bool> insert(std::pair<const key_type, mapped_type> &&P) {
63    return C.insert(std::move(P));
64  }
65
66  unsigned size() const { return C.size(); }
67  bool empty() const { return C.empty(); }
68
69  iterator begin() { return C.begin(); }
70  iterator end() { return C.end(); }
71  const_iterator begin() const { return C.begin(); }
72  const_iterator end() const { return C.end(); }
73
74  // Equality is direct equality of underlying map entries. One implication of
75  // this definition is that a map with (only) keys that map to bottom is not
76  // equal to the empty map.
77  friend bool operator==(const MapLattice &LHS, const MapLattice &RHS) {
78    return LHS.C == RHS.C;
79  }
80
81  friend bool operator!=(const MapLattice &LHS, const MapLattice &RHS) {
82    return !(LHS == RHS);
83  }
84
85  bool contains(const key_type &K) const { return C.find(K) != C.end(); }
86
87  iterator find(const key_type &K) { return C.find(K); }
88  const_iterator find(const key_type &K) const { return C.find(K); }
89
90  mapped_type &operator[](const key_type &K) { return C[K]; }
91
92  /// If an entry exists in one map but not the other, the missing entry is
93  /// treated as implicitly mapping to `bottom`. So, the joined map contains the
94  /// entry as it was in the source map.
95  LatticeJoinEffect join(const MapLattice &Other) {
96    LatticeJoinEffect Effect = LatticeJoinEffect::Unchanged;
97    for (const auto &O : Other.C) {
98      auto It = C.find(O.first);
99      if (It == C.end()) {
100        C.insert(O);
101        Effect = LatticeJoinEffect::Changed;
102      } else if (It->second.join(O.second) == LatticeJoinEffect::Changed)
103        Effect = LatticeJoinEffect::Changed;
104    }
105    return Effect;
106  }
107};
108
109/// Convenience alias that captures the common use of map lattices to model
110/// in-scope variables.
111template <typename ElementLattice>
112using VarMapLattice = MapLattice<const clang::VarDecl *, ElementLattice>;
113
114template <typename Key, typename ElementLattice>
115std::ostream &
116operator<<(std::ostream &Os,
117           const clang::dataflow::MapLattice<Key, ElementLattice> &M) {
118  std::string Separator;
119  Os << "{";
120  for (const auto &E : M) {
121    Os << std::exchange(Separator, ", ") << E.first << " => " << E.second;
122  }
123  Os << "}";
124  return Os;
125}
126
127template <typename ElementLattice>
128std::ostream &
129operator<<(std::ostream &Os,
130           const clang::dataflow::VarMapLattice<ElementLattice> &M) {
131  std::string Separator;
132  Os << "{";
133  for (const auto &E : M) {
134    Os << std::exchange(Separator, ", ") << E.first->getName().str() << " => "
135       << E.second;
136  }
137  Os << "}";
138  return Os;
139}
140} // namespace dataflow
141} // namespace clang
142
143#endif // LLVM_CLANG_ANALYSIS_FLOWSENSITIVE__MAPLATTICE_H
144