1 | //===- llvm/ADT/GraphTraits.h - Graph traits template -----------*- C++ -*-===// |
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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 the little GraphTraits<X> template class that should be |

10 | // specialized by classes that want to be iteratable by generic graph iterators. |

11 | // |

12 | // This file also defines the marker class Inverse that is used to iterate over |

13 | // graphs in a graph defined, inverse ordering... |

14 | // |

15 | //===----------------------------------------------------------------------===// |

16 | |

17 | #ifndef LLVM_ADT_GRAPHTRAITS_H |

18 | #define LLVM_ADT_GRAPHTRAITS_H |

19 | |

20 | #include "llvm/ADT/iterator_range.h" |

21 | |

22 | namespace llvm { |

23 | |

24 | // GraphTraits - This class should be specialized by different graph types... |

25 | // which is why the default version is empty. |

26 | // |

27 | // This template evolved from supporting `BasicBlock` to also later supporting |

28 | // more complex types (e.g. CFG and DomTree). |

29 | // |

30 | // GraphTraits can be used to create a view over a graph interpreting it |

31 | // differently without requiring a copy of the original graph. This could |

32 | // be achieved by carrying more data in NodeRef. See LoopBodyTraits for one |

33 | // example. |

34 | template<class GraphType> |

35 | struct GraphTraits { |

36 | // Elements to provide: |

37 | |

38 | // typedef NodeRef - Type of Node token in the graph, which should |

39 | // be cheap to copy. |

40 | // typedef ChildIteratorType - Type used to iterate over children in graph, |

41 | // dereference to a NodeRef. |

42 | |

43 | // static NodeRef getEntryNode(const GraphType &) |

44 | // Return the entry node of the graph |

45 | |

46 | // static ChildIteratorType child_begin(NodeRef) |

47 | // static ChildIteratorType child_end (NodeRef) |

48 | // Return iterators that point to the beginning and ending of the child |

49 | // node list for the specified node. |

50 | |

51 | // typedef ...iterator nodes_iterator; - dereference to a NodeRef |

52 | // static nodes_iterator nodes_begin(GraphType *G) |

53 | // static nodes_iterator nodes_end (GraphType *G) |

54 | // nodes_iterator/begin/end - Allow iteration over all nodes in the graph |

55 | |

56 | // typedef EdgeRef - Type of Edge token in the graph, which should |

57 | // be cheap to copy. |

58 | // typedef ChildEdgeIteratorType - Type used to iterate over children edges in |

59 | // graph, dereference to a EdgeRef. |

60 | |

61 | // static ChildEdgeIteratorType child_edge_begin(NodeRef) |

62 | // static ChildEdgeIteratorType child_edge_end(NodeRef) |

63 | // Return iterators that point to the beginning and ending of the |

64 | // edge list for the given callgraph node. |

65 | // |

66 | // static NodeRef edge_dest(EdgeRef) |

67 | // Return the destination node of an edge. |

68 | |

69 | // static unsigned size (GraphType *G) |

70 | // Return total number of nodes in the graph |

71 | |

72 | // If anyone tries to use this class without having an appropriate |

73 | // specialization, make an error. If you get this error, it's because you |

74 | // need to include the appropriate specialization of GraphTraits<> for your |

75 | // graph, or you need to define it for a new graph type. Either that or |

76 | // your argument to XXX_begin(...) is unknown or needs to have the proper .h |

77 | // file #include'd. |

78 | using NodeRef = typename GraphType::UnknownGraphTypeError; |

79 | }; |

80 | |

81 | // Inverse - This class is used as a little marker class to tell the graph |

82 | // iterator to iterate over the graph in a graph defined "Inverse" ordering. |

83 | // Not all graphs define an inverse ordering, and if they do, it depends on |

84 | // the graph exactly what that is. Here's an example of usage with the |

85 | // df_iterator: |

86 | // |

87 | // idf_iterator<Method*> I = idf_begin(M), E = idf_end(M); |

88 | // for (; I != E; ++I) { ... } |

89 | // |

90 | // Which is equivalent to: |

91 | // df_iterator<Inverse<Method*>> I = idf_begin(M), E = idf_end(M); |

92 | // for (; I != E; ++I) { ... } |

93 | // |

94 | template <class GraphType> |

95 | struct Inverse { |

96 | const GraphType &Graph; |

97 | |

98 | inline Inverse(const GraphType &G) : Graph(G) {} |

99 | }; |

100 | |

101 | // Provide a partial specialization of GraphTraits so that the inverse of an |

102 | // inverse falls back to the original graph. |

103 | template <class T> struct GraphTraits<Inverse<Inverse<T>>> : GraphTraits<T> {}; |

104 | |

105 | // Provide iterator ranges for the graph traits nodes and children |

106 | template <class GraphType> |

107 | iterator_range<typename GraphTraits<GraphType>::nodes_iterator> |

108 | nodes(const GraphType &G) { |

109 | return make_range(GraphTraits<GraphType>::nodes_begin(G), |

110 | GraphTraits<GraphType>::nodes_end(G)); |

111 | } |

112 | template <class GraphType> |

113 | iterator_range<typename GraphTraits<Inverse<GraphType>>::nodes_iterator> |

114 | inverse_nodes(const GraphType &G) { |

115 | return make_range(GraphTraits<Inverse<GraphType>>::nodes_begin(G), |

116 | GraphTraits<Inverse<GraphType>>::nodes_end(G)); |

117 | } |

118 | |

119 | template <class GraphType> |

120 | iterator_range<typename GraphTraits<GraphType>::ChildIteratorType> |

121 | children(const typename GraphTraits<GraphType>::NodeRef &G) { |

122 | return make_range(GraphTraits<GraphType>::child_begin(G), |

123 | GraphTraits<GraphType>::child_end(G)); |

124 | } |

125 | |

126 | template <class GraphType> |

127 | iterator_range<typename GraphTraits<Inverse<GraphType>>::ChildIteratorType> |

128 | inverse_children(const typename GraphTraits<GraphType>::NodeRef &G) { |

129 | return make_range(GraphTraits<Inverse<GraphType>>::child_begin(G), |

130 | GraphTraits<Inverse<GraphType>>::child_end(G)); |

131 | } |

132 | |

133 | template <class GraphType> |

134 | iterator_range<typename GraphTraits<GraphType>::ChildEdgeIteratorType> |

135 | children_edges(const typename GraphTraits<GraphType>::NodeRef &G) { |

136 | return make_range(GraphTraits<GraphType>::child_edge_begin(G), |

137 | GraphTraits<GraphType>::child_edge_end(G)); |

138 | } |

139 | |

140 | } // end namespace llvm |

141 | |

142 | #endif // LLVM_ADT_GRAPHTRAITS_H |

143 |