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GraphTraits.h
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1 //===- llvm/ADT/GraphTraits.h - Graph traits template -----------*- C++ -*-===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file defines the little GraphTraits<X> template class that should be
11 // specialized by classes that want to be iteratable by generic graph iterators.
12 //
13 // This file also defines the marker class Inverse that is used to iterate over
14 // graphs in a graph defined, inverse ordering...
15 //
16 //===----------------------------------------------------------------------===//
17 
18 #ifndef LLVM_ADT_GRAPHTRAITS_H
19 #define LLVM_ADT_GRAPHTRAITS_H
20 
22 
23 namespace llvm {
24 
25 // GraphTraits - This class should be specialized by different graph types...
26 // which is why the default version is empty.
27 //
28 // This template evolved from supporting `BasicBlock` to also later supporting
29 // more complex types (e.g. CFG and DomTree).
30 //
31 // GraphTraits can be used to create a view over a graph interpreting it
32 // differently without requiring a copy of the original graph. This could
33 // be achieved by carrying more data in NodeRef. See LoopBodyTraits for one
34 // example.
35 template<class GraphType>
36 struct GraphTraits {
37  // Elements to provide:
38 
39  // typedef NodeRef - Type of Node token in the graph, which should
40  // be cheap to copy.
41  // typedef ChildIteratorType - Type used to iterate over children in graph,
42  // dereference to a NodeRef.
43 
44  // static NodeRef getEntryNode(const GraphType &)
45  // Return the entry node of the graph
46 
47  // static ChildIteratorType child_begin(NodeRef)
48  // static ChildIteratorType child_end (NodeRef)
49  // Return iterators that point to the beginning and ending of the child
50  // node list for the specified node.
51 
52  // typedef ...iterator nodes_iterator; - dereference to a NodeRef
53  // static nodes_iterator nodes_begin(GraphType *G)
54  // static nodes_iterator nodes_end (GraphType *G)
55  // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
56 
57  // typedef EdgeRef - Type of Edge token in the graph, which should
58  // be cheap to copy.
59  // typedef ChildEdgeIteratorType - Type used to iterate over children edges in
60  // graph, dereference to a EdgeRef.
61 
62  // static ChildEdgeIteratorType child_edge_begin(NodeRef)
63  // static ChildEdgeIteratorType child_edge_end(NodeRef)
64  // Return iterators that point to the beginning and ending of the
65  // edge list for the given callgraph node.
66  //
67  // static NodeRef edge_dest(EdgeRef)
68  // Return the destination node of an edge.
69 
70  // static unsigned size (GraphType *G)
71  // Return total number of nodes in the graph
72 
73  // If anyone tries to use this class without having an appropriate
74  // specialization, make an error. If you get this error, it's because you
75  // need to include the appropriate specialization of GraphTraits<> for your
76  // graph, or you need to define it for a new graph type. Either that or
77  // your argument to XXX_begin(...) is unknown or needs to have the proper .h
78  // file #include'd.
79  using NodeRef = typename GraphType::UnknownGraphTypeError;
80 };
81 
82 // Inverse - This class is used as a little marker class to tell the graph
83 // iterator to iterate over the graph in a graph defined "Inverse" ordering.
84 // Not all graphs define an inverse ordering, and if they do, it depends on
85 // the graph exactly what that is. Here's an example of usage with the
86 // df_iterator:
87 //
88 // idf_iterator<Method*> I = idf_begin(M), E = idf_end(M);
89 // for (; I != E; ++I) { ... }
90 //
91 // Which is equivalent to:
92 // df_iterator<Inverse<Method*>> I = idf_begin(M), E = idf_end(M);
93 // for (; I != E; ++I) { ... }
94 //
95 template <class GraphType>
96 struct Inverse {
97  const GraphType &Graph;
98 
99  inline Inverse(const GraphType &G) : Graph(G) {}
100 };
101 
102 // Provide a partial specialization of GraphTraits so that the inverse of an
103 // inverse falls back to the original graph.
104 template <class T> struct GraphTraits<Inverse<Inverse<T>>> : GraphTraits<T> {};
105 
106 // Provide iterator ranges for the graph traits nodes and children
107 template <class GraphType>
109 nodes(const GraphType &G) {
112 }
113 template <class GraphType>
115 inverse_nodes(const GraphType &G) {
116  return make_range(GraphTraits<Inverse<GraphType>>::nodes_begin(G),
117  GraphTraits<Inverse<GraphType>>::nodes_end(G));
118 }
119 
120 template <class GraphType>
125 }
126 
127 template <class GraphType>
130  return make_range(GraphTraits<Inverse<GraphType>>::child_begin(G),
131  GraphTraits<Inverse<GraphType>>::child_end(G));
132 }
133 
134 template <class GraphType>
139 }
140 
141 } // end namespace llvm
142 
143 #endif // LLVM_ADT_GRAPHTRAITS_H
iterator_range< typename GraphTraits< GraphType >::ChildIteratorType > children(const typename GraphTraits< GraphType >::NodeRef &G)
Definition: GraphTraits.h:122
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
This provides a very simple, boring adaptor for a begin and end iterator into a range type...
iterator_range< typename GraphTraits< Inverse< GraphType > >::ChildIteratorType > inverse_children(const typename GraphTraits< GraphType >::NodeRef &G)
Definition: GraphTraits.h:129
typename SDNode *::UnknownGraphTypeError NodeRef
Definition: GraphTraits.h:79
iterator_range< typename GraphTraits< GraphType >::ChildEdgeIteratorType > children_edges(const typename GraphTraits< GraphType >::NodeRef &G)
Definition: GraphTraits.h:136
iterator_range< typename GraphTraits< Inverse< GraphType > >::nodes_iterator > inverse_nodes(const GraphType &G)
Definition: GraphTraits.h:115
iterator_range< T > make_range(T x, T y)
Convenience function for iterating over sub-ranges.
const GraphType & Graph
Definition: GraphTraits.h:97
const DataFlowGraph & G
Definition: RDFGraph.cpp:211
A range adaptor for a pair of iterators.
iterator_range< typename GraphTraits< GraphType >::nodes_iterator > nodes(const GraphType &G)
Definition: GraphTraits.h:109
Inverse(const GraphType &G)
Definition: GraphTraits.h:99