1 //===- llvm/ADT/GraphTraits.h - Graph traits template -----------*- 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 /// This file defines the little GraphTraits<X> template class that should be 11 /// specialized by classes that want to be iteratable by generic graph 12 /// iterators. 13 /// 14 /// This file also defines the marker class Inverse that is used to iterate over 15 /// graphs in a graph defined, inverse ordering... 16 /// 17 //===----------------------------------------------------------------------===// 18 19 #ifndef LLVM_ADT_GRAPHTRAITS_H 20 #define LLVM_ADT_GRAPHTRAITS_H 21 22 #include "llvm/ADT/iterator_range.h" 23 24 namespace llvm { 25 26 // GraphTraits - This class should be specialized by different graph types... 27 // which is why the default version is empty. 28 // 29 // This template evolved from supporting `BasicBlock` to also later supporting 30 // more complex types (e.g. CFG and DomTree). 31 // 32 // GraphTraits can be used to create a view over a graph interpreting it 33 // differently without requiring a copy of the original graph. This could 34 // be achieved by carrying more data in NodeRef. See LoopBodyTraits for one 35 // example. 36 template<class GraphType> 37 struct GraphTraits { 38 // Elements to provide: 39 40 // typedef NodeRef - Type of Node token in the graph, which should 41 // be cheap to copy. 42 // typedef ChildIteratorType - Type used to iterate over children in graph, 43 // dereference to a NodeRef. 44 45 // static NodeRef getEntryNode(const GraphType &) 46 // Return the entry node of the graph 47 48 // static ChildIteratorType child_begin(NodeRef) 49 // static ChildIteratorType child_end (NodeRef) 50 // Return iterators that point to the beginning and ending of the child 51 // node list for the specified node. 52 53 // typedef ...iterator nodes_iterator; - dereference to a NodeRef 54 // static nodes_iterator nodes_begin(GraphType *G) 55 // static nodes_iterator nodes_end (GraphType *G) 56 // nodes_iterator/begin/end - Allow iteration over all nodes in the graph 57 58 // typedef EdgeRef - Type of Edge token in the graph, which should 59 // be cheap to copy. 60 // typedef ChildEdgeIteratorType - Type used to iterate over children edges in 61 // graph, dereference to a EdgeRef. 62 63 // static ChildEdgeIteratorType child_edge_begin(NodeRef) 64 // static ChildEdgeIteratorType child_edge_end(NodeRef) 65 // Return iterators that point to the beginning and ending of the 66 // edge list for the given callgraph node. 67 // 68 // static NodeRef edge_dest(EdgeRef) 69 // Return the destination node of an edge. 70 71 // static unsigned size (GraphType *G) 72 // Return total number of nodes in the graph 73 74 // If anyone tries to use this class without having an appropriate 75 // specialization, make an error. If you get this error, it's because you 76 // need to include the appropriate specialization of GraphTraits<> for your 77 // graph, or you need to define it for a new graph type. Either that or 78 // your argument to XXX_begin(...) is unknown or needs to have the proper .h 79 // file #include'd. 80 using NodeRef = typename GraphType::UnknownGraphTypeError; 81 }; 82 83 // Inverse - This class is used as a little marker class to tell the graph 84 // iterator to iterate over the graph in a graph defined "Inverse" ordering. 85 // Not all graphs define an inverse ordering, and if they do, it depends on 86 // the graph exactly what that is. Here's an example of usage with the 87 // df_iterator: 88 // 89 // idf_iterator<Method*> I = idf_begin(M), E = idf_end(M); 90 // for (; I != E; ++I) { ... } 91 // 92 // Which is equivalent to: 93 // df_iterator<Inverse<Method*>> I = idf_begin(M), E = idf_end(M); 94 // for (; I != E; ++I) { ... } 95 // 96 template <class GraphType> 97 struct Inverse { 98 const GraphType &Graph; 99 InverseInverse100 inline Inverse(const GraphType &G) : Graph(G) {} 101 }; 102 103 // Provide a partial specialization of GraphTraits so that the inverse of an 104 // inverse falls back to the original graph. 105 template <class T> struct GraphTraits<Inverse<Inverse<T>>> : GraphTraits<T> {}; 106 107 // Provide iterator ranges for the graph traits nodes and children 108 template <class GraphType> 109 iterator_range<typename GraphTraits<GraphType>::nodes_iterator> 110 nodes(const GraphType &G) { 111 return make_range(GraphTraits<GraphType>::nodes_begin(G), 112 GraphTraits<GraphType>::nodes_end(G)); 113 } 114 template <class GraphType> 115 iterator_range<typename GraphTraits<Inverse<GraphType>>::nodes_iterator> 116 inverse_nodes(const GraphType &G) { 117 return make_range(GraphTraits<Inverse<GraphType>>::nodes_begin(G), 118 GraphTraits<Inverse<GraphType>>::nodes_end(G)); 119 } 120 121 template <class GraphType> 122 iterator_range<typename GraphTraits<GraphType>::ChildIteratorType> 123 children(const typename GraphTraits<GraphType>::NodeRef &G) { 124 return make_range(GraphTraits<GraphType>::child_begin(G), 125 GraphTraits<GraphType>::child_end(G)); 126 } 127 128 template <class GraphType> 129 iterator_range<typename GraphTraits<Inverse<GraphType>>::ChildIteratorType> 130 inverse_children(const typename GraphTraits<GraphType>::NodeRef &G) { 131 return make_range(GraphTraits<Inverse<GraphType>>::child_begin(G), 132 GraphTraits<Inverse<GraphType>>::child_end(G)); 133 } 134 135 template <class GraphType> 136 iterator_range<typename GraphTraits<GraphType>::ChildEdgeIteratorType> 137 children_edges(const typename GraphTraits<GraphType>::NodeRef &G) { 138 return make_range(GraphTraits<GraphType>::child_edge_begin(G), 139 GraphTraits<GraphType>::child_edge_end(G)); 140 } 141 142 } // end namespace llvm 143 144 #endif // LLVM_ADT_GRAPHTRAITS_H 145