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
24namespace 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.
36template<class GraphType>
37struct 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//
96template <class GraphType>
97struct Inverse {
98 const GraphType &Graph;
99
100 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.
105template <class T> struct GraphTraits<Inverse<Inverse<T>>> : GraphTraits<T> {};
106
107// Provide iterator ranges for the graph traits nodes and children
108template <class GraphType>
109iterator_range<typename GraphTraits<GraphType>::nodes_iterator>
110nodes(const GraphType &G) {
111 return make_range(GraphTraits<GraphType>::nodes_begin(G),
112 GraphTraits<GraphType>::nodes_end(G));
113}
114template <class GraphType>
115iterator_range<typename GraphTraits<Inverse<GraphType>>::nodes_iterator>
116inverse_nodes(const GraphType &G) {
117 return make_range(GraphTraits<Inverse<GraphType>>::nodes_begin(G),
118 GraphTraits<Inverse<GraphType>>::nodes_end(G));
119}
120
121template <class GraphType>
122iterator_range<typename GraphTraits<GraphType>::ChildIteratorType>
123children(const typename GraphTraits<GraphType>::NodeRef &G) {
124 return make_range(GraphTraits<GraphType>::child_begin(G),
125 GraphTraits<GraphType>::child_end(G));
126}
127
128template <class GraphType>
129iterator_range<typename GraphTraits<Inverse<GraphType>>::ChildIteratorType>
130inverse_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
135template <class GraphType>
136iterator_range<typename GraphTraits<GraphType>::ChildEdgeIteratorType>
137children_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

source code of include/llvm-17/llvm/ADT/GraphTraits.h