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//===- llvm/ADT/GraphTraits.h - Graph traits template -----------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
/// This file defines the little GraphTraits<X> template class that should be
/// specialized by classes that want to be iteratable by generic graph
/// iterators.
///
/// This file also defines the marker class Inverse that is used to iterate over
/// graphs in a graph defined, inverse ordering...
///
//===----------------------------------------------------------------------===//
#ifndef LLVM_ADT_GRAPHTRAITS_H
#define LLVM_ADT_GRAPHTRAITS_H
#include "llvm/ADT/iterator_range.h"
namespace llvm {
// GraphTraits - This class should be specialized by different graph types...
// which is why the default version is empty.
//
// This template evolved from supporting `BasicBlock` to also later supporting
// more complex types (e.g. CFG and DomTree).
//
// GraphTraits can be used to create a view over a graph interpreting it
// differently without requiring a copy of the original graph. This could
// be achieved by carrying more data in NodeRef. See LoopBodyTraits for one
// example.
template<class GraphType>
struct GraphTraits {
// Elements to provide:
// typedef NodeRef - Type of Node token in the graph, which should
// be cheap to copy.
// typedef ChildIteratorType - Type used to iterate over children in graph,
// dereference to a NodeRef.
// static NodeRef getEntryNode(const GraphType &)
// Return the entry node of the graph
// static ChildIteratorType child_begin(NodeRef)
// static ChildIteratorType child_end (NodeRef)
// Return iterators that point to the beginning and ending of the child
// node list for the specified node.
// typedef ...iterator nodes_iterator; - dereference to a NodeRef
// static nodes_iterator nodes_begin(GraphType *G)
// static nodes_iterator nodes_end (GraphType *G)
// nodes_iterator/begin/end - Allow iteration over all nodes in the graph
// typedef EdgeRef - Type of Edge token in the graph, which should
// be cheap to copy.
// typedef ChildEdgeIteratorType - Type used to iterate over children edges in
// graph, dereference to a EdgeRef.
// static ChildEdgeIteratorType child_edge_begin(NodeRef)
// static ChildEdgeIteratorType child_edge_end(NodeRef)
// Return iterators that point to the beginning and ending of the
// edge list for the given callgraph node.
//
// static NodeRef edge_dest(EdgeRef)
// Return the destination node of an edge.
// static unsigned size (GraphType *G)
// Return total number of nodes in the graph
// If anyone tries to use this class without having an appropriate
// specialization, make an error. If you get this error, it's because you
// need to include the appropriate specialization of GraphTraits<> for your
// graph, or you need to define it for a new graph type. Either that or
// your argument to XXX_begin(...) is unknown or needs to have the proper .h
// file #include'd.
using NodeRef = typename GraphType::UnknownGraphTypeError;
};
// Inverse - This class is used as a little marker class to tell the graph
// iterator to iterate over the graph in a graph defined "Inverse" ordering.
// Not all graphs define an inverse ordering, and if they do, it depends on
// the graph exactly what that is. Here's an example of usage with the
// df_iterator:
//
// idf_iterator<Method*> I = idf_begin(M), E = idf_end(M);
// for (; I != E; ++I) { ... }
//
// Which is equivalent to:
// df_iterator<Inverse<Method*>> I = idf_begin(M), E = idf_end(M);
// for (; I != E; ++I) { ... }
//
template <class GraphType>
struct Inverse {
const GraphType &Graph;
inline Inverse(const GraphType &G) : Graph(G) {}
};
// Provide a partial specialization of GraphTraits so that the inverse of an
// inverse falls back to the original graph.
template <class T> struct GraphTraits<Inverse<Inverse<T>>> : GraphTraits<T> {};
// Provide iterator ranges for the graph traits nodes and children
template <class GraphType>
iterator_range<typename GraphTraits<GraphType>::nodes_iterator>
nodes(const GraphType &G) {
return make_range(GraphTraits<GraphType>::nodes_begin(G),
GraphTraits<GraphType>::nodes_end(G));
}
template <class GraphType>
iterator_range<typename GraphTraits<Inverse<GraphType>>::nodes_iterator>
inverse_nodes(const GraphType &G) {
return make_range(GraphTraits<Inverse<GraphType>>::nodes_begin(G),
GraphTraits<Inverse<GraphType>>::nodes_end(G));
}
template <class GraphType>
iterator_range<typename GraphTraits<GraphType>::ChildIteratorType>
children(const typename GraphTraits<GraphType>::NodeRef &G) {
return make_range(GraphTraits<GraphType>::child_begin(G),
GraphTraits<GraphType>::child_end(G));
}
template <class GraphType>
iterator_range<typename GraphTraits<Inverse<GraphType>>::ChildIteratorType>
inverse_children(const typename GraphTraits<GraphType>::NodeRef &G) {
return make_range(GraphTraits<Inverse<GraphType>>::child_begin(G),
GraphTraits<Inverse<GraphType>>::child_end(G));
}
template <class GraphType>
iterator_range<typename GraphTraits<GraphType>::ChildEdgeIteratorType>
children_edges(const typename GraphTraits<GraphType>::NodeRef &G) {
return make_range(GraphTraits<GraphType>::child_edge_begin(G),
GraphTraits<GraphType>::child_edge_end(G));
}
} // end namespace llvm
#endif // LLVM_ADT_GRAPHTRAITS_H
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