--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/digraph.cc	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,188 @@
+/* Template classes for directed graphs.
+   Copyright (C) 2019-2020 Free Software Foundation, Inc.
+   Contributed by David Malcolm <dmalcolm@redhat.com>.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it
+under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "diagnostic.h"
+#include "graphviz.h"
+#include "digraph.h"
+#include "shortest-paths.h"
+#include "selftest.h"
+
+#if CHECKING_P
+
+namespace selftest {
+
+/* A family of digraph classes for writing selftests.  */
+
+struct test_node;
+struct test_edge;
+struct test_graph;
+struct test_dump_args_t {};
+struct test_cluster;
+
+struct test_graph_traits
+{
+  typedef test_node node_t;
+  typedef test_edge edge_t;
+  typedef test_graph graph_t;
+  typedef test_dump_args_t dump_args_t;
+  typedef test_cluster cluster_t;
+};
+
+struct test_node : public dnode<test_graph_traits>
+{
+  test_node (const char *name, int index) : m_name (name), m_index (index) {}
+  void dump_dot (graphviz_out *, const dump_args_t &) const OVERRIDE
+  {
+  }
+
+  const char *m_name;
+  int m_index;
+};
+
+struct test_edge : public dedge<test_graph_traits>
+{
+  test_edge (node_t *src, node_t *dest)
+  : dedge<test_graph_traits> (src, dest)
+  {}
+
+  void dump_dot (graphviz_out *gv, const dump_args_t &) const OVERRIDE
+  {
+    gv->println ("%s -> %s;", m_src->m_name, m_dest->m_name);
+  }
+};
+
+struct test_graph : public digraph<test_graph_traits>
+{
+  test_node *add_test_node (const char *name)
+  {
+    test_node *result = new test_node (name, m_nodes.length ());
+    add_node (result);
+    return result;
+  }
+
+  test_edge *add_test_edge (test_node *src, test_node *dst)
+  {
+    test_edge *result = new test_edge (src, dst);
+    add_edge (result);
+    return result;
+  }
+};
+
+struct test_cluster : public cluster<test_graph_traits>
+{
+};
+
+struct test_path
+{
+  auto_vec<const test_edge *> m_edges;
+};
+
+/* Smoketest of digraph dumping.  */
+
+static void
+test_dump_to_dot ()
+{
+  test_graph g;
+  test_node *a = g.add_test_node ("a");
+  test_node *b = g.add_test_node ("b");
+  g.add_test_edge (a, b);
+
+  pretty_printer pp;
+  pp.buffer->stream = NULL;
+  test_dump_args_t dump_args;
+  g.dump_dot_to_pp (&pp, NULL, dump_args);
+
+  ASSERT_STR_CONTAINS (pp_formatted_text (&pp),
+		       "a -> b;\n");
+}
+
+/* Test shortest paths from A in this digraph,
+   where edges run top-to-bottom if not otherwise labeled:
+
+      A
+     / \
+    B   C-->D
+    |   |
+    E   |
+     \ /
+      F.  */
+
+static void
+test_shortest_paths ()
+{
+  test_graph g;
+  test_node *a = g.add_test_node ("a");
+  test_node *b = g.add_test_node ("b");
+  test_node *c = g.add_test_node ("d");
+  test_node *d = g.add_test_node ("d");
+  test_node *e = g.add_test_node ("e");
+  test_node *f = g.add_test_node ("f");
+
+  test_edge *ab = g.add_test_edge (a, b);
+  test_edge *ac = g.add_test_edge (a, c);
+  test_edge *cd = g.add_test_edge (c, d);
+  test_edge *be = g.add_test_edge (b, e);
+  g.add_test_edge (e, f);
+  test_edge *cf = g.add_test_edge (c, f);
+
+  shortest_paths<test_graph_traits, test_path> sp (g, a);
+
+  test_path path_to_a = sp.get_shortest_path (a);
+  ASSERT_EQ (path_to_a.m_edges.length (), 0);
+
+  test_path path_to_b = sp.get_shortest_path (b);
+  ASSERT_EQ (path_to_b.m_edges.length (), 1);
+  ASSERT_EQ (path_to_b.m_edges[0], ab);
+
+  test_path path_to_c = sp.get_shortest_path (c);
+  ASSERT_EQ (path_to_c.m_edges.length (), 1);
+  ASSERT_EQ (path_to_c.m_edges[0], ac);
+
+  test_path path_to_d = sp.get_shortest_path (d);
+  ASSERT_EQ (path_to_d.m_edges.length (), 2);
+  ASSERT_EQ (path_to_d.m_edges[0], ac);
+  ASSERT_EQ (path_to_d.m_edges[1], cd);
+
+  test_path path_to_e = sp.get_shortest_path (e);
+  ASSERT_EQ (path_to_e.m_edges.length (), 2);
+  ASSERT_EQ (path_to_e.m_edges[0], ab);
+  ASSERT_EQ (path_to_e.m_edges[1], be);
+
+  test_path path_to_f = sp.get_shortest_path (f);
+  ASSERT_EQ (path_to_f.m_edges.length (), 2);
+  ASSERT_EQ (path_to_f.m_edges[0], ac);
+  ASSERT_EQ (path_to_f.m_edges[1], cf);
+}
+
+/* Run all of the selftests within this file.  */
+
+void
+digraph_cc_tests ()
+{
+  test_dump_to_dot ();
+  test_shortest_paths ();
+}
+
+} // namespace selftest
+
+#endif /* #if CHECKING_P */