NodeIdAccessor.java revision 12651:6ef01bd40ce2 
1/*
2 * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23package org.graalvm.compiler.graph;
24
25/**
26 * An entity that depends upon {@linkplain Graph#maybeCompress() stable} node identifiers.
27 */
28class NodeIdAccessor {
29    final Graph graph;
30    final int epoch;
31
32    NodeIdAccessor(Graph graph) {
33        this.graph = graph;
34        this.epoch = graph.compressions;
35    }
36
37    Graph getGraph() {
38        return graph;
39    }
40
41    /**
42     * Verifies that node identifiers have not changed since this object was created.
43     *
44     * @return true if the check succeeds
45     * @throws VerificationError if the check fails
46     */
47    boolean verifyIdsAreStable() {
48        int compressions = graph.compressions - epoch;
49        if (compressions != 0) {
50            throw new VerificationError("accessing node id in %s across %d graph compression%s", graph, compressions, compressions == 1 ? "" : "s");
51        }
52        return true;
53    }
54
55    /**
56     * Gets the identifier for a node. If assertions are enabled, this method asserts that the
57     * identifier is stable.
58     */
59    int getNodeId(Node node) {
60        assert verifyIdsAreStable();
61        return node.id();
62    }
63}
64