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 */ 23 package org.graalvm.compiler.graph; 24 25 /** 26 * An entity that depends upon {@linkplain Graph#maybeCompress() stable} node identifiers. 27 */ 28 class 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 }