1 /*
   2  * Copyright (c) 2013, 2018, 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 
  24 
  25 package org.graalvm.compiler.graph;
  26 
  27 /**
  28  * An entity that depends upon {@linkplain Graph#maybeCompress() stable} node identifiers.
  29  */
  30 class NodeIdAccessor {
  31     final Graph graph;
  32     final int epoch;
  33 
  34     NodeIdAccessor(Graph graph) {
  35         this.graph = graph;
  36         this.epoch = graph.compressions;
  37     }
  38 
  39     Graph getGraph() {
  40         return graph;
  41     }
  42 
  43     /**
  44      * Verifies that node identifiers have not changed since this object was created.
  45      *
  46      * @return true if the check succeeds
  47      * @throws VerificationError if the check fails
  48      */
  49     boolean verifyIdsAreStable() {
  50         int compressions = graph.compressions - epoch;
  51         if (compressions != 0) {
  52             throw new VerificationError("accessing node id in %s across %d graph compression%s", graph, compressions, compressions == 1 ? "" : "s");
  53         }
  54         return true;
  55     }
  56 
  57     /**
  58      * Gets the identifier for a node. If assertions are enabled, this method asserts that the
  59      * identifier is stable.
  60      */
  61     int getNodeId(Node node) {
  62         assert verifyIdsAreStable();
  63         return node.id();
  64     }
  65 }