1 /*
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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
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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 
NodeIdAccessor(Graph graph)34     NodeIdAccessor(Graph graph) {
35         this.graph = graph;
36         this.epoch = graph.compressions;
37     }
38 
getGraph()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      */
verifyIdsAreStable()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      */
getNodeId(Node node)61     int getNodeId(Node node) {
62         assert verifyIdsAreStable();
63         return node.id();
64     }
65 }
66