--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/com.oracle.graal.graph/src/com/oracle/graal/graph/NodeUnionFind.java	Thu Feb 12 13:42:11 2015 +0100
@@ -0,0 +1,94 @@
+/*
+ * Copyright (c) 2015, 2015, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code 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
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package com.oracle.graal.graph;
+
+/**
+ * Union-find data structure for {@link Node Nodes}.
+ *
+ * All operations have an accumulated worst-case complexity of O(a(n)), where a(n) is the inverse of
+ * the Ackermann function A(n,n).
+ */
+public class NodeUnionFind extends NodeIdAccessor {
+
+    private int[] rank;
+    private int[] parent;
+
+    /**
+     * Create a new union-find data structure for a {@link Graph}. Initially, all nodes are in their
+     * own equivalence set.
+     */
+    public NodeUnionFind(Graph graph) {
+        super(graph);
+        rank = new int[graph.nodeIdCount()];
+        parent = new int[graph.nodeIdCount()];
+        for (int i = 0; i < parent.length; i++) {
+            parent[i] = i;
+        }
+    }
+
+    /**
+     * Merge the equivalence sets of two nodes.
+     *
+     * After calling this function, find(a) == find(b).
+     */
+    public void union(Node a, Node b) {
+        union(getNodeId(a), getNodeId(b));
+    }
+
+    /**
+     * Get a representative element of the equivalence set of a node.
+     *
+     * This function returns the same representative element for all members of the same equivalence
+     * set, i.e., find(a) == find(b) if and only if a and b are in the same set.
+     */
+    public Node find(Node a) {
+        int id = find(getNodeId(a));
+        return graph.getNode(id);
+    }
+
+    public boolean equiv(Node a, Node b) {
+        return find(getNodeId(a)) == find(getNodeId(b));
+    }
+
+    private void union(int a, int b) {
+        int aRoot = find(a);
+        int bRoot = find(b);
+        if (rank[aRoot] < rank[bRoot]) {
+            parent[aRoot] = bRoot;
+        } else {
+            parent[bRoot] = aRoot;
+            if (rank[aRoot] == rank[bRoot]) {
+                rank[aRoot]++;
+            }
+        }
+    }
+
+    private int find(int a) {
+        int ret = a;
+        while (ret != parent[ret]) {
+            parent[ret] = parent[parent[ret]];
+            ret = parent[ret];
+        }
+        return ret;
+    }
+}