--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/com.oracle.jvmci.meta/src/com/oracle/jvmci/meta/MethodIdHolder.java	Wed May 27 00:36:16 2015 +0200
@@ -0,0 +1,93 @@
+/*
+ * Copyright (c) 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.jvmci.meta;
+
+import java.util.*;
+import java.util.function.*;
+
+/**
+ * An object that can be assigned a globally unique identifier for use as a key in a
+ * {@link MethodIdMap}.
+ */
+public interface MethodIdHolder {
+    /**
+     * Sets the unique, positive, non-zero identifier for this method.
+     */
+    void setMethodId(int id);
+
+    /**
+     * Gets the identifier set by {@link #setMethodId(int)} or 0 if no identifier was assigned to
+     * this method.
+     */
+    int getMethodId();
+
+    /**
+     * A singleton class for allocating globally unique method identifiers.
+     */
+    static final class MethodIdAllocator {
+
+        /**
+         * Ensures a given method has a unique identifier.
+         */
+        public int assignId(MethodIdHolder holder) {
+            assert Thread.holdsLock(instance) : "must only be called from within MethodIdHolder.allocateIds";
+            int id = holder.getMethodId();
+            if (id == 0) {
+                id = nextId++;
+                holder.setMethodId(id);
+                if (idVerifierMap != null) {
+                    idVerifierMap.put(holder, id);
+                }
+            } else {
+                assert !idVerifierMap.containsKey(holder) || idVerifierMap.get(holder) == id;
+            }
+            return id;
+        }
+
+        private int nextId = 1;
+        private final Map<MethodIdHolder, Integer> idVerifierMap;
+
+        @SuppressWarnings("all")
+        private MethodIdAllocator() {
+            boolean assertionsEnabled = false;
+            assert assertionsEnabled = true;
+            idVerifierMap = assertionsEnabled ? new HashMap<>() : null;
+        }
+
+        /**
+         * Singleton instance.
+         */
+        private static final MethodIdAllocator instance = new MethodIdAllocator();
+    }
+
+    /**
+     * Executes some given code that ensures some set of {@link ResolvedJavaMethod}s have unique ids
+     * {@linkplain MethodIdHolder#setMethodId(int) assigned} to them. The
+     * {@link Consumer#accept(Object)} method of the given object is called under a global lock.
+     */
+    static void assignIds(Consumer<MethodIdAllocator> methodIdConsumer) {
+        synchronized (MethodIdAllocator.instance) {
+            methodIdConsumer.accept(MethodIdAllocator.instance);
+        }
+    }
+}