--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/Compiler/src/com/sun/c1x/ir/AccessMonitor.java	Wed Apr 27 11:43:22 2011 +0200
@@ -0,0 +1,87 @@
+/*
+ * Copyright (c) 2009, 2011, 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.sun.c1x.ir;
+
+import com.sun.c1x.value.*;
+import com.sun.cri.ci.*;
+
+/**
+ * The {@code AccessMonitor} instruction is the base class of both monitor acquisition and release.
+ *
+ * @author Ben L. Titzer
+ */
+public abstract class AccessMonitor extends StateSplit {
+
+    /**
+     * The object locked or unlocked by this instruction.
+     */
+    private Value object;
+
+    /**
+     * The address of the on-stack lock object or {@code null} if the runtime does not place locks on the stack.
+     */
+    private Value lockAddress;
+
+    /**
+     * The lock number of this monitor access.
+     */
+    public final int lockNumber;
+
+
+    /**
+     * Creates a new AccessMonitor instruction.
+     *
+     * @param object the instruction producing the object
+     * @param lockAddress the address of the on-stack lock object or {@code null} if the runtime does not place locks on the stack
+     * @param stateBefore the state before executing the monitor operation
+     * @param lockNumber the number of the lock being acquired
+     */
+    public AccessMonitor(Value object, Value lockAddress, FrameState stateBefore, int lockNumber) {
+        super(CiKind.Illegal, stateBefore);
+        this.object = object;
+        this.lockAddress = lockAddress;
+        this.lockNumber = lockNumber;
+    }
+
+    /**
+     * Gets the instruction producing the object locked or unlocked by this instruction.
+     */
+    public Value object() {
+        return object;
+    }
+
+    /**
+     * Gets the instruction producing the address of the lock object.
+     */
+    public Value lockAddress() {
+        return lockAddress;
+    }
+
+    @Override
+    public void inputValuesDo(ValueClosure closure) {
+        object = closure.apply(object);
+        if (lockAddress != null) {
+            lockAddress = closure.apply(lockAddress);
+        }
+    }
+}