--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/GraalCompiler/src/com/sun/c1x/ir/StateSplit.java	Wed Apr 27 11:50:44 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 StateSplit} class is the abstract base class of all instructions
+ * that store an immutable copy of the frame state.
+ *
+ * @author Ben L. Titzer
+ */
+public abstract class StateSplit extends Instruction {
+
+    /**
+     * Sentinel denoting an explicitly cleared state.
+     */
+    private static final FrameState CLEARED_STATE = new MutableFrameState(null, -5, 0, 0);
+
+    private FrameState stateBefore;
+
+    /**
+     * Creates a new state split with the specified value type.
+     * @param kind the type of the value that this instruction produces
+     */
+    public StateSplit(CiKind kind, FrameState stateBefore) {
+        super(kind);
+        this.stateBefore = stateBefore;
+    }
+
+    /**
+     * Determines if the state for this instruction has explicitly
+     * been cleared (as opposed to never initialized). Once explicitly
+     * cleared, an instruction must not have it state (re)set.
+     */
+    public boolean isStateCleared() {
+        return stateBefore == CLEARED_STATE;
+    }
+
+    /**
+     * Clears the state for this instruction. Once explicitly
+     * cleared, an instruction must not have it state (re)set.
+     */
+    protected void clearState() {
+        stateBefore = CLEARED_STATE;
+    }
+
+    /**
+     * Records the state of this instruction before it is executed.
+     *
+     * @param stateBefore the state
+     */
+    public final void setStateBefore(FrameState stateBefore) {
+        assert this.stateBefore == null;
+        this.stateBefore = stateBefore;
+    }
+
+    /**
+     * Gets the state for this instruction.
+     * @return the state
+     */
+    @Override
+    public final FrameState stateBefore() {
+        return stateBefore == CLEARED_STATE ? null : stateBefore;
+    }
+}