--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/com.oracle.jvmci.meta/src/com/oracle/jvmci/meta/TriState.java	Wed May 27 00:36:16 2015 +0200
@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2012, 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;
+
+/**
+ * Represents a logic value that can be either {@link #TRUE}, {@link #FALSE}, or {@link #UNKNOWN}.
+ */
+public enum TriState {
+    TRUE,
+    FALSE,
+    UNKNOWN;
+
+    public static TriState get(boolean value) {
+        return value ? TRUE : FALSE;
+    }
+
+    /**
+     * This is optimistic about {@link #UNKNOWN} (it prefers known values over {@link #UNKNOWN}) and
+     * pesimistic about known (it perfers {@link #TRUE} over {@link #FALSE}).
+     */
+    public static TriState merge(TriState a, TriState b) {
+        if (a == TRUE || b == TRUE) {
+            return TRUE;
+        }
+        if (a == FALSE || b == FALSE) {
+            return FALSE;
+        }
+        assert a == UNKNOWN && b == UNKNOWN;
+        return UNKNOWN;
+    }
+
+    public boolean isTrue() {
+        return this == TRUE;
+    }
+
+    public boolean isFalse() {
+        return this == FALSE;
+    }
+
+    public boolean isUnknown() {
+        return this == UNKNOWN;
+    }
+
+    public boolean isKnown() {
+        return this != UNKNOWN;
+    }
+
+    public boolean toBoolean() {
+        if (isTrue()) {
+            return true;
+        } else if (isFalse()) {
+            return false;
+        } else {
+            throw new IllegalStateException("Cannot convert to boolean, TriState is in an unknown state");
+        }
+    }
+}