--- /dev/null	2016-05-31 09:42:47.975716356 -0700
+++ new/src/jdk.vm.compiler/share/classes/org.graalvm.compiler.nodes.test/src/org/graalvm/compiler/nodes/test/ObjectStampJoinTest.java	2016-12-09 00:54:47.662345811 -0800
@@ -0,0 +1,182 @@
+/*
+ * Copyright (c) 2013, 2016, 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 org.graalvm.compiler.nodes.test;
+
+import jdk.vm.ci.meta.JavaKind;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import org.graalvm.compiler.core.common.type.ObjectStamp;
+import org.graalvm.compiler.core.common.type.Stamp;
+import org.graalvm.compiler.core.common.type.StampFactory;
+import org.graalvm.compiler.core.common.type.TypeReference;
+import org.graalvm.compiler.nodes.type.StampTool;
+
+public class ObjectStampJoinTest extends AbstractObjectStampTest {
+
+    // class A
+    // class B extends A
+    // class C extends B implements I
+    // class D extends A
+    // abstract class E extends A
+    // interface I
+
+    @Test
+    public void testJoin0() {
+        Stamp a = StampFactory.object(getType(A.class));
+        Stamp b = StampFactory.object(getType(B.class));
+        Assert.assertEquals(b, join(a, b));
+    }
+
+    @Test
+    public void testJoin1() {
+        Stamp aNonNull = StampFactory.objectNonNull(getType(A.class));
+        Stamp b = StampFactory.object(getType(B.class));
+        Stamp bNonNull = StampFactory.objectNonNull(getType(B.class));
+        Assert.assertEquals(bNonNull, join(aNonNull, b));
+    }
+
+    @Test
+    public void testJoin2() {
+        Stamp aExact = StampFactory.objectNonNull(getType(A.class).asExactReference());
+        Stamp b = StampFactory.object(getType(B.class));
+        Assert.assertEquals(StampFactory.empty(JavaKind.Object), join(aExact, b));
+    }
+
+    @Test
+    public void testJoin3() {
+        Stamp d = StampFactory.object(getType(D.class));
+        Stamp c = StampFactory.object(getType(C.class));
+        Assert.assertTrue(StampTool.isPointerAlwaysNull(join(c, d)));
+    }
+
+    @Test
+    public void testJoin4() {
+        Stamp dExactNonNull = StampFactory.objectNonNull(getType(D.class));
+        Stamp c = StampFactory.object(getType(C.class));
+        Assert.assertEquals(StampFactory.empty(JavaKind.Object), join(c, dExactNonNull));
+    }
+
+    @Test
+    public void testJoin5() {
+        Stamp dExact = StampFactory.object(getType(D.class).asExactReference());
+        Stamp c = StampFactory.object(getType(C.class));
+        Stamp join = join(c, dExact);
+        Assert.assertTrue(StampTool.isPointerAlwaysNull(join));
+        Assert.assertNull(StampTool.typeReferenceOrNull(join));
+        Assert.assertFalse(StampTool.isExactType(join));
+    }
+
+    @Test
+    public void testJoin6() {
+        Stamp dExactNonNull = StampFactory.objectNonNull(getType(D.class).asExactReference());
+        Stamp alwaysNull = StampFactory.alwaysNull();
+        Stamp join = join(alwaysNull, dExactNonNull);
+        Assert.assertFalse(join.hasValues());
+        Assert.assertFalse(StampTool.isPointerAlwaysNull(join));
+    }
+
+    @Test
+    public void testJoin7() {
+        Stamp aExact = StampFactory.object(getType(A.class).asExactReference());
+        Stamp e = StampFactory.object(getType(E.class));
+        Stamp join = join(aExact, e);
+        Assert.assertTrue(StampTool.isPointerAlwaysNull(join));
+        Assert.assertNull(StampTool.typeReferenceOrNull(join));
+        Assert.assertFalse(StampTool.isExactType(join));
+    }
+
+    @Test
+    public void testJoin8() {
+        Stamp bExact = StampFactory.objectNonNull(getType(B.class).asExactReference());
+        Stamp dExact = StampFactory.object(getType(D.class).asExactReference());
+        Stamp join = join(bExact, dExact);
+        Assert.assertFalse(join.hasValues());
+    }
+
+    @Test
+    public void testJoin9() {
+        Stamp bExact = StampFactory.object(getType(B.class).asExactReference());
+        Stamp dExact = StampFactory.object(getType(D.class).asExactReference());
+        Stamp join = join(bExact, dExact);
+        Assert.assertTrue(StampTool.isPointerAlwaysNull(join));
+        Assert.assertNull(StampTool.typeReferenceOrNull(join));
+        Assert.assertNull(StampTool.typeReferenceOrNull(join));
+    }
+
+    @Test
+    public void testJoinInterfaceSimple() {
+        // Tests joining of interface
+        testJoinInterface(A.class, B.class, I.class);
+    }
+
+    @Test
+    public void testJoinInterfaceArray() {
+        // Tests joining of arrays interface
+        testJoinInterface(A[].class, B[].class, I[].class);
+    }
+
+    @Test
+    public void testJoinInterfaceMultiArray() {
+        // Tests joining of multidimensional arrays of interface
+        testJoinInterface(A[][].class, B[][].class, I[][].class);
+    }
+
+    private void testJoinInterface(Class<?> typeA, Class<?> typeB, Class<?> typeI) {
+        testJoinInterface0(typeA, typeI);
+        testJoinInterface1(typeA, typeI);
+        testJoinInterface2(typeB, typeI);
+        testJoinInterface3(typeB, typeI);
+    }
+
+    private void testJoinInterface0(Class<?> typeA, Class<?> typeI) {
+        Stamp a = StampFactory.object(getType(typeA));
+        Stamp i = StampFactory.object(getType(typeI));
+        Assert.assertNotSame(StampFactory.empty(JavaKind.Object), join(a, i));
+    }
+
+    private void testJoinInterface1(Class<?> typeA, Class<?> typeI) {
+        Stamp aNonNull = StampFactory.objectNonNull(getType(typeA));
+        Stamp i = StampFactory.object(getType(typeI));
+        Stamp join = join(aNonNull, i);
+        Assert.assertTrue(join instanceof ObjectStamp);
+        Assert.assertTrue(((ObjectStamp) join).nonNull());
+    }
+
+    private void testJoinInterface2(Class<?> typeB, Class<?> typeI) {
+        Stamp bExact = StampFactory.objectNonNull(getType(typeB).asExactReference());
+        Stamp i = StampFactory.object(getType(typeI));
+        Stamp join = join(i, bExact);
+        Assert.assertEquals(StampFactory.empty(JavaKind.Object), join);
+    }
+
+    private void testJoinInterface3(Class<?> typeB, Class<?> typeI) {
+        Stamp bExact = StampFactory.objectNonNull(getType(typeB).asExactReference());
+        // Create non-trusted reference.
+        Stamp i = StampFactory.object(TypeReference.createWithoutAssumptions(getType(typeI).getType()));
+        Stamp join = join(i, bExact);
+        Assert.assertEquals(bExact, join);
+    }
+
+}