--- a/graal/com.oracle.graal.compiler/src/com/oracle/graal/compiler/GraalCompiler.java	Fri May 10 21:03:53 2013 +0200
+++ b/graal/com.oracle.graal.compiler/src/com/oracle/graal/compiler/GraalCompiler.java	Mon May 13 11:36:09 2013 +0200
@@ -44,6 +44,7 @@
 import com.oracle.graal.phases.graph.*;
 import com.oracle.graal.phases.schedule.*;
 import com.oracle.graal.phases.tiers.*;
+import com.oracle.graal.phases.verify.*;
 import com.oracle.graal.virtual.phases.ea.*;
 
 /**
@@ -124,6 +125,7 @@
         } else {
             Debug.dump(graph, "initial state");
         }
+        new VerifyValueUsage(runtime).apply(graph);
 
         if (GraalOptions.OptCanonicalizer) {
             new CanonicalizerPhase.Instance(runtime, assumptions).apply(graph);

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/com.oracle.graal.phases/src/com/oracle/graal/phases/VerifyPhase.java	Mon May 13 11:36:09 2013 +0200
@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2013, 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.graal.phases;
+
+import com.oracle.graal.nodes.*;
+
+public abstract class VerifyPhase extends Phase {
+
+    @Override
+    protected final void run(StructuredGraph graph) {
+        assert verify(graph);
+    }
+
+    protected abstract boolean verify(StructuredGraph graph);
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/com.oracle.graal.phases/src/com/oracle/graal/phases/verify/VerifyValueUsage.java	Mon May 13 11:36:09 2013 +0200
@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2013, 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.graal.phases.verify;
+
+import com.oracle.graal.api.meta.*;
+import com.oracle.graal.nodes.*;
+import com.oracle.graal.nodes.calc.*;
+import com.oracle.graal.nodes.type.*;
+import com.oracle.graal.phases.*;
+
+public class VerifyValueUsage extends VerifyPhase {
+
+    private MetaAccessProvider runtime;
+
+    public VerifyValueUsage(MetaAccessProvider runtime) {
+        this.runtime = runtime;
+    }
+
+    private boolean checkType(ValueNode node) {
+        if (node.stamp() instanceof ObjectStamp) {
+            ResolvedJavaType valueType = runtime.lookupJavaType(Value.class);
+            ResolvedJavaType nodeType = node.objectStamp().type();
+
+            if (valueType.isAssignableFrom(nodeType)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    @Override
+    protected boolean verify(StructuredGraph graph) {
+        for (ObjectEqualsNode cn : graph.getNodes().filter(ObjectEqualsNode.class)) {
+            String desc = "VerifyValueUsage: " + cn.x() + " or " + cn.y() + " in " + graph.method() + " uses object identity. Should use equals() instead.";
+            if (!graph.method().toString().endsWith("equals(Object)>")) {
+                assert !((checkType(cn.x()) && !(cn.y() instanceof ConstantNode)) || (checkType(cn.y()) && !(cn.x() instanceof ConstantNode))) : desc;
+            }
+        }
+        return true;
+    }
+}