--- a/graal/com.oracle.graal.phases.common/src/com/oracle/graal/phases/common/CanonicalizerPhase.java	Tue Dec 01 08:46:50 2015 -0800
+++ b/graal/com.oracle.graal.phases.common/src/com/oracle/graal/phases/common/CanonicalizerPhase.java	Wed Dec 02 11:06:05 2015 -0800
@@ -242,9 +242,23 @@
                     return true;
                 }
             }
+            assert assertLeafGVN(node, nodeClass);
             return false;
         }
 
+        /**
+         * Ensure that leaf nodes have already been GVN'ed. This is normally handled automatically
+         * but it's possible to add nodes to the graph with looking for duplicates and it's the
+         * responsibility of code that does that to clean it up.
+         */
+        private boolean assertLeafGVN(Node node, NodeClass<?> nodeClass) {
+            if (node.isAlive() && nodeClass.valueNumberable() && nodeClass.isLeafNode()) {
+                Node newNode = node.graph().findDuplicate(node);
+                return (newNode == null || newNode == node);
+            }
+            return true;
+        }
+
         private AutoCloseable getCanonicalizeableContractAssertion(Node node) {
             boolean needsAssertion = false;
             assert (needsAssertion = true) == true;

--- a/graal/com.oracle.graal.virtual/src/com/oracle/graal/virtual/phases/ea/EffectsPhase.java	Tue Dec 01 08:46:50 2015 -0800
+++ b/graal/com.oracle.graal.virtual/src/com/oracle/graal/virtual/phases/ea/EffectsPhase.java	Wed Dec 02 11:06:05 2015 -0800
@@ -122,6 +122,27 @@
     }
 
     protected void postIteration(final StructuredGraph graph, final PhaseContextT context, Set<Node> changedNodes) {
+        /*
+         * The nodes were added without uniqueing them first so GVN the leaf nodes now. The normal
+         * CanonicalizerPhase will GVN non-leaf value numberable nodes.
+         */
+        for (Node node : changedNodes) {
+            if (node.isAlive() && node.getNodeClass().valueNumberable() && node.getNodeClass().isLeafNode()) {
+                Node duplicate = graph.findDuplicate(node);
+                if (duplicate != node) {
+                    if (duplicate == null) {
+                        /*
+                         * There's no version of this constant in the leaf node cache so create a
+                         * copy to add it to the table.
+                         */
+                        duplicate = node.copyWithInputs();
+                        assert duplicate == graph.findDuplicate(duplicate);
+                    }
+                    node.replaceAtUsages(duplicate);
+                    node.safeDelete();
+                }
+            }
+        }
         if (canonicalizer != null) {
             canonicalizer.applyIncremental(graph, context, changedNodes);
         }