--- /dev/null	2016-05-31 09:42:47.975716356 -0700
+++ new/src/jdk.vm.compiler/share/classes/org.graalvm.compiler.phases/src/org/graalvm/compiler/phases/graph/InferStamps.java	2016-12-09 00:56:27.557749064 -0800
@@ -0,0 +1,98 @@
+/*
+ * Copyright (c) 2013, 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 org.graalvm.compiler.phases.graph;
+
+import org.graalvm.compiler.core.common.type.ObjectStamp;
+import org.graalvm.compiler.graph.Node;
+import org.graalvm.compiler.nodes.StructuredGraph;
+import org.graalvm.compiler.nodes.ValueNode;
+import org.graalvm.compiler.nodes.ValuePhiNode;
+
+public class InferStamps {
+
+    /**
+     * Infer the stamps for all Object nodes in the graph, to make the stamps as precise as
+     * possible. For example, this propagates the word-type through phi functions. To handle phi
+     * functions at loop headers, the stamp inference is called until a fix point is reached.
+     * <p>
+     * This method can be used when it is needed that stamps are inferred before the first run of
+     * the canonicalizer. For example, word type rewriting must run before the first run of the
+     * canonicalizer because many nodes are not prepared to see the word type during
+     * canonicalization.
+     */
+    public static void inferStamps(StructuredGraph graph) {
+        /*
+         * We want to make the stamps more precise. For cyclic phi functions, this means we have to
+         * ignore the initial stamp because the imprecise stamp would always propagate around the
+         * cycle. We therefore set the stamp to an illegal stamp, which is automatically ignored
+         * when the phi function performs the "meet" operator on its input stamps.
+         */
+        for (Node n : graph.getNodes()) {
+            if (n instanceof ValuePhiNode) {
+                ValueNode node = (ValueNode) n;
+                if (node.stamp() instanceof ObjectStamp) {
+                    assert node.stamp().hasValues() : "We assume all Phi and Proxy stamps are legal before the analysis";
+                    node.setStamp(node.stamp().empty());
+                }
+            }
+        }
+
+        boolean stampChanged;
+        // The algorithm is not guaranteed to reach a stable state.
+        int z = 0;
+        do {
+            stampChanged = false;
+            /*
+             * We could use GraphOrder.forwardGraph() to process the nodes in a defined order and
+             * propagate long def-use chains in fewer iterations. However, measurements showed that
+             * we have few iterations anyway, and the overhead of computing the order is much higher
+             * than the benefit.
+             */
+            for (Node n : graph.getNodes()) {
+                if (n instanceof ValueNode) {
+                    ValueNode node = (ValueNode) n;
+                    if (node.stamp() instanceof ObjectStamp) {
+                        stampChanged |= node.inferStamp();
+                    }
+                }
+            }
+            ++z;
+        } while (stampChanged && z < 10000);
+
+        /*
+         * Check that all the illegal stamps we introduced above are correctly replaced with real
+         * stamps again.
+         */
+        assert checkNoEmptyStamp(graph);
+    }
+
+    private static boolean checkNoEmptyStamp(StructuredGraph graph) {
+        for (Node n : graph.getNodes()) {
+            if (n instanceof ValuePhiNode) {
+                ValueNode node = (ValueNode) n;
+                assert node.stamp().hasValues() : "Stamp is empty after analysis. This is not necessarily an error, but a condition that we want to investigate (and then maybe relax or remove the assertion).";
+            }
+        }
+        return true;
+    }
+}