--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/com.oracle.graal.compiler/src/com/oracle/graal/compiler/phases/GraphChangeMonitoringPhase.java	Mon Jan 26 09:28:20 2015 -0800
@@ -0,0 +1,92 @@
+/*
+ * Copyright (c) 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.graal.compiler.phases;
+
+import static com.oracle.graal.graph.Graph.NodeEvent.*;
+
+import java.util.stream.*;
+
+import com.oracle.graal.debug.*;
+import com.oracle.graal.debug.Debug.Scope;
+import com.oracle.graal.graph.Graph.NodeEventScope;
+import com.oracle.graal.nodes.*;
+import com.oracle.graal.phases.*;
+import com.oracle.graal.phases.common.util.*;
+import com.oracle.graal.phases.tiers.*;
+
+/**
+ * A utility phase for detecting when a phase would change the graph and reporting extra information
+ * about the effects. The phase is first run on a copy of the graph and if a change in that graph is
+ * detected then it's rerun on the original graph inside a new debug scope under
+ * GraphChangeMonitoringPhase. The message argument can be used to distinguish between the same
+ * phase run at different points.
+ *
+ * @param <C>
+ */
+public class GraphChangeMonitoringPhase<C extends PhaseContext> extends PhaseSuite<C> {
+
+    private final String message;
+
+    public GraphChangeMonitoringPhase(String message, BasePhase<C> phase) {
+        super();
+        this.message = message;
+        appendPhase(phase);
+    }
+
+    public GraphChangeMonitoringPhase(String message) {
+        super();
+        this.message = message;
+    }
+
+    @Override
+    protected void run(StructuredGraph graph, C context) {
+        HashSetNodeEventListener listener = new HashSetNodeEventListener().exclude(INPUT_CHANGED);
+        try (NodeEventScope s = graph.trackNodeEvents(listener)) {
+            StructuredGraph graphCopy = graph.copy();
+            try (Scope s2 = Debug.sandbox("WithoutMonitoring", null)) {
+                super.run(graphCopy, context);
+            } catch (Throwable t) {
+                Debug.handle(t);
+            }
+        }
+        if (!listener.getNodes().isEmpty()) {
+            // rerun it on the real graph in a new Debug scope so Dump and Log can find it.
+            listener = new HashSetNodeEventListener().exclude(INPUT_CHANGED);
+            try (NodeEventScope s = graph.trackNodeEvents(listener)) {
+                try (Scope s2 = Debug.scope("GraphChangeMonitoring." + getName() + "-" + message)) {
+                    if (Debug.isDumpEnabled(BasePhase.PHASE_DUMP_LEVEL)) {
+                        Debug.dump(BasePhase.PHASE_DUMP_LEVEL, graph, "*** Before phase %s", getName());
+                    }
+                    super.run(graph, context);
+                    if (Debug.isDumpEnabled(BasePhase.PHASE_DUMP_LEVEL)) {
+                        Debug.dump(BasePhase.PHASE_DUMP_LEVEL, graph, "*** After phase %s", getName());
+                    }
+                }
+                Debug.log("*** %s %s %s\n", message, graph, listener.getNodes().stream().filter(e -> !e.isAlive()).collect(Collectors.toSet()));
+            }
+        } else {
+            // Go ahead and run it normally even though it should have no effect
+            super.run(graph, context);
+        }
+    }
+}