--- a/graal/com.oracle.truffle.api/src/com/oracle/truffle/api/TruffleOptions.java	Wed Jun 18 14:12:06 2014 +0200
+++ b/graal/com.oracle.truffle.api/src/com/oracle/truffle/api/TruffleOptions.java	Fri Jun 20 15:13:16 2014 +0200
@@ -72,6 +72,13 @@
      */
     public static NodeCost TraceRewritesFilterToCost = parseNodeInfoKind(System.getProperty("truffle.TraceRewritesFilterToCost"));
 
+    /**
+     * Enables the dumping of Node creations and AST rewrites in JSON format.
+     * <p>
+     * Can be set with {@code -Dtruffle.TraceASTJSON=true}.
+     */
+    public static final boolean TraceASTJSON = Boolean.getBoolean("truffle.TraceASTJSON");
+
     private static NodeCost parseNodeInfoKind(String kind) {
         if (kind == null) {
             return null;

--- a/graal/com.oracle.truffle.api/src/com/oracle/truffle/api/nodes/Node.java	Wed Jun 18 14:12:06 2014 +0200
+++ b/graal/com.oracle.truffle.api/src/com/oracle/truffle/api/nodes/Node.java	Fri Jun 20 15:13:16 2014 +0200
@@ -31,6 +31,7 @@
 
 import com.oracle.truffle.api.*;
 import com.oracle.truffle.api.source.*;
+import com.oracle.truffle.api.utilities.*;
 
 /**
  * Abstract base class for all Truffle nodes.
@@ -58,12 +59,15 @@
     }
 
     protected Node() {
-        CompilerAsserts.neverPartOfCompilation();
+        this(null);
     }
 
     protected Node(SourceSection sourceSection) {
         CompilerAsserts.neverPartOfCompilation();
         this.sourceSection = sourceSection;
+        if (TruffleOptions.TraceASTJSON) {
+            JSONHelper.dumpNewNode(this);
+        }
     }
 
     /**
@@ -169,6 +173,9 @@
         }
         boolean isInserted = newChild.parent == null;
         newChild.parent = this;
+        if (TruffleOptions.TraceASTJSON) {
+            JSONHelper.dumpNewChild(this, newChild);
+        }
         newChild.adoptHelper();
         if (isInserted) {
             newChild.onAdopt();
@@ -273,6 +280,9 @@
             this.parent.adoptUnadoptedHelper(newNode);
         }
         reportReplace(this, newNode, reason);
+        if (TruffleOptions.TraceASTJSON) {
+            JSONHelper.dumpReplaceChild(this, newNode, reason);
+        }
         onReplace(newNode, reason);
     }
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/com.oracle.truffle.api/src/com/oracle/truffle/api/utilities/JSONHelper.java	Fri Jun 20 15:13:16 2014 +0200
@@ -0,0 +1,121 @@
+/*
+ * 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.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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.truffle.api.utilities;
+
+import com.oracle.truffle.api.nodes.*;
+import com.oracle.truffle.api.source.*;
+
+/**
+ * Helper function that allows to dump the AST during creation to a JSON format.
+ */
+public class JSONHelper {
+
+    private static StringBuilder AstJsonDumpBuilder = new StringBuilder();
+
+    public static void dumpNewChild(Node parentNode, Node childNode) {
+        if (AstJsonDumpBuilder != null) {
+            AstJsonDumpBuilder.append("{ \"action\": \"insertNode\", \"parentId\": \"" + getID(parentNode) + "\", \"newId\": \"" + getID(childNode) + "\" },\n");
+        }
+    }
+
+    public static void dumpReplaceChild(Node oldNode, Node newNode, CharSequence reason) {
+        if (AstJsonDumpBuilder != null) {
+            AstJsonDumpBuilder.append("{ \"action\": \"replaceNode\", \"oldId\": \"" + getID(oldNode) + "\", \"newId\": \"" + getID(newNode) + "\", \"reason\": " + quote(reason) + " },\n");
+        }
+    }
+
+    public static void dumpNewNode(Node newNode) {
+        if (AstJsonDumpBuilder != null) {
+            AstJsonDumpBuilder.append("{ \"action\": \"createNode\", \"newId\": \"" + getID(newNode) + "\", \"newType\": \"" + getType(newNode) + "\"" + getSourceSectionInfo(newNode) + " },\n");
+        }
+    }
+
+    private static String getSourceSectionInfo(Node newNode) {
+        SourceSection sourceSection = newNode.getSourceSection();
+        if (sourceSection != null) {
+            return ", \"identifier\": \"" + sourceSection.getIdentifier() + "\" ";
+        } else {
+            return "";
+        }
+    }
+
+    public static String getResult() {
+        return AstJsonDumpBuilder.toString();
+    }
+
+    private static String getID(Node newChild) {
+        return String.valueOf(newChild.hashCode());
+    }
+
+    private static String getType(Node node) {
+        return node.getClass().getSimpleName();
+    }
+
+    private static String quote(CharSequence value) {
+        StringBuilder builder = new StringBuilder(value.length() + 2);
+        builder.append('"');
+        for (int i = 0; i < value.length(); i++) {
+            char c = value.charAt(i);
+            switch (c) {
+                case '"':
+                    builder.append("\\\"");
+                    break;
+                case '\\':
+                    builder.append("\\\\");
+                    break;
+                case '\b':
+                    builder.append("\\b");
+                    break;
+                case '\f':
+                    builder.append("\\f");
+                    break;
+                case '\n':
+                    builder.append("\\n");
+                    break;
+                case '\r':
+                    builder.append("\\r");
+                    break;
+                case '\t':
+                    builder.append("\\t");
+                    break;
+                default: {
+                    if (c < ' ') {
+                        builder.append("\\u00");
+                        builder.append(Character.forDigit((c >> 4) & 0xF, 16));
+                        builder.append(Character.forDigit(c & 0xF, 16));
+                    } else {
+                        builder.append(c);
+                    }
+                }
+            }
+        }
+        builder.append('"');
+        return builder.toString();
+    }
+
+    public static void restart() {
+        AstJsonDumpBuilder = new StringBuilder();
+    }
+}