--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/com.oracle.truffle.ruby.nodes/src/com/oracle/truffle/ruby/nodes/objects/instancevariables/ReadInstanceVariableNode.java	Mon Jan 06 17:12:09 2014 +0000
@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2013 Oracle and/or its affiliates. All rights reserved. This
+ * code is released under a tri EPL/GPL/LGPL license. You can use it,
+ * redistribute it and/or modify it under the terms of the:
+ *
+ * Eclipse Public License version 1.0
+ * GNU General Public License version 2
+ * GNU Lesser General Public License version 2.1
+ */
+package com.oracle.truffle.ruby.nodes.objects.instancevariables;
+
+import com.oracle.truffle.api.*;
+import com.oracle.truffle.api.frame.*;
+import com.oracle.truffle.ruby.nodes.*;
+import com.oracle.truffle.ruby.runtime.*;
+import com.oracle.truffle.ruby.runtime.objects.*;
+
+public abstract class ReadInstanceVariableNode extends RubyNode implements ReadNode {
+
+    protected final String name;
+    @Child protected RubyNode receiver;
+
+    public ReadInstanceVariableNode(RubyContext context, SourceSection sourceSection, String name, RubyNode receiver) {
+        super(context, sourceSection);
+        this.name = name;
+        this.receiver = adoptChild(receiver);
+    }
+
+    public ReadInstanceVariableNode respecialize(RubyBasicObject receiverObject) {
+        final StorageLocation storageLocation = receiverObject.getUpdatedObjectLayout().findStorageLocation(name);
+
+        if (storageLocation == null) {
+            return new ReadMissingInstanceVariableNode(getSourceSection(), name, receiver, receiverObject.getObjectLayout(), getContext());
+        }
+
+        if (storageLocation instanceof FixnumStorageLocation) {
+            return new ReadFixnumInstanceVariableNode(getContext(), getSourceSection(), name, receiver, storageLocation.getObjectLayout(), (FixnumStorageLocation) storageLocation);
+        } else if (storageLocation instanceof FloatStorageLocation) {
+            return new ReadFloatInstanceVariableNode(getContext(), getSourceSection(), name, receiver, storageLocation.getObjectLayout(), (FloatStorageLocation) storageLocation);
+        } else {
+            return new ReadObjectInstanceVariableNode(getContext(), getSourceSection(), name, receiver, storageLocation.getObjectLayout(), (ObjectStorageLocation) storageLocation);
+        }
+    }
+
+    public WriteInstanceVariableNode makeWriteNode(RubyNode rhs) {
+        return new UninitializedWriteInstanceVariableNode(getContext(), getEncapsulatingSourceSection(), name, (RubyNode) receiver.copy(), rhs);
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public RubyNode getReceiver() {
+        return receiver;
+    }
+
+    @Override
+    public Object isDefined(VirtualFrame frame) {
+        final RubyContext context = getContext();
+
+        try {
+            final Object receiverObject = receiver.execute(frame);
+            final RubyBasicObject receiverRubyObject = context.getCoreLibrary().box(receiverObject);
+
+            final ObjectLayout layout = receiverRubyObject.getObjectLayout();
+            final StorageLocation storageLocation = layout.findStorageLocation(name);
+
+            if (storageLocation.isSet(receiverRubyObject)) {
+                return context.makeString("instance-variable");
+            } else {
+                return NilPlaceholder.INSTANCE;
+            }
+        } catch (Exception e) {
+            return NilPlaceholder.INSTANCE;
+        }
+    }
+}