RFR(XS): 8080699: Assert failed: Not a Java pointer in JCK test

[Roland Westrelin]

http://cr.openjdk.java.net/~roland/8080699/webrev.00/

When an arraycopy node is eliminated (for a non escaping allocation), its control, src and dest arguments are set to top and it is no longer connected to the rest of the graph through its fall through outputs. It’s not entirely removed from the graph until the next igvn though, and it can be reached through its exception processing outputs. That’s what happens here and ArrayCopyNode::may_modify() assumes dest, that is top, is an oop.

Roland.