RFR(XS): 8073957: assert(ary_src != 0) failed: not an array or instance?

[Roland Westrelin]

Thanks for the comments.

> Depending on the order of IGVN list execution different inputs could be set to top at different time. I would suggest to check all ArrayCopyNode's inputs for top.
> 
> In ideal() or ArrayCopyNode::make() we may need to test inputs (or may be assert) for NULL too.

Does this look ok?

http://cr.openjdk.java.net/~roland/8073957/webrev.01/

in(ArrayCopyNode::Length) is tested for top in ArrayCopyNode::get_length_if_constant()

Roland.