[9] RFR(M): 8146629: Make phase->is_IterGVN() accessible from Node::Identity and Node::Value

[Roland Westrelin]

> I had to merge again with JDK-8139771 (castnode.cpp/hpp):
> http://cr.openjdk.java.net/~thartmann/8146629/webrev.02/

Looks good to me.

Roland.