Request for reviews (XS): 6851386: assert(b->find_node(def) < j,"uses must follow definitions")

[Vladimir Kozlov]

http://cr.openjdk.java.net/~kvn/6851386/webrev.00

Fixed 6851386: assert(b->find_node(def) < j,"uses must follow definitions")

Problem:
The assert added for 6791852 misses the case when
the head of a tight loop is not LoopNode.
In the bugs case it is RegionNode with 4 input edges.

Solution:
Add additional check for a tight loop.

Reviewed by:

Fix verified (y/n): y, bug's test

Other testing:
JPRT