RFR(S): 8224496: Shenandoah compilation fails with assert(is_CountedLoopEnd()) failed: invalid node class

[Roland Westrelin]

http://cr.openjdk.java.net/~roland/8224496/webrev.00/

Expanding a barrier in the outer loop of a strip mined loop nest
confuses the loop strip mining verification logic. This is not a new
problem and the way this relatively rare case has been handled so far is
by turning the outer strip mined loop into a regular loop so the
verification logic doesn't trigger. In the move to the new barrier
scheme, some of that logic was dropped. This fix puts it back and also
fixes a bug that it causes.

Roland.