RFR(M): 8223051: support loops with long (64b) trip counts

[Roland Westrelin]

Hi Tobias,

> Apart from expected test failures (TestIntVect due to failed vectorization and
> UseCountedLoopSafepointsTest due to a missing safepoint) and unrelated/known issues, I'm seeing the
> following failure:

Thanks for taking care of running tests and analyzing results. I've been
investigating the failure you reported and it doesn't appear specific to
the long counted loop patch. I filed JDK-8252696 and will propose a fix
soon.

Roland.