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

[Roland Westrelin]

>>> Tobias might wish to run some regression tests on the final changes.
>
> I've submitted some testing. Will report back once it finished.

Thanks.

>> http://cr.openjdk.java.net/~roland/8223051/webrev.02/
>
> Looks good to me.

Thanks for the review.

> loopnode.cpp:
> - line 504: "check_stride_overflow" is already in 8244504

Right but the one in this webrev is for longs so doesn't have the same
signature.

> loopnode.hpp:
> - line 1462: Shouldn't _loop_invokes/_loop_work also be volatile and be incremented atomically?

I think so too. That they are not incremented atomically implies nobody
uses them AFAICT. If we want all of them to be handled correctly then
someone needs to go over Compile::print_statistics() and all methods it
calls.

Roland.