RFR(xs): 8241581: Add BitMap::count_one_bits variant for arbitrary lengths

[Thomas Stüfe]

Thanks Kim.

On Thu 26. Mar 2020 at 20:42, Kim Barrett <kim.barrett at oracle.com> wrote:

> > On Mar 25, 2020, at 8:35 AM, Thomas Stüfe <thomas.stuefe at gmail.com>
> wrote:
> >
> > Greetings,
> >
> > could I have reviews for this small enhancement please:
> >
> > JBS: https://bugs.openjdk.java.net/browse/JDK-8241581
> > Webrev:
> >
> http://cr.openjdk.java.net/~stuefe/webrevs/bitmap-arbitrary-range-popcount/webrev.00/webrev/
> >
> > This adds the ability to call BitMap::count_one_bits on an arbitrary bit
> > region, not just on the whole BitMap. I need this for the new Metaspace
> > prototype.
> >
> > Note that while it would be cool to use platform dependent popcnt
> > instructions here, that is not the goal of this fix. This just expands on
> > the existing implementation of BitMap::count_one_bits() using the
> algorithm
> > in population:count.hpp.
> >
> > It comes with quite thorough gtests. I ran the gtests on little and big
> > endian machines and all is well. Submit tests also ran through.
> >
> > Thanks, Thomas
>
> Looks good.
>
>