RFR: 8213415: BitMap::word_index_round_up overflow problems

[Kim Barrett]

> On Dec 2, 2019, at 5:10 AM, Stefan Karlsson <stefan.karlsson at oracle.com> wrote:
> 
> On 2019-11-29 21:37, Kim Barrett wrote:
>>> On Nov 29, 2019, at 3:03 AM, Thomas Stüfe <thomas.stuefe at gmail.com> wrote:
>>> 
>>> Side note, I was interested in using smaller types because long term I would like to have a BitMap class in cases where I today use little hand written bitmaps. As it is now, BitMap has a pointer and a size, which makes it a 16byte structure on 64 bit, which is rather fat. The indirection is also often unwanted. I would like to have a BitMap class which contains directly the data as member(s), e.g. one where it just has a 16bit word or, maybe, an array of multiple words. That would make this structure a lot smaller and better suited to be included in space sensitive structures.
>> There was some discussion here in Oracle about this sort of thing a
>> while ago. Looking back over that discussion, I don't think we got
>> very far with a statically sized bitmap, just some handwaving. I think
>> the interest is there, but ideas (and time to persue them!) are
>> needed.
> 
> FWIW, see the usage of BitMapView in zLiveMap.hpp and zLiveMap.inline.hpp.

Thanks - I’d forgotten about that.