RFR: 8307533: Use atomic bitset functions for metadata flags [v2]

[Coleen Phillimore]

On Tue, 9 May 2023 23:38:39 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   remove extra variables in favor of casts to help the template.
>
> The Atomic bitops aren't intended to support other sizes; only the same sizes as Atomic::add and friends.  That narrower
> types are currently supported by the default implementation is an accident.  Platform specializations might not have such
> support, since the underlying platform might not have it.
> 
> If support for narrower types is a (not previously known to me) requirement, some non-trivial changes may be needed.
> Among other things, I think the current very simple platform specialization mechanism won't be sufficient.

@kimbarrett thank you for adding support for u1 types.  I merged with the latest changes.

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PR Comment: https://git.openjdk.org/jdk/pull/13843#issuecomment-1548064187