RFR: 8307495: Specialize atomic bitset functions for aix-ppc [v4]

[Martin Doerr]

On Wed, 8 Oct 2025 12:55:03 GMT, David Briemann <dbriemann at openjdk.org> wrote:

>> Add atomic bitset functions for PPC64.
>> Refactor so that inline assembler code is shared for all PPC64 platforms.
>> Add back a missing "simple guard" to PlatformCpmxchg<1>. Remove some dead Power7 code.
>
> David Briemann has updated the pull request incrementally with one additional commit since the last revision:
> 
>   replace zero register by immediate 0 value

Thanks for cleaning this up and making the inline assembler code more uniform. You could also replace the "%0", "%1", ... in `add_then_fetch` (optional). LGTM either way.

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Marked as reviewed by mdoerr (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/27650#pullrequestreview-3315423924