RFR: 8307495: Specialize atomic bitset functions for aix-ppc [v6]

[Richard Reingruber]

On Fri, 10 Oct 2025 07:51:45 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:
> 
>   cast compare_value to unsigned

src/hotspot/cpu/ppc/atomicAccess_ppc.hpp line 165:

> 163:                                                    T exchange_value,
> 164:                                                    atomic_memory_order order) const {
> 165:   // Note that xchg doesn't necessarily do an acquire

Suggestion:

  STATIC_ASSERT(4 == sizeof(T));
  // Note that xchg doesn't necessarily do an acquire

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/27650#discussion_r2419108660