RFR: 8378675: PPC64: increase instruction cache line size [v3]

[David Briemann]

On Thu, 26 Feb 2026 16:25:58 GMT, Richard Reingruber <rrich at openjdk.org> wrote:

>> But, your point that the changes in os_aix.hpp and os_linux.hpp are unused declarations is true. I think they should get reverted.
>
> Personally I don't like that. It means you have to check if a method really has a definitions on all platform flavours and versions (OS, libc, ...) before you can use them in shared code. That's just tedious.
> And if there's enough laziness in the process of resolving references then only a user might find out that there's no definition for the users platform.

The alternative was to use `os::Linux::get..()` and `os::Aix::get..()` but that requires wrapping these calls in ifdefs, which doesn't look so nice.

We could also add these functions for the other systems with an `uninplemented()` body but then they only fail at runtime. We thought failing at build/link time would be better.

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PR Review Comment: https://git.openjdk.org/jdk/pull/29918#discussion_r2862875667