Integrated: JDK-8331859 : [PPC64] Remove support for Power7 and older

[Suchismith Roy]

On Fri, 19 Jul 2024 17:32:09 GMT, Suchismith Roy <sroy at openjdk.org> wrote:

> JBS Issue: [JDK-8331859](https://bugs.openjdk.org/browse/JDK-8331859) 
> Linux PPC64le requires Power8 since the beginning.
> AIX requires Power8 with the new OpenXL based build ([JDK-8307520](https://bugs.openjdk.org/browse/JDK-8307520)). The old build has been removed in JDK 23 ([JDK-8327701](https://bugs.openjdk.org/browse/JDK-8327701)).
> Linux PPC64 Big Endian is no longer officially supported (only kept alive for development, debugging and testing purposes).
> 
> The following checks for old processors are no longer needed:
> 8: VM_Version::has_lqarx()
> 7: VM_Version::has_popcntw()
> 6: VM_Version::has_cmpb()
> 5: VM_Version::has_popcntb()
> These ones and some more checks for old instructions are no longer needed. All code which is no longer reachable when removing them should also get removed.
> Checks like "PowerArchitecturePPC64 >= 8" (or older) can be removed.
> 
> Atomic::PlatformCmpxchg<1>::operator() can be simplified by using sub-word instructions (lharx, lbarx).
> 
> Temp registers can be removed from cmpxchgb and cmpxchgh.
> 
> Build flags "-mcpu=powerpc64 -mtune=power5" for Big Endian linux should get replaced by "-mcpu=power8 -mtune=power8" as already used for linux PPC64le.

This pull request has now been integrated.

Changeset: 5cdeef81
Author:    Suchismith Roy <sroy at openjdk.org>
Committer: Varada M <varadam at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/5cdeef81ddb4ff1a6160b112f0f8338514d7b0a7
Stats:     1760 lines in 25 files changed: 29 ins; 1494 del; 237 mod

8331859: [PPC64] Remove support for Power7 and older

Reviewed-by: mdoerr

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PR: https://git.openjdk.org/jdk/pull/20262