RFR: 8354650: [PPC64] Try to reduce register definitions [v3]

[duke]

On Tue, 17 Jun 2025 08:29:49 GMT, David Briemann <dbriemann at openjdk.org> wrote:

>> Defines the 32 vector registers and removes the 64 vector scalar register definitions. Reduces Mach registers from 398 to 270.
>
> David Briemann has updated the pull request incrementally with one additional commit since the last revision:
> 
>   beautify code

@dbriemann 
Your change (at version d29e49fcf80345620c0e5c5b1a66689b4bbf32b7) is now ready to be sponsored by a Committer.

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PR Comment: https://git.openjdk.org/jdk/pull/25828#issuecomment-2979732472