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

[Martin Doerr]

On Tue, 17 Jun 2025 08:26:32 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

LGTM. Thanks for improving this!

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Marked as reviewed by mdoerr (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/25828#pullrequestreview-2934656765