RFR: 8343689: AArch64: Optimize MulReduction implementation [v4]

[Mikhail Ablakatov]

On Wed, 2 Jul 2025 01:46:18 GMT, Xiaohong Gong <xgong at openjdk.org> wrote:

>> Well, we don't match it right now for auto-vectorization as it doesn't worth it performance-wise. This might change for future implementations of SVE(2). I'd still prefer to keep it so the set of instructions is complete.
>
> Removing is fine to me, as actually we do not have the case to test the correctness. Or maybe you could just do some  changes locally (e.g. removing the `requires_strict_order` predication and the un-strict-order rule), and test it with VectorAPI cases?

Done: https://github.com/openjdk/jdk/commit/4593a5d717024df01769625993c2b769d8dde311

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PR Review Comment: https://git.openjdk.org/jdk/pull/23181#discussion_r2198125027