RFR: 8371187: [BigEndian Platforms] Vector lane reversal error

[Amit Kumar]

On Thu, 20 Nov 2025 12:05:36 GMT, Varada M <varadam at openjdk.org> wrote:

> This change fixes incorrect lane ordering in reinterpretation operations on big-endian platforms. When converting from wider to narrower lane types like Long to Int, Long to Short, big-endian systems produced reversed sub-lanes.
> The patch adds a maybeSwapOnConverted() and a generic normalizeSubLanesForSpecies() shuffle builder to correct the sub-lane order based on element sizes on big-endian
> 
> JBS: [JDK-8371187](https://bugs.openjdk.org/browse/JDK-8371187)

Fixes the issue for s390x. Tier1 with fastdebug vm doesn't show any regression.

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Marked as reviewed by amitkumar (Committer).

PR Review: https://git.openjdk.org/jdk/pull/28425#pullrequestreview-3528984905