RFR: 8342095: Add autovectorizer support for subword vector casts

[Emanuel Peter]

On Wed, 5 Feb 2025 15:22:05 GMT, Jasmine Karthikeyan <jkarthikeyan at openjdk.org> wrote:

>> @jaskarth
>
> @eme64 I took a look last night and it looks like supporting casting to larger types (other than `char`) just involves changing the filtering logic in `matcher_x86.hpp` and adding more unit tests, without modifying any of the core logic. I think it could make sense to keep it in the same patch, what do you think? Either way would work with me.

I leave it up to you. If it's not much then pack it in the same, else splitting is fine with me too ;)

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PR Review Comment: https://git.openjdk.org/jdk/pull/23413#discussion_r1943188169