RFR: 8348868: AArch64: Add backend support for SelectFromTwoVector [v3]

[Xiaohong Gong]

On Tue, 17 Jun 2025 08:16:01 GMT, Bhavana Kilambi <bkilambi at openjdk.org> wrote:

>> How about just using the negate condition of rule `vselect_from_two_vectors` ? 
>> 
>> predicate(Matcher::vector_element_basic_type(n) != T_BYTE &&
>>           (UseSVE < 2 || Matcher::vector_length_in_bytes(n) < 16));
>
> Hi @XiaohongGong , thanks for your prompt review. I can't use the negate condition here as it will include `T_DOUBLE` and `T_LONG` as well which are not supported. I'll change it to the same basic type check instead.

Yeah, I noticed this as well. Since these types for NEON has been excluded in above function `match_rule_supported_vector()`. Can we just ignore such types? Besides, you have also added the type assertion in the macro assembler implementation.

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PR Review Comment: https://git.openjdk.org/jdk/pull/23570#discussion_r2151640353