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

[Bhavana Kilambi]

On Tue, 17 Jun 2025 02:41:26 GMT, Xiaohong Gong <xgong at openjdk.org> wrote:

>> Bhavana Kilambi has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Addressed review comments and added a JTREG test
>
> src/hotspot/cpu/aarch64/aarch64.ad line 4990:
> 
>> 4988: %{
>> 4989:   constraint(ALLOC_IN_RC(v17_veca_reg));
>> 4990:   match(vReg);
> 
> Not sure whether it's better to use `match(VecA)` here.

`VecA` is also matched in `vReg`. I thought we want to also match `VecD` (for 64bit) and `VecX` (for 128-bit) as well and `vReg` matches all the three of them. What do you think?

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PR Review Comment: https://git.openjdk.org/jdk/pull/23570#discussion_r2151645302