RFR: 8348868: AArch64: Add backend support for SelectFromTwoVector

[Andrew Haley]

On Wed, 19 Feb 2025 09:53:40 GMT, Bhavana Kilambi <bkilambi at openjdk.org> wrote:

>> I'm still curious.
>
> Hi @theRealAph , apologies for the late response. The tbl instruction needs both the source registers to be consecutive and I could not find a way to make the register allocator choose two consecutive registers for this operation and decided to hard code them. As v0-v7 are used for function arguments, v8-v15 are non-volatile which are not needed for this purpose (as we dont want to be preserving these values across function calls), I chose two of the volatile registers from v16-v31 for the source registers. Please let me know if this is the right way to approach.

I suppose it is, yes. Thanks.

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PR Review Comment: https://git.openjdk.org/jdk/pull/23570#discussion_r1963108465