RFR: 8356760: VectorAPI: Optimize VectorMask.fromLong for all-true/all-false cases [v4]

[erifan]

On Tue, 22 Jul 2025 09:04:56 GMT, erifan <duke at openjdk.org> wrote:

>>> Do you mean this check `Matcher::match_rule_supported_vector(opc, vlen, maskall_bt)` ? I think it's necessary ? Because in theory some platforms don't support both `MaskAll` and `Replicate`. Of course, this situation may not exist in reality. If `MaskAll` and `Replicate` are not supported, then `VectorLongToMask` should not be supported either, and this function will not be called.
>> 
>> My suggestion was to check for Op_Replicate here as Op_MaskAll is already checked underneath VectorNode::scalar2vector under an assumption that MaskAll is a special case for replicate applicable to masks
>
> Oh I misunderstood what you meant, now I understand, thank you!

Done, thanks!

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PR Review Comment: https://git.openjdk.org/jdk/pull/25793#discussion_r2227253339