RFR: 8337791: VectorAPI jtreg ABSMaskedByteMaxVectorTests crashes with UseAVX=0 -XX:MaxVectorSize=8 [v3]

[Emanuel Peter]

On Thu, 27 Nov 2025 15:32:15 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> This bug patch fixes a crash seen while querying the bottom type of MachTempNode corresponding to [rxmm0 operand](https://github.com/openjdk/jdk/blob/master/src/hotspot/cpu/x86/x86.ad#L22509) of blend pattern during late scheduling. Here, MaxVectorSize is contrainted to 8 bytes thus during C2 type system initialization, [TypeVect::VECTX ](https://github.com/openjdk/jdk/blob/master/src/hotspot/share/opto/type.cpp#L719) guarded by target supprted vector size remains uninitialized.
>> 
>> Its better to reject matching of VectorBlend in such a scenario.
>> 
>> All exisitng VectorAPI jtreg tests are passing with -XX:UseAVX=0 and -XX:MaxVectorSize=8
>> 
>> Kindly review and share your feedback.
>> 
>> Best Regards,
>> Jatin
>
> Jatin Bhateja has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fine tune matcher check

Ok, that's fine with me too.

It would be nice if you could also attach a regression test, or maybe add an additional run to the existing test, with the required flags for reproducing this issue.

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PR Comment: https://git.openjdk.org/jdk/pull/28533#issuecomment-3586626636