RFR: 8337791: VectorAPI jtreg ABSMaskedByteMaxVectorTests crashes with UseAVX=0 -XX:MaxVectorSize=8 [v8]

[Emanuel Peter]

On Mon, 1 Dec 2025 13:39:09 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 refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:
> 
>   Review comments resolutions

@jatin-bhateja Testing passed, fix looks good to me. Thanks for working on this 😊

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Marked as reviewed by epeter (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/28533#pullrequestreview-3533284691