[lworld+vector] RFR: 8319945: [lworld+vector] Fix vector api jtreg crash with "-XX:-EnableVectorSupport"

[Xiaohong Gong]

On Mon, 27 Nov 2023 04:50:44 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>>> Hi @XiaohongGong , Can you please also add multifield special handling in **_ciInlineKlass::field_index_by_offset(int offset)_**. As of now its only used by C2 and functionalty looks safe.
>> 
>> Yes, considering that it is only used by C2 now, it's safe removing the multifields special handing. I suggest keeping it as it is now. One reason is the code may cannot be tested effectively, another is I'm considering whether we can take a further refactory to the multifields vectorization/scalarization in future. We may just keep the scalarized multifields in ci stage, and do the vectorization just in c2 compiler. So that all the special handling in ci could be cleaned-out. I plan to have a try for this in future.
>
>> > Hi @XiaohongGong , Can you please also add multifield special handling in **_ciInlineKlass::field_index_by_offset(int offset)_**. As of now its only used by C2 and functionalty looks safe.
>> 
>> Yes, considering that it is only used by C2 now, it's safe removing the multifields special handing. I suggest keeping it as it is now. One reason is the code may cannot be tested effectively, another is I'm considering whether we can take a further refactory to the multifields vectorization/scalarization in future. We may just keep the scalarized multifields in ci stage, and do the vectorization just in c2 compiler. So that all the special handling in ci could be cleaned-out. I plan to have a try for this in future.
> 
> Hi @XiaohongGong ,
> 
> Sounds reasonable to me, can you kindly add a TODO in field_index_by_offset for multifile handling, we can remove it once our alternate implementation is in place, other change looks ok to me. In future if it's used by C1 then we may need to introduce special handling for multifield since ci model is shared by compilers. 
> 
> Best Regards,
> Jatin

Thanks for the review @jatin-bhateja !

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PR Comment: https://git.openjdk.org/valhalla/pull/953#issuecomment-1828876937