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[WIP][AArch64][CodeGen] Support select address mode load/store
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Authored by Allen on Jun 12 2022, 5:05 AM.

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Allen created this revision.Jun 12 2022, 5:05 AM
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Allen requested review of this revision.Jun 12 2022, 5:05 AM
Herald added a project: Restricted Project. · View Herald TranscriptJun 12 2022, 5:05 AM

I don't believe we want this functionality. We originally added it but then it got removed by D88994 as unsound because there's no instruction available to load/store predicates that are smaller than <vscale x 16 x i1>. At the C/C++ level we don't expose these "smaller" predicate types and so there shouldn't really be a route needed to load/store them. @Allen Do you have a real world use case where loading/storing them is required?

Allen added a comment.Jun 13 2022, 7:35 AM

I don't believe we want this functionality. We originally added it but then it got removed by D88994 as unsound because there's no instruction available to load/store predicates that are smaller than <vscale x 16 x i1>. At the C/C++ level we don't expose these "smaller" predicate types and so there shouldn't really be a route needed to load/store them. @Allen Do you have a real world use case where loading/storing them is required?

Thanks @paulwalker-arm very much, I don't have a C case. But only my colleague found that the case compilation failed and tried to rectify the fault.
You have a good memory to find this patch D88994, which helps me understand the problem, thanks again!

Allen retitled this revision from [AArch64][CodeGen] Support select address mode load/store to [WIP][AArch64][CodeGen] Support select address mode load/store.Jun 14 2022, 12:38 AM
paulwalker-arm requested changes to this revision.Jul 15 2022, 9:04 AM

Just trying to cleanup my review list since we're agreed either more or different work is required.

This revision now requires changes to proceed.Jul 15 2022, 9:04 AM
Allen abandoned this revision.Jul 15 2022, 5:54 PM

Yes, I think this is not worthless