[libcxx-commits] [PATCH] D144362: [libcxx] Updated <experimental/simd> based on Parallelism-TS N4808

Tue Feb 21 04:26:10 PST 2023

Joy12138 added a comment.

@philnik @Mordante Thanks for your attention to this patch. I don't know how to reply to you all in the comment, so I wrote all replies here.

> Thanks for working on this. Is N4808 voted in? I can only find a draft version.

It seems it is still draft. Should I continue to refer to this document, or which other version?

> Why do you remove all of the old implementation? Is it so radically different from what you want to implement?

> I'm wondering the same. Normally we don't remove code, since it may break existing users.
> However I think our current implementation is so minimal that risk isn't too great.

Yes, although we referred to and followed the original implementation, we have made great adjustments to the overall implementation framework and test framework.

Implementation framework:

Now we use the internal ABI as a template parameter. And we use the template class `simd_storage/mask_storage` to define the storage type of the internal ABI, use the template class `simd_traits/mask_traits` to implement operations of the internal ABI. We put these template specializations of each internal ABI in a seperate header file. We believe that this will help to expand the internal ABI and to make target-specific optimizations in the future.

Test framework:

We also reconstructed the test code structure. Added a test framework to improve test coverage. Because most external user interfaces are related to class `simd/simd_mask`, we have traversed all possible data types and ABI tags combinations of class `simd/simd_mask` in related interface tests.

We have now completed the implementation of a stable version (Refer to this revision: https://reviews.llvm.org/D139421). This stable version included all external user interfaces except the Math Library. And added corresponding external interfaces tests. I hope that the code finally submitted to the upstream will be closer to the current available implementation. So it may be hard to advance on the original implementation. I prefer to remove the original implementation and build our existing framework from the most basic part. I plan to submit the follow-up implementation step by step In the next two months to completely cover all interfaces. I suggest we can consider to land all these patches together after they are reviewed and approved to avoid breaking existing users.

> The synopsis should be updated as we go, to show what has actually been implemented. I am aware that this isn't the case currently, so let's fix this.

> Let's keep the stable names. Section numbers are just a nightmare to maintain and will be wrong. At least they are everywhere they are used currently.

> +1 Especially since these numbers will change if this is adopted on the Standard. Using the stable names gives a higher probability these references remain valid.

> Could you remove all the declaration-only stuff in a separate PR? We normally don't have the interface declared if it's not defined.

Summary (correct me if I misunderstood):

1. No declarations.
2. Give synopsis of implemented interfaces only.
3. Keep original stable names of sections without section numbers.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D144362/new/

https://reviews.llvm.org/D144362