Re: [PATCH v2] libstdc++: add ARM SVE support to std::experimental::simd

[Richard Sandiford <richard.sandiford@arm.com>]

Jonathan Wakely <jwakely@redhat.com> writes:
> On Fri, 8 Mar 2024 at 09:58, Matthias Kretz wrote:
>>
>> Hi,
>>
>> I applied and did extended testing on x86_64 (no regressions) and aarch64
>> using qemu testing SVE 256, 512, and 1024. Looks good!
>>
>> While going through the applied patch I noticed a few style issues that I
>> simply turned into a patch (attached).
>>
> [...]
>>
>> From my side, with the noted changes the patch is ready for merging.
>> @Jonathan, any chance for a green light before GCC 14.1?
>
> As discussed on IRC, please push the revised patch with your
> suggestions incorporated (and post to the lists for posterity).
>
> Thanks, everybody, for the patches and the thorough review.

I'm still worried about:

  #if _GLIBCXX_SIMD_HAVE_SVE
  constexpr inline int __sve_vectorized_size_bytes = __ARM_FEATURE_SVE_BITS / 8;
  #else
  constexpr inline int __sve_vectorized_size_bytes = 0;
  #endif

and the direct use __ARM_FEATURE_SVE_BITS elsewhere, for the reasons
discussed here (including possible ODR problems):

  https://gcc.gnu.org/pipermail/gcc-patches/2023-December/640037.html
  https://gcc.gnu.org/pipermail/gcc-patches/2024-January/643734.html

Logically the vector length should be a template parameter rather than
an invariant.  Has this been resolved?  If not, it feels like a blocker
to me (sorry).

Thanks,
Richard