GLIBC libmvec status

[Bill Schmidt]

On 2/27/20 12:48 PM, GT wrote:
> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> On Thursday, February 27, 2020 9:26 AM, Bill Schmidt <wschmidt@linux.ibm.com> wrote:
>
>> Upon reflection, I agree.  Bert, we need to make changes to the document to
>> reflect this:
>>
>> (1) "Calling convention" should refer to ELFv1 for powerpc64 and ELFv2 for
>> powerpc64le.
> Done. Have provided names and links to respective ABI documents but no longer
> explicitly refer to ELF version.
>
>> (2) "Vector Length" should remove bullet 3, strike the word
>> "nonhomogeneous" in bullet 4, and strike the parenthetical clause in
>> bullet 4.
>> (3) "Ordering of Vector Arguments" should remove the example involving
>> homogeneous aggregates.
>>
> Done.
>
>> It also occurs to me that for bullets 4 and 5 in "Vector Length", the
>> CDT should be long long, not int, since we pass aggregates in pieces in
>> 64-bit registers and/or chunks of memory.
>>
> That determination of Vector Length is common for all architectures and is
> implemented in function simd_clone_compute_base_data_type. If we do really
> need PPC64 to be different, we'll have to allow the function to be replaced
> by architecture-specific versions. Before we do that, do you have
> an example of code which ends up with incorrect vectorization with the
> existing CDT of int?

No, and I'll withdraw the suggestion.  It seems rather arbitrary in any event.

Thanks for the updates!

Bill

>
>> Other small bugs:
>>   - Bullet 4 says "the CDT determine by a) or b) above", but the referents
>> should be "(1) or (2)" instead.
>>   - First line of "Compiler generated variants of vector functions" has
>> a typo ("umasked").
>>
> Done.
>
> The updated document is at:
> https://sourceware.org/glibc/wiki/HomePage?action=AttachFile&do=view&target=powerarchvectfuncabi.html