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Re: [PATCH 1/N] x86_64 vectorization support: vectorized math functions addition to Glibc
- From: "Carlos O'Donell" <carlos at redhat dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>, "Joseph S. Myers" <joseph at codesourcery dot com>
- Cc: "Zamyatin, Igor" <igor dot zamyatin at intel dot com>, Andrew Senkevich <andrew dot n dot senkevich at gmail dot com>, libc-alpha <libc-alpha at sourceware dot org>, "Melik-Adamyan, Areg" <areg dot melik-adamyan at intel dot com>, "jakub at redhat dot com" <jakub at redhat dot com>
- Date: Thu, 11 Sep 2014 20:10:15 -0400
- Subject: Re: [PATCH 1/N] x86_64 vectorization support: vectorized math functions addition to Glibc
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On 09/11/2014 04:57 PM, H.J. Lu wrote:
>> That doesn't answer my question. Maybe glibc 2.21 provides such versions
>> for all x86 ISAs there are at present, up to AVX512 - and then a new
>> extension AVX1024 appears. When GCC 7 is used with glibc 2.21 headers and
>> -mavx1024, it must not try to generate calls to the AVX1024 functions,
>> because glibc 2.21 doesn't have such functions. But maybe glibc 2.26 adds
>> the AVX1024 functions. So something needs to be different in the headers
>> of 2.26 to inform GCC 7 that AVX1024 versions of the functions are
>> available. And I think that means the directive that communicates
>> function availability to the compiler needs to identify the set of ISAs
>> for which versions of the function in question are available.
> Wouldn't it be better to put libmvec in GCC instead?
That's certainly a discussion we can have.
What do you see as the pros and cons?