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Re: [PATCH 1/N] x86_64 vectorization support: vectorized math functions addition to Glibc

On Thu, Sep 11, 2014 at 5:10 PM, Carlos O'Donell <> wrote:
> 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?

It depends on who are the main target users of this library.
If it is mainly for programmers to use them directly in their
applications, mostly independent of compilers, it should be
in glibc.  But if it is mainly used by GCC, it should be in
GCC, just like other run-time libraries.


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