[Bug math/21967] When 512-bit AVX2 wrapper functions in mathvec are used?

["hjl.tools at gmail dot com" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=21967

--- Comment #4 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Andrew Senkevich from comment #3)
> (In reply to H.J. Lu from comment #1)
> > avx2_wrapper is supposed to be used when AVX512F isn't profitable.  But
> > with
> > 
> >   if (CPU_FEATURES_ARCH_P (cpu_features, AVX512DQ_Usable))
> >     return OPTIMIZE (skx);
> > 
> >   if (CPU_FEATURES_ARCH_P (cpu_features, AVX512F_Usable))
> >     return OPTIMIZE (knl);
> > 
> > it is never used.  There is a Prefer_No_AVX512 bit in cpu_features.  But
> > we don't want to use it here since it will disable AVX512 mathvec on Skylake
> > server.  We need a separate bit to control AVX512 mathvec.
> 
> Do you think AVX512 mathvec functions on SKX should be wrappers to AVX2?

Not by default, but with a new ARCH bit.

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