[PATCH] x86: Add MathVec_Prefer_No_AVX512 to cpu-features [BZ #21967]

[Senkevich, Andrew]

> -----Original Message-----
> From: Lu, Hongjiu
> Sent: Friday, September 1, 2017 19:41
> To: GNU C Library <libc-alpha@sourceware.org>
> Cc: Senkevich, Andrew <andrew.senkevich@intel.com>
> Subject: [PATCH] x86: Add MathVec_Prefer_No_AVX512 to cpu-features [BZ
> #21967]
> 
> AVX512 functions in mathvec are used on machines with AVX512.  An AVX2
> wrapper is also provided and it can be used when the AVX512 version isn't
> profitable.  MathVec_Prefer_No_AVX512 is addded to cpu-features.
> If glibc.tune.hwcaps=MathVec_Prefer_No_AVX512 is set in GLIBC_TUNABLES
> environment variable, the AVX2 wrapper will be used.
> 
> Tested on x86-64 machines with and without AVX512.  Also verified
> glibc.tune.hwcaps=MathVec_Prefer_No_AVX512 on AVX512 machine.
> 
> Any comments?

But libc selects AVX2 mem/str on SKX, looks like libmvec should do the same (and backward option MathVec_Prefer_AVX512 needed).


--
Andrew