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RE: [PATCH] x86: Add MathVec_Prefer_No_AVX512 to cpu-features [BZ #21967]
- From: "Senkevich, Andrew" <andrew dot senkevich at intel dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>, GNU C Library <libc-alpha at sourceware dot org>
- Date: Mon, 4 Sep 2017 10:16:17 +0000
- Subject: RE: [PATCH] x86: Add MathVec_Prefer_No_AVX512 to cpu-features [BZ #21967]
- Authentication-results: sourceware.org; auth=none
- Dlp-product: dlpe-windows
- Dlp-reaction: no-action
- Dlp-version: 11.0.0.116
- References: <20170901174034.GA17543@gmail.com>
> -----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