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Re: [PATCH] x86-64: Add sinf with FMA

From: Arjan van de Ven <arjan at linux dot intel dot com>
To: Nick Alcock <nix at esperi dot org dot uk>, "H.J. Lu" <hongjiu dot lu at intel dot com>
Cc: GNU C Library <libc-alpha at sourceware dot org>, "H.J. Lu" <hjl dot tools at gmail dot com>
Date: Fri, 8 Dec 2017 08:04:25 -0800
Subject: Re: [PATCH] x86-64: Add sinf with FMA
Authentication-results: sourceware.org; auth=none
References: <20171204180905.GA31592@gmail.com> <87a7yt5ht6.fsf@esperi.org.uk>

On 12/8/2017 8:02 AM, Nick Alcock wrote:

On 4 Dec 2017, H. J. Lu uttered the following:

On Skylake, bench-sinf reports performance improvement:

             Before        After         Improvement
max        153.996       100.094           54%
min        8.546         6.852             25%
mean       18.1223       14.4616           25%

Any comments?


Do we have any benchmark runs on older processors? They're not remotely
obsolete: Intel is still selling Broadwell server parts, and the vast
majority of SSE2-capable parts out there at present are not as new as
Skylake.

Are we penalizing them? (I'd guess not, but it would be nice to know.)


this is just adding another IFUNC for FMA capable CPUs.. the older CPUs
will keep using the code that they are running today....
so no they're not being penalized.

References:
- [PATCH] x86-64: Add sinf with FMA
  - From: H.J. Lu
- Re: [PATCH] x86-64: Add sinf with FMA
  - From: Nick Alcock

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