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Subject: Re: [PATCH] x86-64: Add sinf with FMA
To: Nick Alcock <nix@esperi.org.uk>, "H.J. Lu" <hongjiu.lu@intel.com>
Cc: GNU C Library <libc-alpha@sourceware.org>, "H.J. Lu" <hjl.tools@gmail.com>
References: <20171204180905.GA31592@gmail.com> <87a7yt5ht6.fsf@esperi.org.uk>
From: Arjan van de Ven <arjan@linux.intel.com>
Message-ID: <8bcc88f1-e9d4-7c94-93ee-93a5ab7c4fa1@linux.intel.com>
Date: Fri, 08 Dec 2017 16:04:00 -0000
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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.