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Re: [PATCH] Rename __memcmp_sse4_2 to __memcmp_sse4_1.


Do you mean AMD? For Intel there is no a machine without SSE4_1 where
sse2 unaligned version is faster than ssse3.

--
Liubov

On Fri, Jul 12, 2013 at 7:01 AM, OndÅej BÃlka <neleai@seznam.cz> wrote:
> On Thu, Jul 11, 2013 at 06:07:49PM +0400, Liubov Dmitrieva wrote:
>> My Silvermont patch in the latest edition doesn't touch memcmp and
>> wmemcmp at all because I didn't see good boost from switching SSE42
>> off for these 2 functions.
>> Now I see why. There are no SSE42 instruction there. :)
>> The patch looks good. I will just check performance regressions for Penryn.
>>
> Now question is if this is also good for other archs. An SSE 4.1 is not
> really needed, we can just replace ptest with pmovmskb test pair and
> performance will be nearly identical so it is worth checking if old
> cores benefit. (I see possible optimizations which I will send later.)
>
>> --
>> Liubov
>>
>> On Wed, Jul 10, 2013 at 10:23 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> > On Wed, Jul 10, 2013 at 11:19 AM, Matt Turner <mattst88@gmail.com> wrote:
>> >> On Wed, Jul 10, 2013 at 11:16 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> >>> On Wed, Jul 10, 2013 at 10:41 AM, Matt Turner <mattst88@gmail.com> wrote:
>> >>>> On Wed, Jul 10, 2013 at 8:30 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> >>>>> On Tue, Jul 9, 2013 at 9:37 PM, Andreas Jaeger <aj@suse.com> wrote:
>> >>>>>> On 07/10/2013 03:17 AM, Matt Turner wrote:
>> >>>>>>> It uses SSE 4.1 instructions (ptest) but no SSE 4.2 instructions.
>> >>>>>>
>> >>>>>> There are two parts to this: It should only run on cpus with those
>> >>>>>> instructions but we also need to ensure that it gives a better
>> >>>>>> performance on such cpus. HJ, Matt, please do run performance tests on a
>> >>>>>> variety of affected cpus to show that this change really helps in all cases,
>> >>>>>>
>> >>>>>> Andreas
>> >>>>>
>> >>>>> Only Penryn has SSE4.1 without SSE4.2.  Liubov, can
>> >>>>> you compare performance of memcmp-sse4.S vs
>> >>>>> memcmp-ssse3.S on Penryn?
>> >>>>
>> >>>> Is it also the case that this path would now be used on Silvermont?
>> >>>
>> >>> It is used on Silvermont since it supports SSE4.2
>> >>>
>> >>> --
>> >>> H.J.
>> >>
>> >> To confirm, setting bit_Slow_SSE4_2 on Silvermont (which we do)
>> >> wouldn't prevent this path from executing?
>> >
>> > I don't think so.  Liubov, can you verify it?
>> >
>> > --
>> > H.J.
>
> --
>
> The cord jumped over and hit the power switch.


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