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Re: [PATCH][Aarch64] Fix vec_perm cost for thunderx2t99
- From: Kyrylo Tkachov <Kyrylo dot Tkachov at arm dot com>
- To: Anton Youdkevitch <anton dot youdkevitch at bell-sw dot com>, Andrew Pinski <pinskia at gmail dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Tue, 5 Nov 2019 12:09:24 +0000
- Subject: Re: [PATCH][Aarch64] Fix vec_perm cost for thunderx2t99
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- References: <20191101140242.GA7200@bell-sw.com> <CA+=Sn1=bxU_+b+U+00rX7NK83Wd2rUxON3XFL5+ZUdY-8Y_85Q@mail.gmail.com> <7aacefa1-461b-45b4-bfbc-09171745825e@arm.com> <54be3456-1750-aba4-2aac-0b458bf0deb2@bell-sw.com>
On 11/5/19 11:54 AM, Anton Youdkevitch wrote:
Kyrill,
On 05.11.2019 14:43, Kyrylo Tkachov wrote:
> Hi Andrew, Anton,
>
> On 11/1/19 11:22 PM, Andrew Pinski wrote:
>> On Fri, Nov 1, 2019 at 7:03 AM Anton Youdkevitch
>> <anton.youdkevitch@bell-sw.com><mailto:anton.youdkevitch@bell-sw.com> wrote:
>>>
>>> Hello,
>>>
>>> Here is the one-liner that fixes the incorrect
>>> vec_perm cost for thunderx2t99 chip.
>>> With the patch applied 526.blender of CPU2017
>>> gets ~5% improvement with no measurable changes
>>> for other benchmarks.
>>>
>>> Bootstrapped OK on aarch64-linux-gnu.
>>>
>>> OK for trunk?
>>
>> Maybe the big question is vec_perm used for both 1 input and 2 input
>> cases? If so maybe splitting the two cases would be important too.
>> Otherwise this is ok from my point of view but I can't approve it.
>>
> I'd be interested to see a testcase/demonstration where this would would
> be beneficial.
Well, since I measured this on SPEC 2017, so, the result is
the overall benchmark score. I can try to extract the relevant
pieces of code that get compiled differently to see if they can
be make into a standalone testcase. I didn't try this yet, though.
Sorry, I was referring to Andrew's suggestion about splitting the costs rather than your change.
>
> In the meantime this patch is ok if it helps thunderx2t99 performance.
>
> 2019-11-01 Anton Youdkevitch <anton.youdkevitch@bell-sw.com><mailto:anton.youdkevitch@bell-sw.com>
>
> * gcc/config/aarch64/aarch64.c (thunderx2t99_vector_cost):
> change vec_perm field
>
> ChangeLog nits:
>
> * Two spaces between name and date+email
>
> * No gcc/ prefix as the relevant ChangeLog file lives in gcc/
>
> * End entry with full stop.
Thanks, will do like this next time.
>
> Anton, do you need someone to commit this for you?
Yes, it would be nice if you can do this for me.
Committed as r277826 with the following adjusted ChangeLog:
2019-11-05 Anton Youdkevitch <anton.youdkevitch@bell-sw.com><mailto:anton.youdkevitch@bell-sw.com>
* config/aarch64/aarch64.c (thunderx2t99_vector_cost):
Change vec_perm field to 10.
Thanks for the patch. If you intend to make more contributions in the future it would be worth sorting a copyright assignment if you haven't done so already.
Kyrill
>
> Thanks,
>
> Kyrill
>
>
>
>>
>> Thanks,
>> Andrew Pinski
>>
>>>
>>> 2019-11-01 Anton Youdkevitch <anton.youdkevitch@bell-sw.com><mailto:anton.youdkevitch@bell-sw.com>
>>>
>>> * gcc/config/aarch64/aarch64.c (thunderx2t99_vector_cost):
>>> change vec_perm field
>>>
>>> --
>>> Thanks,
>>> Anton