[FFmpeg-devel] [PATCH 0/5] Provide optimized neon implementation

[Martin Storsjö]

On Thu, 8 Sep 2022, Hubert Mazur wrote:

> Fix minor issues in the patches.
> Regarding vsse16 I didn't change saba & umlal to sub & smlal.
> It doesn't affect the performance, so left it as it was.
> The majority of changes refer to nsse16:
> - fixed indentation (thanks for pointing out),
> - applied the patch from Martin which fixes the balance
>   within instructions,
> - interleaved instructions - apparently this helped a little
>   to achieve better benchmarks.

Thanks! I measured a small further improvement on A53 with this change; 
from 377 to 370 cycles.

> I have also updated the benchmark results for each function -
> not a huge performance improvement, but worth the effort.
> For nsse and vsse are shown below (these are the biggest changes).
> - vsse16 asm from 64.7 to 59.2,
> - nsse16 asm from 120.0 to 116.5.

It's kinda surprising that the difference is so small, since we reduced 
the amount of work done in the functions quite significantly (IIRC on A53, 
the speedup was something like 1.5x compared with the original), but I 
guess it's understandable if the Graviton 3 is so powerful, that there's 
enough spare execution units so that a bunch of redundant instructions 
doesn't really matter.

Anyway, this revision of the patchset looked good to me, so I pushed it 
now. Thanks!

// Martin