flac dev - Jul 2022 - About SSE intrinsincs in decoder

You do not talk about the SSE 4.1 version in your bench.

Have you tried this use case ?

Thanks !

Le 04/07/2022 ? 19:23, Martijn van Beurden a ?crit?:
> Op ma 4 jul. 2022 om 15:06 schreef olivier tristan <o.tristan at
uvi.net>:
>
>     While I can understand the rationale for manual assembly as 32
>     bits x86
>     is dead, it seems a greater deal to remove all optimization including
>     intrinsic ones.
>
>
> Yes, it does seem a great deal to remove all optimization, but it 
> really isn't. See the pull request associated with that change for 
> more information: https://github.com/xiph/flac/pull/347 I did quite a 
> bit of testing before merging this change, on two different CPUs, each 
> with 3 different compilers, each with 4 variants of the 
> non-intrinsics-accelerated functions. It turns out that there is no 
> performance loss at all, and in many cases this change makes flac 
> actually faster, not slower as one would expect.
>
>     Maybe there should be a an opt in if you don't want to be included
by
>     default but some people including me don't want to see those
>     optimization been removed ?
>
>
> There would be no advantage of that over keeping the original code: it 
> still needs to be maintained and tested, even if it is hidden behind 
> some configuration option. The only case where this patch could be 
> problematic in terms of speed is when one compiles flac to be used on 
> CPUs that do not support SSE2.
-- 
Olivier Tristan
Research & Development
www.uvi.net
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Op di 5 jul. 2022 om 09:41 schreef olivier tristan <o.tristan at uvi.net>:
> You do not talk about the SSE 4.1 version in your bench.
>
> Have you tried this use case ?
>
I compared 4 compiles: one without any changes (so with all variants of the
lpc functions, including the SSE4.1 ones) and three with variants of plain
C code. As both CPUs that were tested had SSE4.1 capability, these
functions were compared with. So yes, current GCC outperforms those SSE4.1
intrinsics functions on 16-bit inputs and comes close on 24-bit inputs.
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