[FFmpeg-devel] [PATCH] avcodec/x86/mathops: use constrained immediate operands

[Nicolas George]

James Almer (12023-07-15):
> Should fix assembling with binutil as >= 2.41
> 
> Signed-off-by: James Almer <jamrial at gmail.com>
> ---
> This is IMO a big breakage. binutil's as has until now clipped these values on
> its own, and never required the compiler to do it.

I confirm it fixes the build failures on up-to-date Debian testing.

OTOH, I ran a benchmark (decoding some x264):

474134     mod
488751 orig
494359     mod
498554 orig
508958 orig
514246 orig
518160     mod
528427 orig
530223     mod
534762     mod
536415 orig
548434 orig
550789 orig
551716     mod
553951 orig
561754 orig
572688     mod
580254     mod
581205 orig
583856     mod
583939 orig
584748 orig
594143 orig
600681     mod
607596     mod
612757     mod
621033 orig
624567 orig
626346     mod
627309     mod
628242     mod
638344     mod

The numbers are the sum of the “user” column of the -benchmark_all
output, on an AMD Ryzen 3 3200U and Debaian stable. The mod lines are
when I disabled the two faulty functions.

They are all over the place, it is hard to be sure, but it seems to
indicate that, as you suspected, the benefit is not that big.

Regards,

-- 
  Nicolas George
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