Re: [FFmpeg-devel] [PATCH] libswscale/x86/yuv2rgb: Add missing EMMS

[Michael Niedermayer <michael@niedermayer.cc>]

[-- Attachment #1.1: Type: text/plain, Size: 1752 bytes --]

On Tue, Jun 11, 2024 at 05:19:06PM +0000, Mario Hros wrote:
> Ping?
> 
> Not including EMMS causes the FPU to become unusable (as the IE and SF bits are set in the status word). This breaks code which, for instance, calls fmod() and is compiled by GCC with the -O3 flag enabled. In that scenario, GCC implements fmod using the FPREM FPU instruction, but because FPU is in the invalid state at that point, the result is NaN.
> 
> This must to breaking other code using FPU also. The original code with inline assembly used EMMS at the end.
> ________________________________
> From: Mario Hros <k3x-devel@outlook.com>
> Sent: Wednesday, June 5, 2024 7:35 PM
> To: ffmpeg-devel@ffmpeg.org <ffmpeg-devel@ffmpeg.org>
> Cc: Mario Hros <k3x-devel@outlook.com>
> Subject: [PATCH] libswscale/x86/yuv2rgb: Add missing EMMS
> 
> Previous rewrite from inline assembly into nasm (commit e934194) missed the required EMMS instruction to bring the x87 FPU back into usable state.
> 
> Signed-off-by: Mario Hros <k3x-devel@outlook.com>
> ---
>  libswscale/x86/yuv_2_rgb.asm | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/libswscale/x86/yuv_2_rgb.asm b/libswscale/x86/yuv_2_rgb.asm
> index e3470fd9ad..7a247797e4 100644
> --- a/libswscale/x86/yuv_2_rgb.asm
> +++ b/libswscale/x86/yuv_2_rgb.asm
> @@ -353,6 +353,7 @@ cglobal %1_420_%2%3, GPR_num, GPR_num, reg_num, parameters
>  add imageq, 8 * depth * time_num
>  add indexq, 4 * time_num
>  js .loop0
> +emms
> 

this feels like its missing a
    %if mmsize == 8

thx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Those who are too smart to engage in politics are punished by being
governed by those who are dumber. -- Plato 

[-- Attachment #1.2: signature.asc --]
[-- Type: application/pgp-signature, Size: 195 bytes --]

[-- Attachment #2: Type: text/plain, Size: 251 bytes --]

_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel

To unsubscribe, visit link above, or email
ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".