[vlc-devel] [vlc-commits] contrib: ffmpeg: add some cflags for arm/neon

[Rémi Denis-Courmont]

Le dimanche 27 novembre 2011 11:18:59 Rafaël Carré, vous avez écrit :
> vlc | branch: master | Rafaël Carré <funman at videolan.org> | Sun Nov 27
> 04:07:19 2011 -0500| [f625f16aa49ce21aec65f02993e02213a6ab31f6] |
> committer: Rafaël Carré
> 
> contrib: ffmpeg: add some cflags for arm/neon
> 
> > http://git.videolan.org/gitweb.cgi/vlc.git/?a=commit;h=f625f16aa49ce21aec
> > 65f02993e02213a6ab31f6
> 
> ---
> 
>  contrib/src/ffmpeg/rules.mak |    6 +++++-
>  1 files changed, 5 insertions(+), 1 deletions(-)
> 
> diff --git a/contrib/src/ffmpeg/rules.mak b/contrib/src/ffmpeg/rules.mak
> index 7622360..a4ca133 100644
> --- a/contrib/src/ffmpeg/rules.mak
> +++ b/contrib/src/ffmpeg/rules.mak
> @@ -43,7 +43,11 @@ endif
> 
>  # ARM stuff
>  ifeq ($(ARCH),arm)
> -FFMPEGCONF += --disable-runtime-cpudetect
> +FFMPEGCONF += --disable-runtime-cpudetect --arch=arm

This is pointless. FFmpeg can detect the architecture. If it did not, there 
would be no point in disabling run-time detection in the first place.

> +ifdef HAVE_NEON
> +FFMPEGCONF += --cpu=cortex-a8 --enable-neon

There are no reasons to hard-code the CPU. There are Cortex-A9 and proprietary 
variants from ARM licensees too, and more are coming. Same goes for FPU.

If you want to do this, set up your toolchain defaults correctly. Or then set 
CFLAGS globally.

> +FFMPEG_CFLAGS +=-mfloat-abi=softfp -mfpu=neon

This will break systems using the VFP enhanced ABI. You should never change 
the float ABI. This belongs in the toolchain defaults. Otherwise, your 
binaries will not interoperate.

> +endif

Basically, I don't see any value in this commit.

-- 
Rémi Denis-Courmont
http://www.remlab.net/
http://fi.linkedin.com/in/remidenis