[Buildroot] [PATCH] gst-ffmpeg: work-around bogus configure logic on SPARC

[Peter Korsgaard <peter@korsgaard.com>]

>>>>> "Thomas" == Thomas Petazzoni <thomas.petazzoni@free-electrons.com> writes:

 > The libav version built into the gst-ffmpeg code produces a bogus
 > binary on SPARC, which causes the following error of the
 > check-bin-arch script:

 >   ERROR: architecture for ./usr/lib/gstreamer-0.10/libgstffmpeg.so is Sparc v8+, should be Sparc
 >   ERROR: architecture for ./usr/lib/gstreamer-0.10/libgstpostproc.so is Sparc v8+, should be Sparc
 >   ERROR: architecture for ./usr/lib/gstreamer-0.10/libgstffmpegscale.so is Sparc v8+, should be Sparc

 > The problem is the following bit of code in
 > gst-lib/ext/libav/configure:

 > elif enabled sparc; then

 >     enabled vis && check_asm vis '"pdist %f0, %f0, %f0"' -mcpu=ultrasparc &&
 >         add_cflags -mcpu=ultrasparc -mtune=ultrasparc

 > I.e, it checks if the architecture supports the pdist
 > instruction... but forces -mcpu to ultrasparc while doing so. So it's
 > like "let's see if this Ultrasparc instruction exists when I force the
 > compiler to think I'm using Ultrasparc", which is non-sensical. This
 > has been fixed later on in libav upstream:

 >   https://git.libav.org/?p=libav.git;a=commit;h=6aa93689abe8c095cec9fa828c2dee3131008995

 > However, this commit cannot be backported as-is since the shell
 > function check_inline_asm did not exist in the old libav version
 > bundled in gst-ffmpeg.

 > Therefore, we take the simpler route of disabling the VIS
 > optimizations on SPARCv8 and Leon3.

 > Fixes:

 >   http://autobuild.buildroot.net/results/e82d179c3d4f92ad7423693a4b1d42379a3f5411/

 > Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

I take these VIS instructions cause runtime errors with the older sparc
cores?

Committed to 2017.02.x, thanks.

-- 
Bye, Peter Korsgaard