[FFmpeg-devel] [PATCH 0/9] DCA (DTS) decoder optimisations for ARMv6

Michael Niedermayer michaelni at gmx.at
Thu Jul 18 23:43:08 CEST 2013

Hi Ben

On Thu, Jul 18, 2013 at 08:59:53PM +0100, Ben Avison wrote:
> Hi Michael,
> On Wed, 17 Jul 2013 14:57:37 +0100, Michael Niedermayer wrote:
> >With this patch i get:
> [a series of build failures]
> In case you haven't noticed, Martin Storsjö has kindly taken it upon
> himself to fix the issues with building for Thumb, and has posted a
> series of updated patches over on the libav mailing list. Rather than
> duplicate the effort, I'd suggest having a go with his patches instead.


> >>Well, this is strange. Those both pass for me. The ones I'm having
> >>trouble with are
> >>
> >>fate-aac-al07_96
> >>fate-aac-al15_44
> >>fate-aac-aref-encode
> >>fate-aac-ln-encode
> >>
> >they pass with qemu
> At the moment, this is looking like it's mostly likely due to a bug in
> the kernel I'm running, so it's not worth worrying about this further.
> >>* perhaps qemu doesn't emulate short vectors?
> >>
> >>I have put together a quick test program below to see if short vectors
> >>are working. I would appreciate it if you could give it a quick try for
> >>me. It prints "Success" on my physical ARM11.
> >
> >segfaults:
> Looks like an ARM/Thumb interworking issue to me: CPSR indicates it's in
> Thumb mode and the backtrace address isn't 4-byte aligned, but the
> disassembly is clearly of ARM code ("bx lr" would have been a 16-bit
> instruction in Thumb mode, for a start). Try sticking a ".thumb" directive
> at the top of the assembly source file. (I'm a little surprised that
> GAS doesn't change the default instruction set to match the way GCC is
> configured, but I guess it is the way it is.)

adding .thumb makes it print "Success"

> Having said that, Martin reckons he's found the reason for the fate test
> failures you experienced as well, so it's now mainly of academic
> interest whether qemu supports short vectors or not. :)

We also have a qemu-arm fate client ...
and if it pointed to some bug in qemu it might have been interresting
to the qemu developers


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

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