On Tue, May 12, 2020 at 10:04:13PM +0300, Martin Storsjö wrote: > On Tue, 12 May 2020, Michael Niedermayer wrote: > > >On Tue, May 12, 2020 at 11:25:34AM +0300, Martin Storsjö wrote: > >>Use this in vf_spp.c, where the get_pixels operation is done on > >>unaligned source addresses. > >> > >>This fixes fate-filter-spp on armv7. > > > >LGTM > > > > > >>--- > >>People more familiar with the other assembly implementations of > >>get_pixels (in particular, x86) can hook them up to > >>get_pixels_unaligned if unaligned use explicitly is ok; as far as I > >>can read at least ff_get_pixels_mmx, it looks like it expects the source > >>to be aligned, but in practice it does seem to run fine even if > >>ff_get_pixels_sse2 is disabled. > >>--- > > > >id suggest that code that has been tested with unaligned data and works > >is enabled > > Well ff_get_pixels_mmx uses "mova", which I'd presume is "aligned", but it > still doesn't seem to crash when used with vf_spp today, even if that one > uses it on unaligned addresses. So I'm not sure if I'm just being lucky, or > is it guaranteed that this "mova" always will work on unaligned addresses? > > As someone who doesn't do much x86 asm, I wouldn't base such an assignment > just on "it seems to work for me".
you can look at libavutil/x86/x86inc.asm
for mmx both mova and movu are mapped to the same instruction
%define mova movq
%define movu movq
Also there is intels instruction set reference that should document alignment
requirements but that doesnt seem to
document alignment requirements in a way that i can easily find from
starting with a random instruction name
but likely someone reading has a link to nice short / table / summary of
alignment requirements
thx
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
Dictatorship: All citizens are under surveillance, all their steps and
actions recorded, for the politicians to enforce control.
Democracy: All politicians are under surveillance, all their steps and
actions recorded, for the citizens to enforce control.
signature.asc
Description: PGP signature
_______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
