Re: [FFmpeg-devel] [PATCH 1/2] x86: Don't hardcode the height to 8 in sad8_xy2_mmx

[Michael Niedermayer <michael@niedermayer.cc>]

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On Thu, Aug 04, 2022 at 10:47:34AM +0300, Martin Storsjö wrote:
> On Wed, 13 Jul 2022, Martin Storsjö wrote:
> 
> > The height is hardcoded in some of the me_cmp functions, but not
> > in all of them. But in the case of all other functions, it's hardcoded
> > in the same place in SIMD functions as in the C reference functions,
> > while this one function differs from the behaviour of the C code.
> > 
> > (Before 542765ce3eccbca587d54262a512cbdb1407230d, there were a
> > couple other sad8_*_mmx functions with similar hardcoded height.)
> > ---
> > libavcodec/x86/me_cmp_init.c | 3 +--
> > 1 file changed, 1 insertion(+), 2 deletions(-)
> > 
> > diff --git a/libavcodec/x86/me_cmp_init.c b/libavcodec/x86/me_cmp_init.c
> > index 61e9396b8f..dcc2621276 100644
> > --- a/libavcodec/x86/me_cmp_init.c
> > +++ b/libavcodec/x86/me_cmp_init.c
> > @@ -202,13 +202,12 @@ static inline int sum_mmx(void)
> > static int sad8_xy2_ ## suf(MpegEncContext *v, uint8_t *blk2,           \
> >                             uint8_t *blk1, ptrdiff_t stride, int h)     \
> > {                                                                       \
> > -    av_assert2(h == 8);                                                     \
> >     __asm__ volatile (                                                  \
> >         "pxor %%mm7, %%mm7     \n\t"                                    \
> >         "pxor %%mm6, %%mm6     \n\t"                                    \
> >         ::);                                                            \
> >                                                                         \
> > -    sad8_4_ ## suf(blk1, blk2, stride, 8);                              \
> > +    sad8_4_ ## suf(blk1, blk2, stride, h);                              \
> >                                                                         \
> >     return sum_ ## suf();                                               \
> > }                                                                       \
> > -- 
> > 2.25.1
> 
> Ping, does this seem reasonable? Michael indicated a desire to make the
> me_cmp functions more general and flexible than what they are today, and
> this would be a first step to making checkasm test such cases.

LGTM assuming it doesnt have any problematic perforamce impact

thx

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

Frequently ignored answer#1 FFmpeg bugs should be sent to our bugtracker. User
questions about the command line tools should be sent to the ffmpeg-user ML.
And questions about how to use libav* should be sent to the libav-user ML.

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