[FFmpeg-devel] [PATCH 1/5] Shrink the size of vp56_mv

[Reimar Döffinger]

On Tue, Jun 15, 2010 at 08:09:46PM +0100, M?ns Rullg?rd wrote:
> Reimar D?ffinger <Reimar.Doeffinger at gmx.de> writes:
> 
> > On Tue, Jun 15, 2010 at 04:58:14PM +0200, Aurelien Jacobs wrote:
> >> On Tue, Jun 15, 2010 at 09:02:14AM -0400, David Conrad wrote:
> >> > ---
> >> >  libavcodec/vp56.h |    4 ++--
> >> >  1 files changed, 2 insertions(+), 2 deletions(-)
> >> > 
> >> > diff --git a/libavcodec/vp56.h b/libavcodec/vp56.h
> >> > index 89eba05..3d98b9e 100644
> >> > --- a/libavcodec/vp56.h
> >> > +++ b/libavcodec/vp56.h
> >> > @@ -60,8 +60,8 @@ typedef struct {
> >> >  } VP56RefDc;
> >> >  
> >> >  struct vp56_mv {
> >> > -    int x;
> >> > -    int y;
> >> > +    int16_t x;
> >> > +    int16_t y;
> >> >  };
> >> 
> >> Looks OK. Apply if you're sure that it can't overflow.
> >
> > Hm, might make sense to benchmark a bit, it might be slower e.g.
> > if it means a lot of sign extension is added to the code...
> 
> What CPU can't load signed half-words from memory?

In addition to what Michael said:
That doesn't help if e.g. there's some code like
mv->x = ...(some int)
if (mv->x ...)
for which this change would result in useless sign extension.