[FFmpeg-devel] [PATCH] dnxhd_mmx: prefer xmm registers below xmm6 when they are available

Michael Niedermayer michaelni
Sun Oct 31 22:01:58 CET 2010

On Sun, Oct 31, 2010 at 04:34:04PM -0200, Ramiro Polla wrote:
> On Sat, Oct 30, 2010 at 6:23 PM, Reimar D?ffinger
> <Reimar.Doeffinger at gmx.de> wrote:
> > On Sat, Oct 30, 2010 at 05:40:50PM -0200, Ramiro Polla wrote:
> >> Instead of marking all xmm registers in the clobber list, some
> >> functions can use registers below xmm6, which makes it no longer an
> >> issue for win64. A few more patches like this one will follow.
> >
> > The reason for this is that at least some code just initialized
> > xmm7 to 0 and reused that over multiple asm blocks.
> > I guess there's not much point for it now anymore though.
> I think in these cases it's because people are so used to having xmm7
> as 0, that xmm7 was used even though other lower registers were
> available.

or more elaborate, (not about this code but in general) at least i tended to
use xmm7 and downward for constants and the others upward from 0 for the rest

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Asymptotically faster algorithms should always be preferred if you have
asymptotical amounts of data
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