[x265] [PATCH 2 of 3] improve duplicate MV check by reduce condition jump

[Deepthi Nandakumar]

Hmm, but arent the benefits very compiler dependent? Since this isnt the
innermost loop, is the readability loss worth it?
On Jun 29, 2015 9:27 PM, "Steve Borho" <steve at borho.org> wrote:

> It is avoiding the C short-circuit logic that is necessary for &&. With
> & the compiler does not have to perform early-out jumps for each
> condition. Instead it does all the & operations then does a single
> conditional jump.
>
> It can often be faster, but you have to take a lot of care that the
> & does the right thing.
>
> On 06/29, Deepthi Nandakumar wrote:
> > Hi,
> >
> > How does this improve the generated asm code/cycles taken?
> >
> > On Sat, Jun 27, 2015 at 7:43 AM, Min Chen <chenm003 at 163.com> wrote:
> >
> > > # HG changeset patch
> > > # User Min Chen <chenm003 at 163.com>
> > > # Date 1435370055 25200
> > > # Node ID a8198965fbf18d7ced2cd8e8acd07fcc4ee6a2b3
> > > # Parent  229602ba850eb11c171d8c3cbb049dda4b41abda
> > > improve duplicate MV check by reduce condition jump
> > > ---
> > >  source/encoder/motion.cpp |    4 ++--
> > >  1 files changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff -r 229602ba850e -r a8198965fbf1 source/encoder/motion.cpp
> > > --- a/source/encoder/motion.cpp Fri Jun 26 18:54:13 2015 -0700
> > > +++ b/source/encoder/motion.cpp Fri Jun 26 18:54:15 2015 -0700
> > > @@ -645,7 +645,7 @@
> > >          for (int i = 0; i < numCandidates; i++)
> > >          {
> > >              MV m = mvc[i].clipped(qmvmin, qmvmax);
> > > -            if (m.notZero() && m != pmv && m != bestpre) // check
> already
> > > measured
> > > +            if (m.notZero() & (m != pmv ? 1 : 0) & (m != bestpre ? 1 :
> > > 0)) // check already measured
> > >              {
> > >                  int cost = ref->lowresQPelCost(fenc, blockOffset, m,
> sad)
> > > + mvcost(m);
> > >                  if (cost < bprecost)
> > > @@ -661,7 +661,7 @@
> > >          for (int i = 0; i < numCandidates; i++)
> > >          {
> > >              MV m = mvc[i].clipped(qmvmin, qmvmax);
> > > -            if (m.notZero() && m != pmv && m != bestpre) // check
> already
> > > measured
> > > +            if (m.notZero() & (m != pmv ? 1 : 0) & (m != bestpre ? 1 :
> > > 0)) // check already measured
> > >              {
> > >                  int cost = subpelCompare(ref, m, sad) + mvcost(m);
> > >                  if (cost < bprecost)
> > >
> > > _______________________________________________
> > > x265-devel mailing list
> > > x265-devel at videolan.org
> > > https://mailman.videolan.org/listinfo/x265-devel
> > >
>
> > _______________________________________________
> > x265-devel mailing list
> > x265-devel at videolan.org
> > https://mailman.videolan.org/listinfo/x265-devel
>
>
> --
> Steve Borho
> _______________________________________________
> x265-devel mailing list
> x265-devel at videolan.org
> https://mailman.videolan.org/listinfo/x265-devel
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.videolan.org/pipermail/x265-devel/attachments/20150629/0f4f3c9b/attachment-0001.html>