[PATCH] shadow: Optimize shadowUpdatePacked(). (#26973)

[Adam Jackson]

On Tue, 2010-09-21 at 10:29 -0400, Matt Turner wrote:
> On Sat, Sep 11, 2010 at 5:55 PM, Matt Turner <mattst88 at gmail.com> wrote:
> > diff --git a/miext/shadow/shpacked.c b/miext/shadow/shpacked.c
> > index 20d2ea1..06606bc 100644
> > --- a/miext/shadow/shpacked.c
> > +++ b/miext/shadow/shpacked.c
> > @@ -102,8 +102,8 @@ shadowUpdatePacked (ScreenPtr           pScreen,
> >                width -= i;
> >                scr += i;
> >  #define PickBit(a,i)   (((a) >> (i)) & 1)
> > -               while (i--)
> > -                   *win++ = *sha++;
> > +               memcpy(win, sha, i * sizeof(FbBits));
> > +               sha += i;
> >            }
> >            shaLine += shaStride;
> >            y++;
> > --
> > 1.7.1
> 
> So, do we want this patch?
> 
> It seems like it does deobfuscate the code a bit, and memcpy is going
> to be more efficient than byte-by-byte copies.

I think this is okay as long as we have the invariant that the shadow
and the shadowed are not allowed to have aliased storage.  Which seems
entirely reasonable, so, yeah, we should take this.

In related news, we never fixed this:

http://lists.freedesktop.org/archives/xorg/2010-February/049026.html

- ajax
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