[x264-devel] NOTE: Altivec/PPC port is broken [PATCH2]

[Guillaume POIRIER]

Hello,

2008/3/21 <maaanuuu at gmx.net>:
> Hello,
>
> Here's a patch that fixes hpel_filter_altivec, although I don't know
> whether this is a correct way to fix it.

Me neither. I've looked at the patch a bit and can't figure out for
the moment why this change is needed. As you said previously, in
practice the original code produces the right output. It must break on
some extreme cases...

> Now all variables used by
> HPEL_CENTRAL_FILTER are set before using them.

That indeed seems reasonable to set variables before using them.
However, I yet can't figure out myself which part of the original C
code tells that these variables must be setup in the way you did in
your patch; why can't they just be set to zero? etc...

> Checkasm doesn't report any errors.

Confirmed here.

> There is just some code duplication in it, is that OK?

For now, I don't mind code duplication. I want to be convinced it's
the right fix :-(

BTW, I found the commit that "triggered" the problem. It's the
AMD64+i364 asm merge patch that allowed to see the problem, since that
patch added a test for hpel.

Guillaume
-- 
A soldier will fight long and hard for a bit of colored ribbon.
 -- Napoleon Bonaparte