[Mesa-dev] [PATCH 3/8] i965 gen6+: Use 1-wide null operands for IF instructions

[Eric Anholt]

On Wed, 14 Dec 2011 08:06:20 -0800, Paul Berry <stereotype441 at gmail.com> wrote:
> On 14 December 2011 02:33, Kenneth Graunke <kenneth at whitecape.org> wrote:
> > I think the point is that the ARF null register doesn't have a value, so
> > null<0,1,0> is just as good as null<4,4,1> or null<8,8,1>.  Either way
> > you get nothing and write nothing.  So width is irrelevant other than
> > dodging this assertion.
> >
> > If we weren't guessing execution size based on the register widths, I'd
> > prefer to just change the null reg to have width 1.  But since we do,
> > that would be a royal pain, and this is nice and simple.  I'm definitely
> > in favor of this patch.
> >
> 
> Agreed.  The whole "guessing execution size" thing has always troubled me,
> but I haven't thought of a good alternative.

Me too.
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