[Mesa-dev] Mesa (master): draw: fix flat shading and screen-space linear interpolation in clipper

[Jose Fonseca]

----- Original Message -----
> On Tue, Jul 10, 2012 at 3:30 PM, Jose Fonseca <jfonseca at vmware.com>
> wrote:
> > Yep. The interfaces are busted.
> >
> > Without native integers we get
> >
> >    DCL SV[0], INSTANCEID
> >    ...
> >    ARL ADDR[0].x, SV[0].xxxx
> >
> > and with integers we get
> >
> >    DCL SV[0], INSTANCEID
> >    ...
> >    UARL ADDR[0].x, SV[0].xxxx
> >
> > Olivier's fix is incorrect. It works on the above cases by guessing
> > the type, but if we have:
> >
> >    DCL SV[0], INSTANCEID
> >    ...
> >    MOV TEMP[0].x, SV[0].xxxx
> >    ARL ADDR[0].x, TEMP[0].xxxx
> >
> > and
> >
> >    DCL SV[0], INSTANCEID
> >    ...
> >    MOV TEMP[0].x, SV[0].xxxx
> >    UARL ADDR[0].x, TEMP[0].xxxx
> >
> > it is impossible to guess -- the change is merely replacing a bug
> > with another.
> >
> >
> > For the record, the problem also happens without LLVM:
> >
> >   DRAW_USE_LLVM=0 draw-instanced -auto
> >
> >
> >
> > Anyway, AFAICT, all hardware out there that really supports
> > INSTANCEID/VERTEXID also supports native integers, so this is a
> > problem specific to the draw module.
> >
> > But given that draw module can support anything, this is actually
> > self inflicted! In short, INSTANCEID/VERTEXID without integers is
> > an historic artifact, that should not exist going forward.
> >
> > The right fix is merely making sure that PIPE_SHADER_CAP_INTEGERS
> > is accurately advertised as 1 by the draw module (just like
> > Stephane secretly did in 45fc069600ddbfe07a0a0cd5280161a8c7c55dd0
> > :)
> 
> I just wanted to tell you Stephane's change cannot work and it even
> has no effect at the moment. The native integer support is global in
> core Mesa. It's because integer uniforms are converted to floats
> based
> on the global NativeInteger flag for all shader stages and that can't
> be fixed easily, because uniforms can be shared between shaders.
> Basically, all drivers must advertise integer support either for all
> shader stages or none.

I see..
 
> Given that, I only see two possible outcomes:
> 
> 1) Disable INSTANCEID support in DX9-level drivers using Draw (that's
> only i915g AFAIK) and only support INSTANCEID with integers.

> 2) Let drivers set the type of system values in Draw, so that Draw
> doesn't have to guess what it should be.

My issue with 2) with this is that TGSI semantics depend on an external state. I think this is ugly and confusing.

If Stephane's OK with 1), I'd prefer taking it.

Jose