[Mesa-dev] [PATCH 05/18] glsl: Fail to link if inter-stage input/outputs are not assigned to stream 0

[Iago Toral]

It may be a bit less confusing to read if I take the inner if out, so
I'll rewrite it like this:

if (input_var || (prog->SeparateShader && consumer == NULL)) {
   matches.record(output_var, input_var);
}

if (input_var && output_var->data.streamId != 0) {
   linker_error(prog, ...);
   return false;
}

On Thu, 2014-06-12 at 07:43 +1200, Chris Forbes wrote:
> I had misread it -- yes, this looks correct.
> 
> On Thu, Jun 12, 2014 at 12:02 AM, Iago Toral <itoral at igalia.com> wrote:
> > I am a bit confused here:
> >
> > Reading the code it looks like input_var should be NULL if there is no
> > consumer stage. In that case, if this is a separable program and there
> > is no consumer, then input_var must be NULL too, in which case the
> > linker_error would never take place.
> >
> > If input_var is not NULL then there has to be a consumer stage, and in
> > that case we should check that we can link both stages, right?
> >
> > Iago
> >
> > On Wed, 2014-06-11 at 20:48 +1200, Chris Forbes wrote:
> >> This would appear to prohibit the use of multiple streams in separable
> >> programs entirely. I don't think that's the right thing.
> >>
> >> On Wed, Jun 11, 2014 at 7:49 PM, Iago Toral Quiroga <itoral at igalia.com> wrote:
> >> > Outputs that are linked to inputs in the next stage must be output to stream 0,
> >> > otherwise we should fail to link.
> >> > ---
> >> >  src/glsl/link_varyings.cpp | 7 +++++++
> >> >  1 file changed, 7 insertions(+)
> >> >
> >> > diff --git a/src/glsl/link_varyings.cpp b/src/glsl/link_varyings.cpp
> >> > index 9883c0b..0066b4e 100644
> >> > --- a/src/glsl/link_varyings.cpp
> >> > +++ b/src/glsl/link_varyings.cpp
> >> > @@ -1343,6 +1343,13 @@ assign_varying_locations(struct gl_context *ctx,
> >> >            * consumer stage, add the output.
> >> >            */
> >> >           if (input_var || (prog->SeparateShader && consumer == NULL)) {
> >> > +            /* Only stream 0 outputs can be consumed in the next stage */
> >> > +            if (input_var && output_var->data.streamId != 0) {
> >> > +               linker_error(prog, "output %s is assigned to stream=%d but "
> >> > +                            "is linked to an input, which requires stream=0",
> >> > +                            output_var->name, output_var->data.streamId);
> >> > +               return false;
> >> > +            }
> >> >              matches.record(output_var, input_var);
> >> >           }
> >> >        }
> >> > --
> >> > 1.9.1
> >> >
> >> > _______________________________________________
> >> > mesa-dev mailing list
> >> > mesa-dev at lists.freedesktop.org
> >> > http://lists.freedesktop.org/mailman/listinfo/mesa-dev
> >>
> >
> >
>