[Mesa-dev] [PATCH] anv: Restrict the nuber of color regions to those actually written

[Jason Ekstrand]

On Thu, Jul 5, 2018 at 6:34 PM Caio Marcelo de Oliveira Filho <
caio.oliveira at intel.com> wrote:

> On Wed, Jun 27, 2018 at 07:00:56PM -0700, Jason Ekstrand wrote:
> > The back-end compiler emits the number of color writes specified by
> > wm_prog_key::nr_color_regions regardless of what nir_store_outputs we
> > have.  Once we've gone through and figured out which render targets
> > actually exist and are written by the shader, we should restrict the key
> > to avoid extra RT write messages.
> > ---
> >  src/intel/vulkan/anv_pipeline.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/src/intel/vulkan/anv_pipeline.c
> b/src/intel/vulkan/anv_pipeline.c
> > index 523202cf3d9..6a27d305dbc 100644
> > --- a/src/intel/vulkan/anv_pipeline.c
> > +++ b/src/intel/vulkan/anv_pipeline.c
> > @@ -965,6 +965,11 @@ anv_pipeline_compile_fs(struct anv_pipeline
> *pipeline,
> >           var->data.location = rt_to_bindings[rt] + FRAG_RESULT_DATA0;
> >        }
> >
> > +      /* Now that we've determined the actual number of render targets,
> adjust
> > +       * the key accordingly.
> > +       */
> > +      key.nr_color_regions = num_rts;
> > +
>
> Question: earlier in the code we call
>
>    populate_wm_prog_key(pipeline, info, &key);
>
> which does
>
>    key->nr_color_regions = pipeline->subpass->color_count;
>
>    key->replicate_alpha = key->nr_color_regions > 1 &&
>                           info->pMultisampleState &&
>                           info->pMultisampleState->alphaToCoverageEnable;
>
> so key->replicate_alpha is calculated based on the old value. Should
> this be (re)calculated using the new value?
>

We could but it would have no effect.  100% of the uses of replicate_alpha
in the back-end have it ANDed with inst->target > 0.

--Jason
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