[Mesa-dev] [PATCH 3/7] nir: fix output offset compute for dvec3/4

[Jason Ekstrand]

On Thu, Nov 8, 2018 at 7:22 AM Alejandro Piñeiro <apinheiro at igalia.com>
wrote:

> The offset compute was working fine for the case of attrib_slots=1,
> and updating the offset for the following varying.
>
> But in the case of attrib_slots=2 (so dvec3/4), we are basically
> splitting the comp_slots needed in two outputs. In that case we can't
> add to the offset the full size of the type.
> ---
>  src/compiler/nir/nir_gather_xfb_info.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/src/compiler/nir/nir_gather_xfb_info.c
> b/src/compiler/nir/nir_gather_xfb_info.c
> index f5d831c6567..01fc2b26624 100644
> --- a/src/compiler/nir/nir_gather_xfb_info.c
> +++ b/src/compiler/nir/nir_gather_xfb_info.c
> @@ -81,7 +81,11 @@ add_var_xfb_outputs(nir_xfb_info *xfb,
>           output->component_mask = (comp_mask >> (s * 4)) & 0xf;
>
>           (*location)++;
> -         *offset += comp_slots * 4;
> +         /* attrib_slots would be only > 1 for doubles. On that case
> +          * comp_slots will be a multiple of 2, so the following doesn't
> need
> +          * to use DIV_ROUND_UP or similar
> +          */
> +         *offset += comp_slots / attrib_slots * 4;
>

Mind adding an assert(comp_slots % attrib_slots == 0)?  Also, can we make
that "(comp_slots / attrib_slots) * 4"?  I don't like thinking about
precedence at that detail.


>        }
>     }
>  }
> --
> 2.14.1
>
>
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