[Mesa-dev] [PATCH 2/6] i965: When gl_PointSize is unwritten, default to 1.0 on Gen4-5.

[Rafael Antognolli]

Reviewed-by: Rafael Antognolli <rafael.antognolli at intel.com>

On Wed, May 10, 2017 at 11:47:26AM -0700, Kenneth Graunke wrote:
> Modern GL specifications say that the point size should be 1.0 when
> gl_PointSize is unwritten and the last enabled stage is a geometry
> or tessellation shader.  If it's a vertex shader, though, both the
> GL specs and ES 3.0 spec say that it's undefined - so since Gen4-5
> only support vertex shaders, there's no actual requirement to do this.
> 
> Since there is a cost associated (an extra dirty bit, which may cause
> SF_STATE to be emitted more often), it may not be a good idea.
> 
> The real benefit is that it makes all generations behave identically.
> And that seems somewhat nice...
> ---
>  src/mesa/drivers/dri/i965/brw_sf_state.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/src/mesa/drivers/dri/i965/brw_sf_state.c b/src/mesa/drivers/dri/i965/brw_sf_state.c
> index ff6b5ebf79b..d5e586d1bf3 100644
> --- a/src/mesa/drivers/dri/i965/brw_sf_state.c
> +++ b/src/mesa/drivers/dri/i965/brw_sf_state.c
> @@ -263,9 +263,8 @@ static void upload_sf_unit( struct brw_context *brw )
>     point_sz = CLAMP(point_sz, 0.125f, 255.875f);
>     sf->sf7.point_size = U_FIXED(point_sz, 3);
>  
> -   /* _NEW_PROGRAM | _NEW_POINT */
> -   sf->sf7.use_point_size_state = !(ctx->VertexProgram.PointSizeEnabled ||
> -				    ctx->Point._Attenuated);
> +   /* _NEW_PROGRAM | _NEW_POINT, BRW_NEW_VUE_MAP_GEOM_OUT */
> +   sf->sf7.use_point_size_state = use_state_point_size(brw);
>     sf->sf7.aa_line_distance_mode = brw->is_g4x || brw->gen == 5;
>  
>     /* might be BRW_NEW_PRIMITIVE if we have to adjust pv for polygons:
> @@ -317,6 +316,7 @@ const struct brw_tracked_state brw_sf_unit = {
>                 BRW_NEW_PROGRAM_CACHE |
>                 BRW_NEW_SF_PROG_DATA |
>                 BRW_NEW_SF_VP |
> +               BRW_NEW_VUE_MAP_GEOM_OUT |
>                 BRW_NEW_URB_FENCE,
>     },
>     .emit = upload_sf_unit,
> -- 
> 2.12.2
> 
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