[Mesa-dev] [PATCH 3/5] glsl: Mark gl_ViewportIndex and gl_Layer varyings as flat.

[Ilia Mirkin]

On Mon, Oct 26, 2015 at 2:03 PM, Kenneth Graunke <kenneth at whitecape.org> wrote:
> Integer varyings need to be flat qualified - all others were already.
> I think we just missed this.  Presumably some hardware passes this via
> sideband and ignores attribute interpolation, so no one has noticed.
>
> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
> Cc: Chris Forbes <chrisf at ijw.co.nz>
> ---
>  src/glsl/builtin_variables.cpp | 39 ++++++++++++++++++++++++++-------------
>  1 file changed, 26 insertions(+), 13 deletions(-)
>
> diff --git a/src/glsl/builtin_variables.cpp b/src/glsl/builtin_variables.cpp
> index a6ad105..07aacd4 100644
> --- a/src/glsl/builtin_variables.cpp
> +++ b/src/glsl/builtin_variables.cpp
> @@ -887,16 +887,22 @@ builtin_variable_generator::generate_uniforms()
>  void
>  builtin_variable_generator::generate_vs_special_vars()
>  {
> +   ir_variable *var;
> +
>     if (state->is_version(130, 300))
>        add_system_value(SYSTEM_VALUE_VERTEX_ID, int_t, "gl_VertexID");
>     if (state->ARB_draw_instanced_enable)
>        add_system_value(SYSTEM_VALUE_INSTANCE_ID, int_t, "gl_InstanceIDARB");
>     if (state->ARB_draw_instanced_enable || state->is_version(140, 300))
>        add_system_value(SYSTEM_VALUE_INSTANCE_ID, int_t, "gl_InstanceID");
> -   if (state->AMD_vertex_shader_layer_enable)
> -      add_output(VARYING_SLOT_LAYER, int_t, "gl_Layer");
> -   if (state->AMD_vertex_shader_viewport_index_enable)
> -      add_output(VARYING_SLOT_VIEWPORT, int_t, "gl_ViewportIndex");
> +   if (state->AMD_vertex_shader_layer_enable) {
> +      var = add_output(VARYING_SLOT_LAYER, int_t, "gl_Layer");
> +      var->data.interpolation = INTERP_QUALIFIER_FLAT;

Not that I *strongly* prefer this, but what we'd do in nouveau/codegen
code (and is IMHO more concise):

add_output(VARYING_SLOT_LAYER, int_t, "gl_Layer")
   ->data.interpolation = INTERP_QUALIFIER_FLAT;

Alternatively, you could just solve this in add_output which should
automatically set the flat interpolation for int types...

FTR I don't strongly prefer either of the above to your solution, just
wanted to point out some alternatives in case you like them more.

> +   }
> +   if (state->AMD_vertex_shader_viewport_index_enable) {
> +      var = add_output(VARYING_SLOT_VIEWPORT, int_t, "gl_ViewportIndex");
> +      var->data.interpolation = INTERP_QUALIFIER_FLAT;
> +   }
>     if (compatibility) {
>        add_input(VERT_ATTRIB_POS, vec4_t, "gl_Vertex");
>        add_input(VERT_ATTRIB_NORMAL, vec3_t, "gl_Normal");
> @@ -954,11 +960,16 @@ builtin_variable_generator::generate_tes_special_vars()
>  void
>  builtin_variable_generator::generate_gs_special_vars()
>  {
> -   add_output(VARYING_SLOT_LAYER, int_t, "gl_Layer");
> -   if (state->is_version(410, 0) || state->ARB_viewport_array_enable)
> -      add_output(VARYING_SLOT_VIEWPORT, int_t, "gl_ViewportIndex");
> +   ir_variable *var;
> +
> +   var = add_output(VARYING_SLOT_LAYER, int_t, "gl_Layer");
> +   var->data.interpolation = INTERP_QUALIFIER_FLAT;
> +   if (state->is_version(410, 0) || state->ARB_viewport_array_enable) {
> +      var = add_output(VARYING_SLOT_VIEWPORT, int_t, "gl_ViewportIndex");
> +      var->data.interpolation = INTERP_QUALIFIER_FLAT;
> +   }
>     if (state->is_version(400, 0) || state->ARB_gpu_shader5_enable)
> -      add_system_value(SYSTEM_VALUE_INVOCATION_ID, int_t, "gl_InvocationID");
> +      var = add_system_value(SYSTEM_VALUE_INVOCATION_ID, int_t, "gl_InvocationID");
>
>     /* Although gl_PrimitiveID appears in tessellation control and tessellation
>      * evaluation shaders, it has a different function there than it has in
> @@ -970,7 +981,6 @@ builtin_variable_generator::generate_gs_special_vars()
>      * the specific case of gl_PrimitiveIDIn.  So we don't need to treat
>      * gl_PrimitiveIDIn as an {ARB,EXT}_geometry_shader4-only variable.
>      */
> -   ir_variable *var;
>     var = add_input(VARYING_SLOT_PRIMITIVE_ID, int_t, "gl_PrimitiveIDIn");
>     var->data.interpolation = INTERP_QUALIFIER_FLAT;
>     var = add_output(VARYING_SLOT_PRIMITIVE_ID, int_t, "gl_PrimitiveID");
> @@ -984,14 +994,15 @@ builtin_variable_generator::generate_gs_special_vars()
>  void
>  builtin_variable_generator::generate_fs_special_vars()
>  {
> +   ir_variable *var;
> +
>     add_input(VARYING_SLOT_POS, vec4_t, "gl_FragCoord");
>     add_input(VARYING_SLOT_FACE, bool_t, "gl_FrontFacing");
>     if (state->is_version(120, 100))
>        add_input(VARYING_SLOT_PNTC, vec2_t, "gl_PointCoord");
>
>     if (state->is_version(150, 0)) {
> -      ir_variable *var =
> -         add_input(VARYING_SLOT_PRIMITIVE_ID, int_t, "gl_PrimitiveID");
> +      var = add_input(VARYING_SLOT_PRIMITIVE_ID, int_t, "gl_PrimitiveID");
>        var->data.interpolation = INTERP_QUALIFIER_FLAT;
>     }
>
> @@ -1043,8 +1054,10 @@ builtin_variable_generator::generate_fs_special_vars()
>     }
>
>     if (state->is_version(430, 0) || state->ARB_fragment_layer_viewport_enable) {
> -      add_input(VARYING_SLOT_LAYER, int_t, "gl_Layer");
> -      add_input(VARYING_SLOT_VIEWPORT, int_t, "gl_ViewportIndex");
> +      var = add_input(VARYING_SLOT_LAYER, int_t, "gl_Layer");
> +      var->data.interpolation = INTERP_QUALIFIER_FLAT;
> +      var = add_input(VARYING_SLOT_VIEWPORT, int_t, "gl_ViewportIndex");
> +      var->data.interpolation = INTERP_QUALIFIER_FLAT;
>     }
>  }
>
> --
> 2.6.2
>
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