[Mesa-dev] [PATCH 3/4] glsl: Set UsesDFdy appropriately for GLSL shaders.

[Brian Paul]

On 07/18/2012 01:16 PM, Paul Berry wrote:
> This patch updates the ir_set_program_inouts_visitor so that it also
> sets gl_fragment_program::UsesDFdy.
>
> This is a bit of a hack (since dFdy() isn't an input or an output),
> but there's no other obvious visitor to squeeze this functionality
> into, and it would be silly to create a brand new visitor just for
> this purpose.
> ---
>   src/glsl/ir_set_program_inouts.cpp |   16 ++++++++++++++--
>   1 files changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/src/glsl/ir_set_program_inouts.cpp b/src/glsl/ir_set_program_inouts.cpp
> index a7415c7..9b82f17 100644
> --- a/src/glsl/ir_set_program_inouts.cpp
> +++ b/src/glsl/ir_set_program_inouts.cpp
> @@ -26,8 +26,8 @@
>    *
>    * Sets the InputsRead and OutputsWritten of Mesa programs.
>    *
> - * Additionally, for fragment shaders, sets the InterpQualifier array and
> - * IsCentroid bitfield.
> + * Additionally, for fragment shaders, sets the InterpQualifier array, the
> + * IsCentroid bitfield, and the UsesDFdy flag.
>    *
>    * Mesa programs (gl_program, not gl_shader_program) have a set of
>    * flags indicating which varyings are read and written.  Computing
> @@ -61,6 +61,7 @@ public:
>
>      virtual ir_visitor_status visit_enter(ir_dereference_array *);
>      virtual ir_visitor_status visit_enter(ir_function_signature *);
> +   virtual ir_visitor_status visit_enter(ir_expression *);
>      virtual ir_visitor_status visit(ir_dereference_variable *);
>      virtual ir_visitor_status visit(ir_variable *);
>
> @@ -169,6 +170,16 @@ ir_set_program_inouts_visitor::visit_enter(ir_function_signature *ir)
>      return visit_continue_with_parent;
>   }
>
> +ir_visitor_status
> +ir_set_program_inouts_visitor::visit_enter(ir_expression *ir)
> +{
> +   if (is_fragment_shader&&  ir->operation == ir_unop_dFdy) {
> +      gl_fragment_program *fprog = (gl_fragment_program *) prog;
> +      fprog->UsesDFdy = true;
> +   }
> +   return visit_continue;
> +}
> +
>   void
>   do_set_program_inouts(exec_list *instructions, struct gl_program *prog,
>                         bool is_fragment_shader)
> @@ -182,6 +193,7 @@ do_set_program_inouts(exec_list *instructions, struct gl_program *prog,
>         memset(((gl_fragment_program *) prog)->InterpQualifier, 0,
>                sizeof(((gl_fragment_program *) prog)->InterpQualifier));
>         ((gl_fragment_program *) prog)->IsCentroid = 0;
> +      ((gl_fragment_program *) prog)->UsesDFdy = false;
>      }
>      visit_list_elements(&v, instructions);
>   }

Reviewed-by: Brian Paul <brianp at vmware.com>

BTW, I thought we had a cast wrapper somewhere for casting gl_program 
to gl_fragment_program or gl_vertex_program, etc. but I can't find it 
at the moment.  It would be good to use wrapper like that instead of 
casts everywhere.  The last hunk has 3 such casts.  A local 'fprog' 
var would make things a bit more readable there.

-Brian