[Mesa-dev] [PATCH] glsl: Make read_from_write_only_variable_visitor ignore .length().

[Iago Toral]

Makes sense,

Reviewed-by: Iago Toral Quiroga <itoral at igalia.com>

On Mon, 2016-01-11 at 16:15 -0800, Kenneth Graunke wrote:
> .length() on an unsized SSBO variable doesn't actually read any data
> from the SSBO, and is allowed on variables marked 'writeonly'.
> 
> Fixes compute shader compilation in Shadow of Mordor.
> 
> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
> ---
>  src/glsl/ast_to_hir.cpp | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/src/glsl/ast_to_hir.cpp b/src/glsl/ast_to_hir.cpp
> index f3966d7..13696a3 100644
> --- a/src/glsl/ast_to_hir.cpp
> +++ b/src/glsl/ast_to_hir.cpp
> @@ -106,6 +106,15 @@ public:
>        return found;
>     }
>  
> +   virtual ir_visitor_status visit_enter(ir_expression *ir)
> +   {
> +      /* .length() doesn't actually read anything */
> +      if (ir->operation == ir_unop_ssbo_unsized_array_length)
> +         return visit_continue_with_parent;
> +
> +      return visit_continue;
> +   }
> +
>  private:
>     ir_variable *found;
>  };