[Mesa-dev] [PATCH] glsl: fix lowering outputs for early/nested returns

[Timothy Arceri]

Hi Lars,

Thankd for working on this, comments below.

On Sun, 2016-04-17 at 13:18 -0400, Lars Hamre wrote:
> Return statements in conditional blocks were not having their
> output varyings lowered correctly.
> 
> This patch fixes the following piglit tests:
> /spec/glsl-1.10/execution/vs-float-main-return
> /spec/glsl-1.10/execution/vs-vec2-main-return
> /spec/glsl-1.10/execution/vs-vec3-main-return
> 
> Signed-off-by: Lars Hamre <chemecse at gmail.com>
> 
> ---
> 
> NOTE: Someone with access will need to commit this after the review
>       process
> 
>  src/compiler/glsl/lower_packed_varyings.cpp | 58
> +++++++++++++++++++++++++++--
>  1 file changed, 54 insertions(+), 4 deletions(-)
> 
> diff --git a/src/compiler/glsl/lower_packed_varyings.cpp
> b/src/compiler/glsl/lower_packed_varyings.cpp
> index 825cc9e..41edada 100644
> --- a/src/compiler/glsl/lower_packed_varyings.cpp
> +++ b/src/compiler/glsl/lower_packed_varyings.cpp
> @@ -724,6 +724,45 @@
> lower_packed_varyings_gs_splicer::visit_leave(ir_emit_vertex *ev)
>     return visit_continue;
>  }
> 
> +/**
> + * Visitor that splices varying packing code before every return.
> + */
> +class lower_packed_varyings_return_splicer : public
> ir_hierarchical_visitor
> +{
> +public:
> +   explicit lower_packed_varyings_return_splicer(void *mem_ctx,
> +                                                 const exec_list
> *instructions);
> +
> +   virtual ir_visitor_status visit_leave(ir_return *ret);
> +
> +private:
> +   /**
> +    * Memory context used to allocate new instructions for the
> shader.
> +    */
> +   void * const mem_ctx;
> +
> +   /**
> +    * Instructions that should be spliced into place before each
> return.
> +    */
> +   const exec_list *instructions;
> +};
> +
> +
> +lower_packed_varyings_return_splicer::lower_packed_varyings_return_s
> plicer(
> +      void *mem_ctx, const exec_list *instructions)
> +   : mem_ctx(mem_ctx), instructions(instructions)
> +{
> +}
> +
> +
> +ir_visitor_status
> +lower_packed_varyings_return_splicer::visit_leave(ir_return *ret)
> +{
> +   foreach_in_list(ir_instruction, ir, this->instructions) {
> +      ret->insert_before(ir->clone(this->mem_ctx, NULL));
> +   }
> +   return visit_continue;
> +}
> 
>  void
>  lower_packed_varyings(void *mem_ctx, unsigned locations_used,
> @@ -757,11 +796,22 @@ lower_packed_varyings(void *mem_ctx, unsigned
> locations_used,
>           /* Now update all the EmitVertex instances */
>           splicer.run(instructions);
>        } else {
> -         /* For other shader types, outputs need to be lowered at
> the end of
> -          * main()
> +         /* For other shader types, outputs need to be lowered
> before each
> +          * return statement and at the end of main()
>            */
> -         main_func_sig->body.append_list(&new_variables);
> -         main_func_sig->body.append_list(&new_instructions);
> +
> +         lower_packed_varyings_return_splicer splicer(mem_ctx,
> &new_instructions);
> +
> +         main_func_sig->body.head->insert_before(&new_variables);
> +
> +         splicer.run(instructions);

This will walk over everything. I don't think you want that you only
want to walk over the instructions in main right? 

For example if you have another function with a return then you would
end up inserting the instructions before that functions return too. You
could probably create a piglit test to detect this.


> +
> +         /* Lower outputs at the end of main() if the last
> instruction is not
> +          * a return statement
> +          */
> +         if (((ir_instruction*)instructions->get_tail())->ir_type !=
> ir_type_return) {
> +            main_func_sig->body.append_list(&new_instructions);
> +         }

Will this work for:


	foo1 = vec2(0.5);
	if (early_return != 0) {
		foo1 = vec2(0.2);
		return;
	}

I assume it will be fine, but would be good to have a piglit test for
this also.

>        }
>     } else {
>        /* Shader inputs need to be lowered at the beginning of main()
> */
> --
> 2.5.5
> 
> _______________________________________________
> mesa-dev mailing list
> mesa-dev at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/mesa-dev