[Mesa-dev] [PATCH 02/59] glsl/standalone: Optimize add-of-neg to subtract

[Iago Toral]

On Tue, 2016-10-25 at 17:59 -0700, Ian Romanick wrote:
> From: Ian Romanick <ian.d.romanick at intel.com>
> 
> This just makes the output of the standalone compiler a little more
> compact.
> 
> Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
> ---
>  src/compiler/glsl/standalone.cpp | 34
> ++++++++++++++++++++++++++++++++++
>  1 file changed, 34 insertions(+)
> 
> diff --git a/src/compiler/glsl/standalone.cpp
> b/src/compiler/glsl/standalone.cpp
> index 055c433..b41d25c 100644
> --- a/src/compiler/glsl/standalone.cpp
> +++ b/src/compiler/glsl/standalone.cpp
> @@ -38,6 +38,37 @@
>  #include "standalone.h"
>  #include "util/string_to_uint_map.h"
>  
> +class add_neg_to_sub_visitor : public ir_hierarchical_visitor {
> +public:
> +   add_neg_to_sub_visitor()
> +   {
> +      /* empty */
> +   }
> +
> +   ir_visitor_status visit_leave(ir_expression *ir)
> +   {
> +      if (ir->operation != ir_binop_add)
> +         return visit_continue;
> +
> +      for (unsigned i = 0; i < 2; i++) {
> +         ir_expression *const op = ir->operands[i]->as_expression();
> +
> +         if (op != NULL && op->operation == ir_unop_neg) {
> +            ir->operation = ir_binop_sub;
> +
> +            /* This ensures that -a + b becomes b - a. */
> +            if (i == 0)
> +               ir->operands[0] = ir->operands[1];
> +
> +            ir->operands[i] = op->operands[0];

I think you meant:

ir->operands[1] = op->operands[0]


> +            break;
> +         }
> +      }
> +
> +      return visit_continue;
> +   }
> +};
> +
>  static const struct standalone_options *options;
>  
>  static void
> @@ -441,6 +472,9 @@ standalone_compile_shader(const struct
> standalone_options *_options,
>           if (!shader)
>              continue;
>  
> +         add_neg_to_sub_visitor v;
> +         visit_list_elements(&v, shader->ir);
> +
>           shader->Program = rzalloc(shader, gl_program);
>           init_gl_program(shader->Program, shader->Stage);
>        }