[Mesa-dev] [PATCH 1/2] glsl: Optimize (not A) or (not B) into not (A and B).

[Erik Faye-Lund]

On Thu, Oct 24, 2013 at 2:19 AM, Matt Turner <mattst88 at gmail.com> wrote:
> A few Serious Sam 3 shaders affected:
>
> instructions in affected programs:     4384 -> 4344 (-0.91%)
> ---
>  src/glsl/opt_algebraic.cpp | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/src/glsl/opt_algebraic.cpp b/src/glsl/opt_algebraic.cpp
> index 37b2f02..3bf0689 100644
> --- a/src/glsl/opt_algebraic.cpp
> +++ b/src/glsl/opt_algebraic.cpp
> @@ -32,8 +32,11 @@
>  #include "ir_visitor.h"
>  #include "ir_rvalue_visitor.h"
>  #include "ir_optimization.h"
> +#include "ir_builder.h"
>  #include "glsl_types.h"
>
> +using namespace ir_builder;
> +
>  namespace {
>
>  /**
> @@ -436,6 +439,15 @@ ir_algebraic_visitor::handle_expression(ir_expression *ir)
>
>          this->progress = true;
>          return new(mem_ctx) ir_constant(ir->type, &data);
> +      } else if (op_expr[0] && op_expr[0]->operation == ir_unop_logic_not &&
> +                 op_expr[1] && op_expr[1]->operation == ir_unop_logic_not) {
> +         /* De Morgan's Law:
> +          *    (not A) or (not B) === not (A and B)
> +          */
> +         temp = logic_not(logic_and(op_expr[0]->operands[0],
> +                                    op_expr[1]->operands[0]));
> +         return swizzle_if_required(ir, temp);
> +         this->progress = true;

Returning before reporting progress?