[Mesa-dev] [v2 PATCH 10/16] glsl: Optimize clamp(x, 0.0, b), where b < 1.0 as min(saturate(x), b)

[Matt Turner]

On Mon, Jul 7, 2014 at 6:57 AM, Abdiel Janulgue
<abdiel.janulgue at linux.intel.com> wrote:
> v2: - Output min(saturate(x),b) instead of saturate(min(x,b)) suggested by Ilia Mirkin
>     - Make sure we do component-wise comparison for vectors (Ian Romanick)
>
> Signed-off-by: Abdiel Janulgue <abdiel.janulgue at linux.intel.com>
> ---
>  src/glsl/opt_algebraic.cpp | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/src/glsl/opt_algebraic.cpp b/src/glsl/opt_algebraic.cpp
> index 2ad561c..bcda7a9 100644
> --- a/src/glsl/opt_algebraic.cpp
> +++ b/src/glsl/opt_algebraic.cpp
> @@ -643,6 +643,16 @@ ir_algebraic_visitor::handle_expression(ir_expression *ir)
>              /* Found a min (max(x, 0), 1.0) */
>              if (outer_const->is_one() && inner_val_a->is_zero())
>                 return saturate(inner_val_b);
> +
> +            unsigned component = 0;
> +            for (int c = 0; c < outer_const->type->vector_elements; c++) {
> +               if (outer_const->get_float_component(c) < 1.0f)
> +                  component++;
> +            }
> +            /* Found a min (max(x, 0.0) b), where b < 1.0 */

Is this case the only thing it finds?

Does it find max(min(x, b), 0.0)?

> +            if ((component == outer_const->type->vector_elements) &&
> +                inner_val_b->is_zero())
> +               return expr(ir_binop_min, saturate(inner_val_a), outer_const);

It seems like it would incorrectly recognize max(min(x, 0.0), b).