[Mesa-dev] [PATCH 2/3] glsl: Optimize clamp(x, 0.0, b), where b < 1.0 as saturate(min(x, b))

[Ian Romanick]

On 06/23/2014 10:32 PM, Abdiel Janulgue wrote:
> Signed-off-by: Abdiel Janulgue <abdiel.janulgue at linux.intel.com>
> ---
>  src/glsl/opt_algebraic.cpp | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/src/glsl/opt_algebraic.cpp b/src/glsl/opt_algebraic.cpp
> index 8d7609d..0d694b6 100644
> --- a/src/glsl/opt_algebraic.cpp
> +++ b/src/glsl/opt_algebraic.cpp
> @@ -589,6 +589,10 @@ 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);
> +
> +            /* Found a min (max(x, 0.0) b), where b < 1.0 */
> +            if ((outer_const->get_float_component(0) < 1.0f) && inner_val_b->is_zero())

I think this won't work correctly for:

   vec4 b = min(max(a, vec4(0)), vec4(0.5, 2, 4, 6));

> +               return saturate(expr(ir_binop_min, inner_val_a, outer_const));
>           }
>        }
>  
>