[Mesa-dev] [PATCH V2 7/9] glsl: Add support for comparing function parameter conversions

[Jordan Justen]

On Sun, May 4, 2014 at 1:24 AM, Chris Forbes <chrisf at ijw.co.nz> wrote:
> The ARB_gpu_shader5 spec says:
>
> "To determine whether the conversion for a single argument in one match is
> better than that for another match, the following rules are applied, in
> order:
>
>   1. An exact match is better than a match involving any implicit
>      conversion.
>
>   2. A match involving an implicit conversion from float to double is
>      better than a match involving any other implicit conversion.
>
>   3. A match involving an implicit conversion from either int or uint to
>      float is better than a match involving an implicit conversion from
>      either int or uint to double.
>
> If none of the rules above apply to a particular pair of conversions,
> neither conversion is considered better than the other."
>
> Signed-off-by: Chris Forbes <chrisf at ijw.co.nz>
> ---
>  src/glsl/ir_function.cpp | 74 ++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 71 insertions(+), 3 deletions(-)
>
> diff --git a/src/glsl/ir_function.cpp b/src/glsl/ir_function.cpp
> index 2b88535..6d2de47 100644
> --- a/src/glsl/ir_function.cpp
> +++ b/src/glsl/ir_function.cpp
> @@ -117,6 +117,73 @@ parameter_lists_match(_mesa_glsl_parse_state *state,
>  }
>
>
> +typedef enum {
> +   PARAMETER_EXACT_MATCH,
> +   PARAMETER_FLOAT_TO_DOUBLE,
> +   PARAMETER_INT_TO_FLOAT,
> +   PARAMETER_INT_TO_DOUBLE,
> +   PARAMETER_OTHER_CONVERSION,
> +} parameter_match_t;

How about a comment noting these are sorted with 'best' match listed first?

> +
> +
> +static parameter_match_t
> +get_parameter_match_type(const ir_variable *param,
> +                         const ir_rvalue *actual)
> +{
> +   const glsl_type *from_type;
> +   const glsl_type *to_type;
> +
> +   if (param->data.mode == ir_var_function_out) {
> +      from_type = param->type;
> +      to_type = actual->type;
> +   } else {
> +      from_type = actual->type;
> +      to_type = param->type;
> +   }
> +
> +   if (from_type == to_type)
> +      return PARAMETER_EXACT_MATCH;
> +
> +   /* XXX: When ARB_gpu_shader_fp64 support is added, check for float->double,
> +    * and int/uint->double conversions
> +    */
> +
> +   if (to_type->base_type == GLSL_TYPE_FLOAT)
> +      return PARAMETER_INT_TO_FLOAT;
> +
> +   /* int -> uint and any other oddball conversions */
> +   return PARAMETER_OTHER_CONVERSION;
> +}
> +
> +
> +static bool
> +is_better_parameter_match(parameter_match_t a_match,
> +                          parameter_match_t b_match)
> +{
> +   /* 1. An exact match is better than a match involving any implicit
> +    * conversion.
> +    *
> +    * 2. A match involving an implicit conversion from float to double
> +    * is better than match involving any other implicit conversion.
> +    *
> +    * 3. A match involving an implicit conversion from either int or uint
> +    * to float is better than a match involving an implicit conversion
> +    * from either int or uint to double.
> +    *
> +    * If none of the rules above apply to a particular pair of conversions,
> +    * neither conversion is considered better than the other.

Maybe reference the GLSL 4.00 spec location for this text?

-Jordan

> +    *
> +    * Notably, the int->uint conversion is *not* considered to be better
> +    * or worse than int/uint->float or int/uint->double.
> +    */
> +
> +   if (a_match >= PARAMETER_INT_TO_FLOAT && b_match == PARAMETER_OTHER_CONVERSION)
> +      return false;
> +
> +   return a_match < b_match;
> +}
> +
> +
>  static ir_function_signature *
>  choose_best_inexact_overload(_mesa_glsl_parse_state *state,
>                               const exec_list *actual_parameters,
> @@ -173,9 +240,10 @@ ir_function::matching_signature(_mesa_glsl_parse_state *state,
>           free(inexact_matches);
>           return sig;
>        case PARAMETER_LIST_INEXACT_MATCH:
> -         inexact_matches = realloc(inexact_matches,
> -                                   sizeof(*inexact_matches) *
> -                                   (num_inexact_matches + 1));
> +         inexact_matches = (ir_function_signature **)
> +               realloc(inexact_matches,
> +                       sizeof(*inexact_matches) *
> +                       (num_inexact_matches + 1));
>           assert(inexact_matches);
>           inexact_matches[num_inexact_matches++] = sig;
>           continue;
> --
> 1.9.2
>
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