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/*

 * Copyright © 2010 Intel Corporation

 *

 * Permission is hereby granted, free of charge, to any person obtaining a

 * copy of this software and associated documentation files (the "Software"),

 * to deal in the Software without restriction, including without limitation

 * the rights to use, copy, modify, merge, publish, distribute, sublicense,

 * and/or sell copies of the Software, and to permit persons to whom the

 * Software is furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice (including the next

 * paragraph) shall be included in all copies or substantial portions of the

 * Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL

 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING

 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER

 * DEALINGS IN THE SOFTWARE.

 */

#include "glsl_types.h"

#include "ir.h"

#include "glsl_parser_extras.h"

#include "main/errors.h"

typedef enum {

   PARAMETER_LIST_NO_MATCH,

   PARAMETER_LIST_EXACT_MATCH,

   PARAMETER_LIST_INEXACT_MATCH /*< Match requires implicit conversion. */

} parameter_list_match_t;

/**

 * \brief Check if two parameter lists match.

 *

 * \param list_a Parameters of the function definition.

 * \param list_b Actual parameters passed to the function.

 * \see matching_signature()

 */

static parameter_list_match_t

parameter_lists_match(_mesa_glsl_parse_state *state,

                      const exec_list *list_a, const exec_list *list_b)

{

   const exec_node *node_a = list_a->head;

   const exec_node *node_b = list_b->head;

   /* This is set to true if there is an inexact match requiring an implicit

    * conversion. */

   bool inexact_match = false;

   for (/* empty */

	; !node_a->is_tail_sentinel()

	; node_a = node_a->next, node_b = node_b->next) {

      /* If all of the parameters from the other parameter list have been

       * exhausted, the lists have different length and, by definition,

       * do not match.

       */

      if (node_b->is_tail_sentinel())

	 return PARAMETER_LIST_NO_MATCH;

      const ir_variable *const param = (ir_variable *) node_a;

      const ir_rvalue *const actual = (ir_rvalue *) node_b;

      if (param->type == actual->type)

	 continue;

      /* Try to find an implicit conversion from actual to param. */

      inexact_match = true;

      switch ((enum ir_variable_mode)(param->data.mode)) {

      case ir_var_auto:

      case ir_var_uniform:

      case ir_var_temporary:

	 /* These are all error conditions.  It is invalid for a parameter to

	  * a function to be declared as auto (not in, out, or inout) or

	  * as uniform.

	  */

	 assert(0);

	 return PARAMETER_LIST_NO_MATCH;

      case ir_var_const_in:

      case ir_var_function_in:

	 if (!actual->type->can_implicitly_convert_to(param->type, state))

	    return PARAMETER_LIST_NO_MATCH;

	 break;

      case ir_var_function_out:

	 if (!param->type->can_implicitly_convert_to(actual->type, state))

	    return PARAMETER_LIST_NO_MATCH;

	 break;

      case ir_var_function_inout:

	 /* Since there are no bi-directional automatic conversions (e.g.,

	  * there is int -> float but no float -> int), inout parameters must

	  * be exact matches.

	  */

	 return PARAMETER_LIST_NO_MATCH;

      default:

	 assert(false);

	 return PARAMETER_LIST_NO_MATCH;

      }

   }

   /* If all of the parameters from the other parameter list have been

    * exhausted, the lists have different length and, by definition, do not

    * match.

    */

   if (!node_b->is_tail_sentinel())

      return PARAMETER_LIST_NO_MATCH;

   if (inexact_match)

      return PARAMETER_LIST_INEXACT_MATCH;

   else

      return PARAMETER_LIST_EXACT_MATCH;

}

/* Classes of parameter match, sorted (mostly) best matches first.

 * See is_better_parameter_match() below for the exceptions.

 * */

typedef enum {

   PARAMETER_EXACT_MATCH,

   PARAMETER_FLOAT_TO_DOUBLE,

   PARAMETER_INT_TO_FLOAT,

   PARAMETER_INT_TO_DOUBLE,

   PARAMETER_OTHER_CONVERSION,

} parameter_match_t;

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)

{

   /* From section 6.1 of the GLSL 4.00 spec (and the ARB_gpu_shader5 spec):

    *

    * 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.

    *

    * [XXX: Not in GLSL 4.0: Only in ARB_gpu_shader5:

    * 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.

    *

    * --

    *

    * 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 bool

is_best_inexact_overload(const exec_list *actual_parameters,

                         ir_function_signature **matches,

                         int num_matches,

                         ir_function_signature *sig)

{

   /* From section 6.1 of the GLSL 4.00 spec (and the ARB_gpu_shader5 spec):

    *

    * "A function definition A is considered a better

    * match than function definition B if:

    *

    *   * for at least one function argument, the conversion for that argument

    *     in A is better than the corresponding conversion in B; and

    *

    *   * there is no function argument for which the conversion in B is better

    *     than the corresponding conversion in A.

    *

    * If a single function definition is considered a better match than every

    * other matching function definition, it will be used.  Otherwise, a

    * semantic error occurs and the shader will fail to compile."

    */

   for (ir_function_signature **other = matches;

        other < matches + num_matches; other++) {

      if (*other == sig)

         continue;

      const exec_node *node_a = sig->parameters.head;

      const exec_node *node_b = (*other)->parameters.head;

      const exec_node *node_p = actual_parameters->head;

      bool better_for_some_parameter = false;

      for (/* empty */

           ; !node_a->is_tail_sentinel()

           ; node_a = node_a->next,

             node_b = node_b->next,

             node_p = node_p->next) {

         parameter_match_t a_match = get_parameter_match_type(

               (const ir_variable *)node_a,

               (const ir_rvalue *)node_p);

         parameter_match_t b_match = get_parameter_match_type(

               (const ir_variable *)node_b,

               (const ir_rvalue *)node_p);

         if (is_better_parameter_match(a_match, b_match))

               better_for_some_parameter = true;

         if (is_better_parameter_match(b_match, a_match))

               return false;     /* B is better for this parameter */

      }

      if (!better_for_some_parameter)

         return false;     /* A must be better than B for some parameter */

   }

   return true;

}

static ir_function_signature *

choose_best_inexact_overload(_mesa_glsl_parse_state *state,

                             const exec_list *actual_parameters,

                             ir_function_signature **matches,

                             int num_matches)

{

   if (num_matches == 0)

      return NULL;

   if (num_matches == 1)

      return *matches;

   /* Without GLSL 4.0 / ARB_gpu_shader5, there is no overload resolution

    * among multiple inexact matches. Note that state may be NULL here if

    * called from the linker; in that case we assume everything supported in

    * any GLSL version is available. */

   if (!state || state->is_version(400, 0) || state->ARB_gpu_shader5_enable) {

      for (ir_function_signature **sig = matches; sig < matches + num_matches; sig++) {

         if (is_best_inexact_overload(actual_parameters, matches, num_matches, *sig))

            return *sig;

      }

   }

   return NULL;   /* no best candidate */

}

ir_function_signature *

ir_function::matching_signature(_mesa_glsl_parse_state *state,

                                const exec_list *actual_parameters,

                                bool allow_builtins)

{

   bool is_exact;

   return matching_signature(state, actual_parameters, allow_builtins,

                             &is_exact);

}

ir_function_signature *

ir_function::matching_signature(_mesa_glsl_parse_state *state,

                                const exec_list *actual_parameters,

                                bool allow_builtins,

                                bool *is_exact)

{

   ir_function_signature **inexact_matches = NULL;

   ir_function_signature **inexact_matches_temp;

   ir_function_signature *match = NULL;

   int num_inexact_matches = 0;

   /* From page 42 (page 49 of the PDF) of the GLSL 1.20 spec:

    *

    * "If an exact match is found, the other signatures are ignored, and

    *  the exact match is used.  Otherwise, if no exact match is found, then

    *  the implicit conversions in Section 4.1.10 "Implicit Conversions" will

    *  be applied to the calling arguments if this can make their types match

    *  a signature.  In this case, it is a semantic error if there are

    *  multiple ways to apply these conversions to the actual arguments of a

    *  call such that the call can be made to match multiple signatures."

    */

   foreach_in_list(ir_function_signature, sig, &this->signatures) {

      /* Skip over any built-ins that aren't available in this shader. */

      if (sig->is_builtin() && (!allow_builtins ||

                                !sig->is_builtin_available(state)))

         continue;

      switch (parameter_lists_match(state, & sig->parameters, actual_parameters)) {

      case PARAMETER_LIST_EXACT_MATCH:

         *is_exact = true;

         free(inexact_matches);

         return sig;

      case PARAMETER_LIST_INEXACT_MATCH:

         inexact_matches_temp = (ir_function_signature **)

               realloc(inexact_matches,

                       sizeof(*inexact_matches) *

                       (num_inexact_matches + 1));

         if (inexact_matches_temp == NULL) {

            _mesa_error_no_memory(__func__);

            free(inexact_matches);

            return NULL;

         }

         inexact_matches = inexact_matches_temp;

         inexact_matches[num_inexact_matches++] = sig;

         continue;

      case PARAMETER_LIST_NO_MATCH:

	 continue;

      default:

	 assert(false);

	 return NULL;

      }

   }

   /* There is no exact match (we would have returned it by now).  If there

    * are multiple inexact matches, the call is ambiguous, which is an error.

    *

    * FINISHME: Report a decent error.  Returning NULL will likely result in

    * FINISHME: a "no matching signature" error; it should report that the

    * FINISHME: call is ambiguous.  But reporting errors from here is hard.

    */

   *is_exact = false;

   match = choose_best_inexact_overload(state, actual_parameters,

                                        inexact_matches, num_inexact_matches);

   free(inexact_matches);

   return match;

}

static bool

parameter_lists_match_exact(const exec_list *list_a, const exec_list *list_b)

{

   const exec_node *node_a = list_a->head;

   const exec_node *node_b = list_b->head;

   for (/* empty */

	; !node_a->is_tail_sentinel() && !node_b->is_tail_sentinel()

	; node_a = node_a->next, node_b = node_b->next) {

      ir_variable *a = (ir_variable *) node_a;

      ir_variable *b = (ir_variable *) node_b;

      /* If the types of the parameters do not match, the parameters lists

       * are different.

       */

      if (a->type != b->type)

         return false;

   }

   /* Unless both lists are exhausted, they differ in length and, by

    * definition, do not match.

    */

   return (node_a->is_tail_sentinel() == node_b->is_tail_sentinel());

}

ir_function_signature *

ir_function::exact_matching_signature(_mesa_glsl_parse_state *state,

                                      const exec_list *actual_parameters)

{

   foreach_in_list(ir_function_signature, sig, &this->signatures) {

      /* Skip over any built-ins that aren't available in this shader. */

      if (sig->is_builtin() && !sig->is_builtin_available(state))

         continue;

      if (parameter_lists_match_exact(&sig->parameters, actual_parameters))

	 return sig;

   }

   return NULL;

}