glsl: Convert ir_call to be a statement rather than a value.

[mesa.git] / src / glsl / ast_function.cpp

/*
 * 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_symbol_table.h"
#include "ast.h"
#include "glsl_types.h"
#include "ir.h"
#include "main/core.h" /* for MIN2 */

static ir_rvalue *
convert_component(ir_rvalue *src, const glsl_type *desired_type);

bool
apply_implicit_conversion(const glsl_type *to, ir_rvalue * &from,
                          struct _mesa_glsl_parse_state *state);

static unsigned
process_parameters(exec_list *instructions, exec_list *actual_parameters,
                   exec_list *parameters,
                   struct _mesa_glsl_parse_state *state)
{
   unsigned count = 0;

   foreach_list (n, parameters) {
      ast_node *const ast = exec_node_data(ast_node, n, link);
      ir_rvalue *result = ast->hir(instructions, state);

      ir_constant *const constant = result->constant_expression_value();
      if (constant != NULL)
         result = constant;

      actual_parameters->push_tail(result);
      count++;
   }

   return count;
}


/**
 * Generate a source prototype for a function signature
 *
 * \param return_type Return type of the function.  May be \c NULL.
 * \param name        Name of the function.
 * \param parameters  List of \c ir_instruction nodes representing the
 *                    parameter list for the function.  This may be either a
 *                    formal (\c ir_variable) or actual (\c ir_rvalue)
 *                    parameter list.  Only the type is used.
 *
 * \return
 * A ralloced string representing the prototype of the function.
 */
char *
prototype_string(const glsl_type *return_type, const char *name,
                 exec_list *parameters)
{
   char *str = NULL;

   if (return_type != NULL)
      str = ralloc_asprintf(NULL, "%s ", return_type->name);

   ralloc_asprintf_append(&str, "%s(", name);

   const char *comma = "";
   foreach_list(node, parameters) {
      const ir_instruction *const param = (ir_instruction *) node;

      ralloc_asprintf_append(&str, "%s%s", comma, param->type->name);
      comma = ", ";
   }

   ralloc_strcat(&str, ")");
   return str;
}

/**
 * Verify that 'out' and 'inout' actual parameters are lvalues.  Also, verify
 * that 'const_in' formal parameters (an extension in our IR) correspond to
 * ir_constant actual parameters.
 */
static bool
verify_parameter_modes(_mesa_glsl_parse_state *state,
                       ir_function_signature *sig,
                       exec_list &actual_ir_parameters,
                       exec_list &actual_ast_parameters)
{
   exec_node *actual_ir_node  = actual_ir_parameters.head;
   exec_node *actual_ast_node = actual_ast_parameters.head;

   foreach_list(formal_node, &sig->parameters) {
      /* The lists must be the same length. */
      assert(!actual_ir_node->is_tail_sentinel());
      assert(!actual_ast_node->is_tail_sentinel());

      const ir_variable *const formal = (ir_variable *) formal_node;
      const ir_rvalue *const actual = (ir_rvalue *) actual_ir_node;
      const ast_expression *const actual_ast =
         exec_node_data(ast_expression, actual_ast_node, link);

      /* FIXME: 'loc' is incorrect (as of 2011-01-21). It is always
       * FIXME: 0:0(0).
       */
      YYLTYPE loc = actual_ast->get_location();

      /* Verify that 'const_in' parameters are ir_constants. */
      if (formal->mode == ir_var_const_in &&
          actual->ir_type != ir_type_constant) {
         _mesa_glsl_error(&loc, state,
                          "parameter `in %s' must be a constant expression",
                          formal->name);
         return false;
      }

      /* Verify that 'out' and 'inout' actual parameters are lvalues. */
      if (formal->mode == ir_var_out || formal->mode == ir_var_inout) {
         const char *mode = NULL;
         switch (formal->mode) {
         case ir_var_out:   mode = "out";   break;
         case ir_var_inout: mode = "inout"; break;
         default:           assert(false);  break;
         }

         /* This AST-based check catches errors like f(i++).  The IR-based
          * is_lvalue() is insufficient because the actual parameter at the
          * IR-level is just a temporary value, which is an l-value.
          */
         if (actual_ast->non_lvalue_description != NULL) {
            _mesa_glsl_error(&loc, state,
                             "function parameter '%s %s' references a %s",
                             mode, formal->name,
                             actual_ast->non_lvalue_description);
            return false;
         }

         if (actual->variable_referenced()
             && actual->variable_referenced()->read_only) {
            _mesa_glsl_error(&loc, state,
                             "function parameter '%s %s' references the "
                             "read-only variable '%s'",
                             mode, formal->name,
                             actual->variable_referenced()->name);
            return false;
         } else if (!actual->is_lvalue()) {
            _mesa_glsl_error(&loc, state,
                             "function parameter '%s %s' is not an lvalue",
                             mode, formal->name);
            return false;
         }
      }

      actual_ir_node  = actual_ir_node->next;
      actual_ast_node = actual_ast_node->next;
   }
   return true;
}

/**
 * If a function call is generated, \c call_ir will point to it on exit.
 * Otherwise \c call_ir will be set to \c NULL.
 */
static ir_rvalue *
generate_call(exec_list *instructions, ir_function_signature *sig,
              YYLTYPE *loc, exec_list *actual_parameters,
              ir_call **call_ir,
              struct _mesa_glsl_parse_state *state)
{
   void *ctx = state;
   exec_list post_call_conversions;

   *call_ir = NULL;

   /* Perform implicit conversion of arguments.  For out parameters, we need
    * to place them in a temporary variable and do the conversion after the
    * call takes place.  Since we haven't emitted the call yet, we'll place
    * the post-call conversions in a temporary exec_list, and emit them later.
    */
   exec_list_iterator actual_iter = actual_parameters->iterator();
   exec_list_iterator formal_iter = sig->parameters.iterator();

   while (actual_iter.has_next()) {
      ir_rvalue *actual = (ir_rvalue *) actual_iter.get();
      ir_variable *formal = (ir_variable *) formal_iter.get();

      assert(actual != NULL);
      assert(formal != NULL);

      if (formal->type->is_numeric() || formal->type->is_boolean()) {
         switch (formal->mode) {
         case ir_var_const_in:
         case ir_var_in: {
            ir_rvalue *converted
               = convert_component(actual, formal->type);
            actual->replace_with(converted);
            break;
         }
         case ir_var_out:
            if (actual->type != formal->type) {
               /* To convert an out parameter, we need to create a
                * temporary variable to hold the value before conversion,
                * and then perform the conversion after the function call
                * returns.
                *
                * This has the effect of transforming code like this:
                *
                *   void f(out int x);
                *   float value;
                *   f(value);
                *
                * Into IR that's equivalent to this:
                *
                *   void f(out int x);
                *   float value;
                *   int out_parameter_conversion;
                *   f(out_parameter_conversion);
                *   value = float(out_parameter_conversion);
                */
               ir_variable *tmp =
                  new(ctx) ir_variable(formal->type,
                                       "out_parameter_conversion",
                                       ir_var_temporary);
               instructions->push_tail(tmp);
               ir_dereference_variable *deref_tmp_1
                  = new(ctx) ir_dereference_variable(tmp);
               ir_dereference_variable *deref_tmp_2
                  = new(ctx) ir_dereference_variable(tmp);
               ir_rvalue *converted_tmp
                  = convert_component(deref_tmp_1, actual->type);
               ir_assignment *assignment
                  = new(ctx) ir_assignment(actual, converted_tmp);
               post_call_conversions.push_tail(assignment);
               actual->replace_with(deref_tmp_2);
            }
            break;
         case ir_var_inout:
            /* Inout parameters should never require conversion, since that
             * would require an implicit conversion to exist both to and
             * from the formal parameter type, and there are no
             * bidirectional implicit conversions.
             */
            assert (actual->type == formal->type);
            break;
         default:
            assert (!"Illegal formal parameter mode");
            break;
         }
      }

      actual_iter.next();
      formal_iter.next();
   }

   /* If the function call is a constant expression, don't generate any
    * instructions; just generate an ir_constant.
    *
    * Function calls were first allowed to be constant expressions in GLSL 1.20.
    */
   if (state->language_version >= 120) {
      ir_constant *value = sig->constant_expression_value(actual_parameters);
      if (value != NULL) {
         return value;
      }
   }

   ir_dereference_variable *deref = NULL;
   if (!sig->return_type->is_void()) {
      /* Create a new temporary to hold the return value. */
      ir_variable *var;

      var = new(ctx) ir_variable(sig->return_type,
                                 ralloc_asprintf(ctx, "%s_retval",
                                                 sig->function_name()),
                                 ir_var_temporary);
      instructions->push_tail(var);

      deref = new(ctx) ir_dereference_variable(var);
   }
   ir_call *call = new(ctx) ir_call(sig, deref, actual_parameters);
   instructions->push_tail(call);

   /* Also emit any necessary out-parameter conversions. */
   instructions->append_list(&post_call_conversions);

   return deref ? deref->clone(ctx, NULL) : NULL;
}

/**
 * Given a function name and parameter list, find the matching signature.
 */
static ir_function_signature *
match_function_by_name(const char *name,
                       exec_list *actual_parameters,
                       struct _mesa_glsl_parse_state *state)
{
   void *ctx = state;
   ir_function *f = state->symbols->get_function(name);
   ir_function_signature *local_sig = NULL;
   ir_function_signature *sig = NULL;

   /* Is the function hidden by a record type constructor? */
   if (state->symbols->get_type(name))
      goto done; /* no match */

   /* Is the function hidden by a variable (impossible in 1.10)? */
   if (state->language_version != 110 && state->symbols->get_variable(name))
      goto done; /* no match */

   if (f != NULL) {
      /* Look for a match in the local shader.  If exact, we're done. */
      bool is_exact = false;
      sig = local_sig = f->matching_signature(actual_parameters, &is_exact);
      if (is_exact)
         goto done;

      if (!state->es_shader && f->has_user_signature()) {
         /* In desktop GL, the presence of a user-defined signature hides any
          * built-in signatures, so we must ignore them.  In contrast, in ES2
          * user-defined signatures add new overloads, so we must proceed.
          */
         goto done;
      }
   }

   /* Local shader has no exact candidates; check the built-ins. */
   _mesa_glsl_initialize_functions(state);
   for (unsigned i = 0; i < state->num_builtins_to_link; i++) {
      ir_function *builtin =
         state->builtins_to_link[i]->symbols->get_function(name);
      if (builtin == NULL)
         continue;

      bool is_exact = false;
      ir_function_signature *builtin_sig =
         builtin->matching_signature(actual_parameters, &is_exact);

      if (builtin_sig == NULL)
         continue;

      /* If the built-in signature is exact, we can stop. */
      if (is_exact) {
         sig = builtin_sig;
         goto done;
      }

      if (sig == NULL) {
         /* We found an inexact match, which is better than nothing.  However,
          * we should keep searching for an exact match.
          */
         sig = builtin_sig;
      }
   }

done:
   if (sig != NULL) {
      /* If the match is from a linked built-in shader, import the prototype. */
      if (sig != local_sig) {
         if (f == NULL) {
            f = new(ctx) ir_function(name);
            state->symbols->add_global_function(f);
            emit_function(state, f);
         }
         f->add_signature(sig->clone_prototype(f, NULL));
      }
   }
   return sig;
}

/**
 * Raise a "no matching function" error, listing all possible overloads the
 * compiler considered so developers can figure out what went wrong.
 */
static void
no_matching_function_error(const char *name,
                           YYLTYPE *loc,
                           exec_list *actual_parameters,
                           _mesa_glsl_parse_state *state)
{
   char *str = prototype_string(NULL, name, actual_parameters);
   _mesa_glsl_error(loc, state, "no matching function for call to `%s'", str);
   ralloc_free(str);

   const char *prefix = "candidates are: ";

   for (int i = -1; i < (int) state->num_builtins_to_link; i++) {
      glsl_symbol_table *syms = i >= 0 ? state->builtins_to_link[i]->symbols
                                       : state->symbols;
      ir_function *f = syms->get_function(name);
      if (f == NULL)
         continue;

      foreach_list (node, &f->signatures) {
         ir_function_signature *sig = (ir_function_signature *) node;

         str = prototype_string(sig->return_type, f->name, &sig->parameters);
         _mesa_glsl_error(loc, state, "%s%s", prefix, str);
         ralloc_free(str);

         prefix = "                ";
      }
   }
}

/**
 * Perform automatic type conversion of constructor parameters
 *
 * This implements the rules in the "Conversion and Scalar Constructors"
 * section (GLSL 1.10 section 5.4.1), not the "Implicit Conversions" rules.
 */
static ir_rvalue *
convert_component(ir_rvalue *src, const glsl_type *desired_type)
{
   void *ctx = ralloc_parent(src);
   const unsigned a = desired_type->base_type;
   const unsigned b = src->type->base_type;
   ir_expression *result = NULL;

   if (src->type->is_error())
      return src;

   assert(a <= GLSL_TYPE_BOOL);
   assert(b <= GLSL_TYPE_BOOL);

   if (a == b)
      return src;

   switch (a) {
   case GLSL_TYPE_UINT:
      switch (b) {
      case GLSL_TYPE_INT:
         result = new(ctx) ir_expression(ir_unop_i2u, src);
         break;
      case GLSL_TYPE_FLOAT:
         result = new(ctx) ir_expression(ir_unop_i2u,
                  new(ctx) ir_expression(ir_unop_f2i, src));
         break;
      case GLSL_TYPE_BOOL:
         result = new(ctx) ir_expression(ir_unop_i2u,
                  new(ctx) ir_expression(ir_unop_b2i, src));
         break;
      }
      break;
   case GLSL_TYPE_INT:
      switch (b) {
      case GLSL_TYPE_UINT:
         result = new(ctx) ir_expression(ir_unop_u2i, src);
         break;
      case GLSL_TYPE_FLOAT:
         result = new(ctx) ir_expression(ir_unop_f2i, src);
         break;
      case GLSL_TYPE_BOOL:
         result = new(ctx) ir_expression(ir_unop_b2i, src);
         break;
      }
      break;
   case GLSL_TYPE_FLOAT:
      switch (b) {
      case GLSL_TYPE_UINT:
         result = new(ctx) ir_expression(ir_unop_u2f, desired_type, src, NULL);
         break;
      case GLSL_TYPE_INT:
         result = new(ctx) ir_expression(ir_unop_i2f, desired_type, src, NULL);
         break;
      case GLSL_TYPE_BOOL:
         result = new(ctx) ir_expression(ir_unop_b2f, desired_type, src, NULL);
         break;
      }
      break;
   case GLSL_TYPE_BOOL:
      switch (b) {
      case GLSL_TYPE_UINT:
         result = new(ctx) ir_expression(ir_unop_i2b,
                  new(ctx) ir_expression(ir_unop_u2i, src));
         break;
      case GLSL_TYPE_INT:
         result = new(ctx) ir_expression(ir_unop_i2b, desired_type, src, NULL);
         break;
      case GLSL_TYPE_FLOAT:
         result = new(ctx) ir_expression(ir_unop_f2b, desired_type, src, NULL);
         break;
      }
      break;
   }

   assert(result != NULL);
   assert(result->type == desired_type);

   /* Try constant folding; it may fold in the conversion we just added. */
   ir_constant *const constant = result->constant_expression_value();
   return (constant != NULL) ? (ir_rvalue *) constant : (ir_rvalue *) result;
}

/**
 * Dereference a specific component from a scalar, vector, or matrix
 */
static ir_rvalue *
dereference_component(ir_rvalue *src, unsigned component)
{
   void *ctx = ralloc_parent(src);
   assert(component < src->type->components());

   /* If the source is a constant, just create a new constant instead of a
    * dereference of the existing constant.
    */
   ir_constant *constant = src->as_constant();
   if (constant)
      return new(ctx) ir_constant(constant, component);

   if (src->type->is_scalar()) {
      return src;
   } else if (src->type->is_vector()) {
      return new(ctx) ir_swizzle(src, component, 0, 0, 0, 1);
   } else {
      assert(src->type->is_matrix());

      /* Dereference a row of the matrix, then call this function again to get
       * a specific element from that row.
       */
      const int c = component / src->type->column_type()->vector_elements;
      const int r = component % src->type->column_type()->vector_elements;
      ir_constant *const col_index = new(ctx) ir_constant(c);
      ir_dereference *const col = new(ctx) ir_dereference_array(src, col_index);

      col->type = src->type->column_type();

      return dereference_component(col, r);
   }

   assert(!"Should not get here.");
   return NULL;
}


static ir_rvalue *
process_array_constructor(exec_list *instructions,
                          const glsl_type *constructor_type,
                          YYLTYPE *loc, exec_list *parameters,
                          struct _mesa_glsl_parse_state *state)
{
   void *ctx = state;
   /* Array constructors come in two forms: sized and unsized.  Sized array
    * constructors look like 'vec4[2](a, b)', where 'a' and 'b' are vec4
    * variables.  In this case the number of parameters must exactly match the
    * specified size of the array.
    *
    * Unsized array constructors look like 'vec4[](a, b)', where 'a' and 'b'
    * are vec4 variables.  In this case the size of the array being constructed
    * is determined by the number of parameters.
    *
    * From page 52 (page 58 of the PDF) of the GLSL 1.50 spec:
    *
    *    "There must be exactly the same number of arguments as the size of
    *    the array being constructed. If no size is present in the
    *    constructor, then the array is explicitly sized to the number of
    *    arguments provided. The arguments are assigned in order, starting at
    *    element 0, to the elements of the constructed array. Each argument
    *    must be the same type as the element type of the array, or be a type
    *    that can be converted to the element type of the array according to
    *    Section 4.1.10 "Implicit Conversions.""
    */
   exec_list actual_parameters;
   const unsigned parameter_count =
      process_parameters(instructions, &actual_parameters, parameters, state);

   if ((parameter_count == 0)
       || ((constructor_type->length != 0)
           && (constructor_type->length != parameter_count))) {
      const unsigned min_param = (constructor_type->length == 0)
         ? 1 : constructor_type->length;

      _mesa_glsl_error(loc, state, "array constructor must have %s %u "
                       "parameter%s",
                       (constructor_type->length != 0) ? "at least" : "exactly",
                       min_param, (min_param <= 1) ? "" : "s");
      return ir_rvalue::error_value(ctx);
   }

   if (constructor_type->length == 0) {
      constructor_type =
         glsl_type::get_array_instance(constructor_type->element_type(),
                                       parameter_count);
      assert(constructor_type != NULL);
      assert(constructor_type->length == parameter_count);
   }

   bool all_parameters_are_constant = true;

   /* Type cast each parameter and, if possible, fold constants. */
   foreach_list_safe(n, &actual_parameters) {
      ir_rvalue *ir = (ir_rvalue *) n;
      ir_rvalue *result = ir;

      /* Apply implicit conversions (not the scalar constructor rules!). See
       * the spec quote above. */
      if (constructor_type->element_type()->is_float()) {
         const glsl_type *desired_type =
            glsl_type::get_instance(GLSL_TYPE_FLOAT,
                                    ir->type->vector_elements,
                                    ir->type->matrix_columns);
         if (result->type->can_implicitly_convert_to(desired_type)) {
            /* Even though convert_component() implements the constructor
             * conversion rules (not the implicit conversion rules), its safe
             * to use it here because we already checked that the implicit
             * conversion is legal.
             */
            result = convert_component(ir, desired_type);
         }
      }

      if (result->type != constructor_type->element_type()) {
         _mesa_glsl_error(loc, state, "type error in array constructor: "
                          "expected: %s, found %s",
                          constructor_type->element_type()->name,
                          result->type->name);
      }

      /* Attempt to convert the parameter to a constant valued expression.
       * After doing so, track whether or not all the parameters to the
       * constructor are trivially constant valued expressions.
       */
      ir_rvalue *const constant = result->constant_expression_value();

      if (constant != NULL)
         result = constant;
      else
         all_parameters_are_constant = false;

      ir->replace_with(result);
   }

   if (all_parameters_are_constant)
      return new(ctx) ir_constant(constructor_type, &actual_parameters);

   ir_variable *var = new(ctx) ir_variable(constructor_type, "array_ctor",
                                           ir_var_temporary);
   instructions->push_tail(var);

   int i = 0;
   foreach_list(node, &actual_parameters) {
      ir_rvalue *rhs = (ir_rvalue *) node;
      ir_rvalue *lhs = new(ctx) ir_dereference_array(var,
                                                     new(ctx) ir_constant(i));

      ir_instruction *assignment = new(ctx) ir_assignment(lhs, rhs, NULL);
      instructions->push_tail(assignment);

      i++;
   }

   return new(ctx) ir_dereference_variable(var);
}


/**
 * Try to convert a record constructor to a constant expression
 */
static ir_constant *
constant_record_constructor(const glsl_type *constructor_type,
                            exec_list *parameters, void *mem_ctx)
{
   foreach_list(node, parameters) {
      ir_constant *constant = ((ir_instruction *) node)->as_constant();
      if (constant == NULL)
         return NULL;
      node->replace_with(constant);
   }

   return new(mem_ctx) ir_constant(constructor_type, parameters);
}


/**
 * Determine if a list consists of a single scalar r-value
 */
bool
single_scalar_parameter(exec_list *parameters)
{
   const ir_rvalue *const p = (ir_rvalue *) parameters->head;
   assert(((ir_rvalue *)p)->as_rvalue() != NULL);

   return (p->type->is_scalar() && p->next->is_tail_sentinel());
}


/**
 * Generate inline code for a vector constructor
 *
 * The generated constructor code will consist of a temporary variable
 * declaration of the same type as the constructor.  A sequence of assignments
 * from constructor parameters to the temporary will follow.
 *
 * \return
 * An \c ir_dereference_variable of the temprorary generated in the constructor
 * body.
 */
ir_rvalue *
emit_inline_vector_constructor(const glsl_type *type,
                               exec_list *instructions,
                               exec_list *parameters,
                               void *ctx)
{
   assert(!parameters->is_empty());

   ir_variable *var = new(ctx) ir_variable(type, "vec_ctor", ir_var_temporary);
   instructions->push_tail(var);

   /* There are two kinds of vector constructors.
    *
    *  - Construct a vector from a single scalar by replicating that scalar to
    *    all components of the vector.
    *
    *  - Construct a vector from an arbirary combination of vectors and
    *    scalars.  The components of the constructor parameters are assigned
    *    to the vector in order until the vector is full.
    */
   const unsigned lhs_components = type->components();
   if (single_scalar_parameter(parameters)) {
      ir_rvalue *first_param = (ir_rvalue *)parameters->head;
      ir_rvalue *rhs = new(ctx) ir_swizzle(first_param, 0, 0, 0, 0,
                                           lhs_components);
      ir_dereference_variable *lhs = new(ctx) ir_dereference_variable(var);
      const unsigned mask = (1U << lhs_components) - 1;

      assert(rhs->type == lhs->type);

      ir_instruction *inst = new(ctx) ir_assignment(lhs, rhs, NULL, mask);
      instructions->push_tail(inst);
   } else {
      unsigned base_component = 0;
      unsigned base_lhs_component = 0;
      ir_constant_data data;
      unsigned constant_mask = 0, constant_components = 0;

      memset(&data, 0, sizeof(data));

      foreach_list(node, parameters) {
         ir_rvalue *param = (ir_rvalue *) node;
         unsigned rhs_components = param->type->components();

         /* Do not try to assign more components to the vector than it has!
          */
         if ((rhs_components + base_lhs_component) > lhs_components) {
            rhs_components = lhs_components - base_lhs_component;
         }

         const ir_constant *const c = param->as_constant();
         if (c != NULL) {
            for (unsigned i = 0; i < rhs_components; i++) {
               switch (c->type->base_type) {
               case GLSL_TYPE_UINT:
                  data.u[i + base_component] = c->get_uint_component(i);
                  break;
               case GLSL_TYPE_INT:
                  data.i[i + base_component] = c->get_int_component(i);
                  break;
               case GLSL_TYPE_FLOAT:
                  data.f[i + base_component] = c->get_float_component(i);
                  break;
               case GLSL_TYPE_BOOL:
                  data.b[i + base_component] = c->get_bool_component(i);
                  break;
               default:
                  assert(!"Should not get here.");
                  break;
               }
            }

            /* Mask of fields to be written in the assignment.
             */
            constant_mask |= ((1U << rhs_components) - 1) << base_lhs_component;
            constant_components += rhs_components;

            base_component += rhs_components;
         }
         /* Advance the component index by the number of components
          * that were just assigned.
          */
         base_lhs_component += rhs_components;
      }

      if (constant_mask != 0) {
         ir_dereference *lhs = new(ctx) ir_dereference_variable(var);
         const glsl_type *rhs_type = glsl_type::get_instance(var->type->base_type,
                                                             constant_components,
                                                             1);
         ir_rvalue *rhs = new(ctx) ir_constant(rhs_type, &data);

         ir_instruction *inst =
            new(ctx) ir_assignment(lhs, rhs, NULL, constant_mask);
         instructions->push_tail(inst);
      }

      base_component = 0;
      foreach_list(node, parameters) {
         ir_rvalue *param = (ir_rvalue *) node;
         unsigned rhs_components = param->type->components();

         /* Do not try to assign more components to the vector than it has!
          */
         if ((rhs_components + base_component) > lhs_components) {
            rhs_components = lhs_components - base_component;
         }

         const ir_constant *const c = param->as_constant();
         if (c == NULL) {
            /* Mask of fields to be written in the assignment.
             */
            const unsigned write_mask = ((1U << rhs_components) - 1)
               << base_component;

            ir_dereference *lhs = new(ctx) ir_dereference_variable(var);

            /* Generate a swizzle so that LHS and RHS sizes match.
             */
            ir_rvalue *rhs =
               new(ctx) ir_swizzle(param, 0, 1, 2, 3, rhs_components);

            ir_instruction *inst =
               new(ctx) ir_assignment(lhs, rhs, NULL, write_mask);
            instructions->push_tail(inst);
         }

         /* Advance the component index by the number of components that were
          * just assigned.
          */
         base_component += rhs_components;
      }
   }
   return new(ctx) ir_dereference_variable(var);
}


/**
 * Generate assignment of a portion of a vector to a portion of a matrix column
 *
 * \param src_base  First component of the source to be used in assignment
 * \param column    Column of destination to be assiged
 * \param row_base  First component of the destination column to be assigned
 * \param count     Number of components to be assigned
 *
 * \note
 * \c src_base + \c count must be less than or equal to the number of components
 * in the source vector.
 */
ir_instruction *
assign_to_matrix_column(ir_variable *var, unsigned column, unsigned row_base,
                        ir_rvalue *src, unsigned src_base, unsigned count,
                        void *mem_ctx)
{
   ir_constant *col_idx = new(mem_ctx) ir_constant(column);
   ir_dereference *column_ref = new(mem_ctx) ir_dereference_array(var, col_idx);

   assert(column_ref->type->components() >= (row_base + count));
   assert(src->type->components() >= (src_base + count));

   /* Generate a swizzle that extracts the number of components from the source
    * that are to be assigned to the column of the matrix.
    */
   if (count < src->type->vector_elements) {
      src = new(mem_ctx) ir_swizzle(src,
                                    src_base + 0, src_base + 1,
                                    src_base + 2, src_base + 3,
                                    count);
   }

   /* Mask of fields to be written in the assignment.
    */
   const unsigned write_mask = ((1U << count) - 1) << row_base;

   return new(mem_ctx) ir_assignment(column_ref, src, NULL, write_mask);
}


/**
 * Generate inline code for a matrix constructor
 *
 * The generated constructor code will consist of a temporary variable
 * declaration of the same type as the constructor.  A sequence of assignments
 * from constructor parameters to the temporary will follow.
 *
 * \return
 * An \c ir_dereference_variable of the temprorary generated in the constructor
 * body.
 */
ir_rvalue *
emit_inline_matrix_constructor(const glsl_type *type,
                               exec_list *instructions,
                               exec_list *parameters,
                               void *ctx)
{
   assert(!parameters->is_empty());

   ir_variable *var = new(ctx) ir_variable(type, "mat_ctor", ir_var_temporary);
   instructions->push_tail(var);

   /* There are three kinds of matrix constructors.
    *
    *  - Construct a matrix from a single scalar by replicating that scalar to
    *    along the diagonal of the matrix and setting all other components to
    *    zero.
    *
    *  - Construct a matrix from an arbirary combination of vectors and
    *    scalars.  The components of the constructor parameters are assigned
    *    to the matrix in colum-major order until the matrix is full.
    *
    *  - Construct a matrix from a single matrix.  The source matrix is copied
    *    to the upper left portion of the constructed matrix, and the remaining
    *    elements take values from the identity matrix.
    */
   ir_rvalue *const first_param = (ir_rvalue *) parameters->head;
   if (single_scalar_parameter(parameters)) {
      /* Assign the scalar to the X component of a vec4, and fill the remaining
       * components with zero.
       */
      ir_variable *rhs_var =
         new(ctx) ir_variable(glsl_type::vec4_type, "mat_ctor_vec",
                              ir_var_temporary);
      instructions->push_tail(rhs_var);

      ir_constant_data zero;
      zero.f[0] = 0.0;
      zero.f[1] = 0.0;
      zero.f[2] = 0.0;
      zero.f[3] = 0.0;

      ir_instruction *inst =
         new(ctx) ir_assignment(new(ctx) ir_dereference_variable(rhs_var),
                                new(ctx) ir_constant(rhs_var->type, &zero),
                                NULL);
      instructions->push_tail(inst);

      ir_dereference *const rhs_ref = new(ctx) ir_dereference_variable(rhs_var);

      inst = new(ctx) ir_assignment(rhs_ref, first_param, NULL, 0x01);
      instructions->push_tail(inst);

      /* Assign the temporary vector to each column of the destination matrix
       * with a swizzle that puts the X component on the diagonal of the
       * matrix.  In some cases this may mean that the X component does not
       * get assigned into the column at all (i.e., when the matrix has more
       * columns than rows).
       */
      static const unsigned rhs_swiz[4][4] = {
         { 0, 1, 1, 1 },
         { 1, 0, 1, 1 },
         { 1, 1, 0, 1 },
         { 1, 1, 1, 0 }
      };

      const unsigned cols_to_init = MIN2(type->matrix_columns,
                                         type->vector_elements);
      for (unsigned i = 0; i < cols_to_init; i++) {
         ir_constant *const col_idx = new(ctx) ir_constant(i);
         ir_rvalue *const col_ref = new(ctx) ir_dereference_array(var, col_idx);

         ir_rvalue *const rhs_ref = new(ctx) ir_dereference_variable(rhs_var);
         ir_rvalue *const rhs = new(ctx) ir_swizzle(rhs_ref, rhs_swiz[i],
                                                    type->vector_elements);

         inst = new(ctx) ir_assignment(col_ref, rhs, NULL);
         instructions->push_tail(inst);
      }

      for (unsigned i = cols_to_init; i < type->matrix_columns; i++) {
         ir_constant *const col_idx = new(ctx) ir_constant(i);
         ir_rvalue *const col_ref = new(ctx) ir_dereference_array(var, col_idx);

         ir_rvalue *const rhs_ref = new(ctx) ir_dereference_variable(rhs_var);
         ir_rvalue *const rhs = new(ctx) ir_swizzle(rhs_ref, 1, 1, 1, 1,
                                                    type->vector_elements);

         inst = new(ctx) ir_assignment(col_ref, rhs, NULL);
         instructions->push_tail(inst);
      }
   } else if (first_param->type->is_matrix()) {
      /* From page 50 (56 of the PDF) of the GLSL 1.50 spec:
       *
       *     "If a matrix is constructed from a matrix, then each component
       *     (column i, row j) in the result that has a corresponding
       *     component (column i, row j) in the argument will be initialized
       *     from there. All other components will be initialized to the
       *     identity matrix. If a matrix argument is given to a matrix
       *     constructor, it is an error to have any other arguments."
       */
      assert(first_param->next->is_tail_sentinel());
      ir_rvalue *const src_matrix = first_param;

      /* If the source matrix is smaller, pre-initialize the relavent parts of
       * the destination matrix to the identity matrix.
       */
      if ((src_matrix->type->matrix_columns < var->type->matrix_columns)
          || (src_matrix->type->vector_elements < var->type->vector_elements)) {

         /* If the source matrix has fewer rows, every column of the destination
          * must be initialized.  Otherwise only the columns in the destination
          * that do not exist in the source must be initialized.
          */
         unsigned col =
            (src_matrix->type->vector_elements < var->type->vector_elements)
            ? 0 : src_matrix->type->matrix_columns;

         const glsl_type *const col_type = var->type->column_type();
         for (/* empty */; col < var->type->matrix_columns; col++) {
            ir_constant_data ident;

            ident.f[0] = 0.0;
            ident.f[1] = 0.0;
            ident.f[2] = 0.0;
            ident.f[3] = 0.0;

            ident.f[col] = 1.0;

            ir_rvalue *const rhs = new(ctx) ir_constant(col_type, &ident);

            ir_rvalue *const lhs =
               new(ctx) ir_dereference_array(var, new(ctx) ir_constant(col));

            ir_instruction *inst = new(ctx) ir_assignment(lhs, rhs, NULL);
            instructions->push_tail(inst);
         }
      }

      /* Assign columns from the source matrix to the destination matrix.
       *
       * Since the parameter will be used in the RHS of multiple assignments,
       * generate a temporary and copy the paramter there.
       */
      ir_variable *const rhs_var =
         new(ctx) ir_variable(first_param->type, "mat_ctor_mat",
                              ir_var_temporary);
      instructions->push_tail(rhs_var);

      ir_dereference *const rhs_var_ref =
         new(ctx) ir_dereference_variable(rhs_var);
      ir_instruction *const inst =
         new(ctx) ir_assignment(rhs_var_ref, first_param, NULL);
      instructions->push_tail(inst);

      const unsigned last_row = MIN2(src_matrix->type->vector_elements,
                                     var->type->vector_elements);
      const unsigned last_col = MIN2(src_matrix->type->matrix_columns,
                                     var->type->matrix_columns);

      unsigned swiz[4] = { 0, 0, 0, 0 };
      for (unsigned i = 1; i < last_row; i++)
         swiz[i] = i;

      const unsigned write_mask = (1U << last_row) - 1;

      for (unsigned i = 0; i < last_col; i++) {
         ir_dereference *const lhs =
            new(ctx) ir_dereference_array(var, new(ctx) ir_constant(i));
         ir_rvalue *const rhs_col =
            new(ctx) ir_dereference_array(rhs_var, new(ctx) ir_constant(i));

         /* If one matrix has columns that are smaller than the columns of the
          * other matrix, wrap the column access of the larger with a swizzle
          * so that the LHS and RHS of the assignment have the same size (and
          * therefore have the same type).
          *
          * It would be perfectly valid to unconditionally generate the
          * swizzles, this this will typically result in a more compact IR tree.
          */
         ir_rvalue *rhs;
         if (lhs->type->vector_elements != rhs_col->type->vector_elements) {
            rhs = new(ctx) ir_swizzle(rhs_col, swiz, last_row);
         } else {
            rhs = rhs_col;
         }

         ir_instruction *inst =
            new(ctx) ir_assignment(lhs, rhs, NULL, write_mask);
         instructions->push_tail(inst);
      }
   } else {
      const unsigned cols = type->matrix_columns;
      const unsigned rows = type->vector_elements;
      unsigned col_idx = 0;
      unsigned row_idx = 0;

      foreach_list (node, parameters) {
         ir_rvalue *const rhs = (ir_rvalue *) node;
         const unsigned components_remaining_this_column = rows - row_idx;
         unsigned rhs_components = rhs->type->components();
         unsigned rhs_base = 0;

         /* Since the parameter might be used in the RHS of two assignments,
          * generate a temporary and copy the paramter there.
          */
         ir_variable *rhs_var =
            new(ctx) ir_variable(rhs->type, "mat_ctor_vec", ir_var_temporary);
         instructions->push_tail(rhs_var);

         ir_dereference *rhs_var_ref =
            new(ctx) ir_dereference_variable(rhs_var);
         ir_instruction *inst = new(ctx) ir_assignment(rhs_var_ref, rhs, NULL);
         instructions->push_tail(inst);

         /* Assign the current parameter to as many components of the matrix
          * as it will fill.
          *
          * NOTE: A single vector parameter can span two matrix columns.  A
          * single vec4, for example, can completely fill a mat2.
          */
         if (rhs_components >= components_remaining_this_column) {
            const unsigned count = MIN2(rhs_components,
                                        components_remaining_this_column);

            rhs_var_ref = new(ctx) ir_dereference_variable(rhs_var);

            ir_instruction *inst = assign_to_matrix_column(var, col_idx,
                                                           row_idx,
                                                           rhs_var_ref, 0,
                                                           count, ctx);
            instructions->push_tail(inst);

            rhs_base = count;

            col_idx++;
            row_idx = 0;
         }

         /* If there is data left in the parameter and components left to be
          * set in the destination, emit another assignment.  It is possible
          * that the assignment could be of a vec4 to the last element of the
          * matrix.  In this case col_idx==cols, but there is still data
          * left in the source parameter.  Obviously, don't emit an assignment
          * to data outside the destination matrix.
          */
         if ((col_idx < cols) && (rhs_base < rhs_components)) {
            const unsigned count = rhs_components - rhs_base;

            rhs_var_ref = new(ctx) ir_dereference_variable(rhs_var);

            ir_instruction *inst = assign_to_matrix_column(var, col_idx,
                                                           row_idx,
                                                           rhs_var_ref,
                                                           rhs_base,
                                                           count, ctx);
            instructions->push_tail(inst);

            row_idx += count;
         }
      }
   }

   return new(ctx) ir_dereference_variable(var);
}


ir_rvalue *
emit_inline_record_constructor(const glsl_type *type,
                               exec_list *instructions,
                               exec_list *parameters,
                               void *mem_ctx)
{
   ir_variable *const var =
      new(mem_ctx) ir_variable(type, "record_ctor", ir_var_temporary);
   ir_dereference_variable *const d = new(mem_ctx) ir_dereference_variable(var);

   instructions->push_tail(var);

   exec_node *node = parameters->head;
   for (unsigned i = 0; i < type->length; i++) {
      assert(!node->is_tail_sentinel());

      ir_dereference *const lhs =
         new(mem_ctx) ir_dereference_record(d->clone(mem_ctx, NULL),
                                            type->fields.structure[i].name);

      ir_rvalue *const rhs = ((ir_instruction *) node)->as_rvalue();
      assert(rhs != NULL);

      ir_instruction *const assign = new(mem_ctx) ir_assignment(lhs, rhs, NULL);

      instructions->push_tail(assign);
      node = node->next;
   }

   return d;
}


ir_rvalue *
ast_function_expression::hir(exec_list *instructions,
                             struct _mesa_glsl_parse_state *state)
{
   void *ctx = state;
   /* There are three sorts of function calls.
    *
    * 1. constructors - The first subexpression is an ast_type_specifier.
    * 2. methods - Only the .length() method of array types.
    * 3. functions - Calls to regular old functions.
    *
    * Method calls are actually detected when the ast_field_selection
    * expression is handled.
    */
   if (is_constructor()) {
      const ast_type_specifier *type = (ast_type_specifier *) subexpressions[0];
      YYLTYPE loc = type->get_location();
      const char *name;

      const glsl_type *const constructor_type = type->glsl_type(& name, state);

      /* constructor_type can be NULL if a variable with the same name as the
       * structure has come into scope.
       */
      if (constructor_type == NULL) {
         _mesa_glsl_error(& loc, state, "unknown type `%s' (structure name "
                          "may be shadowed by a variable with the same name)",
                          type->type_name);
         return ir_rvalue::error_value(ctx);
      }


      /* Constructors for samplers are illegal.
       */
      if (constructor_type->is_sampler()) {
         _mesa_glsl_error(& loc, state, "cannot construct sampler type `%s'",
                          constructor_type->name);
         return ir_rvalue::error_value(ctx);
      }

      if (constructor_type->is_array()) {
         if (state->language_version <= 110) {
            _mesa_glsl_error(& loc, state,
                             "array constructors forbidden in GLSL 1.10");
            return ir_rvalue::error_value(ctx);
         }

         return process_array_constructor(instructions, constructor_type,
                                          & loc, &this->expressions, state);
      }


      /* There are two kinds of constructor call.  Constructors for built-in
       * language types, such as mat4 and vec2, are free form.  The only
       * requirement is that the parameters must provide enough values of the
       * correct scalar type.  Constructors for arrays and structures must
       * have the exact number of parameters with matching types in the
       * correct order.  These constructors follow essentially the same type
       * matching rules as functions.
       */
      if (constructor_type->is_record()) {
         exec_list actual_parameters;

         process_parameters(instructions, &actual_parameters,
                            &this->expressions, state);

         exec_node *node = actual_parameters.head;
         for (unsigned i = 0; i < constructor_type->length; i++) {
            ir_rvalue *ir = (ir_rvalue *) node;

            if (node->is_tail_sentinel()) {
               _mesa_glsl_error(&loc, state,
                                "insufficient parameters to constructor "
                                "for `%s'",
                                constructor_type->name);
               return ir_rvalue::error_value(ctx);
            }

            if (apply_implicit_conversion(constructor_type->fields.structure[i].type,
                                          ir, state)) {
               node->replace_with(ir);
            } else {
               _mesa_glsl_error(&loc, state,
                                "parameter type mismatch in constructor "
                                "for `%s.%s' (%s vs %s)",
                                constructor_type->name,
                                constructor_type->fields.structure[i].name,
                                ir->type->name,
                                constructor_type->fields.structure[i].type->name);
               return ir_rvalue::error_value(ctx);;
            }

            node = node->next;
         }

         if (!node->is_tail_sentinel()) {
            _mesa_glsl_error(&loc, state, "too many parameters in constructor "
                             "for `%s'", constructor_type->name);
            return ir_rvalue::error_value(ctx);
         }

         ir_rvalue *const constant =
            constant_record_constructor(constructor_type, &actual_parameters,
                                        state);

         return (constant != NULL)
            ? constant
            : emit_inline_record_constructor(constructor_type, instructions,
                                             &actual_parameters, state);
      }

      if (!constructor_type->is_numeric() && !constructor_type->is_boolean())
         return ir_rvalue::error_value(ctx);

      /* Total number of components of the type being constructed. */
      const unsigned type_components = constructor_type->components();

      /* Number of components from parameters that have actually been
       * consumed.  This is used to perform several kinds of error checking.
       */
      unsigned components_used = 0;

      unsigned matrix_parameters = 0;
      unsigned nonmatrix_parameters = 0;
      exec_list actual_parameters;

      foreach_list (n, &this->expressions) {
         ast_node *ast = exec_node_data(ast_node, n, link);
         ir_rvalue *result = ast->hir(instructions, state)->as_rvalue();

         /* From page 50 (page 56 of the PDF) of the GLSL 1.50 spec:
          *
          *    "It is an error to provide extra arguments beyond this
          *    last used argument."
          */
         if (components_used >= type_components) {
            _mesa_glsl_error(& loc, state, "too many parameters to `%s' "
                             "constructor",
                             constructor_type->name);
            return ir_rvalue::error_value(ctx);
         }

         if (!result->type->is_numeric() && !result->type->is_boolean()) {
            _mesa_glsl_error(& loc, state, "cannot construct `%s' from a "
                             "non-numeric data type",
                             constructor_type->name);
            return ir_rvalue::error_value(ctx);
         }

         /* Count the number of matrix and nonmatrix parameters.  This
          * is used below to enforce some of the constructor rules.
          */
         if (result->type->is_matrix())
            matrix_parameters++;
         else
            nonmatrix_parameters++;

         actual_parameters.push_tail(result);
         components_used += result->type->components();
      }

      /* From page 28 (page 34 of the PDF) of the GLSL 1.10 spec:
       *
       *    "It is an error to construct matrices from other matrices. This
       *    is reserved for future use."
       */
      if (state->language_version == 110 && matrix_parameters > 0
          && constructor_type->is_matrix()) {
         _mesa_glsl_error(& loc, state, "cannot construct `%s' from a "
                          "matrix in GLSL 1.10",
                          constructor_type->name);
         return ir_rvalue::error_value(ctx);
      }

      /* From page 50 (page 56 of the PDF) of the GLSL 1.50 spec:
       *
       *    "If a matrix argument is given to a matrix constructor, it is
       *    an error to have any other arguments."
       */
      if ((matrix_parameters > 0)
          && ((matrix_parameters + nonmatrix_parameters) > 1)
          && constructor_type->is_matrix()) {
         _mesa_glsl_error(& loc, state, "for matrix `%s' constructor, "
                          "matrix must be only parameter",
                          constructor_type->name);
         return ir_rvalue::error_value(ctx);
      }

      /* From page 28 (page 34 of the PDF) of the GLSL 1.10 spec:
       *
       *    "In these cases, there must be enough components provided in the
       *    arguments to provide an initializer for every component in the
       *    constructed value."
       */
      if (components_used < type_components && components_used != 1
          && matrix_parameters == 0) {
         _mesa_glsl_error(& loc, state, "too few components to construct "
                          "`%s'",
                          constructor_type->name);
         return ir_rvalue::error_value(ctx);
      }

      /* Later, we cast each parameter to the same base type as the
       * constructor.  Since there are no non-floating point matrices, we
       * need to break them up into a series of column vectors.
       */
      if (constructor_type->base_type != GLSL_TYPE_FLOAT) {
         foreach_list_safe(n, &actual_parameters) {
            ir_rvalue *matrix = (ir_rvalue *) n;

            if (!matrix->type->is_matrix())
               continue;

            /* Create a temporary containing the matrix. */
            ir_variable *var = new(ctx) ir_variable(matrix->type, "matrix_tmp",
                                                    ir_var_temporary);
            instructions->push_tail(var);
            instructions->push_tail(new(ctx) ir_assignment(new(ctx)
               ir_dereference_variable(var), matrix, NULL));
            var->constant_value = matrix->constant_expression_value();

            /* Replace the matrix with dereferences of its columns. */
            for (int i = 0; i < matrix->type->matrix_columns; i++) {
               matrix->insert_before(new (ctx) ir_dereference_array(var,
                  new(ctx) ir_constant(i)));
            }
            matrix->remove();
         }
      }

      bool all_parameters_are_constant = true;

      /* Type cast each parameter and, if possible, fold constants.*/
      foreach_list_safe(n, &actual_parameters) {
         ir_rvalue *ir = (ir_rvalue *) n;

         const glsl_type *desired_type =
            glsl_type::get_instance(constructor_type->base_type,
                                    ir->type->vector_elements,
                                    ir->type->matrix_columns);
         ir_rvalue *result = convert_component(ir, desired_type);

         /* Attempt to convert the parameter to a constant valued expression.
          * After doing so, track whether or not all the parameters to the
          * constructor are trivially constant valued expressions.
          */
         ir_rvalue *const constant = result->constant_expression_value();

         if (constant != NULL)
            result = constant;
         else
            all_parameters_are_constant = false;

         if (result != ir) {
            ir->replace_with(result);
         }
      }

      /* If all of the parameters are trivially constant, create a
       * constant representing the complete collection of parameters.
       */
      if (all_parameters_are_constant) {
         return new(ctx) ir_constant(constructor_type, &actual_parameters);
      } else if (constructor_type->is_scalar()) {
         return dereference_component((ir_rvalue *) actual_parameters.head,
                                      0);
      } else if (constructor_type->is_vector()) {
         return emit_inline_vector_constructor(constructor_type,
                                               instructions,
                                               &actual_parameters,
                                               ctx);
      } else {
         assert(constructor_type->is_matrix());
         return emit_inline_matrix_constructor(constructor_type,
                                               instructions,
                                               &actual_parameters,
                                               ctx);
      }
   } else {
      const ast_expression *id = subexpressions[0];
      const char *func_name = id->primary_expression.identifier;
      YYLTYPE loc = id->get_location();
      exec_list actual_parameters;

      process_parameters(instructions, &actual_parameters, &this->expressions,
                         state);

      ir_function_signature *sig =
         match_function_by_name(func_name, &actual_parameters, state);

      ir_call *call = NULL;
      ir_rvalue *value = NULL;
      if (sig == NULL) {
         no_matching_function_error(func_name, &loc, &actual_parameters, state);
         value = ir_rvalue::error_value(ctx);
      } else if (!verify_parameter_modes(state, sig, actual_parameters, this->expressions)) {
         /* an error has already been emitted */
         value = ir_rvalue::error_value(ctx);
      } else {
         value = generate_call(instructions, sig, &loc, &actual_parameters,
                               &call, state);
      }

      return value;
   }

   return ir_rvalue::error_value(ctx);
}