glsl: Track in each ir_variable whether it was ever assigned.

[profile/ivi/mesa.git] / src / glsl / ast_to_hir.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.
 */

/**
 * \file ast_to_hir.c
 * Convert abstract syntax to to high-level intermediate reprensentation (HIR).
 *
 * During the conversion to HIR, the majority of the symantic checking is
 * preformed on the program.  This includes:
 *
 *    * Symbol table management
 *    * Type checking
 *    * Function binding
 *
 * The majority of this work could be done during parsing, and the parser could
 * probably generate HIR directly.  However, this results in frequent changes
 * to the parser code.  Since we do not assume that every system this complier
 * is built on will have Flex and Bison installed, we have to store the code
 * generated by these tools in our version control system.  In other parts of
 * the system we've seen problems where a parser was changed but the generated
 * code was not committed, merge conflicts where created because two developers
 * had slightly different versions of Bison installed, etc.
 *
 * I have also noticed that running Bison generated parsers in GDB is very
 * irritating.  When you get a segfault on '$$ = $1->foo', you can't very
 * well 'print $1' in GDB.
 *
 * As a result, my preference is to put as little C code as possible in the
 * parser (and lexer) sources.
 */

#include "main/core.h" /* for struct gl_extensions */
#include "glsl_symbol_table.h"
#include "glsl_parser_extras.h"
#include "ast.h"
#include "glsl_types.h"
#include "program/hash_table.h"
#include "ir.h"

void
_mesa_ast_to_hir(exec_list *instructions, struct _mesa_glsl_parse_state *state)
{
   _mesa_glsl_initialize_variables(instructions, state);

   state->symbols->language_version = state->language_version;

   state->current_function = NULL;

   state->toplevel_ir = instructions;

   /* Section 4.2 of the GLSL 1.20 specification states:
    * "The built-in functions are scoped in a scope outside the global scope
    *  users declare global variables in.  That is, a shader's global scope,
    *  available for user-defined functions and global variables, is nested
    *  inside the scope containing the built-in functions."
    *
    * Since built-in functions like ftransform() access built-in variables,
    * it follows that those must be in the outer scope as well.
    *
    * We push scope here to create this nesting effect...but don't pop.
    * This way, a shader's globals are still in the symbol table for use
    * by the linker.
    */
   state->symbols->push_scope();

   foreach_list_typed (ast_node, ast, link, & state->translation_unit)
      ast->hir(instructions, state);

   detect_recursion_unlinked(state, instructions);

   state->toplevel_ir = NULL;
}


/**
 * If a conversion is available, convert one operand to a different type
 *
 * The \c from \c ir_rvalue is converted "in place".
 *
 * \param to     Type that the operand it to be converted to
 * \param from   Operand that is being converted
 * \param state  GLSL compiler state
 *
 * \return
 * If a conversion is possible (or unnecessary), \c true is returned.
 * Otherwise \c false is returned.
 */
bool
apply_implicit_conversion(const glsl_type *to, ir_rvalue * &from,
                          struct _mesa_glsl_parse_state *state)
{
   void *ctx = state;
   if (to->base_type == from->type->base_type)
      return true;

   /* This conversion was added in GLSL 1.20.  If the compilation mode is
    * GLSL 1.10, the conversion is skipped.
    */
   if (state->language_version < 120)
      return false;

   /* From page 27 (page 33 of the PDF) of the GLSL 1.50 spec:
    *
    *    "There are no implicit array or structure conversions. For
    *    example, an array of int cannot be implicitly converted to an
    *    array of float. There are no implicit conversions between
    *    signed and unsigned integers."
    */
   /* FINISHME: The above comment is partially a lie.  There is int/uint
    * FINISHME: conversion for immediate constants.
    */
   if (!to->is_float() || !from->type->is_numeric())
      return false;

   /* Convert to a floating point type with the same number of components
    * as the original type - i.e. int to float, not int to vec4.
    */
   to = glsl_type::get_instance(GLSL_TYPE_FLOAT, from->type->vector_elements,
                                from->type->matrix_columns);

   switch (from->type->base_type) {
   case GLSL_TYPE_INT:
      from = new(ctx) ir_expression(ir_unop_i2f, to, from, NULL);
      break;
   case GLSL_TYPE_UINT:
      from = new(ctx) ir_expression(ir_unop_u2f, to, from, NULL);
      break;
   case GLSL_TYPE_BOOL:
      from = new(ctx) ir_expression(ir_unop_b2f, to, from, NULL);
      break;
   default:
      assert(0);
   }

   return true;
}


static const struct glsl_type *
arithmetic_result_type(ir_rvalue * &value_a, ir_rvalue * &value_b,
                       bool multiply,
                       struct _mesa_glsl_parse_state *state, YYLTYPE *loc)
{
   const glsl_type *type_a = value_a->type;
   const glsl_type *type_b = value_b->type;

   /* From GLSL 1.50 spec, page 56:
    *
    *    "The arithmetic binary operators add (+), subtract (-),
    *    multiply (*), and divide (/) operate on integer and
    *    floating-point scalars, vectors, and matrices."
    */
   if (!type_a->is_numeric() || !type_b->is_numeric()) {
      _mesa_glsl_error(loc, state,
                       "Operands to arithmetic operators must be numeric");
      return glsl_type::error_type;
   }


   /*    "If one operand is floating-point based and the other is
    *    not, then the conversions from Section 4.1.10 "Implicit
    *    Conversions" are applied to the non-floating-point-based operand."
    */
   if (!apply_implicit_conversion(type_a, value_b, state)
       && !apply_implicit_conversion(type_b, value_a, state)) {
      _mesa_glsl_error(loc, state,
                       "Could not implicitly convert operands to "
                       "arithmetic operator");
      return glsl_type::error_type;
   }
   type_a = value_a->type;
   type_b = value_b->type;

   /*    "If the operands are integer types, they must both be signed or
    *    both be unsigned."
    *
    * From this rule and the preceeding conversion it can be inferred that
    * both types must be GLSL_TYPE_FLOAT, or GLSL_TYPE_UINT, or GLSL_TYPE_INT.
    * The is_numeric check above already filtered out the case where either
    * type is not one of these, so now the base types need only be tested for
    * equality.
    */
   if (type_a->base_type != type_b->base_type) {
      _mesa_glsl_error(loc, state,
                       "base type mismatch for arithmetic operator");
      return glsl_type::error_type;
   }

   /*    "All arithmetic binary operators result in the same fundamental type
    *    (signed integer, unsigned integer, or floating-point) as the
    *    operands they operate on, after operand type conversion. After
    *    conversion, the following cases are valid
    *
    *    * The two operands are scalars. In this case the operation is
    *      applied, resulting in a scalar."
    */
   if (type_a->is_scalar() && type_b->is_scalar())
      return type_a;

   /*   "* One operand is a scalar, and the other is a vector or matrix.
    *      In this case, the scalar operation is applied independently to each
    *      component of the vector or matrix, resulting in the same size
    *      vector or matrix."
    */
   if (type_a->is_scalar()) {
      if (!type_b->is_scalar())
         return type_b;
   } else if (type_b->is_scalar()) {
      return type_a;
   }

   /* All of the combinations of <scalar, scalar>, <vector, scalar>,
    * <scalar, vector>, <scalar, matrix>, and <matrix, scalar> have been
    * handled.
    */
   assert(!type_a->is_scalar());
   assert(!type_b->is_scalar());

   /*   "* The two operands are vectors of the same size. In this case, the
    *      operation is done component-wise resulting in the same size
    *      vector."
    */
   if (type_a->is_vector() && type_b->is_vector()) {
      if (type_a == type_b) {
         return type_a;
      } else {
         _mesa_glsl_error(loc, state,
                          "vector size mismatch for arithmetic operator");
         return glsl_type::error_type;
      }
   }

   /* All of the combinations of <scalar, scalar>, <vector, scalar>,
    * <scalar, vector>, <scalar, matrix>, <matrix, scalar>, and
    * <vector, vector> have been handled.  At least one of the operands must
    * be matrix.  Further, since there are no integer matrix types, the base
    * type of both operands must be float.
    */
   assert(type_a->is_matrix() || type_b->is_matrix());
   assert(type_a->base_type == GLSL_TYPE_FLOAT);
   assert(type_b->base_type == GLSL_TYPE_FLOAT);

   /*   "* The operator is add (+), subtract (-), or divide (/), and the
    *      operands are matrices with the same number of rows and the same
    *      number of columns. In this case, the operation is done component-
    *      wise resulting in the same size matrix."
    *    * The operator is multiply (*), where both operands are matrices or
    *      one operand is a vector and the other a matrix. A right vector
    *      operand is treated as a column vector and a left vector operand as a
    *      row vector. In all these cases, it is required that the number of
    *      columns of the left operand is equal to the number of rows of the
    *      right operand. Then, the multiply (*) operation does a linear
    *      algebraic multiply, yielding an object that has the same number of
    *      rows as the left operand and the same number of columns as the right
    *      operand. Section 5.10 "Vector and Matrix Operations" explains in
    *      more detail how vectors and matrices are operated on."
    */
   if (! multiply) {
      if (type_a == type_b)
         return type_a;
   } else {
      if (type_a->is_matrix() && type_b->is_matrix()) {
         /* Matrix multiply.  The columns of A must match the rows of B.  Given
          * the other previously tested constraints, this means the vector type
          * of a row from A must be the same as the vector type of a column from
          * B.
          */
         if (type_a->row_type() == type_b->column_type()) {
            /* The resulting matrix has the number of columns of matrix B and
             * the number of rows of matrix A.  We get the row count of A by
             * looking at the size of a vector that makes up a column.  The
             * transpose (size of a row) is done for B.
             */
            const glsl_type *const type =
               glsl_type::get_instance(type_a->base_type,
                                       type_a->column_type()->vector_elements,
                                       type_b->row_type()->vector_elements);
            assert(type != glsl_type::error_type);

            return type;
         }
      } else if (type_a->is_matrix()) {
         /* A is a matrix and B is a column vector.  Columns of A must match
          * rows of B.  Given the other previously tested constraints, this
          * means the vector type of a row from A must be the same as the
          * vector the type of B.
          */
         if (type_a->row_type() == type_b) {
            /* The resulting vector has a number of elements equal to
             * the number of rows of matrix A. */
            const glsl_type *const type =
               glsl_type::get_instance(type_a->base_type,
                                       type_a->column_type()->vector_elements,
                                       1);
            assert(type != glsl_type::error_type);

            return type;
         }
      } else {
         assert(type_b->is_matrix());

         /* A is a row vector and B is a matrix.  Columns of A must match rows
          * of B.  Given the other previously tested constraints, this means
          * the type of A must be the same as the vector type of a column from
          * B.
          */
         if (type_a == type_b->column_type()) {
            /* The resulting vector has a number of elements equal to
             * the number of columns of matrix B. */
            const glsl_type *const type =
               glsl_type::get_instance(type_a->base_type,
                                       type_b->row_type()->vector_elements,
                                       1);
            assert(type != glsl_type::error_type);

            return type;
         }
      }

      _mesa_glsl_error(loc, state, "size mismatch for matrix multiplication");
      return glsl_type::error_type;
   }


   /*    "All other cases are illegal."
    */
   _mesa_glsl_error(loc, state, "type mismatch");
   return glsl_type::error_type;
}


static const struct glsl_type *
unary_arithmetic_result_type(const struct glsl_type *type,
                             struct _mesa_glsl_parse_state *state, YYLTYPE *loc)
{
   /* From GLSL 1.50 spec, page 57:
    *
    *    "The arithmetic unary operators negate (-), post- and pre-increment
    *     and decrement (-- and ++) operate on integer or floating-point
    *     values (including vectors and matrices). All unary operators work
    *     component-wise on their operands. These result with the same type
    *     they operated on."
    */
   if (!type->is_numeric()) {
      _mesa_glsl_error(loc, state,
                       "Operands to arithmetic operators must be numeric");
      return glsl_type::error_type;
   }

   return type;
}

/**
 * \brief Return the result type of a bit-logic operation.
 *
 * If the given types to the bit-logic operator are invalid, return
 * glsl_type::error_type.
 *
 * \param type_a Type of LHS of bit-logic op
 * \param type_b Type of RHS of bit-logic op
 */
static const struct glsl_type *
bit_logic_result_type(const struct glsl_type *type_a,
                      const struct glsl_type *type_b,
                      ast_operators op,
                      struct _mesa_glsl_parse_state *state, YYLTYPE *loc)
{
    if (state->language_version < 130) {
       _mesa_glsl_error(loc, state, "bit operations require GLSL 1.30");
       return glsl_type::error_type;
    }

    /* From page 50 (page 56 of PDF) of GLSL 1.30 spec:
     *
     *     "The bitwise operators and (&), exclusive-or (^), and inclusive-or
     *     (|). The operands must be of type signed or unsigned integers or
     *     integer vectors."
     */
    if (!type_a->is_integer()) {
       _mesa_glsl_error(loc, state, "LHS of `%s' must be an integer",
                         ast_expression::operator_string(op));
       return glsl_type::error_type;
    }
    if (!type_b->is_integer()) {
       _mesa_glsl_error(loc, state, "RHS of `%s' must be an integer",
                        ast_expression::operator_string(op));
       return glsl_type::error_type;
    }

    /*     "The fundamental types of the operands (signed or unsigned) must
     *     match,"
     */
    if (type_a->base_type != type_b->base_type) {
       _mesa_glsl_error(loc, state, "operands of `%s' must have the same "
                        "base type", ast_expression::operator_string(op));
       return glsl_type::error_type;
    }

    /*     "The operands cannot be vectors of differing size." */
    if (type_a->is_vector() &&
        type_b->is_vector() &&
        type_a->vector_elements != type_b->vector_elements) {
       _mesa_glsl_error(loc, state, "operands of `%s' cannot be vectors of "
                        "different sizes", ast_expression::operator_string(op));
       return glsl_type::error_type;
    }

    /*     "If one operand is a scalar and the other a vector, the scalar is
     *     applied component-wise to the vector, resulting in the same type as
     *     the vector. The fundamental types of the operands [...] will be the
     *     resulting fundamental type."
     */
    if (type_a->is_scalar())
        return type_b;
    else
        return type_a;
}

static const struct glsl_type *
modulus_result_type(const struct glsl_type *type_a,
                    const struct glsl_type *type_b,
                    struct _mesa_glsl_parse_state *state, YYLTYPE *loc)
{
   if (state->language_version < 130) {
      _mesa_glsl_error(loc, state,
                       "operator '%%' is reserved in %s",
                       state->version_string);
      return glsl_type::error_type;
   }

   /* From GLSL 1.50 spec, page 56:
    *    "The operator modulus (%) operates on signed or unsigned integers or
    *    integer vectors. The operand types must both be signed or both be
    *    unsigned."
    */
   if (!type_a->is_integer()) {
      _mesa_glsl_error(loc, state, "LHS of operator %% must be an integer.");
      return glsl_type::error_type;
   }
   if (!type_b->is_integer()) {
      _mesa_glsl_error(loc, state, "RHS of operator %% must be an integer.");
      return glsl_type::error_type;
   }
   if (type_a->base_type != type_b->base_type) {
      _mesa_glsl_error(loc, state,
                       "operands of %% must have the same base type");
      return glsl_type::error_type;
   }

   /*    "The operands cannot be vectors of differing size. If one operand is
    *    a scalar and the other vector, then the scalar is applied component-
    *    wise to the vector, resulting in the same type as the vector. If both
    *    are vectors of the same size, the result is computed component-wise."
    */
   if (type_a->is_vector()) {
      if (!type_b->is_vector()
          || (type_a->vector_elements == type_b->vector_elements))
         return type_a;
   } else
      return type_b;

   /*    "The operator modulus (%) is not defined for any other data types
    *    (non-integer types)."
    */
   _mesa_glsl_error(loc, state, "type mismatch");
   return glsl_type::error_type;
}


static const struct glsl_type *
relational_result_type(ir_rvalue * &value_a, ir_rvalue * &value_b,
                       struct _mesa_glsl_parse_state *state, YYLTYPE *loc)
{
   const glsl_type *type_a = value_a->type;
   const glsl_type *type_b = value_b->type;

   /* From GLSL 1.50 spec, page 56:
    *    "The relational operators greater than (>), less than (<), greater
    *    than or equal (>=), and less than or equal (<=) operate only on
    *    scalar integer and scalar floating-point expressions."
    */
   if (!type_a->is_numeric()
       || !type_b->is_numeric()
       || !type_a->is_scalar()
       || !type_b->is_scalar()) {
      _mesa_glsl_error(loc, state,
                       "Operands to relational operators must be scalar and "
                       "numeric");
      return glsl_type::error_type;
   }

   /*    "Either the operands' types must match, or the conversions from
    *    Section 4.1.10 "Implicit Conversions" will be applied to the integer
    *    operand, after which the types must match."
    */
   if (!apply_implicit_conversion(type_a, value_b, state)
       && !apply_implicit_conversion(type_b, value_a, state)) {
      _mesa_glsl_error(loc, state,
                       "Could not implicitly convert operands to "
                       "relational operator");
      return glsl_type::error_type;
   }
   type_a = value_a->type;
   type_b = value_b->type;

   if (type_a->base_type != type_b->base_type) {
      _mesa_glsl_error(loc, state, "base type mismatch");
      return glsl_type::error_type;
   }

   /*    "The result is scalar Boolean."
    */
   return glsl_type::bool_type;
}

/**
 * \brief Return the result type of a bit-shift operation.
 *
 * If the given types to the bit-shift operator are invalid, return
 * glsl_type::error_type.
 *
 * \param type_a Type of LHS of bit-shift op
 * \param type_b Type of RHS of bit-shift op
 */
static const struct glsl_type *
shift_result_type(const struct glsl_type *type_a,
                  const struct glsl_type *type_b,
                  ast_operators op,
                  struct _mesa_glsl_parse_state *state, YYLTYPE *loc)
{
   if (state->language_version < 130) {
      _mesa_glsl_error(loc, state, "bit operations require GLSL 1.30");
      return glsl_type::error_type;
   }

   /* From page 50 (page 56 of the PDF) of the GLSL 1.30 spec:
    *
    *     "The shift operators (<<) and (>>). For both operators, the operands
    *     must be signed or unsigned integers or integer vectors. One operand
    *     can be signed while the other is unsigned."
    */
   if (!type_a->is_integer()) {
      _mesa_glsl_error(loc, state, "LHS of operator %s must be an integer or "
              "integer vector", ast_expression::operator_string(op));
     return glsl_type::error_type;

   }
   if (!type_b->is_integer()) {
      _mesa_glsl_error(loc, state, "RHS of operator %s must be an integer or "
              "integer vector", ast_expression::operator_string(op));
     return glsl_type::error_type;
   }

   /*     "If the first operand is a scalar, the second operand has to be
    *     a scalar as well."
    */
   if (type_a->is_scalar() && !type_b->is_scalar()) {
      _mesa_glsl_error(loc, state, "If the first operand of %s is scalar, the "
              "second must be scalar as well",
              ast_expression::operator_string(op));
     return glsl_type::error_type;
   }

   /* If both operands are vectors, check that they have same number of
    * elements.
    */
   if (type_a->is_vector() &&
      type_b->is_vector() &&
      type_a->vector_elements != type_b->vector_elements) {
      _mesa_glsl_error(loc, state, "Vector operands to operator %s must "
              "have same number of elements",
              ast_expression::operator_string(op));
     return glsl_type::error_type;
   }

   /*     "In all cases, the resulting type will be the same type as the left
    *     operand."
    */
   return type_a;
}

/**
 * Validates that a value can be assigned to a location with a specified type
 *
 * Validates that \c rhs can be assigned to some location.  If the types are
 * not an exact match but an automatic conversion is possible, \c rhs will be
 * converted.
 *
 * \return
 * \c NULL if \c rhs cannot be assigned to a location with type \c lhs_type.
 * Otherwise the actual RHS to be assigned will be returned.  This may be
 * \c rhs, or it may be \c rhs after some type conversion.
 *
 * \note
 * In addition to being used for assignments, this function is used to
 * type-check return values.
 */
ir_rvalue *
validate_assignment(struct _mesa_glsl_parse_state *state,
                    const glsl_type *lhs_type, ir_rvalue *rhs,
                    bool is_initializer)
{
   /* If there is already some error in the RHS, just return it.  Anything
    * else will lead to an avalanche of error message back to the user.
    */
   if (rhs->type->is_error())
      return rhs;

   /* If the types are identical, the assignment can trivially proceed.
    */
   if (rhs->type == lhs_type)
      return rhs;

   /* If the array element types are the same and the size of the LHS is zero,
    * the assignment is okay for initializers embedded in variable
    * declarations.
    *
    * Note: Whole-array assignments are not permitted in GLSL 1.10, but this
    * is handled by ir_dereference::is_lvalue.
    */
   if (is_initializer && lhs_type->is_array() && rhs->type->is_array()
       && (lhs_type->element_type() == rhs->type->element_type())
       && (lhs_type->array_size() == 0)) {
      return rhs;
   }

   /* Check for implicit conversion in GLSL 1.20 */
   if (apply_implicit_conversion(lhs_type, rhs, state)) {
      if (rhs->type == lhs_type)
         return rhs;
   }

   return NULL;
}

static void
mark_whole_array_access(ir_rvalue *access)
{
   ir_dereference_variable *deref = access->as_dereference_variable();

   if (deref && deref->var) {
      deref->var->max_array_access = deref->type->length - 1;
   }
}

ir_rvalue *
do_assignment(exec_list *instructions, struct _mesa_glsl_parse_state *state,
              const char *non_lvalue_description,
              ir_rvalue *lhs, ir_rvalue *rhs, bool is_initializer,
              YYLTYPE lhs_loc)
{
   void *ctx = state;
   bool error_emitted = (lhs->type->is_error() || rhs->type->is_error());

   ir_variable *lhs_var = lhs->variable_referenced();
   if (lhs_var)
      lhs_var->assigned = true;

   if (!error_emitted) {
      if (non_lvalue_description != NULL) {
         _mesa_glsl_error(&lhs_loc, state,
                          "assignment to %s",
                          non_lvalue_description);
         error_emitted = true;
      } else if (lhs->variable_referenced() != NULL
                 && lhs->variable_referenced()->read_only) {
         _mesa_glsl_error(&lhs_loc, state,
                          "assignment to read-only variable '%s'",
                          lhs->variable_referenced()->name);
         error_emitted = true;

      } else if (state->language_version <= 110 && lhs->type->is_array()) {
         /* From page 32 (page 38 of the PDF) of the GLSL 1.10 spec:
          *
          *    "Other binary or unary expressions, non-dereferenced
          *     arrays, function names, swizzles with repeated fields,
          *     and constants cannot be l-values."
          */
         _mesa_glsl_error(&lhs_loc, state, "whole array assignment is not "
                          "allowed in GLSL 1.10 or GLSL ES 1.00.");
         error_emitted = true;
      } else if (!lhs->is_lvalue()) {
         _mesa_glsl_error(& lhs_loc, state, "non-lvalue in assignment");
         error_emitted = true;
      }
   }

   ir_rvalue *new_rhs =
      validate_assignment(state, lhs->type, rhs, is_initializer);
   if (new_rhs == NULL) {
      _mesa_glsl_error(& lhs_loc, state, "type mismatch");
   } else {
      rhs = new_rhs;

      /* If the LHS array was not declared with a size, it takes it size from
       * the RHS.  If the LHS is an l-value and a whole array, it must be a
       * dereference of a variable.  Any other case would require that the LHS
       * is either not an l-value or not a whole array.
       */
      if (lhs->type->array_size() == 0) {
         ir_dereference *const d = lhs->as_dereference();

         assert(d != NULL);

         ir_variable *const var = d->variable_referenced();

         assert(var != NULL);

         if (var->max_array_access >= unsigned(rhs->type->array_size())) {
            /* FINISHME: This should actually log the location of the RHS. */
            _mesa_glsl_error(& lhs_loc, state, "array size must be > %u due to "
                             "previous access",
                             var->max_array_access);
         }

         var->type = glsl_type::get_array_instance(lhs->type->element_type(),
                                                   rhs->type->array_size());
         d->type = var->type;
      }
      mark_whole_array_access(rhs);
      mark_whole_array_access(lhs);
   }

   /* Most callers of do_assignment (assign, add_assign, pre_inc/dec,
    * but not post_inc) need the converted assigned value as an rvalue
    * to handle things like:
    *
    * i = j += 1;
    *
    * So we always just store the computed value being assigned to a
    * temporary and return a deref of that temporary.  If the rvalue
    * ends up not being used, the temp will get copy-propagated out.
    */
   ir_variable *var = new(ctx) ir_variable(rhs->type, "assignment_tmp",
                                           ir_var_temporary);
   ir_dereference_variable *deref_var = new(ctx) ir_dereference_variable(var);
   instructions->push_tail(var);
   instructions->push_tail(new(ctx) ir_assignment(deref_var,
                                                  rhs,
                                                  NULL));
   deref_var = new(ctx) ir_dereference_variable(var);

   if (!error_emitted)
      instructions->push_tail(new(ctx) ir_assignment(lhs, deref_var, NULL));

   return new(ctx) ir_dereference_variable(var);
}

static ir_rvalue *
get_lvalue_copy(exec_list *instructions, ir_rvalue *lvalue)
{
   void *ctx = ralloc_parent(lvalue);
   ir_variable *var;

   var = new(ctx) ir_variable(lvalue->type, "_post_incdec_tmp",
                              ir_var_temporary);
   instructions->push_tail(var);
   var->mode = ir_var_auto;

   instructions->push_tail(new(ctx) ir_assignment(new(ctx) ir_dereference_variable(var),
                                                  lvalue, NULL));

   return new(ctx) ir_dereference_variable(var);
}


ir_rvalue *
ast_node::hir(exec_list *instructions,
              struct _mesa_glsl_parse_state *state)
{
   (void) instructions;
   (void) state;

   return NULL;
}

static ir_rvalue *
do_comparison(void *mem_ctx, int operation, ir_rvalue *op0, ir_rvalue *op1)
{
   int join_op;
   ir_rvalue *cmp = NULL;

   if (operation == ir_binop_all_equal)
      join_op = ir_binop_logic_and;
   else
      join_op = ir_binop_logic_or;

   switch (op0->type->base_type) {
   case GLSL_TYPE_FLOAT:
   case GLSL_TYPE_UINT:
   case GLSL_TYPE_INT:
   case GLSL_TYPE_BOOL:
      return new(mem_ctx) ir_expression(operation, op0, op1);

   case GLSL_TYPE_ARRAY: {
      for (unsigned int i = 0; i < op0->type->length; i++) {
         ir_rvalue *e0, *e1, *result;

         e0 = new(mem_ctx) ir_dereference_array(op0->clone(mem_ctx, NULL),
                                                new(mem_ctx) ir_constant(i));
         e1 = new(mem_ctx) ir_dereference_array(op1->clone(mem_ctx, NULL),
                                                new(mem_ctx) ir_constant(i));
         result = do_comparison(mem_ctx, operation, e0, e1);

         if (cmp) {
            cmp = new(mem_ctx) ir_expression(join_op, cmp, result);
         } else {
            cmp = result;
         }
      }

      mark_whole_array_access(op0);
      mark_whole_array_access(op1);
      break;
   }

   case GLSL_TYPE_STRUCT: {
      for (unsigned int i = 0; i < op0->type->length; i++) {
         ir_rvalue *e0, *e1, *result;
         const char *field_name = op0->type->fields.structure[i].name;

         e0 = new(mem_ctx) ir_dereference_record(op0->clone(mem_ctx, NULL),
                                                 field_name);
         e1 = new(mem_ctx) ir_dereference_record(op1->clone(mem_ctx, NULL),
                                                 field_name);
         result = do_comparison(mem_ctx, operation, e0, e1);

         if (cmp) {
            cmp = new(mem_ctx) ir_expression(join_op, cmp, result);
         } else {
            cmp = result;
         }
      }
      break;
   }

   case GLSL_TYPE_ERROR:
   case GLSL_TYPE_VOID:
   case GLSL_TYPE_SAMPLER:
      /* I assume a comparison of a struct containing a sampler just
       * ignores the sampler present in the type.
       */
      break;

   default:
      assert(!"Should not get here.");
      break;
   }

   if (cmp == NULL)
      cmp = new(mem_ctx) ir_constant(true);

   return cmp;
}

/* For logical operations, we want to ensure that the operands are
 * scalar booleans.  If it isn't, emit an error and return a constant
 * boolean to avoid triggering cascading error messages.
 */
ir_rvalue *
get_scalar_boolean_operand(exec_list *instructions,
                           struct _mesa_glsl_parse_state *state,
                           ast_expression *parent_expr,
                           int operand,
                           const char *operand_name,
                           bool *error_emitted)
{
   ast_expression *expr = parent_expr->subexpressions[operand];
   void *ctx = state;
   ir_rvalue *val = expr->hir(instructions, state);

   if (val->type->is_boolean() && val->type->is_scalar())
      return val;

   if (!*error_emitted) {
      YYLTYPE loc = expr->get_location();
      _mesa_glsl_error(&loc, state, "%s of `%s' must be scalar boolean",
                       operand_name,
                       parent_expr->operator_string(parent_expr->oper));
      *error_emitted = true;
   }

   return new(ctx) ir_constant(true);
}

/**
 * If name refers to a builtin array whose maximum allowed size is less than
 * size, report an error and return true.  Otherwise return false.
 */
static bool
check_builtin_array_max_size(const char *name, unsigned size,
                             YYLTYPE loc, struct _mesa_glsl_parse_state *state)
{
   if ((strcmp("gl_TexCoord", name) == 0)
       && (size > state->Const.MaxTextureCoords)) {
      /* From page 54 (page 60 of the PDF) of the GLSL 1.20 spec:
       *
       *     "The size [of gl_TexCoord] can be at most
       *     gl_MaxTextureCoords."
       */
      _mesa_glsl_error(&loc, state, "`gl_TexCoord' array size cannot "
                       "be larger than gl_MaxTextureCoords (%u)\n",
                       state->Const.MaxTextureCoords);
      return true;
   } else if (strcmp("gl_ClipDistance", name) == 0
              && size > state->Const.MaxClipPlanes) {
      /* From section 7.1 (Vertex Shader Special Variables) of the
       * GLSL 1.30 spec:
       *
       *   "The gl_ClipDistance array is predeclared as unsized and
       *   must be sized by the shader either redeclaring it with a
       *   size or indexing it only with integral constant
       *   expressions. ... The size can be at most
       *   gl_MaxClipDistances."
       */
      _mesa_glsl_error(&loc, state, "`gl_ClipDistance' array size cannot "
                       "be larger than gl_MaxClipDistances (%u)\n",
                       state->Const.MaxClipPlanes);
      return true;
   }
   return false;
}

/**
 * Create the constant 1, of a which is appropriate for incrementing and
 * decrementing values of the given GLSL type.  For example, if type is vec4,
 * this creates a constant value of 1.0 having type float.
 *
 * If the given type is invalid for increment and decrement operators, return
 * a floating point 1--the error will be detected later.
 */
static ir_rvalue *
constant_one_for_inc_dec(void *ctx, const glsl_type *type)
{
   switch (type->base_type) {
   case GLSL_TYPE_UINT:
      return new(ctx) ir_constant((unsigned) 1);
   case GLSL_TYPE_INT:
      return new(ctx) ir_constant(1);
   default:
   case GLSL_TYPE_FLOAT:
      return new(ctx) ir_constant(1.0f);
   }
}

ir_rvalue *
ast_expression::hir(exec_list *instructions,
                    struct _mesa_glsl_parse_state *state)
{
   void *ctx = state;
   static const int operations[AST_NUM_OPERATORS] = {
      -1,               /* ast_assign doesn't convert to ir_expression. */
      -1,               /* ast_plus doesn't convert to ir_expression. */
      ir_unop_neg,
      ir_binop_add,
      ir_binop_sub,
      ir_binop_mul,
      ir_binop_div,
      ir_binop_mod,
      ir_binop_lshift,
      ir_binop_rshift,
      ir_binop_less,
      ir_binop_greater,
      ir_binop_lequal,
      ir_binop_gequal,
      ir_binop_all_equal,
      ir_binop_any_nequal,
      ir_binop_bit_and,
      ir_binop_bit_xor,
      ir_binop_bit_or,
      ir_unop_bit_not,
      ir_binop_logic_and,
      ir_binop_logic_xor,
      ir_binop_logic_or,
      ir_unop_logic_not,

      /* Note: The following block of expression types actually convert
       * to multiple IR instructions.
       */
      ir_binop_mul,     /* ast_mul_assign */
      ir_binop_div,     /* ast_div_assign */
      ir_binop_mod,     /* ast_mod_assign */
      ir_binop_add,     /* ast_add_assign */
      ir_binop_sub,     /* ast_sub_assign */
      ir_binop_lshift,  /* ast_ls_assign */
      ir_binop_rshift,  /* ast_rs_assign */
      ir_binop_bit_and, /* ast_and_assign */
      ir_binop_bit_xor, /* ast_xor_assign */
      ir_binop_bit_or,  /* ast_or_assign */

      -1,               /* ast_conditional doesn't convert to ir_expression. */
      ir_binop_add,     /* ast_pre_inc. */
      ir_binop_sub,     /* ast_pre_dec. */
      ir_binop_add,     /* ast_post_inc. */
      ir_binop_sub,     /* ast_post_dec. */
      -1,               /* ast_field_selection doesn't conv to ir_expression. */
      -1,               /* ast_array_index doesn't convert to ir_expression. */
      -1,               /* ast_function_call doesn't conv to ir_expression. */
      -1,               /* ast_identifier doesn't convert to ir_expression. */
      -1,               /* ast_int_constant doesn't convert to ir_expression. */
      -1,               /* ast_uint_constant doesn't conv to ir_expression. */
      -1,               /* ast_float_constant doesn't conv to ir_expression. */
      -1,               /* ast_bool_constant doesn't conv to ir_expression. */
      -1,               /* ast_sequence doesn't convert to ir_expression. */
   };
   ir_rvalue *result = NULL;
   ir_rvalue *op[3];
   const struct glsl_type *type; /* a temporary variable for switch cases */
   bool error_emitted = false;
   YYLTYPE loc;

   loc = this->get_location();

   switch (this->oper) {
   case ast_assign: {
      op[0] = this->subexpressions[0]->hir(instructions, state);
      op[1] = this->subexpressions[1]->hir(instructions, state);

      result = do_assignment(instructions, state,
                             this->subexpressions[0]->non_lvalue_description,
                             op[0], op[1], false,
                             this->subexpressions[0]->get_location());
      error_emitted = result->type->is_error();
      break;
   }

   case ast_plus:
      op[0] = this->subexpressions[0]->hir(instructions, state);

      type = unary_arithmetic_result_type(op[0]->type, state, & loc);

      error_emitted = type->is_error();

      result = op[0];
      break;

   case ast_neg:
      op[0] = this->subexpressions[0]->hir(instructions, state);

      type = unary_arithmetic_result_type(op[0]->type, state, & loc);

      error_emitted = type->is_error();

      result = new(ctx) ir_expression(operations[this->oper], type,
                                      op[0], NULL);
      break;

   case ast_add:
   case ast_sub:
   case ast_mul:
   case ast_div:
      op[0] = this->subexpressions[0]->hir(instructions, state);
      op[1] = this->subexpressions[1]->hir(instructions, state);

      type = arithmetic_result_type(op[0], op[1],
                                    (this->oper == ast_mul),
                                    state, & loc);
      error_emitted = type->is_error();

      result = new(ctx) ir_expression(operations[this->oper], type,
                                      op[0], op[1]);
      break;

   case ast_mod:
      op[0] = this->subexpressions[0]->hir(instructions, state);
      op[1] = this->subexpressions[1]->hir(instructions, state);

      type = modulus_result_type(op[0]->type, op[1]->type, state, & loc);

      assert(operations[this->oper] == ir_binop_mod);

      result = new(ctx) ir_expression(operations[this->oper], type,
                                      op[0], op[1]);
      error_emitted = type->is_error();
      break;

   case ast_lshift:
   case ast_rshift:
       if (state->language_version < 130) {
          _mesa_glsl_error(&loc, state, "operator %s requires GLSL 1.30",
              operator_string(this->oper));
          error_emitted = true;
       }

       op[0] = this->subexpressions[0]->hir(instructions, state);
       op[1] = this->subexpressions[1]->hir(instructions, state);
       type = shift_result_type(op[0]->type, op[1]->type, this->oper, state,
                                &loc);
       result = new(ctx) ir_expression(operations[this->oper], type,
                                       op[0], op[1]);
       error_emitted = op[0]->type->is_error() || op[1]->type->is_error();
       break;

   case ast_less:
   case ast_greater:
   case ast_lequal:
   case ast_gequal:
      op[0] = this->subexpressions[0]->hir(instructions, state);
      op[1] = this->subexpressions[1]->hir(instructions, state);

      type = relational_result_type(op[0], op[1], state, & loc);

      /* The relational operators must either generate an error or result
       * in a scalar boolean.  See page 57 of the GLSL 1.50 spec.
       */
      assert(type->is_error()
             || ((type->base_type == GLSL_TYPE_BOOL)
                 && type->is_scalar()));

      result = new(ctx) ir_expression(operations[this->oper], type,
                                      op[0], op[1]);
      error_emitted = type->is_error();
      break;

   case ast_nequal:
   case ast_equal:
      op[0] = this->subexpressions[0]->hir(instructions, state);
      op[1] = this->subexpressions[1]->hir(instructions, state);

      /* From page 58 (page 64 of the PDF) of the GLSL 1.50 spec:
       *
       *    "The equality operators equal (==), and not equal (!=)
       *    operate on all types. They result in a scalar Boolean. If
       *    the operand types do not match, then there must be a
       *    conversion from Section 4.1.10 "Implicit Conversions"
       *    applied to one operand that can make them match, in which
       *    case this conversion is done."
       */
      if ((!apply_implicit_conversion(op[0]->type, op[1], state)
           && !apply_implicit_conversion(op[1]->type, op[0], state))
          || (op[0]->type != op[1]->type)) {
         _mesa_glsl_error(& loc, state, "operands of `%s' must have the same "
                          "type", (this->oper == ast_equal) ? "==" : "!=");
         error_emitted = true;
      } else if ((state->language_version <= 110)
                 && (op[0]->type->is_array() || op[1]->type->is_array())) {
         _mesa_glsl_error(& loc, state, "array comparisons forbidden in "
                          "GLSL 1.10");
         error_emitted = true;
      }

      if (error_emitted) {
         result = new(ctx) ir_constant(false);
      } else {
         result = do_comparison(ctx, operations[this->oper], op[0], op[1]);
         assert(result->type == glsl_type::bool_type);
      }
      break;

   case ast_bit_and:
   case ast_bit_xor:
   case ast_bit_or:
      op[0] = this->subexpressions[0]->hir(instructions, state);
      op[1] = this->subexpressions[1]->hir(instructions, state);
      type = bit_logic_result_type(op[0]->type, op[1]->type, this->oper,
                                   state, &loc);
      result = new(ctx) ir_expression(operations[this->oper], type,
                                      op[0], op[1]);
      error_emitted = op[0]->type->is_error() || op[1]->type->is_error();
      break;

   case ast_bit_not:
      op[0] = this->subexpressions[0]->hir(instructions, state);

      if (state->language_version < 130) {
         _mesa_glsl_error(&loc, state, "bit-wise operations require GLSL 1.30");
         error_emitted = true;
      }

      if (!op[0]->type->is_integer()) {
         _mesa_glsl_error(&loc, state, "operand of `~' must be an integer");
         error_emitted = true;
      }

      type = error_emitted ? glsl_type::error_type : op[0]->type;
      result = new(ctx) ir_expression(ir_unop_bit_not, type, op[0], NULL);
      break;

   case ast_logic_and: {
      exec_list rhs_instructions;
      op[0] = get_scalar_boolean_operand(instructions, state, this, 0,
                                         "LHS", &error_emitted);
      op[1] = get_scalar_boolean_operand(&rhs_instructions, state, this, 1,
                                         "RHS", &error_emitted);

      if (rhs_instructions.is_empty()) {
         result = new(ctx) ir_expression(ir_binop_logic_and, op[0], op[1]);
         type = result->type;
      } else {
         ir_variable *const tmp = new(ctx) ir_variable(glsl_type::bool_type,
                                                       "and_tmp",
                                                       ir_var_temporary);
         instructions->push_tail(tmp);

         ir_if *const stmt = new(ctx) ir_if(op[0]);
         instructions->push_tail(stmt);

         stmt->then_instructions.append_list(&rhs_instructions);
         ir_dereference *const then_deref = new(ctx) ir_dereference_variable(tmp);
         ir_assignment *const then_assign =
            new(ctx) ir_assignment(then_deref, op[1], NULL);
         stmt->then_instructions.push_tail(then_assign);

         ir_dereference *const else_deref = new(ctx) ir_dereference_variable(tmp);
         ir_assignment *const else_assign =
            new(ctx) ir_assignment(else_deref, new(ctx) ir_constant(false), NULL);
         stmt->else_instructions.push_tail(else_assign);

         result = new(ctx) ir_dereference_variable(tmp);
         type = tmp->type;
      }
      break;
   }

   case ast_logic_or: {
      exec_list rhs_instructions;
      op[0] = get_scalar_boolean_operand(instructions, state, this, 0,
                                         "LHS", &error_emitted);
      op[1] = get_scalar_boolean_operand(&rhs_instructions, state, this, 1,
                                         "RHS", &error_emitted);

      if (rhs_instructions.is_empty()) {
         result = new(ctx) ir_expression(ir_binop_logic_or, op[0], op[1]);
         type = result->type;
      } else {
         ir_variable *const tmp = new(ctx) ir_variable(glsl_type::bool_type,
                                                       "or_tmp",
                                                       ir_var_temporary);
         instructions->push_tail(tmp);

         ir_if *const stmt = new(ctx) ir_if(op[0]);
         instructions->push_tail(stmt);

         ir_dereference *const then_deref = new(ctx) ir_dereference_variable(tmp);
         ir_assignment *const then_assign =
            new(ctx) ir_assignment(then_deref, new(ctx) ir_constant(true), NULL);
         stmt->then_instructions.push_tail(then_assign);

         stmt->else_instructions.append_list(&rhs_instructions);
         ir_dereference *const else_deref = new(ctx) ir_dereference_variable(tmp);
         ir_assignment *const else_assign =
            new(ctx) ir_assignment(else_deref, op[1], NULL);
         stmt->else_instructions.push_tail(else_assign);

         result = new(ctx) ir_dereference_variable(tmp);
         type = tmp->type;
      }
      break;
   }

   case ast_logic_xor:
      /* From page 33 (page 39 of the PDF) of the GLSL 1.10 spec:
       *
       *    "The logical binary operators and (&&), or ( | | ), and
       *     exclusive or (^^). They operate only on two Boolean
       *     expressions and result in a Boolean expression."
       */
      op[0] = get_scalar_boolean_operand(instructions, state, this, 0, "LHS",
                                         &error_emitted);
      op[1] = get_scalar_boolean_operand(instructions, state, this, 1, "RHS",
                                         &error_emitted);

      result = new(ctx) ir_expression(operations[this->oper], glsl_type::bool_type,
                                      op[0], op[1]);
      break;

   case ast_logic_not:
      op[0] = get_scalar_boolean_operand(instructions, state, this, 0,
                                         "operand", &error_emitted);

      result = new(ctx) ir_expression(operations[this->oper], glsl_type::bool_type,
                                      op[0], NULL);
      break;

   case ast_mul_assign:
   case ast_div_assign:
   case ast_add_assign:
   case ast_sub_assign: {
      op[0] = this->subexpressions[0]->hir(instructions, state);
      op[1] = this->subexpressions[1]->hir(instructions, state);

      type = arithmetic_result_type(op[0], op[1],
                                    (this->oper == ast_mul_assign),
                                    state, & loc);

      ir_rvalue *temp_rhs = new(ctx) ir_expression(operations[this->oper], type,
                                                   op[0], op[1]);

      result = do_assignment(instructions, state,
                             this->subexpressions[0]->non_lvalue_description,
                             op[0]->clone(ctx, NULL), temp_rhs, false,
                             this->subexpressions[0]->get_location());
      error_emitted = (op[0]->type->is_error());

      /* GLSL 1.10 does not allow array assignment.  However, we don't have to
       * explicitly test for this because none of the binary expression
       * operators allow array operands either.
       */

      break;
   }

   case ast_mod_assign: {
      op[0] = this->subexpressions[0]->hir(instructions, state);
      op[1] = this->subexpressions[1]->hir(instructions, state);

      type = modulus_result_type(op[0]->type, op[1]->type, state, & loc);

      assert(operations[this->oper] == ir_binop_mod);

      ir_rvalue *temp_rhs;
      temp_rhs = new(ctx) ir_expression(operations[this->oper], type,
                                        op[0], op[1]);

      result = do_assignment(instructions, state,
                             this->subexpressions[0]->non_lvalue_description,
                             op[0]->clone(ctx, NULL), temp_rhs, false,
                             this->subexpressions[0]->get_location());
      error_emitted = type->is_error();
      break;
   }

   case ast_ls_assign:
   case ast_rs_assign: {
      op[0] = this->subexpressions[0]->hir(instructions, state);
      op[1] = this->subexpressions[1]->hir(instructions, state);
      type = shift_result_type(op[0]->type, op[1]->type, this->oper, state,
                               &loc);
      ir_rvalue *temp_rhs = new(ctx) ir_expression(operations[this->oper],
                                                   type, op[0], op[1]);
      result = do_assignment(instructions, state,
                             this->subexpressions[0]->non_lvalue_description,
                             op[0]->clone(ctx, NULL), temp_rhs, false,
                             this->subexpressions[0]->get_location());
      error_emitted = op[0]->type->is_error() || op[1]->type->is_error();
      break;
   }

   case ast_and_assign:
   case ast_xor_assign:
   case ast_or_assign: {
      op[0] = this->subexpressions[0]->hir(instructions, state);
      op[1] = this->subexpressions[1]->hir(instructions, state);
      type = bit_logic_result_type(op[0]->type, op[1]->type, this->oper,
                                   state, &loc);
      ir_rvalue *temp_rhs = new(ctx) ir_expression(operations[this->oper],
                                                   type, op[0], op[1]);
      result = do_assignment(instructions, state,
                             this->subexpressions[0]->non_lvalue_description,
                             op[0]->clone(ctx, NULL), temp_rhs, false,
                             this->subexpressions[0]->get_location());
      error_emitted = op[0]->type->is_error() || op[1]->type->is_error();
      break;
   }

   case ast_conditional: {
      /* From page 59 (page 65 of the PDF) of the GLSL 1.50 spec:
       *
       *    "The ternary selection operator (?:). It operates on three
       *    expressions (exp1 ? exp2 : exp3). This operator evaluates the
       *    first expression, which must result in a scalar Boolean."
       */
      op[0] = get_scalar_boolean_operand(instructions, state, this, 0,
                                         "condition", &error_emitted);

      /* The :? operator is implemented by generating an anonymous temporary
       * followed by an if-statement.  The last instruction in each branch of
       * the if-statement assigns a value to the anonymous temporary.  This
       * temporary is the r-value of the expression.
       */
      exec_list then_instructions;
      exec_list else_instructions;

      op[1] = this->subexpressions[1]->hir(&then_instructions, state);
      op[2] = this->subexpressions[2]->hir(&else_instructions, state);

      /* From page 59 (page 65 of the PDF) of the GLSL 1.50 spec:
       *
       *     "The second and third expressions can be any type, as
       *     long their types match, or there is a conversion in
       *     Section 4.1.10 "Implicit Conversions" that can be applied
       *     to one of the expressions to make their types match. This
       *     resulting matching type is the type of the entire
       *     expression."
       */
      if ((!apply_implicit_conversion(op[1]->type, op[2], state)
           && !apply_implicit_conversion(op[2]->type, op[1], state))
          || (op[1]->type != op[2]->type)) {
         YYLTYPE loc = this->subexpressions[1]->get_location();

         _mesa_glsl_error(& loc, state, "Second and third operands of ?: "
                          "operator must have matching types.");
         error_emitted = true;
         type = glsl_type::error_type;
      } else {
         type = op[1]->type;
      }

      /* From page 33 (page 39 of the PDF) of the GLSL 1.10 spec:
       *
       *    "The second and third expressions must be the same type, but can
       *    be of any type other than an array."
       */
      if ((state->language_version <= 110) && type->is_array()) {
         _mesa_glsl_error(& loc, state, "Second and third operands of ?: "
                          "operator must not be arrays.");
         error_emitted = true;
      }

      ir_constant *cond_val = op[0]->constant_expression_value();
      ir_constant *then_val = op[1]->constant_expression_value();
      ir_constant *else_val = op[2]->constant_expression_value();

      if (then_instructions.is_empty()
          && else_instructions.is_empty()
          && (cond_val != NULL) && (then_val != NULL) && (else_val != NULL)) {
         result = (cond_val->value.b[0]) ? then_val : else_val;
      } else {
         ir_variable *const tmp =
            new(ctx) ir_variable(type, "conditional_tmp", ir_var_temporary);
         instructions->push_tail(tmp);

         ir_if *const stmt = new(ctx) ir_if(op[0]);
         instructions->push_tail(stmt);

         then_instructions.move_nodes_to(& stmt->then_instructions);
         ir_dereference *const then_deref =
            new(ctx) ir_dereference_variable(tmp);
         ir_assignment *const then_assign =
            new(ctx) ir_assignment(then_deref, op[1], NULL);
         stmt->then_instructions.push_tail(then_assign);

         else_instructions.move_nodes_to(& stmt->else_instructions);
         ir_dereference *const else_deref =
            new(ctx) ir_dereference_variable(tmp);
         ir_assignment *const else_assign =
            new(ctx) ir_assignment(else_deref, op[2], NULL);
         stmt->else_instructions.push_tail(else_assign);

         result = new(ctx) ir_dereference_variable(tmp);
      }
      break;
   }

   case ast_pre_inc:
   case ast_pre_dec: {
      this->non_lvalue_description = (this->oper == ast_pre_inc)
         ? "pre-increment operation" : "pre-decrement operation";

      op[0] = this->subexpressions[0]->hir(instructions, state);
      op[1] = constant_one_for_inc_dec(ctx, op[0]->type);

      type = arithmetic_result_type(op[0], op[1], false, state, & loc);

      ir_rvalue *temp_rhs;
      temp_rhs = new(ctx) ir_expression(operations[this->oper], type,
                                        op[0], op[1]);

      result = do_assignment(instructions, state,
                             this->subexpressions[0]->non_lvalue_description,
                             op[0]->clone(ctx, NULL), temp_rhs, false,
                             this->subexpressions[0]->get_location());
      error_emitted = op[0]->type->is_error();
      break;
   }

   case ast_post_inc:
   case ast_post_dec: {
      this->non_lvalue_description = (this->oper == ast_post_inc)
         ? "post-increment operation" : "post-decrement operation";
      op[0] = this->subexpressions[0]->hir(instructions, state);
      op[1] = constant_one_for_inc_dec(ctx, op[0]->type);

      error_emitted = op[0]->type->is_error() || op[1]->type->is_error();

      type = arithmetic_result_type(op[0], op[1], false, state, & loc);

      ir_rvalue *temp_rhs;
      temp_rhs = new(ctx) ir_expression(operations[this->oper], type,
                                        op[0], op[1]);

      /* Get a temporary of a copy of the lvalue before it's modified.
       * This may get thrown away later.
       */
      result = get_lvalue_copy(instructions, op[0]->clone(ctx, NULL));

      (void)do_assignment(instructions, state,
                          this->subexpressions[0]->non_lvalue_description,
                          op[0]->clone(ctx, NULL), temp_rhs, false,
                          this->subexpressions[0]->get_location());

      error_emitted = op[0]->type->is_error();
      break;
   }

   case ast_field_selection:
      result = _mesa_ast_field_selection_to_hir(this, instructions, state);
      break;

   case ast_array_index: {
      YYLTYPE index_loc = subexpressions[1]->get_location();

      op[0] = subexpressions[0]->hir(instructions, state);
      op[1] = subexpressions[1]->hir(instructions, state);

      error_emitted = op[0]->type->is_error() || op[1]->type->is_error();

      ir_rvalue *const array = op[0];

      result = new(ctx) ir_dereference_array(op[0], op[1]);

      /* Do not use op[0] after this point.  Use array.
       */
      op[0] = NULL;


      if (error_emitted)
         break;

      if (!array->type->is_array()
          && !array->type->is_matrix()
          && !array->type->is_vector()) {
         _mesa_glsl_error(& index_loc, state,
                          "cannot dereference non-array / non-matrix / "
                          "non-vector");
         error_emitted = true;
      }

      if (!op[1]->type->is_integer()) {
         _mesa_glsl_error(& index_loc, state,
                          "array index must be integer type");
         error_emitted = true;
      } else if (!op[1]->type->is_scalar()) {
         _mesa_glsl_error(& index_loc, state,
                          "array index must be scalar");
         error_emitted = true;
      }

      /* If the array index is a constant expression and the array has a
       * declared size, ensure that the access is in-bounds.  If the array
       * index is not a constant expression, ensure that the array has a
       * declared size.
       */
      ir_constant *const const_index = op[1]->constant_expression_value();
      if (const_index != NULL) {
         const int idx = const_index->value.i[0];
         const char *type_name;
         unsigned bound = 0;

         if (array->type->is_matrix()) {
            type_name = "matrix";
         } else if (array->type->is_vector()) {
            type_name = "vector";
         } else {
            type_name = "array";
         }

         /* From page 24 (page 30 of the PDF) of the GLSL 1.50 spec:
          *
          *    "It is illegal to declare an array with a size, and then
          *    later (in the same shader) index the same array with an
          *    integral constant expression greater than or equal to the
          *    declared size. It is also illegal to index an array with a
          *    negative constant expression."
          */
         if (array->type->is_matrix()) {
            if (array->type->row_type()->vector_elements <= idx) {
               bound = array->type->row_type()->vector_elements;
            }
         } else if (array->type->is_vector()) {
            if (array->type->vector_elements <= idx) {
               bound = array->type->vector_elements;
            }
         } else {
            if ((array->type->array_size() > 0)
                && (array->type->array_size() <= idx)) {
               bound = array->type->array_size();
            }
         }

         if (bound > 0) {
            _mesa_glsl_error(& loc, state, "%s index must be < %u",
                             type_name, bound);
            error_emitted = true;
         } else if (idx < 0) {
            _mesa_glsl_error(& loc, state, "%s index must be >= 0",
                             type_name);
            error_emitted = true;
         }

         if (array->type->is_array()) {
            /* If the array is a variable dereference, it dereferences the
             * whole array, by definition.  Use this to get the variable.
             *
             * FINISHME: Should some methods for getting / setting / testing
             * FINISHME: array access limits be added to ir_dereference?
             */
            ir_variable *const v = array->whole_variable_referenced();
            if ((v != NULL) && (unsigned(idx) > v->max_array_access)) {
               v->max_array_access = idx;

               /* Check whether this access will, as a side effect, implicitly
                * cause the size of a built-in array to be too large.
                */
               if (check_builtin_array_max_size(v->name, idx+1, loc, state))
                  error_emitted = true;
            }
         }
      } else if (array->type->array_size() == 0) {
         _mesa_glsl_error(&loc, state, "unsized array index must be constant");
      } else {
         if (array->type->is_array()) {
            /* whole_variable_referenced can return NULL if the array is a
             * member of a structure.  In this case it is safe to not update
             * the max_array_access field because it is never used for fields
             * of structures.
             */
            ir_variable *v = array->whole_variable_referenced();
            if (v != NULL)
               v->max_array_access = array->type->array_size() - 1;
         }
      }

      /* From page 23 (29 of the PDF) of the GLSL 1.30 spec:
       *
       *    "Samplers aggregated into arrays within a shader (using square
       *    brackets [ ]) can only be indexed with integral constant
       *    expressions [...]."
       *
       * This restriction was added in GLSL 1.30.  Shaders using earlier version
       * of the language should not be rejected by the compiler front-end for
       * using this construct.  This allows useful things such as using a loop
       * counter as the index to an array of samplers.  If the loop in unrolled,
       * the code should compile correctly.  Instead, emit a warning.
       */
      if (array->type->is_array() &&
          array->type->element_type()->is_sampler() &&
          const_index == NULL) {

         if (state->language_version == 100) {
            _mesa_glsl_warning(&loc, state,
                               "sampler arrays indexed with non-constant "
                               "expressions is optional in GLSL ES 1.00");
         } else if (state->language_version < 130) {
            _mesa_glsl_warning(&loc, state,
                               "sampler arrays indexed with non-constant "
                               "expressions is forbidden in GLSL 1.30 and "
                               "later");
         } else {
            _mesa_glsl_error(&loc, state,
                             "sampler arrays indexed with non-constant "
                             "expressions is forbidden in GLSL 1.30 and "
                             "later");
            error_emitted = true;
         }
      }

      if (error_emitted)
         result->type = glsl_type::error_type;

      break;
   }

   case ast_function_call:
      /* Should *NEVER* get here.  ast_function_call should always be handled
       * by ast_function_expression::hir.
       */
      assert(0);
      break;

   case ast_identifier: {
      /* ast_identifier can appear several places in a full abstract syntax
       * tree.  This particular use must be at location specified in the grammar
       * as 'variable_identifier'.
       */
      ir_variable *var = 
         state->symbols->get_variable(this->primary_expression.identifier);

      if (var != NULL) {
         var->used = true;
         result = new(ctx) ir_dereference_variable(var);
      } else {
         _mesa_glsl_error(& loc, state, "`%s' undeclared",
                          this->primary_expression.identifier);

         result = ir_rvalue::error_value(ctx);
         error_emitted = true;
      }
      break;
   }

   case ast_int_constant:
      result = new(ctx) ir_constant(this->primary_expression.int_constant);
      break;

   case ast_uint_constant:
      result = new(ctx) ir_constant(this->primary_expression.uint_constant);
      break;

   case ast_float_constant:
      result = new(ctx) ir_constant(this->primary_expression.float_constant);
      break;

   case ast_bool_constant:
      result = new(ctx) ir_constant(bool(this->primary_expression.bool_constant));
      break;

   case ast_sequence: {
      /* It should not be possible to generate a sequence in the AST without
       * any expressions in it.
       */
      assert(!this->expressions.is_empty());

      /* The r-value of a sequence is the last expression in the sequence.  If
       * the other expressions in the sequence do not have side-effects (and
       * therefore add instructions to the instruction list), they get dropped
       * on the floor.
       */
      exec_node *previous_tail_pred = NULL;
      YYLTYPE previous_operand_loc = loc;

      foreach_list_typed (ast_node, ast, link, &this->expressions) {
         /* If one of the operands of comma operator does not generate any
          * code, we want to emit a warning.  At each pass through the loop
          * previous_tail_pred will point to the last instruction in the
          * stream *before* processing the previous operand.  Naturally,
          * instructions->tail_pred will point to the last instruction in the
          * stream *after* processing the previous operand.  If the two
          * pointers match, then the previous operand had no effect.
          *
          * The warning behavior here differs slightly from GCC.  GCC will
          * only emit a warning if none of the left-hand operands have an
          * effect.  However, it will emit a warning for each.  I believe that
          * there are some cases in C (especially with GCC extensions) where
          * it is useful to have an intermediate step in a sequence have no
          * effect, but I don't think these cases exist in GLSL.  Either way,
          * it would be a giant hassle to replicate that behavior.
          */
         if (previous_tail_pred == instructions->tail_pred) {
            _mesa_glsl_warning(&previous_operand_loc, state,
                               "left-hand operand of comma expression has "
                               "no effect");
         }

         /* tail_pred is directly accessed instead of using the get_tail()
          * method for performance reasons.  get_tail() has extra code to
          * return NULL when the list is empty.  We don't care about that
          * here, so using tail_pred directly is fine.
          */
         previous_tail_pred = instructions->tail_pred;
         previous_operand_loc = ast->get_location();

         result = ast->hir(instructions, state);
      }

      /* Any errors should have already been emitted in the loop above.
       */
      error_emitted = true;
      break;
   }
   }
   type = NULL; /* use result->type, not type. */
   assert(result != NULL);

   if (result->type->is_error() && !error_emitted)
      _mesa_glsl_error(& loc, state, "type mismatch");

   return result;
}


ir_rvalue *
ast_expression_statement::hir(exec_list *instructions,
                              struct _mesa_glsl_parse_state *state)
{
   /* It is possible to have expression statements that don't have an
    * expression.  This is the solitary semicolon:
    *
    * for (i = 0; i < 5; i++)
    *     ;
    *
    * In this case the expression will be NULL.  Test for NULL and don't do
    * anything in that case.
    */
   if (expression != NULL)
      expression->hir(instructions, state);

   /* Statements do not have r-values.
    */
   return NULL;
}


ir_rvalue *
ast_compound_statement::hir(exec_list *instructions,
                            struct _mesa_glsl_parse_state *state)
{
   if (new_scope)
      state->symbols->push_scope();

   foreach_list_typed (ast_node, ast, link, &this->statements)
      ast->hir(instructions, state);

   if (new_scope)
      state->symbols->pop_scope();

   /* Compound statements do not have r-values.
    */
   return NULL;
}


static const glsl_type *
process_array_type(YYLTYPE *loc, const glsl_type *base, ast_node *array_size,
                   struct _mesa_glsl_parse_state *state)
{
   unsigned length = 0;

   /* From page 19 (page 25) of the GLSL 1.20 spec:
    *
    *     "Only one-dimensional arrays may be declared."
    */
   if (base->is_array()) {
      _mesa_glsl_error(loc, state,
                       "invalid array of `%s' (only one-dimensional arrays "
                       "may be declared)",
                       base->name);
      return glsl_type::error_type;
   }

   if (array_size != NULL) {
      exec_list dummy_instructions;
      ir_rvalue *const ir = array_size->hir(& dummy_instructions, state);
      YYLTYPE loc = array_size->get_location();

      if (ir != NULL) {
         if (!ir->type->is_integer()) {
            _mesa_glsl_error(& loc, state, "array size must be integer type");
         } else if (!ir->type->is_scalar()) {
            _mesa_glsl_error(& loc, state, "array size must be scalar type");
         } else {
            ir_constant *const size = ir->constant_expression_value();

            if (size == NULL) {
               _mesa_glsl_error(& loc, state, "array size must be a "
                                "constant valued expression");
            } else if (size->value.i[0] <= 0) {
               _mesa_glsl_error(& loc, state, "array size must be > 0");
            } else {
               assert(size->type == ir->type);
               length = size->value.u[0];

               /* If the array size is const (and we've verified that
                * it is) then no instructions should have been emitted
                * when we converted it to HIR.  If they were emitted,
                * then either the array size isn't const after all, or
                * we are emitting unnecessary instructions.
                */
               assert(dummy_instructions.is_empty());
            }
         }
      }
   } else if (state->es_shader) {
      /* Section 10.17 of the GLSL ES 1.00 specification states that unsized
       * array declarations have been removed from the language.
       */
      _mesa_glsl_error(loc, state, "unsized array declarations are not "
                       "allowed in GLSL ES 1.00.");
   }

   return glsl_type::get_array_instance(base, length);
}


const glsl_type *
ast_type_specifier::glsl_type(const char **name,
                              struct _mesa_glsl_parse_state *state) const
{
   const struct glsl_type *type;

   type = state->symbols->get_type(this->type_name);
   *name = this->type_name;

   if (this->is_array) {
      YYLTYPE loc = this->get_location();
      type = process_array_type(&loc, type, this->array_size, state);
   }

   return type;
}


static void
apply_type_qualifier_to_variable(const struct ast_type_qualifier *qual,
                                 ir_variable *var,
                                 struct _mesa_glsl_parse_state *state,
                                 YYLTYPE *loc)
{
   if (qual->flags.q.invariant) {
      if (var->used) {
         _mesa_glsl_error(loc, state,
                          "variable `%s' may not be redeclared "
                          "`invariant' after being used",
                          var->name);
      } else {
         var->invariant = 1;
      }
   }

   if (qual->flags.q.constant || qual->flags.q.attribute
       || qual->flags.q.uniform
       || (qual->flags.q.varying && (state->target == fragment_shader)))
      var->read_only = 1;

   if (qual->flags.q.centroid)
      var->centroid = 1;

   if (qual->flags.q.attribute && state->target != vertex_shader) {
      var->type = glsl_type::error_type;
      _mesa_glsl_error(loc, state,
                       "`attribute' variables may not be declared in the "
                       "%s shader",
                       _mesa_glsl_shader_target_name(state->target));
   }

   /* From page 25 (page 31 of the PDF) of the GLSL 1.10 spec:
    *
    *     "The varying qualifier can be used only with the data types
    *     float, vec2, vec3, vec4, mat2, mat3, and mat4, or arrays of
    *     these."
    */
   if (qual->flags.q.varying) {
      const glsl_type *non_array_type;

      if (var->type && var->type->is_array())
         non_array_type = var->type->fields.array;
      else
         non_array_type = var->type;

      if (non_array_type && non_array_type->base_type != GLSL_TYPE_FLOAT) {
         var->type = glsl_type::error_type;
         _mesa_glsl_error(loc, state,
                          "varying variables must be of base type float");
      }
   }

   /* If there is no qualifier that changes the mode of the variable, leave
    * the setting alone.
    */
   if (qual->flags.q.in && qual->flags.q.out)
      var->mode = ir_var_inout;
   else if (qual->flags.q.attribute || qual->flags.q.in
            || (qual->flags.q.varying && (state->target == fragment_shader)))
      var->mode = ir_var_in;
   else if (qual->flags.q.out
            || (qual->flags.q.varying && (state->target == vertex_shader)))
      var->mode = ir_var_out;
   else if (qual->flags.q.uniform)
      var->mode = ir_var_uniform;

   if (state->all_invariant && (state->current_function == NULL)) {
      switch (state->target) {
      case vertex_shader:
         if (var->mode == ir_var_out)
            var->invariant = true;
         break;
      case geometry_shader:
         if ((var->mode == ir_var_in) || (var->mode == ir_var_out))
            var->invariant = true;
         break;
      case fragment_shader:
         if (var->mode == ir_var_in)
            var->invariant = true;
         break;
      }
   }

   if (qual->flags.q.flat)
      var->interpolation = INTERP_QUALIFIER_FLAT;
   else if (qual->flags.q.noperspective)
      var->interpolation = INTERP_QUALIFIER_NOPERSPECTIVE;
   else if (qual->flags.q.smooth)
      var->interpolation = INTERP_QUALIFIER_SMOOTH;
   else
      var->interpolation = INTERP_QUALIFIER_NONE;

   if (var->interpolation != INTERP_QUALIFIER_NONE &&
       !(state->target == vertex_shader && var->mode == ir_var_out) &&
       !(state->target == fragment_shader && var->mode == ir_var_in)) {
      const char *qual_string = NULL;
      switch (var->interpolation) {
      case INTERP_QUALIFIER_FLAT:
         qual_string = "flat";
         break;
      case INTERP_QUALIFIER_NOPERSPECTIVE:
         qual_string = "noperspective";
         break;
      case INTERP_QUALIFIER_SMOOTH:
         qual_string = "smooth";
         break;
      }

      _mesa_glsl_error(loc, state,
                       "interpolation qualifier `%s' can only be applied to "
                       "vertex shader outputs and fragment shader inputs.",
                       qual_string);

   }

   var->pixel_center_integer = qual->flags.q.pixel_center_integer;
   var->origin_upper_left = qual->flags.q.origin_upper_left;
   if ((qual->flags.q.origin_upper_left || qual->flags.q.pixel_center_integer)
       && (strcmp(var->name, "gl_FragCoord") != 0)) {
      const char *const qual_string = (qual->flags.q.origin_upper_left)
         ? "origin_upper_left" : "pixel_center_integer";

      _mesa_glsl_error(loc, state,
                       "layout qualifier `%s' can only be applied to "
                       "fragment shader input `gl_FragCoord'",
                       qual_string);
   }

   if (qual->flags.q.explicit_location) {
      const bool global_scope = (state->current_function == NULL);
      bool fail = false;
      const char *string = "";

      /* In the vertex shader only shader inputs can be given explicit
       * locations.
       *
       * In the fragment shader only shader outputs can be given explicit
       * locations.
       */
      switch (state->target) {
      case vertex_shader:
         if (!global_scope || (var->mode != ir_var_in)) {
            fail = true;
            string = "input";
         }
         break;

      case geometry_shader:
         _mesa_glsl_error(loc, state,
                          "geometry shader variables cannot be given "
                          "explicit locations\n");
         break;

      case fragment_shader:
         if (!global_scope || (var->mode != ir_var_out)) {
            fail = true;
            string = "output";
         }
         break;
      };

      if (fail) {
         _mesa_glsl_error(loc, state,
                          "only %s shader %s variables can be given an "
                          "explicit location\n",
                          _mesa_glsl_shader_target_name(state->target),
                          string);
      } else {
         var->explicit_location = true;

         /* This bit of silliness is needed because invalid explicit locations
          * are supposed to be flagged during linking.  Small negative values
          * biased by VERT_ATTRIB_GENERIC0 or FRAG_RESULT_DATA0 could alias
          * built-in values (e.g., -16+VERT_ATTRIB_GENERIC0 = VERT_ATTRIB_POS).
          * The linker needs to be able to differentiate these cases.  This
          * ensures that negative values stay negative.
          */
         if (qual->location >= 0) {
            var->location = (state->target == vertex_shader)
               ? (qual->location + VERT_ATTRIB_GENERIC0)
               : (qual->location + FRAG_RESULT_DATA0);
         } else {
            var->location = qual->location;
         }
         if (qual->flags.q.explicit_index) {
            var->explicit_index = true;
            var->index = qual->index;
         }
      }
   } else if (qual->flags.q.explicit_index) {
         _mesa_glsl_error(loc, state,
                          "explicit index requires explicit location\n");
   }

   /* Does the declaration use the 'layout' keyword?
    */
   const bool uses_layout = qual->flags.q.pixel_center_integer
      || qual->flags.q.origin_upper_left
      || qual->flags.q.explicit_location; /* no need for index since it relies on location */

   /* Does the declaration use the deprecated 'attribute' or 'varying'
    * keywords?
    */
   const bool uses_deprecated_qualifier = qual->flags.q.attribute
      || qual->flags.q.varying;

   /* Is the 'layout' keyword used with parameters that allow relaxed checking.
    * Many implementations of GL_ARB_fragment_coord_conventions_enable and some
    * implementations (only Mesa?) GL_ARB_explicit_attrib_location_enable
    * allowed the layout qualifier to be used with 'varying' and 'attribute'.
    * These extensions and all following extensions that add the 'layout'
    * keyword have been modified to require the use of 'in' or 'out'.
    *
    * The following extension do not allow the deprecated keywords:
    *
    *    GL_AMD_conservative_depth
    *    GL_ARB_conservative_depth
    *    GL_ARB_gpu_shader5
    *    GL_ARB_separate_shader_objects
    *    GL_ARB_tesselation_shader
    *    GL_ARB_transform_feedback3
    *    GL_ARB_uniform_buffer_object
    *
    * It is unknown whether GL_EXT_shader_image_load_store or GL_NV_gpu_shader5
    * allow layout with the deprecated keywords.
    */
   const bool relaxed_layout_qualifier_checking =
      state->ARB_fragment_coord_conventions_enable;

   if (uses_layout && uses_deprecated_qualifier) {
      if (relaxed_layout_qualifier_checking) {
         _mesa_glsl_warning(loc, state,
                            "`layout' qualifier may not be used with "
                            "`attribute' or `varying'");
      } else {
         _mesa_glsl_error(loc, state,
                          "`layout' qualifier may not be used with "
                          "`attribute' or `varying'");
      }
   }

   /* Layout qualifiers for gl_FragDepth, which are enabled by extension
    * AMD_conservative_depth.
    */
   int depth_layout_count = qual->flags.q.depth_any
      + qual->flags.q.depth_greater
      + qual->flags.q.depth_less
      + qual->flags.q.depth_unchanged;
   if (depth_layout_count > 0
       && !state->AMD_conservative_depth_enable
       && !state->ARB_conservative_depth_enable) {
       _mesa_glsl_error(loc, state,
                        "extension GL_AMD_conservative_depth or "
                        "GL_ARB_conservative_depth must be enabled "
                        "to use depth layout qualifiers");
   } else if (depth_layout_count > 0
              && strcmp(var->name, "gl_FragDepth") != 0) {
       _mesa_glsl_error(loc, state,
                        "depth layout qualifiers can be applied only to "
                        "gl_FragDepth");
   } else if (depth_layout_count > 1
              && strcmp(var->name, "gl_FragDepth") == 0) {
      _mesa_glsl_error(loc, state,
                       "at most one depth layout qualifier can be applied to "
                       "gl_FragDepth");
   }
   if (qual->flags.q.depth_any)
      var->depth_layout = ir_depth_layout_any;
   else if (qual->flags.q.depth_greater)
      var->depth_layout = ir_depth_layout_greater;
   else if (qual->flags.q.depth_less)
      var->depth_layout = ir_depth_layout_less;
   else if (qual->flags.q.depth_unchanged)
       var->depth_layout = ir_depth_layout_unchanged;
   else
       var->depth_layout = ir_depth_layout_none;
}

/**
 * Get the variable that is being redeclared by this declaration
 *
 * Semantic checks to verify the validity of the redeclaration are also
 * performed.  If semantic checks fail, compilation error will be emitted via
 * \c _mesa_glsl_error, but a non-\c NULL pointer will still be returned.
 *
 * \returns
 * A pointer to an existing variable in the current scope if the declaration
 * is a redeclaration, \c NULL otherwise.
 */
ir_variable *
get_variable_being_redeclared(ir_variable *var, ast_declaration *decl,
                              struct _mesa_glsl_parse_state *state)
{
   /* Check if this declaration is actually a re-declaration, either to
    * resize an array or add qualifiers to an existing variable.
    *
    * This is allowed for variables in the current scope, or when at
    * global scope (for built-ins in the implicit outer scope).
    */
   ir_variable *earlier = state->symbols->get_variable(decl->identifier);
   if (earlier == NULL ||
       (state->current_function != NULL &&
        !state->symbols->name_declared_this_scope(decl->identifier))) {
      return NULL;
   }


   YYLTYPE loc = decl->get_location();

   /* From page 24 (page 30 of the PDF) of the GLSL 1.50 spec,
    *
    * "It is legal to declare an array without a size and then
    *  later re-declare the same name as an array of the same
    *  type and specify a size."
    */
   if ((earlier->type->array_size() == 0)
       && var->type->is_array()
       && (var->type->element_type() == earlier->type->element_type())) {
      /* FINISHME: This doesn't match the qualifiers on the two
       * FINISHME: declarations.  It's not 100% clear whether this is
       * FINISHME: required or not.
       */

      const unsigned size = unsigned(var->type->array_size());
      check_builtin_array_max_size(var->name, size, loc, state);
      if ((size > 0) && (size <= earlier->max_array_access)) {
         _mesa_glsl_error(& loc, state, "array size must be > %u due to "
                          "previous access",
                          earlier->max_array_access);
      }

      earlier->type = var->type;
      delete var;
      var = NULL;
   } else if (state->ARB_fragment_coord_conventions_enable
              && strcmp(var->name, "gl_FragCoord") == 0
              && earlier->type == var->type
              && earlier->mode == var->mode) {
      /* Allow redeclaration of gl_FragCoord for ARB_fcc layout
       * qualifiers.
       */
      earlier->origin_upper_left = var->origin_upper_left;
      earlier->pixel_center_integer = var->pixel_center_integer;

      /* According to section 4.3.7 of the GLSL 1.30 spec,
       * the following built-in varaibles can be redeclared with an
       * interpolation qualifier:
       *    * gl_FrontColor
       *    * gl_BackColor
       *    * gl_FrontSecondaryColor
       *    * gl_BackSecondaryColor
       *    * gl_Color
       *    * gl_SecondaryColor
       */
   } else if (state->language_version >= 130
              && (strcmp(var->name, "gl_FrontColor") == 0
                  || strcmp(var->name, "gl_BackColor") == 0
                  || strcmp(var->name, "gl_FrontSecondaryColor") == 0
                  || strcmp(var->name, "gl_BackSecondaryColor") == 0
                  || strcmp(var->name, "gl_Color") == 0
                  || strcmp(var->name, "gl_SecondaryColor") == 0)
              && earlier->type == var->type
              && earlier->mode == var->mode) {
      earlier->interpolation = var->interpolation;

      /* Layout qualifiers for gl_FragDepth. */
   } else if ((state->AMD_conservative_depth_enable ||
               state->ARB_conservative_depth_enable)
              && strcmp(var->name, "gl_FragDepth") == 0
              && earlier->type == var->type
              && earlier->mode == var->mode) {

      /** From the AMD_conservative_depth spec:
       *     Within any shader, the first redeclarations of gl_FragDepth
       *     must appear before any use of gl_FragDepth.
       */
      if (earlier->used) {
         _mesa_glsl_error(&loc, state,
                          "the first redeclaration of gl_FragDepth "
                          "must appear before any use of gl_FragDepth");
      }

      /* Prevent inconsistent redeclaration of depth layout qualifier. */
      if (earlier->depth_layout != ir_depth_layout_none
          && earlier->depth_layout != var->depth_layout) {
         _mesa_glsl_error(&loc, state,
                          "gl_FragDepth: depth layout is declared here "
                          "as '%s, but it was previously declared as "
                          "'%s'",
                          depth_layout_string(var->depth_layout),
                          depth_layout_string(earlier->depth_layout));
      }

      earlier->depth_layout = var->depth_layout;

   } else {
      _mesa_glsl_error(&loc, state, "`%s' redeclared", decl->identifier);
   }

   return earlier;
}

/**
 * Generate the IR for an initializer in a variable declaration
 */
ir_rvalue *
process_initializer(ir_variable *var, ast_declaration *decl,
                    ast_fully_specified_type *type,
                    exec_list *initializer_instructions,
                    struct _mesa_glsl_parse_state *state)
{
   ir_rvalue *result = NULL;

   YYLTYPE initializer_loc = decl->initializer->get_location();

   /* From page 24 (page 30 of the PDF) of the GLSL 1.10 spec:
    *
    *    "All uniform variables are read-only and are initialized either
    *    directly by an application via API commands, or indirectly by
    *    OpenGL."
    */
   if ((state->language_version <= 110)
       && (var->mode == ir_var_uniform)) {
      _mesa_glsl_error(& initializer_loc, state,
                       "cannot initialize uniforms in GLSL 1.10");
   }

   if (var->type->is_sampler()) {
      _mesa_glsl_error(& initializer_loc, state,
                       "cannot initialize samplers");
   }

   if ((var->mode == ir_var_in) && (state->current_function == NULL)) {
      _mesa_glsl_error(& initializer_loc, state,
                       "cannot initialize %s shader input / %s",
                       _mesa_glsl_shader_target_name(state->target),
                       (state->target == vertex_shader)
                       ? "attribute" : "varying");
   }

   ir_dereference *const lhs = new(state) ir_dereference_variable(var);
   ir_rvalue *rhs = decl->initializer->hir(initializer_instructions,
                                           state);

   /* Calculate the constant value if this is a const or uniform
    * declaration.
    */
   if (type->qualifier.flags.q.constant
       || type->qualifier.flags.q.uniform) {
      ir_rvalue *new_rhs = validate_assignment(state, var->type, rhs, true);
      if (new_rhs != NULL) {
         rhs = new_rhs;

         ir_constant *constant_value = rhs->constant_expression_value();
         if (!constant_value) {
            _mesa_glsl_error(& initializer_loc, state,
                             "initializer of %s variable `%s' must be a "
                             "constant expression",
                             (type->qualifier.flags.q.constant)
                             ? "const" : "uniform",
                             decl->identifier);
            if (var->type->is_numeric()) {
               /* Reduce cascading errors. */
               var->constant_value = ir_constant::zero(state, var->type);
            }
         } else {
            rhs = constant_value;
            var->constant_value = constant_value;
         }
      } else {
         _mesa_glsl_error(&initializer_loc, state,
                          "initializer of type %s cannot be assigned to "
                          "variable of type %s",
                          rhs->type->name, var->type->name);
         if (var->type->is_numeric()) {
            /* Reduce cascading errors. */
            var->constant_value = ir_constant::zero(state, var->type);
         }
      }
   }

   if (rhs && !rhs->type->is_error()) {
      bool temp = var->read_only;
      if (type->qualifier.flags.q.constant)
         var->read_only = false;

      /* Never emit code to initialize a uniform.
       */
      const glsl_type *initializer_type;
      if (!type->qualifier.flags.q.uniform) {
         result = do_assignment(initializer_instructions, state,
                                NULL,
                                lhs, rhs, true,
                                type->get_location());
         initializer_type = result->type;
      } else
         initializer_type = rhs->type;

      var->constant_initializer = rhs->constant_expression_value();
      var->has_initializer = true;

      /* If the declared variable is an unsized array, it must inherrit
       * its full type from the initializer.  A declaration such as
       *
       *     uniform float a[] = float[](1.0, 2.0, 3.0, 3.0);
       *
       * becomes
       *
       *     uniform float a[4] = float[](1.0, 2.0, 3.0, 3.0);
       *
       * The assignment generated in the if-statement (below) will also
       * automatically handle this case for non-uniforms.
       *
       * If the declared variable is not an array, the types must
       * already match exactly.  As a result, the type assignment
       * here can be done unconditionally.  For non-uniforms the call
       * to do_assignment can change the type of the initializer (via
       * the implicit conversion rules).  For uniforms the initializer
       * must be a constant expression, and the type of that expression
       * was validated above.
       */
      var->type = initializer_type;

      var->read_only = temp;
   }

   return result;
}

ir_rvalue *
ast_declarator_list::hir(exec_list *instructions,
                         struct _mesa_glsl_parse_state *state)
{
   void *ctx = state;
   const struct glsl_type *decl_type;
   const char *type_name = NULL;
   ir_rvalue *result = NULL;
   YYLTYPE loc = this->get_location();

   /* From page 46 (page 52 of the PDF) of the GLSL 1.50 spec:
    *
    *     "To ensure that a particular output variable is invariant, it is
    *     necessary to use the invariant qualifier. It can either be used to
    *     qualify a previously declared variable as being invariant
    *
    *         invariant gl_Position; // make existing gl_Position be invariant"
    *
    * In these cases the parser will set the 'invariant' flag in the declarator
    * list, and the type will be NULL.
    */
   if (this->invariant) {
      assert(this->type == NULL);

      if (state->current_function != NULL) {
         _mesa_glsl_error(& loc, state,
                          "All uses of `invariant' keyword must be at global "
                          "scope\n");
      }

      foreach_list_typed (ast_declaration, decl, link, &this->declarations) {
         assert(!decl->is_array);
         assert(decl->array_size == NULL);
         assert(decl->initializer == NULL);

         ir_variable *const earlier =
            state->symbols->get_variable(decl->identifier);
         if (earlier == NULL) {
            _mesa_glsl_error(& loc, state,
                             "Undeclared variable `%s' cannot be marked "
                             "invariant\n", decl->identifier);
         } else if ((state->target == vertex_shader)
               && (earlier->mode != ir_var_out)) {
            _mesa_glsl_error(& loc, state,
                             "`%s' cannot be marked invariant, vertex shader "
                             "outputs only\n", decl->identifier);
         } else if ((state->target == fragment_shader)
               && (earlier->mode != ir_var_in)) {
            _mesa_glsl_error(& loc, state,
                             "`%s' cannot be marked invariant, fragment shader "
                             "inputs only\n", decl->identifier);
         } else if (earlier->used) {
            _mesa_glsl_error(& loc, state,
                             "variable `%s' may not be redeclared "
                             "`invariant' after being used",
                             earlier->name);
         } else {
            earlier->invariant = true;
         }
      }

      /* Invariant redeclarations do not have r-values.
       */
      return NULL;
   }

   assert(this->type != NULL);
   assert(!this->invariant);

   /* The type specifier may contain a structure definition.  Process that
    * before any of the variable declarations.
    */
   (void) this->type->specifier->hir(instructions, state);

   decl_type = this->type->specifier->glsl_type(& type_name, state);
   if (this->declarations.is_empty()) {
      /* If there is no structure involved in the program text, there are two
       * possible scenarios:
       *
       * - The program text contained something like 'vec4;'.  This is an
       *   empty declaration.  It is valid but weird.  Emit a warning.
       *
       * - The program text contained something like 'S;' and 'S' is not the
       *   name of a known structure type.  This is both invalid and weird.
       *   Emit an error.
       *
       * Note that if decl_type is NULL and there is a structure involved,
       * there must have been some sort of error with the structure.  In this
       * case we assume that an error was already generated on this line of
       * code for the structure.  There is no need to generate an additional,
       * confusing error.
       */
      assert(this->type->specifier->structure == NULL || decl_type != NULL
             || state->error);
      if (this->type->specifier->structure == NULL) {
         if (decl_type != NULL) {
            _mesa_glsl_warning(&loc, state, "empty declaration");
         } else {
            _mesa_glsl_error(&loc, state,
                             "invalid type `%s' in empty declaration",
                             type_name);
         }
      }
   }

   foreach_list_typed (ast_declaration, decl, link, &this->declarations) {
      const struct glsl_type *var_type;
      ir_variable *var;

      /* FINISHME: Emit a warning if a variable declaration shadows a
       * FINISHME: declaration at a higher scope.
       */

      if ((decl_type == NULL) || decl_type->is_void()) {
         if (type_name != NULL) {
            _mesa_glsl_error(& loc, state,
                             "invalid type `%s' in declaration of `%s'",
                             type_name, decl->identifier);
         } else {
            _mesa_glsl_error(& loc, state,
                             "invalid type in declaration of `%s'",
                             decl->identifier);
         }
         continue;
      }

      if (decl->is_array) {
         var_type = process_array_type(&loc, decl_type, decl->array_size,
                                       state);
         if (var_type->is_error())
            continue;
      } else {
         var_type = decl_type;
      }

      var = new(ctx) ir_variable(var_type, decl->identifier, ir_var_auto);

      /* From page 22 (page 28 of the PDF) of the GLSL 1.10 specification;
       *
       *     "Global variables can only use the qualifiers const,
       *     attribute, uni form, or varying. Only one may be
       *     specified.
       *
       *     Local variables can only use the qualifier const."
       *
       * This is relaxed in GLSL 1.30.  It is also relaxed by any extension
       * that adds the 'layout' keyword.
       */
      if ((state->language_version < 130)
          && !state->ARB_explicit_attrib_location_enable
          && !state->ARB_fragment_coord_conventions_enable) {
         if (this->type->qualifier.flags.q.out) {
            _mesa_glsl_error(& loc, state,
                             "`out' qualifier in declaration of `%s' "
                             "only valid for function parameters in %s.",
                             decl->identifier, state->version_string);
         }
         if (this->type->qualifier.flags.q.in) {
            _mesa_glsl_error(& loc, state,
                             "`in' qualifier in declaration of `%s' "
                             "only valid for function parameters in %s.",
                             decl->identifier, state->version_string);
         }
         /* FINISHME: Test for other invalid qualifiers. */
      }

      apply_type_qualifier_to_variable(& this->type->qualifier, var, state,
                                       & loc);

      if (this->type->qualifier.flags.q.invariant) {
         if ((state->target == vertex_shader) && !(var->mode == ir_var_out ||
                                                   var->mode == ir_var_inout)) {
            /* FINISHME: Note that this doesn't work for invariant on
             * a function signature outval
             */
            _mesa_glsl_error(& loc, state,
                             "`%s' cannot be marked invariant, vertex shader "
                             "outputs only\n", var->name);
         } else if ((state->target == fragment_shader) &&
                    !(var->mode == ir_var_in || var->mode == ir_var_inout)) {
            /* FINISHME: Note that this doesn't work for invariant on
             * a function signature inval
             */
            _mesa_glsl_error(& loc, state,
                             "`%s' cannot be marked invariant, fragment shader "
                             "inputs only\n", var->name);
         }
      }

      if (state->current_function != NULL) {
         const char *mode = NULL;
         const char *extra = "";

         /* There is no need to check for 'inout' here because the parser will
          * only allow that in function parameter lists.
          */
         if (this->type->qualifier.flags.q.attribute) {
            mode = "attribute";
         } else if (this->type->qualifier.flags.q.uniform) {
            mode = "uniform";
         } else if (this->type->qualifier.flags.q.varying) {
            mode = "varying";
         } else if (this->type->qualifier.flags.q.in) {
            mode = "in";
            extra = " or in function parameter list";
         } else if (this->type->qualifier.flags.q.out) {
            mode = "out";
            extra = " or in function parameter list";
         }

         if (mode) {
            _mesa_glsl_error(& loc, state,
                             "%s variable `%s' must be declared at "
                             "global scope%s",
                             mode, var->name, extra);
         }
      } else if (var->mode == ir_var_in) {
         var->read_only = true;

         if (state->target == vertex_shader) {
            bool error_emitted = false;

            /* From page 31 (page 37 of the PDF) of the GLSL 1.50 spec:
             *
             *    "Vertex shader inputs can only be float, floating-point
             *    vectors, matrices, signed and unsigned integers and integer
             *    vectors. Vertex shader inputs can also form arrays of these
             *    types, but not structures."
             *
             * From page 31 (page 27 of the PDF) of the GLSL 1.30 spec:
             *
             *    "Vertex shader inputs can only be float, floating-point
             *    vectors, matrices, signed and unsigned integers and integer
             *    vectors. They cannot be arrays or structures."
             *
             * From page 23 (page 29 of the PDF) of the GLSL 1.20 spec:
             *
             *    "The attribute qualifier can be used only with float,
             *    floating-point vectors, and matrices. Attribute variables
             *    cannot be declared as arrays or structures."
             */
            const glsl_type *check_type = var->type->is_array()
               ? var->type->fields.array : var->type;

            switch (check_type->base_type) {
            case GLSL_TYPE_FLOAT:
               break;
            case GLSL_TYPE_UINT:
            case GLSL_TYPE_INT:
               if (state->language_version > 120)
                  break;
               /* FALLTHROUGH */
            default:
               _mesa_glsl_error(& loc, state,
                                "vertex shader input / attribute cannot have "
                                "type %s`%s'",
                                var->type->is_array() ? "array of " : "",
                                check_type->name);
               error_emitted = true;
            }

            if (!error_emitted && (state->language_version <= 130)
                && var->type->is_array()) {
               _mesa_glsl_error(& loc, state,
                                "vertex shader input / attribute cannot have "
                                "array type");
               error_emitted = true;
            }
         }
      }

      /* Integer vertex outputs must be qualified with 'flat'.
       *
       * From section 4.3.6 of the GLSL 1.30 spec:
       *    "If a vertex output is a signed or unsigned integer or integer
       *    vector, then it must be qualified with the interpolation qualifier
       *    flat."
       */
      if (state->language_version >= 130
          && state->target == vertex_shader
          && state->current_function == NULL
          && var->type->is_integer()
          && var->mode == ir_var_out
          && var->interpolation != INTERP_QUALIFIER_FLAT) {

         _mesa_glsl_error(&loc, state, "If a vertex output is an integer, "
                          "then it must be qualified with 'flat'");
      }


      /* Interpolation qualifiers cannot be applied to 'centroid' and
       * 'centroid varying'.
       *
       * From page 29 (page 35 of the PDF) of the GLSL 1.30 spec:
       *    "interpolation qualifiers may only precede the qualifiers in,
       *    centroid in, out, or centroid out in a declaration. They do not apply
       *    to the deprecated storage qualifiers varying or centroid varying."
       */
      if (state->language_version >= 130
          && this->type->qualifier.has_interpolation()
          && this->type->qualifier.flags.q.varying) {

         const char *i = this->type->qualifier.interpolation_string();
         assert(i != NULL);
         const char *s;
         if (this->type->qualifier.flags.q.centroid)
            s = "centroid varying";
         else
            s = "varying";

         _mesa_glsl_error(&loc, state,
                          "qualifier '%s' cannot be applied to the "
                          "deprecated storage qualifier '%s'", i, s);
      }


      /* Interpolation qualifiers can only apply to vertex shader outputs and
       * fragment shader inputs.
       *
       * From page 29 (page 35 of the PDF) of the GLSL 1.30 spec:
       *    "Outputs from a vertex shader (out) and inputs to a fragment
       *    shader (in) can be further qualified with one or more of these
       *    interpolation qualifiers"
       */
      if (state->language_version >= 130
          && this->type->qualifier.has_interpolation()) {

         const char *i = this->type->qualifier.interpolation_string();
         assert(i != NULL);

         switch (state->target) {
         case vertex_shader:
            if (this->type->qualifier.flags.q.in) {
               _mesa_glsl_error(&loc, state,
                                "qualifier '%s' cannot be applied to vertex "
                                "shader inputs", i);
            }
            break;
         case fragment_shader:
            if (this->type->qualifier.flags.q.out) {
               _mesa_glsl_error(&loc, state,
                                "qualifier '%s' cannot be applied to fragment "
                                "shader outputs", i);
            }
            break;
         default:
            assert(0);
         }
      }


      /* From section 4.3.4 of the GLSL 1.30 spec:
       *    "It is an error to use centroid in in a vertex shader."
       */
      if (state->language_version >= 130
          && this->type->qualifier.flags.q.centroid
          && this->type->qualifier.flags.q.in
          && state->target == vertex_shader) {

         _mesa_glsl_error(&loc, state,
                          "'centroid in' cannot be used in a vertex shader");
      }


      /* Precision qualifiers exists only in GLSL versions 1.00 and >= 1.30.
       */
      if (this->type->specifier->precision != ast_precision_none
          && state->language_version != 100
          && state->language_version < 130) {

         _mesa_glsl_error(&loc, state,
                          "precision qualifiers are supported only in GLSL ES "
                          "1.00, and GLSL 1.30 and later");
      }


      /* Precision qualifiers only apply to floating point and integer types.
       *
       * From section 4.5.2 of the GLSL 1.30 spec:
       *    "Any floating point or any integer declaration can have the type
       *    preceded by one of these precision qualifiers [...] Literal
       *    constants do not have precision qualifiers. Neither do Boolean
       *    variables.
       *
       * In GLSL ES, sampler types are also allowed.
       *
       * From page 87 of the GLSL ES spec:
       *    "RESOLUTION: Allow sampler types to take a precision qualifier."
       */
      if (this->type->specifier->precision != ast_precision_none
          && !var->type->is_float()
          && !var->type->is_integer()
          && !(var->type->is_sampler() && state->es_shader)
          && !(var->type->is_array()
               && (var->type->fields.array->is_float()
                   || var->type->fields.array->is_integer()))) {

         _mesa_glsl_error(&loc, state,
                          "precision qualifiers apply only to floating point"
                          "%s types", state->es_shader ? ", integer, and sampler"
                                                       : "and integer");
      }

      /* From page 17 (page 23 of the PDF) of the GLSL 1.20 spec:
       *
       *    "[Sampler types] can only be declared as function
       *    parameters or uniform variables (see Section 4.3.5
       *    "Uniform")".
       */
      if (var_type->contains_sampler() &&
          !this->type->qualifier.flags.q.uniform) {
         _mesa_glsl_error(&loc, state, "samplers must be declared uniform");
      }

      /* Process the initializer and add its instructions to a temporary
       * list.  This list will be added to the instruction stream (below) after
       * the declaration is added.  This is done because in some cases (such as
       * redeclarations) the declaration may not actually be added to the
       * instruction stream.
       */
      exec_list initializer_instructions;
      ir_variable *earlier = get_variable_being_redeclared(var, decl, state);

      if (decl->initializer != NULL) {
         result = process_initializer((earlier == NULL) ? var : earlier,
                                      decl, this->type,
                                      &initializer_instructions, state);
      }

      /* From page 23 (page 29 of the PDF) of the GLSL 1.10 spec:
       *
       *     "It is an error to write to a const variable outside of
       *      its declaration, so they must be initialized when
       *      declared."
       */
      if (this->type->qualifier.flags.q.constant && decl->initializer == NULL) {
         _mesa_glsl_error(& loc, state,
                          "const declaration of `%s' must be initialized",
                          decl->identifier);
      }

      /* If the declaration is not a redeclaration, there are a few additional
       * semantic checks that must be applied.  In addition, variable that was
       * created for the declaration should be added to the IR stream.
       */
      if (earlier == NULL) {
         /* From page 15 (page 21 of the PDF) of the GLSL 1.10 spec,
          *
          *   "Identifiers starting with "gl_" are reserved for use by
          *   OpenGL, and may not be declared in a shader as either a
          *   variable or a function."
          */
         if (strncmp(decl->identifier, "gl_", 3) == 0)
            _mesa_glsl_error(& loc, state,
                             "identifier `%s' uses reserved `gl_' prefix",
                             decl->identifier);
         else if (strstr(decl->identifier, "__")) {
            /* From page 14 (page 20 of the PDF) of the GLSL 1.10
             * spec:
             *
             *     "In addition, all identifiers containing two
             *      consecutive underscores (__) are reserved as
             *      possible future keywords."
             */
            _mesa_glsl_error(& loc, state,
                             "identifier `%s' uses reserved `__' string",
                             decl->identifier);
         }

         /* Add the variable to the symbol table.  Note that the initializer's
          * IR was already processed earlier (though it hasn't been emitted
          * yet), without the variable in scope.
          *
          * This differs from most C-like languages, but it follows the GLSL
          * specification.  From page 28 (page 34 of the PDF) of the GLSL 1.50
          * spec:
          *
          *     "Within a declaration, the scope of a name starts immediately
          *     after the initializer if present or immediately after the name
          *     being declared if not."
          */
         if (!state->symbols->add_variable(var)) {
            YYLTYPE loc = this->get_location();
            _mesa_glsl_error(&loc, state, "name `%s' already taken in the "
                             "current scope", decl->identifier);
            continue;
         }

         /* Push the variable declaration to the top.  It means that all the
          * variable declarations will appear in a funny last-to-first order,
          * but otherwise we run into trouble if a function is prototyped, a
          * global var is decled, then the function is defined with usage of
          * the global var.  See glslparsertest's CorrectModule.frag.
          */
         instructions->push_head(var);
      }

      instructions->append_list(&initializer_instructions);
   }


   /* Generally, variable declarations do not have r-values.  However,
    * one is used for the declaration in
    *
    * while (bool b = some_condition()) {
    *   ...
    * }
    *
    * so we return the rvalue from the last seen declaration here.
    */
   return result;
}


ir_rvalue *
ast_parameter_declarator::hir(exec_list *instructions,
                              struct _mesa_glsl_parse_state *state)
{
   void *ctx = state;
   const struct glsl_type *type;
   const char *name = NULL;
   YYLTYPE loc = this->get_location();

   type = this->type->specifier->glsl_type(& name, state);

   if (type == NULL) {
      if (name != NULL) {
         _mesa_glsl_error(& loc, state,
                          "invalid type `%s' in declaration of `%s'",
                          name, this->identifier);
      } else {
         _mesa_glsl_error(& loc, state,
                          "invalid type in declaration of `%s'",
                          this->identifier);
      }

      type = glsl_type::error_type;
   }

   /* From page 62 (page 68 of the PDF) of the GLSL 1.50 spec:
    *
    *    "Functions that accept no input arguments need not use void in the
    *    argument list because prototypes (or definitions) are required and
    *    therefore there is no ambiguity when an empty argument list "( )" is
    *    declared. The idiom "(void)" as a parameter list is provided for
    *    convenience."
    *
    * Placing this check here prevents a void parameter being set up
    * for a function, which avoids tripping up checks for main taking
    * parameters and lookups of an unnamed symbol.
    */
   if (type->is_void()) {
      if (this->identifier != NULL)
         _mesa_glsl_error(& loc, state,
                          "named parameter cannot have type `void'");

      is_void = true;
      return NULL;
   }

   if (formal_parameter && (this->identifier == NULL)) {
      _mesa_glsl_error(& loc, state, "formal parameter lacks a name");
      return NULL;
   }

   /* This only handles "vec4 foo[..]".  The earlier specifier->glsl_type(...)
    * call already handled the "vec4[..] foo" case.
    */
   if (this->is_array) {
      type = process_array_type(&loc, type, this->array_size, state);
   }

   if (!type->is_error() && type->array_size() == 0) {
      _mesa_glsl_error(&loc, state, "arrays passed as parameters must have "
                       "a declared size.");
      type = glsl_type::error_type;
   }

   is_void = false;
   ir_variable *var = new(ctx) ir_variable(type, this->identifier, ir_var_in);

   /* Apply any specified qualifiers to the parameter declaration.  Note that
    * for function parameters the default mode is 'in'.
    */
   apply_type_qualifier_to_variable(& this->type->qualifier, var, state, & loc);

   /* From page 17 (page 23 of the PDF) of the GLSL 1.20 spec:
    *
    *    "Samplers cannot be treated as l-values; hence cannot be used
    *    as out or inout function parameters, nor can they be assigned
    *    into."
    */
   if ((var->mode == ir_var_inout || var->mode == ir_var_out)
       && type->contains_sampler()) {
      _mesa_glsl_error(&loc, state, "out and inout parameters cannot contain samplers");
      type = glsl_type::error_type;
   }

   /* From page 39 (page 45 of the PDF) of the GLSL 1.10 spec:
    *
    *    "When calling a function, expressions that do not evaluate to
    *     l-values cannot be passed to parameters declared as out or inout."
    *
    * From page 32 (page 38 of the PDF) of the GLSL 1.10 spec:
    *
    *    "Other binary or unary expressions, non-dereferenced arrays,
    *     function names, swizzles with repeated fields, and constants
    *     cannot be l-values."
    *
    * So for GLSL 1.10, passing an array as an out or inout parameter is not
    * allowed.  This restriction is removed in GLSL 1.20, and in GLSL ES.
    */
   if ((var->mode == ir_var_inout || var->mode == ir_var_out)
       && type->is_array() && state->language_version == 110) {
      _mesa_glsl_error(&loc, state, "Arrays cannot be out or inout parameters in GLSL 1.10");
      type = glsl_type::error_type;
   }

   instructions->push_tail(var);

   /* Parameter declarations do not have r-values.
    */
   return NULL;
}


void
ast_parameter_declarator::parameters_to_hir(exec_list *ast_parameters,
                                            bool formal,
                                            exec_list *ir_parameters,
                                            _mesa_glsl_parse_state *state)
{
   ast_parameter_declarator *void_param = NULL;
   unsigned count = 0;

   foreach_list_typed (ast_parameter_declarator, param, link, ast_parameters) {
      param->formal_parameter = formal;
      param->hir(ir_parameters, state);

      if (param->is_void)
         void_param = param;

      count++;
   }

   if ((void_param != NULL) && (count > 1)) {
      YYLTYPE loc = void_param->get_location();

      _mesa_glsl_error(& loc, state,
                       "`void' parameter must be only parameter");
   }
}


void
emit_function(_mesa_glsl_parse_state *state, ir_function *f)
{
   /* IR invariants disallow function declarations or definitions
    * nested within other function definitions.  But there is no
    * requirement about the relative order of function declarations
    * and definitions with respect to one another.  So simply insert
    * the new ir_function block at the end of the toplevel instruction
    * list.
    */
   state->toplevel_ir->push_tail(f);
}


ir_rvalue *
ast_function::hir(exec_list *instructions,
                  struct _mesa_glsl_parse_state *state)
{
   void *ctx = state;
   ir_function *f = NULL;
   ir_function_signature *sig = NULL;
   exec_list hir_parameters;

   const char *const name = identifier;

   /* New functions are always added to the top-level IR instruction stream,
    * so this instruction list pointer is ignored.  See also emit_function
    * (called below).
    */
   (void) instructions;

   /* From page 21 (page 27 of the PDF) of the GLSL 1.20 spec,
    *
    *   "Function declarations (prototypes) cannot occur inside of functions;
    *   they must be at global scope, or for the built-in functions, outside
    *   the global scope."
    *
    * From page 27 (page 33 of the PDF) of the GLSL ES 1.00.16 spec,
    *
    *   "User defined functions may only be defined within the global scope."
    *
    * Note that this language does not appear in GLSL 1.10.
    */
   if ((state->current_function != NULL) && (state->language_version != 110)) {
      YYLTYPE loc = this->get_location();
      _mesa_glsl_error(&loc, state,
                       "declaration of function `%s' not allowed within "
                       "function body", name);
   }

   /* From page 15 (page 21 of the PDF) of the GLSL 1.10 spec,
    *
    *   "Identifiers starting with "gl_" are reserved for use by
    *   OpenGL, and may not be declared in a shader as either a
    *   variable or a function."
    */
   if (strncmp(name, "gl_", 3) == 0) {
      YYLTYPE loc = this->get_location();
      _mesa_glsl_error(&loc, state,
                       "identifier `%s' uses reserved `gl_' prefix", name);
   }

   /* Convert the list of function parameters to HIR now so that they can be
    * used below to compare this function's signature with previously seen
    * signatures for functions with the same name.
    */
   ast_parameter_declarator::parameters_to_hir(& this->parameters,
                                               is_definition,
                                               & hir_parameters, state);

   const char *return_type_name;
   const glsl_type *return_type =
      this->return_type->specifier->glsl_type(& return_type_name, state);

   if (!return_type) {
      YYLTYPE loc = this->get_location();
      _mesa_glsl_error(&loc, state,
                       "function `%s' has undeclared return type `%s'",
                       name, return_type_name);
      return_type = glsl_type::error_type;
   }

   /* From page 56 (page 62 of the PDF) of the GLSL 1.30 spec:
    * "No qualifier is allowed on the return type of a function."
    */
   if (this->return_type->has_qualifiers()) {
      YYLTYPE loc = this->get_location();
      _mesa_glsl_error(& loc, state,
                       "function `%s' return type has qualifiers", name);
   }

   /* From page 17 (page 23 of the PDF) of the GLSL 1.20 spec:
    *
    *    "[Sampler types] can only be declared as function parameters
    *    or uniform variables (see Section 4.3.5 "Uniform")".
    */
   if (return_type->contains_sampler()) {
      YYLTYPE loc = this->get_location();
      _mesa_glsl_error(&loc, state,
                       "function `%s' return type can't contain a sampler",
                       name);
   }

   /* Verify that this function's signature either doesn't match a previously
    * seen signature for a function with the same name, or, if a match is found,
    * that the previously seen signature does not have an associated definition.
    */
   f = state->symbols->get_function(name);
   if (f != NULL && (state->es_shader || f->has_user_signature())) {
      sig = f->exact_matching_signature(&hir_parameters);
      if (sig != NULL) {
         const char *badvar = sig->qualifiers_match(&hir_parameters);
         if (badvar != NULL) {
            YYLTYPE loc = this->get_location();

            _mesa_glsl_error(&loc, state, "function `%s' parameter `%s' "
                             "qualifiers don't match prototype", name, badvar);
         }

         if (sig->return_type != return_type) {
            YYLTYPE loc = this->get_location();

            _mesa_glsl_error(&loc, state, "function `%s' return type doesn't "
                             "match prototype", name);
         }

         if (is_definition && sig->is_defined) {
            YYLTYPE loc = this->get_location();

            _mesa_glsl_error(& loc, state, "function `%s' redefined", name);
         }
      }
   } else {
      f = new(ctx) ir_function(name);
      if (!state->symbols->add_function(f)) {
         /* This function name shadows a non-function use of the same name. */
         YYLTYPE loc = this->get_location();

         _mesa_glsl_error(&loc, state, "function name `%s' conflicts with "
                          "non-function", name);
         return NULL;
      }

      emit_function(state, f);
   }

   /* Verify the return type of main() */
   if (strcmp(name, "main") == 0) {
      if (! return_type->is_void()) {
         YYLTYPE loc = this->get_location();

         _mesa_glsl_error(& loc, state, "main() must return void");
      }

      if (!hir_parameters.is_empty()) {
         YYLTYPE loc = this->get_location();

         _mesa_glsl_error(& loc, state, "main() must not take any parameters");
      }
   }

   /* Finish storing the information about this new function in its signature.
    */
   if (sig == NULL) {
      sig = new(ctx) ir_function_signature(return_type);
      f->add_signature(sig);
   }

   sig->replace_parameters(&hir_parameters);
   signature = sig;

   /* Function declarations (prototypes) do not have r-values.
    */
   return NULL;
}


ir_rvalue *
ast_function_definition::hir(exec_list *instructions,
                             struct _mesa_glsl_parse_state *state)
{
   prototype->is_definition = true;
   prototype->hir(instructions, state);

   ir_function_signature *signature = prototype->signature;
   if (signature == NULL)
      return NULL;

   assert(state->current_function == NULL);
   state->current_function = signature;
   state->found_return = false;

   /* Duplicate parameters declared in the prototype as concrete variables.
    * Add these to the symbol table.
    */
   state->symbols->push_scope();
   foreach_iter(exec_list_iterator, iter, signature->parameters) {
      ir_variable *const var = ((ir_instruction *) iter.get())->as_variable();

      assert(var != NULL);

      /* The only way a parameter would "exist" is if two parameters have
       * the same name.
       */
      if (state->symbols->name_declared_this_scope(var->name)) {
         YYLTYPE loc = this->get_location();

         _mesa_glsl_error(& loc, state, "parameter `%s' redeclared", var->name);
      } else {
         state->symbols->add_variable(var);
      }
   }

   /* Convert the body of the function to HIR. */
   this->body->hir(&signature->body, state);
   signature->is_defined = true;

   state->symbols->pop_scope();

   assert(state->current_function == signature);
   state->current_function = NULL;

   if (!signature->return_type->is_void() && !state->found_return) {
      YYLTYPE loc = this->get_location();
      _mesa_glsl_error(& loc, state, "function `%s' has non-void return type "
                       "%s, but no return statement",
                       signature->function_name(),
                       signature->return_type->name);
   }

   /* Function definitions do not have r-values.
    */
   return NULL;
}


ir_rvalue *
ast_jump_statement::hir(exec_list *instructions,
                        struct _mesa_glsl_parse_state *state)
{
   void *ctx = state;

   switch (mode) {
   case ast_return: {
      ir_return *inst;
      assert(state->current_function);

      if (opt_return_value) {
         ir_rvalue *const ret = opt_return_value->hir(instructions, state);

         /* The value of the return type can be NULL if the shader says
          * 'return foo();' and foo() is a function that returns void.
          *
          * NOTE: The GLSL spec doesn't say that this is an error.  The type
          * of the return value is void.  If the return type of the function is
          * also void, then this should compile without error.  Seriously.
          */
         const glsl_type *const ret_type =
            (ret == NULL) ? glsl_type::void_type : ret->type;

         /* Implicit conversions are not allowed for return values. */
         if (state->current_function->return_type != ret_type) {
            YYLTYPE loc = this->get_location();

            _mesa_glsl_error(& loc, state,
                             "`return' with wrong type %s, in function `%s' "
                             "returning %s",
                             ret_type->name,
                             state->current_function->function_name(),
                             state->current_function->return_type->name);
         }

         inst = new(ctx) ir_return(ret);
      } else {
         if (state->current_function->return_type->base_type !=
             GLSL_TYPE_VOID) {
            YYLTYPE loc = this->get_location();

            _mesa_glsl_error(& loc, state,
                             "`return' with no value, in function %s returning "
                             "non-void",
                             state->current_function->function_name());
         }
         inst = new(ctx) ir_return;
      }

      state->found_return = true;
      instructions->push_tail(inst);
      break;
   }

   case ast_discard:
      if (state->target != fragment_shader) {
         YYLTYPE loc = this->get_location();

         _mesa_glsl_error(& loc, state,
                          "`discard' may only appear in a fragment shader");
      }
      instructions->push_tail(new(ctx) ir_discard);
      break;

   case ast_break:
   case ast_continue:
      if (mode == ast_continue &&
          state->loop_nesting_ast == NULL) {
         YYLTYPE loc = this->get_location();

         _mesa_glsl_error(& loc, state,
                          "continue may only appear in a loop");
      } else if (mode == ast_break &&
                 state->loop_nesting_ast == NULL &&
                 state->switch_state.switch_nesting_ast == NULL) {
         YYLTYPE loc = this->get_location();

         _mesa_glsl_error(& loc, state,
                          "break may only appear in a loop or a switch");
      } else {
         /* For a loop, inline the for loop expression again,
          * since we don't know where near the end of
          * the loop body the normal copy of it
          * is going to be placed.
          */
         if (state->loop_nesting_ast != NULL &&
             mode == ast_continue &&
             state->loop_nesting_ast->rest_expression) {
            state->loop_nesting_ast->rest_expression->hir(instructions,
                                                          state);
         }

         if (state->switch_state.is_switch_innermost &&
             mode == ast_break) {
            /* Force break out of switch by setting is_break switch state.
             */
            ir_variable *const is_break_var = state->switch_state.is_break_var;
            ir_dereference_variable *const deref_is_break_var =
               new(ctx) ir_dereference_variable(is_break_var);
            ir_constant *const true_val = new(ctx) ir_constant(true);
            ir_assignment *const set_break_var =
               new(ctx) ir_assignment(deref_is_break_var,
                                      true_val,
                                      NULL);
            
            instructions->push_tail(set_break_var);
         }
         else {
            ir_loop_jump *const jump = 
               new(ctx) ir_loop_jump((mode == ast_break)
                                     ? ir_loop_jump::jump_break
                                     : ir_loop_jump::jump_continue);
            instructions->push_tail(jump);
         }
      }

      break;
   }

   /* Jump instructions do not have r-values.
    */
   return NULL;
}


ir_rvalue *
ast_selection_statement::hir(exec_list *instructions,
                             struct _mesa_glsl_parse_state *state)
{
   void *ctx = state;

   ir_rvalue *const condition = this->condition->hir(instructions, state);

   /* From page 66 (page 72 of the PDF) of the GLSL 1.50 spec:
    *
    *    "Any expression whose type evaluates to a Boolean can be used as the
    *    conditional expression bool-expression. Vector types are not accepted
    *    as the expression to if."
    *
    * The checks are separated so that higher quality diagnostics can be
    * generated for cases where both rules are violated.
    */
   if (!condition->type->is_boolean() || !condition->type->is_scalar()) {
      YYLTYPE loc = this->condition->get_location();

      _mesa_glsl_error(& loc, state, "if-statement condition must be scalar "
                       "boolean");
   }

   ir_if *const stmt = new(ctx) ir_if(condition);

   if (then_statement != NULL) {
      state->symbols->push_scope();
      then_statement->hir(& stmt->then_instructions, state);
      state->symbols->pop_scope();
   }

   if (else_statement != NULL) {
      state->symbols->push_scope();
      else_statement->hir(& stmt->else_instructions, state);
      state->symbols->pop_scope();
   }

   instructions->push_tail(stmt);

   /* if-statements do not have r-values.
    */
   return NULL;
}


ir_rvalue *
ast_switch_statement::hir(exec_list *instructions,
                          struct _mesa_glsl_parse_state *state)
{
   void *ctx = state;

   ir_rvalue *const test_expression =
      this->test_expression->hir(instructions, state);

   /* From page 66 (page 55 of the PDF) of the GLSL 1.50 spec:
    *
    *    "The type of init-expression in a switch statement must be a 
    *     scalar integer." 
    *
    * The checks are separated so that higher quality diagnostics can be
    * generated for cases where the rule is violated.
    */
   if (!test_expression->type->is_integer()) {
      YYLTYPE loc = this->test_expression->get_location();

      _mesa_glsl_error(& loc,
                       state,
                       "switch-statement expression must be scalar "
                       "integer");
   }

   /* Track the switch-statement nesting in a stack-like manner.
    */
   struct glsl_switch_state saved = state->switch_state;

   state->switch_state.is_switch_innermost = true;
   state->switch_state.switch_nesting_ast = this;
   state->switch_state.labels_ht = hash_table_ctor(0, hash_table_pointer_hash,
                                                   hash_table_pointer_compare);
   state->switch_state.previous_default = NULL;

   /* Initalize is_fallthru state to false.
    */
   ir_rvalue *const is_fallthru_val = new (ctx) ir_constant(false);
   state->switch_state.is_fallthru_var =
      new(ctx) ir_variable(glsl_type::bool_type,
                           "switch_is_fallthru_tmp",
                           ir_var_temporary);
   instructions->push_tail(state->switch_state.is_fallthru_var);

   ir_dereference_variable *deref_is_fallthru_var =
      new(ctx) ir_dereference_variable(state->switch_state.is_fallthru_var);
   instructions->push_tail(new(ctx) ir_assignment(deref_is_fallthru_var,
                                                  is_fallthru_val,
                                                  NULL));

   /* Initalize is_break state to false.
    */
   ir_rvalue *const is_break_val = new (ctx) ir_constant(false);
   state->switch_state.is_break_var = new(ctx) ir_variable(glsl_type::bool_type,
                                                           "switch_is_break_tmp",
                                                           ir_var_temporary);
   instructions->push_tail(state->switch_state.is_break_var);

   ir_dereference_variable *deref_is_break_var =
      new(ctx) ir_dereference_variable(state->switch_state.is_break_var);
   instructions->push_tail(new(ctx) ir_assignment(deref_is_break_var,
                                                  is_break_val,
                                                  NULL));

   /* Cache test expression.
    */
   test_to_hir(instructions, state);
   
   /* Emit code for body of switch stmt.
    */
   body->hir(instructions, state);

   hash_table_dtor(state->switch_state.labels_ht);

   state->switch_state = saved;

     /* Switch statements do not have r-values.
      */
     return NULL;
  }


  void
  ast_switch_statement::test_to_hir(exec_list *instructions,
                                    struct _mesa_glsl_parse_state *state)
  {
     void *ctx = state;

     /* Cache value of test expression.
      */
     ir_rvalue *const test_val =
        test_expression->hir(instructions,
                             state);

     state->switch_state.test_var = new(ctx) ir_variable(glsl_type::int_type,
                                                         "switch_test_tmp",
                                                         ir_var_temporary);
     ir_dereference_variable *deref_test_var =
        new(ctx) ir_dereference_variable(state->switch_state.test_var);

     instructions->push_tail(state->switch_state.test_var);
     instructions->push_tail(new(ctx) ir_assignment(deref_test_var,
                                                    test_val,
                                                    NULL));
  }


  ir_rvalue *
  ast_switch_body::hir(exec_list *instructions,
                       struct _mesa_glsl_parse_state *state)
  {
     if (stmts != NULL)
        stmts->hir(instructions, state);

     /* Switch bodies do not have r-values.
      */
     return NULL;
  }


  ir_rvalue *
  ast_case_statement_list::hir(exec_list *instructions,
                               struct _mesa_glsl_parse_state *state)
  {
     foreach_list_typed (ast_case_statement, case_stmt, link, & this->cases)
        case_stmt->hir(instructions, state);

     /* Case statements do not have r-values.
      */
     return NULL;
  }


  ir_rvalue *
  ast_case_statement::hir(exec_list *instructions,
                          struct _mesa_glsl_parse_state *state)
  {
     labels->hir(instructions, state);

     /* Conditionally set fallthru state based on break state.
      */
     ir_constant *const false_val = new(state) ir_constant(false);
     ir_dereference_variable *const deref_is_fallthru_var =
        new(state) ir_dereference_variable(state->switch_state.is_fallthru_var);
     ir_dereference_variable *const deref_is_break_var =
        new(state) ir_dereference_variable(state->switch_state.is_break_var);
     ir_assignment *const reset_fallthru_on_break =
        new(state) ir_assignment(deref_is_fallthru_var,
                                 false_val,
                                 deref_is_break_var);
     instructions->push_tail(reset_fallthru_on_break);

     /* Guard case statements depending on fallthru state.
      */
     ir_dereference_variable *const deref_fallthru_guard =
        new(state) ir_dereference_variable(state->switch_state.is_fallthru_var);
     ir_if *const test_fallthru = new(state) ir_if(deref_fallthru_guard);

     foreach_list_typed (ast_node, stmt, link, & this->stmts)
        stmt->hir(& test_fallthru->then_instructions, state);

     instructions->push_tail(test_fallthru);

     /* Case statements do not have r-values.
      */
     return NULL;
  }


  ir_rvalue *
  ast_case_label_list::hir(exec_list *instructions,
                           struct _mesa_glsl_parse_state *state)
  {
     foreach_list_typed (ast_case_label, label, link, & this->labels)
        label->hir(instructions, state);

     /* Case labels do not have r-values.
      */
     return NULL;
  }


  ir_rvalue *
  ast_case_label::hir(exec_list *instructions,
                      struct _mesa_glsl_parse_state *state)
  {
     void *ctx = state;

     ir_dereference_variable *deref_fallthru_var =
        new(ctx) ir_dereference_variable(state->switch_state.is_fallthru_var);

     ir_rvalue *const true_val = new(ctx) ir_constant(true);

     /* If not default case, ...
      */
     if (this->test_value != NULL) {
        /* Conditionally set fallthru state based on
         * comparison of cached test expression value to case label.
         */
        ir_rvalue *const label_rval = this->test_value->hir(instructions, state);
        ir_constant *label_const = label_rval->constant_expression_value();

        if (!label_const) {
           YYLTYPE loc = this->test_value->get_location();

           _mesa_glsl_error(& loc, state,
                            "switch statement case label must be a "
                            "constant expression");

           /* Stuff a dummy value in to allow processing to continue. */
           label_const = new(ctx) ir_constant(0);
        } else {
           ast_expression *previous_label = (ast_expression *)
              hash_table_find(state->switch_state.labels_ht,
                              (void *)(uintptr_t)label_const->value.u[0]);

           if (previous_label) {
              YYLTYPE loc = this->test_value->get_location();
              _mesa_glsl_error(& loc, state,
                               "duplicate case value");

              loc = previous_label->get_location();
              _mesa_glsl_error(& loc, state,
                               "this is the previous case label");
           } else {
              hash_table_insert(state->switch_state.labels_ht,
                                this->test_value,
                                (void *)(uintptr_t)label_const->value.u[0]);
           }
        }

        ir_dereference_variable *deref_test_var =
           new(ctx) ir_dereference_variable(state->switch_state.test_var);

        ir_rvalue *const test_cond = new(ctx) ir_expression(ir_binop_all_equal,
                                                            glsl_type::bool_type,
                                                            label_const,
                                                            deref_test_var);

        ir_assignment *set_fallthru_on_test =
           new(ctx) ir_assignment(deref_fallthru_var,
                                  true_val,
                                  test_cond);

        instructions->push_tail(set_fallthru_on_test);
     } else { /* default case */
        if (state->switch_state.previous_default) {
           printf("a\n");
           YYLTYPE loc = this->get_location();
           _mesa_glsl_error(& loc, state,
                               "multiple default labels in one switch");

           printf("b\n");

           loc = state->switch_state.previous_default->get_location();
           _mesa_glsl_error(& loc, state,
                            "this is the first default label");
        }
        state->switch_state.previous_default = this;

        /* Set falltrhu state.
         */
        ir_assignment *set_fallthru =
           new(ctx) ir_assignment(deref_fallthru_var,
                                  true_val,
                                  NULL);

        instructions->push_tail(set_fallthru);
     }

     /* Case statements do not have r-values.
      */
     return NULL;
  }


  void
  ast_iteration_statement::condition_to_hir(ir_loop *stmt,
                                            struct _mesa_glsl_parse_state *state)
  {
     void *ctx = state;

     if (condition != NULL) {
        ir_rvalue *const cond =
           condition->hir(& stmt->body_instructions, state);

        if ((cond == NULL)
            || !cond->type->is_boolean() || !cond->type->is_scalar()) {
           YYLTYPE loc = condition->get_location();

           _mesa_glsl_error(& loc, state,
                            "loop condition must be scalar boolean");
        } else {
           /* As the first code in the loop body, generate a block that looks
            * like 'if (!condition) break;' as the loop termination condition.
            */
           ir_rvalue *const not_cond =
              new(ctx) ir_expression(ir_unop_logic_not, glsl_type::bool_type, cond,
                                     NULL);

           ir_if *const if_stmt = new(ctx) ir_if(not_cond);

           ir_jump *const break_stmt =
              new(ctx) ir_loop_jump(ir_loop_jump::jump_break);

           if_stmt->then_instructions.push_tail(break_stmt);
           stmt->body_instructions.push_tail(if_stmt);
        }
     }
  }


  ir_rvalue *
  ast_iteration_statement::hir(exec_list *instructions,
                               struct _mesa_glsl_parse_state *state)
  {
     void *ctx = state;

     /* For-loops and while-loops start a new scope, but do-while loops do not.
      */
     if (mode != ast_do_while)
        state->symbols->push_scope();

     if (init_statement != NULL)
        init_statement->hir(instructions, state);

     ir_loop *const stmt = new(ctx) ir_loop();
     instructions->push_tail(stmt);

     /* Track the current loop nesting.
      */
     ast_iteration_statement *nesting_ast = state->loop_nesting_ast;

     state->loop_nesting_ast = this;

     /* Likewise, indicate that following code is closest to a loop,
      * NOT closest to a switch.
      */
     bool saved_is_switch_innermost = state->switch_state.is_switch_innermost;
     state->switch_state.is_switch_innermost = false;

     if (mode != ast_do_while)
        condition_to_hir(stmt, state);

     if (body != NULL)
        body->hir(& stmt->body_instructions, state);

     if (rest_expression != NULL)
        rest_expression->hir(& stmt->body_instructions, state);

     if (mode == ast_do_while)
        condition_to_hir(stmt, state);

     if (mode != ast_do_while)
        state->symbols->pop_scope();

     /* Restore previous nesting before returning.
      */
     state->loop_nesting_ast = nesting_ast;
     state->switch_state.is_switch_innermost = saved_is_switch_innermost;

   /* Loops do not have r-values.
    */
   return NULL;
}


ir_rvalue *
ast_type_specifier::hir(exec_list *instructions,
                          struct _mesa_glsl_parse_state *state)
{
   if (!this->is_precision_statement && this->structure == NULL)
      return NULL;

   YYLTYPE loc = this->get_location();

   if (this->precision != ast_precision_none
       && state->language_version != 100
       && state->language_version < 130) {
      _mesa_glsl_error(&loc, state,
                       "precision qualifiers exist only in "
                       "GLSL ES 1.00, and GLSL 1.30 and later");
      return NULL;
   }
   if (this->precision != ast_precision_none
       && this->structure != NULL) {
      _mesa_glsl_error(&loc, state,
                       "precision qualifiers do not apply to structures");
      return NULL;
   }

   /* If this is a precision statement, check that the type to which it is
    * applied is either float or int.
    *
    * From section 4.5.3 of the GLSL 1.30 spec:
    *    "The precision statement
    *       precision precision-qualifier type;
    *    can be used to establish a default precision qualifier. The type
    *    field can be either int or float [...].  Any other types or
    *    qualifiers will result in an error.
    */
   if (this->is_precision_statement) {
      assert(this->precision != ast_precision_none);
      assert(this->structure == NULL); /* The check for structures was
                                        * performed above. */
      if (this->is_array) {
         _mesa_glsl_error(&loc, state,
                          "default precision statements do not apply to "
                          "arrays");
         return NULL;
      }
      if (strcmp(this->type_name, "float") != 0 &&
          strcmp(this->type_name, "int") != 0) {
         _mesa_glsl_error(&loc, state,
                          "default precision statements apply only to types "
                          "float and int");
         return NULL;
      }

      /* FINISHME: Translate precision statements into IR. */
      return NULL;
   }

   if (this->structure != NULL)
      return this->structure->hir(instructions, state);

   return NULL;
}


ir_rvalue *
ast_struct_specifier::hir(exec_list *instructions,
                          struct _mesa_glsl_parse_state *state)
{
   unsigned decl_count = 0;

   /* Make an initial pass over the list of structure fields to determine how
    * many there are.  Each element in this list is an ast_declarator_list.
    * This means that we actually need to count the number of elements in the
    * 'declarations' list in each of the elements.
    */
   foreach_list_typed (ast_declarator_list, decl_list, link,
                       &this->declarations) {
      foreach_list_const (decl_ptr, & decl_list->declarations) {
         decl_count++;
      }
   }

   /* Allocate storage for the structure fields and process the field
    * declarations.  As the declarations are processed, try to also convert
    * the types to HIR.  This ensures that structure definitions embedded in
    * other structure definitions are processed.
    */
   glsl_struct_field *const fields = ralloc_array(state, glsl_struct_field,
                                                  decl_count);

   unsigned i = 0;
   foreach_list_typed (ast_declarator_list, decl_list, link,
                       &this->declarations) {
      const char *type_name;

      decl_list->type->specifier->hir(instructions, state);

      /* Section 10.9 of the GLSL ES 1.00 specification states that
       * embedded structure definitions have been removed from the language.
       */
      if (state->es_shader && decl_list->type->specifier->structure != NULL) {
         YYLTYPE loc = this->get_location();
         _mesa_glsl_error(&loc, state, "Embedded structure definitions are "
                          "not allowed in GLSL ES 1.00.");
      }

      const glsl_type *decl_type =
         decl_list->type->specifier->glsl_type(& type_name, state);

      foreach_list_typed (ast_declaration, decl, link,
                          &decl_list->declarations) {
         const struct glsl_type *field_type = decl_type;
         if (decl->is_array) {
            YYLTYPE loc = decl->get_location();
            field_type = process_array_type(&loc, decl_type, decl->array_size,
                                            state);
         }
         fields[i].type = (field_type != NULL)
            ? field_type : glsl_type::error_type;
         fields[i].name = decl->identifier;
         i++;
      }
   }

   assert(i == decl_count);

   const glsl_type *t =
      glsl_type::get_record_instance(fields, decl_count, this->name);

   YYLTYPE loc = this->get_location();
   if (!state->symbols->add_type(name, t)) {
      _mesa_glsl_error(& loc, state, "struct `%s' previously defined", name);
   } else {
      const glsl_type **s = reralloc(state, state->user_structures,
                                     const glsl_type *,
                                     state->num_user_structures + 1);
      if (s != NULL) {
         s[state->num_user_structures] = t;
         state->user_structures = s;
         state->num_user_structures++;
      }
   }

   /* Structure type definitions do not have r-values.
    */
   return NULL;
}