/* Language-level data type conversion for GNU C.
   Copyright (C) 1987, 1988, 1991 Free Software Foundation, Inc.

This file is part of GNU CC.

GNU CC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU CC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU CC; see the file COPYING.  If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */


/* This file contains the functions for converting C expressions
   to different data types.  The only entry point is `convert'.
   Every language front end must have a `convert' function
   but what kind of conversions it does will depend on the language.  */

#include "config.h"
#include "tree.h"
#include "flags.h"
#include "convert.h"
#ifdef GPC
#include "gpc-defs.h"
#endif

/* Change of width--truncation and extension of integers or reals--
   is represented with NOP_EXPR.  Proper functioning of many things
   assumes that no other conversions can be NOP_EXPRs.

   Conversion between integer and pointer is represented with CONVERT_EXPR.
   Converting integer to real uses FLOAT_EXPR
   and real to integer uses FIX_TRUNC_EXPR.

   Here is a list of all the functions that assume that widening and
   narrowing is always done with a NOP_EXPR:
     In convert.c, convert_to_integer.
     In c-typeck.c, build_binary_op (boolean ops), and truthvalue_conversion.
     In expr.c: expand_expr, for operands of a MULT_EXPR.
     In fold-const.c: fold.
     In tree.c: get_narrower and get_unwidened.  */

/* Subroutines of `convert'.  */

#ifdef GPC

extern tree boolean_false_node;
extern tree boolean_true_node;

static tree
convert_to_boolean (type, expr)
     tree type, expr;
{
  register tree intype = TREE_TYPE (expr);
  register enum tree_code form = TREE_CODE (intype);
  
  if (integer_zerop (expr))
    return boolean_false_node;
  if (integer_onep (expr))
    return boolean_true_node;

  if (form == BOOLEAN_TYPE)
    return build1 (NOP_EXPR, type, expr);

  if (form == INTEGER_TYPE)
      return build1 (CONVERT_EXPR, type, expr);

  error ("cannot convert to a boolean type");

  return boolean_false_node;
}

static tree
convert_to_char (type, expr)
     tree type, expr;
{
  register tree intype = TREE_TYPE (expr);
  register enum tree_code form = TREE_CODE (intype);
  
  if (form == CHAR_TYPE)
    return build1 (NOP_EXPR, type, expr);

  /* @@ If it does not fit? */
  if (form == INTEGER_TYPE)
    return build1 (CONVERT_EXPR, type, expr);

  error ("cannot convert to a char type");

  {
    register tree tem = build_int_2 (0, 0);
    TREE_TYPE (tem) = type;
    return tem;
  }
}

/* @@@@@

   A hack to fix inline function set_type arguments,
   when the sets are subranges of the same base_type.
   I think this should be taken care of earlier.
   Occurs only with high optimization levels.

   FIXME!!!
 */
static tree
convert_sets (type, e)
     tree type, e;
{
  tree intype = TREE_TYPE (e);
  enum tree_code form = TREE_CODE (intype);
  tree e_base;
  tree t_base = base_type (TREE_TYPE (type));
  
  if (form != SET_TYPE)
    return NULL_TREE;

  e_base = base_type (TREE_TYPE (intype));

  if (TYPE_MAIN_VARIANT (t_base) != TYPE_MAIN_VARIANT (e_base))
    return NULL_TREE;

  return build1 (CONVERT_EXPR, type, e);
}
#endif /* GPC */

/* Create an expression whose value is that of EXPR,
   converted to type TYPE.  The TREE_TYPE of the value
   is always TYPE.  This function implements all reasonable
   conversions; callers should filter out those that are
   not permitted by the language being compiled.  */

tree
convert (type, expr)
     tree type, expr;
{
  register tree e = expr;
  register enum tree_code code = TREE_CODE (type);

  if (type == TREE_TYPE (expr)
      || TREE_CODE (expr) == ERROR_MARK)
    return expr;
  if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr)))
    return fold (build1 (NOP_EXPR, type, expr));
  if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
    return error_mark_node;
  if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
    {
      error ("void value not ignored as it ought to be");
      return error_mark_node;
    }
  if (code == VOID_TYPE)
    return build1 (CONVERT_EXPR, type, e);
#if 0
  /* This is incorrect.  A truncation can't be stripped this way.
     Extensions will be stripped by the use of get_unwidened.  */
  if (TREE_CODE (expr) == NOP_EXPR)
    return convert (type, TREE_OPERAND (expr, 0));
#endif
  if (code == INTEGER_TYPE || code == ENUMERAL_TYPE)
    return fold (convert_to_integer (type, e));
  if (code == POINTER_TYPE)
#ifdef GPC
    {
      /* @@@ REFERENCE_TYPE not utilized fully in GPC.
       *     Should be re-implemented. (I implemented var parameters
       *     before GCC had REFERENCE_TYPE)
       */
      if (TREE_CODE (TREE_TYPE (e)) == REFERENCE_TYPE)
	return fold (build1 (CONVERT_EXPR, type, e));
      
      return fold (convert_to_pointer (type, e));
    }

  /* @@@ This is ugly;, see above; FIXME */
  if (code == SET_TYPE)
    {
      tree converted = convert_sets (type, e);
      if (converted)
	return converted;
    }

#if 1
  /* @@@@@@@@@@ FIXME FIXME
     Note: I am not sure this is the correct place
     to try to fix the problem:
     	-O6 in alpha compiling zap.pas
     traps here. But should the reference_type be trapped
     earlier??
   */
  if (code == REFERENCE_TYPE)
    {
      if (TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE)
	return fold (build1 (CONVERT_EXPR, type, e));
      
      return fold (build1 (CONVERT_EXPR, type,
			   fold (convert_to_pointer
				 (build_pointer_type (TREE_TYPE (type)),
				  e))));
    }
#endif /* @@@@ FIXME FIXME */
#else
    return fold (convert_to_pointer (type, e));
#endif /* GPC */
  if (code == REAL_TYPE)
    return fold (convert_to_real (type, e));
  if (code == COMPLEX_TYPE)
    return fold (convert_to_complex (type, e));
#ifdef GPC
  if (code == BOOLEAN_TYPE)
    return fold (convert_to_boolean (type, e));
  if (code == CHAR_TYPE)
    return fold (convert_to_char (type, e));
#endif

  error ("conversion to non-scalar type requested");
  return error_mark_node;
}
