/* Language-indepednent node constructors for parse phase of GNU compiler.
   Copyright (C) 1987, 1988 Free Software Foundation, Inc.

This file is part of GNU CC.

GNU CC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY.  No author or distributor
accepts responsibility to anyone for the consequences of using it
or for whether it serves any particular purpose or works at all,
unless he says so in writing.  Refer to the GNU CC General Public
License for full details.

Everyone is granted permission to copy, modify and redistribute
GNU CC, but only under the conditions described in the
GNU CC General Public License.   A copy of this license is
supposed to have been given to you along with GNU CC so you
can know your rights and responsibilities.  It should be in a
file named COPYING.  Among other things, the copyright notice
and this notice must be preserved on all copies.  */


/* This file contains the functions for converting C expressions
   to different data types.  */

#include "config.h"
#include "tree.h"

/* Subroutines of `convert'.  */

/* 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.  */

static tree
convert_to_pointer (type, expr)
     tree type, expr;
{
  register tree intype = TREE_TYPE (expr);
  register enum tree_code form = TREE_CODE (intype);
  
  if (integer_zerop (expr))
    {
      if (type == TREE_TYPE (null_pointer_node))
	return null_pointer_node;
      expr = build_int_2 (0, 0);
      TREE_TYPE (expr) = type;
      return expr;
    }

  if (form == POINTER_TYPE)
    return build (NOP_EXPR, type, expr);


  if (form == INTEGER_TYPE || form == ENUMERAL_TYPE)
    {
      if (type_precision (intype) == POINTER_SIZE)
	return build (CONVERT_EXPR, type, expr);
      return convert_to_pointer (type,
				 convert (type_for_size (POINTER_SIZE, 0),
					  expr));
    }

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

  return null_pointer_node;
}

/* The result of this is always supposed to be a newly created tree node
   not in use in any existing structure.  */

static tree
convert_to_integer (type, expr)
     tree type, expr;
{
  register tree intype = TREE_TYPE (expr);
  register enum tree_code form = TREE_CODE (intype);
  extern tree build_binary_op_nodefault ();
  extern tree build_unary_op ();

  if (form == POINTER_TYPE)
    {
      if (integer_zerop (expr))
	expr = integer_zero_node;
      else
	expr = fold (build (CONVERT_EXPR,
			    type_for_size (POINTER_SIZE, 0), expr));
      intype = TREE_TYPE (expr);
      form = TREE_CODE (intype);
      if (intype == type)
	return expr;
    }

  if (form == INTEGER_TYPE || form == ENUMERAL_TYPE)
    {
      register int outprec = TYPE_PRECISION (type);
      register int inprec = TYPE_PRECISION (intype);
      register enum tree_code ex_form = TREE_CODE (expr);

      if (outprec >= inprec)
	return build (NOP_EXPR, type, expr);

/* Here detect when we can distribute the truncation down past some arithmetic.
   For example, if adding two longs and converting to an int,
   we can equally well convert both to ints and then add.
   For the operations handled here, such truncation distribution
   is always safe.
   It is desirable in these cases:
   1) when truncating down to full-word from a larger size
   2) when truncating takes no work.
   3) when at least one operand of the arithmetic has been extended
   (as by C's default conversions).  In this case we need two conversions
   if we do the arithmetic as already requested, so we might as well
   truncate both and then combine.  Perhaps that way we need only one.

   Note that in general we cannot do the arithmetic in a type
   shorter than the desired result of conversion, even if the operands
   are both extended from a shorter type, because they might overflow
   if combined in that type.  The exceptions to this--the times when
   two narrow values can be combined in their narrow type even to
   make a wider result--are handled by "shorten" in build_binary_op.  */

      switch (ex_form)
	{
	case RSHIFT_EXPR:
	  /* We can pass truncation down through right shifting
	     when the shift count is a negative constant.  */
	  if (TREE_CODE (TREE_OPERAND (expr, 1)) != INTEGER_CST
	      || TREE_INT_CST_LOW (TREE_OPERAND (expr, 1)) > 0)
	    break;
	  goto trunc1;

	case LSHIFT_EXPR:
	  /* We can pass truncation down through left shifting
	     when the shift count is a positive constant.  */
	  if (TREE_CODE (TREE_OPERAND (expr, 1)) != INTEGER_CST
	      || TREE_INT_CST_LOW (TREE_OPERAND (expr, 1)) < 0)
	    break;
	  /* In this case, shifting is like multiplication.  */

	case PLUS_EXPR:
	case MINUS_EXPR:
	case MULT_EXPR:
	case MAX_EXPR:
	case MIN_EXPR:
	case BIT_AND_EXPR:
	case BIT_IOR_EXPR:
	case BIT_XOR_EXPR:
	case BIT_ANDTC_EXPR:
	trunc1:
	  {
	    tree arg0 = get_unwidened (TREE_OPERAND (expr, 0), type);
	    tree arg1 = get_unwidened (TREE_OPERAND (expr, 1), type);

	    if (outprec >= BITS_PER_WORD
		|| TRULY_NOOP_TRUNCATION (outprec, inprec)
		|| inprec > TYPE_PRECISION (TREE_TYPE (arg0))
		|| inprec > TYPE_PRECISION (TREE_TYPE (arg1)))
	      {
		/* Do the arithmetic in type TYPEX,
		   then convert result to TYPE.  */
		register tree typex = type;

		/* Can't do arithmetic in enumeral types
		   so use an integer type that will hold the values.  */
		if (TREE_CODE (typex) == ENUMERAL_TYPE)
		  typex = type_for_size (TYPE_PRECISION (typex),
					 TREE_UNSIGNED (typex));

		/* But now perhaps TYPEX is as wide as INPREC.
		   In that case, do nothing special here.
		   (Otherwise would recurse infinitely in convert.  */
		if (TYPE_PRECISION (typex) != inprec)
		  {
		    /* Don't do unsigned arithmetic where signed was wanted,
		       or vice versa.  */
		    typex = (TREE_UNSIGNED (TREE_TYPE (expr))
			     ? unsigned_type (typex) : signed_type (typex));
		    return convert (type,
				    build_binary_op_nodefault (ex_form,
							       convert (typex, arg0),
							       convert (typex, arg1)));
		  }
	      }
	  }
	  break;

	case EQ_EXPR:
	case NE_EXPR:
	case GT_EXPR:
	case GE_EXPR:
	case LT_EXPR:
	case LE_EXPR:
	case TRUTH_AND_EXPR:
	case TRUTH_ANDIF_EXPR:
	case TRUTH_OR_EXPR:
	case TRUTH_ORIF_EXPR:
	case TRUTH_NOT_EXPR:
	  /* If we want result of comparison converted to a byte,
	     we can just regard it as a byte, since it is 0 or 1.  */
	  TREE_TYPE (expr) = type;
	  return expr;

	case NEGATE_EXPR:
	case BIT_NOT_EXPR:
	case ABS_EXPR:
	  {
	    register tree typex = type;

	    /* Can't do arithmetic in enumeral types
	       so use an integer type that will hold the values.  */
	    if (TREE_CODE (typex) == ENUMERAL_TYPE)
	      typex = type_for_size (TYPE_PRECISION (typex),
				     TREE_UNSIGNED (typex));

	    /* But now perhaps TYPEX is as wide as INPREC.
	       In that case, do nothing special here.
	       (Otherwise would recurse infinitely in convert.  */
	    if (TYPE_PRECISION (typex) != inprec)
	      {
		/* Don't do unsigned arithmetic where signed was wanted,
		   or vice versa.  */
		typex = (TREE_UNSIGNED (TREE_TYPE (expr))
			 ? unsigned_type (typex) : signed_type (typex));
		return convert (type,
				build_unary_op (ex_form,
						convert (typex, TREE_OPERAND (expr, 0)),
						1));
	      }
	  }

	case NOP_EXPR:
	  /* If truncating after truncating, might as well do all at once.
	     If truncating after extending, we may get rid of wasted work.  */
	  return convert (type, get_unwidened (TREE_OPERAND (expr, 0), type));

	case COND_EXPR:
	  /* Can treat the two alternative values like the operands
	     of an arithmetic expression.  */
	  {
	    tree arg1 = get_unwidened (TREE_OPERAND (expr, 1), type);
	    tree arg2 = get_unwidened (TREE_OPERAND (expr, 2), type);

	    if (outprec >= BITS_PER_WORD
		|| TRULY_NOOP_TRUNCATION (outprec, inprec)
		|| inprec > TYPE_PRECISION (TREE_TYPE (arg1))
		|| inprec > TYPE_PRECISION (TREE_TYPE (arg2)))
	      {
		/* Do the arithmetic in type TYPEX,
		   then convert result to TYPE.  */
		register tree typex = type;

		/* Can't do arithmetic in enumeral types
		   so use an integer type that will hold the values.  */
		if (TREE_CODE (typex) == ENUMERAL_TYPE)
		  typex = type_for_size (TYPE_PRECISION (typex),
					 TREE_UNSIGNED (typex));

		/* But now perhaps TYPEX is as wide as INPREC.
		   In that case, do nothing special here.
		   (Otherwise would recurse infinitely in convert.  */
		if (TYPE_PRECISION (typex) != inprec)
		  {
		    /* Don't do unsigned arithmetic where signed was wanted,
		       or vice versa.  */
		    typex = (TREE_UNSIGNED (TREE_TYPE (expr))
			     ? unsigned_type (typex) : signed_type (typex));
		    return convert (type,
				    build (COND_EXPR, typex,
					   TREE_OPERAND (expr, 0),
					   convert (typex, arg1),
					   convert (typex, arg2)));
		  }
	      }
	  }

	}

      return build (NOP_EXPR, type, expr);
    }

  if (form == REAL_TYPE)
    return build (FIX_TRUNC_EXPR, type, expr);

  error ("aggregate value used where an integer was expected");

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

static tree
convert_to_real (type, expr)
     tree type, expr;
{
  register enum tree_code form = TREE_CODE (TREE_TYPE (expr));
  extern int flag_float_store;

  if (form == REAL_TYPE)
    return build (flag_float_store ? CONVERT_EXPR : NOP_EXPR,
		  type, expr);

  if (form == INTEGER_TYPE || form == ENUMERAL_TYPE)
    return build (FLOAT_EXPR, type, expr);

  if (form == POINTER_TYPE)
    error ("pointer value used where a float was expected");
  else
    error ("aggregate value used where a float was expected");

  {
    register tree tem = make_node (REAL_CST);
    TREE_TYPE (tem) = type;
    TREE_REAL_CST (tem) = 0;
    return tem;
  }
}

/* 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 (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 build (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)
    return fold (convert_to_pointer (type, e));
  if (code == REAL_TYPE)
    return fold (convert_to_real (type, e));

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