dp_fint.c

广州斯道2410普及版II的源代码

/* IEEE754 floating point arithmetic
 * double precision: common utilities
 */
/*
 * MIPS floating point support
 * Copyright (C) 1994-2000 Algorithmics Ltd.  All rights reserved.
 * http://www.algor.co.uk
 *
 * ########################################################################
 *
 *  This program is free software; you can distribute it and/or modify it
 *  under the terms of the GNU General Public License (Version 2) as
 *  published by the Free Software Foundation.
 *
 *  This program is distributed in the hope 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 this program; if not, write to the Free Software Foundation, Inc.,
 *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
 *
 * ########################################################################
 */


#include "ieee754dp.h"

ieee754dp ieee754dp_fint(int x)
{
	COMPXDP;

	CLEARCX;

	if (x == 0)
		return ieee754dp_zero(0);
	if (x == 1 || x == -1)
		return ieee754dp_one(x < 0);
	if (x == 10 || x == -10)
		return ieee754dp_ten(x < 0);

	xs = (x < 0);
	if (xs) {
		if (x == (1 << 31))
			xm = ((unsigned) 1 << 31);	/* max neg can't be safely negated */
		else
			xm = -x;
	} else {
		xm = x;
	}

#if 1
	/* normalize - result can never be inexact or overflow */
	xe = DP_MBITS;
	while ((xm >> DP_MBITS) == 0) {
		xm <<= 1;
		xe--;
	}
	return builddp(xs, xe + DP_EBIAS, xm & ~DP_HIDDEN_BIT);
#else
	/* normalize */
	xe = DP_MBITS + 3;
	while ((xm >> (DP_MBITS + 3)) == 0) {
		xm <<= 1;
		xe--;
	}
	DPNORMRET1(xs, xe, xm, "fint", x);
#endif
}

ieee754dp ieee754dp_funs(unsigned int u)
{
	if ((int) u < 0)
		return ieee754dp_add(ieee754dp_1e31(),
				     ieee754dp_fint(u & ~(1 << 31)));
	return ieee754dp_fint(u);
}