dp_flong.c 1.54 KB
Newer Older
Linus Torvalds's avatar
Linus Torvalds committed
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
/* IEEE754 floating point arithmetic
 * double precision: common utilities
 */
/*
 * MIPS floating point support
 * Copyright (C) 1994-2000 Algorithmics Ltd.
 *
 *  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.,
19
 *  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA.
Linus Torvalds's avatar
Linus Torvalds committed
20 21 22 23
 */

#include "ieee754dp.h"

24
union ieee754dp ieee754dp_flong(s64 x)
Linus Torvalds's avatar
Linus Torvalds committed
25
{
26 27 28
	u64 xm;
	int xe;
	int xs;
Linus Torvalds's avatar
Linus Torvalds committed
29

30
	ieee754_clearcx();
Linus Torvalds's avatar
Linus Torvalds committed
31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49

	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 == (1ULL << 63))
			xm = (1ULL << 63);	/* max neg can't be safely negated */
		else
			xm = -x;
	} else {
		xm = x;
	}

	/* normalize */
50 51
	xe = DP_FBITS + 3;
	if (xm >> (DP_FBITS + 1 + 3)) {
Linus Torvalds's avatar
Linus Torvalds committed
52
		/* shunt out overflow bits */
53
		while (xm >> (DP_FBITS + 1 + 3)) {
Linus Torvalds's avatar
Linus Torvalds committed
54 55 56 57
			XDPSRSX1();
		}
	} else {
		/* normalize in grs extended double precision */
58
		while ((xm >> (DP_FBITS + 3)) == 0) {
Linus Torvalds's avatar
Linus Torvalds committed
59 60 61 62
			xm <<= 1;
			xe--;
		}
	}
63 64

	return ieee754dp_format(xs, xe, xm);
Linus Torvalds's avatar
Linus Torvalds committed
65
}