s_nextafterl.c revision 1.5 
1/*	$NetBSD: s_nextafterl.c,v 1.5 2014/01/31 19:38:47 matt Exp $	*/
2
3/* @(#)s_nextafter.c 5.1 93/09/24 */
4/*
5 * ====================================================
6 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
7 *
8 * Developed at SunPro, a Sun Microsystems, Inc. business.
9 * Permission to use, copy, modify, and distribute this
10 * software is freely granted, provided that this notice
11 * is preserved.
12 * ====================================================
13 */
14
15#include <sys/cdefs.h>
16__RCSID("$NetBSD: s_nextafterl.c,v 1.5 2014/01/31 19:38:47 matt Exp $");
17
18#include <float.h>
19#include <math.h>
20#include <machine/ieee.h>
21
22#ifdef __HAVE_LONG_DOUBLE
23
24#ifdef EXT_EXP_INFNAN
25#if LDBL_MAX_EXP != 0x4000
26#error "Unsupported long double format"
27#endif
28
29#ifdef LDBL_IMPLICIT_NBIT
30#define	LDBL_NBIT	0
31#endif
32
33/*
34 * IEEE functions
35 *      nextafterl(x,y)
36 *      return the next machine floating-point number of x in the
37 *      direction toward y.
38 *   Special cases:
39 *	If x == y, y shall be returned
40 *	If x or y is NaN, a NaN shall be returned
41 */
42long double
43nextafterl(long double x, long double y)
44{
45	volatile long double t;
46	union ieee_ext_u ux, uy;
47
48	ux.extu_ld = x;
49	uy.extu_ld = y;
50
51	if ((ux.extu_exp == EXT_EXP_INFNAN &&
52		((ux.extu_frach &~ LDBL_NBIT)|ux.extu_fracl) != 0) ||
53	    (uy.extu_exp == EXT_EXP_INFNAN &&
54		((uy.extu_frach &~ LDBL_NBIT)|uy.extu_fracl) != 0))
55		return x+y;			/* x or y is nan */
56
57	if (x == y) return y;			/* x=y, return y */
58
59	if (x == 0.0) {
60		ux.extu_frach = 0;		/* return +-minsubnormal */
61		ux.extu_fracl = 1;
62		ux.extu_sign = uy.extu_sign;
63		t = ux.extu_ld * ux.extu_ld;
64		if (t == ux.extu_ld)
65			return t;
66		else
67			return ux.extu_ld;	/* raise underflow flag */
68	}
69
70	if ((x>0.0) ^ (x<y)) {			/* x -= ulp */
71		if (ux.extu_fracl == 0) {
72			if ((ux.extu_frach & ~LDBL_NBIT) == 0)
73				ux.extu_exp -= 1;
74			ux.extu_frach = (ux.extu_frach - 1) |
75					(ux.extu_frach & LDBL_NBIT);
76		}
77		ux.extu_fracl -= 1;
78	} else {				/* x += ulp */
79		ux.extu_fracl += 1;
80		if (ux.extu_fracl == 0) {
81			ux.extu_frach = (ux.extu_frach + 1) |
82					(ux.extu_frach & LDBL_NBIT);
83			if ((ux.extu_frach & ~LDBL_NBIT) == 0)
84				ux.extu_exp += 1;
85		}
86	}
87
88	if (ux.extu_exp == EXT_EXP_INFNAN)
89		return x+x;			/* overflow  */
90
91	if (ux.extu_exp == 0) {			/* underflow */
92#ifndef LDBL_IMPLICIT_NBIT
93		mask_nbit_l(ux);
94#endif
95		t = ux.extu_ld * ux.extu_ld;
96		if (t != ux.extu_ld)		/* raise underflow flag */
97			return ux.extu_ld;
98	}
99
100	return ux.extu_ld;
101}
102#endif
103
104#endif /* __HAVE_LONG_DOUBLE */
105