s_nextafterl.c revision 1.6 
1/*	$NetBSD: s_nextafterl.c,v 1.6 2019/04/27 23:04:32 kamil 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 1.6 2019/04/27 23:04:32 kamil 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__strong_alias(nexttowardl, nextafterl)
34
35/*
36 * IEEE functions
37 *      nextafterl(x,y)
38 *      return the next machine floating-point number of x in the
39 *      direction toward y.
40 *   Special cases:
41 *	If x == y, y shall be returned
42 *	If x or y is NaN, a NaN shall be returned
43 */
44long double
45nextafterl(long double x, long double y)
46{
47	volatile long double t;
48	union ieee_ext_u ux, uy;
49
50	ux.extu_ld = x;
51	uy.extu_ld = y;
52
53	if ((ux.extu_exp == EXT_EXP_INFNAN &&
54		((ux.extu_frach &~ LDBL_NBIT)|ux.extu_fracl) != 0) ||
55	    (uy.extu_exp == EXT_EXP_INFNAN &&
56		((uy.extu_frach &~ LDBL_NBIT)|uy.extu_fracl) != 0))
57		return x+y;			/* x or y is nan */
58
59	if (x == y) return y;			/* x=y, return y */
60
61	if (x == 0.0) {
62		ux.extu_frach = 0;		/* return +-minsubnormal */
63		ux.extu_fracl = 1;
64		ux.extu_sign = uy.extu_sign;
65		t = ux.extu_ld * ux.extu_ld;
66		if (t == ux.extu_ld)
67			return t;
68		else
69			return ux.extu_ld;	/* raise underflow flag */
70	}
71
72	if ((x>0.0) ^ (x<y)) {			/* x -= ulp */
73		if (ux.extu_fracl == 0) {
74			if ((ux.extu_frach & ~LDBL_NBIT) == 0)
75				ux.extu_exp -= 1;
76			ux.extu_frach = (ux.extu_frach - 1) |
77					(ux.extu_frach & LDBL_NBIT);
78		}
79		ux.extu_fracl -= 1;
80	} else {				/* x += ulp */
81		ux.extu_fracl += 1;
82		if (ux.extu_fracl == 0) {
83			ux.extu_frach = (ux.extu_frach + 1) |
84					(ux.extu_frach & LDBL_NBIT);
85			if ((ux.extu_frach & ~LDBL_NBIT) == 0)
86				ux.extu_exp += 1;
87		}
88	}
89
90	if (ux.extu_exp == EXT_EXP_INFNAN)
91		return x+x;			/* overflow  */
92
93	if (ux.extu_exp == 0) {			/* underflow */
94#ifndef LDBL_IMPLICIT_NBIT
95		mask_nbit_l(ux);
96#endif
97		t = ux.extu_ld * ux.extu_ld;
98		if (t != ux.extu_ld)		/* raise underflow flag */
99			return ux.extu_ld;
100	}
101
102	return ux.extu_ld;
103}
104#endif
105
106#endif /* __HAVE_LONG_DOUBLE */
107