summary refs log tree commit diff
path: root/math/s_nextafter.c
blob: 9c678b79c57c0efb9cf3e8fd412deb284daf94c9 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
/* @(#)s_nextafter.c 5.1 93/09/24 */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

#if defined(LIBM_SCCS) && !defined(lint)
static char rcsid[] = "$NetBSD: s_nextafter.c,v 1.8 1995/05/10 20:47:58 jtc Exp $";
#endif

/* IEEE functions
 *	nextafter(x,y)
 *	return the next machine floating-point number of x in the
 *	direction toward y.
 *   Special cases:
 */

/* Ugly hack so that the aliasing works.  */
#define __nexttoward __internal___nexttoward
#define nexttoward __internal_nexttoward

#include <math.h>
#include "math_private.h"
#include <float.h>

#ifdef __STDC__
	double __nextafter(double x, double y)
#else
	double __nextafter(x,y)
	double x,y;
#endif
{
	int32_t hx,hy,ix,iy;
	u_int32_t lx,ly;

	EXTRACT_WORDS(hx,lx,x);
	EXTRACT_WORDS(hy,ly,y);
	ix = hx&0x7fffffff;		/* |x| */
	iy = hy&0x7fffffff;		/* |y| */

	if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) ||   /* x is nan */
	   ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0))     /* y is nan */
	   return x+y;
	if(x==y) return y;		/* x=y, return y */
	if((ix|lx)==0) {			/* x == 0 */
	    INSERT_WORDS(x,hy&0x80000000,1);	/* return +-minsubnormal */
	    y = x*x;
	    if(y==x) return y; else return x;	/* raise underflow flag */
	}
	if(hx>=0) {				/* x > 0 */
	    if(hx>hy||((hx==hy)&&(lx>ly))) {	/* x > y, x -= ulp */
		if(lx==0) hx -= 1;
		lx -= 1;
	    } else {				/* x < y, x += ulp */
		lx += 1;
		if(lx==0) hx += 1;
	    }
	} else {				/* x < 0 */
	    if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */
		if(lx==0) hx -= 1;
		lx -= 1;
	    } else {				/* x > y, x += ulp */
		lx += 1;
		if(lx==0) hx += 1;
	    }
	}
	hy = hx&0x7ff00000;
	if(hy>=0x7ff00000) {
	  x = x+x;	/* overflow  */
	  if (FLT_EVAL_METHOD != 0 && FLT_EVAL_METHOD != 1)
	    asm ("" : "=m"(x) : "m"(x));
	  return x;	/* overflow  */
	}
	if(hy<0x00100000) {		/* underflow */
	    y = x*x;
	    if(y!=x) {		/* raise underflow flag */
	        INSERT_WORDS(y,hx,lx);
		return y;
	    }
	}
	INSERT_WORDS(x,hx,lx);
	return x;
}
weak_alias (__nextafter, nextafter)
#ifdef NO_LONG_DOUBLE
strong_alias (__nextafter, __nextafterl)
weak_alias (__nextafter, nextafterl)
strong_alias (__nextafter, __nexttowardl)
weak_alias (__nexttowardl, nexttowardl)
#undef __nexttoward
strong_alias (__nextafter, __nexttoward)
#undef nexttoward
weak_alias (__nextafter, nexttoward)
#endif