1/* s_nexttoward.c
2 * Special i387 version
3 * Conversion from s_nextafter.c by Ulrich Drepper, Cygnus Support,
4 * drepper@cygnus.com.
5 */
6
7/*
8 * ====================================================
9 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
10 *
11 * Developed at SunPro, a Sun Microsystems, Inc. business.
12 * Permission to use, copy, modify, and distribute this
13 * software is freely granted, provided that this notice
14 * is preserved.
15 * ====================================================
16 */
17
18#if defined(LIBM_SCCS) && !defined(lint)
19static char rcsid[] = "$NetBSD: $";
20#endif
21
22/* IEEE functions
23 * nexttoward(x,y)
24 * return the next machine floating-point number of x in the
25 * direction toward y.
26 * Special cases:
27 */
28
29#include <errno.h>
30#include <math.h>
31#include <math_private.h>
32#include <float.h>
33
34double __nexttoward(double x, long double y)
35{
36 int32_t hx,ix,iy;
37 uint32_t lx,hy,ly,esy;
38
39 EXTRACT_WORDS(hx,lx,x);
40 GET_LDOUBLE_WORDS(esy,hy,ly,y);
41 ix = hx&0x7fffffff; /* |x| */
42 iy = esy&0x7fff; /* |y| */
43
44 /* Intel's extended format has the normally implicit 1 explicit
45 present. Sigh! */
46 if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */
47 ((iy>=0x7fff)&&((hy&0x7fffffff)|ly)!=0)) /* y is nan */
48 return x+y;
49 if((long double) x==y) return y; /* x=y, return y */
50 if((ix|lx)==0) { /* x == 0 */
51 double u;
52 INSERT_WORDS(x,(esy&0x8000)<<16,1); /* return +-minsub */
53 u = math_opt_barrier (x);
54 u = u * u;
55 math_force_eval (u); /* raise underflow flag */
56 return x;
57 }
58 if(hx>=0) { /* x > 0 */
59 if (x > y) { /* x -= ulp */
60 if(lx==0) hx -= 1;
61 lx -= 1;
62 } else { /* x < y, x += ulp */
63 lx += 1;
64 if(lx==0) hx += 1;
65 }
66 } else { /* x < 0 */
67 if (x < y) { /* x -= ulp */
68 if(lx==0) hx -= 1;
69 lx -= 1;
70 } else { /* x > y, x += ulp */
71 lx += 1;
72 if(lx==0) hx += 1;
73 }
74 }
75 hy = hx&0x7ff00000;
76 if(hy>=0x7ff00000) {
77 double u = x+x; /* overflow */
78 math_force_eval (u);
79 __set_errno (ERANGE);
80 }
81 if(hy<0x00100000) {
82 double u = x*x; /* underflow */
83 math_force_eval (u); /* raise underflow flag */
84 __set_errno (ERANGE);
85 }
86 INSERT_WORDS(x,hx,lx);
87 return x;
88}
89weak_alias (__nexttoward, nexttoward)
90#ifdef NO_LONG_DOUBLE
91strong_alias (__nexttoward, __nexttowardl)
92weak_alias (__nexttoward, nexttowardl)
93#endif
94