1 /* s_nexttoward.c
2 * Conversion from s_nextafter.c by Ulrich Drepper, Cygnus Support,
3 * drepper@cygnus.com and Jakub Jelinek, jj@ultra.linux.cz.
4 */
5
6 /*
7 * ====================================================
8 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
9 *
10 * Developed at SunPro, a Sun Microsystems, Inc. business.
11 * Permission to use, copy, modify, and distribute this
12 * software is freely granted, provided that this notice
13 * is preserved.
14 * ====================================================
15 */
16
17 #if defined(LIBM_SCCS) && !defined(lint)
18 static char rcsid[] = "$NetBSD: $";
19 #endif
20
21 /* IEEE functions
22 * nexttoward(x,y)
23 * return the next machine floating-point number of x in the
24 * direction toward y.
25 * Special cases:
26 */
27
28 #include <errno.h>
29 #include <math.h>
30 #include <math-barriers.h>
31 #include <math_private.h>
32 #include <float.h>
33
__nexttoward(double x,_Float128 y)34 double __nexttoward(double x, _Float128 y)
35 {
36 int32_t hx,ix;
37 int64_t hy,iy;
38 uint32_t lx;
39 uint64_t ly;
40
41 EXTRACT_WORDS(hx,lx,x);
42 GET_LDOUBLE_WORDS64(hy,ly,y);
43 ix = hx&0x7fffffff; /* |x| */
44 iy = hy&0x7fffffffffffffffLL; /* |y| */
45
46 if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */
47 ((iy>=0x7fff000000000000LL)&&((iy-0x7fff000000000000LL)|ly)!=0))
48 /* y is nan */
49 return x+y;
50 if((_Float128) x==y) return y; /* x=y, return y */
51 if((ix|lx)==0) { /* x == 0 */
52 double u;
53 INSERT_WORDS(x,(uint32_t)((hy>>32)&0x80000000),1);/* return +-minsub */
54 u = math_opt_barrier (x);
55 u = u * u;
56 math_force_eval (u); /* raise underflow flag */
57 return x;
58 }
59 if(hx>=0) { /* x > 0 */
60 if (x > y) { /* x -= ulp */
61 if(lx==0) hx -= 1;
62 lx -= 1;
63 } else { /* x < y, x += ulp */
64 lx += 1;
65 if(lx==0) hx += 1;
66 }
67 } else { /* x < 0 */
68 if (x < y) { /* x -= ulp */
69 if(lx==0) hx -= 1;
70 lx -= 1;
71 } else { /* x > y, x += ulp */
72 lx += 1;
73 if(lx==0) hx += 1;
74 }
75 }
76 hy = hx&0x7ff00000;
77 if(hy>=0x7ff00000) {
78 double u = x+x; /* overflow */
79 math_force_eval (u);
80 __set_errno (ERANGE);
81 }
82 if(hy<0x00100000) {
83 double u = x*x; /* underflow */
84 math_force_eval (u); /* raise underflow flag */
85 __set_errno (ERANGE);
86 }
87 INSERT_WORDS(x,hx,lx);
88 return x;
89 }
90 weak_alias (__nexttoward, nexttoward)
91