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)
19 static 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-barriers.h>
32 #include <math_private.h>
33 #include <float.h>
34
__nexttoward(double x,long double y)35 double __nexttoward(double x, long double y)
36 {
37 int32_t hx,ix,iy;
38 uint32_t lx,hy,ly,esy;
39
40 EXTRACT_WORDS(hx,lx,x);
41 GET_LDOUBLE_WORDS(esy,hy,ly,y);
42 ix = hx&0x7fffffff; /* |x| */
43 iy = esy&0x7fff; /* |y| */
44
45 /* Intel's extended format has the normally implicit 1 explicit
46 present. Sigh! */
47 if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */
48 ((iy>=0x7fff)&&((hy&0x7fffffff)|ly)!=0)) /* y is nan */
49 return x+y;
50 if((long double) x==y) return y; /* x=y, return y */
51 if((ix|lx)==0) { /* x == 0 */
52 double u;
53 INSERT_WORDS(x,(esy&0x8000)<<16,1); /* 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 #ifdef NO_LONG_DOUBLE
92 strong_alias (__nexttoward, __nexttowardl)
93 weak_alias (__nexttoward, nexttowardl)
94 #endif
95