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 | |
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 | |