1 | /* s_logbl.c -- long double version of s_logb.c. |
2 | * Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz. |
3 | */ |
4 | |
5 | /* |
6 | * ==================================================== |
7 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
8 | * |
9 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
10 | * Permission to use, copy, modify, and distribute this |
11 | * software is freely granted, provided that this notice |
12 | * is preserved. |
13 | * ==================================================== |
14 | */ |
15 | |
16 | #if defined(LIBM_SCCS) && !defined(lint) |
17 | static char rcsid[] = "$NetBSD: $" ; |
18 | #endif |
19 | |
20 | /* |
21 | * long double logbl(x) |
22 | * IEEE 754 logb. Included to pass IEEE test suite. Not recommend. |
23 | * Use ilogb instead. |
24 | */ |
25 | |
26 | #include <math.h> |
27 | #include <math_private.h> |
28 | #include <libm-alias-ldouble.h> |
29 | |
30 | _Float128 |
31 | __logbl (_Float128 x) |
32 | { |
33 | int64_t lx, hx, ex; |
34 | |
35 | GET_LDOUBLE_WORDS64 (hx, lx, x); |
36 | hx &= 0x7fffffffffffffffLL; /* high |x| */ |
37 | if ((hx | lx) == 0) |
38 | return -1.0 / fabsl (x); |
39 | if (hx >= 0x7fff000000000000LL) |
40 | return x * x; |
41 | if ((ex = hx >> 48) == 0) /* IEEE 754 logb */ |
42 | { |
43 | /* POSIX specifies that denormal number is treated as |
44 | though it were normalized. */ |
45 | int ma; |
46 | if (hx == 0) |
47 | ma = __builtin_clzll (lx) + 64; |
48 | else |
49 | ma = __builtin_clzll (hx); |
50 | ex -= ma - 16; |
51 | } |
52 | return (_Float128) (ex - 16383); |
53 | } |
54 | |
55 | libm_alias_ldouble (__logb, logb) |
56 | |