1 | /* s_logbl.c -- long double version of s_logb.c. |
2 | */ |
3 | |
4 | /* |
5 | * ==================================================== |
6 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
7 | * |
8 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
9 | * Permission to use, copy, modify, and distribute this |
10 | * software is freely granted, provided that this notice |
11 | * is preserved. |
12 | * ==================================================== |
13 | */ |
14 | |
15 | #if defined(LIBM_SCCS) && !defined(lint) |
16 | static char rcsid[] = "$NetBSD: $" ; |
17 | #endif |
18 | |
19 | /* |
20 | * long double logbl(x) |
21 | * IEEE 754 logb. Included to pass IEEE test suite. Not recommend. |
22 | * Use ilogb instead. |
23 | */ |
24 | |
25 | #include <math.h> |
26 | #include <math_private.h> |
27 | #include <libm-alias-ldouble.h> |
28 | #include <math-use-builtins.h> |
29 | |
30 | _Float128 |
31 | __logbl (_Float128 x) |
32 | { |
33 | #if USE_LOGBL_BUILTIN |
34 | return __builtin_logbl (x); |
35 | #else |
36 | /* Use generic implementation. */ |
37 | int64_t lx, hx, ex; |
38 | |
39 | GET_LDOUBLE_WORDS64 (hx, lx, x); |
40 | hx &= 0x7fffffffffffffffLL; /* high |x| */ |
41 | if ((hx | lx) == 0) |
42 | return -1.0 / fabsl (x); |
43 | if (hx >= 0x7fff000000000000LL) |
44 | return x * x; |
45 | if ((ex = hx >> 48) == 0) /* IEEE 754 logb */ |
46 | { |
47 | /* POSIX specifies that denormal number is treated as |
48 | though it were normalized. */ |
49 | int ma; |
50 | if (hx == 0) |
51 | ma = __builtin_clzll (lx) + 64; |
52 | else |
53 | ma = __builtin_clzll (hx); |
54 | ex -= ma - 16; |
55 | } |
56 | return (_Float128) (ex - 16383); |
57 | #endif /* ! USE_LOGBL_BUILTIN */ |
58 | } |
59 | |
60 | libm_alias_ldouble (__logb, logb) |
61 | |