blob: 2c0e3ef12d8867a343a128898d546c84a38a19c3 (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
|
/* Compute radix independent exponent.
Copyright (C) 2011-2020 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@gmail.com>, 2011.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <math.h>
#include <math_private.h>
#include <libm-alias-double.h>
#include <fix-int-fp-convert-zero.h>
double
__logb (double x)
{
int64_t ix, ex;
EXTRACT_WORDS64 (ix, x);
ix &= UINT64_C(0x7fffffffffffffff);
if (ix == 0)
return -1.0 / fabs (x);
ex = ix >> 52;
if (ex == 0x7ff)
return x * x;
if (__glibc_unlikely (ex == 0))
{
int m = __builtin_clzll (ix);
ex -= m - 12;
}
if (FIX_INT_FP_CONVERT_ZERO && ex == 1023)
return 0.0;
return (double) (ex - 1023);
}
#ifndef __logb
libm_alias_double (__logb, logb)
#endif
|
