| /* Compute radix independent exponent. |
| Copyright (C) 2011-2018 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 |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include <math.h> |
| |
| #include <math_private.h> |
| #include <libm-alias-double.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; |
| } |
| return (double) (ex - 1023); |
| } |
| #ifndef __logb |
| libm_alias_double (__logb, logb) |
| #endif |
