| lh | 9ed821d | 2023-04-07 01:36:19 -0700 | [diff] [blame^] | 1 | /* Compute 2^x. |
| 2 | Copyright (C) 2012-2015 Free Software Foundation, Inc. |
| 3 | This file is part of the GNU C Library. |
| 4 | |
| 5 | The GNU C Library is free software; you can redistribute it and/or |
| 6 | modify it under the terms of the GNU Lesser General Public |
| 7 | License as published by the Free Software Foundation; either |
| 8 | version 2.1 of the License, or (at your option) any later version. |
| 9 | |
| 10 | The GNU C Library is distributed in the hope that it will be useful, |
| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 13 | Lesser General Public License for more details. |
| 14 | |
| 15 | You should have received a copy of the GNU Lesser General Public |
| 16 | License along with the GNU C Library; if not, see |
| 17 | <http://www.gnu.org/licenses/>. */ |
| 18 | |
| 19 | #include <math.h> |
| 20 | #include <math_private.h> |
| 21 | #include <float.h> |
| 22 | |
| 23 | /* To avoid spurious underflows, use this definition to treat IBM long |
| 24 | double as approximating an IEEE-style format. */ |
| 25 | #if LDBL_MANT_DIG == 106 |
| 26 | # undef LDBL_EPSILON |
| 27 | # define LDBL_EPSILON 0x1p-106L |
| 28 | #endif |
| 29 | |
| 30 | long double |
| 31 | __ieee754_exp2l (long double x) |
| 32 | { |
| 33 | if (__glibc_likely (isless (x, (long double) LDBL_MAX_EXP))) |
| 34 | { |
| 35 | if (__builtin_expect (isgreaterequal (x, (long double) (LDBL_MIN_EXP |
| 36 | - LDBL_MANT_DIG |
| 37 | - 1)), 1)) |
| 38 | { |
| 39 | int intx = (int) x; |
| 40 | long double fractx = x - intx; |
| 41 | if (fabsl (fractx) < LDBL_EPSILON / 4.0L) |
| 42 | return __scalbnl (1.0L + fractx, intx); |
| 43 | return __scalbnl (__ieee754_expl (M_LN2l * fractx), intx); |
| 44 | } |
| 45 | else |
| 46 | { |
| 47 | /* Underflow or exact zero. */ |
| 48 | if (isinf (x)) |
| 49 | return 0; |
| 50 | else |
| 51 | return LDBL_MIN * LDBL_MIN; |
| 52 | } |
| 53 | } |
| 54 | else |
| 55 | /* Infinity, NaN or overflow. */ |
| 56 | return LDBL_MAX * x; |
| 57 | } |
| 58 | strong_alias (__ieee754_exp2l, __exp2l_finite) |