1 | /* Compute 2^x. |
2 | Copyright (C) 2012-2022 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 | <https://www.gnu.org/licenses/>. */ |
18 | |
19 | #include <math.h> |
20 | #include <math_private.h> |
21 | #include <math-underflow.h> |
22 | #include <float.h> |
23 | |
24 | FLOAT |
25 | M_DECL_FUNC (__ieee754_exp2) (FLOAT x) |
26 | { |
27 | if (__glibc_likely (isless (x, (FLOAT) M_MAX_EXP))) |
28 | { |
29 | if (__builtin_expect (isgreaterequal (x, (FLOAT) (M_MIN_EXP - M_MANT_DIG |
30 | - 1)), 1)) |
31 | { |
32 | int intx = (int) x; |
33 | FLOAT fractx = x - intx; |
34 | FLOAT result; |
35 | if (M_FABS (fractx) < M_EPSILON / 4) |
36 | result = M_SCALBN (1 + fractx, intx); |
37 | else |
38 | result = M_SCALBN (M_EXP (M_MLIT (M_LN2) * fractx), intx); |
39 | math_check_force_underflow_nonneg (result); |
40 | return result; |
41 | } |
42 | else |
43 | { |
44 | /* Underflow or exact zero. */ |
45 | if (isinf (x)) |
46 | return 0; |
47 | else |
48 | return M_MIN * M_MIN; |
49 | } |
50 | } |
51 | else |
52 | /* Infinity, NaN or overflow. */ |
53 | return M_MAX * x; |
54 | } |
55 | declare_mgen_finite_alias (__ieee754_exp2, __exp2) |
56 | |