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48e44791 | 1 | /* Compute 2^x. |
b168057a | 2 | Copyright (C) 2012-2015 Free Software Foundation, Inc. |
48e44791 JM |
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 | ||
b6ab06ce | 19 | #include <math.h> |
9277c064 | 20 | #include <math_private.h> |
48e44791 | 21 | #include <float.h> |
b6ab06ce | 22 | |
03d95bd4 JM |
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 | ||
b6ab06ce UD |
30 | long double |
31 | __ieee754_exp2l (long double x) | |
32 | { | |
a1ffb40e | 33 | if (__glibc_likely (isless (x, (long double) LDBL_MAX_EXP))) |
48e44791 JM |
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; | |
03d95bd4 JM |
41 | if (fabsl (fractx) < LDBL_EPSILON / 4.0L) |
42 | return __scalbnl (1.0L + fractx, intx); | |
48e44791 JM |
43 | return __scalbnl (__ieee754_expl (M_LN2l * fractx), intx); |
44 | } | |
45 | else | |
46 | { | |
47 | /* Underflow or exact zero. */ | |
d81f90cc | 48 | if (isinf (x)) |
48e44791 JM |
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; | |
b6ab06ce | 57 | } |
0ac5ae23 | 58 | strong_alias (__ieee754_exp2l, __exp2l_finite) |