1 /* Compute 2^x.
2 Copyright (C) 2012-2018 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 "quadmath-imp.h"
20
21 __float128
exp2q(__float128 x)22 exp2q (__float128 x)
23 {
24 if (__glibc_likely (__builtin_isless (x, (__float128) FLT128_MAX_EXP)))
25 {
26 if (__builtin_expect (__builtin_isgreaterequal (x, (__float128) (FLT128_MIN_EXP - FLT128_MANT_DIG
27 - 1)), 1))
28 {
29 int intx = (int) x;
30 __float128 fractx = x - intx;
31 __float128 result;
32 if (fabsq (fractx) < FLT128_EPSILON / 4)
33 result = scalbnq (1 + fractx, intx);
34 else
35 result = scalbnq (expq (M_LN2q * fractx), intx);
36 math_check_force_underflow_nonneg (result);
37 return result;
38 }
39 else
40 {
41 /* Underflow or exact zero. */
42 if (isinfq (x))
43 return 0;
44 else
45 return FLT128_MIN * FLT128_MIN;
46 }
47 }
48 else
49 /* Infinity, NaN or overflow. */
50 return FLT128_MAX * x;
51 }
52