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145
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1 /* Compute 2^x.
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2 Copyright (C) 2012-2018 Free Software Foundation, Inc.
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3 This file is part of the GNU C Library.
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4
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5 The GNU C Library is free software; you can redistribute it and/or
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6 modify it under the terms of the GNU Lesser General Public
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7 License as published by the Free Software Foundation; either
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8 version 2.1 of the License, or (at your option) any later version.
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9
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10 The GNU C Library is distributed in the hope that it will be useful,
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11 but WITHOUT ANY WARRANTY; without even the implied warranty of
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12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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13 Lesser General Public License for more details.
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14
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15 You should have received a copy of the GNU Lesser General Public
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16 License along with the GNU C Library; if not, see
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17 <http://www.gnu.org/licenses/>. */
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18
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19 #include "quadmath-imp.h"
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20
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21 __float128
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22 exp2q (__float128 x)
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23 {
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24 if (__glibc_likely (__builtin_isless (x, (__float128) FLT128_MAX_EXP)))
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25 {
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26 if (__builtin_expect (__builtin_isgreaterequal (x, (__float128) (FLT128_MIN_EXP - FLT128_MANT_DIG
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27 - 1)), 1))
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28 {
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29 int intx = (int) x;
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30 __float128 fractx = x - intx;
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31 __float128 result;
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32 if (fabsq (fractx) < FLT128_EPSILON / 4)
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33 result = scalbnq (1 + fractx, intx);
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34 else
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35 result = scalbnq (expq (M_LN2q * fractx), intx);
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36 math_check_force_underflow_nonneg (result);
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37 return result;
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38 }
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39 else
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40 {
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41 /* Underflow or exact zero. */
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42 if (isinfq (x))
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43 return 0;
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44 else
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45 return FLT128_MIN * FLT128_MIN;
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46 }
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47 }
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48 else
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49 /* Infinity, NaN or overflow. */
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50 return FLT128_MAX * x;
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51 }
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