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56 lines
1.6 KiB
C
56 lines
1.6 KiB
C
/* Compute 2^x.
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Copyright (C) 2012-2020 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <math.h>
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#include <math_private.h>
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#include <math-underflow.h>
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#include <float.h>
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FLOAT
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M_DECL_FUNC (__ieee754_exp2) (FLOAT x)
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{
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if (__glibc_likely (isless (x, (FLOAT) M_MAX_EXP)))
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{
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if (__builtin_expect (isgreaterequal (x, (FLOAT) (M_MIN_EXP - M_MANT_DIG
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- 1)), 1))
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{
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int intx = (int) x;
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FLOAT fractx = x - intx;
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FLOAT result;
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if (M_FABS (fractx) < M_EPSILON / 4)
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result = M_SCALBN (1 + fractx, intx);
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else
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result = M_SCALBN (M_EXP (M_MLIT (M_LN2) * fractx), intx);
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math_check_force_underflow_nonneg (result);
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return result;
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}
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else
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{
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/* Underflow or exact zero. */
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if (isinf (x))
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return 0;
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else
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return M_MIN * M_MIN;
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}
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}
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else
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/* Infinity, NaN or overflow. */
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return M_MAX * x;
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}
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declare_mgen_finite_alias (__ieee754_exp2, __exp2)
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