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81 lines
1.8 KiB
C
81 lines
1.8 KiB
C
/* Round double to integer away from zero.
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Copyright (C) 1997-2018 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
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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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<http://www.gnu.org/licenses/>. */
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#include <math.h>
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#include <math_private.h>
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#include <libm-alias-double.h>
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double
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__round (double x)
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{
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int32_t i0, j0;
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uint32_t i1;
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EXTRACT_WORDS (i0, i1, x);
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j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
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if (j0 < 20)
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{
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if (j0 < 0)
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{
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i0 &= 0x80000000;
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if (j0 == -1)
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i0 |= 0x3ff00000;
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i1 = 0;
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}
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else
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{
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uint32_t i = 0x000fffff >> j0;
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if (((i0 & i) | i1) == 0)
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/* X is integral. */
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return x;
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i0 += 0x00080000 >> j0;
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i0 &= ~i;
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i1 = 0;
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}
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}
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else if (j0 > 51)
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{
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if (j0 == 0x400)
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/* Inf or NaN. */
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return x + x;
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else
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return x;
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}
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else
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{
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uint32_t i = 0xffffffff >> (j0 - 20);
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if ((i1 & i) == 0)
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/* X is integral. */
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return x;
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uint32_t j = i1 + (1 << (51 - j0));
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if (j < i1)
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i0 += 1;
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i1 = j;
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i1 &= ~i;
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}
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INSERT_WORDS (x, i0, i1);
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return x;
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}
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libm_alias_double (__round, round)
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