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91 lines
2.8 KiB
C
91 lines
2.8 KiB
C
/* Round double value to long long int.
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Copyright (C) 1997-2016 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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<http://www.gnu.org/licenses/>. */
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#include <limits.h>
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#include <math.h>
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#include <math_ldbl_opt.h>
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#include <math_private.h>
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#include <stdint.h>
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/* Round to the nearest integer, with values exactly on a 0.5 boundary
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rounded away from zero, regardless of the current rounding mode.
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If (long long)x, when x is out of range of a long long, clips at
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LLONG_MAX or LLONG_MIN, then this implementation also clips. */
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long long int
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__llround (double x)
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{
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long long xr;
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if (HAVE_PPC_FCTIDZ)
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xr = (long long) x;
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else
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{
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/* Avoid incorrect exceptions from libgcc conversions (as of GCC
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5): <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59412>. */
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if (fabs (x) < 0x1p31)
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xr = (long long int) (long int) x;
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else
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{
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uint64_t i0;
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EXTRACT_WORDS64 (i0, x);
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int exponent = ((i0 >> 52) & 0x7ff) - 0x3ff;
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if (exponent < 63)
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{
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unsigned long long int mant
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= (i0 & ((1ULL << 52) - 1)) | (1ULL << 52);
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if (exponent < 52)
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/* llround is not required to raise "inexact". */
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mant >>= 52 - exponent;
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else
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mant <<= exponent - 52;
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xr = (long long int) ((i0 & (1ULL << 63)) != 0 ? -mant : mant);
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}
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else if (x == (double) LLONG_MIN)
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xr = LLONG_MIN;
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else
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xr = (long long int) (long int) x << 32;
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}
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}
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/* Avoid spurious "inexact" converting LLONG_MAX to double, and from
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subtraction when the result is out of range, by returning early
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for arguments large enough that no rounding is needed. */
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if (!(fabs (x) < 0x1p52))
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return xr;
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double xrf = (double) xr;
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if (x >= 0.0)
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{
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if (x - xrf >= 0.5)
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xr += (long long) ((unsigned long long) xr + 1) > 0;
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}
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else
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{
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if (xrf - x >= 0.5)
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xr -= (long long) ((unsigned long long) xr - 1) < 0;
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}
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return xr;
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}
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weak_alias (__llround, llround)
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#ifdef NO_LONG_DOUBLE
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strong_alias (__llround, __llroundl)
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weak_alias (__llround, llroundl)
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#endif
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#if LONG_DOUBLE_COMPAT (libm, GLIBC_2_1)
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compat_symbol (libm, __llround, llroundl, GLIBC_2_1);
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#endif
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