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126 lines
3.4 KiB
C
126 lines
3.4 KiB
C
/* Round to int long double floating-point values without raising inexact.
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IBM extended format long double version.
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Copyright (C) 2006, 2008 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, write to the Free
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Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA. */
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/* This has been coded in assembler because GCC makes such a mess of it
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when it's coded in C. */
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#include <math.h>
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#include <fenv.h>
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#include <math_ldbl_opt.h>
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#include <float.h>
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#include <ieee754.h>
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#ifdef __STDC__
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long double
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__nearbyintl (long double x)
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#else
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long double
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__nearbyintl (x)
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long double x;
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#endif
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{
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fenv_t env;
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static const long double TWO52 = 4503599627370496.0L;
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union ibm_extended_long_double u;
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u.d = x;
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if (fabs (u.dd[0]) < TWO52)
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{
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double high = u.dd[0];
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feholdexcept (&env);
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if (high > 0.0)
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{
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high += TWO52;
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high -= TWO52;
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if (high == -0.0) high = 0.0;
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}
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else if (high < 0.0)
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{
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high -= TWO52;
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high += TWO52;
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if (high == 0.0) high = -0.0;
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}
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u.dd[0] = high;
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u.dd[1] = 0.0;
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fesetenv (&env);
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}
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else if (fabs (u.dd[1]) < TWO52 && u.dd[1] != 0.0)
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{
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double high, low, tau;
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/* In this case we have to round the low double and handle any
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adjustment to the high double that may be caused by rounding
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(up). This is complicated by the fact that the high double
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may already be rounded and the low double may have the
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opposite sign to compensate. */
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feholdexcept (&env);
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if (u.dd[0] > 0.0)
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{
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if (u.dd[1] > 0.0)
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{
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/* If the high/low doubles are the same sign then simply
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round the low double. */
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high = u.dd[0];
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low = u.dd[1];
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}
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else if (u.dd[1] < 0.0)
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{
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/* Else the high double is pre rounded and we need to
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adjust for that. */
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tau = __nextafter (u.dd[0], 0.0);
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tau = (u.dd[0] - tau) * 2.0;
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high = u.dd[0] - tau;
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low = u.dd[1] + tau;
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}
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low += TWO52;
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low -= TWO52;
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}
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else if (u.dd[0] < 0.0)
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{
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if (u.dd[1] < 0.0)
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{
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/* If the high/low doubles are the same sign then simply
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round the low double. */
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high = u.dd[0];
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low = u.dd[1];
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}
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else if (u.dd[1] > 0.0)
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{
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/* Else the high double is pre rounded and we need to
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adjust for that. */
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tau = __nextafter (u.dd[0], 0.0);
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tau = (u.dd[0] - tau) * 2.0;
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high = u.dd[0] - tau;
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low = u.dd[1] + tau;
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}
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low = TWO52 - low;
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low = -(low - TWO52);
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}
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u.dd[0] = high + low;
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u.dd[1] = high - u.dd[0] + low;
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fesetenv (&env);
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}
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return u.d;
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}
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long_double_symbol (libm, __nearbyintl, nearbyintl);
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