mirror of
https://sourceware.org/git/glibc.git
synced 2024-12-29 05:51:10 +00:00
ce8fc784e6
Various remquo implementations produce a zero remainder with the wrong sign (a zero remainder should always have the sign of the first argument, as specified in IEEE 754) in round-downward mode, resulting from the sign of 0 - 0. This patch checks for zero results and fixes their sign accordingly. Tested for x86_64, x86, mips64 and powerpc. [BZ #17987] * sysdeps/ieee754/dbl-64/s_remquo.c (__remquo): Ensure sign of zero result does not depend on the sign resulting from subtraction. * sysdeps/ieee754/dbl-64/wordsize-64/s_remquo.c (__remquo): Likewise. * sysdeps/ieee754/flt-32/s_remquof.c (__remquof): Likewise. * sysdeps/ieee754/ldbl-128/s_remquol.c (__remquol): Likewise. * sysdeps/ieee754/ldbl-128ibm/s_remquol.c (__remquol): Likewise. * sysdeps/ieee754/ldbl-96/s_remquol.c (__remquol): Likewise. * math/libm-test.inc (remquo_test_data): Add more tests.
118 lines
2.7 KiB
C
118 lines
2.7 KiB
C
/* Compute remainder and a congruent to the quotient.
|
|
Copyright (C) 1997-2015 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997 and
|
|
Jakub Jelinek <jj@ultra.linux.cz>, 1999.
|
|
|
|
The GNU C Library is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU Lesser General Public
|
|
License as published by the Free Software Foundation; either
|
|
version 2.1 of the License, or (at your option) any later version.
|
|
|
|
The GNU C Library is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
Lesser General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Lesser General Public
|
|
License along with the GNU C Library; if not, see
|
|
<http://www.gnu.org/licenses/>. */
|
|
|
|
#include <math.h>
|
|
|
|
#include <math_private.h>
|
|
#include <math_ldbl_opt.h>
|
|
|
|
|
|
static const long double zero = 0.0;
|
|
|
|
|
|
long double
|
|
__remquol (long double x, long double y, int *quo)
|
|
{
|
|
int64_t hx,hy;
|
|
u_int64_t sx,lx,ly,qs;
|
|
int cquo;
|
|
double xhi, xlo, yhi, ylo;
|
|
|
|
ldbl_unpack (x, &xhi, &xlo);
|
|
EXTRACT_WORDS64 (hx, xhi);
|
|
EXTRACT_WORDS64 (lx, xlo);
|
|
ldbl_unpack (y, &yhi, &ylo);
|
|
EXTRACT_WORDS64 (hy, yhi);
|
|
EXTRACT_WORDS64 (ly, ylo);
|
|
sx = hx & 0x8000000000000000ULL;
|
|
qs = sx ^ (hy & 0x8000000000000000ULL);
|
|
hy &= 0x7fffffffffffffffLL;
|
|
hx &= 0x7fffffffffffffffLL;
|
|
|
|
/* Purge off exception values. */
|
|
if (hy == 0)
|
|
return (x * y) / (x * y); /* y = 0 */
|
|
if ((hx >= 0x7ff0000000000000LL) /* x not finite */
|
|
|| (hy > 0x7ff0000000000000LL)) /* y is NaN */
|
|
return (x * y) / (x * y);
|
|
|
|
if (hy <= 0x7fbfffffffffffffLL)
|
|
x = __ieee754_fmodl (x, 8 * y); /* now x < 8y */
|
|
|
|
if (((hx - hy) | (lx - ly)) == 0)
|
|
{
|
|
*quo = qs ? -1 : 1;
|
|
return zero * x;
|
|
}
|
|
|
|
x = fabsl (x);
|
|
y = fabsl (y);
|
|
cquo = 0;
|
|
|
|
if (hy <= 0x7fcfffffffffffffLL && x >= 4 * y)
|
|
{
|
|
x -= 4 * y;
|
|
cquo += 4;
|
|
}
|
|
if (hy <= 0x7fdfffffffffffffLL && x >= 2 * y)
|
|
{
|
|
x -= 2 * y;
|
|
cquo += 2;
|
|
}
|
|
|
|
if (hy < 0x0020000000000000LL)
|
|
{
|
|
if (x + x > y)
|
|
{
|
|
x -= y;
|
|
++cquo;
|
|
if (x + x >= y)
|
|
{
|
|
x -= y;
|
|
++cquo;
|
|
}
|
|
}
|
|
}
|
|
else
|
|
{
|
|
long double y_half = 0.5L * y;
|
|
if (x > y_half)
|
|
{
|
|
x -= y;
|
|
++cquo;
|
|
if (x >= y_half)
|
|
{
|
|
x -= y;
|
|
++cquo;
|
|
}
|
|
}
|
|
}
|
|
|
|
*quo = qs ? -cquo : cquo;
|
|
|
|
/* Ensure correct sign of zero result in round-downward mode. */
|
|
if (x == 0.0L)
|
|
x = 0.0L;
|
|
if (sx)
|
|
x = -x;
|
|
return x;
|
|
}
|
|
long_double_symbol (libm, __remquol, remquol);
|