mirror of
https://sourceware.org/git/glibc.git
synced 2024-12-11 13:50:06 +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.
112 lines
2.4 KiB
C
112 lines
2.4 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.
|
|
|
|
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>
|
|
|
|
|
|
static const long double zero = 0.0;
|
|
|
|
|
|
long double
|
|
__remquol (long double x, long double p, int *quo)
|
|
{
|
|
int32_t ex,ep,hx,hp;
|
|
u_int32_t sx,lx,lp;
|
|
int cquo,qs;
|
|
|
|
GET_LDOUBLE_WORDS (ex, hx, lx, x);
|
|
GET_LDOUBLE_WORDS (ep, hp, lp, p);
|
|
sx = ex & 0x8000;
|
|
qs = (sx ^ (ep & 0x8000)) >> 15;
|
|
ep &= 0x7fff;
|
|
ex &= 0x7fff;
|
|
|
|
/* Purge off exception values. */
|
|
if ((ep | hp | lp) == 0)
|
|
return (x * p) / (x * p); /* p = 0 */
|
|
if ((ex == 0x7fff) /* x not finite */
|
|
|| ((ep == 0x7fff) /* p is NaN */
|
|
&& ((hp | lp) != 0)))
|
|
return (x * p) / (x * p);
|
|
|
|
if (ep <= 0x7ffb)
|
|
x = __ieee754_fmodl (x, 8 * p); /* now x < 8p */
|
|
|
|
if (((ex - ep) | (hx - hp) | (lx - lp)) == 0)
|
|
{
|
|
*quo = qs ? -1 : 1;
|
|
return zero * x;
|
|
}
|
|
|
|
x = fabsl (x);
|
|
p = fabsl (p);
|
|
cquo = 0;
|
|
|
|
if (ep <= 0x7ffc && x >= 4 * p)
|
|
{
|
|
x -= 4 * p;
|
|
cquo += 4;
|
|
}
|
|
if (ep <= 0x7ffd && x >= 2 * p)
|
|
{
|
|
x -= 2 * p;
|
|
cquo += 2;
|
|
}
|
|
|
|
if (ep < 0x0002)
|
|
{
|
|
if (x + x > p)
|
|
{
|
|
x -= p;
|
|
++cquo;
|
|
if (x + x >= p)
|
|
{
|
|
x -= p;
|
|
++cquo;
|
|
}
|
|
}
|
|
}
|
|
else
|
|
{
|
|
long double p_half = 0.5 * p;
|
|
if (x > p_half)
|
|
{
|
|
x -= p;
|
|
++cquo;
|
|
if (x >= p_half)
|
|
{
|
|
x -= p;
|
|
++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;
|
|
}
|
|
weak_alias (__remquol, remquol)
|