65 lines
2.1 KiB
C
65 lines
2.1 KiB
C
|
/* signbit() macro: Determine the sign bit of a floating-point number.
|
||
|
|
Copyright (C) 2007, 2009-2018 Free Software Foundation, Inc.
|
||
|
|
|
||
|
|
This program is free software: you can redistribute it and/or modify
|
||
|
|
it under the terms of the GNU General Public License as published by
|
||
|
|
the Free Software Foundation; either version 3 of the License, or
|
||
|
|
(at your option) any later version.
|
||
|
|
|
||
|
|
This program 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 General Public License for more details.
|
||
|
|
|
||
|
|
You should have received a copy of the GNU General Public License
|
||
|
|
along with this program. If not, see <https://www.gnu.org/licenses/>. */
|
||
|
|
|
||
|
|
#include <config.h>
|
||
|
|
|
||
|
|
/* Specification. */
|
||
|
|
#include <math.h>
|
||
|
|
|
||
|
|
#include <string.h>
|
||
|
|
#include "isnanl-nolibm.h"
|
||
|
|
#include "float+.h"
|
||
|
|
|
||
|
|
#ifdef gl_signbitl_OPTIMIZED_MACRO
|
||
|
|
# undef gl_signbitl
|
||
|
|
#endif
|
||
|
|
|
||
|
|
int
|
||
|
|
gl_signbitl (long double arg)
|
||
|
|
{
|
||
|
|
#if defined LDBL_SIGNBIT_WORD && defined LDBL_SIGNBIT_BIT
|
||
|
|
/* The use of a union to extract the bits of the representation of a
|
||
|
|
'long double' is safe in practice, despite of the "aliasing rules" of
|
||
|
|
C99, because the GCC docs say
|
||
|
|
"Even with '-fstrict-aliasing', type-punning is allowed, provided the
|
||
|
|
memory is accessed through the union type."
|
||
|
|
and similarly for other compilers. */
|
||
|
|
# define NWORDS \
|
||
|
|
((sizeof (long double) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
|
||
|
|
union { long double value; unsigned int word[NWORDS]; } m;
|
||
|
|
m.value = arg;
|
||
|
|
return (m.word[LDBL_SIGNBIT_WORD] >> LDBL_SIGNBIT_BIT) & 1;
|
||
|
|
#elif HAVE_COPYSIGNL_IN_LIBC
|
||
|
|
return copysignl (1.0L, arg) < 0;
|
||
|
|
#else
|
||
|
|
/* This does not do the right thing for NaN, but this is irrelevant for
|
||
|
|
most use cases. */
|
||
|
|
if (isnanl (arg))
|
||
|
|
return 0;
|
||
|
|
if (arg < 0.0L)
|
||
|
|
return 1;
|
||
|
|
else if (arg == 0.0L)
|
||
|
|
{
|
||
|
|
/* Distinguish 0.0L and -0.0L. */
|
||
|
|
static long double plus_zero = 0.0L;
|
||
|
|
long double arg_mem = arg;
|
||
|
|
return (memcmp (&plus_zero, &arg_mem, SIZEOF_LDBL) != 0);
|
||
|
|
}
|
||
|
|
else
|
||
|
|
return 0;
|
||
|
|
#endif
|
||
|
|
}
|