/* signbit() macro: Determine the sign bit of a floating-point number.
- Copyright (C) 2007 Free Software Foundation, Inc.
+ Copyright (C) 2007, 2009-2011 Free Software Foundation, Inc.
- This program is free software; you can redistribute it and/or modify
+ 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 2, or (at your option)
- any later version.
+ 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, write to the Free Software Foundation,
- Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include <config.h>
#include "isnanl-nolibm.h"
#include "float+.h"
-#undef gl_signbitl
+#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. */