| /* signbit() macro: Determine the sign bit of a floating-point number. |
| Copyright (C) 2007, 2009-2012 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 <http://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 |
| } |