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Diffstat (limited to 'lib/isnan.c')
| -rw-r--r-- | lib/isnan.c | 161 |
1 files changed, 161 insertions, 0 deletions
diff --git a/lib/isnan.c b/lib/isnan.c new file mode 100644 index 00000000..f24f5761 --- /dev/null +++ b/lib/isnan.c @@ -0,0 +1,161 @@ +/* Test for NaN that does not need libm. + Copyright (C) 2007-2008 Free Software Foundation, Inc. + + This program 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 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 Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with this program. If not, see <http://www.gnu.org/licenses/>. */ + +/* Written by Bruno Haible <bruno@clisp.org>, 2007. */ + +#include <config.h> + +#include <float.h> +#include <string.h> + +#include "float+.h" + +#ifdef USE_LONG_DOUBLE +# define FUNC rpl_isnanl +# define DOUBLE long double +# define MAX_EXP LDBL_MAX_EXP +# define MIN_EXP LDBL_MIN_EXP +# if defined LDBL_EXPBIT0_WORD && defined LDBL_EXPBIT0_BIT +# define KNOWN_EXPBIT0_LOCATION +# define EXPBIT0_WORD LDBL_EXPBIT0_WORD +# define EXPBIT0_BIT LDBL_EXPBIT0_BIT +# endif +# define SIZE SIZEOF_LDBL +# define L_(literal) literal##L +#elif ! defined USE_FLOAT +# define FUNC rpl_isnand +# define DOUBLE double +# define MAX_EXP DBL_MAX_EXP +# define MIN_EXP DBL_MIN_EXP +# if defined DBL_EXPBIT0_WORD && defined DBL_EXPBIT0_BIT +# define KNOWN_EXPBIT0_LOCATION +# define EXPBIT0_WORD DBL_EXPBIT0_WORD +# define EXPBIT0_BIT DBL_EXPBIT0_BIT +# endif +# define SIZE SIZEOF_DBL +# define L_(literal) literal +#else /* defined USE_FLOAT */ +# define FUNC rpl_isnanf +# define DOUBLE float +# define MAX_EXP FLT_MAX_EXP +# define MIN_EXP FLT_MIN_EXP +# if defined FLT_EXPBIT0_WORD && defined FLT_EXPBIT0_BIT +# define KNOWN_EXPBIT0_LOCATION +# define EXPBIT0_WORD FLT_EXPBIT0_WORD +# define EXPBIT0_BIT FLT_EXPBIT0_BIT +# endif +# define SIZE SIZEOF_FLT +# define L_(literal) literal##f +#endif + +#define EXP_MASK ((MAX_EXP - MIN_EXP) | 7) + +#define NWORDS \ + ((sizeof (DOUBLE) + sizeof (unsigned int) - 1) / sizeof (unsigned int)) +typedef union { DOUBLE value; unsigned int word[NWORDS]; } memory_double; + +int +FUNC (DOUBLE x) +{ +#ifdef KNOWN_EXPBIT0_LOCATION +# if defined USE_LONG_DOUBLE && ((defined __ia64 && LDBL_MANT_DIG == 64) || (defined __x86_64__ || defined __amd64__) || (defined __i386 || defined __i386__ || defined _I386 || defined _M_IX86 || defined _X86_)) + /* Special CPU dependent code is needed to treat bit patterns outside the + IEEE 754 specification (such as Pseudo-NaNs, Pseudo-Infinities, + Pseudo-Zeroes, Unnormalized Numbers, and Pseudo-Denormals) as NaNs. + These bit patterns are: + - exponent = 0x0001..0x7FFF, mantissa bit 63 = 0, + - exponent = 0x0000, mantissa bit 63 = 1. + The NaN bit pattern is: + - exponent = 0x7FFF, mantissa >= 0x8000000000000001. */ + memory_double m; + unsigned int exponent; + + m.value = x; + exponent = (m.word[EXPBIT0_WORD] >> EXPBIT0_BIT) & EXP_MASK; +# ifdef WORDS_BIGENDIAN + /* Big endian: EXPBIT0_WORD = 0, EXPBIT0_BIT = 16. */ + if (exponent == 0) + return 1 & (m.word[0] >> 15); + else if (exponent == EXP_MASK) + return (((m.word[0] ^ 0x8000U) << 16) | m.word[1] | (m.word[2] >> 16)) != 0; + else + return 1 & ~(m.word[0] >> 15); +# else + /* Little endian: EXPBIT0_WORD = 2, EXPBIT0_BIT = 0. */ + if (exponent == 0) + return (m.word[1] >> 31); + else if (exponent == EXP_MASK) + return ((m.word[1] ^ 0x80000000U) | m.word[0]) != 0; + else + return (m.word[1] >> 31) ^ 1; +# endif +# else + /* Be careful to not do any floating-point operation on x, such as x == x, + because x may be a signaling NaN. */ +# if defined __SUNPRO_C || defined __DECC || (defined __sgi && !defined __GNUC__) + /* The Sun C 5.0 compilers and the Compaq (ex-DEC) 6.4 compilers don't + recognize the initializers as constant expressions. The latter compiler + also fails when constant-folding 0.0 / 0.0 even when constant-folding is + not required. The SGI MIPSpro C compiler complains about "floating-point + operation result is out of range". */ + static DOUBLE zero = L_(0.0); + memory_double nan; + DOUBLE plus_inf = L_(1.0) / L_(0.0); + DOUBLE minus_inf = -L_(1.0) / L_(0.0); + nan.value = zero / zero; +# else + static memory_double nan = { L_(0.0) / L_(0.0) }; + static DOUBLE plus_inf = L_(1.0) / L_(0.0); + static DOUBLE minus_inf = -L_(1.0) / L_(0.0); +# endif + { + memory_double m; + + /* A NaN can be recognized through its exponent. But exclude +Infinity and + -Infinity, which have the same exponent. */ + m.value = x; + if (((m.word[EXPBIT0_WORD] ^ nan.word[EXPBIT0_WORD]) + & (EXP_MASK << EXPBIT0_BIT)) + == 0) + return (memcmp (&m.value, &plus_inf, SIZE) != 0 + && memcmp (&m.value, &minus_inf, SIZE) != 0); + else + return 0; + } +# endif +#else + /* The configuration did not find sufficient information. Give up about + the signaling NaNs, handle only the quiet NaNs. */ + if (x == x) + { +# if defined USE_LONG_DOUBLE && ((defined __ia64 && LDBL_MANT_DIG == 64) || (defined __x86_64__ || defined __amd64__) || (defined __i386 || defined __i386__ || defined _I386 || defined _M_IX86 || defined _X86_)) + /* Detect any special bit patterns that pass ==; see comment above. */ + memory_double m1; + memory_double m2; + + memset (&m1.value, 0, SIZE); + memset (&m2.value, 0, SIZE); + m1.value = x; + m2.value = x + (x ? 0.0L : -0.0L); + if (memcmp (&m1.value, &m2.value, SIZE) != 0) + return 1; +# endif + return 0; + } + else + return 1; +#endif +} |