1/* Test for NaN that does not need libm.
2   Copyright (C) 2007-2010 Free Software Foundation, Inc.
3
4   This program is free software: you can redistribute it and/or modify
5   it under the terms of the GNU General Public License as published by
6   the Free Software Foundation; either version 3 of the License, or
7   (at your option) any later version.
8
9   This program is distributed in the hope that it will be useful,
10   but WITHOUT ANY WARRANTY; without even the implied warranty of
11   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12   GNU General Public License for more details.
13
14   You should have received a copy of the GNU General Public License
15   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
16
17/* Written by Bruno Haible <bruno@clisp.org>, 2007.  */
18
19#include <config.h>
20
21/* Specification.  */
22#ifdef USE_LONG_DOUBLE
23/* Specification found in math.h or isnanl-nolibm.h.  */
24extern int rpl_isnanl (long double x);
25#elif ! defined USE_FLOAT
26/* Specification found in math.h or isnand-nolibm.h.  */
27extern int rpl_isnand (double x);
28#else /* defined USE_FLOAT */
29/* Specification found in math.h or isnanf-nolibm.h.  */
30extern int rpl_isnanf (float x);
31#endif
32
33#include <float.h>
34#include <string.h>
35
36#include "float+.h"
37
38#ifdef USE_LONG_DOUBLE
39# define FUNC rpl_isnanl
40# define DOUBLE long double
41# define MAX_EXP LDBL_MAX_EXP
42# define MIN_EXP LDBL_MIN_EXP
43# if defined LDBL_EXPBIT0_WORD && defined LDBL_EXPBIT0_BIT
44#  define KNOWN_EXPBIT0_LOCATION
45#  define EXPBIT0_WORD LDBL_EXPBIT0_WORD
46#  define EXPBIT0_BIT LDBL_EXPBIT0_BIT
47# endif
48# define SIZE SIZEOF_LDBL
49# define L_(literal) literal##L
50#elif ! defined USE_FLOAT
51# define FUNC rpl_isnand
52# define DOUBLE double
53# define MAX_EXP DBL_MAX_EXP
54# define MIN_EXP DBL_MIN_EXP
55# if defined DBL_EXPBIT0_WORD && defined DBL_EXPBIT0_BIT
56#  define KNOWN_EXPBIT0_LOCATION
57#  define EXPBIT0_WORD DBL_EXPBIT0_WORD
58#  define EXPBIT0_BIT DBL_EXPBIT0_BIT
59# endif
60# define SIZE SIZEOF_DBL
61# define L_(literal) literal
62#else /* defined USE_FLOAT */
63# define FUNC rpl_isnanf
64# define DOUBLE float
65# define MAX_EXP FLT_MAX_EXP
66# define MIN_EXP FLT_MIN_EXP
67# if defined FLT_EXPBIT0_WORD && defined FLT_EXPBIT0_BIT
68#  define KNOWN_EXPBIT0_LOCATION
69#  define EXPBIT0_WORD FLT_EXPBIT0_WORD
70#  define EXPBIT0_BIT FLT_EXPBIT0_BIT
71# endif
72# define SIZE SIZEOF_FLT
73# define L_(literal) literal##f
74#endif
75
76#define EXP_MASK ((MAX_EXP - MIN_EXP) | 7)
77
78#define NWORDS \
79  ((sizeof (DOUBLE) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
80typedef union { DOUBLE value; unsigned int word[NWORDS]; } memory_double;
81
82int
83FUNC (DOUBLE x)
84{
85#ifdef KNOWN_EXPBIT0_LOCATION
86# 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_))
87  /* Special CPU dependent code is needed to treat bit patterns outside the
88     IEEE 754 specification (such as Pseudo-NaNs, Pseudo-Infinities,
89     Pseudo-Zeroes, Unnormalized Numbers, and Pseudo-Denormals) as NaNs.
90     These bit patterns are:
91       - exponent = 0x0001..0x7FFF, mantissa bit 63 = 0,
92       - exponent = 0x0000, mantissa bit 63 = 1.
93     The NaN bit pattern is:
94       - exponent = 0x7FFF, mantissa >= 0x8000000000000001.  */
95  memory_double m;
96  unsigned int exponent;
97
98  m.value = x;
99  exponent = (m.word[EXPBIT0_WORD] >> EXPBIT0_BIT) & EXP_MASK;
100#  ifdef WORDS_BIGENDIAN
101  /* Big endian: EXPBIT0_WORD = 0, EXPBIT0_BIT = 16.  */
102  if (exponent == 0)
103    return 1 & (m.word[0] >> 15);
104  else if (exponent == EXP_MASK)
105    return (((m.word[0] ^ 0x8000U) << 16) | m.word[1] | (m.word[2] >> 16)) != 0;
106  else
107    return 1 & ~(m.word[0] >> 15);
108#  else
109  /* Little endian: EXPBIT0_WORD = 2, EXPBIT0_BIT = 0.  */
110  if (exponent == 0)
111    return (m.word[1] >> 31);
112  else if (exponent == EXP_MASK)
113    return ((m.word[1] ^ 0x80000000U) | m.word[0]) != 0;
114  else
115    return (m.word[1] >> 31) ^ 1;
116#  endif
117# else
118  /* Be careful to not do any floating-point operation on x, such as x == x,
119     because x may be a signaling NaN.  */
120#  if defined __SUNPRO_C || defined __DECC || (defined __sgi && !defined __GNUC__)
121  /* The Sun C 5.0 compilers and the Compaq (ex-DEC) 6.4 compilers don't
122     recognize the initializers as constant expressions.  The latter compiler
123     also fails when constant-folding 0.0 / 0.0 even when constant-folding is
124     not required.  The SGI MIPSpro C compiler complains about "floating-point
125     operation result is out of range".  */
126  static DOUBLE zero = L_(0.0);
127  memory_double nan;
128  DOUBLE plus_inf = L_(1.0) / L_(0.0);
129  DOUBLE minus_inf = -L_(1.0) / L_(0.0);
130  nan.value = zero / zero;
131#  else
132  static memory_double nan = { L_(0.0) / L_(0.0) };
133  static DOUBLE plus_inf = L_(1.0) / L_(0.0);
134  static DOUBLE minus_inf = -L_(1.0) / L_(0.0);
135#  endif
136  {
137    memory_double m;
138
139    /* A NaN can be recognized through its exponent.  But exclude +Infinity and
140       -Infinity, which have the same exponent.  */
141    m.value = x;
142    if (((m.word[EXPBIT0_WORD] ^ nan.word[EXPBIT0_WORD])
143         & (EXP_MASK << EXPBIT0_BIT))
144        == 0)
145      return (memcmp (&m.value, &plus_inf, SIZE) != 0
146              && memcmp (&m.value, &minus_inf, SIZE) != 0);
147    else
148      return 0;
149  }
150# endif
151#else
152  /* The configuration did not find sufficient information.  Give up about
153     the signaling NaNs, handle only the quiet NaNs.  */
154  if (x == x)
155    {
156# 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_))
157      /* Detect any special bit patterns that pass ==; see comment above.  */
158      memory_double m1;
159      memory_double m2;
160
161      memset (&m1.value, 0, SIZE);
162      memset (&m2.value, 0, SIZE);
163      m1.value = x;
164      m2.value = x + (x ? 0.0L : -0.0L);
165      if (memcmp (&m1.value, &m2.value, SIZE) != 0)
166        return 1;
167# endif
168      return 0;
169    }
170  else
171    return 1;
172#endif
173}
174