1 /* Test for NaN that does not need libm.
2 Copyright (C) 2007-2023 Free Software Foundation, Inc.
3
4 This file is free software: you can redistribute it and/or modify
5 it under the terms of the GNU Lesser General Public License as
6 published by the Free Software Foundation; either version 2.1 of the
7 License, or (at your option) any later version.
8
9 This file 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 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public License
15 along with this program. If not, see <https://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. */
24 extern int rpl_isnanl (long double x) _GL_ATTRIBUTE_CONST;
25 #elif ! defined USE_FLOAT
26 /* Specification found in math.h or isnand-nolibm.h. */
27 extern int rpl_isnand (double x);
28 #else /* defined USE_FLOAT */
29 /* Specification found in math.h or isnanf-nolibm.h. */
30 extern 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))
80 typedef union { DOUBLE value; unsigned int word[NWORDS]; } memory_double;
81
82 /* Most hosts nowadays use IEEE floating point, so they use IEC 60559
83 representations, have infinities and NaNs, and do not trap on
84 exceptions. Define IEEE_FLOATING_POINT if this host is one of the
85 typical ones. The C23 macro __STDC_IEC_60559_BFP__ macro (or its cousin,
86 the now-obsolescent C11 macro __STDC_IEC_559__) is close to what is
87 wanted here, but is not quite right because this file does not require
88 all the features of C23 Annex F (and works even with pre-C11 platforms,
89 for that matter). */
90
91 #define IEEE_FLOATING_POINT (FLT_RADIX == 2 && FLT_MANT_DIG == 24 \
92 && FLT_MIN_EXP == -125 && FLT_MAX_EXP == 128)
93
94 int
95 FUNC (DOUBLE x)
96 {
97 #if defined KNOWN_EXPBIT0_LOCATION && IEEE_FLOATING_POINT
98 # 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_)) && !HAVE_SAME_LONG_DOUBLE_AS_DOUBLE
99 /* Special CPU dependent code is needed to treat bit patterns outside the
100 IEEE 754 specification (such as Pseudo-NaNs, Pseudo-Infinities,
101 Pseudo-Zeroes, Unnormalized Numbers, and Pseudo-Denormals) as NaNs.
102 These bit patterns are:
103 - exponent = 0x0001..0x7FFF, mantissa bit 63 = 0,
104 - exponent = 0x0000, mantissa bit 63 = 1.
105 The NaN bit pattern is:
106 - exponent = 0x7FFF, mantissa >= 0x8000000000000001. */
107 memory_double m;
108 unsigned int exponent;
109
110 m.value = x;
111 exponent = (m.word[EXPBIT0_WORD] >> EXPBIT0_BIT) & EXP_MASK;
112 # ifdef WORDS_BIGENDIAN
113 /* Big endian: EXPBIT0_WORD = 0, EXPBIT0_BIT = 16. */
114 if (exponent == 0)
115 return 1 & (m.word[0] >> 15);
116 else if (exponent == EXP_MASK)
117 return (((m.word[0] ^ 0x8000U) << 16) | m.word[1] | (m.word[2] >> 16)) != 0;
118 else
119 return 1 & ~(m.word[0] >> 15);
120 # else
121 /* Little endian: EXPBIT0_WORD = 2, EXPBIT0_BIT = 0. */
122 if (exponent == 0)
123 return (m.word[1] >> 31);
124 else if (exponent == EXP_MASK)
125 return ((m.word[1] ^ 0x80000000U) | m.word[0]) != 0;
126 else
127 return (m.word[1] >> 31) ^ 1;
128 # endif
129 # else
130 /* Be careful to not do any floating-point operation on x, such as x == x,
131 because x may be a signaling NaN. */
132 # if defined __SUNPRO_C || defined __ICC || defined _MSC_VER \
133 || defined __DECC || defined __TINYC__ \
134 || (defined __sgi && !defined __GNUC__)
135 /* The Sun C 5.0, Intel ICC 10.0, Microsoft Visual C/C++ 9.0, Compaq (ex-DEC)
136 6.4, and TinyCC compilers don't recognize the initializers as constant
137 expressions. The Compaq compiler also fails when constant-folding
138 0.0 / 0.0 even when constant-folding is not required. The Microsoft
139 Visual C/C++ compiler also fails when constant-folding 1.0 / 0.0 even
140 when constant-folding is not required. The SGI MIPSpro C compiler
141 complains about "floating-point operation result is out of range". */
142 static DOUBLE zero = L_(0.0);
143 memory_double nan;
144 DOUBLE plus_inf = L_(1.0) / zero;
145 DOUBLE minus_inf = -L_(1.0) / zero;
146 nan.value = zero / zero;
147 # else
148 static memory_double nan = { L_(0.0) / L_(0.0) };
149 static DOUBLE plus_inf = L_(1.0) / L_(0.0);
150 static DOUBLE minus_inf = -L_(1.0) / L_(0.0);
151 # endif
152 {
153 memory_double m;
154
155 /* A NaN can be recognized through its exponent. But exclude +Infinity and
156 -Infinity, which have the same exponent. */
157 m.value = x;
158 if (((m.word[EXPBIT0_WORD] ^ nan.word[EXPBIT0_WORD])
159 & (EXP_MASK << EXPBIT0_BIT))
160 == 0)
161 return (memcmp (&m.value, &plus_inf, SIZE) != 0
162 && memcmp (&m.value, &minus_inf, SIZE) != 0);
163 else
164 return 0;
165 }
166 # endif
167 #else
168 /* The configuration did not find sufficient information, or does
169 not use IEEE floating point. Give up about the signaling NaNs;
170 handle only the quiet NaNs. */
171 if (x == x)
172 {
173 # 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_)) && !HAVE_SAME_LONG_DOUBLE_AS_DOUBLE
174 /* Detect any special bit patterns that pass ==; see comment above. */
175 memory_double m1;
176 memory_double m2;
177
178 memset (&m1.value, 0, SIZE);
179 memset (&m2.value, 0, SIZE);
180 m1.value = x;
181 m2.value = x + (x ? 0.0L : -0.0L);
182 if (memcmp (&m1.value, &m2.value, SIZE) != 0)
183 return 1;
184 # endif
185 return 0;
186 }
187 else
188 return 1;
189 #endif
190 }