1/* Test for NaN that does not need libm.
2   Copyright (C) 2007-2022 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.  */
24extern int rpl_isnanl (long double x) _GL_ATTRIBUTE_CONST;
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
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 C11 macro __STDC_IEC_559__ is close to what is
86   wanted here, but is not quite right because this file does not require
87   all the features of C11 Annex F (and does not require C11 at all,
88   for that matter).  */
89
90#define IEEE_FLOATING_POINT (FLT_RADIX == 2 && FLT_MANT_DIG == 24 \
91                             && FLT_MIN_EXP == -125 && FLT_MAX_EXP == 128)
92
93int
94FUNC (DOUBLE x)
95{
96#if defined KNOWN_EXPBIT0_LOCATION && IEEE_FLOATING_POINT
97# 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
98  /* Special CPU dependent code is needed to treat bit patterns outside the
99     IEEE 754 specification (such as Pseudo-NaNs, Pseudo-Infinities,
100     Pseudo-Zeroes, Unnormalized Numbers, and Pseudo-Denormals) as NaNs.
101     These bit patterns are:
102       - exponent = 0x0001..0x7FFF, mantissa bit 63 = 0,
103       - exponent = 0x0000, mantissa bit 63 = 1.
104     The NaN bit pattern is:
105       - exponent = 0x7FFF, mantissa >= 0x8000000000000001.  */
106  memory_double m;
107  unsigned int exponent;
108
109  m.value = x;
110  exponent = (m.word[EXPBIT0_WORD] >> EXPBIT0_BIT) & EXP_MASK;
111#  ifdef WORDS_BIGENDIAN
112  /* Big endian: EXPBIT0_WORD = 0, EXPBIT0_BIT = 16.  */
113  if (exponent == 0)
114    return 1 & (m.word[0] >> 15);
115  else if (exponent == EXP_MASK)
116    return (((m.word[0] ^ 0x8000U) << 16) | m.word[1] | (m.word[2] >> 16)) != 0;
117  else
118    return 1 & ~(m.word[0] >> 15);
119#  else
120  /* Little endian: EXPBIT0_WORD = 2, EXPBIT0_BIT = 0.  */
121  if (exponent == 0)
122    return (m.word[1] >> 31);
123  else if (exponent == EXP_MASK)
124    return ((m.word[1] ^ 0x80000000U) | m.word[0]) != 0;
125  else
126    return (m.word[1] >> 31) ^ 1;
127#  endif
128# else
129  /* Be careful to not do any floating-point operation on x, such as x == x,
130     because x may be a signaling NaN.  */
131#  if defined __SUNPRO_C || defined __ICC || defined _MSC_VER \
132      || defined __DECC || defined __TINYC__ \
133      || (defined __sgi && !defined __GNUC__)
134  /* The Sun C 5.0, Intel ICC 10.0, Microsoft Visual C/C++ 9.0, Compaq (ex-DEC)
135     6.4, and TinyCC compilers don't recognize the initializers as constant
136     expressions.  The Compaq compiler also fails when constant-folding
137     0.0 / 0.0 even when constant-folding is not required.  The Microsoft
138     Visual C/C++ compiler also fails when constant-folding 1.0 / 0.0 even
139     when constant-folding is not required. The SGI MIPSpro C compiler
140     complains about "floating-point operation result is out of range".  */
141  static DOUBLE zero = L_(0.0);
142  memory_double nan;
143  DOUBLE plus_inf = L_(1.0) / zero;
144  DOUBLE minus_inf = -L_(1.0) / zero;
145  nan.value = zero / zero;
146#  else
147  static memory_double nan = { L_(0.0) / L_(0.0) };
148  static DOUBLE plus_inf = L_(1.0) / L_(0.0);
149  static DOUBLE minus_inf = -L_(1.0) / L_(0.0);
150#  endif
151  {
152    memory_double m;
153
154    /* A NaN can be recognized through its exponent.  But exclude +Infinity and
155       -Infinity, which have the same exponent.  */
156    m.value = x;
157    if (((m.word[EXPBIT0_WORD] ^ nan.word[EXPBIT0_WORD])
158         & (EXP_MASK << EXPBIT0_BIT))
159        == 0)
160      return (memcmp (&m.value, &plus_inf, SIZE) != 0
161              && memcmp (&m.value, &minus_inf, SIZE) != 0);
162    else
163      return 0;
164  }
165# endif
166#else
167  /* The configuration did not find sufficient information, or does
168     not use IEEE floating point.  Give up about the signaling NaNs;
169     handle only the quiet NaNs.  */
170  if (x == x)
171    {
172# 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
173      /* Detect any special bit patterns that pass ==; see comment above.  */
174      memory_double m1;
175      memory_double m2;
176
177      memset (&m1.value, 0, SIZE);
178      memset (&m2.value, 0, SIZE);
179      m1.value = x;
180      m2.value = x + (x ? 0.0L : -0.0L);
181      if (memcmp (&m1.value, &m2.value, SIZE) != 0)
182        return 1;
183# endif
184      return 0;
185    }
186  else
187    return 1;
188#endif
189}
190