/* Test for NaN that does not need libm.
   Copyright (C) 2007-2017 Free Software Foundation, Inc.

   This program is free software: you can redistribute it and/or
   modify it under the terms of either:

     * 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.

   or

     * the GNU General Public License as published by the Free
       Software Foundation; either version 2 of the License, or (at your
       option) any later version.

   or both in parallel, as here.
   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 <https://www.gnu.org/licenses/>.  */

/* Written by Bruno Haible <bruno@clisp.org>, 2007.  */

#include <config.h>

/* Specification.  */
#ifdef USE_LONG_DOUBLE
/* Specification found in math.h or isnanl-nolibm.h.  */
extern int rpl_isnanl (long double x) _GL_ATTRIBUTE_CONST;
#elif ! defined USE_FLOAT
/* Specification found in math.h or isnand-nolibm.h.  */
extern int rpl_isnand (double x);
#else /* defined USE_FLOAT */
/* Specification found in math.h or isnanf-nolibm.h.  */
extern int rpl_isnanf (float x);
#endif

#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;

/* Most hosts nowadays use IEEE floating point, so they use IEC 60559
   representations, have infinities and NaNs, and do not trap on
   exceptions.  Define IEEE_FLOATING_POINT if this host is one of the
   typical ones.  The C11 macro __STDC_IEC_559__ is close to what is
   wanted here, but is not quite right because this file does not require
   all the features of C11 Annex F (and does not require C11 at all,
   for that matter).  */

#define IEEE_FLOATING_POINT (FLT_RADIX == 2 && FLT_MANT_DIG == 24 \
                             && FLT_MIN_EXP == -125 && FLT_MAX_EXP == 128)

int
FUNC (DOUBLE x)
{
#if defined KNOWN_EXPBIT0_LOCATION && IEEE_FLOATING_POINT
# 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
  /* 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 __ICC || defined _MSC_VER \
      || defined __DECC || defined __TINYC__ \
      || (defined __sgi && !defined __GNUC__)
  /* The Sun C 5.0, Intel ICC 10.0, Microsoft Visual C/C++ 9.0, Compaq (ex-DEC)
     6.4, and TinyCC compilers don't recognize the initializers as constant
     expressions.  The Compaq compiler also fails when constant-folding
     0.0 / 0.0 even when constant-folding is not required.  The Microsoft
     Visual C/C++ compiler also fails when constant-folding 1.0 / 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) / zero;
  DOUBLE minus_inf = -L_(1.0) / zero;
  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, or does
     not use IEEE floating point.  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_)) && !HAVE_SAME_LONG_DOUBLE_AS_DOUBLE
      /* 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
}