/* Macros for quiet not-a-number.
Copyright (C) 2023-2025 Free Software Foundation, Inc.
This file 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 2.1 of the
License, or (at your option) any later version.
This file 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 <https://www.gnu.org/licenses/>. */
#ifndef _SIGNED_NAN_H
#define _SIGNED_NAN_H
/* This file uses _GL_UNUSED. */
#if !_GL_CONFIG_H_INCLUDED
#error "Please include config.h first."
#endif
#include <math.h>
#include "nan.h"
#ifdef __cplusplus
extern "C" {
#endif
/* Returns - x, implemented by inverting the sign bit,
so that it works also on 'float' NaN values. */
_GL_UNUSED static float
minus_NaNf (float x)
{
#if defined __mips__
/* The mips instruction neg.s may have no effect on NaNs.
Therefore, invert the sign bit using integer operations. */
union { unsigned int i; float value; } u;
u.value = x;
u.i ^= 1U << 31;
return u.value;
#else
return - x;
#endif
}
/* Returns a quiet 'float' NaN with sign bit == 0. */
_GL_UNUSED static float
positive_NaNf ()
{
/* 'volatile' works around a GCC bug:
<https://gcc.gnu.org/PR111655> */
float volatile nan = NaNf ();
return (signbit (nan) ? minus_NaNf (nan) : nan);
}
/* Returns a quiet 'float' NaN with sign bit == 1. */
_GL_UNUSED static float
negative_NaNf ()
{
/* 'volatile' works around a GCC bug:
<https://gcc.gnu.org/PR111655> */
float volatile nan = NaNf ();
return (signbit (nan) ? nan : minus_NaNf (nan));
}
/* Returns - x, implemented by inverting the sign bit,
so that it works also on 'double' NaN values. */
_GL_UNUSED static double
minus_NaNd (double x)
{
#if defined __mips__
/* The mips instruction neg.d may have no effect on NaNs.
Therefore, invert the sign bit using integer operations. */
union { unsigned long long i; double value; } u;
u.value = x;
u.i ^= 1ULL << 63;
return u.value;
#else
return - x;
#endif
}
/* Returns a quiet 'double' NaN with sign bit == 0. */
_GL_UNUSED static double
positive_NaNd ()
{
/* 'volatile' works around a GCC bug:
<https://gcc.gnu.org/PR111655> */
double volatile nan = NaNd ();
return (signbit (nan) ? minus_NaNd (nan) : nan);
}
/* Returns a quiet 'double' NaN with sign bit == 1. */
_GL_UNUSED static double
negative_NaNd ()
{
/* 'volatile' works around a GCC bug:
<https://gcc.gnu.org/PR111655> */
double volatile nan = NaNd ();
return (signbit (nan) ? nan : minus_NaNd (nan));
}
/* Returns - x, implemented by inverting the sign bit,
so that it works also on 'long double' NaN values. */
_GL_UNUSED static long double
minus_NaNl (long double x)
{
return - x;
}
/* Returns a quiet 'long double' NaN with sign bit == 0. */
_GL_UNUSED static long double
positive_NaNl ()
{
/* 'volatile' works around a GCC bug:
<https://gcc.gnu.org/PR111655> */
long double volatile nan = NaNl ();
return (signbit (nan) ? minus_NaNl (nan) : nan);
}
/* Returns a quiet 'long double' NaN with sign bit == 1. */
_GL_UNUSED static long double
negative_NaNl ()
{
/* 'volatile' works around a GCC bug:
<https://gcc.gnu.org/PR111655> */
long double volatile nan = NaNl ();
return (signbit (nan) ? nan : minus_NaNl (nan));
}
#ifdef __cplusplus
}
#endif
#endif /* _SIGNED_NAN_H */
