138 lines
3.7 KiB
C
138 lines
3.7 KiB
C
/* Macros for quiet not-a-number.
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Copyright (C) 2023-2025 Free Software Foundation, Inc.
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This file is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation; either version 2.1 of the
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License, or (at your option) any later version.
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This file is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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#ifndef _SIGNED_NAN_H
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#define _SIGNED_NAN_H
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#include <math.h>
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#include "nan.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* Returns - x, implemented by inverting the sign bit,
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so that it works also on 'float' NaN values. */
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_GL_UNUSED static float
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minus_NaNf (float x)
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{
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#if defined __mips__
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/* The mips instruction neg.s may have no effect on NaNs.
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Therefore, invert the sign bit using integer operations. */
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union { unsigned int i; float value; } u;
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u.value = x;
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u.i ^= 1U << 31;
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return u.value;
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#else
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return - x;
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#endif
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}
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/* Returns a quiet 'float' NaN with sign bit == 0. */
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_GL_UNUSED static float
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positive_NaNf ()
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{
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/* 'volatile' works around a GCC bug:
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<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111655> */
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float volatile nan = NaNf ();
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return (signbit (nan) ? minus_NaNf (nan) : nan);
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}
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/* Returns a quiet 'float' NaN with sign bit == 1. */
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_GL_UNUSED static float
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negative_NaNf ()
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{
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/* 'volatile' works around a GCC bug:
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<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111655> */
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float volatile nan = NaNf ();
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return (signbit (nan) ? nan : minus_NaNf (nan));
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}
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/* Returns - x, implemented by inverting the sign bit,
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so that it works also on 'double' NaN values. */
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_GL_UNUSED static double
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minus_NaNd (double x)
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{
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#if defined __mips__
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/* The mips instruction neg.d may have no effect on NaNs.
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Therefore, invert the sign bit using integer operations. */
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union { unsigned long long i; double value; } u;
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u.value = x;
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u.i ^= 1ULL << 63;
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return u.value;
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#else
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return - x;
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#endif
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}
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/* Returns a quiet 'double' NaN with sign bit == 0. */
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_GL_UNUSED static double
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positive_NaNd ()
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{
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/* 'volatile' works around a GCC bug:
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<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111655> */
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double volatile nan = NaNd ();
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return (signbit (nan) ? minus_NaNd (nan) : nan);
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}
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/* Returns a quiet 'double' NaN with sign bit == 1. */
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_GL_UNUSED static double
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negative_NaNd ()
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{
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/* 'volatile' works around a GCC bug:
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<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111655> */
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double volatile nan = NaNd ();
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return (signbit (nan) ? nan : minus_NaNd (nan));
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}
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/* Returns - x, implemented by inverting the sign bit,
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so that it works also on 'long double' NaN values. */
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_GL_UNUSED static long double
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minus_NaNl (long double x)
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{
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return - x;
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}
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/* Returns a quiet 'long double' NaN with sign bit == 0. */
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_GL_UNUSED static long double
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positive_NaNl ()
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{
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/* 'volatile' works around a GCC bug:
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<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111655> */
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long double volatile nan = NaNl ();
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return (signbit (nan) ? minus_NaNl (nan) : nan);
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}
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/* Returns a quiet 'long double' NaN with sign bit == 1. */
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_GL_UNUSED static long double
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negative_NaNl ()
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{
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/* 'volatile' works around a GCC bug:
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<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111655> */
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long double volatile nan = NaNl ();
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return (signbit (nan) ? nan : minus_NaNl (nan));
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}
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#ifdef __cplusplus
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}
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#endif
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#endif /* _SIGNED_NAN_H */
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