/* Total order of absolute value for 'float'.
Copyright 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 3 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/>. */
/* Written by Paul Eggert and Bruno Haible. */
#include <config.h>
/* Specification. */
#include <math.h>
#include <string.h>
#include "verify.h"
int
totalordermagf (float const *x, float const *y)
{
/* If one of *X, *Y is a NaN and the other isn't, the answer is easy:
the NaN is "greater" than the other argument. */
int xn = isnanf (*x);
int yn = isnanf (*y);
if (!xn != !yn)
return yn;
/* If none of *X, *Y is a NaN, the '<=' operator on the absolute values
does the job, including for -Infinity and +Infinity. */
if (!xn)
return (signbit (*x) ? - *x : *x) <= (signbit (*y) ? - *y : *y);
/* At this point, *X and *Y are NaNs. */
#if defined FLT_SIGNBIT_WORD && defined FLT_SIGNBIT_BIT
/* The use of a union to extract the bits of the representation of a
'float' is safe in practice, despite of the "aliasing rules" of
C99, because the GCC docs say
"Even with '-fstrict-aliasing', type-punning is allowed, provided the
memory is accessed through the union type."
and similarly for other compilers. */
# define NWORDS \
((sizeof (float) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
union { unsigned int word[NWORDS]; float value; }
xu = {0}, yu = {0};
# if 0
xu.value = *x;
yu.value = *y;
# else
# if defined __GNUC__ || defined __clang__
/* Prevent gcc and clang from reusing the values of *x and *y (fetched above)
in optimized inlined memcpy expansions.
Seen with gcc <https://gcc.gnu.org/PR114659>
and with clang 16.0.6 on OpenBSD 7.5. */
__asm__ __volatile__ ("" : : : "memory");
# endif
/* On 32-bit x86 processors, as well as on x86_64 processors with
CC="gcc -mfpmath=387", the evaluation of *x and *y above is done through
an 'flds' instruction, which converts a signalling NaN to a quiet NaN. See
<https://lists.gnu.org/archive/html/bug-gnulib/2023-10/msg00060.html>
for details. Use memcpy to avoid this. */
memcpy (&xu.value, x, sizeof (float));
memcpy (&yu.value, y, sizeof (float));
# endif
verify (NWORDS == 1);
return ((xu.word[0] & ~(1U << FLT_SIGNBIT_BIT)) /* *X without its sign bit */
# if defined __hppa || (defined __mips__ && !MIPS_NAN2008_FLOAT) || defined __sh__
/* Invert the most significant bit of the mantissa field.
Cf. snan.h. */
^ (1U << 22)
# endif
) <=
((yu.word[0] & ~(1U << FLT_SIGNBIT_BIT)) /* *Y without its sign bit */
# if defined __hppa || (defined __mips__ && !MIPS_NAN2008_FLOAT) || defined __sh__
/* Invert the most significant bit of the mantissa field.
Cf. snan.h. */
^ (1U << 22)
# endif
);
#else
# error "Please port gnulib totalordermagf.c to your platform!"
#endif
}
