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/* Compute x * y + z as ternary operation.
Copyright (C) 2010-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Jakub Jelinek <jakub@redhat.com>, 2010.
The GNU C Library 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.
The GNU C Library 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 the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <math.h>
#include <fenv.h>
#include <ieee754.h>
#include <math-barriers.h>
#include <fenv_private.h>
#include <libm-alias-float.h>
#include <math-use-builtins.h>
/* This implementation relies on double being more than twice as
precise as float and uses rounding to odd in order to avoid problems
with double rounding.
See a paper by Boldo and Melquiond:
http://www.lri.fr/~melquion/doc/08-tc.pdf */
float
__fmaf (float x, float y, float z)
{
#if USE_FMAF_BUILTIN
return __builtin_fmaf (x, y, z);
#else
/* Use generic implementation. */
fenv_t env;
/* Multiplication is always exact. */
double temp = (double) x * (double) y;
/* Ensure correct sign of an exact zero result by performing the
addition in the original rounding mode in that case. */
if (temp == -z)
return (float) temp + z;
union ieee754_double u;
libc_feholdexcept_setround (&env, FE_TOWARDZERO);
/* Perform addition with round to odd. */
u.d = temp + (double) z;
/* Ensure the addition is not scheduled after fetestexcept call. */
math_force_eval (u.d);
/* Reset rounding mode and test for inexact simultaneously. */
int j = libc_feupdateenv_test (&env, FE_INEXACT) != 0;
if ((u.ieee.mantissa1 & 1) == 0 && u.ieee.exponent != 0x7ff)
u.ieee.mantissa1 |= j;
/* And finally truncation with round to nearest. */
return (float) u.d;
#endif /* ! USE_FMAF_BUILTIN */
}
#ifndef __fmaf
libm_alias_float (__fma, fma)
#endif
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