mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-26 15:00:06 +00:00
65 lines
2.1 KiB
C
65 lines
2.1 KiB
C
/* Compute x * y + z as ternary operation.
|
|
Copyright (C) 2010-2016 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
|
|
<http://www.gnu.org/licenses/>. */
|
|
|
|
#include <math.h>
|
|
#include <fenv.h>
|
|
#include <ieee754.h>
|
|
#include <math_private.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)
|
|
{
|
|
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;
|
|
}
|
|
#ifndef __fmaf
|
|
weak_alias (__fmaf, fmaf)
|
|
#endif
|