]>
git.ipfire.org Git - thirdparty/glibc.git/blob - sysdeps/ieee754/dbl-64/s_fmaf.c
1 /* Compute x * y + z as ternary operation.
2 Copyright (C) 2010, 2011 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Jakub Jelinek <jakub@redhat.com>, 2010.
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <http://www.gnu.org/licenses/>. */
23 #include <math_private.h>
25 /* This implementation relies on double being more than twice as
26 precise as float and uses rounding to odd in order to avoid problems
28 See a paper by Boldo and Melquiond:
29 http://www.lri.fr/~melquion/doc/08-tc.pdf */
32 __fmaf (float x
, float y
, float z
)
35 /* Multiplication is always exact. */
36 double temp
= (double) x
* (double) y
;
37 union ieee754_double u
;
39 libc_feholdexcept_setround (&env
, FE_TOWARDZERO
);
41 /* Perform addition with round to odd. */
42 u
.d
= temp
+ (double) z
;
44 /* Reset rounding mode and test for inexact simultaneously. */
45 int j
= libc_feupdateenv_test (&env
, FE_INEXACT
) != 0;
47 if ((u
.ieee
.mantissa1
& 1) == 0 && u
.ieee
.exponent
!= 0x7ff)
48 u
.ieee
.mantissa1
|= j
;
50 /* And finally truncation with round to nearest. */
54 weak_alias (__fmaf
, fmaf
)