1/* Compute x * y + z as ternary operation.
2 Copyright (C) 2010-2018 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Jakub Jelinek <jakub@redhat.com>, 2010.
5
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.
10
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.
15
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/>. */
19
20#include <math.h>
21#include <fenv.h>
22#include <ieee754.h>
23#include <math-barriers.h>
24#include <math_private.h>
25#include <libm-alias-float.h>
26
27/* This implementation relies on double being more than twice as
28 precise as float and uses rounding to odd in order to avoid problems
29 with double rounding.
30 See a paper by Boldo and Melquiond:
31 http://www.lri.fr/~melquion/doc/08-tc.pdf */
32
33float
34__fmaf (float x, float y, float z)
35{
36 fenv_t env;
37
38 /* Multiplication is always exact. */
39 double temp = (double) x * (double) y;
40
41 /* Ensure correct sign of an exact zero result by performing the
42 addition in the original rounding mode in that case. */
43 if (temp == -z)
44 return (float) temp + z;
45
46 union ieee754_double u;
47
48 libc_feholdexcept_setround (&env, FE_TOWARDZERO);
49
50 /* Perform addition with round to odd. */
51 u.d = temp + (double) z;
52 /* Ensure the addition is not scheduled after fetestexcept call. */
53 math_force_eval (u.d);
54
55 /* Reset rounding mode and test for inexact simultaneously. */
56 int j = libc_feupdateenv_test (&env, FE_INEXACT) != 0;
57
58 if ((u.ieee.mantissa1 & 1) == 0 && u.ieee.exponent != 0x7ff)
59 u.ieee.mantissa1 |= j;
60
61 /* And finally truncation with round to nearest. */
62 return (float) u.d;
63}
64#ifndef __fmaf
65libm_alias_float (__fma, fma)
66#endif
67