| /* Compute x * y + z as ternary operation. |
| Copyright (C) 2010-2014 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> |
| |
| /* This implementation relies on long double being more than twice as |
| precise as double 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 */ |
| |
| double |
| __fma (double x, double y, double z) |
| { |
| fenv_t env; |
| /* Multiplication is always exact. */ |
| long double temp = (long double) x * (long 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 (double) temp + z; |
| |
| union ieee854_long_double u; |
| feholdexcept (&env); |
| fesetround (FE_TOWARDZERO); |
| /* Perform addition with round to odd. */ |
| u.d = temp + (long double) z; |
| if ((u.ieee.mantissa3 & 1) == 0 && u.ieee.exponent != 0x7fff) |
| u.ieee.mantissa3 |= fetestexcept (FE_INEXACT) != 0; |
| feupdateenv (&env); |
| /* And finally truncation with round to nearest. */ |
| return (double) u.d; |
| } |
| #ifndef __fma |
| weak_alias (__fma, fma) |
| #endif |
