| /* 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> |
| #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 |