mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-26 06:50:07 +00:00
09245377da
Since floating-point operation may trigger floating-point exceptions, we call math_opt_barrier inside if to prevent code motion. [BZ #19465] * sysdeps/ieee754/dbl-64/s_fma.c (__fma): Call math_opt_barrier inside if. * sysdeps/ieee754/ldbl-128/s_fmal.c (__fmal): Likewise. * sysdeps/ieee754/ldbl-96/s_fma.c (__fma): Likewise. * sysdeps/ieee754/ldbl-96/s_fmal.c (__fmal): Likewise.
102 lines
3.1 KiB
C
102 lines
3.1 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 <float.h>
|
|
#include <math.h>
|
|
#include <fenv.h>
|
|
#include <ieee754.h>
|
|
#include <math_private.h>
|
|
|
|
/* This implementation uses rounding to odd 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)
|
|
{
|
|
if (__glibc_unlikely (isinf (z)))
|
|
{
|
|
/* If z is Inf, but x and y are finite, the result should be
|
|
z rather than NaN. */
|
|
if (isfinite (x) && isfinite (y))
|
|
return (z + x) + y;
|
|
return (x * y) + z;
|
|
}
|
|
|
|
/* Ensure correct sign of exact 0 + 0. */
|
|
if (__glibc_unlikely ((x == 0 || y == 0) && z == 0))
|
|
{
|
|
x = math_opt_barrier (x);
|
|
return x * y + z;
|
|
}
|
|
|
|
fenv_t env;
|
|
feholdexcept (&env);
|
|
fesetround (FE_TONEAREST);
|
|
|
|
/* Multiplication m1 + m2 = x * y using Dekker's algorithm. */
|
|
#define C ((1ULL << (LDBL_MANT_DIG + 1) / 2) + 1)
|
|
long double x1 = (long double) x * C;
|
|
long double y1 = (long double) y * C;
|
|
long double m1 = (long double) x * y;
|
|
x1 = (x - x1) + x1;
|
|
y1 = (y - y1) + y1;
|
|
long double x2 = x - x1;
|
|
long double y2 = y - y1;
|
|
long double m2 = (((x1 * y1 - m1) + x1 * y2) + x2 * y1) + x2 * y2;
|
|
|
|
/* Addition a1 + a2 = z + m1 using Knuth's algorithm. */
|
|
long double a1 = z + m1;
|
|
long double t1 = a1 - z;
|
|
long double t2 = a1 - t1;
|
|
t1 = m1 - t1;
|
|
t2 = z - t2;
|
|
long double a2 = t1 + t2;
|
|
/* Ensure the arithmetic is not scheduled after feclearexcept call. */
|
|
math_force_eval (m2);
|
|
math_force_eval (a2);
|
|
feclearexcept (FE_INEXACT);
|
|
|
|
/* If the result is an exact zero, ensure it has the correct sign. */
|
|
if (a1 == 0 && m2 == 0)
|
|
{
|
|
feupdateenv (&env);
|
|
/* Ensure that round-to-nearest value of z + m1 is not reused. */
|
|
z = math_opt_barrier (z);
|
|
return z + m1;
|
|
}
|
|
|
|
fesetround (FE_TOWARDZERO);
|
|
/* Perform m2 + a2 addition with round to odd. */
|
|
a2 = a2 + m2;
|
|
|
|
/* Add that to a1 again using rounding to odd. */
|
|
union ieee854_long_double u;
|
|
u.d = a1 + a2;
|
|
if ((u.ieee.mantissa1 & 1) == 0 && u.ieee.exponent != 0x7fff)
|
|
u.ieee.mantissa1 |= fetestexcept (FE_INEXACT) != 0;
|
|
feupdateenv (&env);
|
|
|
|
/* Add finally round to double precision. */
|
|
return u.d;
|
|
}
|
|
#ifndef __fma
|
|
weak_alias (__fma, fma)
|
|
#endif
|