mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-25 14:30:06 +00:00
b26901b26e
It turns out the __SSE2_MATH__ conditional in sysdeps/x86/fpu/s_ffma.c does not cover all cases where the x86 fenv_private.h macros might manipulate one of the SSE and 387 floating-point state, while the actual fma implementation uses the other. Specifically, in the 32-bit case, with a compiler not defaulting to -mfpmath=sse, but testing on a processor with hardware FMA support, the multiarch fma function implementations will end up using SSE, while the fenv_private.h macros will use the 387 state for double. Change the conditional to use the default macros rather than the optimized ones in all cases except when the compiler inlines an fma instruction (in which case, since all those instructions are SSE instructions and -mfpmath=sse must be in effect for them to be inlined, the optimized macros will only use the SSE state and it's OK for them to only use the SSE state). Tested for x86_64 and x86. H.J. reports in <https://sourceware.org/pipermail/libc-alpha/2021-September/131367.html> that it fixes the problems he observed.
51 lines
1.8 KiB
C
51 lines
1.8 KiB
C
/* Fused multiply-add of double value, narrowing the result to float.
|
|
x86 version.
|
|
Copyright (C) 2021 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
|
|
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
|
|
<https://www.gnu.org/licenses/>. */
|
|
|
|
#define f32fmaf64 __hide_f32fmaf64
|
|
#define f32fmaf32x __hide_f32fmaf32x
|
|
#define ffmal __hide_ffmal
|
|
#include <math.h>
|
|
#undef f32fmaf64
|
|
#undef f32fmaf32x
|
|
#undef ffmal
|
|
|
|
#include <math-narrow.h>
|
|
|
|
#ifndef __FP_FAST_FMA
|
|
/* Depending on the details of the glibc configuration, fma might use
|
|
either SSE or 387 arithmetic; ensure that both parts of the
|
|
floating-point state are handled in the round-to-odd code. If
|
|
__FP_FAST_FMA is defined, that implies that the compiler is using
|
|
SSE floating point and that the fma call will be inlined, so the
|
|
x86 macros will work with only the SSE state and that is
|
|
sufficient. */
|
|
# undef libc_feholdexcept_setround
|
|
# define libc_feholdexcept_setround default_libc_feholdexcept_setround
|
|
# undef libc_feupdateenv_test
|
|
# define libc_feupdateenv_test default_libc_feupdateenv_test
|
|
#endif
|
|
|
|
float
|
|
__ffma (double x, double y, double z)
|
|
{
|
|
NARROW_FMA_ROUND_TO_ODD (x, y, z, float, union ieee754_double, , mantissa1,
|
|
false);
|
|
}
|
|
libm_alias_float_double (fma)
|