mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-08 22:30:07 +00:00
i686: Do not raise exception traps on fesetexcept (BZ 30989)
According to ISO C23 (7.6.4.4), fesetexcept is supposed to set floating-point exception flags without raising a trap (unlike feraiseexcept, which is supposed to raise a trap if feenableexcept was called with the appropriate argument). The flags can be set in the 387 unit or in the SSE unit. To set a flag, it is sufficient to do it in the SSE unit, because that is guaranteed to not trap. However, on i386 CPUs that have only a 387 unit, set the flags in the 387, as long as this cannot trap. Checked on i686-linux-gnu. Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This commit is contained in:
parent
ecb1e7220d
commit
47a9eeb9ba
@ -19,6 +19,7 @@
|
||||
#include <fenv.h>
|
||||
#include <stdio.h>
|
||||
#include <math-tests.h>
|
||||
#include <math-barriers.h>
|
||||
|
||||
static int
|
||||
do_test (void)
|
||||
@ -41,12 +42,32 @@ do_test (void)
|
||||
|
||||
/* Verify fesetexcept does not cause exception traps. For architectures
|
||||
where setting the exception might result in traps the function should
|
||||
return a nonzero value. */
|
||||
return a nonzero value.
|
||||
Also check if the function does not alter the exception mask. */
|
||||
ret = fesetexcept (FE_ALL_EXCEPT);
|
||||
|
||||
_Static_assert (!(EXCEPTION_SET_FORCES_TRAP && !EXCEPTION_TESTS(float)),
|
||||
"EXCEPTION_SET_FORCES_TRAP only makes sense if the "
|
||||
"architecture suports exceptions");
|
||||
{
|
||||
int exc_before = fegetexcept ();
|
||||
ret = fesetexcept (FE_ALL_EXCEPT);
|
||||
int exc_after = fegetexcept ();
|
||||
if (exc_before != exc_after)
|
||||
{
|
||||
puts ("fesetexcept (FE_ALL_EXCEPT) changed the exceptions mask");
|
||||
return 1;
|
||||
}
|
||||
}
|
||||
|
||||
/* Execute some floating-point operations, since on some CPUs exceptions
|
||||
triggers a trap only at the next floating-point instruction. */
|
||||
volatile double a = 1.0;
|
||||
volatile double b = a + a;
|
||||
math_force_eval (b);
|
||||
volatile long double al = 1.0L;
|
||||
volatile long double bl = al + al;
|
||||
math_force_eval (bl);
|
||||
|
||||
if (ret == 0)
|
||||
{
|
||||
@ -72,5 +93,4 @@ do_test (void)
|
||||
return result;
|
||||
}
|
||||
|
||||
#define TEST_FUNCTION do_test ()
|
||||
#include "../test-skeleton.c"
|
||||
#include <support/test-driver.c>
|
||||
|
@ -17,15 +17,53 @@
|
||||
<https://www.gnu.org/licenses/>. */
|
||||
|
||||
#include <fenv.h>
|
||||
#include <ldsodefs.h>
|
||||
|
||||
int
|
||||
fesetexcept (int excepts)
|
||||
{
|
||||
fenv_t temp;
|
||||
/* The flags can be set in the 387 unit or in the SSE unit. To set a flag,
|
||||
it is sufficient to do it in the SSE unit, because that is guaranteed to
|
||||
not trap. However, on i386 CPUs that have only a 387 unit, set the flags
|
||||
in the 387, as long as this cannot trap. */
|
||||
|
||||
__asm__ ("fnstenv %0" : "=m" (*&temp));
|
||||
temp.__status_word |= excepts & FE_ALL_EXCEPT;
|
||||
__asm__ ("fldenv %0" : : "m" (*&temp));
|
||||
excepts &= FE_ALL_EXCEPT;
|
||||
|
||||
if (CPU_FEATURE_USABLE (SSE))
|
||||
{
|
||||
/* Get the control word of the SSE unit. */
|
||||
unsigned int mxcsr;
|
||||
__asm__ ("stmxcsr %0" : "=m" (*&mxcsr));
|
||||
|
||||
/* Set relevant flags. */
|
||||
mxcsr |= excepts;
|
||||
|
||||
/* Put the new data in effect. */
|
||||
__asm__ ("ldmxcsr %0" : : "m" (*&mxcsr));
|
||||
}
|
||||
else
|
||||
{
|
||||
fenv_t temp;
|
||||
|
||||
/* Note: fnstenv masks all floating-point exceptions until the fldenv
|
||||
or fldcw below. */
|
||||
__asm__ ("fnstenv %0" : "=m" (*&temp));
|
||||
|
||||
/* Set relevant flags. */
|
||||
temp.__status_word |= excepts;
|
||||
|
||||
if ((~temp.__control_word) & excepts)
|
||||
{
|
||||
/* Setting the exception flags may trigger a trap (at the next
|
||||
floating-point instruction, but that does not matter).
|
||||
ISO C23 (7.6.4.4) does not allow it. */
|
||||
__asm__ volatile ("fldcw %0" : : "m" (*&temp.__control_word));
|
||||
return -1;
|
||||
}
|
||||
|
||||
/* Store the new status word (along with the rest of the environment). */
|
||||
__asm__ ("fldenv %0" : : "m" (*&temp));
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
29
sysdeps/i386/fpu/math-tests-trap-force.h
Normal file
29
sysdeps/i386/fpu/math-tests-trap-force.h
Normal file
@ -0,0 +1,29 @@
|
||||
/* Configuration for math tests: support for setting exception flags
|
||||
without causing enabled traps. i686 version.
|
||||
Copyright (C) 2023 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/>. */
|
||||
|
||||
#ifndef I386_FPU_MATH_TESTS_TRAP_FORCE_H
|
||||
#define I386_FPU_MATH_TESTS_TRAP_FORCE_H 1
|
||||
|
||||
#include <cpu-features.h>
|
||||
|
||||
/* Setting exception flags in FPU Status Register results in enabled traps for
|
||||
those exceptions being taken. */
|
||||
#define EXCEPTION_SET_FORCES_TRAP !CPU_FEATURE_USABLE (SSE)
|
||||
|
||||
#endif /* math-tests-trap-force.h. */
|
@ -22,17 +22,8 @@
|
||||
#include <stdbool.h>
|
||||
#include <stdint.h>
|
||||
#include <stdio.h>
|
||||
|
||||
static bool
|
||||
have_sse2 (void)
|
||||
{
|
||||
unsigned int eax, ebx, ecx, edx;
|
||||
|
||||
if (!__get_cpuid (1, &eax, &ebx, &ecx, &edx))
|
||||
return false;
|
||||
|
||||
return (edx & bit_SSE2) != 0;
|
||||
}
|
||||
#include <cpu-features.h>
|
||||
#include <support/check.h>
|
||||
|
||||
static uint32_t
|
||||
get_sse_mxcsr (void)
|
||||
@ -164,13 +155,9 @@ sse_tests (void)
|
||||
static int
|
||||
do_test (void)
|
||||
{
|
||||
if (!have_sse2 ())
|
||||
{
|
||||
puts ("CPU does not support SSE2, cannot test");
|
||||
return 0;
|
||||
}
|
||||
if (!CPU_FEATURE_USABLE (SSE2))
|
||||
FAIL_UNSUPPORTED ("CPU does not support SSE2");
|
||||
return sse_tests ();
|
||||
}
|
||||
|
||||
#define TEST_FUNCTION do_test ()
|
||||
#include <test-skeleton.c>
|
||||
#include <support/test-driver.c>
|
||||
|
Loading…
Reference in New Issue
Block a user