math: x86 floor traps when FE_INEXACT is enabled (BZ 31601)

The implementations of floor functions using x87 floating point (i386 and
86_64 long double only) traps when FE_INEXACT is enabled.  Although
this is a GNU extension outside the scope of the C standard, other
architectures that also support traps do not show this behavior.

The fix moves the implementation to a common one that holds any
exceptions with a 'fnclex' (libc_feholdexcept_setround_387).

Checked on x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
This commit is contained in:
Adhemerval Zanella 2024-04-03 16:39:18 -03:00
parent 637bfc392f
commit 932544efa4
9 changed files with 144 additions and 140 deletions

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@ -511,6 +511,7 @@ tests = \
test-fetestexceptflag \ test-fetestexceptflag \
test-fexcept \ test-fexcept \
test-fexcept-traps \ test-fexcept-traps \
test-floor-except-2 \
test-flt-eval-method \ test-flt-eval-method \
test-fp-ilogb-constants \ test-fp-ilogb-constants \
test-fp-llogb-constants \ test-fp-llogb-constants \
@ -991,6 +992,7 @@ CFLAGS-test-fe-snans-always-signal.c += $(config-cflags-signaling-nans)
CFLAGS-test-nan-const.c += -fno-builtin CFLAGS-test-nan-const.c += -fno-builtin
CFLAGS-test-ceil-except-2.c += -fno-builtin CFLAGS-test-ceil-except-2.c += -fno-builtin
CFLAGS-test-floor-except-2.c += -fno-builtin
include ../Rules include ../Rules

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@ -0,0 +1,67 @@
/* Test floor functions do not disable exception traps.
Copyright (C) 2024 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/>. */
#include <fenv.h>
#include <math.h>
#include <stdio.h>
#ifndef FE_INEXACT
# define FE_INEXACT 0
#endif
#define TEST_FUNC(NAME, FLOAT, SUFFIX) \
static int \
NAME (void) \
{ \
int result = 0; \
volatile FLOAT a, b __attribute__ ((unused)); \
a = 1.5; \
/* floor must work when traps on "inexact" are enabled. */ \
b = floor ## SUFFIX (a); \
/* And it must have left those traps enabled. */ \
if (fegetexcept () == FE_INEXACT) \
puts ("PASS: " #FLOAT); \
else \
{ \
puts ("FAIL: " #FLOAT); \
result = 1; \
} \
return result; \
}
TEST_FUNC (float_test, float, f)
TEST_FUNC (double_test, double, )
TEST_FUNC (ldouble_test, long double, l)
static int
do_test (void)
{
if (feenableexcept (FE_INEXACT) == -1)
{
puts ("enabling FE_INEXACT traps failed, cannot test");
return 77;
}
int result = float_test ();
feenableexcept (FE_INEXACT);
result |= double_test ();
feenableexcept (FE_INEXACT);
result |= ldouble_test ();
return result;
}
#include <support/test-driver.c>

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@ -1,34 +0,0 @@
/*
* Public domain.
*/
#include <machine/asm.h>
#include <libm-alias-double.h>
RCSID("$NetBSD: s_floor.S,v 1.4 1995/05/09 00:01:59 jtc Exp $")
ENTRY(__floor)
fldl 4(%esp)
subl $32,%esp
cfi_adjust_cfa_offset (32)
fnstenv 4(%esp) /* store fpu environment */
/* We use here %edx although only the low 1 bits are defined.
But none of the operations should care and they are faster
than the 16 bit operations. */
movl $0x400,%edx /* round towards -oo */
orl 4(%esp),%edx
andl $0xf7ff,%edx
movl %edx,(%esp)
fldcw (%esp) /* load modified control word */
frndint /* round */
fldenv 4(%esp) /* restore original environment */
addl $32,%esp
cfi_adjust_cfa_offset (-32)
ret
END (__floor)
libm_alias_double (__floor, floor)

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@ -0,0 +1,25 @@
/* Return smallest integral value not less than argument. i386 version.
Copyright (C) 2024 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/>. */
#include <libm-alias-double.h>
#define FUNC __floor
#define TYPE double
#define FE_OPTION FE_DOWNWARD
#include "s_nearestint_387_template.c"
libm_alias_double (__floor, floor)

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@ -1,34 +0,0 @@
/*
* Public domain.
*/
#include <machine/asm.h>
#include <libm-alias-float.h>
RCSID("$NetBSD: s_floorf.S,v 1.3 1995/05/09 00:04:32 jtc Exp $")
ENTRY(__floorf)
flds 4(%esp)
subl $32,%esp
cfi_adjust_cfa_offset (32)
fnstenv 4(%esp) /* store fpu environment */
/* We use here %edx although only the low 1 bits are defined.
But none of the operations should care and they are faster
than the 16 bit operations. */
movl $0x400,%edx /* round towards -oo */
orl 4(%esp),%edx
andl $0xf7ff,%edx
movl %edx,(%esp)
fldcw (%esp) /* load modified control word */
frndint /* round */
fldenv 4(%esp) /* restore original environment */
addl $32,%esp
cfi_adjust_cfa_offset (-32)
ret
END (__floorf)
libm_alias_float (__floor, floor)

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@ -0,0 +1,25 @@
/* Largest integral value not greater than argument i386 version.
Copyright (C) 2024 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/>. */
#include <libm-alias-float.h>
#define FUNC __floorf
#define TYPE float
#define FE_OPTION FE_DOWNWARD
#include "s_nearestint_387_template.c"
libm_alias_float (__floor, floor)

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@ -1,39 +0,0 @@
/*
* Public domain.
*/
#include <libm-alias-ldouble.h>
#include <machine/asm.h>
RCSID("$NetBSD: $")
ENTRY(__floorl)
fldt 4(%esp)
subl $32,%esp
cfi_adjust_cfa_offset (32)
fnstenv 4(%esp) /* store fpu environment */
/* We use here %edx although only the low 1 bits are defined.
But none of the operations should care and they are faster
than the 16 bit operations. */
movl $0x400,%edx /* round towards -oo */
orl 4(%esp),%edx
andl $0xf7ff,%edx
movl %edx,(%esp)
fldcw (%esp) /* load modified control word */
frndint /* round */
/* Preserve "invalid" exceptions from sNaN input. */
fnstsw
andl $0x1, %eax
orl %eax, 8(%esp)
fldenv 4(%esp) /* restore original environment */
addl $32,%esp
cfi_adjust_cfa_offset (-32)
ret
END (__floorl)
libm_alias_ldouble (__floor, floor)

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@ -0,0 +1,25 @@
/* Return largest integral value not less than argument. x86 version.
Copyright (C) 2024 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/>. */
#include <libm-alias-ldouble.h>
#define FUNC __floorl
#define TYPE long double
#define FE_OPTION FE_DOWNWARD
#include "s_nearestint_387_template.c"
libm_alias_ldouble (__floor, floor)

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@ -1,33 +0,0 @@
/*
* Public domain.
*/
#include <libm-alias-ldouble.h>
#include <machine/asm.h>
ENTRY(__floorl)
fldt 8(%rsp)
fnstenv -28(%rsp) /* store fpu environment */
/* We use here %edx although only the low 1 bits are defined.
But none of the operations should care and they are faster
than the 16 bit operations. */
movl $0x400,%edx /* round towards -oo */
orl -28(%rsp),%edx
andl $0xf7ff,%edx
movl %edx,-32(%rsp)
fldcw -32(%rsp) /* load modified control word */
frndint /* round */
/* Preserve "invalid" exceptions from sNaN input. */
fnstsw
andl $0x1, %eax
orl %eax, -24(%rsp)
fldenv -28(%rsp) /* restore original environment */
ret
END (__floorl)
libm_alias_ldouble (__floor, floor)