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math: x86 trunc traps when FE_INEXACT is enabled (BZ 31603)

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The implementations of trunc functions using x87 floating point (i386 and
x86_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 16:39:19 -03:00
parent 932544efa4
commit 44ccc2465c
6 changed files with 87 additions and 93 deletions
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2
math/Makefile
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@ -539,6 +539,7 @@ tests = \
test-tgmath-int \
test-tgmath-ret \
test-tgmath2 \
test-trunc-except-2 \
tst-CMPLX \
tst-CMPLX2 \
tst-definitions \
@ -993,6 +994,7 @@ CFLAGS-test-nan-const.c += -fno-builtin
CFLAGS-test-ceil-except-2.c += -fno-builtin
CFLAGS-test-floor-except-2.c += -fno-builtin
CFLAGS-test-trunc-except-2.c += -fno-builtin
include ../Rules

67
math/test-trunc-except-2.c Normal file
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@ -0,0 +1,67 @@
/* Test trunc 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; \
/* trunc must work when traps on "inexact" are enabled. */ \
b = trunc ## 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>

24
sysdeps/i386/fpu/s_trunc.S → sysdeps/i386/fpu/s_trunc.c
View File

@ -1,5 +1,5 @@
/* Truncate double value.
Copyright (C) 1997-2024 Free Software Foundation, Inc.
/* Round to integer, toward zero. 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
@ -16,22 +16,10 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <machine/asm.h>
#include <libm-alias-double.h>
ENTRY(__trunc)
fldl 4(%esp)
subl $32, %esp
cfi_adjust_cfa_offset (32)
fnstenv 4(%esp)
movl $0xc00, %edx
orl 4(%esp), %edx
movl %edx, (%esp)
fldcw (%esp)
frndint
fldenv 4(%esp)
addl $32, %esp
cfi_adjust_cfa_offset (-32)
ret
END(__trunc)
#define FUNC __trunc
#define TYPE double
#define FE_OPTION FE_TOWARDZERO
#include "s_nearestint_387_template.c"
libm_alias_double (__trunc, trunc)

24
sysdeps/i386/fpu/s_truncf.S → sysdeps/i386/fpu/s_truncf.c
View File

@ -1,5 +1,5 @@
/* Truncate float value.
Copyright (C) 1997-2024 Free Software Foundation, Inc.
/* Round to integer, toward zero. 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
@ -16,22 +16,10 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <machine/asm.h>
#include <libm-alias-float.h>
ENTRY(__truncf)
flds 4(%esp)
subl $32, %esp
cfi_adjust_cfa_offset (32)
fnstenv 4(%esp)
movl $0xc00, %edx
orl 4(%esp), %edx
movl %edx, (%esp)
fldcw (%esp)
frndint
fldenv 4(%esp)
addl $32, %esp
cfi_adjust_cfa_offset (-32)
ret
END(__truncf)
#define FUNC __truncf
#define TYPE float
#define FE_OPTION FE_TOWARDZERO
#include "s_nearestint_387_template.c"
libm_alias_float (__trunc, trunc)

40
sysdeps/i386/fpu/s_truncl.S
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@ -1,40 +0,0 @@
/* Truncate long double value.
Copyright (C) 1997-2024 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>
#include <machine/asm.h>
ENTRY(__truncl)
fldt 4(%esp)
subl $32, %esp
cfi_adjust_cfa_offset (32)
fnstenv 4(%esp)
movl $0xc00, %edx
orl 4(%esp), %edx
movl %edx, (%esp)
fldcw (%esp)
frndint
fnstsw
andl $0x1, %eax
orl %eax, 8(%esp)
fldenv 4(%esp)
addl $32, %esp
cfi_adjust_cfa_offset (-32)
ret
END(__truncl)
libm_alias_ldouble (__trunc, trunc)

23
sysdeps/x86_64/fpu/s_truncl.S → sysdeps/x86/fpu/s_truncl.c
View File

@ -1,5 +1,5 @@
/* Truncate long double value.
Copyright (C) 1997-2024 Free Software Foundation, Inc.
/* Round to integer, toward zero. 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
@ -17,20 +17,9 @@
<https://www.gnu.org/licenses/>. */
#include <libm-alias-ldouble.h>
#include <machine/asm.h>
ENTRY(__truncl)
fldt 8(%rsp)
fnstenv -28(%rsp)
movl $0xc00, %edx
orl -28(%rsp), %edx
movl %edx, -32(%rsp)
fldcw -32(%rsp)
frndint
fnstsw
andl $0x1, %eax
orl %eax, -24(%rsp)
fldenv -28(%rsp)
ret
END(__truncl)
#define FUNC __truncl
#define TYPE long double
#define FE_OPTION FE_TOWARDZERO
#include "s_nearestint_387_template.c"
libm_alias_ldouble (__trunc, trunc)