[3/3] math: math: x86 trunc traps when FE_INEXACT is enabled (BZ 31603)
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Commit Message
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.
---
math/Makefile | 2 +
math/test-trunc-except-2.c | 67 +++++++++++++++++++
sysdeps/i386/fpu/{s_trunc.S => s_trunc.c} | 24 ++-----
sysdeps/i386/fpu/{s_truncf.S => s_truncf.c} | 24 ++-----
sysdeps/i386/fpu/s_truncl.S | 40 -----------
.../fpu/s_truncl.S => x86/fpu/s_truncl.c} | 23 ++-----
6 files changed, 87 insertions(+), 93 deletions(-)
create mode 100644 math/test-trunc-except-2.c
rename sysdeps/i386/fpu/{s_trunc.S => s_trunc.c} (69%)
rename sysdeps/i386/fpu/{s_truncf.S => s_truncf.c} (68%)
delete mode 100644 sysdeps/i386/fpu/s_truncl.S
rename sysdeps/{x86_64/fpu/s_truncl.S => x86/fpu/s_truncl.c} (70%)
Comments
On Wed, Apr 3, 2024 at 12:39 PM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
> 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.
> ---
> math/Makefile | 2 +
> math/test-trunc-except-2.c | 67 +++++++++++++++++++
> sysdeps/i386/fpu/{s_trunc.S => s_trunc.c} | 24 ++-----
> sysdeps/i386/fpu/{s_truncf.S => s_truncf.c} | 24 ++-----
> sysdeps/i386/fpu/s_truncl.S | 40 -----------
> .../fpu/s_truncl.S => x86/fpu/s_truncl.c} | 23 ++-----
> 6 files changed, 87 insertions(+), 93 deletions(-)
> create mode 100644 math/test-trunc-except-2.c
> rename sysdeps/i386/fpu/{s_trunc.S => s_trunc.c} (69%)
> rename sysdeps/i386/fpu/{s_truncf.S => s_truncf.c} (68%)
> delete mode 100644 sysdeps/i386/fpu/s_truncl.S
> rename sysdeps/{x86_64/fpu/s_truncl.S => x86/fpu/s_truncl.c} (70%)
>
> diff --git a/math/Makefile b/math/Makefile
> index 121fe2881a..a9fef9e2db 100644
> --- a/math/Makefile
> +++ b/math/Makefile
> @@ -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
>
> diff --git a/math/test-trunc-except-2.c b/math/test-trunc-except-2.c
> new file mode 100644
> index 0000000000..8933c6ab41
> --- /dev/null
> +++ b/math/test-trunc-except-2.c
> @@ -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>
> diff --git a/sysdeps/i386/fpu/s_trunc.S b/sysdeps/i386/fpu/s_trunc.c
> similarity index 69%
> rename from sysdeps/i386/fpu/s_trunc.S
> rename to sysdeps/i386/fpu/s_trunc.c
> index 40e45c9f9c..ac16f4967c 100644
> --- a/sysdeps/i386/fpu/s_trunc.S
> +++ b/sysdeps/i386/fpu/s_trunc.c
> @@ -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)
> diff --git a/sysdeps/i386/fpu/s_truncf.S b/sysdeps/i386/fpu/s_truncf.c
> similarity index 68%
> rename from sysdeps/i386/fpu/s_truncf.S
> rename to sysdeps/i386/fpu/s_truncf.c
> index 0b26e09d61..240d3507ef 100644
> --- a/sysdeps/i386/fpu/s_truncf.S
> +++ b/sysdeps/i386/fpu/s_truncf.c
> @@ -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)
> diff --git a/sysdeps/i386/fpu/s_truncl.S b/sysdeps/i386/fpu/s_truncl.S
> deleted file mode 100644
> index dfd0ca4a57..0000000000
> --- a/sysdeps/i386/fpu/s_truncl.S
> +++ /dev/null
> @@ -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)
> diff --git a/sysdeps/x86_64/fpu/s_truncl.S b/sysdeps/x86/fpu/s_truncl.c
> similarity index 70%
> rename from sysdeps/x86_64/fpu/s_truncl.S
> rename to sysdeps/x86/fpu/s_truncl.c
> index e3d64a84e8..e2bac7fa38 100644
> --- a/sysdeps/x86_64/fpu/s_truncl.S
> +++ b/sysdeps/x86/fpu/s_truncl.c
> @@ -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)
> --
> 2.34.1
>
LGTM.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
Thanks.
Hi HJ,
there is a typo in the subject: "math: math:" should be "math:", no?
Paul
On 04/04/24 02:27, Paul Zimmermann wrote:
> Hi HJ,
>
> there is a typo in the subject: "math: math:" should be "math:", no?
>
Yeah, I will fix it.
@@ -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
new file mode 100644
@@ -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>
similarity index 69%
rename from sysdeps/i386/fpu/s_trunc.S
rename to sysdeps/i386/fpu/s_trunc.c
@@ -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)
similarity index 68%
rename from sysdeps/i386/fpu/s_truncf.S
rename to sysdeps/i386/fpu/s_truncf.c
@@ -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)
deleted file mode 100644
@@ -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)
similarity index 70%
rename from sysdeps/x86_64/fpu/s_truncl.S
rename to sysdeps/x86/fpu/s_truncl.c
@@ -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)