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* [glibc] math: x86 trunc traps when FE_INEXACT is enabled (BZ 31603)
@ 2024-04-04 17:36 Adhemerval Zanella
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From: Adhemerval Zanella @ 2024-04-04 17:36 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=44ccc2465c6af5bd811d8258bf744aaafd5392fc
commit 44ccc2465c6af5bd811d8258bf744aaafd5392fc
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Wed Apr 3 16:39:19 2024 -0300
math: x86 trunc traps when FE_INEXACT is enabled (BZ 31603)
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>
Diff:
---
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 -------------
.../{x86_64/fpu/s_truncl.S => x86/fpu/s_truncl.c} | 23 ++------
6 files changed, 87 insertions(+), 93 deletions(-)
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)
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