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>

3 files changed, 12 insertions, 76 deletions

diff --git a/sysdeps/i386/fpu/s_trunc.S b/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
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)