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>

9 files changed, 144 insertions, 140 deletions

diff --git a/math/Makefile b/math/Makefile
index d2a740e..121fe28 100644
--- a/math/Makefile
+++ b/math/Makefile
@@ -511,6 +511,7 @@ tests = \
   test-fetestexceptflag \
   test-fexcept \
   test-fexcept-traps \
+  test-floor-except-2 \
   test-flt-eval-method \
   test-fp-ilogb-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-ceil-except-2.c += -fno-builtin
+CFLAGS-test-floor-except-2.c += -fno-builtin
 
 include ../Rules
 
diff --git a/math/test-floor-except-2.c b/math/test-floor-except-2.c
new file mode 100644
index 0000000..d99e835
--- /dev/null
+++ b/math/test-floor-except-2.c
@@ -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>
diff --git a/sysdeps/i386/fpu/s_floor.S b/sysdeps/i386/fpu/s_floor.S
deleted file mode 100644
index 7143fdc..0000000
--- a/sysdeps/i386/fpu/s_floor.S
+++ /dev/null
@@ -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	$32,%esp
-	cfi_adjust_cfa_offset (-32)
-	ret
-END (__floor)
-libm_alias_double (__floor, floor)
diff --git a/sysdeps/i386/fpu/s_floor.c b/sysdeps/i386/fpu/s_floor.c
new file mode 100644
index 0000000..cc50e33
--- /dev/null
+++ b/sysdeps/i386/fpu/s_floor.c
@@ -0,0 +1,25 @@
+/* Return smallest integral value not less than argument.  i386 version.
+   Copyright (C) 2024 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <libm-alias-double.h>
+
+#define FUNC       __floor
+#define TYPE       double
+#define FE_OPTION  FE_DOWNWARD
+#include "s_nearestint_387_template.c"
+libm_alias_double (__floor, floor)
diff --git a/sysdeps/i386/fpu/s_floorf.S b/sysdeps/i386/fpu/s_floorf.S
deleted file mode 100644
index 8fad9c0..0000000
--- a/sysdeps/i386/fpu/s_floorf.S
+++ /dev/null
@@ -1,34 +0,0 @@
-/*
- * Public domain.
- */
-
-#include <machine/asm.h>
-#include <libm-alias-float.h>
-
-RCSID("$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	$32,%esp
-	cfi_adjust_cfa_offset (-32)
-	ret
-END (__floorf)
-libm_alias_float (__floor, floor)
diff --git a/sysdeps/i386/fpu/s_floorf.c b/sysdeps/i386/fpu/s_floorf.c
new file mode 100644
index 0000000..fa9454e
--- /dev/null
+++ b/sysdeps/i386/fpu/s_floorf.c
@@ -0,0 +1,25 @@
+/* Largest integral value not greater than argument  i386 version.
+   Copyright (C) 2024 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <libm-alias-float.h>
+
+#define FUNC       __floorf
+#define TYPE       float
+#define FE_OPTION  FE_DOWNWARD
+#include "s_nearestint_387_template.c"
+libm_alias_float (__floor, floor)
diff --git a/sysdeps/i386/fpu/s_floorl.S b/sysdeps/i386/fpu/s_floorl.S
deleted file mode 100644
index 3ec28b4..0000000
--- a/sysdeps/i386/fpu/s_floorl.S
+++ /dev/null
@@ -1,39 +0,0 @@
-/*
- * Public domain.
- */
-
-#include <libm-alias-ldouble.h>
-#include <machine/asm.h>
-
-RCSID("$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)
diff --git a/sysdeps/x86/fpu/s_floorl.c b/sysdeps/x86/fpu/s_floorl.c
new file mode 100644
index 0000000..9c92d33
--- /dev/null
+++ b/sysdeps/x86/fpu/s_floorl.c
@@ -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)
diff --git a/sysdeps/x86_64/fpu/s_floorl.S b/sysdeps/x86_64/fpu/s_floorl.S
deleted file mode 100644
index b74d1a4..0000000
--- a/sysdeps/x86_64/fpu/s_floorl.S
+++ /dev/null
@@ -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)