[AArch64] Add inlines for signbit
Commit Message
Add AArch64 inlines for __signbit, __signbitf and __signbitl which default to the GCC builtin
functions.
Is there a reason this couldn't be done by default in math.h similar to isgreater (unlike
__builtin_isinf et al, GCC implements signbit efficiently and correctly).
OK for commit?
2015-04-15 Wilco Dijkstra <wdijkstr@arm.com>
* sysdeps/aarch64/fpu/bits/mathinline.h: New file.
(__signbit): New function, use __builtin_signbit.
(__signbitf): Likewise. (__signbitl): Likewise.
---
sysdeps/aarch64/fpu/bits/mathinline.h | 49 +++++++++++++++++++++++++++++++++++
1 file changed, 49 insertions(+)
create mode 100644 sysdeps/aarch64/fpu/bits/mathinline.h
Comments
On Wed, 15 Apr 2015, Wilco Dijkstra wrote:
> Is there a reason this couldn't be done by default in math.h similar to isgreater (unlike
> __builtin_isinf et al, GCC implements signbit efficiently and correctly).
It is, however, not type-generic in GCC
<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=36757>, so you'd still need
to have a macro expansion checking sizeof.
> Joseph Myers wrote:
> On Wed, 15 Apr 2015, Wilco Dijkstra wrote:
>
> > Is there a reason this couldn't be done by default in math.h similar to isgreater (unlike
> > __builtin_isinf et al, GCC implements signbit efficiently and correctly).
>
> It is, however, not type-generic in GCC
> <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=36757>, so you'd still need
> to have a macro expansion checking sizeof.
Yes indeed. However the issue is how to deal with the targets that currently
define inlines. Would it be reasonable just to leave them and add a signbit
expansion for GCC >= 3.0 that directly uses the builtins?
(if we define __signbit(f/l) to be __builtin_signbit(f/l), things may go
wrong as the various mathinlines don't do an undef first).
Eg. in math.h:
#if defined __USE_ISOC99 && __GNUC_PREREQ(2,97)
# undef signbit
# ifdef __NO_LONG_DOUBLE_MATH
# define signbit(x) \
(sizeof (x) == sizeof (float) ? __builtin_signbitf (x) : __builtin_signbit (x))
# else
...
Wilco
On Mon, 27 Apr 2015, Wilco Dijkstra wrote:
> > Joseph Myers wrote:
> > On Wed, 15 Apr 2015, Wilco Dijkstra wrote:
> >
> > > Is there a reason this couldn't be done by default in math.h similar to isgreater (unlike
> > > __builtin_isinf et al, GCC implements signbit efficiently and correctly).
> >
> > It is, however, not type-generic in GCC
> > <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=36757>, so you'd still need
> > to have a macro expansion checking sizeof.
>
> Yes indeed. However the issue is how to deal with the targets that currently
> define inlines. Would it be reasonable just to leave them and add a signbit
> expansion for GCC >= 3.0 that directly uses the builtins?
> (if we define __signbit(f/l) to be __builtin_signbit(f/l), things may go
> wrong as the various mathinlines don't do an undef first).
I'd think defining __signbit to __builtin_signbit, etc., would be
appropriate (with conditionals in the mathinline.h files to disable their
local definitions for GCC versions where __builtin_signbit works and is at
least as good for that architecture). It would also cover cases within
glibc that directly use the __signbit etc. names (although arguably those
should move to using the type-generic macros; likewise direct uses of e.g.
__finite, __isnan).
new file mode 100644
@@ -0,0 +1,49 @@
+/* Inline math functions for AArch64.
+ Copyright (C) 2015 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
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _MATH_H
+# error "Never use <bits/mathinline.h> directly; include <math.h> instead."
+#endif
+
+#ifndef __extern_inline
+# define __MATH_INLINE __inline
+#else
+# define __MATH_INLINE __extern_inline
+#endif
+
+#ifdef __USE_ISOC99
+
+__MATH_INLINE int
+__NTH (__signbitf (float __x))
+{
+ return __builtin_signbitf (__x);
+}
+
+__MATH_INLINE int
+__NTH (__signbit (double __x))
+{
+ return __builtin_signbit (__x);
+}
+
+__MATH_INLINE int
+__NTH (__signbitl (long double __x))
+{
+ return __builtin_signbitl (__x);
+}
+
+#endif /* C99 */