arm: Implement memchr ifunc selection in C

This patch refactor ARM memchr ifunc selector to a C implementation.
No functional change is expected, including ifunc resolution rules.

It also reorganize the ifunc options code:

  1. The memchr_impl.S is renamed to memchr_neon.S and multiple
     compilation options (which route to armv6t2/memchr one) is
     removed.  The code to build if __ARM_NEON__ is defined is
     also simplified.

  2. A memchr_noneon is added (which as build along previous ifunc
     resolution) and includes the armv6t2 direct.

  3. Same as 2. for loader object.

Alongside the aforementioned changes, it also some cleanus:

  - Internal memchr definition (__GI_memcpy) is now a hidden
    symbol.
  - No need to create hidden definition for the ifunc variants.

Checked on armv7-linux-gnueabihf and with a build for arm-linux-gnueabi,
arm-linux-gnueabihf with and without multiarch support and with both
GCC 7.1 and GCC mainline.

	* sysdeps/arm/armv7/multiarch/Makefile [$(subdir) = string]
	(sysdeps_routines): Add memchr_noneon.
	* sysdeps/arm/armv7/multiarch/ifunc-memchr.h: New file.
	* sysdeps/arm/armv7/multiarch/memchr_noneon.S: Likewise.
	* sysdeps/arm/armv7/multiarch/rtld-memchr.S: Likewise.
	* sysdeps/arm/armv7/multiarch/memchr.S: Remove file.
	* sysdeps/arm/armv7/multiarch/memchr.c: New file.
	* sysdeps/arm/armv7/multiarch/memchr_impl.S: Move to ...
	* sysdeps/arm/armv7/multiarch/memchr_neon.S: ... here.

Signed-off-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>

1 files changed, 35 insertions, 0 deletions

diff --git a/sysdeps/arm/armv7/multiarch/memchr.c b/sysdeps/arm/armv7/multiarch/memchr.c
new file mode 100644
index 0000000000..906bcd5b5b
--- /dev/null
+++ b/sysdeps/arm/armv7/multiarch/memchr.c
@@ -0,0 +1,35 @@
+/* Multiple versions of memchr.
+   All versions must be listed in ifunc-impl-list.c.
+   Copyright (C) 2017 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/>.  */
+
+/* For __ARM_NEON__ memchr_neon.S defines memchr directly and ifunc
+   is not used.  */
+#if IS_IN (libc) && !defined (__ARM_NEON__)
+# define memchr __redirect_memchr
+# include <string.h>
+# undef memchr
+
+# include <arm-ifunc.h>
+
+# define SYMBOL_NAME memchr
+# include "ifunc-memchr.h"
+
+arm_libc_ifunc_redirected (__redirect_memchr, memchr, IFUNC_SELECTOR);
+
+arm_libc_ifunc_hidden_def (__redirect_memchr, memchr);
+#endif