S390: Implement mempcpy with help of memcpy. [BZ #19765]

There exist optimized memcpy functions on s390, but no optimized mempcpy.
This patch adds mempcpy entry points in memcpy.S files, which
use the memcpy implementation. Now mempcpy itself is also an IFUNC function
as memcpy is and the variants are listed in ifunc-impl-list.c.

The s390 string.h does not define _HAVE_STRING_ARCH_mempcpy.
Instead mempcpy string/string.h inlines memcpy() + n.
If n is constant and small enough, GCC emits instructions like mvi or mvc
and avoids the function call to memcpy.
If n is not constant, then memcpy is called and n is added afterwards.
If _HAVE_STRING_ARCH_mempcpy would be defined, mempcpy would be called in
every case.

According to PR70140 "Inefficient expansion of __builtin_mempcpy"
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70140) GCC should handle a
call to mempcpy in the same way as memcpy. Then either the mempcpy macro
in string/string.h has to be removed or _HAVE_STRING_ARCH_mempcpy has to
be defined for S390.

ChangeLog:

	[BZ #19765]
	* sysdeps/s390/mempcpy.S: New File.
	* sysdeps/s390/multiarch/mempcpy.c: Likewise.
	* sysdeps/s390/multiarch/Makefile (sysdep_routines): Add mempcpy.
	* sysdeps/s390/multiarch/ifunc-impl-list.c (__libc_ifunc_impl_list):
	Add mempcpy variants.
	* sysdeps/s390/s390-32/memcpy.S: Add mempcpy entry point.
	(memcpy): Adjust to be usable from mempcpy entry point.
	(__memcpy_mvcle): Likewise.
	* sysdeps/s390/s390-64/memcpy.S: Likewise.
	* sysdeps/s390/s390-32/multiarch/memcpy-s390.S: Add entry points
	____mempcpy_z196, ____mempcpy_z10 and add __GI_ symbols for mempcpy.
	(__memcpy_z196): Adjust to be usable from mempcpy entry point.
	(__memcpy_z10): Likewise.
	* sysdeps/s390/s390-64/multiarch/memcpy-s390x.S: Likewise.

3 files changed, 35 insertions, 1 deletions

diff --git a/sysdeps/s390/multiarch/Makefile b/sysdeps/s390/multiarch/Makefile
index 0805b07..89324ca 100644
--- a/sysdeps/s390/multiarch/Makefile
+++ b/sysdeps/s390/multiarch/Makefile
@@ -18,7 +18,8 @@ sysdep_routines += strlen strlen-vx strlen-c \
 		   memchr memchr-vx \
 		   rawmemchr rawmemchr-vx rawmemchr-c \
 		   memccpy memccpy-vx memccpy-c \
-		   memrchr memrchr-vx memrchr-c
+		   memrchr memrchr-vx memrchr-c \
+		   mempcpy
 endif
 
 ifeq ($(subdir),wcsmbs)
diff --git a/sysdeps/s390/multiarch/ifunc-impl-list.c b/sysdeps/s390/multiarch/ifunc-impl-list.c
index 62a4359..89898ec 100644
--- a/sysdeps/s390/multiarch/ifunc-impl-list.c
+++ b/sysdeps/s390/multiarch/ifunc-impl-list.c
@@ -69,6 +69,13 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
 			      S390_IS_Z10 (stfle_bits), __memcpy_z10)
 	      IFUNC_IMPL_ADD (array, i, memcpy, 1, __memcpy_default))
 
+  IFUNC_IMPL (i, name, mempcpy,
+	      IFUNC_IMPL_ADD (array, i, mempcpy,
+			      S390_IS_Z196 (stfle_bits), ____mempcpy_z196)
+	      IFUNC_IMPL_ADD (array, i, mempcpy,
+			      S390_IS_Z10 (stfle_bits), ____mempcpy_z10)
+	      IFUNC_IMPL_ADD (array, i, mempcpy, 1, ____mempcpy_default))
+
 #endif /* SHARED */
 
 #ifdef HAVE_S390_VX_ASM_SUPPORT
diff --git a/sysdeps/s390/multiarch/mempcpy.c b/sysdeps/s390/multiarch/mempcpy.c
new file mode 100644
index 0000000..34d8329
--- /dev/null
+++ b/sysdeps/s390/multiarch/mempcpy.c
@@ -0,0 +1,26 @@
+/* Multiple versions of mempcpy.
+   Copyright (C) 2016 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/>.  */
+
+
+#if defined SHARED && IS_IN (libc)
+# include <ifunc-resolve.h>
+s390_libc_ifunc (__mempcpy)
+
+__asm__ (".weak mempcpy\n\t"
+	 ".set mempcpy,__mempcpy\n\t");
+#endif