For reference, the attached commit (commitdiff [1]) from glibc shows the
changes made in string/string.h.
[1]
https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=05a910f7b420c2b831f35ba90e61c80f001c0606
>From 05a910f7b420c2b831f35ba90e61c80f001c0606 Mon Sep 17 00:00:00 2001
From: Wilco Dijkstra <wdijk...@arm.com>
Date: Wed, 5 Aug 2015 15:58:15 +0100
Subject: [PATCH] Improve performance of mempcpy by inlining and using memcpy. Enable
this for all targets except sparc which has an optimized mempcpy
implementation.
---
ChangeLog | 6 ++++++
string/string.h | 19 +++++++++++++++++++
sysdeps/sparc/bits/string.h | 3 +++
3 files changed, 28 insertions(+), 0 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 65592c3..4a45eed 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
2015-08-05 Wilco Dijkstra <wdijk...@arm.com>
+ * string/string.h: (mempcpy): Redirect to __mempcpy_inline.
+ (__mempcpy): Likewise. (__mempcpy_inline): New inline function.
+ * sysdeps/sparc/bits/string.h: (_HAVE_STRING_ARCH_mempcpy): Define.
+
+2015-08-05 Wilco Dijkstra <wdijk...@arm.com>
+
* string/memccpy.c (memccpy):
Improve performance by using memchr/memcpy/__mempcpy.
diff --git a/string/string.h b/string/string.h
index 54a4d39..3ab7103 100644
--- a/string/string.h
+++ b/string/string.h
@@ -636,6 +636,25 @@ extern char *basename (const char *__filename) __THROW __nonnull ((1));
# endif
#endif
+#if defined __USE_GNU && defined __OPTIMIZE__ \
+ && defined __extern_always_inline && __GNUC_PREREQ (3,2)
+# if !defined _FORCE_INLINES && !defined _HAVE_STRING_ARCH_mempcpy
+
+#undef mempcpy
+#undef __mempcpy
+#define mempcpy(dest, src, n) __mempcpy_inline (dest, src, n)
+#define __mempcpy(dest, src, n) __mempcpy_inline (dest, src, n)
+
+__extern_always_inline void *
+__mempcpy_inline (void *__restrict __dest,
+ const void *__restrict __src, size_t __n)
+{
+ return (char *) memcpy (__dest, __src, __n) + __n;
+}
+
+# endif
+#endif
+
__END_DECLS
#endif /* string.h */
diff --git a/sysdeps/sparc/bits/string.h b/sysdeps/sparc/bits/string.h
index 36fbb4c..4eb9447 100644
--- a/sysdeps/sparc/bits/string.h
+++ b/sysdeps/sparc/bits/string.h
@@ -26,3 +26,6 @@
/* sparc32 and sparc64 strchr(x, '\0') perform better than
__rawmemchr(x, '\0'). */
#define _HAVE_STRING_ARCH_strchr 1
+
+/* Don't inline mempcpy into memcpy as sparc has an optimized mempcpy. */
+#define _HAVE_STRING_ARCH_mempcpy 1
--
1.7.1