[PATCH] Inline mempcpy

[Wilco Dijkstra]

> Joseph Myers wrote:
> On Mon, 18 May 2015, Wilco Dijkstra wrote:
> 
> This seems plausible, subject to getting per-architecture agreement (for
> each architecture with mempcpy.S) on whether to define
> _HAVE_STRING_ARCH_mempcpy.  Although there may be the question of whether
> __extern_always_inline should be defined at all for !__GNUC_PREREQ (3,2)
> (i.e. when the always_inline attribute isn't supported).

It would be good to fix the *always_inline defines, but I for now I've added
an extra check for __GNUC_PREREQ (3,2) to be sure we don't fail to inline on
really old GCCs. So here's the actual patch - I've disabled inlining for SPARC, 
and from previous comments it seems people prefer the inline mempcpy on x64/x86 
and PPC (I've included the maintainers for those arches to agree/veto).

OK for commit?

Wilco

ChangeLog: 
2015-05-20  Wilco Dijkstra  <wdijkstr@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.

---
 string/string.h             | 19 +++++++++++++++++++
 sysdeps/sparc/bits/string.h |  3 +++
 2 files changed, 22 insertions(+)

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
-- 
1.9.1