Accelerate memcpy() by around 32% on large, dword-aligned copies.

src/arch/i386/core/i386_string.c

@@ -0,0 +1,63 @@
+/*
+ * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program 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
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+/** @file
+ *
+ * Optimised string operations
+ *
+ */
+
+#include <string.h>
+
+/**
+ * Copy memory area
+ *
+ * @v dest		Destination address
+ * @v src		Source address
+ * @v len		Length
+ * @ret dest		Destination address
+ */
+__attribute__ (( regparm ( 3 ) )) void * __memcpy ( void *dest,
+						    const void *src,
+						    size_t len ) {
+	void *edi = dest;
+	const void *esi = src;
+	int discard_ecx;
+
+	/* We often do large dword-aligned and dword-length block
+	 * moves.  Using movsl rather than movsb speeds these up by
+	 * around 32%.
+	 */
+	if ( len >> 2 ) {
+		__asm__ __volatile__ ( "rep movsl"
+				       : "=&D" ( edi ), "=&S" ( esi ),
+				         "=&c" ( discard_ecx )
+				       : "0" ( edi ), "1" ( esi ),
+				         "2" ( len >> 2 )
+				       : "memory" );
+	}
+	if ( len & 0x02 ) {
+		__asm__ __volatile__ ( "movsw" : "=&D" ( edi ), "=&S" ( esi )
+				       : "0" ( edi ), "1" ( esi ) : "memory" );
+	}
+	if ( len & 0x01 ) {
+		__asm__ __volatile__ ( "movsb" : "=&D" ( edi ), "=&S" ( esi )
+				       : "0" ( edi ), "1" ( esi ) : "memory" );
+	}
+	return dest;
+}

src/arch/i386/include/bits/string.h

@@ -22,6 +22,12 @@
  */
 
 #define __HAVE_ARCH_MEMCPY
+
+extern __attribute__ (( regparm ( 3 ) )) void * __memcpy ( void *dest,
+							   const void *src,
+							   size_t len );
+
+#if 0
 static inline __attribute__ (( always_inline )) void *
 __memcpy ( void *dest, const void *src, size_t len ) {
 	int d0, d1, d2;
@@ -31,6 +37,7 @@ __memcpy ( void *dest, const void *src, size_t len ) {
 			       : "memory" );
 	return dest; 
 }
+#endif
 
 static inline __attribute__ (( always_inline )) void *
 __constant_memcpy ( void *dest, const void *src, size_t len ) {