[x86_64] Add support for compilation as an x86_64 binary

Currently the only supported platform for x86_64 is EFI.

Building an EFI64 gPXE requires a version of gcc that supports
__attribute__((ms_abi)).  This currently means a development build of
gcc; the feature should be present when gcc 4.4 is released.

In the meantime; you can grab a suitable gcc tree from

  git://git.etherboot.org/scm/people/mcb30/gcc/.git

src/arch/x86/core/x86_string.c

@@ -0,0 +1,61 @@
+/*
+ * 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
+ */
+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;
+}