arm64: klib: Optimised memory functions

This patch introduces AArch64-specific memory functions (memcpy,
memmove, memchr, memset). These functions are not optimised for any CPU
implementation but can be used as a starting point once hardware is
available.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/lib/memmove.S

@@ -0,0 +1,57 @@
+/*
+ * Copyright (C) 2013 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * 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, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/linkage.h>
+#include <asm/assembler.h>
+
+/*
+ * Move a buffer from src to test (alignment handled by the hardware).
+ * If dest <= src, call memcpy, otherwise copy in reverse order.
+ *
+ * Parameters:
+ *	x0 - dest
+ *	x1 - src
+ *	x2 - n
+ * Returns:
+ *	x0 - dest
+ */
+ENTRY(memmove)
+	cmp	x0, x1
+	b.ls	memcpy
+	add	x4, x0, x2
+	add	x1, x1, x2
+	subs	x2, x2, #8
+	b.mi	2f
+1:	ldr	x3, [x1, #-8]!
+	subs	x2, x2, #8
+	str	x3, [x4, #-8]!
+	b.pl	1b
+2:	adds	x2, x2, #4
+	b.mi	3f
+	ldr	w3, [x1, #-4]!
+	sub	x2, x2, #4
+	str	w3, [x4, #-4]!
+3:	adds	x2, x2, #2
+	b.mi	4f
+	ldrh	w3, [x1, #-2]!
+	sub	x2, x2, #2
+	strh	w3, [x4, #-2]!
+4:	adds	x2, x2, #1
+	b.mi	5f
+	ldrb	w3, [x1, #-1]
+	strb	w3, [x4, #-1]
+5:	ret
+ENDPROC(memmove)