nds32: Library functions

This patch add support for various library functions.

Signed-off-by: Vincent Chen <vincentc@andestech.com>
Signed-off-by: Greentime Hu <greentime@andestech.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

arch/nds32/lib/memset.S

@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2005-2017 Andes Technology Corporation
+
+#include <linux/linkage.h>
+
+	.text
+ENTRY(memset)
+	move	$r5, $r0		! Return value
+	beqz	$r2, end_memset		! Exit when len = 0
+	srli	$p1, $r2, 2		! $p1 is how many words to copy
+	andi	$r2, $r2, 3		! How many bytes are less than a word
+	beqz	$p1, byte_set		! When n is less than a word
+
+	! set $r1 from ??????ab to abababab
+	andi	$r1, $r1, #0x00ff	! $r1 = 000000ab
+	slli	$p0, $r1, #8		! $p0 = 0000ab00
+	or	$r1, $r1, $p0		! $r1 = 0000abab
+	slli	$p0, $r1, #16		! $p0 = abab0000
+	or	$r1, $r1, $p0		! $r1 = abababab
+word_set:
+	addi	$p1, $p1, #-1		! How many words left to copy
+	smw.bim	$r1, [$r0], $r1		! Copy the word to det
+	bnez	$p1, word_set		! Still words to set, continue looping
+	beqz	$r2, end_memset		! No left byte to set
+byte_set:				! Less than 4 bytes left to set
+	addi	$r2, $r2, #-1		! Decrease len by 1
+	sbi.bi	$r1, [$r0], #1		! Set data of the next byte to $r1
+	bnez	$r2, byte_set		! Still bytes left to set
+end_memset:
+	move	$r0, $r5
+	ret
+
+ENDPROC(memset)