1// SPDX-License-Identifier: GPL-2.0
2// Copyright (C) 2005-2017 Andes Technology Corporation
3
4#include <linux/linkage.h>
5
6/*
7  void *memmove(void *dst, const void *src, int n);
8
9  dst: $r0
10  src: $r1
11  n  : $r2
12  ret: $r0 - pointer to the memory area dst.
13*/
14	.text
15
16ENTRY(memmove)
17	move	$r5, $r0		! Set return value = det
18	beq	$r0, $r1, exit_memcpy	! Exit when det = src
19	beqz	$r2, exit_memcpy	! Exit when n = 0
20	pushm	$t0, $t1		! Save reg
21	srli	$p1, $r2, #2		! $p1 is how many words to copy
22
23	! Avoid data lost when memory overlap
24	! Copy data reversely when src < dst
25	slt	$p0, $r0, $r1		! check if $r0 < $r1
26	beqz	$p0, do_reverse		! branch if dst > src
27
28	! No reverse, dst < src
29	andi	$r2, $r2, #3		! How many bytes are less than a word
30	li	$t0, #1			! Determining copy direction in byte_cpy
31	beqz	$p1, byte_cpy		! When n is less than a word
32
33word_cpy:
34	lmw.bim	$p0, [$r1], $p0		! Read a word from src
35	addi	$p1, $p1, #-1		! How many words left to copy
36	smw.bim	$p0, [$r0], $p0		! Copy the word to det
37	bnez	$p1, word_cpy		! If remained words > 0
38	beqz	$r2, end_memcpy		! No left bytes to copy
39	b	byte_cpy
40
41do_reverse:
42	add	$r0, $r0, $r2		! Start with the end of $r0
43	add	$r1, $r1, $r2		! Start with the end of $r1
44	andi	$r2, $r2, #3		! How many bytes are less than a word
45	li	$t0, #-1		! Determining copy direction in byte_cpy
46	beqz	$p1, reverse_byte_cpy	! When n is less than a word
47
48reverse_word_cpy:
49	lmw.adm	$p0, [$r1], $p0		! Read a word from src
50	addi	$p1, $p1, #-1		! How many words left to copy
51	smw.adm	$p0, [$r0], $p0		! Copy the word to det
52	bnez	$p1, reverse_word_cpy	! If remained words > 0
53	beqz	$r2, end_memcpy		! No left bytes to copy
54
55reverse_byte_cpy:
56	addi	$r0, $r0, #-1
57	addi	$r1, $r1, #-1
58byte_cpy:				! Less than 4 bytes to copy now
59	lb.bi	$p0, [$r1], $t0		! Read a byte from src
60	addi	$r2, $r2, #-1		! How many bytes left to copy
61	sb.bi	$p0, [$r0], $t0		! copy the byte to det
62	bnez	$r2, byte_cpy		! If remained bytes > 0
63
64end_memcpy:
65	popm	$t0, $t1
66exit_memcpy:
67	move	$r0, $r5
68	ret
69
70ENDPROC(memmove)
71