1/*
2 * Copyright 2010 Tilera Corporation. All Rights Reserved.
3 *
4 *   This program is free software; you can redistribute it and/or
5 *   modify it under the terms of the GNU General Public License
6 *   as published by the Free Software Foundation, version 2.
7 *
8 *   This program is distributed in the hope that it will be useful, but
9 *   WITHOUT ANY WARRANTY; without even the implied warranty of
10 *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
11 *   NON INFRINGEMENT.  See the GNU General Public License for
12 *   more details.
13 */
14
15#include <linux/types.h>
16#include <linux/string.h>
17#include <linux/module.h>
18
19void *memmove(void *dest, const void *src, size_t n)
20{
21	if ((const char *)src >= (char *)dest + n
22	    || (char *)dest >= (const char *)src + n) {
23		/* We found no overlap, so let memcpy do all the heavy
24		 * lifting (prefetching, etc.)
25		 */
26		return memcpy(dest, src, n);
27	}
28
29	if (n != 0) {
30		const uint8_t *in;
31		uint8_t x;
32		uint8_t *out;
33		int stride;
34
35		if (src < dest) {
36			/* copy backwards */
37			in = (const uint8_t *)src + n - 1;
38			out = (uint8_t *)dest + n - 1;
39			stride = -1;
40		} else {
41			/* copy forwards */
42			in = (const uint8_t *)src;
43			out = (uint8_t *)dest;
44			stride = 1;
45		}
46
47		/* Manually software-pipeline this loop. */
48		x = *in;
49		in += stride;
50
51		while (--n != 0) {
52			*out = x;
53			out += stride;
54			x = *in;
55			in += stride;
56		}
57
58		*out = x;
59	}
60
61	return dest;
62}
63EXPORT_SYMBOL(memmove);
64