1 /*
2  * Copyright 2011 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 
19 #undef strlen
20 
strlen(const char * s)21 size_t strlen(const char *s)
22 {
23 	/* Get an aligned pointer. */
24 	const uintptr_t s_int = (uintptr_t) s;
25 	const uint64_t *p = (const uint64_t *)(s_int & -8);
26 
27 	/* Read the first word, but force bytes before the string to be nonzero.
28 	 * This expression works because we know shift counts are taken mod 64.
29 	 */
30 	uint64_t v = *p | ((1ULL << (s_int << 3)) - 1);
31 
32 	uint64_t bits;
33 	while ((bits = __insn_v1cmpeqi(v, 0)) == 0)
34 		v = *++p;
35 
36 	return ((const char *)p) + (__insn_ctz(bits) >> 3) - s;
37 }
38 EXPORT_SYMBOL(strlen);
39