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#include "string-endian.h"
19
20void *memchr(const void *s, int c, size_t n)
21{
22	const uint64_t *last_word_ptr;
23	const uint64_t *p;
24	const char *last_byte_ptr;
25	uintptr_t s_int;
26	uint64_t goal, before_mask, v, bits;
27	char *ret;
28
29	if (__builtin_expect(n == 0, 0)) {
30		/* Don't dereference any memory if the array is empty. */
31		return NULL;
32	}
33
34	/* Get an aligned pointer. */
35	s_int = (uintptr_t) s;
36	p = (const uint64_t *)(s_int & -8);
37
38	/* Create eight copies of the byte for which we are looking. */
39	goal = copy_byte(c);
40
41	/* Read the first word, but munge it so that bytes before the array
42	 * will not match goal.
43	 */
44	before_mask = MASK(s_int);
45	v = (*p | before_mask) ^ (goal & before_mask);
46
47	/* Compute the address of the last byte. */
48	last_byte_ptr = (const char *)s + n - 1;
49
50	/* Compute the address of the word containing the last byte. */
51	last_word_ptr = (const uint64_t *)((uintptr_t) last_byte_ptr & -8);
52
53	while ((bits = __insn_v1cmpeq(v, goal)) == 0) {
54		if (__builtin_expect(p == last_word_ptr, 0)) {
55			/* We already read the last word in the array,
56			 * so give up.
57			 */
58			return NULL;
59		}
60		v = *++p;
61	}
62
63	/* We found a match, but it might be in a byte past the end
64	 * of the array.
65	 */
66	ret = ((char *)p) + (CFZ(bits) >> 3);
67	return (ret <= last_byte_ptr) ? ret : NULL;
68}
69EXPORT_SYMBOL(memchr);
70