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
20char *strchr(const char *s, int c)
21{
22	int z, g;
23
24	/* Get an aligned pointer. */
25	const uintptr_t s_int = (uintptr_t) s;
26	const uint64_t *p = (const uint64_t *)(s_int & -8);
27
28	/* Create eight copies of the byte for which we are looking. */
29	const uint64_t goal = copy_byte(c);
30
31	/* Read the first aligned word, but force bytes before the string to
32	 * match neither zero nor goal (we make sure the high bit of each
33	 * byte is 1, and the low 7 bits are all the opposite of the goal
34	 * byte).
35	 */
36	const uint64_t before_mask = MASK(s_int);
37	uint64_t v = (*p | before_mask) ^ (goal & __insn_v1shrui(before_mask, 1));
38
39	uint64_t zero_matches, goal_matches;
40	while (1) {
41		/* Look for a terminating '\0'. */
42		zero_matches = __insn_v1cmpeqi(v, 0);
43
44		/* Look for the goal byte. */
45		goal_matches = __insn_v1cmpeq(v, goal);
46
47		if (__builtin_expect((zero_matches | goal_matches) != 0, 0))
48			break;
49
50		v = *++p;
51	}
52
53	z = CFZ(zero_matches);
54	g = CFZ(goal_matches);
55
56	/* If we found c before '\0' we got a match. Note that if c == '\0'
57	 * then g == z, and we correctly return the address of the '\0'
58	 * rather than NULL.
59	 */
60	return (g <= z) ? ((char *)p) + (g >> 3) : NULL;
61}
62EXPORT_SYMBOL(strchr);
63