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
19#undef strchr
20
21char *strchr(const char *s, int c)
22{
23	int z, g;
24
25	/* Get an aligned pointer. */
26	const uintptr_t s_int = (uintptr_t) s;
27	const uint32_t *p = (const uint32_t *)(s_int & -4);
28
29	/* Create four copies of the byte for which we are looking. */
30	const uint32_t goal = 0x01010101 * (uint8_t) c;
31
32	/* Read the first aligned word, but force bytes before the string to
33	 * match neither zero nor goal (we make sure the high bit of each
34	 * byte is 1, and the low 7 bits are all the opposite of the goal
35	 * byte).
36	 *
37	 * Note that this shift count expression works because we know shift
38	 * counts are taken mod 32.
39	 */
40	const uint32_t before_mask = (1 << (s_int << 3)) - 1;
41	uint32_t v = (*p | before_mask) ^ (goal & __insn_shrib(before_mask, 1));
42
43	uint32_t zero_matches, goal_matches;
44	while (1) {
45		/* Look for a terminating '\0'. */
46		zero_matches = __insn_seqb(v, 0);
47
48		/* Look for the goal byte. */
49		goal_matches = __insn_seqb(v, goal);
50
51		if (__builtin_expect(zero_matches | goal_matches, 0))
52			break;
53
54		v = *++p;
55	}
56
57	z = __insn_ctz(zero_matches);
58	g = __insn_ctz(goal_matches);
59
60	/* If we found c before '\0' we got a match. Note that if c == '\0'
61	 * then g == z, and we correctly return the address of the '\0'
62	 * rather than NULL.
63	 */
64	return (g <= z) ? ((char *)p) + (g >> 3) : NULL;
65}
66EXPORT_SYMBOL(strchr);

 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
 
 
19char *strchr(const char *s, int c)
20{
21	int z, g;
22
23	/* Get an aligned pointer. */
24	const uintptr_t s_int = (uintptr_t) s;
25	const uint32_t *p = (const uint32_t *)(s_int & -4);
26
27	/* Create four copies of the byte for which we are looking. */
28	const uint32_t goal = 0x01010101 * (uint8_t) c;
29
30	/* Read the first aligned word, but force bytes before the string to
31	 * match neither zero nor goal (we make sure the high bit of each
32	 * byte is 1, and the low 7 bits are all the opposite of the goal
33	 * byte).
34	 *
35	 * Note that this shift count expression works because we know shift
36	 * counts are taken mod 32.
37	 */
38	const uint32_t before_mask = (1 << (s_int << 3)) - 1;
39	uint32_t v = (*p | before_mask) ^ (goal & __insn_shrib(before_mask, 1));
40
41	uint32_t zero_matches, goal_matches;
42	while (1) {
43		/* Look for a terminating '\0'. */
44		zero_matches = __insn_seqb(v, 0);
45
46		/* Look for the goal byte. */
47		goal_matches = __insn_seqb(v, goal);
48
49		if (__builtin_expect(zero_matches | goal_matches, 0))
50			break;
51
52		v = *++p;
53	}
54
55	z = __insn_ctz(zero_matches);
56	g = __insn_ctz(goal_matches);
57
58	/* If we found c before '\0' we got a match. Note that if c == '\0'
59	 * then g == z, and we correctly return the address of the '\0'
60	 * rather than NULL.
61	 */
62	return (g <= z) ? ((char *)p) + (g >> 3) : NULL;
63}
64EXPORT_SYMBOL(strchr);