[mirror_ubuntu-artful-kernel.git] / arch / tile / lib / memchr_64.c

/*
 * Copyright 2011 Tilera Corporation. All Rights Reserved.
 *
 *   This program is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU General Public License
 *   as published by the Free Software Foundation, version 2.
 *
 *   This program is distributed in the hope that it will be useful, but
 *   WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
 *   NON INFRINGEMENT.  See the GNU General Public License for
 *   more details.
 */

#include <linux/types.h>
#include <linux/string.h>
#include <linux/module.h>
#include "string-endian.h"

void *memchr(const void *s, int c, size_t n)
{
	const uint64_t *last_word_ptr;
	const uint64_t *p;
	const char *last_byte_ptr;
	uintptr_t s_int;
	uint64_t goal, before_mask, v, bits;
	char *ret;

	if (__builtin_expect(n == 0, 0)) {
		/* Don't dereference any memory if the array is empty. */
		return NULL;
	}

	/* Get an aligned pointer. */
	s_int = (uintptr_t) s;
	p = (const uint64_t *)(s_int & -8);

	/* Create eight copies of the byte for which we are looking. */
	goal = copy_byte(c);

	/* Read the first word, but munge it so that bytes before the array
	 * will not match goal.
	 */
	before_mask = MASK(s_int);
	v = (*p | before_mask) ^ (goal & before_mask);

	/* Compute the address of the last byte. */
	last_byte_ptr = (const char *)s + n - 1;

	/* Compute the address of the word containing the last byte. */
	last_word_ptr = (const uint64_t *)((uintptr_t) last_byte_ptr & -8);

	while ((bits = __insn_v1cmpeq(v, goal)) == 0) {
		if (__builtin_expect(p == last_word_ptr, 0)) {
			/* We already read the last word in the array,
			 * so give up.
			 */
			return NULL;
		}
		v = *++p;
	}

	/* We found a match, but it might be in a byte past the end
	 * of the array.
	 */
	ret = ((char *)p) + (CFZ(bits) >> 3);
	return (ret <= last_byte_ptr) ? ret : NULL;
}
EXPORT_SYMBOL(memchr);
Commit	Line	Data
18aecc2b CM	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>
1efea40d	18	#include "string-endian.h"
18aecc2b CM	19
	20	void 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. */
c53c70a9	39	goal = copy_byte(c);
18aecc2b CM	40
	41	/* Read the first word, but munge it so that bytes before the array
	42	* will not match goal.
18aecc2b	43	*/
1efea40d	44	before_mask = MASK(s_int);
18aecc2b CM	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	*/
1efea40d	66	ret = ((char *)p) + (CFZ(bits) >> 3);
18aecc2b CM	67	return (ret <= last_byte_ptr) ? ret : NULL;
	68	}
	69	EXPORT_SYMBOL(memchr);