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Commit 5916700c authored by Ken Steele's avatar Ken Steele Committed by Chris Metcalf
Browse files

tile: optimize strnlen using SIMD instructions 



Using strlen as a model, add length checking to create strnlen.

Signed-off-by: default avatarKen Steele <ken@tilera.com>
Signed-off-by: default avatarChris Metcalf <cmetcalf@tilera.com>
parent c53c70a9

arch/tile/include/asm/string.h

+2 −0
Original line number Diff line number Diff line
@@ -21,8 +21,10 @@ 
#define __HAVE_ARCH_MEMMOVE

#define __HAVE_ARCH_STRCHR

#define __HAVE_ARCH_STRLEN

#define __HAVE_ARCH_STRNLEN



extern __kernel_size_t strlen(const char *);

extern __kernel_size_t strnlen(const char *, __kernel_size_t);

extern char *strchr(const char *s, int c);

extern void *memchr(const void *s, int c, size_t n);

extern void *memset(void *, int, __kernel_size_t);

arch/tile/lib/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -4,7 +4,7 @@ 


lib-y = cacheflush.o checksum.o cpumask.o delay.o uaccess.o \

	memmove.o memcpy_$(BITS).o memchr_$(BITS).o memset_$(BITS).o \

	strchr_$(BITS).o strlen_$(BITS).o

	strchr_$(BITS).o strlen_$(BITS).o strnlen_$(BITS).o



ifeq ($(CONFIG_TILEGX),y)

CFLAGS_REMOVE_memcpy_user_64.o = -fno-omit-frame-pointer

arch/tile/lib/strnlen_32.c

0 → 100644
+47 −0
Original line number Diff line number Diff line 
/*

 * Copyright 2013 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>



size_t strnlen(const char *s, size_t count)

{

	/* Get an aligned pointer. */

	const uintptr_t s_int = (uintptr_t) s;

	const uint32_t *p = (const uint32_t *)(s_int & -4);

	size_t bytes_read = sizeof(*p) - (s_int & (sizeof(*p) - 1));

	size_t len;

	uint32_t v, bits;



	/* Avoid page fault risk by not reading any bytes when count is 0. */

	if (count == 0)

		return 0;



	/* Read first word, but force bytes before the string to be nonzero. */

	v = *p | ((1 << ((s_int << 3) & 31)) - 1);



	while ((bits = __insn_seqb(v, 0)) == 0) {

		if (bytes_read >= count) {

			/* Read COUNT bytes and didn't find the terminator. */

			return count;

		}

		v = *++p;

		bytes_read += sizeof(v);

	}



	len = ((const char *) p) + (__insn_ctz(bits) >> 3) - s;

	return (len < count ? len : count);

}

EXPORT_SYMBOL(strnlen);

arch/tile/lib/strnlen_64.c

0 → 100644
+48 −0
Original line number Diff line number Diff line 
/*

 * Copyright 2013 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"



size_t strnlen(const char *s, size_t count)

{

	/* Get an aligned pointer. */

	const uintptr_t s_int = (uintptr_t) s;

	const uint64_t *p = (const uint64_t *)(s_int & -8);

	size_t bytes_read = sizeof(*p) - (s_int & (sizeof(*p) - 1));

	size_t len;

	uint64_t v, bits;



	/* Avoid page fault risk by not reading any bytes when count is 0. */

	if (count == 0)

		return 0;



	/* Read and MASK the first word. */

	v = *p | MASK(s_int);



	while ((bits = __insn_v1cmpeqi(v, 0)) == 0) {

		if (bytes_read >= count) {

			/* Read COUNT bytes and didn't find the terminator. */

			return count;

		}

		v = *++p;

		bytes_read += sizeof(v);

	}



	len = ((const char *) p) + (CFZ(bits) >> 3) - s;

	return (len < count ? len : count);

}

EXPORT_SYMBOL(strnlen);