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/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2008 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
.file "strlen.s"
/*
* strlen(s)
*
* Given string s, return length (not including the terminating null).
*
* Fast assembler language version of the following C-program strlen
* which represents the `standard' for the C-library.
*
* size_t
* strlen(s)
* register const char *s;
* {
* register const char *s0 = s + 1;
*
* while (*s++ != '\0')
* ;
* return (s - s0);
* }
*/
#include <sys/asm_linkage.h>
! The object of strlen is to, as quickly as possible, find the
! null byte. To this end, we attempt to get our string aligned
! and then blast across it using Alan Mycroft's algorithm for
! finding null bytes. If we are not aligned, the string is
! checked a byte at a time until it is. Once this occurs,
! we can proceed word-wise across it. Once a word with a
! zero byte has been found, we then check the word a byte
! at a time until we've located the zero byte, and return
! the proper length.
.align 32
ENTRY(strlen)
andcc %o0, 3, %o4 ! is src word aligned
bz,pt %icc, .nowalgnd
mov %o0, %o2
cmp %o4, 2 ! is src half-word aligned
be,a,pn %icc, .s2algn
lduh [%o2], %o1
ldub [%o2], %o1
tst %o1 ! byte zero?
bz,pn %icc, .done
cmp %o4, 3 ! src is byte aligned
be,pn %icc, .nowalgnd
inc 1, %o2
lduh [%o2], %o1
.s2algn:
srl %o1, 8, %o4
tst %o4
bz,pn %icc, .done
andcc %o1, 0xff, %g0
bz,pn %icc, .done
inc 1, %o2
inc 1, %o2
.nowalgnd:
ld [%o2], %o1
sethi %hi(0x01010101), %o4
sethi %hi(0x80808080), %o5
or %o4, %lo(0x01010101), %o4
or %o5, %lo(0x80808080), %o5
andn %o5, %o1, %o3
sub %o1, %o4, %g1
andcc %o3, %g1, %g0
bnz,a,pn %icc, .nullfound
sethi %hi(0xff000000), %o4
ld [%o2+4], %o1
inc 4, %o2
.loop: ! this should be aligned to 32
inc 4, %o2
andn %o5, %o1, %o3 ! %o5 = ~word & 0x80808080
sub %o1, %o4, %g1 ! %g1 = word - 0x01010101
andcc %o3, %g1, %g0
bz,a,pt %icc, .loop
ld [%o2], %o1
dec 4, %o2
sethi %hi(0xff000000), %o4
.nullfound:
andcc %o1, %o4, %g0
bz,pn %icc, .done ! first byte zero
srl %o4, 8, %o4
andcc %o1, %o4, %g0
bz,pn %icc, .done ! second byte zero
inc 1, %o2
srl %o4, 8, %o4
andcc %o1, %o4, %g0
bz,pn %icc, .done ! thrid byte zero
inc 1, %o2
inc 1, %o2 ! fourth byte zero
.done:
retl
sub %o2, %o0, %o0
SET_SIZE(strlen)
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