diff options
Diffstat (limited to 'usr/src/lib/libc/sparc/gen/strlen.s')
| -rw-r--r-- | usr/src/lib/libc/sparc/gen/strlen.s | 141 |
1 files changed, 141 insertions, 0 deletions
diff --git a/usr/src/lib/libc/sparc/gen/strlen.s b/usr/src/lib/libc/sparc/gen/strlen.s new file mode 100644 index 0000000000..09da4ed196 --- /dev/null +++ b/usr/src/lib/libc/sparc/gen/strlen.s @@ -0,0 +1,141 @@ +/* + * CDDL HEADER START + * + * The contents of this file are subject to the terms of the + * Common Development and Distribution License, Version 1.0 only + * (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 2003 Sun Microsystems, Inc. All rights reserved. + * Use is subject to license terms. + */ + + +.ident "%Z%%M% %I% %E% SMI" + + .file "%M%" + +/* + * 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> +#include "synonyms.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) + |