usr/src/lib/libc/gen/gen.vax/strcmp.s

/*
 * Copyright (c) 1983 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#if defined(LIBC_SCCS) && !defined(lint)
        .asciz "@(#)strcmp.s    5.5 (Berkeley) 6/27/88"
#endif /* LIBC_SCCS and not lint */

/*
 * Compare string s1 lexicographically to string s2.
 * Return:
 *      0       s1 == s2
 *      > 0     s1 > s2
 *      < 0     s2 < s2
 *
 * strcmp(s1, s2)
 *      char *s1, *s2;
 */
#include "DEFS.h"

ENTRY(strcmp, 0)
        movl    4(ap),r1        # r1 = s1
        movl    8(ap),r3        # r3 = s2
        subb3   (r3),(r1),r0    # quick check for first char different
        beql    1f              # have to keep checking
        cvtbl   r0,r0
        ret
1:
        clrl    r5              # calculate min bytes to next page boundry
        subb3   r1,$255,r5      # r5 = (bytes - 1) to end of page for s1
        subb3   r3,$255,r0      # r0 = (bytes - 1) to end of page for s2
        cmpb    r0,r5           # r5 = min(r0, r5);
        bgtru   2f
        movb    r0,r5
2:
        incl    r5              # r5 = min bytes to next page boundry
        cmpc3   r5,(r1),(r3)    # compare strings
        bneq    3f
        subl2   r5,r1           # check if found null yet
        locc    $0,r5,(r1)
        beql    1b              # not yet done, continue checking
        subl2   r0,r3
        mnegb   (r3),r0         # r0 = '\0' - *s2
        cvtbl   r0,r0
        ret
3:
        subl2   r0,r5           # check for null in matching string
        subl2   r5,r1
        locc    $0,r5,(r1)
        bneq    4f
        subb3   (r3),(r1),r0    # r0 = *s1 - *s2
        cvtbl   r0,r0
        ret
4:
        clrl    r0              # both the same to null
        ret