usr/src/lib/libc/vax/string/strncmp.s

/*      strncmp.s       4.1     84/11/01        */

/*
 * Compare at most n characters of string
 * s1 lexicographically to string s2.
 * Return:
 *      0       s1 == s2
 *      > 0     s1 > s2
 *      < 0     s2 < s2
 *
 * strncmp(s1, s2, n)
 *      char *s1, *s2;
 *      int n;
 */
        .globl  _strncmp

_strncmp:
        .word   0x0
        movl    12(ap),r5       # r5 = n
        movq    4(ap),r3        # r3 = s1; r4 = s2
1:
        locc    $0,$65535,(r4)  # look for '\0' in s2
        bneq    2f
        cmpl    r5,$65535       # n > chunk size?
        bgtr    4f              # yes
        movl    r5,r1           # no, compare only n bytes
        jbr     5f
4:
        subl2   $65535,r5       # adjust n
        cmpc3   $65535,(r4),(r3)# compare full block
        bneq    3f
        movl    r1,r4           # advance s2
        jbr     1b              # matched, next block
2:
        subl2   r4,r1           # calculate length
        incl    r1              # +1 for '\0'
        cmpl    r1,r5           # length <= n
        bleq    5f              # yes, compare full string
        movl    r5,r1           # no, compare only n bytes
5:
        cmpc3   r1,(r4),(r3)    # compare remainder
        bneq    3f
        ret                     # r0 = 0 already
3:
        subb3   (r1),(r3),r0    # r0 = *s1 - *s2
        cvtbl   r0,r0
        ret