usr/src/lib/libc/hp300/string/bcmp.s

/*-
 * Copyright (c) 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * the Systems Programming Group of the University of Utah Computer
 * Science Department.
 *
 * %sccs.include.redist.c%
 */

#if defined(LIBC_SCCS) && !defined(lint)
        .asciz "@(#)bcmp.s      5.1 (Berkeley) %G%"
#endif /* LIBC_SCCS and not lint */

/* bcmp(s1, s2, n) */

#include "DEFS.h"

/*
 * This is probably not the best we can do, but it is still 2-10 times
 * faster than the C version in the portable gen directory.
 *
 * Things that might help:
 *      - longword align when possible (only on the 68020)
 *      - use nested DBcc instructions or use one and limit size to 64K
 */
ENTRY(bcmp)
        movl    sp@(4),a0       /* string 1 */
        movl    sp@(8),a1       /* string 2 */
        movl    sp@(12),d0      /* length */
        jeq     bcdone          /* if zero, nothing to do */
        movl    a0,d1
        btst    #0,d1           /* string 1 address odd? */
        jeq     bceven          /* no, skip alignment */
        cmpmb   a0@+,a1@+       /* yes, compare a byte */
        jne     bcnoteq         /* not equal, return non-zero */
        subql   #1,d0           /* adjust count */
        jeq     bcdone          /* count 0, reutrn zero */
bceven:
        movl    a1,d1
        btst    #0,d1           /* string 2 address odd? */
        jne     bcbloop         /* yes, no hope for alignment, compare bytes */
        movl    d0,d1           /* no, both even */
        lsrl    #2,d1           /* convert count to longword count */
        jeq     bcbloop         /* count 0, skip longword loop */
bclloop:
        cmpml   a0@+,a1@+       /* compare a longword */
        jne     bcnoteq         /* not equal, return non-zero */
        subql   #1,d1           /* adjust count */
        jne     bclloop         /* still more, keep comparing */
        andl    #3,d0           /* what remains */
        jeq     bcdone          /* nothing, all done */
bcbloop:
        cmpmb   a0@+,a1@+       /* compare a byte */
        jne     bcnoteq         /* not equal, return non-zero */
        subql   #1,d0           /* adjust count */
        jne     bcbloop         /* still more, keep going */
        rts
bcnoteq:
        moveq   #1,d0
bcdone:
        rts