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

/*-
 * Copyright (c) 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * %sccs.include.redist.c%
 */

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

/*
 * void *memmove(dst, src, size)
 * returns dst
 *
 * This optimises the usual case (count < 65536) at the expense
 * of some extra memory references and branches when count >= 65536.
 */

#include "DEFS.h"

ENTRY(memmove, 0)
        movzwl  $65535,r0       /* r0 = 64K (needed below) */
        movq    8(ap),r1        /* r1 = src, r2 = length */
        movl    4(ap),r3        /* r3 = dst */
        cmpl    r1,r3
        bgtru   1f              /* normal forward case */
        beql    2f              /* equal, nothing to do */
        addl2   r2,r1           /* overlaps iff src<dst but src+len>dst */
        cmpl    r1,r3
        bgtru   4f              /* overlapping, must move backwards */
        subl2   r2,r1

1:      /* move forward */
        cmpl    r2,r0
        bgtru   3f              /* stupid movc3 limitation */
        movc3   r2,(r1),(r3)    /* move it all */
2:
        movl    4(ap),r0        /* return original dst */
        ret
3:
        subl2   r0,12(ap)       /* adjust length by 64K */
        movc3   r0,(r1),(r3)    /* move 64K */
        movl    12(ap),r2
        decw    r0              /* from 0 to 65535 */
        brb     1b              /* retry */

4:      /* move backward */
        addl2   r2,r3
5:
        cmpl    r2,r0
        bgtru   6f              /* stupid movc3 limitation */
        subl2   r2,r1
        subl2   r2,r3
        movc3   r2,(r1),(r3)    /* move it all */
        movl    4(ap),r0        /* return original dst */
        ret
6:
        subl2   r0,12(ap)       /* adjust length by 64K */
        subl2   r0,r1
        subl2   r0,r3
        movc3   r0,(r1),(r3)    /* move 64K */
        movl    12(ap),r2
        decw    r0
        subl2   r0,r1
        subl2   r0,r3
        brb     5b