usr/src/usr.lib/sendmail/src/bmove.11.s

/
/  Sendmail
/  Copyright (c) 1983  Eric P. Allman
/  Berkeley, California
/
/  Copyright (c) 1983 Regents of the University of California.
/  All rights reserved.  The Berkeley software License Agreement
/  specifies the terms and conditions for redistribution.
/
/       @(#)bmove.11.s  4.2 (Berkeley) 6/7/85
/
/
/  BMOVE -- block move
/
/
/       This is a highly optimized version of the old C-language
/       bmove routine; it's function (should be) identical.
/       It uses a fancy algorithm to move words instead of bytes
/       whenever possible.
/
/       In C the routine is:
/               char *bmove(a, b, l)
/               char    *a, *b;
/               int     l;
/               {
/                       register int    n;
/                       register char   *p, *q;
/                       p = a;
/                       q = b;
/                       n = l;
/                       while (n--)
/                               *q++ = *p++;
/                       return (q);
/               }
/
/       Parameters:
/               a [4(sp)] -- source area
/               b [6(sp)] -- target area
/               l [10(sp)] -- byte count
/
/       Returns:
/               Pointer to end of target area.
/
/       History:
/               3/14/79 [rse] -- added odd to odd case
/               2/9/78 [bob] -- converted from "C"
/
/

.globl  _bmove

_bmove:
        mov     r2,-(sp)        / save r2
        mov     4(sp),r1        / get src address
        mov     6(sp),r0        / get dst address

        / determine whether to use word or byte move
        mov     r0,r2           / r2 will reflect the three cases
        bic     $177776,r2      / keep only last bit of dst
        ror     4(sp)           / get least significant bit of src
        adc     r2              / add it in.
        beq     wordm           / both on even boundary
        dec     r2              / check for odd case
        bgt     wordodd         / both on odd boundary

        mov     10(sp),r2       / get count
        beq     done
bytem:
        movb    (r1)+,(r0)+     / copy next byte
        sob     r2,bytem        / branch until done
        br      done

wordm:
        mov     10(sp),r2       / get count
wordt:
        beq     done
        asr     r2              / get word count
        bcs     odd             / count was odd
even:
        mov     (r1)+,(r0)+     / copy word
        sob     r2,even         / more to do if non-zero
        br      done

wordodd:
        mov     10(sp),r2       / get count
        beq     done
        movb    (r1)+,(r0)+     / copy byte
        dec     r2              / dec count
        br      wordt           / now treat as an even word move

odd:
        beq     odd2            / special case of count = 1
odd1:
        mov     (r1)+,(r0)+     / copy word
        sob     r2,odd1         / continue
odd2:
        movb    (r1)+,(r0)+     / count was odd. do last one

done:
        mov     (sp)+,r2        / restore r2
        rts     pc              / return