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Path: utzoo!watmath!clyde!rutgers!seismo!munnari!otc!metro!ipso!runx!clubmac
From: clubmac@runx.UUCP
Newsgroups: comp.sys.mac
Subject: LSC ++ and -- operators
Message-ID: <654@runx.OZ>
Date: Tue, 10-Feb-87 22:55:25 EST
Article-I.D.: runx.654
Posted: Tue Feb 10 22:55:25 1987
Date-Received: Fri, 13-Feb-87 05:43:05 EST
Organization: RUNX Un*x Timeshare.  Sydney, Australia.
Lines: 44


Here is something I found on a local BBS...

I just discovered that the postfix ++ -- operators are less efficient than
prefix ++ and --.
if you have a block like :

    {
        register char *a,*b;
        *(a++) = *(b++);
    }

it translates to   :
    
    movea.l A4,A0 ; A4 holds b
    movea.l A3,A1 ; A1 holds a
    move.b (A0),(A1)
    moveq   #1,A3
    moveq   #1,A4

but if you have a block like :

    {
        register char *a,*b;
        *(a) = *(b);
        a++;b++;
    }

it translates to   :

    move.b (A4),(A3)
    moveq   #1,A3
    moveq   #1,A4

You dont get the above problem with prefix ++ and --.

MORAL : Dont assume - disassemble your code !

John Lim

---------------

Anybody know anything about this?

Jason Haines