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From: n67786@lehtori.tut.fi (Nieminen Tero)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Pascal deficiency?
Message-ID: <N67786.90Dec18174755@lehtori.tut.fi>
Date: 18 Dec 90 16:47:55 GMT
References: <13650001@hpspdra.HP.COM> <1990Dec18.042748.6765@d.cs.okstate.edu>
Sender: news@assari.tut.fi (USENET News System)
Organization: Tampere Univ. of Technology, Finland.
Lines: 30
In-Reply-To: minich@d.cs.okstate.edu's message of 18 Dec 90 04:27:48 GMT


     I also tried {x += 1;} and it produced identical asm to BETA, which is
   OK. What I don't understand is what the heck is going on around what I
   marked "ick." Surely such a minute optimisation as not reading back what
   you just wrote is not too difficult to code. (Of course, I don't write
   compilers, either. :-) However, I think the ideal would be to replace
   ALPHA's

	+0004  MOVEQ      #$01,D0           | tmp = 1;
	+0006  MOVE.W     D0,-$0002(A6)     | x   = tmp;     <== ick
	+000A  MOVE.W     -$0002(A6),D0     | tmp = x;       <==
	+000E  ADDQ.W     #$1,D0            | tmp = tmp + 1;
	+0010  MOVE.W     D0,-$0002(A6)     | x   = tmp;

   with

	       MOVEQ.W    #$1,-$0002(A6)    | x = 1;
	       ADDQ.W     #$1,-$0002(A6)    | x = x + 1;

   and be done with it.

OK. Would someone out there with a Motorola 68000/020/030 (or most
notably 040 manual) check which one uses the leas clock sycles. Don't be
that easily fooled by the number of lines of code produced if speed is
what you are after. Operations on registers (ie. the move-to-reg
add-to-reg) tend to be a lot faster in Motorola processors (especially
040) than operations on memory locations.
  Just my 0.02 worth.
--
   Tero Nieminen                    Tampere University of Technology
   n67786@cc.tut.fi                 Tampere, Finland, Europe