Path: utzoo!attcan!uunet!yale!mfci!colwell
From: colwell@mfci.UUCP (Bob Colwell)
Newsgroups: comp.arch
Subject: Re: RISC machines and scoreboarding
Message-ID: <454@m3.mfci.UUCP>
Date: 29 Jun 88 02:09:25 GMT
References: <1082@nud.UUCP> <2438@winchester.mips.COM> <1098@nud.UUCP> <2465@winchester.mips.COM> <318@mucmot.UUCP>
Sender: root@mfci.UUCP
Reply-To: colwell@mfci.UUCP (Bob Colwell)
Organization: Multiflow Computer Inc., Branford Ct. 06405
Lines: 35

In article <318@mucmot.UUCP> ron@mucmot.UUCP (Ron Voss) writes:
>In article <2465@winchester.mips.COM>, mash@mips.COM (John Mashey) writes:
>> 	c) Figuring that a RISC compiler should do optimization, but worrying
>> 	that this feature might be buggy, is like worrying about the safety
>> 	of flying in a 747 and bringing your own seat-belt because you
>> 	don't really trust Boeing to remember to include them :-)
>
>I have observed a few cases where hours were wasted searching for a
>programming bug, only to find that the CISC (68020) compiler's optimizer
>is buggy (so one turns on the optimizer only for a release, since it
>slows compilations anyway, thoughouly test again after turning on, etc.).
>
>Are there really *good* reasons to put more trust in RISC optimizers?

Ron, I couldn't let that one slide on by.  I think it's a truism that
good designers produce good designs, including compilers/optimizers,
and not-so-good designers produce everything else.  My experience has
been that the quality of a piece of software is a far stronger
function of the abilities of its creators than of its intrinsic
complexity.

One could perhaps make the case the a RISC optimizer is likely to be
intrinsically less complex than its CISC counterpart due to the
more-easily-understood machine spec, but it's probably impossible to
prove, and I don't think it's as strong an argument as the above.

I also have the feeling that more talented designers are turning
their attentions to compilers than ever before, so perhaps the
overall quality of this kind of software is improving, but I won't
even try to defend that thesis if you don't like it.

Bob Colwell            mfci!colwell@uunet.uucp
Multiflow Computer
175 N. Main St.
Branford, CT 06405     203-488-6090