Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!henry
From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.arch
Subject: Re: better late... (really, fast NS32000 multiplies)
Message-ID: <5720@utzoo.UUCP>
Date: Mon, 24-Jun-85 12:24:19 EDT
Article-I.D.: utzoo.5720
Posted: Mon Jun 24 12:24:19 1985
Date-Received: Mon, 24-Jun-85 12:24:19 EDT
References: <254@greipa.UUCP>, <836@mako.UUCP>
Organization: U of Toronto Zoology
Lines: 16

> I disagree with Henry Spencer in saying that multiplies are uncommon.  In
> particular, the small integer multiply operation is used in index scaling,
> particularly whenever index math is performed, and it is important that a
> compiler do its best on these, as they are often inside loops.

Guilty.  I forgot about that.  Although I would speculate that most arrays
(particularly in C) are one-dimensional and their members are one of the
primitive data types, a situation that would seem tailor-made for indexed
addressing modes to do all the work.

Yes, I know there are programs that use multidimensional arrays with
complicated members, and whose running times might be seriously affected
by slow multiplies.  I merely conjecture that they are in the minority.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry