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From: mcglk@scott.stat.washington.edu (Ken McGlothlen)
Newsgroups: comp.arch
Subject: Re: The VAX Always Uses Fewer Instructions
Keywords: VAX MIPS
Message-ID: <914@entropy.ms.washington.edu>
Date: 16 Jun 88 04:12:00 GMT
References: <6921@cit-vax.Caltech.Edu> <28200161@urbsdc> <10595@sol.ARPA> <11981@mimsy.UUCP>
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Reply-To: mcglk@scott.biostat.washington.edu
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In article <11981@mimsy.UUCP> chris@mimsy.UUCP (Chris Torek) writes:
+----------
| In article <10595@sol.ARPA> crowl@cs.rochester.edu (Lawrence Crowl) writes:
| +----------
| |  For example, the loop to add two vectors into a third on the VAX is:
| |
| |    top: addl3 (rA)+, (rB)+, (rC)+
| |         sobgeq rD, top
| |
| |  which takes seven bytes for two instructions.
| +----------
| True.  An optimising compiler might expand the loop, however:
|
| [... case expansion example ...]
|
| This pushes the size up to (I think) 70 bytes.  Too bad the RISC
| machines are still faster anyway :-) .
|
| [... more examples ...]
|
| All of this just goes to show that the VAX provides too many ways to
| do things!
| -- 
| In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
| Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris
+----------

Oh, please.

Guess we're gonna have to not only bash that ultra-complex VAX architecture,
but while we're at it, may as well bash C, too.  I mean, we've got so many
ways of adding five to an integer variable!

     i = i + 5;
     i += 5;
     i++; i++; i++; i++; i++;
     for( j = 0 ; j < 5 ; j++ )  i++;

Yup.  Definitely too complex.  I think we oughta just keep the "++" operator.

I still haven't seen any good arguments as to why RISC is so much better or
faster.  I'm kind of fond of the VAX instruction set, and you can do a heck
of a lot more with one line of its instruction set than you can with five
or ten lines of RISC code.  Is having eighty or so registers all that much
faster?

				--Ken McGlothlen
				  mcglk@scott.biostat.washington.edu
				  mcglk@max.acs.washington.edu