Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84 exptools; site ihdev.UUCP
Path: utzoo!watmath!clyde!cbosgd!ihnp4!ihdev!pdg
From: pdg@ihdev.UUCP (P. D. Guthrie)
Newsgroups: net.lang.c
Subject: Re: C "optimization"
Message-ID: <403@ihdev.UUCP>
Date: Sun, 17-Nov-85 16:28:51 EST
Article-I.D.: ihdev.403
Posted: Sun Nov 17 16:28:51 1985
Date-Received: Tue, 19-Nov-85 03:59:02 EST
References: <2539@sjuvax.UUCP>
Reply-To: pdg@ihdev.UUCP (55224-P. D. Guthrie)
Distribution: net
Organization: AT&T Bell Laboratories
Lines: 23

In article <2539@sjuvax.UUCP> jss@sjuvax.UUCP (J. Shapiro) writes:
>
>In the process of finding out that no one seems to do this, I have lost
>some respect for the UNIX "optimizer".  Now, can anyone mail me a
>coherent reasoning for why UNIX cc is so inexcuseably stupid (at the
>moment our postings are going out, but our incoming feed is dead)?
>Can someone redeem my respect for the optimizer?
>

I enjoyed the comparison between the UNIX and VMS optimizers (left out
for brevity), and I my only reaction is that it is typical of DEC
compilers to produce super-optimized code.  The Tops-20 Fortran Compiler
is another example, and seems to store "synonyms" for the contents of
every register, to leave out unnecessary calculations.  When I was
writing a Fortran compiler on a DEC-20,  it seemed at first that the
best way to see how to generate code was to look at the output of DEC's
Fortran compiler,  but that proved to be fruitless, as it would use very
strange DEC-20 instructions to optimize the code down to nothing.
I would be interested to know if there have been any articles published
on DEC's optimization methods.
					Paul Guthrie
					ihnp4!ihdev!pdg
PS, sorry to talk about Fortrash in this enlightened newsgroup :-}