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From: kbierman@sun.com
Newsgroups: comp.compilers
Subject: Re: Encripted source as an ANDF
Message-ID: <4001@ima.ima.isc.com>
Date: 30 May 89 18:34:04 GMT
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Reply-To: kbierman@sun.com
Organization: Sun Microsystems, Mountain View
Lines: 49
Approved: compilers@ima.UUCP
In-Reply-To: <3990@ima.ima.isc.com>

In article <3990@ima.ima.isc.com> it is written:
>.... talks about two type of "optimizers" here, i.e. SOURCE => ANDF and
>ANDF => MACHINE_CODE.  One of these possibilities is totally silly, in the
>current context.
>
>The real beauty of the simple idea I proposed was that almost everybody
>already has a C compiler.  In the scheme I suggested, this compiler would
>also serve (without major modifications) and the ANDF compiler.
>
>Given this assumption, it should be obvious that there would be no need
>whatsoever for a SOURCE => ANDF "optimizer" since the ANDF => MACHINE_CODE
>transformation (i.e. "normal" compliation") would (presumably) already
>have a good optimizer.

.... more stuff about "good optimizing compilers"

The real fly in the ointment is that C semantics sabatoge many of the
best optimizations currently available to other languages (like most
good fortran compilers). 

A _few_ are

1) unconstrained pointers, 
2) "for" vs "do"
   (while the author of the proposal may think it best to reduce
   directly to GOTO's, DO loops ensure that the control variable may
   not be modified by anything in its body ... thus allowing many
   interesting optimizations ... w/o having to do extensive analysis)
   
3) lack of knowledge about rules of complex arithmetic
4) trig functions (built into fortran) and many other items of interest in
   the "real "go fast"" community. 

Try compiling C on your local supercomputer (or many RISC machines)
vs. fortran ... typically the fortran optimizer generates much tighter
code. 

This is not to say Fortran is "better" than C; it simply features well
suited to numerical computation and automatic optimization thereof.
-- 
Keith H. Bierman      |*My thoughts are my own. Only my work belongs to Sun*
It's Not My Fault     |	Marketing Technical Specialist    ! kbierman@sun.com
I Voted for Bill &    |   Languages and Performance Tools. 
Opus  (* strange as it may seem, I do more engineering now     *)
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