X-Authentication-Warning:	sal.physics.ucsb.edu: dwhysong owned process doing -bs
Date:	Mon, 10 May 1999 10:07:07 -0700 (PDT)
From:	David Whysong <dwhysong AT physics DOT ucsb DOT edu>
To:	pgcc AT delorie DOT com
Subject:	Re: Optimization question
Message-ID:	<Pine.LNX.4.04.9905100957550.13449-100000@sal.physics.ucsb.edu>
MIME-Version:	1.0
Reply-To:	pgcc AT delorie DOT com

"Bernd Melchers" wrote:

> good compilers should optimize such expressions by itself, the method
> is called "common subexpression optimization".

That's exactly what I thought, but...

This morning I've been playing around with assembler dumps. Doing
subexpression elimination by hand has reduced the number of fmul
instructions considerably (as verified by "grep fmul junk.c | wc"),
though for some reason there are a few more fadd instructions.

Dave

David Whysong                                       dwhysong AT physics DOT ucsb DOT edu
Astrophysics graduate student         University of California, Santa Barbara
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