Xref: utzoo comp.arch:17021 comp.lang.misc:5128
Path: utzoo!censor!geac!yunexus!oz
From: oz@yunexus.yorku.ca (Ozan Yigit)
Newsgroups: comp.arch,comp.lang.misc
Subject: Re: Compiler Costs
Message-ID: <12409@yunexus.YorkU.CA>
Date: 7 Jul 90 04:51:00 GMT
References: <1797@apctrc.UUCP>
Sender: news@yunexus.YorkU.CA
Reply-To: oz@yunexus.UUCP (Ozan Yigit)
Organization: York U. Communications Research & Development
Lines: 17

In article <1797@apctrc.UUCP> zrra07@backus (Randall R. Appleton) writes:
>In other words, if I take my average well written program, compiled
>with a good optimizing compiler, and re-write it in assembler, what sort
>of speedup should I expect to see?

When I was a young & budding assembler hack, I tried this on several
compiler outputs. At that time, VMS fortran and C compilers were
considered very good. I was able to out-optimize them by as much as 30%.
[As I said, I was young :-)] These days, compilers like GCC come very
close, and while I am convinced that for a moderate chunk of code, a
determined hacker can still out-optimize a compiler, I fail to see its
value except in some very special cases. [I had to improve a chess program
once, by re-writing its bitmap routines (which got called zillions of
times) in assembler. It was about 30 lines of code, and made about 40%
speed improvement] 

oz