Re: Code quality (Willem Jan Withagen)
Mon, 1 Feb 1993 10:04:24 GMT

          From comp.compilers

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Newsgroups: comp.compilers
From: (Willem Jan Withagen)
Keywords: optimize, performance
Organization: Eindhoven University of Technology, The Netherlands
References: 93-01-017 93-01-033
Date: Mon, 1 Feb 1993 10:04:24 GMT

>On the other hand: ... I've heard of software companies for which compile
>time is everything, who refuse to add optimizations that will make -O more
>than twice as slow as non-optimizing.

On the third hand: :-)

I've got this large set of modules which are based on a few tree
structures. Now if I change something in those structures, I've got to
recompile >50k lines. Once everything is stable, it doesn't need
recompilation that often. But to emphasize your remark.

  Compiling the largest module with -W0,-opt,0 (Apollo-ees for noptimisation)
  it takes about 15 secs to compile. (CPU time that is, Wall time > 1.30)
  Doing the same with -W0,-opt,3 it takes over 2.5 minutes :{
  (And all this takeing a mere 15 minutes of wallclock time :{{ )

And the fun part with this is:

There's a rather large switch inside, and the compiler manages to mess up
its table, and generate eronous code, or backend failures. Which get fixed
once in a while by using level 3 optimisation. (Hence I knew the time.)
Supposedly GCC has some of the same features, most compilers are not very
often exersized at the nopt. level and have relatively more bugs in that

Once programs are finished and release upon the poor user, I'll start
optimising. (And test before release). Only when a program has run
flawlessly for a long while I'll take out all the asserts to get your last

>The marketplace takes all kinds.

Which I fully underscribe, as you've guessed.

Willem Jan Withagen

Digital Information Systems Group, Room EH 10.35
Eindhoven University of Technology
P.O. 513 Tel: +31-40-473401,Fax: +31-40-448375
5600 MB Eindhoven The Netherlands
X400: C=nl;ADMD=400net;PRMD=surf;O=tue;OU=ele;OU=eb;S=WJW;

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