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Date:      Thu, 23 Mar 2000 11:15:27 -0800 (PST)
From:      Charles Cox <cscox@stanford.edu>
To:        Cy Schubert - ITSD Open Systems Group <Cy.Schubert@uumail.gov.bc.ca>
Cc:        Andrew Gallatin <gallatin@cs.duke.edu>, obrien@FreeBSD.ORG, Howard Leadmon <howardl@account.abs.net>, freebsd-alpha@FreeBSD.ORG, freebsd-stable@FreeBSD.ORG
Subject:   Re: Compiler problems with -O2 (was Re: CVS Trouble, even  under 4.0-RELEASE (alpha) HELP!)
Message-ID:  <Pine.GSO.4.21.0003231108220.4480-100000@cardinal0.Stanford.EDU>
In-Reply-To: <200003231425.GAA01222@cwsys.cwsent.com>

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I would like to add that some of us who do a lot of numerically intensive
programming, and that need to squeeze every last available cycle out of
our CPU's would really appreciate having -O2 available for userland
programs.  To me, getting rid of the -O2+ switch would be like outlawing
cars because someone had a really bad car accident.  Just like driving a
car, using gcc and the -O2 switch safely are the USER's 
responsibility.  Having said this though, I do fully support having
comments in make.conf, and documentation elsewhere that cautions against
compiling a kernel with -O2.

CC


 On Thu, 23 Mar 2000, Cy Schubert - ITSD Open Systems Group
wrote:

> In message <14553.19348.115781.273817@grasshopper.cs.duke.edu>, Andrew 
> Gallatin
>  writes:
> > 
> > David O'Brien writes:
> >  > On Wed, Mar 22, 2000 at 03:03:09PM -0500, Howard Leadmon wrote:
> >  > > want to avoid, or at least note the problem with -O2 as I have been usin
> > g
> >  > > that when making software on my Intel machines for a long time, so just 
> >  > > assumed it was OK to do the same on the Alpha..
> >  > 
> >  > It isn't officially OK from the perspective of the FreeBSD Project.  "-O2"
> >  > has been the cause of problems on the i386 arch too.  Thus my constant
> >  > yelling about it that nobody pays attention to.
> >  > 
> >  > I'm on the virge of turning off "-O2" on both Alpha and i386.
> > 
> > You certainly have my vote.
> > 
> > I take it the O2 bugs are not unique to us, but rather they are
> > generic across all OSes that gcc version 2.95.2 runs on?  Do the gcc
> > people know these problems exist?
> 
> How about a compromise?  Just print a nasty message every time -O2 is 
> specified:
> 
> BEWARE:  -O2 may cause some applications to break or may cause your 
> system to fail to boot.  Be sure you absolutely know what you are doing 
> before using -O2 optimisation.
> 
> Then enclose it in stars (*) or bangs (!).
> 
> 
> Regards,                       Phone:  (250)387-8437
> Cy Schubert                      Fax:  (250)387-5766
> Team Leader, Sun/DEC Team   Internet:  Cy.Schubert@osg.gov.bc.ca
> Open Systems Group, ITSD, ISTA
> Province of BC
> 
> 
> 
> 
> 
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