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Date:      Tue, 12 Dec 2000 09:35:13 -0800 (PST)
From:      John Polstra <TrimYourCC@polstra.com>
To:        stable@freebsd.org
Subject:   Re: Different gcc optimisations cause IP packet CRC problems
Message-ID:  <200012121735.eBCHZDj48175@vashon.polstra.com>
In-Reply-To: <Pine.BSF.4.21.0012111544260.36265-100000@plato.salford.ac.uk>
References:  <Pine.BSF.4.21.0012111544260.36265-100000@plato.salford.ac.uk>

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In article
<Pine.BSF.4.21.0012111544260.36265-100000@plato.salford.ac.uk>, Mark
Powell <M.S.Powell@salford.ac.uk> wrote:
> I hadn't seen those comments. I didn't think gcc could be *that*
> broken.  Cheers.

I'm going to go out on a limb here and say that I have serious doubts
it's really a gcc bug.  I think the problem is most likely that
the constraint specifications are incorrect in some of our "asm"
statements.

BSD/OS uses -O2 to build kernels, and it works fine for several
versions of GCC including 2.95.2 (if I remember the version number
correctly).  And their kernel isn't all that different from ours.

A systematic review of all our "asm" statments would probably find
some bugs which, when fixed, would allow us to use -O2 for building
kernels.  No, I'm not volunteering. :-)

John
-- 
  John Polstra                                               jdp@polstra.com
  John D. Polstra & Co., Inc.                        Seattle, Washington USA
  "Disappointment is a good sign of basic intelligence."  -- Chögyam Trungpa



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