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Subject: Re: Bad gcc-4.1.0 leads to Power4 crashes... and power5 too, actually
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Linas Vepstas <linas@austin.ibm.com>
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Date: Thu, 21 Dec 2006 08:28:54 +1100
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On Wed, 2006-12-20 at 15:19 -0600, Linas Vepstas wrote:
> On Tue, Dec 19, 2006 at 07:46:50PM -0600, Peter Bergner wrote:
> > On Tue, 2006-12-19 at 18:46 -0600, Linas Vepstas wrote:
> > > Per xchat, here's the update. I'm guessing I'm using a broken
> > > compiler, as per chain of evidence below ...
> > [snip]
> > > However, I also note that the following scrolled by:
> > > init/main.c:81:2: warning: #warning gcc-4.1.0 is known to miscompile the
> > > kernel. A different compiler version is recommended.
> > 
> > It may be due to this GCC bug which Olaf ran into a while back:
> > 
> >   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24644
> > 
> > You can verify whether you have a broken compiler by compiling
> > the minimal test case I posted in comment #15.  If you see r13
> > being copied into another register and then used, then you have
> > a broken compiler.
> 
> No, that's not it. I'd be surprised, as I was using the SuSE
> SLES10 gcc-4.1.0-28.4.ppc.rpm compiler, which would have that fix.
> 
> I'm trying to figure out how to try a different compiler,
> I'm hoping that 3.3 can still compile new kernels.
> 
> I'll try to stare at the dump a bit too, now.

I've been using 4.1.2 from debian/ubuntu happily lately.

Ben.