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Re: BUG: GCC-4.4.x changes the function frame on some functions
- From: Thomas Gleixner <tglx at linutronix dot de>
- To: Linus Torvalds <torvalds at linux-foundation dot org>
- Cc: Jeff Law <law at redhat dot com>, rostedt at goodmis dot org, "H. Peter Anvin" <hpa at zytor dot com>, David Daney <ddaney at caviumnetworks dot com>, Andrew Haley <aph at redhat dot com>, Richard Guenther <richard dot guenther at gmail dot com>, Ingo Molnar <mingo at elte dot hu>, LKML <linux-kernel at vger dot kernel dot org>, Andrew Morton <akpm at linux-foundation dot org>, Heiko Carstens <heiko dot carstens at de dot ibm dot com>, feng dot tang at intel dot com, Fr??d??ric Weisbecker <fweisbec at gmail dot com>, Peter Zijlstra <peterz at infradead dot org>, jakub at redhat dot com, gcc at gcc dot gnu dot org
- Date: Fri, 20 Nov 2009 03:14:12 +0100 (CET)
- Subject: Re: BUG: GCC-4.4.x changes the function frame on some functions
- References: <viy9pk4xossnb6m2v041qu00.1258665258503@email.android.com> <4B05B7AD.20500@redhat.com> <1258670580.22249.1002.camel@gandalf.stny.rr.com> <4B05DBBF.5000804@redhat.com> <alpine.LFD.2.00.0911200122190.24119@localhost.localdomain> <alpine.LFD.2.00.0911191652430.2793@localhost.localdomain> <alpine.LFD.2.00.0911200206570.24119@localhost.localdomain>
On Fri, 20 Nov 2009, Thomas Gleixner wrote:
> On Thu, 19 Nov 2009, Linus Torvalds wrote:
> > On Fri, 20 Nov 2009, Thomas Gleixner wrote:
> > >
> > > While testing various kernel configs we found out that the problem
> > > comes and goes. Finally I started to compare the gcc command line
> > > options and after some fiddling it turned out that the following
> > > minimal deltas change the code generator behaviour:
> > >
> > > Bad: -march=pentium-mmx -Wa,-mtune=generic32
> > > Good: -march=i686 -mtune=generic -Wa,-mtune=generic32
> > > Good: -march=pentium-mmx -mtune-generic -Wa,-mtune=generic32
Found some more:
Bad: -march=k6 -Wa,-mtune=generic32
Bad: -march=geode -Wa,-mtune=generic32
Bad: -march=c3 -Wa,-mtune=generic32
That seems every thing which has MMX support but no SSE and is somehow
compatible to the pentium-mmx.
Looks like the code generator optimization for those was done after
consuming the secret gcc-shrooms.
Thanks,
tglx