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Re: BUG: GCC-4.4.x changes the function frame on some functions
- From: Andrew Haley <aph at redhat dot com>
- To: Thomas Gleixner <tglx at linutronix dot de>
- 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>, Linus Torvalds <torvalds at linux-foundation dot org>, 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 12:04:07 +0000
- 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>
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
>
> I'm not supposed to understand the logic behind that, right ?
I don't either. I'm seeing:
timer_stats_update_stats: timer_stats_update_stats:
pushl %edi <
leal 8(%esp), %edi <
andl $-16, %esp <
pushl -4(%edi) <
pushl %ebp pushl %ebp
movl %esp, %ebp movl %esp, %ebp
pushl %edi | andl $-16, %esp
pushl %esi | subl $112, %esp
pushl %ebx | movl %ebx, 100(%esp)
subl $108, %esp | movl %esi, 104(%esp)
> movl %edi, 108(%esp)
call mcount call mcount
where the only difference is -mtune=generic. I'm investigating.
Andrew.