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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: Ingo Molnar <mingo at elte dot hu>, "H. Peter Anvin" <hpa at zytor dot com>, 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>, Steven Rostedt <rostedt at goodmis dot org>, Peter Zijlstra <peterz at infradead dot org>, jakub at redhat dot com, gcc at gcc dot gnu dot org
- Date: Thu, 19 Nov 2009 16:17:49 +0000
- Subject: Re: BUG: GCC-4.4.x changes the function frame on some functions
- References: <alpine.LFD.2.00.0911181933540.24119@localhost.localdomain> <tip-887a29f59b93cf54e21814869a4ab6e80b6fa623@git.kernel.org> <20091119072040.GA23579@elte.hu> <alpine.LFD.2.00.0911191053390.24119@localhost.localdomain> <alpine.LFD.2.00.0911191423190.24119@localhost.localdomain> <alpine.LFD.2.00.0911191607440.24119@localhost.localdomain> <4B0567E0.5080803@redhat.com> <alpine.LFD.2.00.0911191704110.24119@localhost.localdomain>
Thomas Gleixner wrote:
> On Thu, 19 Nov 2009, Andrew Haley wrote:
>> Thomas Gleixner wrote:
>>> There is no real obvious reason why the edi magic needs to be done
>>> _before_
>>>
>>> push %ebp
>>> mov %esp,%ebp
>> Sure there is: unless you do the adjustment first %ebp won't be 16-aligned.
>
> And why is this not done in 99% of the functions in the kernel, just
> in this one and some random others ?
If I could see the function I might be able to tell you. It's either a
performance enhancement, something to do with SSE, or it's a bug.
Andrew.