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Date: Fri, 13 Feb 2004 14:35:43 -0800
From: David Daney <ddaney@avtrex.com>
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To: Thiemo Seufer <ica2_ts@csv.ica.uni-stuttgart.de>
CC: Ralf Baechle <ralf@linux-mips.org>,
	"Maciej W. Rozycki" <macro@ds2.pg.gda.pl>,
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Subject: Re: [patch] Prevent dead code/data removal with gcc 3.4
References: <Pine.LNX.4.55.0402131453360.15042@jurand.ds.pg.gda.pl> <20040213145316.GA23810@linux-mips.org> <20040213222253.GA20118@rembrandt.csv.ica.uni-stuttgart.de>
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Thiemo Seufer wrote:

>Ralf Baechle wrote:
>  
>
>>On Fri, Feb 13, 2004 at 03:20:27PM +0100, Maciej W. Rozycki wrote:
>>
>>    
>>
>>>2. It changes inline-assembly function prologues to be embedded within the
>>>functions, which makes them a bit safer as they can now explicitly refer
>>>to the "regs" struct and assures the code won't be removed or reordered.
>>>      
>>>
>>It is possible that gcc changes one of the registers before save_static
>>and I can't imagine there's a reliable way to fix this in the inline
>>version.
>>    
>>
>
>As long as __asm__ __volatile__ works as documented, this can't happen.
>  
>
My understanding is that with gcc-3.4 that __asm__ __volatile__ does not 
protect against dead code removal.  If the code is not dead __volatile__ 
works as documented, but dead code removal still happens.

David Daney.