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From: Andi Kleen <ak@suse.de>
Organization: SUSE Linux Products GmbH, Nuernberg, GF: Markus Rex, HRB 16746 (AG Nuernberg)
To: Satyam Sharma <ssatyam@cse.iitk.ac.in>
Subject: Re: [PATCH 3/8] i386: bitops: Rectify bogus "+m" constraints
Date: Mon, 23 Jul 2007 18:37:27 +0200
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On Monday 23 July 2007 18:05:43 Satyam Sharma wrote:
> From: Satyam Sharma <ssatyam@cse.iitk.ac.in>
> 
> [3/8] i386: bitops: Rectify bogus "+m" constraints
> 
> From the gcc manual:
> 
>   Extended asm supports input-output or read-write operands. Use the
>   constraint character `+' to indicate such an operand and list it with
>   the output operands. You should only use read-write operands when the
>   constraints for the operand (or the operand in which only some of the
>   bits are to be changed) allow a register.
> 
> So, using the "+" constraint modifier for memory, like "+m" is bogus.
> We must simply specify "=m" which handles the case correctly.

I checked with Honza (cc'ed) and he stated that the + are really needed
at least in newer gcc.

-Andi