Re: [PATCH] ARMv7 Oprofile support

[Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx>]

On Thu, Sep 04, 2008 at 09:25:42AM -0500, Woodruff, Richard wrote:
> Hi Jean,
> 
> > From: Jean Pihet <jpihet@xxxxxxxxxx>
> > Date: Tue, 6 May 2008 17:21:44 +0200
> 
> One thing I noticed was I think the patch should add the "memory"
> qualifier to clobber list for asm's calls with output operands (=r).
> There is a little bit of mixed C where the compiler should be told to
> make sure to update local variables which may be in memory.

Why?  Merely reading a register doesn't affect memory.

> Looking at other kernel code I see a lot of code adds condition codes
> "cc" to the clobber list also, but it looks like condition codes are
> only updated when the target (Rd) is the "pc" for a MRC.  The pc won't
> be chosen with a %0 so those seem unnecessary.

They're there to ensure that the compiler doesn't do anything silly.

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