Re: [Xen-devel] [PATCH] xen: arm: let the compiler choose the dummy register for TLB flush asm

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2013-04-24 at 15:17 +0100, Tim Deegan wrote:
> At 14:21 +0100 on 24 Apr (1366813285), Ian Campbell wrote:
> > While staring at some disassembly I noticed that the compiler was jumping
> > through hoops to preserve the function argument (in r0) simply so it could 
> > use
> > r0 as the dummy argument to the tlb flush cp register writes.
> > 
> > Remove the enforced use of r0 and use an output constraint for the dummy
> > register so there is no need to initialise the dummy.
> 
> Since we don't care about the register's contents and it's not changed,
> can we just drop the variable and constraint entirely?

and just hard code the r0? I hadn't though of that, I suppose we could
yes.

Ian.



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