Re: [Qemu-ppc] Implement instructions: yield, mdoio, mdoom

[David Gibson]

On Thu, Jun 23, 2016 at 08:10:08PM -0500, address@hidden wrote:
> In target-ppc/translate.c, the gen_or() function now has the ability
> to pause the CPU via gen_pause().  However gen_or() does not implement
> the PPC instructions yield (rs,ra,rb=27), mdoio (29), or mdoom (30),
> which could be handled by simply calling gen_pause() for them.

Uh.. having a glance at the description of these in the arch, I don't
think treating them as pause is correct.  I don't see anything we can
do with these in TCG that's better than the no-op we currently treat
them as.

> I could either:
>   1. Add explicit code for registers 27, 29, and 30, or
>   2. Change the existing code to call gen_pause() whenever rs!=0
>     (simple noop).
> 
> My rationale for #2 is that it is simpler, and seems likely to be
> right for future encodings of "or".
> 
> Comments solicited.
> 
> Aaron.
> 

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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