Re: [Qemu-devel] [PATCH 07/16] tcg: Return NULL temp for TCG_CALL_DUMMY_ARG

[Richard Henderson]

On 06/27/2017 01:47 AM, Alex Bennée wrote:
> Richard Henderson <address@hidden> writes:
>
> > Signed-off-by: Richard Henderson <address@hidden>
> > ---
> >   tcg/tcg.h | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/tcg/tcg.h b/tcg/tcg.h
> > index 3b35344..6c357e7 100644
> > --- a/tcg/tcg.h
> > +++ b/tcg/tcg.h
> > @@ -730,7 +730,7 @@ extern bool parallel_cpus;
> >
> >   static inline TCGTemp *arg_temp(TCGArg a)
> >   {
> > -    return &tcg_ctx.temps[a];
> > +    return a == TCG_CALL_DUMMY_ARG ? NULL : &tcg_ctx.temps[a];
> >   }
>
> It doesn't look like a lot of calls to arg_temp are able to deal with a
> NULL return and may well immediately deref the value. Are we sure the
> cases the TCG_CALL_DUMMY arg is involved are narrowly defined?

They only appear as arguments to a call opcode.


r~