Re: [PATCH v3 13/14] tcg/arm: Reserve a register for guest_base

[Richard Henderson]

On 8/20/21 2:03 AM, Peter Maydell wrote:
> > -        } else if (datalo != addend) {
> > +        } else if (scratch_addend) {
> >               tcg_out_ld32_rwb(s, COND_AL, datalo, addend, addrlo);
> >               tcg_out_ld32_12(s, COND_AL, datahi, addend, 4);
> >           } else {
>
> I don't understand this change. Yes, we can trash the addend
> register, but if it's the same as 'datalo' then the second load
> is not going to DTRT... Shouldn't this be
>    if (scratch_addend && datalo != addend)
> ?

Previously, addend was *always* a scratch register, TCG_REG_TMP or such.
Afterward, addend may be TCG_REG_GUEST_BASE, which should not be modified.
At no point is there overlap between addend and data{hi,lo}.

r~