Re: [PATCH v4 06/36] tcg: Introduce tcg_target_call_oarg_reg

[Richard Henderson]

On 1/25/23 11:09, Alex Bennée wrote:
> > -static const int tcg_target_call_oarg_regs[2] = {
> > -    TCG_REG_R0, TCG_REG_R1
> > -};
> > +
> > +static TCGReg tcg_target_call_oarg_reg(TCGCallReturnKind kind, int slot)
> > +{
> > +    tcg_debug_assert(kind == TCG_CALL_RET_NORMAL);
> > +    tcg_debug_assert(slot >= 0 && slot <= 3);
> > +    return TCG_REG_R0 + slot;
> > +}
>
> So this is now returning allocations of TCG_REG_R0 to TCG_REG_R3?

Yes, should have mentioned in the patch description.  Done.


> Do we
> have to take care to get things right if slot is ever bigger w.r.t.
> tcg_target_reg_alloc_order?

No, reg_alloc_order is optimization for call-saved vs call-clobbered vs call arguments. 
It should not affect correctness at all.  Nor will it ever affect call return -- those 
registers die immediately before the call, and become live with these values immediately 
after the call.


r~