Re: [Qemu-devel] [RFC PATCH 1/6] target/ppc: introduce get_fpr() and set_fpr() helpers for FP register access

[Mark Cave-Ayland]

On 10/12/2018 05:17, David Gibson wrote:

> On Fri, Dec 07, 2018 at 08:56:30AM +0000, Mark Cave-Ayland wrote:
>> These helpers allow us to move FP register values to/from the specified 
>> TCGv_i64
>> argument.
>>
>> To prevent FP helpers accessing the cpu_fpr array directly, add extra TCG
>> temporaries as required.
> 
> It's not obvious to me why that's a desirable thing.  I'm assuming
> it's somehow necessary for the stuff later in the series, but I think
> we need a brief rationale here to explain why this isn't just adding
> extra reg copies for the sake of it.

Ah okay. It's because the VSX registers extend the set of VMX and FPR registers 
(see
the cpu_vsrh() and cpu_vsrl() helpers at the top of
target/ppc/translate/vsx-impl.inc.c). So in order to remove the static TCGv_i64
arrays then these helpers must also be converted.


ATB,

Mark.