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Re: [PATCH] Add support for fpscr for Power / PowerPC targets
> > > For PowerPC, the fpscr regnum is 70, which was an unused slot. For
>> > Power, I chose to use the first available slot (71). The other change
>> > that this patch makes is to make MQ unavailable for all PowerPC
>> > targets except for the 601 processors (which is as it should be).
>
>>
>> Kevin, is there any reason to not just use the same slot for both POWER
>> and PowerPC?
>
>
> It would be nice if we could, but I don't see how it can be done without
> either
>
> 1) renumbering some registers for some processors.
> or
> 2) assigning fpscr to a really high slot that's larger than any
> current register.
>
> I didn't want to do (1) because existing stubs would likely break.
> (But see below).
>
> I didn't want to do (2) because that would introduce a really large
> gap between fpscr and the rest of the registers for most processors.
>
> Slot 70 was an unused slot for PowerPC, but it was used for ``mq'' for
> Power. The next available slot for Power was 71, so that's what I used
> for Power.
>
> Also, for PowerPC, slot 70 was already in the set of PPC_UISA_SPRS and
> that's exactly where fpscr belongs.
>
> If we don't mind a minor violation of (1), I could reassign mq to slot 71
> for Power. That would free up slot 70 so that Power would also have
> fpscr available at the same slot number as PowerPC. This might be a
> relatively safe thing to do since it's likely that there aren't many
> (any?) existing stubs for the Power architecture. It'll require some
> adjustments to rs6000-nat.c, but I'm willing to make those adjustments.
>
> Opinions?
Thanks for explaining this. I guess just add the above as a comment.
Andrew