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Re: [PATCHv4] Add support for O32 FPXX ABI

Matthew Fortune <> writes:
>> > -  /* Single-precision coprocessor loads and moves are OK too.  */
>> > +  /* Single-precision coprocessor loads and moves are OK for 32-bit
>> registers,
>> > +     otherwise it depends on oddspreg.  */
>> >    if ((insn->pinfo & FP_S)
>> > -      && (insn->pinfo & (INSN_COPROC_MEMORY_DELAY | INSN_STORE_MEMORY
>> > +      && (insn->pinfo & INSN_FP_32_MOVE))
>> > +    return FPR_SIZE == 32 || oddspreg;
>> Why do you need a new flag for this?
> There are two reasons for this. The lwxc1 instruction is just an
> INSN_LOAD_MEMORY. I could however just add that to the list of flags to
> check (and remove INSN_COPROC_MEMORY_DELAY if the LOAD is added)...

Sounds good.

> but the bigger reason is that the micromips mtc1/mfc1 instructions are
> not INSN_COPROC_MOVE_DELAY so there is no flag to detect them. This
> has never been a problem before as there has always been 32 single
> precision registers for micromips but now that may be restricted to 16
> depending on ABI. I could just attach a new flag to the micromips
> instructions which lack any other flag but it seems clearer to attach
> it to the others too.  The only other option is to add
> INSN_COPROC_MOVE_DELAY to the mtc1/mfc1 instructions in micromips even
> though that is something of a lie. What do you think is cleanest?

I think the last one is probably best.  We could remove the _DELAY
from the name too, since the delay is only conditional anyway.

> I would also like to get rid of all the ctc1/cfc1/cttc1/cftc1 instructions
> that allow the use of floating point register names: $f0. The problem with
> these is that they don't actually write floating point registers but they
> will interact with the oddspreg logic as their operands have type
> OP_REG_FP. Anything relying on ctc1 $0, $f[0-31] is probably expecting the
> wrong thing to happen anyway. If that's OK I'll do a separate patch?

It's always dangerous to change something long-standing like that, but
I agree it's weird.  OTOH "ctc1 $0, $31" could be seen as confusing too
(it isn't GPR 31).

Let's assume it's OK for now and see if there are any objections.


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