Re: Re: [f-cpu] reg. rotation [Was: New suggestion about call convention]

[whygee@club-internet.fr]

hi,

>De: cedric
>
>hi,
>
>> cedric wrote:
>> >dmove syntax will be more like this (if it exist) :
>> >	dmove r2, r1
>> >the behaviour will be :
>> >	r1 = r2
>> >	r1^1 = r2^1
>> >But I don't know if it will possible to implement it, but it's a good idea
>> > I think.
>
>> i don't think so (TM)
>
>Are you sure ?

absolutely.
I will need another, better reason than "it is possible"
to be convinced that it is really necessary.

> I was thinking that we currently need a mecanism to read r1 and 
>r1^1 and to write r2 and r2^2 at the same cycle,

so this will require to discard the condition field.
do you remember that the "move" instructions are conditional ?

> if we implement all the instruction specified in the manual.
i don't understand why there should be a relation with the other
instructions.

> I don't see where will be the overhead in hardware,

it's not orthogonal with the move instructions.

> but I think it can be usefull for a lot of code.
> So why not ?

Why make something that will become complex
in the next generations of F-CPU ?

> (A more precise answer will be appreciate ;-)

try to think about the decoding+issue logic
of a more complex implementation of F-CPU,
for example one that executes 2 (or more)
instructions per cycle.

>	Cedric
YG

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