Re: [fpu] FPU operations

[Jamil Khatib <jamilkhatib75@yahoo.com>]

Hi,
 
> I have a question about FP operations performed by
> FPU (I am adding FP
> instructions to OR1K - only single precision at the
> moment). 

OK thats fine for now

Anyway
> I'll list some of the operations that would be nice
> to have and I hope
> someone can comment if they are simple enough to be
> supported by FPU.
> 
> So basic operations that should be supported are:
> 
> - SF add (SF stands for single precision FP)
> - SF sub (should this be done with neg+add
> combination?)
I prefer to have two instructions but in the FPU it
will be mapped to teh same unit with a selection bit

> - SF mul

I think we need div

> - SF compare
compare for equality only?

> - conversion operations (should integer<->SF be done
> by basic FPU or is
> there any other idea? Also don't forget if you want
> DF then we need
> SF<->DF)
> 
yes we need it but I think there should be also the
ability to use the rounding method in a seperate
instruction may be?

> Extra operations (desired but not really required
> IMO):
> - SF div
> - SF mac (or you can call it madd. Anyway it would
> be nice to have this
> one. It is easy to implement it if FP Add and Mul
> hardware is separate)

If we are going to define MAC we should have a
seperate block for it

> - SF sqrt
At least not full implementation

> - SF neg (MIPS, SPARC & PPC have it - is it required
> by the standard?)
I do not think it is requeired

> - SF abs (MIPS, SPARC & PPC have it - is it required
> by the standard?)
> 
It is not a big problem so lets do it

> Instructions like floating point moves between FP
> registers or
> load/stores to/from FP registers are performed
> directly over FP
> register file (no processing required) so I didin't
> mentioned them
> above (I only listed operations that FP calculation
> hardware should be
> able to do).
> 
Yes

> I can list FP instructions of MIPS, SPARC and other
> processor
> architectures if there is interest. 
> 
> regards,
> Damjan
> 
> 
Regards
Jamil Khatib

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