Re: [f-cpu] Trying to clean up the ROP2 mess

[Michael Riepe <michael@stud.uni-hannover.de>]

On Thu, Jan 09, 2003 at 11:52:30PM +0100, Yann Guidon wrote:

> well, i think that the s- prefix on the logic operations looks confusing.
> why not try the following : when no size prefix is given, it operates on 
> the whole register ?

There is no room for that. The current encoding:

	31-24	opcode+function
	23-22	result chunk size
	21-20	combine chunk size
	19-18	rop2 mode flags
	17-12	r3
	11- 6	r2
	 5- 0	r1

leaves absolutely no room for a SIMD bit that could make a difference
between `and' (`sand' in my proposal) and `and.64'.

> this would avoid the silly questions like : what does the "sand" 
> instruction do ? :-)
> (cf : my "sel" and "poivre" instructions...)

I still wait for the request to rename `widen' to `sex'...

> >[...]
> >  
> >
> >>well, we don't converge on these last details but the encoding i 
> >>proposed is able to do that
> >>(except that there are 2 size fields, one for the writeback size and one 
> >>for the combine chunk size).
> >>    
> >>
> >That's one of the problems. Since you re-used the SIMD flag for the
> >additional size flags,
> >
> 
> ??? did i miss something ?

See above.

> > there is no longer a way to specify a register-wide
> >operation (remember that registers may be much wider than 64 bits).
> >Besides that, the second size flag makes the encoding inconsistent
> >with the majority of instructions (one goal is to keep the decoder
> >simple!). For the same reason, I dropped the secondary size flags from
> >the original `widen' instruction.
> >  
> >
> This second size flag is necessary and since it's not going to be larger 
> than 64 bits/chunks,
> it's not as complex as the main size flags. So it can probably become 
> inconsistent,
> but it remains consistent with itself (00=8 bits (default), 01= 16 bits, 
> 10= 32 bits, 11=64 bits)
> This is not the same problem with wide, IIRC...

I wonder what it's necessary for.

> >>>I will implement this encoding scheme in the next release of my
> >>>assembler/disassembler/emulator trio.
> >>>
> >>you're going to have too much fun : you're insane :-)
> >>    
> >>
> >Did you try to install my fctools package? ;)
> >
> hell, i don't have any decently running linux box ....
> shame on me ...

When you do it, look at the output from ./configure ;)

-- 
 Michael "Tired" Riepe <Michael.Riepe@stud.uni-hannover.de>
 "All I wanna do is have a little fun before I die"
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