Re: [hatari-devel] Adding Aranym features for Hatari?

[Eero Tamminen <oak@xxxxxxxxxxxxxx>]

Hi,

On lauantai 20 lokakuu 2012, Thomas Huth wrote:
> schrieb Eero Tamminen <oak@xxxxxxxxxxxxxx>:
> > On tiistai 16 lokakuu 2012, Eero Tamminen wrote:
> [...]
> 
> > I did today an initial code for basic NatFeats support:
> > http://hg.tuxfamily.org/mercurialroot/hatari/hatari/rev/50958d336a1a
> 
> Your change breaks compiling the WinUAE cpu core :-( Could you please
> fix that?

Fixed.

I'm not sure about this stuff on exit from the opcode handlers:
	regs.ir = regs.irc;

Only WinUAE core has that.

I added it also to natfeat opcode handlers, but is it e.g. needed
only in case one is doing a trap handler like GEMDOS or VDI?


> > I've modeled it on how it works in Aranym.  I'm not sure whether
> > the status register stuff is needed, but as it was used in Aranym,
> > I added it here also.

Any comments on that?

Aranym code actually stores and restores all normal registers too,
but I guess that was for some potential extra stuff that its
natfeat features could do...

 
> > It doesn't yet raise bus error / priviledge exception in case
> > the arguments or supervisor mode isn't correct.  How I can invoke
> > those in Hatari?
> 
> For Bus Error, you can use M68000_BusError(), for priviledge exception
> you could try something like Exception(8,0,M68000_EXC_SRC_CPU).
> Anyway, you've got to make sure to skip the m68k_incpc() and other
> remaining code when you did that, so that the CPU can correctly
> continue with the exception handler.

Thanks.  What about the status register stuff, should re-setting
that be skipped too?


What about this VDI check():
------------
        if (VDI_OldPC && pc >= 0xfa0000 && pc < 0xfc0000)                                                                                                            
        {                                                                                                                                                            
                VDI_Complete();                                                                                                                                      
                                                                                                                                                                     
                /* Set PC back to where originated from to continue 
instruction decoding */                                                                          
                m68k_setpc(VDI_OldPC);                                                                                                                               
                VDI_OldPC = 0;                                                                                                                                       
        }                                                                                                                                                            
        else                                                                                                                                                         
        {                                                                                                                                                            
                /* illegal instruction */                                                                                                                            
                op_illg(opcode);                                                                                                                                     
        }                                                                                                                                                            
                                                                                                                                                                     
        get_word_prefetch (0);                                                                                                                                       
        regs.ir = regs.irc;                                                                                                                                          
        get_word_prefetch(2); 
------------

I think this check was needed when GEMDOS emu enables cartridge stuff,
which causes also VDI opcode to be set up, but some demo/game
was using that illegal opcode for its protection.

Should the extra stuff be skipped also after op_illg()?


	- Eero