[Simh] fprint_sym and parse_sym limitation

[Paul Koning]

> On Sep 11, 2015, at 4:43 PM, J. David Bryan <jdbryan at acm.org> wrote:
> 
> On Friday, September 11, 2015 at 15:32, Paul Koning wrote:
> 
>> Not quite.  It would break existing simulators that use the addr field
>> for register radix without masking it. 
> 
> But existing simulators wouldn't be passing any user-defined REG_* flags, 
> so "(rptr->flags & REG_UFMASK) | rdx" would be equal to "rdx", and they'd 
> receive the radix just as before.

Yes, good point.

> 
> 
>> If you want to disregard that case, would it not be just as simple,
>> but more powerful, to pass the index into the registers array as
>> "addr"?  Then all you need is to find the regs vector from the UNIT
>> pointer, and index that with addr, and you have all the information you
>> might want about that register -- its flags, name, or the register
>> number if you want to use that. 
> 
> Assume that I have three CPU registers that I want to format identically.  
> How do I tell if I've been called for one of these?  If I receive the 
> index, then I'd have to do:
> 
>  if (addr == 3 || addr == 7 || addr == 12) ...
> 
> or:
> 
>  if (strcmp (cpu_reg [addr].name, "CIR") == 0 ||
>      strcmp (cpu_reg [addr].name, "NIR") == 0 ||
>      strcmp (cpu_reg [addr].name, "XIR") == 0) ...
> 
> whereas with a user-defined flag, it's:
> 
>  if (addr & REG_IR) ...


I'd do: if (cpu_reg[addr].flags & REG_IR) ...

	paul