Re: Adapting an Ada compiler to generate 8051 code (Again?! ;-)

["Randy Brukardt" <randy@rrsoftware.com>]

"Luke A. Guest" <laguest@archeia.com> wrote in message 
news:s44du6$ugk$1@gioia.aioe.org...
> On 01/04/2021 00:20, Randy Brukardt wrote:
>> "Luke A. Guest" <laguest@archeia.com> wrote in message
>> news:s40urd$qbp$1@gioia.aioe.org...
>> ...
>>> AVR isn't really an accumulator arch, it's got 32 registers. Even the 
>>> 6502
>>> has a port, but that uses the zero page as virtual registers. The Z80
>>> cannot do that as it starts executing from address 0 iirc.
>>
>> The Z-80 has enough registers for Ada (or at least a reasonable 
>> subtest) --
>> see the original Janus/Ada compilers. If you want *real* registers, even 
>> the
>
> I know of the original Janus for Z80, never used it, is it a real Ada 
> compiler or is it a Pascal like Ada?

It was an Ada 83 subset. Don't remember the exact details, but it covered a 
substantial part of the language, including packages and exceptions. The 
validated Ada 83 compilers were direct descendants, and the current compiler 
is directly descended from that.

> Have you considered compiling it as a cross compiler on Linux?

Sadly, we've lost the back-end. When I was moving and going to junk the last 
machine with a working 5 1/4" floppy, I decided to copy all of the old stuff 
into the version control system. But I wasn't able to read the disks with 
the source to the last pass.

I didn't concern myself too much with losing that, as that backend predated 
J-Code and thus any modern version would need to be rewritten anyway to mate 
with a modern front-end. I did manage to recover the runtime, which would be 
more work to reproduce anyway -- especially the floating point library.

>> x86 doesn't have enough registers for reasonable code optimizations. A
>
> Tell me about it. Always hated the x86 when I was on m68k, look I have 8 
> Data and 8 Address registers, you have what? 4 useable ones!

6 registers on the x86 (as SP and BP have special purposes -- one can use 
them [especially BP] in a pinch but you have to save the contents). It's 
just enough to be more than enough for most simple purposes and thus a bit 
of longer term register allocation is needed. The Z-80 for instance didn't 
need any register allocation as with essentially 3 there wasn't any point in 
trying to keep anything there.

                          Randy.