PDP8 / ETOS

[Rick Murphy]

At 06:47 AM 10/20/2015, Noel Chiappa wrote:
>     > From: Rick Murphy
>
>     > Lots and lots of fun like that. What an space optimizer would do if
>     > there was one. :)
>
>Wow. You did all that by hand?

Yup. Lots of work. That's kind of why I find the implication that I 
don't know what's going on here somewhat disconcerting. :)

>If so, with a program that big, wouldn't it have made sense to try and 
>write
>a separate post-processor to do all those optimizations? Surely it 
>wouldn't
>have been that much work, compared to going through the entire compiler
>output!

As with most things, it initially looked to be more work to write 
something to parse the code and optimize it. Some of the work was 
pretty much rote, but a lot of it took some judgement to find more 
compact code. It wasn't until I described the effort that I actually 
considered calling it "space optimization".  Oh, and some of this was 
painfully impacted by the limits of the compiler symbol table sizes, 
thus a lot of constants don't get meaningful names.

Ugh. I wouldn't have volunteered for this. I still want to get it to 
the point where 28K is possible, but that'll take a new optimization 
that I haven't yet thought of. :) Basically, at this point, it's really 
a FPP assembler version of Adventure slightly assisted by the Fortran 
compiler. I'm pretty proud of the idle loop blinkenlights, though. 
Looks good on my PiDP-8.
     -Rick