Re: CPS thoughts

[Andy Wingo]

On Tue 21 May 2013 05:21, Noah Lavine <address@hidden> writes:

>      * Missing distinction between original names and unique names.
>     
>
> Yes, I agree. I think it even reuses original names sometimes, which is
> not good. I should just rename everything.

You should have two names: the original ones and the gensyms that come
from tree-il.  Creating new gensyms should happen when copying or
fabricating new nodes, as peval does, but in most cases you don't need
to do it, and in any case it can be tricky.

I would take tree-il as the guide here.

>      * Missing source information.
>     
>
> The issue here is not that it's hard to pass source information through
> to the compiler, but that I haven't figured out what to do with it when
> I have it. I imagine that your ELF work has solved this problem.

I haven't handled source information yet, but to the CPS->RTL compiler
it will look like emitting special instructions, like the tree-il->glil
compiler emits <glil-source> nodes.

>       * Missing procedure properties.
>     
> Can you explain what you mean? Does the compiler need to handle
> procedure properties specially?

This is lambda-properties.  You just pass them through, and add them to
the begin-program in the RTL.

Note that wip-rtl-may-2013 and the RTL branches that are under review
for master are slightly different from the ones you have.  Their
begin-program has a second argument, the procedure properties, and the
first argument is a label and not a name.  They have begin-*-arity and
end-arity for marking arity information and performing arity prologues.
There are some slight changes to instructions but not much.  OTOH they
do have some better type checking and a disassembler that works, so many
things should be easier ;) Compare the rtl.test there and your rtl.test
for details.

>       * Why is there no "let" that can bind functions?  You don't always
>     want
>        to set up a recursive binding environment.
>     
>      * Lambdas are missing lambda* and case-lambda support.
>     
> With these two, it's just that I haven't implemented it yet. I'll try to
> do it quickly, although I don't know how much time I'll have to work on
> it.

Understood.  However the question of language is fundamental for
enabling collaboration on this code.  I would be very happy to see a CPS
language definition that could express all of Tree-IL.  I don't think
this would take a lot of work -- it is perfectly acceptable to throw
"unimplemented" for those parts of the compiler that aren't there yet,
but the language itself should be adequately expressive.  IMHO anyway.

Do you think you will have time to do that over the next few days or so?
Apologies for the pressure, just that I would like to do some things in
this area and am not sure how best to do them :)

> Sounds great! I think the compiler stuff is fairly separate from the RTL
> stuff - when I've rebased it occasionally, it hasn't been a problem.

Excellent :)  Note the changes I mentioned above.

Cheers,

Andy
-- 
http://wingolog.org/