Re: Lightning Bindings

[Ludovic Courtès]

Hi Noah!

Noah Lavine <address@hidden> writes:

> Here is my understanding of the three approaches:
>
> The approach in my project was to make machine code a Guile datatype,
> which you could allocate with a special init function and write to
> with writing functions which are just Guile versions of the Lightning
> macros. It could be called as a function through the dynamic FFI.
>
> The approach in the other guile-lightning project is to represent the
> Lightning code as a Guile list which mirrors the Lightning virtual
> instruction set. When a list is completely built, it would then be
> passed to a special function (written in C) to assemble it. It also
> has some infrastructure for labels and a special method of calling
> these functions, neither of which I understand yet.
>
> The approach in your plan for JIT, as I understand it, is to implement
> this completely in the C layer. The machine code would be stored as
> part of the representation of a procedure, and would be invisible from
> the Scheme side.

Yes.

> The reason I did not use the approach of the other guile-lightning, to
> make a list and then assemble it, was that it seemed inelegant and
> possibly slow

It depends on when and how the instruction stream is written.  From a
usability viewpoint, having a simple s-exp for asm instructions is
nice (and elegant, IMO).

OTOH, I find the ‘make-integer-id’ example at
<http://github.com/noahl/guile-lightning/blob/master/binds.scm> quite
elegant too.

BTW, note that end-of-buffer situations must be handled, somehow.  If
the whole call generation procedure is burried in a single C functions,
it can hide these details to the application.  Otherwise, it’d be up to
the application to handle this situation, e.g., by linking two code
buffers together and adding a jump instruction in the first one to the
second one.

Anyway, these are just random thoughts.

Thanks,
Ludo’.