Re: wip-rtl, solstice edition

[Ludovic Courtès]

Hello, and happy Solstice!  :-)

Andy Wingo <address@hidden> skribis:

> First of all, I have changed the on-disk format for .go files to be ELF,
> even for the old Guile 2.0-style bytecode.  This increases the file size
> somewhat, though the memory footprint is the same.  What it gives us,
> though, is extensibility.

Neat.

> For me, my next steps are:
>
>  1) Convert the ELF parser and linker to use symbols instead of the raw
>     ELF codes, as the DWARF parser does.  It's more convenient and not
>     significantly different, performance-wise.

Yes.  The one at
<https://gitorious.org/guile-dlhacks/guile-dlhacks/blobs/master/dlhacks/elf.scm>
could use more comments, docstrings, and tests, if you ask me.  :-)

>  2) Add enough debugging information so that procedure-name works, and
>     that we can determine the bounds of procedures.  (Determining where
>     a procedure ends is a precondition for being able to disassemble
>     it!)
>
>  3) Create tests for all of the opcodes.  This task is somewhat
>     decoupled from the previous tasks; if people want to help out, see
>     libguile/vm-engine.c and test-suite/tests/rtl.test.

I’m afraid that writing tests after code may either not happen, or may
be unable to uncover bugs if it’s written by the same person, or may be
difficult for someone without a clear picture of the API.

WDYT?

That said, I’ll look into all this as time permits, and see what I can
contribute myself.

>  4) Update the tools (debugger, frame printer, etc) to be able to deal
>     with the new debugging format.

Sounds like a nice plan!

> So, that's the status.  Apologies for there being no overview yet; I
> will try to write something about that soon.  I reckon we are about a
> month away from a VM that works well, and has good debugging
> information, and two or three months away from a merge to master
> (meaning, we compile all of Scheme).  At that point we could look to
> release the first 2.2 beta release, aiming at a final 2.2 sometime early
> next year.

Didn’t you once say “2.2 will have native compilation”?  ;-)

Seriously though, that seems like a good plan.  I wonder what Noah’s
attempts at JITing the 2.0 bytecode would have achieved, though, if we
think of both JIT and the new VM as an “interim solution” before AOT
native compilation.

Thanks for the update, and thanks for all the work!

Ludo’.