[LLVMdev] Re: LLVM and PyPy

[holger krekel]

Hi Chris,

[Chris Lattner Fri, Oct 31, 2003 at 10:58:45AM -0600]
> On Fri, 31 Oct 2003, Armin Rigo & Holger Krekel wrote:
> 
> > Hello Chris,
> >
> > We have been investigating your project and the good documentation
> > and are very impressed. If we understood your goals correctly
> > this seems like a good match for our ongoing and active PyPy project,
> > a reimplementation of the Python language in Python.
> 
> Cool.  We are all big fans of Python here.  :)

That's good because we might want to recode some LLVM functionalities
in Python :-)

> > We'll definitely try using LLVM as our low-level backend.
> > But actually we contact you now to ask you if you'd be interested
> > in some bidirectional collaboration.
> 
> I've read up a bit on PyPy, and it looks like LLVM could be a nice way to
> get the JIT type interface that you would like.  Also, making use of the
> LLVM optimizer can make your staticly generated code nice and fast.  :)

Yes, but we also would want to dynamically emit and execute LLVM code. 
But a static translation is indeed our first goal :-)

> We've tossed around the idea of creating C bindings
> for LLVM, which would make interfacing from other languages easier than
> going directly to the C++ API, but we just haven't had a chance to yet.
> Maybe you guys would be interested in helping with that project?

Thinking some more about it, we would probably try to translate our PyPy
implementation into LLVM-code and also generate some glue-LLVM-code
which allows us to programmatically drive LLVM from Python.  Is LLVM
able to "drive" itself? I mean can the LLVM-low-level object code
generate LLVM-low-level object code and then execute it? 

This would fit nicely with PyPy because we are running ourselves (in
'abstract interpretation' mode) in order to generate a low-level
representation of ourselves.  This low-level representation is already
close to LLVM's low-level view. So if the LLVM-code gets executed
(beeing a python interpreter) it should be able to just-in-time-compile
new LLVM code and execute it.  With our architecture, for such a JIT we
could reuse a good part of the code we already have for generating our
low-level representation.   It's a rather self-referential thing (also
see our logo: http://codespeak.net/pypy/ :-). 

> > On another level, some of the PyPy core developers are actually also
> > involved with the 'codespeak' site which aims at connecting interesting
> > open source projects and provide new collaborative development services.
> > The PyPy project is extensively using subversion which is a very interesting
> > (and stable) alternative to cvs.  So if you need any help with setting
> > up some publically accessible infrastructure the codespeak guys will
> > certainly welcome you.
> 
> At this point, we're working like crazy to get important features
> implemented in LLVM.  We certainly acknowledge that CVS has severe
> deficiencies, but in the near future we'll probably stay with it.
> Perhaps after SVN 1.0 comes out... :)

then we may want to mirror your cvs repo to subversion :-) 
The reason is that we want to provide consistent versions of all 
the libraries/modules/projects we use.  And subversion makes
this rather easy (if the other project is svn-controled, too), 
e.g. you can say 'i want to follow the HEAD version of LLVM
in this branch' or 'i want to use this stable version of LLVM
for my own stable-release'. Then you can just issue 'svn up' and
you will have the desired versions on your working-copy. 
However, i can understand that you don't want to consider 
subversion right now and will stop advertising now :-)

cheers,

    holger