[LLVMdev] Pyston: a Python JIT on LLVM

[Kevin Modzelewski]

Hi all,

I've been lurking on the list for a bit, and I'm excited to finally talk
about what I'm working on: Pyston, a JIT for
Python<https://tech.dropbox.com/2014/04/introducing-pyston-an-upcoming-jit-based-python-implementation/>.
 It's still extremely early on, but I'm happy that I can open source the
code <https://github.com/dropbox/pyston> for viewing and discussion.

It contains experimental but working implementations of a few things that I
thought might be interesting to the community; they are certainly not
production-quality implementations, but I hope they can be at least a data
point for people interested in the functionality:
- It contains a working cross-module
inliner<https://github.com/dropbox/pyston/blob/master/src/codegen/opt/inliner.cpp>,
which can be necessary for doing inlining with MCJIT.
- It has a build system that allows compiling a runtime file both into the
JIT itself, as well as into the stdlib bitcode file for inlining into JIT'd
code.
- It contains a working inline cache system that uses the
llvm.experimental.patchpoint() intrinsic.  It also has some new support for
using the PreserveAll calling convention so that the inline cache fastpaths
can often avoid spilling registers.
- It has a few optimization passes that are optimized for Pyston, but could
be applicable to other dynamic languages; in particular it has an escape
analysis for GC'd
memory<https://github.com/dropbox/pyston/blob/master/src/codegen/opt/escape_analysis.cpp>that
helps lower GC'd memory to registers if the variable is local
(something that is probably rare in static languages, but very common in
Python).
- Some perf debugging tools, ex for getting instruction-level profiles of
JIT'd code.


There's still a very, very long way to go for Pyston, but it couldn't have
even started without LLVM, so I hope I can give something back!

kmod
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