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Zing Falcon

Over the last few years, I helped to develop the Falcon compiler for the Azul Zing VM. Somewhat unfortunately, there's fairly little public information on the project. (Marketing has never exactly been Azul's strength.) This page exists to consolidate known public information along with some basic factual overview.

What is it?

Falcon is a LLVM-based in memory compiler for java bytecode to x86-64 assembly. It is the top tier compiler for the Azul Zing VM. It is a heavily optimizing just in time compiler which is fed with high quality profiling information collected in lower tiers of execution.

Falcon's strength is the ability to emit high quality code resulting in runtime performance for workloads on Zing which absolutely trounces the competition. Almost more interestingly, because it uses the same underlying compiler technology as Clang, Falcon can generate high performance code for just about anything Clang can. With Falcon, it is routine and common to see vectorization of common loop idioms native for the platform of execution.

Falcon's largest weakness is compile time. It's very much not a classic just in time compiler design; there's a reason I called it an "in memory compiler" above. While the team has done a lot to mitigate this (which I can't talk about here), there do remain cases where this is observable.

Public Talks

The best intro talk is probably the keynote that I gave at the 2017 LLVM Developers Meeting. Beyond that, there have been a number of talks presented by members of the team over the development life cycle. I'm listing the ones I know of in reverse chronological order.

  • An Update on Optimizing Multiple Exit Loops. Philip Reames. Tech Talk, 2020 LLVM Virtual Developers Meeting.
  • Control-flow sensitive escape analysis in Falcon JIT. Artur Pilipenko. Tech Talk, 2020 LLVM Virtual Developers Meeting.
  • Truly Final Optimization in Zing VM. Anna Thomas. Tech Talk, JVM Language Summit 2018.
  • Falcon: An optimizing Java JIT. Philip Reames, Keynote, 2017 LLVM Developers Meeting
  • A Quick Intro to Falcon. Philip Reames. Lightning Talk, JVM Language Summit 2017.
  • Expressing high level optimizations within LLVM. Artur Pilipenko. Tech Talk, 2017 European LLVM Developers Meeting.
  • LLVM for a managed language: what we’ve learned. Sanjoy Das and Philip Reames. Tech Talk, 2015 LLVM Developers Meeting
  • Supporting Precise Relocating Garbage Collection in LLVM. Sanjoy Das and Philip Reames. Tech Talk, 2014 LLVM Developers Meeting

Other Citable Stuff

Introducing the Falcon JIT Compiler

See also the blog posts linked to the launch at the bottom.

Using ZVM with the Falcon Compiler

These are the public docs for the Zing product. Here you can find the command line options to see the underlying LLVM IR - mostly interesting for compiler folks. This is also the only public place I can find which gives the original release date (Dec 2016) and on by default date (March 2017). Be cautious of the docs in generally though, they're frequently hilariously out of date and sometimes just wrong.

Truly Final Optimization in Zing VM

A nice written version of the 2018 JVMLS talk mentioned above.