Unladen Swallow dead, not resting
The Unladen Swallow implementation of Python is dead, not resting, according to developers who have worked on the project. Unladen Swallow was an attempt to optimise Python by using an LLVM based Just In Time (JIT) compiler to execute the code. There was excitement about the project in 2009, but 2010 saw speculation voiced on whether it was still a going concern. Two of the Google developers who "owned" the project were moved to other jobs in November 2010. Meanwhile, the community's focus moved to the PyPy Python JIT.
Now, in a blog posting, Reid Kleckner, who interned on the project at Google, said "As is apparent by now, no one has really been doing any work directly on Unladen Swallow or in porting it to py3k". He explained that the primary reason for the end of the project, which saw its last release in 2009, was a lack of sponsorship from within Google. Kleckner said that Python code within Google tended not to be performance critical and where it was, deployment of Unladen Swallow was difficult.
This led those internal customers to find other ways of solving their problems. The developers had considered pursuing the project in their spare time in 2010. During 2010 though, the PyPy developers moved towards implementing C extensions, SWIG wrappers and x86 64-bit support; all of that contributed to the developers feeling Unladen Swallow had become less relevant.
Kleckner does note that the project did do LLVM work which benefitted other LLVM JIT projects such as Parrot and Rubinius, such as removing the 16 MB limitation on JITed code. Kleckner feels though that LLVM, in it's current state, is best suited as a static compiler optimiser and is not ideal for systems which wish to dynamically optimise their code depending on previous runs.