RLLVMCompile is an experimental R compiler that uses LLVM through RLLVM, currently being developed by Duncan Temple Lang.
We might compile the same code in different ways for different contexts. As a result, a single one-size-fits-all approach to compiling R is probably too restrictive. Furthermore, we want to be able to explore new approaches easily w/o having to recompile all of R or learn a new compilation framework tha is specific to R.
One of the strengths of LLVM is that it embeddable and extensible and provides a user-level API. A compiler for R should also do the same. We have learned that a centralized code source that requires a core group to make all "official" and "distributed" changes limits innovation (but does improve stability).
Vince Buffalo and I started this package several years ago (late 2010) after the development of the Rllvm package. Unfortunately, I had other committments (the book XML and Web Technologies with R, and another "Data Science in R: A Case Studies Approach to Computational Reasoning and Problem Solving"). I am now getting back to this project and hope to push it forward quite a bit by early 2015.