RLLVMCompile is an experimental R compiler that uses LLVM through RLLVM, currently being developed by Duncan Temple Lang.
The goal of this is to provide an R programmer-level framework for compiling R-like code. This is different from building a compiler that requires changing the code for the interpreter or developing an different implementation of R, i.e. separate from GNU R. The idea is that we can translate R-like code to LLVM instructions, create those instructions using the Rllvm package and then generate native/compiled code and invoke it from the R session, serialize it for use in other sessions or even applications (e.g. JavaScript, Python).
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.