From the CLASP page:

> Clasp is a new Common Lisp implementation that seamlessly interoperates with C++ libraries and programs using LLVM for compilation to native code. This allows Clasp to take advantage of a vast array of preexisting libraries and programs, such as out of the scientific computing ecosystem. Embedding them in a Common Lisp environment allows you to make use of rapid prototyping, incremental development, and other capabilities that make it a powerful language.

you wrote:

> This project uses LLVM's API, which is sadly difficult to utilize outside of C++.

I would guess that you could use LLVM's API via CLASP. The author initially wrote ( https://drmeister.wordpress.com/2014/09/18/announcing-clasp/) :

> Clasp exposes the LLVM C++ library within Common Lisp providing a rich, dynamic, programming environment for exploring the LLVM library and for writing new compilers that generate LLVM-IR.

Then you could write the parser/compiler in Lisp, which supports manipulating s-expressions on a simpler level than C++ does.