Yes, it's using JIT compilation (last I checked, they are using LLVM as the backend). Combined with a language design that takes JIT compilation into account fr

Yes, it's using JIT compilation (last I checked, they are using LLVM as the backend). Combined with a language design that takes JIT compilation into account from the get-go, making the problem much easier than trying to use a JIT later on (see e.g. PyPy).