Even though you'll be outputting LLVM as the intermediate representation, I think you'll still have to think a lot about the design of the internal structures a

Even though you'll be outputting LLVM as the intermediate representation, I think you'll still have to think a lot about the design of the internal structures and the operation of the "virtual machine" so to speak (although there isn't one in the traditional sense). You'll still need to think about how functions interact, what anonymous functions/lambdas boil down to, etc. To that end, it may be interesting to study the source of J, Klong, Kona, etc. There are a lot of older papers about representation and performance in APL as well.