Nice jokes and great hacks aside however, unless you're interviewing for a compiler engineer position, That is absolutely overkill for this type of question to the point of unreadability. One can argue that the 'question' is too generic for this systems/compiler developer position. I would just ask you about basic LLVM internals instead.

To those 'serious' interviewers with 10x developer syndrome looking at this as an 'optimal solution', just don't tell candidates to do this on a whiteboard in >20 mins. You might as well ask for a candidate to do it in LLVM IR.

EDIT: Even though the whole post is a great hack and a joke as I already outlined earlier, it still looks like some HNers still can't take/see jokes! %:O)