You’re doing it right, actually -cpu -dump-llvm-ir is the right way to dump LLVM IR generated by the CPU backend.  The problem is the output is pretty overwhelming because you get all of libjit’s IR dumped in addition to the IR generated for your model.
You’ll see two big sections in the dumped output: “before optimizations” and “after optimizations”.  The “after” section will just have your model code, since it’s after we do inlining, specialization and prune unused functions.  Look for @jitmain (or @main) in either section to see where the model code starts.