Can you take classical code and compile it to quantum code?
Doubly-controlled NOT gates are universal  with respect to classical functions. Quantum computers can perform doubly-controlled NOTs. So even a quantum computer not allowed to perform fancy operations involving superposition, and not allowed to perform irreversible operations such as measuring or clearing a bit, can perform any classical computation.

For example, a quantum computer can basically directly run the gates making up a VanRentergem addition circuit:



Quantum computers are actually slightly better at reversible computation than classical computers. Classically you sometimes need an extra scratch bit to compute a function, because of permutation parity issues, but quantum shenanigans get that down to zero. Though of course emulating irreversible functions still requires introducing new scratch bits each time.