Function reg_overlap 

pub unsafe extern "C" fn reg_overlap(
    r1: reg_id_t,
    r2: reg_id_t,
) -> bool_

Assumes that \p r1 and \p r2 are both DR_REG_ constants. Returns true iff \p r1’s register overlaps \p r2’s register (e.g., if \p r1 == DR_REG_AX and \p r2 == DR_REG_EAX).