This paper presents a Relative-Priority Genetic Algorithm (RPGA) designed for tackling Integrated Mapping and Scheduling (IMS) problems, frequently encountered in High-Level Synthesis. RPGA features a unique encoding and decoding mechanism specifically crafted for IMS problems, notably those involving OR nodes that denote alternative operation paths. Through comprehensive benchmarking experiments, RPGA demonstrates remarkable superiority in solution quality and convergence speed when compared to established meta-heuristics.