This paper presents a programmable FIR core with a compact adder-based computing engine and an automatic code generator. The FIR core saves 50% area of conventional MAC-based cores in the 0.13/spl mu/m implementation. Besides, the complexity-aware code generator synthesizes optimized FIR programs for a user-defined sampling period. It explores an optimal scaling factor with common subexpression elimination automatically. In our simulations, the proposed approach reduces about 10% /spl sim/ 18% computing time of MAC-based FIR cores with comparable filtering performance.