This brief presents an energy-efficient and high-performance XNOR-bitcount architecture exploiting the benefits of computing-in-memory (CiM) and unique properties of spin-transfer torque magnetic RAM (STT-MRAM) based on double-barrier magnetic tunnel junctions (DMTJs). Our work proposes hardware and algorithmic optimizations, benchmarked against a state-of-the-art CiM-based XNOR-bitcount design. Simulation results show that our hardware optimization reduces the storage requirement (-50%) for each XNOR-bitcount operation. The proposed algorithmic optimization improves execution time and energy consumption by about 30% (78%) and 26% (85%), respectively, for single (5 sequential) 9-bit XNOR-bitcount operations. As a case study, our solution is demonstrated for shape analysis using bit-quads.