Simultaneous resource binding and interconnection optimization based on a distributed register-file microarchitecture

Behavior synthesis and optimization beyond the register-transfer level require an efficient utilization of the underlying platform features. This article presents a platform-based resource binding approach based on a Distributed Register-File Microarchitecture (DRFM), which makes efficient use of distributed embedded memory blocks as register files in modern FPGAs. DRFM contains multiple islands, each having a local register file, a functional unit pool, and data-routing logic. Compared to the traditional discrete-register counterpart, a DRFM allows use of the platform-featured on-chip memory or register-file IP blocks to implement its local register files, and this results in a substantial saving of multiplexing logic and global interconnects. DRFM provides a useful architectural template and a direct optimization objective for minimizing interisland connections for synthesis algorithms. Given the scheduling solution and resource (functional units) constraints, two novel algorithms in the resource binding stage are developed based on DRFM: (i) a simultaneous DRFM clustering and binding algorithm, which decides the configuration of DRFM and the assignment of operations into islands with the focus on optimizing global connections; (ii) a data-forwarding scheduling algorithm, which takes advantage of the operation slacks to handle the read-port restriction of register files. On the Xilinx Virtex4 FPGA platform, experimental results with a set of real-life test cases show a 50% logic area reduction achieved by applying our approach, with a 14.6% performance improvement, compared to the traditional discrete-register-based approach. Also, experiments on small-size designs show that our algorithm produces the same number of total connections and at most one more maximum feeding-in connection compared to optimal solutions generated by ILP.