Improving Scalability of Exact Modulo Scheduling with Specialized Conflict-Driven Learning

Loop pipelining is an important optimization in high-level synthesis to enable high-throughput pipelined execution of loop iterations. However, current pipeline scheduling approach relies on fundamentally inexact heuristics based on ad hoc priority functions and lacks guarantee on achieving the best throughput. To address this shortcoming, we propose a scheduling algorithm based on system of integer difference constraints (SDC) and Boolean satisfiability (SAT) to exactly handle various pipeline scheduling constraints. Our techniques take advantage of conflict-driven learning and problem-specific specialization to optimally yet efficiently derive pipelining solutions. Experiments demonstrate that our approach achieves notable speedup in comparison to integer linear programming based techniques.