An efficient compilation of coarse-grained reconfigurable architectures utilizing pre-optimized sub-graph mappings

In recent years, IoT devices have become widespread, and energy-efficient coarse-grained reconfigurable architectures (CGRAs) have attracted attention. CGRAs comprise several processing units called processing elements (PEs) arranged in a two-dimensional array. The operations of PEs and the interconnections between them are adaptively changed depending on a target application, and this contributes to a higher energy efficiency compared to general-purpose processors. The application kernel executed on CGRAs is represented as a data flow graph (DFG), and CGRA compilers are responsible for mapping the DFG onto the PE array. Thus, mapping algorithms significantly influence the performance and power efficiency of CGRAs as well as the compile time. This paper proposes POCOCO, a compiler framework for CGRAs that can use pre-optimized subgraph mappings. This contributes to reducing the compiler optimization task. To leverage the subgraph mappings, we extend an existing mapping method based on a genetic algorithm. Experiments on three architectures demonstrated that the proposed method reduces the optimization time by 48%, on an average, for the best case of the three architectures.