Compiling synchronous languages to optimal move code for exposed datapath architectures

Abstract

Conventional processor architectures are limited in exploiting instruction level parallelism (ILP). One of the reasons for this limitation is their relatively low number of registers. Thus, recent processor architectures expose their datapaths so that the compiler can take care of directly transporting results from processing units to other processing units. Among these architectures, the Synchronous Control Asynchronous Dataflow (SCAD) architecture is a recently proposed exposed datapath architecture whose goal is to completely bypass the use of registers. Processor architectures with a high degree of ILP like SCAD are particularly useful for executing synchronous programs: The execution of a synchronous program is a sequence of reaction steps that consist of atomic actions that have to be executed in dataflow order. Synchronous programs typically provide a lot of ILP so that exposed datapath architectures may execute these programs efficiently. However, optimal code generation for SCAD is a big challenge: Previous work already showed how one can compile basic blocks to optimal move code for SCAD by means of answer set programming (ASP). This paper extends this approach in order to compile complete synchronous programs instead of only basic blocks to optimal move code. As a result, an ASP-based compiler was developed to translate Quartz programs to move code for the SCAD architecture by maximizing the use of the available ILP in the program while respecting the available resource limitations of the available processor.