Pencil A Platform-Neutral Compute Intermediate Language for DSL Compilers

Programming accelerators such as GPUs with low-level APIs and languages like OpenCL and CUDA is difficult, error prone, and not performance-portable. Automatic parallelization and domain specific languages (DSLs) have been proposed to hide this complexity and to regain some performance portability. In this presentation, I will present PENCIL (Platform-Neutral Compute Intermediate Language) and present some details about how it is compiled. PENCIL is a rigorously defined subset of GNU C99 with specific programming rules and few extensions. Adherence to this subset and the use of these extensions enable compilers to exploit parallelism and to better optimize code when targeting accelerators. We intend PENCIL both as a portable language to facilitate accelerator programming, and as an intermediate language for DSL compilers. We validate the potential of PENCIL on a state-of-the-art polyhedral compiler, extending the applicability of the compiler to dynamic, data-dependent control flow and non-affine array accesses.