Using type transformations to generate program variants for FPGA design space exploration

We present preliminary results with the TyTra design flow. Our aim is to create a parallelising compiler for high-performance scientific code on heterogeneous platforms, with a focus on Field-Programmable Gate Arrays (FPGAs). Using the functional language Idris, we show how this programming paradigm facilitates generation of different correct-by-construction program variants through type transformations. We have developed a custom Intermediate Representation (IR) language, the TyTra-IR, which is similar to the LLVM IR, with extensions to express parallelism, allowing us to designs variants associated with each program variant. The key innovation of the TyTra-IR is the ability to construct and cost design variants for FPGAs. Our prototype compiler generates Verilog code for FPGA synthesis from a given IR description. Using a real-world Successive Over-Relaxation (SOR) kernel, we illustrate generation of program variants in Idris, their representation in TyTra-IR, and evaluation of variants using our cost-model. We compare the estimates from the cost-model with results from synthesis and simulation of equivalent HDL.