A Compiler Phase to Optimally Split GPU Wavefronts for Safety-Critical Systems

We present a compiler phase for GPUs enabled with predictable wavefront splitting (PWSG) that implements an optimal algorithm to split diverging GPU wavefronts into separate scheduleable entities. This algorithm selects branches in the GPU kernel that guarantee the lowest worst-case execution time (WCET) for the kernel. We implement our algorithm in a compiler flow for an AMD GPU, and we deploy the resulting binary on a gem5 micro-architectural implementation of the AMD GCN3 GPU. We evaluate our implementation on an extensive set of synthetic benchmarks. Our experiments show that by automatically selecting points in the GPU kernel to split wavefronts, we are able to reduce the WCET ranging from 34% to 52% reduction compared to five alternative approaches.