Learning to compile smartly for program size reduction

Compiler optimization passes are an important tool for improving program efficiency and reducing program size, but manually selecting optimization passes can be time-consuming and error-prone. While human experts have identified a few fixed sequences of optimization passes (e.g., the Clang -Oz passes) that perform well for a wide variety of programs, these sequences are not conditioned on specific programs. In this paper, we propose a novel approach that learns a policy to select passes for program size reduction, allowing for customization and adaptation to specific programs. Our approach uses a search mechanism that helps identify useful pass sequences and a GNN with customized attention that selects the optimal sequence to use. Crucially it is able to generalize to new, unseen programs, making it more flexible and general than previous approaches. We evaluate our approach on a range of programs and show that it leads to size reduction compared to traditional optimization techniques. Our results demonstrate the potential of a single policy that is able to optimize many programs.