Extending Global Optimizations in the OpenUH Compiler for OpenMP

This paper presents our design and implementation of a framework for analyzing and optimizing OpenMP programs within the OpenUH compiler, which is based on Open64. The paper describes the existing analyses and optimizations in OpenUH, and explains why the compiler may not apply classical optimizations to OpenMP programs directly. It then presents an enhanced compiler framework including Parallel Control Flow Graph and Concurrent SSA that represent both intra-thread and inter-thread data flow. With this framework, the compiler is able to perform traditional compiler optimizations on OpenMP programs, and it further increases the opportunities for more aggressive optimizations for OpenMP. We describe our current implementation in the OpenUH compiler and use a code example to demonstrate the optimizations enabled by the new framework. This framework may lead to a significant improvement in the performance of the translated code.