Automatic Streamization in GCC

Multi-cores and multi-processors became ubiquitous during the last few years, and the trend is to increase the number of simple, power-efficient, and slower cores per chip. One of the results is that the performance of single-threaded applications did not significantly improve, or even declined, on new processors, which heightened the interest in compiler automatic parallelization techniques. Our objective is to develop a framework in GCC to transform loops into pipelines of concurrent tasks using streams to communicate and synchronize. This transformation can either rely on user hints (pragmas) or on static analysis of control and data dependences. Our focus is to fully automate this transformation, which requires an integration with the Graphite polyhedral loop optimization framework and will lead to the development of runtime optimizations based on this polyhedral representation. This approach is complementary with the existing parallelization passes. This paper presents the steamization technique, the optimizations it enables, the interaction with other optimizations, and the necessary extensions to Graphite/PCP (polyhedral compilation package) for its integration.