Optimizing embedded applications using programmer-inserted hints

This paper explores the possibility of exploiting programmer-inserted hints in the application code to improve performance beyond what could be achieved using an optimizing compiler. These hints can be beneficial in two scenarios: (1) when compiler analysis fails to identify opportunity and/or legality for a potential optimization; and (2) when it is not a good idea to invoke an optimization at the point the opportunity is first encountered during execution. Our goal is to strike a balance between two extremes - pure compiler-based scheme (i.e., user-transparent approach) and pure user-based scheme (i.e., assembly programming). In particular, we defend a strategy where a few programmer-inserted hints can enable the compiler to do much better job than the pure compiler approach without requiring the programmer to encode low-level optimizations.