Broadway: A Compiler for Exploiting the Domain-Specific Semantics of Software Libraries

This paper describes the Broadway compiler and our experiences in using it to support domain-specific compiler optimizations. Our goal is to provide compiler support for a wide range of domains and to do so in the context of existing programming languages. Therefore, we focus on a technique that we call library-level optimization, which recognizes and exploits the domain-specific semantics of software libraries. The key to our system is a separation of concerns: compiler expertise is built into the Broadway compiler machinery, while domain expertise resides in separate annotation files that are provided by domain experts. We describe how this system can optimize parallel linear algebra codes written using the PLAPACK library. We find that our annotations effectively capture PLAPACK expertise at several levels of abstraction and that our compiler can automatically apply this expertise to produce considerable performance improvements. Our approach shows that the abstraction and modularity found in modern software can be as much an asset to the compiler as it is to the programmer.