Experience Integrating a New Compiler and a New Garbage Collector Into Rotor

Microsoft’s Rotor is a shared-source CLI implementation intended for use as a research platform. It is particularly attractive for research because of its complete implementation and extensive libraries, and because its modular design allows different implementations of certain components (e.g., just-in-time compilers). Our group has independently developed a highperformance just-in-time (JIT) compiler and garbage collector, and wanted to take advantage of Rotor as a platform for experimenting with these components. In this paper, we describe our experiences integrating these components into Rotor, and evaluate the flexibility of Rotor’s modular design toward this goal. We found the just-in-time (JIT) compiler easier to integrate than the garbage collector because Rotor has a well defined interface for the former but not the latter. However, the JIT integration required changes to Rotor to support multiple JITs, which included implementing a new code manager and supporting a second JIT manager. We detail the changes to our just-in-time compiler to support Rotor’s calling conventions, helper functions, and exception model. The garbage collector integration was complicated by the many places in Rotor where components make assumptions about the garbage collector’s implementation. It was also necessary to reconcile the different assumptions made by our garbage collector and Rotor about object layout, virtual-method table layout, and thread structures.