GC-Safe Interprocedural Unboxing

Modern approaches to garbage collection (GC ) require information about which variables and fields contain GC-managed pointers. Interprocedural flow analysis can be used to eliminate otherwise unnecessary heap allocated objects (unboxing), but must maintain the necessary GC information. We define a core language which models compiler correctness with respect to the GC, and develop a correctness specification for interprocedural unboxing optimizations. We prove that any optimization which satisfies our specification will preserve GC safety properties and program semantics, and give a practical unboxing algorithm satisfying this specification.