Abstract

Abstract We compare the efficiency of type-based unboxing strategies with that of simpler, untyped unboxing optimizations, building on our practical experience with the Gallium and Objective Caml compilers. We find the untyped optimizations to perform as well on the best case and significantly better in the worst case. 1 Introduction In Pascal or C, the actual types of all data are always known at compile-time, allowing the compilers to base data representation decisions on this typing information, thus supporting efficient memory layout of data structures as well as efficient calling conventions for functions. This is no longer true for languages featuring polymorphism and type abstraction, such as ML: there, the static, compile-time type information does not always determine the actual, run-time type of a data (e.g. when the static type contains type variables or abstract type identifiers).

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