Tag-free garbage collection using explicit type parameters

We have constructed a practical tag-free garbage collector based on explicit type parameterization of polymorphic functions, for a dialect of ML. The collector relies on type information derived from an explicitly-typed 2nd-order representation of the program, generated by the compiler as a byproduct of ordinary Hindley-Milner type inference. Runtime type manipulations are performed lazily to minimize execution overhead. We present details of our implementation approach, and preliminary performance measurements suggesting that the overhead of passing type information explicitly can be made acceptably small.