Supercompiling Overloaded Functions

A naı̈ve translation of recursive cases in type class instances will give code that allocates a new dictionary and copies the data from the input dictionary to the new dictionary for the recursive call. This record creation allocates memory and leads to bad performance for a conceptually simple and rather common operation, for example equality between lists. We present a positive supercompilation algorithm, parametrized with respect to evaluation order, and show how this algorithm can remove these allocations resulting in both time and space savings. We also show how a small extension to the folding mechanism of our supercompiler can give similar effects the static argument transformation at nearly no extra cost.