Strengthening supercompilation for call-by-value languages

A termination preserving supercompiler for a call-by-value language sometimes fails to remove intermediate structures that a supercompiler for a call-by-name language would remove. This discrepancy in power stems from the fact that many function bodies are either non-linear in use of an important variable or often start with a pattern match on their first argument and are therefore not strict in all their arguments. As a consequence, intermediate structures are left in the output program, making it slower. We present a revised supercompilation algorithm for a call-by-value language that propagates let-bindings into case-branches and uses termination analysis to remove dead code. This allows the algorithm to remove all intermediate structures for common examples where previous algorithms for call-by-value languages had to leave the intermediate structures in place.Godkänd; 2010; 20110214 (pj)ESI