An investigation of Jones optimality and BTI-universal specializers

Jones optimality implies that a program specializer is strong enough to remove an entire level of self-interpretation. This paper argues that Jones optimality, which was originally devised as a criterion for self-applicable specializers, plays a fundamental role in the use of a binding-time improvement prepass prior to specialization. We establish that, regardless of the binding-time improvements applied to a subject program (no matter how extensively), a specializer that is not Jones-optimal is strictly weaker than a specializer that is Jones-optimal. We describe the main approaches that increase the strength of a specializer without requiring its modification, namely incremental specialization and the interpretive approach, and show that they are equally powerful when the specializer is bti-universal. Since this includes the generation of program specializers from interpreters, the theoretical possibility of bootstrapping powerful specializers is established.