Call Unfolding Strategies for Equational Logic Programs

For a programming system based on term rewrite rules such as equational logic programming, a serious efficiency problem of the generated code is the creation of terms that only serve to drive further pattern matching. In this paper, we define a terminating call unfolding strategy based on finegrain partial evaluation that removes much of this unnecessary term allocation for programs in intermediate EM code generated from equational logic programs. Our approach is based on calculation, for each instruction, of two sets that reflect the usage of registers in finite execution paths of the program. These sets are calculated using fixed-point iteration over the graph representation of the intermediate code. 1 Introduction Finding call unfolding strategies for partial evaluation is an annoying problem. On the one hand, the basic problem--- knowing how much unfolding is necessary to expose a particular computation if it occurs---is undecidable. Nearly any recursive definition can lead to u..