Representation Analysis for Coercion Placement

This paper presents a global approach to representation analysis based on program-wide data and control ow information. Boxing and unboxing coercions can be placed around any variable occurrence, not only where values are produced and consumed. The analysis rst constructs a graph representing all legal coercion placements , then selects one of them. Assigning unboxed representations to as many variables as possible does not necessarily minimize execution time (or the number of executed coercions); we present and measure several heuristics. When combined with function cloning, the analysis is powerful enough to eliminate almost all coercions from several nonstrict programs, including a simple polymorphic type checker.