A region inference algorithm

Abstract

Region Inference is a program analysis which infers lifetimes of values. It is targeted at a runtime model in which the store consists of a stack of regions and memory management predominantly consists of pushing and popping regions, rather than performing garbage collection. Region Inference has previously been specified by a set of inference rules which formalize when regions may be allocated and deallocated. This article presents an algorithm which implements the specification. We prove that the algorithm is sound with respect to the region inference rules and that it always terminates even though the region inference rules permit polymorphic recursion in regions. The algorithm is the result of several years of experiments with region inference algorithms in the ML Kit, a compiler from Standard ML to assembly language. We report on practical experience with the algorithm and give hints on how to implement it.

A Retrospective on Region-Based Memory Management

“…The first is syntax-directed and based on algorithm W [16] and fixed-point iteration for dealing with polymorphic recursion. It was completed in 1996 and documented in two journal papers [50,51]. The second algorithm is constraint-based and has the nice property of separating the generation of constraints from the constraint solving.…”

Region-Based Memory Management for a Dynamically-Typed Language

“…Based on the typing rules in Section 3, the actual values of region variables and effect variables are computed. This can be carried out in a way similar to the ordinary region inference [18]. Finally, letregion is inserted in the place where the side condition of T-Reg is met.…”

“…Finally, letregion is inserted in the place where the side condition of T-Reg is met. (Actually, inference of regions and effects and insertion of letregion have to be carried out in an interleaving manner to handle region polymorphism [18]. )…”

Scoped Types for Real-Time Java

“…Lastly, Java being an inherently concurrent language, multi-threading must be supported. The resulting design is a distinctive programming model which differs from existing region-based models such as the MLKit [34].…”

“…At the time of this writing, Boyapati's system has not yet been shown sound [6]. Work on regions for functional languages did not take concurrency into account [34,35].…”