Copy elimination in functional languages

  • Authors:

  • K. Gopinath;J. L. Hennessy

  • Affiliations:

  • Computer Systems Lab, CIS 034, Stanford University, CA;Computer Systems Lab, CIS 034, Stanford University, CA

  • Venue:
  • POPL '89 Proceedings of the 16th ACM SIGPLAN-SIGACT symposium on Principles of programming languages
  • Year:
  • 1989

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Abstract

Copy elimination is an important optimization for compiling functional languages. Copies arise because these languages lack the concepts of state and variable; hence updating an object involves a copy in a naive implementation. Copies are also possible if proper targeting has not been carried out inside functions and across function calls. Targeting is the proper selection of a storage area for evaluating an expression. By abstracting a collection of functions by a target operator, we compute targets of function bodies that can then be used to define an optimized interpreter to eliminate copies due to updates and copies across function calls. The language we consider is typed lambda calculus with higher-order functions and special constructs for array operations. Our approach can eliminate copies in divide and conquer problems like quicksort and bitonic sort that previous approaches could not handle.We also present some results of implementing a compiler for a single assignment language called SAL on some small but tough programs. Our results indicate that it is possible to approach a performance comparable to imperative languages like Pascal.