Constraint Systems for Useless Variable Elimination

Superfluous variables are often produced as the byproducts of program transformations, compilation, and poorly written code. These variables are irrelevant to the computational outcome of their programs. Eliminating them as a means of higherlevel optimization may increase program execution speed. This paper explores an implementation of Wand and Siveroni’s algorithm for useless variable elimination. The algorithm is shown to remove superfluous variables that are accessed, updated, and passed between functions, as well as collapse let expressions when all the let expression’s variables are superfluous. The algorithm does not preserve non-termination nor remove variables whose contributions are constant.

• Type: Conference
• Year: 1999
• Where: POPL
• Authors: Mitchell Wand, Igor Siveroni
• Keywords: Let Expression, Let Expression Variables, POPL 1999, Programming Languages, Superfluous Variables