Constant propagation

Abstract

Constant propagation is a well-known static compiler technique in which values of variables which are determined to be constants can be passed to expressions which use these constants. Code size reduction, bounds propagation, and dead-code elimination are some of the optimizations which benefit from this analysis.In this'paper, we present a new method for detecting constants, based upon an optimistic demand-driven recursive solver, as opposed to more traditional iterative solvers. The problem with iterative solvers is that they may evaluate an expression many times, while our technique evaluates each expression only once. To consider conditional code, wc augment the standard Static Single Assignment (SSA) form with merge operators called v-functions, adapted from the interpretable Gated Single Assignment (GSA) model.