Copy Propagation subsumes Constant Propagation

TL;DR

This paper presents a unified framework for constant and copy propagation, showing that constant propagation is a special case of copy propagation, and introduces a new analysis that combines both optimizations.

Contribution

It provides a generic definition for copy propagation, unifying it with constant propagation through a novel data flow analysis approach.

Findings

Constant propagation is a special case of copy propagation.

A unified data flow analysis for both transformations is formulated.

The approach simplifies and potentially improves compiler optimization processes.

Abstract

Constant propagation and copy propagation are code transformations that may avoid some load operations and can enable other optimizations. In literature, constant and copy propagations are considered two independent transformations requiring two different data flow analyses. Here we give a generic definition for copy propagation which enables us to view constant propagation as a particular case of copy propagation and formulate a novel data flow analysis that unifies these two transformations.