In compiler theory, common subexpression elimination is a compiler optimization that searches for instances of identical expressions, and analyzes whether it is worthwhile replacing them with a single variable holding the computed value.

What is common subexpression and how do you eliminate it?

Common Subexpression Elimination is an optimization that searches for instances of identical expressions, and replaces them with a single variable holding the computed value.

What do you mean by redundant expression elimination?

An expression is called partially redundant if the value computed by the expression is already available on some but not all paths through a program to that expression. An expression is fully redundant if the value computed by the expression is available on all paths through the program to that expression.