RE Elimination . CS640 GMU Fall 2009. 2. Redundant Expressions. DefinitionAn expression x op y is redundant at a point p if it has already been computed and no intervening operations redefined x or yOptimization for a redundant expressionPreserve the result of earlier computationsReplace subsequent evaluations with references to the saved valueSafetyNeed to prove that x op y is redundant TodayRedundancy elimination at different levels.