Partial-Redundancy Elimination Minimize the number of expression evaluations Consider all possible execution sequences in a flow graph,and look at the number of times an expression such as x +y is evaluated. 。 By moving around the places where x +y is evaluated and keeping the result in a temporary variable when necessary,we often can reduce the number of evaluations of this expression along many of the execution paths. CS308 Compiler Theory 2Partial-Redundancy Elimination • Minimize the number of expression evaluations • Consider all possible execution sequences in a flow graph, and look at the number of times an expression such as x + y is evaluated. • By moving around the places where x + y is evaluated and keeping the result in a temporary variable when necessary, we often can reduce the number of evaluations of this expression along many of the execution number of evaluations of this expression along many of the execution paths. CS308 Compiler Theory 2