A COMPLIER CODE OPTIMIZATION METHOD FOR A SOURCE PROGRAM HAVING A FIRST AND SECOND ARRAY DEFINITION AND USE STATEMENT IN A LOOP

A dataflow analysis processing of a compiler is executed when a loop of a source program includes a first array definition statement determining a value of an element of an array and an array use statement using the value of the element of the array. Whether or not a second array definition statement exists in a path from the first array definition statement to the array use statement in the program and whether or not the second array definition statement may possibly rewrite the value of the array defined by the first array definition statement are judged by comparing the subscripts associated with the array definition and the array use. For a pair of each array definition statement and each array use statement, a step for generating array definition/use relationship data from the first array definition statement to the array use statement only when the possibility of the rewriting is present. In the program transformation processing, the program transformation processing is achieved only when the array definition/use relationship data contains only an array definition/use relationship for which the result of the program execution is not changed by the program transformation.