4. The method of claim 3 wherein said effects class is a first effects class, the method further comprising the step of said compiler back end calling a second one of said predetermined routines in said compiler front end to determine a second effects class for a second one of said tuples included in said flow graph, said second effects class representing memory locations upon which said second tuple may depend, said compiler front end using said dependency indicator that is associated with said second tuple.
5. The method of claim 4 wherein said flow graph comprises one or more blocks, each block corresponding to a portion of said source program and each block including a sequence of tuples with no entry or exit between the first tuple and the last tuple of said sequence, and the method further comprising the step of computing, by said compiler back end for a first one of said blocks, a basic block effects indicator by calling said first predetermined routine in said compiler front end, said basic block effects indicator representing memory locations that may be modified by a tuple which is included in said first block.