Method for improving global common subexpression elimination and code motion in an optimizing compiler

摘要

A method for use during the optimizatin phase of an optimizing compiler for performing global common subexpression elimination and code motion which comprises:PPDetermining the code `basis` for the object program which includes examining each basic block of code and determining the `basis` items on which each computation depends wherein `basis` items are defined as operands which are referenced in a basic block before being computed. The method next determines the "kill set" for each `basis` item. Following this UEX, DEX, and THRU are determined for each basic block using the previously determined `basis` and "kill set" information. AVAIL and INSERT are computed from UEX, DEX, and THRU, and appropriate code insertions are made at those locations indicated by the preceding step, and finally redundant code is removed using the AVAIL set.