Effectiveness of Inlining, Common Subexpression and Deadcode Elimination in Optimizing Compilers

Abstract- One of the most difficult and least understood problems in the design of the compilers is the generation of good object code. The most common criteria by which the goodness of a program is judged are its running time and size. Since the optimization is important during compilation, the way of obtaining optimal code must be done in appropriate way. Performing optimization is to decide when to optimize and what to optimize. Optimizing compilers are of great importance in resulting the better object programs. Due to the undecidable nature of those compilers, getting optimal optimization depth is of challenging issue. The development of a model for attaining optimization depth can be greater achievement towards the compiler optimization. As a part of which, major optimization passes, viz. inlining, common subexpression elimination and deadcode elimination, has been implemented, tested and analyzed for various instances of inputs to verify the depth. With inlining, we can improve run-time performance by replacing the text of a function call with the body of the called function itself. While using common subexpression elimination, it decreases the execution time of the program by avoiding multiple evaluations of the same expression with reduced number of computations. And at the same context, deadcode elimination aims to rectify the dead code instructions, whose removal reduces code size and eliminates unnecessary computations