Empirical Studies of Java Optimizations

Traditionally, compilers perform a dual task: they transform a program from the source code (such as C or C++) to machine code, and also optimize the program to make it run faster. Common optimizations include constant propagation and folding, method inlining, dead code elimination, and many others. Java compliers are different from C or C++ compilers: most Java compliers transform Java source code into platform-independent byte code which is later executed by Java Virtual Machine (JVM), usually equipped with a Just-In-Time compiler (JIT) to compile byte code to native machine code on the fly. In this setup, program optimizations can be performed at two levels: by the compiler (while converting Java code into byte code) and by JVM when byte code is compiled to native code as the program is executed. In this project, we investigate optimizations that are performed by the compiler, javac, and by JVM. We compare our test program efficiency with that of a non-optimized program in order to detect optimizations being performed on the programs, and to determine at which level they are performed. Our testing programs are specifically designed to detect individual program optimizations. Our research is a work in progress. We present the current results and discuss techniques for detecting optimizations and also for determining whether these optimizations are performed at compile time or run time.