Dept of Computer & Information Sciences University of Delaware

1. Dept of Computer & Information Sciences University of Delaware JikesRVM

2. Contents • Introduction to JikesRVM • Optimizations • IRs (Intermediate Representations) • Editing JikesRVM • Steps For Project1 • Questions

3. Introduction to JikesRVM • This is not a Java source compiler. • JikesRVM is a Virtual Machine. • Open Source. • Converts from Byte code  Machine Code

4. Functions of the RVM • Loads the required class files • Converts the class files (OS independent bytecode) to machine code (OS and Architecture dependent) • Optimizes byte code in the process of the above conversion. • Tracks Compilation time and provides rudimentary profiling.

5. Compilation • Download the gz file from source forge • http://downloads.sourceforge.net/jikesrvm/jikesrvm-3.0.1.tar.bz2 • by using the command wget <web link> • Untar the file “tar –zxf jikesrvm-3.0.1.tar.bz2” • Inside the jikesrvm directory create a new .ant.properties file • http://www.cis.udel.edu/~skulkarn/ta_files/.ant.properties

6. Compilation II • Run command “java-config -s sun-jdk-1.6” • Inside this directory run “ant” and this would create the executable image of the rvm. • Binaries are stored in (jikesrvm-3.0.1/dist/FastAdaptiveGenMS_x86_64-linux) folder • Compile your source code with javac • Run using the “rvm” binary present in the above folder. • You may want to add this directory to the PATH environment variable.

7. Optimization • There are different levels of optimizations from O0 to O3. • List of optimizations that are performed in all the different optimization levels are available at • http://www.cis.udel.edu/~skulkarn/ta_files/OptLevels.tar.gz • In brief no of steps in various optimization levels are: • Each level of optimization is a super set of the previous level.

8. Intermediate Representations For more information please go thru http://www.ugrad.cs.ubc.ca/~cs411/2006W2/handouts/jikes-IR-shane-brewer.pdf

9. Editing the JikesRVM • Adding of a new command line argument • The list of files that govern and define the parameters are at “jikesrvm-3.0.0/rvm/src-generated/options” • I wanted to add a parameter that could switch off multiple optimizations at the same time, so I added “V LIST_TO_SKIP String \"123\“List of optimizations to skip” • Remember that the number of new lines also are important. So do not upset those. • You will have to clean the previous build by using “ant very-clean” command • Build again by “ant” command.

10. Important source directories • Package responsible for choosing the optimizations is org.jikesrvm.compilers.opt.driver • OptimizationPlanner.java: is responsible for creating the list of optimizations that the code would go through. • CompilationPlan.java: Performs those optimizations in the order that was set in OptimizationPlanner. • Actuall implementations of the optimizations can be found under the root package org.jikesrvm.compilers.opt e.g. LocalCastOptimization.java is the implementation LocalCastOptimization.

11. Steps for Project1 • Step1 and Step 2 are straightfwd. • Step3: use “time rvm <command line parameters>” • Step4: Based on the different optimizations that you would like to switch off, find and compare the results of running time. E.g. You might want to switch off “Local ConstantProp” or “Branch Optimizations” and see the effect it has on the running times.

12. Questions? Most of the files and this presentation is available at http://www.cis.udel.edu/~skulkarn/ta.html