Dept of Computer

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JikesRVM

• Dept of Computer Information Sciences
• University of Delaware

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Contents

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

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Introduction to JikesRVM

• This is not a Java source compiler.
• JikesRVM is a Virtual Machine.
• Open Source.
• Converts from Byte code ? Machine Code

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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.

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Compilation

• Download the gz file from source forge
• http//downloads.sourceforge.net/jikesrvm/jikesrvm
  -3.0.1.tar.bz2
• by using the command wget ltweb linkgt
• 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.pr
  operties

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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/FastAd
  aptiveGenMS_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.

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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/OptLeve
  ls.tar.gz
• In brief no of steps in various optimization
  levels are
• Each level of optimization is a super set of the
  previous level.

O0 44
O1 53
O2 53

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

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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.

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Steps for Project1

• Step1 and Step 2 are straightfwd.
• Step3 use time rvm ltcommand line parametersgt
• 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.

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