Prince781/csc255-a3

cs-255-llvm-pass-skeleton

The given code is a skeleton of a llvm pass using llvm-8 on cycle machine.

Prepration

0. Add LLVM binaries to your path (optional)

# Add in your .bash_profile or other shell config
export PATH=/localdisk/cs255/llvm-project/bin:$PATH

1. Add LLVM_HOME in your environment:

export LLVM_HOME=/localdisk/cs255/llvm-project

2. Use CMake and Make to compile your pass to runtime lib

mkdir build
cd build
cmake ..
make

3. Use your pass

• One liner: clang -Xclang -load -Xclang build/skeleton/libSkeletonPass.so test.cpp
• Inside the test/Makefile, you can find out the way that use opt to use your own pass.

Hints

1. To do dependence testing, your first step is to find loops in the program.

   • Check how to use other llvm pass in your own pass
   • http://llvm.org/doxygen/classllvm_1_1Loop.html
   • https://llvm.org/doxygen/classllvm_1_1LoopInfo.html

2. Get induction variables in the loops you found.

   • Check how to use ScalarEvolution pass and how other llvm pass like indvars (Induction Variable Simplify) use it
   • http://llvm.org/doxygen/classllvm_1_1ScalarEvolution.html#a30bd18ac905eacf3601bc6a553a9ff49

Reference

• https://www.cs.cornell.edu/~asampson/blog/clangpass.html
• https://github.com/abenkhadra/llvm-pass-tutorial