betterIR

betterIR is my personal research and development lab where I implement various compiler optimizations as out-of-tree LLVM passes. Currently, this repository implements:

• Liveness analysis
• Dead code elimination
• Dead store elimination

Compile

To build this project, the following dependencies are required:

• CMake 3.0.0+
• LLVM >= 8.0
• Python 3.x.x (to run the tester)

Follow the steps below to compile this project: 0. Navigate to the root directory of this repository after cloning it.

1. In the CMakeLists.txt, specify the path to llvm x and set the path to the LLVM_INS variable.
2. Set the version of LLVM that you gen for finding the CMake package of the appropriate version.
3. mkdir build && cd build && cmake ..
4. make

Assuming the build was successful, you will see a directory called lib containing the shared object libraries for each of the built passes.

Run

The passes may either be run manually by using the LLVM's opt tool: opt -load-pass-plugin <path-to-shared-object-file> -passes=<name-of-pass> <input-IR-file> -S -o <output-IR-file> -debug

Alternatively, the tester may also be used to optimize a collection of files:

1. Configure tests/config.json:
   1. tests-dir: full path to the directory containing the test suite for the pass. The directory must contain the directories input and output, where the input directory contains *.ll files which will be optimized.
   2. opt: full path to the LLVM's optimizer executable.
   3. lib-path: path to the pass' shared object file
2. Run python3 tests/tester.py tests/config.json