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branchRead

BranchRead is an LLVM Compiler Pass designed to analyze C programs. Its primary function is to identify and catalog all branching points within the C source code. This is achieved by generating a comprehensive dictionary, which maps each branch to its corresponding line number. Additionally, during the execution of the C program, BranchRead actively monitors and outputs the line number of the current target branch being executed. This enhances the visibility of program flow and aids in debugging and analysis.

Prerequisite

Ninja

  1. sudo apt-get update -y
  2. sudo apt-get install -y ninja-build

LLVM Clang Opt

For this project, I am using the latest version available, which is LLVM-18.

  • You can install LLVM-18 through the following commends: wget https://apt.llvm.org/llvm.sh chmod +x llvm.sh sudo ./llvm.sh 18

  • Then export path as following: export PATH="/usr/lib/llvm-18/bin/:$PATH"

  • You can check the version by: llvm-config --version clang --version opt --version

  • The output should be similar as shown below:

  • Please note that installing the same version of LLVM as your local LLVM source file is crucial to avoid errors.

Compile LLVM

  1. git clone https://github.com/llvm/llvm-project.git
  2. cd llvm-project
  3. cmake -S llvm -B build -G Ninja -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_PROJECTS="clang;lld"
  4. ninja -C build check-llvm
  5. ninja -C build

Compile new passes

  1. Copy and Paste the whole directory into llvm-project/llvm/lib/Transforms
  2. In the CMakeLists.txt file, add add_subdirectory(KeyPoints)
  3. In the llvm-project folder, use ninja -C build
  4. The new pass should be successfully added.

Test the new passes

  1. In the testfile folder
  2. Compile the test files with the following commends: (Use -O1 because it can output most desirable outcome in this project)
    1. clang -O1 -g -emit-llvm test1.c -c -o test1.bc
    2. clang -O1 -g -emit-llvm test2.c -c -o test2.bc
  3. Transform the bc file with the new pass:
    1. opt -load-pass-plugin ~/llvm-project/build/lib/KeyPoints.so -passes=keyPoints -o test1-2.bc test1.bc
    2. opt -load-pass-plugin ~/llvm-project/build/lib/KeyPoints.so -passes=keyPoints -o test2-2.bc test2.bc
  4. run the transformed bc file
    1. lli test1-2.bc
    2. lli test2-2.bc
  5. The dictionary.txt file that contains all the branches will also be generated when transforming the bc file with the new pass in the testfile folder.

Remain issue

Currently, there are still some segmentation errors related with the inner loop and more complicated conditions.