During June 2025, Jiantong Zhang enhanced the llvm/clangir repository by implementing improved GCov coverage tracking for multi-file basic blocks. Leveraging C++ and Shell, Jiantong introduced new data structures and logic to accurately track line origins within basic blocks, ensuring that coverage statistics correctly attribute lines to their respective source files. This work addressed previous issues of over-filtering and under-counting, aligning LLVM’s GCov behavior with that of GCC. The feature required a deep understanding of code coverage tools, compiler development, and debugging, resulting in more reliable and precise coverage reporting for complex, multi-file codebases without introducing any new bugs.