Eugene Rozen worked on the zephyrproject-rtos/gcc repository, focusing on improving the reliability of profile-guided optimization in C++ by addressing a critical bug in AutoFDO count propagation. He analyzed discrepancies between call graph node counts and entry block counts, implementing a fix that preserved profiling data integrity and resolved regressions observed in MySQL HAMMERDB tests. His work involved deep code analysis and compiler optimization, ensuring that profiling information was accurately maintained throughout the AutoFDO pipeline. This contribution enhanced the stability and accuracy of test results, enabling more dependable optimization decisions and demonstrating a strong grasp of complex compiler internals.