Modern compiler optimization pipelines are large and complex, and it is rather cumbersome and error-prone for compiler developers to preserve debugging information across optimization passes. An optimization can add, remove, or reorder code and variables, which makes it difficult to associate the generated code statements and values with the source code statements and values. Moreover recent proposals for automatic generation of optimizations (e.g., through search algorithms) have not previously considered the preservation of debugging information.We demonstrate the application of a blackbox equivalence checker to automatically populate the debugging information in the debug headers of the optimized executables compiled from C programs. A blackbox equivalence checker can automatically compute equivalence proofs between the original source code and the optimized executable code without the knowledge of the exact transformations performed by the compiler/optimizer. We present an algorithm that uses these formal equivalence proofs to improve the executable’s debugging headers. We evaluate this approach on benchmarks derived from the Testsuite of Vectorizing Compilers (TSVC) compiled through three different compilers: GCC, ClangLLVM, and ICC. We demonstrate significant improvements in the debuggability of the optimized executable code in these experiments. The benefits of these improvements can be transparently realized through any standard debugger, such as GDB, to debug the updated executable.