For GCC I just added a debug counter facility. You could tell it what value a given debug counter should stop on from the command line.

This also made automatic minimization of bugs much easier and faster.

One thing that other (applicable). projects dont seem to do that llvm and gcc were quite good at was using automatic tooling to minimize test cases for bugs. Find a large test case causing an issue. Run automatic minimizer and leave it alone for a bit, come back to minimal test case that reproduces your issue