Amusing anecdote - back in 1982, I took a 2 week compiler course from Hennessy and Ullman at Stanford. I decided to implement the data flow analysis techniques in my C compiler. It appeared as Datalight Optimum C.

The benchmarks used by the computer magazines were all dead code, and so the flow analysis deleted them. The journalists sadly concluded and wrote that DC was an utterly broken compiler :-(

This problem persisted until a year or two later when Borland and Microsoft caught up. They had much better marketing teams (!). The benchmarks got changed.