I had the same experience. I was given a small performance issue with iterators to diagnose and had help from someone more experienced in that area. I learned

I had the same experience. I was given a small performance issue with iterators to diagnose and had help from someone more experienced in that area. I learned about how llvm does loop optimization and wrote a small null loop optimization pass. It turned out to be related to another problem and not need, but the experience was terrific.