I originally got into writing compilers because I was convinced I could write a better code generator. I succeeded for about 10 years in doing very well with code generation. But then all the complexities of the evolving C++ (and D!) took up most of my time, and I haven't been able to work much on the optimizer since.

Fortunately, D compilers gdc and ldc take advantage of the gcc and llvm optimizers to stay even with everyone else.