Compilers are getting smarter over time. Better analyses and clever optimization schemes are being designed and implemented. In my opinion though, as a compiler

Compilers are getting smarter over time. Better analyses and clever optimization schemes are being designed and implemented. In my opinion though, as a compiler writer, the best route is to make languages easier to analyze. Things like purity and referential transparency (e.g.: as seen in Haskell) make code analysis and transformation much simpler. They enable things like pattern-matching type transformations on code. If the compiler has to reason about pointers, invisible side-effects and alias analysis, it greatly limits the kinds of things that can be inferred about a program.