Optimizations are not turned on for debug builds and never have been. The issue is that LLVM is still pretty heavyweight even when not optimizing. An entirely s

Optimizations are not turned on for debug builds and never have been. The issue is that LLVM is still pretty heavyweight even when not optimizing. An entirely separate backend is needed. As Steve mentioned, there is a global build cache already. We have an incremental compiler. It's not as incremental as it could be, however. We already have an extensive system, crater, that can measure build time improvements.