Whole-program optimizations are powerful tools that can dramatically improve performance, size and other aspects of programs. Because they depend on global knowledge, they must typically be reapplied to the whole program when small changes are made, which makes them too slow for the development cycle. This is an issue for some environments that require, or benefit a lot from, whole-program optimizations, such as compilation to JavaScript or to the Dalvik VM, because their development cycle is slowed down either by the lack of optimizations, or by the time spent on applying them.