Common Subexpression Elimination in Dotty

Common subexpression elimination is a well-known compiler optimisa- tion that improves running time of compiled applications by avoiding the repetition of the same computation. Although it has been implemented on a low level such as bytecode, it misses multiple opportunities that are available on high level, such as optimizing lazy vals. We developed and implemented the transformation for Scala in a new mini-phase in the Dotty Compiler.