[sanxiyn]

For example, Unison is an alternative code generator for LLVM, which uses constraint programming to do combined register allocation and instruction selection. It is very slow, but it does generate optimal (not just improved!) code, within its performance model.

http://unison-code.github.io/

[htfy96]

Thanks for the information. It seems that it is a super optimizer[0].

[0]: https://en.wikipedia.org/wiki/Superoptimization

[sanxiyn]

Unison is not a superoptimizer. Superoptimizer is evem slower.