I appreciate it if you can drop some information/papers/open source project urls that are related to superoptimization. Although I am targeting RISC-V ISA, there might be some other research works / open source projects available in the LLVM community.
STOKE & Souper are the most well supported & maintained superoptimization tools out there. They are very different: STOKE does genetic search, while Souper uses only SMT solvers for (symbolic) search.
There’s also Rosette, which does a hybrid of concrete & symbolic search (mixing concrete search with other techniques seems to be the way to go).
I would also look at the SyGuS competition (syntax-guided synthesis). These tools, such as CVC4, can be used for superoptimization as well.
In terms of tools, I think that’s it. In terms of papers, there are plenty of research groups working on synthesis in general.
To be fair, this was mostly used for consultancy into specific hot code
blocks. Since then I moved on to other things but still hold a keen
interest in Superoptimization.
S10 was built upon greenthumb:
I have been meaning to open source S10 but writing the documentation,
cleaning up the code, etc is taking quite a bit of time although it's
one of my priorities for 2021.
In any case, if you want to know more or if I can help any further, feel
free to drop me an email.