To be clear: that is a distinct project that merely relies on a similar set of techniques at a high level.
If my understanding of Souper is correct, it's using synthesis to improve optimization rules inside LLVM. Lens, on the other hand, uses synthesis to optimize code directly with some neat algorithmic improvements to prune the search space. It targets ARM and, of all things, GreenArrays (a weird, extremely low-energy Forth-based architecture).
To be clear: I think both projects are interesting, as are other efforts in the field (ie Aiken at Stanford has done some cool stuff). Program synthesis is a topic I'm definitely interested in. But if you're interested more in LLVM and less in synthesis in general, this paper is going to be less interesting.
GreenArrays's main claim to fame is that it's a fully asynchronous architecture (no central clock). Oh, and it's from Chuck Moore (the Forth guy and kinda the Mike Pall of hardware design).
Yeah, the project came out of Chlorophyll[1] which was a compiler for GreenArrays that used program synthesis for optimization.
I imagine ARM has more immediate practical applications and useful benchmarks, but it came second—I assume out of a collaboration with Qualcomm Research.
https://www.eecs.berkeley.edu/~mangpo/www/papers/lens-asplos...