This is solc-verify, an auto-verifier compiler for Solidity.
What is Solc Verify?
Solc Verify is the extended alternative to the mainstream Solidity code compiler, it carries out formal verification of code along with compilation. Developers can verify the functional correctness of their smart contracts. A task that would need extra packages/toolchains if done with the normal compiler. The project has been forked +5k times!