ChilIR, Chil Intermediate Representation, (pronounced chiller) is an s-expression-based IR for elaborated hardware. ChilIR is intended to behave similarly to FIRRTL.
ChilIR is intended to be integrated with Chil and its simulator.
Alternatives exist: FIRRTL & CIRCT. Why create another alternative?
Chil is built on top of Lisp, which makes parsing s-expressions trivial compared to the other formats. Using s-expressions would simplify the simulator’s internals, because Lisp already expects everything as s-expressions.