There was some interesting discussion between the LLHD[1] and MLIR[2] folks about just this topic recently[3]. My takeaway: modeling behavioral HDL semantics in the IR is a huge mess that has to account for all of the complexity in the existing HDL landscape. However, there is hope for modeling structural HDL semantics in an IR that could be the target for many languages.
You mentioned LLVM, and I think of MLIR as sort of a successor to LLVM. I'm hopeful that a low-level HDL IR is standardized as an MLIR dialect, so the compiler ecosystem and the hardware ecosystem can start to unite.
https://github.com/masc-ucsc/livehd