You may be interested in the current initiative around compiler plugins [1]. One of the explicit design goals is offload to alternative backends like GPUs or Wasm, but you could see how that would extend to something like Cranelift as well.

That said, LLVM codegen performance is very much a tail wagging the dog thing, and I wish upstream put a significantly larger focus on it [2]

[1] https://hackmd.io/bVhb97Q4QTWeBQw8Rq4IFw?view [2] https://www.npopov.com/2020/05/10/Make-LLVM-fast-again.html