Assuming you are serious, there is https://github.com/bytecodealliance/wasmtime/tree/main/crane... which is written in Rust and is targeted to become the default debug backend in rustc. LLVM has accumulated a lot of optimizations contributed by various groups and people over more than a decade. It's hard to catch up to that by virtue of resource limits.
I was being sarcastic, when Cranelift becomes the official reference implementation then I shut up.
Is there a reason to replace LLVM? Are there still memory bugs that are popping up and causing issues?