Although I'm not sure the "self hosted compiler" is the same as "llvm free backend".
It's not. The self-hosted compiler still uses llvm, and it's still slow because of it.
"self-hosted compiler" in this case means moving all the non-LLVM code (which was previously in C++) to Zig itself.
One thing I hate about LLVM is that once you get into the ecosystem to get “another alternative” or “abandon LLVM” it’s like hell, you get all these nice cool features then implementing a custom compiler for debugging can be much much harder than that