It seems like a lot of work but also doable to create something that is orders of magnitude faster than LLVM for unoptimized debug builds. Furthermore, the Zig compiler might be an easier thing to work with than LLVM/Clang for doing productionizing of optimization research.
I read the claims and comments differently than you, fwiw. It definitely reads like people who think they can make it both faster and better.
LLVM already has decades of research applied to it to make it produce fast code, it will be incredibly challenging to even match its performance across all the targets it supports let alone improve on it in significant ways. It would be better to spend the time building an optimization pipeline for Zig itself and being more thoughtful about what code you send to LLVM versus trying to replace it wholesale.
For reference to anyone else, this is what they’re referring to
https://webkit.org/blog/5852/introducing-the-b3-jit-compiler...