No. LLVM is faster than GCC so most likely it'll be slower. If the way the frontend generates code for the backend is completely different then there's a chance

No. LLVM is faster than GCC so most likely it'll be slower. If the way the frontend generates code for the backend is completely different then there's a chance it won't be terrible and will have reasonable build speeds. However there's a chance it'll be inconsistent with llvm output but chances are noone will notice or care if it's not buggy