> I can’t say a 10% improvement is making LLVM fast again, we would need a 10x improvement for it to deserve that label. But it’s a start…

It’s a shame, one of the standout feature of llvm/clang used to be that it was faster than GCC. Today, an optimized build with gcc is faster than a debug build with clang. I don’t know if a 10x improvement is feasible, though; tcc is between 10-20x faster than gcc and clang, and part of the reason is that it does a lot less. The architecture of such a compiler may by necessity be too generic.

Here’s a table listing build times for one of my projects with and without optimizations in gcc, clang, and tcc. Tcc w/optimizations shown only for completeness; the time isn’t appreciably different. 20 runs each.

  ┌─────────────────────────────┬──────────┬──────────┬──────────┬─────────┬────────────┬────────────┐
  │                             │Clang -O2 │Clang -O0 │GCC -O2   │GCC -O0  │TCC -O2     │TCC -O0     │
  ├─────────────────────────────┼──────────┼──────────┼──────────┼─────────┼────────────┼────────────┤
  │Average time (s)             │1.49 ±0.11│1.24 ±0.08│1.06 ±0.08│0.8 ±0.04│0.072 ±0.011│0.072 ±0.014│
  ├─────────────────────────────┼──────────┼──────────┼──────────┼─────────┼────────────┼────────────┤
  │Speedup compared to clang -O2│        - │     1.20 │     1.40 │    1.86 │      20.59 │      20.69 │
  ├─────────────────────────────┼──────────┼──────────┼──────────┼─────────┼────────────┼────────────┤
  │Slowdown compared to TCC     │    20.68 │    17.20 │    17.72 │   11.12 │          - │          - │
  └─────────────────────────────┴──────────┴──────────┴──────────┴─────────┴────────────┴────────────┘