But they all still optimize their JITs to prioritize compilation speed & RAM usage (JIT'd code is dirty pages after all) over maximum optimizations. This is why you see things like WebKits multi-tier JIT strategy: https://webkit.org/blog/3362/introducing-the-webkit-ftl-jit/

They still want to swap in that JIT'd result ASAP since after all by the time it's been flagged for compilation it's already too late & is a hot hot hot function.