Any compiler that gets used at runtime (branded JIT, usually) ends up growing performance hacks or being written from scratch to run quickly. Javascript is prone to using multiple compilers based on how frequently code was executed. That's also what the whole -O0 -O3 -flto -thin-lto -pgo etc flags are about, granting permissions to burn different amounts of time during compilation.

It's really easy to accidentally write code that walks off a performance cliff on unexpected input, but that's likely to get hacked around if someone reports it as slow compilers do annoy people.