Just to add a bit of color to what you're saying, Java has (historically at least) worked fairly hard to NOT do any optimization in the first pass. JVM bytecode

Just to add a bit of color to what you're saying, Java has (historically at least) worked fairly hard to NOT do any optimization in the first pass. JVM bytecode is a fairly straightforward trivial translation of Java code. JITs do have much more information to leverage for optimization. But they have 2 balancing acts: 1) All the tracking, profiling, and compilation machinery they need to operate concurrently need to cost less than the advantages they bring. There's amortization here in longer running programs. 2) Much of that optimisation goes into bringing languages UP to speed, let alone pull ahead. JITed languages don't just have more information at runtime but typically have much less at compile time. Take Java and C++ for example. In Java, every call is a virtual call and worse, any call outside of your class can look completly different at runtime (besides the signature) than it did at compile time. Then add all the classloading/bytecode weaving that's actually common. C++ on the other hand knows what's virtual, what's not, what's linked from another lib up front.