[twic]

I'm not sure i would agree that the JVM and its ilk do LTO. They compile code to machine code at runtime, after loading the code it calls, and often after spending some time interpreting it. That means they can do interprocedural optimisations of the kind LTO can do (and then some). But they don't have the separate stages of compilation and linking that many ahead-of-time compiled languages do, which means they don't do linking, which surely means they can't do link-time optimisation!

[foobazgt]

This is incorrect. The JVM has an explicitly separate link phase [0]. The difference with AOT compilers is that linking is deferred until runtime. Rather than saying there's no link phase, you should think of it like as if your favorite AOT compiled language could support LTO on dlopen.

0) https://docs.oracle.com/javase/specs/jvms/se7/html/jvms-5.ht...

[twic]

The linking mentioned there has nothing to do with the linking in LTO. It happens before JITting, and is neither a barrier to nor an opportunity for optimisation.