Bytecode verification is not a large part of compilation time for Java. For HotSpot server, verification is dwarfed by building the IR, repeatedly walking and transforming it, generating code, and register allocation. Keep in mind that HotSpot will very likely inline a ton of methods, making the compilation unit large. Many passes are at least slightly superlinear, so that makes compilation time explode.

That said, I ported C1 (the client compiler) to Java back in my Maxine VM days, about 2009. At that time on typical x86 processors it was easily hitting 1.8MB/s (of bytecode) compilation time. You can work backward to how many lines of code a second that is (and sure, you aren't paying the cost of the frontend), but yeah, that is in the ballpark for 1MLOC/s I think. And that's with an optimizing compiler with IR and regalloc!

I wonder if it’d be possible / useful to implement a rust or C compiler that worked that way. Basically instant startup time after a code change is a delightful feature.