Comment by mgaunard

Static linking is also an optimization barrier.

LTO is really a different thing, where you recompile when you link. You could technically do that as part of the dynamic linker too, but I don't think anyone is doing it.

There is a surprisingly high number of software development houses that don't (or can't) use LTO, either because of secrecy, scalability issues or simply not having good enough build processes to ensure they don't breach the ODR.