Just going by the new stuff that you could have taught back in 2004-2006 that you likely didn't, there's SSA construction, SLP vectorization, automatic peephole superoptimization, and that's just things I could name off the top of my head (and were papers for my qualifying exam :-P).

What hasn't changed is the compiler textbooks, which tend to have way too heavy a focus on how to build a parser generator and almost nothing on how you actually architect a compiler, let alone designing modern computer architecture. But this is a gripe which has been around for decades.