I would expect a little benefit from devirt (but maybe in-TU optimizations are getting that already?), but if a program is pessimized enough, LTO's improvements

I would expect a little benefit from devirt (but maybe in-TU optimizations are getting that already?), but if a program is pessimized enough, LTO's improvements won't be measurable. And programs full of pointer-chasing are quite pessimized; highly-OO code is a common example, which includes almost all GUIs, even in C++.