sudo emerge -avuDUg world

--changed-use, -U:

• Tells emerge to include installed packages where USE flags have changed since installation. This option also implies the --selective option. Unlike --newuse, the --changed-use option does not trigger reinstallation when flags that the user has not enabled are added or removed.

--getbinpkg [ y | n ], -g:

• Using the server and location defined in PORTAGE_BINHOST (see make.conf(5)), portage will download the information from each binary package found and it will use that information to help build the dependency list. This option implies -k. (Use -gK for binary-only merging.)