Tested on a couple of amd64 systems, both against the real root filesystem (ZFS) and against a md configuration of zfs mirror, raidz, ufs mirror and non-redundant configurations.
Tested on an armv6 board (BeagleBone Black) and an aarch64 system (Overdrive 1000).
Note that on armv6 and other installations with MBR disk layouts, the autodetection will fail to find any devices because the partition type isn't 'efi'.