smatch, __builtin_unreachable() and uninitialized var...

hi!

While using smatch with OpenZFS code, we have stepped on this issue:

/home/runner/work/zfs/zfs/zfs/module/icp/algs/aes/aes_modes.c:90 =
aes_encrypt_contiguous_blocks() error: uninitialized symbol 'rv'.


The function is using conditional call to function, which return value =
is stored to rv and the =E2=80=9Cimpossible=E2=80=9D else leg is marked =
with __builtin_unreachable() as seen there:

=
https://github.com/openzfs/zfs/blob/master/module/icp/algs/aes/aes_modes.c=
#L77

it would be nice if smatch could use __builtin_unreachable() there to =
avoid this error=E2=80=A6

thanks,
toomas