This reverts r371177 (git commit f879c6875563c0a8cd838f1e13b14dd33558f1f8)
It caused PR43566 by removing empty, address-taken MachineBasicBlocks.
Such blocks may have references from blockaddress or other operands, and
need more consideration to be removed.
See the PR for a test case to use when relanding.
llvm-svn: 373805