Updating dominators for exit-blocks of the unrolled loops is not enough,
as shown in PR27157. The proper way is to update dominators for all
dominance-children of original loop blocks.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265605 91177308-0d34-0410-b5e6-96231b3b80d8