Update dominator info for the middle blocks created while spliting
exit edge to preserve LCSSA.

Fix dominance frontier update during loop unswitch. This fixes PR 1589.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40695 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed