Add assertion on DT availability during LI update in UpdateAnalysisInformation

This came up during discussions in llvm-commits for
rL321653: Check for unreachable preds before updating LI in
UpdateAnalysisInformation

The assert provides hints to passes to require both DT and LI if we plan on
updating LI through this function.

Tests run: make check

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@321805 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed