Reapplying r281895 (and follow-up r281964) after fixing pr30468.
The additional fix is:
When adding debug information to a lowered phi node in mem2reg
check that we have a valid insertion point after the phi for adding
the debug information.
This change addresses the issue in pr30468 where a lowered phi was
added before a catchswitch and no debug information should be added
after the phi in this case.
Differential Revision: https://reviews.llvm.org/D24797
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@282155
91177308-0d34-0410-b5e6-
96231b3b80d8