halting analysis, it is illegal to delete a call to a read-only function.
The correct solution is almost certainly to add a "must halt" attribute and
only allow deletions in its presence.
XFAIL the relevant testcase for now.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@102831 91177308-0d34-0410-b5e6-96231b3b80d8