which was an expensive checks failure due to a bug in the checking. This
patch in essence reverts the original fix for PR3393, and refixes it by a
tweak to the way expensive checking is done.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@89454 91177308-0d34-0410-b5e6-96231b3b80d8