help the dragonegg builders, and no test case at this point, but this
was one dimly plausible case I spotted by inspection. Hopefully will get
a testcase from those bots soon-ish, and will tidy this up with proper
testing.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165869 91177308-0d34-0410-b5e6-96231b3b80d8