When you have multiple LCSSA (single-operand) PHIs that are converted
into two-operand PHIs due to versioning, only assert that the PHI
currently being converted has a single operand. I.e. we don't want to
check PHIs that were converted earlier in the loop.
Fixes PR27023.
Thanks to Karl-Johan Karlsson for the minimized testcase!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@264081 91177308-0d34-0410-b5e6-96231b3b80d8
