Always rename, never give a redef error. We could check for collapsed type
planes and generate an error if that's not the cause, but the 99.9999
percentile case will be that its the result of collapsed type planes. So,
rather than doing an expensive check, just rename.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@34047 91177308-0d34-0410-b5e6-96231b3b80d8