The variant generation for commutative/associative patterns would simply
delete the first output from the list assuming that it was identical to
the original pattern. This does not have to be the case, and a legitimate
variant could actually be removed that way.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@305556 91177308-0d34-0410-b5e6-96231b3b80d8