operands of the expression being written was wrongly thought to be reusable as
an inner node of the expression resulting in it turning up as both an inner node
*and* a leaf, creating a cycle in the def-use graph. This would have caused the
verifier to blow up if things had gotten that far, however it managed to provoke
an infinite loop first.
llvm-svn: 168291
20bd7fa0f7