* Do not allow nodes which produce chain results (e.g. loads) to be folded if

* Do not allow nodes which produce chain results (e.g. loads) to be folded if
  it has more than one real use (non-chain uses).
* Record folded chain producing node in CodeGenMap.
* Do not fold a chain producing node if it has already been selected as an
  operand of a chain use.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@24647 91177308-0d34-0410-b5e6-96231b3b80d8