Instructions that are inserted in a basic block can still be decorated
with addOperand(MO).
Make the two-argument addOperand() function contain the actual
implementation. This function will now always have a valid MF reference
that it can use for memory allocation.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@170798 91177308-0d34-0410-b5e6-96231b3b80d8