LowerCallTo returns a pair with the return value of the call as the first
element and the chain associated with the return value as the second element. If
we lower a call that has a void return value, LowerCallTo returns an SDValue
with a NULL SDNode and the chain for the call. Thus makeLibCall by just
returning the first value makes it impossible for you to set up the chain so
that the call is not eliminated as dead code.
I also updated all references to makeLibCall to reflect the new return type.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188300 91177308-0d34-0410-b5e6-96231b3b80d8
3add0679d2