For COFF only: dwarf debug info output a label reference as a section relative item only when it's one of dw_from strp, sec_offset, ref_addr or op_call_ref instead of going by size.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188296 91177308-0d34-0410-b5e6-96231b3b80d8
Output DW_AT_stmt_list dwarf debug info as DW_FORM_sec_offset instead of DW_FORM_data4 as it is a section offset (fixes the coff/dwarf debug info statement locations)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188297 91177308-0d34-0410-b5e6-96231b3b80d8
Update makeLibCall to return both the call and the chain associated with the libcall instead of just the call. This allows us to specify libcalls that return void.

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