Get the previous sibling of this DIE object.
Declared in <llvm/DebugInfo/DWARF/DWARFDie.h>
<llvm/DebugInfo/DWARF/DWARFDie.h>
DWARFDie getPreviousSibling() const;
a valid DWARFDie instance if this object has a sibling or an invalid DWARFDie instance if it doesn't.