code: Node createIf(Node cond, Node then) {
      return IR.ifNode(cond, then);
    }
docs: Returns a new IF node.
  
  <p>Blocks have no type information, so this is functionally the same as calling {@code
  IR.ifNode(cond, then)}. It exists so that a pass can be consistent about always using {@code
  AstFactory} to create new nodes.