Other jumps are expressed by either GOTO_EXPR or
RETURN_EXPR.
The operand of a GOTO_EXPR must be either a label or a
variable containing the address to jump to.
The operand of a RETURN_EXPR is either NULL_TREE,
RESULT_DECL, or a MODIFY_EXPR which sets the return
value. It would be nice to move the MODIFY_EXPR into a
separate statement, but the special return semantics in
expand_return make that difficult. It may still happen in
the future, perhaps by moving most of that logic into
expand_assignment.