switch (t) {
    default:
        if (isstore(t)) {
        case Tcall:
        case Ovastart:
            /* operations without result */
            r = R;
            k = Kw;
            op = t;
            goto DoOp;
        }
        err("label, instruction or jump expected");
    case ...
    ...
    }
DoOp:
    ...