layui中栅格化布局显示一排

<div class="layui-row">
        <div class="layui-col-xs6 layui-col-sm6 layui-col-md8">
          <input name="verification_code" placeholder="验证码" type="text" class="layui-input input-val">
        </div>
        <div class="layui-col-xs6 layui-col-sm6 layui-col-md4">
          <canvas id="canvas" width="100%" height="48"
            style="float: right; border: 1px solid #ccc;border-radius: 5px;cursor: pointer;"></canvas>
        </div>
      </div>