TLM peek 何时会失败？

Question

我正在研究 OVM 驱动程序定序器通信。我在 ovm 驱动程序中使用 try_get_item() 但它仍然卡住了。在我的音序器中，我重新定义了 try_next_item 并在 m_req_fifo.peek(t) 之前和之后打印了一条显示语句；执行 peek 之前的语句，但不执行 peek 之后的语句。我什至使用 m_req_fifo.size() 显示了 m_req_fifo 的大小，它打印出 1。为什么即使大小为 1，peek 也没有返回任何内容？下面给出修改后的try_next_item（只是增加了显示）。 After PEEK行永远不会在行行398之后执行，fifo大小为1

   virtual task try_next_item(output REQ t);
    int selected_sequence;
    time arb_time;
    ovm_sequence_base seq;

    if (get_next_item_called == 1) begin
      ovm_report_error(get_full_name(), "get_next_item/try_next_item called twice without item_done or get in between", OVM_NONE);
      return;
    end

    wait_for_sequences();
    selected_sequence = choose_next_request();
    if (selected_sequence == -1) begin
      t = null;
      return;
    end
    set_arbitration_completed(arb_sequence_q[selected_sequence].request_id);
    seq = arb_sequence_q[selected_sequence].sequence_ptr;
    arb_sequence_q.delete(selected_sequence);
    m_update_lists();
    sequence_item_requested = 1;
    get_next_item_called = 1;
    $display("Line 398 with fifo size %0d\n", m_req_fifo.size());
    m_req_fifo.peek(t);

    $display("After PEEK\n");
    wait_for_sequences();

    // attempt to get the item; if it fails, produce an error and return
    if (!m_req_fifo.try_peek(t))
      ovm_report_error("TRY_NEXT_BLOCKED", {"try_next_item: the selected sequence '",
        seq.get_full_name(), "' did not produce an item during wait_for_sequences(). ",
        "Sequences should not consume time between calls to start_item and finish_item. ",
        "Returning null item."}, OVM_NONE);

  endtask

Answer 1

uvm_tlm_fifo::size() 不是 return FIFO 中的元素数量，而是它的容量（即它可以容纳的最大元素数量）。您要查找的函数是 uvm_tlm_fifo::used()，其中 return 是存储元素的数量。

函数名称根本不直观，我记得我花了几个小时试图理解一些与您的代码类似的代码，直到在文档中注意到我使用了错误的方法。

TLM peek 何时会失败？

When can TLM peek fail?

methodology

system-verilog

uvm