{"id":18346,"date":"2023-05-24T20:02:20","date_gmt":"2023-05-25T00:02:20","guid":{"rendered":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/?p=18346"},"modified":"2026-03-27T08:51:39","modified_gmt":"2026-03-27T12:51:39","slug":"bent-tools-and-other-horrors-from-the-garden-and-uvm-debug-or-are-you-still-debugging-with-display","status":"publish","type":"post","link":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/2023\/05\/24\/bent-tools-and-other-horrors-from-the-garden-and-uvm-debug-or-are-you-still-debugging-with-display\/","title":{"rendered":"Bent Tools and other Horrors From the Garden and UVM Debug – or Are You Still Debugging with $display?"},"content":{"rendered":"\n

I can’t take credit for the great flowers in the garden. It’s the tremendous rain we’ve had in California this year – and anyhow, my wife is the gardener in the house.<\/p>\n\n\n\n

But it’s my job to do some weeding. While meditative, it is disagreeable to me.<\/p>\n\n\n\n

But back to UVM Debug and Visualizer.<\/p>\n\n\n\n

I was using my “weeding tool” to get between some bricks and I needed a pry bar, push, push, got it! Oops. Bent the weeding tool. I got it unbent, but it has a kink in it which tells everyone who sees it – “my owner used the wrong tool”.<\/p>\n\n\n\n

UVM Debug<\/h2>\n\n\n\n

For the UVM, I can’t tell you how many people I’ve heard say they use $display for their debug. “Too hard to bring up the GUI”. “I just have a couple things to debug”. “Real engineers don’t use GUIs”. “I’ve been working on this block or derivatives for many years – I know where the bugs are”.<\/p>\n\n\n\n

But really.<\/p>\n\n\n\n

It’s Better In the Waves<\/h2>\n\n\n\n

The waveform window in a GUI allows you to correlate things. You can even find causality. $display can’t do that. Just line after line after line of text and text and text.<\/p>\n\n\n\n

Why would I use anything except $display or `uvm_info? I’ve been doing that forever…<\/p>\n\n\n\n

\"\"
Code that flips a coin to construct 1 of 3 types – polymorphism working for you<\/figcaption><\/figure>\n\n\n\n

Use $display or `uvm_info…<\/p>\n\n\n\n

    $display(\"DEBUG INFO: t=%p\", t);\n    `uvm_info({\"DEBUG INFO: \", get_type_name()}, t.convert2string(), UVM_MEDIUM)<\/code><\/pre>\n\n\n\n
Get useful? information? Sort of useful. Sort of information.<\/p>\n\n\n\n
    # DEBUG INFO: t='{m_leaf_name:\"t1\", m_inst_id:3458, use_uvm_seeding:1,    m_inst_count:3462, __m_uvm_status_container:@uvm_status_container@1, events:@uvm_object_string_pool__3@392, begin_event:@uvm_event@179, end_event:@uvm_event@180, m_transaction_id:-1, begin_time:18446744073709551615, end_time:18446744073709551615, accept_time:18446744073709551615, initiator:null, stream_handle:0, tr_handle:0, record_enable:0, m_recorder:null, m_sequence_id:-1, m_use_sequence_info:0, m_depth:-1, m_sequencer:null, m_parent_sequence:null, print_sequence_info:0, m_client_str:\"\", m_client:null, m_rh:null, issued1:0, issued2:0, rw:0, addr:0, data:0, bits:'{a:0, b:0, c:1}, sstruct:'{a:0, d:0}, id:33, delay:5, loop_count:0, static_array:'{0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, dynamic_array:'{0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, queue:'{}, color:\"\", type_name:\"sequence_item_A\", g_id:34}\n\n    # UVM_INFO vip_a\/agentA.sv(486) @ 2601: uvm_test_top.i2_agentA.sequencer@@ggp_seq_A2.gp_seq.p_seq.A_seq [DEBUG INFO: sequence_A] id=33:: WRITE(0, 0) <'{0, 0, 0, 0, 0, 0, 0, 0, 0, 0},'{0, 0, 0, 0, 0, 0, 0, 0, 0, 0},'{}>\n<\/code><\/pre>\n\n\n\n
Pretty, huh!?<\/p>\n\n\n\n
What about hovering over values and exploring other variables? What about seeing all the values of ‘t’ throughout this loop (Hint: put it in the wave window)<\/p>\n\n\n\n
Classes in the Waves<\/h2>\n\n\n\n
What if you wanted to know more? Go add more $display. What if you wanted to see this variable ‘t’ from that sequence in the wave window? What if you could put the variable ‘t’ – a class handle in the wave window?<\/p>\n\n\n\n
\"\"
Put the ‘t’ from a sequence object in the wave window<\/figcaption><\/figure>\n\n\n\n
What if you wanted to put a handful of sequence objects in the wave window? They have a lifetime. They don’t exist. Then they are constructed. Then later, they are garbage collected.<\/p>\n\n\n\n
\"\"
Handful of “interesting” sequence objects in the wave window<\/figcaption><\/figure>\n\n\n\n
Got Queues? Associative Arrays? Dynamic Arrays?<\/h2>\n\n\n\n
Simple code. A transaction class with an ‘id’ field. A container class ‘C’ which has a variety of dynamic structures – ‘incoming’ – an associative array; ‘output’ – a dynamic array; and ‘q’ – a queue.<\/p>\n\n\n\n
\"\"<\/figure>\n\n\n\n
Click, click, click. Add to Wave. See the Associative array filling and changing. Same for the Dynamic array. And the Queue. Pushing and popping.<\/p>\n\n\n\n
\"\"
Associative array, Dynamic Array and A queue in a class in the wave window<\/figcaption><\/figure>\n\n\n\n
End<\/h2>\n\n\n\n
And did I mention? This is all postsim. You can do it in livesim too. But postsim. Yes.<\/p>\n\n\n\n
What can $display do for you? It’s like that bent garden tool. Use the right tools and be more productive.<\/p>\n\n\n\n
Try Visualizer. It won’t bite. You might even find that bug faster.<\/p>\n\n\n\n
What tools have you bent in the garden? Or better – what have you invented to give you the visibility that you need for debug?<\/p>\n\n\n\n
Safe debugging.<\/p>\n\n\n\n
\"UVM
Ceonothus ‘Dark Star’ (California Lilac)<\/a> – In my front yard, never subject to any of my bent garden tools<\/figcaption><\/figure>\n","protected":false},"excerpt":{"rendered":"
I can’t take credit for the great flowers in the garden. It’s the tremendous rain we’ve had in California this…<\/p>\n","protected":false},"author":71540,"featured_media":18347,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"spanish_translation":"","french_translation":"","german_translation":"","italian_translation":"","polish_translation":"","japanese_translation":"","chinese_translation":"","footnotes":""},"categories":[983,1,982,10],"tags":[419,506,718,751,787],"industry":[53],"product":[205,1124],"coauthors":[961],"class_list":["post-18346","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uvm","category-news","category-systemverilog","category-tips-tricks","tag-debug","tag-functional-verification","tag-simulation","tag-systemverilog","tag-uvm","industry-electronics-semiconductors","product-questa","product-visualizer"],"featured_image_url":"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/54\/2023\/05\/PXL_20230416_201010009.MP_-scaled-e1684968385671.jpg","_links":{"self":[{"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/posts\/18346","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/users\/71540"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/comments?post=18346"}],"version-history":[{"count":5,"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/posts\/18346\/revisions"}],"predecessor-version":[{"id":18395,"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/posts\/18346\/revisions\/18395"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/media\/18347"}],"wp:attachment":[{"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/media?parent=18346"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/categories?post=18346"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/tags?post=18346"},{"taxonomy":"industry","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/industry?post=18346"},{"taxonomy":"product","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/product?post=18346"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/coauthors?post=18346"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}