Proposed Solution<\/strong>: Use DPI-C to record C variables in the wave database alongside the RTL signals. Compare. Find the bug.<\/p>\n\n\n\n Wait. I can turn my Imaginary Day Dream Helmet off. DPI-C can record C variables by adding just a little bit of code.<\/p>\n\n\n\n My GOLDEN C code model has an array with 3 dimensions. (See line 7). It is the critical data structure. That’s what we want to record. The C code is already “time-based” simply by calling back into SystemVerilog using the ‘tictoc(1)’ call on line 54, below. Each call to tictoc(N) waits for N clocks, where the clock is defined back in the SV module.<\/p>\n\n\n\n Simply add a single line – a call to a function named ‘record_data(data)’ (line 53). We’ll implement record_data() as an “export DPI-C” function back in the SV module.<\/p>\n\n\n\n Cost: Change our C code : “Add One Line<\/strong>” (Line 53 – The gold line below).<\/p>\n\n\n\n The SystemVerilog variable ‘data’ is declared in our RTL module as a 3x3x3 array of 7 bits. That is the place we will “record the C variable”. (Line 56 below)<\/p>\n\n\n\n “Recording” happens on line 62, when record_data() gets called. The argument ‘i’ was pushed onto the stack in C (line 53 above), and is then passed to the SV record_data() implementation and “recorded” by being assigned to the variable named ‘data’ (line 62 below).<\/p>\n\n\n\n That’s it.<\/p>\n\n\n\n Cost: Change our SystemVerilog Module. “Add a DPI-C export function and variable<\/strong>“. 5 lines total. (Lines 56 and 60-63 – The gold lines above).<\/p>\n\n\n\n The SystemVerilog module is calculating a fancy algorithm based on a randomized 3x3x3 array of integers. There is a C model which is the golden source. Our SystemVerilog has 10,000 instances of these calculators. Each instance starts its own C model thread with a call to ‘calculate_algorithm(data)’.<\/p>\n\n\n\n The C model makes calculations about the input data, and those calculations get recorded in the wave database. The RTL does the same. The results should match.<\/p>\n\n\n\n In the image below, we’ve zoomed in and are inspecting the 9995th calculator.<\/p>\n\n\n\n Finally, using our regular debug tools, we can compare the C variable memory with the RTL variable memory and find the mismatch (highlighted in RED below).<\/p>\n\n\n\n Total cost: Add 6 lines of code. (The gold lines above)<\/p>\n\n\n\n Total fun. Complete source code is available demonstrating this bit of FUN. <\/p>\n\n\n\n If you want to hear more about DPI-C, please consider attending this Virtual DVCON US 2021<\/a> Session – Tuesday, March 2, 3:00-5:00<\/strong> – “Advanced Methodologies 1<\/a>” for the paper “Making Your DPI-C Interface a Fast River of Data<\/a>“<\/p>\n\n\n\n Happy Verifying!<\/p>\n\n\n\n <\/p>\n","protected":false},"excerpt":{"rendered":" Pandemic? Cold freeze? No Power? Ugh. What a 12 months. And all that’s unfolded. I’m looking for some fun. I…<\/p>\n","protected":false},"author":75444,"featured_media":15858,"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":[1],"tags":[421,908,751,831,909],"industry":[],"product":[],"coauthors":[],"class_list":["post-15855","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news","tag-debugging","tag-dpi-c","tag-systemverilog","tag-verilog","tag-waveform"],"featured_image_url":"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/54\/2021\/02\/DPI-C-Recording-C-Variables-In-The-Waveform.jpg","_links":{"self":[{"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/posts\/15855","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\/75444"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/comments?post=15855"}],"version-history":[{"count":5,"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/posts\/15855\/revisions"}],"predecessor-version":[{"id":15927,"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/posts\/15855\/revisions\/15927"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/media\/15858"}],"wp:attachment":[{"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/media?parent=15855"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/categories?post=15855"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/tags?post=15855"},{"taxonomy":"industry","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/industry?post=15855"},{"taxonomy":"product","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/product?post=15855"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/verificationhorizons\/wp-json\/wp\/v2\/coauthors?post=15855"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Ok. Go.<\/h2>\n\n\n\n
The C Code<\/h3>\n\n\n\n
C Code:<\/h4>\n\n\n\n
...\n 7 typedef int <\/strong>data_t[3][3][3];<\/span>\n...\n 25 \n 26 int<\/strong>\n 27 calculate_algorithm(data_t v) {\n 28 data_t data;\n 29 \n 30 int <\/strong>value, xvalue;\n 31 int <\/strong>i, j, k;\n 32 int <\/strong>sort[100];\n...\n 46 for <\/strong>(i = 0; i < 3; i++) {\n 47 for <\/strong>(j = 0; j < 3; j++) {\n 48 for <\/strong>(k = 0; k < 3; k++) {\n 49 value = v[i][j][k];\n 50 data[i][j][k] = value;\n 51 sort[value] = 1;\n...\n 53 record_data(data);<\/span>\n 54 tictoc<\/span>(1);\n 55 }\n 56 }\n 57 }\n...<\/code><\/pre>\n\n\n\nThe SystemVerilog Code<\/h3>\n\n\n\n
SystemVerilog Code:<\/strong><\/h4>\n\n\n\n
49 export <\/strong>\"DPI-C\" task <\/strong>tictoc;\n 50 task <\/strong>tictoc(int<\/strong> times);\n 51 repeat <\/strong>(times)\n 52 @(posedge<\/strong> clk);\n 53 endtask\n<\/strong>\n 54 \n 55 typedef bit <\/strong>[6:0] data_t [3][3][3];\n 56 data_t data;<\/span>\n 57 \n 58 import <\/strong>\"DPI-C\" context task <\/strong>calculate_algorithm(\n 59 inout<\/strong> data_t data);\n \n 60 export <\/strong>\"DPI-C\" function <\/strong>record_data;\n 61 function void <\/strong>record_data(input<\/strong> data_t i);\n 62 data = i;\n 63 endfunction<\/strong><\/span>\n... \n 67 R_array r_array;\n 68 \n 69 initial begin<\/strong>\n...\n 76 if <\/strong>(r_array.randomize()<\/span> == 0) begin<\/strong>\n 77 $display(\"Error: Randomize failed\");\n 78 end<\/strong>\n 79 local_data = r_array.data;\n 80 $display(\"INFO: Starting %m.data=%p\", local_data);\n 81 calculate_algorithm(local_data);<\/span>\n 82 $display(\"INFO: Finished %m.data=%p\", local_data);\n...\n 86 end<\/strong><\/code><\/pre>\n\n\n\nThe Story<\/h3>\n\n\n\n
![\"\"](\"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/54\/2021\/02\/DPI-C-Recording-C-Variables-In-The-Waveform-9995-1024x577.jpg\")
![\"\"](\"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/54\/2021\/02\/DPI-C-Compare-C-and-RTL-Memory-Element-1024x365.jpg\")
Conclusion<\/h2>\n\n\n\n