SystemVerilog probes · 64bVivado: supported

an unpacked union: typedef union { logic [7:0] byte_v; logic [3:0] nib; } (no packed), one member written and read

Vivado: supported. The open-source chain: all four stages pass.

What does Vivado do with it?

Supported. UG901 v2023.2 Ch.10 Table 27 (p.286): 'Unpacked unions: Supported'

What does the open-source chain do with it?

since #28 rtl: PASS: iverilog refuses the design, 'design.sv:1: sorry: Unpacked structs not supported.', and dewfpga sim goes on with 'design.sv:1: note [sim-from-build]' (the simulation runs on the design as the build reads it, 'read by yosys-slang, the second reader', written back as Verilog and compiled with the testbench and yosys' cell models), then 'PASS'; since #4; built by yosys-slang, yosys' own reader refused this code (the note in bit.log); iverilog alone refuses it, 'design.sv:1: sorry: Unpacked structs not supported.'; bit: 'pnr ok: 8 LUT, 0 FF, no clocked paths, timing not applicable (full log: top.log)'; netlist: PASS, 'EQV SKIP: iverilog cannot compile the RTL, so only the testbench checked the netlist'

Which error pages explain the messages?

• sim-from-build: Not an error: iverilog refused a construct in the design, so the testbench ran against the design as the build elaborates it, read by the reader the note names.

What is the probe's code?

From test/sv/64b_unpacked_union.

design.sv

typedef union { logic [7:0] byte_v; logic [3:0] nib; } view_t;   // an unpacked union (no 'packed')
module top(input logic [15:0] sw, output logic [15:0] led);
  view_t u;
  always_comb begin
    u.byte_v = sw[7:0];
    led = {8'd0, ~u.byte_v};
  end
endmodule

tb.sv

module tb;
  reg [15:0] sw = 16'h0000;
  wire [15:0] led;
  integer i;
  top dut(.sw(sw), .led(led));
  initial begin
    for (i = 0; i < 256; i = i + 1) begin
      sw = {8'hA5, i[7:0]}; #1
      if (!(led === {8'd0, ~sw[7:0]})) begin $display("FAIL: the unpacked union (sw=%h led=%h)", sw, led); $finish; end
    end
    $display("PASS"); $finish;
  end
endmodule

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