Add regression test for issue #1181.

ivtest/ivltests/br_gh1181.v

@@ -0,0 +1,42 @@
+module top_module();
+  wire data_bus; // Bidirectional data bus
+
+  module_a u_module_a (
+    .data(data_bus)
+  );
+
+  module_b u_module_b (
+    .data(data_bus)
+  );
+endmodule
+
+module module_a (
+  inout wire data
+);
+  // Drive the data bus with 1 when module_a is active
+  assign data = 1'b1;
+endmodule
+
+module module_b (
+  inout wire data
+);
+  // Read data from the bus
+  wire data_in = data;
+
+  // Set data to high impedance to allow other modules to drive the bus
+  assign data = 1'bz;
+endmodule
+
+module tb();
+
+top_module dut();
+
+initial begin
+  #0;
+  if (dut.data_bus === 1'b1)
+    $display("PASSED");
+  else
+    $display("FAILED");
+end
+
+endmodule

ivtest/regress-vvp.list

@@ -60,6 +60,7 @@ br_gh1143g			vvp_tests/br_gh1143g.json
 br_gh1143h			vvp_tests/br_gh1143h.json
 br_gh1155			vvp_tests/br_gh1155.json
 br_gh1163			vvp_tests/br_gh1163.json
+br_gh1181			vvp_tests/br_gh1181.json
 ca_time_real`			vvp_tests/ca_time_real.json
 case1				vvp_tests/case1.json
 case2				vvp_tests/case2.json

ivtest/vvp_tests/br_gh1181.json

@@ -0,0 +1,4 @@
+{
+    "type"   : "normal-vlog95",
+    "source" : "br_gh1181.v"
+}