Add regression tests for issue #1074.

ivtest/ivltests/br_gh1074a.v

@@ -0,0 +1,24 @@
+module test();
+
+bit [7:0] a;
+bit [7:0] b;
+bit [7:0] c;
+bit [7:0] d;
+
+assign a[7:4] = 4'b0010;
+assign b[7:6] = 2'b01;
+assign b[5:4] = 2'b10;
+
+assign c = 8'bx;
+
+assign d = c + b - a;
+
+initial begin
+  #0 $display("%b %b %b %b", a, b, c, d);
+  if (d === 8'b01000000)
+    $display("PASSED");
+  else
+    $display("FAILED");
+end
+
+endmodule

ivtest/ivltests/br_gh1074b.v

@@ -0,0 +1,24 @@
+module test();
+
+bit [7:0] a;
+bit [7:0] b;
+bit [7:0] c;
+bit [7:0] d;
+
+assign a[7:4] = 4'b0010;
+assign b[7:6] = 2'b01;
+assign b[5:4] = a[5:4];
+
+assign c = 8'bz;
+
+assign d = c + b - a;
+
+initial begin
+  #0 $display("%b %b %b %b", a, b, c, d);
+  if (d === 8'b01000000)
+    $display("PASSED");
+  else
+    $display("FAILED");
+end
+
+endmodule

ivtest/regress-vvp.list

@@ -32,6 +32,8 @@ br_gh710c			vvp_tests/br_gh710c.json
 br_gh939			vvp_tests/br_gh939.json
 br_gh1018			vvp_tests/br_gh1018.json
 br_gh1029			vvp_tests/br_gh1029.json
+br_gh1075a			vvp_tests/br_gh1074a.json
+br_gh1075b			vvp_tests/br_gh1074b.json
 ca_time_real`			vvp_tests/ca_time_real.json
 case1				vvp_tests/case1.json
 case2				vvp_tests/case2.json

ivtest/vvp_tests/br_gh1074a.json

@@ -0,0 +1,5 @@
+{
+    "type"   : "normal",
+    "source" : "br_gh1074a.v",
+    "iverilog-args" : [ "-g2009" ]
+}

ivtest/vvp_tests/br_gh1074b.json

@@ -0,0 +1,5 @@
+{
+    "type"   : "normal",
+    "source" : "br_gh1074b.v",
+    "iverilog-args" : [ "-g2009" ]
+}