Add regression test for br_gh661 and test for correct $random behaviour.

ivtest/ivltests/br_gh661a.v

@@ -0,0 +1,40 @@
+module test;
+
+localparam NOM_COUNT = 1000;
+localparam MIN_COUNT = NOM_COUNT - 200;
+localparam MAX_COUNT = NOM_COUNT + 200;
+
+integer histogram[255:0];
+
+integer i;
+
+reg [7:0] value;
+
+reg failed;
+
+initial begin
+  failed = 0;
+  for (i = 0; i < 256; i++) begin
+    histogram[i] = 0;
+  end
+  for (i = 0; i < 256*NOM_COUNT; i = i + 1) begin
+    value = $urandom_range(32'hffffffff, 32'h0) >> 24;
+    histogram[value] += 1;
+  end
+  for (i = 0; i < 256; i++) begin
+    if (histogram[i] < MIN_COUNT) begin
+      $display("Bin %3d count %0d", i, histogram[i]);
+      failed = 1;
+    end
+    if (histogram[i] > MAX_COUNT) begin
+      $display("Bin %3d count %0d", i, histogram[i]);
+      failed = 1;
+    end
+  end
+  if (failed)
+    $display("FAILED");
+  else
+    $display("PASSED");
+end
+
+endmodule

ivtest/ivltests/br_gh661b.v

@@ -0,0 +1,45 @@
+module test;
+
+localparam NOM_COUNT = 1000;
+localparam MIN_COUNT = NOM_COUNT - 200;
+localparam MAX_COUNT = NOM_COUNT + 200;
+
+integer histogram[255:0];
+
+integer i;
+
+reg [31:0] value;
+
+reg failed;
+
+initial begin
+  failed = 0;
+  for (i = 0; i < 256; i++) begin
+    histogram[i] = 0;
+  end
+  for (i = 0; i < 256*NOM_COUNT; i = i + 1) begin
+    value = $urandom_range(32'h1ff, 32'h100) - 32'h100;
+    if (value[31:8] != 0) begin
+       $display("Random value %h not in range", value + 32'h100);
+       $display("FAILED");
+       $finish(0);
+    end
+    histogram[value] += 1;
+  end
+  for (i = 0; i < 256; i++) begin
+    if (histogram[i] < MIN_COUNT) begin
+      $display("Bin %3d count %0d", i, histogram[i]);
+      failed = 1;
+    end
+    if (histogram[i] > MAX_COUNT) begin
+      $display("Bin %3d count %0d", i, histogram[i]);
+      failed = 1;
+    end
+  end
+  if (failed)
+    $display("FAILED");
+  else
+    $display("PASSED");
+end
+
+endmodule

ivtest/ivltests/random.v

@@ -0,0 +1,11 @@
+module test;
+
+integer i;
+
+initial begin
+  for (i = 0; i < 1000; i++) begin
+    $display("%h", $random);
+  end
+end
+
+endmodule

ivtest/regress-sv.list

@@ -207,6 +207,8 @@ br_gh540		normal,-g2009		ivltests
 br_gh553		normal,-g2009		ivltests
 br_gh556		normal,-g2009		ivltests
 br_gh568		normal,-g2009		ivltests
+br_gh661a		normal,-g2009		ivltests
+br_gh661b		normal,-g2009		ivltests
 br_ml20171017		normal,-g2009		ivltests
 br_ml20180227		CE,-g2009		ivltests
 br_ml20180309a		normal,-g2009		ivltests

ivtest/regress-vlg.list

@@ -1435,6 +1435,7 @@ queue			normal			ivltests
 queue_fail		RE			ivltests gold=queue_fail.gold
 queue_stat		normal			ivltests gold=queue_stat.gold
 ram16x1			normal			ivltests # Sitting here for a long time?
+random			normal			ivltests gold=random.gold
 readmem-error		normal			ivltests gold=readmem-error.gold
 readmem-invalid		RE			ivltests gold=readmem-invalid.gold
 readmemb1		normal			ivltests # basic $readmemb - uses readmemh1.dat

ivtest/regress-vlog95.list

@@ -211,6 +211,8 @@ br1008			CE			ivltests
 br1019			CE			ivltests
 br_gh556		CE,-g2009		ivltests
 br_gh632c		CE			ivltests
+br_gh661a		CE			ivltests
+br_gh661b		CE			ivltests
 br_ml20171017		CE			ivltests
 genvar_scopes		CE			ivltests
 meminit2		CE			ivltests