Add regression test for return in tasks

Check support for using the return statement in a task.
 * That it is possible to exit form a task using the `return` statement
   without affecting other concurrently running instances of the same task
 * That it is possible to use return in a named block in a task
 * That using a return value in a task results in a elaboration error
 * Returning from inside a parallel block in a task results in a
   elaboration error

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>

ivtest/ivltests/task_return1.v

@@ -0,0 +1,31 @@
+// Check that it is possible to exit from a task using the return statement with
+// affecting other concurrently running instances of the same task.
+
+module test;
+
+  task automatic t(input integer a, output integer b);
+    if (a == 0) begin
+      b = 1;
+      return;
+    end
+    #10
+    b = 100;
+  endtask
+
+  integer b1;
+  integer b2;
+
+  initial begin
+    fork
+      t(0, b1);
+      t(1, b2);
+    join
+
+    if (b1 == 1 && b2 == 100) begin
+      $display("PASSED");
+    end else begin
+      $display("FAILED b1=%0d, b2=%0d", b1, b2);
+    end
+  end
+
+endmodule

ivtest/ivltests/task_return2.v

@@ -0,0 +1,22 @@
+// Check that it is possible to return from a named sub-block of a task using a
+// `return` statement.
+
+module test;
+
+  task t(input integer a);
+    begin : subblock
+      if (a == 1) begin : condition
+        return;
+      end
+    end
+    $display("FAILED");
+    $finish;
+  endtask
+
+  initial begin
+    t(1);
+    #10
+    $display("PASSED");
+  end
+
+endmodule

ivtest/ivltests/task_return_fail1.v

@@ -0,0 +1,15 @@
+// Check that using a return value when using the return statement in a task
+// results in an error.
+
+module test;
+
+  task t;
+    return 10; // This is an error, tasks can not have return values.
+  endtask
+
+  initial begin
+    t();
+    $display("FAILED");
+  end
+
+endmodule

ivtest/ivltests/task_return_fail2.v

@@ -0,0 +1,18 @@
+// Check that using a return statment inside a parallel block in a task results
+// in an error.
+
+module test;
+
+  task t;
+    fork
+      // This is an error it is not possible to return from inside a parallel block
+      return;
+    join
+  endtask
+
+  initial begin
+    t();
+    $display("FAILED");
+  end
+
+endmodule

ivtest/regress-vvp.list

@@ -36,3 +36,7 @@ struct_packed_write_read2	vvp_tests/struct_packed_write_read2.json
 sv_foreach9			vvp_tests/sv_foreach9.json
 sv_foreach10			vvp_tests/sv_foreach10.json
 sdf_header			vvp_tests/sdf_header.json
+task_return1			vvp_tests/task_return1.json
+task_return2			vvp_tests/task_return2.json
+task_return_fail1		vvp_tests/task_return_fail1.json
+task_return_fail2		vvp_tests/task_return_fail2.json

ivtest/vvp_tests/task_return1.json

@@ -0,0 +1,5 @@
+{
+    "type"          : "normal",
+    "source"        : "task_return1.v",
+    "iverilog-args" : [ "-g2005-sv" ]
+}

ivtest/vvp_tests/task_return2.json

@@ -0,0 +1,5 @@
+{
+    "type"          : "normal",
+    "source"        : "task_return2.v",
+    "iverilog-args" : [ "-g2005-sv" ]
+}

ivtest/vvp_tests/task_return_fail1.json

@@ -0,0 +1,5 @@
+{
+    "type"          : "CE",
+    "source"        : "task_return_fail1.v",
+    "iverilog-args" : [ "-g2005-sv" ]
+}

ivtest/vvp_tests/task_return_fail2.json

@@ -0,0 +1,5 @@
+{
+    "type"          : "CE",
+    "source"        : "task_return_fail2.v",
+    "iverilog-args" : [ "-g2005-sv" ]
+}