Add AssertOn check for assert

Insert the check AssertOn to allow disabling of asserts.
Asserts can be disabled by not using the `--assert` flag or by calling
`AssertOn(false)`, or passing the "+verilator+noassert" runtime flag.
Add tests for this behavior.
Bad tests check that the assert still causes a stop.
Non bad tests check that asserts are properly disabled and cause no stop
of the simulation.

Fixes #2162.

Signed-off-by: Tobias Wölfel <tobias.woelfel@mailbox.org>

Changes

@@ -5,6 +5,7 @@ The contributors that suggested a given feature are shown in []. Thanks!
 
 * Verilator 4.029 devel
 
+***   Add assertOn check for assert. [Tobias Wölfel]
 ***   Add +verilator+noassert flag to disable assert checking. [Tobias Wölfel]
 
 * Verilator 4.028 2020-02-08

src/V3Assert.cpp

@@ -150,7 +150,7 @@ private:
             // It's more LIKELY that we'll take the NULL if clause
             // than the sim-killing else clause:
             ifp->branchPred(VBranchPred::BP_LIKELY);
-            bodysp = ifp;
+            bodysp = newIfAssertOn(ifp);
         } else {
             nodep->v3fatalSrc("Unknown node type");
         }

test_regress/t/t_assert_disabled.pl

@@ -0,0 +1,19 @@
+#!/usr/bin/perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2003-2009 by Wilson Snyder. This program is free software; you can
+# redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+
+scenarios(simulator => 1);
+
+top_filename("t/t_assert_on.v");
+
+compile();
+
+execute();
+
+ok(1);
+1;

test_regress/t/t_assert_enabled_bad.pl

@@ -0,0 +1,24 @@
+#!/usr/bin/perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2003-2009 by Wilson Snyder. This program is free software; you can
+# redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+
+scenarios(simulator => 1);
+
+top_filename("t/t_assert_on.v");
+
+compile(
+    verilator_flags2 => ['--assert'],
+    nc_flags2 => ['+assert'],
+    );
+
+execute(
+    fails => 1,
+    );
+
+ok(1);
+1;

test_regress/t/t_assert_enabled_off.pl

@@ -0,0 +1,23 @@
+#!/usr/bin/perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2003-2009 by Wilson Snyder. This program is free software; you can
+# redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+
+scenarios(vlt => 1);
+
+top_filename("t/t_assert_on.v");
+
+compile(
+    verilator_flags2 => ["--assert"],
+    );
+
+execute(
+    all_run_flags => ["+verilator+noassert"],
+);
+
+ok(1);
+1;

test_regress/t/t_assert_enabled_on_bad.pl

@@ -0,0 +1,23 @@
+#!/usr/bin/perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2003-2009 by Wilson Snyder. This program is free software; you can
+# redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+
+scenarios(vlt => 1);
+
+top_filename("t/t_assert_on.v");
+
+compile(
+    verilator_flags2 => ["--assert"],
+    );
+
+execute(
+    fails => 1,
+    );
+
+ok(1);
+1;

test_regress/t/t_assert_on.v

@@ -0,0 +1,18 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed into the Public Domain, for any use,
+// without warranty, 2007 by Wilson Snyder.
+
+module t (/*AUTOARG*/
+   // Inputs
+   clk
+   );
+
+   input clk;
+
+   always @ (posedge clk) begin
+      assert (0);
+      $finish;
+   end
+
+endmodule