Support simple disable within task (#6334)

src/V3LinkJump.cpp

@@ -187,8 +187,12 @@ class LinkJumpVisitor final : public VNVisitor {
         FileLine* const fl = nodep->fileline();
         const std::string targetName = nodep->targetp()->name();
         if (m_ftaskp) {
+            if (!m_ftaskp->exists([targetp = nodep->targetp()](const AstNodeBlock* blockp)
+                                      -> bool { return blockp == targetp; })) {
+                // Disabling a fork, which is within the same task, is not a problem
                 nodep->v3warn(E_UNSUPPORTED, "Unsupported: disabling fork from task / function");
             }
+        }
         AstPackage* const topPkgp = v3Global.rootp()->dollarUnitPkgAddp();
         AstClass* const processClassp
             = VN_AS(getMemberp(v3Global.rootp()->stdPackagep(), "process"), Class);

test_regress/t/t_disable_inside.v

@@ -10,13 +10,11 @@ module t (  /*AUTOARG*/);
     fork : fork_blk
       begin
         x = 1;
-        #2;
+        disable fork_blk;
         x = 2;
       end
     join_none
     #1;
-    disable fork_blk;
-    #2;
     if (x != 1) $stop;
     $write("*-* All Finished *-*\n");
     $finish;

test_regress/t/t_disable_task_simple.py

@@ -0,0 +1,18 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2024 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.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios('simulator')
+
+test.compile(timing_loop=True, verilator_flags2=["--timing"])
+
+test.execute()
+
+test.passes()

test_regress/t/t_disable_task_simple.v

@@ -0,0 +1,45 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2025 by Antmicro.
+// SPDX-License-Identifier: CC0-1.0
+
+class Cls;
+  int x = 0;
+  int y = 0;
+
+  task disable_outside_fork;
+    fork : fork_blk
+      begin
+        x = 1;
+        #2;
+        x = 2;
+      end
+    join_none
+    #1;
+    disable fork_blk;
+  endtask
+
+  task disable_inside_fork;
+    fork : fork_blk
+      begin
+        y = 1;
+        disable fork_blk;
+        y = 2;
+      end
+    join_none
+  endtask
+endclass
+
+module t (  /*AUTOARG*/);
+  initial begin
+    Cls c = new;
+    c.disable_outside_fork();
+    #2;
+    if (c.x != 1) $stop;
+    c.disable_inside_fork();
+    if (c.y != 1) $stop;
+    $write("*-* All Finished *-*\n");
+    $finish;
+  end
+endmodule