Fix of localize for super constructors with function calls as arguments (#6330)

src/V3Localize.cpp

@@ -45,6 +45,9 @@ class LocalizeVisitor final : public VNVisitor {
     //  AstVarScope::user3p()   ->  Set of CFuncs referencing this VarScope. (via m_accessors)
     //  AstCFunc::user4p()      ->  Multimap of 'VarScope -> VarRefs that reference that VarScope'
     //                              in this function. (via m_references)
+    //  AstVarScope::user4()    ->  Bool indicating VarScope cannot be optimized
+    //                              - compared to AstVarScope::user1 this guarantees that this
+    //                              scope won't be optimized.
     const VNUser1InUse m_user1InUse;
     const VNUser3InUse m_user3InUse;
     const VNUser4InUse m_user4InUse;
@@ -60,11 +63,15 @@ class LocalizeVisitor final : public VNVisitor {
     // STATE - for current visit position (use VL_RESTORER)
     AstCFunc* m_cfuncp = nullptr;  // Current active function
     uint32_t m_nodeDepth = 0;  // Node depth under m_cfuncp
+    bool m_inSuperConstructorCallStmt = false;  // If under super constructor call statement
 
     // METHODS
     bool isOptimizable(AstVarScope* nodep) {
         // Don't want to malloc/free the backing store all the time
         if (VN_IS(nodep->dtypep(), NBACommitQueueDType)) return false;
+        // Variables used in super constructor call can't be localized, because
+        // in C++ there is no way to declare them before base class constructor call
+        if (nodep->user4()) return false;
         return ((!nodep->user1()  // Not marked as not optimizable, or ...
                                   // .. a block temp used in a single CFunc
                  || (nodep->varp()->varType() == VVarType::BLOCKTEMP
@@ -147,6 +154,14 @@ class LocalizeVisitor final : public VNVisitor {
         iterateChildrenConst(nodep);
     }
 
+    void visit(AstCNew* nodep) override {
+        VL_RESTORER(m_inSuperConstructorCallStmt);
+        m_inSuperConstructorCallStmt
+            = m_cfuncp->isConstructor() && VN_IS(nodep->backp(), StmtExpr);
+        m_cfuncp->user1(true);  // Mark caller as not a leaf function
+        iterateChildren(nodep);
+    }
+
     void visit(AstCCall* nodep) override {
         m_cfuncp->user1(true);  // Mark caller as not a leaf function
         iterateChildrenConst(nodep);
@@ -195,8 +210,11 @@ class LocalizeVisitor final : public VNVisitor {
         // Remember the reference so we can fix it up later (we always need this as well)
         m_references(m_cfuncp).emplace(varScopep, nodep);
 
-        // Check if already marked as not optimizable
-        if (!varScopep->user1()) {
+        if (m_inSuperConstructorCallStmt) {
+            // Variable used in super constructor call can't be localized
+            varScopep->user1(true);
+            varScopep->user4(true);
+        } else if (!varScopep->user1()) {  // Check if already marked as not optimizable
             // Note: we only check read variables, as it's ok to localize (and in fact discard)
             // any variables that are only written but never read.
             if (nodep->access().isReadOrRW() && !varScopep->user2()) {

test_regress/t/t_class_super_new3.py

@@ -0,0 +1,18 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2025 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()
+
+test.execute()
+
+test.passes()

test_regress/t/t_class_super_new3.v

@@ -0,0 +1,29 @@
+// 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 Base;
+  int j;
+  function new(int x);
+    j = x;
+  endfunction
+  static function int get_default();
+    return 8;
+  endfunction
+endclass
+class Derived extends Base;
+  function new();
+    super.new(get_default());
+  endfunction
+endclass
+
+module t;
+  initial begin
+    Derived d = new;
+    if (d.j != 8) $stop;
+    $write("*-* All Finished *-*\n");
+    $finish;
+  end
+endmodule