Fix unsupported `if` virtual interface warning (#6558) (#6861)

src/V3AstNodeOther.h

@@ -2185,6 +2185,12 @@ public:
                 && !isSc() && !isPrimaryIO() && !isConst() && !isDouble() && !isString());
     }
     bool isClassMember() const { return varType() == VVarType::MEMBER; }
+    bool isVirtIface() const {
+        if (AstIfaceRefDType* const dtp = VN_CAST(dtypep(), IfaceRefDType)) {
+            return dtp->isVirtual();
+        }
+        return false;
+    }
     bool isStatementTemp() const { return varType() == VVarType::STMTTEMP; }
     bool isXTemp() const { return varType() == VVarType::XTEMP; }
     bool isParam() const { return varType().isParam(); }

src/V3Gate.cpp

@@ -156,8 +156,8 @@ public:
             UINFO(6, "New vertex " << vscp);
             vVtxp = new GateVarVertex{this, vscp};
             vscp->user1p(vVtxp);
-            if (vscp->varp()->sensIfacep()) {
-                // Can be used in a class method, which cannot be tracked statically
+            if (vscp->varp()->sensIfacep() || vscp->varp()->isVirtIface()) {
+                // Can be read/written to via the referenced actual interface
                 vVtxp->clearReducibleAndDedupable("VirtIface");
                 vVtxp->setConsumed("VirtIface");
             }

src/V3Localize.cpp

@@ -192,6 +192,7 @@ class LocalizeVisitor final : public VNVisitor {
             && !nodep->varp()->isStatic()  // Not a static variable
             && !nodep->varp()->isClassMember()  // Statically exists in design hierarchy
             && !nodep->varp()->sensIfacep()  // Not sensitive to an interface
+            && !nodep->varp()->isVirtIface()  // Not interface pointer
             && !nodep->varp()->valuep()  // Does not have an initializer
         ) {
             UINFO(4, "Consider for localization: " << nodep);

src/V3SchedVirtIface.cpp

@@ -104,12 +104,13 @@ private:
         });
     }
     // Error on write across a virtual interface boundary
-    static void unsupportedWriteToVirtIface(AstNode* nodep, const char* locationp) {
+    static void unsupportedWriteToVirtIfaceMember(AstNode* nodep, const char* locationp) {
         if (!nodep) return;
-        foreachWrittenVirtIface(nodep, [locationp](AstVarRef* const selp, AstIface*) {
-            selp->v3warn(E_UNSUPPORTED,
-                         "Unsupported: Write to virtual interface in " << locationp);
-        });
+        foreachWrittenVirtIfaceMember(
+            nodep, [locationp](AstVarRef* const selp, AstIface*, AstVar* varp) {
+                selp->v3warn(E_UNSUPPORTED,
+                             "Unsupported: Write to virtual interface in " << locationp);
+            });
     }
     // Create trigger var for the given interface if it doesn't exist; return a write ref to it
     AstVarRef* createVirtIfaceTriggerRefp(FileLine* const flp, AstIface* ifacep) {
@@ -164,7 +165,7 @@ private:
         iterateChildren(nodep);
     }
     void visit(AstNodeIf* nodep) override {
-        unsupportedWriteToVirtIface(nodep->condp(), "if condition");
+        unsupportedWriteToVirtIfaceMember(nodep->condp(), "if condition");
         {
             VL_RESTORER(m_trigAssignp);
             VL_RESTORER(m_trigAssignIfacep);
@@ -201,7 +202,7 @@ private:
         }
     }
     void visit(AstLoopTest* nodep) override {
-        unsupportedWriteToVirtIface(nodep->condp(), "loop condition");
+        unsupportedWriteToVirtIfaceMember(nodep->condp(), "loop condition");
     }
     void visit(AstJumpBlock* nodep) override {
         {

src/V3Width.cpp

@@ -3371,8 +3371,6 @@ class WidthVisitor final : public VNVisitor {
                     nodep->varp(varp);
                     AstIface* const ifacep = adtypep->ifacep();
                     varp->sensIfacep(ifacep);
-                    nodep->fromp()->foreach(
-                        [ifacep](AstVarRef* const refp) { refp->varp()->sensIfacep(ifacep); });
                     nodep->didWidth(true);
                     return;
                 }

test_regress/t/t_interface_virtual_cond.py

@@ -0,0 +1,16 @@
+#!/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('linter')
+
+test.compile()
+
+test.passes()

test_regress/t/t_interface_virtual_cond.v

@@ -0,0 +1,27 @@
+// 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
+
+interface Bus;
+  logic [15:0] data;
+endinterface
+
+module t;
+  Bus intf();
+  virtual Bus vif;
+
+  function logic get_vif(inout virtual Bus vif);
+    vif = intf;
+    return 0;
+  endfunction
+
+  initial begin
+    if (get_vif(vif));
+    while (get_vif(vif));
+    do ; while (get_vif(vif));
+    for (int i = 0; get_vif(vif); i++);
+  end
+
+endmodule

test_regress/t/t_interface_virtual_unsup.out

@@ -1,11 +1,11 @@
-%Error-UNSUPPORTED: t/t_interface_virtual_unsup.v:22:22: Unsupported: Write to virtual interface in if condition
-   22 |       if (write_data(vif.data)) $write("dummy op");
+%Error-UNSUPPORTED: t/t_interface_virtual_unsup.v:24:22: Unsupported: Write to virtual interface in if condition
+   24 |       if (write_data(vif.data)) $write("dummy op");
       |                      ^~~
                     ... For error description see https://verilator.org/warn/UNSUPPORTED?v=latest
-%Error-UNSUPPORTED: t/t_interface_virtual_unsup.v:23:25: Unsupported: Write to virtual interface in loop condition
-   23 |       while (write_data(vif.data));
+%Error-UNSUPPORTED: t/t_interface_virtual_unsup.v:25:25: Unsupported: Write to virtual interface in loop condition
+   25 |       while (write_data(vif.data));
       |                         ^~~
-%Error-UNSUPPORTED: t/t_interface_virtual_unsup.v:24:30: Unsupported: Write to virtual interface in loop condition
-   24 |       do ; while (write_data(vif.data));
+%Error-UNSUPPORTED: t/t_interface_virtual_unsup.v:26:30: Unsupported: Write to virtual interface in loop condition
+   26 |       do ; while (write_data(vif.data));
       |                              ^~~
 %Error: Exiting due to

test_regress/t/t_interface_virtual_unsup.v

@@ -4,6 +4,8 @@
 // any use, without warranty, 2023 by Wilson Snyder.
 // SPDX-License-Identifier: CC0-1.0
 
+// NOTE: Once this is supported, t_interface_virtual_cond is no longer needed
+
 interface Bus;
    logic [15:0] data;
 endinterface