From 86f6ac2960ce33dbad3f959543543c25aaa04dc1 Mon Sep 17 00:00:00 2001
From: Wilson Snyder <wsnyder@wsnyder.org>
Date: Tue, 8 Apr 2025 20:48:57 -0400
Subject: [PATCH] Fix port default values with `--coverage-line` creating `0=0`
 (#5920).

---
 Changes                                       |  1 +
 src/V3Inline.cpp                              | 21 +++++++++++++++++++
 .../t/t_module_input_default_value.py         |  3 ++-
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/Changes b/Changes
index a51416c57..e3e210a7e 100644
--- a/Changes
+++ b/Changes
@@ -72,6 +72,7 @@ Verilator 5.035 devel
 * Fix `new this` (#5909).
 * Fix LATCH warning for automatic variables (#5918). [Yutetsu TAKATSUKASA]
 * Fix %% on elaboration severity tasks (#5922). [Ethan Sifferman]
+* Fix port default values with `--coverage-line` creating `0=0` (#5920). [Drew Ranck]
 
 
 Verilator 5.034 2025-02-24
diff --git a/src/V3Inline.cpp b/src/V3Inline.cpp
index d308eaaf3..a7092fbb0 100644
--- a/src/V3Inline.cpp
+++ b/src/V3Inline.cpp
@@ -252,6 +252,7 @@ class InlineRelinkVisitor final : public VNVisitor {
     std::unordered_set<std::string> m_renamedInterfaces;  // Name of renamed interface variables
     AstNodeModule* const m_modp;  // Current module
     const AstCell* const m_cellp;  // Cell being cloned
+    bool m_initialStatic = false;  // Inside InitialStatic
 
     // VISITORS
     void visit(AstCellInline* nodep) override {
@@ -290,6 +291,7 @@ class InlineRelinkVisitor final : public VNVisitor {
             if (exprconstp) {
                 m_modp->addStmtsp(new AstAssignW{flp, new AstVarRef{flp, nodep, VAccess::WRITE},
                                                  exprconstp->cloneTree(false)});
+                nodep->user4(true);  // Making assignment to it
             } else if (nodep->user3()) {
                 // Public variable at the lower module end - we need to make sure we propagate
                 // the logic changes up and down; if we aliased, we might
@@ -305,6 +307,7 @@ class InlineRelinkVisitor final : public VNVisitor {
                 UINFO(9, "assign to public and unpacked: " << nodep << endl);
                 exprvarrefp = exprvarrefp->cloneTree(false);
                 exprvarrefp->access(VAccess::READ);
+                nodep->user4(true);  // Making assignment to it
                 m_modp->addStmtsp(
                     new AstAssignW{flp, new AstVarRef{flp, nodep, VAccess::WRITE}, exprvarrefp});
             } else if (nodep->isIfaceRef()) {
@@ -322,6 +325,7 @@ class InlineRelinkVisitor final : public VNVisitor {
                 exprvarrefp->access(VAccess::READ);
                 AstVarRef* const nodeVarRefp = new AstVarRef{flp, nodep, VAccess::WRITE};
                 if (nodep->isForced() && nodep->direction() == VDirection::INPUT) {
+                    nodep->user4(true);  // Making assignment to it
                     m_modp->addStmtsp(new AstAssignW{flp, nodeVarRefp, exprvarrefp});
                 } else if (nodep->isForced() && nodep->direction() == VDirection::OUTPUT) {
                     exprvarrefp->access(VAccess::WRITE);
@@ -374,6 +378,22 @@ class InlineRelinkVisitor final : public VNVisitor {
         nodep->name(m_cellp->name() + "__DOT__" + nodep->name());
         iterateChildren(nodep);
     }
+    void visit(AstInitialStatic* nodep) override {
+        VL_RESTORER(m_initialStatic);
+        m_initialStatic = true;
+        iterateChildren(nodep);
+    }
+    void visit(AstNodeAssign* nodep) override {
+        if (AstVarRef* const varrefp = VN_CAST(nodep->lhsp(), VarRef)) {
+            if (m_initialStatic && varrefp->varp()->user2() && varrefp->varp()->user4()) {
+                // Initial assignment to i/o we are overriding, can remove
+                UINFO(9, "Remove InitialStatic " << nodep << endl);
+                VL_DO_DANGLING(pushDeletep(nodep->unlinkFrBack()), nodep);
+                return;
+            }
+        }
+        iterateChildren(nodep);
+    }
     void visit(AstVarRef* nodep) override {
         if (nodep->varp()->user2p()  // It's being converted to an alias.
             && !nodep->varp()->user3()
@@ -470,6 +490,7 @@ class InlineVisitor final : public VNVisitor {
     //   AstVar::user2p()       // AstVarRef*/AstConst*  Points to signal this
     //                          // is a direct connect to
     //   AstVar::user3()        // bool    Don't alias the user2, keep it as signal
+    //   AstVar::user4()        // bool    Was input, remove InitialStatic Assign
     //   AstCell::user4         // AstCell* of the created clone
     const VNUser4InUse m_inuser4;
 
diff --git a/test_regress/t/t_module_input_default_value.py b/test_regress/t/t_module_input_default_value.py
index d4f986441..c5190cc16 100755
--- a/test_regress/t/t_module_input_default_value.py
+++ b/test_regress/t/t_module_input_default_value.py
@@ -11,7 +11,8 @@ import vltest_bootstrap
 
 test.scenarios('simulator')
 
-test.compile()
+# Coverage for Issue #5920
+test.compile(verilator_flags2=['--coverage-line'])
 
 test.execute()