From 62ffe43a82c667c4acc67954c3c653cf552d9e24 Mon Sep 17 00:00:00 2001
From: Wilson Snyder <wsnyder@wsnyder.org>
Date: Mon, 30 Mar 2026 19:06:02 -0400
Subject: [PATCH] Fix port assignment to large arrays (#6904).

Fixes #6904.
---
 Changes                                   |  1 +
 src/V3EmitCBase.cpp                       |  4 +++-
 src/V3EmitCFunc.h                         | 14 +++++++++-----
 test_regress/t/t_var_pins_array_assign.py | 18 ++++++++++++++++++
 test_regress/t/t_var_pins_array_assign.v  | 15 +++++++++++++++
 5 files changed, 46 insertions(+), 6 deletions(-)
 create mode 100755 test_regress/t/t_var_pins_array_assign.py
 create mode 100644 test_regress/t/t_var_pins_array_assign.v

diff --git a/Changes b/Changes
index 73b88b1f9..939ed5694 100644
--- a/Changes
+++ b/Changes
@@ -74,6 +74,7 @@ Verilator 5.047 devel
 * Fix super constructor calls with local variables (#6214) (#6933). [Igor Zaworski, Antmicro Ltd.]
 * Fix `local::` false error in randomize() with on parameterized class (#6680) (#7293). [Yilou Wang]
 * Fix false recursive definition error (#6769) (#7118). [Alex Zhou]
+* Fix port assignment to large arrays (#6904).
 * Fix interface localparam dependencies and arbitrary nesting (#6936) (#7128) (#7188) (#7190). [em2machine]
 * Fix errant integer promotion (#7012). [Todd Strader]
 * Fix randc solver hang with wide variables (#7068) (#7248). [Yilou Wang]
diff --git a/src/V3EmitCBase.cpp b/src/V3EmitCBase.cpp
index 64d4b4cdd..71e92bc16 100644
--- a/src/V3EmitCBase.cpp
+++ b/src/V3EmitCBase.cpp
@@ -207,7 +207,9 @@ void EmitCBaseVisitorConst::emitVarDecl(const AstVar* nodep, bool asRef) {
         if (asRef && refNeedParens) puts(")");
         emitDeclArrayBrackets(nodep);
         puts(";\n");
-    } else if (nodep->isPrimaryIO() && basicp && !basicp->isOpaque()) {
+    } else if (nodep->isPrimaryIO() && basicp && !basicp->isOpaque()
+               && !nodep->dtypep()->skipRefp()->isCompound()
+               && !VN_IS(nodep->dtypep()->skipRefp(), UnpackArrayDType)) {
         if (nodep->isInout()) {
             putns(nodep, "VL_INOUT");
         } else if (nodep->isWritable()) {
diff --git a/src/V3EmitCFunc.h b/src/V3EmitCFunc.h
index 3f77aaef2..ec06cb0ba 100644
--- a/src/V3EmitCFunc.h
+++ b/src/V3EmitCFunc.h
@@ -511,6 +511,8 @@ public:
         bool decind = false;
         bool rhs = true;
         bool reverseUnpack = false;  // Set for descending CvtPackedToArray
+        const AstUnpackArrayDType* const unpackDtp
+            = VN_CAST(nodep->dtypep()->skipRefp(), UnpackArrayDType);
         if (AstSel* const selp = VN_CAST(nodep->lhsp(), Sel)) {
             UASSERT_OBJ(selp->widthMin() == selp->widthConst(), selp, "Width mismatch");
             if (selp->widthMin() == 1) {
@@ -580,10 +582,7 @@ public:
             rhs = false;
             iterateAndNextConstNull(castp->fromp());
             // Descending unpacked dest: reverse after unpack
-            if (const AstUnpackArrayDType* const unpackDtp
-                = VN_CAST(nodep->dtypep()->skipRefp(), UnpackArrayDType)) {
-                if (!unpackDtp->declRange().ascending()) reverseUnpack = true;
-            }
+            if (unpackDtp && !unpackDtp->declRange().ascending()) reverseUnpack = true;
         } else if (const AstCvtArrayToArray* const castp
                    = VN_CAST(nodep->rhsp(), CvtArrayToArray)) {
             if (castp->reverse()) {
@@ -608,6 +607,7 @@ public:
                    // and means using '=' and bypasses using emitConstantW.
                    // Whuch we don't want to do as slows compiler down.
                    && !VN_IS(nodep->rhsp(), VarRef)  //
+                   && !VN_IS(nodep->rhsp(), InitArray)  //
                    && !VN_IS(nodep->rhsp(), AssocSel)  //
                    && !VN_IS(nodep->rhsp(), MemberSel)  //
                    && !VN_IS(nodep->rhsp(), StructSel)  //
@@ -616,7 +616,7 @@ public:
             // Wide functions assign into the array directly, don't need separate assign statement
             m_wideTempRefp = VN_AS(nodep->lhsp(), VarRef);
             paren = false;
-        } else if (nodep->isWide() && !VN_IS(nodep->dtypep()->skipRefp(), UnpackArrayDType)
+        } else if (nodep->isWide() && !unpackDtp
                    && !VN_IS(nodep->rhsp(), Const)) {
             putnbs(nodep, "VL_ASSIGN_W(");
             puts(cvtToStr(nodep->widthMin()) + ", ");
@@ -630,6 +630,10 @@ public:
             decind = true;
             if (!VN_IS(nodep->rhsp(), Const)) ofp()->putBreak();
             putns(nodep, "= ");
+            if (unpackDtp && VN_IS(nodep->rhsp(), InitArray)) {
+                // Emit "VlUnpacked<type, depth>{{...InitArray...}}"
+                puts(unpackDtp->cType("", false, false, false));
+            }
         }
         if (rhs) iterateAndNextConstNull(nodep->rhsp());
         if (paren) puts(")");
diff --git a/test_regress/t/t_var_pins_array_assign.py b/test_regress/t/t_var_pins_array_assign.py
new file mode 100755
index 000000000..8a938befd
--- /dev/null
+++ b/test_regress/t/t_var_pins_array_assign.py
@@ -0,0 +1,18 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# 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-FileCopyrightText: 2026 Wilson Snyder
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios('simulator')
+
+test.compile()
+
+test.execute()
+
+test.passes()
diff --git a/test_regress/t/t_var_pins_array_assign.v b/test_regress/t/t_var_pins_array_assign.v
new file mode 100644
index 000000000..69772fe30
--- /dev/null
+++ b/test_regress/t/t_var_pins_array_assign.v
@@ -0,0 +1,15 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain.
+// SPDX-FileCopyrightText: 2026 Wilson Snyder
+// SPDX-License-Identifier: CC0-1.0
+
+module t (
+    output logic [64:0] output_vec[257]
+);
+
+  assign output_vec = '{default: 1};
+
+  initial $finish;
+
+endmodule