Fix unpacked array expansion (#3861)

docs/CONTRIBUTORS

@@ -60,6 +60,7 @@ Jeremy Bennett
 Jevin Sweval
 Jiacheng Qian
 Jiuyang Liu
+Joey Liu
 John Coiner
 John Demme
 Jonathan Drolet

src/V3EmitCFunc.h

@@ -358,7 +358,7 @@ 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()) {
+        } else if (nodep->isWide() && !VN_IS(nodep->dtypep()->skipRefp(), UnpackArrayDType)) {
             putbs("VL_ASSIGN_W(");
             puts(cvtToStr(nodep->widthMin()) + ",");
             iterateAndNextNull(nodep->lhsp());

src/V3Expand.cpp

@@ -848,6 +848,10 @@ private:
     }
     void visit(AstNodeAssign* nodep) override {
         if (nodep->user1SetOnce()) return;  // Process once
+        if (VN_IS(nodep->dtypep()->skipRefp(), UnpackArrayDType)) {
+            return;  // Skip for UnpackArrayDType
+        }
+
         VL_RESTORER(m_stmtp);
         m_stmtp = nodep;
         iterateChildren(nodep);

test_regress/t/t_unpack_array_direct_assignment.pl

@@ -0,0 +1,24 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2023 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
+
+scenarios(simulator => 1);
+
+top_filename("t/t_unpack_array_no_expand.v");
+
+compile(
+    verilator_flags2 => ['-fno-expand'],
+    );
+
+execute(
+    check_finished => 1,
+    );
+
+ok(1);
+1;

test_regress/t/t_unpack_array_no_expand.pl

@@ -0,0 +1,21 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2023 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
+
+scenarios(simulator => 1);
+
+compile(
+    );
+
+execute(
+    check_finished => 1,
+    );
+
+ok(1);
+1;

test_regress/t/t_unpack_array_no_expand.v

@@ -0,0 +1,42 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2023 by Wilson Snyder.
+// SPDX-License-Identifier: CC0-1.0
+
+module t
+  (
+   output logic [255:0] data_out
+   );
+   localparam int       NUM_STAGES = 3;
+
+   /* verilator lint_off ALWCOMBORDER */
+   /* verilator lint_off UNOPTFLAT */
+
+`define INPUT 256'hbabecafe
+
+   logic [255:0]        stage_data [NUM_STAGES+1];
+
+   genvar               stage;
+   generate
+      always_comb begin
+         stage_data[0] = `INPUT;
+      end
+      for (stage = 0; stage < NUM_STAGES; ++stage) begin : stage_gen
+         always_comb begin
+            stage_data[stage+1] = stage_data[stage];
+         end
+      end
+   endgenerate
+
+   /* verilator lint_on UNOPTFLAT */
+   /* verilator lint_on ALWCOMBORDER */
+
+   always_comb begin
+      data_out = stage_data[NUM_STAGES];
+      if (data_out !== `INPUT) $stop;
+      $write("*-* All Finished *-*\n");
+      $finish;
+   end
+
+endmodule