Fix --lib-create wrapper port order (#8626)

src/V3VariableOrder.cpp

@@ -177,10 +177,17 @@ class VariableOrder final {
 
     // cppcheck-suppress constParameterPointer
     void orderModuleVars(AstNodeModule* modp) {
+        // Top level ports stay first in source order, as a --lib-create wrapper must match
+        // the interface of the module it replaces
+        std::vector<AstVar*> portps;
         // Unlink all module variables from the module, compute attributes
         for (AstNode *nodep = modp->stmtsp(), *nextp; nodep; nodep = nextp) {
             nextp = nodep->nextp();
             if (AstVar* const varp = VN_CAST(nodep, Var)) {
+                if (modp->isTop() && varp->isIO()) {
+                    portps.push_back(varp);
+                    continue;
+                }
                 m_varps.push_back(varp);
 
                 // Compute attributes up front
@@ -207,6 +214,7 @@ class VariableOrder final {
                 mtaskSortVars(m_varps);
             }
         }
+        m_varps.insert(m_varps.begin(), portps.begin(), portps.end());
     }
 
 public:

test_regress/t/t_lib_port_order.py

@@ -0,0 +1,30 @@
+#!/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('vlt_all')
+
+lib_dir = test.obj_dir + "/sub"
+test.mkdir_ok(lib_dir)
+
+test.run(logfile=lib_dir + "/verilator.log",
+         cmd=[
+             "perl", os.environ["VERILATOR_ROOT"] + "/bin/verilator", "-cc", "-Mdir", lib_dir,
+             "--lib-create", "sub", "--prefix", "Vsub", "+define+LIB_CREATE", test.top_filename
+         ],
+         verilator_run=True)
+
+test.run(logfile=lib_dir + "/make.log", cmd=[os.environ["MAKE"], "-C", lib_dir, "-f", "Vsub.mk"])
+
+test.compile(verilator_flags2=["--binary", "-LDFLAGS", "sub/libsub.a", lib_dir + "/sub.sv"])
+
+test.execute()
+
+test.passes()

test_regress/t/t_lib_port_order.v

@@ -0,0 +1,77 @@
+// 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
+
+// verilog_format: off
+`define stop $stop
+`define checkh(gotv,expv) do if ((gotv) !== (expv)) begin $write("%%Error: %s:%0d:  got='h%x exp='h%x\n", `__FILE__,`__LINE__, (gotv), (expv)); `stop; end while(0);
+// verilog_format: on
+
+`ifdef LIB_CREATE
+// This is built with --lib-create. The ports have different sizes, so ordering
+// variables for layout would reorder them.
+
+module sub (
+    input logic [62:0] wide,
+    input logic clk,
+    input logic [6:0] narrow,
+    output logic [30:0] sum,
+    output logic flag
+);
+
+  always_ff @(posedge clk) begin
+    sum <= wide[30:0] + {24'd0, narrow};
+    flag <= ^wide;
+  end
+
+endmodule
+
+`else
+// This is built as the top level
+
+module top;
+
+  logic clk = 1'b0;
+  int cyc = 0;
+  logic [62:0] wide = 63'h01234567_89abcdef;
+  logic [6:0] narrow = 7'h5a;
+  logic [30:0] sum;
+  logic flag;
+  logic [30:0] exp_sum;
+  logic exp_flag;
+
+  always #5 clk = ~clk;
+
+  // Positional connections need the library wrapper to keep the source port order
+  sub sub_i (
+      wide,
+      clk,
+      narrow,
+      sum,
+      flag
+  );
+
+  always @(posedge clk) begin
+    cyc <= cyc + 1;
+    wide <= {wide[61:0], wide[62] ^ wide[61]};
+    narrow <= narrow + 7'd3;
+    exp_sum <= wide[30:0] + {24'd0, narrow};
+    exp_flag <= ^wide;
+  end
+
+  always @(negedge clk) begin
+    if (cyc > 0) begin
+      `checkh(sum, exp_sum);
+      `checkh(flag, exp_flag);
+    end
+    if (cyc == 20) begin
+      $write("*-* All Finished *-*\n");
+      $finish;
+    end
+  end
+
+endmodule
+
+`endif