Tests: Add t_param_default_override (#4920)

test_regress/t/t_param_default_override.py

@@ -0,0 +1,18 @@
+#!/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('simulator')
+
+test.compile(verilator_flags2=['--binary -Wno-MULTITOP'])
+
+test.execute()
+
+test.passes()

test_regress/t/t_param_default_override.v

@@ -0,0 +1,58 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2024 by Josse Van Delm.
+// SPDX-License-Identifier: CC0-1.0
+
+// verilator lint_off WIDTH
+
+module m2 #(parameter int N = 4)
+   (input [N-1:0] i0, i1,
+    input s,
+    output [N-1:0] y);
+
+   assign y = s ? i1 : i0;
+endmodule
+
+module m4 #(parameter int N = 4)
+   (input [N-1:0] i0, i1, i2, i3,
+    input [1:0] S,
+    output [N-1:0] y);
+
+   wire [N-1:0] o_low, o_high;
+
+   // See issue #4920 - use of m4 without parameter overrides
+   // caused the other use of m4(#(6)) to irop the #(N) below
+   m2 #(N) lowm( .i0(i0), .i1(i1), .s(S[0]), .y(o_low));
+   m2 #(N) highm( .i0(i2), .i1(i3), .s(S[0]), .y(o_high));
+   m2 #(N) finalm( .i0(o_low), .i1(o_high), .s(S[1]), .y(y));
+
+endmodule
+
+module m8 #(parameter int N = 4)
+  (input [N-1:0] i0, i1, i2, i3, i4, i5, i6, i7,
+   input [2:0] S,
+   output [N-1:0] y);
+
+   wire [N-1:0] o_low, o_high;
+
+   m4 #(N) lowm(.i0(i0), .i1(i1), .i2(i2), .i3(i3), .S(S[1:0]), .y(o_low));
+   m4 #(N) highm(.i0(i4), .i1(i5), .i2(i6), .i3(i7), .S(S[1:0]), .y(o_high));
+   m2 #(N) finalm(.i0(o_low), .i1(o_high), .s(S[2]), .y(y));
+
+endmodule
+
+module t ();
+   reg [5:0] i0, i1, i2, i3;
+   reg [1:0] S;
+   wire [5:0] Y;
+
+   m4 #(6) iut(.i0(i0), .i1(i1), .i2(i2), .i3(i3), .S(S), .y(Y));
+
+   initial begin
+      i0 = 6'b000000; i1 = 6'b000001; i2 = 6'b000010; i3 = 6'b000100;
+      S = 2'b00; #10;
+      S = 2'b01; #10;
+      $write("*-* All Finished *-*\n");
+   end
+endmodule