Tests: add test for incrementing/decrementing array index

Signed-off-by: Maciej Sobkowski <msobkowski@antmicro.com>

test_regress/t/t_array_index_increment.pl

@@ -0,0 +1,21 @@
+#!/usr/bin/perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2003 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.
+
+scenarios(simulator => 1);
+
+compile(
+    );
+
+execute(
+    check_finished => 1,
+    );
+
+ok(1);
+1;
+

test_regress/t/t_array_index_increment.v

@@ -0,0 +1,27 @@
+module t (/*AUTOARG*/
+   // Inputs
+   clk
+   );
+   input clk;
+
+   localparam string TEST_STRING = "test";
+   localparam CHECK_DECREMENT = decrement_array_idx();
+   localparam CHECK_INCREMENT = increment_array_idx();
+
+   function byte decrement_array_idx();
+      int pos = TEST_STRING.len() - 1;
+      decrement_array_idx = TEST_STRING[--pos];
+   endfunction
+
+   function byte increment_array_idx();
+      int pos = 0;
+      increment_array_idx = TEST_STRING[++pos];
+   endfunction
+
+   initial begin
+      if (CHECK_DECREMENT != "s") $stop;
+      if (CHECK_INCREMENT != "e") $stop;
+      $write("*-* All Finished *-*\n");
+      $finish;
+   end
+endmodule