Fix $time not rounding up (#4790) (#4792)

include/verilated_funcs.h

@@ -305,7 +305,8 @@ uint64_t VerilatedContext::time() const VL_MT_SAFE {
 // Time scaled from 1-per-precision into a module's time units ("Unit"-ed, not "United")
 // Optimized assuming scale is always constant.
 // Can't use multiply in Q flavor, as might lose precision
-#define VL_TIME_UNITED_Q(scale) (VL_TIME_Q() / static_cast<QData>(scale))
+#define VL_TIME_ROUND(t, p) (((t) + ((p) / 2)) / (p))
+#define VL_TIME_UNITED_Q(scale) VL_TIME_ROUND(VL_TIME_Q(), static_cast<QData>(scale))
 #define VL_TIME_UNITED_D(scale) (VL_TIME_D() / static_cast<double>(scale))
 
 // Return time precision as multiplier of time units

test_regress/t/t_time.pl

@@ -0,0 +1,23 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2019 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(linter => 1);
+
+compile(
+    verilator_flags2 => ["--exe --main --timing"],
+    make_main => 0,
+    );
+
+execute(
+    check_finished => 1,
+    );
+
+ok(1);
+1;

test_regress/t/t_time.v

@@ -0,0 +1,75 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2024 by Paul Wright.
+// SPDX-License-Identifier: CC0-1.0
+
+/* Working through the $time example from IEEE Std 1364-2005
+** Section 17.7.1
+** The example uses a 10ns timeunit with a 1ns timeprecision
+** For 16ns $time should return 2
+** For 32ns $time should return 3
+**/
+
+module t ();
+   timeunit 10ns;
+   timeprecision 1ns;
+
+   longint should_be_2, should_be_3;
+   real should_be_1p6, should_be_3p2;
+
+   initial
+    begin : initial_blk1
+     should_be_2 = 0;
+     should_be_3 = 0;
+     #(16ns);
+     $display("$time=%d, $realtime=%g", $time(), $realtime());
+     should_be_2 = $time();
+     should_be_1p6 = $realtime();
+     #(16ns);
+     $display("$time=%d, $realtime=%g", $time(), $realtime());
+     should_be_3 = $time();
+     should_be_3p2 = $realtime();
+     #(16ns);
+     $finish(1);
+    end
+   initial
+     begin : initial_blk2
+      #(100ns);
+      $display("%%Error: We should not get here");
+      $finish(1);
+     end
+
+   function bit real_chk(input real tvar, input real evar);
+     begin
+      real diff;
+      diff = tvar - evar;
+      return (diff < 1e-9) && (diff > -1e-9);
+     end
+   endfunction
+
+   final
+     begin : last_blk
+      if (should_be_2 != 2)
+       begin
+        $display("%%Error: should_be_2 = %0d",
+                 should_be_2);
+        $stop;
+      end
+      if (should_be_3 != 3)
+       begin
+        $display("%%Error: should_be_3 = %0d",
+                 should_be_3);
+        $stop;
+      end
+      $display("Info: should_be_2 = %0d", should_be_2);
+      $display("Info: should_be_3 = %0d", should_be_3);
+
+      chk_2 :   assert(should_be_2 == 2);
+      chk_3 :   assert(should_be_3 == 3);
+      chk_1p6 : assert(real_chk(should_be_1p6, 1.6));
+      chk_3p2 : assert(real_chk(should_be_3p2, 3.2));
+      $write("*-* All Finished *-*\n");
+     end
+
+endmodule