From a5ddd10e31b089637f1e85712f3cdef3bb6025d9 Mon Sep 17 00:00:00 2001
From: Geza Lore <gezalore@gmail.com>
Date: Wed, 27 Jul 2022 10:45:33 +0100
Subject: [PATCH] Tests: compare VCD files both ways

vcddiff is a bit broken, and sometimes 'vcddiff a b' fails while the
files are indeed equivalent. There is a chance however that 'vcddif b a'
will succeed in this case, so compare trace files both ways when
checking test results and claim success if vcddiff succeeds in at least
one direction.
---
 test_regress/driver.pl | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/test_regress/driver.pl b/test_regress/driver.pl
index ae0ed4f36..22a2a67f8 100755
--- a/test_regress/driver.pl
+++ b/test_regress/driver.pl
@@ -2259,10 +2259,15 @@ sub vcd_identical {
         print "\t$cmd\n" if $::Debug;
         $out = `$cmd`;
         if ($? != 0 || $out ne '') {
-            print $out;
-            $self->error("VCD miscompares $fn1 $fn2\n");
-            $self->copy_if_golden($fn1, $fn2);
-            return 0;
+            $cmd = qq{vcddiff "$fn2" "$fn1"};
+            print "\t$cmd\n" if $::Debug;
+            $out = `$cmd`;
+            if ($? != 0 || $out ne '') {
+                print $out;
+                $self->error("VCD miscompares $fn2 $fn1\n");
+                $self->copy_if_golden($fn1, $fn2);
+                return 0;
+            }
         }
     }
     {