tests: Don't treat new stats as a cause for failures

We currently fail the stat diff stage of tests if there are new
stats. This is usually undesirable since this would require any change
that adds a stat to also update the regressions.

Change-Id: Ieadebac6fd17534e1b49b6b9a1d56f037a423325
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/3962
Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>

tests/testing/units.py

@@ -270,6 +270,10 @@ class DiffStatFile(TestUnit):
         self.stat_diff = os.path.join(_test_base, "diff-out")
 
     def _run(self):
+        STATUS_OK = 0
+        STATUS_NEW_STATS = 1
+        STATUS_FAILED = 2
+
         stats = "stats.txt"
 
         cmd = [
@@ -281,9 +285,9 @@ class DiffStatFile(TestUnit):
                            stderr=subprocess.PIPE) as p:
             status, stdout, stderr = p.call()
 
-        if status == 0:
+        if status in (STATUS_OK, STATUS_NEW_STATS):
             return self.ok(stdout=stdout, stderr=stderr)
-        if status == 1:
+        elif status == STATUS_FAILED:
             return self.failure("Statistics mismatch",
                                 stdout=stdout, stderr=stderr)
         else: