QDir: when sorting by time, get last modification times as UTC directly

PASS   : tst_QDir_10000::sorted_byTime()
RESULT : tst_QDir_10000::sorted_byTime():
     345 msecs per iteration (total: 345, iterations: 1)

PASS   : tst_QDir_10000::sorted_byTime()
RESULT : tst_QDir_10000::sorted_byTime():
     0.000015 msecs per iteration (total: 54, iterations: 262144)

Change-Id: I7976c8668aa821d2b7ed3f774f29bdf1ba4a99d1
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 2 insertions, 10 deletions

diff --git a/src/corelib/io/qdir.cpp b/src/corelib/io/qdir.cpp
index 3e42ad0979..547512bf59 100644
--- a/src/corelib/io/qdir.cpp
+++ b/src/corelib/io/qdir.cpp
@@ -219,16 +219,8 @@ bool QDirSortItemComparator::operator()(const QDirSortItem &n1, const QDirSortIt
 
     switch (sortBy) {
       case QDir::Time: {
-        QDateTime firstModified = f1->item.lastModified();
-        QDateTime secondModified = f2->item.lastModified();
-
-        // QDateTime by default will do all sorts of conversions on these to
-        // find timezones, which is incredibly expensive. As we aren't
-        // presenting these to the user, we don't care (at all) about the
-        // local timezone, so force them to UTC to avoid that conversion.
-        firstModified.setTimeZone(QTimeZone::UTC);
-        secondModified.setTimeZone(QTimeZone::UTC);
-
+        const QDateTime firstModified = f1->item.lastModified(QTimeZone::UTC);
+        const QDateTime secondModified = f2->item.lastModified(QTimeZone::UTC);
         r = firstModified.msecsTo(secondModified);
         break;
       }