QList: iterate forward in operator==

After much head-scratching, we found no reason for the backwards iteration.
Indeed, forward iteration should be slightly faster than backwards, because
it operates in the direction in which cache-lines are filled, usually.

This is in preparation of using std algorithms instead of hand-written
loops. It avoids having to use std::reverse_iterator.

Change-Id: I31be6ad2b6d78ccce7e8a8f8f8b9e0af62f7471b
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 4 insertions, 5 deletions

diff --git a/src/corelib/tools/qlist.h b/src/corelib/tools/qlist.h
index 326a276f40..b56afe15c2 100644
--- a/src/corelib/tools/qlist.h
+++ b/src/corelib/tools/qlist.h
@@ -770,11 +770,10 @@ Q_OUTOFLINE_TEMPLATE bool QList<T>::operator==(const QList<T> &l) const
         return true;
     if (p.size() != l.p.size())
         return false;
-    Node *i = reinterpret_cast<Node *>(p.end());
-    Node *b = reinterpret_cast<Node *>(p.begin());
-    Node *li = reinterpret_cast<Node *>(l.p.end());
-    while (i != b) {
-        --i; --li;
+    Node *i = reinterpret_cast<Node *>(p.begin());
+    Node *e = reinterpret_cast<Node *>(p.end());
+    Node *li = reinterpret_cast<Node *>(l.p.begin());
+    for (; i != e; ++i, ++li) {
         if (!(i->t() == li->t()))
             return false;
     }