From f6e0aa3a0f3e5577b2672667d9e416d35dce849d Mon Sep 17 00:00:00 2001
From: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>
Date: Tue, 20 Sep 2011 11:13:47 +0200
Subject: don't calculate hash when the map is empty and we are not inserting
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the alternative would be splitting the function into two separate
overloads. that might result in better branch prediction, but will
create a bit more code.

Change-Id: Ia2c685bbb34a9681c71f2249d073dd960368209a
Reviewed-on: http://codereview.qt-project.org/5332
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Samuel Rødal <samuel.rodal@nokia.com>
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>
---
 src/corelib/tools/qhash.h | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/corelib/tools/qhash.h b/src/corelib/tools/qhash.h
index a2d9434904..55c3efa307 100644
--- a/src/corelib/tools/qhash.h
+++ b/src/corelib/tools/qhash.h
@@ -879,8 +879,13 @@ Q_OUTOFLINE_TEMPLATE typename QHash<Key, T>::Node **QHash<Key, T>::findNode(cons
                                                                             uint *ahp) const
 {
     Node **node;
-    uint h = qHash(akey);
+    uint h;
 
+    if (d->numBuckets || ahp) {
+        h = qHash(akey);
+        if (ahp)
+            *ahp = h;
+    }
     if (d->numBuckets) {
         node = reinterpret_cast<Node **>(&d->buckets[h % d->numBuckets]);
         Q_ASSERT(*node == e || (*node)->next);
@@ -889,8 +894,6 @@ Q_OUTOFLINE_TEMPLATE typename QHash<Key, T>::Node **QHash<Key, T>::findNode(cons
     } else {
         node = const_cast<Node **>(reinterpret_cast<const Node * const *>(&e));
     }
-    if (ahp)
-        *ahp = h;
     return node;
 }
 
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