From 46ebcb6176c25c294c5edbeaaa757fe0ce53903e Mon Sep 17 00:00:00 2001
From: Daniel Teske <daniel.teske@digia.com>
Date: Fri, 5 Sep 2014 11:51:01 +0200
Subject: Speed up QStringList::removeDuplicates by ~2x

QSet::contains needs to hash the string, which is unnecessary, since we
can just check if the size of the set changed.

Change-Id: I2c7a42bae6cdf351533d5a582a42079658fa7729
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
---
 src/corelib/tools/qstringlist.cpp | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

(limited to 'src/corelib/tools')

diff --git a/src/corelib/tools/qstringlist.cpp b/src/corelib/tools/qstringlist.cpp
index 0d37b6ea58..cd14bb8b78 100644
--- a/src/corelib/tools/qstringlist.cpp
+++ b/src/corelib/tools/qstringlist.cpp
@@ -751,11 +751,13 @@ int QtPrivate::QStringList_removeDuplicates(QStringList *that)
     int j = 0;
     QSet<QString> seen;
     seen.reserve(n);
+    int setSize = 0;
     for (int i = 0; i < n; ++i) {
         const QString &s = that->at(i);
-        if (seen.contains(s))
-            continue;
         seen.insert(s);
+        if (setSize == seen.size()) // unchanged size => was already seen
+            continue;
+        ++setSize;
         if (j != i)
             that->swap(i, j);
         ++j;
-- 
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