[clazy] [Bug 361691] Suggestion to turn string into QStringLiteral instead of QLatin1String

[Sergio Martins via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=361691

--- Comment #5 from Sergio Martins <smartins at kde.org> ---
I don't have the original, but just wrote this:

#include <QString>
#include <QDebug>

#define N 100000000

bool testQStringLiteral()
{
    qDebug() << "QStringLiteral";
    bool result = false;
    QString s;
    for (int i = 0; i < N; ++i)
    {
        result |= s.contains(QStringLiteral("foo"));
    }
    return result;
}

bool testQLatin1String()
{
    qDebug() << "QLatin1String";
    bool result = false;
    QString s;
    for (int i = 0; i < N; ++i)
    {
        result |= s.contains(QLatin1String("foo"));
    }
    return result;
}

int main(int argv, char **)
{
    if (argv == 1) {
        return testQLatin1String();
    } else {
        return testQStringLiteral();
    }
}

serj ~/lixo/st $ perf stat ./st 1
QStringLiteral

 Performance counter stats for './st 1':

        574.619866      task-clock (msec)         #    0.999 CPUs utilized      
                 2      context-switches          #    0.003 K/sec              
                 0      cpu-migrations            #    0.000 K/sec              
               301      page-faults               #    0.524 K/sec              
        1818862143      cycles                    #    3.165 GHz                
   <not supported>      stalled-cycles-frontend  
   <not supported>      stalled-cycles-backend   
        5707478658      instructions              #    3.14  insns per cycle    
        1001376209      branches                  # 1742.676 M/sec              
             35138      branch-misses             #    0.00% of all branches    

       0.575097370 seconds time elapsed

serj ~/lixo/st $ perf stat ./st  
QLatin1String

 Performance counter stats for './st':

       1175.225780      task-clock (msec)         #    1.000 CPUs utilized      
                 2      context-switches          #    0.002 K/sec              
                 0      cpu-migrations            #    0.000 K/sec              
               300      page-faults               #    0.255 K/sec              
        3733101298      cycles                    #    3.176 GHz                
   <not supported>      stalled-cycles-frontend  
   <not supported>      stalled-cycles-backend   
       12508151290      instructions              #    3.35  insns per cycle    
        2101498161      branches                  # 1788.165 M/sec              
             38406      branch-misses             #    0.00% of all branches    

       1.175587617 seconds time elapsed

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