#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();
    }
}

 
$ time ./qttester 
QLatin1String

real    0m1.450s
user    0m1.448s
sys     0m0.004s
$ time ./qttester 1
QStringLiteral

real    0m0.655s
user    0m0.652s
sys     0m0.000s