I have an example that reproduces the bug.

#include <qapplication.h>
#include <qimage.h>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QImage image(128, 256, QImage::Format_ARGB32);
    image.fill(Qt::darkGreen);
    QImage scaled = image.scaled(154, 308, Qt::KeepAspectRatio,
                                 Qt::SmoothTransformation);
    return a.exec();
}

The application always crashes inside the qt_qimageScaleAARGBA_up_xy function. I investigated the problem. This function was optimized after the Qt4.8.6 version.
How can I fix this algorithm and test the fix?
It is really blocker on OS X because this function is required for the Retina support tasks.