Regression: Javascript JIT Engine broken in Qt 5.8 RC (Linux, gcc-64)

There is a problem with the Javascript/QML Engine in Qt 5.8 RC. When I run this minimal example with qmlscene 5.8 on my system I get erroneous runtime behaviour:

import QtQuick 2.7

Text {
    function broken(n) {
        var x = 2.;
        console.log("x start = " + x);
        while (n/x > 1000) {
            x += 2.;
            console.log("x in while = " + x);
        }
        console.log("x end = " + x);
        return x;
    }

    text: (broken(4000) === 4) ? "result ok" : "error in js engine?"
}

With Qt 5.7, I get the expected result:

qml: x start = 2
qml: x in while = 4
qml: x end = 4

With Qt 5.8 RC, I get (for given parameters):

qml: x start = 2
qml: x in while = 4
qml: x end = 0

Reordering the print statements in the code sometimes result in a working program. Some parameters even cause an endless loop with x being corrupted within the loop.

I reproduced this on two different Ubuntu 16.10 machines with the gcc-64 build. I cannot reproduce this on Windows with the msvc2013-64 build.