OptimizeRenderList Taking up to 30% of cycles in SW-Rendering, QRegion to blame

When selecting the Software backend for rendering, QAbstractSoftwareRenderer::optimizeRenderList can take up to 30% of your rendering costs.

See an attached Screenshot from a 5.13.2 build, filtered for runtime (scrolling), startup omitted in an undisclosed QML application.

See how optimizeRenderList as well as renderNodes() suffers mainly from the QRegion ops
{{QRegion::operator+=(const QRegion& ) }}
and
{{ QRegion::intersected(const QRect&) }}