Emplace() implemented with std::rotate is just awful on my system
(Ubuntu 18.04 GCC 7.5.0). Custom code is much faster, so go for
it. Cannot really use insert() code, which is also fast, because
it doesn't forward-reference values but copies them always
Changes in performance (approximately) for emplacing 100k elements
into the middle:
Complex 7600ms -> 1700ms
Movable 7600ms -> 200ms
Task-number: QTBUG-86583
Change-Id: If883c9b8498a89e757f3806aea11f8fd3aa3c709
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
250b69ace4