QDateTimePrivate: inherit QSharedData and other cleanups

Don't manage the ref-count yourself, as this requires the code to use
the QAtomic copy ctor, which we want to remove going forward. Using
QSharedData, we can let the compiler write the code for us.

Since 'ref' this way moves to the first spot in the list of effective
members, creating a 4B hole between itself and 'msecs', swap 'status'
and 'msecs' to fill the hole:

  offset:   0       8      16      24
            |       |       |       |
  without   v       v       v       v
  adj.mnt: |*R*|   | msecs | S | U | TZ....
  before:  | msecs | S | U |*R*|   | TZ...
  after:   |*R*| S | msecs | U |   | TZ....

This keeps the padding out of the critical first word, which improves
latency. That said, for accessing the members the old layout surely was
optimal. This layout optimizes copies and pessimizes access to 'msecs'
on 32-bit platforms without the Critical Word First optimization.

Requires adjustments to tst_toolsupport and the qhooks version.

Also default members using NSDMI, consequently drop the manual default
ctor.

Change-Id: I3c48e68694ad29b28a13aa47ea0f283fae52edd7
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

0 files changed, 0 insertions, 0 deletions