WhenAllContext: optimize atomic operations

The old code performed one load-acquire (in the assertion) and one
ordered(!) fetch_sub() (in the pre-decrement operator) where one
relaxed fetch_sub() would suffice (it's just a counter).

Fix by caching the result of the relaxed fetch_sub() and performing
the following checks on the cached result.

As drive-bys, rename the atomic member variable (to catch any outside
uses) and make the ctor explicit.

Found by locally disabling the QAtomic<T> -> T implicit conversion
operators.

Change-Id: Ifdc11c2c4807b71f4cab2ba9f5405ace7d8d71a9
Reviewed-by: Sona Kurazyan <sona.kurazyan@qt.io>

0 files changed, 0 insertions, 0 deletions