In C++, type punning with a union is not allowed. It will result in
compiler defined behavior at best, and undefined behavior at worst.
Specifically, if QRgba64 is passed to a function by value, the different
members of a struct might be passed in separate registers. This means
that any write to the quint64 might not blank out the values of the
struct whenever the compiler looses track with TBAA.
Change-Id: I991b5492fe4bb13a14bb670fef5bf13dacbe6c0a
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@theqtcompany.com>
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