Avi Kivity 7dfd7de8cd future: optimize data-less future<> ...

A future that does not carry any data (future<>) and its sibling (promise<>)
are heavily used in the code.  We can optimize them by overlaying the
future's payload, which in this case can only be an std::exception_ptr,
with the future state, as a pointer and an enum have disjoint values.

This of course depends on std::exception_ptr being implemented as a pointer,
but as it happens, it is.

With this, sizeof(future<>) is reduced from 24 bytes to 16 bytes.

2014-12-09 10:08:48 +02:00

20 KiB

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