Does SEV() clear or set the Event register?

Question

Does SEV() clear or set the Event register?
and why do we use it between two WFE() calls? 
 __WFE(); 
__SEV();
__WFE();

Einar Thorsrud · Accepted Answer

Update: Corrected answer. 
 Yes. SEV signals an event. WFE, on the other hand, will put the CPU to sleep and wait for an event, then wake up and clear the event. If the event was already set, WFE will clear the event and return it immediately. 
 This way of using two WFE calls is a power-optimization. See this thread and this post for details.

Does SEV() clear or set the Event register?

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