There may be some tie-in with STM here too, where a particular optimization doesn't commit if the optimization gives up in the middle, or is preempted before it gets done. But maybe it's all done with cooperative multitasking. (But maybe STM is how they cooperate...)
Just a half-baked thought. It's just when you said "an optimization completes" I heard "an optimization commits", which implied that an optimization could also roll back if it needed to. Larry
