Messages in this thread | | | Date | Sun, 9 Jul 2006 15:18:36 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [patch] spinlocks: remove 'volatile' |
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On Sun, 9 Jul 2006, Pavel Machek wrote: > > volatile int a; a=1; a=2; > > ...under old definition, there's nothing to optimize but AFAICT, your > definition allows optimizing out a=1.
If 'a' can alias anything, then by definition the first 'a=1' could have changed something else than the second one. Otherwise, it couldn't have aliased "anything", it would have aliased only something _particular_.
IOW, you can think of "aliasing anything" as being equivalent to saying "the address is indeterminate". Two writes could literally go to two different things.
But yeah, maybe that's not really perfect either. It leaves the read-vs-read orderign still open.
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