> On Thu, 23 Aug 2007, Segher Boessenkool wrote: > The combining, which I've mentioned *multiple*times* is > > if (atomic_read(&x) <= 1) > > and dammit, if that doesn't result in a *single* instruction, the code > generation is pure and utter crap. > > It should result in > > cmpl $1,offset(reg) > > and nothing else. And there is no way in hell you are doing that with > "atomic_read()" being inline asm.
Sorry, Linus, I don't agree. The whole point of 'volatile' is to say to the compiler, "DO NOT OPTIMIZE THIS. What you think is harmless may break things you do not and should not understand." The combination of the read and the compare into a single operation is a compiler optimization. While it would not be unreasonable to still allow this optimization (since I cannot think of any situations in which it could be harmful), it is just as reasonable not to. DS - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
