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    SubjectRe: [RFC/PATCH] doc: volatile considered evil
    Jeremy Fitzhardinge wrote:
    > David Rientjes wrote:
    >> Since 'volatile' has two different semantics depending on the context in
    >> which it is used, this warning should be appended to include the fact that
    >> it is legitimate to use for inline assembly.
    >>
    >
    >
    > It's probably worth noting that "asm volatile (...)" doesn't mean what
    > many people think it means: specifically, it *does not* prevent the asm
    > from being reordered with respect to the surrounding code. It may not
    > even prevent it from being reordered with respect to other asm
    > volatiles. *All* it means is that the asm code will be emitted even if
    > the compiler doesn't think its results will be used. Note that an
    > "asm()" with no outputs is implicitly "asm volatile()" - on the grounds
    > that it would be otherwise useless as far as gcc can tell.
    >
    > If you need to guarantee ordering of asm statements, you must do it
    > explicitly, with either a "memory" clobber, or some finer-grain
    > serialization variable (like the _proxy_pda stuff). It would be useful
    > if you could tell gcc "I'm passing this variable to the asm for
    > serialization purposes, but there's no need to generate any explicit
    > references to it", but as far as I know there's no support for that.
    >
    > J

    The doc. should just be talking about "volatile" in C mostly.
    Any asm volatile comments are "extra".

    --
    ~Randy
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