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    SubjectRe: [PATCH 6/8] i386: bitops: Don't mark memory as clobbered unnecessarily
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    On Mon, 2007-07-23 at 10:55 -0700, Linus Torvalds wrote:
    > > The goal is to let gcc generate good, beautiful, optimized code.
    >
    > No. The point is to let gcc generate *correct* code.
    >
    > It's either "=m" together with "memory", or it's "+m".

    In fact, it's more than that... the bitops that return a value are often
    used to have hand-made spinlock semantics. I'm sure we would get funky
    bugs if loads or stores leaked out of the locked region. I think a full
    "memory" clobber should be kept around for those cases.

    (That's also why on ppc, we give them a few more barriers)

    Ben.

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