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    SubjectRe: [PATCH 13/15] x86: add cmpxchg_flag() variant
    On 08/24/2011 01:38 PM, Jeremy Fitzhardinge wrote:
    > On 08/24/2011 01:31 PM, H. Peter Anvin wrote:
    >> The sete is actually more expensive than the compare for the single-word
    >> case. The double-word case is a different matter.
    >
    > Hm, setcc has a longer latency but a higher throughput, is that
    > correct? Still, its recommended where you can use it to avoid a branch.

    Yes, but you don't know when that is (the compiler does, of course.)

    > I was also thinking that using it reduces register pressure, since you
    > don't need to keep the "old" value around, so it dies sooner.

    ... but you burn a register for the intermediate flag value, so you're
    just as bad off.

    -hpa


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