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    SubjectRe: [PATCH 2/5] bitops: compile time optimization for hweight_long(CONSTANT)
    On 02/03/2010 10:47 AM, Peter Zijlstra wrote:
    > On Wed, 2010-02-03 at 19:14 +0100, Borislav Petkov wrote:
    >
    >> alternative("call hweightXX", "popcnt", X86_FEATURE_POPCNT)
    >
    > Make sure to apply a 0xff bitmask to the popcnt r16 call for hweight8(),
    > and hweight64() needs a bit of magic for 32bit, but yes, something like
    > that ought to work nicely.
    >

    Arguably the "best" option is to have the alternative being a jump to an
    out-of-line stub which does the necessary parameter marshalling before
    calling a stub. This technique is already used in a few other places.

    -hpa


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