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    SubjectRe: [RFC][PATCH] Faster generic_fls
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    Alan Cox <alan@lxorguk.ukuu.org.uk> writes:

    > On Mer, 2003-04-30 at 17:16, Linus Torvalds wrote:
    > > Clearly you're not going to make _one_ load to get fls, since having a
    > > 4GB lookup array for a 32-bit fls would be "somewhat" wasteful.
    >
    > It ought to be basically the same as ffs because if I remember rightly
    >
    > ffs(x^(x-1)) == fls(x)

    I don't think so. Maybe you are thinking of ffs(x) == fls(x & -x). So
    you can calculate ffs with fls, but not easily the other way round.

    --
    Falk
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