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    SubjectRe: Runaway cron task on 2.5.63/4 bk?
    Linus Torvalds wrote:
    >
    > On Tue, 11 Mar 2003, Andrew Morton wrote:
    >
    >>gcc will generate 64bit * 64bit multiplies without resorting to
    >>any library code
    >
    >
    > However, gcc is unable to do-the-right-thing and generate 32x32->64
    > multiplies, or 32x64->64 multiplies, even though those are both a _lot_
    > faster than the full 64x64->64 case.
    >
    > And in quite a _lot_ of cases, that's actually what you want. It might
    > actually make sense to add a "do_mul()" thing to allow architectures to do
    > these cases right, since gcc doesn't.
    >
    >
    >>and you can probably do the division with do_div().
    >
    >
    > Yes. This is the same issue - gcc will always promote a 64-bit divide to
    > be _fully_ 64-bit, even if the mixed-size 64/32 -> [64,32] case is much
    > faster and simpler. Which is why do_div() exists in the first place.

    Often the 64/32 -> [32,32] is all that is needed and that is even
    faster if we could get to it.
    >
    > Linus
    >
    > -
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    --
    George Anzinger george@mvista.com
    High-res-timers: http://sourceforge.net/projects/high-res-timers/
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