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    Subject[PATCH 2/6] bitops: compile time optimization for hweight_long(CONSTANT)
    This allows use of hweight_long() in BUILD_BUG_ON().
    Suggested by Jamie.

    CC: Jamie Lokier <jamie@shareable.org>
    CC: Roland Dreier <rdreier@cisco.com>
    Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
    ---
    include/linux/bitops.h | 12 ++++++++----
    1 file changed, 8 insertions(+), 4 deletions(-)

    --- linux.orig/include/linux/bitops.h 2010-01-09 12:13:00.000000000 +0800
    +++ linux/include/linux/bitops.h 2010-01-09 12:21:50.000000000 +0800
    @@ -40,10 +40,14 @@ static __inline__ int get_count_order(un
    return order;
    }

    -static inline unsigned long hweight_long(unsigned long w)
    -{
    - return sizeof(w) == 4 ? hweight32(w) : hweight64(w);
    -}
    +#define hweight_long(x) \
    +( \
    + __builtin_constant_p(x) ? \
    + __builtin_popcountl(x) : \
    + (sizeof(x) <= 4 ? \
    + hweight32(x) : \
    + hweight64(x)) \
    +)

    /**
    * rol32 - rotate a 32-bit value left



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