__fls.h

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#ifndef _ASM_GENERIC_BITOPS___FLS_H_
#define _ASM_GENERIC_BITOPS___FLS_H_

#include <asm/types.h>

static __always_inline unsigned long __fls(unsigned long word)
{
    int num = BITS_PER_LONG - 1;

#if BITS_PER_LONG == 64
    if (!(word & (~0ul << 32))) {
        num -= 32;
        word <<= 32;
    }
#endif
    if (!(word & (~0ul << (BITS_PER_LONG-16)))) {
        num -= 16;
        word <<= 16;
    }
    if (!(word & (~0ul << (BITS_PER_LONG-8)))) {
        num -= 8;
        word <<= 8;
    }
    if (!(word & (~0ul << (BITS_PER_LONG-4)))) {
        num -= 4;
        word <<= 4;
    }
    if (!(word & (~0ul << (BITS_PER_LONG-2)))) {
        num -= 2;
        word <<= 2;
    }
    if (!(word & (~0ul << (BITS_PER_LONG-1))))
        num -= 1;
    return num;
}

#endif /* _ASM_GENERIC_BITOPS___FLS_H_ */