what's the difference __set_64bit_constant from __set_64bit_var ?

[Jason Luo <jasonl@turbolinux.com.cn>]

Hello,
   There are two inline function called __set_64bit_constant and 
__set_64bit_var.

static inline void __set_64bit_constant (unsigned long long *ptr,
                                                unsigned long long value)
{
       __set_64bit(ptr,(unsigned int)(value), (unsigned 
int)((value)>>32ULL));
}
#define ll_low(x)       *(((unsigned int*)&(x))+0)
#define ll_high(x)      *(((unsigned int*)&(x))+1)

static inline void __set_64bit_var (unsigned long long *ptr,
                        unsigned long long value)
{
       __set_64bit(ptr,ll_low(value), ll_high(value));
}

why __set_64bit_constant shift right  the unsigned long long value but 
__set_64bit_var call ll_high/ll_low
to gain the  high or low valude?
I think __set_64bit_constant can call  ll_low/ll_high and __set_64_var 
can use shift right.



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