Well, in the second version I did replace a 'call _hweightXX' with
the actual popcnt opcode so the alternatives is only needed to do the
replacement during boot. We might just as well do
if (X86_FEATURE_POPCNT)
__hw_popcnt()
else
__software_hweight()
The only advantage of the alternatives is that it would save us the
if-else test above each time we do cpumask_weight. However, the if-else
approach is much more readable and obviates the need for all that macro
magic and taking special care of calling c function from within asm. And
since we do not call cpumask_weight all that often I'll honestly opt for
alternative-less solution...