ref: e228d9b24953a72ca8e10c0b8024f3ac9ce1fcb4
dir: /src/plan9/popcount.c/
#include "platform.h"
int
fl_popcount(unsigned int w)
{
w -= (w >> 1) & 0x55555555U;
w = (w & 0x33333333U) + ((w >> 2) & 0x33333333U);
w = (w + (w >> 4)) & 0x0F0F0F0FU;
w = (w * 0x01010101U) >> 24;
return w;
}