4 /* These algorithms were snarfed from various places. I did not come up with them myself */
6 inline cell popcount(cell x)
9 u64 k1 = 0x5555555555555555ll;
10 u64 k2 = 0x3333333333333333ll;
11 u64 k4 = 0x0f0f0f0f0f0f0f0fll;
12 u64 kf = 0x0101010101010101ll;
22 x = x - ((x >> 1) & k1); // put count of each 2 bits into those 2 bits
23 x = (x & k2) + ((x >> 2) & k2); // put count of each 4 bits into those 4 bits
24 x = (x + (x >> 4)) & k4 ; // put count of each 8 bits into those 8 bits
25 x = (x * kf) >> ks; // returns 8 most significant bits of x + (x<<8) + (x<<16) + (x<<24) + ...
30 inline cell log2(cell x)
32 #if defined(FACTOR_X86)
34 asm ("bsr %1, %0;":"=r"(n):"r"(x));
35 #elif defined(FACTOR_AMD64)
37 asm ("bsr %1, %0;":"=r"(n):"r"(x));
41 if (x >= (u64)1 << 32) { x >>= 32; n += 32; }
43 if (x >= (u32)1 << 16) { x >>= 16; n += 16; }
44 if (x >= (u32)1 << 8) { x >>= 8; n += 8; }
45 if (x >= (u32)1 << 4) { x >>= 4; n += 4; }
46 if (x >= (u32)1 << 2) { x >>= 2; n += 2; }
47 if (x >= (u32)1 << 1) { n += 1; }
52 inline cell rightmost_clear_bit(cell x)
54 return log2(~x & (x + 1));
57 inline cell rightmost_set_bit(cell x)