4 inline cell log2(cell x)
7 #if defined(FACTOR_X86) || defined(FACTOR_AMD64)
8 asm ("bsr %1, %0;":"=r"(n):"r"(x));
9 #elif defined(FACTOR_PPC)
10 asm ("cntlzw %1, %0;":"=r"(n):"r"(x));
13 #error Unsupported CPU
18 inline cell rightmost_clear_bit(cell x)
20 return log2(~x & (x + 1));
23 inline cell rightmost_set_bit(cell x)
28 inline cell popcount(cell x)
31 u64 k1 = 0x5555555555555555ll;
32 u64 k2 = 0x3333333333333333ll;
33 u64 k4 = 0x0f0f0f0f0f0f0f0fll;
34 u64 kf = 0x0101010101010101ll;
44 x = x - ((x >> 1) & k1); // put count of each 2 bits into those 2 bits
45 x = (x & k2) + ((x >> 2) & k2); // put count of each 4 bits into those 4 bits
46 x = (x + (x >> 4)) & k4 ; // put count of each 8 bits into those 8 bits
47 x = (x * kf) >> ks; // returns 8 most significant bits of x + (x<<8) + (x<<16) + (x<<24) + ...