4 /* These algorithms were snarfed from various places. I did not come up with them myself */
6 inline cell popcount(u64 x)
8 u64 k1 = 0x5555555555555555ll;
9 u64 k2 = 0x3333333333333333ll;
10 u64 k4 = 0x0f0f0f0f0f0f0f0fll;
11 u64 kf = 0x0101010101010101ll;
12 x = x - ((x >> 1) & k1); // put count of each 2 bits into those 2 bits
13 x = (x & k2) + ((x >> 2) & k2); // put count of each 4 bits into those 4 bits
14 x = (x + (x >> 4)) & k4 ; // put count of each 8 bits into those 8 bits
15 x = (x * kf) >> 56; // returns 8 most significant bits of x + (x<<8) + (x<<16) + (x<<24) + ...
20 inline cell log2(u64 x)
24 asm ("bsr %1, %0;":"=r"(n):"r"((cell)x));
27 if (x >= (u64)1 << 32) { x >>= 32; n += 32; }
28 if (x >= (u64)1 << 16) { x >>= 16; n += 16; }
29 if (x >= (u64)1 << 8) { x >>= 8; n += 8; }
30 if (x >= (u64)1 << 4) { x >>= 4; n += 4; }
31 if (x >= (u64)1 << 2) { x >>= 2; n += 2; }
32 if (x >= (u64)1 << 1) { n += 1; }
37 inline cell log2(u16 x)
39 #if defined(FACTOR_X86) || defined(FACTOR_AMD64)
41 asm ("bsr %1, %0;":"=r"(n):"r"((cell)x));
44 if (x >= 1 << 8) { x >>= 8; n += 8; }
45 if (x >= 1 << 4) { x >>= 4; n += 4; }
46 if (x >= 1 << 2) { x >>= 2; n += 2; }
47 if (x >= 1 << 1) { n += 1; }
52 inline cell rightmost_clear_bit(u64 x)
54 return log2(~x & (x + 1));
57 inline cell rightmost_set_bit(u64 x)
62 inline cell rightmost_set_bit(u16 x)
64 return log2((u16)(x & -x));