Scans the bits in v from the most significant bit to the least significant bit, looking for the first set bit.
The bit number of the first bit set. The return value is undefined if v is zero.
assert(bsr(0x21) == 5); assert(bsr((ulong.max >> 15) - 1) == 48);
See Implementation
Scans the bits in v from the most significant bit to the least significant bit, looking for the first set bit.