FLS64(9) Basic C Library Functions FLS64(9)NAMEfls64 - find last set bit in a 64-bit word
SYNOPSIS
int fls64(__u64 x);
ARGUMENTS
x
the word to search
DESCRIPTION
This is defined in a similar way as the libc and compiler builtin
ffsll, but returns the position of the most significant set bit.
fls64(value) returns 0 if value is 0 or the position of the last set
bit if value is nonzero. The last (most significant) bit is at position
64.
COPYRIGHTKernel Hackers Manual 3.11 November 2013 FLS64(9)