func math/bits.Len

4 uses

	math/bits (current package)
		bits.go#L19: func LeadingZeros(x uint) int { return UintSize - Len(x) }
		bits.go#L296: func Len(x uint) int {

	math/big
		nat.go#L657: 		return i*_W + bits.Len(uint(x[i]))
		natdiv.go#L720: 	recDepth := 2 * bits.Len(uint(len(v)))