return int64(ntz64(^x))
}

// logX returns logarithm of n base 2.
// n must be a positive power of 2 (isPowerOfTwoX returns true).
func log8(n int8) int64 {
	return int64(bits.Len8(uint8(n))) - 1
}
func log16(n int16) int64 {
	return int64(bits.Len16(uint16(n))) - 1
}
func log32(n int32) int64 {
	return int64(bits.Len32(uint32(n))) - 1
}
func log64(n int64) int64 {
	return int64(bits.Len64(uint64(n))) - 1
}