top |= top >> 16
		top |= top >> 16 >> 16 // ">> 32" doesn't compile on 32-bit architectures
		return i*_W + bits.Len(top)
	}
	return 0
}

// trailingZeroBits returns the number of consecutive least significant zero
// bits of x.
func (x nat) trailingZeroBits() uint {
	if len(x) == 0 {
		return 0
	}
	var i uint
	for x[i] == 0 {
		i++
	}
	// x[i] != 0

// The result is 0 for |x| == 0 and |x| == Inf.
func (x *Float) MinPrec() uint {
	if x.form != finite {
		return 0
	}
	return uint(len(x.mant))*_W - x.mant.trailingZeroBits()
}

// Mode returns the rounding mode of x.
func (x *Float) Mode() RoundingMode {
	return x.mode
}

// Acc returns the accuracy of x produced by the most recent