// and it's Below if we truncate (Exact results require no rounding).
		// For a negative result (z.neg) it is exactly the opposite.
		z.acc = makeAcc(inc != z.neg)

		if inc {
			// add 1 to mantissa
			if addVW(z.mant, z.mant, lsb) != 0 {
				// mantissa overflow => adjust exponent
				if z.exp >= MaxExp {
					// exponent overflow
					z.form = inf
					return
				}
				z.exp++