This directive disables unroll of the loop before which it has been used and is the opposite of UNROLL.
!DIR$ NOUNROLL
Example
subroutine func1(a, b)
integer :: m = 10
integer :: i, a(m), b(m)
!dir$ nounroll
do i = 1, m
b(i) = a(i) + 1
end do
end subroutine func1