Detect data dependencies in loops in parallelized subroutine

[clementval]

Ability to detect data dependency in loops would be nice for the automatic generation of directive. In the example below, if we can detect that the i loop has no dependency, we can generate a !$acc loop directive instead of locking it with an !$acc loop seq directive.

do i = 1, ni
  do k = 1, nk
  end do 

  do k = 1, nk
  end do 

  do k = 1, nk
  end do 
end do

!$acc loop 
do i = 1, ni
  !$acc loop seq
  do k = 1, nk
  end do 

  !$acc loop seq
  do k = 1, nk
  end do 

  !$acc loop seq
  do k = 1, nk
  end do 
end do