Another possible OpenMP SIMD compiler bug

We've been adding lots of OpenMP SIMD instructions to our electronic structure code (http://elk.sourceforge.net/) and successfully sped it up.

But we've also encountered a few potential compiler bugs along the the way. The first was reported here: https://software.intel.com/en-us/forums/intel-fortran-compiler-for-linux...

I think there may be another. Here is the simplest code which still has the problem:
 

program test
use modbug
implicit none
integer i
complex(8) z1
complex(8), allocatable :: x(:),y(:)
complex(8) zf
external zf

n=10

allocate(r(n))
allocate(x(n),y(n))

r(:)=1
x(:)=1
y(:)=1

z1=zf(x,y)

print *,z1

end program

complex(8) function zf(x,y)
use modbug
implicit none
complex(8), intent(in) :: x(n)
complex(8), intent(in) :: y(n)
! local variables
integer i
zf=0.d0
!$OMP SIMD
do i=1,n
  zf=zf+r(i)*conjg(x(i))*y(i)
end do
return
end function

A module in a separate file is also needed:

module modbug

integer n
real(8), allocatable :: r(:)

end module

The code is compiled with

ifort -O3 -ip -axCORE-AVX2,AVX,SSE4.2 -qopenmp modbug.f90 test.f90

on our Intel Xeon E5-2680 cluster with Intel Fortran 18.0.0.

The correct output should be 10.0, but with the SIMD directive the code returns 5.0 instead.

If the module file is included in the same file as the code then the compiler reports:

test.f90(35): warning #15552: loop was not vectorized with "simd"

and the code works fine.