Question on optimization directive IVDEP

Hello,

consider the code:

module ifc_ivdep_test
contains
  subroutine sub1 (z, x, y)
    real, intent(out) :: z(:)
    real, intent(in)  :: x(:)
    real, intent(in)  :: y(:)
!dir$ ivdep
    z = x * y           ! OK
  end subroutine sub1
  subroutine sub2 (z, x, y)
    real, intent(out) :: z(:,:)
    real, intent(in)  :: x(:,:)
    real, intent(in)  :: y(:,:)
!dir$ ivdep
    z = x * y           ! Warning
  end subroutine sub2
end module ifc_ivdep_test

Compiling this code gives a warning:

% ifort -V -c ifc_ivdep_test.f90
Intel(R) Fortran Compiler XE for applications running on IA-32, Version 15.0.5.223 Build 20150805
Copyright (C) 1985-2015 Intel Corporation.  All rights reserved.
FOR NON-COMMERCIAL USE ONLY

 Intel(R) Fortran 15.0-1818
ifc_ivdep_test.f90(14): warning #7866: The statement following this DEC loop optimization directive must be an iterative do-stmt, a vector assignment, an OMP do-directive or a parallel-do-directive, or an OMP simd-directive or a do-simd-directive.
!dir$ ivdep
------^

I am contemplating the restrictions I read from this warning.  The rank-1 array expression in sub1 appears fine.  Is there a reason to reject the rank-2 expression in sub2?  Assuming that only the innermost implicit loop is eligible for vectorization, it would be natural to assume the directive to apply to that loop.

Just wondering,

Harald