Diagnostic 15414: Loop was not vectorized: loop body became empty after optimizations

Product Version: Intel(R) Visual Fortran Compiler XE 15.0.0.070

Cause:

The vectorization report generated when using Visual Fortran Compiler's optimization options (-O2  -Qopt-report:2) states that loop was not vectorized since loop body became empty after optimizations.

Example:

An example below will generate the following remark in optimization report:

integer function foo(a, b, n)
    implicit none
    integer, intent(in) :: n
    real, intent(inout) :: a
    real, intent (in)   :: b
    integer :: i

    do i=1,n
           a = b + 1
    end do

    foo = a

end function 

Report from: Vector optimizations [vec]

LOOP BEGIN at f15414.f90(8,5)
   remark #15414: loop was not vectorized: nothing to vectorize since loop body became empty after optimizations
LOOP END

Resolution:

In the example above, there is only one expression inside the loop. When moved outside the loop as a result of the compiler's optimization process there is nothing else left inside the loop to vectorize. 

See also:

Requirements for Vectorizable Loops

Vectorization Essentials

Vectorization and Optimization Reports

Back to the list of vectorization diagnostics for Intel Fortran