Diagnostic 15527: Loop Was Not Vectorized: Function Call To xxx Cannot Be Vectorized

Product Version: Intel® Visual Fortran Compiler XE 15.0 or a later version 

Cause:

The vectorization report generated when using Visual Fortran Compiler's optimization options ( /O2 /Qopt-report:2 /Qopt-report-phase:vec ) states that loop was not vectorized since loop with function call cannot be vectorized.

Example:

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

subroutine bar(a) 
    implicit none
    include 'omp_lib.h' 
    
    integer (kind=omp_lock_kind) a 
    call omp_init_lock(a) 
end subroutine bar
 
subroutine foo(a,n) 
       include 'omp_lib.h' 
       integer (kind=omp_lock_kind) a(n)

       do i=1,n
        call bar (a(i))
       end do
end subroutine foo

ifort -c /O2 /Qopt-report:2 /Qopt-report-phase:vec /Qopt-report-file:stdout f15527.f90

Report from: Vector optimizations [vec]

 LOOP BEGIN at f15527.f90(14,8)

   f15527.f90(6,10):remark #15527: simd loop was not vectorized: function call to omp_init_lock cannot be vectorized

LOOP END

Resolution:

In order for the loop to be vectorized there should be no special operators and no function or subroutine calls, unless these are inlined, either manually or automatically by the compiler, or they are SIMD (vectorized) functions.

See also:

Requirements for Vectorizable Loops

Vectorization Essentials

Vectorization and Optimization Reports

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