Diagnostic 15532: Loop was not vectorized: compile time constraints prevent loop optimization

Product Version: Intel(R) 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 ) states that compile time constraints prevent optimization.

Example:

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

subroutine foo(a, n)
    
       implicit none
       integer, intent(in) :: n
       double precision, intent(inout) :: a(n)
       integer :: bar
       integer :: i
       
       i=0
 100   CONTINUE
       a(i)=0
       i=i+1
       if (i .lt. bar()) goto 100
       
  end subroutine foo

Report from: Loop nest, Vector & Auto-parallelization optimizations [loop, vec, par]

  LOOP BEGIN  
      remark #15532: loop was not vectorized: compile time constraints prevent loop optimization. Consider using -O3.
 
  LOOP END

Resolution:

GOTO statements prevent vectorization since loop iteration count cannot be computed.

See also:

Requirements for Vectorizable Loops

Vectorization Essentials

Vectorization and Optimization Reports

Back to the list of vectorization diagnostics for Intel Fortran

For more complete information about compiler optimizations, see our Optimization Notice.