Diagnostic 15537: Loop was not vectorized: implied FP exception model prevents usage of SVML library.

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

Cause:

The vectorization report generated when using Visual Fortran Compiler's  flags and optimization options

( -O2   -fpe:0   -Qopt-report:2  ) states that loop was not vectorized due to Floating-Point exception handling .

Example:

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

subroutine foo (a, l, n)
       implicit none
       integer, intent(in) :: n
       double precision, intent(inout) :: a(n)
       integer :: l(n)
       integer :: i

       do i=1,n
           l(i) = mod(a(i), 1.0)
       end do
end subroutine foo

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

  LOOP BEGIN  f15537.f90(8,8)

    remark #15537: loop was not vectorized: implied FP exception model prevents usage of SVML library needed for truncation or integer divide/remainder. Consider changing compiler flags and/or directives in the source to enable fast FP model and to mask FP exceptions
 
  LOOP END

Resolution:

Masking FP exceptions -fpe:1 and setting  a threshold for the vectorization of loops to 0  -Qvec-threshold:0 will get the loop vectorized:

LOOP BEGIN  f15537.f90(8,8)

   remark #15300: LOOP WAS VECTORIZED

LOOP END

See also:

Requirements for Vectorizable Loops

Vectorization Essentials

Vectorization and Optimization Reports

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