Product Version: Intel(R) Visual Fortran Compiler XE 15.0 or a later version
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 all memory references cannot be an aligned vector load.
An example below will generate the following remark in optimization report:
integer function foo(a, n) implicit none integer, intent(in) :: n real, intent(inout) :: a(n) integer :: i do i=1,n if (a(2*i) .eq. 0) goto 100 end do 100 CONTINUE foo = i end function foo
ifort -c /O2 /Qopt-report:2 /Qopt-report-phase:vec /Qopt-report-file:stdout f15524.f90
Report from: Vector optimizations [vec]
LOOP BEGIN at f15524.f90(8,8)
remark #15524: loop was not vectorized: search loop cannot be vectorized unless all memory references can be aligned vector load.
In search loop vectorization if a “vector load” fits entirely within a cache line, and if such a vector load has one non-speculatively accessed element, it is safe for the compiler to speculatively load all other elements (within the same cache line) in such a vector load.
Rewriting the code and avoiding GOTO statements will get this loop vectorized.