ifort 17.0.0 AVX dot_product bug on i5-6300HQ with -O2 -xHost

I may have found a compiler bug on Linux, for ifort version 17.0.0 on a Debian 'testing' distribution (uname -a: Linux e5470 4.6.0-1-amd64 #1 SMP Debian 4.6.4-1 (2016-07-18) x86_64 GNU/Linux).

The following Fortran code snippet hangs indefinitely within the loop, with CPU at 100%, if compiled with optimization options -O2 -xHost. It works with a previous ifort release; with gfortran; or if the inner loop 'dot_product' is rewritten term by term, as in the listing below.

subroutine k2r_foldinto_WScell(kvec_conventional,nplanes,bzplanes_array,already_inside_before_folding, && kvec_folded)
  implicit none integer,parameter :: ndimens=3
  real(kind(0.d0)),intent(IN) :: kvec_conventional(ndimens)
  integer,intent(IN) :: nplanes
  real(kind(0.d0)),intent(IN) :: bzplanes_array(ndimens+1,nplanes) ! Indexed in: xyz d/2, iplane.
  logical,intent(OUT) :: already_inside_before_folding

  real(kind(0.d0)) kvec_folded(ndimens), & ! Indexed in: xyz.& kvec_relative(ndimens), && bz_distance_squared, max_bz_distance_squared
  integer iplane,closest_bz !, idimen

  already_inside_before_folding = .true.
  kvec_folded(1:ndimens) = kvec_conventional(1:ndimens) ! Assume initially that no folding is needed.
234 continue
  max_bz_distance_squared = dot_product( kvec_folded, kvec_folded ) ! Get the search started: distance from Gamma.

  closest_bz = 0 ! Initial trial assumption that the point is closest to the BZ instance around Gamma, conventionally labeled as 0.
  do iplane=1,nplanes
     kvec_relative(1:ndimens) = kvec_folded(1:ndimens) - bzplanes_array(1:ndimens,iplane) ! Intel ifort 17.0.0 bug with -O2 and -mavx:
   ! bz_distance_squared = dot_product( kvec_relative,kvec_relative )
   ! Workaround:
    bz_distance_squared = kvec_relative(1)*kvec_relative(1) + &&                   kvec_relative(2)*kvec_relative(2) + &&                   kvec_relative(3)*kvec_relative(3)
      if( bz_distance_squared.lt.max_bz_distance_squared ) then
        max_bz_distance_squared = bz_distance_squared
        closest_bz = iplane
      endif
    enddo ! iplane
    if( closest_bz.gt.0 ) then
      kvec_folded(1:ndimens) = kvec_folded(1:3) - bzplanes_array(1:ndimens,closest_bz)
      already_inside_before_folding = .false.
      goto 234
    endif
end subroutine k2r_foldinto_WScell

Thanks for any possible confirmation/feedback,

--

Alberto.