message: Since clang on bgq also defines __bg__, check for __xlC__ and the
  version that it represents.
diff: @@ -474,7 +474,7 @@ template <typename scalar_t, typename layout_t, typename data_t>
  inline scalar_t TDet(const layout_t &a, const data_t &A)
  {
  MFEM_STATIC_ASSERT(layout_t::rank == 2, "invalid rank");
  -#ifndef __bg__
  +#if !defined(__xlC__) || (__xlC__ >= 0x0d00)
  return internal::MatrixOps<layout_t::dim_1,layout_t::dim_2>::
  template Det<scalar_t>(a, A);
  #else
  