[Bug tree-optimization/82518] [8 regression] gfortran.fortran-torture/execute/in-pack.f90 fails on armeb since r252917

["wilco.dijkstra at arm dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82518

--- Comment #49 from Wilco <wilco.dijkstra at arm dot com> ---
AArch64 does this:

(define_expand "vec_store_lanesoi<mode>"
  [(set (match_operand:OI 0 "aarch64_simd_struct_operand" "=Utv")
        (unspec:OI [(match_operand:OI 1 "register_operand" "w")
                    (unspec:VQ [(const_int 0)] UNSPEC_VSTRUCTDUMMY)]
                   UNSPEC_ST2))]
  "TARGET_SIMD"
{
  if (BYTES_BIG_ENDIAN)
    {
      rtx tmp = gen_reg_rtx (OImode);
      rtx mask = aarch64_reverse_mask (<MODE>mode, <nunits>);
      emit_insn (gen_aarch64_rev_reglistoi (tmp, operands[1], mask));
      emit_insn (gen_aarch64_simd_st2<mode> (operands[0], tmp));
    }
  else
    emit_insn (gen_aarch64_simd_st2<mode> (operands[0], operands[1]));
  DONE;
})

ARM seems to be missing the swap:

(define_expand "vec_store_lanesoi<mode>"
  [(set (match_operand:OI 0 "neon_struct_operand")
        (unspec:OI [(match_operand:OI 1 "s_register_operand")
                    (unspec:VQ2 [(const_int 0)] UNSPEC_VSTRUCTDUMMY)]
                   UNSPEC_VST2))]
  "TARGET_NEON")

So clearly looks like a backend issue.