default_secondary_reload: class vs scratch_class

[DJ Delorie]

In default_secondary_reload, we have this code:

          if (reg_class_subset_p (reload_class, insn_class))
            {
              gcc_assert (scratch_class == class);
              class = NO_REGS;

Why doesn't it allow the scratch class to be a superset of the desired
class?  I'm trying to build am33_2.0-linux-gnu, and I'm getting to
here with scratch_class GENERAL_REGS and class DATA_OR_EXTENDED_REGS.
reload_class and insn_class are ADDRESS_REGS.