rl78 vs cse vs memory_address_addr_space

[DJ Delorie]

In this bit of code in explow.c:

  /* By passing constant addresses through registers
     we get a chance to cse them.  */
  if (! cse_not_expected && CONSTANT_P (x) && CONSTANT_ADDRESS_P (x))
    x = force_reg (address_mode, x);

On the rl78 it results in code that's a bit too complex for later
passes to be optimized fully.  Is there any way to indicate that the
above force_reg() is bad for a particular target?