SMALL_REGISTER_CLASSES

[Jeffrey A Law]

  In message < 199801200202.PAA11726@ongaonga.chch.cri.nz >you write:
  > 
  > Looking through the GCC code I get the impression that
  > SMALL_REGISTER_CLASSES has been used to infer that a target has only a
  > few registers, rather than its original meaning, where it signified
  > that registers explicity mentioned in the RTL had to be used as spill
  > registers.
No, it still means those registers need to be used as spills, it just happens
that machines with few registers tend to also have registers which are
explicitly mentioned in RTL and must still be able to use them as spills.

The combination doesn't take place because you'd be extending the lifetime
of a hard register.  You want to avoid doing that at all costs when
SMALL_REGISTER_CLASSES is true.

jeff