gengc/sap problem

[William_Lott@ARDATH.SLISP.CS.CMU.EDU]

Rob,

There seems to be a problem with my gengc stuff with respect to the SAP
move vops.  Sample lossage:

Error in function c::bad-costs-error.
#<TN t1> is not valid as the first argument to the
c:move VOP, since the TN's primitive type system-area-pointer allows SCs:
  (mips::sap-reg)
which cannot be coerced or loaded into the allowed SCs:
  (mips::any-reg mips::descriptor-reg)
Current cost info inconsistent with that in effect at compile time.  Recompile.
Compilation order may be incorrect.

This used to work, and I didn't change anything in the backend.  I have no
idea whats wrong.  The backend compiled cleanly (for details, look in
.../wlott/gengc/compile-backend.log), but it can't compile code anymore
(.../wlott/gengc/compile-lisp.log).  Any help or hints you could give me
would be greatly appreciated.

-William