Cross-compilation notes.

To build a cross compiler:

(load "tools:setup")
(comf "tools:setup" :load t)
(c::new-backend "<name>" '(<features-to-add>) '(<features-to-remove>))
(setf (search-list "target:") '(<object-dir> <source-dir>))
(load "tools:comxcom")

To load a cross compiler:

(gc-off)
(lisp::clear-auto-gc-trigger)
(setf (search-list "target:") '("sparcalpha:" "clisp:src/alpha/")
      (search-list "c:") '("target:compiler/")
      (search-list "vm:") '("c:sparc/" "c:generic/")
      (search-list "assem:") '("target:assembly/" "target:assembly/sparc/"))
(load "target:tools/setup")
(c::new-backend "<name>" '(<features-to-add>) '(<features-to-remove>))
(load "c:loadbackend")
;; ### Is this still needed?
(macrolet ((frob (&rest syms)
	     `(progn ,@(mapcar #'(lambda (sym)
				   `(defconstant ,sym
				      (symbol-value
				       (find-symbol ,(symbol-name sym)
						    :vm))))
			       syms))))
  (frob MIPS:BYTE-BITS MIPS:SIMPLE-ARRAY-DOUBLE-FLOAT-TYPE 
    MIPS:SIMPLE-ARRAY-SINGLE-FLOAT-TYPE MIPS:SIMPLE-ARRAY-TYPE 
    MIPS:SIMPLE-ARRAY-UNSIGNED-BYTE-16-TYPE 
    MIPS:SIMPLE-ARRAY-UNSIGNED-BYTE-2-TYPE 
    MIPS:SIMPLE-ARRAY-UNSIGNED-BYTE-32-TYPE 
    MIPS:SIMPLE-ARRAY-UNSIGNED-BYTE-4-TYPE
    MIPS:SIMPLE-ARRAY-UNSIGNED-BYTE-8-TYPE 
    MIPS:SIMPLE-BIT-VECTOR-TYPE
    MIPS:SIMPLE-STRING-TYPE MIPS:SIMPLE-VECTOR-TYPE 
    MIPS:VECTOR-DATA-OFFSET MIPS:WORD-BITS))
(setf (c:backend-info-environment c:*target-backend*)
      (list* (make-info-environment)
	     (compact-info-environment
	      (first (c:backend-info-environment c:*target-backend*))
	      :name "SPARC backend")
	     (rest (c:backend-info-environment c:*target-backend*))))
;; Not, of course, if this is part of a bootstrap file.
(setf (search-list "target:") '("sunosalpha:"))
(setf c:*backend* c:*target-backend*)
(lisp::purify)
(gc-on)



Remaining problems:

- The name->type-class mapping for aliens is in a single hash table.  Needs
to be moved into the info environemnt or made part of the backend.  Then
new alien-type-methods need to be loaded with the backend.

- The make-array deftransform in arraytran is VM specific, and should be
somewhere else.