anchor.diff:                 (format t "   ~S~%" r))))
            (let ((current-range-start (live-range-start range))
                  (current-vreg (live-range-vreg-id range)))
  -           (insert-into-vreg-set spilled-vregs current-vreg)
  +           (setf spilled-vregs (insert-into-vreg-set spilled-vregs current-vreg))
              ;; Expire old ranges.
              (setf live (remove-if (lambda (x)
                                      (< (live-range-end x) current-range-start))
  
positive.code:                      (vector-push-extend (ir:virtual-register-kind vreg) slot-classes)))
             (when (and (eql (aref slot-classes i) (ir:virtual-register-kind vreg))
                        (not (dolist (entry (aref slots i) nil)
                               (when (vreg-set-contains (aref interference-graph entry) vreg-id)
                                 (return t)))))
               ;; Does not interfere with any register in this slot.
               (push vreg-id (aref slots i))
  
negative.code:         (mapcar #'add (ir:instruction-inputs inst))
          (mapcar #'add (ir:instruction-outputs inst))))
      (values vreg-to-id id-to-vreg)))
  
  (deftype vreg-id () 'fixnum)
  
  (defun make-linear-allocator (backend-function architecture &key ordering)
    (multiple-value-bind (basic-blocks bb-preds bb-succs)
  