anchor.diff:         for i from 0
          for inst in (allocator-instruction-ordering allocator)
          do (format t "~D: " i) (ir::print-instruction inst)))
  -  (let ((result (make-hash-table))
  +  (let ((result (make-hash-table :synchronized nil :test 'eq))
           (spilled-ranges (sort (all-spilled-ranges allocator)
                                 #'<
                                 :key #'live-range-start))
  
positive.code:              (setf (gethash current-vreg result) '()))
             ;; Add new interference edges.
             (dolist (range live)
               (when (not (eql (live-range-vreg range) current-vreg))
                 (pushnew current-vreg (gethash (live-range-vreg range) result))
                 (pushnew (live-range-vreg range) (gethash current-vreg result))))
             (push range live)))
      result))
  
  
negative.code:     (loop
         with starts = (allocator-range-starts allocator)
         with active-ranges = '()
         with active-vreg-to-range-table = (make-hash-table :synchronized nil)
         with range-allocations = (allocator-range-allocations allocator)
         for index from 0
         for inst in (allocator-instruction-ordering allocator)
  