anchor.diff:      result))
   
   (defclass linear-allocator ()
  -  ((%function :initarg :function :reader allocator-backend-function)
  +  ((%vreg-to-id-table :initarg :vreg-to-id :reader allocator-vreg-to-id-table)
  +   (%id-vreg-table :initarg :id-to-vreg :reader allocator-id-to-vreg-table)
  +   (%function :initarg :function :reader allocator-backend-function)
      (%ordering :initarg :ordering :reader allocator-instruction-ordering)
      (%architecture :initarg :architecture :reader allocator-architecture)
      (%live-in :initarg :live-in :reader allocator-live-in)
  
positive.code:              (let* ((start (gethash vreg vreg-liveness-start))
                      (range (make-instance 'live-range
                                            :vreg vreg
                                            :start start
                                            :end end
                                            :conflicts (if zombiep '() (gethash vreg vreg-conflicts))
  
negative.code:               (clobbers (make-hash-table :test 'eq :synchronized nil)))
            (dolist (inst order)
              (setf (gethash inst clobbers) (instruction-all-clobbers inst architecture mv-flow live-in live-out)))
            (multiple-value-bind (vreg-to-id id-to-vreg)
                (number-virtual-registers backend-function)
              (make-instance 'linear-allocator
                             :function backend-function
                             :ordering order
                             :architecture architecture
                             :live-in live-in
                             :live-out live-out
                             :mv-flow mv-flow
                             :cfg-preds bb-preds
                             :instruction-clobbers clobbers
                             :debug-variable-value-map debug-map
                             :max-debug-p (= (sys.c::optimize-quality (ir::ast backend-function) 'debug) 3)
                             :vreg-to-id vreg-to-id
                             :id-to-vreg id-to-vreg)))))))
  
  (defun virtual-registers-used-by-debug-info (allocator inst)
    (if (max-debug-p allocator)
  