anchor.diff:    (let ((type-error-label (gensym))
           (bignum-path (gensym "alr-sb64-bignum"))
           (value-extracted (gensym "alr-sb64-value-extracted"))
  -        (constant-offset (and (constant-type-p offset `(signed-byte ,(- 64 sys.int::+n-fixnum-bits+)))
  +        (constant-offset (and (constant-type-p offset `(signed-byte ,(- 32 sys.int::+n-fixnum-bits+)))
                                 (second offset))))
       (emit-trailer (bignum-path)
         ;; Check for bignumness.
  
positive.code: (defmacro define-u-b-object-ref (name width read-op write-op register)
    `(progn
       (defbuiltin ,name (object offset) ()
         (let ((constant-offset (and (constant-type-p offset `(signed-byte ,(- 64 sys.int::+n-fixnum-bits+)))
                                     (second offset))))
           (unless constant-offset
             (load-in-reg :rdi offset t)
  
negative.code:         (bignum-path (gensym "alr-ub64-bignum"))
          (len-2-bignum (gensym "alr-ub64-len-2-bignum"))
          (value-extracted (gensym "alr-ub64-value-extracted"))
          (constant-offset (and (constant-type-p offset `(signed-byte ,(- 32 sys.int::+n-fixnum-bits+)))
                                (second offset))))
      (emit-trailer (bignum-path)
        ;; Check for bignumness.
  