+ #!-#.(cl:if (cl:= sb!vm:word-shift sb!vm:n-fixnum-tag-bits) '(and) '(or))
+ (progn
+ ;; FIXME: This can't be efficient, but LEA (my first choice)
+ ;; doesn't do subtraction.
+ (inst shl skip (- word-shift n-fixnum-tag-bits))
+ (inst sub src skip)
+ (inst shr skip (- word-shift n-fixnum-tag-bits)))