+#16
+(do ((i 0 (1+ i)))
+ ((= i (the (integer 0 100) n)))
+ ...)
+
+It is commonly expected for Python to derive (FIXNUMP I). (If ``='' is
+replaced with ``>='', Python will do.)
+--------------------------------------------------------------------------------
+#17
+Type tests for (ARRAY BIT), (ARRAY T) and similar go through full
+%TYPEP, even though it is relatively simple to establish the arrayness
+of an object and also to obtain the element type of an array. As of
+sbcl-0.8.12.30, this affects at least DUMP-OBJECT through
+COMPOUND-OBJECT-P, and (LABELS MAYBE-EMIT-MAKE-LOAD-FORMS GROVEL)
+through TYPEP UNBOXED-ARRAY, within the compiler itself.
+--------------------------------------------------------------------------------
+#18
+(lambda (x) (declare (null x)) (sxhash x)) goes through SYMBOL-HASH
+rather than either constant-folding or manipulating NIL-VALUE or
+NULL-TN directly.
+--------------------------------------------------------------------------------
+#19
+ (let ((dx (if (foo)
+ (list x)
+ (list y z))))
+ (declare (dynamic-extent dx))
+ ...)
+
+DX is not allocated on stack.
+--------------------------------------------------------------------------------
+#20
+(defun-with-dx foo (x)
+ (flet ((make (x)
+ (let ((l (list nil nil)))
+ (setf (first l) x)
+ (setf (second l) (1- x))
+ l)))
+ (let ((l (make x)))
+ (declare (dynamic-extent l))
+ (mapc #'print l))))
+
+Result of MAKE is not stack allocated, which means that
+stack-allocation of structures is impossible.
+--------------------------------------------------------------------------------
+#21
+(defun-with-dx foo ()
+ (let ((dx (list (list 1 2) (list 3 4))))
+ (declare (dynamic-extent dx))
+ ...))
+
+External list in DX is allocated on stack, but internal are not.
+--------------------------------------------------------------------------------
+#22
+IR2 does not perform unused code flushing.
+--------------------------------------------------------------------------------
+#23
+Python does not know that &REST lists are LISTs (and cannot derive it).
+--------------------------------------------------------------------------------
+#24
+a. Iterations on &REST lists, returning them as VALUES could be
+ rewritten with &MORE vectors.
+b. Implement local unknown-values mv-call (useful for fast type checking).
+--------------------------------------------------------------------------------
+#25
+EQL is implemented generically in situations where this isn't necessary.
+
+(defun f (x y)
+ (declare (type (or symbol fixnum) x)
+ (optimize speed (safety 0) (debug 0)))
+ (eql x y))
+
+SUBTYPEP is smart enough to determine that this type is a subtype
+of (and (or (not number) fixnum) (not character))
+
+This sitation where the type is (OR NULL FIXNUM) comes up
+in cl-bench, for example in the value returned by POSITION.
+--------------------------------------------------------------------------------
+#26
+SBCL cannot derive upper bound for I and uses generic arithmetic here:
+
+(defun foo (l)
+ (declare (vector l))
+ (dotimes (i (length l))
+ (if (block nil
+ (map-foo (lambda (x) (if x (return t)))
+ l))
+ t
+ nil)))
+
+(So the constraint propagator or a possible future SSA-convertor
+should know the connection between an NLE and its CLEANUP.)