+#11
+(inverted variant of #9)
+
+(lambda (x)
+ (let ((y (sap-alien x c-string)))
+ (list (alien-sap y)
+ (alien-sap y))))
+
+It could be optimized to
+
+(lambda (x) (list x x))
+
+(if Y were used only once, the current compiler would optimize it)
+--------------------------------------------------------------------------------
+#12
+(typep (truly-the (simple-array * (*)) x) 'simple-vector)
+
+tests lowtag.
+--------------------------------------------------------------------------------
+#13
+FAST-+/FIXNUM and similar should accept unboxed arguments in interests
+of representation selection. Problem: inter-TN dependencies.
+--------------------------------------------------------------------------------
+#14
+The derived type of (/ (THE (DOUBLE-FLOAT (0D0)) X) (THE (DOUBLE-FLOAT
+1D0) Y)) is (DOUBLE-FLOAT 0.0d0). While it might be reasonable, it is
+better to derive (OR (MEMBER 0.0d0) (DOUBLE-FLOAT (0.0d0))).
+--------------------------------------------------------------------------------
+#15
+On the alpha, the system is reluctant to refer directly to a constant bignum,
+preferring to load a large constant through a slow sequence of instructions,
+then cons up a bignum for it:
+
+(LAMBDA (A)
+ (DECLARE (OPTIMIZE (SAFETY 1) (SPEED 3) (DEBUG 1))
+ (TYPE (INTEGER -10000 10000) A)
+ (IGNORABLE A))
+ (CASE A
+ ((89 125 16) (ASH A (MIN 18 -706)))
+ (T (DPB -3 (BYTE 30 30) -1))))
+--------------------------------------------------------------------------------
+#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.
+--------------------------------------------------------------------------------
+#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.
+--------------------------------------------------------------------------------
+#22
+IR2 does not perform unused code flushing.
+--------------------------------------------------------------------------------
+#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).
+--------------------------------------------------------------------------------
+#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.)
+--------------------------------------------------------------------------------
+#27
+Initialization of stack-allocated arrays is inefficient: we always
+fill the vector with zeroes, even when it is not needed (as for
+platforms with conservative GC or for arrays of unboxed objectes) and
+is performed later explicitely.
+
+(This is harder than it might look at first glance, as MAKE-ARRAY is smart
+enough to eliminate something like ':initial-element 0'. Such an optimization
+is valid if the vector is being allocated in the heap, but not if it is being
+allocated on the stack. You could remove this optimization, but that makes
+the heap-allocated case somewhat slower...)
+
+To do this, extend ALLOCATE-VECTOR with ALLOW-JUNK argument, and when
+stack allocating don't zero if it is true -- and probably ALLOW-JUNK iff
+the vector is a specialized one (cannot have pointers.)
+--------------------------------------------------------------------------------
+#28
+a. Accessing raw slots in structure instances is more inefficient than
+it could be; if we placed raw slots before the header word, we would
+not need to do arithmetic at runtime to access them. (But beware:
+this would complicate handling of the interior pointer).
+
+b. (Also note that raw slots are currently disabled on HPPA)
+--------------------------------------------------------------------------------
+#29
+Python is overly zealous when converting high-level CL functions, such
+as MIN/MAX, LOGBITP, and LOGTEST, to low-level CL functions. Reducing
+Python's aggressiveness would make it easier to effect changes such as
+
+x86-64:
+* direct MIN/MAX on {SINGLE,DOUBLE}-FLOATs ({MIN,MAX}S{S,D})
+
+x86-64:
+* direct LOGBITP on word-sized integers and fixnums (BT + JC)
+
+x86{,-64}/PPC:
+* branch-free MIN/MAX on word-sized integers and fixnums (floats could
+ be handled too, modulo safety considerations on the PPC)
+
+x86-64:
+* efficient LOGTESTs on word-sized integers and fixnums (TEST)
+
+etc., etc.
+
+(The framework for this has been implemented as of 0.9.9.18; see the
+vm-support-routine COMBINATION-IMPLEMENTATION-STYLE and its use in
+src/compiler/ir1opt.lisp, IR1-OPTIMIZE-COMBINATION. The above
+optimizations are left as an exercise for the reader.)
+--------------------------------------------------------------------------------
+#30
+(defun foo (x y)
+ (< x y))
+
+FOO's IR1 representation is roughly:
+
+(defun foo (x y)
+ (if (< x y)
+ T
+ NIL))
+
+However, if a full call is generated for < (and similarly for other
+predicate functions), then the IF is unnecessary, since the return value
+of (< x y) is already T or NIL.
+--------------------------------------------------------------------------------
+#31
+The typecheck generated for a declaration like (integer 0 45) on x86 looks
+like:
+
+; 12B: F6C203 TEST DL, 3
+; 12E: 753B JNE L1
+; 130: 8BC2 MOV EAX, EDX
+; 132: 83F800 CMP EAX, 0
+; 135: 7C34 JL L1
+; 137: 8BC2 MOV EAX, EDX
+; 139: 3DB4000000 CMP EAX, 180
+; 13E: 7F2B JNLE L1
+
+A better code sequence for this would be: