1 ;;;; the basics of the PCL wrapper cache mechanism
3 ;;;; This software is part of the SBCL system. See the README file for
6 ;;;; This software is derived from software originally released by Xerox
7 ;;;; Corporation. Copyright and release statements follow. Later modifications
8 ;;;; to the software are in the public domain and are provided with
9 ;;;; absolutely no warranty. See the COPYING and CREDITS files for more
12 ;;;; copyright information from original PCL sources:
14 ;;;; Copyright (c) 1985, 1986, 1987, 1988, 1989, 1990 Xerox Corporation.
15 ;;;; All rights reserved.
17 ;;;; Use and copying of this software and preparation of derivative works based
18 ;;;; upon this software are permitted. Any distribution of this software or
19 ;;;; derivative works must comply with all applicable United States export
22 ;;;; This software is made available AS IS, and Xerox Corporation makes no
23 ;;;; warranty about the software, its performance or its conformity to any
28 ;;; The caching algorithm implemented:
30 ;;; << put a paper here >>
32 ;;; For now, understand that as far as most of this code goes, a cache
33 ;;; has two important properties. The first is the number of wrappers
34 ;;; used as keys in each cache line. Throughout this code, this value
35 ;;; is always called NKEYS. The second is whether or not the cache
36 ;;; lines of a cache store a value. Throughout this code, this always
39 ;;; Depending on these values, there are three kinds of caches.
41 ;;; NKEYS = 1, VALUEP = NIL
43 ;;; In this kind of cache, each line is 1 word long. No cache locking
44 ;;; is needed since all read's in the cache are a single value.
45 ;;; Nevertheless line 0 (location 0) is reserved, to ensure that
46 ;;; invalid wrappers will not get a first probe hit.
48 ;;; To keep the code simpler, a cache lock count does appear in
49 ;;; location 0 of these caches, that count is incremented whenever
50 ;;; data is written to the cache. But, the actual lookup code (see
51 ;;; make-dlap) doesn't need to do locking when reading the cache.
53 ;;; NKEYS = 1, VALUEP = T
55 ;;; In this kind of cache, each line is 2 words long. Cache locking
56 ;;; must be done to ensure the synchronization of cache reads. Line 0
57 ;;; of the cache (location 0) is reserved for the cache lock count.
58 ;;; Location 1 of the cache is unused (in effect wasted).
62 ;;; In this kind of cache, the 0 word of the cache holds the lock
63 ;;; count. The 1 word of the cache is line 0. Line 0 of these caches
66 ;;; This is done because in this sort of cache, the overhead of doing
67 ;;; the cache probe is high enough that the 1+ required to offset the
68 ;;; location is not a significant cost. In addition, because of the
69 ;;; larger line sizes, the space that would be wasted by reserving
70 ;;; line 0 to hold the lock count is more significant.
74 ;;; A cache is essentially just a vector. The use of the individual
75 ;;; `words' in the vector depends on particular properties of the
76 ;;; cache as described above.
78 ;;; This defines an abstraction for caches in terms of their most
79 ;;; obvious implementation as simple vectors. But, please notice that
80 ;;; part of the implementation of this abstraction, is the function
81 ;;; lap-out-cache-ref. This means that most port-specific
82 ;;; modifications to the implementation of caches will require
83 ;;; corresponding port-specific modifications to the lap code
85 (defmacro cache-vector-ref (cache-vector location)
86 `(svref (the simple-vector ,cache-vector)
87 (sb-ext:truly-the fixnum ,location)))
89 (defmacro cache-vector-size (cache-vector)
90 `(array-dimension (the simple-vector ,cache-vector) 0))
92 (defun allocate-cache-vector (size)
93 (make-array size :adjustable nil))
95 (defmacro cache-vector-lock-count (cache-vector)
96 `(cache-vector-ref ,cache-vector 0))
98 (defun flush-cache-vector-internal (cache-vector)
99 (sb-sys:without-interrupts
100 (fill (the simple-vector cache-vector) nil)
101 (setf (cache-vector-lock-count cache-vector) 0))
104 (defmacro modify-cache (cache-vector &body body)
105 `(sb-sys:without-interrupts
106 (multiple-value-prog1
108 (let ((old-count (cache-vector-lock-count ,cache-vector)))
109 (declare (fixnum old-count))
110 (setf (cache-vector-lock-count ,cache-vector)
111 (if (= old-count most-positive-fixnum)
112 1 (the fixnum (1+ old-count))))))))
114 (deftype field-type ()
115 '(mod #.sb-kernel:layout-clos-hash-length))
117 (eval-when (:compile-toplevel :load-toplevel :execute)
118 (defun power-of-two-ceiling (x)
120 ;;(expt 2 (ceiling (log x 2)))
121 (the fixnum (ash 1 (integer-length (1- x)))))
124 (defconstant +nkeys-limit+ 256)
126 (defstruct (cache (:constructor make-cache ())
127 (:copier copy-cache-internal))
129 (nkeys 1 :type (integer 1 #.+nkeys-limit+))
130 (valuep nil :type (member nil t))
131 (nlines 0 :type fixnum)
132 (field 0 :type field-type)
133 (limit-fn #'default-limit-fn :type function)
134 (mask 0 :type fixnum)
135 (size 0 :type fixnum)
136 (line-size 1 :type (integer 1 #.(power-of-two-ceiling (1+ +nkeys-limit+))))
137 (max-location 0 :type fixnum)
138 (vector #() :type simple-vector)
139 (overflow nil :type list))
141 #-sb-fluid (declaim (sb-ext:freeze-type cache))
143 (defmacro cache-lock-count (cache)
144 `(cache-vector-lock-count (cache-vector ,cache)))
146 ;;; some facilities for allocation and freeing caches as they are needed
148 ;;; This is done on the assumption that a better port of PCL will
149 ;;; arrange to cons these all in the same static area. Given that, the
150 ;;; fact that PCL tries to reuse them should be a win.
152 (defvar *free-cache-vectors* (make-hash-table :size 16 :test 'eql))
154 ;;; Return a cache that has had FLUSH-CACHE-VECTOR-INTERNAL called on
155 ;;; it. This returns a cache of exactly the size requested, it won't
156 ;;; ever return a larger cache.
157 (defun get-cache-vector (size)
158 (let ((entry (gethash size *free-cache-vectors*)))
159 (sb-sys:without-interrupts
161 (setf (gethash size *free-cache-vectors*) (cons 0 nil))
162 (get-cache-vector size))
165 (flush-cache-vector-internal (allocate-cache-vector size)))
167 (let ((cache (cdr entry)))
168 (setf (cdr entry) (cache-vector-ref cache 0))
169 (flush-cache-vector-internal cache)))))))
171 (defun free-cache-vector (cache-vector)
172 (let ((entry (gethash (cache-vector-size cache-vector) *free-cache-vectors*)))
173 (sb-sys:without-interrupts
176 "attempt to free a cache-vector not allocated by GET-CACHE-VECTOR")
177 (let ((thread (cdr entry)))
178 (loop (unless thread (return))
179 (when (eq thread cache-vector)
180 (error "freeing a cache twice"))
181 (setq thread (cache-vector-ref thread 0)))
182 (flush-cache-vector-internal cache-vector) ; to help the GC
183 (setf (cache-vector-ref cache-vector 0) (cdr entry))
184 (setf (cdr entry) cache-vector)
187 ;;; This is just for debugging and analysis. It shows the state of the
188 ;;; free cache resource.
190 (defun show-free-cache-vectors ()
192 (maphash (lambda (s e) (push (list s e) elements)) *free-cache-vectors*)
193 (setq elements (sort elements #'< :key #'car))
195 (let* ((size (car e))
197 (allocated (car entry))
200 (loop (when (null head) (return t))
201 (setq head (cache-vector-ref head 0))
204 "~&There are ~4D caches of size ~4D. (~D free ~3D%)"
208 (floor (* 100 (/ free (float allocated)))))))))
210 ;;;; wrapper cache numbers
212 ;;; The constant WRAPPER-CACHE-NUMBER-ADDS-OK controls the number of
213 ;;; non-zero bits wrapper cache numbers will have.
215 ;;; The value of this constant is the number of wrapper cache numbers
216 ;;; which can be added and still be certain the result will be a
217 ;;; fixnum. This is used by all the code that computes primary cache
218 ;;; locations from multiple wrappers.
220 ;;; The value of this constant is used to derive the next two which
221 ;;; are the forms of this constant which it is more convenient for the
222 ;;; runtime code to use.
223 (defconstant wrapper-cache-number-length
224 (integer-length sb-kernel:layout-clos-hash-max))
225 (defconstant wrapper-cache-number-mask sb-kernel:layout-clos-hash-max)
226 (defconstant wrapper-cache-number-adds-ok
227 (truncate most-positive-fixnum sb-kernel:layout-clos-hash-max))
229 ;;;; wrappers themselves
231 ;;; This caching algorithm requires that wrappers have more than one
232 ;;; wrapper cache number. You should think of these multiple numbers
233 ;;; as being in columns. That is, for a given cache, the same column
234 ;;; of wrapper cache numbers will be used.
236 ;;; If at some point the cache distribution of a cache gets bad, the
237 ;;; cache can be rehashed by switching to a different column.
239 ;;; The columns are referred to by field number which is that number
240 ;;; which, when used as a second argument to wrapper-ref, will return
241 ;;; that column of wrapper cache number.
243 ;;; This code is written to allow flexibility as to how many wrapper
244 ;;; cache numbers will be in each wrapper, and where they will be
245 ;;; located. It is also set up to allow port specific modifications to
246 ;;; `pack' the wrapper cache numbers on machines where the addressing
247 ;;; modes make that a good idea.
249 ;;; In SBCL, as in CMU CL, we want to do type checking as early as
250 ;;; possible; structures help this. The structures are hard-wired to
251 ;;; have a fixed number of cache hash values, and that number must
252 ;;; correspond to the number of cache lines we use.
253 (defconstant wrapper-cache-number-vector-length
254 sb-kernel:layout-clos-hash-length)
256 (unless (boundp '*the-class-t*)
257 (setq *the-class-t* nil))
259 (defmacro wrapper-class (wrapper)
260 `(sb-kernel:class-pcl-class (sb-kernel:layout-class ,wrapper)))
261 (defmacro wrapper-no-of-instance-slots (wrapper)
262 `(sb-kernel:layout-length ,wrapper))
264 (defmacro wrapper-instance-slots-layout (wrapper)
265 `(%wrapper-instance-slots-layout ,wrapper))
266 (defmacro wrapper-class-slots (wrapper)
267 `(%wrapper-class-slots ,wrapper))
268 (defmacro wrapper-cache-number-vector (x) x)
270 ;;; This is called in BRAID when we are making wrappers for classes
271 ;;; whose slots are not initialized yet, and which may be built-in
272 ;;; classes. We pass in the class name in addition to the class.
273 (defun boot-make-wrapper (length name &optional class)
274 (let ((found (cl:find-class name nil)))
277 (unless (sb-kernel:class-pcl-class found)
278 (setf (sb-kernel:class-pcl-class found) class))
279 (aver (eq (sb-kernel:class-pcl-class found) class))
280 (let ((layout (sb-kernel:class-layout found)))
284 (make-wrapper-internal
286 :class (sb-kernel:make-standard-class :name name :pcl-class class))))))
288 ;;; The following variable may be set to a STANDARD-CLASS that has
289 ;;; already been created by the lisp code and which is to be redefined
290 ;;; by PCL. This allows STANDARD-CLASSes to be defined and used for
291 ;;; type testing and dispatch before PCL is loaded.
292 (defvar *pcl-class-boot* nil)
294 ;;; In SBCL, as in CMU CL, the layouts (a.k.a wrappers) for built-in
295 ;;; and structure classes already exist when PCL is initialized, so we
296 ;;; don't necessarily always make a wrapper. Also, we help maintain
297 ;;; the mapping between CL:CLASS and PCL::CLASS objects.
298 (defun make-wrapper (length class)
300 ((typep class 'std-class)
301 (make-wrapper-internal
304 (let ((owrap (class-wrapper class)))
306 (sb-kernel:layout-class owrap))
307 ((*subtypep (class-of class)
308 *the-class-standard-class*)
309 (cond ((and *pcl-class-boot*
310 (eq (slot-value class 'name) *pcl-class-boot*))
311 (let ((found (cl:find-class (slot-value class 'name))))
312 (unless (sb-kernel:class-pcl-class found)
313 (setf (sb-kernel:class-pcl-class found) class))
314 (aver (eq (sb-kernel:class-pcl-class found) class))
317 (sb-kernel:make-standard-class :pcl-class class))))
319 (sb-kernel:make-random-pcl-class :pcl-class class))))))
321 (let* ((found (cl:find-class (slot-value class 'name)))
322 (layout (sb-kernel:class-layout found)))
323 (unless (sb-kernel:class-pcl-class found)
324 (setf (sb-kernel:class-pcl-class found) class))
325 (aver (eq (sb-kernel:class-pcl-class found) class))
329 (defconstant +first-wrapper-cache-number-index+ 0)
331 (declaim (inline next-wrapper-cache-number-index))
332 (defun next-wrapper-cache-number-index (field-number)
333 (and (< field-number #.(1- wrapper-cache-number-vector-length))
336 ;;; FIXME: Why are there two layers here, with one operator trivially
337 ;;; defined in terms of the other? It'd be nice either to have a
338 ;;; comment explaining why the separation is valuable, or to collapse
339 ;;; it into a single layer.
341 ;;; FIXME (?): These are logically inline functions, but they need to
342 ;;; be SETFable, and for now it seems not worth the trouble to DEFUN
343 ;;; both inline FOO and inline (SETF FOO) for each one instead of a
344 ;;; single macro. Perhaps the best thing would be to make them
345 ;;; immutable (since it seems sort of surprising and gross to be able
346 ;;; to modify hash values) so that they can become inline functions
347 ;;; with no muss or fuss. I (WHN) didn't do this only because I didn't
348 ;;; know whether any code anywhere depends on the values being
350 (defmacro cache-number-vector-ref (cnv n)
351 `(wrapper-cache-number-vector-ref ,cnv ,n))
352 (defmacro wrapper-cache-number-vector-ref (wrapper n)
353 `(sb-kernel:layout-clos-hash ,wrapper ,n))
355 (declaim (inline wrapper-class*))
356 (defun wrapper-class* (wrapper)
357 (or (wrapper-class wrapper)
358 (find-structure-class
359 (cl:class-name (sb-kernel:layout-class wrapper)))))
361 ;;; The wrapper cache machinery provides general mechanism for
362 ;;; trapping on the next access to any instance of a given class. This
363 ;;; mechanism is used to implement the updating of instances when the
364 ;;; class is redefined (MAKE-INSTANCES-OBSOLETE). The same mechanism
365 ;;; is also used to update generic function caches when there is a
366 ;;; change to the superclasses of a class.
368 ;;; Basically, a given wrapper can be valid or invalid. If it is
369 ;;; invalid, it means that any attempt to do a wrapper cache lookup
370 ;;; using the wrapper should trap. Also, methods on
371 ;;; SLOT-VALUE-USING-CLASS check the wrapper validity as well. This is
372 ;;; done by calling CHECK-WRAPPER-VALIDITY.
374 (declaim (inline invalid-wrapper-p))
375 (defun invalid-wrapper-p (wrapper)
376 (not (null (sb-kernel:layout-invalid wrapper))))
378 (defvar *previous-nwrappers* (make-hash-table))
380 (defun invalidate-wrapper (owrapper state nwrapper)
381 (aver (member state '(:flush :obsolete) :test #'eq))
382 (let ((new-previous ()))
383 ;; First off, a previous call to INVALIDATE-WRAPPER may have
384 ;; recorded OWRAPPER as an NWRAPPER to update to. Since OWRAPPER
385 ;; is about to be invalid, it no longer makes sense to update to
388 ;; We go back and change the previously invalidated wrappers so
389 ;; that they will now update directly to NWRAPPER. This
390 ;; corresponds to a kind of transitivity of wrapper updates.
391 (dolist (previous (gethash owrapper *previous-nwrappers*))
392 (when (eq state :obsolete)
393 (setf (car previous) :obsolete))
394 (setf (cadr previous) nwrapper)
395 (push previous new-previous))
397 (let ((ocnv (wrapper-cache-number-vector owrapper)))
398 (dotimes (i sb-kernel:layout-clos-hash-length)
399 (setf (cache-number-vector-ref ocnv i) 0)))
401 (push (setf (sb-kernel:layout-invalid owrapper) (list state nwrapper))
404 (setf (gethash owrapper *previous-nwrappers*) ()
405 (gethash nwrapper *previous-nwrappers*) new-previous)))
407 (defun check-wrapper-validity (instance)
408 (let* ((owrapper (wrapper-of instance))
409 (state (sb-kernel:layout-invalid owrapper)))
414 (flush-cache-trap owrapper (cadr state) instance))
416 (obsolete-instance-trap owrapper (cadr state) instance))))))
418 (declaim (inline check-obsolete-instance))
419 (defun check-obsolete-instance (instance)
420 (when (invalid-wrapper-p (sb-kernel:layout-of instance))
421 (check-wrapper-validity instance)))
423 (defvar *free-caches* nil)
425 (defun get-cache (nkeys valuep limit-fn nlines)
426 (let ((cache (or (sb-sys:without-interrupts (pop *free-caches*))
428 (declare (type cache cache))
429 (multiple-value-bind (cache-mask actual-size line-size nlines)
430 (compute-cache-parameters nkeys valuep nlines)
431 (setf (cache-nkeys cache) nkeys
432 (cache-valuep cache) valuep
433 (cache-nlines cache) nlines
434 (cache-field cache) +first-wrapper-cache-number-index+
435 (cache-limit-fn cache) limit-fn
436 (cache-mask cache) cache-mask
437 (cache-size cache) actual-size
438 (cache-line-size cache) line-size
439 (cache-max-location cache) (let ((line (1- nlines)))
442 (1+ (* line line-size))))
443 (cache-vector cache) (get-cache-vector actual-size)
444 (cache-overflow cache) nil)
447 (defun get-cache-from-cache (old-cache new-nlines
448 &optional (new-field +first-wrapper-cache-number-index+))
449 (let ((nkeys (cache-nkeys old-cache))
450 (valuep (cache-valuep old-cache))
451 (cache (or (sb-sys:without-interrupts (pop *free-caches*))
453 (declare (type cache cache))
454 (multiple-value-bind (cache-mask actual-size line-size nlines)
455 (if (= new-nlines (cache-nlines old-cache))
456 (values (cache-mask old-cache) (cache-size old-cache)
457 (cache-line-size old-cache) (cache-nlines old-cache))
458 (compute-cache-parameters nkeys valuep new-nlines))
459 (setf (cache-owner cache) (cache-owner old-cache)
460 (cache-nkeys cache) nkeys
461 (cache-valuep cache) valuep
462 (cache-nlines cache) nlines
463 (cache-field cache) new-field
464 (cache-limit-fn cache) (cache-limit-fn old-cache)
465 (cache-mask cache) cache-mask
466 (cache-size cache) actual-size
467 (cache-line-size cache) line-size
468 (cache-max-location cache) (let ((line (1- nlines)))
471 (1+ (* line line-size))))
472 (cache-vector cache) (get-cache-vector actual-size)
473 (cache-overflow cache) nil)
476 (defun copy-cache (old-cache)
477 (let* ((new-cache (copy-cache-internal old-cache))
478 (size (cache-size old-cache))
479 (old-vector (cache-vector old-cache))
480 (new-vector (get-cache-vector size)))
481 (declare (simple-vector old-vector new-vector))
482 (dotimes-fixnum (i size)
483 (setf (svref new-vector i) (svref old-vector i)))
484 (setf (cache-vector new-cache) new-vector)
487 (defun free-cache (cache)
488 (free-cache-vector (cache-vector cache))
489 (setf (cache-vector cache) #())
490 (setf (cache-owner cache) nil)
491 (push cache *free-caches*)
494 (defun compute-line-size (x)
495 (power-of-two-ceiling x))
497 (defun compute-cache-parameters (nkeys valuep nlines-or-cache-vector)
498 ;;(declare (values cache-mask actual-size line-size nlines))
499 (declare (fixnum nkeys))
501 (let* ((line-size (if valuep 2 1))
502 (cache-size (if (typep nlines-or-cache-vector 'fixnum)
506 (power-of-two-ceiling
507 nlines-or-cache-vector))))
508 (cache-vector-size nlines-or-cache-vector))))
509 (declare (fixnum line-size cache-size))
510 (values (logxor (the fixnum (1- cache-size)) (the fixnum (1- line-size)))
513 (the (values fixnum t) (floor cache-size line-size))))
514 (let* ((line-size (power-of-two-ceiling (if valuep (1+ nkeys) nkeys)))
515 (cache-size (if (typep nlines-or-cache-vector 'fixnum)
519 (power-of-two-ceiling
520 nlines-or-cache-vector))))
521 (1- (cache-vector-size nlines-or-cache-vector)))))
522 (declare (fixnum line-size cache-size))
523 (values (logxor (the fixnum (1- cache-size)) (the fixnum (1- line-size)))
524 (the fixnum (1+ cache-size))
526 (the (values fixnum t) (floor cache-size line-size))))))
528 ;;; the various implementations of computing a primary cache location from
529 ;;; wrappers. Because some implementations of this must run fast there are
530 ;;; several implementations of the same algorithm.
532 ;;; The algorithm is:
534 ;;; SUM over the wrapper cache numbers,
535 ;;; ENSURING that the result is a fixnum
536 ;;; MASK the result against the mask argument.
538 ;;; The basic functional version. This is used by the cache miss code to
539 ;;; compute the primary location of an entry.
540 (defun compute-primary-cache-location (field mask wrappers)
542 (declare (type field-type field) (fixnum mask))
543 (if (not (listp wrappers))
545 (the fixnum (wrapper-cache-number-vector-ref wrappers field)))
546 (let ((location 0) (i 0))
547 (declare (fixnum location i))
548 (dolist (wrapper wrappers)
549 ;; First add the cache number of this wrapper to location.
550 (let ((wrapper-cache-number (wrapper-cache-number-vector-ref wrapper
552 (declare (fixnum wrapper-cache-number))
553 (if (zerop wrapper-cache-number)
554 (return-from compute-primary-cache-location 0)
556 (the fixnum (+ location wrapper-cache-number)))))
557 ;; Then, if we are working with lots of wrappers, deal with
558 ;; the wrapper-cache-number-mask stuff.
559 (when (and (not (zerop i))
560 (zerop (mod i wrapper-cache-number-adds-ok)))
562 (logand location wrapper-cache-number-mask)))
564 (the fixnum (1+ (logand mask location))))))
566 ;;; This version is called on a cache line. It fetches the wrappers
567 ;;; from the cache line and determines the primary location. Various
568 ;;; parts of the cache filling code call this to determine whether it
569 ;;; is appropriate to displace a given cache entry.
571 ;;; If this comes across a wrapper whose CACHE-NO is 0, it returns the
572 ;;; symbol invalid to suggest to its caller that it would be provident
573 ;;; to blow away the cache line in question.
574 (defun compute-primary-cache-location-from-location (to-cache
577 (from-cache to-cache))
578 (declare (type cache to-cache from-cache) (fixnum from-location))
580 (cache-vector (cache-vector from-cache))
581 (field (cache-field to-cache))
582 (mask (cache-mask to-cache))
583 (nkeys (cache-nkeys to-cache)))
584 (declare (type field-type field) (fixnum result mask nkeys)
585 (simple-vector cache-vector))
586 (dotimes-fixnum (i nkeys)
587 (let* ((wrapper (cache-vector-ref cache-vector (+ i from-location)))
588 (wcn (wrapper-cache-number-vector-ref wrapper field)))
589 (declare (fixnum wcn))
590 (setq result (+ result wcn)))
591 (when (and (not (zerop i))
592 (zerop (mod i wrapper-cache-number-adds-ok)))
593 (setq result (logand result wrapper-cache-number-mask))))
596 (the fixnum (1+ (logand mask result))))))
598 ;;; NIL means nothing so far, no actual arg info has NILs
600 ;;; CLASS seen all sorts of metaclasses
601 ;;; (specifically, more than one of the next 4 values)
602 ;;; T means everything so far is the class T
603 ;;; STANDARD-CLASS seen only standard classes
604 ;;; BUILT-IN-CLASS seen only built in classes
605 ;;; STRUCTURE-CLASS seen only structure classes
606 (defun raise-metatype (metatype new-specializer)
607 (let ((slot (find-class 'slot-class))
608 (std (find-class 'std-class))
609 (standard (find-class 'standard-class))
610 (fsc (find-class 'funcallable-standard-class))
611 (structure (find-class 'structure-class))
612 (built-in (find-class 'built-in-class)))
613 (flet ((specializer->metatype (x)
614 (let ((meta-specializer
615 (if (eq *boot-state* 'complete)
616 (class-of (specializer-class x))
618 (cond ((eq x *the-class-t*) t)
619 ((*subtypep meta-specializer std)
621 ((*subtypep meta-specializer standard)
623 ((*subtypep meta-specializer fsc)
625 ((*subtypep meta-specializer structure)
627 ((*subtypep meta-specializer built-in)
629 ((*subtypep meta-specializer slot)
631 (t (error "PCL cannot handle the specializer ~S (meta-specializer ~S)."
633 meta-specializer))))))
634 ;; We implement the following table. The notation is
635 ;; that X and Y are distinct meta specializer names.
637 ;; NIL <anything> ===> <anything>
640 (let ((new-metatype (specializer->metatype new-specializer)))
641 (cond ((eq new-metatype 'slot-instance) 'class)
642 ((null metatype) new-metatype)
643 ((eq metatype new-metatype) new-metatype)
646 (defmacro with-dfun-wrappers ((args metatypes)
647 (dfun-wrappers invalid-wrapper-p
648 &optional wrappers classes types)
649 invalid-arguments-form
651 `(let* ((args-tail ,args) (,invalid-wrapper-p nil) (invalid-arguments-p nil)
652 (,dfun-wrappers nil) (dfun-wrappers-tail nil)
654 `((wrappers-rev nil) (types-rev nil) (classes-rev nil))))
655 (dolist (mt ,metatypes)
657 (setq invalid-arguments-p t)
659 (let* ((arg (pop args-tail))
662 `((class *the-class-t*)
665 (setq wrapper (wrapper-of arg))
666 (when (invalid-wrapper-p wrapper)
667 (setq ,invalid-wrapper-p t)
668 (setq wrapper (check-wrapper-validity arg)))
669 (cond ((null ,dfun-wrappers)
670 (setq ,dfun-wrappers wrapper))
671 ((not (consp ,dfun-wrappers))
672 (setq dfun-wrappers-tail (list wrapper))
673 (setq ,dfun-wrappers (cons ,dfun-wrappers dfun-wrappers-tail)))
675 (let ((new-dfun-wrappers-tail (list wrapper)))
676 (setf (cdr dfun-wrappers-tail) new-dfun-wrappers-tail)
677 (setf dfun-wrappers-tail new-dfun-wrappers-tail))))
679 `((setq class (wrapper-class* wrapper))
680 (setq type `(class-eq ,class)))))
682 `((push wrapper wrappers-rev)
683 (push class classes-rev)
684 (push type types-rev)))))
685 (if invalid-arguments-p
686 ,invalid-arguments-form
687 (let* (,@(when wrappers
688 `((,wrappers (nreverse wrappers-rev))
689 (,classes (nreverse classes-rev))
690 (,types (mapcar (lambda (class)
695 ;;;; some support stuff for getting a hold of symbols that we need when
696 ;;;; building the discriminator codes. It's OK for these to be interned
697 ;;;; symbols because we don't capture any user code in the scope in which
698 ;;;; these symbols are bound.
700 (defvar *dfun-arg-symbols* '(.ARG0. .ARG1. .ARG2. .ARG3.))
702 (defun dfun-arg-symbol (arg-number)
703 (or (nth arg-number (the list *dfun-arg-symbols*))
704 (intern (format nil ".ARG~A." arg-number) *pcl-package*)))
706 (defvar *slot-vector-symbols* '(.SLOTS0. .SLOTS1. .SLOTS2. .SLOTS3.))
708 (defun slot-vector-symbol (arg-number)
709 (or (nth arg-number (the list *slot-vector-symbols*))
710 (intern (format nil ".SLOTS~A." arg-number) *pcl-package*)))
712 ;; FIXME: There ought to be a good way to factor out the idiom:
714 ;; (dotimes (i (length metatypes))
715 ;; (push (dfun-arg-symbol i) lambda-list))
717 ;; used in the following four functions into common code that we can
718 ;; declare inline or something. --njf 2001-12-20
719 (defun make-dfun-lambda-list (metatypes applyp)
720 (let ((lambda-list nil))
721 (dotimes (i (length metatypes))
722 (push (dfun-arg-symbol i) lambda-list))
724 (push '&rest lambda-list)
725 (push '.dfun-rest-arg. lambda-list))
726 (nreverse lambda-list)))
728 (defun make-dlap-lambda-list (metatypes applyp)
729 (let ((lambda-list nil))
730 (dotimes (i (length metatypes))
731 (push (dfun-arg-symbol i) lambda-list))
732 ;; FIXME: This is translated directly from the old PCL code.
733 ;; It didn't have a (PUSH '.DFUN-REST-ARG. LAMBDA-LIST) or
734 ;; something similar, so we don't either. It's hard to see how
735 ;; this could be correct, since &REST wants an argument after
736 ;; it. This function works correctly because the caller
737 ;; magically tacks on something after &REST. The calling functions
738 ;; (in dlisp.lisp) should be fixed and this function rewritten.
741 (push '&rest lambda-list))
742 (nreverse lambda-list)))
744 ;; FIXME: The next two functions suffer from having a `.DFUN-REST-ARG.'
745 ;; in their lambda lists, but no corresponding `&REST' symbol. We assume
746 ;; this should be the case by analogy with the previous two functions.
747 ;; It works, and I don't know why. Check the calling functions and
748 ;; fix these too. --njf 2001-12-20
749 (defun make-emf-call (metatypes applyp fn-variable &optional emf-type)
751 (let ((required nil))
752 (dotimes (i (length metatypes))
753 (push (dfun-arg-symbol i) required))
754 (nreverse required))))
755 `(,(if (eq emf-type 'fast-method-call)
756 'invoke-effective-method-function-fast
757 'invoke-effective-method-function)
758 ,fn-variable ,applyp ,@required ,@(when applyp `(.dfun-rest-arg.)))))
760 (defun make-fast-method-call-lambda-list (metatypes applyp)
761 (let ((reversed-lambda-list nil))
762 (push '.pv-cell. reversed-lambda-list)
763 (push '.next-method-call. reversed-lambda-list)
764 (dotimes (i (length metatypes))
765 (push (dfun-arg-symbol i) reversed-lambda-list))
767 (push '.dfun-rest-arg. reversed-lambda-list))
768 (nreverse reversed-lambda-list)))
770 (defmacro with-local-cache-functions ((cache) &body body)
771 `(let ((.cache. ,cache))
772 (declare (type cache .cache.))
773 (labels ((cache () .cache.)
774 (nkeys () (cache-nkeys .cache.))
775 (line-size () (cache-line-size .cache.))
776 (vector () (cache-vector .cache.))
777 (valuep () (cache-valuep .cache.))
778 (nlines () (cache-nlines .cache.))
779 (max-location () (cache-max-location .cache.))
780 (limit-fn () (cache-limit-fn .cache.))
781 (size () (cache-size .cache.))
782 (mask () (cache-mask .cache.))
783 (field () (cache-field .cache.))
784 (overflow () (cache-overflow .cache.))
786 ;; Return T IFF this cache location is reserved. The
787 ;; only time this is true is for line number 0 of an
790 (line-reserved-p (line)
791 (declare (fixnum line))
795 (location-reserved-p (location)
796 (declare (fixnum location))
800 ;; Given a line number, return the cache location.
801 ;; This is the value that is the second argument to
802 ;; cache-vector-ref. Basically, this deals with the
803 ;; offset of nkeys>1 caches and multiplies by line
806 (line-location (line)
807 (declare (fixnum line))
808 (when (line-reserved-p line)
809 (error "line is reserved"))
811 (the fixnum (* line (line-size)))
812 (the fixnum (1+ (the fixnum (* line (line-size)))))))
814 ;; Given a cache location, return the line. This is
815 ;; the inverse of LINE-LOCATION.
817 (location-line (location)
818 (declare (fixnum location))
820 (floor location (line-size))
821 (floor (the fixnum (1- location)) (line-size))))
823 ;; Given a line number, return the wrappers stored at
824 ;; that line. As usual, if nkeys=1, this returns a
825 ;; single value. Only when nkeys>1 does it return a
826 ;; list. An error is signalled if the line is
829 (line-wrappers (line)
830 (declare (fixnum line))
831 (when (line-reserved-p line) (error "Line is reserved."))
832 (location-wrappers (line-location line)))
834 (location-wrappers (location) ; avoid multiplies caused by line-location
835 (declare (fixnum location))
837 (cache-vector-ref (vector) location)
838 (let ((list (make-list (nkeys)))
840 (declare (simple-vector vector))
841 (dotimes (i (nkeys) list)
844 (cache-vector-ref vector (+ location i)))))))
846 ;; Given a line number, return true IFF the line's
847 ;; wrappers are the same as wrappers.
849 (line-matches-wrappers-p (line wrappers)
850 (declare (fixnum line))
851 (and (not (line-reserved-p line))
852 (location-matches-wrappers-p (line-location line)
855 (location-matches-wrappers-p (loc wrappers) ; must not be reserved
856 (declare (fixnum loc))
857 (let ((cache-vector (vector)))
858 (declare (simple-vector cache-vector))
860 (eq wrappers (cache-vector-ref cache-vector loc))
861 (dotimes (i (nkeys) t)
863 (unless (eq (pop wrappers)
864 (cache-vector-ref cache-vector (+ loc i)))
867 ;; Given a line number, return the value stored at that line.
868 ;; If valuep is NIL, this returns NIL. As with line-wrappers,
869 ;; an error is signalled if the line is reserved.
872 (declare (fixnum line))
873 (when (line-reserved-p line) (error "Line is reserved."))
874 (location-value (line-location line)))
876 (location-value (loc)
877 (declare (fixnum loc))
879 (cache-vector-ref (vector) (+ loc (nkeys)))))
881 ;; Given a line number, return true IFF that line has data in
882 ;; it. The state of the wrappers stored in the line is not
883 ;; checked. An error is signalled if line is reserved.
885 (when (line-reserved-p line) (error "Line is reserved."))
886 (not (null (cache-vector-ref (vector) (line-location line)))))
888 ;; Given a line number, return true IFF the line is full and
889 ;; there are no invalid wrappers in the line, and the line's
890 ;; wrappers are different from wrappers.
891 ;; An error is signalled if the line is reserved.
893 (line-valid-p (line wrappers)
894 (declare (fixnum line))
895 (when (line-reserved-p line) (error "Line is reserved."))
896 (location-valid-p (line-location line) wrappers))
898 (location-valid-p (loc wrappers)
899 (declare (fixnum loc))
900 (let ((cache-vector (vector))
901 (wrappers-mismatch-p (null wrappers)))
902 (declare (simple-vector cache-vector))
903 (dotimes (i (nkeys) wrappers-mismatch-p)
905 (let ((wrapper (cache-vector-ref cache-vector (+ loc i))))
906 (when (or (null wrapper)
907 (invalid-wrapper-p wrapper))
909 (unless (and wrappers
914 (setq wrappers-mismatch-p t))))))
916 ;; How many unreserved lines separate line-1 and line-2.
918 (line-separation (line-1 line-2)
919 (declare (fixnum line-1 line-2))
920 (let ((diff (the fixnum (- line-2 line-1))))
921 (declare (fixnum diff))
923 (setq diff (+ diff (nlines)))
924 (when (line-reserved-p 0)
925 (setq diff (1- diff))))
928 ;; Given a cache line, get the next cache line. This will not
929 ;; return a reserved line.
932 (declare (fixnum line))
933 (if (= line (the fixnum (1- (nlines))))
934 (if (line-reserved-p 0) 1 0)
935 (the fixnum (1+ line))))
938 (declare (fixnum loc))
939 (if (= loc (max-location))
943 (the fixnum (+ loc (line-size)))))
945 ;; Given a line which has a valid entry in it, this
946 ;; will return the primary cache line of the wrappers
947 ;; in that line. We just call
948 ;; COMPUTE-PRIMARY-CACHE-LOCATION-FROM-LOCATION, this
949 ;; is an easier packaging up of the call to it.
952 (declare (fixnum line))
953 (location-line (line-primary-location line)))
955 (line-primary-location (line)
956 (declare (fixnum line))
957 (compute-primary-cache-location-from-location
958 (cache) (line-location line))))
959 (declare (ignorable #'cache #'nkeys #'line-size #'vector #'valuep
960 #'nlines #'max-location #'limit-fn #'size
961 #'mask #'field #'overflow #'line-reserved-p
962 #'location-reserved-p #'line-location
963 #'location-line #'line-wrappers #'location-wrappers
964 #'line-matches-wrappers-p
965 #'location-matches-wrappers-p
966 #'line-value #'location-value #'line-full-p
967 #'line-valid-p #'location-valid-p
968 #'line-separation #'next-line #'next-location
969 #'line-primary #'line-primary-location))
972 ;;; Here is where we actually fill, recache and expand caches.
974 ;;; The functions FILL-CACHE and PROBE-CACHE are the ONLY external
975 ;;; entrypoints into this code.
977 ;;; FILL-CACHE returns 1 value: a new cache
979 ;;; a wrapper field number
982 ;;; an absolute cache size (the size of the actual vector)
983 ;;; It tries to re-adjust the cache every time it makes a new fill.
984 ;;; The intuition here is that we want uniformity in the number of
985 ;;; probes needed to find an entry. Furthermore, adjusting has the
986 ;;; nice property of throwing out any entries that are invalid.
987 (defvar *cache-expand-threshold* 1.25)
989 (defun fill-cache (cache wrappers value &optional free-cache-p)
991 ;; FILL-CACHE won't return if WRAPPERS is nil, might as well check..
993 (error "fill-cache: WRAPPERS arg is NIL!"))
995 (or (fill-cache-p nil cache wrappers value)
996 (and (< (ceiling (* (cache-count cache) 1.25))
997 (if (= (cache-nkeys cache) 1)
998 (1- (cache-nlines cache))
999 (cache-nlines cache)))
1000 (adjust-cache cache wrappers value free-cache-p))
1001 (expand-cache cache wrappers value free-cache-p)))
1003 (defvar *check-cache-p* nil)
1005 (defmacro maybe-check-cache (cache)
1007 (when *check-cache-p*
1008 (check-cache ,cache))
1011 (defun check-cache (cache)
1012 (with-local-cache-functions (cache)
1013 (let ((location (if (= (nkeys) 1) 0 1))
1014 (limit (funcall (limit-fn) (nlines))))
1015 (dotimes-fixnum (i (nlines) cache)
1016 (when (and (not (location-reserved-p location))
1018 (let* ((home-loc (compute-primary-cache-location-from-location
1020 (home (location-line (if (location-reserved-p home-loc)
1021 (next-location home-loc)
1023 (sep (when home (line-separation home i))))
1024 (when (and sep (> sep limit))
1025 (error "bad cache ~S ~@
1026 value at location ~W: ~W lines from its home. The limit is ~W."
1027 cache location sep limit))))
1028 (setq location (next-location location))))))
1030 (defun probe-cache (cache wrappers &optional default limit-fn)
1031 ;;(declare (values value))
1033 ;; FIXME: This and another earlier test on a WRAPPERS arg can
1034 ;; be compact assertoids.
1035 (error "WRAPPERS arg is NIL!"))
1036 (with-local-cache-functions (cache)
1037 (let* ((location (compute-primary-cache-location (field) (mask) wrappers))
1038 (limit (funcall (or limit-fn (limit-fn)) (nlines))))
1039 (declare (fixnum location limit))
1040 (when (location-reserved-p location)
1041 (setq location (next-location location)))
1042 (dotimes-fixnum (i (1+ limit))
1043 (when (location-matches-wrappers-p location wrappers)
1044 (return-from probe-cache (or (not (valuep))
1045 (location-value location))))
1046 (setq location (next-location location)))
1047 (dolist (entry (overflow))
1048 (when (equal (car entry) wrappers)
1049 (return-from probe-cache (or (not (valuep))
1053 (defun map-cache (function cache &optional set-p)
1054 (with-local-cache-functions (cache)
1055 (let ((set-p (and set-p (valuep))))
1056 (dotimes-fixnum (i (nlines) cache)
1057 (unless (or (line-reserved-p i) (not (line-valid-p i nil)))
1058 (let ((value (funcall function (line-wrappers i) (line-value i))))
1060 (setf (cache-vector-ref (vector) (+ (line-location i) (nkeys)))
1062 (dolist (entry (overflow))
1063 (let ((value (funcall function (car entry) (cdr entry))))
1065 (setf (cdr entry) value))))))
1068 (defun cache-count (cache)
1069 (with-local-cache-functions (cache)
1071 (declare (fixnum count))
1072 (dotimes-fixnum (i (nlines) count)
1073 (unless (line-reserved-p i)
1074 (when (line-full-p i)
1077 (defun entry-in-cache-p (cache wrappers value)
1078 (declare (ignore value))
1079 (with-local-cache-functions (cache)
1080 (dotimes-fixnum (i (nlines))
1081 (unless (line-reserved-p i)
1082 (when (equal (line-wrappers i) wrappers)
1085 ;;; returns T or NIL
1086 (defun fill-cache-p (forcep cache wrappers value)
1087 (with-local-cache-functions (cache)
1088 (let* ((location (compute-primary-cache-location (field) (mask) wrappers))
1089 (primary (location-line location)))
1090 (declare (fixnum location primary))
1091 (multiple-value-bind (free emptyp)
1092 (find-free-cache-line primary cache wrappers)
1093 (when (or forcep emptyp)
1095 (push (cons (line-wrappers free) (line-value free))
1096 (cache-overflow cache)))
1097 ;;(fill-line free wrappers value)
1099 (declare (fixnum line))
1100 (when (line-reserved-p line)
1101 (error "attempt to fill a reserved line"))
1102 (let ((loc (line-location line))
1103 (cache-vector (vector)))
1104 (declare (fixnum loc) (simple-vector cache-vector))
1105 (cond ((= (nkeys) 1)
1106 (setf (cache-vector-ref cache-vector loc) wrappers)
1108 (setf (cache-vector-ref cache-vector (1+ loc)) value)))
1111 (declare (fixnum i))
1112 (dolist (w wrappers)
1113 (setf (cache-vector-ref cache-vector (+ loc i)) w)
1114 (setq i (the fixnum (1+ i)))))
1116 (setf (cache-vector-ref cache-vector (+ loc (nkeys)))
1118 (maybe-check-cache cache))))))))
1120 (defun fill-cache-from-cache-p (forcep cache from-cache from-line)
1121 (declare (fixnum from-line))
1122 (with-local-cache-functions (cache)
1123 (let ((primary (location-line
1124 (compute-primary-cache-location-from-location
1125 cache (line-location from-line) from-cache))))
1126 (declare (fixnum primary))
1127 (multiple-value-bind (free emptyp)
1128 (find-free-cache-line primary cache)
1129 (when (or forcep emptyp)
1131 (push (cons (line-wrappers free) (line-value free))
1132 (cache-overflow cache)))
1133 ;;(transfer-line from-cache-vector from-line cache-vector free)
1134 (let ((from-cache-vector (cache-vector from-cache))
1135 (to-cache-vector (vector))
1137 (declare (fixnum to-line))
1138 (if (line-reserved-p to-line)
1139 (error "transferring something into a reserved cache line")
1140 (let ((from-loc (line-location from-line))
1141 (to-loc (line-location to-line)))
1142 (declare (fixnum from-loc to-loc))
1143 (modify-cache to-cache-vector
1144 (dotimes-fixnum (i (line-size))
1145 (setf (cache-vector-ref to-cache-vector
1147 (cache-vector-ref from-cache-vector
1148 (+ from-loc i)))))))
1149 (maybe-check-cache cache)))))))
1151 ;;; Returns NIL or (values <field> <cache-vector>)
1153 ;;; This is only called when it isn't possible to put the entry in the
1154 ;;; cache the easy way. That is, this function assumes that
1155 ;;; FILL-CACHE-P has been called as returned NIL.
1157 ;;; If this returns NIL, it means that it wasn't possible to find a
1158 ;;; wrapper field for which all of the entries could be put in the
1159 ;;; cache (within the limit).
1160 (defun adjust-cache (cache wrappers value free-old-cache-p)
1161 (with-local-cache-functions (cache)
1162 (let ((ncache (get-cache-from-cache cache (nlines) (field))))
1163 (do ((nfield (cache-field ncache) (next-wrapper-cache-number-index nfield)))
1164 ((null nfield) (free-cache ncache) nil)
1165 (setf (cache-field ncache) nfield)
1166 (labels ((try-one-fill-from-line (line)
1167 (fill-cache-from-cache-p nil ncache cache line))
1168 (try-one-fill (wrappers value)
1169 (fill-cache-p nil ncache wrappers value)))
1170 (if (and (dotimes-fixnum (i (nlines) t)
1171 (when (and (null (line-reserved-p i))
1172 (line-valid-p i wrappers))
1173 (unless (try-one-fill-from-line i) (return nil))))
1174 (dolist (wrappers+value (cache-overflow cache) t)
1175 (unless (try-one-fill (car wrappers+value) (cdr wrappers+value))
1177 (try-one-fill wrappers value))
1178 (progn (when free-old-cache-p (free-cache cache))
1179 (return (maybe-check-cache ncache)))
1180 (flush-cache-vector-internal (cache-vector ncache))))))))
1182 ;;; returns: (values <cache>)
1183 (defun expand-cache (cache wrappers value free-old-cache-p)
1184 ;;(declare (values cache))
1185 (with-local-cache-functions (cache)
1186 (let ((ncache (get-cache-from-cache cache (* (nlines) 2))))
1187 (labels ((do-one-fill-from-line (line)
1188 (unless (fill-cache-from-cache-p nil ncache cache line)
1189 (do-one-fill (line-wrappers line) (line-value line))))
1190 (do-one-fill (wrappers value)
1191 (setq ncache (or (adjust-cache ncache wrappers value t)
1192 (fill-cache-p t ncache wrappers value))))
1193 (try-one-fill (wrappers value)
1194 (fill-cache-p nil ncache wrappers value)))
1195 (dotimes-fixnum (i (nlines))
1196 (when (and (null (line-reserved-p i))
1197 (line-valid-p i wrappers))
1198 (do-one-fill-from-line i)))
1199 (dolist (wrappers+value (cache-overflow cache))
1200 (unless (try-one-fill (car wrappers+value) (cdr wrappers+value))
1201 (do-one-fill (car wrappers+value) (cdr wrappers+value))))
1202 (unless (try-one-fill wrappers value)
1203 (do-one-fill wrappers value))
1204 (when free-old-cache-p (free-cache cache))
1205 (maybe-check-cache ncache)))))
1207 ;;; This is the heart of the cache filling mechanism. It implements
1208 ;;; the decisions about where entries are placed.
1210 ;;; Find a line in the cache at which a new entry can be inserted.
1213 ;;; <empty?> is <line> in fact empty?
1214 (defun find-free-cache-line (primary cache &optional wrappers)
1215 ;;(declare (values line empty?))
1216 (declare (fixnum primary))
1217 (with-local-cache-functions (cache)
1218 (when (line-reserved-p primary) (setq primary (next-line primary)))
1219 (let ((limit (funcall (limit-fn) (nlines)))
1222 (p primary) (s primary))
1223 (declare (fixnum p s limit))
1226 ;; Try to find a free line starting at <s>. <p> is the
1227 ;; primary line of the entry we are finding a free
1228 ;; line for, it is used to compute the separations.
1229 (do* ((line s (next-line line))
1230 (nsep (line-separation p s) (1+ nsep)))
1232 (declare (fixnum line nsep))
1233 (when (null (line-valid-p line wrappers)) ;If this line is empty or
1234 (push line lines) ;invalid, just use it.
1235 (return-from find-free))
1236 (when (and wrappedp (>= line primary))
1237 ;; have gone all the way around the cache, time to quit
1238 (return-from find-free-cache-line (values primary nil)))
1239 (let ((osep (line-separation (line-primary line) line)))
1240 (when (>= osep limit)
1241 (return-from find-free-cache-line (values primary nil)))
1242 (when (cond ((= nsep limit) t)
1243 ((= nsep osep) (zerop (random 2)))
1246 ;; See whether we can displace what is in this line so that we
1247 ;; can use the line.
1248 (when (= line (the fixnum (1- (nlines)))) (setq wrappedp t))
1249 (setq p (line-primary line))
1250 (setq s (next-line line))
1253 (when (= line (the fixnum (1- (nlines)))) (setq wrappedp t)))))
1254 ;; Do all the displacing.
1256 (when (null (cdr lines)) (return nil))
1257 (let ((dline (pop lines))
1259 (declare (fixnum dline line))
1260 ;;Copy from line to dline (dline is known to be free).
1261 (let ((from-loc (line-location line))
1262 (to-loc (line-location dline))
1263 (cache-vector (vector)))
1264 (declare (fixnum from-loc to-loc) (simple-vector cache-vector))
1265 (modify-cache cache-vector
1266 (dotimes-fixnum (i (line-size))
1267 (setf (cache-vector-ref cache-vector
1269 (cache-vector-ref cache-vector
1271 (setf (cache-vector-ref cache-vector
1274 (values (car lines) t))))
1276 (defun default-limit-fn (nlines)
1282 (defvar *empty-cache* (make-cache)) ; for defstruct slot initial value forms