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:classoid-pcl-class (sb-kernel:layout-classoid ,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 (sb-kernel:find-classoid name nil)))
277 (unless (sb-kernel:classoid-pcl-class found)
278 (setf (sb-kernel:classoid-pcl-class found) class))
279 (aver (eq (sb-kernel:classoid-pcl-class found) class))
280 (let ((layout (sb-kernel:classoid-layout found)))
284 (make-wrapper-internal
286 :classoid (sb-kernel:make-standard-classoid
287 :name name :pcl-class class))))))
289 ;;; The following variable may be set to a STANDARD-CLASS that has
290 ;;; already been created by the lisp code and which is to be redefined
291 ;;; by PCL. This allows STANDARD-CLASSes to be defined and used for
292 ;;; type testing and dispatch before PCL is loaded.
293 (defvar *pcl-class-boot* nil)
295 ;;; In SBCL, as in CMU CL, the layouts (a.k.a wrappers) for built-in
296 ;;; and structure classes already exist when PCL is initialized, so we
297 ;;; don't necessarily always make a wrapper. Also, we help maintain
298 ;;; the mapping between CL:CLASS and SB-KERNEL:CLASSOID objects.
299 (defun make-wrapper (length class)
301 ((typep class 'std-class)
302 (make-wrapper-internal
305 (let ((owrap (class-wrapper class)))
307 (sb-kernel:layout-classoid owrap))
308 ((*subtypep (class-of class)
309 *the-class-standard-class*)
310 (cond ((and *pcl-class-boot*
311 (eq (slot-value class 'name) *pcl-class-boot*))
312 (let ((found (sb-kernel:find-classoid
313 (slot-value class 'name))))
314 (unless (sb-kernel:classoid-pcl-class found)
315 (setf (sb-kernel:classoid-pcl-class found) class))
316 (aver (eq (sb-kernel:classoid-pcl-class found) class))
319 (sb-kernel:make-standard-classoid :pcl-class class))))
321 (sb-kernel:make-random-pcl-classoid :pcl-class class))))))
323 (let* ((found (sb-kernel:find-classoid (slot-value class 'name)))
324 (layout (sb-kernel:classoid-layout found)))
325 (unless (sb-kernel:classoid-pcl-class found)
326 (setf (sb-kernel:classoid-pcl-class found) class))
327 (aver (eq (sb-kernel:classoid-pcl-class found) class))
331 (defconstant +first-wrapper-cache-number-index+ 0)
333 (declaim (inline next-wrapper-cache-number-index))
334 (defun next-wrapper-cache-number-index (field-number)
335 (and (< field-number #.(1- wrapper-cache-number-vector-length))
338 ;;; FIXME: Why are there two layers here, with one operator trivially
339 ;;; defined in terms of the other? It'd be nice either to have a
340 ;;; comment explaining why the separation is valuable, or to collapse
341 ;;; it into a single layer.
343 ;;; FIXME (?): These are logically inline functions, but they need to
344 ;;; be SETFable, and for now it seems not worth the trouble to DEFUN
345 ;;; both inline FOO and inline (SETF FOO) for each one instead of a
346 ;;; single macro. Perhaps the best thing would be to make them
347 ;;; immutable (since it seems sort of surprising and gross to be able
348 ;;; to modify hash values) so that they can become inline functions
349 ;;; with no muss or fuss. I (WHN) didn't do this only because I didn't
350 ;;; know whether any code anywhere depends on the values being
352 (defmacro cache-number-vector-ref (cnv n)
353 `(wrapper-cache-number-vector-ref ,cnv ,n))
354 (defmacro wrapper-cache-number-vector-ref (wrapper n)
355 `(sb-kernel:layout-clos-hash ,wrapper ,n))
357 (declaim (inline wrapper-class*))
358 (defun wrapper-class* (wrapper)
359 (or (wrapper-class wrapper)
360 (find-structure-class
361 (sb-kernel:classoid-name (sb-kernel:layout-classoid wrapper)))))
363 ;;; The wrapper cache machinery provides general mechanism for
364 ;;; trapping on the next access to any instance of a given class. This
365 ;;; mechanism is used to implement the updating of instances when the
366 ;;; class is redefined (MAKE-INSTANCES-OBSOLETE). The same mechanism
367 ;;; is also used to update generic function caches when there is a
368 ;;; change to the superclasses of a class.
370 ;;; Basically, a given wrapper can be valid or invalid. If it is
371 ;;; invalid, it means that any attempt to do a wrapper cache lookup
372 ;;; using the wrapper should trap. Also, methods on
373 ;;; SLOT-VALUE-USING-CLASS check the wrapper validity as well. This is
374 ;;; done by calling CHECK-WRAPPER-VALIDITY.
376 (declaim (inline invalid-wrapper-p))
377 (defun invalid-wrapper-p (wrapper)
378 (not (null (sb-kernel:layout-invalid wrapper))))
380 (defvar *previous-nwrappers* (make-hash-table))
382 (defun invalidate-wrapper (owrapper state nwrapper)
383 (aver (member state '(:flush :obsolete) :test #'eq))
384 (let ((new-previous ()))
385 ;; First off, a previous call to INVALIDATE-WRAPPER may have
386 ;; recorded OWRAPPER as an NWRAPPER to update to. Since OWRAPPER
387 ;; is about to be invalid, it no longer makes sense to update to
390 ;; We go back and change the previously invalidated wrappers so
391 ;; that they will now update directly to NWRAPPER. This
392 ;; corresponds to a kind of transitivity of wrapper updates.
393 (dolist (previous (gethash owrapper *previous-nwrappers*))
394 (when (eq state :obsolete)
395 (setf (car previous) :obsolete))
396 (setf (cadr previous) nwrapper)
397 (push previous new-previous))
399 (let ((ocnv (wrapper-cache-number-vector owrapper)))
400 (dotimes (i sb-kernel:layout-clos-hash-length)
401 (setf (cache-number-vector-ref ocnv i) 0)))
403 (push (setf (sb-kernel:layout-invalid owrapper) (list state nwrapper))
406 (setf (gethash owrapper *previous-nwrappers*) ()
407 (gethash nwrapper *previous-nwrappers*) new-previous)))
409 (defun check-wrapper-validity (instance)
410 (let* ((owrapper (wrapper-of instance))
411 (state (sb-kernel:layout-invalid owrapper)))
416 (flush-cache-trap owrapper (cadr state) instance))
418 (obsolete-instance-trap owrapper (cadr state) instance))))))
420 (declaim (inline check-obsolete-instance))
421 (defun check-obsolete-instance (instance)
422 (when (invalid-wrapper-p (sb-kernel:layout-of instance))
423 (check-wrapper-validity instance)))
425 (defvar *free-caches* nil)
427 (defun get-cache (nkeys valuep limit-fn nlines)
428 (let ((cache (or (sb-sys:without-interrupts (pop *free-caches*))
430 (declare (type cache cache))
431 (multiple-value-bind (cache-mask actual-size line-size nlines)
432 (compute-cache-parameters nkeys valuep nlines)
433 (setf (cache-nkeys cache) nkeys
434 (cache-valuep cache) valuep
435 (cache-nlines cache) nlines
436 (cache-field cache) +first-wrapper-cache-number-index+
437 (cache-limit-fn cache) limit-fn
438 (cache-mask cache) cache-mask
439 (cache-size cache) actual-size
440 (cache-line-size cache) line-size
441 (cache-max-location cache) (let ((line (1- nlines)))
444 (1+ (* line line-size))))
445 (cache-vector cache) (get-cache-vector actual-size)
446 (cache-overflow cache) nil)
449 (defun get-cache-from-cache (old-cache new-nlines
450 &optional (new-field +first-wrapper-cache-number-index+))
451 (let ((nkeys (cache-nkeys old-cache))
452 (valuep (cache-valuep old-cache))
453 (cache (or (sb-sys:without-interrupts (pop *free-caches*))
455 (declare (type cache cache))
456 (multiple-value-bind (cache-mask actual-size line-size nlines)
457 (if (= new-nlines (cache-nlines old-cache))
458 (values (cache-mask old-cache) (cache-size old-cache)
459 (cache-line-size old-cache) (cache-nlines old-cache))
460 (compute-cache-parameters nkeys valuep new-nlines))
461 (setf (cache-owner cache) (cache-owner old-cache)
462 (cache-nkeys cache) nkeys
463 (cache-valuep cache) valuep
464 (cache-nlines cache) nlines
465 (cache-field cache) new-field
466 (cache-limit-fn cache) (cache-limit-fn old-cache)
467 (cache-mask cache) cache-mask
468 (cache-size cache) actual-size
469 (cache-line-size cache) line-size
470 (cache-max-location cache) (let ((line (1- nlines)))
473 (1+ (* line line-size))))
474 (cache-vector cache) (get-cache-vector actual-size)
475 (cache-overflow cache) nil)
478 (defun copy-cache (old-cache)
479 (let* ((new-cache (copy-cache-internal old-cache))
480 (size (cache-size old-cache))
481 (old-vector (cache-vector old-cache))
482 (new-vector (get-cache-vector size)))
483 (declare (simple-vector old-vector new-vector))
484 (dotimes-fixnum (i size)
485 (setf (svref new-vector i) (svref old-vector i)))
486 (setf (cache-vector new-cache) new-vector)
489 (defun free-cache (cache)
490 (free-cache-vector (cache-vector cache))
491 (setf (cache-vector cache) #())
492 (setf (cache-owner cache) nil)
493 (push cache *free-caches*)
496 (defun compute-line-size (x)
497 (power-of-two-ceiling x))
499 (defun compute-cache-parameters (nkeys valuep nlines-or-cache-vector)
500 ;;(declare (values cache-mask actual-size line-size nlines))
501 (declare (fixnum nkeys))
503 (let* ((line-size (if valuep 2 1))
504 (cache-size (if (typep nlines-or-cache-vector 'fixnum)
508 (power-of-two-ceiling
509 nlines-or-cache-vector))))
510 (cache-vector-size nlines-or-cache-vector))))
511 (declare (fixnum line-size cache-size))
512 (values (logxor (the fixnum (1- cache-size)) (the fixnum (1- line-size)))
515 (the (values fixnum t) (floor cache-size line-size))))
516 (let* ((line-size (power-of-two-ceiling (if valuep (1+ nkeys) nkeys)))
517 (cache-size (if (typep nlines-or-cache-vector 'fixnum)
521 (power-of-two-ceiling
522 nlines-or-cache-vector))))
523 (1- (cache-vector-size nlines-or-cache-vector)))))
524 (declare (fixnum line-size cache-size))
525 (values (logxor (the fixnum (1- cache-size)) (the fixnum (1- line-size)))
526 (the fixnum (1+ cache-size))
528 (the (values fixnum t) (floor cache-size line-size))))))
530 ;;; the various implementations of computing a primary cache location from
531 ;;; wrappers. Because some implementations of this must run fast there are
532 ;;; several implementations of the same algorithm.
534 ;;; The algorithm is:
536 ;;; SUM over the wrapper cache numbers,
537 ;;; ENSURING that the result is a fixnum
538 ;;; MASK the result against the mask argument.
540 ;;; The basic functional version. This is used by the cache miss code to
541 ;;; compute the primary location of an entry.
542 (defun compute-primary-cache-location (field mask wrappers)
544 (declare (type field-type field) (fixnum mask))
545 (if (not (listp wrappers))
547 (the fixnum (wrapper-cache-number-vector-ref wrappers field)))
548 (let ((location 0) (i 0))
549 (declare (fixnum location i))
550 (dolist (wrapper wrappers)
551 ;; First add the cache number of this wrapper to location.
552 (let ((wrapper-cache-number (wrapper-cache-number-vector-ref wrapper
554 (declare (fixnum wrapper-cache-number))
555 (if (zerop wrapper-cache-number)
556 (return-from compute-primary-cache-location 0)
558 (the fixnum (+ location wrapper-cache-number)))))
559 ;; Then, if we are working with lots of wrappers, deal with
560 ;; the wrapper-cache-number-mask stuff.
561 (when (and (not (zerop i))
562 (zerop (mod i wrapper-cache-number-adds-ok)))
564 (logand location wrapper-cache-number-mask)))
566 (the fixnum (1+ (logand mask location))))))
568 ;;; This version is called on a cache line. It fetches the wrappers
569 ;;; from the cache line and determines the primary location. Various
570 ;;; parts of the cache filling code call this to determine whether it
571 ;;; is appropriate to displace a given cache entry.
573 ;;; If this comes across a wrapper whose CACHE-NO is 0, it returns the
574 ;;; symbol invalid to suggest to its caller that it would be provident
575 ;;; to blow away the cache line in question.
576 (defun compute-primary-cache-location-from-location (to-cache
579 (from-cache to-cache))
580 (declare (type cache to-cache from-cache) (fixnum from-location))
582 (cache-vector (cache-vector from-cache))
583 (field (cache-field to-cache))
584 (mask (cache-mask to-cache))
585 (nkeys (cache-nkeys to-cache)))
586 (declare (type field-type field) (fixnum result mask nkeys)
587 (simple-vector cache-vector))
588 (dotimes-fixnum (i nkeys)
589 (let* ((wrapper (cache-vector-ref cache-vector (+ i from-location)))
590 (wcn (wrapper-cache-number-vector-ref wrapper field)))
591 (declare (fixnum wcn))
592 (setq result (+ result wcn)))
593 (when (and (not (zerop i))
594 (zerop (mod i wrapper-cache-number-adds-ok)))
595 (setq result (logand result wrapper-cache-number-mask))))
598 (the fixnum (1+ (logand mask result))))))
600 ;;; NIL means nothing so far, no actual arg info has NILs
602 ;;; CLASS seen all sorts of metaclasses
603 ;;; (specifically, more than one of the next 4 values)
604 ;;; T means everything so far is the class T
605 ;;; STANDARD-CLASS seen only standard classes
606 ;;; BUILT-IN-CLASS seen only built in classes
607 ;;; STRUCTURE-CLASS seen only structure classes
608 (defun raise-metatype (metatype new-specializer)
609 (let ((slot (find-class 'slot-class))
610 (std (find-class 'std-class))
611 (standard (find-class 'standard-class))
612 (fsc (find-class 'funcallable-standard-class))
613 (structure (find-class 'structure-class))
614 (built-in (find-class 'built-in-class)))
615 (flet ((specializer->metatype (x)
616 (let ((meta-specializer
617 (if (eq *boot-state* 'complete)
618 (class-of (specializer-class x))
620 (cond ((eq x *the-class-t*) t)
621 ((*subtypep meta-specializer std)
623 ((*subtypep meta-specializer standard)
625 ((*subtypep meta-specializer fsc)
627 ((*subtypep meta-specializer structure)
629 ((*subtypep meta-specializer built-in)
631 ((*subtypep meta-specializer slot)
633 (t (error "PCL cannot handle the specializer ~S (meta-specializer ~S)."
635 meta-specializer))))))
636 ;; We implement the following table. The notation is
637 ;; that X and Y are distinct meta specializer names.
639 ;; NIL <anything> ===> <anything>
642 (let ((new-metatype (specializer->metatype new-specializer)))
643 (cond ((eq new-metatype 'slot-instance) 'class)
644 ((null metatype) new-metatype)
645 ((eq metatype new-metatype) new-metatype)
648 (defmacro with-dfun-wrappers ((args metatypes)
649 (dfun-wrappers invalid-wrapper-p
650 &optional wrappers classes types)
651 invalid-arguments-form
653 `(let* ((args-tail ,args) (,invalid-wrapper-p nil) (invalid-arguments-p nil)
654 (,dfun-wrappers nil) (dfun-wrappers-tail nil)
656 `((wrappers-rev nil) (types-rev nil) (classes-rev nil))))
657 (dolist (mt ,metatypes)
659 (setq invalid-arguments-p t)
661 (let* ((arg (pop args-tail))
664 `((class *the-class-t*)
667 (setq wrapper (wrapper-of arg))
668 (when (invalid-wrapper-p wrapper)
669 (setq ,invalid-wrapper-p t)
670 (setq wrapper (check-wrapper-validity arg)))
671 (cond ((null ,dfun-wrappers)
672 (setq ,dfun-wrappers wrapper))
673 ((not (consp ,dfun-wrappers))
674 (setq dfun-wrappers-tail (list wrapper))
675 (setq ,dfun-wrappers (cons ,dfun-wrappers dfun-wrappers-tail)))
677 (let ((new-dfun-wrappers-tail (list wrapper)))
678 (setf (cdr dfun-wrappers-tail) new-dfun-wrappers-tail)
679 (setf dfun-wrappers-tail new-dfun-wrappers-tail))))
681 `((setq class (wrapper-class* wrapper))
682 (setq type `(class-eq ,class)))))
684 `((push wrapper wrappers-rev)
685 (push class classes-rev)
686 (push type types-rev)))))
687 (if invalid-arguments-p
688 ,invalid-arguments-form
689 (let* (,@(when wrappers
690 `((,wrappers (nreverse wrappers-rev))
691 (,classes (nreverse classes-rev))
692 (,types (mapcar (lambda (class)
697 ;;;; some support stuff for getting a hold of symbols that we need when
698 ;;;; building the discriminator codes. It's OK for these to be interned
699 ;;;; symbols because we don't capture any user code in the scope in which
700 ;;;; these symbols are bound.
702 (defvar *dfun-arg-symbols* '(.ARG0. .ARG1. .ARG2. .ARG3.))
704 (defun dfun-arg-symbol (arg-number)
705 (or (nth arg-number (the list *dfun-arg-symbols*))
706 (intern (format nil ".ARG~A." arg-number) *pcl-package*)))
708 (defvar *slot-vector-symbols* '(.SLOTS0. .SLOTS1. .SLOTS2. .SLOTS3.))
710 (defun slot-vector-symbol (arg-number)
711 (or (nth arg-number (the list *slot-vector-symbols*))
712 (intern (format nil ".SLOTS~A." arg-number) *pcl-package*)))
714 ;; FIXME: There ought to be a good way to factor out the idiom:
716 ;; (dotimes (i (length metatypes))
717 ;; (push (dfun-arg-symbol i) lambda-list))
719 ;; used in the following four functions into common code that we can
720 ;; declare inline or something. --njf 2001-12-20
721 (defun make-dfun-lambda-list (metatypes applyp)
722 (let ((lambda-list nil))
723 (dotimes (i (length metatypes))
724 (push (dfun-arg-symbol i) lambda-list))
726 (push '&rest lambda-list)
727 (push '.dfun-rest-arg. lambda-list))
728 (nreverse lambda-list)))
730 (defun make-dlap-lambda-list (metatypes applyp)
731 (let ((lambda-list nil))
732 (dotimes (i (length metatypes))
733 (push (dfun-arg-symbol i) lambda-list))
734 ;; FIXME: This is translated directly from the old PCL code.
735 ;; It didn't have a (PUSH '.DFUN-REST-ARG. LAMBDA-LIST) or
736 ;; something similar, so we don't either. It's hard to see how
737 ;; this could be correct, since &REST wants an argument after
738 ;; it. This function works correctly because the caller
739 ;; magically tacks on something after &REST. The calling functions
740 ;; (in dlisp.lisp) should be fixed and this function rewritten.
743 (push '&rest lambda-list))
744 (nreverse lambda-list)))
746 ;; FIXME: The next two functions suffer from having a `.DFUN-REST-ARG.'
747 ;; in their lambda lists, but no corresponding `&REST' symbol. We assume
748 ;; this should be the case by analogy with the previous two functions.
749 ;; It works, and I don't know why. Check the calling functions and
750 ;; fix these too. --njf 2001-12-20
751 (defun make-emf-call (metatypes applyp fn-variable &optional emf-type)
753 (let ((required nil))
754 (dotimes (i (length metatypes))
755 (push (dfun-arg-symbol i) required))
756 (nreverse required))))
757 `(,(if (eq emf-type 'fast-method-call)
758 'invoke-effective-method-function-fast
759 'invoke-effective-method-function)
760 ,fn-variable ,applyp ,@required ,@(when applyp `(.dfun-rest-arg.)))))
762 (defun make-fast-method-call-lambda-list (metatypes applyp)
763 (let ((reversed-lambda-list nil))
764 (push '.pv-cell. reversed-lambda-list)
765 (push '.next-method-call. reversed-lambda-list)
766 (dotimes (i (length metatypes))
767 (push (dfun-arg-symbol i) reversed-lambda-list))
769 (push '.dfun-rest-arg. reversed-lambda-list))
770 (nreverse reversed-lambda-list)))
772 (defmacro with-local-cache-functions ((cache) &body body)
773 `(let ((.cache. ,cache))
774 (declare (type cache .cache.))
775 (labels ((cache () .cache.)
776 (nkeys () (cache-nkeys .cache.))
777 (line-size () (cache-line-size .cache.))
778 (vector () (cache-vector .cache.))
779 (valuep () (cache-valuep .cache.))
780 (nlines () (cache-nlines .cache.))
781 (max-location () (cache-max-location .cache.))
782 (limit-fn () (cache-limit-fn .cache.))
783 (size () (cache-size .cache.))
784 (mask () (cache-mask .cache.))
785 (field () (cache-field .cache.))
786 (overflow () (cache-overflow .cache.))
788 ;; Return T IFF this cache location is reserved. The
789 ;; only time this is true is for line number 0 of an
792 (line-reserved-p (line)
793 (declare (fixnum line))
797 (location-reserved-p (location)
798 (declare (fixnum location))
802 ;; Given a line number, return the cache location.
803 ;; This is the value that is the second argument to
804 ;; cache-vector-ref. Basically, this deals with the
805 ;; offset of nkeys>1 caches and multiplies by line
808 (line-location (line)
809 (declare (fixnum line))
810 (when (line-reserved-p line)
811 (error "line is reserved"))
813 (the fixnum (* line (line-size)))
814 (the fixnum (1+ (the fixnum (* line (line-size)))))))
816 ;; Given a cache location, return the line. This is
817 ;; the inverse of LINE-LOCATION.
819 (location-line (location)
820 (declare (fixnum location))
822 (floor location (line-size))
823 (floor (the fixnum (1- location)) (line-size))))
825 ;; Given a line number, return the wrappers stored at
826 ;; that line. As usual, if nkeys=1, this returns a
827 ;; single value. Only when nkeys>1 does it return a
828 ;; list. An error is signalled if the line is
831 (line-wrappers (line)
832 (declare (fixnum line))
833 (when (line-reserved-p line) (error "Line is reserved."))
834 (location-wrappers (line-location line)))
836 (location-wrappers (location) ; avoid multiplies caused by line-location
837 (declare (fixnum location))
839 (cache-vector-ref (vector) location)
840 (let ((list (make-list (nkeys)))
842 (declare (simple-vector vector))
843 (dotimes (i (nkeys) list)
846 (cache-vector-ref vector (+ location i)))))))
848 ;; Given a line number, return true IFF the line's
849 ;; wrappers are the same as wrappers.
851 (line-matches-wrappers-p (line wrappers)
852 (declare (fixnum line))
853 (and (not (line-reserved-p line))
854 (location-matches-wrappers-p (line-location line)
857 (location-matches-wrappers-p (loc wrappers) ; must not be reserved
858 (declare (fixnum loc))
859 (let ((cache-vector (vector)))
860 (declare (simple-vector cache-vector))
862 (eq wrappers (cache-vector-ref cache-vector loc))
863 (dotimes (i (nkeys) t)
865 (unless (eq (pop wrappers)
866 (cache-vector-ref cache-vector (+ loc i)))
869 ;; Given a line number, return the value stored at that line.
870 ;; If valuep is NIL, this returns NIL. As with line-wrappers,
871 ;; an error is signalled if the line is reserved.
874 (declare (fixnum line))
875 (when (line-reserved-p line) (error "Line is reserved."))
876 (location-value (line-location line)))
878 (location-value (loc)
879 (declare (fixnum loc))
881 (cache-vector-ref (vector) (+ loc (nkeys)))))
883 ;; Given a line number, return true IFF that line has data in
884 ;; it. The state of the wrappers stored in the line is not
885 ;; checked. An error is signalled if line is reserved.
887 (when (line-reserved-p line) (error "Line is reserved."))
888 (not (null (cache-vector-ref (vector) (line-location line)))))
890 ;; Given a line number, return true IFF the line is full and
891 ;; there are no invalid wrappers in the line, and the line's
892 ;; wrappers are different from wrappers.
893 ;; An error is signalled if the line is reserved.
895 (line-valid-p (line wrappers)
896 (declare (fixnum line))
897 (when (line-reserved-p line) (error "Line is reserved."))
898 (location-valid-p (line-location line) wrappers))
900 (location-valid-p (loc wrappers)
901 (declare (fixnum loc))
902 (let ((cache-vector (vector))
903 (wrappers-mismatch-p (null wrappers)))
904 (declare (simple-vector cache-vector))
905 (dotimes (i (nkeys) wrappers-mismatch-p)
907 (let ((wrapper (cache-vector-ref cache-vector (+ loc i))))
908 (when (or (null wrapper)
909 (invalid-wrapper-p wrapper))
911 (unless (and wrappers
916 (setq wrappers-mismatch-p t))))))
918 ;; How many unreserved lines separate line-1 and line-2.
920 (line-separation (line-1 line-2)
921 (declare (fixnum line-1 line-2))
922 (let ((diff (the fixnum (- line-2 line-1))))
923 (declare (fixnum diff))
925 (setq diff (+ diff (nlines)))
926 (when (line-reserved-p 0)
927 (setq diff (1- diff))))
930 ;; Given a cache line, get the next cache line. This will not
931 ;; return a reserved line.
934 (declare (fixnum line))
935 (if (= line (the fixnum (1- (nlines))))
936 (if (line-reserved-p 0) 1 0)
937 (the fixnum (1+ line))))
940 (declare (fixnum loc))
941 (if (= loc (max-location))
945 (the fixnum (+ loc (line-size)))))
947 ;; Given a line which has a valid entry in it, this
948 ;; will return the primary cache line of the wrappers
949 ;; in that line. We just call
950 ;; COMPUTE-PRIMARY-CACHE-LOCATION-FROM-LOCATION, this
951 ;; is an easier packaging up of the call to it.
954 (declare (fixnum line))
955 (location-line (line-primary-location line)))
957 (line-primary-location (line)
958 (declare (fixnum line))
959 (compute-primary-cache-location-from-location
960 (cache) (line-location line))))
961 (declare (ignorable #'cache #'nkeys #'line-size #'vector #'valuep
962 #'nlines #'max-location #'limit-fn #'size
963 #'mask #'field #'overflow #'line-reserved-p
964 #'location-reserved-p #'line-location
965 #'location-line #'line-wrappers #'location-wrappers
966 #'line-matches-wrappers-p
967 #'location-matches-wrappers-p
968 #'line-value #'location-value #'line-full-p
969 #'line-valid-p #'location-valid-p
970 #'line-separation #'next-line #'next-location
971 #'line-primary #'line-primary-location))
974 ;;; Here is where we actually fill, recache and expand caches.
976 ;;; The functions FILL-CACHE and PROBE-CACHE are the ONLY external
977 ;;; entrypoints into this code.
979 ;;; FILL-CACHE returns 1 value: a new cache
981 ;;; a wrapper field number
984 ;;; an absolute cache size (the size of the actual vector)
985 ;;; It tries to re-adjust the cache every time it makes a new fill.
986 ;;; The intuition here is that we want uniformity in the number of
987 ;;; probes needed to find an entry. Furthermore, adjusting has the
988 ;;; nice property of throwing out any entries that are invalid.
989 (defvar *cache-expand-threshold* 1.25)
991 (defun fill-cache (cache wrappers value &optional free-cache-p)
993 ;; FILL-CACHE won't return if WRAPPERS is nil, might as well check..
995 (error "fill-cache: WRAPPERS arg is NIL!"))
997 (or (fill-cache-p nil cache wrappers value)
998 (and (< (ceiling (* (cache-count cache) 1.25))
999 (if (= (cache-nkeys cache) 1)
1000 (1- (cache-nlines cache))
1001 (cache-nlines cache)))
1002 (adjust-cache cache wrappers value free-cache-p))
1003 (expand-cache cache wrappers value free-cache-p)))
1005 (defvar *check-cache-p* nil)
1007 (defmacro maybe-check-cache (cache)
1009 (when *check-cache-p*
1010 (check-cache ,cache))
1013 (defun check-cache (cache)
1014 (with-local-cache-functions (cache)
1015 (let ((location (if (= (nkeys) 1) 0 1))
1016 (limit (funcall (limit-fn) (nlines))))
1017 (dotimes-fixnum (i (nlines) cache)
1018 (when (and (not (location-reserved-p location))
1020 (let* ((home-loc (compute-primary-cache-location-from-location
1022 (home (location-line (if (location-reserved-p home-loc)
1023 (next-location home-loc)
1025 (sep (when home (line-separation home i))))
1026 (when (and sep (> sep limit))
1027 (error "bad cache ~S ~@
1028 value at location ~W: ~W lines from its home. The limit is ~W."
1029 cache location sep limit))))
1030 (setq location (next-location location))))))
1032 (defun probe-cache (cache wrappers &optional default limit-fn)
1033 ;;(declare (values value))
1035 ;; FIXME: This and another earlier test on a WRAPPERS arg can
1036 ;; be compact assertoids.
1037 (error "WRAPPERS arg is NIL!"))
1038 (with-local-cache-functions (cache)
1039 (let* ((location (compute-primary-cache-location (field) (mask) wrappers))
1040 (limit (funcall (or limit-fn (limit-fn)) (nlines))))
1041 (declare (fixnum location limit))
1042 (when (location-reserved-p location)
1043 (setq location (next-location location)))
1044 (dotimes-fixnum (i (1+ limit))
1045 (when (location-matches-wrappers-p location wrappers)
1046 (return-from probe-cache (or (not (valuep))
1047 (location-value location))))
1048 (setq location (next-location location)))
1049 (dolist (entry (overflow))
1050 (when (equal (car entry) wrappers)
1051 (return-from probe-cache (or (not (valuep))
1055 (defun map-cache (function cache &optional set-p)
1056 (with-local-cache-functions (cache)
1057 (let ((set-p (and set-p (valuep))))
1058 (dotimes-fixnum (i (nlines) cache)
1059 (unless (or (line-reserved-p i) (not (line-valid-p i nil)))
1060 (let ((value (funcall function (line-wrappers i) (line-value i))))
1062 (setf (cache-vector-ref (vector) (+ (line-location i) (nkeys)))
1064 (dolist (entry (overflow))
1065 (let ((value (funcall function (car entry) (cdr entry))))
1067 (setf (cdr entry) value))))))
1070 (defun cache-count (cache)
1071 (with-local-cache-functions (cache)
1073 (declare (fixnum count))
1074 (dotimes-fixnum (i (nlines) count)
1075 (unless (line-reserved-p i)
1076 (when (line-full-p i)
1079 (defun entry-in-cache-p (cache wrappers value)
1080 (declare (ignore value))
1081 (with-local-cache-functions (cache)
1082 (dotimes-fixnum (i (nlines))
1083 (unless (line-reserved-p i)
1084 (when (equal (line-wrappers i) wrappers)
1087 ;;; returns T or NIL
1088 (defun fill-cache-p (forcep cache wrappers value)
1089 (with-local-cache-functions (cache)
1090 (let* ((location (compute-primary-cache-location (field) (mask) wrappers))
1091 (primary (location-line location)))
1092 (declare (fixnum location primary))
1093 (multiple-value-bind (free emptyp)
1094 (find-free-cache-line primary cache wrappers)
1095 (when (or forcep emptyp)
1097 (push (cons (line-wrappers free) (line-value free))
1098 (cache-overflow cache)))
1099 ;;(fill-line free wrappers value)
1101 (declare (fixnum line))
1102 (when (line-reserved-p line)
1103 (error "attempt to fill a reserved line"))
1104 (let ((loc (line-location line))
1105 (cache-vector (vector)))
1106 (declare (fixnum loc) (simple-vector cache-vector))
1107 (cond ((= (nkeys) 1)
1108 (setf (cache-vector-ref cache-vector loc) wrappers)
1110 (setf (cache-vector-ref cache-vector (1+ loc)) value)))
1113 (declare (fixnum i))
1114 (dolist (w wrappers)
1115 (setf (cache-vector-ref cache-vector (+ loc i)) w)
1116 (setq i (the fixnum (1+ i)))))
1118 (setf (cache-vector-ref cache-vector (+ loc (nkeys)))
1120 (maybe-check-cache cache))))))))
1122 (defun fill-cache-from-cache-p (forcep cache from-cache from-line)
1123 (declare (fixnum from-line))
1124 (with-local-cache-functions (cache)
1125 (let ((primary (location-line
1126 (compute-primary-cache-location-from-location
1127 cache (line-location from-line) from-cache))))
1128 (declare (fixnum primary))
1129 (multiple-value-bind (free emptyp)
1130 (find-free-cache-line primary cache)
1131 (when (or forcep emptyp)
1133 (push (cons (line-wrappers free) (line-value free))
1134 (cache-overflow cache)))
1135 ;;(transfer-line from-cache-vector from-line cache-vector free)
1136 (let ((from-cache-vector (cache-vector from-cache))
1137 (to-cache-vector (vector))
1139 (declare (fixnum to-line))
1140 (if (line-reserved-p to-line)
1141 (error "transferring something into a reserved cache line")
1142 (let ((from-loc (line-location from-line))
1143 (to-loc (line-location to-line)))
1144 (declare (fixnum from-loc to-loc))
1145 (modify-cache to-cache-vector
1146 (dotimes-fixnum (i (line-size))
1147 (setf (cache-vector-ref to-cache-vector
1149 (cache-vector-ref from-cache-vector
1150 (+ from-loc i)))))))
1151 (maybe-check-cache cache)))))))
1153 ;;; Returns NIL or (values <field> <cache-vector>)
1155 ;;; This is only called when it isn't possible to put the entry in the
1156 ;;; cache the easy way. That is, this function assumes that
1157 ;;; FILL-CACHE-P has been called as returned NIL.
1159 ;;; If this returns NIL, it means that it wasn't possible to find a
1160 ;;; wrapper field for which all of the entries could be put in the
1161 ;;; cache (within the limit).
1162 (defun adjust-cache (cache wrappers value free-old-cache-p)
1163 (with-local-cache-functions (cache)
1164 (let ((ncache (get-cache-from-cache cache (nlines) (field))))
1165 (do ((nfield (cache-field ncache) (next-wrapper-cache-number-index nfield)))
1166 ((null nfield) (free-cache ncache) nil)
1167 (setf (cache-field ncache) nfield)
1168 (labels ((try-one-fill-from-line (line)
1169 (fill-cache-from-cache-p nil ncache cache line))
1170 (try-one-fill (wrappers value)
1171 (fill-cache-p nil ncache wrappers value)))
1172 (if (and (dotimes-fixnum (i (nlines) t)
1173 (when (and (null (line-reserved-p i))
1174 (line-valid-p i wrappers))
1175 (unless (try-one-fill-from-line i) (return nil))))
1176 (dolist (wrappers+value (cache-overflow cache) t)
1177 (unless (try-one-fill (car wrappers+value) (cdr wrappers+value))
1179 (try-one-fill wrappers value))
1180 (progn (when free-old-cache-p (free-cache cache))
1181 (return (maybe-check-cache ncache)))
1182 (flush-cache-vector-internal (cache-vector ncache))))))))
1184 ;;; returns: (values <cache>)
1185 (defun expand-cache (cache wrappers value free-old-cache-p)
1186 ;;(declare (values cache))
1187 (with-local-cache-functions (cache)
1188 (let ((ncache (get-cache-from-cache cache (* (nlines) 2))))
1189 (labels ((do-one-fill-from-line (line)
1190 (unless (fill-cache-from-cache-p nil ncache cache line)
1191 (do-one-fill (line-wrappers line) (line-value line))))
1192 (do-one-fill (wrappers value)
1193 (setq ncache (or (adjust-cache ncache wrappers value t)
1194 (fill-cache-p t ncache wrappers value))))
1195 (try-one-fill (wrappers value)
1196 (fill-cache-p nil ncache wrappers value)))
1197 (dotimes-fixnum (i (nlines))
1198 (when (and (null (line-reserved-p i))
1199 (line-valid-p i wrappers))
1200 (do-one-fill-from-line i)))
1201 (dolist (wrappers+value (cache-overflow cache))
1202 (unless (try-one-fill (car wrappers+value) (cdr wrappers+value))
1203 (do-one-fill (car wrappers+value) (cdr wrappers+value))))
1204 (unless (try-one-fill wrappers value)
1205 (do-one-fill wrappers value))
1206 (when free-old-cache-p (free-cache cache))
1207 (maybe-check-cache ncache)))))
1209 ;;; This is the heart of the cache filling mechanism. It implements
1210 ;;; the decisions about where entries are placed.
1212 ;;; Find a line in the cache at which a new entry can be inserted.
1215 ;;; <empty?> is <line> in fact empty?
1216 (defun find-free-cache-line (primary cache &optional wrappers)
1217 ;;(declare (values line empty?))
1218 (declare (fixnum primary))
1219 (with-local-cache-functions (cache)
1220 (when (line-reserved-p primary) (setq primary (next-line primary)))
1221 (let ((limit (funcall (limit-fn) (nlines)))
1224 (p primary) (s primary))
1225 (declare (fixnum p s limit))
1228 ;; Try to find a free line starting at <s>. <p> is the
1229 ;; primary line of the entry we are finding a free
1230 ;; line for, it is used to compute the separations.
1231 (do* ((line s (next-line line))
1232 (nsep (line-separation p s) (1+ nsep)))
1234 (declare (fixnum line nsep))
1235 (when (null (line-valid-p line wrappers)) ;If this line is empty or
1236 (push line lines) ;invalid, just use it.
1237 (return-from find-free))
1238 (when (and wrappedp (>= line primary))
1239 ;; have gone all the way around the cache, time to quit
1240 (return-from find-free-cache-line (values primary nil)))
1241 (let ((osep (line-separation (line-primary line) line)))
1242 (when (>= osep limit)
1243 (return-from find-free-cache-line (values primary nil)))
1244 (when (cond ((= nsep limit) t)
1245 ((= nsep osep) (zerop (random 2)))
1248 ;; See whether we can displace what is in this line so that we
1249 ;; can use the line.
1250 (when (= line (the fixnum (1- (nlines)))) (setq wrappedp t))
1251 (setq p (line-primary line))
1252 (setq s (next-line line))
1255 (when (= line (the fixnum (1- (nlines)))) (setq wrappedp t)))))
1256 ;; Do all the displacing.
1258 (when (null (cdr lines)) (return nil))
1259 (let ((dline (pop lines))
1261 (declare (fixnum dline line))
1262 ;;Copy from line to dline (dline is known to be free).
1263 (let ((from-loc (line-location line))
1264 (to-loc (line-location dline))
1265 (cache-vector (vector)))
1266 (declare (fixnum from-loc to-loc) (simple-vector cache-vector))
1267 (modify-cache cache-vector
1268 (dotimes-fixnum (i (line-size))
1269 (setf (cache-vector-ref cache-vector
1271 (cache-vector-ref cache-vector
1273 (setf (cache-vector-ref cache-vector
1276 (values (car lines) t))))
1278 (defun default-limit-fn (nlines)
1284 (defvar *empty-cache* (make-cache)) ; for defstruct slot initial value forms