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 ;;; Ye olde CMUCL comment follows, but it seems likely that the paper
29 ;;; that would be inserted would resemble Kiczales and Rodruigez,
30 ;;; Efficient Method Dispatch in PCL, ACM 1990. Some of the details
31 ;;; changed between that paper and "May Day PCL" of 1992; some other
32 ;;; details have changed since, but reading that paper gives the broad
35 ;;; The caching algorithm implemented:
37 ;;; << put a paper here >>
39 ;;; For now, understand that as far as most of this code goes, a cache
40 ;;; has two important properties. The first is the number of wrappers
41 ;;; used as keys in each cache line. Throughout this code, this value
42 ;;; is always called NKEYS. The second is whether or not the cache
43 ;;; lines of a cache store a value. Throughout this code, this always
46 ;;; Depending on these values, there are three kinds of caches.
48 ;;; NKEYS = 1, VALUEP = NIL
50 ;;; In this kind of cache, each line is 1 word long. No cache locking
51 ;;; is needed since all read's in the cache are a single value.
52 ;;; Nevertheless line 0 (location 0) is reserved, to ensure that
53 ;;; invalid wrappers will not get a first probe hit.
55 ;;; To keep the code simpler, a cache lock count does appear in
56 ;;; location 0 of these caches, that count is incremented whenever
57 ;;; data is written to the cache. But, the actual lookup code (see
58 ;;; make-dlap) doesn't need to do locking when reading the cache.
60 ;;; NKEYS = 1, VALUEP = T
62 ;;; In this kind of cache, each line is 2 words long. Cache locking
63 ;;; must be done to ensure the synchronization of cache reads. Line 0
64 ;;; of the cache (location 0) is reserved for the cache lock count.
65 ;;; Location 1 of the cache is unused (in effect wasted).
69 ;;; In this kind of cache, the 0 word of the cache holds the lock
70 ;;; count. The 1 word of the cache is line 0. Line 0 of these caches
73 ;;; This is done because in this sort of cache, the overhead of doing
74 ;;; the cache probe is high enough that the 1+ required to offset the
75 ;;; location is not a significant cost. In addition, because of the
76 ;;; larger line sizes, the space that would be wasted by reserving
77 ;;; line 0 to hold the lock count is more significant.
81 ;;; A cache is essentially just a vector. The use of the individual
82 ;;; `words' in the vector depends on particular properties of the
83 ;;; cache as described above.
85 ;;; This defines an abstraction for caches in terms of their most
86 ;;; obvious implementation as simple vectors. But, please notice that
87 ;;; part of the implementation of this abstraction, is the function
88 ;;; lap-out-cache-ref. This means that most port-specific
89 ;;; modifications to the implementation of caches will require
90 ;;; corresponding port-specific modifications to the lap code
92 (defmacro cache-vector-ref
(cache-vector location
)
93 `(svref (the simple-vector
,cache-vector
)
94 (sb-ext:truly-the fixnum
,location
)))
96 (defmacro cache-vector-size
(cache-vector)
97 `(array-dimension (the simple-vector
,cache-vector
) 0))
99 (defmacro cache-vector-lock-count
(cache-vector)
100 `(cache-vector-ref ,cache-vector
0))
102 (defun flush-cache-vector-internal (cache-vector)
103 ;; FIXME: To my eye this PCL-LOCK implies we should be holding the
104 ;; lock whenever we play with any cache vector, which doesn't seem
105 ;; to be true. On the other hand that would be too expensive as
106 ;; well, since it would mean serialization across all GFs.
108 (fill (the simple-vector cache-vector
) nil
)
109 (setf (cache-vector-lock-count cache-vector
) 0))
112 ;;; Return an empty cache vector
113 (defun get-cache-vector (size)
114 (declare (type (and unsigned-byte fixnum
) size
))
115 (let ((cv (make-array size
:initial-element nil
)))
116 (setf (cache-vector-lock-count cv
) 0)
119 (defmacro modify-cache
(cache-vector &body body
)
121 (multiple-value-prog1
123 (let ((old-count (cache-vector-lock-count ,cache-vector
)))
124 (declare (fixnum old-count
))
125 (setf (cache-vector-lock-count ,cache-vector
)
126 (if (= old-count most-positive-fixnum
)
130 (deftype field-type
()
131 '(mod #.layout-clos-hash-length
))
133 (eval-when (:compile-toplevel
:load-toplevel
:execute
)
134 (declaim (ftype (function (fixnum) (values (and unsigned-byte fixnum
) &optional
))
135 power-of-two-ceiling
))
136 (defun power-of-two-ceiling (x)
137 ;; (expt 2 (ceiling (log x 2)))
138 (ash 1 (integer-length (1- x
)))))
140 ;;; FIXME: We should probably keep just one of these -- or at least use just
142 (declaim (inline compute-line-size
))
143 (defun compute-line-size (x)
144 (power-of-two-ceiling x
))
146 (defconstant +nkeys-limit
+ 256)
148 (defstruct (cache (:constructor make-cache
())
149 (:copier copy-cache-internal
))
151 (nkeys 1 :type
(integer 1 #.
+nkeys-limit
+))
152 (valuep nil
:type
(member nil t
))
153 (nlines 0 :type fixnum
)
154 (field 0 :type field-type
)
155 (limit-fn #'default-limit-fn
:type function
)
156 (mask 0 :type fixnum
)
157 (size 0 :type fixnum
)
158 (line-size 1 :type
(integer 1 #.
(power-of-two-ceiling (1+ +nkeys-limit
+))))
159 (max-location 0 :type fixnum
)
160 (vector #() :type simple-vector
)
161 (overflow nil
:type list
))
163 #-sb-fluid
(declaim (sb-ext:freeze-type cache
))
165 ;;;; wrapper cache numbers
167 ;;; The constant WRAPPER-CACHE-NUMBER-ADDS-OK controls the number of
168 ;;; non-zero bits wrapper cache numbers will have.
170 ;;; The value of this constant is the number of wrapper cache numbers
171 ;;; which can be added and still be certain the result will be a
172 ;;; fixnum. This is used by all the code that computes primary cache
173 ;;; locations from multiple wrappers.
175 ;;; The value of this constant is used to derive the next two which
176 ;;; are the forms of this constant which it is more convenient for the
177 ;;; runtime code to use.
178 (defconstant wrapper-cache-number-length
179 (integer-length layout-clos-hash-max
))
180 (defconstant wrapper-cache-number-mask layout-clos-hash-max
)
181 (defconstant wrapper-cache-number-adds-ok
182 (truncate most-positive-fixnum layout-clos-hash-max
))
184 ;;;; wrappers themselves
186 ;;; This caching algorithm requires that wrappers have more than one
187 ;;; wrapper cache number. You should think of these multiple numbers
188 ;;; as being in columns. That is, for a given cache, the same column
189 ;;; of wrapper cache numbers will be used.
191 ;;; If at some point the cache distribution of a cache gets bad, the
192 ;;; cache can be rehashed by switching to a different column.
194 ;;; The columns are referred to by field number which is that number
195 ;;; which, when used as a second argument to wrapper-ref, will return
196 ;;; that column of wrapper cache number.
198 ;;; This code is written to allow flexibility as to how many wrapper
199 ;;; cache numbers will be in each wrapper, and where they will be
200 ;;; located. It is also set up to allow port specific modifications to
201 ;;; `pack' the wrapper cache numbers on machines where the addressing
202 ;;; modes make that a good idea.
204 ;;; In SBCL, as in CMU CL, we want to do type checking as early as
205 ;;; possible; structures help this. The structures are hard-wired to
206 ;;; have a fixed number of cache hash values, and that number must
207 ;;; correspond to the number of cache lines we use.
208 (defconstant wrapper-cache-number-vector-length
209 layout-clos-hash-length
)
211 (unless (boundp '*the-class-t
*)
212 (setq *the-class-t
* nil
))
214 (defmacro wrapper-class
(wrapper)
215 `(classoid-pcl-class (layout-classoid ,wrapper
)))
216 (defmacro wrapper-no-of-instance-slots
(wrapper)
217 `(layout-length ,wrapper
))
219 ;;; This is called in BRAID when we are making wrappers for classes
220 ;;; whose slots are not initialized yet, and which may be built-in
221 ;;; classes. We pass in the class name in addition to the class.
222 (defun boot-make-wrapper (length name
&optional class
)
223 (let ((found (find-classoid name nil
)))
226 (unless (classoid-pcl-class found
)
227 (setf (classoid-pcl-class found
) class
))
228 (aver (eq (classoid-pcl-class found
) class
))
229 (let ((layout (classoid-layout found
)))
233 (make-wrapper-internal
235 :classoid
(make-standard-classoid
236 :name name
:pcl-class class
))))))
238 ;;; The following variable may be set to a STANDARD-CLASS that has
239 ;;; already been created by the lisp code and which is to be redefined
240 ;;; by PCL. This allows STANDARD-CLASSes to be defined and used for
241 ;;; type testing and dispatch before PCL is loaded.
242 (defvar *pcl-class-boot
* nil
)
244 ;;; In SBCL, as in CMU CL, the layouts (a.k.a wrappers) for built-in
245 ;;; and structure classes already exist when PCL is initialized, so we
246 ;;; don't necessarily always make a wrapper. Also, we help maintain
247 ;;; the mapping between CL:CLASS and SB-KERNEL:CLASSOID objects.
248 (defun make-wrapper (length class
)
250 ((or (typep class
'std-class
)
251 (typep class
'forward-referenced-class
))
252 (make-wrapper-internal
255 (let ((owrap (class-wrapper class
)))
257 (layout-classoid owrap
))
258 ((or (*subtypep
(class-of class
) *the-class-standard-class
*)
259 (*subtypep
(class-of class
) *the-class-funcallable-standard-class
*)
260 (typep class
'forward-referenced-class
))
261 (cond ((and *pcl-class-boot
*
262 (eq (slot-value class
'name
) *pcl-class-boot
*))
263 (let ((found (find-classoid
264 (slot-value class
'name
))))
265 (unless (classoid-pcl-class found
)
266 (setf (classoid-pcl-class found
) class
))
267 (aver (eq (classoid-pcl-class found
) class
))
270 (let ((name (slot-value class
'name
)))
271 (make-standard-classoid :pcl-class class
272 :name
(and (symbolp name
) name
))))))
274 (bug "Got to T branch in ~S" 'make-wrapper
))))))
276 (let* ((found (find-classoid (slot-value class
'name
)))
277 (layout (classoid-layout found
)))
278 (unless (classoid-pcl-class found
)
279 (setf (classoid-pcl-class found
) class
))
280 (aver (eq (classoid-pcl-class found
) class
))
284 (defconstant +first-wrapper-cache-number-index
+ 0)
286 (declaim (inline next-wrapper-cache-number-index
))
287 (defun next-wrapper-cache-number-index (field-number)
288 (and (< field-number
#.
(1- wrapper-cache-number-vector-length
))
291 ;;; FIXME: Why are there two layers here, with one operator trivially
292 ;;; defined in terms of the other? It'd be nice either to have a
293 ;;; comment explaining why the separation is valuable, or to collapse
294 ;;; it into a single layer.
296 ;;; Second FIXME deleted from here. Setting the "hash" values is OK:
297 ;;; that's part of the magic we need to do to obsolete things. The
298 ;;; hash values are used as indexes to the cache vectors. Nikodemus
299 ;;; thinks both "layers" should go away, and we should just use the
300 ;;; LAYOUT-CLOS-HASH directly.
301 (defmacro cache-number-vector-ref
(cnv n
)
302 `(wrapper-cache-number-vector-ref ,cnv
,n
))
303 (defmacro wrapper-cache-number-vector-ref
(wrapper n
)
304 `(layout-clos-hash ,wrapper
,n
))
306 (declaim (inline wrapper-class
*))
307 (defun wrapper-class* (wrapper)
308 (or (wrapper-class wrapper
)
309 (ensure-non-standard-class
310 (classoid-name (layout-classoid wrapper
)))))
312 ;;; The wrapper cache machinery provides general mechanism for
313 ;;; trapping on the next access to any instance of a given class. This
314 ;;; mechanism is used to implement the updating of instances when the
315 ;;; class is redefined (MAKE-INSTANCES-OBSOLETE). The same mechanism
316 ;;; is also used to update generic function caches when there is a
317 ;;; change to the superclasses of a class.
319 ;;; Basically, a given wrapper can be valid or invalid. If it is
320 ;;; invalid, it means that any attempt to do a wrapper cache lookup
321 ;;; using the wrapper should trap. Also, methods on
322 ;;; SLOT-VALUE-USING-CLASS check the wrapper validity as well. This is
323 ;;; done by calling CHECK-WRAPPER-VALIDITY.
325 (declaim (inline invalid-wrapper-p
))
326 (defun invalid-wrapper-p (wrapper)
327 (not (null (layout-invalid wrapper
))))
329 ;;; FIXME: This needs a lock
330 (defvar *previous-nwrappers
* (make-hash-table))
332 (defun invalidate-wrapper (owrapper state nwrapper
)
333 (aver (member state
'(:flush
:obsolete
) :test
#'eq
))
334 (let ((new-previous ()))
335 ;; First off, a previous call to INVALIDATE-WRAPPER may have
336 ;; recorded OWRAPPER as an NWRAPPER to update to. Since OWRAPPER
337 ;; is about to be invalid, it no longer makes sense to update to
340 ;; We go back and change the previously invalidated wrappers so
341 ;; that they will now update directly to NWRAPPER. This
342 ;; corresponds to a kind of transitivity of wrapper updates.
343 (dolist (previous (gethash owrapper
*previous-nwrappers
*))
344 (when (eq state
:obsolete
)
345 (setf (car previous
) :obsolete
))
346 (setf (cadr previous
) nwrapper
)
347 (push previous new-previous
))
349 (dotimes (i layout-clos-hash-length
)
350 (setf (cache-number-vector-ref owrapper i
) 0))
351 ;; FIXME: We could save a whopping cons by using (STATE . WRAPPER)
353 (push (setf (layout-invalid owrapper
) (list state nwrapper
))
356 (remhash owrapper
*previous-nwrappers
*)
357 (setf (gethash nwrapper
*previous-nwrappers
*) new-previous
)))
359 (defun check-wrapper-validity (instance)
360 (let* ((owrapper (wrapper-of instance
))
361 (state (layout-invalid owrapper
)))
362 (aver (not (eq state
:uninitialized
)))
365 ;; FIXME: I can't help thinking that, while this does cure the
366 ;; symptoms observed from some class redefinitions, this isn't
367 ;; the place to be doing this flushing. Nevertheless... --
371 ;; We assume in this case, that the :INVALID is from a
372 ;; previous call to REGISTER-LAYOUT for a superclass of
373 ;; INSTANCE's class. See also the comment above
374 ;; FORCE-CACHE-FLUSHES. Paul Dietz has test cases for this.
376 (force-cache-flushes (class-of instance
))
377 (check-wrapper-validity instance
))
381 (flush-cache-trap owrapper
(cadr state
) instance
))
383 (obsolete-instance-trap owrapper
(cadr state
) instance
)))))))
385 (declaim (inline check-obsolete-instance
))
386 (defun check-obsolete-instance (instance)
387 (when (invalid-wrapper-p (layout-of instance
))
388 (check-wrapper-validity instance
)))
391 (defun get-cache (nkeys valuep limit-fn nlines
)
392 (let ((cache (make-cache)))
393 (declare (type cache cache
))
394 (multiple-value-bind (cache-mask actual-size line-size nlines
)
395 (compute-cache-parameters nkeys valuep nlines
)
396 (setf (cache-nkeys cache
) nkeys
397 (cache-valuep cache
) valuep
398 (cache-nlines cache
) nlines
399 (cache-field cache
) +first-wrapper-cache-number-index
+
400 (cache-limit-fn cache
) limit-fn
401 (cache-mask cache
) cache-mask
402 (cache-size cache
) actual-size
403 (cache-line-size cache
) line-size
404 (cache-max-location cache
) (let ((line (1- nlines
)))
407 (1+ (* line line-size
))))
408 (cache-vector cache
) (get-cache-vector actual-size
)
409 (cache-overflow cache
) nil
)
412 (defun get-cache-from-cache (old-cache new-nlines
413 &optional
(new-field +first-wrapper-cache-number-index
+))
414 (let ((nkeys (cache-nkeys old-cache
))
415 (valuep (cache-valuep old-cache
))
416 (cache (make-cache)))
417 (declare (type cache cache
))
418 (multiple-value-bind (cache-mask actual-size line-size nlines
)
419 (if (= new-nlines
(cache-nlines old-cache
))
420 (values (cache-mask old-cache
) (cache-size old-cache
)
421 (cache-line-size old-cache
) (cache-nlines old-cache
))
422 (compute-cache-parameters nkeys valuep new-nlines
))
423 (setf (cache-owner cache
) (cache-owner old-cache
)
424 (cache-nkeys cache
) nkeys
425 (cache-valuep cache
) valuep
426 (cache-nlines cache
) nlines
427 (cache-field cache
) new-field
428 (cache-limit-fn cache
) (cache-limit-fn old-cache
)
429 (cache-mask cache
) cache-mask
430 (cache-size cache
) actual-size
431 (cache-line-size cache
) line-size
432 (cache-max-location cache
) (let ((line (1- nlines
)))
435 (1+ (* line line-size
))))
436 (cache-vector cache
) (get-cache-vector actual-size
)
437 (cache-overflow cache
) nil
)
440 (defun copy-cache (old-cache)
441 (let* ((new-cache (copy-cache-internal old-cache
))
442 (size (cache-size old-cache
))
443 (old-vector (cache-vector old-cache
))
444 (new-vector (get-cache-vector size
)))
445 (declare (simple-vector old-vector new-vector
))
446 (dotimes-fixnum (i size
)
447 (setf (svref new-vector i
) (svref old-vector i
)))
448 (setf (cache-vector new-cache
) new-vector
)
451 (defun compute-cache-parameters (nkeys valuep nlines-or-cache-vector
)
452 ;;(declare (values cache-mask actual-size line-size nlines))
453 (declare (fixnum nkeys
))
455 (let* ((line-size (if valuep
2 1))
456 (cache-size (etypecase nlines-or-cache-vector
459 (power-of-two-ceiling nlines-or-cache-vector
)))
461 (cache-vector-size nlines-or-cache-vector
)))))
462 (declare (type (and unsigned-byte fixnum
) line-size cache-size
))
463 (values (logxor (1- cache-size
) (1- line-size
))
466 (floor cache-size line-size
)))
467 (let* ((line-size (power-of-two-ceiling (if valuep
(1+ nkeys
) nkeys
)))
468 (cache-size (etypecase nlines-or-cache-vector
471 (power-of-two-ceiling nlines-or-cache-vector
)))
473 (1- (cache-vector-size nlines-or-cache-vector
))))))
474 (declare (fixnum line-size cache-size
))
475 (values (logxor (1- cache-size
) (1- line-size
))
478 (floor cache-size line-size
)))))
480 ;;; the various implementations of computing a primary cache location from
481 ;;; wrappers. Because some implementations of this must run fast there are
482 ;;; several implementations of the same algorithm.
484 ;;; The algorithm is:
486 ;;; SUM over the wrapper cache numbers,
487 ;;; ENSURING that the result is a fixnum
488 ;;; MASK the result against the mask argument.
490 ;;; The basic functional version. This is used by the cache miss code to
491 ;;; compute the primary location of an entry.
492 (defun compute-primary-cache-location (field mask wrappers
)
493 (declare (type field-type field
) (fixnum mask
))
494 (if (not (listp wrappers
))
496 (the fixnum
(wrapper-cache-number-vector-ref wrappers field
)))
499 (declare (fixnum location i
))
500 (dolist (wrapper wrappers
)
501 ;; First add the cache number of this wrapper to location.
502 (let ((wrapper-cache-number (wrapper-cache-number-vector-ref wrapper
504 (declare (fixnum wrapper-cache-number
))
505 (if (zerop wrapper-cache-number
)
506 (return-from compute-primary-cache-location
0)
507 (incf location wrapper-cache-number
)))
508 ;; Then, if we are working with lots of wrappers, deal with
509 ;; the wrapper-cache-number-mask stuff.
510 (when (and (not (zerop i
))
511 (zerop (mod i wrapper-cache-number-adds-ok
)))
513 (logand location wrapper-cache-number-mask
)))
515 (1+ (logand mask location
)))))
517 ;;; This version is called on a cache line. It fetches the wrappers
518 ;;; from the cache line and determines the primary location. Various
519 ;;; parts of the cache filling code call this to determine whether it
520 ;;; is appropriate to displace a given cache entry.
522 ;;; If this comes across a wrapper whose CACHE-NO is 0, it returns the
523 ;;; symbol invalid to suggest to its caller that it would be provident
524 ;;; to blow away the cache line in question.
525 (defun compute-primary-cache-location-from-location (to-cache
528 (from-cache to-cache
))
529 (declare (type cache to-cache from-cache
) (fixnum from-location
))
531 (cache-vector (cache-vector from-cache
))
532 (field (cache-field to-cache
))
533 (mask (cache-mask to-cache
))
534 (nkeys (cache-nkeys to-cache
)))
535 (declare (type field-type field
) (fixnum result mask nkeys
)
536 (simple-vector cache-vector
))
537 (dotimes-fixnum (i nkeys
)
538 (let* ((wrapper (cache-vector-ref cache-vector
(+ i from-location
)))
539 (wcn (wrapper-cache-number-vector-ref wrapper field
)))
540 (declare (fixnum wcn
))
542 (when (and (not (zerop i
))
543 (zerop (mod i wrapper-cache-number-adds-ok
)))
544 (setq result
(logand result wrapper-cache-number-mask
))))
547 (1+ (logand mask result
)))))
549 ;;; NIL: means nothing so far, no actual arg info has NILs in the
552 ;;; CLASS: seen all sorts of metaclasses (specifically, more than one
553 ;;; of the next 5 values) or else have seen something which doesn't
554 ;;; fall into a single category (SLOT-INSTANCE, FORWARD).
556 ;;; T: means everything so far is the class T
557 ;;; STANDARD-INSTANCE: seen only standard classes
558 ;;; BUILT-IN-INSTANCE: seen only built in classes
559 ;;; STRUCTURE-INSTANCE: seen only structure classes
560 ;;; CONDITION-INSTANCE: seen only condition classes
561 (defun raise-metatype (metatype new-specializer
)
562 (let ((slot (find-class 'slot-class
))
563 (standard (find-class 'standard-class
))
564 (fsc (find-class 'funcallable-standard-class
))
565 (condition (find-class 'condition-class
))
566 (structure (find-class 'structure-class
))
567 (built-in (find-class 'built-in-class
))
568 (frc (find-class 'forward-referenced-class
)))
569 (flet ((specializer->metatype
(x)
570 (let ((meta-specializer
571 (if (eq *boot-state
* 'complete
)
572 (class-of (specializer-class x
))
575 ((eq x
*the-class-t
*) t
)
576 ((*subtypep meta-specializer standard
) 'standard-instance
)
577 ((*subtypep meta-specializer fsc
) 'standard-instance
)
578 ((*subtypep meta-specializer condition
) 'condition-instance
)
579 ((*subtypep meta-specializer structure
) 'structure-instance
)
580 ((*subtypep meta-specializer built-in
) 'built-in-instance
)
581 ((*subtypep meta-specializer slot
) 'slot-instance
)
582 ((*subtypep meta-specializer frc
) 'forward
)
583 (t (error "~@<PCL cannot handle the specializer ~S ~
584 (meta-specializer ~S).~@:>"
585 new-specializer meta-specializer
))))))
586 ;; We implement the following table. The notation is
587 ;; that X and Y are distinct meta specializer names.
589 ;; NIL <anything> ===> <anything>
592 (let ((new-metatype (specializer->metatype new-specializer
)))
593 (cond ((eq new-metatype
'slot-instance
) 'class
)
594 ((eq new-metatype
'forward
) 'class
)
595 ((null metatype
) new-metatype
)
596 ((eq metatype new-metatype
) new-metatype
)
599 (defmacro with-dfun-wrappers
((args metatypes
)
600 (dfun-wrappers invalid-wrapper-p
601 &optional wrappers classes types
)
602 invalid-arguments-form
604 `(let* ((args-tail ,args
) (,invalid-wrapper-p nil
) (invalid-arguments-p nil
)
605 (,dfun-wrappers nil
) (dfun-wrappers-tail nil
)
607 `((wrappers-rev nil
) (types-rev nil
) (classes-rev nil
))))
608 (dolist (mt ,metatypes
)
610 (setq invalid-arguments-p t
)
612 (let* ((arg (pop args-tail
))
615 `((class *the-class-t
*)
618 (setq wrapper
(wrapper-of arg
))
619 (when (invalid-wrapper-p wrapper
)
620 (setq ,invalid-wrapper-p t
)
621 (setq wrapper
(check-wrapper-validity arg
)))
622 (cond ((null ,dfun-wrappers
)
623 (setq ,dfun-wrappers wrapper
))
624 ((not (consp ,dfun-wrappers
))
625 (setq dfun-wrappers-tail
(list wrapper
))
626 (setq ,dfun-wrappers
(cons ,dfun-wrappers dfun-wrappers-tail
)))
628 (let ((new-dfun-wrappers-tail (list wrapper
)))
629 (setf (cdr dfun-wrappers-tail
) new-dfun-wrappers-tail
)
630 (setf dfun-wrappers-tail new-dfun-wrappers-tail
))))
632 `((setq class
(wrapper-class* wrapper
))
633 (setq type
`(class-eq ,class
)))))
635 `((push wrapper wrappers-rev
)
636 (push class classes-rev
)
637 (push type types-rev
)))))
638 (if invalid-arguments-p
639 ,invalid-arguments-form
640 (let* (,@(when wrappers
641 `((,wrappers
(nreverse wrappers-rev
))
642 (,classes
(nreverse classes-rev
))
643 (,types
(mapcar (lambda (class)
648 ;;;; some support stuff for getting a hold of symbols that we need when
649 ;;;; building the discriminator codes. It's OK for these to be interned
650 ;;;; symbols because we don't capture any user code in the scope in which
651 ;;;; these symbols are bound.
653 (declaim (list *dfun-arg-symbols
*))
654 (defvar *dfun-arg-symbols
* '(.ARG0. .ARG1. .ARG2. .ARG3.
))
656 (defun dfun-arg-symbol (arg-number)
657 (or (nth arg-number
*dfun-arg-symbols
*)
658 (format-symbol *pcl-package
* ".ARG~A." arg-number
)))
660 (declaim (list *slot-vector-symbols
*))
661 (defvar *slot-vector-symbols
* '(.SLOTS0. .SLOTS1. .SLOTS2. .SLOTS3.
))
663 (defun slot-vector-symbol (arg-number)
664 (or (nth arg-number
*slot-vector-symbols
*)
665 (format-symbol *pcl-package
* ".SLOTS~A." arg-number
)))
667 (declaim (inline make-dfun-required-args
))
668 (defun make-dfun-required-args (metatypes)
669 ;; Micro-optimizations 'R Us
670 (labels ((rec (types i
)
673 (cons (dfun-arg-symbol i
)
674 (rec (cdr types
) (1+ i
))))))
677 (defun make-dfun-lambda-list (metatypes applyp
)
678 (let ((required (make-dfun-required-args metatypes
)))
681 ;; Use &MORE arguments to avoid consing up an &REST list
682 ;; that we might not need at all. See MAKE-EMF-CALL and
683 ;; INVOKE-EFFECTIVE-METHOD-FUNCTION for the other
685 '(&more .dfun-more-context. .dfun-more-count.
))
688 (defun make-dlap-lambda-list (metatypes applyp
)
689 (let* ((required (make-dfun-required-args metatypes
))
690 (lambda-list (if applyp
691 (append required
'(&more .more-context. .more-count.
))
693 ;; Return the full lambda list, the required arguments, a form
694 ;; that will generate a rest-list, and a list of the &MORE
699 '((sb-c::%listify-rest-args
701 (the (and unsigned-byte fixnum
)
704 '(.more-context. .more-count.
)))))
706 (defun make-emf-call (metatypes applyp fn-variable
&optional emf-type
)
707 (let ((required (make-dfun-required-args metatypes
)))
708 `(,(if (eq emf-type
'fast-method-call
)
709 'invoke-effective-method-function-fast
710 'invoke-effective-method-function
)
713 :required-args
,required
714 ;; INVOKE-EFFECTIVE-METHOD-FUNCTION will decide whether to use
715 ;; the :REST-ARG version or the :MORE-ARG version depending on
716 ;; the type of the EMF.
717 :rest-arg
,(if applyp
718 ;; Creates a list from the &MORE arguments.
719 '((sb-c::%listify-rest-args
721 (the (and unsigned-byte fixnum
)
724 :more-arg
,(when applyp
725 '(.dfun-more-context. .dfun-more-count.
)))))
727 (defun make-fast-method-call-lambda-list (metatypes applyp
)
728 (list* '.pv-cell.
'.next-method-call.
729 (make-dfun-lambda-list metatypes applyp
)))
732 (defmacro with-local-cache-functions
((cache) &body body
)
733 `(let ((.cache.
,cache
))
734 (declare (type cache .cache.
))
735 (labels ((cache () .cache.
)
736 (nkeys () (cache-nkeys .cache.
))
737 (line-size () (cache-line-size .cache.
))
738 (c-vector () (cache-vector .cache.
))
739 (valuep () (cache-valuep .cache.
))
740 (nlines () (cache-nlines .cache.
))
741 (max-location () (cache-max-location .cache.
))
742 (limit-fn () (cache-limit-fn .cache.
))
743 (size () (cache-size .cache.
))
744 (mask () (cache-mask .cache.
))
745 (field () (cache-field .cache.
))
746 (overflow () (cache-overflow .cache.
))
748 ;; Return T IFF this cache location is reserved. The
749 ;; only time this is true is for line number 0 of an
752 (line-reserved-p (line)
753 (declare (fixnum line
))
757 (location-reserved-p (location)
758 (declare (fixnum location
))
762 ;; Given a line number, return the cache location.
763 ;; This is the value that is the second argument to
764 ;; cache-vector-ref. Basically, this deals with the
765 ;; offset of nkeys>1 caches and multiplies by line
768 (line-location (line)
769 (declare (fixnum line
))
770 (when (line-reserved-p line
)
771 (error "line is reserved"))
773 (the fixnum
(* line
(line-size)))
774 (the fixnum
(1+ (the fixnum
(* line
(line-size)))))))
776 ;; Given a cache location, return the line. This is
777 ;; the inverse of LINE-LOCATION.
779 (location-line (location)
780 (declare (fixnum location
))
782 (floor location
(line-size))
783 (floor (the fixnum
(1- location
)) (line-size))))
785 ;; Given a line number, return the wrappers stored at
786 ;; that line. As usual, if nkeys=1, this returns a
787 ;; single value. Only when nkeys>1 does it return a
788 ;; list. An error is signalled if the line is
791 (line-wrappers (line)
792 (declare (fixnum line
))
793 (when (line-reserved-p line
) (error "Line is reserved."))
794 (location-wrappers (line-location line
)))
796 (location-wrappers (location) ; avoid multiplies caused by line-location
797 (declare (fixnum location
))
799 (cache-vector-ref (c-vector) location
)
800 (let ((list (make-list (nkeys)))
802 (declare (simple-vector vector
))
803 (dotimes (i (nkeys) list
)
806 (cache-vector-ref vector
(+ location i
)))))))
808 ;; Given a line number, return true IFF the line's
809 ;; wrappers are the same as wrappers.
811 (line-matches-wrappers-p (line wrappers
)
812 (declare (fixnum line
))
813 (and (not (line-reserved-p line
))
814 (location-matches-wrappers-p (line-location line
)
817 (location-matches-wrappers-p (loc wrappers
) ; must not be reserved
818 (declare (fixnum loc
))
819 (let ((cache-vector (c-vector)))
820 (declare (simple-vector cache-vector
))
822 (eq wrappers
(cache-vector-ref cache-vector loc
))
823 (dotimes (i (nkeys) t
)
825 (unless (eq (pop wrappers
)
826 (cache-vector-ref cache-vector
(+ loc i
)))
829 ;; Given a line number, return the value stored at that line.
830 ;; If valuep is NIL, this returns NIL. As with line-wrappers,
831 ;; an error is signalled if the line is reserved.
834 (declare (fixnum line
))
835 (when (line-reserved-p line
) (error "Line is reserved."))
836 (location-value (line-location line
)))
838 (location-value (loc)
839 (declare (fixnum loc
))
841 (cache-vector-ref (c-vector) (+ loc
(nkeys)))))
843 ;; Given a line number, return true IFF that line has data in
844 ;; it. The state of the wrappers stored in the line is not
845 ;; checked. An error is signalled if line is reserved.
847 (when (line-reserved-p line
) (error "Line is reserved."))
848 (not (null (cache-vector-ref (c-vector) (line-location line
)))))
850 ;; Given a line number, return true IFF the line is full and
851 ;; there are no invalid wrappers in the line, and the line's
852 ;; wrappers are different from wrappers.
853 ;; An error is signalled if the line is reserved.
855 (line-valid-p (line wrappers
)
856 (declare (fixnum line
))
857 (when (line-reserved-p line
) (error "Line is reserved."))
858 (location-valid-p (line-location line
) wrappers
))
860 (location-valid-p (loc wrappers
)
861 (declare (fixnum loc
))
862 (let ((cache-vector (c-vector))
863 (wrappers-mismatch-p (null wrappers
)))
864 (declare (simple-vector cache-vector
))
865 (dotimes (i (nkeys) wrappers-mismatch-p
)
867 (let ((wrapper (cache-vector-ref cache-vector
(+ loc i
))))
868 (when (or (null wrapper
)
869 (invalid-wrapper-p wrapper
))
871 (unless (and wrappers
876 (setq wrappers-mismatch-p t
))))))
878 ;; How many unreserved lines separate line-1 and line-2.
880 (line-separation (line-1 line-2
)
881 (declare (fixnum line-1 line-2
))
882 (let ((diff (the fixnum
(- line-2 line-1
))))
883 (declare (fixnum diff
))
885 (setq diff
(+ diff
(nlines)))
886 (when (line-reserved-p 0)
887 (setq diff
(1- diff
))))
890 ;; Given a cache line, get the next cache line. This will not
891 ;; return a reserved line.
894 (declare (fixnum line
))
895 (if (= line
(the fixnum
(1- (nlines))))
896 (if (line-reserved-p 0) 1 0)
897 (the fixnum
(1+ line
))))
900 (declare (fixnum loc
))
901 (if (= loc
(max-location))
905 (the fixnum
(+ loc
(line-size)))))
907 ;; Given a line which has a valid entry in it, this
908 ;; will return the primary cache line of the wrappers
909 ;; in that line. We just call
910 ;; COMPUTE-PRIMARY-CACHE-LOCATION-FROM-LOCATION, this
911 ;; is an easier packaging up of the call to it.
914 (declare (fixnum line
))
915 (location-line (line-primary-location line
)))
917 (line-primary-location (line)
918 (declare (fixnum line
))
919 (compute-primary-cache-location-from-location
920 (cache) (line-location line
))))
921 (declare (ignorable #'cache
#'nkeys
#'line-size
#'c-vector
#'valuep
922 #'nlines
#'max-location
#'limit-fn
#'size
923 #'mask
#'field
#'overflow
#'line-reserved-p
924 #'location-reserved-p
#'line-location
925 #'location-line
#'line-wrappers
#'location-wrappers
926 #'line-matches-wrappers-p
927 #'location-matches-wrappers-p
928 #'line-value
#'location-value
#'line-full-p
929 #'line-valid-p
#'location-valid-p
930 #'line-separation
#'next-line
#'next-location
931 #'line-primary
#'line-primary-location
))
934 ;;; Here is where we actually fill, recache and expand caches.
936 ;;; The functions FILL-CACHE and PROBE-CACHE are the ONLY external
937 ;;; entrypoints into this code.
939 ;;; FILL-CACHE returns 1 value: a new cache
941 ;;; a wrapper field number
944 ;;; an absolute cache size (the size of the actual vector)
945 ;;; It tries to re-adjust the cache every time it makes a new fill.
946 ;;; The intuition here is that we want uniformity in the number of
947 ;;; probes needed to find an entry. Furthermore, adjusting has the
948 ;;; nice property of throwing out any entries that are invalid.
949 (defvar *cache-expand-threshold
* 1.25)
951 (defun fill-cache (cache wrappers value
)
952 ;; FILL-CACHE won't return if WRAPPERS is nil, might as well check..
954 (or (fill-cache-p nil cache wrappers value
)
955 (and (< (ceiling (* (cache-count cache
) *cache-expand-threshold
*))
956 (if (= (cache-nkeys cache
) 1)
957 (1- (cache-nlines cache
))
958 (cache-nlines cache
)))
959 (adjust-cache cache wrappers value
))
960 (expand-cache cache wrappers value
)))
962 (defvar *check-cache-p
* nil
)
964 (defmacro maybe-check-cache
(cache)
966 (when *check-cache-p
*
967 (check-cache ,cache
))
970 (defun check-cache (cache)
971 (with-local-cache-functions (cache)
972 (let ((location (if (= (nkeys) 1) 0 1))
973 (limit (funcall (limit-fn) (nlines))))
974 (dotimes-fixnum (i (nlines) cache
)
975 (when (and (not (location-reserved-p location
))
977 (let* ((home-loc (compute-primary-cache-location-from-location
979 (home (location-line (if (location-reserved-p home-loc
)
980 (next-location home-loc
)
982 (sep (when home
(line-separation home i
))))
983 (when (and sep
(> sep limit
))
984 (error "bad cache ~S ~@
985 value at location ~W: ~W lines from its home. The limit is ~W."
986 cache location sep limit
))))
987 (setq location
(next-location location
))))))
989 (defun probe-cache (cache wrappers
&optional default limit-fn
)
991 (with-local-cache-functions (cache)
992 (let* ((location (compute-primary-cache-location (field) (mask) wrappers
))
993 (limit (funcall (or limit-fn
(limit-fn)) (nlines))))
994 (declare (fixnum location limit
))
995 (when (location-reserved-p location
)
996 (setq location
(next-location location
)))
997 (dotimes-fixnum (i (1+ limit
))
998 (when (location-matches-wrappers-p location wrappers
)
999 (return-from probe-cache
(or (not (valuep))
1000 (location-value location
))))
1001 (setq location
(next-location location
)))
1002 (dolist (entry (overflow))
1003 (when (equal (car entry
) wrappers
)
1004 (return-from probe-cache
(or (not (valuep))
1008 (defun map-cache (function cache
&optional set-p
)
1009 (with-local-cache-functions (cache)
1010 (let ((set-p (and set-p
(valuep))))
1011 (dotimes-fixnum (i (nlines) cache
)
1012 (unless (or (line-reserved-p i
) (not (line-valid-p i nil
)))
1013 (let ((value (funcall function
(line-wrappers i
) (line-value i
))))
1015 ;; FIXME: Cache modification: should we not be holding a lock?
1016 (setf (cache-vector-ref (c-vector) (+ (line-location i
) (nkeys)))
1018 (dolist (entry (overflow))
1019 (let ((value (funcall function
(car entry
) (cdr entry
))))
1021 (setf (cdr entry
) value
))))))
1024 (defun cache-count (cache)
1025 (with-local-cache-functions (cache)
1027 (declare (fixnum count
))
1028 (dotimes-fixnum (i (nlines) count
)
1029 (unless (line-reserved-p i
)
1030 (when (line-full-p i
)
1033 (defun entry-in-cache-p (cache wrappers value
)
1034 (declare (ignore value
))
1035 (with-local-cache-functions (cache)
1036 (dotimes-fixnum (i (nlines))
1037 (unless (line-reserved-p i
)
1038 (when (equal (line-wrappers i
) wrappers
)
1041 ;;; returns T or NIL
1043 ;;; FIXME: Deceptive name as this has side-effects.
1044 (defun fill-cache-p (forcep cache wrappers value
)
1045 (with-local-cache-functions (cache)
1046 (let* ((location (compute-primary-cache-location (field) (mask) wrappers
))
1047 (primary (location-line location
)))
1048 (declare (fixnum location primary
))
1049 ;; FIXME: I tried (aver (> location 0)) and (aver (not
1050 ;; (location-reserved-p location))) here, on the basis that
1051 ;; particularly passing a LOCATION of 0 for a cache with more
1052 ;; than one key would cause PRIMARY to be -1. However, the
1053 ;; AVERs triggered during the bootstrap, and removing them
1054 ;; didn't cause anything to break, so I've left them removed.
1055 ;; I'm still confused as to what is right. -- CSR, 2006-04-20
1056 (multiple-value-bind (free emptyp
)
1057 (find-free-cache-line primary cache wrappers
)
1058 (when (or forcep emptyp
)
1060 (push (cons (line-wrappers free
) (line-value free
))
1061 (cache-overflow cache
)))
1062 ;; (fill-line free wrappers value)
1064 (declare (fixnum line
))
1065 (when (line-reserved-p line
)
1066 (error "attempt to fill a reserved line"))
1067 (let ((loc (line-location line
))
1068 (cache-vector (c-vector)))
1069 (declare (fixnum loc
) (simple-vector cache-vector
))
1070 ;; FIXME: Cache modifications: should we not be holding
1072 (cond ((= (nkeys) 1)
1073 (setf (cache-vector-ref cache-vector loc
) wrappers
)
1075 (setf (cache-vector-ref cache-vector
(1+ loc
)) value
)))
1078 (declare (fixnum i
))
1079 (dolist (w wrappers
)
1080 (setf (cache-vector-ref cache-vector
(+ loc i
)) w
)
1081 (setq i
(the fixnum
(1+ i
)))))
1083 (setf (cache-vector-ref cache-vector
(+ loc
(nkeys)))
1085 (maybe-check-cache cache
))))))))
1087 ;;; FIXME: Deceptive name as this has side-effects
1088 (defun fill-cache-from-cache-p (forcep cache from-cache from-line
)
1089 (declare (fixnum from-line
))
1090 (with-local-cache-functions (cache)
1091 (let ((primary (location-line
1092 (compute-primary-cache-location-from-location
1093 cache
(line-location from-line
) from-cache
))))
1094 (declare (fixnum primary
))
1095 (multiple-value-bind (free emptyp
)
1096 (find-free-cache-line primary cache
)
1097 (when (or forcep emptyp
)
1099 (push (cons (line-wrappers free
) (line-value free
))
1100 (cache-overflow cache
)))
1101 ;;(transfer-line from-cache-vector from-line cache-vector free)
1102 (let ((from-cache-vector (cache-vector from-cache
))
1103 (to-cache-vector (c-vector))
1105 (declare (fixnum to-line
))
1106 (if (line-reserved-p to-line
)
1107 (error "transferring something into a reserved cache line")
1108 (let ((from-loc (line-location from-line
))
1109 (to-loc (line-location to-line
)))
1110 (declare (fixnum from-loc to-loc
))
1111 (modify-cache to-cache-vector
1112 (dotimes-fixnum (i (line-size))
1113 (setf (cache-vector-ref to-cache-vector
1115 (cache-vector-ref from-cache-vector
1116 (+ from-loc i
)))))))
1117 (maybe-check-cache cache
)))))))
1119 ;;; Returns NIL or (values <field> <cache-vector>)
1121 ;;; This is only called when it isn't possible to put the entry in the
1122 ;;; cache the easy way. That is, this function assumes that
1123 ;;; FILL-CACHE-P has been called as returned NIL.
1125 ;;; If this returns NIL, it means that it wasn't possible to find a
1126 ;;; wrapper field for which all of the entries could be put in the
1127 ;;; cache (within the limit).
1128 (defun adjust-cache (cache wrappers value
)
1129 (with-local-cache-functions (cache)
1130 (let ((ncache (get-cache-from-cache cache
(nlines) (field))))
1131 (do ((nfield (cache-field ncache
)
1132 (next-wrapper-cache-number-index nfield
)))
1134 (setf (cache-field ncache
) nfield
)
1135 (labels ((try-one-fill-from-line (line)
1136 (fill-cache-from-cache-p nil ncache cache line
))
1137 (try-one-fill (wrappers value
)
1138 (fill-cache-p nil ncache wrappers value
)))
1139 (if (and (dotimes-fixnum (i (nlines) t
)
1140 (when (and (null (line-reserved-p i
))
1141 (line-valid-p i wrappers
))
1142 (unless (try-one-fill-from-line i
) (return nil
))))
1143 (dolist (wrappers+value
(cache-overflow cache
) t
)
1144 (unless (try-one-fill (car wrappers
+value
) (cdr wrappers
+value
))
1146 (try-one-fill wrappers value
))
1147 (return (maybe-check-cache ncache
))
1148 (flush-cache-vector-internal (cache-vector ncache
))))))))
1150 ;;; returns: (values <cache>)
1151 (defun expand-cache (cache wrappers value
)
1152 ;;(declare (values cache))
1153 (with-local-cache-functions (cache)
1154 (let ((ncache (get-cache-from-cache cache
(* (nlines) 2))))
1155 (labels ((do-one-fill-from-line (line)
1156 (unless (fill-cache-from-cache-p nil ncache cache line
)
1157 (do-one-fill (line-wrappers line
) (line-value line
))))
1158 (do-one-fill (wrappers value
)
1159 (setq ncache
(or (adjust-cache ncache wrappers value
)
1160 (fill-cache-p t ncache wrappers value
))))
1161 (try-one-fill (wrappers value
)
1162 (fill-cache-p nil ncache wrappers value
)))
1163 (dotimes-fixnum (i (nlines))
1164 (when (and (null (line-reserved-p i
))
1165 (line-valid-p i wrappers
))
1166 (do-one-fill-from-line i
)))
1167 (dolist (wrappers+value
(cache-overflow cache
))
1168 (unless (try-one-fill (car wrappers
+value
) (cdr wrappers
+value
))
1169 (do-one-fill (car wrappers
+value
) (cdr wrappers
+value
))))
1170 (unless (try-one-fill wrappers value
)
1171 (do-one-fill wrappers value
))
1172 (maybe-check-cache ncache
)))))
1174 (defvar *pcl-misc-random-state
* (make-random-state))
1176 ;;; This is the heart of the cache filling mechanism. It implements
1177 ;;; the decisions about where entries are placed.
1179 ;;; Find a line in the cache at which a new entry can be inserted.
1182 ;;; <empty?> is <line> in fact empty?
1183 (defun find-free-cache-line (primary cache
&optional wrappers
)
1184 ;;(declare (values line empty?))
1185 (declare (fixnum primary
))
1186 (with-local-cache-functions (cache)
1187 (when (line-reserved-p primary
) (setq primary
(next-line primary
)))
1188 (let ((limit (funcall (limit-fn) (nlines)))
1191 (p primary
) (s primary
))
1192 (declare (fixnum p s limit
))
1195 ;; Try to find a free line starting at <s>. <p> is the
1196 ;; primary line of the entry we are finding a free
1197 ;; line for, it is used to compute the separations.
1198 (do* ((line s
(next-line line
))
1199 (nsep (line-separation p s
) (1+ nsep
)))
1201 (declare (fixnum line nsep
))
1202 (when (null (line-valid-p line wrappers
)) ;If this line is empty or
1203 (push line lines
) ;invalid, just use it.
1204 (return-from find-free
))
1205 (when (and wrappedp
(>= line primary
))
1206 ;; have gone all the way around the cache, time to quit
1207 (return-from find-free-cache-line
(values primary nil
)))
1208 (let ((osep (line-separation (line-primary line
) line
)))
1209 (when (>= osep limit
)
1210 (return-from find-free-cache-line
(values primary nil
)))
1211 (when (cond ((= nsep limit
) t
)
1213 (zerop (random 2 *pcl-misc-random-state
*)))
1216 ;; See whether we can displace what is in this line so that we
1217 ;; can use the line.
1218 (when (= line
(the fixnum
(1- (nlines)))) (setq wrappedp t
))
1219 (setq p
(line-primary line
))
1220 (setq s
(next-line line
))
1223 (when (= line
(the fixnum
(1- (nlines)))) (setq wrappedp t
)))))
1224 ;; Do all the displacing.
1226 (when (null (cdr lines
)) (return nil
))
1227 (let ((dline (pop lines
))
1229 (declare (fixnum dline line
))
1230 ;;Copy from line to dline (dline is known to be free).
1231 (let ((from-loc (line-location line
))
1232 (to-loc (line-location dline
))
1233 (cache-vector (c-vector)))
1234 (declare (fixnum from-loc to-loc
) (simple-vector cache-vector
))
1235 (modify-cache cache-vector
1236 (dotimes-fixnum (i (line-size))
1237 (setf (cache-vector-ref cache-vector
1239 (cache-vector-ref cache-vector
1241 (setf (cache-vector-ref cache-vector
1244 (values (car lines
) t
))))
1246 (defun default-limit-fn (nlines)