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 ;;; WRAPPER-STATE returns T (not generalized boolean, but T exactly)
265 ;;; iff the wrapper is valid. Any other return value denotes some
266 ;;; invalid state. Special conventions have been set up for certain
267 ;;; invalid states, e.g. obsoleteness or flushedness, but I (WHN
268 ;;; 19991204) haven't been motivated to reverse engineer them from the
269 ;;; code and document them here.
271 ;;; FIXME: We have removed the persistent use of this function throughout
272 ;;; the PCL codebase, instead opting to use INVALID-WRAPPER-P, which
273 ;;; abstractly tests the return result of this function for invalidness.
274 ;;; However, part of the original comment that is still applicable follows.
275 ;;; --njf, 2002-05-02
277 ;;; FIXME: It would probably be even better to switch the sense of the
278 ;;; WRAPPER-STATE function, renaming it to WRAPPER-INVALID and making it
279 ;;; synonymous with LAYOUT-INVALID. Then the INVALID-WRAPPER-P function
280 ;;; would become trivial and would go away (replaced with
281 ;;; WRAPPER-INVALID), since all the various invalid wrapper states would
282 ;;; become generalized boolean "true" values. -- WHN 19991204
283 #-sb-fluid (declaim (inline wrapper-state (setf wrapper-state)))
284 (defun wrapper-state (wrapper)
285 (let ((invalid (sb-kernel:layout-invalid wrapper)))
286 (cond ((null invalid)
289 ;; some non-PCL object. INVALID is probably :INVALID. We
290 ;; should arguably compute the new wrapper here instead of
291 ;; returning NIL, but we don't bother, since
292 ;; OBSOLETE-INSTANCE-TRAP can't use it.
296 (defun (setf wrapper-state) (new-value wrapper)
297 (setf (sb-kernel:layout-invalid wrapper)
302 (defmacro wrapper-instance-slots-layout (wrapper)
303 `(%wrapper-instance-slots-layout ,wrapper))
304 (defmacro wrapper-class-slots (wrapper)
305 `(%wrapper-class-slots ,wrapper))
306 (defmacro wrapper-cache-number-vector (x) x)
308 ;;; This is called in BRAID when we are making wrappers for classes
309 ;;; whose slots are not initialized yet, and which may be built-in
310 ;;; classes. We pass in the class name in addition to the class.
311 (defun boot-make-wrapper (length name &optional class)
312 (let ((found (cl:find-class name nil)))
315 (unless (sb-kernel:class-pcl-class found)
316 (setf (sb-kernel:class-pcl-class found) class))
317 (aver (eq (sb-kernel:class-pcl-class found) class))
318 (let ((layout (sb-kernel:class-layout found)))
322 (make-wrapper-internal
324 :class (sb-kernel:make-standard-class :name name :pcl-class class))))))
326 ;;; The following variable may be set to a STANDARD-CLASS that has
327 ;;; already been created by the lisp code and which is to be redefined
328 ;;; by PCL. This allows STANDARD-CLASSes to be defined and used for
329 ;;; type testing and dispatch before PCL is loaded.
330 (defvar *pcl-class-boot* nil)
332 ;;; In SBCL, as in CMU CL, the layouts (a.k.a wrappers) for built-in
333 ;;; and structure classes already exist when PCL is initialized, so we
334 ;;; don't necessarily always make a wrapper. Also, we help maintain
335 ;;; the mapping between CL:CLASS and PCL::CLASS objects.
336 (defun make-wrapper (length class)
338 ((typep class 'std-class)
339 (make-wrapper-internal
342 (let ((owrap (class-wrapper class)))
344 (sb-kernel:layout-class owrap))
345 ((*subtypep (class-of class)
346 *the-class-standard-class*)
347 (cond ((and *pcl-class-boot*
348 (eq (slot-value class 'name) *pcl-class-boot*))
349 (let ((found (cl:find-class (slot-value class 'name))))
350 (unless (sb-kernel:class-pcl-class found)
351 (setf (sb-kernel:class-pcl-class found) class))
352 (aver (eq (sb-kernel:class-pcl-class found) class))
355 (sb-kernel:make-standard-class :pcl-class class))))
357 (sb-kernel:make-random-pcl-class :pcl-class class))))))
359 (let* ((found (cl:find-class (slot-value class 'name)))
360 (layout (sb-kernel:class-layout found)))
361 (unless (sb-kernel:class-pcl-class found)
362 (setf (sb-kernel:class-pcl-class found) class))
363 (aver (eq (sb-kernel:class-pcl-class found) class))
367 (defconstant +first-wrapper-cache-number-index+ 0)
369 (declaim (inline next-wrapper-cache-number-index))
370 (defun next-wrapper-cache-number-index (field-number)
371 (and (< field-number #.(1- wrapper-cache-number-vector-length))
374 ;;; FIXME: Why are there two layers here, with one operator trivially
375 ;;; defined in terms of the other? It'd be nice either to have a
376 ;;; comment explaining why the separation is valuable, or to collapse
377 ;;; it into a single layer.
379 ;;; FIXME (?): These are logically inline functions, but they need to
380 ;;; be SETFable, and for now it seems not worth the trouble to DEFUN
381 ;;; both inline FOO and inline (SETF FOO) for each one instead of a
382 ;;; single macro. Perhaps the best thing would be to make them
383 ;;; immutable (since it seems sort of surprising and gross to be able
384 ;;; to modify hash values) so that they can become inline functions
385 ;;; with no muss or fuss. I (WHN) didn't do this only because I didn't
386 ;;; know whether any code anywhere depends on the values being
388 (defmacro cache-number-vector-ref (cnv n)
389 `(wrapper-cache-number-vector-ref ,cnv ,n))
390 (defmacro wrapper-cache-number-vector-ref (wrapper n)
391 `(sb-kernel:layout-clos-hash ,wrapper ,n))
393 (declaim (inline wrapper-class*))
394 (defun wrapper-class* (wrapper)
395 (or (wrapper-class wrapper)
396 (find-structure-class
397 (cl:class-name (sb-kernel:layout-class wrapper)))))
399 ;;; The wrapper cache machinery provides general mechanism for
400 ;;; trapping on the next access to any instance of a given class. This
401 ;;; mechanism is used to implement the updating of instances when the
402 ;;; class is redefined (MAKE-INSTANCES-OBSOLETE). The same mechanism
403 ;;; is also used to update generic function caches when there is a
404 ;;; change to the superclasses of a class.
406 ;;; Basically, a given wrapper can be valid or invalid. If it is
407 ;;; invalid, it means that any attempt to do a wrapper cache lookup
408 ;;; using the wrapper should trap. Also, methods on
409 ;;; SLOT-VALUE-USING-CLASS check the wrapper validity as well. This is
410 ;;; done by calling CHECK-WRAPPER-VALIDITY.
412 (declaim (inline invalid-wrapper-p))
413 (defun invalid-wrapper-p (wrapper)
414 (neq (wrapper-state wrapper) t))
416 (defvar *previous-nwrappers* (make-hash-table))
418 (defun invalidate-wrapper (owrapper state nwrapper)
421 (let ((new-previous ()))
422 ;; First off, a previous call to INVALIDATE-WRAPPER may have
423 ;; recorded OWRAPPER as an NWRAPPER to update to. Since
424 ;; OWRAPPER is about to be invalid, it no longer makes sense to
427 ;; We go back and change the previously invalidated wrappers so
428 ;; that they will now update directly to NWRAPPER. This
429 ;; corresponds to a kind of transitivity of wrapper updates.
430 (dolist (previous (gethash owrapper *previous-nwrappers*))
431 (when (eq state :obsolete)
432 (setf (car previous) :obsolete))
433 (setf (cadr previous) nwrapper)
434 (push previous new-previous))
436 (let ((ocnv (wrapper-cache-number-vector owrapper)))
437 (dotimes (i sb-kernel:layout-clos-hash-length)
438 (setf (cache-number-vector-ref ocnv i) 0)))
439 (push (setf (wrapper-state owrapper) (list state nwrapper))
442 (setf (gethash owrapper *previous-nwrappers*) ()
443 (gethash nwrapper *previous-nwrappers*) new-previous)))))
445 (defun check-wrapper-validity (instance)
446 (let* ((owrapper (wrapper-of instance)))
447 (if (not (invalid-wrapper-p owrapper))
449 (let* ((state (wrapper-state owrapper))
453 (flush-cache-trap owrapper (cadr state) instance))
455 (obsolete-instance-trap owrapper (cadr state) instance)))))
456 ;; This little bit of error checking is superfluous. It only
457 ;; checks to see whether the person who implemented the trap
458 ;; handling screwed up. Since that person is hacking
459 ;; internal PCL code, and is not a user, this should be
460 ;; needless. Also, since this directly slows down instance
461 ;; update and generic function cache refilling, feel free to
462 ;; take it out sometime soon.
464 ;; FIXME: We probably need to add a #+SB-PARANOID feature to
465 ;; make stuff like this optional. Until then, it stays in.
466 (cond ((neq nwrapper (wrapper-of instance))
467 (error "wrapper returned from trap not wrapper of instance"))
468 ((invalid-wrapper-p nwrapper)
469 (error "wrapper returned from trap invalid")))
472 (defvar *free-caches* nil)
474 (defun get-cache (nkeys valuep limit-fn nlines)
475 (let ((cache (or (sb-sys:without-interrupts (pop *free-caches*))
477 (declare (type cache cache))
478 (multiple-value-bind (cache-mask actual-size line-size nlines)
479 (compute-cache-parameters nkeys valuep nlines)
480 (setf (cache-nkeys cache) nkeys
481 (cache-valuep cache) valuep
482 (cache-nlines cache) nlines
483 (cache-field cache) +first-wrapper-cache-number-index+
484 (cache-limit-fn cache) limit-fn
485 (cache-mask cache) cache-mask
486 (cache-size cache) actual-size
487 (cache-line-size cache) line-size
488 (cache-max-location cache) (let ((line (1- nlines)))
491 (1+ (* line line-size))))
492 (cache-vector cache) (get-cache-vector actual-size)
493 (cache-overflow cache) nil)
496 (defun get-cache-from-cache (old-cache new-nlines
497 &optional (new-field +first-wrapper-cache-number-index+))
498 (let ((nkeys (cache-nkeys old-cache))
499 (valuep (cache-valuep old-cache))
500 (cache (or (sb-sys:without-interrupts (pop *free-caches*))
502 (declare (type cache cache))
503 (multiple-value-bind (cache-mask actual-size line-size nlines)
504 (if (= new-nlines (cache-nlines old-cache))
505 (values (cache-mask old-cache) (cache-size old-cache)
506 (cache-line-size old-cache) (cache-nlines old-cache))
507 (compute-cache-parameters nkeys valuep new-nlines))
508 (setf (cache-owner cache) (cache-owner old-cache)
509 (cache-nkeys cache) nkeys
510 (cache-valuep cache) valuep
511 (cache-nlines cache) nlines
512 (cache-field cache) new-field
513 (cache-limit-fn cache) (cache-limit-fn old-cache)
514 (cache-mask cache) cache-mask
515 (cache-size cache) actual-size
516 (cache-line-size cache) line-size
517 (cache-max-location cache) (let ((line (1- nlines)))
520 (1+ (* line line-size))))
521 (cache-vector cache) (get-cache-vector actual-size)
522 (cache-overflow cache) nil)
525 (defun copy-cache (old-cache)
526 (let* ((new-cache (copy-cache-internal old-cache))
527 (size (cache-size old-cache))
528 (old-vector (cache-vector old-cache))
529 (new-vector (get-cache-vector size)))
530 (declare (simple-vector old-vector new-vector))
531 (dotimes-fixnum (i size)
532 (setf (svref new-vector i) (svref old-vector i)))
533 (setf (cache-vector new-cache) new-vector)
536 (defun free-cache (cache)
537 (free-cache-vector (cache-vector cache))
538 (setf (cache-vector cache) #())
539 (setf (cache-owner cache) nil)
540 (push cache *free-caches*)
543 (defun compute-line-size (x)
544 (power-of-two-ceiling x))
546 (defun compute-cache-parameters (nkeys valuep nlines-or-cache-vector)
547 ;;(declare (values cache-mask actual-size line-size nlines))
548 (declare (fixnum nkeys))
550 (let* ((line-size (if valuep 2 1))
551 (cache-size (if (typep nlines-or-cache-vector 'fixnum)
555 (power-of-two-ceiling
556 nlines-or-cache-vector))))
557 (cache-vector-size nlines-or-cache-vector))))
558 (declare (fixnum line-size cache-size))
559 (values (logxor (the fixnum (1- cache-size)) (the fixnum (1- line-size)))
562 (the (values fixnum t) (floor cache-size line-size))))
563 (let* ((line-size (power-of-two-ceiling (if valuep (1+ nkeys) nkeys)))
564 (cache-size (if (typep nlines-or-cache-vector 'fixnum)
568 (power-of-two-ceiling
569 nlines-or-cache-vector))))
570 (1- (cache-vector-size nlines-or-cache-vector)))))
571 (declare (fixnum line-size cache-size))
572 (values (logxor (the fixnum (1- cache-size)) (the fixnum (1- line-size)))
573 (the fixnum (1+ cache-size))
575 (the (values fixnum t) (floor cache-size line-size))))))
577 ;;; the various implementations of computing a primary cache location from
578 ;;; wrappers. Because some implementations of this must run fast there are
579 ;;; several implementations of the same algorithm.
581 ;;; The algorithm is:
583 ;;; SUM over the wrapper cache numbers,
584 ;;; ENSURING that the result is a fixnum
585 ;;; MASK the result against the mask argument.
587 ;;; The basic functional version. This is used by the cache miss code to
588 ;;; compute the primary location of an entry.
589 (defun compute-primary-cache-location (field mask wrappers)
591 (declare (type field-type field) (fixnum mask))
592 (if (not (listp wrappers))
594 (the fixnum (wrapper-cache-number-vector-ref wrappers field)))
595 (let ((location 0) (i 0))
596 (declare (fixnum location i))
597 (dolist (wrapper wrappers)
598 ;; First add the cache number of this wrapper to location.
599 (let ((wrapper-cache-number (wrapper-cache-number-vector-ref wrapper
601 (declare (fixnum wrapper-cache-number))
602 (if (zerop wrapper-cache-number)
603 (return-from compute-primary-cache-location 0)
605 (the fixnum (+ location wrapper-cache-number)))))
606 ;; Then, if we are working with lots of wrappers, deal with
607 ;; the wrapper-cache-number-mask stuff.
608 (when (and (not (zerop i))
609 (zerop (mod i wrapper-cache-number-adds-ok)))
611 (logand location wrapper-cache-number-mask)))
613 (the fixnum (1+ (logand mask location))))))
615 ;;; This version is called on a cache line. It fetches the wrappers
616 ;;; from the cache line and determines the primary location. Various
617 ;;; parts of the cache filling code call this to determine whether it
618 ;;; is appropriate to displace a given cache entry.
620 ;;; If this comes across a wrapper whose CACHE-NO is 0, it returns the
621 ;;; symbol invalid to suggest to its caller that it would be provident
622 ;;; to blow away the cache line in question.
623 (defun compute-primary-cache-location-from-location (to-cache
626 (from-cache to-cache))
627 (declare (type cache to-cache from-cache) (fixnum from-location))
629 (cache-vector (cache-vector from-cache))
630 (field (cache-field to-cache))
631 (mask (cache-mask to-cache))
632 (nkeys (cache-nkeys to-cache)))
633 (declare (type field-type field) (fixnum result mask nkeys)
634 (simple-vector cache-vector))
635 (dotimes-fixnum (i nkeys)
636 (let* ((wrapper (cache-vector-ref cache-vector (+ i from-location)))
637 (wcn (wrapper-cache-number-vector-ref wrapper field)))
638 (declare (fixnum wcn))
639 (setq result (+ result wcn)))
640 (when (and (not (zerop i))
641 (zerop (mod i wrapper-cache-number-adds-ok)))
642 (setq result (logand result wrapper-cache-number-mask))))
645 (the fixnum (1+ (logand mask result))))))
647 ;;; NIL means nothing so far, no actual arg info has NILs
649 ;;; CLASS seen all sorts of metaclasses
650 ;;; (specifically, more than one of the next 4 values)
651 ;;; T means everything so far is the class T
652 ;;; STANDARD-CLASS seen only standard classes
653 ;;; BUILT-IN-CLASS seen only built in classes
654 ;;; STRUCTURE-CLASS seen only structure classes
655 (defun raise-metatype (metatype new-specializer)
656 (let ((slot (find-class 'slot-class))
657 (std (find-class 'std-class))
658 (standard (find-class 'standard-class))
659 (fsc (find-class 'funcallable-standard-class))
660 (structure (find-class 'structure-class))
661 (built-in (find-class 'built-in-class)))
662 (flet ((specializer->metatype (x)
663 (let ((meta-specializer
664 (if (eq *boot-state* 'complete)
665 (class-of (specializer-class x))
667 (cond ((eq x *the-class-t*) t)
668 ((*subtypep meta-specializer std)
670 ((*subtypep meta-specializer standard)
672 ((*subtypep meta-specializer fsc)
674 ((*subtypep meta-specializer structure)
676 ((*subtypep meta-specializer built-in)
678 ((*subtypep meta-specializer slot)
680 (t (error "PCL cannot handle the specializer ~S (meta-specializer ~S)."
682 meta-specializer))))))
683 ;; We implement the following table. The notation is
684 ;; that X and Y are distinct meta specializer names.
686 ;; NIL <anything> ===> <anything>
689 (let ((new-metatype (specializer->metatype new-specializer)))
690 (cond ((eq new-metatype 'slot-instance) 'class)
691 ((null metatype) new-metatype)
692 ((eq metatype new-metatype) new-metatype)
695 (defmacro with-dfun-wrappers ((args metatypes)
696 (dfun-wrappers invalid-wrapper-p
697 &optional wrappers classes types)
698 invalid-arguments-form
700 `(let* ((args-tail ,args) (,invalid-wrapper-p nil) (invalid-arguments-p nil)
701 (,dfun-wrappers nil) (dfun-wrappers-tail nil)
703 `((wrappers-rev nil) (types-rev nil) (classes-rev nil))))
704 (dolist (mt ,metatypes)
706 (setq invalid-arguments-p t)
708 (let* ((arg (pop args-tail))
711 `((class *the-class-t*)
714 (setq wrapper (wrapper-of arg))
715 (when (invalid-wrapper-p wrapper)
716 (setq ,invalid-wrapper-p t)
717 (setq wrapper (check-wrapper-validity arg)))
718 (cond ((null ,dfun-wrappers)
719 (setq ,dfun-wrappers wrapper))
720 ((not (consp ,dfun-wrappers))
721 (setq dfun-wrappers-tail (list wrapper))
722 (setq ,dfun-wrappers (cons ,dfun-wrappers dfun-wrappers-tail)))
724 (let ((new-dfun-wrappers-tail (list wrapper)))
725 (setf (cdr dfun-wrappers-tail) new-dfun-wrappers-tail)
726 (setf dfun-wrappers-tail new-dfun-wrappers-tail))))
728 `((setq class (wrapper-class* wrapper))
729 (setq type `(class-eq ,class)))))
731 `((push wrapper wrappers-rev)
732 (push class classes-rev)
733 (push type types-rev)))))
734 (if invalid-arguments-p
735 ,invalid-arguments-form
736 (let* (,@(when wrappers
737 `((,wrappers (nreverse wrappers-rev))
738 (,classes (nreverse classes-rev))
739 (,types (mapcar (lambda (class)
744 ;;;; some support stuff for getting a hold of symbols that we need when
745 ;;;; building the discriminator codes. It's OK for these to be interned
746 ;;;; symbols because we don't capture any user code in the scope in which
747 ;;;; these symbols are bound.
749 (defvar *dfun-arg-symbols* '(.ARG0. .ARG1. .ARG2. .ARG3.))
751 (defun dfun-arg-symbol (arg-number)
752 (or (nth arg-number (the list *dfun-arg-symbols*))
753 (intern (format nil ".ARG~A." arg-number) *pcl-package*)))
755 (defvar *slot-vector-symbols* '(.SLOTS0. .SLOTS1. .SLOTS2. .SLOTS3.))
757 (defun slot-vector-symbol (arg-number)
758 (or (nth arg-number (the list *slot-vector-symbols*))
759 (intern (format nil ".SLOTS~A." arg-number) *pcl-package*)))
761 ;; FIXME: There ought to be a good way to factor out the idiom:
763 ;; (dotimes (i (length metatypes))
764 ;; (push (dfun-arg-symbol i) lambda-list))
766 ;; used in the following four functions into common code that we can
767 ;; declare inline or something. --njf 2001-12-20
768 (defun make-dfun-lambda-list (metatypes applyp)
769 (let ((lambda-list nil))
770 (dotimes (i (length metatypes))
771 (push (dfun-arg-symbol i) lambda-list))
773 (push '&rest lambda-list)
774 (push '.dfun-rest-arg. lambda-list))
775 (nreverse lambda-list)))
777 (defun make-dlap-lambda-list (metatypes applyp)
778 (let ((lambda-list nil))
779 (dotimes (i (length metatypes))
780 (push (dfun-arg-symbol i) lambda-list))
781 ;; FIXME: This is translated directly from the old PCL code.
782 ;; It didn't have a (PUSH '.DFUN-REST-ARG. LAMBDA-LIST) or
783 ;; something similar, so we don't either. It's hard to see how
784 ;; this could be correct, since &REST wants an argument after
785 ;; it. This function works correctly because the caller
786 ;; magically tacks on something after &REST. The calling functions
787 ;; (in dlisp.lisp) should be fixed and this function rewritten.
790 (push '&rest lambda-list))
791 (nreverse lambda-list)))
793 ;; FIXME: The next two functions suffer from having a `.DFUN-REST-ARG.'
794 ;; in their lambda lists, but no corresponding `&REST' symbol. We assume
795 ;; this should be the case by analogy with the previous two functions.
796 ;; It works, and I don't know why. Check the calling functions and
797 ;; fix these too. --njf 2001-12-20
798 (defun make-emf-call (metatypes applyp fn-variable &optional emf-type)
800 (let ((required nil))
801 (dotimes (i (length metatypes))
802 (push (dfun-arg-symbol i) required))
803 (nreverse required))))
804 `(,(if (eq emf-type 'fast-method-call)
805 'invoke-effective-method-function-fast
806 'invoke-effective-method-function)
807 ,fn-variable ,applyp ,@required ,@(when applyp `(.dfun-rest-arg.)))))
809 (defun make-fast-method-call-lambda-list (metatypes applyp)
810 (let ((reversed-lambda-list nil))
811 (push '.pv-cell. reversed-lambda-list)
812 (push '.next-method-call. reversed-lambda-list)
813 (dotimes (i (length metatypes))
814 (push (dfun-arg-symbol i) reversed-lambda-list))
816 (push '.dfun-rest-arg. reversed-lambda-list))
817 (nreverse reversed-lambda-list)))
819 (defmacro with-local-cache-functions ((cache) &body body)
820 `(let ((.cache. ,cache))
821 (declare (type cache .cache.))
822 (labels ((cache () .cache.)
823 (nkeys () (cache-nkeys .cache.))
824 (line-size () (cache-line-size .cache.))
825 (vector () (cache-vector .cache.))
826 (valuep () (cache-valuep .cache.))
827 (nlines () (cache-nlines .cache.))
828 (max-location () (cache-max-location .cache.))
829 (limit-fn () (cache-limit-fn .cache.))
830 (size () (cache-size .cache.))
831 (mask () (cache-mask .cache.))
832 (field () (cache-field .cache.))
833 (overflow () (cache-overflow .cache.))
835 ;; Return T IFF this cache location is reserved. The
836 ;; only time this is true is for line number 0 of an
839 (line-reserved-p (line)
840 (declare (fixnum line))
844 (location-reserved-p (location)
845 (declare (fixnum location))
849 ;; Given a line number, return the cache location.
850 ;; This is the value that is the second argument to
851 ;; cache-vector-ref. Basically, this deals with the
852 ;; offset of nkeys>1 caches and multiplies by line
855 (line-location (line)
856 (declare (fixnum line))
857 (when (line-reserved-p line)
858 (error "line is reserved"))
860 (the fixnum (* line (line-size)))
861 (the fixnum (1+ (the fixnum (* line (line-size)))))))
863 ;; Given a cache location, return the line. This is
864 ;; the inverse of LINE-LOCATION.
866 (location-line (location)
867 (declare (fixnum location))
869 (floor location (line-size))
870 (floor (the fixnum (1- location)) (line-size))))
872 ;; Given a line number, return the wrappers stored at
873 ;; that line. As usual, if nkeys=1, this returns a
874 ;; single value. Only when nkeys>1 does it return a
875 ;; list. An error is signalled if the line is
878 (line-wrappers (line)
879 (declare (fixnum line))
880 (when (line-reserved-p line) (error "Line is reserved."))
881 (location-wrappers (line-location line)))
883 (location-wrappers (location) ; avoid multiplies caused by line-location
884 (declare (fixnum location))
886 (cache-vector-ref (vector) location)
887 (let ((list (make-list (nkeys)))
889 (declare (simple-vector vector))
890 (dotimes (i (nkeys) list)
893 (cache-vector-ref vector (+ location i)))))))
895 ;; Given a line number, return true IFF the line's
896 ;; wrappers are the same as wrappers.
898 (line-matches-wrappers-p (line wrappers)
899 (declare (fixnum line))
900 (and (not (line-reserved-p line))
901 (location-matches-wrappers-p (line-location line)
904 (location-matches-wrappers-p (loc wrappers) ; must not be reserved
905 (declare (fixnum loc))
906 (let ((cache-vector (vector)))
907 (declare (simple-vector cache-vector))
909 (eq wrappers (cache-vector-ref cache-vector loc))
910 (dotimes (i (nkeys) t)
912 (unless (eq (pop wrappers)
913 (cache-vector-ref cache-vector (+ loc i)))
916 ;; Given a line number, return the value stored at that line.
917 ;; If valuep is NIL, this returns NIL. As with line-wrappers,
918 ;; an error is signalled if the line is reserved.
921 (declare (fixnum line))
922 (when (line-reserved-p line) (error "Line is reserved."))
923 (location-value (line-location line)))
925 (location-value (loc)
926 (declare (fixnum loc))
928 (cache-vector-ref (vector) (+ loc (nkeys)))))
930 ;; Given a line number, return true IFF that line has data in
931 ;; it. The state of the wrappers stored in the line is not
932 ;; checked. An error is signalled if line is reserved.
934 (when (line-reserved-p line) (error "Line is reserved."))
935 (not (null (cache-vector-ref (vector) (line-location line)))))
937 ;; Given a line number, return true IFF the line is full and
938 ;; there are no invalid wrappers in the line, and the line's
939 ;; wrappers are different from wrappers.
940 ;; An error is signalled if the line is reserved.
942 (line-valid-p (line wrappers)
943 (declare (fixnum line))
944 (when (line-reserved-p line) (error "Line is reserved."))
945 (location-valid-p (line-location line) wrappers))
947 (location-valid-p (loc wrappers)
948 (declare (fixnum loc))
949 (let ((cache-vector (vector))
950 (wrappers-mismatch-p (null wrappers)))
951 (declare (simple-vector cache-vector))
952 (dotimes (i (nkeys) wrappers-mismatch-p)
954 (let ((wrapper (cache-vector-ref cache-vector (+ loc i))))
955 (when (or (null wrapper)
956 (invalid-wrapper-p wrapper))
958 (unless (and wrappers
963 (setq wrappers-mismatch-p t))))))
965 ;; How many unreserved lines separate line-1 and line-2.
967 (line-separation (line-1 line-2)
968 (declare (fixnum line-1 line-2))
969 (let ((diff (the fixnum (- line-2 line-1))))
970 (declare (fixnum diff))
972 (setq diff (+ diff (nlines)))
973 (when (line-reserved-p 0)
974 (setq diff (1- diff))))
977 ;; Given a cache line, get the next cache line. This will not
978 ;; return a reserved line.
981 (declare (fixnum line))
982 (if (= line (the fixnum (1- (nlines))))
983 (if (line-reserved-p 0) 1 0)
984 (the fixnum (1+ line))))
987 (declare (fixnum loc))
988 (if (= loc (max-location))
992 (the fixnum (+ loc (line-size)))))
994 ;; Given a line which has a valid entry in it, this
995 ;; will return the primary cache line of the wrappers
996 ;; in that line. We just call
997 ;; COMPUTE-PRIMARY-CACHE-LOCATION-FROM-LOCATION, this
998 ;; is an easier packaging up of the call to it.
1000 (line-primary (line)
1001 (declare (fixnum line))
1002 (location-line (line-primary-location line)))
1004 (line-primary-location (line)
1005 (declare (fixnum line))
1006 (compute-primary-cache-location-from-location
1007 (cache) (line-location line))))
1008 (declare (ignorable #'cache #'nkeys #'line-size #'vector #'valuep
1009 #'nlines #'max-location #'limit-fn #'size
1010 #'mask #'field #'overflow #'line-reserved-p
1011 #'location-reserved-p #'line-location
1012 #'location-line #'line-wrappers #'location-wrappers
1013 #'line-matches-wrappers-p
1014 #'location-matches-wrappers-p
1015 #'line-value #'location-value #'line-full-p
1016 #'line-valid-p #'location-valid-p
1017 #'line-separation #'next-line #'next-location
1018 #'line-primary #'line-primary-location))
1021 ;;; Here is where we actually fill, recache and expand caches.
1023 ;;; The functions FILL-CACHE and PROBE-CACHE are the ONLY external
1024 ;;; entrypoints into this code.
1026 ;;; FILL-CACHE returns 1 value: a new cache
1028 ;;; a wrapper field number
1031 ;;; an absolute cache size (the size of the actual vector)
1032 ;;; It tries to re-adjust the cache every time it makes a new fill.
1033 ;;; The intuition here is that we want uniformity in the number of
1034 ;;; probes needed to find an entry. Furthermore, adjusting has the
1035 ;;; nice property of throwing out any entries that are invalid.
1036 (defvar *cache-expand-threshold* 1.25)
1038 (defun fill-cache (cache wrappers value &optional free-cache-p)
1040 ;; FILL-CACHE won't return if WRAPPERS is nil, might as well check..
1042 (error "fill-cache: WRAPPERS arg is NIL!"))
1044 (or (fill-cache-p nil cache wrappers value)
1045 (and (< (ceiling (* (cache-count cache) 1.25))
1046 (if (= (cache-nkeys cache) 1)
1047 (1- (cache-nlines cache))
1048 (cache-nlines cache)))
1049 (adjust-cache cache wrappers value free-cache-p))
1050 (expand-cache cache wrappers value free-cache-p)))
1052 (defvar *check-cache-p* nil)
1054 (defmacro maybe-check-cache (cache)
1056 (when *check-cache-p*
1057 (check-cache ,cache))
1060 (defun check-cache (cache)
1061 (with-local-cache-functions (cache)
1062 (let ((location (if (= (nkeys) 1) 0 1))
1063 (limit (funcall (limit-fn) (nlines))))
1064 (dotimes-fixnum (i (nlines) cache)
1065 (when (and (not (location-reserved-p location))
1067 (let* ((home-loc (compute-primary-cache-location-from-location
1069 (home (location-line (if (location-reserved-p home-loc)
1070 (next-location home-loc)
1072 (sep (when home (line-separation home i))))
1073 (when (and sep (> sep limit))
1074 (error "bad cache ~S ~@
1075 value at location ~W: ~W lines from its home. The limit is ~W."
1076 cache location sep limit))))
1077 (setq location (next-location location))))))
1079 (defun probe-cache (cache wrappers &optional default limit-fn)
1080 ;;(declare (values value))
1082 ;; FIXME: This and another earlier test on a WRAPPERS arg can
1083 ;; be compact assertoids.
1084 (error "WRAPPERS arg is NIL!"))
1085 (with-local-cache-functions (cache)
1086 (let* ((location (compute-primary-cache-location (field) (mask) wrappers))
1087 (limit (funcall (or limit-fn (limit-fn)) (nlines))))
1088 (declare (fixnum location limit))
1089 (when (location-reserved-p location)
1090 (setq location (next-location location)))
1091 (dotimes-fixnum (i (1+ limit))
1092 (when (location-matches-wrappers-p location wrappers)
1093 (return-from probe-cache (or (not (valuep))
1094 (location-value location))))
1095 (setq location (next-location location)))
1096 (dolist (entry (overflow))
1097 (when (equal (car entry) wrappers)
1098 (return-from probe-cache (or (not (valuep))
1102 (defun map-cache (function cache &optional set-p)
1103 (with-local-cache-functions (cache)
1104 (let ((set-p (and set-p (valuep))))
1105 (dotimes-fixnum (i (nlines) cache)
1106 (unless (or (line-reserved-p i) (not (line-valid-p i nil)))
1107 (let ((value (funcall function (line-wrappers i) (line-value i))))
1109 (setf (cache-vector-ref (vector) (+ (line-location i) (nkeys)))
1111 (dolist (entry (overflow))
1112 (let ((value (funcall function (car entry) (cdr entry))))
1114 (setf (cdr entry) value))))))
1117 (defun cache-count (cache)
1118 (with-local-cache-functions (cache)
1120 (declare (fixnum count))
1121 (dotimes-fixnum (i (nlines) count)
1122 (unless (line-reserved-p i)
1123 (when (line-full-p i)
1126 (defun entry-in-cache-p (cache wrappers value)
1127 (declare (ignore value))
1128 (with-local-cache-functions (cache)
1129 (dotimes-fixnum (i (nlines))
1130 (unless (line-reserved-p i)
1131 (when (equal (line-wrappers i) wrappers)
1134 ;;; returns T or NIL
1135 (defun fill-cache-p (forcep cache wrappers value)
1136 (with-local-cache-functions (cache)
1137 (let* ((location (compute-primary-cache-location (field) (mask) wrappers))
1138 (primary (location-line location)))
1139 (declare (fixnum location primary))
1140 (multiple-value-bind (free emptyp)
1141 (find-free-cache-line primary cache wrappers)
1142 (when (or forcep emptyp)
1144 (push (cons (line-wrappers free) (line-value free))
1145 (cache-overflow cache)))
1146 ;;(fill-line free wrappers value)
1148 (declare (fixnum line))
1149 (when (line-reserved-p line)
1150 (error "attempt to fill a reserved line"))
1151 (let ((loc (line-location line))
1152 (cache-vector (vector)))
1153 (declare (fixnum loc) (simple-vector cache-vector))
1154 (cond ((= (nkeys) 1)
1155 (setf (cache-vector-ref cache-vector loc) wrappers)
1157 (setf (cache-vector-ref cache-vector (1+ loc)) value)))
1160 (declare (fixnum i))
1161 (dolist (w wrappers)
1162 (setf (cache-vector-ref cache-vector (+ loc i)) w)
1163 (setq i (the fixnum (1+ i)))))
1165 (setf (cache-vector-ref cache-vector (+ loc (nkeys)))
1167 (maybe-check-cache cache))))))))
1169 (defun fill-cache-from-cache-p (forcep cache from-cache from-line)
1170 (declare (fixnum from-line))
1171 (with-local-cache-functions (cache)
1172 (let ((primary (location-line
1173 (compute-primary-cache-location-from-location
1174 cache (line-location from-line) from-cache))))
1175 (declare (fixnum primary))
1176 (multiple-value-bind (free emptyp)
1177 (find-free-cache-line primary cache)
1178 (when (or forcep emptyp)
1180 (push (cons (line-wrappers free) (line-value free))
1181 (cache-overflow cache)))
1182 ;;(transfer-line from-cache-vector from-line cache-vector free)
1183 (let ((from-cache-vector (cache-vector from-cache))
1184 (to-cache-vector (vector))
1186 (declare (fixnum to-line))
1187 (if (line-reserved-p to-line)
1188 (error "transferring something into a reserved cache line")
1189 (let ((from-loc (line-location from-line))
1190 (to-loc (line-location to-line)))
1191 (declare (fixnum from-loc to-loc))
1192 (modify-cache to-cache-vector
1193 (dotimes-fixnum (i (line-size))
1194 (setf (cache-vector-ref to-cache-vector
1196 (cache-vector-ref from-cache-vector
1197 (+ from-loc i)))))))
1198 (maybe-check-cache cache)))))))
1200 ;;; Returns NIL or (values <field> <cache-vector>)
1202 ;;; This is only called when it isn't possible to put the entry in the
1203 ;;; cache the easy way. That is, this function assumes that
1204 ;;; FILL-CACHE-P has been called as returned NIL.
1206 ;;; If this returns NIL, it means that it wasn't possible to find a
1207 ;;; wrapper field for which all of the entries could be put in the
1208 ;;; cache (within the limit).
1209 (defun adjust-cache (cache wrappers value free-old-cache-p)
1210 (with-local-cache-functions (cache)
1211 (let ((ncache (get-cache-from-cache cache (nlines) (field))))
1212 (do ((nfield (cache-field ncache) (next-wrapper-cache-number-index nfield)))
1213 ((null nfield) (free-cache ncache) nil)
1214 (setf (cache-field ncache) nfield)
1215 (labels ((try-one-fill-from-line (line)
1216 (fill-cache-from-cache-p nil ncache cache line))
1217 (try-one-fill (wrappers value)
1218 (fill-cache-p nil ncache wrappers value)))
1219 (if (and (dotimes-fixnum (i (nlines) t)
1220 (when (and (null (line-reserved-p i))
1221 (line-valid-p i wrappers))
1222 (unless (try-one-fill-from-line i) (return nil))))
1223 (dolist (wrappers+value (cache-overflow cache) t)
1224 (unless (try-one-fill (car wrappers+value) (cdr wrappers+value))
1226 (try-one-fill wrappers value))
1227 (progn (when free-old-cache-p (free-cache cache))
1228 (return (maybe-check-cache ncache)))
1229 (flush-cache-vector-internal (cache-vector ncache))))))))
1231 ;;; returns: (values <cache>)
1232 (defun expand-cache (cache wrappers value free-old-cache-p)
1233 ;;(declare (values cache))
1234 (with-local-cache-functions (cache)
1235 (let ((ncache (get-cache-from-cache cache (* (nlines) 2))))
1236 (labels ((do-one-fill-from-line (line)
1237 (unless (fill-cache-from-cache-p nil ncache cache line)
1238 (do-one-fill (line-wrappers line) (line-value line))))
1239 (do-one-fill (wrappers value)
1240 (setq ncache (or (adjust-cache ncache wrappers value t)
1241 (fill-cache-p t ncache wrappers value))))
1242 (try-one-fill (wrappers value)
1243 (fill-cache-p nil ncache wrappers value)))
1244 (dotimes-fixnum (i (nlines))
1245 (when (and (null (line-reserved-p i))
1246 (line-valid-p i wrappers))
1247 (do-one-fill-from-line i)))
1248 (dolist (wrappers+value (cache-overflow cache))
1249 (unless (try-one-fill (car wrappers+value) (cdr wrappers+value))
1250 (do-one-fill (car wrappers+value) (cdr wrappers+value))))
1251 (unless (try-one-fill wrappers value)
1252 (do-one-fill wrappers value))
1253 (when free-old-cache-p (free-cache cache))
1254 (maybe-check-cache ncache)))))
1256 ;;; This is the heart of the cache filling mechanism. It implements
1257 ;;; the decisions about where entries are placed.
1259 ;;; Find a line in the cache at which a new entry can be inserted.
1262 ;;; <empty?> is <line> in fact empty?
1263 (defun find-free-cache-line (primary cache &optional wrappers)
1264 ;;(declare (values line empty?))
1265 (declare (fixnum primary))
1266 (with-local-cache-functions (cache)
1267 (when (line-reserved-p primary) (setq primary (next-line primary)))
1268 (let ((limit (funcall (limit-fn) (nlines)))
1271 (p primary) (s primary))
1272 (declare (fixnum p s limit))
1275 ;; Try to find a free line starting at <s>. <p> is the
1276 ;; primary line of the entry we are finding a free
1277 ;; line for, it is used to compute the separations.
1278 (do* ((line s (next-line line))
1279 (nsep (line-separation p s) (1+ nsep)))
1281 (declare (fixnum line nsep))
1282 (when (null (line-valid-p line wrappers)) ;If this line is empty or
1283 (push line lines) ;invalid, just use it.
1284 (return-from find-free))
1285 (when (and wrappedp (>= line primary))
1286 ;; have gone all the way around the cache, time to quit
1287 (return-from find-free-cache-line (values primary nil)))
1288 (let ((osep (line-separation (line-primary line) line)))
1289 (when (>= osep limit)
1290 (return-from find-free-cache-line (values primary nil)))
1291 (when (cond ((= nsep limit) t)
1292 ((= nsep osep) (zerop (random 2)))
1295 ;; See whether we can displace what is in this line so that we
1296 ;; can use the line.
1297 (when (= line (the fixnum (1- (nlines)))) (setq wrappedp t))
1298 (setq p (line-primary line))
1299 (setq s (next-line line))
1302 (when (= line (the fixnum (1- (nlines)))) (setq wrappedp t)))))
1303 ;; Do all the displacing.
1305 (when (null (cdr lines)) (return nil))
1306 (let ((dline (pop lines))
1308 (declare (fixnum dline line))
1309 ;;Copy from line to dline (dline is known to be free).
1310 (let ((from-loc (line-location line))
1311 (to-loc (line-location dline))
1312 (cache-vector (vector)))
1313 (declare (fixnum from-loc to-loc) (simple-vector cache-vector))
1314 (modify-cache cache-vector
1315 (dotimes-fixnum (i (line-size))
1316 (setf (cache-vector-ref cache-vector
1318 (cache-vector-ref cache-vector
1320 (setf (cache-vector-ref cache-vector
1323 (values (car lines) t))))
1325 (defun default-limit-fn (nlines)
1331 (defvar *empty-cache* (make-cache)) ; for defstruct slot initial value forms