1 ;;;; This file contains the code that finds the initial components and
2 ;;;; DFO, and recomputes the DFO if it is invalidated.
4 ;;;; This software is part of the SBCL system. See the README file for
7 ;;;; This software is derived from the CMU CL system, which was
8 ;;;; written at Carnegie Mellon University and released into the
9 ;;;; public domain. The software is in the public domain and is
10 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
11 ;;;; files for more information.
15 ;;; Find the DFO for a component, deleting any unreached blocks and
16 ;;; merging any other components we reach. We repeatedly iterate over
17 ;;; the entry points, since new ones may show up during the walk.
18 (declaim (ftype (function (component) (values)) find-dfo))
19 (defun find-dfo (component)
20 (clear-flags component)
21 (setf (component-reanalyze component) nil)
22 (let ((head (component-head component)))
24 ((dolist (ep (block-succ head) t)
25 (unless (block-flag ep)
26 (find-dfo-aux ep head component)
29 (declare (fixnum num))
30 (do-blocks-backwards (block component :both)
31 (if (block-flag block)
32 (setf (block-number block) (incf num))
33 (setf (block-delete-p block) t)))
34 (do-blocks (block component)
35 (unless (block-flag block)
36 (delete-block block))))
39 ;;; Move all the code and entry points from OLD to NEW. The code in
40 ;;; OLD is inserted at the head of NEW. This is also called during LET
41 ;;; conversion when we are about in insert the body of a LET in a
42 ;;; different component. [A local call can be to a different component
43 ;;; before FIND-INITIAL-DFO runs.]
44 (declaim (ftype (function (component component) (values)) join-components))
45 (defun join-components (new old)
46 (aver (eq (component-kind new) (component-kind old)))
47 (let ((old-head (component-head old))
48 (old-tail (component-tail old))
49 (head (component-head new))
50 (tail (component-tail new)))
52 (do-blocks (block old)
53 (setf (block-flag block) nil)
54 (setf (block-component block) new))
56 (let ((old-next (block-next old-head))
57 (old-last (block-prev old-tail))
58 (next (block-next head)))
59 (unless (eq old-next old-tail)
60 (setf (block-next head) old-next)
61 (setf (block-prev old-next) head)
63 (setf (block-prev next) old-last)
64 (setf (block-next old-last) next))
66 (setf (block-next old-head) old-tail)
67 (setf (block-prev old-tail) old-head))
69 (setf (component-lambdas new)
70 (nconc (component-lambdas old) (component-lambdas new)))
71 (setf (component-lambdas old) nil)
72 (setf (component-new-funs new) (nconc (component-new-funs old)
73 (component-new-funs new))
74 (component-new-funs old) nil)
76 (dolist (xp (block-pred old-tail))
77 (unlink-blocks xp old-tail)
78 (link-blocks xp tail))
79 (dolist (ep (block-succ old-head))
80 (unlink-blocks old-head ep)
81 (link-blocks head ep)))
84 ;;; Do a depth-first walk from BLOCK, inserting ourself in the DFO
85 ;;; after HEAD. If we somehow find ourselves in another component,
86 ;;; then we join that component to our component.
87 (declaim (ftype (function (cblock cblock component) (values)) find-dfo-aux))
88 (defun find-dfo-aux (block head component)
89 (unless (eq (block-component block) component)
90 (join-components component (block-component block)))
91 (unless (block-flag block)
92 (setf (block-flag block) t)
93 (dolist (succ (block-succ block))
94 (find-dfo-aux succ head component))
95 (remove-from-dfo block)
96 (add-to-dfo block head))
99 ;;; This function is called on each block by FIND-INITIAL-DFO-AUX
100 ;;; before it walks the successors. It looks at the home CLAMBDA's
101 ;;; BIND block to see whether that block is in some other component:
102 ;;; -- If the block is in the initial component, then do
103 ;;; DFO-WALK-DEPENDENCY-GRAPH on the home function to move it
105 ;;; -- If the block is in some other component, join COMPONENT into
106 ;;; it and return that component.
107 ;;; -- If the home function is deleted, do nothing. BLOCK must
108 ;;; eventually be discovered to be unreachable as well. This can
109 ;;; happen when we have a NLX into a function with no references.
110 ;;; The escape function still has refs (in the deleted function).
112 ;;; This ensures that all the blocks in a given environment will be in
113 ;;; the same component, even when they might not seem reachable from
114 ;;; the environment entry. Consider the case of code that is only
115 ;;; reachable from a non-local exit.
116 (defun scavenge-home-dependency-graph (block component)
117 (declare (type cblock block) (type component component))
118 (let ((home-lambda (block-home-lambda block)))
119 (if (eq (functional-kind home-lambda) :deleted)
121 (let ((home-component (lambda-component home-lambda)))
122 (cond ((eq (component-kind home-component) :initial)
123 (dfo-scavenge-dependency-graph home-lambda component))
124 ((eq home-component component)
127 (join-components home-component component)
130 ;;; This is somewhat similar to FIND-DFO-AUX, except that it merges
131 ;;; the current component with any strange component, rather than the
132 ;;; other way around. This is more efficient in the common case where
133 ;;; the current component doesn't have much stuff in it.
135 ;;; We return the current component as a result, allowing the caller
136 ;;; to detect when the old current component has been merged with
139 ;;; We walk blocks in initial components as though they were already
140 ;;; in the current component, moving them to the current component in
141 ;;; the process. The blocks are inserted at the head of the current
143 (defun find-initial-dfo-aux (block component)
144 (declare (type cblock block) (type component component))
145 (let ((this (block-component block)))
147 ((not (or (eq this component)
148 (eq (component-kind this) :initial)))
149 (join-components this component)
151 ((block-flag block) component)
153 (setf (block-flag block) t)
154 (let ((current (scavenge-home-dependency-graph block component)))
155 (dolist (succ (block-succ block))
156 (setq current (find-initial-dfo-aux succ current)))
157 (remove-from-dfo block)
158 (add-to-dfo block (component-head current))
161 ;;; Return a list of all the home lambdas that reference FUN (may
162 ;;; contain duplications).
164 ;;; References to functions which local call analysis could not (or
165 ;;; were chosen not) to local call convert will appear as references
166 ;;; to XEP lambdas. We can ignore references to XEPs that appear in
167 ;;; :TOPLEVEL components, since environment analysis goes to special
168 ;;; effort to allow closing over of values from a separate top level
169 ;;; component. (And now that HAS-EXTERNAL-REFERENCES-P-ness
170 ;;; generalizes :TOPLEVEL-ness, we ignore those too.) All other
171 ;;; references must cause components to be joined.
173 ;;; References in deleted functions are also ignored, since this code
174 ;;; will be deleted eventually.
175 (defun find-reference-funs (fun)
177 (dolist (ref (leaf-refs fun))
178 (let* ((home (node-home-lambda ref))
179 (home-kind (functional-kind home))
180 (home-externally-visible-p
181 (or (eq home-kind :toplevel)
182 (functional-has-external-references-p home))))
183 (unless (or (and home-externally-visible-p
184 (eq (functional-kind fun) :external))
185 (eq home-kind :deleted))
189 ;;; If CLAMBDA is not already in COMPONENT, just return that
190 ;;; component. Otherwise, move the code for CLAMBDA and all lambdas it
191 ;;; physically depends on (either because of calls or because of
192 ;;; closure relationships) into COMPONENT, or possibly into another
193 ;;; COMPONENT that we find to be related. Return whatever COMPONENT we
194 ;;; actually merged into.
196 ;;; (Note: The analogous CMU CL code only scavenged call-based
197 ;;; dependencies, not closure dependencies. That seems to've been by
198 ;;; oversight, not by design, as per the bug reported by WHN on
199 ;;; cmucl-imp ca. 2001-11-29 and explained by DTC shortly after.)
201 ;;; FIXME: Very likely we should be scavenging NLX-based dependencies
202 ;;; here too. OTOH, there's a lot of global weirdness in NLX handling,
203 ;;; so it might be taken care of some other way that I haven't figured
204 ;;; out yet. Perhaps the best way to address this would be to try to
205 ;;; construct a NLX-based test case which fails in the same way as the
206 ;;; closure-based test case on cmucl-imp 2001-11-29.)
208 ;;; If the function is in an initial component, then we move its head
209 ;;; and tail to COMPONENT and add it to COMPONENT's lambdas. It is
210 ;;; harmless to move the tail (even though the return might be
211 ;;; unreachable) because if the return is unreachable it (and its
212 ;;; successor link) will be deleted in the post-deletion pass.
214 ;;; We then do a FIND-DFO-AUX starting at the head of CLAMBDA. If this
215 ;;; flow-graph walk encounters another component (which can only
216 ;;; happen due to a non-local exit), then we move code into that
217 ;;; component instead. We then recurse on all functions called from
218 ;;; CLAMBDA, moving code into whichever component the preceding call
221 ;;; If CLAMBDA is in the initial component, but the BLOCK-FLAG is set
222 ;;; in the bind block, then we just return COMPONENT, since we must
223 ;;; have already reached this function in the current walk (or the
224 ;;; component would have been changed).
226 ;;; If the function is an XEP, then we also walk all functions that
227 ;;; contain references to the XEP. This is done so that environment
228 ;;; analysis doesn't need to cross component boundaries. This also
229 ;;; ensures that conversion of a full call to a local call won't
230 ;;; result in a need to join components, since the components will
232 (defun dfo-scavenge-dependency-graph (clambda component)
233 (declare (type clambda clambda) (type component component))
234 (assert (not (eql (lambda-kind clambda) :deleted)))
235 (let* ((bind-block (node-block (lambda-bind clambda)))
236 (old-lambda-component (block-component bind-block))
237 (return (lambda-return clambda)))
239 ((eq old-lambda-component component)
241 ((not (eq (component-kind old-lambda-component) :initial))
242 (join-components old-lambda-component component)
243 old-lambda-component)
244 ((block-flag bind-block)
247 (push clambda (component-lambdas component))
248 (setf (component-lambdas old-lambda-component)
249 (delete clambda (component-lambdas old-lambda-component)))
250 (link-blocks (component-head component) bind-block)
251 (unlink-blocks (component-head old-lambda-component) bind-block)
253 (let ((return-block (node-block return)))
254 (link-blocks return-block (component-tail component))
255 (unlink-blocks return-block (component-tail old-lambda-component))))
256 (let ((res (find-initial-dfo-aux bind-block component)))
257 (declare (type component res))
258 ;; Scavenge call relationships.
259 (let ((calls (if (eq (lambda-kind clambda) :external)
260 (append (find-reference-funs clambda)
261 (lambda-calls clambda))
262 (lambda-calls clambda))))
264 (let ((call-home (lambda-home call)))
265 (setf res (dfo-scavenge-dependency-graph call-home res)))))
266 ;; Scavenge closure-over relationships: if FUN refers to a
267 ;; variable whose home lambda is not FUN, then the home lambda
268 ;; should be in the same component as FUN. (sbcl-0.6.13, and
269 ;; CMU CL, didn't do this, leading to the occasional failure
270 ;; when physenv analysis, which is local to each component,
271 ;; would bogusly conclude that a closed-over variable was
272 ;; unused and thus delete it. See e.g. cmucl-imp 2001-11-29.)
273 (dolist (var (lambda-refers-to-vars clambda))
274 (unless (null (lambda-var-refs var)) ; i.e. unless deleted
275 (let ((var-home-home (lambda-home (lambda-var-home var))))
276 (unless (eql (lambda-kind var-home-home) :deleted)
278 (dfo-scavenge-dependency-graph var-home-home res))))))
282 ;;; Return true if CLAMBDA either is an XEP or has EXITS to some of
284 (defun has-xep-or-nlx (clambda)
285 (declare (type clambda clambda))
286 (or (eq (functional-kind clambda) :external)
287 (let ((entries (lambda-entries clambda)))
289 (find-if #'entry-exits entries)))))
291 ;;; Compute the result of FIND-INITIAL-DFO given the list of all
292 ;;; resulting components. Components with a :TOPLEVEL lambda, but no
293 ;;; normal XEPs or potential non-local exits are marked as :TOPLEVEL.
294 ;;; If there is a :TOPLEVEL lambda, and also a normal XEP, then we
295 ;;; treat the component as normal, but also return such components in
296 ;;; a list as the third value. Components with no entry of any sort
298 (defun separate-toplevelish-components (components)
299 (declare (list components))
303 (dolist (component components)
304 (unless (eq (block-next (component-head component))
305 (component-tail component))
306 (let* ((funs (component-lambdas component))
307 (has-top (find :toplevel funs :key #'functional-kind))
308 (has-external-references
309 (some #'functional-has-external-references-p funs)))
310 (cond (;; The FUNCTIONAL-HAS-EXTERNAL-REFERENCES-P concept
311 ;; is newer than the rest of this function, and
312 ;; doesn't really seem to fit into its mindset. Here
313 ;; we mark components which contain such FUNCTIONs
314 ;; them as :COMPLEX-TOPLEVEL, since they do get
315 ;; executed at run time, and since it's not valid to
316 ;; delete them just because they don't have any
317 ;; references from pure :TOPLEVEL components. -- WHN
318 has-external-references
319 (setf (component-kind component) :complex-toplevel)
321 (real-top component))
322 ((or (some #'has-xep-or-nlx funs)
323 (and has-top (rest funs)))
324 (setf (component-name component)
325 (find-component-name component))
328 (setf (component-kind component) :complex-toplevel)
329 (real-top component)))
331 (setf (component-kind component) :toplevel)
332 (setf (component-name component) "top level form")
335 (delete-component component))))))
337 (values (real) (top) (real-top))))
339 ;; COMPONENTs want strings for names, LEAF-DEBUG-NAMEs mightn't be
341 (defun component-name-from-functional-debug-name (functional)
342 (declare (type functional functional))
343 (let ((leaf-debug-name (leaf-debug-name functional)))
345 (if (stringp leaf-debug-name)
347 (debug-namify "function ~S" leaf-debug-name)))))
349 ;;; Given a list of top level lambdas, return
350 ;;; (VALUES NONTOP-COMPONENTS TOP-COMPONENTS HAIRY-TOP-COMPONENTS).
351 ;;; Each of the three values returned is a list of COMPONENTs:
352 ;;; NONTOP-COMPONENTS = non-top-level-ish COMPONENTs;
353 ;;; TOP-COMPONENTS = top-level-ish COMPONENTs;
354 ;;; HAIRY-TOP-COMPONENTS = a subset of NONTOP-COMPONENTS, those
355 ;;; elements which include a top-level-ish lambda.
357 ;;; We assign the DFO for each component, and delete any unreachable
358 ;;; blocks. We assume that the FLAGS have already been cleared.
359 (defun find-initial-dfo (toplevel-lambdas)
360 (declare (list toplevel-lambdas))
361 (collect ((components))
362 ;; We iterate over the lambdas in each initial component, trying
363 ;; to put each function in its own component, but joining it to
364 ;; an existing component if we find that there are references
365 ;; between them. Any code that is left in an initial component
366 ;; must be unreachable, so we can delete it. Stray links to the
367 ;; initial component tail (due NIL function terminated blocks)
368 ;; are moved to the appropriate new component tail.
369 (dolist (toplevel-lambda toplevel-lambdas)
370 (let* ((block (lambda-block toplevel-lambda))
371 (old-component (block-component block))
372 (old-component-lambdas (component-lambdas old-component))
374 (aver (member toplevel-lambda old-component-lambdas))
375 (dolist (component-lambda old-component-lambdas)
376 (aver (member (functional-kind component-lambda)
377 '(:optional :external :toplevel nil :escape
379 (unless new-component
380 (setf new-component (make-empty-component))
381 (setf (component-name new-component)
382 ;; This isn't necessarily an ideal name for the
383 ;; component, since it might end up with multiple
384 ;; lambdas in it, not just this one, but it does
385 ;; seem a better name than just "<unknown>".
386 (component-name-from-functional-debug-name
388 (let ((res (dfo-scavenge-dependency-graph component-lambda
390 (when (eq res new-component)
391 (aver (not (position new-component (components))))
392 (components new-component)
393 (setq new-component nil))))
394 (when (eq (component-kind old-component) :initial)
395 (aver (null (component-lambdas old-component)))
396 (let ((tail (component-tail old-component)))
397 (dolist (pred (block-pred tail))
398 (let ((pred-component (block-component pred)))
399 (unless (eq pred-component old-component)
400 (unlink-blocks pred tail)
401 (link-blocks pred (component-tail pred-component))))))
402 (delete-component old-component))))
404 ;; When we are done, we assign DFNs.
405 (dolist (component (components))
407 (declare (fixnum num))
408 (do-blocks-backwards (block component :both)
409 (setf (block-number block) (incf num)))))
411 ;; Pull out top-level-ish code.
412 (separate-toplevelish-components (components))))
414 ;;; Insert the code in LAMBDA at the end of RESULT-LAMBDA.
415 (defun merge-1-toplevel-lambda (result-lambda lambda)
416 (declare (type clambda result-lambda lambda))
418 ;; Delete the lambda, and combine the LETs and entries.
419 (setf (functional-kind lambda) :deleted)
420 (dolist (let (lambda-lets lambda))
421 (setf (lambda-home let) result-lambda)
422 (setf (lambda-physenv let) (lambda-physenv result-lambda))
423 (push let (lambda-lets result-lambda)))
424 (setf (lambda-entries result-lambda)
425 (nconc (lambda-entries result-lambda)
426 (lambda-entries lambda)))
428 (let* ((bind (lambda-bind lambda))
429 (bind-block (node-block bind))
430 (component (block-component bind-block))
431 (result-component (lambda-component result-lambda))
432 (result-return-block (node-block (lambda-return result-lambda))))
434 ;; Move blocks into the new COMPONENT, and move any nodes directly
435 ;; in the old LAMBDA into the new one (with LETs implicitly moved
436 ;; by changing their home.)
437 (do-blocks (block component)
438 (do-nodes (node cont block)
439 (let ((lexenv (node-lexenv node)))
440 (when (eq (lexenv-lambda lexenv) lambda)
441 (setf (lexenv-lambda lexenv) result-lambda))))
442 (setf (block-component block) result-component))
444 ;; Splice the blocks into the new DFO, and unlink them from the
445 ;; old component head and tail. Non-return blocks that jump to the
446 ;; tail (NIL-returning calls) are switched to go to the new tail.
447 (let* ((head (component-head component))
448 (first (block-next head))
449 (tail (component-tail component))
450 (last (block-prev tail))
451 (prev (block-prev result-return-block)))
452 (setf (block-next prev) first)
453 (setf (block-prev first) prev)
454 (setf (block-next last) result-return-block)
455 (setf (block-prev result-return-block) last)
456 (dolist (succ (block-succ head))
457 (unlink-blocks head succ))
458 (dolist (pred (block-pred tail))
459 (unlink-blocks pred tail)
460 (let ((last (block-last pred)))
461 (unless (return-p last)
462 (aver (basic-combination-p last))
463 (link-blocks pred (component-tail result-component))))))
465 (let ((lambdas (component-lambdas component)))
466 (aver (and (null (rest lambdas))
467 (eq (first lambdas) lambda))))
469 ;; Switch the end of the code from the return block to the start of
471 (dolist (pred (block-pred result-return-block))
472 (unlink-blocks pred result-return-block)
473 (link-blocks pred bind-block))
476 ;; If there is a return, then delete it (making the preceding node
477 ;; the last node) and link the block to the result return. There
478 ;; is always a preceding REF NIL node in top level lambdas.
479 (let ((return (lambda-return lambda)))
481 (let ((return-block (node-block return))
482 (result (return-result return)))
483 (setf (block-last return-block) (continuation-use result))
485 (delete-continuation result)
486 (link-blocks return-block result-return-block))))))
488 ;;; Given a non-empty list of top level LAMBDAs, smash them into a
489 ;;; top level lambda and component, returning these as values. We use
490 ;;; the first lambda and its component, putting the other code in that
491 ;;; component and deleting the other lambdas.
492 (defun merge-toplevel-lambdas (lambdas)
493 (declare (cons lambdas))
494 (let* ((result-lambda (first lambdas))
495 (result-return (lambda-return result-lambda)))
499 ;; Make sure the result's return node starts a block so that we
500 ;; can splice code in before it.
501 (let ((prev (node-prev
503 (return-result result-return)))))
504 (when (continuation-use prev)
505 (node-ends-block (continuation-use prev)))
507 (let ((new (make-continuation)))
508 (delete-continuation-use use)
509 (add-continuation-use use new))))
511 (dolist (lambda (rest lambdas))
512 (merge-1-toplevel-lambda result-lambda lambda)))
514 (dolist (lambda (rest lambdas))
515 (setf (functional-entry-fun lambda) nil)
516 (delete-component (lambda-component lambda)))))
518 (values (lambda-component result-lambda) result-lambda)))