/[cmucl]/src/compiler/ir1opt.lisp
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Revision 1.38 - (hide annotations)
Fri Dec 20 20:47:56 1991 UTC (22 years, 4 months ago) by ram
Branch: MAIN
Changes since 1.37: +3 -2 lines
Do inconsistent derived type warning only when *CHECK-CONSISTENCY* is T.  It
seems that we do derive inconsistent types in dead code.
1 wlott 1.1 ;;; -*- Package: C; Log: C.Log -*-
2     ;;;
3     ;;; **********************************************************************
4 ram 1.24 ;;; This code was written as part of the CMU Common Lisp project at
5     ;;; Carnegie Mellon University, and has been placed in the public domain.
6     ;;; If you want to use this code or any part of CMU Common Lisp, please contact
7     ;;; Scott Fahlman or slisp-group@cs.cmu.edu.
8     ;;;
9     (ext:file-comment
10 ram 1.38 "$Header: /tiger/var/lib/cvsroots/cmucl/src/compiler/ir1opt.lisp,v 1.38 1991/12/20 20:47:56 ram Exp $")
11 ram 1.24 ;;;
12 wlott 1.1 ;;; **********************************************************************
13     ;;;
14     ;;; This file implements the IR1 optimization phase of the compiler. IR1
15     ;;; optimization is a grab-bag of optimizations that don't make major changes
16     ;;; to the block-level control flow and don't use flow analysis. These
17     ;;; optimizations can mostly be classified as "meta-evaluation", but there is a
18     ;;; sizable top-down component as well.
19     ;;;
20     ;;; Written by Rob MacLachlan
21     ;;;
22     (in-package 'c)
23    
24    
25     ;;;; Interface for obtaining results of constant folding:
26    
27     ;;; Constant-Continuation-P -- Interface
28     ;;;
29     ;;; Return true if the sole use of Cont is a reference to a constant leaf.
30     ;;;
31     (proclaim '(function constant-continuation-p (continuation) boolean))
32     (defun constant-continuation-p (cont)
33     (let ((use (continuation-use cont)))
34     (and (ref-p use)
35     (constant-p (ref-leaf use)))))
36    
37    
38     ;;; Continuation-Value -- Interface
39     ;;;
40     ;;; Return the constant value for a continuation whose only use is a
41     ;;; constant node.
42     ;;;
43     (proclaim '(function continuation-value (continuation) t))
44     (defun continuation-value (cont)
45 ram 1.10 (assert (constant-continuation-p cont))
46 wlott 1.1 (constant-value (ref-leaf (continuation-use cont))))
47    
48    
49     ;;;; Interface for obtaining results of type inference:
50    
51     ;;; CONTINUATION-PROVEN-TYPE -- Interface
52     ;;;
53     ;;; Return a (possibly values) type that describes what we have proven about
54     ;;; the type of Cont without taking any type assertions into consideration.
55     ;;; This is just the union of the NODE-DERIVED-TYPE of all the uses. Most
56     ;;; often people use CONTINUATION-DERIVED-TYPE or CONTINUATION-TYPE instead of
57     ;;; using this function directly.
58     ;;;
59     (defun continuation-proven-type (cont)
60     (declare (type continuation cont))
61     (ecase (continuation-kind cont)
62     ((:block-start :deleted-block-start)
63     (let ((uses (block-start-uses (continuation-block cont))))
64     (if uses
65     (do ((res (node-derived-type (first uses))
66     (values-type-union (node-derived-type (first current))
67     res))
68     (current (rest uses) (rest current)))
69     ((null current) res))
70     *empty-type*)))
71     (:inside-block
72     (node-derived-type (continuation-use cont)))))
73    
74    
75     ;;; Continuation-Derived-Type -- Interface
76     ;;;
77     ;;; Our best guess for the type of this continuation's value. Note that
78     ;;; this may be Values or Function type, which cannot be passed as an argument
79     ;;; to the normal type operations. See Continuation-Type. This may be called
80     ;;; on deleted continuations, always returning *.
81     ;;;
82     ;;; What we do is call CONTINUATION-PROVEN-TYPE and check whether the result
83     ;;; is a subtype of the assertion. If so, return the proven type and set
84     ;;; TYPE-CHECK to nil. Otherwise, return the intersection of the asserted and
85     ;;; proven types, and set TYPE-CHECK T. If TYPE-CHECK already has a non-null
86     ;;; value, then preserve it. Only in the somewhat unusual circumstance of
87     ;;; a newly discovered assertion will we change TYPE-CHECK from NIL to T.
88     ;;;
89     ;;; The result value is cached in the Continuation-%Derived-Type. If the
90     ;;; slot is true, just return that value, otherwise recompute and stash the
91     ;;; value there.
92     ;;;
93     (proclaim '(inline continuation-derived-type))
94     (defun continuation-derived-type (cont)
95     (declare (type continuation cont))
96     (or (continuation-%derived-type cont)
97     (%continuation-derived-type cont)))
98     ;;;
99     (defun %continuation-derived-type (cont)
100     (declare (type continuation cont))
101     (let ((proven (continuation-proven-type cont))
102     (asserted (continuation-asserted-type cont)))
103     (cond ((values-subtypep proven asserted)
104     (setf (continuation-%type-check cont) nil)
105     (setf (continuation-%derived-type cont) proven))
106     (t
107     (unless (or (continuation-%type-check cont)
108     (not (continuation-dest cont))
109     (eq asserted *universal-type*))
110     (setf (continuation-%type-check cont) t))
111    
112     (setf (continuation-%derived-type cont)
113     (values-type-intersection asserted proven))))))
114    
115    
116     ;;; CONTINUATION-TYPE-CHECK -- Interface
117     ;;;
118     ;;; Call CONTINUATION-DERIVED-TYPE to make sure the slot is up to date, then
119     ;;; return it.
120     ;;;
121     (proclaim '(inline continuation-type-check))
122     (defun continuation-type-check (cont)
123     (declare (type continuation cont))
124     (continuation-derived-type cont)
125     (continuation-%type-check cont))
126    
127    
128     ;;; Continuation-Type -- Interface
129     ;;;
130     ;;; Return the derived type for Cont's first value. This is guaranteed not
131     ;;; to be a Values or Function type.
132     ;;;
133 wlott 1.14 (proclaim '(function continuation-type (continuation) ctype))
134 wlott 1.1 (defun continuation-type (cont)
135     (single-value-type (continuation-derived-type cont)))
136    
137    
138     ;;;; Interface routines used by optimizers:
139    
140     ;;; Reoptimize-Continuation -- Interface
141     ;;;
142     ;;; This function is called by optimizers to indicate that something
143     ;;; interesting has happened to the value of Cont. Optimizers must make sure
144     ;;; that they don't call for reoptimization when nothing has happened, since
145     ;;; optimization will fail to terminate.
146     ;;;
147     ;;; We clear any cached type for the continuation and set the reoptimize
148     ;;; flags on everything in sight, unless the continuation is deleted (in which
149     ;;; case we do nothing.)
150     ;;;
151     ;;; Since this can get called curing IR1 conversion, we have to be careful
152     ;;; not to fly into space when the Dest's Prev is missing.
153     ;;;
154     (defun reoptimize-continuation (cont)
155     (declare (type continuation cont))
156 ram 1.29 (unless (member (continuation-kind cont) '(:deleted :unused))
157 wlott 1.1 (setf (continuation-%derived-type cont) nil)
158     (let ((dest (continuation-dest cont)))
159     (when dest
160     (setf (continuation-reoptimize cont) t)
161     (setf (node-reoptimize dest) t)
162     (let ((prev (node-prev dest)))
163     (when prev
164     (let* ((block (continuation-block prev))
165     (component (block-component block)))
166 ram 1.18 (when (typep dest 'cif)
167     (setf (block-test-modified block) t))
168 wlott 1.1 (setf (block-reoptimize block) t)
169     (setf (component-reoptimize component) t))))))
170     (do-uses (node cont)
171     (setf (block-type-check (node-block node)) t)))
172     (undefined-value))
173    
174    
175     ;;; Derive-Node-Type -- Interface
176     ;;;
177     ;;; Annotate Node to indicate that its result has been proven to be typep to
178     ;;; RType. After IR1 conversion has happened, this is the only correct way to
179     ;;; supply information discovered about a node's type. If you fuck with the
180     ;;; Node-Derived-Type directly, then information may be lost and reoptimization
181     ;;; may not happen.
182     ;;;
183     ;;; What we do is intersect Rtype with Node's Derived-Type. If the
184     ;;; intersection is different from the old type, then we do a
185     ;;; Reoptimize-Continuation on the Node-Cont.
186     ;;;
187     (defun derive-node-type (node rtype)
188     (declare (type node node) (type ctype rtype))
189     (let ((node-type (node-derived-type node)))
190     (unless (eq node-type rtype)
191     (let ((int (values-type-intersection node-type rtype)))
192     (when (type/= node-type int)
193 ram 1.38 (when (and *check-consistency*
194     (eq int *empty-type*)
195 ram 1.34 (not (eq rtype *empty-type*)))
196     (let ((*compiler-error-context* node))
197     (compiler-warning
198     "New inferred type ~S conflicts with old type:~
199     ~% ~S~%*** Bug?"
200     (type-specifier rtype) (type-specifier node-type))))
201 wlott 1.1 (setf (node-derived-type node) int)
202     (reoptimize-continuation (node-cont node))))))
203     (undefined-value))
204    
205    
206     ;;; Assert-Continuation-Type -- Interface
207     ;;;
208     ;;; Similar to Derive-Node-Type, but asserts that it is an error for Cont's
209     ;;; value not to be typep to Type. If we improve the assertion, we set
210 ram 1.11 ;;; TYPE-CHECK and TYPE-ASSERTED to guarantee that the new assertion will be
211     ;;; checked.
212 wlott 1.1 ;;;
213     (defun assert-continuation-type (cont type)
214     (declare (type continuation cont) (type ctype type))
215     (let ((cont-type (continuation-asserted-type cont)))
216     (unless (eq cont-type type)
217     (let ((int (values-type-intersection cont-type type)))
218     (when (type/= cont-type int)
219     (setf (continuation-asserted-type cont) int)
220     (do-uses (node cont)
221 ram 1.11 (setf (block-attributep (block-flags (node-block node))
222     type-check type-asserted)
223     t))
224 wlott 1.1 (reoptimize-continuation cont)))))
225     (undefined-value))
226    
227    
228     ;;; Assert-Call-Type -- Interface
229     ;;;
230     ;;; Assert that Call is to a function of the specified Type. It is assumed
231     ;;; that the call is legal and has only constants in the keyword positions.
232     ;;;
233     (defun assert-call-type (call type)
234     (declare (type combination call) (type function-type type))
235     (derive-node-type call (function-type-returns type))
236     (let ((args (combination-args call)))
237     (dolist (req (function-type-required type))
238     (when (null args) (return-from assert-call-type))
239     (let ((arg (pop args)))
240     (assert-continuation-type arg req)))
241     (dolist (opt (function-type-optional type))
242     (when (null args) (return-from assert-call-type))
243     (let ((arg (pop args)))
244     (assert-continuation-type arg opt)))
245    
246     (let ((rest (function-type-rest type)))
247     (when rest
248     (dolist (arg args)
249     (assert-continuation-type arg rest))))
250    
251     (dolist (key (function-type-keywords type))
252     (let ((name (key-info-name key)))
253     (do ((arg args (cddr arg)))
254     ((null arg))
255     (when (eq (continuation-value (first arg)) name)
256     (assert-continuation-type
257     (second arg) (key-info-type key)))))))
258     (undefined-value))
259    
260    
261     ;;; IR1-Optimize -- Interface
262     ;;;
263     ;;; Do one forward pass over Component, deleting unreachable blocks and
264 ram 1.11 ;;; doing IR1 optimizations. We can ignore all blocks that don't have the
265     ;;; Reoptimize flag set. If Component-Reoptimize is true when we are done,
266 wlott 1.1 ;;; then another iteration would be beneficial.
267     ;;;
268     ;;; We delete blocks when there is either no predecessor or the block is in
269     ;;; a lambda that has been deleted. These blocks would eventually be deleted
270     ;;; by DFO recomputation, but doing it here immediately makes the effect
271     ;;; avaliable to IR1 optimization.
272     ;;;
273     (defun ir1-optimize (component)
274     (declare (type component component))
275     (setf (component-reoptimize component) nil)
276     (do-blocks (block component)
277     (cond
278     ((or (block-delete-p block)
279     (null (block-pred block))
280 ram 1.11 (eq (functional-kind (block-home-lambda block)) :deleted))
281 wlott 1.1 (delete-block block))
282     (t
283     (loop
284     (let ((succ (block-succ block)))
285     (unless (and succ (null (rest succ)))
286     (return)))
287    
288     (let ((last (block-last block)))
289     (typecase last
290     (cif
291     (flush-dest (if-test last))
292     (when (unlink-node last) (return)))
293     (exit
294     (when (maybe-delete-exit last) (return)))))
295    
296     (unless (join-successor-if-possible block)
297     (return)))
298    
299 ram 1.11 (when (and (block-reoptimize block) (block-component block))
300 wlott 1.1 (assert (not (block-delete-p block)))
301     (ir1-optimize-block block))
302    
303 ram 1.11 (when (and (block-flush-p block) (block-component block))
304 wlott 1.1 (assert (not (block-delete-p block)))
305     (flush-dead-code block)))))
306    
307     (undefined-value))
308    
309    
310     ;;; IR1-Optimize-Block -- Internal
311     ;;;
312     ;;; Loop over the nodes in Block, looking for stuff that needs to be
313     ;;; optimized. We dispatch off of the type of each node with its reoptimize
314     ;;; flag set:
315     ;;; -- With a combination, we call Propagate-Function-Change whenever the
316     ;;; function changes, and call IR1-Optimize-Combination if any argument
317     ;;; changes.
318     ;;; -- With an Exit, we derive the node's type from the Value's type. We don't
319     ;;; propagate Cont's assertion to the Value, since if we did, this would
320     ;;; move the checking of Cont's assertion to the exit. This wouldn't work
321     ;;; with Catch and UWP, where the Exit node is just a placeholder for the
322     ;;; actual unknown exit.
323     ;;;
324     ;;; Note that we clear the node & block reoptimize flags *before* doing the
325     ;;; optimization. This ensures that the node or block will be reoptimized if
326 ram 1.19 ;;; necessary. We leave the NODE-OPTIMIZE flag set going into
327 wlott 1.1 ;;; IR1-OPTIMIZE-RETURN, since it wants to clear the flag itself.
328     ;;;
329     (defun ir1-optimize-block (block)
330     (declare (type cblock block))
331     (setf (block-reoptimize block) nil)
332 ram 1.19 (do-nodes (node cont block :restart-p t)
333 wlott 1.1 (when (node-reoptimize node)
334     (setf (node-reoptimize node) nil)
335     (typecase node
336     (ref)
337     (combination
338     (when (continuation-reoptimize (basic-combination-fun node))
339     (propagate-function-change node))
340 ram 1.30 (ir1-optimize-combination node)
341 ram 1.29 (unless (node-deleted node)
342 ram 1.30 (maybe-terminate-block node nil)))
343 wlott 1.1 (cif
344     (ir1-optimize-if node))
345     (creturn
346     (setf (node-reoptimize node) t)
347     (ir1-optimize-return node))
348 ram 1.6 (mv-combination
349 ram 1.21 (ir1-optimize-mv-combination node))
350 wlott 1.1 (exit
351     (let ((value (exit-value node)))
352     (when value
353     (derive-node-type node (continuation-derived-type value)))))
354     (cset
355     (ir1-optimize-set node)))))
356     (undefined-value))
357    
358    
359     ;;; Join-Successor-If-Possible -- Internal
360     ;;;
361     ;;; We cannot combine with a successor block if:
362     ;;; 1] The successor has more than one predecessor.
363     ;;; 2] The last node's Cont is also used somewhere else.
364     ;;; 3] The successor is the current block (infinite loop).
365     ;;; 4] The next block has a different cleanup, and thus we may want to insert
366     ;;; cleanup code between the two blocks at some point.
367     ;;; 5] The next block has a different home lambda, and thus the control
368     ;;; transfer is a non-local exit.
369     ;;;
370     ;;; If we succeed, we return true, otherwise false.
371     ;;;
372     ;;; Joining is easy when the successor's Start continuation is the same from
373     ;;; our Last's Cont. If they differ, then we can still join when the last
374     ;;; continuation has no next and the next continuation has no uses. In this
375 ram 1.5 ;;; case, we replace the next continuation with the last before joining the
376 wlott 1.1 ;;; blocks.
377     ;;;
378     (defun join-successor-if-possible (block)
379     (declare (type cblock block))
380     (let ((next (first (block-succ block))))
381 ram 1.11 (when (block-start next)
382 wlott 1.1 (let* ((last (block-last block))
383     (last-cont (node-cont last))
384 ram 1.11 (next-cont (block-start next)))
385 wlott 1.1 (cond ((or (rest (block-pred next))
386 ram 1.5 (not (eq (continuation-use last-cont) last))
387 wlott 1.1 (eq next block)
388 ram 1.11 (not (eq (block-end-cleanup block)
389     (block-start-cleanup next)))
390     (not (eq (block-home-lambda block)
391     (block-home-lambda next))))
392 wlott 1.1 nil)
393 ram 1.5 ((eq last-cont next-cont)
394 wlott 1.1 (join-blocks block next)
395     t)
396 ram 1.5 ((and (null (block-start-uses next))
397     (eq (continuation-kind last-cont) :inside-block))
398     (let ((next-node (continuation-next next-cont)))
399 ram 1.30 ;;
400     ;; If next-cont does have a dest, it must be unreachable,
401     ;; since there are no uses. DELETE-CONTINUATION will mark the
402     ;; dest block as delete-p [and also this block, unless it is
403     ;; no longer backward reachable from the dest block.]
404 ram 1.5 (delete-continuation next-cont)
405     (setf (node-prev next-node) last-cont)
406     (setf (continuation-next last-cont) next-node)
407     (setf (block-start next) last-cont)
408     (join-blocks block next))
409 wlott 1.1 t)
410     (t
411     nil))))))
412    
413    
414     ;;; Join-Blocks -- Internal
415     ;;;
416     ;;; Join together two blocks which have the same ending/starting
417     ;;; continuation. The code in Block2 is moved into Block1 and Block2 is
418 ram 1.11 ;;; deleted from the DFO. We combine the optimize flags for the two blocks so
419     ;;; that any indicated optimization gets done.
420 wlott 1.1 ;;;
421     (defun join-blocks (block1 block2)
422     (declare (type cblock block1 block2))
423     (let* ((last (block-last block2))
424     (last-cont (node-cont last))
425     (succ (block-succ block2))
426     (start2 (block-start block2)))
427     (do ((cont start2 (node-cont (continuation-next cont))))
428     ((eq cont last-cont)
429     (when (eq (continuation-kind last-cont) :inside-block)
430     (setf (continuation-block last-cont) block1)))
431     (setf (continuation-block cont) block1))
432    
433     (unlink-blocks block1 block2)
434     (dolist (block succ)
435     (unlink-blocks block2 block)
436     (link-blocks block1 block))
437    
438     (setf (block-last block1) last)
439     (setf (continuation-kind start2) :inside-block))
440    
441 ram 1.11 (setf (block-flags block1)
442     (attributes-union (block-flags block1)
443     (block-flags block2)
444     (block-attributes type-asserted test-modified)))
445 wlott 1.1
446     (let ((next (block-next block2))
447     (prev (block-prev block2)))
448     (setf (block-next prev) next)
449     (setf (block-prev next) prev))
450    
451     (undefined-value))
452    
453    
454     ;;;; Local call return type propagation:
455    
456     ;;; Find-Result-Type -- Internal
457     ;;;
458     ;;; This function is called on RETURN nodes that have their REOPTIMIZE flag
459     ;;; set. It iterates over the uses of the RESULT, looking for interesting
460     ;;; stuff to update the TAIL-SET:
461 ram 1.34 ;;; -- If a use is a tail local call, then we check that the called function
462     ;;; has the tail set Tails. If we encounter any different tail set, we
463     ;;; return true. If NODE-TAIL-P is not set, we also call
464     ;;; CONVERT-TAIL-LOCAL-CALL, which changes the succesor of the call to be
465     ;;; the called function and checks if the call can become an assignment.
466 wlott 1.1 ;;; -- If a use isn't a local call, then we union its type together with the
467     ;;; types of other such uses. We assign to the RETURN-RESULT-TYPE the
468     ;;; intersection of this type with the RESULT's asserted type. We can make
469     ;;; this intersection now (potentially before type checking) because this
470     ;;; assertion on the result will eventually be checked (if appropriate.)
471     ;;;
472     (defun find-result-type (node tails)
473     (declare (type creturn node))
474     (let ((result (return-result node))
475     (retry nil))
476     (collect ((use-union *empty-type* values-type-union))
477     (do-uses (use result)
478 ram 1.34 (cond ((and (basic-combination-p use)
479     (eq (basic-combination-kind use) :local)
480     (immediately-used-p result use))
481     (when (merge-tail-sets use tails)
482     (setq retry t))
483     (maybe-convert-tail-local-call use))
484     (t
485     (use-union (node-derived-type use)))))
486 wlott 1.1 (let ((int (values-type-intersection
487     (continuation-asserted-type result)
488     (use-union))))
489     (setf (return-result-type node) int)))
490     retry))
491    
492    
493     ;;; Merge-Tail-Sets -- Internal
494     ;;;
495     ;;; This function handles merging the tail sets if Call is a call to a
496     ;;; function with a different TAIL-SET than Ret-Set. We return true if we do
497     ;;; anything.
498     ;;;
499     ;;; It is assumed that Call sends its value to a RETURN node. We
500     ;;; destructively modify the set for the returning function to represent both,
501     ;;; and then change all the functions in callee's set to reference the first.
502     ;;;
503     (defun merge-tail-sets (call ret-set)
504     (declare (type basic-combination call) (type tail-set ret-set))
505     (let ((fun-set (lambda-tail-set (combination-lambda call))))
506 ram 1.34 (unless (eq ret-set fun-set)
507 wlott 1.1 (let ((funs (tail-set-functions fun-set)))
508     (dolist (fun funs)
509     (setf (lambda-tail-set fun) ret-set))
510     (setf (tail-set-functions ret-set)
511     (nconc (tail-set-functions ret-set) funs)))
512     t)))
513    
514    
515     ;;; IR1-Optimize-Return -- Internal
516     ;;;
517     ;;; Do stuff to realize that something has changed about the value delivered
518     ;;; to a return node. Since we consider the return values of all functions in
519     ;;; the tail set to be equivalent, this amounts to bringing the entire tail set
520     ;;; up to date. We iterate over the returns for all the functions in the tail
521     ;;; set, reanalyzing them all (not treating Node specially.)
522     ;;;
523     ;;; During this iteration, we may discover new functions that should be
524     ;;; added to the tail set. If this happens, we restart the iteration over the
525     ;;; TAIL-SET-FUNCTIONS. Note that this really doesn't duplicate much work, as
526     ;;; we clear the NODE-REOPTIMIZE flags in the return nodes as we go, thus we
527     ;;; don't call FIND-RESULT-TYPE on any given return more than once.
528     ;;;
529     ;;; Restarting the iteration doesn't disturb the computation of the result
530     ;;; type RES, since we will just be adding more types to the union. (or when
531     ;;; we iterate over a return multiple times, unioning in the same type more
532     ;;; than once.)
533     ;;;
534     ;;; When we are done, we check if the new type is different from the old
535     ;;; TAIL-SET-TYPE. If so, we set the type and also reoptimize all the
536     ;;; continuations for references to functions in the tail set. This will
537     ;;; cause IR1-OPTIMIZE-COMBINATION to derive the new type as the results of the
538     ;;; calls.
539     ;;;
540     (defun ir1-optimize-return (node)
541     (declare (type creturn node))
542     (let ((tails (lambda-tail-set (return-lambda node))))
543     (collect ((res *empty-type* values-type-union))
544     (loop
545     (block RETRY
546     (let ((funs (tail-set-functions tails)))
547     (dolist (fun funs)
548     (let ((return (lambda-return fun)))
549 ram 1.34 (when return
550     (when (node-reoptimize return)
551     (setf (node-reoptimize node) nil)
552     (when (find-result-type return tails) (return-from RETRY)))
553     (res (return-result-type return))))))
554 wlott 1.1 (return)))
555    
556     (when (type/= (res) (tail-set-type tails))
557     (setf (tail-set-type tails) (res))
558     (dolist (fun (tail-set-functions tails))
559     (dolist (ref (leaf-refs fun))
560     (reoptimize-continuation (node-cont ref)))))))
561    
562     (undefined-value))
563    
564    
565     ;;; IR1-Optimize-If -- Internal
566     ;;;
567     ;;; If the test has multiple uses, replicate the node when possible. Also
568     ;;; check if the predicate is known to be true or false, deleting the IF node
569     ;;; in favor of the appropriate branch when this is the case.
570     ;;;
571     (defun ir1-optimize-if (node)
572     (declare (type cif node))
573     (let ((test (if-test node))
574     (block (node-block node)))
575    
576     (when (and (eq (block-start block) test)
577     (eq (continuation-next test) node)
578     (rest (block-start-uses block)))
579     (do-uses (use test)
580     (when (immediately-used-p test use)
581     (convert-if-if use node)
582     (when (continuation-use test) (return)))))
583    
584     (let* ((type (continuation-type test))
585     (victim
586     (cond ((constant-continuation-p test)
587     (if (continuation-value test)
588     (if-alternative node)
589     (if-consequent node)))
590     ((not (types-intersect type *null-type*))
591     (if-alternative node))
592     ((type= type *null-type*)
593     (if-consequent node)))))
594     (when victim
595     (flush-dest test)
596     (when (rest (block-succ block))
597     (unlink-blocks block victim))
598     (setf (component-reanalyze (block-component (node-block node))) t)
599     (unlink-node node))))
600     (undefined-value))
601    
602    
603     ;;; Convert-If-If -- Internal
604     ;;;
605     ;;; Create a new copy of an IF Node that tests the value of the node Use.
606     ;;; The test must have >1 use, and must be immediately used by Use. Node must
607     ;;; be the only node in its block (implying that block-start = if-test).
608     ;;;
609     ;;; This optimization has an effect semantically similar to the
610     ;;; source-to-source transformation:
611     ;;; (IF (IF A B C) D E) ==>
612     ;;; (IF A (IF B D E) (IF C D E))
613     ;;;
614     (defun convert-if-if (use node)
615     (declare (type node use) (type cif node))
616     (with-ir1-environment node
617     (let* ((block (node-block node))
618     (test (if-test node))
619     (cblock (if-consequent node))
620     (ablock (if-alternative node))
621     (use-block (node-block use))
622     (dummy-cont (make-continuation))
623     (new-cont (make-continuation))
624 ram 1.11 (new-node (make-if :test new-cont
625 wlott 1.1 :consequent cblock :alternative ablock))
626     (new-block (continuation-starts-block new-cont)))
627     (prev-link new-node new-cont)
628     (setf (continuation-dest new-cont) new-node)
629     (add-continuation-use new-node dummy-cont)
630     (setf (block-last new-block) new-node)
631    
632     (unlink-blocks use-block block)
633     (delete-continuation-use use)
634     (add-continuation-use use new-cont)
635     (link-blocks use-block new-block)
636    
637     (link-blocks new-block cblock)
638     (link-blocks new-block ablock)
639    
640     (reoptimize-continuation test)
641     (reoptimize-continuation new-cont)
642     (setf (component-reanalyze *current-component*) t)))
643     (undefined-value))
644    
645    
646     ;;;; Exit IR1 optimization:
647    
648     ;;; Maybe-Delete-Exit -- Interface
649     ;;;
650     ;;; This function attempts to delete an exit node, returning true if it
651     ;;; deletes the block as a consequence:
652     ;;; -- If the exit is degenerate (has no Entry), then we don't do anything,
653     ;;; since there is nothing to be done.
654     ;;; -- If the exit node and its Entry have the same home lambda then we know
655     ;;; the exit is local, and can delete the exit. We change uses of the
656     ;;; Exit-Value to be uses of the original continuation, then unlink the
657     ;;; node.
658     ;;; -- If there is no value (as in a GO), then we skip the value semantics.
659     ;;;
660     ;;; This function is also called by environment analysis, since it wants all
661     ;;; exits to be optimized even if normal optimization was omitted.
662     ;;;
663     (defun maybe-delete-exit (node)
664     (declare (type exit node))
665     (let ((value (exit-value node))
666     (entry (exit-entry node))
667     (cont (node-cont node)))
668     (when (and entry
669 ram 1.11 (eq (node-home-lambda node) (node-home-lambda entry)))
670     (setf (entry-exits entry) (delete node (entry-exits entry)))
671 wlott 1.1 (prog1
672     (unlink-node node)
673     (when value
674     (substitute-continuation-uses cont value))))))
675    
676    
677     ;;;; Combination IR1 optimization:
678    
679     ;;; Ir1-Optimize-Combination -- Internal
680     ;;;
681     ;;; Do IR1 optimizations on a Combination node.
682     ;;;
683     (proclaim '(function ir1-optimize-combination (combination) void))
684     (defun ir1-optimize-combination (node)
685     (let ((args (basic-combination-args node))
686     (kind (basic-combination-kind node)))
687     (case kind
688     (:local
689     (let ((fun (combination-lambda node)))
690     (if (eq (functional-kind fun) :let)
691     (propagate-let-args node fun)
692     (propagate-local-call-args node fun))))
693     (:full
694     (dolist (arg args)
695     (when arg
696     (setf (continuation-reoptimize arg) nil))))
697     (t
698     (dolist (arg args)
699     (when arg
700     (setf (continuation-reoptimize arg) nil)))
701    
702     (let ((attr (function-info-attributes kind)))
703     (when (and (ir1-attributep attr foldable)
704     (not (ir1-attributep attr call))
705     (every #'constant-continuation-p args)
706     (continuation-dest (node-cont node)))
707     (constant-fold-call node)
708     (return-from ir1-optimize-combination)))
709 ram 1.18
710 wlott 1.1 (let ((fun (function-info-derive-type kind)))
711     (when fun
712     (let ((res (funcall fun node)))
713     (when res
714     (derive-node-type node res)))))
715 ram 1.18
716 wlott 1.1 (let ((fun (function-info-optimizer kind)))
717     (unless (and fun (funcall fun node))
718     (dolist (x (function-info-transforms kind))
719 ram 1.28 (unless (ir1-transform node x)
720 wlott 1.2 (return))))))))
721 wlott 1.1
722     (undefined-value))
723    
724    
725 ram 1.29 ;;; MAYBE-TERMINATE-BLOCK -- Interface
726     ;;;
727     ;;; If Call is to a function that doesn't return (type NIL), then terminate
728 ram 1.31 ;;; the block there, and link it to the component tail. We also change the
729     ;;; call's CONT to be a dummy continuation to prevent the use from confusing
730     ;;; things.
731 ram 1.29 ;;;
732 ram 1.30 ;;; Except when called during IR1, we delete the continuation if it has no
733     ;;; other uses. (If it does have other uses, we reoptimize.)
734     ;;;
735 ram 1.31 ;;; Termination on the basis of a continuation type assertion is inhibited
736     ;;; when:
737     ;;; -- The continuation is deleted (hence the assertion is spurious), or
738     ;;; -- We are in IR1 conversion (where THE assertions are subject to
739     ;;; weakening.)
740     ;;;
741 ram 1.30 (defun maybe-terminate-block (call ir1-p)
742 ram 1.29 (declare (type basic-combination call))
743 ram 1.32 (let* ((block (node-block call))
744     (cont (node-cont call))
745     (tail (component-tail (block-component block)))
746     (succ (first (block-succ block))))
747     (unless (or (and (eq call (block-last block)) (eq succ tail))
748     (block-delete-p block))
749     (when (or (and (eq (continuation-asserted-type cont) *empty-type*)
750     (not (or ir1-p (eq (continuation-kind cont) :deleted))))
751     (eq (node-derived-type call) *empty-type*))
752     (cond (ir1-p
753     (delete-continuation-use call)
754     (cond
755     ((block-last block)
756     (assert (and (eq (block-last block) call)
757     (eq (continuation-kind cont) :block-start))))
758     (t
759     (setf (block-last block) call)
760     (link-blocks block (continuation-starts-block cont)))))
761 ram 1.30 (t
762 ram 1.32 (node-ends-block call)
763     (delete-continuation-use call)
764     (if (eq (continuation-kind cont) :unused)
765     (delete-continuation cont)
766     (reoptimize-continuation cont))))
767    
768     (unlink-blocks block (first (block-succ block)))
769     (assert (not (block-succ block)))
770     (link-blocks block tail)
771     (add-continuation-use call (make-continuation))
772     t))))
773 ram 1.30
774 ram 1.29
775 wlott 1.1 ;;; Recognize-Known-Call -- Interface
776     ;;;
777     ;;; If Call is a call to a known function, mark it as such by setting the
778     ;;; Kind. In addition to a direct check for the function name in the table, we
779     ;;; also must check for slot accessors. If the function is a slot accessor,
780     ;;; then we set the combination kind to the function info of %Slot-Setter or
781     ;;; %Slot-Accessor, as appropriate.
782     ;;;
783 ram 1.19 ;;; If convert-again is true, and the function has a source-transform or
784     ;;; inline-expansion, or if the function is conditional, and the destination of
785     ;;; the value is not an IF, then instead of making the existing call known, we
786     ;;; change it to be a call to a lambda that just re-calls the function. This
787     ;;; gives IR1 transformation another go at the call, in the case where the call
788     ;;; wasn't obviously known during the initial IR1 conversion.
789     ;;;
790     (defun recognize-known-call (call &optional convert-again)
791 wlott 1.1 (declare (type combination call))
792     (let* ((fun (basic-combination-fun call))
793     (name (continuation-function-name fun)))
794     (when name
795     (let ((info (info function info name)))
796 ram 1.19 (cond
797     ((and info convert-again
798     (or (info function source-transform name)
799     (info function inline-expansion name)
800     (and (ir1-attributep (function-info-attributes info)
801     predicate)
802     (let ((dest (continuation-dest (node-cont call))))
803     (and dest (not (if-p dest)))))))
804     (let ((dums (loop repeat (length (combination-args call))
805     collect (gensym))))
806     (transform-call call
807     `(lambda ,dums
808     (,name ,@dums)))))
809     (info
810     (setf (basic-combination-kind call) info))
811     ((slot-accessor-p (ref-leaf (continuation-use fun)))
812     (setf (basic-combination-kind call)
813     (info function info
814     (if (consp name)
815     '%slot-setter
816     '%slot-accessor))))))))
817 wlott 1.1 (undefined-value))
818    
819    
820     ;;; Propagate-Function-Change -- Internal
821     ;;;
822     ;;; Called by Ir1-Optimize when the function for a call has changed.
823     ;;; If the call is to a functional, then we attempt to convert it to a local
824     ;;; call, otherwise we check the call for legality with respect to the new
825     ;;; type; if it is illegal, we mark the Ref as :Notline and punt.
826     ;;;
827     ;;; If we do have a good type for the call, we propagate type information from
828     ;;; the type to the arg and result continuations. If we discover that the call
829     ;;; is to a known global function, then we mark the combination as known.
830     ;;;
831     (defun propagate-function-change (call)
832     (declare (type combination call))
833     (let* ((fun (combination-fun call))
834     (use (continuation-use fun))
835     (type (continuation-derived-type fun))
836     (*compiler-error-context* call))
837     (setf (continuation-reoptimize fun) nil)
838     (cond ((or (not (ref-p use))
839     (eq (ref-inlinep use) :notinline)))
840     ((functional-p (ref-leaf use))
841     (let ((leaf (ref-leaf use)))
842     (cond ((eq (combination-kind call) :local)
843 ram 1.34 (unless (member (functional-kind leaf)
844     '(:let :assignment))
845     (derive-node-type
846     call (tail-set-type (lambda-tail-set leaf)))))
847 wlott 1.1 ((not (eq (ref-inlinep use) :notinline))
848     (convert-call-if-possible use call)
849     (maybe-let-convert leaf)))))
850     ((not (function-type-p type)))
851     ((valid-function-use call type
852     :argument-test #'always-subtypep
853     :result-test #'always-subtypep
854     :error-function #'compiler-warning
855     :warning-function #'compiler-note)
856     (assert-call-type call type)
857 ram 1.19 (recognize-known-call call t))
858 wlott 1.1 (t
859     (setf (ref-inlinep use) :notinline))))
860    
861     (undefined-value))
862    
863    
864     ;;;; Known function optimization:
865    
866 ram 1.15 ;;;
867     ;;; A hashtable from combination nodes to things describing how an
868 ram 1.28 ;;; optimization of the node failed. The value is an alist (Transform . Args),
869     ;;; where Transform is the structure describing the transform that failed, and
870     ;;; Args is either a list of format arguments for the note, or the
871     ;;; FUNCTION-TYPE that would have enabled the transformation but failed to
872     ;;; match.
873 ram 1.15 ;;;
874     (defvar *failed-optimizations* (make-hash-table :test #'eq))
875    
876    
877     ;;; RECORD-OPTIMIZATION-FAILURE -- Internal
878     ;;;
879     ;;; Add a failed optimization note to *FAILED-OPTIMZATIONS* for Node, Fun
880 ram 1.28 ;;; and Args. If there is already a note for Node and Transform, replace it,
881 ram 1.15 ;;; otherwise add a new one.
882     ;;;
883 ram 1.28 (defun record-optimization-failure (node transform args)
884     (declare (type combination node) (type transform transform)
885 ram 1.15 (type (or function-type list) args))
886 ram 1.28 (let ((found (assoc transform (gethash node *failed-optimizations*))))
887 ram 1.15 (if found
888     (setf (cdr found) args)
889 ram 1.28 (push (cons transform args)
890 ram 1.15 (gethash node *failed-optimizations*))))
891     (undefined-value))
892    
893    
894 wlott 1.1 ;;; IR1-Transform -- Internal
895     ;;;
896     ;;; Attempt to transform Node using Function, subject to the call type
897     ;;; constraint Type. If we are inhibited from doing the transform for some
898     ;;; reason and Flame is true, then we make a note of the message in
899 wlott 1.2 ;;; *failed-optimizations* for IR1 finalize to pick up. We return true if
900     ;;; the transform failed, and thus further transformation should be
901     ;;; attempted. We return false if either the transform suceeded or was
902     ;;; aborted.
903 wlott 1.1 ;;;
904 ram 1.28 (defun ir1-transform (node transform)
905     (declare (type combination node) (type transform transform))
906     (let* ((type (transform-type transform))
907     (fun (transform-function transform))
908     (constrained (function-type-p type))
909     (flame (policy node (> speed brevity)))
910     (*compiler-error-context* node))
911 wlott 1.1 (cond ((or (not constrained)
912 ram 1.19 (valid-function-use node type :strict-result t))
913 wlott 1.1 (multiple-value-bind
914     (severity args)
915     (catch 'give-up
916     (transform-call node (funcall fun node))
917     (values :none nil))
918     (ecase severity
919 ram 1.15 (:none
920     (remhash node *failed-optimizations*)
921     nil)
922 wlott 1.1 (:aborted
923     (setf (combination-kind node) :full)
924     (setf (ref-inlinep (continuation-use (combination-fun node)))
925     :notinline)
926     (when args
927 wlott 1.2 (apply #'compiler-warning args))
928 ram 1.15 (remhash node *failed-optimizations*)
929 wlott 1.2 nil)
930 wlott 1.1 (:failure
931 ram 1.15 (if args
932     (when flame
933 ram 1.28 (record-optimization-failure node transform args))
934 ram 1.15 (setf (gethash node *failed-optimizations*)
935 ram 1.28 (remove transform
936     (gethash node *failed-optimizations*)
937 ram 1.15 :key #'car)))
938 wlott 1.2 t))))
939 wlott 1.1 ((and flame
940     (valid-function-use node type
941     :argument-test #'types-intersect
942     :result-test #'values-types-intersect))
943 ram 1.28 (record-optimization-failure node transform type)
944 wlott 1.13 t)
945     (t
946 wlott 1.2 t))))
947 wlott 1.1
948    
949     ;;; GIVE-UP, ABORT-TRANSFORM -- Interface
950     ;;;
951     ;;; Just throw the severity and args...
952     ;;;
953     (proclaim '(function give-up (&rest t) nil))
954     (defun give-up (&rest args)
955     "This function is used to throw out of an IR1 transform, aborting this
956     attempt to transform the call, but admitting the possibility that this or
957     some other transform will later suceed. If arguments are supplied, they are
958     format arguments for an efficiency note."
959     (throw 'give-up (values :failure args)))
960     ;;;
961     (defun abort-transform (&rest args)
962     "This function is used to throw out of an IR1 transform and force a normal
963     call to the function at run time. No further optimizations will be
964     attempted."
965     (throw 'give-up (values :aborted args)))
966    
967    
968     ;;; Transform-Call -- Internal
969     ;;;
970     ;;; Take the lambda-expression Res, IR1 convert it in the proper
971     ;;; environment, and then install it as the function for the call Node. We do
972     ;;; local call analysis so that the new function is integrated into the control
973     ;;; flow. We set the Reanalyze flag in the component to cause the DFO to be
974     ;;; recomputed at soonest convenience.
975     ;;;
976     (defun transform-call (node res)
977     (declare (type combination node) (list res))
978     (with-ir1-environment node
979 ram 1.11 (let ((new-fun (ir1-convert-global-lambda res))
980 wlott 1.1 (ref (continuation-use (combination-fun node))))
981     (change-ref-leaf ref new-fun)
982     (setf (combination-kind node) :full)
983     (local-call-analyze *current-component*)))
984     (undefined-value))
985    
986    
987     ;;; Constant-Fold-Call -- Internal
988     ;;;
989     ;;; Replace a call to a foldable function of constant arguments with the
990     ;;; result of evaluating the form. We insert the resulting constant node after
991     ;;; the call, stealing the call's continuation. We give the call a
992     ;;; continuation with no Dest, which should cause it and its arguments to go
993     ;;; away. If there is an error during the evaluation, we give a warning and
994     ;;; leave the call alone, making the call a full call and marking it as
995     ;;; :notinline to make sure that it stays that way.
996     ;;;
997     ;;; For now, if the result is other than one value, we don't fold it.
998     ;;;
999     (defun constant-fold-call (call)
1000     (declare (type combination call))
1001     (let* ((args (mapcar #'continuation-value (combination-args call)))
1002     (ref (continuation-use (combination-fun call)))
1003     (fun (leaf-name (ref-leaf ref))))
1004    
1005     (multiple-value-bind (values win)
1006     (careful-call fun args call "constant folding")
1007     (cond
1008     ((not win)
1009     (setf (ref-inlinep ref) :notinline)
1010     (setf (combination-kind call) :full))
1011     ((= (length values) 1)
1012     (with-ir1-environment call
1013 wlott 1.37 (when (producing-fasl-file)
1014     (maybe-emit-make-load-forms (first values)))
1015 wlott 1.1 (let* ((leaf (find-constant (first values)))
1016     (node (make-ref (leaf-type leaf)
1017     leaf
1018     nil))
1019     (dummy (make-continuation))
1020     (cont (node-cont call))
1021     (block (node-block call))
1022     (next (continuation-next cont)))
1023     (push node (leaf-refs leaf))
1024     (setf (leaf-ever-used leaf) t)
1025    
1026     (delete-continuation-use call)
1027     (add-continuation-use call dummy)
1028     (prev-link node dummy)
1029     (add-continuation-use node cont)
1030     (setf (continuation-next cont) next)
1031     (when (eq call (block-last block))
1032     (setf (block-last block) node))
1033 ram 1.19 (reoptimize-continuation cont))))
1034     (t
1035     (let ((dummies (loop repeat (length args)
1036     collect (gensym))))
1037     (transform-call
1038     call
1039     `(lambda ,dummies
1040     (declare (ignore ,@dummies))
1041     (values ,@(mapcar #'(lambda (x) `',x) values)))))))))
1042 wlott 1.1
1043     (undefined-value))
1044    
1045    
1046     ;;;; Local call optimization:
1047    
1048     ;;; Propagate-To-Refs -- Internal
1049     ;;;
1050     ;;; Propagate Type to Leaf and its Refs, marking things changed. If the
1051     ;;; leaf type is a function type, then just leave it alone, since TYPE is never
1052     ;;; going to be more specific than that (and TYPE-INTERSECTION would choke.)
1053     ;;;
1054     (defun propagate-to-refs (leaf type)
1055     (declare (type leaf leaf) (type ctype type))
1056     (let ((var-type (leaf-type leaf)))
1057     (unless (function-type-p var-type)
1058     (let ((int (type-intersection var-type type)))
1059     (when (type/= int var-type)
1060     (setf (leaf-type leaf) int)
1061     (dolist (ref (leaf-refs leaf))
1062     (derive-node-type ref int))))
1063     (undefined-value))))
1064    
1065    
1066     ;;; PROPAGATE-FROM-SETS -- Internal
1067     ;;;
1068     ;;; Figure out the type of a LET variable that has sets. We compute the
1069     ;;; union of the initial value Type and the types of all the set values and to
1070     ;;; a PROPAGATE-TO-REFS with this type.
1071     ;;;
1072     (defun propagate-from-sets (var type)
1073 ram 1.6 (collect ((res type type-union))
1074 wlott 1.1 (dolist (set (basic-var-sets var))
1075     (res (continuation-type (set-value set)))
1076     (setf (node-reoptimize set) nil))
1077     (propagate-to-refs var (res)))
1078     (undefined-value))
1079    
1080    
1081     ;;; IR1-OPTIMIZE-SET -- Internal
1082     ;;;
1083     ;;; If a let variable, find the initial value's type and do
1084     ;;; PROPAGATE-FROM-SETS. We also derive the VALUE's type as the node's type.
1085     ;;;
1086     (defun ir1-optimize-set (node)
1087     (declare (type cset node))
1088     (let ((var (set-var node)))
1089     (when (and (lambda-var-p var) (leaf-refs var))
1090     (let ((home (lambda-var-home var)))
1091     (when (eq (functional-kind home) :let)
1092     (let ((iv (let-var-initial-value var)))
1093     (setf (continuation-reoptimize iv) nil)
1094     (propagate-from-sets var (continuation-type iv)))))))
1095    
1096     (derive-node-type node (continuation-type (set-value node)))
1097     (undefined-value))
1098    
1099    
1100 ram 1.17 ;;; CONSTANT-REFERENCE-P -- Interface
1101 ram 1.7 ;;;
1102     ;;; Return true if the value of Ref will always be the same (and is thus
1103     ;;; legal to substitute.)
1104     ;;;
1105     (defun constant-reference-p (ref)
1106     (declare (type ref ref))
1107     (let ((leaf (ref-leaf ref)))
1108     (typecase leaf
1109     (constant t)
1110     (functional t)
1111     (lambda-var
1112     (null (lambda-var-sets leaf)))
1113     (global-var
1114     (case (global-var-kind leaf)
1115     (:global-function
1116     (not (eq (ref-inlinep ref) :notinline)))
1117     (:constant t))))))
1118    
1119    
1120     ;;; SUBSTITUTE-SINGLE-USE-CONTINUATION -- Internal
1121     ;;;
1122     ;;; If we have a non-set let var with a single use, then (if possible)
1123     ;;; replace the variable reference's CONT with the arg continuation. This is
1124     ;;; inhibited when:
1125     ;;; -- CONT has other uses, or
1126     ;;; -- CONT receives multiple values, or
1127 ram 1.9 ;;; -- the reference is in a different environment from the variable, or
1128     ;;; -- either continuation has a funky TYPE-CHECK annotation.
1129 ram 1.27 ;;; -- the var's DEST has a different policy than the ARG's (think safety).
1130 ram 1.7 ;;;
1131     ;;; We change the Ref to be a reference to NIL with unused value, and let it
1132     ;;; be flushed as dead code. A side-effect of this substitution is to delete
1133     ;;; the variable.
1134     ;;;
1135     (defun substitute-single-use-continuation (arg var)
1136     (declare (type continuation arg) (type lambda-var var))
1137     (let* ((ref (first (leaf-refs var)))
1138     (cont (node-cont ref))
1139     (dest (continuation-dest cont)))
1140     (when (and (eq (continuation-use cont) ref)
1141     dest
1142     (not (typep dest '(or creturn exit mv-combination)))
1143 ram 1.11 (eq (node-home-lambda ref)
1144 ram 1.9 (lambda-home (lambda-var-home var)))
1145     (member (continuation-type-check arg) '(t nil))
1146 ram 1.27 (member (continuation-type-check cont) '(t nil))
1147     (eq (lexenv-cookie (node-lexenv dest))
1148     (lexenv-cookie (node-lexenv (continuation-dest arg)))))
1149 ram 1.25 (assert (member (continuation-kind arg)
1150     '(:block-start :deleted-block-start :inside-block)))
1151 ram 1.7 (assert-continuation-type arg (continuation-asserted-type cont))
1152 ram 1.34 (setf (node-derived-type ref) *wild-type*)
1153 ram 1.7 (change-ref-leaf ref (find-constant nil))
1154     (substitute-continuation arg cont)
1155     (reoptimize-continuation arg)
1156     t)))
1157    
1158    
1159 ram 1.19 ;;; DELETE-LET -- Interface
1160     ;;;
1161     ;;; Delete a Let, removing the call and bind nodes, and warning about any
1162     ;;; unreferenced variables. Note that FLUSH-DEAD-CODE will come along right
1163     ;;; away and delete the REF and then the lambda, since we flush the FUN
1164     ;;; continuation.
1165     ;;;
1166     (defun delete-let (fun)
1167     (declare (type clambda fun))
1168     (assert (eq (functional-kind fun) :let))
1169     (note-unreferenced-vars fun)
1170     (let ((call (let-combination fun)))
1171     (flush-dest (combination-fun call))
1172     (unlink-node call)
1173     (unlink-node (lambda-bind fun))
1174     (setf (lambda-bind fun) nil))
1175     (undefined-value))
1176    
1177    
1178 wlott 1.1 ;;; Propagate-Let-Args -- Internal
1179     ;;;
1180     ;;; This function is called when one of the arguments to a LET changes. We
1181     ;;; look at each changed argument. If the corresponding variable is set, then
1182     ;;; we call PROPAGATE-FROM-SETS. Otherwise, we consider substituting for the
1183     ;;; variable, and also propagate derived-type information for the arg to all
1184     ;;; the Var's refs.
1185     ;;;
1186 ram 1.16 ;;; Substitution is inhibited when the arg leaf's derived type isn't a
1187     ;;; subtype of the argument's asserted type. This prevents type checking from
1188     ;;; being defeated, and also ensures that the best representation for the
1189     ;;; variable can be used.
1190 wlott 1.1 ;;;
1191 ram 1.26 ;;; Substitution of individual references is inhibited if the reference is
1192     ;;; in a different component from the home. This can only happen with closures
1193     ;;; over top-level lambda vars. In such cases, the references may have already
1194     ;;; been compiled, and thus can't be retroactively modified.
1195     ;;;
1196 ram 1.19 ;;; If all of the variables are deleted (have no references) when we are
1197     ;;; done, then we delete the let.
1198     ;;;
1199 wlott 1.1 ;;; Note that we are responsible for clearing the Continuation-Reoptimize
1200     ;;; flags.
1201     ;;;
1202     (defun propagate-let-args (call fun)
1203     (declare (type combination call) (type clambda fun))
1204 ram 1.19 (loop for arg in (combination-args call)
1205     and var in (lambda-vars fun) do
1206     (when (and arg (continuation-reoptimize arg))
1207     (setf (continuation-reoptimize arg) nil)
1208     (cond
1209     ((lambda-var-sets var)
1210     (propagate-from-sets var (continuation-type arg)))
1211     ((let ((use (continuation-use arg)))
1212     (when (ref-p use)
1213     (let ((leaf (ref-leaf use)))
1214     (when (and (constant-reference-p use)
1215     (values-subtypep (leaf-type leaf)
1216     (continuation-asserted-type arg)))
1217     (propagate-to-refs var (continuation-type arg))
1218 ram 1.26 (let ((this-comp (block-component (node-block use))))
1219     (substitute-leaf-if
1220     #'(lambda (ref)
1221     (cond ((eq (block-component (node-block ref))
1222     this-comp)
1223     t)
1224     (t
1225     (assert (eq (functional-kind (lambda-home fun))
1226     :top-level))
1227     nil)))
1228     leaf var))
1229 ram 1.19 t)))))
1230     ((and (null (rest (leaf-refs var)))
1231     (substitute-single-use-continuation arg var)))
1232     (t
1233     (propagate-to-refs var (continuation-type arg))))))
1234    
1235     (when (every #'null (combination-args call))
1236     (delete-let fun))
1237    
1238 wlott 1.1 (undefined-value))
1239    
1240    
1241     ;;; Propagate-Local-Call-Args -- Internal
1242     ;;;
1243     ;;; This function is called when one of the args to a non-let local call
1244     ;;; changes. For each changed argument corresponding to an unset variable, we
1245     ;;; compute the union of the types across all calls and propagate this type
1246     ;;; information to the var's refs.
1247     ;;;
1248     ;;; If the function has an XEP, then we don't do anything, since we won't
1249     ;;; discover anything.
1250     ;;;
1251     ;;; We can clear the Continuation-Reoptimize flags for arguments in all calls
1252     ;;; corresponding to changed arguments in Call, since the only use in IR1
1253     ;;; optimization of the Reoptimize flag for local call args is right here.
1254     ;;;
1255     (defun propagate-local-call-args (call fun)
1256     (declare (type combination call) (type clambda fun))
1257    
1258     (unless (functional-entry-function fun)
1259     (let* ((vars (lambda-vars fun))
1260     (union (mapcar #'(lambda (arg var)
1261     (when (and arg
1262     (continuation-reoptimize arg)
1263     (null (basic-var-sets var)))
1264     (continuation-type arg)))
1265     (basic-combination-args call)
1266     vars))
1267     (this-ref (continuation-use (basic-combination-fun call))))
1268    
1269     (dolist (arg (basic-combination-args call))
1270     (when arg
1271     (setf (continuation-reoptimize arg) nil)))
1272    
1273     (dolist (ref (leaf-refs fun))
1274     (unless (eq ref this-ref)
1275     (setq union
1276     (mapcar #'(lambda (this-arg old)
1277     (when old
1278     (setf (continuation-reoptimize this-arg) nil)
1279     (type-union (continuation-type this-arg) old)))
1280     (basic-combination-args
1281     (continuation-dest (node-cont ref)))
1282     union))))
1283    
1284     (mapc #'(lambda (var type)
1285     (when type
1286     (propagate-to-refs var type)))
1287     vars union)))
1288    
1289 ram 1.6 (undefined-value))
1290    
1291    
1292 ram 1.19 ;;;; Multiple values optimization:
1293    
1294 ram 1.21 ;;; IR1-OPTIMIZE-MV-COMBINATION -- Internal
1295     ;;;
1296 ram 1.32 ;;; Do stuff to notice a change to a MV combination node. There are two
1297     ;;; main branches here:
1298     ;;; -- If the call is local, then it is already a MV let, or should become one.
1299     ;;; Note that although all :LOCAL MV calls must eventually be converted to
1300     ;;; :MV-LETs, there can be a window when the call is local, but has not
1301     ;;; been let converted yet. This is because the entry-point lambdas may
1302     ;;; have stray references (in other entry points) that have not been
1303     ;;; deleted yet.
1304     ;;; -- The call is full. This case is somewhat similar to the non-MV
1305     ;;; combination optimization: we propagate return type information and
1306     ;;; notice non-returning calls. We also have an optimization
1307     ;;; which tries to convert MV-CALLs into MV-binds.
1308 ram 1.21 ;;;
1309     (defun ir1-optimize-mv-combination (node)
1310 ram 1.31 (cond
1311     ((eq (basic-combination-kind node) :local)
1312     (let ((fun (basic-combination-fun node)))
1313     (when (continuation-reoptimize fun)
1314     (setf (continuation-reoptimize fun) nil)
1315     (maybe-let-convert (combination-lambda node))))
1316     (setf (continuation-reoptimize (first (basic-combination-args node))) nil)
1317 ram 1.32 (when (eq (functional-kind (combination-lambda node)) :mv-let)
1318     (unless (convert-mv-bind-to-let node)
1319     (ir1-optimize-mv-bind node))))
1320 ram 1.31 (t
1321     (let* ((fun (basic-combination-fun node))
1322     (fun-changed (continuation-reoptimize fun))
1323     (args (basic-combination-args node)))
1324     (when fun-changed
1325     (setf (continuation-reoptimize fun) nil)
1326     (let ((type (continuation-type fun)))
1327     (when (function-type-p type)
1328     (derive-node-type node (function-type-returns type))))
1329     (maybe-terminate-block node nil)
1330     (let ((use (continuation-use fun)))
1331     (when (and (ref-p use) (functional-p (ref-leaf use))
1332     (not (eq (ref-inlinep use) :notinline)))
1333     (convert-call-if-possible use node)
1334     (maybe-let-convert (ref-leaf use)))))
1335     (unless (or (eq (basic-combination-kind node) :local)
1336     (eq (continuation-function-name fun) '%throw))
1337     (ir1-optimize-mv-call node))
1338     (dolist (arg args)
1339     (setf (continuation-reoptimize arg) nil)))))
1340 ram 1.21 (undefined-value))
1341    
1342    
1343 ram 1.6 ;;; IR1-OPTIMIZE-MV-BIND -- Internal
1344     ;;;
1345     ;;; Propagate derived type info from the values continuation to the vars.
1346     ;;;
1347     (defun ir1-optimize-mv-bind (node)
1348     (declare (type mv-combination node))
1349     (let ((arg (first (basic-combination-args node)))
1350     (vars (lambda-vars (combination-lambda node))))
1351     (multiple-value-bind (types nvals)
1352     (values-types (continuation-derived-type arg))
1353     (unless (eq nvals :unknown)
1354     (mapc #'(lambda (var type)
1355     (if (basic-var-sets var)
1356     (propagate-from-sets var type)
1357     (propagate-to-refs var type)))
1358     vars
1359     (append types
1360     (make-list (max (- (length vars) nvals) 0)
1361     :initial-element *null-type*)))))
1362    
1363     (setf (continuation-reoptimize arg) nil))
1364 wlott 1.1 (undefined-value))
1365 ram 1.19
1366    
1367 ram 1.21 ;;; IR1-OPTIMIZE-MV-CALL -- Internal
1368 ram 1.19 ;;;
1369 ram 1.21 ;;; If possible, convert a general MV call to an MV-BIND. We can do this
1370     ;;; if:
1371 ram 1.22 ;;; -- The call has only one argument, and
1372 ram 1.21 ;;; -- The function has a known fixed number of arguments, or
1373 ram 1.22 ;;; -- The argument yields a known fixed number of values.
1374 ram 1.21 ;;;
1375     ;;; What we do is change the function in the MV-CALL to be a lambda that "looks
1376     ;;; like an MV bind", which allows IR1-OPTIMIZE-MV-COMBINATION to notice that
1377     ;;; this call can be converted (the next time around.) This new lambda just
1378 ram 1.31 ;;; calls the actual function with the MV-BIND variables as arguments. Note
1379     ;;; that this new MV bind is not let-converted immediately, as there are going
1380     ;;; to be stray references from the entry-point functions until they get
1381     ;;; deleted.
1382 ram 1.21 ;;;
1383     ;;; In order to avoid loss of argument count checking, we only do the
1384     ;;; transformation according to a known number of expected argument if safety
1385     ;;; is unimportant. We can always convert if we know the number of actual
1386     ;;; values, since the normal call that we build will still do any appropriate
1387     ;;; argument count checking.
1388     ;;;
1389     ;;; We only attempt the transformation if the called function is a constant
1390     ;;; reference. This allows us to just splice the leaf into the new function,
1391     ;;; instead of trying to somehow bind the function expression. The leaf must
1392     ;;; be constant because we are evaluating it again in a different place. This
1393     ;;; also has the effect of squelching multiple warnings when there is an
1394     ;;; argument count error.
1395     ;;;
1396     (defun ir1-optimize-mv-call (node)
1397     (let ((fun (basic-combination-fun node))
1398     (*compiler-error-context* node)
1399 ram 1.22 (ref (continuation-use (basic-combination-fun node)))
1400     (args (basic-combination-args node)))
1401 ram 1.21
1402 ram 1.22 (unless (and (ref-p ref) (constant-reference-p ref)
1403     args (null (rest args)))
1404 ram 1.21 (return-from ir1-optimize-mv-call))
1405    
1406     (multiple-value-bind (min max)
1407     (function-type-nargs (continuation-type fun))
1408 ram 1.22 (let ((total-nvals
1409     (multiple-value-bind
1410     (types nvals)
1411     (values-types (continuation-derived-type (first args)))
1412     (declare (ignore types))
1413     (if (eq nvals :unknown) nil nvals))))
1414 ram 1.21
1415 ram 1.22 (when total-nvals
1416     (when (and min (< total-nvals min))
1417     (compiler-warning
1418     "MULTIPLE-VALUE-CALL with ~R values when the function expects ~
1419     at least ~R."
1420     total-nvals min)
1421     (setf (ref-inlinep ref) :notinline)
1422     (return-from ir1-optimize-mv-call))
1423     (when (and max (> total-nvals max))
1424     (compiler-warning
1425     "MULTIPLE-VALUE-CALL with ~R values when the function expects ~
1426     at most ~R."
1427     total-nvals max)
1428     (setf (ref-inlinep ref) :notinline)
1429     (return-from ir1-optimize-mv-call)))
1430 ram 1.21
1431 ram 1.22 (let ((count (cond (total-nvals)
1432     ((and (policy node (zerop safety)) (eql min max))
1433     min)
1434     (t nil))))
1435     (when count
1436     (with-ir1-environment node
1437     (let* ((dums (loop repeat count collect (gensym)))
1438     (ignore (gensym))
1439     (fun (ir1-convert-lambda
1440     `(lambda (&optional ,@dums &rest ,ignore)
1441     (declare (ignore ,ignore))
1442     (funcall ,(ref-leaf ref) ,@dums)))))
1443     (change-ref-leaf ref fun)
1444     (assert (eq (basic-combination-kind node) :full))
1445     (local-call-analyze *current-component*)
1446 ram 1.23 (assert (eq (basic-combination-kind node) :local)))))))))
1447 ram 1.21 (undefined-value))
1448    
1449    
1450     ;;; CONVERT-MV-BIND-TO-LET -- Internal
1451     ;;;
1452 ram 1.19 ;;; If we see:
1453     ;;; (multiple-value-bind (x y)
1454     ;;; (values xx yy)
1455     ;;; ...)
1456     ;;; Convert to:
1457     ;;; (let ((x xx)
1458     ;;; (y yy))
1459     ;;; ...)
1460     ;;;
1461     ;;; What we actually do is convert the VALUES combination into a normal let
1462 ram 1.31 ;;; combination calling the original :MV-LET lambda. If there are extra args to
1463 ram 1.19 ;;; VALUES, discard the corresponding continuations. If there are insufficient
1464     ;;; args, insert references to NIL.
1465     ;;;
1466 ram 1.21 (defun convert-mv-bind-to-let (call)
1467     (declare (type mv-combination call))
1468     (let* ((arg (first (basic-combination-args call)))
1469     (use (continuation-use arg)))
1470     (when (and (combination-p use)
1471     (eq (continuation-function-name (combination-fun use))
1472     'values))
1473     (let* ((fun (combination-lambda call))
1474 ram 1.19 (vars (lambda-vars fun))
1475 ram 1.21 (vals (combination-args use))
1476 ram 1.19 (nvars (length vars))
1477     (nvals (length vals)))
1478     (cond ((> nvals nvars)
1479     (mapc #'flush-dest (subseq vals nvars))
1480     (setq vals (subseq vals 0 nvars)))
1481     ((< nvals nvars)
1482 ram 1.21 (with-ir1-environment use
1483     (let ((node-prev (node-prev use)))
1484     (setf (node-prev use) nil)
1485 ram 1.19 (setf (continuation-next node-prev) nil)
1486     (collect ((res vals))
1487 ram 1.21 (loop as cont = (make-continuation use)
1488 ram 1.19 and prev = node-prev then cont
1489     repeat (- nvars nvals)
1490     do (reference-constant prev cont nil)
1491     (res cont))
1492     (setq vals (res)))
1493 ram 1.21 (prev-link use (car (last vals)))))))
1494     (setf (combination-args use) vals)
1495     (flush-dest (combination-fun use))
1496     (let ((fun-cont (basic-combination-fun call)))
1497     (setf (continuation-dest fun-cont) use)
1498     (setf (combination-fun use) fun-cont))
1499     (setf (combination-kind use) :local)
1500 ram 1.19 (setf (functional-kind fun) :let)
1501 ram 1.21 (flush-dest (first (basic-combination-args call)))
1502     (unlink-node call)
1503 ram 1.19 (when vals
1504 ram 1.20 (reoptimize-continuation (first vals)))
1505 ram 1.21 (propagate-to-args use fun))
1506     t)))
1507    
1508    
1509     ;;; VALUES-LIST IR1 optimizer -- Internal
1510     ;;;
1511     ;;; If we see:
1512     ;;; (values-list (list x y z))
1513     ;;;
1514     ;;; Convert to:
1515     ;;; (values x y z)
1516     ;;;
1517     ;;; In implementation, this is somewhat similar to CONVERT-MV-BIND-TO-LET. We
1518     ;;; grab the args of LIST and make them args of the VALUES-LIST call, flushing
1519     ;;; the old argument continuation (allowing the LIST to be flushed.)
1520     ;;;
1521     (defoptimizer (values-list optimizer) ((list) node)
1522     (let ((use (continuation-use list)))
1523     (when (and (combination-p use)
1524     (eq (continuation-function-name (combination-fun use))
1525     'list))
1526     (change-ref-leaf (continuation-use (combination-fun node))
1527     (find-free-function 'values "in a strange place"))
1528     (setf (combination-kind node) :full)
1529     (let ((args (combination-args use)))
1530     (dolist (arg args)
1531     (setf (continuation-dest arg) node))
1532     (setf (combination-args use) nil)
1533     (flush-dest list)
1534     (setf (combination-args node) args))
1535 ram 1.19 t)))
1536    
1537    
1538     ;;; VALUES IR1 transform -- Internal
1539     ;;;
1540     ;;; If VALUES appears in a non-MV context, then effectively convert it to a
1541     ;;; PROG1. This allows the computation of the additional values to become dead
1542     ;;; code.
1543     ;;;
1544     (deftransform values ((&rest vals) * * :node node)
1545     (when (typep (continuation-dest (node-cont node))
1546     '(or creturn exit mv-combination))
1547     (give-up))
1548 ram 1.34 (setf (node-derived-type node) *wild-type*)
1549 ram 1.33 (if vals
1550     (let ((dummies (loop repeat (1- (length vals))
1551 ram 1.19 collect (gensym))))
1552 ram 1.33 `(lambda (val ,@dummies)
1553     (declare (ignore ,@dummies))
1554     val))
1555     'nil))
1556 wlott 1.1
1557    
1558     ;;; Flush-Dead-Code -- Internal
1559     ;;;
1560     ;;; Delete any nodes in Block whose value is unused and have no
1561     ;;; side-effects. We can delete sets of lexical variables when the set
1562     ;;; variable has no references.
1563     ;;;
1564     ;;; [### For now, don't delete potentially flushable calls when they have the
1565     ;;; Call attribute. Someday we should look at the funcitonal args to determine
1566     ;;; if they have any side-effects.]
1567     ;;;
1568     (defun flush-dead-code (block)
1569     (declare (type cblock block))
1570     (do-nodes-backwards (node cont block)
1571     (unless (continuation-dest cont)
1572     (typecase node
1573     (ref
1574     (delete-ref node)
1575     (unlink-node node))
1576     (combination
1577     (let ((info (combination-kind node)))
1578     (when (function-info-p info)
1579     (let ((attr (function-info-attributes info)))
1580     (when (and (ir1-attributep attr flushable)
1581     (not (ir1-attributep attr call)))
1582     (flush-dest (combination-fun node))
1583     (dolist (arg (combination-args node))
1584     (flush-dest arg))
1585     (unlink-node node))))))
1586     (exit
1587     (let ((value (exit-value node)))
1588     (when value
1589     (flush-dest value)
1590     (setf (exit-value node) nil))))
1591     (cset
1592     (let ((var (set-var node)))
1593     (when (and (lambda-var-p var)
1594     (null (leaf-refs var)))
1595     (flush-dest (set-value node))
1596     (setf (basic-var-sets var)
1597     (delete node (basic-var-sets var)))
1598     (unlink-node node)))))))
1599    
1600     (setf (block-flush-p block) nil)
1601     (undefined-value))

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