1 ;;;; This file implements the environment analysis phase for the
2 ;;;; compiler. This phase annotates IR1 with a hierarchy environment
3 ;;;; structures, determining the physical environment that each LAMBDA
4 ;;;; allocates its variables and finding what values are closed over
5 ;;;; by each physical environment.
7 ;;;; This software is part of the SBCL system. See the README file for
10 ;;;; This software is derived from the CMU CL system, which was
11 ;;;; written at Carnegie Mellon University and released into the
12 ;;;; public domain. The software is in the public domain and is
13 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
14 ;;;; files for more information.
18 ;;; Do environment analysis on the code in COMPONENT. This involves
20 ;;; 1. Make a PHYSENV structure for each non-LET LAMBDA, assigning
21 ;;; the LAMBDA-PHYSENV for all LAMBDAs.
22 ;;; 2. Find all values that need to be closed over by each
23 ;;; physical environment.
24 ;;; 3. Scan the blocks in the component closing over non-local-exit
26 ;;; 4. Delete all non-top-level functions with no references. This
27 ;;; should only get functions with non-NULL kinds, since normal
28 ;;; functions are deleted when their references go to zero.
29 (defun physenv-analyze (component)
30 (declare (type component component))
31 (aver (every (lambda (x)
32 (eq (functional-kind x) :deleted))
33 (component-new-functionals component)))
34 (setf (component-new-functionals component) ())
35 (dolist (clambda (component-lambdas component))
36 (reinit-lambda-physenv clambda))
37 (mapc #'add-lambda-vars-and-let-vars-to-closures
38 (component-lambdas component))
40 (find-non-local-exits component)
41 (recheck-dynamic-extent-lvars component)
42 (find-cleanup-points component)
43 (tail-annotate component)
44 (analyze-indirect-lambda-vars component)
46 (dolist (fun (component-lambdas component))
47 (when (null (leaf-refs fun))
48 (let ((kind (functional-kind fun)))
49 (unless (or (eq kind :toplevel)
50 (functional-has-external-references-p fun))
51 (aver (member kind '(:optional :cleanup :escape)))
52 (setf (functional-kind fun) nil)
53 (delete-functional fun)))))
55 (setf (component-nlx-info-generated-p component) t)
58 ;;; This is to be called on a COMPONENT with top level LAMBDAs before
59 ;;; the compilation of the associated non-top-level code to detect
60 ;;; closed over top level variables. We just do COMPUTE-CLOSURE on all
61 ;;; the lambdas. This will pre-allocate environments for all the
62 ;;; functions with closed-over top level variables. The post-pass will
63 ;;; use the existing structure, rather than allocating a new one. We
64 ;;; return true if we discover any possible closure vars.
65 (defun pre-physenv-analyze-toplevel (component)
66 (declare (type component component))
68 (dolist (lambda (component-lambdas component))
69 (when (add-lambda-vars-and-let-vars-to-closures lambda)
73 ;;; If CLAMBDA has a PHYSENV, return it, otherwise assign an empty one
75 (defun get-lambda-physenv (clambda)
76 (declare (type clambda clambda))
77 (let ((homefun (lambda-home clambda)))
78 (or (lambda-physenv homefun)
79 (let ((res (make-physenv :lambda homefun)))
80 (setf (lambda-physenv homefun) res)
81 ;; All the LETLAMBDAs belong to HOMEFUN, and share the same
82 ;; PHYSENV. Thus, (1) since HOMEFUN's PHYSENV was NIL,
83 ;; theirs should be NIL too, and (2) since we're modifying
84 ;; HOMEFUN's PHYSENV, we should modify theirs, too.
85 (dolist (letlambda (lambda-lets homefun))
86 (aver (eql (lambda-home letlambda) homefun))
87 (aver (null (lambda-physenv letlambda)))
88 (setf (lambda-physenv letlambda) res))
91 ;;; If FUN has no physical environment, assign one, otherwise clean up
92 ;;; the old physical environment and the INDIRECT flag on LAMBDA-VARs.
93 ;;; This is necessary because pre-analysis is done before
95 (defun reinit-lambda-physenv (fun)
96 (let ((old (lambda-physenv (lambda-home fun))))
98 (setf (physenv-closure old) nil)
100 (dolist (var (lambda-vars fun))
101 (setf (lambda-var-indirect var) nil))))
103 (map nil #'clear (lambda-lets fun))))
105 (get-lambda-physenv fun))))
108 ;;; Get NODE's environment, assigning one if necessary.
109 (defun get-node-physenv (node)
110 (declare (type node node))
111 (get-lambda-physenv (node-home-lambda node)))
113 ;;; private guts of ADD-LAMBDA-VARS-AND-LET-VARS-TO-CLOSURES
115 ;;; This is the old CMU CL COMPUTE-CLOSURE, which only works on
116 ;;; LAMBDA-VARS directly, not on the LAMBDA-VARS of LAMBDA-LETS. It
117 ;;; seems never to be valid to use this operation alone, so in SBCL,
118 ;;; it's private, and the public interface,
119 ;;; ADD-LAMBDA-VARS-AND-LET-VARS-TO-CLOSURES, always runs over all the
120 ;;; variables, not only the LAMBDA-VARS of CLAMBDA itself but also
121 ;;; the LAMBDA-VARS of CLAMBDA's LAMBDA-LETS.
122 (defun %add-lambda-vars-to-closures (clambda)
123 (let ((physenv (get-lambda-physenv clambda))
125 (note-unreferenced-vars clambda)
126 (dolist (var (lambda-vars clambda))
127 (dolist (ref (leaf-refs var))
128 (let ((ref-physenv (get-node-physenv ref)))
129 (unless (eq ref-physenv physenv)
130 (when (lambda-var-sets var)
131 (setf (lambda-var-indirect var) t))
132 (setq did-something t)
133 (close-over var ref-physenv physenv))))
134 (dolist (set (basic-var-sets var))
136 ;; Variables which are set but never referenced can be
137 ;; optimized away, and closing over them here would just
138 ;; interfere with that. (In bug 147, it *did* interfere with
139 ;; that, causing confusion later. This UNLESS solves that
140 ;; problem, but I (WHN) am not 100% sure it's best to solve
141 ;; the problem this way instead of somehow solving it
142 ;; somewhere upstream and just doing (AVER (LEAF-REFS VAR))
144 (unless (null (leaf-refs var))
146 (let ((set-physenv (get-node-physenv set)))
147 (unless (eq set-physenv physenv)
148 (setf did-something t
149 (lambda-var-indirect var) t)
150 (close-over var set-physenv physenv))))))
153 ;;; Find any variables in CLAMBDA -- either directly in LAMBDA-VARS or
154 ;;; in the LAMBDA-VARS of elements of LAMBDA-LETS -- with references
155 ;;; outside of the home environment and close over them. If a
156 ;;; closed-over variable is set, then we set the INDIRECT flag so that
157 ;;; we will know the closed over value is really a pointer to the
158 ;;; value cell. We also warn about unreferenced variables here, just
159 ;;; because it's a convenient place to do it. We return true if we
160 ;;; close over anything.
161 (defun add-lambda-vars-and-let-vars-to-closures (clambda)
162 (declare (type clambda clambda))
163 (let ((did-something nil))
164 (when (%add-lambda-vars-to-closures clambda)
165 (setf did-something t))
166 (dolist (lambda-let (lambda-lets clambda))
167 ;; There's no need to recurse through full COMPUTE-CLOSURE
168 ;; here, since LETS only go one layer deep.
169 (aver (null (lambda-lets lambda-let)))
170 (when (%add-lambda-vars-to-closures lambda-let)
171 (setf did-something t)))
174 (defun xep-allocator (xep)
175 (let ((entry (functional-entry-fun xep)))
176 (functional-allocator entry)))
178 ;;; Make sure that THING is closed over in REF-PHYSENV and in all
179 ;;; PHYSENVs for the functions that reference REF-PHYSENV's function
180 ;;; (not just calls). HOME-PHYSENV is THING's home environment. When we
181 ;;; reach the home environment, we stop propagating the closure.
182 (defun close-over (thing ref-physenv home-physenv)
183 (declare (type physenv ref-physenv home-physenv))
184 (let ((flooded-physenvs nil))
185 (labels ((flood (flooded-physenv)
186 (unless (or (eql flooded-physenv home-physenv)
187 (member flooded-physenv flooded-physenvs))
188 (push flooded-physenv flooded-physenvs)
189 (unless (memq thing (physenv-closure flooded-physenv))
190 (push thing (physenv-closure flooded-physenv))
191 (let ((lambda (physenv-lambda flooded-physenv)))
192 (cond ((eq (functional-kind lambda) :external)
193 (let* ((alloc-node (xep-allocator lambda))
194 (alloc-lambda (node-home-lambda alloc-node))
195 (alloc-physenv (get-lambda-physenv alloc-lambda)))
196 (flood alloc-physenv)
197 (dolist (ref (leaf-refs lambda))
199 (get-node-physenv ref) alloc-physenv))))
200 (t (dolist (ref (leaf-refs lambda))
201 ;; FIXME: This assertion looks
202 ;; reasonable, but does not work for
205 (let ((dest (node-dest ref)))
206 (aver (basic-combination-p dest))
207 (aver (eq (basic-combination-kind dest) :local)))
208 (flood (get-node-physenv ref))))))))))
209 (flood ref-physenv)))
212 ;;; Find LAMBDA-VARs that are marked as needing to support indirect
213 ;;; access (SET at some point after initial creation) that are present
214 ;;; in CLAMBDAs not marked as being DYNAMIC-EXTENT (meaning that the
215 ;;; value-cell involved must be able to survive past the extent of the
216 ;;; allocating frame), and mark them (the LAMBDA-VARs) as needing
217 ;;; explicit value-cells. Because they are already closed-over, the
218 ;;; LAMBDA-VARs already appear in the closures of all of the CLAMBDAs
219 ;;; that need checking.
220 (defun analyze-indirect-lambda-vars (component)
221 (dolist (fun (component-lambdas component))
222 (let ((entry-fun (functional-entry-fun fun)))
223 ;; We also check the ENTRY-FUN, as XEPs for LABELS or FLET
224 ;; functions aren't set to be DX even if their underlying
225 ;; CLAMBDAs are, and if we ever get LET-bound anonymous function
226 ;; DX working, it would mark the XEP as being DX but not the
227 ;; "real" CLAMBDA. This works because a FUNCTIONAL-ENTRY-FUN is
228 ;; either NULL, a self-pointer (for :TOPLEVEL functions), a
229 ;; pointer from an XEP to its underlying function (for :EXTERNAL
230 ;; functions), or a pointer from an underlying function to its
231 ;; XEP (for non-:TOPLEVEL functions with XEPs).
232 (unless (or (leaf-dynamic-extent fun)
233 ;; Functions without XEPs can be treated as if they
234 ;; are DYNAMIC-EXTENT, even without being so
235 ;; declared, as any escaping closure which /isn't/
236 ;; DYNAMIC-EXTENT but calls one of these functions
237 ;; will also close over the required variables, thus
238 ;; forcing the allocation of value cells. Since the
239 ;; XEP is stored in the ENTRY-FUN slot, we can pick
240 ;; off the non-XEP case here.
242 (leaf-dynamic-extent entry-fun))
243 (let ((closure (physenv-closure (lambda-physenv fun))))
244 (dolist (var closure)
245 (when (and (lambda-var-p var)
246 (lambda-var-indirect var))
247 (setf (lambda-var-explicit-value-cell var) t))))))))
251 #!-sb-fluid (declaim (inline should-exit-check-tag-p))
252 (defun exit-should-check-tag-p (exit)
253 (declare (type exit exit))
254 (not (zerop (policy exit check-tag-existence))))
256 ;;; Insert the entry stub before the original exit target, and add a
257 ;;; new entry to the PHYSENV-NLX-INFO. The %NLX-ENTRY call in the
258 ;;; stub is passed the NLX-INFO as an argument so that the back end
259 ;;; knows what entry is being done.
261 ;;; The link from the EXIT block to the entry stub is changed to be a
262 ;;; link from the component head. Similarly, the EXIT block is linked
263 ;;; to the component tail. This leaves the entry stub reachable, but
264 ;;; makes the flow graph less confusing to flow analysis.
266 ;;; If a CATCH or an UNWIND-protect, then we set the LEXENV for the
267 ;;; last node in the cleanup code to be the enclosing environment, to
268 ;;; represent the fact that the binding was undone as a side effect of
269 ;;; the exit. This will cause a lexical exit to be broken up if we are
270 ;;; actually exiting the scope (i.e. a BLOCK), and will also do any
271 ;;; other cleanups that may have to be done on the way.
272 (defun insert-nlx-entry-stub (exit env)
273 (declare (type physenv env) (type exit exit))
274 (let* ((exit-block (node-block exit))
275 (next-block (first (block-succ exit-block)))
276 (entry (exit-entry exit))
277 (cleanup (entry-cleanup entry))
278 (info (make-nlx-info cleanup exit))
279 (new-block (insert-cleanup-code exit-block next-block
283 (component (block-component new-block)))
284 (unlink-blocks exit-block new-block)
285 (link-blocks exit-block (component-tail component))
286 (link-blocks (component-head component) new-block)
288 (setf (exit-nlx-info exit) info)
289 (setf (nlx-info-target info) new-block)
290 (setf (nlx-info-safe-p info) (exit-should-check-tag-p exit))
291 (push info (physenv-nlx-info env))
292 (push info (cleanup-info cleanup))
293 (when (member (cleanup-kind cleanup) '(:catch :unwind-protect))
294 (setf (node-lexenv (block-last new-block))
295 (node-lexenv entry))))
299 ;;; Do stuff necessary to represent a non-local exit from the node
300 ;;; EXIT into ENV. This is called for each non-local exit node, of
301 ;;; which there may be several per exit continuation. This is what we
303 ;;; -- If there isn't any NLX-INFO entry in the environment, make
304 ;;; an entry stub, otherwise just move the exit block link to
305 ;;; the component tail.
306 ;;; -- Close over the NLX-INFO in the exit environment.
307 ;;; -- If the exit is from an :ESCAPE function, then substitute a
308 ;;; constant reference to NLX-INFO structure for the escape
309 ;;; function reference. This will cause the escape function to
310 ;;; be deleted (although not removed from the DFO.) The escape
311 ;;; function is no longer needed, and we don't want to emit code
313 ;;; -- Change the %NLX-ENTRY call to use the NLX lvar so that 1) there
314 ;;; will be a use to represent the NLX use; 2) make life easier for
315 ;;; the stack analysis.
316 (defun note-non-local-exit (env exit)
317 (declare (type physenv env) (type exit exit))
318 (let ((lvar (node-lvar exit))
319 (exit-fun (node-home-lambda exit))
320 (info (find-nlx-info exit)))
322 (let ((block (node-block exit)))
323 (aver (= (length (block-succ block)) 1))
324 (unlink-blocks block (first (block-succ block)))
325 (link-blocks block (component-tail (block-component block)))
326 (setf (exit-nlx-info exit) info)
327 (unless (nlx-info-safe-p info)
328 (setf (nlx-info-safe-p info)
329 (exit-should-check-tag-p exit)))))
331 (insert-nlx-entry-stub exit env)
332 (setq info (exit-nlx-info exit))
334 (close-over info (node-physenv exit) env)
335 (when (eq (functional-kind exit-fun) :escape)
337 (setf (node-derived-type x) *wild-type*))
338 (leaf-refs exit-fun))
339 (substitute-leaf (find-constant info) exit-fun))
341 (let ((node (block-last (nlx-info-target info))))
342 (unless (node-lvar node)
343 (aver (eq lvar (node-lvar exit)))
344 (setf (node-derived-type node) (lvar-derived-type lvar))
345 (add-lvar-use node lvar)))))
348 ;;; Iterate over the EXITs in COMPONENT, calling NOTE-NON-LOCAL-EXIT
349 ;;; when we find a block that ends in a non-local EXIT node. We also
350 ;;; ensure that all EXIT nodes are either non-local or degenerate by
351 ;;; calling IR1-OPTIMIZE-EXIT on local exits. This makes life simpler
352 ;;; for later phases.
353 (defun find-non-local-exits (component)
354 (declare (type component component))
355 (dolist (lambda (component-lambdas component))
356 (dolist (entry (lambda-entries lambda))
357 (dolist (exit (entry-exits entry))
358 (let ((target-physenv (node-physenv entry)))
359 (if (eq (node-physenv exit) target-physenv)
360 (maybe-delete-exit exit)
361 (note-non-local-exit target-physenv exit))))))
364 ;;;; final decision on stack allocation of dynamic-extent structures
365 (defun recheck-dynamic-extent-lvars (component)
366 (declare (type component component))
367 (dolist (lambda (component-lambdas component))
368 (loop for entry in (lambda-entries lambda)
369 for cleanup = (entry-cleanup entry)
370 do (when (eq (cleanup-kind cleanup) :dynamic-extent)
371 (collect ((real-dx-lvars))
372 (loop for what in (cleanup-info cleanup)
375 (let ((dx (car what))
377 (cond ((lvar-good-for-dx-p lvar dx component)
378 ;; Since the above check does deep
379 ;; checks. we need to deal with the deep
380 ;; results in here as well.
381 (dolist (cell (handle-nested-dynamic-extent-lvars
383 (let ((real (principal-lvar (cdr cell))))
384 (setf (lvar-dynamic-extent real) cleanup)
385 (real-dx-lvars real))))
387 (note-no-stack-allocation lvar)
388 (setf (lvar-dynamic-extent lvar) nil)))))
391 (arg (first (basic-combination-args call)))
392 (funs (lvar-value arg))
395 (binding* ((() (leaf-dynamic-extent fun)
397 (xep (functional-entry-fun fun)
399 (closure (physenv-closure
400 (get-lambda-physenv xep))))
404 (setf (leaf-dynamic-extent fun) nil)))))
406 (setf (lvar-dynamic-extent arg) cleanup)
407 (real-dx-lvars arg))))))
408 (let ((real-dx-lvars (delete-duplicates (real-dx-lvars))))
409 (setf (cleanup-info cleanup) real-dx-lvars)
410 (setf (component-dx-lvars component)
411 (append real-dx-lvars (component-dx-lvars component))))))))
414 ;;;; cleanup emission
416 ;;; Zoom up the cleanup nesting until we hit CLEANUP1, accumulating
417 ;;; cleanup code as we go. When we are done, convert the cleanup code
418 ;;; in an implicit MV-PROG1. We have to force local call analysis of
419 ;;; new references to UNWIND-PROTECT cleanup functions. If we don't
420 ;;; actually have to do anything, then we don't insert any cleanup
421 ;;; code. (FIXME: There's some confusion here, left over from CMU CL
422 ;;; comments. CLEANUP1 isn't mentioned in the code of this function.
423 ;;; It is in code elsewhere, but if the comments for this function
424 ;;; mention it they should explain the relationship to the other code.)
426 ;;; If we do insert cleanup code, we check that BLOCK1 doesn't end in
427 ;;; a "tail" local call.
429 ;;; We don't need to adjust the ending cleanup of the cleanup block,
430 ;;; since the cleanup blocks are inserted at the start of the DFO, and
431 ;;; are thus never scanned.
432 (defun emit-cleanups (block1 block2)
433 (declare (type cblock block1 block2))
436 (let ((cleanup2 (block-start-cleanup block2)))
437 (do ((cleanup (block-end-cleanup block1)
438 (node-enclosing-cleanup (cleanup-mess-up cleanup))))
439 ((eq cleanup cleanup2))
440 (let* ((node (cleanup-mess-up cleanup))
441 (args (when (basic-combination-p node)
442 (basic-combination-args node))))
443 (ecase (cleanup-kind cleanup)
445 (code `(%special-unbind ',(lvar-value (first args)))))
447 (code `(%catch-breakup)))
449 (code `(%unwind-protect-breakup))
450 (let ((fun (ref-leaf (lvar-uses (second args)))))
452 (code `(%funcall ,fun))))
454 (dolist (nlx (cleanup-info cleanup))
455 (code `(%lexical-exit-breakup ',nlx))))
457 (when (not (null (cleanup-info cleanup)))
458 (code `(%cleanup-point)))))))
461 (aver (not (node-tail-p (block-last block1))))
462 (insert-cleanup-code block1 block2
465 (dolist (fun (reanalyze-funs))
466 (locall-analyze-fun-1 fun)))))
470 ;;; Loop over the blocks in COMPONENT, calling EMIT-CLEANUPS when we
471 ;;; see a successor in the same environment with a different cleanup.
472 ;;; We ignore the cleanup transition if it is to a cleanup enclosed by
473 ;;; the current cleanup, since in that case we are just messing up the
474 ;;; environment, hence this is not the place to clean it.
475 (defun find-cleanup-points (component)
476 (declare (type component component))
477 (do-blocks (block1 component)
478 (let ((env1 (block-physenv block1))
479 (cleanup1 (block-end-cleanup block1)))
480 (dolist (block2 (block-succ block1))
481 (when (block-start block2)
482 (let ((env2 (block-physenv block2))
483 (cleanup2 (block-start-cleanup block2)))
484 (unless (or (not (eq env2 env1))
485 (eq cleanup1 cleanup2)
487 (eq (node-enclosing-cleanup
488 (cleanup-mess-up cleanup2))
490 (emit-cleanups block1 block2)))))))
493 ;;; Mark optimizable tail-recursive uses of function result
494 ;;; continuations with the corresponding TAIL-SET.
495 (defun tail-annotate (component)
496 (declare (type component component))
497 (dolist (fun (component-lambdas component))
498 (let ((ret (lambda-return fun)))
499 ;; Nodes whose type is NIL (i.e. don't return) such as calls to
500 ;; ERROR are never annotated as TAIL-P, in order to preserve
501 ;; debugging information.
503 ;; FIXME: It might be better to add another DEFKNOWN property
504 ;; (e.g. NO-TAIL-RECURSION) and use it for error-handling
505 ;; functions like ERROR, instead of spreading this special case
506 ;; net so widely. --WHN?
508 ;; Why is that bad? Because this non-elimination of
509 ;; non-returning tail calls causes the XEP for FOO appear in
510 ;; backtrace for (defun foo (x) (error "foo ~S" x)) wich seems
511 ;; less then optimal. --NS 2005-02-28
513 (let ((result (return-result ret)))
514 (do-uses (use result)
515 (when (and (policy use merge-tail-calls)
516 (basic-combination-p use)
517 (immediately-used-p result use)
518 (or (not (eq (node-derived-type use) *empty-type*))
519 (eq (basic-combination-kind use) :local)))
520 (setf (node-tail-p use) t)))))))