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-functions component)))
34 (setf (component-new-functions component) ())
35 (dolist (fun (component-lambdas component))
36 (reinit-lambda-physenv fun))
37 (dolist (fun (component-lambdas component))
39 (dolist (let (lambda-lets fun))
40 (compute-closure let)))
42 (find-non-local-exits component)
43 (find-cleanup-points component)
44 (tail-annotate 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)))))
57 ;;; This is to be called on a COMPONENT with top level LAMBDAs before
58 ;;; the compilation of the associated non-top-level code to detect
59 ;;; closed over top level variables. We just do COMPUTE-CLOSURE on all
60 ;;; the lambdas. This will pre-allocate environments for all the
61 ;;; functions with closed-over top level variables. The post-pass will
62 ;;; use the existing structure, rather than allocating a new one. We
63 ;;; return true if we discover any possible closure vars.
64 (defun pre-physenv-analyze-toplevel (component)
65 (declare (type component component))
67 (dolist (lambda (component-lambdas component))
68 (when (compute-closure lambda)
70 (dolist (let (lambda-lets lambda))
71 (when (compute-closure let)
75 ;;; This is like old CMU CL PRE-ENVIRONMENT-ANALYZE-TOPLEVEL, except
76 ;;; (1) It's been brought into the post-0.7.0 world where the property
77 ;;; HAS-EXTERNAL-REFERENCES-P is orthogonal to the property of
78 ;;; being specialized/optimized for locall at top level.
79 ;;; (2) There's no return value, since we don't care whether we
80 ;;; find any possible closure variables.
82 ;;; I wish I could find an explanation of why
83 ;;; PRE-ENVIRONMENT-ANALYZE-TOPLEVEL is important. The old CMU CL
85 ;;; Called on component with top level lambdas before the
86 ;;; compilation of the associated non-top-level code to detect
87 ;;; closed over top level variables. We just do COMPUTE-CLOSURE on
88 ;;; all the lambdas. This will pre-allocate environments for all
89 ;;; the functions with closed-over top level variables. The
90 ;;; post-pass will use the existing structure, rather than
91 ;;; allocating a new one. We return true if we discover any
92 ;;; possible closure vars.
93 ;;; But that doesn't seem to explain why it's important. I do observe
94 ;;; that when it's not done, compiler assertions occasionally fail. My
95 ;;; tentative hypothesis is that other environment analysis expects to
96 ;;; bottom out on the outermost enclosing thing, and (insert
97 ;;; mysterious reason here) it's important to set up bottomed-out-here
98 ;;; environments before anything else. -- WHN 2001-09-30
99 (defun preallocate-physenvs-for-toplevelish-lambdas (component)
100 (/show "entering PREALLOCATE-PHYSENVS-FOR-TOPLEVELISH-LAMDBAS" component)
101 (dolist (clambda (component-lambdas component))
102 (/show clambda (lambda-vars clambda) (lambda-toplevelish-p clambda))
103 (when (lambda-toplevelish-p clambda)
104 (compute-closure clambda)))
105 (/show "leaving PREALLOCATE-PHYSENVS-FOR-TOPLEVELISH-LAMDBAS" component)
108 ;;; If CLAMBDA has a PHYSENV , return it, otherwise assign an empty one.
109 (defun get-lambda-physenv (clambda)
110 (declare (type clambda clambda))
111 (let ((homefun (lambda-home clambda)))
112 (or (lambda-physenv homefun)
113 (let ((res (make-physenv :function homefun)))
114 (setf (lambda-physenv homefun) res)
115 (dolist (letlambda (lambda-lets homefun))
116 ;; This assertion is to make explicit an
117 ;; apparently-otherwise-undocumented property of existing
118 ;; code: We never overwrite an old LAMBDA-PHYSENV.
120 (aver (null (lambda-physenv letlambda)))
121 ;; I *think* this is true regardless of LAMBDA-KIND.
123 (aver (eql (lambda-home letlambda) homefun))
124 (setf (lambda-physenv letlambda) res))
127 ;;; If FUN has no physical environment, assign one, otherwise clean up
128 ;;; the old physical environment, removing/flagging variables that
129 ;;; have no sets or refs. If a var has no references, we remove it
130 ;;; from the closure. If it has no sets, we clear the INDIRECT flag.
131 ;;; This is necessary because pre-analysis is done before
133 (defun reinit-lambda-physenv (fun)
134 (let ((old (lambda-physenv (lambda-home fun))))
136 (setf (physenv-closure old)
137 (delete-if (lambda (x)
138 (and (lambda-var-p x)
139 (null (leaf-refs x))))
140 (physenv-closure old)))
142 (dolist (var (lambda-vars fun))
143 (unless (lambda-var-sets var)
144 (setf (lambda-var-indirect var) nil)))))
146 (map nil #'clear (lambda-lets fun))))
148 (get-lambda-physenv fun))))
151 ;;; Get NODE's environment, assigning one if necessary.
152 (defun get-node-physenv (node)
153 (declare (type node node))
154 (get-lambda-physenv (node-home-lambda node)))
156 ;;; Find any variables in FUN with references outside of the home
157 ;;; environment and close over them. If a closed over variable is set,
158 ;;; then we set the INDIRECT flag so that we will know the closed over
159 ;;; value is really a pointer to the value cell. We also warn about
160 ;;; unreferenced variables here, just because it's a convenient place
161 ;;; to do it. We return true if we close over anything.
162 (defun compute-closure (fun)
163 (declare (type clambda fun))
164 (let ((env (get-lambda-physenv fun))
166 (note-unreferenced-vars fun)
167 (dolist (var (lambda-vars fun))
168 (dolist (ref (leaf-refs var))
169 (let ((ref-env (get-node-physenv ref)))
170 (unless (eq ref-env env)
171 (when (lambda-var-sets var)
172 (setf (lambda-var-indirect var) t))
173 (setq did-something t)
174 (close-over var ref-env env))))
175 (dolist (set (basic-var-sets var))
176 (let ((set-env (get-node-physenv set)))
177 (unless (eq set-env env)
178 (setq did-something t)
179 (setf (lambda-var-indirect var) t)
180 (close-over var set-env env)))))
183 ;;; Make sure that THING is closed over in REF-ENV and in all
184 ;;; environments for the functions that reference REF-ENV's function
185 ;;; (not just calls.) HOME-ENV is THING's home environment. When we
186 ;;; reach the home environment, we stop propagating the closure.
187 (defun close-over (thing ref-env home-env)
188 (declare (type physenv ref-env home-env))
189 (cond ((eq ref-env home-env))
190 ((member thing (physenv-closure ref-env)))
192 (push thing (physenv-closure ref-env))
193 (dolist (call (leaf-refs (physenv-function ref-env)))
194 (close-over thing (get-node-physenv call) home-env))))
199 ;;; Insert the entry stub before the original exit target, and add a
200 ;;; new entry to the PHYSENV-NLX-INFO. The %NLX-ENTRY call in the
201 ;;; stub is passed the NLX-INFO as an argument so that the back end
202 ;;; knows what entry is being done.
204 ;;; The link from the EXIT block to the entry stub is changed to be a
205 ;;; link to the component head. Similarly, the EXIT block is linked to
206 ;;; the component tail. This leaves the entry stub reachable, but
207 ;;; makes the flow graph less confusing to flow analysis.
209 ;;; If a CATCH or an UNWIND-protect, then we set the LEXENV for the
210 ;;; last node in the cleanup code to be the enclosing environment, to
211 ;;; represent the fact that the binding was undone as a side-effect of
212 ;;; the exit. This will cause a lexical exit to be broken up if we are
213 ;;; actually exiting the scope (i.e. a BLOCK), and will also do any
214 ;;; other cleanups that may have to be done on the way.
215 (defun insert-nlx-entry-stub (exit env)
216 (declare (type physenv env) (type exit exit))
217 (let* ((exit-block (node-block exit))
218 (next-block (first (block-succ exit-block)))
219 (cleanup (entry-cleanup (exit-entry exit)))
220 (info (make-nlx-info :cleanup cleanup
221 :continuation (node-cont exit)))
222 (entry (exit-entry exit))
223 (new-block (insert-cleanup-code exit-block next-block
226 (entry-cleanup entry)))
227 (component (block-component new-block)))
228 (unlink-blocks exit-block new-block)
229 (link-blocks exit-block (component-tail component))
230 (link-blocks (component-head component) new-block)
232 (setf (nlx-info-target info) new-block)
233 (push info (physenv-nlx-info env))
234 (push info (cleanup-nlx-info cleanup))
235 (when (member (cleanup-kind cleanup) '(:catch :unwind-protect))
236 (setf (node-lexenv (block-last new-block))
237 (node-lexenv entry))))
241 ;;; Do stuff necessary to represent a non-local exit from the node
242 ;;; EXIT into ENV. This is called for each non-local exit node, of
243 ;;; which there may be several per exit continuation. This is what we
245 ;;; -- If there isn't any NLX-Info entry in the environment, make
246 ;;; an entry stub, otherwise just move the exit block link to
247 ;;; the component tail.
248 ;;; -- Close over the NLX-Info in the exit environment.
249 ;;; -- If the exit is from an :Escape function, then substitute a
250 ;;; constant reference to NLX-Info structure for the escape
251 ;;; function reference. This will cause the escape function to
252 ;;; be deleted (although not removed from the DFO.) The escape
253 ;;; function is no longer needed, and we don't want to emit code
254 ;;; for it. We then also change the %NLX-ENTRY call to use the
255 ;;; NLX continuation so that there will be a use to represent
257 (defun note-non-local-exit (env exit)
258 (declare (type physenv env) (type exit exit))
259 (let ((entry (exit-entry exit))
260 (cont (node-cont exit))
261 (exit-fun (node-home-lambda exit)))
263 (if (find-nlx-info entry cont)
264 (let ((block (node-block exit)))
265 (aver (= (length (block-succ block)) 1))
266 (unlink-blocks block (first (block-succ block)))
267 (link-blocks block (component-tail (block-component block))))
268 (insert-nlx-entry-stub exit env))
270 (let ((info (find-nlx-info entry cont)))
272 (close-over info (node-physenv exit) env)
273 (when (eq (functional-kind exit-fun) :escape)
275 (setf (node-derived-type x) *wild-type*))
276 (leaf-refs exit-fun))
277 (substitute-leaf (find-constant info) exit-fun)
278 (let ((node (block-last (nlx-info-target info))))
279 (delete-continuation-use node)
280 (add-continuation-use node (nlx-info-continuation info))))))
284 ;;; Iterate over the EXITs in COMPONENT, calling NOTE-NON-LOCAL-EXIT
285 ;;; when we find a block that ends in a non-local EXIT node. We also
286 ;;; ensure that all EXIT nodes are either non-local or degenerate by
287 ;;; calling IR1-OPTIMIZE-EXIT on local exits. This makes life simpler
288 ;;; for later phases.
289 (defun find-non-local-exits (component)
290 (declare (type component component))
291 (dolist (lambda (component-lambdas component))
292 (dolist (entry (lambda-entries lambda))
293 (dolist (exit (entry-exits entry))
294 (let ((target-env (node-physenv entry)))
295 (if (eq (node-physenv exit) target-env)
296 (maybe-delete-exit exit)
297 (note-non-local-exit target-env exit))))))
301 ;;;; cleanup emission
303 ;;; Zoom up the cleanup nesting until we hit CLEANUP1, accumulating
304 ;;; cleanup code as we go. When we are done, convert the cleanup code
305 ;;; in an implicit MV-PROG1. We have to force local call analysis of
306 ;;; new references to UNWIND-PROTECT cleanup functions. If we don't
307 ;;; actually have to do anything, then we don't insert any cleanup
310 ;;; If we do insert cleanup code, we check that BLOCK1 doesn't end in
311 ;;; a "tail" local call.
313 ;;; We don't need to adjust the ending cleanup of the cleanup block,
314 ;;; since the cleanup blocks are inserted at the start of the DFO, and
315 ;;; are thus never scanned.
316 (defun emit-cleanups (block1 block2)
317 (declare (type cblock block1 block2))
320 (let ((cleanup2 (block-start-cleanup block2)))
321 (do ((cleanup (block-end-cleanup block1)
322 (node-enclosing-cleanup (cleanup-mess-up cleanup))))
323 ((eq cleanup cleanup2))
324 (let* ((node (cleanup-mess-up cleanup))
325 (args (when (basic-combination-p node)
326 (basic-combination-args node))))
327 (ecase (cleanup-kind cleanup)
329 (code `(%special-unbind ',(continuation-value (first args)))))
331 (code `(%catch-breakup)))
333 (code `(%unwind-protect-breakup))
334 (let ((fun (ref-leaf (continuation-use (second args)))))
336 (code `(%funcall ,fun))))
338 (dolist (nlx (cleanup-nlx-info cleanup))
339 (code `(%lexical-exit-breakup ',nlx)))))))
342 (aver (not (node-tail-p (block-last block1))))
343 (insert-cleanup-code block1 block2
346 (dolist (fun (reanalyze-funs))
347 (local-call-analyze-1 fun)))))
351 ;;; Loop over the blocks in COMPONENT, calling EMIT-CLEANUPS when we
352 ;;; see a successor in the same environment with a different cleanup.
353 ;;; We ignore the cleanup transition if it is to a cleanup enclosed by
354 ;;; the current cleanup, since in that case we are just messing up the
355 ;;; environment, hence this is not the place to clean it.
356 (defun find-cleanup-points (component)
357 (declare (type component component))
358 (do-blocks (block1 component)
359 (let ((env1 (block-physenv block1))
360 (cleanup1 (block-end-cleanup block1)))
361 (dolist (block2 (block-succ block1))
362 (when (block-start block2)
363 (let ((env2 (block-physenv block2))
364 (cleanup2 (block-start-cleanup block2)))
365 (unless (or (not (eq env2 env1))
366 (eq cleanup1 cleanup2)
368 (eq (node-enclosing-cleanup
369 (cleanup-mess-up cleanup2))
371 (emit-cleanups block1 block2)))))))
374 ;;; Mark all tail-recursive uses of function result continuations with
375 ;;; the corresponding TAIL-SET. Nodes whose type is NIL (i.e. don't
376 ;;; return) such as calls to ERROR are never annotated as tail in
377 ;;; order to preserve debugging information.
378 (defun tail-annotate (component)
379 (declare (type component component))
380 (dolist (fun (component-lambdas component))
381 (let ((ret (lambda-return fun)))
383 (let ((result (return-result ret)))
384 (do-uses (use result)
385 (when (and (immediately-used-p result use)
386 (or (not (eq (node-derived-type use) *empty-type*))
387 (not (basic-combination-p use))
388 (eq (basic-combination-kind use) :local)))
389 (setf (node-tail-p use) t)))))))