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 :top-level)
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-top-level (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-TOP-LEVEL, 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-TOP-LEVEL 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-top-levelish-lambdas (component)
100 (dolist (clambda (component-lambdas component))
101 (when (lambda-top-levelish-p clambda)
102 (compute-closure clambda)))
105 ;;; If CLAMBDA has a PHYSENV , return it, otherwise assign an empty one.
106 (defun get-lambda-physenv (clambda)
107 (declare (type clambda clambda))
108 (let ((homefun (lambda-home clambda)))
109 (or (lambda-physenv homefun)
110 (let ((res (make-physenv :function homefun)))
111 (setf (lambda-physenv homefun) res)
112 (dolist (letlambda (lambda-lets homefun))
113 ;; This assertion is to make explicit an
114 ;; apparently-otherwise-undocumented property of existing
115 ;; code: We never overwrite an old LAMBDA-PHYSENV.
117 (aver (null (lambda-physenv letlambda)))
118 ;; I *think* this is true regardless of LAMBDA-KIND.
120 (aver (eql (lambda-home letlambda) homefun))
121 (setf (lambda-physenv letlambda) res))
124 ;;; If FUN has no physical environment, assign one, otherwise clean up
125 ;;; the old physical environment, removing/flagging variables that
126 ;;; have no sets or refs. If a var has no references, we remove it
127 ;;; from the closure. If it has no sets, we clear the INDIRECT flag.
128 ;;; This is necessary because pre-analysis is done before
130 (defun reinit-lambda-physenv (fun)
131 (let ((old (lambda-physenv (lambda-home fun))))
133 (setf (physenv-closure old)
134 (delete-if #'(lambda (x)
135 (and (lambda-var-p x)
136 (null (leaf-refs x))))
137 (physenv-closure old)))
139 (dolist (var (lambda-vars fun))
140 (unless (lambda-var-sets var)
141 (setf (lambda-var-indirect var) nil)))))
143 (dolist (let (lambda-lets fun))
146 (get-lambda-physenv fun))))
149 ;;; Get NODE's environment, assigning one if necessary.
150 (defun get-node-physenv (node)
151 (declare (type node node))
152 (get-lambda-physenv (node-home-lambda node)))
154 ;;; Find any variables in FUN with references outside of the home
155 ;;; environment and close over them. If a closed over variable is set,
156 ;;; then we set the INDIRECT flag so that we will know the closed over
157 ;;; value is really a pointer to the value cell. We also warn about
158 ;;; unreferenced variables here, just because it's a convenient place
159 ;;; to do it. We return true if we close over anything.
160 (defun compute-closure (fun)
161 (declare (type clambda fun))
162 (let ((env (get-lambda-physenv fun))
164 (note-unreferenced-vars fun)
165 (dolist (var (lambda-vars fun))
166 (dolist (ref (leaf-refs var))
167 (let ((ref-env (get-node-physenv ref)))
168 (unless (eq ref-env env)
169 (when (lambda-var-sets var)
170 (setf (lambda-var-indirect var) t))
171 (setq did-something t)
172 (close-over var ref-env env))))
173 (dolist (set (basic-var-sets var))
174 (let ((set-env (get-node-physenv set)))
175 (unless (eq set-env env)
176 (setq did-something t)
177 (setf (lambda-var-indirect var) t)
178 (close-over var set-env env)))))
181 ;;; Make sure that THING is closed over in REF-ENV and in all
182 ;;; environments for the functions that reference REF-ENV's function
183 ;;; (not just calls.) HOME-ENV is THING's home environment. When we
184 ;;; reach the home environment, we stop propagating the closure.
185 (defun close-over (thing ref-env home-env)
186 (declare (type physenv ref-env home-env))
187 (cond ((eq ref-env home-env))
188 ((member thing (physenv-closure ref-env)))
190 (push thing (physenv-closure ref-env))
191 (dolist (call (leaf-refs (physenv-function ref-env)))
192 (close-over thing (get-node-physenv call) home-env))))
197 ;;; Insert the entry stub before the original exit target, and add a
198 ;;; new entry to the PHYSENV-NLX-INFO. The %NLX-ENTRY call in the
199 ;;; stub is passed the NLX-INFO as an argument so that the back end
200 ;;; knows what entry is being done.
202 ;;; The link from the EXIT block to the entry stub is changed to be a
203 ;;; link to the component head. Similarly, the EXIT block is linked to
204 ;;; the component tail. This leaves the entry stub reachable, but
205 ;;; makes the flow graph less confusing to flow analysis.
207 ;;; If a CATCH or an UNWIND-protect, then we set the LEXENV for the
208 ;;; last node in the cleanup code to be the enclosing environment, to
209 ;;; represent the fact that the binding was undone as a side-effect of
210 ;;; the exit. This will cause a lexical exit to be broken up if we are
211 ;;; actually exiting the scope (i.e. a BLOCK), and will also do any
212 ;;; other cleanups that may have to be done on the way.
213 (defun insert-nlx-entry-stub (exit env)
214 (declare (type physenv env) (type exit exit))
215 (let* ((exit-block (node-block exit))
216 (next-block (first (block-succ exit-block)))
217 (cleanup (entry-cleanup (exit-entry exit)))
218 (info (make-nlx-info :cleanup cleanup
219 :continuation (node-cont exit)))
220 (entry (exit-entry exit))
221 (new-block (insert-cleanup-code exit-block next-block
224 (entry-cleanup entry)))
225 (component (block-component new-block)))
226 (unlink-blocks exit-block new-block)
227 (link-blocks exit-block (component-tail component))
228 (link-blocks (component-head component) new-block)
230 (setf (nlx-info-target info) new-block)
231 (push info (physenv-nlx-info env))
232 (push info (cleanup-nlx-info cleanup))
233 (when (member (cleanup-kind cleanup) '(:catch :unwind-protect))
234 (setf (node-lexenv (block-last new-block))
235 (node-lexenv entry))))
239 ;;; Do stuff necessary to represent a non-local exit from the node
240 ;;; EXIT into ENV. This is called for each non-local exit node, of
241 ;;; which there may be several per exit continuation. This is what we
243 ;;; -- If there isn't any NLX-Info entry in the environment, make
244 ;;; an entry stub, otherwise just move the exit block link to
245 ;;; the component tail.
246 ;;; -- Close over the NLX-Info in the exit environment.
247 ;;; -- If the exit is from an :Escape function, then substitute a
248 ;;; constant reference to NLX-Info structure for the escape
249 ;;; function reference. This will cause the escape function to
250 ;;; be deleted (although not removed from the DFO.) The escape
251 ;;; function is no longer needed, and we don't want to emit code
252 ;;; for it. We then also change the %NLX-ENTRY call to use the
253 ;;; NLX continuation so that there will be a use to represent
255 (defun note-non-local-exit (env exit)
256 (declare (type physenv env) (type exit exit))
257 (let ((entry (exit-entry exit))
258 (cont (node-cont exit))
259 (exit-fun (node-home-lambda exit)))
261 (if (find-nlx-info entry cont)
262 (let ((block (node-block exit)))
263 (aver (= (length (block-succ block)) 1))
264 (unlink-blocks block (first (block-succ block)))
265 (link-blocks block (component-tail (block-component block))))
266 (insert-nlx-entry-stub exit env))
268 (let ((info (find-nlx-info entry cont)))
270 (close-over info (node-physenv exit) env)
271 (when (eq (functional-kind exit-fun) :escape)
273 (setf (node-derived-type x) *wild-type*))
274 (leaf-refs exit-fun))
275 (substitute-leaf (find-constant info) exit-fun)
276 (let ((node (block-last (nlx-info-target info))))
277 (delete-continuation-use node)
278 (add-continuation-use node (nlx-info-continuation info))))))
282 ;;; Iterate over the EXITs in COMPONENT, calling NOTE-NON-LOCAL-EXIT
283 ;;; when we find a block that ends in a non-local EXIT node. We also
284 ;;; ensure that all EXIT nodes are either non-local or degenerate by
285 ;;; calling IR1-OPTIMIZE-EXIT on local exits. This makes life simpler
286 ;;; for later phases.
287 (defun find-non-local-exits (component)
288 (declare (type component component))
289 (dolist (lambda (component-lambdas component))
290 (dolist (entry (lambda-entries lambda))
291 (dolist (exit (entry-exits entry))
292 (let ((target-env (node-physenv entry)))
293 (if (eq (node-physenv exit) target-env)
294 (maybe-delete-exit exit)
295 (note-non-local-exit target-env exit))))))
299 ;;;; cleanup emission
301 ;;; Zoom up the cleanup nesting until we hit CLEANUP1, accumulating
302 ;;; cleanup code as we go. When we are done, convert the cleanup code
303 ;;; in an implicit MV-PROG1. We have to force local call analysis of
304 ;;; new references to UNWIND-PROTECT cleanup functions. If we don't
305 ;;; actually have to do anything, then we don't insert any cleanup
308 ;;; If we do insert cleanup code, we check that BLOCK1 doesn't end in
309 ;;; a "tail" local call.
311 ;;; We don't need to adjust the ending cleanup of the cleanup block,
312 ;;; since the cleanup blocks are inserted at the start of the DFO, and
313 ;;; are thus never scanned.
314 (defun emit-cleanups (block1 block2)
315 (declare (type cblock block1 block2))
318 (let ((cleanup2 (block-start-cleanup block2)))
319 (do ((cleanup (block-end-cleanup block1)
320 (node-enclosing-cleanup (cleanup-mess-up cleanup))))
321 ((eq cleanup cleanup2))
322 (let* ((node (cleanup-mess-up cleanup))
323 (args (when (basic-combination-p node)
324 (basic-combination-args node))))
325 (ecase (cleanup-kind cleanup)
327 (code `(%special-unbind ',(continuation-value (first args)))))
329 (code `(%catch-breakup)))
331 (code `(%unwind-protect-breakup))
332 (let ((fun (ref-leaf (continuation-use (second args)))))
334 (code `(%funcall ,fun))))
336 (dolist (nlx (cleanup-nlx-info cleanup))
337 (code `(%lexical-exit-breakup ',nlx)))))))
340 (aver (not (node-tail-p (block-last block1))))
341 (insert-cleanup-code block1 block2
344 (dolist (fun (reanalyze-funs))
345 (local-call-analyze-1 fun)))))
349 ;;; Loop over the blocks in COMPONENT, calling EMIT-CLEANUPS when we
350 ;;; see a successor in the same environment with a different cleanup.
351 ;;; We ignore the cleanup transition if it is to a cleanup enclosed by
352 ;;; the current cleanup, since in that case we are just messing up the
353 ;;; environment, hence this is not the place to clean it.
354 (defun find-cleanup-points (component)
355 (declare (type component component))
356 (do-blocks (block1 component)
357 (let ((env1 (block-physenv block1))
358 (cleanup1 (block-end-cleanup block1)))
359 (dolist (block2 (block-succ block1))
360 (when (block-start block2)
361 (let ((env2 (block-physenv block2))
362 (cleanup2 (block-start-cleanup block2)))
363 (unless (or (not (eq env2 env1))
364 (eq cleanup1 cleanup2)
366 (eq (node-enclosing-cleanup
367 (cleanup-mess-up cleanup2))
369 (emit-cleanups block1 block2)))))))
372 ;;; Mark all tail-recursive uses of function result continuations with
373 ;;; the corresponding TAIL-SET. Nodes whose type is NIL (i.e. don't
374 ;;; return) such as calls to ERROR are never annotated as tail in
375 ;;; order to preserve debugging information.
376 (defun tail-annotate (component)
377 (declare (type component component))
378 (dolist (fun (component-lambdas component))
379 (let ((ret (lambda-return fun)))
381 (let ((result (return-result ret)))
382 (do-uses (use result)
383 (when (and (immediately-used-p result use)
384 (or (not (eq (node-derived-type use) *empty-type*))
385 (not (basic-combination-p use))
386 (eq (basic-combination-kind use) :local)))
387 (setf (node-tail-p use) t)))))))