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1 ;;;; This file contains the code that finds the initial components and
2 ;;;; DFO, and recomputes the DFO if it is invalidated.
4 ;;;; This software is part of the SBCL system. See the README file for
5 ;;;; more information.
6 ;;;;
7 ;;;; This software is derived from the CMU CL system, which was
8 ;;;; written at Carnegie Mellon University and released into the
9 ;;;; public domain. The software is in the public domain and is
10 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
11 ;;;; files for more information.
15 ;;; Find the DFO for a component, deleting any unreached blocks and
16 ;;; merging any other components we reach. We repeatedly iterate over
17 ;;; the entry points, since new ones may show up during the walk.
37 ;;; Move all the code and entry points from OLD to NEW. The code in
38 ;;; OLD is inserted at the head of NEW. This is also called during LET
39 ;;; conversion when we are about in insert the body of a LET in a
40 ;;; different component. [A local call can be to a different component
41 ;;; before FIND-INITIAL-DFO runs.]
83 ;;; Do a depth-first walk from BLOCK, inserting ourself in the DFO
84 ;;; after HEAD. If we somehow find ourselves in another component,
85 ;;; then we join that component to our component.
98 ;;; This function is called on each block by FIND-INITIAL-DFO-AUX
99 ;;; before it walks the successors. It looks at the home CLAMBDA's
100 ;;; BIND block to see whether that block is in some other component:
101 ;;; -- If the block is in the initial component, then do
102 ;;; DFO-SCAVENGE-DEPENDENCY-GRAPH on the home function to move it
103 ;;; into COMPONENT.
104 ;;; -- If the block is in some other component, join COMPONENT into
105 ;;; it and return that component.
106 ;;; -- If the home function is deleted, do nothing. BLOCK must
107 ;;; eventually be discovered to be unreachable as well. This can
108 ;;; happen when we have a NLX into a function with no references.
109 ;;; The escape function still has refs (in the deleted function).
110 ;;;
111 ;;; This ensures that all the blocks in a given environment will be in
112 ;;; the same component, even when they might not seem reachable from
113 ;;; the environment entry. Consider the case of code that is only
114 ;;; reachable from a non-local exit.
119 component
124 component)
127 home-component))))))
129 ;;; This is somewhat similar to FIND-DFO-AUX, except that it merges
130 ;;; the current component with any strange component, rather than the
131 ;;; other way around. This is more efficient in the common case where
132 ;;; the current component doesn't have much stuff in it.
133 ;;;
134 ;;; We return the current component as a result, allowing the caller
135 ;;; to detect when the old current component has been merged with
136 ;;; another.
137 ;;;
138 ;;; We walk blocks in initial components as though they were already
139 ;;; in the current component, moving them to the current component in
140 ;;; the process. The blocks are inserted at the head of the current
141 ;;; component.
149 this)
158 current)))))
160 ;;; Return a list of all the home lambdas that reference FUN (may
161 ;;; contain duplications).
162 ;;;
163 ;;; References to functions which local call analysis could not (or
164 ;;; were chosen not) to local call convert will appear as references
165 ;;; to XEP lambdas. We can ignore references to XEPs that appear in
166 ;;; :TOPLEVEL components, since environment analysis goes to special
167 ;;; effort to allow closing over of values from a separate top level
168 ;;; component. (And now that HAS-EXTERNAL-REFERENCES-P-ness
169 ;;; generalizes :TOPLEVEL-ness, we ignore those too.) All other
170 ;;; references must cause components to be joined.
171 ;;;
172 ;;; References in deleted functions are also ignored, since this code
173 ;;; will be deleted eventually.
188 ;;; If CLAMBDA is already in COMPONENT, just return that
189 ;;; component. Otherwise, move the code for CLAMBDA and all lambdas it
190 ;;; physically depends on (either because of calls or because of
191 ;;; closure relationships) into COMPONENT, or possibly into another
192 ;;; COMPONENT that we find to be related. Return whatever COMPONENT we
193 ;;; actually merged into.
194 ;;;
195 ;;; (Note: The analogous CMU CL code only scavenged call-based
196 ;;; dependencies, not closure dependencies. That seems to've been by
197 ;;; oversight, not by design, as per the bug reported by WHN on
198 ;;; cmucl-imp ca. 2001-11-29 and explained by DTC shortly after.)
199 ;;;
200 ;;; If the function is in an initial component, then we move its head
201 ;;; and tail to COMPONENT and add it to COMPONENT's lambdas. It is
202 ;;; harmless to move the tail (even though the return might be
203 ;;; unreachable) because if the return is unreachable it (and its
204 ;;; successor link) will be deleted in the post-deletion pass.
205 ;;;
206 ;;; We then do a FIND-DFO-AUX starting at the head of CLAMBDA. If this
207 ;;; flow-graph walk encounters another component (which can only
208 ;;; happen due to a non-local exit), then we move code into that
209 ;;; component instead. We then recurse on all functions called from
210 ;;; CLAMBDA, moving code into whichever component the preceding call
211 ;;; returned.
212 ;;;
213 ;;; If CLAMBDA is in the initial component, but the BLOCK-FLAG is set
214 ;;; in the bind block, then we just return COMPONENT, since we must
215 ;;; have already reached this function in the current walk (or the
216 ;;; component would have been changed).
217 ;;;
218 ;;; If the function is an XEP, then we also walk all functions that
219 ;;; contain references to the XEP. This is done so that environment
220 ;;; analysis doesn't need to cross component boundaries. This also
221 ;;; ensures that conversion of a full call to a local call won't
222 ;;; result in a need to join components, since the components will
223 ;;; already be one.
232 component)
235 old-lambda-component)
237 component)
250 ;; Scavenge related lambdas.
254 res)))
258 ;; Scavenge call relationship.
261 ;; Scavenge closure over a variable: if CLAMBDA
262 ;; refers to a variable whose home lambda is not
263 ;; CLAMBDA, then the home lambda should be in the
264 ;; same component as CLAMBDA. (sbcl-0.6.13, and CMU
265 ;; CL, didn't do this, leading to the occasional
266 ;; failure when physenv analysis, which is local to
267 ;; each component, would bogusly conclude that a
268 ;; closed-over variable was unused and thus delete
269 ;; it. See e.g. cmucl-imp 2001-11-29.)
274 ;; Scavenge closure over an entry for nonlocal exit.
275 ;; This is basically parallel to closure over a
276 ;; variable above.
288 ;; Voila.
289 res)))))
291 ;;; Return true if CLAMBDA either is an XEP or has EXITS to some of
292 ;;; its ENTRIES.
300 ;;; Compute the result of FIND-INITIAL-DFO given the list of all
301 ;;; resulting components. Components with a :TOPLEVEL lambda, but no
302 ;;; normal XEPs or potential non-local exits are marked as :TOPLEVEL.
303 ;;; If there is a :TOPLEVEL lambda, and also a normal XEP, then we
304 ;;; treat the component as normal, but also return such components in
305 ;;; a list as the third value. Components with no entry of any sort
306 ;;; are deleted.
320 ;; is newer than the rest of this function, and
321 ;; doesn't really seem to fit into its mindset. Here
322 ;; we mark components which contain such FUNCTIONs
323 ;; them as :COMPLEX-TOPLEVEL, since they do get
324 ;; executed at run time, and since it's not valid to
325 ;; delete them just because they don't have any
326 ;; references from pure :TOPLEVEL components. -- WHN
327 has-external-references
348 ;;; COMPONENTs want strings for names, LEAF-DEBUG-NAMEs mightn't be
349 ;;; strings...
355 leaf-debug-name
358 ;;; Given a list of top level lambdas, return
359 ;;; (VALUES NONTOP-COMPONENTS TOP-COMPONENTS HAIRY-TOP-COMPONENTS).
360 ;;; Each of the three values returned is a list of COMPONENTs:
361 ;;; NONTOP-COMPONENTS = non-top-level-ish COMPONENTs;
362 ;;; TOP-COMPONENTS = top-level-ish COMPONENTs;
363 ;;; HAIRY-TOP-COMPONENTS = a subset of NONTOP-COMPONENTS, those
364 ;;; elements which include a top-level-ish lambda.
365 ;;;
366 ;;; We assign the DFO for each component, and delete any unreachable
367 ;;; blocks. We assume that the FLAGS have already been cleared.
371 ;; We iterate over the lambdas in each initial component, trying
372 ;; to put each function in its own component, but joining it to
373 ;; an existing component if we find that there are references
374 ;; between them. Any code that is left in an initial component
375 ;; must be unreachable, so we can delete it. Stray links to the
376 ;; initial component tail (due to NIL function terminated blocks)
377 ;; are moved to the appropriate new component tail.
390 ;; This isn't necessarily an ideal name for the
391 ;; component, since it might end up with multiple
392 ;; lambdas in it, not just this one, but it does
393 ;; seem a better name than just "<unknown>".
395 component-lambda)))
397 new-component)))
412 ;; When we are done, we assign DFNs.
419 ;; Pull out top-level-ish code.
421 \f
422 ;;; Insert the code in LAMBDA at the end of RESULT-LAMBDA.
426 ;; Delete the lambda, and combine the LETs and entries.
442 ;; Move blocks into the new COMPONENT, and move any nodes directly
443 ;; in the old LAMBDA into the new one (with LETs implicitly moved
444 ;; by changing their home.)
452 ;; Splice the blocks into the new DFO, and unlink them from the
453 ;; old component head and tail. Non-return blocks that jump to the
454 ;; tail (NIL-returning calls) are switched to go to the new tail.
477 ;; Switch the end of the code from the return block to the start of
478 ;; the next chunk.
484 ;; If there is a return, then delete it (making the preceding node
485 ;; the last node) and link the block to the result return. There
486 ;; is always a preceding REF NIL node in top level lambdas.
493 ;;; Given a non-empty list of top level LAMBDAs, smash them into a
494 ;;; top level lambda and component, returning these as values. We use
495 ;;; the first lambda and its component, putting the other code in that
496 ;;; component and deleting the other lambdas.
504 ;; Make sure the result's return node starts a block so that we
505 ;; can splice code in before it.