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c9784e6d | 1 | /* CFG cleanup for trees. |
6ac01510 ILT |
2 | Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007 |
3 | Free Software Foundation, Inc. | |
c9784e6d KH |
4 | |
5 | This file is part of GCC. | |
6 | ||
7 | GCC is free software; you can redistribute it and/or modify | |
8 | it under the terms of the GNU General Public License as published by | |
9dcd6f09 | 9 | the Free Software Foundation; either version 3, or (at your option) |
c9784e6d KH |
10 | any later version. |
11 | ||
12 | GCC is distributed in the hope that it will be useful, | |
13 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
15 | GNU General Public License for more details. | |
16 | ||
17 | You should have received a copy of the GNU General Public License | |
9dcd6f09 NC |
18 | along with GCC; see the file COPYING3. If not see |
19 | <http://www.gnu.org/licenses/>. */ | |
c9784e6d KH |
20 | |
21 | #include "config.h" | |
22 | #include "system.h" | |
23 | #include "coretypes.h" | |
24 | #include "tm.h" | |
25 | #include "tree.h" | |
26 | #include "rtl.h" | |
27 | #include "tm_p.h" | |
28 | #include "hard-reg-set.h" | |
29 | #include "basic-block.h" | |
30 | #include "output.h" | |
6ac01510 | 31 | #include "toplev.h" |
c9784e6d KH |
32 | #include "flags.h" |
33 | #include "function.h" | |
34 | #include "expr.h" | |
35 | #include "ggc.h" | |
36 | #include "langhooks.h" | |
37 | #include "diagnostic.h" | |
38 | #include "tree-flow.h" | |
39 | #include "timevar.h" | |
40 | #include "tree-dump.h" | |
41 | #include "tree-pass.h" | |
42 | #include "toplev.h" | |
43 | #include "except.h" | |
44 | #include "cfgloop.h" | |
45 | #include "cfglayout.h" | |
46 | #include "hashtab.h" | |
47 | #include "tree-ssa-propagate.h" | |
17684618 | 48 | #include "tree-scalar-evolution.h" |
c9784e6d | 49 | |
672987e8 ZD |
50 | /* The set of blocks in that at least one of the following changes happened: |
51 | -- the statement at the end of the block was changed | |
52 | -- the block was newly created | |
53 | -- the set of the predecessors of the block changed | |
54 | -- the set of the successors of the block changed | |
55 | ??? Maybe we could track these changes separately, since they determine | |
56 | what cleanups it makes sense to try on the block. */ | |
57 | bitmap cfgcleanup_altered_bbs; | |
58 | ||
c9784e6d KH |
59 | /* Remove any fallthru edge from EV. Return true if an edge was removed. */ |
60 | ||
61 | static bool | |
62 | remove_fallthru_edge (VEC(edge,gc) *ev) | |
63 | { | |
64 | edge_iterator ei; | |
65 | edge e; | |
66 | ||
67 | FOR_EACH_EDGE (e, ei, ev) | |
68 | if ((e->flags & EDGE_FALLTHRU) != 0) | |
69 | { | |
672987e8 | 70 | remove_edge_and_dominated_blocks (e); |
c9784e6d KH |
71 | return true; |
72 | } | |
73 | return false; | |
74 | } | |
75 | ||
76 | /* Disconnect an unreachable block in the control expression starting | |
77 | at block BB. */ | |
78 | ||
79 | static bool | |
80 | cleanup_control_expr_graph (basic_block bb, block_stmt_iterator bsi) | |
81 | { | |
82 | edge taken_edge; | |
83 | bool retval = false; | |
84 | tree expr = bsi_stmt (bsi), val; | |
85 | ||
86 | if (!single_succ_p (bb)) | |
87 | { | |
88 | edge e; | |
89 | edge_iterator ei; | |
6ac01510 ILT |
90 | bool warned; |
91 | ||
92 | fold_defer_overflow_warnings (); | |
c9784e6d KH |
93 | |
94 | switch (TREE_CODE (expr)) | |
95 | { | |
96 | case COND_EXPR: | |
52270a3c | 97 | val = fold (COND_EXPR_COND (expr)); |
c9784e6d KH |
98 | break; |
99 | ||
100 | case SWITCH_EXPR: | |
52270a3c | 101 | val = fold (SWITCH_COND (expr)); |
c9784e6d | 102 | if (TREE_CODE (val) != INTEGER_CST) |
6ac01510 ILT |
103 | { |
104 | fold_undefer_and_ignore_overflow_warnings (); | |
105 | return false; | |
106 | } | |
c9784e6d KH |
107 | break; |
108 | ||
109 | default: | |
110 | gcc_unreachable (); | |
111 | } | |
112 | ||
113 | taken_edge = find_taken_edge (bb, val); | |
114 | if (!taken_edge) | |
6ac01510 ILT |
115 | { |
116 | fold_undefer_and_ignore_overflow_warnings (); | |
117 | return false; | |
118 | } | |
c9784e6d KH |
119 | |
120 | /* Remove all the edges except the one that is always executed. */ | |
6ac01510 | 121 | warned = false; |
c9784e6d KH |
122 | for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); ) |
123 | { | |
124 | if (e != taken_edge) | |
125 | { | |
6ac01510 ILT |
126 | if (!warned) |
127 | { | |
128 | fold_undefer_overflow_warnings | |
129 | (true, expr, WARN_STRICT_OVERFLOW_CONDITIONAL); | |
130 | warned = true; | |
131 | } | |
132 | ||
c9784e6d KH |
133 | taken_edge->probability += e->probability; |
134 | taken_edge->count += e->count; | |
672987e8 | 135 | remove_edge_and_dominated_blocks (e); |
c9784e6d KH |
136 | retval = true; |
137 | } | |
138 | else | |
139 | ei_next (&ei); | |
140 | } | |
6ac01510 ILT |
141 | if (!warned) |
142 | fold_undefer_and_ignore_overflow_warnings (); | |
c9784e6d KH |
143 | if (taken_edge->probability > REG_BR_PROB_BASE) |
144 | taken_edge->probability = REG_BR_PROB_BASE; | |
145 | } | |
146 | else | |
147 | taken_edge = single_succ_edge (bb); | |
148 | ||
672987e8 | 149 | bitmap_set_bit (cfgcleanup_altered_bbs, bb->index); |
736432ee | 150 | bsi_remove (&bsi, true); |
c9784e6d KH |
151 | taken_edge->flags = EDGE_FALLTHRU; |
152 | ||
c9784e6d KH |
153 | return retval; |
154 | } | |
155 | ||
672987e8 ZD |
156 | /* Try to remove superfluous control structures in basic block BB. Returns |
157 | true if anything changes. */ | |
c9784e6d KH |
158 | |
159 | static bool | |
672987e8 | 160 | cleanup_control_flow_bb (basic_block bb) |
c9784e6d | 161 | { |
c9784e6d KH |
162 | block_stmt_iterator bsi; |
163 | bool retval = false; | |
164 | tree stmt; | |
165 | ||
672987e8 ZD |
166 | /* If the last statement of the block could throw and now cannot, |
167 | we need to prune cfg. */ | |
168 | retval |= tree_purge_dead_eh_edges (bb); | |
169 | ||
170 | bsi = bsi_last (bb); | |
171 | if (bsi_end_p (bsi)) | |
172 | return retval; | |
173 | ||
174 | stmt = bsi_stmt (bsi); | |
175 | ||
176 | if (TREE_CODE (stmt) == COND_EXPR | |
177 | || TREE_CODE (stmt) == SWITCH_EXPR) | |
178 | retval |= cleanup_control_expr_graph (bb, bsi); | |
179 | /* If we had a computed goto which has a compile-time determinable | |
180 | destination, then we can eliminate the goto. */ | |
181 | else if (TREE_CODE (stmt) == GOTO_EXPR | |
182 | && TREE_CODE (GOTO_DESTINATION (stmt)) == ADDR_EXPR | |
183 | && (TREE_CODE (TREE_OPERAND (GOTO_DESTINATION (stmt), 0)) | |
184 | == LABEL_DECL)) | |
c9784e6d | 185 | { |
672987e8 ZD |
186 | edge e; |
187 | tree label; | |
188 | edge_iterator ei; | |
189 | basic_block target_block; | |
c9784e6d | 190 | |
672987e8 ZD |
191 | /* First look at all the outgoing edges. Delete any outgoing |
192 | edges which do not go to the right block. For the one | |
193 | edge which goes to the right block, fix up its flags. */ | |
194 | label = TREE_OPERAND (GOTO_DESTINATION (stmt), 0); | |
195 | target_block = label_to_block (label); | |
196 | for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); ) | |
c9784e6d | 197 | { |
672987e8 ZD |
198 | if (e->dest != target_block) |
199 | remove_edge_and_dominated_blocks (e); | |
200 | else | |
c9784e6d | 201 | { |
672987e8 ZD |
202 | /* Turn off the EDGE_ABNORMAL flag. */ |
203 | e->flags &= ~EDGE_ABNORMAL; | |
c9784e6d | 204 | |
672987e8 ZD |
205 | /* And set EDGE_FALLTHRU. */ |
206 | e->flags |= EDGE_FALLTHRU; | |
207 | ei_next (&ei); | |
208 | } | |
c9784e6d KH |
209 | } |
210 | ||
672987e8 ZD |
211 | bitmap_set_bit (cfgcleanup_altered_bbs, bb->index); |
212 | bitmap_set_bit (cfgcleanup_altered_bbs, target_block->index); | |
213 | ||
214 | /* Remove the GOTO_EXPR as it is not needed. The CFG has all the | |
215 | relevant information we need. */ | |
216 | bsi_remove (&bsi, true); | |
217 | retval = true; | |
c9784e6d | 218 | } |
672987e8 ZD |
219 | |
220 | /* Check for indirect calls that have been turned into | |
221 | noreturn calls. */ | |
222 | else if (noreturn_call_p (stmt) && remove_fallthru_edge (bb->succs)) | |
223 | retval = true; | |
224 | ||
c9784e6d KH |
225 | return retval; |
226 | } | |
227 | ||
228 | /* Return true if basic block BB does nothing except pass control | |
229 | flow to another block and that we can safely insert a label at | |
230 | the start of the successor block. | |
231 | ||
232 | As a precondition, we require that BB be not equal to | |
233 | ENTRY_BLOCK_PTR. */ | |
234 | ||
235 | static bool | |
236 | tree_forwarder_block_p (basic_block bb, bool phi_wanted) | |
237 | { | |
238 | block_stmt_iterator bsi; | |
9d335249 AH |
239 | edge_iterator ei; |
240 | edge e, succ; | |
241 | basic_block dest; | |
c9784e6d KH |
242 | |
243 | /* BB must have a single outgoing edge. */ | |
244 | if (single_succ_p (bb) != 1 | |
245 | /* If PHI_WANTED is false, BB must not have any PHI nodes. | |
246 | Otherwise, BB must have PHI nodes. */ | |
247 | || (phi_nodes (bb) != NULL_TREE) != phi_wanted | |
248 | /* BB may not be a predecessor of EXIT_BLOCK_PTR. */ | |
249 | || single_succ (bb) == EXIT_BLOCK_PTR | |
250 | /* Nor should this be an infinite loop. */ | |
251 | || single_succ (bb) == bb | |
252 | /* BB may not have an abnormal outgoing edge. */ | |
253 | || (single_succ_edge (bb)->flags & EDGE_ABNORMAL)) | |
254 | return false; | |
255 | ||
256 | #if ENABLE_CHECKING | |
257 | gcc_assert (bb != ENTRY_BLOCK_PTR); | |
258 | #endif | |
259 | ||
260 | /* Now walk through the statements backward. We can ignore labels, | |
261 | anything else means this is not a forwarder block. */ | |
262 | for (bsi = bsi_last (bb); !bsi_end_p (bsi); bsi_prev (&bsi)) | |
263 | { | |
264 | tree stmt = bsi_stmt (bsi); | |
265 | ||
266 | switch (TREE_CODE (stmt)) | |
267 | { | |
268 | case LABEL_EXPR: | |
269 | if (DECL_NONLOCAL (LABEL_EXPR_LABEL (stmt))) | |
270 | return false; | |
271 | break; | |
272 | ||
273 | default: | |
274 | return false; | |
275 | } | |
276 | } | |
277 | ||
278 | if (find_edge (ENTRY_BLOCK_PTR, bb)) | |
279 | return false; | |
280 | ||
281 | if (current_loops) | |
282 | { | |
283 | basic_block dest; | |
284 | /* Protect loop latches, headers and preheaders. */ | |
285 | if (bb->loop_father->header == bb) | |
286 | return false; | |
287 | dest = EDGE_SUCC (bb, 0)->dest; | |
288 | ||
289 | if (dest->loop_father->header == dest) | |
290 | return false; | |
291 | } | |
292 | ||
9d335249 AH |
293 | /* If we have an EH edge leaving this block, make sure that the |
294 | destination of this block has only one predecessor. This ensures | |
295 | that we don't get into the situation where we try to remove two | |
296 | forwarders that go to the same basic block but are handlers for | |
297 | different EH regions. */ | |
298 | succ = single_succ_edge (bb); | |
299 | dest = succ->dest; | |
300 | FOR_EACH_EDGE (e, ei, bb->preds) | |
301 | { | |
302 | if (e->flags & EDGE_EH) | |
303 | { | |
304 | if (!single_pred_p (dest)) | |
305 | return false; | |
306 | } | |
307 | } | |
308 | ||
c9784e6d KH |
309 | return true; |
310 | } | |
311 | ||
312 | /* Return true if BB has at least one abnormal incoming edge. */ | |
313 | ||
314 | static inline bool | |
315 | has_abnormal_incoming_edge_p (basic_block bb) | |
316 | { | |
317 | edge e; | |
318 | edge_iterator ei; | |
319 | ||
320 | FOR_EACH_EDGE (e, ei, bb->preds) | |
321 | if (e->flags & EDGE_ABNORMAL) | |
322 | return true; | |
323 | ||
324 | return false; | |
325 | } | |
326 | ||
327 | /* If all the PHI nodes in DEST have alternatives for E1 and E2 and | |
328 | those alternatives are equal in each of the PHI nodes, then return | |
329 | true, else return false. */ | |
330 | ||
331 | static bool | |
332 | phi_alternatives_equal (basic_block dest, edge e1, edge e2) | |
333 | { | |
334 | int n1 = e1->dest_idx; | |
335 | int n2 = e2->dest_idx; | |
336 | tree phi; | |
337 | ||
338 | for (phi = phi_nodes (dest); phi; phi = PHI_CHAIN (phi)) | |
339 | { | |
340 | tree val1 = PHI_ARG_DEF (phi, n1); | |
341 | tree val2 = PHI_ARG_DEF (phi, n2); | |
342 | ||
343 | gcc_assert (val1 != NULL_TREE); | |
344 | gcc_assert (val2 != NULL_TREE); | |
345 | ||
346 | if (!operand_equal_for_phi_arg_p (val1, val2)) | |
347 | return false; | |
348 | } | |
349 | ||
350 | return true; | |
351 | } | |
352 | ||
672987e8 | 353 | /* Removes forwarder block BB. Returns false if this failed. */ |
c9784e6d KH |
354 | |
355 | static bool | |
672987e8 | 356 | remove_forwarder_block (basic_block bb) |
c9784e6d KH |
357 | { |
358 | edge succ = single_succ_edge (bb), e, s; | |
359 | basic_block dest = succ->dest; | |
360 | tree label; | |
361 | tree phi; | |
362 | edge_iterator ei; | |
363 | block_stmt_iterator bsi, bsi_to; | |
364 | bool seen_abnormal_edge = false; | |
365 | ||
366 | /* We check for infinite loops already in tree_forwarder_block_p. | |
367 | However it may happen that the infinite loop is created | |
368 | afterwards due to removal of forwarders. */ | |
369 | if (dest == bb) | |
370 | return false; | |
371 | ||
372 | /* If the destination block consists of a nonlocal label, do not merge | |
373 | it. */ | |
374 | label = first_stmt (dest); | |
375 | if (label | |
376 | && TREE_CODE (label) == LABEL_EXPR | |
377 | && DECL_NONLOCAL (LABEL_EXPR_LABEL (label))) | |
378 | return false; | |
379 | ||
380 | /* If there is an abnormal edge to basic block BB, but not into | |
381 | dest, problems might occur during removal of the phi node at out | |
382 | of ssa due to overlapping live ranges of registers. | |
383 | ||
384 | If there is an abnormal edge in DEST, the problems would occur | |
385 | anyway since cleanup_dead_labels would then merge the labels for | |
386 | two different eh regions, and rest of exception handling code | |
387 | does not like it. | |
388 | ||
389 | So if there is an abnormal edge to BB, proceed only if there is | |
390 | no abnormal edge to DEST and there are no phi nodes in DEST. */ | |
391 | if (has_abnormal_incoming_edge_p (bb)) | |
392 | { | |
393 | seen_abnormal_edge = true; | |
394 | ||
395 | if (has_abnormal_incoming_edge_p (dest) | |
396 | || phi_nodes (dest) != NULL_TREE) | |
397 | return false; | |
398 | } | |
399 | ||
400 | /* If there are phi nodes in DEST, and some of the blocks that are | |
401 | predecessors of BB are also predecessors of DEST, check that the | |
402 | phi node arguments match. */ | |
403 | if (phi_nodes (dest)) | |
404 | { | |
405 | FOR_EACH_EDGE (e, ei, bb->preds) | |
406 | { | |
407 | s = find_edge (e->src, dest); | |
408 | if (!s) | |
409 | continue; | |
410 | ||
411 | if (!phi_alternatives_equal (dest, succ, s)) | |
412 | return false; | |
413 | } | |
414 | } | |
415 | ||
416 | /* Redirect the edges. */ | |
417 | for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei)); ) | |
418 | { | |
672987e8 ZD |
419 | bitmap_set_bit (cfgcleanup_altered_bbs, e->src->index); |
420 | ||
c9784e6d KH |
421 | if (e->flags & EDGE_ABNORMAL) |
422 | { | |
423 | /* If there is an abnormal edge, redirect it anyway, and | |
424 | move the labels to the new block to make it legal. */ | |
425 | s = redirect_edge_succ_nodup (e, dest); | |
426 | } | |
427 | else | |
428 | s = redirect_edge_and_branch (e, dest); | |
429 | ||
430 | if (s == e) | |
431 | { | |
432 | /* Create arguments for the phi nodes, since the edge was not | |
433 | here before. */ | |
434 | for (phi = phi_nodes (dest); phi; phi = PHI_CHAIN (phi)) | |
435 | add_phi_arg (phi, PHI_ARG_DEF (phi, succ->dest_idx), s); | |
436 | } | |
c9784e6d KH |
437 | } |
438 | ||
439 | if (seen_abnormal_edge) | |
440 | { | |
441 | /* Move the labels to the new block, so that the redirection of | |
442 | the abnormal edges works. */ | |
443 | ||
444 | bsi_to = bsi_start (dest); | |
445 | for (bsi = bsi_start (bb); !bsi_end_p (bsi); ) | |
446 | { | |
447 | label = bsi_stmt (bsi); | |
448 | gcc_assert (TREE_CODE (label) == LABEL_EXPR); | |
736432ee | 449 | bsi_remove (&bsi, false); |
c9784e6d KH |
450 | bsi_insert_before (&bsi_to, label, BSI_CONTINUE_LINKING); |
451 | } | |
452 | } | |
453 | ||
672987e8 ZD |
454 | bitmap_set_bit (cfgcleanup_altered_bbs, dest->index); |
455 | ||
c9784e6d KH |
456 | /* Update the dominators. */ |
457 | if (dom_info_available_p (CDI_DOMINATORS)) | |
458 | { | |
459 | basic_block dom, dombb, domdest; | |
460 | ||
461 | dombb = get_immediate_dominator (CDI_DOMINATORS, bb); | |
462 | domdest = get_immediate_dominator (CDI_DOMINATORS, dest); | |
463 | if (domdest == bb) | |
464 | { | |
465 | /* Shortcut to avoid calling (relatively expensive) | |
466 | nearest_common_dominator unless necessary. */ | |
467 | dom = dombb; | |
468 | } | |
469 | else | |
470 | dom = nearest_common_dominator (CDI_DOMINATORS, domdest, dombb); | |
471 | ||
472 | set_immediate_dominator (CDI_DOMINATORS, dest, dom); | |
473 | } | |
474 | ||
475 | /* And kill the forwarder block. */ | |
476 | delete_basic_block (bb); | |
477 | ||
478 | return true; | |
479 | } | |
480 | ||
672987e8 ZD |
481 | /* Split basic blocks on calls in the middle of a basic block that are now |
482 | known not to return, and remove the unreachable code. */ | |
c9784e6d KH |
483 | |
484 | static bool | |
672987e8 | 485 | split_bbs_on_noreturn_calls (void) |
c9784e6d | 486 | { |
c9784e6d | 487 | bool changed = false; |
672987e8 ZD |
488 | tree stmt; |
489 | basic_block bb; | |
c9784e6d | 490 | |
672987e8 ZD |
491 | /* Detect cases where a mid-block call is now known not to return. */ |
492 | if (cfun->gimple_df) | |
493 | while (VEC_length (tree, MODIFIED_NORETURN_CALLS (cfun))) | |
494 | { | |
495 | stmt = VEC_pop (tree, MODIFIED_NORETURN_CALLS (cfun)); | |
496 | bb = bb_for_stmt (stmt); | |
497 | if (bb == NULL | |
498 | || last_stmt (bb) == stmt | |
499 | || !noreturn_call_p (stmt)) | |
500 | continue; | |
501 | ||
502 | changed = true; | |
503 | split_block (bb, stmt); | |
504 | remove_fallthru_edge (bb->succs); | |
505 | } | |
c9784e6d | 506 | |
c9784e6d KH |
507 | return changed; |
508 | } | |
509 | ||
e5c95afe ZD |
510 | /* If OMP_RETURN in basic block BB is unreachable, remove it. */ |
511 | ||
512 | static bool | |
513 | cleanup_omp_return (basic_block bb) | |
514 | { | |
515 | tree stmt = last_stmt (bb); | |
516 | basic_block control_bb; | |
517 | ||
518 | if (stmt == NULL_TREE | |
519 | || TREE_CODE (stmt) != OMP_RETURN | |
520 | || !single_pred_p (bb)) | |
521 | return false; | |
522 | ||
523 | control_bb = single_pred (bb); | |
524 | stmt = last_stmt (control_bb); | |
525 | ||
526 | if (TREE_CODE (stmt) != OMP_SECTIONS_SWITCH) | |
527 | return false; | |
528 | ||
529 | /* The block with the control statement normally has two entry edges -- one | |
530 | from entry, one from continue. If continue is removed, return is | |
531 | unreachable, so we remove it here as well. */ | |
532 | if (EDGE_COUNT (control_bb->preds) == 2) | |
533 | return false; | |
534 | ||
535 | gcc_assert (EDGE_COUNT (control_bb->preds) == 1); | |
536 | remove_edge_and_dominated_blocks (single_pred_edge (bb)); | |
537 | return true; | |
538 | } | |
539 | ||
672987e8 ZD |
540 | /* Tries to cleanup cfg in basic block BB. Returns true if anything |
541 | changes. */ | |
c9784e6d | 542 | |
89e80dd4 | 543 | static bool |
672987e8 | 544 | cleanup_tree_cfg_bb (basic_block bb) |
c9784e6d | 545 | { |
672987e8 | 546 | bool retval = false; |
c9784e6d | 547 | |
e5c95afe ZD |
548 | if (cleanup_omp_return (bb)) |
549 | return true; | |
c9784e6d | 550 | |
e5c95afe ZD |
551 | retval = cleanup_control_flow_bb (bb); |
552 | ||
7825308e ILT |
553 | /* Forwarder blocks can carry line number information which is |
554 | useful when debugging, so we only clean them up when | |
555 | optimizing. */ | |
556 | ||
672987e8 ZD |
557 | if (optimize > 0 |
558 | && tree_forwarder_block_p (bb, false) | |
559 | && remove_forwarder_block (bb)) | |
560 | return true; | |
c9784e6d | 561 | |
89e80dd4 DN |
562 | /* Merging the blocks may create new opportunities for folding |
563 | conditional branches (due to the elimination of single-valued PHI | |
564 | nodes). */ | |
672987e8 ZD |
565 | if (single_succ_p (bb) |
566 | && can_merge_blocks_p (bb, single_succ (bb))) | |
567 | { | |
568 | merge_blocks (bb, single_succ (bb)); | |
569 | return true; | |
570 | } | |
571 | ||
572 | return retval; | |
573 | } | |
574 | ||
575 | /* Iterate the cfg cleanups, while anything changes. */ | |
576 | ||
577 | static bool | |
578 | cleanup_tree_cfg_1 (void) | |
579 | { | |
580 | bool retval = false; | |
581 | basic_block bb; | |
582 | unsigned i, n; | |
583 | ||
584 | retval |= split_bbs_on_noreturn_calls (); | |
585 | ||
586 | /* Prepare the worklists of altered blocks. */ | |
587 | cfgcleanup_altered_bbs = BITMAP_ALLOC (NULL); | |
588 | ||
589 | /* During forwarder block cleanup, we may redirect edges out of | |
590 | SWITCH_EXPRs, which can get expensive. So we want to enable | |
591 | recording of edge to CASE_LABEL_EXPR. */ | |
592 | start_recording_case_labels (); | |
89e80dd4 | 593 | |
672987e8 ZD |
594 | /* Start by iterating over all basic blocks. We cannot use FOR_EACH_BB, |
595 | since the basic blocks may get removed. */ | |
596 | n = last_basic_block; | |
597 | for (i = NUM_FIXED_BLOCKS; i < n; i++) | |
598 | { | |
599 | bb = BASIC_BLOCK (i); | |
600 | if (bb) | |
601 | retval |= cleanup_tree_cfg_bb (bb); | |
602 | } | |
603 | ||
604 | /* Now process the altered blocks, as long as any are available. */ | |
605 | while (!bitmap_empty_p (cfgcleanup_altered_bbs)) | |
606 | { | |
607 | i = bitmap_first_set_bit (cfgcleanup_altered_bbs); | |
608 | bitmap_clear_bit (cfgcleanup_altered_bbs, i); | |
609 | if (i < NUM_FIXED_BLOCKS) | |
610 | continue; | |
611 | ||
612 | bb = BASIC_BLOCK (i); | |
613 | if (!bb) | |
614 | continue; | |
615 | ||
616 | retval |= cleanup_tree_cfg_bb (bb); | |
617 | ||
618 | /* Rerun split_bbs_on_noreturn_calls, in case we have altered any noreturn | |
619 | calls. */ | |
620 | retval |= split_bbs_on_noreturn_calls (); | |
621 | } | |
622 | ||
623 | end_recording_case_labels (); | |
624 | BITMAP_FREE (cfgcleanup_altered_bbs); | |
89e80dd4 DN |
625 | return retval; |
626 | } | |
627 | ||
628 | ||
e3594cb3 DN |
629 | /* Remove unreachable blocks and other miscellaneous clean up work. |
630 | Return true if the flowgraph was modified, false otherwise. */ | |
89e80dd4 | 631 | |
592c303d ZD |
632 | static bool |
633 | cleanup_tree_cfg_noloop (void) | |
89e80dd4 | 634 | { |
672987e8 | 635 | bool changed; |
89e80dd4 DN |
636 | |
637 | timevar_push (TV_TREE_CLEANUP_CFG); | |
638 | ||
e3594cb3 | 639 | /* Iterate until there are no more cleanups left to do. If any |
672987e8 ZD |
640 | iteration changed the flowgraph, set CHANGED to true. |
641 | ||
642 | If dominance information is available, there cannot be any unreachable | |
643 | blocks. */ | |
2b28c07a | 644 | if (!dom_info_available_p (CDI_DOMINATORS)) |
e3594cb3 | 645 | { |
672987e8 ZD |
646 | changed = delete_unreachable_blocks (); |
647 | calculate_dominance_info (CDI_DOMINATORS); | |
e3594cb3 | 648 | } |
672987e8 | 649 | else |
30251f7a ZD |
650 | { |
651 | #ifdef ENABLE_CHECKING | |
652 | verify_dominators (CDI_DOMINATORS); | |
653 | #endif | |
654 | changed = false; | |
655 | } | |
c9784e6d | 656 | |
672987e8 ZD |
657 | changed |= cleanup_tree_cfg_1 (); |
658 | ||
2b28c07a | 659 | gcc_assert (dom_info_available_p (CDI_DOMINATORS)); |
c9784e6d KH |
660 | compact_blocks (); |
661 | ||
662 | #ifdef ENABLE_CHECKING | |
663 | verify_flow_info (); | |
664 | #endif | |
89e80dd4 | 665 | |
c9784e6d | 666 | timevar_pop (TV_TREE_CLEANUP_CFG); |
89e80dd4 | 667 | |
592c303d | 668 | if (changed && current_loops) |
f87000d0 | 669 | loops_state_set (LOOPS_NEED_FIXUP); |
592c303d | 670 | |
e3594cb3 | 671 | return changed; |
c9784e6d KH |
672 | } |
673 | ||
592c303d | 674 | /* Repairs loop structures. */ |
c9784e6d | 675 | |
592c303d ZD |
676 | static void |
677 | repair_loop_structures (void) | |
c9784e6d | 678 | { |
592c303d ZD |
679 | bitmap changed_bbs = BITMAP_ALLOC (NULL); |
680 | fix_loop_structure (changed_bbs); | |
c9784e6d | 681 | |
592c303d ZD |
682 | /* This usually does nothing. But sometimes parts of cfg that originally |
683 | were inside a loop get out of it due to edge removal (since they | |
684 | become unreachable by back edges from latch). */ | |
f87000d0 | 685 | if (loops_state_satisfies_p (LOOP_CLOSED_SSA)) |
592c303d | 686 | rewrite_into_loop_closed_ssa (changed_bbs, TODO_update_ssa); |
c9784e6d | 687 | |
592c303d | 688 | BITMAP_FREE (changed_bbs); |
c9784e6d KH |
689 | |
690 | #ifdef ENABLE_CHECKING | |
592c303d | 691 | verify_loop_structure (); |
c9784e6d | 692 | #endif |
592c303d ZD |
693 | scev_reset (); |
694 | ||
f87000d0 | 695 | loops_state_clear (LOOPS_NEED_FIXUP); |
592c303d ZD |
696 | } |
697 | ||
698 | /* Cleanup cfg and repair loop structures. */ | |
699 | ||
700 | bool | |
701 | cleanup_tree_cfg (void) | |
702 | { | |
703 | bool changed = cleanup_tree_cfg_noloop (); | |
704 | ||
705 | if (current_loops != NULL | |
f87000d0 | 706 | && loops_state_satisfies_p (LOOPS_NEED_FIXUP)) |
592c303d ZD |
707 | repair_loop_structures (); |
708 | ||
1994bfea | 709 | return changed; |
c9784e6d KH |
710 | } |
711 | ||
712 | /* Merge the PHI nodes at BB into those at BB's sole successor. */ | |
713 | ||
714 | static void | |
715 | remove_forwarder_block_with_phi (basic_block bb) | |
716 | { | |
717 | edge succ = single_succ_edge (bb); | |
718 | basic_block dest = succ->dest; | |
719 | tree label; | |
720 | basic_block dombb, domdest, dom; | |
721 | ||
722 | /* We check for infinite loops already in tree_forwarder_block_p. | |
723 | However it may happen that the infinite loop is created | |
724 | afterwards due to removal of forwarders. */ | |
725 | if (dest == bb) | |
726 | return; | |
727 | ||
728 | /* If the destination block consists of a nonlocal label, do not | |
729 | merge it. */ | |
730 | label = first_stmt (dest); | |
731 | if (label | |
732 | && TREE_CODE (label) == LABEL_EXPR | |
733 | && DECL_NONLOCAL (LABEL_EXPR_LABEL (label))) | |
734 | return; | |
735 | ||
736 | /* Redirect each incoming edge to BB to DEST. */ | |
737 | while (EDGE_COUNT (bb->preds) > 0) | |
738 | { | |
739 | edge e = EDGE_PRED (bb, 0), s; | |
740 | tree phi; | |
741 | ||
742 | s = find_edge (e->src, dest); | |
743 | if (s) | |
744 | { | |
745 | /* We already have an edge S from E->src to DEST. If S and | |
746 | E->dest's sole successor edge have the same PHI arguments | |
747 | at DEST, redirect S to DEST. */ | |
748 | if (phi_alternatives_equal (dest, s, succ)) | |
749 | { | |
750 | e = redirect_edge_and_branch (e, dest); | |
ea7e6d5a | 751 | redirect_edge_var_map_clear (e); |
c9784e6d KH |
752 | continue; |
753 | } | |
754 | ||
755 | /* PHI arguments are different. Create a forwarder block by | |
756 | splitting E so that we can merge PHI arguments on E to | |
757 | DEST. */ | |
758 | e = single_succ_edge (split_edge (e)); | |
759 | } | |
760 | ||
761 | s = redirect_edge_and_branch (e, dest); | |
762 | ||
763 | /* redirect_edge_and_branch must not create a new edge. */ | |
764 | gcc_assert (s == e); | |
765 | ||
766 | /* Add to the PHI nodes at DEST each PHI argument removed at the | |
767 | destination of E. */ | |
768 | for (phi = phi_nodes (dest); phi; phi = PHI_CHAIN (phi)) | |
769 | { | |
770 | tree def = PHI_ARG_DEF (phi, succ->dest_idx); | |
771 | ||
772 | if (TREE_CODE (def) == SSA_NAME) | |
773 | { | |
ea7e6d5a AH |
774 | edge_var_map_vector head; |
775 | edge_var_map *vm; | |
776 | size_t i; | |
c9784e6d KH |
777 | |
778 | /* If DEF is one of the results of PHI nodes removed during | |
779 | redirection, replace it with the PHI argument that used | |
780 | to be on E. */ | |
ea7e6d5a AH |
781 | head = redirect_edge_var_map_vector (e); |
782 | for (i = 0; VEC_iterate (edge_var_map, head, i, vm); ++i) | |
c9784e6d | 783 | { |
ea7e6d5a AH |
784 | tree old_arg = redirect_edge_var_map_result (vm); |
785 | tree new_arg = redirect_edge_var_map_def (vm); | |
c9784e6d KH |
786 | |
787 | if (def == old_arg) | |
788 | { | |
789 | def = new_arg; | |
790 | break; | |
791 | } | |
792 | } | |
793 | } | |
794 | ||
795 | add_phi_arg (phi, def, s); | |
796 | } | |
797 | ||
ea7e6d5a | 798 | redirect_edge_var_map_clear (e); |
c9784e6d KH |
799 | } |
800 | ||
801 | /* Update the dominators. */ | |
802 | dombb = get_immediate_dominator (CDI_DOMINATORS, bb); | |
803 | domdest = get_immediate_dominator (CDI_DOMINATORS, dest); | |
804 | if (domdest == bb) | |
805 | { | |
806 | /* Shortcut to avoid calling (relatively expensive) | |
807 | nearest_common_dominator unless necessary. */ | |
808 | dom = dombb; | |
809 | } | |
810 | else | |
811 | dom = nearest_common_dominator (CDI_DOMINATORS, domdest, dombb); | |
812 | ||
813 | set_immediate_dominator (CDI_DOMINATORS, dest, dom); | |
814 | ||
815 | /* Remove BB since all of BB's incoming edges have been redirected | |
816 | to DEST. */ | |
817 | delete_basic_block (bb); | |
818 | } | |
819 | ||
820 | /* This pass merges PHI nodes if one feeds into another. For example, | |
821 | suppose we have the following: | |
822 | ||
823 | goto <bb 9> (<L9>); | |
824 | ||
825 | <L8>:; | |
826 | tem_17 = foo (); | |
827 | ||
828 | # tem_6 = PHI <tem_17(8), tem_23(7)>; | |
829 | <L9>:; | |
830 | ||
831 | # tem_3 = PHI <tem_6(9), tem_2(5)>; | |
832 | <L10>:; | |
833 | ||
834 | Then we merge the first PHI node into the second one like so: | |
835 | ||
836 | goto <bb 9> (<L10>); | |
837 | ||
838 | <L8>:; | |
839 | tem_17 = foo (); | |
840 | ||
841 | # tem_3 = PHI <tem_23(7), tem_2(5), tem_17(8)>; | |
842 | <L10>:; | |
843 | */ | |
844 | ||
c2924966 | 845 | static unsigned int |
c9784e6d KH |
846 | merge_phi_nodes (void) |
847 | { | |
5ed6ace5 | 848 | basic_block *worklist = XNEWVEC (basic_block, n_basic_blocks); |
c9784e6d KH |
849 | basic_block *current = worklist; |
850 | basic_block bb; | |
851 | ||
852 | calculate_dominance_info (CDI_DOMINATORS); | |
853 | ||
854 | /* Find all PHI nodes that we may be able to merge. */ | |
855 | FOR_EACH_BB (bb) | |
856 | { | |
857 | basic_block dest; | |
858 | ||
859 | /* Look for a forwarder block with PHI nodes. */ | |
860 | if (!tree_forwarder_block_p (bb, true)) | |
861 | continue; | |
862 | ||
863 | dest = single_succ (bb); | |
864 | ||
865 | /* We have to feed into another basic block with PHI | |
866 | nodes. */ | |
867 | if (!phi_nodes (dest) | |
868 | /* We don't want to deal with a basic block with | |
869 | abnormal edges. */ | |
870 | || has_abnormal_incoming_edge_p (bb)) | |
871 | continue; | |
872 | ||
873 | if (!dominated_by_p (CDI_DOMINATORS, dest, bb)) | |
874 | { | |
875 | /* If BB does not dominate DEST, then the PHI nodes at | |
876 | DEST must be the only users of the results of the PHI | |
877 | nodes at BB. */ | |
878 | *current++ = bb; | |
879 | } | |
ea65cd37 JL |
880 | else |
881 | { | |
882 | tree phi; | |
338b5886 | 883 | unsigned int dest_idx = single_succ_edge (bb)->dest_idx; |
ea65cd37 JL |
884 | |
885 | /* BB dominates DEST. There may be many users of the PHI | |
886 | nodes in BB. However, there is still a trivial case we | |
887 | can handle. If the result of every PHI in BB is used | |
888 | only by a PHI in DEST, then we can trivially merge the | |
889 | PHI nodes from BB into DEST. */ | |
890 | for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi)) | |
891 | { | |
892 | tree result = PHI_RESULT (phi); | |
ea65cd37 JL |
893 | use_operand_p imm_use; |
894 | tree use_stmt; | |
895 | ||
896 | /* If the PHI's result is never used, then we can just | |
897 | ignore it. */ | |
bfc646bf | 898 | if (has_zero_uses (result)) |
ea65cd37 JL |
899 | continue; |
900 | ||
901 | /* Get the single use of the result of this PHI node. */ | |
902 | if (!single_imm_use (result, &imm_use, &use_stmt) | |
903 | || TREE_CODE (use_stmt) != PHI_NODE | |
338b5886 KH |
904 | || bb_for_stmt (use_stmt) != dest |
905 | || PHI_ARG_DEF (use_stmt, dest_idx) != result) | |
ea65cd37 JL |
906 | break; |
907 | } | |
908 | ||
c0220ea4 | 909 | /* If the loop above iterated through all the PHI nodes |
ea65cd37 JL |
910 | in BB, then we can merge the PHIs from BB into DEST. */ |
911 | if (!phi) | |
912 | *current++ = bb; | |
913 | } | |
c9784e6d KH |
914 | } |
915 | ||
916 | /* Now let's drain WORKLIST. */ | |
917 | while (current != worklist) | |
918 | { | |
919 | bb = *--current; | |
920 | remove_forwarder_block_with_phi (bb); | |
921 | } | |
922 | ||
923 | free (worklist); | |
c2924966 | 924 | return 0; |
c9784e6d KH |
925 | } |
926 | ||
927 | static bool | |
928 | gate_merge_phi (void) | |
929 | { | |
930 | return 1; | |
931 | } | |
932 | ||
8ddbbcae JH |
933 | struct gimple_opt_pass pass_merge_phi = |
934 | { | |
935 | { | |
936 | GIMPLE_PASS, | |
c9784e6d KH |
937 | "mergephi", /* name */ |
938 | gate_merge_phi, /* gate */ | |
939 | merge_phi_nodes, /* execute */ | |
940 | NULL, /* sub */ | |
941 | NULL, /* next */ | |
942 | 0, /* static_pass_number */ | |
943 | TV_TREE_MERGE_PHI, /* tv_id */ | |
944 | PROP_cfg | PROP_ssa, /* properties_required */ | |
945 | 0, /* properties_provided */ | |
946 | 0, /* properties_destroyed */ | |
947 | 0, /* todo_flags_start */ | |
948 | TODO_dump_func | TODO_ggc_collect /* todo_flags_finish */ | |
8ddbbcae JH |
949 | | TODO_verify_ssa |
950 | } | |
c9784e6d | 951 | }; |