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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 | ||
726a989a | 76 | |
c9784e6d KH |
77 | /* Disconnect an unreachable block in the control expression starting |
78 | at block BB. */ | |
79 | ||
80 | static bool | |
726a989a | 81 | cleanup_control_expr_graph (basic_block bb, gimple_stmt_iterator gsi) |
c9784e6d KH |
82 | { |
83 | edge taken_edge; | |
84 | bool retval = false; | |
726a989a RB |
85 | gimple stmt = gsi_stmt (gsi); |
86 | tree val; | |
c9784e6d KH |
87 | |
88 | if (!single_succ_p (bb)) | |
89 | { | |
90 | edge e; | |
91 | edge_iterator ei; | |
6ac01510 ILT |
92 | bool warned; |
93 | ||
94 | fold_defer_overflow_warnings (); | |
726a989a | 95 | val = gimple_fold (stmt); |
c9784e6d KH |
96 | taken_edge = find_taken_edge (bb, val); |
97 | if (!taken_edge) | |
6ac01510 ILT |
98 | { |
99 | fold_undefer_and_ignore_overflow_warnings (); | |
100 | return false; | |
101 | } | |
c9784e6d KH |
102 | |
103 | /* Remove all the edges except the one that is always executed. */ | |
6ac01510 | 104 | warned = false; |
c9784e6d KH |
105 | for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); ) |
106 | { | |
107 | if (e != taken_edge) | |
108 | { | |
6ac01510 ILT |
109 | if (!warned) |
110 | { | |
111 | fold_undefer_overflow_warnings | |
726a989a | 112 | (true, stmt, WARN_STRICT_OVERFLOW_CONDITIONAL); |
6ac01510 ILT |
113 | warned = true; |
114 | } | |
115 | ||
c9784e6d KH |
116 | taken_edge->probability += e->probability; |
117 | taken_edge->count += e->count; | |
672987e8 | 118 | remove_edge_and_dominated_blocks (e); |
c9784e6d KH |
119 | retval = true; |
120 | } | |
121 | else | |
122 | ei_next (&ei); | |
123 | } | |
6ac01510 ILT |
124 | if (!warned) |
125 | fold_undefer_and_ignore_overflow_warnings (); | |
c9784e6d KH |
126 | if (taken_edge->probability > REG_BR_PROB_BASE) |
127 | taken_edge->probability = REG_BR_PROB_BASE; | |
128 | } | |
129 | else | |
130 | taken_edge = single_succ_edge (bb); | |
131 | ||
672987e8 | 132 | bitmap_set_bit (cfgcleanup_altered_bbs, bb->index); |
726a989a | 133 | gsi_remove (&gsi, true); |
c9784e6d KH |
134 | taken_edge->flags = EDGE_FALLTHRU; |
135 | ||
c9784e6d KH |
136 | return retval; |
137 | } | |
138 | ||
672987e8 ZD |
139 | /* Try to remove superfluous control structures in basic block BB. Returns |
140 | true if anything changes. */ | |
c9784e6d KH |
141 | |
142 | static bool | |
672987e8 | 143 | cleanup_control_flow_bb (basic_block bb) |
c9784e6d | 144 | { |
726a989a | 145 | gimple_stmt_iterator gsi; |
c9784e6d | 146 | bool retval = false; |
726a989a | 147 | gimple stmt; |
c9784e6d | 148 | |
672987e8 ZD |
149 | /* If the last statement of the block could throw and now cannot, |
150 | we need to prune cfg. */ | |
726a989a | 151 | retval |= gimple_purge_dead_eh_edges (bb); |
672987e8 | 152 | |
726a989a RB |
153 | gsi = gsi_last_bb (bb); |
154 | if (gsi_end_p (gsi)) | |
672987e8 ZD |
155 | return retval; |
156 | ||
726a989a | 157 | stmt = gsi_stmt (gsi); |
672987e8 | 158 | |
726a989a RB |
159 | if (gimple_code (stmt) == GIMPLE_COND |
160 | || gimple_code (stmt) == GIMPLE_SWITCH) | |
161 | retval |= cleanup_control_expr_graph (bb, gsi); | |
162 | else if (gimple_code (stmt) == GIMPLE_GOTO | |
163 | && TREE_CODE (gimple_goto_dest (stmt)) == ADDR_EXPR | |
164 | && (TREE_CODE (TREE_OPERAND (gimple_goto_dest (stmt), 0)) | |
672987e8 | 165 | == LABEL_DECL)) |
c9784e6d | 166 | { |
726a989a RB |
167 | /* If we had a computed goto which has a compile-time determinable |
168 | destination, then we can eliminate the goto. */ | |
672987e8 ZD |
169 | edge e; |
170 | tree label; | |
171 | edge_iterator ei; | |
172 | basic_block target_block; | |
c9784e6d | 173 | |
672987e8 ZD |
174 | /* First look at all the outgoing edges. Delete any outgoing |
175 | edges which do not go to the right block. For the one | |
176 | edge which goes to the right block, fix up its flags. */ | |
726a989a | 177 | label = TREE_OPERAND (gimple_goto_dest (stmt), 0); |
672987e8 ZD |
178 | target_block = label_to_block (label); |
179 | for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); ) | |
c9784e6d | 180 | { |
672987e8 ZD |
181 | if (e->dest != target_block) |
182 | remove_edge_and_dominated_blocks (e); | |
183 | else | |
c9784e6d | 184 | { |
672987e8 ZD |
185 | /* Turn off the EDGE_ABNORMAL flag. */ |
186 | e->flags &= ~EDGE_ABNORMAL; | |
c9784e6d | 187 | |
672987e8 ZD |
188 | /* And set EDGE_FALLTHRU. */ |
189 | e->flags |= EDGE_FALLTHRU; | |
190 | ei_next (&ei); | |
191 | } | |
c9784e6d KH |
192 | } |
193 | ||
672987e8 ZD |
194 | bitmap_set_bit (cfgcleanup_altered_bbs, bb->index); |
195 | bitmap_set_bit (cfgcleanup_altered_bbs, target_block->index); | |
196 | ||
197 | /* Remove the GOTO_EXPR as it is not needed. The CFG has all the | |
198 | relevant information we need. */ | |
726a989a | 199 | gsi_remove (&gsi, true); |
672987e8 | 200 | retval = true; |
c9784e6d | 201 | } |
672987e8 ZD |
202 | |
203 | /* Check for indirect calls that have been turned into | |
204 | noreturn calls. */ | |
726a989a RB |
205 | else if (is_gimple_call (stmt) |
206 | && gimple_call_noreturn_p (stmt) | |
207 | && remove_fallthru_edge (bb->succs)) | |
672987e8 ZD |
208 | retval = true; |
209 | ||
c9784e6d KH |
210 | return retval; |
211 | } | |
212 | ||
213 | /* Return true if basic block BB does nothing except pass control | |
214 | flow to another block and that we can safely insert a label at | |
215 | the start of the successor block. | |
216 | ||
217 | As a precondition, we require that BB be not equal to | |
218 | ENTRY_BLOCK_PTR. */ | |
219 | ||
220 | static bool | |
221 | tree_forwarder_block_p (basic_block bb, bool phi_wanted) | |
222 | { | |
726a989a | 223 | gimple_stmt_iterator gsi; |
9d335249 AH |
224 | edge_iterator ei; |
225 | edge e, succ; | |
226 | basic_block dest; | |
c9784e6d KH |
227 | |
228 | /* BB must have a single outgoing edge. */ | |
229 | if (single_succ_p (bb) != 1 | |
230 | /* If PHI_WANTED is false, BB must not have any PHI nodes. | |
231 | Otherwise, BB must have PHI nodes. */ | |
726a989a | 232 | || gimple_seq_empty_p (phi_nodes (bb)) == phi_wanted |
c9784e6d KH |
233 | /* BB may not be a predecessor of EXIT_BLOCK_PTR. */ |
234 | || single_succ (bb) == EXIT_BLOCK_PTR | |
235 | /* Nor should this be an infinite loop. */ | |
236 | || single_succ (bb) == bb | |
237 | /* BB may not have an abnormal outgoing edge. */ | |
238 | || (single_succ_edge (bb)->flags & EDGE_ABNORMAL)) | |
239 | return false; | |
240 | ||
241 | #if ENABLE_CHECKING | |
242 | gcc_assert (bb != ENTRY_BLOCK_PTR); | |
243 | #endif | |
244 | ||
245 | /* Now walk through the statements backward. We can ignore labels, | |
246 | anything else means this is not a forwarder block. */ | |
726a989a | 247 | for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi); gsi_prev (&gsi)) |
c9784e6d | 248 | { |
726a989a | 249 | gimple stmt = gsi_stmt (gsi); |
c9784e6d | 250 | |
726a989a | 251 | switch (gimple_code (stmt)) |
c9784e6d | 252 | { |
726a989a RB |
253 | case GIMPLE_LABEL: |
254 | if (DECL_NONLOCAL (gimple_label_label (stmt))) | |
c9784e6d KH |
255 | return false; |
256 | break; | |
257 | ||
258 | default: | |
259 | return false; | |
260 | } | |
261 | } | |
262 | ||
263 | if (find_edge (ENTRY_BLOCK_PTR, bb)) | |
264 | return false; | |
265 | ||
266 | if (current_loops) | |
267 | { | |
268 | basic_block dest; | |
269 | /* Protect loop latches, headers and preheaders. */ | |
270 | if (bb->loop_father->header == bb) | |
271 | return false; | |
272 | dest = EDGE_SUCC (bb, 0)->dest; | |
273 | ||
274 | if (dest->loop_father->header == dest) | |
275 | return false; | |
276 | } | |
277 | ||
9d335249 AH |
278 | /* If we have an EH edge leaving this block, make sure that the |
279 | destination of this block has only one predecessor. This ensures | |
280 | that we don't get into the situation where we try to remove two | |
281 | forwarders that go to the same basic block but are handlers for | |
282 | different EH regions. */ | |
283 | succ = single_succ_edge (bb); | |
284 | dest = succ->dest; | |
285 | FOR_EACH_EDGE (e, ei, bb->preds) | |
286 | { | |
287 | if (e->flags & EDGE_EH) | |
288 | { | |
289 | if (!single_pred_p (dest)) | |
290 | return false; | |
291 | } | |
292 | } | |
293 | ||
c9784e6d KH |
294 | return true; |
295 | } | |
296 | ||
297 | /* Return true if BB has at least one abnormal incoming edge. */ | |
298 | ||
299 | static inline bool | |
300 | has_abnormal_incoming_edge_p (basic_block bb) | |
301 | { | |
302 | edge e; | |
303 | edge_iterator ei; | |
304 | ||
305 | FOR_EACH_EDGE (e, ei, bb->preds) | |
306 | if (e->flags & EDGE_ABNORMAL) | |
307 | return true; | |
308 | ||
309 | return false; | |
310 | } | |
311 | ||
312 | /* If all the PHI nodes in DEST have alternatives for E1 and E2 and | |
313 | those alternatives are equal in each of the PHI nodes, then return | |
314 | true, else return false. */ | |
315 | ||
316 | static bool | |
317 | phi_alternatives_equal (basic_block dest, edge e1, edge e2) | |
318 | { | |
319 | int n1 = e1->dest_idx; | |
320 | int n2 = e2->dest_idx; | |
726a989a | 321 | gimple_stmt_iterator gsi; |
c9784e6d | 322 | |
726a989a | 323 | for (gsi = gsi_start_phis (dest); !gsi_end_p (gsi); gsi_next (&gsi)) |
c9784e6d | 324 | { |
726a989a RB |
325 | gimple phi = gsi_stmt (gsi); |
326 | tree val1 = gimple_phi_arg_def (phi, n1); | |
327 | tree val2 = gimple_phi_arg_def (phi, n2); | |
c9784e6d KH |
328 | |
329 | gcc_assert (val1 != NULL_TREE); | |
330 | gcc_assert (val2 != NULL_TREE); | |
331 | ||
332 | if (!operand_equal_for_phi_arg_p (val1, val2)) | |
333 | return false; | |
334 | } | |
335 | ||
336 | return true; | |
337 | } | |
338 | ||
672987e8 | 339 | /* Removes forwarder block BB. Returns false if this failed. */ |
c9784e6d KH |
340 | |
341 | static bool | |
672987e8 | 342 | remove_forwarder_block (basic_block bb) |
c9784e6d KH |
343 | { |
344 | edge succ = single_succ_edge (bb), e, s; | |
345 | basic_block dest = succ->dest; | |
726a989a | 346 | gimple label; |
c9784e6d | 347 | edge_iterator ei; |
726a989a | 348 | gimple_stmt_iterator gsi, gsi_to; |
c9784e6d KH |
349 | bool seen_abnormal_edge = false; |
350 | ||
351 | /* We check for infinite loops already in tree_forwarder_block_p. | |
352 | However it may happen that the infinite loop is created | |
353 | afterwards due to removal of forwarders. */ | |
354 | if (dest == bb) | |
355 | return false; | |
356 | ||
357 | /* If the destination block consists of a nonlocal label, do not merge | |
358 | it. */ | |
359 | label = first_stmt (dest); | |
360 | if (label | |
726a989a RB |
361 | && gimple_code (label) == GIMPLE_LABEL |
362 | && DECL_NONLOCAL (gimple_label_label (label))) | |
c9784e6d KH |
363 | return false; |
364 | ||
365 | /* If there is an abnormal edge to basic block BB, but not into | |
366 | dest, problems might occur during removal of the phi node at out | |
367 | of ssa due to overlapping live ranges of registers. | |
368 | ||
369 | If there is an abnormal edge in DEST, the problems would occur | |
370 | anyway since cleanup_dead_labels would then merge the labels for | |
371 | two different eh regions, and rest of exception handling code | |
372 | does not like it. | |
373 | ||
374 | So if there is an abnormal edge to BB, proceed only if there is | |
375 | no abnormal edge to DEST and there are no phi nodes in DEST. */ | |
376 | if (has_abnormal_incoming_edge_p (bb)) | |
377 | { | |
378 | seen_abnormal_edge = true; | |
379 | ||
380 | if (has_abnormal_incoming_edge_p (dest) | |
726a989a | 381 | || !gimple_seq_empty_p (phi_nodes (dest))) |
c9784e6d KH |
382 | return false; |
383 | } | |
384 | ||
385 | /* If there are phi nodes in DEST, and some of the blocks that are | |
386 | predecessors of BB are also predecessors of DEST, check that the | |
387 | phi node arguments match. */ | |
726a989a | 388 | if (!gimple_seq_empty_p (phi_nodes (dest))) |
c9784e6d KH |
389 | { |
390 | FOR_EACH_EDGE (e, ei, bb->preds) | |
391 | { | |
392 | s = find_edge (e->src, dest); | |
393 | if (!s) | |
394 | continue; | |
395 | ||
396 | if (!phi_alternatives_equal (dest, succ, s)) | |
397 | return false; | |
398 | } | |
399 | } | |
400 | ||
401 | /* Redirect the edges. */ | |
402 | for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei)); ) | |
403 | { | |
672987e8 ZD |
404 | bitmap_set_bit (cfgcleanup_altered_bbs, e->src->index); |
405 | ||
c9784e6d KH |
406 | if (e->flags & EDGE_ABNORMAL) |
407 | { | |
408 | /* If there is an abnormal edge, redirect it anyway, and | |
409 | move the labels to the new block to make it legal. */ | |
410 | s = redirect_edge_succ_nodup (e, dest); | |
411 | } | |
412 | else | |
413 | s = redirect_edge_and_branch (e, dest); | |
414 | ||
415 | if (s == e) | |
416 | { | |
417 | /* Create arguments for the phi nodes, since the edge was not | |
418 | here before. */ | |
726a989a RB |
419 | for (gsi = gsi_start_phis (dest); |
420 | !gsi_end_p (gsi); | |
421 | gsi_next (&gsi)) | |
422 | { | |
423 | gimple phi = gsi_stmt (gsi); | |
424 | add_phi_arg (phi, gimple_phi_arg_def (phi, succ->dest_idx), s); | |
425 | } | |
c9784e6d | 426 | } |
c9784e6d KH |
427 | } |
428 | ||
429 | if (seen_abnormal_edge) | |
430 | { | |
431 | /* Move the labels to the new block, so that the redirection of | |
432 | the abnormal edges works. */ | |
726a989a RB |
433 | gsi_to = gsi_start_bb (dest); |
434 | for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); ) | |
c9784e6d | 435 | { |
726a989a RB |
436 | label = gsi_stmt (gsi); |
437 | gcc_assert (gimple_code (label) == GIMPLE_LABEL); | |
438 | gsi_remove (&gsi, false); | |
439 | gsi_insert_before (&gsi_to, label, GSI_CONTINUE_LINKING); | |
c9784e6d KH |
440 | } |
441 | } | |
442 | ||
672987e8 ZD |
443 | bitmap_set_bit (cfgcleanup_altered_bbs, dest->index); |
444 | ||
c9784e6d KH |
445 | /* Update the dominators. */ |
446 | if (dom_info_available_p (CDI_DOMINATORS)) | |
447 | { | |
448 | basic_block dom, dombb, domdest; | |
449 | ||
450 | dombb = get_immediate_dominator (CDI_DOMINATORS, bb); | |
451 | domdest = get_immediate_dominator (CDI_DOMINATORS, dest); | |
452 | if (domdest == bb) | |
453 | { | |
454 | /* Shortcut to avoid calling (relatively expensive) | |
455 | nearest_common_dominator unless necessary. */ | |
456 | dom = dombb; | |
457 | } | |
458 | else | |
459 | dom = nearest_common_dominator (CDI_DOMINATORS, domdest, dombb); | |
460 | ||
461 | set_immediate_dominator (CDI_DOMINATORS, dest, dom); | |
462 | } | |
463 | ||
464 | /* And kill the forwarder block. */ | |
465 | delete_basic_block (bb); | |
466 | ||
467 | return true; | |
468 | } | |
469 | ||
672987e8 ZD |
470 | /* Split basic blocks on calls in the middle of a basic block that are now |
471 | known not to return, and remove the unreachable code. */ | |
c9784e6d KH |
472 | |
473 | static bool | |
672987e8 | 474 | split_bbs_on_noreturn_calls (void) |
c9784e6d | 475 | { |
c9784e6d | 476 | bool changed = false; |
726a989a | 477 | gimple stmt; |
672987e8 | 478 | basic_block bb; |
c9784e6d | 479 | |
672987e8 ZD |
480 | /* Detect cases where a mid-block call is now known not to return. */ |
481 | if (cfun->gimple_df) | |
726a989a | 482 | while (VEC_length (gimple, MODIFIED_NORETURN_CALLS (cfun))) |
672987e8 | 483 | { |
726a989a RB |
484 | stmt = VEC_pop (gimple, MODIFIED_NORETURN_CALLS (cfun)); |
485 | bb = gimple_bb (stmt); | |
672987e8 ZD |
486 | if (bb == NULL |
487 | || last_stmt (bb) == stmt | |
726a989a | 488 | || !gimple_call_noreturn_p (stmt)) |
672987e8 ZD |
489 | continue; |
490 | ||
491 | changed = true; | |
492 | split_block (bb, stmt); | |
493 | remove_fallthru_edge (bb->succs); | |
494 | } | |
c9784e6d | 495 | |
c9784e6d KH |
496 | return changed; |
497 | } | |
498 | ||
726a989a | 499 | /* If GIMPLE_OMP_RETURN in basic block BB is unreachable, remove it. */ |
e5c95afe ZD |
500 | |
501 | static bool | |
502 | cleanup_omp_return (basic_block bb) | |
503 | { | |
726a989a | 504 | gimple stmt = last_stmt (bb); |
e5c95afe ZD |
505 | basic_block control_bb; |
506 | ||
726a989a RB |
507 | if (stmt == NULL |
508 | || gimple_code (stmt) != GIMPLE_OMP_RETURN | |
e5c95afe ZD |
509 | || !single_pred_p (bb)) |
510 | return false; | |
511 | ||
512 | control_bb = single_pred (bb); | |
513 | stmt = last_stmt (control_bb); | |
514 | ||
726a989a | 515 | if (gimple_code (stmt) != GIMPLE_OMP_SECTIONS_SWITCH) |
e5c95afe ZD |
516 | return false; |
517 | ||
518 | /* The block with the control statement normally has two entry edges -- one | |
519 | from entry, one from continue. If continue is removed, return is | |
520 | unreachable, so we remove it here as well. */ | |
521 | if (EDGE_COUNT (control_bb->preds) == 2) | |
522 | return false; | |
523 | ||
524 | gcc_assert (EDGE_COUNT (control_bb->preds) == 1); | |
525 | remove_edge_and_dominated_blocks (single_pred_edge (bb)); | |
526 | return true; | |
527 | } | |
528 | ||
672987e8 ZD |
529 | /* Tries to cleanup cfg in basic block BB. Returns true if anything |
530 | changes. */ | |
c9784e6d | 531 | |
89e80dd4 | 532 | static bool |
672987e8 | 533 | cleanup_tree_cfg_bb (basic_block bb) |
c9784e6d | 534 | { |
672987e8 | 535 | bool retval = false; |
c9784e6d | 536 | |
e5c95afe ZD |
537 | if (cleanup_omp_return (bb)) |
538 | return true; | |
c9784e6d | 539 | |
e5c95afe ZD |
540 | retval = cleanup_control_flow_bb (bb); |
541 | ||
7825308e ILT |
542 | /* Forwarder blocks can carry line number information which is |
543 | useful when debugging, so we only clean them up when | |
544 | optimizing. */ | |
672987e8 ZD |
545 | if (optimize > 0 |
546 | && tree_forwarder_block_p (bb, false) | |
547 | && remove_forwarder_block (bb)) | |
548 | return true; | |
c9784e6d | 549 | |
89e80dd4 DN |
550 | /* Merging the blocks may create new opportunities for folding |
551 | conditional branches (due to the elimination of single-valued PHI | |
552 | nodes). */ | |
672987e8 ZD |
553 | if (single_succ_p (bb) |
554 | && can_merge_blocks_p (bb, single_succ (bb))) | |
555 | { | |
556 | merge_blocks (bb, single_succ (bb)); | |
557 | return true; | |
558 | } | |
559 | ||
560 | return retval; | |
561 | } | |
562 | ||
563 | /* Iterate the cfg cleanups, while anything changes. */ | |
564 | ||
565 | static bool | |
566 | cleanup_tree_cfg_1 (void) | |
567 | { | |
568 | bool retval = false; | |
569 | basic_block bb; | |
570 | unsigned i, n; | |
571 | ||
572 | retval |= split_bbs_on_noreturn_calls (); | |
573 | ||
574 | /* Prepare the worklists of altered blocks. */ | |
575 | cfgcleanup_altered_bbs = BITMAP_ALLOC (NULL); | |
576 | ||
577 | /* During forwarder block cleanup, we may redirect edges out of | |
578 | SWITCH_EXPRs, which can get expensive. So we want to enable | |
579 | recording of edge to CASE_LABEL_EXPR. */ | |
580 | start_recording_case_labels (); | |
89e80dd4 | 581 | |
672987e8 ZD |
582 | /* Start by iterating over all basic blocks. We cannot use FOR_EACH_BB, |
583 | since the basic blocks may get removed. */ | |
584 | n = last_basic_block; | |
585 | for (i = NUM_FIXED_BLOCKS; i < n; i++) | |
586 | { | |
587 | bb = BASIC_BLOCK (i); | |
588 | if (bb) | |
589 | retval |= cleanup_tree_cfg_bb (bb); | |
590 | } | |
591 | ||
592 | /* Now process the altered blocks, as long as any are available. */ | |
593 | while (!bitmap_empty_p (cfgcleanup_altered_bbs)) | |
594 | { | |
595 | i = bitmap_first_set_bit (cfgcleanup_altered_bbs); | |
596 | bitmap_clear_bit (cfgcleanup_altered_bbs, i); | |
597 | if (i < NUM_FIXED_BLOCKS) | |
598 | continue; | |
599 | ||
600 | bb = BASIC_BLOCK (i); | |
601 | if (!bb) | |
602 | continue; | |
603 | ||
604 | retval |= cleanup_tree_cfg_bb (bb); | |
605 | ||
606 | /* Rerun split_bbs_on_noreturn_calls, in case we have altered any noreturn | |
607 | calls. */ | |
608 | retval |= split_bbs_on_noreturn_calls (); | |
609 | } | |
610 | ||
611 | end_recording_case_labels (); | |
612 | BITMAP_FREE (cfgcleanup_altered_bbs); | |
89e80dd4 DN |
613 | return retval; |
614 | } | |
615 | ||
616 | ||
e3594cb3 DN |
617 | /* Remove unreachable blocks and other miscellaneous clean up work. |
618 | Return true if the flowgraph was modified, false otherwise. */ | |
89e80dd4 | 619 | |
592c303d ZD |
620 | static bool |
621 | cleanup_tree_cfg_noloop (void) | |
89e80dd4 | 622 | { |
672987e8 | 623 | bool changed; |
89e80dd4 DN |
624 | |
625 | timevar_push (TV_TREE_CLEANUP_CFG); | |
626 | ||
e3594cb3 | 627 | /* Iterate until there are no more cleanups left to do. If any |
672987e8 ZD |
628 | iteration changed the flowgraph, set CHANGED to true. |
629 | ||
630 | If dominance information is available, there cannot be any unreachable | |
631 | blocks. */ | |
2b28c07a | 632 | if (!dom_info_available_p (CDI_DOMINATORS)) |
e3594cb3 | 633 | { |
672987e8 ZD |
634 | changed = delete_unreachable_blocks (); |
635 | calculate_dominance_info (CDI_DOMINATORS); | |
e3594cb3 | 636 | } |
672987e8 | 637 | else |
30251f7a ZD |
638 | { |
639 | #ifdef ENABLE_CHECKING | |
640 | verify_dominators (CDI_DOMINATORS); | |
641 | #endif | |
642 | changed = false; | |
643 | } | |
c9784e6d | 644 | |
672987e8 ZD |
645 | changed |= cleanup_tree_cfg_1 (); |
646 | ||
2b28c07a | 647 | gcc_assert (dom_info_available_p (CDI_DOMINATORS)); |
c9784e6d KH |
648 | compact_blocks (); |
649 | ||
650 | #ifdef ENABLE_CHECKING | |
651 | verify_flow_info (); | |
652 | #endif | |
89e80dd4 | 653 | |
c9784e6d | 654 | timevar_pop (TV_TREE_CLEANUP_CFG); |
89e80dd4 | 655 | |
592c303d | 656 | if (changed && current_loops) |
f87000d0 | 657 | loops_state_set (LOOPS_NEED_FIXUP); |
592c303d | 658 | |
e3594cb3 | 659 | return changed; |
c9784e6d KH |
660 | } |
661 | ||
592c303d | 662 | /* Repairs loop structures. */ |
c9784e6d | 663 | |
592c303d ZD |
664 | static void |
665 | repair_loop_structures (void) | |
c9784e6d | 666 | { |
592c303d ZD |
667 | bitmap changed_bbs = BITMAP_ALLOC (NULL); |
668 | fix_loop_structure (changed_bbs); | |
c9784e6d | 669 | |
592c303d ZD |
670 | /* This usually does nothing. But sometimes parts of cfg that originally |
671 | were inside a loop get out of it due to edge removal (since they | |
672 | become unreachable by back edges from latch). */ | |
f87000d0 | 673 | if (loops_state_satisfies_p (LOOP_CLOSED_SSA)) |
592c303d | 674 | rewrite_into_loop_closed_ssa (changed_bbs, TODO_update_ssa); |
c9784e6d | 675 | |
592c303d | 676 | BITMAP_FREE (changed_bbs); |
c9784e6d KH |
677 | |
678 | #ifdef ENABLE_CHECKING | |
592c303d | 679 | verify_loop_structure (); |
c9784e6d | 680 | #endif |
592c303d ZD |
681 | scev_reset (); |
682 | ||
f87000d0 | 683 | loops_state_clear (LOOPS_NEED_FIXUP); |
592c303d ZD |
684 | } |
685 | ||
686 | /* Cleanup cfg and repair loop structures. */ | |
687 | ||
688 | bool | |
689 | cleanup_tree_cfg (void) | |
690 | { | |
691 | bool changed = cleanup_tree_cfg_noloop (); | |
692 | ||
693 | if (current_loops != NULL | |
f87000d0 | 694 | && loops_state_satisfies_p (LOOPS_NEED_FIXUP)) |
592c303d ZD |
695 | repair_loop_structures (); |
696 | ||
1994bfea | 697 | return changed; |
c9784e6d KH |
698 | } |
699 | ||
700 | /* Merge the PHI nodes at BB into those at BB's sole successor. */ | |
701 | ||
702 | static void | |
703 | remove_forwarder_block_with_phi (basic_block bb) | |
704 | { | |
705 | edge succ = single_succ_edge (bb); | |
706 | basic_block dest = succ->dest; | |
726a989a | 707 | gimple label; |
c9784e6d KH |
708 | basic_block dombb, domdest, dom; |
709 | ||
710 | /* We check for infinite loops already in tree_forwarder_block_p. | |
711 | However it may happen that the infinite loop is created | |
712 | afterwards due to removal of forwarders. */ | |
713 | if (dest == bb) | |
714 | return; | |
715 | ||
716 | /* If the destination block consists of a nonlocal label, do not | |
717 | merge it. */ | |
718 | label = first_stmt (dest); | |
719 | if (label | |
726a989a RB |
720 | && gimple_code (label) == GIMPLE_LABEL |
721 | && DECL_NONLOCAL (gimple_label_label (label))) | |
c9784e6d KH |
722 | return; |
723 | ||
724 | /* Redirect each incoming edge to BB to DEST. */ | |
725 | while (EDGE_COUNT (bb->preds) > 0) | |
726 | { | |
727 | edge e = EDGE_PRED (bb, 0), s; | |
726a989a | 728 | gimple_stmt_iterator gsi; |
c9784e6d KH |
729 | |
730 | s = find_edge (e->src, dest); | |
731 | if (s) | |
732 | { | |
733 | /* We already have an edge S from E->src to DEST. If S and | |
734 | E->dest's sole successor edge have the same PHI arguments | |
735 | at DEST, redirect S to DEST. */ | |
736 | if (phi_alternatives_equal (dest, s, succ)) | |
737 | { | |
738 | e = redirect_edge_and_branch (e, dest); | |
ea7e6d5a | 739 | redirect_edge_var_map_clear (e); |
c9784e6d KH |
740 | continue; |
741 | } | |
742 | ||
743 | /* PHI arguments are different. Create a forwarder block by | |
744 | splitting E so that we can merge PHI arguments on E to | |
745 | DEST. */ | |
746 | e = single_succ_edge (split_edge (e)); | |
747 | } | |
748 | ||
749 | s = redirect_edge_and_branch (e, dest); | |
750 | ||
751 | /* redirect_edge_and_branch must not create a new edge. */ | |
752 | gcc_assert (s == e); | |
753 | ||
754 | /* Add to the PHI nodes at DEST each PHI argument removed at the | |
755 | destination of E. */ | |
726a989a RB |
756 | for (gsi = gsi_start_phis (dest); |
757 | !gsi_end_p (gsi); | |
758 | gsi_next (&gsi)) | |
c9784e6d | 759 | { |
726a989a RB |
760 | gimple phi = gsi_stmt (gsi); |
761 | tree def = gimple_phi_arg_def (phi, succ->dest_idx); | |
c9784e6d KH |
762 | |
763 | if (TREE_CODE (def) == SSA_NAME) | |
764 | { | |
ea7e6d5a AH |
765 | edge_var_map_vector head; |
766 | edge_var_map *vm; | |
767 | size_t i; | |
c9784e6d KH |
768 | |
769 | /* If DEF is one of the results of PHI nodes removed during | |
770 | redirection, replace it with the PHI argument that used | |
771 | to be on E. */ | |
ea7e6d5a AH |
772 | head = redirect_edge_var_map_vector (e); |
773 | for (i = 0; VEC_iterate (edge_var_map, head, i, vm); ++i) | |
c9784e6d | 774 | { |
ea7e6d5a AH |
775 | tree old_arg = redirect_edge_var_map_result (vm); |
776 | tree new_arg = redirect_edge_var_map_def (vm); | |
c9784e6d KH |
777 | |
778 | if (def == old_arg) | |
779 | { | |
780 | def = new_arg; | |
781 | break; | |
782 | } | |
783 | } | |
784 | } | |
785 | ||
786 | add_phi_arg (phi, def, s); | |
787 | } | |
788 | ||
ea7e6d5a | 789 | redirect_edge_var_map_clear (e); |
c9784e6d KH |
790 | } |
791 | ||
792 | /* Update the dominators. */ | |
793 | dombb = get_immediate_dominator (CDI_DOMINATORS, bb); | |
794 | domdest = get_immediate_dominator (CDI_DOMINATORS, dest); | |
795 | if (domdest == bb) | |
796 | { | |
797 | /* Shortcut to avoid calling (relatively expensive) | |
798 | nearest_common_dominator unless necessary. */ | |
799 | dom = dombb; | |
800 | } | |
801 | else | |
802 | dom = nearest_common_dominator (CDI_DOMINATORS, domdest, dombb); | |
803 | ||
804 | set_immediate_dominator (CDI_DOMINATORS, dest, dom); | |
805 | ||
806 | /* Remove BB since all of BB's incoming edges have been redirected | |
807 | to DEST. */ | |
808 | delete_basic_block (bb); | |
809 | } | |
810 | ||
811 | /* This pass merges PHI nodes if one feeds into another. For example, | |
812 | suppose we have the following: | |
813 | ||
814 | goto <bb 9> (<L9>); | |
815 | ||
816 | <L8>:; | |
817 | tem_17 = foo (); | |
818 | ||
819 | # tem_6 = PHI <tem_17(8), tem_23(7)>; | |
820 | <L9>:; | |
821 | ||
822 | # tem_3 = PHI <tem_6(9), tem_2(5)>; | |
823 | <L10>:; | |
824 | ||
825 | Then we merge the first PHI node into the second one like so: | |
826 | ||
827 | goto <bb 9> (<L10>); | |
828 | ||
829 | <L8>:; | |
830 | tem_17 = foo (); | |
831 | ||
832 | # tem_3 = PHI <tem_23(7), tem_2(5), tem_17(8)>; | |
833 | <L10>:; | |
834 | */ | |
835 | ||
c2924966 | 836 | static unsigned int |
c9784e6d KH |
837 | merge_phi_nodes (void) |
838 | { | |
5ed6ace5 | 839 | basic_block *worklist = XNEWVEC (basic_block, n_basic_blocks); |
c9784e6d KH |
840 | basic_block *current = worklist; |
841 | basic_block bb; | |
842 | ||
843 | calculate_dominance_info (CDI_DOMINATORS); | |
844 | ||
845 | /* Find all PHI nodes that we may be able to merge. */ | |
846 | FOR_EACH_BB (bb) | |
847 | { | |
848 | basic_block dest; | |
849 | ||
850 | /* Look for a forwarder block with PHI nodes. */ | |
851 | if (!tree_forwarder_block_p (bb, true)) | |
852 | continue; | |
853 | ||
854 | dest = single_succ (bb); | |
855 | ||
856 | /* We have to feed into another basic block with PHI | |
857 | nodes. */ | |
858 | if (!phi_nodes (dest) | |
859 | /* We don't want to deal with a basic block with | |
860 | abnormal edges. */ | |
861 | || has_abnormal_incoming_edge_p (bb)) | |
862 | continue; | |
863 | ||
864 | if (!dominated_by_p (CDI_DOMINATORS, dest, bb)) | |
865 | { | |
866 | /* If BB does not dominate DEST, then the PHI nodes at | |
867 | DEST must be the only users of the results of the PHI | |
868 | nodes at BB. */ | |
869 | *current++ = bb; | |
870 | } | |
ea65cd37 JL |
871 | else |
872 | { | |
726a989a | 873 | gimple_stmt_iterator gsi; |
338b5886 | 874 | unsigned int dest_idx = single_succ_edge (bb)->dest_idx; |
ea65cd37 JL |
875 | |
876 | /* BB dominates DEST. There may be many users of the PHI | |
877 | nodes in BB. However, there is still a trivial case we | |
878 | can handle. If the result of every PHI in BB is used | |
879 | only by a PHI in DEST, then we can trivially merge the | |
880 | PHI nodes from BB into DEST. */ | |
726a989a RB |
881 | for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); |
882 | gsi_next (&gsi)) | |
ea65cd37 | 883 | { |
726a989a RB |
884 | gimple phi = gsi_stmt (gsi); |
885 | tree result = gimple_phi_result (phi); | |
ea65cd37 | 886 | use_operand_p imm_use; |
726a989a | 887 | gimple use_stmt; |
ea65cd37 JL |
888 | |
889 | /* If the PHI's result is never used, then we can just | |
890 | ignore it. */ | |
bfc646bf | 891 | if (has_zero_uses (result)) |
ea65cd37 JL |
892 | continue; |
893 | ||
894 | /* Get the single use of the result of this PHI node. */ | |
895 | if (!single_imm_use (result, &imm_use, &use_stmt) | |
726a989a RB |
896 | || gimple_code (use_stmt) != GIMPLE_PHI |
897 | || gimple_bb (use_stmt) != dest | |
898 | || gimple_phi_arg_def (use_stmt, dest_idx) != result) | |
ea65cd37 JL |
899 | break; |
900 | } | |
901 | ||
c0220ea4 | 902 | /* If the loop above iterated through all the PHI nodes |
ea65cd37 | 903 | in BB, then we can merge the PHIs from BB into DEST. */ |
726a989a | 904 | if (gsi_end_p (gsi)) |
ea65cd37 JL |
905 | *current++ = bb; |
906 | } | |
c9784e6d KH |
907 | } |
908 | ||
909 | /* Now let's drain WORKLIST. */ | |
910 | while (current != worklist) | |
911 | { | |
912 | bb = *--current; | |
913 | remove_forwarder_block_with_phi (bb); | |
914 | } | |
915 | ||
916 | free (worklist); | |
c2924966 | 917 | return 0; |
c9784e6d KH |
918 | } |
919 | ||
920 | static bool | |
921 | gate_merge_phi (void) | |
922 | { | |
923 | return 1; | |
924 | } | |
925 | ||
8ddbbcae JH |
926 | struct gimple_opt_pass pass_merge_phi = |
927 | { | |
928 | { | |
929 | GIMPLE_PASS, | |
c9784e6d KH |
930 | "mergephi", /* name */ |
931 | gate_merge_phi, /* gate */ | |
932 | merge_phi_nodes, /* execute */ | |
933 | NULL, /* sub */ | |
934 | NULL, /* next */ | |
935 | 0, /* static_pass_number */ | |
936 | TV_TREE_MERGE_PHI, /* tv_id */ | |
937 | PROP_cfg | PROP_ssa, /* properties_required */ | |
938 | 0, /* properties_provided */ | |
939 | 0, /* properties_destroyed */ | |
940 | 0, /* todo_flags_start */ | |
941 | TODO_dump_func | TODO_ggc_collect /* todo_flags_finish */ | |
8ddbbcae JH |
942 | | TODO_verify_ssa |
943 | } | |
c9784e6d | 944 | }; |