]>
Commit | Line | Data |
---|---|---|
c9784e6d | 1 | /* CFG cleanup for trees. |
66647d44 | 2 | Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008 |
6ac01510 | 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; |
c9784e6d KH |
224 | |
225 | /* BB must have a single outgoing edge. */ | |
226 | if (single_succ_p (bb) != 1 | |
227 | /* If PHI_WANTED is false, BB must not have any PHI nodes. | |
228 | Otherwise, BB must have PHI nodes. */ | |
726a989a | 229 | || gimple_seq_empty_p (phi_nodes (bb)) == phi_wanted |
c9784e6d KH |
230 | /* BB may not be a predecessor of EXIT_BLOCK_PTR. */ |
231 | || single_succ (bb) == EXIT_BLOCK_PTR | |
232 | /* Nor should this be an infinite loop. */ | |
233 | || single_succ (bb) == bb | |
234 | /* BB may not have an abnormal outgoing edge. */ | |
235 | || (single_succ_edge (bb)->flags & EDGE_ABNORMAL)) | |
236 | return false; | |
237 | ||
238 | #if ENABLE_CHECKING | |
239 | gcc_assert (bb != ENTRY_BLOCK_PTR); | |
240 | #endif | |
241 | ||
1d65f45c RH |
242 | /* There should not be an edge coming from entry, or an EH edge. */ |
243 | { | |
244 | edge_iterator ei; | |
245 | edge e; | |
246 | ||
247 | FOR_EACH_EDGE (e, ei, bb->preds) | |
248 | if (e->src == ENTRY_BLOCK_PTR || (e->flags & EDGE_EH)) | |
249 | return false; | |
250 | } | |
251 | ||
c9784e6d KH |
252 | /* Now walk through the statements backward. We can ignore labels, |
253 | anything else means this is not a forwarder block. */ | |
726a989a | 254 | for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi); gsi_prev (&gsi)) |
c9784e6d | 255 | { |
726a989a | 256 | gimple stmt = gsi_stmt (gsi); |
c9784e6d | 257 | |
726a989a | 258 | switch (gimple_code (stmt)) |
c9784e6d | 259 | { |
726a989a RB |
260 | case GIMPLE_LABEL: |
261 | if (DECL_NONLOCAL (gimple_label_label (stmt))) | |
c9784e6d KH |
262 | return false; |
263 | break; | |
264 | ||
b5b8b0ac AO |
265 | /* ??? For now, hope there's a corresponding debug |
266 | assignment at the destination. */ | |
267 | case GIMPLE_DEBUG: | |
268 | break; | |
269 | ||
c9784e6d KH |
270 | default: |
271 | return false; | |
272 | } | |
273 | } | |
274 | ||
c9784e6d KH |
275 | if (current_loops) |
276 | { | |
277 | basic_block dest; | |
278 | /* Protect loop latches, headers and preheaders. */ | |
279 | if (bb->loop_father->header == bb) | |
280 | return false; | |
281 | dest = EDGE_SUCC (bb, 0)->dest; | |
282 | ||
283 | if (dest->loop_father->header == dest) | |
284 | return false; | |
285 | } | |
c9784e6d KH |
286 | return true; |
287 | } | |
288 | ||
289 | /* Return true if BB has at least one abnormal incoming edge. */ | |
290 | ||
291 | static inline bool | |
292 | has_abnormal_incoming_edge_p (basic_block bb) | |
293 | { | |
294 | edge e; | |
295 | edge_iterator ei; | |
296 | ||
297 | FOR_EACH_EDGE (e, ei, bb->preds) | |
298 | if (e->flags & EDGE_ABNORMAL) | |
299 | return true; | |
300 | ||
301 | return false; | |
302 | } | |
303 | ||
304 | /* If all the PHI nodes in DEST have alternatives for E1 and E2 and | |
305 | those alternatives are equal in each of the PHI nodes, then return | |
306 | true, else return false. */ | |
307 | ||
308 | static bool | |
309 | phi_alternatives_equal (basic_block dest, edge e1, edge e2) | |
310 | { | |
311 | int n1 = e1->dest_idx; | |
312 | int n2 = e2->dest_idx; | |
726a989a | 313 | gimple_stmt_iterator gsi; |
c9784e6d | 314 | |
726a989a | 315 | for (gsi = gsi_start_phis (dest); !gsi_end_p (gsi); gsi_next (&gsi)) |
c9784e6d | 316 | { |
726a989a RB |
317 | gimple phi = gsi_stmt (gsi); |
318 | tree val1 = gimple_phi_arg_def (phi, n1); | |
319 | tree val2 = gimple_phi_arg_def (phi, n2); | |
c9784e6d KH |
320 | |
321 | gcc_assert (val1 != NULL_TREE); | |
322 | gcc_assert (val2 != NULL_TREE); | |
323 | ||
324 | if (!operand_equal_for_phi_arg_p (val1, val2)) | |
325 | return false; | |
326 | } | |
327 | ||
328 | return true; | |
329 | } | |
330 | ||
672987e8 | 331 | /* Removes forwarder block BB. Returns false if this failed. */ |
c9784e6d KH |
332 | |
333 | static bool | |
672987e8 | 334 | remove_forwarder_block (basic_block bb) |
c9784e6d KH |
335 | { |
336 | edge succ = single_succ_edge (bb), e, s; | |
337 | basic_block dest = succ->dest; | |
726a989a | 338 | gimple label; |
c9784e6d | 339 | edge_iterator ei; |
726a989a | 340 | gimple_stmt_iterator gsi, gsi_to; |
c9784e6d KH |
341 | bool seen_abnormal_edge = false; |
342 | ||
343 | /* We check for infinite loops already in tree_forwarder_block_p. | |
344 | However it may happen that the infinite loop is created | |
345 | afterwards due to removal of forwarders. */ | |
346 | if (dest == bb) | |
347 | return false; | |
348 | ||
349 | /* If the destination block consists of a nonlocal label, do not merge | |
350 | it. */ | |
351 | label = first_stmt (dest); | |
352 | if (label | |
726a989a RB |
353 | && gimple_code (label) == GIMPLE_LABEL |
354 | && DECL_NONLOCAL (gimple_label_label (label))) | |
c9784e6d KH |
355 | return false; |
356 | ||
357 | /* If there is an abnormal edge to basic block BB, but not into | |
358 | dest, problems might occur during removal of the phi node at out | |
359 | of ssa due to overlapping live ranges of registers. | |
360 | ||
361 | If there is an abnormal edge in DEST, the problems would occur | |
362 | anyway since cleanup_dead_labels would then merge the labels for | |
363 | two different eh regions, and rest of exception handling code | |
364 | does not like it. | |
365 | ||
366 | So if there is an abnormal edge to BB, proceed only if there is | |
367 | no abnormal edge to DEST and there are no phi nodes in DEST. */ | |
368 | if (has_abnormal_incoming_edge_p (bb)) | |
369 | { | |
370 | seen_abnormal_edge = true; | |
371 | ||
372 | if (has_abnormal_incoming_edge_p (dest) | |
726a989a | 373 | || !gimple_seq_empty_p (phi_nodes (dest))) |
c9784e6d KH |
374 | return false; |
375 | } | |
376 | ||
377 | /* If there are phi nodes in DEST, and some of the blocks that are | |
378 | predecessors of BB are also predecessors of DEST, check that the | |
379 | phi node arguments match. */ | |
726a989a | 380 | if (!gimple_seq_empty_p (phi_nodes (dest))) |
c9784e6d KH |
381 | { |
382 | FOR_EACH_EDGE (e, ei, bb->preds) | |
383 | { | |
384 | s = find_edge (e->src, dest); | |
385 | if (!s) | |
386 | continue; | |
387 | ||
388 | if (!phi_alternatives_equal (dest, succ, s)) | |
389 | return false; | |
390 | } | |
391 | } | |
392 | ||
393 | /* Redirect the edges. */ | |
394 | for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei)); ) | |
395 | { | |
672987e8 ZD |
396 | bitmap_set_bit (cfgcleanup_altered_bbs, e->src->index); |
397 | ||
c9784e6d KH |
398 | if (e->flags & EDGE_ABNORMAL) |
399 | { | |
400 | /* If there is an abnormal edge, redirect it anyway, and | |
401 | move the labels to the new block to make it legal. */ | |
402 | s = redirect_edge_succ_nodup (e, dest); | |
403 | } | |
404 | else | |
405 | s = redirect_edge_and_branch (e, dest); | |
406 | ||
407 | if (s == e) | |
408 | { | |
409 | /* Create arguments for the phi nodes, since the edge was not | |
410 | here before. */ | |
726a989a RB |
411 | for (gsi = gsi_start_phis (dest); |
412 | !gsi_end_p (gsi); | |
413 | gsi_next (&gsi)) | |
414 | { | |
415 | gimple phi = gsi_stmt (gsi); | |
f5045c96 AM |
416 | source_location l = gimple_phi_arg_location_from_edge (phi, succ); |
417 | add_phi_arg (phi, gimple_phi_arg_def (phi, succ->dest_idx), s, l); | |
726a989a | 418 | } |
c9784e6d | 419 | } |
c9784e6d KH |
420 | } |
421 | ||
422 | if (seen_abnormal_edge) | |
423 | { | |
424 | /* Move the labels to the new block, so that the redirection of | |
425 | the abnormal edges works. */ | |
726a989a RB |
426 | gsi_to = gsi_start_bb (dest); |
427 | for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); ) | |
c9784e6d | 428 | { |
726a989a | 429 | label = gsi_stmt (gsi); |
b5b8b0ac AO |
430 | gcc_assert (gimple_code (label) == GIMPLE_LABEL |
431 | || is_gimple_debug (label)); | |
726a989a | 432 | gsi_remove (&gsi, false); |
b5b8b0ac | 433 | gsi_insert_before (&gsi_to, label, GSI_SAME_STMT); |
c9784e6d KH |
434 | } |
435 | } | |
436 | ||
672987e8 ZD |
437 | bitmap_set_bit (cfgcleanup_altered_bbs, dest->index); |
438 | ||
c9784e6d KH |
439 | /* Update the dominators. */ |
440 | if (dom_info_available_p (CDI_DOMINATORS)) | |
441 | { | |
442 | basic_block dom, dombb, domdest; | |
443 | ||
444 | dombb = get_immediate_dominator (CDI_DOMINATORS, bb); | |
445 | domdest = get_immediate_dominator (CDI_DOMINATORS, dest); | |
446 | if (domdest == bb) | |
447 | { | |
448 | /* Shortcut to avoid calling (relatively expensive) | |
449 | nearest_common_dominator unless necessary. */ | |
450 | dom = dombb; | |
451 | } | |
452 | else | |
453 | dom = nearest_common_dominator (CDI_DOMINATORS, domdest, dombb); | |
454 | ||
455 | set_immediate_dominator (CDI_DOMINATORS, dest, dom); | |
456 | } | |
457 | ||
458 | /* And kill the forwarder block. */ | |
459 | delete_basic_block (bb); | |
460 | ||
461 | return true; | |
462 | } | |
463 | ||
672987e8 ZD |
464 | /* Split basic blocks on calls in the middle of a basic block that are now |
465 | known not to return, and remove the unreachable code. */ | |
c9784e6d KH |
466 | |
467 | static bool | |
672987e8 | 468 | split_bbs_on_noreturn_calls (void) |
c9784e6d | 469 | { |
c9784e6d | 470 | bool changed = false; |
726a989a | 471 | gimple stmt; |
672987e8 | 472 | basic_block bb; |
c9784e6d | 473 | |
672987e8 ZD |
474 | /* Detect cases where a mid-block call is now known not to return. */ |
475 | if (cfun->gimple_df) | |
726a989a | 476 | while (VEC_length (gimple, MODIFIED_NORETURN_CALLS (cfun))) |
672987e8 | 477 | { |
726a989a RB |
478 | stmt = VEC_pop (gimple, MODIFIED_NORETURN_CALLS (cfun)); |
479 | bb = gimple_bb (stmt); | |
4d731f17 JJ |
480 | /* BB might be deleted at this point, so verify first |
481 | BB is present in the cfg. */ | |
672987e8 | 482 | if (bb == NULL |
4d731f17 JJ |
483 | || bb->index < NUM_FIXED_BLOCKS |
484 | || bb->index >= n_basic_blocks | |
485 | || BASIC_BLOCK (bb->index) != bb | |
672987e8 | 486 | || last_stmt (bb) == stmt |
726a989a | 487 | || !gimple_call_noreturn_p (stmt)) |
672987e8 ZD |
488 | continue; |
489 | ||
490 | changed = true; | |
491 | split_block (bb, stmt); | |
492 | remove_fallthru_edge (bb->succs); | |
493 | } | |
c9784e6d | 494 | |
c9784e6d KH |
495 | return changed; |
496 | } | |
497 | ||
726a989a | 498 | /* If GIMPLE_OMP_RETURN in basic block BB is unreachable, remove it. */ |
e5c95afe ZD |
499 | |
500 | static bool | |
501 | cleanup_omp_return (basic_block bb) | |
502 | { | |
726a989a | 503 | gimple stmt = last_stmt (bb); |
e5c95afe ZD |
504 | basic_block control_bb; |
505 | ||
726a989a RB |
506 | if (stmt == NULL |
507 | || gimple_code (stmt) != GIMPLE_OMP_RETURN | |
e5c95afe ZD |
508 | || !single_pred_p (bb)) |
509 | return false; | |
510 | ||
511 | control_bb = single_pred (bb); | |
512 | stmt = last_stmt (control_bb); | |
513 | ||
726a989a | 514 | if (gimple_code (stmt) != GIMPLE_OMP_SECTIONS_SWITCH) |
e5c95afe ZD |
515 | return false; |
516 | ||
517 | /* The block with the control statement normally has two entry edges -- one | |
518 | from entry, one from continue. If continue is removed, return is | |
519 | unreachable, so we remove it here as well. */ | |
520 | if (EDGE_COUNT (control_bb->preds) == 2) | |
521 | return false; | |
522 | ||
523 | gcc_assert (EDGE_COUNT (control_bb->preds) == 1); | |
524 | remove_edge_and_dominated_blocks (single_pred_edge (bb)); | |
525 | return true; | |
526 | } | |
527 | ||
672987e8 ZD |
528 | /* Tries to cleanup cfg in basic block BB. Returns true if anything |
529 | changes. */ | |
c9784e6d | 530 | |
89e80dd4 | 531 | static bool |
672987e8 | 532 | cleanup_tree_cfg_bb (basic_block bb) |
c9784e6d | 533 | { |
672987e8 | 534 | bool retval = false; |
c9784e6d | 535 | |
e5c95afe ZD |
536 | if (cleanup_omp_return (bb)) |
537 | return true; | |
c9784e6d | 538 | |
e5c95afe | 539 | retval = cleanup_control_flow_bb (bb); |
b8698a0f | 540 | |
7825308e ILT |
541 | /* Forwarder blocks can carry line number information which is |
542 | useful when debugging, so we only clean them up when | |
543 | optimizing. */ | |
672987e8 ZD |
544 | if (optimize > 0 |
545 | && tree_forwarder_block_p (bb, false) | |
546 | && remove_forwarder_block (bb)) | |
547 | return true; | |
c9784e6d | 548 | |
89e80dd4 DN |
549 | /* Merging the blocks may create new opportunities for folding |
550 | conditional branches (due to the elimination of single-valued PHI | |
551 | nodes). */ | |
672987e8 ZD |
552 | if (single_succ_p (bb) |
553 | && can_merge_blocks_p (bb, single_succ (bb))) | |
554 | { | |
555 | merge_blocks (bb, single_succ (bb)); | |
556 | return true; | |
557 | } | |
558 | ||
559 | return retval; | |
560 | } | |
561 | ||
562 | /* Iterate the cfg cleanups, while anything changes. */ | |
563 | ||
564 | static bool | |
565 | cleanup_tree_cfg_1 (void) | |
566 | { | |
567 | bool retval = false; | |
568 | basic_block bb; | |
569 | unsigned i, n; | |
570 | ||
571 | retval |= split_bbs_on_noreturn_calls (); | |
572 | ||
573 | /* Prepare the worklists of altered blocks. */ | |
574 | cfgcleanup_altered_bbs = BITMAP_ALLOC (NULL); | |
575 | ||
576 | /* During forwarder block cleanup, we may redirect edges out of | |
577 | SWITCH_EXPRs, which can get expensive. So we want to enable | |
578 | recording of edge to CASE_LABEL_EXPR. */ | |
579 | start_recording_case_labels (); | |
89e80dd4 | 580 | |
672987e8 ZD |
581 | /* Start by iterating over all basic blocks. We cannot use FOR_EACH_BB, |
582 | since the basic blocks may get removed. */ | |
583 | n = last_basic_block; | |
584 | for (i = NUM_FIXED_BLOCKS; i < n; i++) | |
585 | { | |
586 | bb = BASIC_BLOCK (i); | |
587 | if (bb) | |
588 | retval |= cleanup_tree_cfg_bb (bb); | |
589 | } | |
590 | ||
591 | /* Now process the altered blocks, as long as any are available. */ | |
592 | while (!bitmap_empty_p (cfgcleanup_altered_bbs)) | |
593 | { | |
594 | i = bitmap_first_set_bit (cfgcleanup_altered_bbs); | |
595 | bitmap_clear_bit (cfgcleanup_altered_bbs, i); | |
596 | if (i < NUM_FIXED_BLOCKS) | |
597 | continue; | |
598 | ||
599 | bb = BASIC_BLOCK (i); | |
600 | if (!bb) | |
601 | continue; | |
602 | ||
603 | retval |= cleanup_tree_cfg_bb (bb); | |
604 | ||
605 | /* Rerun split_bbs_on_noreturn_calls, in case we have altered any noreturn | |
606 | calls. */ | |
607 | retval |= split_bbs_on_noreturn_calls (); | |
608 | } | |
b8698a0f | 609 | |
672987e8 ZD |
610 | end_recording_case_labels (); |
611 | BITMAP_FREE (cfgcleanup_altered_bbs); | |
89e80dd4 DN |
612 | return retval; |
613 | } | |
614 | ||
615 | ||
e3594cb3 DN |
616 | /* Remove unreachable blocks and other miscellaneous clean up work. |
617 | Return true if the flowgraph was modified, false otherwise. */ | |
89e80dd4 | 618 | |
592c303d ZD |
619 | static bool |
620 | cleanup_tree_cfg_noloop (void) | |
89e80dd4 | 621 | { |
672987e8 | 622 | bool changed; |
89e80dd4 DN |
623 | |
624 | timevar_push (TV_TREE_CLEANUP_CFG); | |
625 | ||
e3594cb3 | 626 | /* Iterate until there are no more cleanups left to do. If any |
672987e8 ZD |
627 | iteration changed the flowgraph, set CHANGED to true. |
628 | ||
629 | If dominance information is available, there cannot be any unreachable | |
630 | blocks. */ | |
2b28c07a | 631 | if (!dom_info_available_p (CDI_DOMINATORS)) |
e3594cb3 | 632 | { |
672987e8 ZD |
633 | changed = delete_unreachable_blocks (); |
634 | calculate_dominance_info (CDI_DOMINATORS); | |
e3594cb3 | 635 | } |
672987e8 | 636 | else |
30251f7a ZD |
637 | { |
638 | #ifdef ENABLE_CHECKING | |
639 | verify_dominators (CDI_DOMINATORS); | |
640 | #endif | |
641 | changed = false; | |
642 | } | |
c9784e6d | 643 | |
672987e8 ZD |
644 | changed |= cleanup_tree_cfg_1 (); |
645 | ||
2b28c07a | 646 | gcc_assert (dom_info_available_p (CDI_DOMINATORS)); |
c9784e6d KH |
647 | compact_blocks (); |
648 | ||
649 | #ifdef ENABLE_CHECKING | |
650 | verify_flow_info (); | |
651 | #endif | |
89e80dd4 | 652 | |
c9784e6d | 653 | timevar_pop (TV_TREE_CLEANUP_CFG); |
89e80dd4 | 654 | |
592c303d | 655 | if (changed && current_loops) |
f87000d0 | 656 | loops_state_set (LOOPS_NEED_FIXUP); |
592c303d | 657 | |
e3594cb3 | 658 | return changed; |
c9784e6d KH |
659 | } |
660 | ||
592c303d | 661 | /* Repairs loop structures. */ |
c9784e6d | 662 | |
592c303d ZD |
663 | static void |
664 | repair_loop_structures (void) | |
c9784e6d | 665 | { |
592c303d ZD |
666 | bitmap changed_bbs = BITMAP_ALLOC (NULL); |
667 | fix_loop_structure (changed_bbs); | |
c9784e6d | 668 | |
592c303d ZD |
669 | /* This usually does nothing. But sometimes parts of cfg that originally |
670 | were inside a loop get out of it due to edge removal (since they | |
671 | become unreachable by back edges from latch). */ | |
f87000d0 | 672 | if (loops_state_satisfies_p (LOOP_CLOSED_SSA)) |
592c303d | 673 | rewrite_into_loop_closed_ssa (changed_bbs, TODO_update_ssa); |
c9784e6d | 674 | |
592c303d | 675 | BITMAP_FREE (changed_bbs); |
c9784e6d KH |
676 | |
677 | #ifdef ENABLE_CHECKING | |
592c303d | 678 | verify_loop_structure (); |
c9784e6d | 679 | #endif |
592c303d ZD |
680 | scev_reset (); |
681 | ||
f87000d0 | 682 | loops_state_clear (LOOPS_NEED_FIXUP); |
592c303d ZD |
683 | } |
684 | ||
685 | /* Cleanup cfg and repair loop structures. */ | |
686 | ||
687 | bool | |
688 | cleanup_tree_cfg (void) | |
689 | { | |
690 | bool changed = cleanup_tree_cfg_noloop (); | |
691 | ||
692 | if (current_loops != NULL | |
f87000d0 | 693 | && loops_state_satisfies_p (LOOPS_NEED_FIXUP)) |
592c303d ZD |
694 | repair_loop_structures (); |
695 | ||
1994bfea | 696 | return changed; |
c9784e6d KH |
697 | } |
698 | ||
699 | /* Merge the PHI nodes at BB into those at BB's sole successor. */ | |
700 | ||
701 | static void | |
702 | remove_forwarder_block_with_phi (basic_block bb) | |
703 | { | |
704 | edge succ = single_succ_edge (bb); | |
705 | basic_block dest = succ->dest; | |
726a989a | 706 | gimple label; |
c9784e6d KH |
707 | basic_block dombb, domdest, dom; |
708 | ||
709 | /* We check for infinite loops already in tree_forwarder_block_p. | |
710 | However it may happen that the infinite loop is created | |
711 | afterwards due to removal of forwarders. */ | |
712 | if (dest == bb) | |
713 | return; | |
714 | ||
715 | /* If the destination block consists of a nonlocal label, do not | |
716 | merge it. */ | |
717 | label = first_stmt (dest); | |
718 | if (label | |
726a989a RB |
719 | && gimple_code (label) == GIMPLE_LABEL |
720 | && DECL_NONLOCAL (gimple_label_label (label))) | |
c9784e6d KH |
721 | return; |
722 | ||
723 | /* Redirect each incoming edge to BB to DEST. */ | |
724 | while (EDGE_COUNT (bb->preds) > 0) | |
725 | { | |
726 | edge e = EDGE_PRED (bb, 0), s; | |
726a989a | 727 | gimple_stmt_iterator gsi; |
c9784e6d KH |
728 | |
729 | s = find_edge (e->src, dest); | |
730 | if (s) | |
731 | { | |
732 | /* We already have an edge S from E->src to DEST. If S and | |
733 | E->dest's sole successor edge have the same PHI arguments | |
734 | at DEST, redirect S to DEST. */ | |
735 | if (phi_alternatives_equal (dest, s, succ)) | |
736 | { | |
737 | e = redirect_edge_and_branch (e, dest); | |
ea7e6d5a | 738 | redirect_edge_var_map_clear (e); |
c9784e6d KH |
739 | continue; |
740 | } | |
741 | ||
742 | /* PHI arguments are different. Create a forwarder block by | |
743 | splitting E so that we can merge PHI arguments on E to | |
744 | DEST. */ | |
745 | e = single_succ_edge (split_edge (e)); | |
746 | } | |
747 | ||
748 | s = redirect_edge_and_branch (e, dest); | |
749 | ||
750 | /* redirect_edge_and_branch must not create a new edge. */ | |
751 | gcc_assert (s == e); | |
752 | ||
753 | /* Add to the PHI nodes at DEST each PHI argument removed at the | |
754 | destination of E. */ | |
726a989a RB |
755 | for (gsi = gsi_start_phis (dest); |
756 | !gsi_end_p (gsi); | |
757 | gsi_next (&gsi)) | |
c9784e6d | 758 | { |
726a989a RB |
759 | gimple phi = gsi_stmt (gsi); |
760 | tree def = gimple_phi_arg_def (phi, succ->dest_idx); | |
f5045c96 | 761 | source_location locus = gimple_phi_arg_location_from_edge (phi, succ); |
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; | |
f5045c96 | 781 | locus = redirect_edge_var_map_location (vm); |
c9784e6d KH |
782 | break; |
783 | } | |
784 | } | |
785 | } | |
786 | ||
f5045c96 | 787 | add_phi_arg (phi, def, s, locus); |
c9784e6d KH |
788 | } |
789 | ||
ea7e6d5a | 790 | redirect_edge_var_map_clear (e); |
c9784e6d KH |
791 | } |
792 | ||
793 | /* Update the dominators. */ | |
794 | dombb = get_immediate_dominator (CDI_DOMINATORS, bb); | |
795 | domdest = get_immediate_dominator (CDI_DOMINATORS, dest); | |
796 | if (domdest == bb) | |
797 | { | |
798 | /* Shortcut to avoid calling (relatively expensive) | |
799 | nearest_common_dominator unless necessary. */ | |
800 | dom = dombb; | |
801 | } | |
802 | else | |
803 | dom = nearest_common_dominator (CDI_DOMINATORS, domdest, dombb); | |
804 | ||
805 | set_immediate_dominator (CDI_DOMINATORS, dest, dom); | |
806 | ||
807 | /* Remove BB since all of BB's incoming edges have been redirected | |
808 | to DEST. */ | |
809 | delete_basic_block (bb); | |
810 | } | |
811 | ||
812 | /* This pass merges PHI nodes if one feeds into another. For example, | |
813 | suppose we have the following: | |
814 | ||
815 | goto <bb 9> (<L9>); | |
816 | ||
817 | <L8>:; | |
818 | tem_17 = foo (); | |
819 | ||
820 | # tem_6 = PHI <tem_17(8), tem_23(7)>; | |
821 | <L9>:; | |
822 | ||
823 | # tem_3 = PHI <tem_6(9), tem_2(5)>; | |
824 | <L10>:; | |
825 | ||
826 | Then we merge the first PHI node into the second one like so: | |
827 | ||
828 | goto <bb 9> (<L10>); | |
829 | ||
830 | <L8>:; | |
831 | tem_17 = foo (); | |
832 | ||
833 | # tem_3 = PHI <tem_23(7), tem_2(5), tem_17(8)>; | |
834 | <L10>:; | |
835 | */ | |
836 | ||
c2924966 | 837 | static unsigned int |
c9784e6d KH |
838 | merge_phi_nodes (void) |
839 | { | |
5ed6ace5 | 840 | basic_block *worklist = XNEWVEC (basic_block, n_basic_blocks); |
c9784e6d KH |
841 | basic_block *current = worklist; |
842 | basic_block bb; | |
843 | ||
844 | calculate_dominance_info (CDI_DOMINATORS); | |
845 | ||
846 | /* Find all PHI nodes that we may be able to merge. */ | |
847 | FOR_EACH_BB (bb) | |
848 | { | |
849 | basic_block dest; | |
850 | ||
851 | /* Look for a forwarder block with PHI nodes. */ | |
852 | if (!tree_forwarder_block_p (bb, true)) | |
853 | continue; | |
854 | ||
855 | dest = single_succ (bb); | |
856 | ||
857 | /* We have to feed into another basic block with PHI | |
858 | nodes. */ | |
859 | if (!phi_nodes (dest) | |
860 | /* We don't want to deal with a basic block with | |
861 | abnormal edges. */ | |
862 | || has_abnormal_incoming_edge_p (bb)) | |
863 | continue; | |
864 | ||
865 | if (!dominated_by_p (CDI_DOMINATORS, dest, bb)) | |
866 | { | |
867 | /* If BB does not dominate DEST, then the PHI nodes at | |
868 | DEST must be the only users of the results of the PHI | |
869 | nodes at BB. */ | |
870 | *current++ = bb; | |
871 | } | |
ea65cd37 JL |
872 | else |
873 | { | |
726a989a | 874 | gimple_stmt_iterator gsi; |
338b5886 | 875 | unsigned int dest_idx = single_succ_edge (bb)->dest_idx; |
ea65cd37 JL |
876 | |
877 | /* BB dominates DEST. There may be many users of the PHI | |
878 | nodes in BB. However, there is still a trivial case we | |
879 | can handle. If the result of every PHI in BB is used | |
880 | only by a PHI in DEST, then we can trivially merge the | |
881 | PHI nodes from BB into DEST. */ | |
726a989a RB |
882 | for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); |
883 | gsi_next (&gsi)) | |
ea65cd37 | 884 | { |
726a989a RB |
885 | gimple phi = gsi_stmt (gsi); |
886 | tree result = gimple_phi_result (phi); | |
ea65cd37 | 887 | use_operand_p imm_use; |
726a989a | 888 | gimple use_stmt; |
ea65cd37 JL |
889 | |
890 | /* If the PHI's result is never used, then we can just | |
891 | ignore it. */ | |
bfc646bf | 892 | if (has_zero_uses (result)) |
ea65cd37 JL |
893 | continue; |
894 | ||
895 | /* Get the single use of the result of this PHI node. */ | |
896 | if (!single_imm_use (result, &imm_use, &use_stmt) | |
726a989a RB |
897 | || gimple_code (use_stmt) != GIMPLE_PHI |
898 | || gimple_bb (use_stmt) != dest | |
899 | || gimple_phi_arg_def (use_stmt, dest_idx) != result) | |
ea65cd37 JL |
900 | break; |
901 | } | |
902 | ||
c0220ea4 | 903 | /* If the loop above iterated through all the PHI nodes |
ea65cd37 | 904 | in BB, then we can merge the PHIs from BB into DEST. */ |
726a989a | 905 | if (gsi_end_p (gsi)) |
ea65cd37 JL |
906 | *current++ = bb; |
907 | } | |
c9784e6d KH |
908 | } |
909 | ||
910 | /* Now let's drain WORKLIST. */ | |
911 | while (current != worklist) | |
912 | { | |
913 | bb = *--current; | |
914 | remove_forwarder_block_with_phi (bb); | |
915 | } | |
916 | ||
917 | free (worklist); | |
c2924966 | 918 | return 0; |
c9784e6d KH |
919 | } |
920 | ||
921 | static bool | |
922 | gate_merge_phi (void) | |
923 | { | |
924 | return 1; | |
925 | } | |
926 | ||
b8698a0f | 927 | struct gimple_opt_pass pass_merge_phi = |
8ddbbcae JH |
928 | { |
929 | { | |
930 | GIMPLE_PASS, | |
c9784e6d KH |
931 | "mergephi", /* name */ |
932 | gate_merge_phi, /* gate */ | |
933 | merge_phi_nodes, /* execute */ | |
934 | NULL, /* sub */ | |
935 | NULL, /* next */ | |
936 | 0, /* static_pass_number */ | |
937 | TV_TREE_MERGE_PHI, /* tv_id */ | |
938 | PROP_cfg | PROP_ssa, /* properties_required */ | |
939 | 0, /* properties_provided */ | |
940 | 0, /* properties_destroyed */ | |
941 | 0, /* todo_flags_start */ | |
942 | TODO_dump_func | TODO_ggc_collect /* todo_flags_finish */ | |
8ddbbcae JH |
943 | | TODO_verify_ssa |
944 | } | |
c9784e6d | 945 | }; |