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c9784e6d | 1 | /* CFG cleanup for trees. |
d1e082c2 | 2 | Copyright (C) 2001-2013 Free Software Foundation, Inc. |
c9784e6d KH |
3 | |
4 | This file is part of GCC. | |
5 | ||
6 | GCC is free software; you can redistribute it and/or modify | |
7 | it under the terms of the GNU General Public License as published by | |
9dcd6f09 | 8 | the Free Software Foundation; either version 3, or (at your option) |
c9784e6d KH |
9 | any later version. |
10 | ||
11 | GCC is distributed in the hope that it will be useful, | |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
14 | GNU General Public License for more details. | |
15 | ||
16 | You should have received a copy of the GNU General Public License | |
9dcd6f09 NC |
17 | along with GCC; see the file COPYING3. If not see |
18 | <http://www.gnu.org/licenses/>. */ | |
c9784e6d KH |
19 | |
20 | #include "config.h" | |
21 | #include "system.h" | |
22 | #include "coretypes.h" | |
23 | #include "tm.h" | |
24 | #include "tree.h" | |
c9784e6d | 25 | #include "tm_p.h" |
c9784e6d | 26 | #include "basic-block.h" |
718f9c0f | 27 | #include "diagnostic-core.h" |
c9784e6d KH |
28 | #include "flags.h" |
29 | #include "function.h" | |
c9784e6d KH |
30 | #include "ggc.h" |
31 | #include "langhooks.h" | |
c9784e6d | 32 | #include "tree-flow.h" |
c9784e6d | 33 | #include "tree-pass.h" |
c9784e6d KH |
34 | #include "except.h" |
35 | #include "cfgloop.h" | |
c9784e6d KH |
36 | #include "hashtab.h" |
37 | #include "tree-ssa-propagate.h" | |
17684618 | 38 | #include "tree-scalar-evolution.h" |
c9784e6d | 39 | |
672987e8 ZD |
40 | /* The set of blocks in that at least one of the following changes happened: |
41 | -- the statement at the end of the block was changed | |
42 | -- the block was newly created | |
43 | -- the set of the predecessors of the block changed | |
44 | -- the set of the successors of the block changed | |
45 | ??? Maybe we could track these changes separately, since they determine | |
46 | what cleanups it makes sense to try on the block. */ | |
47 | bitmap cfgcleanup_altered_bbs; | |
48 | ||
c9784e6d KH |
49 | /* Remove any fallthru edge from EV. Return true if an edge was removed. */ |
50 | ||
51 | static bool | |
9771b263 | 52 | remove_fallthru_edge (vec<edge, va_gc> *ev) |
c9784e6d KH |
53 | { |
54 | edge_iterator ei; | |
55 | edge e; | |
56 | ||
57 | FOR_EACH_EDGE (e, ei, ev) | |
58 | if ((e->flags & EDGE_FALLTHRU) != 0) | |
59 | { | |
0107dca2 RB |
60 | if (e->flags & EDGE_COMPLEX) |
61 | e->flags &= ~EDGE_FALLTHRU; | |
62 | else | |
63 | remove_edge_and_dominated_blocks (e); | |
c9784e6d KH |
64 | return true; |
65 | } | |
66 | return false; | |
67 | } | |
68 | ||
726a989a | 69 | |
c9784e6d KH |
70 | /* Disconnect an unreachable block in the control expression starting |
71 | at block BB. */ | |
72 | ||
73 | static bool | |
726a989a | 74 | cleanup_control_expr_graph (basic_block bb, gimple_stmt_iterator gsi) |
c9784e6d KH |
75 | { |
76 | edge taken_edge; | |
77 | bool retval = false; | |
726a989a RB |
78 | gimple stmt = gsi_stmt (gsi); |
79 | tree val; | |
c9784e6d KH |
80 | |
81 | if (!single_succ_p (bb)) | |
82 | { | |
83 | edge e; | |
84 | edge_iterator ei; | |
6ac01510 | 85 | bool warned; |
37530014 | 86 | location_t loc; |
6ac01510 ILT |
87 | |
88 | fold_defer_overflow_warnings (); | |
37530014 RG |
89 | loc = gimple_location (stmt); |
90 | switch (gimple_code (stmt)) | |
91 | { | |
92 | case GIMPLE_COND: | |
fea4ea73 EB |
93 | val = fold_binary_loc (loc, gimple_cond_code (stmt), |
94 | boolean_type_node, | |
95 | gimple_cond_lhs (stmt), | |
96 | gimple_cond_rhs (stmt)); | |
97 | break; | |
37530014 RG |
98 | |
99 | case GIMPLE_SWITCH: | |
100 | val = gimple_switch_index (stmt); | |
101 | break; | |
102 | ||
103 | default: | |
104 | val = NULL_TREE; | |
105 | } | |
c9784e6d KH |
106 | taken_edge = find_taken_edge (bb, val); |
107 | if (!taken_edge) | |
6ac01510 ILT |
108 | { |
109 | fold_undefer_and_ignore_overflow_warnings (); | |
110 | return false; | |
111 | } | |
c9784e6d KH |
112 | |
113 | /* Remove all the edges except the one that is always executed. */ | |
6ac01510 | 114 | warned = false; |
c9784e6d KH |
115 | for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); ) |
116 | { | |
117 | if (e != taken_edge) | |
118 | { | |
6ac01510 ILT |
119 | if (!warned) |
120 | { | |
121 | fold_undefer_overflow_warnings | |
726a989a | 122 | (true, stmt, WARN_STRICT_OVERFLOW_CONDITIONAL); |
6ac01510 ILT |
123 | warned = true; |
124 | } | |
125 | ||
c9784e6d KH |
126 | taken_edge->probability += e->probability; |
127 | taken_edge->count += e->count; | |
672987e8 | 128 | remove_edge_and_dominated_blocks (e); |
c9784e6d KH |
129 | retval = true; |
130 | } | |
131 | else | |
132 | ei_next (&ei); | |
133 | } | |
6ac01510 ILT |
134 | if (!warned) |
135 | fold_undefer_and_ignore_overflow_warnings (); | |
c9784e6d KH |
136 | if (taken_edge->probability > REG_BR_PROB_BASE) |
137 | taken_edge->probability = REG_BR_PROB_BASE; | |
138 | } | |
139 | else | |
140 | taken_edge = single_succ_edge (bb); | |
141 | ||
672987e8 | 142 | bitmap_set_bit (cfgcleanup_altered_bbs, bb->index); |
726a989a | 143 | gsi_remove (&gsi, true); |
c9784e6d KH |
144 | taken_edge->flags = EDGE_FALLTHRU; |
145 | ||
c9784e6d KH |
146 | return retval; |
147 | } | |
148 | ||
672987e8 ZD |
149 | /* Try to remove superfluous control structures in basic block BB. Returns |
150 | true if anything changes. */ | |
c9784e6d KH |
151 | |
152 | static bool | |
672987e8 | 153 | cleanup_control_flow_bb (basic_block bb) |
c9784e6d | 154 | { |
726a989a | 155 | gimple_stmt_iterator gsi; |
c9784e6d | 156 | bool retval = false; |
726a989a | 157 | gimple stmt; |
c9784e6d | 158 | |
672987e8 ZD |
159 | /* If the last statement of the block could throw and now cannot, |
160 | we need to prune cfg. */ | |
726a989a | 161 | retval |= gimple_purge_dead_eh_edges (bb); |
672987e8 | 162 | |
726a989a RB |
163 | gsi = gsi_last_bb (bb); |
164 | if (gsi_end_p (gsi)) | |
672987e8 ZD |
165 | return retval; |
166 | ||
726a989a | 167 | stmt = gsi_stmt (gsi); |
672987e8 | 168 | |
726a989a RB |
169 | if (gimple_code (stmt) == GIMPLE_COND |
170 | || gimple_code (stmt) == GIMPLE_SWITCH) | |
171 | retval |= cleanup_control_expr_graph (bb, gsi); | |
172 | else if (gimple_code (stmt) == GIMPLE_GOTO | |
173 | && TREE_CODE (gimple_goto_dest (stmt)) == ADDR_EXPR | |
174 | && (TREE_CODE (TREE_OPERAND (gimple_goto_dest (stmt), 0)) | |
672987e8 | 175 | == LABEL_DECL)) |
c9784e6d | 176 | { |
726a989a RB |
177 | /* If we had a computed goto which has a compile-time determinable |
178 | destination, then we can eliminate the goto. */ | |
672987e8 ZD |
179 | edge e; |
180 | tree label; | |
181 | edge_iterator ei; | |
182 | basic_block target_block; | |
c9784e6d | 183 | |
672987e8 ZD |
184 | /* First look at all the outgoing edges. Delete any outgoing |
185 | edges which do not go to the right block. For the one | |
186 | edge which goes to the right block, fix up its flags. */ | |
726a989a | 187 | label = TREE_OPERAND (gimple_goto_dest (stmt), 0); |
672987e8 ZD |
188 | target_block = label_to_block (label); |
189 | for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); ) | |
c9784e6d | 190 | { |
672987e8 ZD |
191 | if (e->dest != target_block) |
192 | remove_edge_and_dominated_blocks (e); | |
193 | else | |
c9784e6d | 194 | { |
672987e8 ZD |
195 | /* Turn off the EDGE_ABNORMAL flag. */ |
196 | e->flags &= ~EDGE_ABNORMAL; | |
c9784e6d | 197 | |
672987e8 ZD |
198 | /* And set EDGE_FALLTHRU. */ |
199 | e->flags |= EDGE_FALLTHRU; | |
200 | ei_next (&ei); | |
201 | } | |
c9784e6d KH |
202 | } |
203 | ||
672987e8 ZD |
204 | bitmap_set_bit (cfgcleanup_altered_bbs, bb->index); |
205 | bitmap_set_bit (cfgcleanup_altered_bbs, target_block->index); | |
206 | ||
207 | /* Remove the GOTO_EXPR as it is not needed. The CFG has all the | |
208 | relevant information we need. */ | |
726a989a | 209 | gsi_remove (&gsi, true); |
672987e8 | 210 | retval = true; |
c9784e6d | 211 | } |
672987e8 ZD |
212 | |
213 | /* Check for indirect calls that have been turned into | |
214 | noreturn calls. */ | |
726a989a RB |
215 | else if (is_gimple_call (stmt) |
216 | && gimple_call_noreturn_p (stmt) | |
217 | && remove_fallthru_edge (bb->succs)) | |
672987e8 ZD |
218 | retval = true; |
219 | ||
c9784e6d KH |
220 | return retval; |
221 | } | |
222 | ||
223 | /* Return true if basic block BB does nothing except pass control | |
224 | flow to another block and that we can safely insert a label at | |
225 | the start of the successor block. | |
226 | ||
227 | As a precondition, we require that BB be not equal to | |
228 | ENTRY_BLOCK_PTR. */ | |
229 | ||
230 | static bool | |
231 | tree_forwarder_block_p (basic_block bb, bool phi_wanted) | |
232 | { | |
726a989a | 233 | gimple_stmt_iterator gsi; |
f99fcb3b | 234 | location_t locus; |
c9784e6d KH |
235 | |
236 | /* BB must have a single outgoing edge. */ | |
237 | if (single_succ_p (bb) != 1 | |
238 | /* If PHI_WANTED is false, BB must not have any PHI nodes. | |
239 | Otherwise, BB must have PHI nodes. */ | |
726a989a | 240 | || gimple_seq_empty_p (phi_nodes (bb)) == phi_wanted |
c9784e6d KH |
241 | /* BB may not be a predecessor of EXIT_BLOCK_PTR. */ |
242 | || single_succ (bb) == EXIT_BLOCK_PTR | |
243 | /* Nor should this be an infinite loop. */ | |
244 | || single_succ (bb) == bb | |
245 | /* BB may not have an abnormal outgoing edge. */ | |
246 | || (single_succ_edge (bb)->flags & EDGE_ABNORMAL)) | |
247 | return false; | |
248 | ||
77a74ed7 | 249 | gcc_checking_assert (bb != ENTRY_BLOCK_PTR); |
c9784e6d | 250 | |
f99fcb3b JJ |
251 | locus = single_succ_edge (bb)->goto_locus; |
252 | ||
1d65f45c RH |
253 | /* There should not be an edge coming from entry, or an EH edge. */ |
254 | { | |
255 | edge_iterator ei; | |
256 | edge e; | |
257 | ||
258 | FOR_EACH_EDGE (e, ei, bb->preds) | |
259 | if (e->src == ENTRY_BLOCK_PTR || (e->flags & EDGE_EH)) | |
260 | return false; | |
f99fcb3b JJ |
261 | /* If goto_locus of any of the edges differs, prevent removing |
262 | the forwarder block for -O0. */ | |
263 | else if (optimize == 0 && e->goto_locus != locus) | |
264 | return false; | |
1d65f45c RH |
265 | } |
266 | ||
c9784e6d KH |
267 | /* Now walk through the statements backward. We can ignore labels, |
268 | anything else means this is not a forwarder block. */ | |
726a989a | 269 | for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi); gsi_prev (&gsi)) |
c9784e6d | 270 | { |
726a989a | 271 | gimple stmt = gsi_stmt (gsi); |
c9784e6d | 272 | |
726a989a | 273 | switch (gimple_code (stmt)) |
c9784e6d | 274 | { |
726a989a RB |
275 | case GIMPLE_LABEL: |
276 | if (DECL_NONLOCAL (gimple_label_label (stmt))) | |
c9784e6d | 277 | return false; |
f99fcb3b JJ |
278 | if (optimize == 0 && gimple_location (stmt) != locus) |
279 | return false; | |
c9784e6d KH |
280 | break; |
281 | ||
b5b8b0ac AO |
282 | /* ??? For now, hope there's a corresponding debug |
283 | assignment at the destination. */ | |
284 | case GIMPLE_DEBUG: | |
285 | break; | |
286 | ||
c9784e6d KH |
287 | default: |
288 | return false; | |
289 | } | |
290 | } | |
291 | ||
c9784e6d KH |
292 | if (current_loops) |
293 | { | |
294 | basic_block dest; | |
295 | /* Protect loop latches, headers and preheaders. */ | |
296 | if (bb->loop_father->header == bb) | |
297 | return false; | |
298 | dest = EDGE_SUCC (bb, 0)->dest; | |
299 | ||
300 | if (dest->loop_father->header == dest) | |
301 | return false; | |
302 | } | |
c9784e6d KH |
303 | return true; |
304 | } | |
305 | ||
c9784e6d KH |
306 | /* If all the PHI nodes in DEST have alternatives for E1 and E2 and |
307 | those alternatives are equal in each of the PHI nodes, then return | |
308 | true, else return false. */ | |
309 | ||
310 | static bool | |
311 | phi_alternatives_equal (basic_block dest, edge e1, edge e2) | |
312 | { | |
313 | int n1 = e1->dest_idx; | |
314 | int n2 = e2->dest_idx; | |
726a989a | 315 | gimple_stmt_iterator gsi; |
c9784e6d | 316 | |
726a989a | 317 | for (gsi = gsi_start_phis (dest); !gsi_end_p (gsi); gsi_next (&gsi)) |
c9784e6d | 318 | { |
726a989a RB |
319 | gimple phi = gsi_stmt (gsi); |
320 | tree val1 = gimple_phi_arg_def (phi, n1); | |
321 | tree val2 = gimple_phi_arg_def (phi, n2); | |
c9784e6d KH |
322 | |
323 | gcc_assert (val1 != NULL_TREE); | |
324 | gcc_assert (val2 != NULL_TREE); | |
325 | ||
326 | if (!operand_equal_for_phi_arg_p (val1, val2)) | |
327 | return false; | |
328 | } | |
329 | ||
330 | return true; | |
331 | } | |
332 | ||
672987e8 | 333 | /* Removes forwarder block BB. Returns false if this failed. */ |
c9784e6d KH |
334 | |
335 | static bool | |
672987e8 | 336 | remove_forwarder_block (basic_block bb) |
c9784e6d KH |
337 | { |
338 | edge succ = single_succ_edge (bb), e, s; | |
339 | basic_block dest = succ->dest; | |
726a989a | 340 | gimple label; |
c9784e6d | 341 | edge_iterator ei; |
726a989a | 342 | gimple_stmt_iterator gsi, gsi_to; |
70235ab9 | 343 | bool can_move_debug_stmts; |
c9784e6d KH |
344 | |
345 | /* We check for infinite loops already in tree_forwarder_block_p. | |
346 | However it may happen that the infinite loop is created | |
347 | afterwards due to removal of forwarders. */ | |
348 | if (dest == bb) | |
349 | return false; | |
350 | ||
28e5ca15 RB |
351 | /* If the destination block consists of a nonlocal label or is a |
352 | EH landing pad, do not merge it. */ | |
c9784e6d KH |
353 | label = first_stmt (dest); |
354 | if (label | |
726a989a | 355 | && gimple_code (label) == GIMPLE_LABEL |
28e5ca15 RB |
356 | && (DECL_NONLOCAL (gimple_label_label (label)) |
357 | || EH_LANDING_PAD_NR (gimple_label_label (label)) != 0)) | |
c9784e6d KH |
358 | return false; |
359 | ||
360 | /* If there is an abnormal edge to basic block BB, but not into | |
361 | dest, problems might occur during removal of the phi node at out | |
362 | of ssa due to overlapping live ranges of registers. | |
363 | ||
364 | If there is an abnormal edge in DEST, the problems would occur | |
365 | anyway since cleanup_dead_labels would then merge the labels for | |
366 | two different eh regions, and rest of exception handling code | |
367 | does not like it. | |
368 | ||
369 | So if there is an abnormal edge to BB, proceed only if there is | |
370 | no abnormal edge to DEST and there are no phi nodes in DEST. */ | |
31ff2426 NF |
371 | if (bb_has_abnormal_pred (bb) |
372 | && (bb_has_abnormal_pred (dest) | |
1197e789 RG |
373 | || !gimple_seq_empty_p (phi_nodes (dest)))) |
374 | return false; | |
c9784e6d KH |
375 | |
376 | /* If there are phi nodes in DEST, and some of the blocks that are | |
377 | predecessors of BB are also predecessors of DEST, check that the | |
378 | phi node arguments match. */ | |
726a989a | 379 | if (!gimple_seq_empty_p (phi_nodes (dest))) |
c9784e6d KH |
380 | { |
381 | FOR_EACH_EDGE (e, ei, bb->preds) | |
382 | { | |
383 | s = find_edge (e->src, dest); | |
384 | if (!s) | |
385 | continue; | |
386 | ||
387 | if (!phi_alternatives_equal (dest, succ, s)) | |
388 | return false; | |
389 | } | |
390 | } | |
391 | ||
dc764d10 | 392 | can_move_debug_stmts = MAY_HAVE_DEBUG_STMTS && single_pred_p (dest); |
70235ab9 | 393 | |
c9784e6d KH |
394 | /* Redirect the edges. */ |
395 | for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei)); ) | |
396 | { | |
672987e8 ZD |
397 | bitmap_set_bit (cfgcleanup_altered_bbs, e->src->index); |
398 | ||
c9784e6d KH |
399 | if (e->flags & EDGE_ABNORMAL) |
400 | { | |
401 | /* If there is an abnormal edge, redirect it anyway, and | |
402 | move the labels to the new block to make it legal. */ | |
403 | s = redirect_edge_succ_nodup (e, dest); | |
404 | } | |
405 | else | |
406 | s = redirect_edge_and_branch (e, dest); | |
407 | ||
408 | if (s == e) | |
409 | { | |
410 | /* Create arguments for the phi nodes, since the edge was not | |
411 | here before. */ | |
726a989a RB |
412 | for (gsi = gsi_start_phis (dest); |
413 | !gsi_end_p (gsi); | |
414 | gsi_next (&gsi)) | |
415 | { | |
416 | gimple phi = gsi_stmt (gsi); | |
f5045c96 | 417 | source_location l = gimple_phi_arg_location_from_edge (phi, succ); |
2724573f RB |
418 | tree def = gimple_phi_arg_def (phi, succ->dest_idx); |
419 | add_phi_arg (phi, unshare_expr (def), s, l); | |
726a989a | 420 | } |
c9784e6d | 421 | } |
c9784e6d KH |
422 | } |
423 | ||
1197e789 RG |
424 | /* Move nonlocal labels and computed goto targets as well as user |
425 | defined labels and labels with an EH landing pad number to the | |
426 | new block, so that the redirection of the abnormal edges works, | |
427 | jump targets end up in a sane place and debug information for | |
428 | labels is retained. */ | |
429 | gsi_to = gsi_start_bb (dest); | |
430 | for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); ) | |
431 | { | |
432 | tree decl; | |
433 | label = gsi_stmt (gsi); | |
434 | if (is_gimple_debug (label)) | |
435 | break; | |
436 | decl = gimple_label_label (label); | |
437 | if (EH_LANDING_PAD_NR (decl) != 0 | |
438 | || DECL_NONLOCAL (decl) | |
439 | || FORCED_LABEL (decl) | |
440 | || !DECL_ARTIFICIAL (decl)) | |
441 | { | |
442 | gsi_remove (&gsi, false); | |
443 | gsi_insert_before (&gsi_to, label, GSI_SAME_STMT); | |
444 | } | |
445 | else | |
446 | gsi_next (&gsi); | |
447 | } | |
448 | ||
dc764d10 | 449 | /* Move debug statements if the destination has a single predecessor. */ |
70235ab9 | 450 | if (can_move_debug_stmts) |
c9784e6d | 451 | { |
1197e789 RG |
452 | gsi_to = gsi_after_labels (dest); |
453 | for (gsi = gsi_after_labels (bb); !gsi_end_p (gsi); ) | |
c9784e6d | 454 | { |
70235ab9 JJ |
455 | gimple debug = gsi_stmt (gsi); |
456 | if (!is_gimple_debug (debug)) | |
1197e789 | 457 | break; |
726a989a | 458 | gsi_remove (&gsi, false); |
70235ab9 | 459 | gsi_insert_before (&gsi_to, debug, GSI_SAME_STMT); |
c9784e6d KH |
460 | } |
461 | } | |
462 | ||
672987e8 ZD |
463 | bitmap_set_bit (cfgcleanup_altered_bbs, dest->index); |
464 | ||
c9784e6d KH |
465 | /* Update the dominators. */ |
466 | if (dom_info_available_p (CDI_DOMINATORS)) | |
467 | { | |
468 | basic_block dom, dombb, domdest; | |
469 | ||
470 | dombb = get_immediate_dominator (CDI_DOMINATORS, bb); | |
471 | domdest = get_immediate_dominator (CDI_DOMINATORS, dest); | |
472 | if (domdest == bb) | |
473 | { | |
474 | /* Shortcut to avoid calling (relatively expensive) | |
475 | nearest_common_dominator unless necessary. */ | |
476 | dom = dombb; | |
477 | } | |
478 | else | |
479 | dom = nearest_common_dominator (CDI_DOMINATORS, domdest, dombb); | |
480 | ||
481 | set_immediate_dominator (CDI_DOMINATORS, dest, dom); | |
482 | } | |
483 | ||
484 | /* And kill the forwarder block. */ | |
485 | delete_basic_block (bb); | |
486 | ||
487 | return true; | |
488 | } | |
489 | ||
566d09ef JH |
490 | /* STMT is a call that has been discovered noreturn. Fixup the CFG |
491 | and remove LHS. Return true if something changed. */ | |
492 | ||
493 | bool | |
494 | fixup_noreturn_call (gimple stmt) | |
495 | { | |
496 | basic_block bb = gimple_bb (stmt); | |
497 | bool changed = false; | |
498 | ||
499 | if (gimple_call_builtin_p (stmt, BUILT_IN_RETURN)) | |
500 | return false; | |
501 | ||
502 | /* First split basic block if stmt is not last. */ | |
503 | if (stmt != gsi_stmt (gsi_last_bb (bb))) | |
504 | split_block (bb, stmt); | |
505 | ||
506 | changed |= remove_fallthru_edge (bb->succs); | |
507 | ||
508 | /* If there is LHS, remove it. */ | |
509 | if (gimple_call_lhs (stmt)) | |
510 | { | |
511 | tree op = gimple_call_lhs (stmt); | |
512 | gimple_call_set_lhs (stmt, NULL_TREE); | |
02d635a2 | 513 | |
acb6411a | 514 | /* We need to remove SSA name to avoid checking errors. |
566d09ef | 515 | All uses are dominated by the noreturn and thus will |
02d635a2 JH |
516 | be removed afterwards. |
517 | We proactively remove affected non-PHI statements to avoid | |
518 | fixup_cfg from trying to update them and crashing. */ | |
566d09ef JH |
519 | if (TREE_CODE (op) == SSA_NAME) |
520 | { | |
521 | use_operand_p use_p; | |
522 | imm_use_iterator iter; | |
523 | gimple use_stmt; | |
02d635a2 JH |
524 | bitmap_iterator bi; |
525 | unsigned int bb_index; | |
526 | ||
527 | bitmap blocks = BITMAP_ALLOC (NULL); | |
566d09ef JH |
528 | |
529 | FOR_EACH_IMM_USE_STMT (use_stmt, iter, op) | |
02d635a2 JH |
530 | { |
531 | if (gimple_code (use_stmt) != GIMPLE_PHI) | |
532 | bitmap_set_bit (blocks, gimple_bb (use_stmt)->index); | |
533 | else | |
534 | FOR_EACH_IMM_USE_ON_STMT (use_p, iter) | |
535 | SET_USE (use_p, error_mark_node); | |
536 | } | |
537 | EXECUTE_IF_SET_IN_BITMAP (blocks, 0, bb_index, bi) | |
538 | delete_basic_block (BASIC_BLOCK (bb_index)); | |
539 | BITMAP_FREE (blocks); | |
540 | release_ssa_name (op); | |
566d09ef JH |
541 | } |
542 | update_stmt (stmt); | |
543 | changed = true; | |
544 | } | |
8ba0479e JJ |
545 | /* Similarly remove VDEF if there is any. */ |
546 | else if (gimple_vdef (stmt)) | |
547 | update_stmt (stmt); | |
566d09ef JH |
548 | return changed; |
549 | } | |
550 | ||
551 | ||
672987e8 ZD |
552 | /* Split basic blocks on calls in the middle of a basic block that are now |
553 | known not to return, and remove the unreachable code. */ | |
c9784e6d KH |
554 | |
555 | static bool | |
672987e8 | 556 | split_bbs_on_noreturn_calls (void) |
c9784e6d | 557 | { |
c9784e6d | 558 | bool changed = false; |
726a989a | 559 | gimple stmt; |
672987e8 | 560 | basic_block bb; |
c9784e6d | 561 | |
672987e8 ZD |
562 | /* Detect cases where a mid-block call is now known not to return. */ |
563 | if (cfun->gimple_df) | |
9771b263 | 564 | while (vec_safe_length (MODIFIED_NORETURN_CALLS (cfun))) |
672987e8 | 565 | { |
9771b263 | 566 | stmt = MODIFIED_NORETURN_CALLS (cfun)->pop (); |
726a989a | 567 | bb = gimple_bb (stmt); |
4d731f17 JJ |
568 | /* BB might be deleted at this point, so verify first |
569 | BB is present in the cfg. */ | |
672987e8 | 570 | if (bb == NULL |
4d731f17 | 571 | || bb->index < NUM_FIXED_BLOCKS |
30f1e6de | 572 | || bb->index >= last_basic_block |
4d731f17 | 573 | || BASIC_BLOCK (bb->index) != bb |
726a989a | 574 | || !gimple_call_noreturn_p (stmt)) |
672987e8 ZD |
575 | continue; |
576 | ||
566d09ef | 577 | changed |= fixup_noreturn_call (stmt); |
672987e8 | 578 | } |
c9784e6d | 579 | |
c9784e6d KH |
580 | return changed; |
581 | } | |
582 | ||
672987e8 ZD |
583 | /* Tries to cleanup cfg in basic block BB. Returns true if anything |
584 | changes. */ | |
c9784e6d | 585 | |
89e80dd4 | 586 | static bool |
672987e8 | 587 | cleanup_tree_cfg_bb (basic_block bb) |
c9784e6d | 588 | { |
65e7bfe3 | 589 | bool retval = cleanup_control_flow_bb (bb); |
b8698a0f | 590 | |
f99fcb3b | 591 | if (tree_forwarder_block_p (bb, false) |
672987e8 ZD |
592 | && remove_forwarder_block (bb)) |
593 | return true; | |
c9784e6d | 594 | |
89e80dd4 DN |
595 | /* Merging the blocks may create new opportunities for folding |
596 | conditional branches (due to the elimination of single-valued PHI | |
597 | nodes). */ | |
672987e8 ZD |
598 | if (single_succ_p (bb) |
599 | && can_merge_blocks_p (bb, single_succ (bb))) | |
600 | { | |
601 | merge_blocks (bb, single_succ (bb)); | |
602 | return true; | |
603 | } | |
604 | ||
605 | return retval; | |
606 | } | |
607 | ||
608 | /* Iterate the cfg cleanups, while anything changes. */ | |
609 | ||
610 | static bool | |
611 | cleanup_tree_cfg_1 (void) | |
612 | { | |
613 | bool retval = false; | |
614 | basic_block bb; | |
615 | unsigned i, n; | |
616 | ||
617 | retval |= split_bbs_on_noreturn_calls (); | |
618 | ||
619 | /* Prepare the worklists of altered blocks. */ | |
620 | cfgcleanup_altered_bbs = BITMAP_ALLOC (NULL); | |
621 | ||
622 | /* During forwarder block cleanup, we may redirect edges out of | |
623 | SWITCH_EXPRs, which can get expensive. So we want to enable | |
624 | recording of edge to CASE_LABEL_EXPR. */ | |
625 | start_recording_case_labels (); | |
89e80dd4 | 626 | |
672987e8 ZD |
627 | /* Start by iterating over all basic blocks. We cannot use FOR_EACH_BB, |
628 | since the basic blocks may get removed. */ | |
629 | n = last_basic_block; | |
630 | for (i = NUM_FIXED_BLOCKS; i < n; i++) | |
631 | { | |
632 | bb = BASIC_BLOCK (i); | |
633 | if (bb) | |
634 | retval |= cleanup_tree_cfg_bb (bb); | |
635 | } | |
636 | ||
637 | /* Now process the altered blocks, as long as any are available. */ | |
638 | while (!bitmap_empty_p (cfgcleanup_altered_bbs)) | |
639 | { | |
640 | i = bitmap_first_set_bit (cfgcleanup_altered_bbs); | |
641 | bitmap_clear_bit (cfgcleanup_altered_bbs, i); | |
642 | if (i < NUM_FIXED_BLOCKS) | |
643 | continue; | |
644 | ||
645 | bb = BASIC_BLOCK (i); | |
646 | if (!bb) | |
647 | continue; | |
648 | ||
649 | retval |= cleanup_tree_cfg_bb (bb); | |
650 | ||
651 | /* Rerun split_bbs_on_noreturn_calls, in case we have altered any noreturn | |
652 | calls. */ | |
653 | retval |= split_bbs_on_noreturn_calls (); | |
654 | } | |
b8698a0f | 655 | |
672987e8 ZD |
656 | end_recording_case_labels (); |
657 | BITMAP_FREE (cfgcleanup_altered_bbs); | |
89e80dd4 DN |
658 | return retval; |
659 | } | |
660 | ||
661 | ||
e3594cb3 DN |
662 | /* Remove unreachable blocks and other miscellaneous clean up work. |
663 | Return true if the flowgraph was modified, false otherwise. */ | |
89e80dd4 | 664 | |
592c303d ZD |
665 | static bool |
666 | cleanup_tree_cfg_noloop (void) | |
89e80dd4 | 667 | { |
672987e8 | 668 | bool changed; |
89e80dd4 DN |
669 | |
670 | timevar_push (TV_TREE_CLEANUP_CFG); | |
671 | ||
e3594cb3 | 672 | /* Iterate until there are no more cleanups left to do. If any |
672987e8 ZD |
673 | iteration changed the flowgraph, set CHANGED to true. |
674 | ||
675 | If dominance information is available, there cannot be any unreachable | |
676 | blocks. */ | |
2b28c07a | 677 | if (!dom_info_available_p (CDI_DOMINATORS)) |
e3594cb3 | 678 | { |
672987e8 ZD |
679 | changed = delete_unreachable_blocks (); |
680 | calculate_dominance_info (CDI_DOMINATORS); | |
e3594cb3 | 681 | } |
672987e8 | 682 | else |
30251f7a ZD |
683 | { |
684 | #ifdef ENABLE_CHECKING | |
685 | verify_dominators (CDI_DOMINATORS); | |
686 | #endif | |
687 | changed = false; | |
688 | } | |
c9784e6d | 689 | |
672987e8 ZD |
690 | changed |= cleanup_tree_cfg_1 (); |
691 | ||
2b28c07a | 692 | gcc_assert (dom_info_available_p (CDI_DOMINATORS)); |
c9784e6d KH |
693 | compact_blocks (); |
694 | ||
695 | #ifdef ENABLE_CHECKING | |
696 | verify_flow_info (); | |
697 | #endif | |
89e80dd4 | 698 | |
c9784e6d | 699 | timevar_pop (TV_TREE_CLEANUP_CFG); |
89e80dd4 | 700 | |
592c303d | 701 | if (changed && current_loops) |
f87000d0 | 702 | loops_state_set (LOOPS_NEED_FIXUP); |
592c303d | 703 | |
e3594cb3 | 704 | return changed; |
c9784e6d KH |
705 | } |
706 | ||
592c303d | 707 | /* Repairs loop structures. */ |
c9784e6d | 708 | |
592c303d ZD |
709 | static void |
710 | repair_loop_structures (void) | |
c9784e6d | 711 | { |
a222c01a | 712 | bitmap changed_bbs; |
8e89b5b5 | 713 | unsigned n_new_loops; |
a222c01a | 714 | |
cc360b36 SB |
715 | calculate_dominance_info (CDI_DOMINATORS); |
716 | ||
a222c01a MM |
717 | timevar_push (TV_REPAIR_LOOPS); |
718 | changed_bbs = BITMAP_ALLOC (NULL); | |
8e89b5b5 | 719 | n_new_loops = fix_loop_structure (changed_bbs); |
c9784e6d | 720 | |
592c303d ZD |
721 | /* This usually does nothing. But sometimes parts of cfg that originally |
722 | were inside a loop get out of it due to edge removal (since they | |
8e89b5b5 RB |
723 | become unreachable by back edges from latch). Also a former |
724 | irreducible loop can become reducible - in this case force a full | |
725 | rewrite into loop-closed SSA form. */ | |
f87000d0 | 726 | if (loops_state_satisfies_p (LOOP_CLOSED_SSA)) |
8e89b5b5 RB |
727 | rewrite_into_loop_closed_ssa (n_new_loops ? NULL : changed_bbs, |
728 | TODO_update_ssa); | |
c9784e6d | 729 | |
592c303d | 730 | BITMAP_FREE (changed_bbs); |
c9784e6d KH |
731 | |
732 | #ifdef ENABLE_CHECKING | |
592c303d | 733 | verify_loop_structure (); |
c9784e6d | 734 | #endif |
592c303d ZD |
735 | scev_reset (); |
736 | ||
a222c01a | 737 | timevar_pop (TV_REPAIR_LOOPS); |
592c303d ZD |
738 | } |
739 | ||
740 | /* Cleanup cfg and repair loop structures. */ | |
741 | ||
742 | bool | |
743 | cleanup_tree_cfg (void) | |
744 | { | |
745 | bool changed = cleanup_tree_cfg_noloop (); | |
746 | ||
747 | if (current_loops != NULL | |
f87000d0 | 748 | && loops_state_satisfies_p (LOOPS_NEED_FIXUP)) |
592c303d ZD |
749 | repair_loop_structures (); |
750 | ||
1994bfea | 751 | return changed; |
c9784e6d KH |
752 | } |
753 | ||
a9e0d843 RB |
754 | /* Tries to merge the PHI nodes at BB into those at BB's sole successor. |
755 | Returns true if successful. */ | |
c9784e6d | 756 | |
a9e0d843 | 757 | static bool |
c9784e6d KH |
758 | remove_forwarder_block_with_phi (basic_block bb) |
759 | { | |
760 | edge succ = single_succ_edge (bb); | |
761 | basic_block dest = succ->dest; | |
726a989a | 762 | gimple label; |
c9784e6d KH |
763 | basic_block dombb, domdest, dom; |
764 | ||
765 | /* We check for infinite loops already in tree_forwarder_block_p. | |
766 | However it may happen that the infinite loop is created | |
767 | afterwards due to removal of forwarders. */ | |
768 | if (dest == bb) | |
a9e0d843 | 769 | return false; |
c9784e6d KH |
770 | |
771 | /* If the destination block consists of a nonlocal label, do not | |
772 | merge it. */ | |
773 | label = first_stmt (dest); | |
774 | if (label | |
726a989a RB |
775 | && gimple_code (label) == GIMPLE_LABEL |
776 | && DECL_NONLOCAL (gimple_label_label (label))) | |
a9e0d843 | 777 | return false; |
c9784e6d KH |
778 | |
779 | /* Redirect each incoming edge to BB to DEST. */ | |
780 | while (EDGE_COUNT (bb->preds) > 0) | |
781 | { | |
782 | edge e = EDGE_PRED (bb, 0), s; | |
726a989a | 783 | gimple_stmt_iterator gsi; |
c9784e6d KH |
784 | |
785 | s = find_edge (e->src, dest); | |
786 | if (s) | |
787 | { | |
788 | /* We already have an edge S from E->src to DEST. If S and | |
789 | E->dest's sole successor edge have the same PHI arguments | |
790 | at DEST, redirect S to DEST. */ | |
791 | if (phi_alternatives_equal (dest, s, succ)) | |
792 | { | |
793 | e = redirect_edge_and_branch (e, dest); | |
ea7e6d5a | 794 | redirect_edge_var_map_clear (e); |
c9784e6d KH |
795 | continue; |
796 | } | |
797 | ||
798 | /* PHI arguments are different. Create a forwarder block by | |
799 | splitting E so that we can merge PHI arguments on E to | |
800 | DEST. */ | |
801 | e = single_succ_edge (split_edge (e)); | |
802 | } | |
803 | ||
804 | s = redirect_edge_and_branch (e, dest); | |
805 | ||
806 | /* redirect_edge_and_branch must not create a new edge. */ | |
807 | gcc_assert (s == e); | |
808 | ||
809 | /* Add to the PHI nodes at DEST each PHI argument removed at the | |
810 | destination of E. */ | |
726a989a RB |
811 | for (gsi = gsi_start_phis (dest); |
812 | !gsi_end_p (gsi); | |
813 | gsi_next (&gsi)) | |
c9784e6d | 814 | { |
726a989a RB |
815 | gimple phi = gsi_stmt (gsi); |
816 | tree def = gimple_phi_arg_def (phi, succ->dest_idx); | |
f5045c96 | 817 | source_location locus = gimple_phi_arg_location_from_edge (phi, succ); |
c9784e6d KH |
818 | |
819 | if (TREE_CODE (def) == SSA_NAME) | |
820 | { | |
9771b263 | 821 | edge_var_map_vector *head; |
ea7e6d5a AH |
822 | edge_var_map *vm; |
823 | size_t i; | |
c9784e6d KH |
824 | |
825 | /* If DEF is one of the results of PHI nodes removed during | |
826 | redirection, replace it with the PHI argument that used | |
827 | to be on E. */ | |
ea7e6d5a | 828 | head = redirect_edge_var_map_vector (e); |
6fa5e0ed | 829 | FOR_EACH_VEC_SAFE_ELT (head, i, vm) |
c9784e6d | 830 | { |
ea7e6d5a AH |
831 | tree old_arg = redirect_edge_var_map_result (vm); |
832 | tree new_arg = redirect_edge_var_map_def (vm); | |
c9784e6d KH |
833 | |
834 | if (def == old_arg) | |
835 | { | |
836 | def = new_arg; | |
f5045c96 | 837 | locus = redirect_edge_var_map_location (vm); |
c9784e6d KH |
838 | break; |
839 | } | |
840 | } | |
841 | } | |
842 | ||
9e227d60 | 843 | add_phi_arg (phi, def, s, locus); |
c9784e6d KH |
844 | } |
845 | ||
ea7e6d5a | 846 | redirect_edge_var_map_clear (e); |
c9784e6d KH |
847 | } |
848 | ||
849 | /* Update the dominators. */ | |
850 | dombb = get_immediate_dominator (CDI_DOMINATORS, bb); | |
851 | domdest = get_immediate_dominator (CDI_DOMINATORS, dest); | |
852 | if (domdest == bb) | |
853 | { | |
854 | /* Shortcut to avoid calling (relatively expensive) | |
855 | nearest_common_dominator unless necessary. */ | |
856 | dom = dombb; | |
857 | } | |
858 | else | |
859 | dom = nearest_common_dominator (CDI_DOMINATORS, domdest, dombb); | |
860 | ||
861 | set_immediate_dominator (CDI_DOMINATORS, dest, dom); | |
862 | ||
863 | /* Remove BB since all of BB's incoming edges have been redirected | |
864 | to DEST. */ | |
865 | delete_basic_block (bb); | |
a9e0d843 RB |
866 | |
867 | return true; | |
c9784e6d KH |
868 | } |
869 | ||
870 | /* This pass merges PHI nodes if one feeds into another. For example, | |
871 | suppose we have the following: | |
872 | ||
873 | goto <bb 9> (<L9>); | |
874 | ||
875 | <L8>:; | |
876 | tem_17 = foo (); | |
877 | ||
878 | # tem_6 = PHI <tem_17(8), tem_23(7)>; | |
879 | <L9>:; | |
880 | ||
881 | # tem_3 = PHI <tem_6(9), tem_2(5)>; | |
882 | <L10>:; | |
883 | ||
884 | Then we merge the first PHI node into the second one like so: | |
885 | ||
886 | goto <bb 9> (<L10>); | |
887 | ||
888 | <L8>:; | |
889 | tem_17 = foo (); | |
890 | ||
891 | # tem_3 = PHI <tem_23(7), tem_2(5), tem_17(8)>; | |
892 | <L10>:; | |
893 | */ | |
894 | ||
c2924966 | 895 | static unsigned int |
c9784e6d KH |
896 | merge_phi_nodes (void) |
897 | { | |
5ed6ace5 | 898 | basic_block *worklist = XNEWVEC (basic_block, n_basic_blocks); |
c9784e6d KH |
899 | basic_block *current = worklist; |
900 | basic_block bb; | |
901 | ||
902 | calculate_dominance_info (CDI_DOMINATORS); | |
903 | ||
904 | /* Find all PHI nodes that we may be able to merge. */ | |
905 | FOR_EACH_BB (bb) | |
906 | { | |
907 | basic_block dest; | |
908 | ||
909 | /* Look for a forwarder block with PHI nodes. */ | |
910 | if (!tree_forwarder_block_p (bb, true)) | |
911 | continue; | |
912 | ||
913 | dest = single_succ (bb); | |
914 | ||
915 | /* We have to feed into another basic block with PHI | |
916 | nodes. */ | |
8eacd016 | 917 | if (gimple_seq_empty_p (phi_nodes (dest)) |
c9784e6d KH |
918 | /* We don't want to deal with a basic block with |
919 | abnormal edges. */ | |
31ff2426 | 920 | || bb_has_abnormal_pred (bb)) |
c9784e6d KH |
921 | continue; |
922 | ||
923 | if (!dominated_by_p (CDI_DOMINATORS, dest, bb)) | |
924 | { | |
925 | /* If BB does not dominate DEST, then the PHI nodes at | |
926 | DEST must be the only users of the results of the PHI | |
927 | nodes at BB. */ | |
928 | *current++ = bb; | |
929 | } | |
ea65cd37 JL |
930 | else |
931 | { | |
726a989a | 932 | gimple_stmt_iterator gsi; |
338b5886 | 933 | unsigned int dest_idx = single_succ_edge (bb)->dest_idx; |
ea65cd37 JL |
934 | |
935 | /* BB dominates DEST. There may be many users of the PHI | |
936 | nodes in BB. However, there is still a trivial case we | |
937 | can handle. If the result of every PHI in BB is used | |
938 | only by a PHI in DEST, then we can trivially merge the | |
939 | PHI nodes from BB into DEST. */ | |
726a989a RB |
940 | for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); |
941 | gsi_next (&gsi)) | |
ea65cd37 | 942 | { |
726a989a RB |
943 | gimple phi = gsi_stmt (gsi); |
944 | tree result = gimple_phi_result (phi); | |
ea65cd37 | 945 | use_operand_p imm_use; |
726a989a | 946 | gimple use_stmt; |
ea65cd37 JL |
947 | |
948 | /* If the PHI's result is never used, then we can just | |
949 | ignore it. */ | |
bfc646bf | 950 | if (has_zero_uses (result)) |
ea65cd37 JL |
951 | continue; |
952 | ||
953 | /* Get the single use of the result of this PHI node. */ | |
954 | if (!single_imm_use (result, &imm_use, &use_stmt) | |
726a989a RB |
955 | || gimple_code (use_stmt) != GIMPLE_PHI |
956 | || gimple_bb (use_stmt) != dest | |
957 | || gimple_phi_arg_def (use_stmt, dest_idx) != result) | |
ea65cd37 JL |
958 | break; |
959 | } | |
960 | ||
c0220ea4 | 961 | /* If the loop above iterated through all the PHI nodes |
ea65cd37 | 962 | in BB, then we can merge the PHIs from BB into DEST. */ |
726a989a | 963 | if (gsi_end_p (gsi)) |
ea65cd37 JL |
964 | *current++ = bb; |
965 | } | |
c9784e6d KH |
966 | } |
967 | ||
968 | /* Now let's drain WORKLIST. */ | |
a9e0d843 | 969 | bool changed = false; |
c9784e6d KH |
970 | while (current != worklist) |
971 | { | |
972 | bb = *--current; | |
a9e0d843 | 973 | changed |= remove_forwarder_block_with_phi (bb); |
c9784e6d | 974 | } |
c9784e6d | 975 | free (worklist); |
a9e0d843 RB |
976 | |
977 | /* Removing forwarder blocks can cause formerly irreducible loops | |
978 | to become reducible if we merged two entry blocks. */ | |
979 | if (changed | |
980 | && current_loops) | |
981 | loops_state_set (LOOPS_NEED_FIXUP); | |
982 | ||
c2924966 | 983 | return 0; |
c9784e6d KH |
984 | } |
985 | ||
986 | static bool | |
987 | gate_merge_phi (void) | |
988 | { | |
989 | return 1; | |
990 | } | |
991 | ||
27a4cd48 DM |
992 | namespace { |
993 | ||
994 | const pass_data pass_data_merge_phi = | |
8ddbbcae | 995 | { |
27a4cd48 DM |
996 | GIMPLE_PASS, /* type */ |
997 | "mergephi", /* name */ | |
998 | OPTGROUP_NONE, /* optinfo_flags */ | |
999 | true, /* has_gate */ | |
1000 | true, /* has_execute */ | |
1001 | TV_TREE_MERGE_PHI, /* tv_id */ | |
1002 | ( PROP_cfg | PROP_ssa ), /* properties_required */ | |
1003 | 0, /* properties_provided */ | |
1004 | 0, /* properties_destroyed */ | |
1005 | 0, /* todo_flags_start */ | |
1006 | TODO_verify_ssa, /* todo_flags_finish */ | |
c9784e6d | 1007 | }; |
27a4cd48 DM |
1008 | |
1009 | class pass_merge_phi : public gimple_opt_pass | |
1010 | { | |
1011 | public: | |
1012 | pass_merge_phi(gcc::context *ctxt) | |
1013 | : gimple_opt_pass(pass_data_merge_phi, ctxt) | |
1014 | {} | |
1015 | ||
1016 | /* opt_pass methods: */ | |
1017 | opt_pass * clone () { return new pass_merge_phi (ctxt_); } | |
1018 | bool gate () { return gate_merge_phi (); } | |
1019 | unsigned int execute () { return merge_phi_nodes (); } | |
1020 | ||
1021 | }; // class pass_merge_phi | |
1022 | ||
1023 | } // anon namespace | |
1024 | ||
1025 | gimple_opt_pass * | |
1026 | make_pass_merge_phi (gcc::context *ctxt) | |
1027 | { | |
1028 | return new pass_merge_phi (ctxt); | |
1029 | } |