1 | /* Generic SSA value propagation engine. |
2 | Copyright (C) 2004-2024 Free Software Foundation, Inc. |
3 | Contributed by Diego Novillo <dnovillo@redhat.com> |
4 | |
5 | This file is part of GCC. |
6 | |
7 | GCC is free software; you can redistribute it and/or modify it |
8 | under the terms of the GNU General Public License as published by the |
9 | Free Software Foundation; either version 3, or (at your option) any |
10 | later version. |
11 | |
12 | GCC is distributed in the hope that it will be useful, but WITHOUT |
13 | ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
14 | FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
15 | for more details. |
16 | |
17 | You should have received a copy of the GNU General Public License |
18 | along with GCC; see the file COPYING3. If not see |
19 | <http://www.gnu.org/licenses/>. */ |
20 | |
21 | #include "config.h" |
22 | #include "system.h" |
23 | #include "coretypes.h" |
24 | #include "backend.h" |
25 | #include "tree.h" |
26 | #include "gimple.h" |
27 | #include "ssa.h" |
28 | #include "gimple-pretty-print.h" |
29 | #include "dumpfile.h" |
30 | #include "gimple-iterator.h" |
31 | #include "gimple-fold.h" |
32 | #include "tree-eh.h" |
33 | #include "gimplify.h" |
34 | #include "tree-cfg.h" |
35 | #include "tree-ssa.h" |
36 | #include "tree-ssa-propagate.h" |
37 | #include "domwalk.h" |
38 | #include "cfgloop.h" |
39 | #include "tree-cfgcleanup.h" |
40 | #include "cfganal.h" |
41 | #include "tree-ssa-dce.h" |
42 | |
43 | /* This file implements a generic value propagation engine based on |
44 | the same propagation used by the SSA-CCP algorithm [1]. |
45 | |
46 | Propagation is performed by simulating the execution of every |
47 | statement that produces the value being propagated. Simulation |
48 | proceeds as follows: |
49 | |
50 | 1- Initially, all edges of the CFG are marked not executable and |
51 | the CFG worklist is seeded with all the statements in the entry |
52 | basic block (block 0). |
53 | |
54 | 2- Every statement S is simulated with a call to the call-back |
55 | function SSA_PROP_VISIT_STMT. This evaluation may produce 3 |
56 | results: |
57 | |
58 | SSA_PROP_NOT_INTERESTING: Statement S produces nothing of |
59 | interest and does not affect any of the work lists. |
60 | The statement may be simulated again if any of its input |
61 | operands change in future iterations of the simulator. |
62 | |
63 | SSA_PROP_VARYING: The value produced by S cannot be determined |
64 | at compile time. Further simulation of S is not required. |
65 | If S is a conditional jump, all the outgoing edges for the |
66 | block are considered executable and added to the work |
67 | list. |
68 | |
69 | SSA_PROP_INTERESTING: S produces a value that can be computed |
70 | at compile time. Its result can be propagated into the |
71 | statements that feed from S. Furthermore, if S is a |
72 | conditional jump, only the edge known to be taken is added |
73 | to the work list. Edges that are known not to execute are |
74 | never simulated. |
75 | |
76 | 3- PHI nodes are simulated with a call to SSA_PROP_VISIT_PHI. The |
77 | return value from SSA_PROP_VISIT_PHI has the same semantics as |
78 | described in #2. |
79 | |
80 | 4- Three work lists are kept. Statements are only added to these |
81 | lists if they produce one of SSA_PROP_INTERESTING or |
82 | SSA_PROP_VARYING. |
83 | |
84 | CFG_BLOCKS contains the list of blocks to be simulated. |
85 | Blocks are added to this list if their incoming edges are |
86 | found executable. |
87 | |
88 | SSA_EDGE_WORKLIST contains the list of statements that we |
89 | need to revisit. |
90 | |
91 | 5- Simulation terminates when all three work lists are drained. |
92 | |
93 | Before calling ssa_propagate, it is important to clear |
94 | prop_simulate_again_p for all the statements in the program that |
95 | should be simulated. This initialization allows an implementation |
96 | to specify which statements should never be simulated. |
97 | |
98 | It is also important to compute def-use information before calling |
99 | ssa_propagate. |
100 | |
101 | References: |
102 | |
103 | [1] Constant propagation with conditional branches, |
104 | Wegman and Zadeck, ACM TOPLAS 13(2):181-210. |
105 | |
106 | [2] Building an Optimizing Compiler, |
107 | Robert Morgan, Butterworth-Heinemann, 1998, Section 8.9. |
108 | |
109 | [3] Advanced Compiler Design and Implementation, |
110 | Steven Muchnick, Morgan Kaufmann, 1997, Section 12.6 */ |
111 | |
112 | /* Worklists of control flow edge destinations. This contains |
113 | the CFG order number of the blocks so we can iterate in CFG |
114 | order by visiting in bit-order. We use two worklists to |
115 | first make forward progress before iterating. */ |
116 | static bitmap cfg_blocks; |
117 | static int *bb_to_cfg_order; |
118 | static int *cfg_order_to_bb; |
119 | |
120 | /* Worklists of SSA edges which will need reexamination as their |
121 | definition has changed. SSA edges are def-use edges in the SSA |
122 | web. For each D-U edge, we store the target statement or PHI node |
123 | UID in a bitmap. UIDs order stmts in execution order. We use |
124 | two worklists to first make forward progress before iterating. */ |
125 | static bitmap ssa_edge_worklist; |
126 | static vec<gimple *> uid_to_stmt; |
127 | |
128 | /* Current RPO index in the iteration. */ |
129 | static int curr_order; |
130 | |
131 | |
132 | /* We have just defined a new value for VAR. If IS_VARYING is true, |
133 | add all immediate uses of VAR to VARYING_SSA_EDGES, otherwise add |
134 | them to INTERESTING_SSA_EDGES. */ |
135 | |
136 | static void |
137 | add_ssa_edge (tree var) |
138 | { |
139 | imm_use_iterator iter; |
140 | use_operand_p use_p; |
141 | |
142 | FOR_EACH_IMM_USE_FAST (use_p, iter, var) |
143 | { |
144 | gimple *use_stmt = USE_STMT (use_p); |
145 | if (!prop_simulate_again_p (s: use_stmt)) |
146 | continue; |
147 | |
148 | /* If we did not yet simulate the block wait for this to happen |
149 | and do not add the stmt to the SSA edge worklist. */ |
150 | basic_block use_bb = gimple_bb (g: use_stmt); |
151 | if (! (use_bb->flags & BB_VISITED)) |
152 | continue; |
153 | |
154 | /* If this is a use on a not yet executable edge do not bother to |
155 | queue it. */ |
156 | if (gimple_code (g: use_stmt) == GIMPLE_PHI |
157 | && !(EDGE_PRED (use_bb, PHI_ARG_INDEX_FROM_USE (use_p))->flags |
158 | & EDGE_EXECUTABLE)) |
159 | continue; |
160 | |
161 | if (bitmap_set_bit (ssa_edge_worklist, gimple_uid (g: use_stmt))) |
162 | { |
163 | uid_to_stmt[gimple_uid (g: use_stmt)] = use_stmt; |
164 | if (dump_file && (dump_flags & TDF_DETAILS)) |
165 | { |
166 | fprintf (stream: dump_file, format: "ssa_edge_worklist: adding SSA use in " ); |
167 | print_gimple_stmt (dump_file, use_stmt, 0, TDF_SLIM); |
168 | } |
169 | } |
170 | } |
171 | } |
172 | |
173 | |
174 | /* Add edge E to the control flow worklist. */ |
175 | |
176 | static void |
177 | add_control_edge (edge e) |
178 | { |
179 | basic_block bb = e->dest; |
180 | if (bb == EXIT_BLOCK_PTR_FOR_FN (cfun)) |
181 | return; |
182 | |
183 | /* If the edge had already been executed, skip it. */ |
184 | if (e->flags & EDGE_EXECUTABLE) |
185 | return; |
186 | |
187 | e->flags |= EDGE_EXECUTABLE; |
188 | |
189 | int bb_order = bb_to_cfg_order[bb->index]; |
190 | bitmap_set_bit (cfg_blocks, bb_order); |
191 | |
192 | if (dump_file && (dump_flags & TDF_DETAILS)) |
193 | fprintf (stream: dump_file, format: "Adding destination of edge (%d -> %d) to worklist\n" , |
194 | e->src->index, e->dest->index); |
195 | } |
196 | |
197 | |
198 | /* Simulate the execution of STMT and update the work lists accordingly. */ |
199 | |
200 | void |
201 | ssa_propagation_engine::simulate_stmt (gimple *stmt) |
202 | { |
203 | enum ssa_prop_result val = SSA_PROP_NOT_INTERESTING; |
204 | edge taken_edge = NULL; |
205 | tree output_name = NULL_TREE; |
206 | |
207 | /* Pull the stmt off the SSA edge worklist. */ |
208 | bitmap_clear_bit (ssa_edge_worklist, gimple_uid (g: stmt)); |
209 | |
210 | /* Don't bother visiting statements that are already |
211 | considered varying by the propagator. */ |
212 | if (!prop_simulate_again_p (s: stmt)) |
213 | return; |
214 | |
215 | if (gimple_code (g: stmt) == GIMPLE_PHI) |
216 | { |
217 | val = visit_phi (as_a <gphi *> (p: stmt)); |
218 | output_name = gimple_phi_result (gs: stmt); |
219 | } |
220 | else |
221 | val = visit_stmt (stmt, &taken_edge, &output_name); |
222 | |
223 | if (val == SSA_PROP_VARYING) |
224 | { |
225 | prop_set_simulate_again (s: stmt, visit_p: false); |
226 | |
227 | /* If the statement produced a new varying value, add the SSA |
228 | edges coming out of OUTPUT_NAME. */ |
229 | if (output_name) |
230 | add_ssa_edge (var: output_name); |
231 | |
232 | /* If STMT transfers control out of its basic block, add |
233 | all outgoing edges to the work list. */ |
234 | if (stmt_ends_bb_p (stmt)) |
235 | { |
236 | edge e; |
237 | edge_iterator ei; |
238 | basic_block bb = gimple_bb (g: stmt); |
239 | FOR_EACH_EDGE (e, ei, bb->succs) |
240 | add_control_edge (e); |
241 | } |
242 | return; |
243 | } |
244 | else if (val == SSA_PROP_INTERESTING) |
245 | { |
246 | /* If the statement produced new value, add the SSA edges coming |
247 | out of OUTPUT_NAME. */ |
248 | if (output_name) |
249 | add_ssa_edge (var: output_name); |
250 | |
251 | /* If we know which edge is going to be taken out of this block, |
252 | add it to the CFG work list. */ |
253 | if (taken_edge) |
254 | add_control_edge (e: taken_edge); |
255 | } |
256 | |
257 | /* If there are no SSA uses on the stmt whose defs are simulated |
258 | again then this stmt will be never visited again. */ |
259 | bool has_simulate_again_uses = false; |
260 | use_operand_p use_p; |
261 | ssa_op_iter iter; |
262 | if (gimple_code (g: stmt) == GIMPLE_PHI) |
263 | { |
264 | edge_iterator ei; |
265 | edge e; |
266 | tree arg; |
267 | FOR_EACH_EDGE (e, ei, gimple_bb (stmt)->preds) |
268 | if (!(e->flags & EDGE_EXECUTABLE) |
269 | || ((arg = PHI_ARG_DEF_FROM_EDGE (stmt, e)) |
270 | && TREE_CODE (arg) == SSA_NAME |
271 | && !SSA_NAME_IS_DEFAULT_DEF (arg) |
272 | && prop_simulate_again_p (SSA_NAME_DEF_STMT (arg)))) |
273 | { |
274 | has_simulate_again_uses = true; |
275 | break; |
276 | } |
277 | } |
278 | else |
279 | FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE) |
280 | { |
281 | gimple *def_stmt = SSA_NAME_DEF_STMT (USE_FROM_PTR (use_p)); |
282 | if (!gimple_nop_p (g: def_stmt) |
283 | && prop_simulate_again_p (s: def_stmt)) |
284 | { |
285 | has_simulate_again_uses = true; |
286 | break; |
287 | } |
288 | } |
289 | if (!has_simulate_again_uses) |
290 | { |
291 | if (dump_file && (dump_flags & TDF_DETAILS)) |
292 | fprintf (stream: dump_file, format: "marking stmt to be not simulated again\n" ); |
293 | prop_set_simulate_again (s: stmt, visit_p: false); |
294 | } |
295 | } |
296 | |
297 | |
298 | /* Simulate the execution of BLOCK. Evaluate the statement associated |
299 | with each variable reference inside the block. */ |
300 | |
301 | void |
302 | ssa_propagation_engine::simulate_block (basic_block block) |
303 | { |
304 | gimple_stmt_iterator gsi; |
305 | |
306 | /* There is nothing to do for the exit block. */ |
307 | if (block == EXIT_BLOCK_PTR_FOR_FN (cfun)) |
308 | return; |
309 | |
310 | if (dump_file && (dump_flags & TDF_DETAILS)) |
311 | fprintf (stream: dump_file, format: "\nSimulating block %d\n" , block->index); |
312 | |
313 | /* Always simulate PHI nodes, even if we have simulated this block |
314 | before. */ |
315 | for (gsi = gsi_start_phis (block); !gsi_end_p (i: gsi); gsi_next (i: &gsi)) |
316 | simulate_stmt (stmt: gsi_stmt (i: gsi)); |
317 | |
318 | /* If this is the first time we've simulated this block, then we |
319 | must simulate each of its statements. */ |
320 | if (! (block->flags & BB_VISITED)) |
321 | { |
322 | gimple_stmt_iterator j; |
323 | unsigned int normal_edge_count; |
324 | edge e, normal_edge; |
325 | edge_iterator ei; |
326 | |
327 | for (j = gsi_start_bb (bb: block); !gsi_end_p (i: j); gsi_next (i: &j)) |
328 | simulate_stmt (stmt: gsi_stmt (i: j)); |
329 | |
330 | /* Note that we have simulated this block. */ |
331 | block->flags |= BB_VISITED; |
332 | |
333 | /* We cannot predict when abnormal and EH edges will be executed, so |
334 | once a block is considered executable, we consider any |
335 | outgoing abnormal edges as executable. |
336 | |
337 | TODO: This is not exactly true. Simplifying statement might |
338 | prove it non-throwing and also computed goto can be handled |
339 | when destination is known. |
340 | |
341 | At the same time, if this block has only one successor that is |
342 | reached by non-abnormal edges, then add that successor to the |
343 | worklist. */ |
344 | normal_edge_count = 0; |
345 | normal_edge = NULL; |
346 | FOR_EACH_EDGE (e, ei, block->succs) |
347 | { |
348 | if (e->flags & (EDGE_ABNORMAL | EDGE_EH)) |
349 | add_control_edge (e); |
350 | else |
351 | { |
352 | normal_edge_count++; |
353 | normal_edge = e; |
354 | } |
355 | } |
356 | |
357 | if (normal_edge_count == 1) |
358 | add_control_edge (e: normal_edge); |
359 | } |
360 | } |
361 | |
362 | |
363 | /* Initialize local data structures and work lists. */ |
364 | |
365 | static void |
366 | ssa_prop_init (void) |
367 | { |
368 | edge e; |
369 | edge_iterator ei; |
370 | basic_block bb; |
371 | |
372 | /* Worklists of SSA edges. */ |
373 | ssa_edge_worklist = BITMAP_ALLOC (NULL); |
374 | bitmap_tree_view (ssa_edge_worklist); |
375 | |
376 | /* Worklist of basic-blocks. */ |
377 | bb_to_cfg_order = XNEWVEC (int, last_basic_block_for_fn (cfun) + 1); |
378 | cfg_order_to_bb = XNEWVEC (int, n_basic_blocks_for_fn (cfun)); |
379 | int n = pre_and_rev_post_order_compute_fn (cfun, NULL, |
380 | cfg_order_to_bb, false); |
381 | for (int i = 0; i < n; ++i) |
382 | bb_to_cfg_order[cfg_order_to_bb[i]] = i; |
383 | cfg_blocks = BITMAP_ALLOC (NULL); |
384 | |
385 | /* Initially assume that every edge in the CFG is not executable. |
386 | (including the edges coming out of the entry block). Mark blocks |
387 | as not visited, blocks not yet visited will have all their statements |
388 | simulated once an incoming edge gets executable. */ |
389 | set_gimple_stmt_max_uid (cfun, maxid: 0); |
390 | for (int i = 0; i < n; ++i) |
391 | { |
392 | gimple_stmt_iterator si; |
393 | bb = BASIC_BLOCK_FOR_FN (cfun, cfg_order_to_bb[i]); |
394 | |
395 | for (si = gsi_start_phis (bb); !gsi_end_p (i: si); gsi_next (i: &si)) |
396 | { |
397 | gimple *stmt = gsi_stmt (i: si); |
398 | gimple_set_uid (g: stmt, uid: inc_gimple_stmt_max_uid (cfun)); |
399 | } |
400 | |
401 | for (si = gsi_start_bb (bb); !gsi_end_p (i: si); gsi_next (i: &si)) |
402 | { |
403 | gimple *stmt = gsi_stmt (i: si); |
404 | gimple_set_uid (g: stmt, uid: inc_gimple_stmt_max_uid (cfun)); |
405 | } |
406 | |
407 | bb->flags &= ~BB_VISITED; |
408 | FOR_EACH_EDGE (e, ei, bb->succs) |
409 | e->flags &= ~EDGE_EXECUTABLE; |
410 | } |
411 | uid_to_stmt.safe_grow (len: gimple_stmt_max_uid (cfun), exact: true); |
412 | } |
413 | |
414 | |
415 | /* Free allocated storage. */ |
416 | |
417 | static void |
418 | ssa_prop_fini (void) |
419 | { |
420 | BITMAP_FREE (cfg_blocks); |
421 | free (ptr: bb_to_cfg_order); |
422 | free (ptr: cfg_order_to_bb); |
423 | BITMAP_FREE (ssa_edge_worklist); |
424 | uid_to_stmt.release (); |
425 | } |
426 | |
427 | |
428 | /* Entry point to the propagation engine. |
429 | |
430 | The VISIT_STMT virtual function is called for every statement |
431 | visited and the VISIT_PHI virtual function is called for every PHI |
432 | node visited. */ |
433 | |
434 | void |
435 | ssa_propagation_engine::ssa_propagate (void) |
436 | { |
437 | ssa_prop_init (); |
438 | |
439 | curr_order = 0; |
440 | |
441 | /* Iterate until the worklists are empty. We iterate both blocks |
442 | and stmts in RPO order, prioritizing backedge processing. |
443 | Seed the algorithm by adding the successors of the entry block to the |
444 | edge worklist. */ |
445 | edge e; |
446 | edge_iterator ei; |
447 | FOR_EACH_EDGE (e, ei, ENTRY_BLOCK_PTR_FOR_FN (cfun)->succs) |
448 | { |
449 | e->flags &= ~EDGE_EXECUTABLE; |
450 | add_control_edge (e); |
451 | } |
452 | while (1) |
453 | { |
454 | int next_block_order = (bitmap_empty_p (map: cfg_blocks) |
455 | ? -1 : bitmap_first_set_bit (cfg_blocks)); |
456 | int next_stmt_uid = (bitmap_empty_p (map: ssa_edge_worklist) |
457 | ? -1 : bitmap_first_set_bit (ssa_edge_worklist)); |
458 | if (next_block_order == -1 && next_stmt_uid == -1) |
459 | break; |
460 | |
461 | int next_stmt_bb_order = -1; |
462 | gimple *next_stmt = NULL; |
463 | if (next_stmt_uid != -1) |
464 | { |
465 | next_stmt = uid_to_stmt[next_stmt_uid]; |
466 | next_stmt_bb_order = bb_to_cfg_order[gimple_bb (g: next_stmt)->index]; |
467 | } |
468 | |
469 | /* Pull the next block to simulate off the worklist if it comes first. */ |
470 | if (next_block_order != -1 |
471 | && (next_stmt_bb_order == -1 |
472 | || next_block_order <= next_stmt_bb_order)) |
473 | { |
474 | curr_order = next_block_order; |
475 | bitmap_clear_bit (cfg_blocks, next_block_order); |
476 | basic_block bb |
477 | = BASIC_BLOCK_FOR_FN (cfun, cfg_order_to_bb [next_block_order]); |
478 | simulate_block (block: bb); |
479 | } |
480 | /* Else simulate from the SSA edge worklist. */ |
481 | else |
482 | { |
483 | curr_order = next_stmt_bb_order; |
484 | if (dump_file && (dump_flags & TDF_DETAILS)) |
485 | { |
486 | fprintf (stream: dump_file, format: "\nSimulating statement: " ); |
487 | print_gimple_stmt (dump_file, next_stmt, 0, dump_flags); |
488 | } |
489 | simulate_stmt (stmt: next_stmt); |
490 | } |
491 | } |
492 | |
493 | ssa_prop_fini (); |
494 | } |
495 | |
496 | /* Return true if STMT is of the form 'mem_ref = RHS', where 'mem_ref' |
497 | is a non-volatile pointer dereference, a structure reference or a |
498 | reference to a single _DECL. Ignore volatile memory references |
499 | because they are not interesting for the optimizers. */ |
500 | |
501 | bool |
502 | stmt_makes_single_store (gimple *stmt) |
503 | { |
504 | tree lhs; |
505 | |
506 | if (gimple_code (g: stmt) != GIMPLE_ASSIGN |
507 | && gimple_code (g: stmt) != GIMPLE_CALL) |
508 | return false; |
509 | |
510 | if (!gimple_vdef (g: stmt)) |
511 | return false; |
512 | |
513 | lhs = gimple_get_lhs (stmt); |
514 | |
515 | /* A call statement may have a null LHS. */ |
516 | if (!lhs) |
517 | return false; |
518 | |
519 | return (!TREE_THIS_VOLATILE (lhs) |
520 | && (DECL_P (lhs) |
521 | || REFERENCE_CLASS_P (lhs))); |
522 | } |
523 | |
524 | |
525 | /* Propagation statistics. */ |
526 | struct prop_stats_d |
527 | { |
528 | long num_const_prop; |
529 | long num_copy_prop; |
530 | long num_stmts_folded; |
531 | }; |
532 | |
533 | static struct prop_stats_d prop_stats; |
534 | |
535 | // range_query default methods to drive from a value_of_expr() ranther than |
536 | // range_of_expr. |
537 | |
538 | tree |
539 | substitute_and_fold_engine::value_on_edge (edge, tree expr) |
540 | { |
541 | return value_of_expr (expr); |
542 | } |
543 | |
544 | tree |
545 | substitute_and_fold_engine::value_of_stmt (gimple *stmt, tree name) |
546 | { |
547 | if (!name) |
548 | name = gimple_get_lhs (stmt); |
549 | |
550 | gcc_checking_assert (!name || name == gimple_get_lhs (stmt)); |
551 | |
552 | if (name) |
553 | return value_of_expr (expr: name); |
554 | return NULL_TREE; |
555 | } |
556 | |
557 | bool |
558 | substitute_and_fold_engine::range_of_expr (vrange &, tree, gimple *) |
559 | { |
560 | return false; |
561 | } |
562 | |
563 | /* Replace USE references in statement STMT with the values stored in |
564 | PROP_VALUE. Return true if at least one reference was replaced. */ |
565 | |
566 | bool |
567 | substitute_and_fold_engine::replace_uses_in (gimple *stmt) |
568 | { |
569 | bool replaced = false; |
570 | use_operand_p use; |
571 | ssa_op_iter iter; |
572 | |
573 | FOR_EACH_SSA_USE_OPERAND (use, stmt, iter, SSA_OP_USE) |
574 | { |
575 | tree tuse = USE_FROM_PTR (use); |
576 | tree val = value_of_expr (expr: tuse, stmt); |
577 | |
578 | if (val == tuse || val == NULL_TREE) |
579 | continue; |
580 | |
581 | if (gimple_code (g: stmt) == GIMPLE_ASM |
582 | && !may_propagate_copy_into_asm (tuse)) |
583 | continue; |
584 | |
585 | if (!may_propagate_copy (tuse, val)) |
586 | continue; |
587 | |
588 | if (TREE_CODE (val) != SSA_NAME) |
589 | prop_stats.num_const_prop++; |
590 | else |
591 | prop_stats.num_copy_prop++; |
592 | |
593 | propagate_value (use, val); |
594 | |
595 | replaced = true; |
596 | } |
597 | |
598 | return replaced; |
599 | } |
600 | |
601 | |
602 | /* Replace propagated values into all the arguments for PHI using the |
603 | values from PROP_VALUE. */ |
604 | |
605 | bool |
606 | substitute_and_fold_engine::replace_phi_args_in (gphi *phi) |
607 | { |
608 | size_t i; |
609 | bool replaced = false; |
610 | |
611 | for (i = 0; i < gimple_phi_num_args (gs: phi); i++) |
612 | { |
613 | tree arg = gimple_phi_arg_def (gs: phi, index: i); |
614 | |
615 | if (TREE_CODE (arg) == SSA_NAME) |
616 | { |
617 | edge e = gimple_phi_arg_edge (phi, i); |
618 | tree val = value_on_edge (e, expr: arg); |
619 | |
620 | if (val && val != arg && may_propagate_copy (arg, val)) |
621 | { |
622 | if (TREE_CODE (val) != SSA_NAME) |
623 | prop_stats.num_const_prop++; |
624 | else |
625 | prop_stats.num_copy_prop++; |
626 | |
627 | propagate_value (PHI_ARG_DEF_PTR (phi, i), val); |
628 | replaced = true; |
629 | |
630 | /* If we propagated a copy and this argument flows |
631 | through an abnormal edge, update the replacement |
632 | accordingly. */ |
633 | if (TREE_CODE (val) == SSA_NAME |
634 | && e->flags & EDGE_ABNORMAL |
635 | && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (val)) |
636 | { |
637 | /* This can only occur for virtual operands, since |
638 | for the real ones SSA_NAME_OCCURS_IN_ABNORMAL_PHI (val)) |
639 | would prevent replacement. */ |
640 | gcc_checking_assert (virtual_operand_p (val)); |
641 | SSA_NAME_OCCURS_IN_ABNORMAL_PHI (val) = 1; |
642 | } |
643 | } |
644 | } |
645 | } |
646 | |
647 | if (dump_file && (dump_flags & TDF_DETAILS)) |
648 | { |
649 | if (!replaced) |
650 | fprintf (stream: dump_file, format: "No folding possible\n" ); |
651 | else |
652 | { |
653 | fprintf (stream: dump_file, format: "Folded into: " ); |
654 | print_gimple_stmt (dump_file, phi, 0, TDF_SLIM); |
655 | fprintf (stream: dump_file, format: "\n" ); |
656 | } |
657 | } |
658 | |
659 | return replaced; |
660 | } |
661 | |
662 | |
663 | class substitute_and_fold_dom_walker : public dom_walker |
664 | { |
665 | public: |
666 | substitute_and_fold_dom_walker (cdi_direction direction, |
667 | class substitute_and_fold_engine *engine) |
668 | : dom_walker (direction), |
669 | something_changed (false), |
670 | substitute_and_fold_engine (engine) |
671 | { |
672 | dceworklist = BITMAP_ALLOC (NULL); |
673 | stmts_to_fixup.create (nelems: 0); |
674 | need_eh_cleanup = BITMAP_ALLOC (NULL); |
675 | need_ab_cleanup = BITMAP_ALLOC (NULL); |
676 | } |
677 | ~substitute_and_fold_dom_walker () |
678 | { |
679 | BITMAP_FREE (dceworklist); |
680 | stmts_to_fixup.release (); |
681 | BITMAP_FREE (need_eh_cleanup); |
682 | BITMAP_FREE (need_ab_cleanup); |
683 | } |
684 | |
685 | edge before_dom_children (basic_block) final override; |
686 | void after_dom_children (basic_block bb) final override |
687 | { |
688 | substitute_and_fold_engine->post_fold_bb (bb); |
689 | } |
690 | |
691 | bool something_changed; |
692 | bitmap dceworklist; |
693 | vec<gimple *> stmts_to_fixup; |
694 | bitmap need_eh_cleanup; |
695 | bitmap need_ab_cleanup; |
696 | |
697 | class substitute_and_fold_engine *substitute_and_fold_engine; |
698 | |
699 | private: |
700 | void foreach_new_stmt_in_bb (gimple_stmt_iterator old_gsi, |
701 | gimple_stmt_iterator new_gsi); |
702 | }; |
703 | |
704 | /* Call post_new_stmt for each new statement that has been added |
705 | to the current BB. OLD_GSI is the statement iterator before the BB |
706 | changes ocurred. NEW_GSI is the iterator which may contain new |
707 | statements. */ |
708 | |
709 | void |
710 | substitute_and_fold_dom_walker::foreach_new_stmt_in_bb |
711 | (gimple_stmt_iterator old_gsi, |
712 | gimple_stmt_iterator new_gsi) |
713 | { |
714 | basic_block bb = gsi_bb (i: new_gsi); |
715 | if (gsi_end_p (i: old_gsi)) |
716 | old_gsi = gsi_start_bb (bb); |
717 | else |
718 | gsi_next (i: &old_gsi); |
719 | while (gsi_stmt (i: old_gsi) != gsi_stmt (i: new_gsi)) |
720 | { |
721 | gimple *stmt = gsi_stmt (i: old_gsi); |
722 | substitute_and_fold_engine->post_new_stmt (stmt); |
723 | gsi_next (i: &old_gsi); |
724 | } |
725 | } |
726 | |
727 | bool |
728 | substitute_and_fold_engine::propagate_into_phi_args (basic_block bb) |
729 | { |
730 | edge e; |
731 | edge_iterator ei; |
732 | bool propagated = false; |
733 | |
734 | /* Visit BB successor PHI nodes and replace PHI args. */ |
735 | FOR_EACH_EDGE (e, ei, bb->succs) |
736 | { |
737 | for (gphi_iterator gpi = gsi_start_phis (e->dest); |
738 | !gsi_end_p (i: gpi); gsi_next (i: &gpi)) |
739 | { |
740 | gphi *phi = gpi.phi (); |
741 | use_operand_p use_p = PHI_ARG_DEF_PTR_FROM_EDGE (phi, e); |
742 | tree arg = USE_FROM_PTR (use_p); |
743 | if (TREE_CODE (arg) != SSA_NAME |
744 | || virtual_operand_p (op: arg)) |
745 | continue; |
746 | tree val = value_on_edge (e, expr: arg); |
747 | if (val |
748 | && is_gimple_min_invariant (val) |
749 | && may_propagate_copy (arg, val)) |
750 | { |
751 | propagate_value (use_p, val); |
752 | propagated = true; |
753 | } |
754 | } |
755 | } |
756 | return propagated; |
757 | } |
758 | |
759 | edge |
760 | substitute_and_fold_dom_walker::before_dom_children (basic_block bb) |
761 | { |
762 | substitute_and_fold_engine->pre_fold_bb (bb); |
763 | |
764 | /* Propagate known values into PHI nodes. */ |
765 | for (gphi_iterator i = gsi_start_phis (bb); |
766 | !gsi_end_p (i); |
767 | gsi_next (i: &i)) |
768 | { |
769 | gphi *phi = i.phi (); |
770 | tree res = gimple_phi_result (gs: phi); |
771 | if (virtual_operand_p (op: res)) |
772 | continue; |
773 | if (dump_file && (dump_flags & TDF_DETAILS)) |
774 | { |
775 | fprintf (stream: dump_file, format: "Folding PHI node: " ); |
776 | print_gimple_stmt (dump_file, phi, 0, TDF_SLIM); |
777 | } |
778 | if (res && TREE_CODE (res) == SSA_NAME) |
779 | { |
780 | tree sprime = substitute_and_fold_engine->value_of_expr (expr: res, phi); |
781 | if (sprime |
782 | && sprime != res |
783 | && may_propagate_copy (res, sprime)) |
784 | { |
785 | if (dump_file && (dump_flags & TDF_DETAILS)) |
786 | { |
787 | fprintf (stream: dump_file, format: "Queued PHI for removal. Folds to: " ); |
788 | print_generic_expr (dump_file, sprime); |
789 | fprintf (stream: dump_file, format: "\n" ); |
790 | } |
791 | bitmap_set_bit (dceworklist, SSA_NAME_VERSION (res)); |
792 | continue; |
793 | } |
794 | } |
795 | something_changed |= substitute_and_fold_engine->replace_phi_args_in (phi); |
796 | } |
797 | |
798 | /* Propagate known values into stmts. In some case it exposes |
799 | more trivially deletable stmts to walk backward. */ |
800 | for (gimple_stmt_iterator i = gsi_start_bb (bb); |
801 | !gsi_end_p (i); |
802 | gsi_next (i: &i)) |
803 | { |
804 | bool did_replace; |
805 | gimple *stmt = gsi_stmt (i); |
806 | |
807 | substitute_and_fold_engine->pre_fold_stmt (stmt); |
808 | |
809 | if (dump_file && (dump_flags & TDF_DETAILS)) |
810 | { |
811 | fprintf (stream: dump_file, format: "Folding statement: " ); |
812 | print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM); |
813 | } |
814 | |
815 | /* No point propagating into a stmt we have a value for we |
816 | can propagate into all uses. Mark it for removal instead. */ |
817 | tree lhs = gimple_get_lhs (stmt); |
818 | if (lhs && TREE_CODE (lhs) == SSA_NAME) |
819 | { |
820 | tree sprime = substitute_and_fold_engine->value_of_stmt (stmt, name: lhs); |
821 | if (sprime |
822 | && sprime != lhs |
823 | && may_propagate_copy (lhs, sprime) |
824 | && !stmt_could_throw_p (cfun, stmt) |
825 | && !gimple_has_side_effects (stmt)) |
826 | { |
827 | if (dump_file && (dump_flags & TDF_DETAILS)) |
828 | { |
829 | fprintf (stream: dump_file, format: "Queued stmt for removal. Folds to: " ); |
830 | print_generic_expr (dump_file, sprime); |
831 | fprintf (stream: dump_file, format: "\n" ); |
832 | } |
833 | bitmap_set_bit (dceworklist, SSA_NAME_VERSION (lhs)); |
834 | continue; |
835 | } |
836 | } |
837 | |
838 | /* Replace the statement with its folded version and mark it |
839 | folded. */ |
840 | did_replace = false; |
841 | gimple *old_stmt = stmt; |
842 | bool was_noreturn = false; |
843 | bool can_make_abnormal_goto = false; |
844 | if (is_gimple_call (gs: stmt)) |
845 | { |
846 | was_noreturn = gimple_call_noreturn_p (s: stmt); |
847 | can_make_abnormal_goto = stmt_can_make_abnormal_goto (stmt); |
848 | } |
849 | |
850 | /* Replace real uses in the statement. */ |
851 | did_replace |= substitute_and_fold_engine->replace_uses_in (stmt); |
852 | |
853 | gimple_stmt_iterator prev_gsi = i; |
854 | gsi_prev (i: &prev_gsi); |
855 | |
856 | /* If we made a replacement, fold the statement. */ |
857 | if (did_replace) |
858 | { |
859 | fold_stmt (&i, follow_single_use_edges); |
860 | stmt = gsi_stmt (i); |
861 | gimple_set_modified (s: stmt, modifiedp: true); |
862 | } |
863 | /* Also fold if we want to fold all statements. */ |
864 | else if (substitute_and_fold_engine->fold_all_stmts |
865 | && fold_stmt (&i, follow_single_use_edges)) |
866 | { |
867 | did_replace = true; |
868 | stmt = gsi_stmt (i); |
869 | gimple_set_modified (s: stmt, modifiedp: true); |
870 | } |
871 | |
872 | /* Some statements may be simplified using propagator |
873 | specific information. Do this before propagating |
874 | into the stmt to not disturb pass specific information. */ |
875 | update_stmt_if_modified (s: stmt); |
876 | if (substitute_and_fold_engine->fold_stmt (&i)) |
877 | { |
878 | did_replace = true; |
879 | prop_stats.num_stmts_folded++; |
880 | stmt = gsi_stmt (i); |
881 | gimple_set_modified (s: stmt, modifiedp: true); |
882 | } |
883 | |
884 | /* If this is a control statement the propagator left edges |
885 | unexecuted on force the condition in a way consistent with |
886 | that. See PR66945 for cases where the propagator can end |
887 | up with a different idea of a taken edge than folding |
888 | (once undefined behavior is involved). */ |
889 | if (gimple_code (g: stmt) == GIMPLE_COND) |
890 | { |
891 | if ((EDGE_SUCC (bb, 0)->flags & EDGE_EXECUTABLE) |
892 | ^ (EDGE_SUCC (bb, 1)->flags & EDGE_EXECUTABLE)) |
893 | { |
894 | if (((EDGE_SUCC (bb, 0)->flags & EDGE_TRUE_VALUE) != 0) |
895 | == ((EDGE_SUCC (bb, 0)->flags & EDGE_EXECUTABLE) != 0)) |
896 | gimple_cond_make_true (gs: as_a <gcond *> (p: stmt)); |
897 | else |
898 | gimple_cond_make_false (gs: as_a <gcond *> (p: stmt)); |
899 | gimple_set_modified (s: stmt, modifiedp: true); |
900 | did_replace = true; |
901 | } |
902 | } |
903 | |
904 | /* Now cleanup. */ |
905 | if (did_replace) |
906 | { |
907 | foreach_new_stmt_in_bb (old_gsi: prev_gsi, new_gsi: i); |
908 | |
909 | /* If we cleaned up EH information from the statement, |
910 | remove EH edges. */ |
911 | if (maybe_clean_or_replace_eh_stmt (old_stmt, stmt)) |
912 | bitmap_set_bit (need_eh_cleanup, bb->index); |
913 | |
914 | /* If we turned a call with possible abnormal control transfer |
915 | into one that doesn't, remove abnormal edges. */ |
916 | if (can_make_abnormal_goto |
917 | && !stmt_can_make_abnormal_goto (stmt)) |
918 | bitmap_set_bit (need_ab_cleanup, bb->index); |
919 | |
920 | /* If we turned a not noreturn call into a noreturn one |
921 | schedule it for fixup. */ |
922 | if (!was_noreturn |
923 | && is_gimple_call (gs: stmt) |
924 | && gimple_call_noreturn_p (s: stmt)) |
925 | stmts_to_fixup.safe_push (obj: stmt); |
926 | |
927 | if (gimple_assign_single_p (gs: stmt)) |
928 | { |
929 | tree rhs = gimple_assign_rhs1 (gs: stmt); |
930 | |
931 | if (TREE_CODE (rhs) == ADDR_EXPR) |
932 | recompute_tree_invariant_for_addr_expr (rhs); |
933 | } |
934 | |
935 | /* Determine what needs to be done to update the SSA form. */ |
936 | update_stmt_if_modified (s: stmt); |
937 | if (!is_gimple_debug (gs: stmt)) |
938 | something_changed = true; |
939 | } |
940 | |
941 | if (dump_file && (dump_flags & TDF_DETAILS)) |
942 | { |
943 | if (did_replace) |
944 | { |
945 | fprintf (stream: dump_file, format: "Folded into: " ); |
946 | print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM); |
947 | fprintf (stream: dump_file, format: "\n" ); |
948 | } |
949 | else |
950 | fprintf (stream: dump_file, format: "Not folded\n" ); |
951 | } |
952 | } |
953 | |
954 | something_changed |= substitute_and_fold_engine->propagate_into_phi_args (bb); |
955 | |
956 | return NULL; |
957 | } |
958 | |
959 | |
960 | |
961 | /* Perform final substitution and folding of propagated values. |
962 | Process the whole function if BLOCK is null, otherwise only |
963 | process the blocks that BLOCK dominates. In the latter case, |
964 | it is the caller's responsibility to ensure that dominator |
965 | information is available and up-to-date. |
966 | |
967 | PROP_VALUE[I] contains the single value that should be substituted |
968 | at every use of SSA name N_I. If PROP_VALUE is NULL, no values are |
969 | substituted. |
970 | |
971 | If FOLD_FN is non-NULL the function will be invoked on all statements |
972 | before propagating values for pass specific simplification. |
973 | |
974 | DO_DCE is true if trivially dead stmts can be removed. |
975 | |
976 | If DO_DCE is true, the statements within a BB are walked from |
977 | last to first element. Otherwise we scan from first to last element. |
978 | |
979 | Return TRUE when something changed. */ |
980 | |
981 | bool |
982 | substitute_and_fold_engine::substitute_and_fold (basic_block block) |
983 | { |
984 | if (dump_file && (dump_flags & TDF_DETAILS)) |
985 | fprintf (stream: dump_file, format: "\nSubstituting values and folding statements\n\n" ); |
986 | |
987 | memset (s: &prop_stats, c: 0, n: sizeof (prop_stats)); |
988 | |
989 | /* Don't call calculate_dominance_info when iterating over a subgraph. |
990 | Callers that are using the interface this way are likely to want to |
991 | iterate over several disjoint subgraphs, and it would be expensive |
992 | in enable-checking builds to revalidate the whole dominance tree |
993 | each time. */ |
994 | if (block) |
995 | gcc_assert (dom_info_state (CDI_DOMINATORS)); |
996 | else |
997 | calculate_dominance_info (CDI_DOMINATORS); |
998 | substitute_and_fold_dom_walker walker (CDI_DOMINATORS, this); |
999 | walker.walk (block ? block : ENTRY_BLOCK_PTR_FOR_FN (cfun)); |
1000 | |
1001 | simple_dce_from_worklist (walker.dceworklist, walker.need_eh_cleanup); |
1002 | if (!bitmap_empty_p (map: walker.need_eh_cleanup)) |
1003 | gimple_purge_all_dead_eh_edges (walker.need_eh_cleanup); |
1004 | if (!bitmap_empty_p (map: walker.need_ab_cleanup)) |
1005 | gimple_purge_all_dead_abnormal_call_edges (walker.need_ab_cleanup); |
1006 | |
1007 | /* Fixup stmts that became noreturn calls. This may require splitting |
1008 | blocks and thus isn't possible during the dominator walk. Do this |
1009 | in reverse order so we don't inadvertedly remove a stmt we want to |
1010 | fixup by visiting a dominating now noreturn call first. */ |
1011 | while (!walker.stmts_to_fixup.is_empty ()) |
1012 | { |
1013 | gimple *stmt = walker.stmts_to_fixup.pop (); |
1014 | if (dump_file && dump_flags & TDF_DETAILS) |
1015 | { |
1016 | fprintf (stream: dump_file, format: "Fixing up noreturn call " ); |
1017 | print_gimple_stmt (dump_file, stmt, 0); |
1018 | fprintf (stream: dump_file, format: "\n" ); |
1019 | } |
1020 | fixup_noreturn_call (stmt); |
1021 | } |
1022 | |
1023 | statistics_counter_event (cfun, "Constants propagated" , |
1024 | prop_stats.num_const_prop); |
1025 | statistics_counter_event (cfun, "Copies propagated" , |
1026 | prop_stats.num_copy_prop); |
1027 | statistics_counter_event (cfun, "Statements folded" , |
1028 | prop_stats.num_stmts_folded); |
1029 | |
1030 | return walker.something_changed; |
1031 | } |
1032 | |
1033 | |
1034 | /* Return true if we may propagate ORIG into DEST, false otherwise. |
1035 | If DEST_NOT_ABNORMAL_PHI_EDGE_P is true then assume the propagation does |
1036 | not happen into a PHI argument which flows in from an abnormal edge |
1037 | which relaxes some constraints. */ |
1038 | |
1039 | bool |
1040 | may_propagate_copy (tree dest, tree orig, bool dest_not_abnormal_phi_edge_p) |
1041 | { |
1042 | tree type_d = TREE_TYPE (dest); |
1043 | tree type_o = TREE_TYPE (orig); |
1044 | |
1045 | /* If ORIG is a default definition which flows in from an abnormal edge |
1046 | then the copy can be propagated. It is important that we do so to avoid |
1047 | uninitialized copies. */ |
1048 | if (TREE_CODE (orig) == SSA_NAME |
1049 | && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (orig) |
1050 | && SSA_NAME_IS_DEFAULT_DEF (orig) |
1051 | && (SSA_NAME_VAR (orig) == NULL_TREE |
1052 | || VAR_P (SSA_NAME_VAR (orig)))) |
1053 | ; |
1054 | /* Otherwise if ORIG just flows in from an abnormal edge then the copy cannot |
1055 | be propagated. */ |
1056 | else if (TREE_CODE (orig) == SSA_NAME |
1057 | && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (orig)) |
1058 | return false; |
1059 | /* Similarly if DEST flows in from an abnormal edge then the copy cannot be |
1060 | propagated. If we know we do not propagate into such a PHI argument this |
1061 | does not apply. */ |
1062 | else if (!dest_not_abnormal_phi_edge_p |
1063 | && TREE_CODE (dest) == SSA_NAME |
1064 | && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (dest)) |
1065 | return false; |
1066 | |
1067 | /* Do not copy between types for which we *do* need a conversion. */ |
1068 | if (!useless_type_conversion_p (type_d, type_o)) |
1069 | return false; |
1070 | |
1071 | /* Generally propagating virtual operands is not ok as that may |
1072 | create overlapping life-ranges. */ |
1073 | if (TREE_CODE (dest) == SSA_NAME && virtual_operand_p (op: dest)) |
1074 | return false; |
1075 | |
1076 | /* Anything else is OK. */ |
1077 | return true; |
1078 | } |
1079 | |
1080 | /* Like may_propagate_copy, but use as the destination expression |
1081 | the principal expression (typically, the RHS) contained in |
1082 | statement DEST. This is more efficient when working with the |
1083 | gimple tuples representation. */ |
1084 | |
1085 | bool |
1086 | may_propagate_copy_into_stmt (gimple *dest, tree orig) |
1087 | { |
1088 | tree type_d; |
1089 | tree type_o; |
1090 | |
1091 | /* If the statement is a switch or a single-rhs assignment, |
1092 | then the expression to be replaced by the propagation may |
1093 | be an SSA_NAME. Fortunately, there is an explicit tree |
1094 | for the expression, so we delegate to may_propagate_copy. */ |
1095 | |
1096 | if (gimple_assign_single_p (gs: dest)) |
1097 | return may_propagate_copy (dest: gimple_assign_rhs1 (gs: dest), orig, dest_not_abnormal_phi_edge_p: true); |
1098 | else if (gswitch *dest_swtch = dyn_cast <gswitch *> (p: dest)) |
1099 | return may_propagate_copy (dest: gimple_switch_index (gs: dest_swtch), orig, dest_not_abnormal_phi_edge_p: true); |
1100 | |
1101 | /* In other cases, the expression is not materialized, so there |
1102 | is no destination to pass to may_propagate_copy. On the other |
1103 | hand, the expression cannot be an SSA_NAME, so the analysis |
1104 | is much simpler. */ |
1105 | |
1106 | if (TREE_CODE (orig) == SSA_NAME |
1107 | && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (orig)) |
1108 | return false; |
1109 | |
1110 | if (is_gimple_assign (gs: dest)) |
1111 | type_d = TREE_TYPE (gimple_assign_lhs (dest)); |
1112 | else if (gimple_code (g: dest) == GIMPLE_COND) |
1113 | type_d = boolean_type_node; |
1114 | else if (is_gimple_call (gs: dest) |
1115 | && gimple_call_lhs (gs: dest) != NULL_TREE) |
1116 | type_d = TREE_TYPE (gimple_call_lhs (dest)); |
1117 | else |
1118 | gcc_unreachable (); |
1119 | |
1120 | type_o = TREE_TYPE (orig); |
1121 | |
1122 | if (!useless_type_conversion_p (type_d, type_o)) |
1123 | return false; |
1124 | |
1125 | return true; |
1126 | } |
1127 | |
1128 | /* Similarly, but we know that we're propagating into an ASM_EXPR. */ |
1129 | |
1130 | bool |
1131 | may_propagate_copy_into_asm (tree dest ATTRIBUTE_UNUSED) |
1132 | { |
1133 | return true; |
1134 | } |
1135 | |
1136 | |
1137 | /* Replace *OP_P with value VAL (assumed to be a constant or another SSA_NAME). |
1138 | |
1139 | Use this version when not const/copy propagating values. For example, |
1140 | PRE uses this version when building expressions as they would appear |
1141 | in specific blocks taking into account actions of PHI nodes. |
1142 | |
1143 | The statement in which an expression has been replaced should be |
1144 | folded using fold_stmt_inplace. */ |
1145 | |
1146 | void |
1147 | replace_exp (use_operand_p op_p, tree val) |
1148 | { |
1149 | if (TREE_CODE (val) == SSA_NAME || CONSTANT_CLASS_P (val)) |
1150 | SET_USE (op_p, val); |
1151 | else |
1152 | SET_USE (op_p, unshare_expr (val)); |
1153 | } |
1154 | |
1155 | |
1156 | /* Propagate the value VAL (assumed to be a constant or another SSA_NAME) |
1157 | into the operand pointed to by OP_P. |
1158 | |
1159 | Use this version for const/copy propagation as it will perform additional |
1160 | checks to ensure validity of the const/copy propagation. */ |
1161 | |
1162 | void |
1163 | propagate_value (use_operand_p op_p, tree val) |
1164 | { |
1165 | if (flag_checking) |
1166 | { |
1167 | bool ab = (is_a <gphi *> (USE_STMT (op_p)) |
1168 | && (gimple_phi_arg_edge (phi: as_a <gphi *> (USE_STMT (op_p)), |
1169 | PHI_ARG_INDEX_FROM_USE (op_p)) |
1170 | ->flags & EDGE_ABNORMAL)); |
1171 | gcc_assert (may_propagate_copy (USE_FROM_PTR (op_p), val, !ab)); |
1172 | } |
1173 | replace_exp (op_p, val); |
1174 | } |
1175 | |
1176 | |
1177 | /* Propagate the value VAL (assumed to be a constant or another SSA_NAME) |
1178 | into the tree pointed to by OP_P. |
1179 | |
1180 | Use this version for const/copy propagation when SSA operands are not |
1181 | available. It will perform the additional checks to ensure validity of |
1182 | the const/copy propagation, but will not update any operand information. |
1183 | Be sure to mark the stmt as modified. */ |
1184 | |
1185 | void |
1186 | propagate_tree_value (tree *op_p, tree val) |
1187 | { |
1188 | if (TREE_CODE (val) == SSA_NAME) |
1189 | *op_p = val; |
1190 | else |
1191 | *op_p = unshare_expr (val); |
1192 | } |
1193 | |
1194 | |
1195 | /* Like propagate_tree_value, but use as the operand to replace |
1196 | the principal expression (typically, the RHS) contained in the |
1197 | statement referenced by iterator GSI. Note that it is not |
1198 | always possible to update the statement in-place, so a new |
1199 | statement may be created to replace the original. */ |
1200 | |
1201 | void |
1202 | propagate_tree_value_into_stmt (gimple_stmt_iterator *gsi, tree val) |
1203 | { |
1204 | gimple *stmt = gsi_stmt (i: *gsi); |
1205 | |
1206 | if (is_gimple_assign (gs: stmt)) |
1207 | { |
1208 | tree expr = NULL_TREE; |
1209 | if (gimple_assign_single_p (gs: stmt)) |
1210 | expr = gimple_assign_rhs1 (gs: stmt); |
1211 | propagate_tree_value (op_p: &expr, val); |
1212 | gimple_assign_set_rhs_from_tree (gsi, expr); |
1213 | } |
1214 | else if (gcond *cond_stmt = dyn_cast <gcond *> (p: stmt)) |
1215 | { |
1216 | tree lhs = NULL_TREE; |
1217 | tree rhs = build_zero_cst (TREE_TYPE (val)); |
1218 | propagate_tree_value (op_p: &lhs, val); |
1219 | gimple_cond_set_code (gs: cond_stmt, code: NE_EXPR); |
1220 | gimple_cond_set_lhs (gs: cond_stmt, lhs); |
1221 | gimple_cond_set_rhs (gs: cond_stmt, rhs); |
1222 | } |
1223 | else if (is_gimple_call (gs: stmt) |
1224 | && gimple_call_lhs (gs: stmt) != NULL_TREE) |
1225 | { |
1226 | tree expr = NULL_TREE; |
1227 | propagate_tree_value (op_p: &expr, val); |
1228 | replace_call_with_value (gsi, expr); |
1229 | } |
1230 | else if (gswitch *swtch_stmt = dyn_cast <gswitch *> (p: stmt)) |
1231 | propagate_tree_value (op_p: gimple_switch_index_ptr (gs: swtch_stmt), val); |
1232 | else |
1233 | gcc_unreachable (); |
1234 | } |
1235 | |
1236 | /* Check exits of each loop in FUN, walk over loop closed PHIs in |
1237 | each exit basic block and propagate degenerate PHIs. */ |
1238 | |
1239 | unsigned |
1240 | clean_up_loop_closed_phi (function *fun) |
1241 | { |
1242 | gphi *phi; |
1243 | tree rhs; |
1244 | tree lhs; |
1245 | gphi_iterator gsi; |
1246 | |
1247 | /* Avoid possibly quadratic work when scanning for loop exits across |
1248 | all loops of a nest. */ |
1249 | if (!loops_state_satisfies_p (flags: LOOPS_HAVE_RECORDED_EXITS)) |
1250 | return 0; |
1251 | |
1252 | /* replace_uses_by might purge dead EH edges and we want it to also |
1253 | remove dominated blocks. */ |
1254 | calculate_dominance_info (CDI_DOMINATORS); |
1255 | |
1256 | /* Walk over loop in function. */ |
1257 | for (auto loop : loops_list (fun, 0)) |
1258 | { |
1259 | /* Check each exit edege of loop. */ |
1260 | auto_vec<edge> exits = get_loop_exit_edges (loop); |
1261 | for (edge e : exits) |
1262 | if (single_pred_p (bb: e->dest)) |
1263 | /* Walk over loop-closed PHIs. */ |
1264 | for (gsi = gsi_start_phis (e->dest); !gsi_end_p (i: gsi);) |
1265 | { |
1266 | phi = gsi.phi (); |
1267 | rhs = gimple_phi_arg_def (gs: phi, index: 0); |
1268 | lhs = gimple_phi_result (gs: phi); |
1269 | |
1270 | if (virtual_operand_p (op: rhs)) |
1271 | { |
1272 | imm_use_iterator iter; |
1273 | use_operand_p use_p; |
1274 | gimple *stmt; |
1275 | |
1276 | FOR_EACH_IMM_USE_STMT (stmt, iter, lhs) |
1277 | FOR_EACH_IMM_USE_ON_STMT (use_p, iter) |
1278 | SET_USE (use_p, rhs); |
1279 | |
1280 | if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs)) |
1281 | SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs) = 1; |
1282 | remove_phi_node (&gsi, true); |
1283 | } |
1284 | else if (may_propagate_copy (dest: lhs, orig: rhs)) |
1285 | { |
1286 | /* Dump details. */ |
1287 | if (dump_file && (dump_flags & TDF_DETAILS)) |
1288 | { |
1289 | fprintf (stream: dump_file, format: " Replacing '" ); |
1290 | print_generic_expr (dump_file, lhs, dump_flags); |
1291 | fprintf (stream: dump_file, format: "' with '" ); |
1292 | print_generic_expr (dump_file, rhs, dump_flags); |
1293 | fprintf (stream: dump_file, format: "'\n" ); |
1294 | } |
1295 | |
1296 | replace_uses_by (lhs, rhs); |
1297 | remove_phi_node (&gsi, true); |
1298 | } |
1299 | else |
1300 | gsi_next (i: &gsi); |
1301 | } |
1302 | } |
1303 | |
1304 | return 0; |
1305 | } |
1306 | |