]>
Commit | Line | Data |
---|---|---|
1 | /* SSA Dominator optimizations for trees | |
2 | Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007 | |
3 | Free Software Foundation, Inc. | |
4 | Contributed by Diego Novillo <dnovillo@redhat.com> | |
5 | ||
6 | This file is part of GCC. | |
7 | ||
8 | GCC is free software; you can redistribute it and/or modify | |
9 | it under the terms of the GNU General Public License as published by | |
10 | the Free Software Foundation; either version 2, or (at your option) | |
11 | any later version. | |
12 | ||
13 | GCC is distributed in the hope that it will be useful, | |
14 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
16 | GNU General Public License for more details. | |
17 | ||
18 | You should have received a copy of the GNU General Public License | |
19 | along with GCC; see the file COPYING. If not, write to | |
20 | the Free Software Foundation, 51 Franklin Street, Fifth Floor, | |
21 | Boston, MA 02110-1301, USA. */ | |
22 | ||
23 | #include "config.h" | |
24 | #include "system.h" | |
25 | #include "coretypes.h" | |
26 | #include "tm.h" | |
27 | #include "tree.h" | |
28 | #include "flags.h" | |
29 | #include "rtl.h" | |
30 | #include "tm_p.h" | |
31 | #include "ggc.h" | |
32 | #include "basic-block.h" | |
33 | #include "cfgloop.h" | |
34 | #include "output.h" | |
35 | #include "expr.h" | |
36 | #include "function.h" | |
37 | #include "diagnostic.h" | |
38 | #include "timevar.h" | |
39 | #include "tree-dump.h" | |
40 | #include "tree-flow.h" | |
41 | #include "domwalk.h" | |
42 | #include "real.h" | |
43 | #include "tree-pass.h" | |
44 | #include "tree-ssa-propagate.h" | |
45 | #include "langhooks.h" | |
46 | #include "params.h" | |
47 | ||
48 | /* This file implements optimizations on the dominator tree. */ | |
49 | ||
50 | ||
51 | /* Structure for recording edge equivalences as well as any pending | |
52 | edge redirections during the dominator optimizer. | |
53 | ||
54 | Computing and storing the edge equivalences instead of creating | |
55 | them on-demand can save significant amounts of time, particularly | |
56 | for pathological cases involving switch statements. | |
57 | ||
58 | These structures live for a single iteration of the dominator | |
59 | optimizer in the edge's AUX field. At the end of an iteration we | |
60 | free each of these structures and update the AUX field to point | |
61 | to any requested redirection target (the code for updating the | |
62 | CFG and SSA graph for edge redirection expects redirection edge | |
63 | targets to be in the AUX field for each edge. */ | |
64 | ||
65 | struct edge_info | |
66 | { | |
67 | /* If this edge creates a simple equivalence, the LHS and RHS of | |
68 | the equivalence will be stored here. */ | |
69 | tree lhs; | |
70 | tree rhs; | |
71 | ||
72 | /* Traversing an edge may also indicate one or more particular conditions | |
73 | are true or false. The number of recorded conditions can vary, but | |
74 | can be determined by the condition's code. So we have an array | |
75 | and its maximum index rather than use a varray. */ | |
76 | tree *cond_equivalences; | |
77 | unsigned int max_cond_equivalences; | |
78 | }; | |
79 | ||
80 | ||
81 | /* Hash table with expressions made available during the renaming process. | |
82 | When an assignment of the form X_i = EXPR is found, the statement is | |
83 | stored in this table. If the same expression EXPR is later found on the | |
84 | RHS of another statement, it is replaced with X_i (thus performing | |
85 | global redundancy elimination). Similarly as we pass through conditionals | |
86 | we record the conditional itself as having either a true or false value | |
87 | in this table. */ | |
88 | static htab_t avail_exprs; | |
89 | ||
90 | /* Stack of available expressions in AVAIL_EXPRs. Each block pushes any | |
91 | expressions it enters into the hash table along with a marker entry | |
92 | (null). When we finish processing the block, we pop off entries and | |
93 | remove the expressions from the global hash table until we hit the | |
94 | marker. */ | |
95 | static VEC(tree,heap) *avail_exprs_stack; | |
96 | ||
97 | /* Stack of statements we need to rescan during finalization for newly | |
98 | exposed variables. | |
99 | ||
100 | Statement rescanning must occur after the current block's available | |
101 | expressions are removed from AVAIL_EXPRS. Else we may change the | |
102 | hash code for an expression and be unable to find/remove it from | |
103 | AVAIL_EXPRS. */ | |
104 | typedef tree *tree_p; | |
105 | DEF_VEC_P(tree_p); | |
106 | DEF_VEC_ALLOC_P(tree_p,heap); | |
107 | ||
108 | static VEC(tree_p,heap) *stmts_to_rescan; | |
109 | ||
110 | /* Structure for entries in the expression hash table. | |
111 | ||
112 | This requires more memory for the hash table entries, but allows us | |
113 | to avoid creating silly tree nodes and annotations for conditionals, | |
114 | eliminates 2 global hash tables and two block local varrays. | |
115 | ||
116 | It also allows us to reduce the number of hash table lookups we | |
117 | have to perform in lookup_avail_expr and finally it allows us to | |
118 | significantly reduce the number of calls into the hashing routine | |
119 | itself. */ | |
120 | ||
121 | struct expr_hash_elt | |
122 | { | |
123 | /* The value (lhs) of this expression. */ | |
124 | tree lhs; | |
125 | ||
126 | /* The expression (rhs) we want to record. */ | |
127 | tree rhs; | |
128 | ||
129 | /* The stmt pointer if this element corresponds to a statement. */ | |
130 | tree stmt; | |
131 | ||
132 | /* The hash value for RHS/ann. */ | |
133 | hashval_t hash; | |
134 | }; | |
135 | ||
136 | /* Stack of dest,src pairs that need to be restored during finalization. | |
137 | ||
138 | A NULL entry is used to mark the end of pairs which need to be | |
139 | restored during finalization of this block. */ | |
140 | static VEC(tree,heap) *const_and_copies_stack; | |
141 | ||
142 | /* Track whether or not we have changed the control flow graph. */ | |
143 | static bool cfg_altered; | |
144 | ||
145 | /* Bitmap of blocks that have had EH statements cleaned. We should | |
146 | remove their dead edges eventually. */ | |
147 | static bitmap need_eh_cleanup; | |
148 | ||
149 | /* Statistics for dominator optimizations. */ | |
150 | struct opt_stats_d | |
151 | { | |
152 | long num_stmts; | |
153 | long num_exprs_considered; | |
154 | long num_re; | |
155 | long num_const_prop; | |
156 | long num_copy_prop; | |
157 | }; | |
158 | ||
159 | static struct opt_stats_d opt_stats; | |
160 | ||
161 | struct eq_expr_value | |
162 | { | |
163 | tree src; | |
164 | tree dst; | |
165 | }; | |
166 | ||
167 | /* Local functions. */ | |
168 | static void optimize_stmt (struct dom_walk_data *, | |
169 | basic_block bb, | |
170 | block_stmt_iterator); | |
171 | static tree lookup_avail_expr (tree, bool); | |
172 | static hashval_t avail_expr_hash (const void *); | |
173 | static hashval_t real_avail_expr_hash (const void *); | |
174 | static int avail_expr_eq (const void *, const void *); | |
175 | static void htab_statistics (FILE *, htab_t); | |
176 | static void record_cond (tree, tree); | |
177 | static void record_const_or_copy (tree, tree); | |
178 | static void record_equality (tree, tree); | |
179 | static void record_equivalences_from_phis (basic_block); | |
180 | static void record_equivalences_from_incoming_edge (basic_block); | |
181 | static bool eliminate_redundant_computations (tree); | |
182 | static void record_equivalences_from_stmt (tree, int, stmt_ann_t); | |
183 | static void dom_thread_across_edge (struct dom_walk_data *, edge); | |
184 | static void dom_opt_finalize_block (struct dom_walk_data *, basic_block); | |
185 | static void dom_opt_initialize_block (struct dom_walk_data *, basic_block); | |
186 | static void propagate_to_outgoing_edges (struct dom_walk_data *, basic_block); | |
187 | static void remove_local_expressions_from_table (void); | |
188 | static void restore_vars_to_original_value (void); | |
189 | static edge single_incoming_edge_ignoring_loop_edges (basic_block); | |
190 | ||
191 | ||
192 | /* Allocate an EDGE_INFO for edge E and attach it to E. | |
193 | Return the new EDGE_INFO structure. */ | |
194 | ||
195 | static struct edge_info * | |
196 | allocate_edge_info (edge e) | |
197 | { | |
198 | struct edge_info *edge_info; | |
199 | ||
200 | edge_info = XCNEW (struct edge_info); | |
201 | ||
202 | e->aux = edge_info; | |
203 | return edge_info; | |
204 | } | |
205 | ||
206 | /* Free all EDGE_INFO structures associated with edges in the CFG. | |
207 | If a particular edge can be threaded, copy the redirection | |
208 | target from the EDGE_INFO structure into the edge's AUX field | |
209 | as required by code to update the CFG and SSA graph for | |
210 | jump threading. */ | |
211 | ||
212 | static void | |
213 | free_all_edge_infos (void) | |
214 | { | |
215 | basic_block bb; | |
216 | edge_iterator ei; | |
217 | edge e; | |
218 | ||
219 | FOR_EACH_BB (bb) | |
220 | { | |
221 | FOR_EACH_EDGE (e, ei, bb->preds) | |
222 | { | |
223 | struct edge_info *edge_info = (struct edge_info *) e->aux; | |
224 | ||
225 | if (edge_info) | |
226 | { | |
227 | if (edge_info->cond_equivalences) | |
228 | free (edge_info->cond_equivalences); | |
229 | free (edge_info); | |
230 | e->aux = NULL; | |
231 | } | |
232 | } | |
233 | } | |
234 | } | |
235 | ||
236 | /* Jump threading, redundancy elimination and const/copy propagation. | |
237 | ||
238 | This pass may expose new symbols that need to be renamed into SSA. For | |
239 | every new symbol exposed, its corresponding bit will be set in | |
240 | VARS_TO_RENAME. */ | |
241 | ||
242 | static unsigned int | |
243 | tree_ssa_dominator_optimize (void) | |
244 | { | |
245 | struct dom_walk_data walk_data; | |
246 | unsigned int i; | |
247 | ||
248 | memset (&opt_stats, 0, sizeof (opt_stats)); | |
249 | ||
250 | /* Create our hash tables. */ | |
251 | avail_exprs = htab_create (1024, real_avail_expr_hash, avail_expr_eq, free); | |
252 | avail_exprs_stack = VEC_alloc (tree, heap, 20); | |
253 | const_and_copies_stack = VEC_alloc (tree, heap, 20); | |
254 | stmts_to_rescan = VEC_alloc (tree_p, heap, 20); | |
255 | need_eh_cleanup = BITMAP_ALLOC (NULL); | |
256 | ||
257 | /* Setup callbacks for the generic dominator tree walker. */ | |
258 | walk_data.walk_stmts_backward = false; | |
259 | walk_data.dom_direction = CDI_DOMINATORS; | |
260 | walk_data.initialize_block_local_data = NULL; | |
261 | walk_data.before_dom_children_before_stmts = dom_opt_initialize_block; | |
262 | walk_data.before_dom_children_walk_stmts = optimize_stmt; | |
263 | walk_data.before_dom_children_after_stmts = propagate_to_outgoing_edges; | |
264 | walk_data.after_dom_children_before_stmts = NULL; | |
265 | walk_data.after_dom_children_walk_stmts = NULL; | |
266 | walk_data.after_dom_children_after_stmts = dom_opt_finalize_block; | |
267 | /* Right now we only attach a dummy COND_EXPR to the global data pointer. | |
268 | When we attach more stuff we'll need to fill this out with a real | |
269 | structure. */ | |
270 | walk_data.global_data = NULL; | |
271 | walk_data.block_local_data_size = 0; | |
272 | walk_data.interesting_blocks = NULL; | |
273 | ||
274 | /* Now initialize the dominator walker. */ | |
275 | init_walk_dominator_tree (&walk_data); | |
276 | ||
277 | calculate_dominance_info (CDI_DOMINATORS); | |
278 | cfg_altered = false; | |
279 | ||
280 | /* We need to know which edges exit loops so that we can | |
281 | aggressively thread through loop headers to an exit | |
282 | edge. */ | |
283 | loop_optimizer_init (AVOID_CFG_MODIFICATIONS); | |
284 | if (current_loops) | |
285 | { | |
286 | mark_loop_exit_edges (); | |
287 | loop_optimizer_finalize (); | |
288 | } | |
289 | ||
290 | /* Clean up the CFG so that any forwarder blocks created by loop | |
291 | canonicalization are removed. */ | |
292 | cleanup_tree_cfg (); | |
293 | calculate_dominance_info (CDI_DOMINATORS); | |
294 | ||
295 | /* We need accurate information regarding back edges in the CFG | |
296 | for jump threading. */ | |
297 | mark_dfs_back_edges (); | |
298 | ||
299 | /* Recursively walk the dominator tree optimizing statements. */ | |
300 | walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR); | |
301 | ||
302 | { | |
303 | block_stmt_iterator bsi; | |
304 | basic_block bb; | |
305 | FOR_EACH_BB (bb) | |
306 | { | |
307 | for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) | |
308 | update_stmt_if_modified (bsi_stmt (bsi)); | |
309 | } | |
310 | } | |
311 | ||
312 | /* If we exposed any new variables, go ahead and put them into | |
313 | SSA form now, before we handle jump threading. This simplifies | |
314 | interactions between rewriting of _DECL nodes into SSA form | |
315 | and rewriting SSA_NAME nodes into SSA form after block | |
316 | duplication and CFG manipulation. */ | |
317 | update_ssa (TODO_update_ssa); | |
318 | ||
319 | free_all_edge_infos (); | |
320 | ||
321 | /* Thread jumps, creating duplicate blocks as needed. */ | |
322 | cfg_altered |= thread_through_all_blocks (); | |
323 | ||
324 | if (cfg_altered) | |
325 | free_dominance_info (CDI_DOMINATORS); | |
326 | ||
327 | /* Removal of statements may make some EH edges dead. Purge | |
328 | such edges from the CFG as needed. */ | |
329 | if (!bitmap_empty_p (need_eh_cleanup)) | |
330 | { | |
331 | tree_purge_all_dead_eh_edges (need_eh_cleanup); | |
332 | bitmap_zero (need_eh_cleanup); | |
333 | } | |
334 | ||
335 | /* Finally, remove everything except invariants in SSA_NAME_VALUE. | |
336 | ||
337 | Long term we will be able to let everything in SSA_NAME_VALUE | |
338 | persist. However, for now, we know this is the safe thing to do. */ | |
339 | for (i = 0; i < num_ssa_names; i++) | |
340 | { | |
341 | tree name = ssa_name (i); | |
342 | tree value; | |
343 | ||
344 | if (!name) | |
345 | continue; | |
346 | ||
347 | value = SSA_NAME_VALUE (name); | |
348 | if (value && !is_gimple_min_invariant (value)) | |
349 | SSA_NAME_VALUE (name) = NULL; | |
350 | } | |
351 | ||
352 | /* Debugging dumps. */ | |
353 | if (dump_file && (dump_flags & TDF_STATS)) | |
354 | dump_dominator_optimization_stats (dump_file); | |
355 | ||
356 | /* Delete our main hashtable. */ | |
357 | htab_delete (avail_exprs); | |
358 | ||
359 | /* And finalize the dominator walker. */ | |
360 | fini_walk_dominator_tree (&walk_data); | |
361 | ||
362 | /* Free asserted bitmaps and stacks. */ | |
363 | BITMAP_FREE (need_eh_cleanup); | |
364 | ||
365 | VEC_free (tree, heap, avail_exprs_stack); | |
366 | VEC_free (tree, heap, const_and_copies_stack); | |
367 | VEC_free (tree_p, heap, stmts_to_rescan); | |
368 | return 0; | |
369 | } | |
370 | ||
371 | static bool | |
372 | gate_dominator (void) | |
373 | { | |
374 | return flag_tree_dom != 0; | |
375 | } | |
376 | ||
377 | struct tree_opt_pass pass_dominator = | |
378 | { | |
379 | "dom", /* name */ | |
380 | gate_dominator, /* gate */ | |
381 | tree_ssa_dominator_optimize, /* execute */ | |
382 | NULL, /* sub */ | |
383 | NULL, /* next */ | |
384 | 0, /* static_pass_number */ | |
385 | TV_TREE_SSA_DOMINATOR_OPTS, /* tv_id */ | |
386 | PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */ | |
387 | 0, /* properties_provided */ | |
388 | 0, /* properties_destroyed */ | |
389 | 0, /* todo_flags_start */ | |
390 | TODO_dump_func | |
391 | | TODO_update_ssa | |
392 | | TODO_cleanup_cfg | |
393 | | TODO_verify_ssa, /* todo_flags_finish */ | |
394 | 0 /* letter */ | |
395 | }; | |
396 | ||
397 | ||
398 | /* Given a stmt CONDSTMT containing a COND_EXPR, canonicalize the | |
399 | COND_EXPR into a canonical form. */ | |
400 | ||
401 | static void | |
402 | canonicalize_comparison (tree condstmt) | |
403 | { | |
404 | tree cond = COND_EXPR_COND (condstmt); | |
405 | tree op0; | |
406 | tree op1; | |
407 | enum tree_code code = TREE_CODE (cond); | |
408 | ||
409 | if (!COMPARISON_CLASS_P (cond)) | |
410 | return; | |
411 | ||
412 | op0 = TREE_OPERAND (cond, 0); | |
413 | op1 = TREE_OPERAND (cond, 1); | |
414 | ||
415 | /* If it would be profitable to swap the operands, then do so to | |
416 | canonicalize the statement, enabling better optimization. | |
417 | ||
418 | By placing canonicalization of such expressions here we | |
419 | transparently keep statements in canonical form, even | |
420 | when the statement is modified. */ | |
421 | if (tree_swap_operands_p (op0, op1, false)) | |
422 | { | |
423 | /* For relationals we need to swap the operands | |
424 | and change the code. */ | |
425 | if (code == LT_EXPR | |
426 | || code == GT_EXPR | |
427 | || code == LE_EXPR | |
428 | || code == GE_EXPR) | |
429 | { | |
430 | TREE_SET_CODE (cond, swap_tree_comparison (code)); | |
431 | swap_tree_operands (condstmt, | |
432 | &TREE_OPERAND (cond, 0), | |
433 | &TREE_OPERAND (cond, 1)); | |
434 | /* If one operand was in the operand cache, but the other is | |
435 | not, because it is a constant, this is a case that the | |
436 | internal updating code of swap_tree_operands can't handle | |
437 | properly. */ | |
438 | if (TREE_CODE_CLASS (TREE_CODE (op0)) | |
439 | != TREE_CODE_CLASS (TREE_CODE (op1))) | |
440 | update_stmt (condstmt); | |
441 | } | |
442 | } | |
443 | } | |
444 | ||
445 | /* Initialize local stacks for this optimizer and record equivalences | |
446 | upon entry to BB. Equivalences can come from the edge traversed to | |
447 | reach BB or they may come from PHI nodes at the start of BB. */ | |
448 | ||
449 | static void | |
450 | dom_opt_initialize_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED, | |
451 | basic_block bb) | |
452 | { | |
453 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
454 | fprintf (dump_file, "\n\nOptimizing block #%d\n\n", bb->index); | |
455 | ||
456 | /* Push a marker on the stacks of local information so that we know how | |
457 | far to unwind when we finalize this block. */ | |
458 | VEC_safe_push (tree, heap, avail_exprs_stack, NULL_TREE); | |
459 | VEC_safe_push (tree, heap, const_and_copies_stack, NULL_TREE); | |
460 | ||
461 | record_equivalences_from_incoming_edge (bb); | |
462 | ||
463 | /* PHI nodes can create equivalences too. */ | |
464 | record_equivalences_from_phis (bb); | |
465 | } | |
466 | ||
467 | /* Given an expression EXPR (a relational expression or a statement), | |
468 | initialize the hash table element pointed to by ELEMENT. */ | |
469 | ||
470 | static void | |
471 | initialize_hash_element (tree expr, tree lhs, struct expr_hash_elt *element) | |
472 | { | |
473 | /* Hash table elements may be based on conditional expressions or statements. | |
474 | ||
475 | For the former case, we have no annotation and we want to hash the | |
476 | conditional expression. In the latter case we have an annotation and | |
477 | we want to record the expression the statement evaluates. */ | |
478 | if (COMPARISON_CLASS_P (expr) || TREE_CODE (expr) == TRUTH_NOT_EXPR) | |
479 | { | |
480 | element->stmt = NULL; | |
481 | element->rhs = expr; | |
482 | } | |
483 | else if (TREE_CODE (expr) == COND_EXPR) | |
484 | { | |
485 | element->stmt = expr; | |
486 | element->rhs = COND_EXPR_COND (expr); | |
487 | } | |
488 | else if (TREE_CODE (expr) == SWITCH_EXPR) | |
489 | { | |
490 | element->stmt = expr; | |
491 | element->rhs = SWITCH_COND (expr); | |
492 | } | |
493 | else if (TREE_CODE (expr) == RETURN_EXPR && TREE_OPERAND (expr, 0)) | |
494 | { | |
495 | element->stmt = expr; | |
496 | element->rhs = GIMPLE_STMT_OPERAND (TREE_OPERAND (expr, 0), 1); | |
497 | } | |
498 | else if (TREE_CODE (expr) == GOTO_EXPR) | |
499 | { | |
500 | element->stmt = expr; | |
501 | element->rhs = GOTO_DESTINATION (expr); | |
502 | } | |
503 | else | |
504 | { | |
505 | element->stmt = expr; | |
506 | element->rhs = GENERIC_TREE_OPERAND (expr, 1); | |
507 | } | |
508 | ||
509 | element->lhs = lhs; | |
510 | element->hash = avail_expr_hash (element); | |
511 | } | |
512 | ||
513 | /* Remove all the expressions in LOCALS from TABLE, stopping when there are | |
514 | LIMIT entries left in LOCALs. */ | |
515 | ||
516 | static void | |
517 | remove_local_expressions_from_table (void) | |
518 | { | |
519 | /* Remove all the expressions made available in this block. */ | |
520 | while (VEC_length (tree, avail_exprs_stack) > 0) | |
521 | { | |
522 | struct expr_hash_elt element; | |
523 | tree expr = VEC_pop (tree, avail_exprs_stack); | |
524 | ||
525 | if (expr == NULL_TREE) | |
526 | break; | |
527 | ||
528 | initialize_hash_element (expr, NULL, &element); | |
529 | htab_remove_elt_with_hash (avail_exprs, &element, element.hash); | |
530 | } | |
531 | } | |
532 | ||
533 | /* Use the source/dest pairs in CONST_AND_COPIES_STACK to restore | |
534 | CONST_AND_COPIES to its original state, stopping when we hit a | |
535 | NULL marker. */ | |
536 | ||
537 | static void | |
538 | restore_vars_to_original_value (void) | |
539 | { | |
540 | while (VEC_length (tree, const_and_copies_stack) > 0) | |
541 | { | |
542 | tree prev_value, dest; | |
543 | ||
544 | dest = VEC_pop (tree, const_and_copies_stack); | |
545 | ||
546 | if (dest == NULL) | |
547 | break; | |
548 | ||
549 | prev_value = VEC_pop (tree, const_and_copies_stack); | |
550 | SSA_NAME_VALUE (dest) = prev_value; | |
551 | } | |
552 | } | |
553 | ||
554 | /* A trivial wrapper so that we can present the generic jump | |
555 | threading code with a simple API for simplifying statements. */ | |
556 | static tree | |
557 | simplify_stmt_for_jump_threading (tree stmt, tree within_stmt ATTRIBUTE_UNUSED) | |
558 | { | |
559 | return lookup_avail_expr (stmt, false); | |
560 | } | |
561 | ||
562 | /* Wrapper for common code to attempt to thread an edge. For example, | |
563 | it handles lazily building the dummy condition and the bookkeeping | |
564 | when jump threading is successful. */ | |
565 | ||
566 | static void | |
567 | dom_thread_across_edge (struct dom_walk_data *walk_data, edge e) | |
568 | { | |
569 | /* If we don't already have a dummy condition, build it now. */ | |
570 | if (! walk_data->global_data) | |
571 | { | |
572 | tree dummy_cond = build2 (NE_EXPR, boolean_type_node, | |
573 | integer_zero_node, integer_zero_node); | |
574 | dummy_cond = build3 (COND_EXPR, void_type_node, dummy_cond, NULL, NULL); | |
575 | walk_data->global_data = dummy_cond; | |
576 | } | |
577 | ||
578 | thread_across_edge (walk_data->global_data, e, false, | |
579 | &const_and_copies_stack, | |
580 | simplify_stmt_for_jump_threading); | |
581 | } | |
582 | ||
583 | /* We have finished processing the dominator children of BB, perform | |
584 | any finalization actions in preparation for leaving this node in | |
585 | the dominator tree. */ | |
586 | ||
587 | static void | |
588 | dom_opt_finalize_block (struct dom_walk_data *walk_data, basic_block bb) | |
589 | { | |
590 | tree last; | |
591 | ||
592 | ||
593 | /* If we have an outgoing edge to a block with multiple incoming and | |
594 | outgoing edges, then we may be able to thread the edge. ie, we | |
595 | may be able to statically determine which of the outgoing edges | |
596 | will be traversed when the incoming edge from BB is traversed. */ | |
597 | if (single_succ_p (bb) | |
598 | && (single_succ_edge (bb)->flags & EDGE_ABNORMAL) == 0 | |
599 | && potentially_threadable_block (single_succ (bb))) | |
600 | { | |
601 | dom_thread_across_edge (walk_data, single_succ_edge (bb)); | |
602 | } | |
603 | else if ((last = last_stmt (bb)) | |
604 | && TREE_CODE (last) == COND_EXPR | |
605 | && (COMPARISON_CLASS_P (COND_EXPR_COND (last)) | |
606 | || TREE_CODE (COND_EXPR_COND (last)) == SSA_NAME) | |
607 | && EDGE_COUNT (bb->succs) == 2 | |
608 | && (EDGE_SUCC (bb, 0)->flags & EDGE_ABNORMAL) == 0 | |
609 | && (EDGE_SUCC (bb, 1)->flags & EDGE_ABNORMAL) == 0) | |
610 | { | |
611 | edge true_edge, false_edge; | |
612 | ||
613 | extract_true_false_edges_from_block (bb, &true_edge, &false_edge); | |
614 | ||
615 | /* Only try to thread the edge if it reaches a target block with | |
616 | more than one predecessor and more than one successor. */ | |
617 | if (potentially_threadable_block (true_edge->dest)) | |
618 | { | |
619 | struct edge_info *edge_info; | |
620 | unsigned int i; | |
621 | ||
622 | /* Push a marker onto the available expression stack so that we | |
623 | unwind any expressions related to the TRUE arm before processing | |
624 | the false arm below. */ | |
625 | VEC_safe_push (tree, heap, avail_exprs_stack, NULL_TREE); | |
626 | VEC_safe_push (tree, heap, const_and_copies_stack, NULL_TREE); | |
627 | ||
628 | edge_info = (struct edge_info *) true_edge->aux; | |
629 | ||
630 | /* If we have info associated with this edge, record it into | |
631 | our equivalency tables. */ | |
632 | if (edge_info) | |
633 | { | |
634 | tree *cond_equivalences = edge_info->cond_equivalences; | |
635 | tree lhs = edge_info->lhs; | |
636 | tree rhs = edge_info->rhs; | |
637 | ||
638 | /* If we have a simple NAME = VALUE equivalency record it. */ | |
639 | if (lhs && TREE_CODE (lhs) == SSA_NAME) | |
640 | record_const_or_copy (lhs, rhs); | |
641 | ||
642 | /* If we have 0 = COND or 1 = COND equivalences, record them | |
643 | into our expression hash tables. */ | |
644 | if (cond_equivalences) | |
645 | for (i = 0; i < edge_info->max_cond_equivalences; i += 2) | |
646 | { | |
647 | tree expr = cond_equivalences[i]; | |
648 | tree value = cond_equivalences[i + 1]; | |
649 | ||
650 | record_cond (expr, value); | |
651 | } | |
652 | } | |
653 | ||
654 | dom_thread_across_edge (walk_data, true_edge); | |
655 | ||
656 | /* And restore the various tables to their state before | |
657 | we threaded this edge. */ | |
658 | remove_local_expressions_from_table (); | |
659 | } | |
660 | ||
661 | /* Similarly for the ELSE arm. */ | |
662 | if (potentially_threadable_block (false_edge->dest)) | |
663 | { | |
664 | struct edge_info *edge_info; | |
665 | unsigned int i; | |
666 | ||
667 | VEC_safe_push (tree, heap, const_and_copies_stack, NULL_TREE); | |
668 | edge_info = (struct edge_info *) false_edge->aux; | |
669 | ||
670 | /* If we have info associated with this edge, record it into | |
671 | our equivalency tables. */ | |
672 | if (edge_info) | |
673 | { | |
674 | tree *cond_equivalences = edge_info->cond_equivalences; | |
675 | tree lhs = edge_info->lhs; | |
676 | tree rhs = edge_info->rhs; | |
677 | ||
678 | /* If we have a simple NAME = VALUE equivalency record it. */ | |
679 | if (lhs && TREE_CODE (lhs) == SSA_NAME) | |
680 | record_const_or_copy (lhs, rhs); | |
681 | ||
682 | /* If we have 0 = COND or 1 = COND equivalences, record them | |
683 | into our expression hash tables. */ | |
684 | if (cond_equivalences) | |
685 | for (i = 0; i < edge_info->max_cond_equivalences; i += 2) | |
686 | { | |
687 | tree expr = cond_equivalences[i]; | |
688 | tree value = cond_equivalences[i + 1]; | |
689 | ||
690 | record_cond (expr, value); | |
691 | } | |
692 | } | |
693 | ||
694 | /* Now thread the edge. */ | |
695 | dom_thread_across_edge (walk_data, false_edge); | |
696 | ||
697 | /* No need to remove local expressions from our tables | |
698 | or restore vars to their original value as that will | |
699 | be done immediately below. */ | |
700 | } | |
701 | } | |
702 | ||
703 | remove_local_expressions_from_table (); | |
704 | restore_vars_to_original_value (); | |
705 | ||
706 | /* If we queued any statements to rescan in this block, then | |
707 | go ahead and rescan them now. */ | |
708 | while (VEC_length (tree_p, stmts_to_rescan) > 0) | |
709 | { | |
710 | tree *stmt_p = VEC_last (tree_p, stmts_to_rescan); | |
711 | tree stmt = *stmt_p; | |
712 | basic_block stmt_bb = bb_for_stmt (stmt); | |
713 | ||
714 | if (stmt_bb != bb) | |
715 | break; | |
716 | ||
717 | VEC_pop (tree_p, stmts_to_rescan); | |
718 | pop_stmt_changes (stmt_p); | |
719 | } | |
720 | } | |
721 | ||
722 | /* PHI nodes can create equivalences too. | |
723 | ||
724 | Ignoring any alternatives which are the same as the result, if | |
725 | all the alternatives are equal, then the PHI node creates an | |
726 | equivalence. */ | |
727 | ||
728 | static void | |
729 | record_equivalences_from_phis (basic_block bb) | |
730 | { | |
731 | tree phi; | |
732 | ||
733 | for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi)) | |
734 | { | |
735 | tree lhs = PHI_RESULT (phi); | |
736 | tree rhs = NULL; | |
737 | int i; | |
738 | ||
739 | for (i = 0; i < PHI_NUM_ARGS (phi); i++) | |
740 | { | |
741 | tree t = PHI_ARG_DEF (phi, i); | |
742 | ||
743 | /* Ignore alternatives which are the same as our LHS. Since | |
744 | LHS is a PHI_RESULT, it is known to be a SSA_NAME, so we | |
745 | can simply compare pointers. */ | |
746 | if (lhs == t) | |
747 | continue; | |
748 | ||
749 | /* If we have not processed an alternative yet, then set | |
750 | RHS to this alternative. */ | |
751 | if (rhs == NULL) | |
752 | rhs = t; | |
753 | /* If we have processed an alternative (stored in RHS), then | |
754 | see if it is equal to this one. If it isn't, then stop | |
755 | the search. */ | |
756 | else if (! operand_equal_for_phi_arg_p (rhs, t)) | |
757 | break; | |
758 | } | |
759 | ||
760 | /* If we had no interesting alternatives, then all the RHS alternatives | |
761 | must have been the same as LHS. */ | |
762 | if (!rhs) | |
763 | rhs = lhs; | |
764 | ||
765 | /* If we managed to iterate through each PHI alternative without | |
766 | breaking out of the loop, then we have a PHI which may create | |
767 | a useful equivalence. We do not need to record unwind data for | |
768 | this, since this is a true assignment and not an equivalence | |
769 | inferred from a comparison. All uses of this ssa name are dominated | |
770 | by this assignment, so unwinding just costs time and space. */ | |
771 | if (i == PHI_NUM_ARGS (phi) | |
772 | && may_propagate_copy (lhs, rhs)) | |
773 | SSA_NAME_VALUE (lhs) = rhs; | |
774 | } | |
775 | } | |
776 | ||
777 | /* Ignoring loop backedges, if BB has precisely one incoming edge then | |
778 | return that edge. Otherwise return NULL. */ | |
779 | static edge | |
780 | single_incoming_edge_ignoring_loop_edges (basic_block bb) | |
781 | { | |
782 | edge retval = NULL; | |
783 | edge e; | |
784 | edge_iterator ei; | |
785 | ||
786 | FOR_EACH_EDGE (e, ei, bb->preds) | |
787 | { | |
788 | /* A loop back edge can be identified by the destination of | |
789 | the edge dominating the source of the edge. */ | |
790 | if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest)) | |
791 | continue; | |
792 | ||
793 | /* If we have already seen a non-loop edge, then we must have | |
794 | multiple incoming non-loop edges and thus we return NULL. */ | |
795 | if (retval) | |
796 | return NULL; | |
797 | ||
798 | /* This is the first non-loop incoming edge we have found. Record | |
799 | it. */ | |
800 | retval = e; | |
801 | } | |
802 | ||
803 | return retval; | |
804 | } | |
805 | ||
806 | /* Record any equivalences created by the incoming edge to BB. If BB | |
807 | has more than one incoming edge, then no equivalence is created. */ | |
808 | ||
809 | static void | |
810 | record_equivalences_from_incoming_edge (basic_block bb) | |
811 | { | |
812 | edge e; | |
813 | basic_block parent; | |
814 | struct edge_info *edge_info; | |
815 | ||
816 | /* If our parent block ended with a control statement, then we may be | |
817 | able to record some equivalences based on which outgoing edge from | |
818 | the parent was followed. */ | |
819 | parent = get_immediate_dominator (CDI_DOMINATORS, bb); | |
820 | ||
821 | e = single_incoming_edge_ignoring_loop_edges (bb); | |
822 | ||
823 | /* If we had a single incoming edge from our parent block, then enter | |
824 | any data associated with the edge into our tables. */ | |
825 | if (e && e->src == parent) | |
826 | { | |
827 | unsigned int i; | |
828 | ||
829 | edge_info = (struct edge_info *) e->aux; | |
830 | ||
831 | if (edge_info) | |
832 | { | |
833 | tree lhs = edge_info->lhs; | |
834 | tree rhs = edge_info->rhs; | |
835 | tree *cond_equivalences = edge_info->cond_equivalences; | |
836 | ||
837 | if (lhs) | |
838 | record_equality (lhs, rhs); | |
839 | ||
840 | if (cond_equivalences) | |
841 | { | |
842 | for (i = 0; i < edge_info->max_cond_equivalences; i += 2) | |
843 | { | |
844 | tree expr = cond_equivalences[i]; | |
845 | tree value = cond_equivalences[i + 1]; | |
846 | ||
847 | record_cond (expr, value); | |
848 | } | |
849 | } | |
850 | } | |
851 | } | |
852 | } | |
853 | ||
854 | /* Dump SSA statistics on FILE. */ | |
855 | ||
856 | void | |
857 | dump_dominator_optimization_stats (FILE *file) | |
858 | { | |
859 | long n_exprs; | |
860 | ||
861 | fprintf (file, "Total number of statements: %6ld\n\n", | |
862 | opt_stats.num_stmts); | |
863 | fprintf (file, "Exprs considered for dominator optimizations: %6ld\n", | |
864 | opt_stats.num_exprs_considered); | |
865 | ||
866 | n_exprs = opt_stats.num_exprs_considered; | |
867 | if (n_exprs == 0) | |
868 | n_exprs = 1; | |
869 | ||
870 | fprintf (file, " Redundant expressions eliminated: %6ld (%.0f%%)\n", | |
871 | opt_stats.num_re, PERCENT (opt_stats.num_re, | |
872 | n_exprs)); | |
873 | fprintf (file, " Constants propagated: %6ld\n", | |
874 | opt_stats.num_const_prop); | |
875 | fprintf (file, " Copies propagated: %6ld\n", | |
876 | opt_stats.num_copy_prop); | |
877 | ||
878 | fprintf (file, "\nHash table statistics:\n"); | |
879 | ||
880 | fprintf (file, " avail_exprs: "); | |
881 | htab_statistics (file, avail_exprs); | |
882 | } | |
883 | ||
884 | ||
885 | /* Dump SSA statistics on stderr. */ | |
886 | ||
887 | void | |
888 | debug_dominator_optimization_stats (void) | |
889 | { | |
890 | dump_dominator_optimization_stats (stderr); | |
891 | } | |
892 | ||
893 | ||
894 | /* Dump statistics for the hash table HTAB. */ | |
895 | ||
896 | static void | |
897 | htab_statistics (FILE *file, htab_t htab) | |
898 | { | |
899 | fprintf (file, "size %ld, %ld elements, %f collision/search ratio\n", | |
900 | (long) htab_size (htab), | |
901 | (long) htab_elements (htab), | |
902 | htab_collisions (htab)); | |
903 | } | |
904 | ||
905 | /* Enter a statement into the true/false expression hash table indicating | |
906 | that the condition COND has the value VALUE. */ | |
907 | ||
908 | static void | |
909 | record_cond (tree cond, tree value) | |
910 | { | |
911 | struct expr_hash_elt *element = XCNEW (struct expr_hash_elt); | |
912 | void **slot; | |
913 | ||
914 | initialize_hash_element (cond, value, element); | |
915 | ||
916 | slot = htab_find_slot_with_hash (avail_exprs, (void *)element, | |
917 | element->hash, INSERT); | |
918 | if (*slot == NULL) | |
919 | { | |
920 | *slot = (void *) element; | |
921 | VEC_safe_push (tree, heap, avail_exprs_stack, cond); | |
922 | } | |
923 | else | |
924 | free (element); | |
925 | } | |
926 | ||
927 | /* Build a new conditional using NEW_CODE, OP0 and OP1 and store | |
928 | the new conditional into *p, then store a boolean_true_node | |
929 | into *(p + 1). */ | |
930 | ||
931 | static void | |
932 | build_and_record_new_cond (enum tree_code new_code, tree op0, tree op1, tree *p) | |
933 | { | |
934 | *p = build2 (new_code, boolean_type_node, op0, op1); | |
935 | p++; | |
936 | *p = boolean_true_node; | |
937 | } | |
938 | ||
939 | /* Record that COND is true and INVERTED is false into the edge information | |
940 | structure. Also record that any conditions dominated by COND are true | |
941 | as well. | |
942 | ||
943 | For example, if a < b is true, then a <= b must also be true. */ | |
944 | ||
945 | static void | |
946 | record_conditions (struct edge_info *edge_info, tree cond, tree inverted) | |
947 | { | |
948 | tree op0, op1; | |
949 | ||
950 | if (!COMPARISON_CLASS_P (cond)) | |
951 | return; | |
952 | ||
953 | op0 = TREE_OPERAND (cond, 0); | |
954 | op1 = TREE_OPERAND (cond, 1); | |
955 | ||
956 | switch (TREE_CODE (cond)) | |
957 | { | |
958 | case LT_EXPR: | |
959 | case GT_EXPR: | |
960 | if (FLOAT_TYPE_P (TREE_TYPE (op0))) | |
961 | { | |
962 | edge_info->max_cond_equivalences = 12; | |
963 | edge_info->cond_equivalences = XNEWVEC (tree, 12); | |
964 | build_and_record_new_cond (ORDERED_EXPR, op0, op1, | |
965 | &edge_info->cond_equivalences[8]); | |
966 | build_and_record_new_cond (LTGT_EXPR, op0, op1, | |
967 | &edge_info->cond_equivalences[10]); | |
968 | } | |
969 | else | |
970 | { | |
971 | edge_info->max_cond_equivalences = 8; | |
972 | edge_info->cond_equivalences = XNEWVEC (tree, 8); | |
973 | } | |
974 | ||
975 | build_and_record_new_cond ((TREE_CODE (cond) == LT_EXPR | |
976 | ? LE_EXPR : GE_EXPR), | |
977 | op0, op1, &edge_info->cond_equivalences[4]); | |
978 | build_and_record_new_cond (NE_EXPR, op0, op1, | |
979 | &edge_info->cond_equivalences[6]); | |
980 | break; | |
981 | ||
982 | case GE_EXPR: | |
983 | case LE_EXPR: | |
984 | if (FLOAT_TYPE_P (TREE_TYPE (op0))) | |
985 | { | |
986 | edge_info->max_cond_equivalences = 6; | |
987 | edge_info->cond_equivalences = XNEWVEC (tree, 6); | |
988 | build_and_record_new_cond (ORDERED_EXPR, op0, op1, | |
989 | &edge_info->cond_equivalences[4]); | |
990 | } | |
991 | else | |
992 | { | |
993 | edge_info->max_cond_equivalences = 4; | |
994 | edge_info->cond_equivalences = XNEWVEC (tree, 4); | |
995 | } | |
996 | break; | |
997 | ||
998 | case EQ_EXPR: | |
999 | if (FLOAT_TYPE_P (TREE_TYPE (op0))) | |
1000 | { | |
1001 | edge_info->max_cond_equivalences = 10; | |
1002 | edge_info->cond_equivalences = XNEWVEC (tree, 10); | |
1003 | build_and_record_new_cond (ORDERED_EXPR, op0, op1, | |
1004 | &edge_info->cond_equivalences[8]); | |
1005 | } | |
1006 | else | |
1007 | { | |
1008 | edge_info->max_cond_equivalences = 8; | |
1009 | edge_info->cond_equivalences = XNEWVEC (tree, 8); | |
1010 | } | |
1011 | build_and_record_new_cond (LE_EXPR, op0, op1, | |
1012 | &edge_info->cond_equivalences[4]); | |
1013 | build_and_record_new_cond (GE_EXPR, op0, op1, | |
1014 | &edge_info->cond_equivalences[6]); | |
1015 | break; | |
1016 | ||
1017 | case UNORDERED_EXPR: | |
1018 | edge_info->max_cond_equivalences = 16; | |
1019 | edge_info->cond_equivalences = XNEWVEC (tree, 16); | |
1020 | build_and_record_new_cond (NE_EXPR, op0, op1, | |
1021 | &edge_info->cond_equivalences[4]); | |
1022 | build_and_record_new_cond (UNLE_EXPR, op0, op1, | |
1023 | &edge_info->cond_equivalences[6]); | |
1024 | build_and_record_new_cond (UNGE_EXPR, op0, op1, | |
1025 | &edge_info->cond_equivalences[8]); | |
1026 | build_and_record_new_cond (UNEQ_EXPR, op0, op1, | |
1027 | &edge_info->cond_equivalences[10]); | |
1028 | build_and_record_new_cond (UNLT_EXPR, op0, op1, | |
1029 | &edge_info->cond_equivalences[12]); | |
1030 | build_and_record_new_cond (UNGT_EXPR, op0, op1, | |
1031 | &edge_info->cond_equivalences[14]); | |
1032 | break; | |
1033 | ||
1034 | case UNLT_EXPR: | |
1035 | case UNGT_EXPR: | |
1036 | edge_info->max_cond_equivalences = 8; | |
1037 | edge_info->cond_equivalences = XNEWVEC (tree, 8); | |
1038 | build_and_record_new_cond ((TREE_CODE (cond) == UNLT_EXPR | |
1039 | ? UNLE_EXPR : UNGE_EXPR), | |
1040 | op0, op1, &edge_info->cond_equivalences[4]); | |
1041 | build_and_record_new_cond (NE_EXPR, op0, op1, | |
1042 | &edge_info->cond_equivalences[6]); | |
1043 | break; | |
1044 | ||
1045 | case UNEQ_EXPR: | |
1046 | edge_info->max_cond_equivalences = 8; | |
1047 | edge_info->cond_equivalences = XNEWVEC (tree, 8); | |
1048 | build_and_record_new_cond (UNLE_EXPR, op0, op1, | |
1049 | &edge_info->cond_equivalences[4]); | |
1050 | build_and_record_new_cond (UNGE_EXPR, op0, op1, | |
1051 | &edge_info->cond_equivalences[6]); | |
1052 | break; | |
1053 | ||
1054 | case LTGT_EXPR: | |
1055 | edge_info->max_cond_equivalences = 8; | |
1056 | edge_info->cond_equivalences = XNEWVEC (tree, 8); | |
1057 | build_and_record_new_cond (NE_EXPR, op0, op1, | |
1058 | &edge_info->cond_equivalences[4]); | |
1059 | build_and_record_new_cond (ORDERED_EXPR, op0, op1, | |
1060 | &edge_info->cond_equivalences[6]); | |
1061 | break; | |
1062 | ||
1063 | default: | |
1064 | edge_info->max_cond_equivalences = 4; | |
1065 | edge_info->cond_equivalences = XNEWVEC (tree, 4); | |
1066 | break; | |
1067 | } | |
1068 | ||
1069 | /* Now store the original true and false conditions into the first | |
1070 | two slots. */ | |
1071 | edge_info->cond_equivalences[0] = cond; | |
1072 | edge_info->cond_equivalences[1] = boolean_true_node; | |
1073 | edge_info->cond_equivalences[2] = inverted; | |
1074 | edge_info->cond_equivalences[3] = boolean_false_node; | |
1075 | } | |
1076 | ||
1077 | /* A helper function for record_const_or_copy and record_equality. | |
1078 | Do the work of recording the value and undo info. */ | |
1079 | ||
1080 | static void | |
1081 | record_const_or_copy_1 (tree x, tree y, tree prev_x) | |
1082 | { | |
1083 | SSA_NAME_VALUE (x) = y; | |
1084 | ||
1085 | VEC_reserve (tree, heap, const_and_copies_stack, 2); | |
1086 | VEC_quick_push (tree, const_and_copies_stack, prev_x); | |
1087 | VEC_quick_push (tree, const_and_copies_stack, x); | |
1088 | } | |
1089 | ||
1090 | ||
1091 | /* Return the loop depth of the basic block of the defining statement of X. | |
1092 | This number should not be treated as absolutely correct because the loop | |
1093 | information may not be completely up-to-date when dom runs. However, it | |
1094 | will be relatively correct, and as more passes are taught to keep loop info | |
1095 | up to date, the result will become more and more accurate. */ | |
1096 | ||
1097 | int | |
1098 | loop_depth_of_name (tree x) | |
1099 | { | |
1100 | tree defstmt; | |
1101 | basic_block defbb; | |
1102 | ||
1103 | /* If it's not an SSA_NAME, we have no clue where the definition is. */ | |
1104 | if (TREE_CODE (x) != SSA_NAME) | |
1105 | return 0; | |
1106 | ||
1107 | /* Otherwise return the loop depth of the defining statement's bb. | |
1108 | Note that there may not actually be a bb for this statement, if the | |
1109 | ssa_name is live on entry. */ | |
1110 | defstmt = SSA_NAME_DEF_STMT (x); | |
1111 | defbb = bb_for_stmt (defstmt); | |
1112 | if (!defbb) | |
1113 | return 0; | |
1114 | ||
1115 | return defbb->loop_depth; | |
1116 | } | |
1117 | ||
1118 | ||
1119 | /* Record that X is equal to Y in const_and_copies. Record undo | |
1120 | information in the block-local vector. */ | |
1121 | ||
1122 | static void | |
1123 | record_const_or_copy (tree x, tree y) | |
1124 | { | |
1125 | tree prev_x = SSA_NAME_VALUE (x); | |
1126 | ||
1127 | if (TREE_CODE (y) == SSA_NAME) | |
1128 | { | |
1129 | tree tmp = SSA_NAME_VALUE (y); | |
1130 | if (tmp) | |
1131 | y = tmp; | |
1132 | } | |
1133 | ||
1134 | record_const_or_copy_1 (x, y, prev_x); | |
1135 | } | |
1136 | ||
1137 | /* Similarly, but assume that X and Y are the two operands of an EQ_EXPR. | |
1138 | This constrains the cases in which we may treat this as assignment. */ | |
1139 | ||
1140 | static void | |
1141 | record_equality (tree x, tree y) | |
1142 | { | |
1143 | tree prev_x = NULL, prev_y = NULL; | |
1144 | ||
1145 | if (TREE_CODE (x) == SSA_NAME) | |
1146 | prev_x = SSA_NAME_VALUE (x); | |
1147 | if (TREE_CODE (y) == SSA_NAME) | |
1148 | prev_y = SSA_NAME_VALUE (y); | |
1149 | ||
1150 | /* If one of the previous values is invariant, or invariant in more loops | |
1151 | (by depth), then use that. | |
1152 | Otherwise it doesn't matter which value we choose, just so | |
1153 | long as we canonicalize on one value. */ | |
1154 | if (TREE_INVARIANT (y)) | |
1155 | ; | |
1156 | else if (TREE_INVARIANT (x) || (loop_depth_of_name (x) <= loop_depth_of_name (y))) | |
1157 | prev_x = x, x = y, y = prev_x, prev_x = prev_y; | |
1158 | else if (prev_x && TREE_INVARIANT (prev_x)) | |
1159 | x = y, y = prev_x, prev_x = prev_y; | |
1160 | else if (prev_y && TREE_CODE (prev_y) != VALUE_HANDLE) | |
1161 | y = prev_y; | |
1162 | ||
1163 | /* After the swapping, we must have one SSA_NAME. */ | |
1164 | if (TREE_CODE (x) != SSA_NAME) | |
1165 | return; | |
1166 | ||
1167 | /* For IEEE, -0.0 == 0.0, so we don't necessarily know the sign of a | |
1168 | variable compared against zero. If we're honoring signed zeros, | |
1169 | then we cannot record this value unless we know that the value is | |
1170 | nonzero. */ | |
1171 | if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (x))) | |
1172 | && (TREE_CODE (y) != REAL_CST | |
1173 | || REAL_VALUES_EQUAL (dconst0, TREE_REAL_CST (y)))) | |
1174 | return; | |
1175 | ||
1176 | record_const_or_copy_1 (x, y, prev_x); | |
1177 | } | |
1178 | ||
1179 | /* Returns true when STMT is a simple iv increment. It detects the | |
1180 | following situation: | |
1181 | ||
1182 | i_1 = phi (..., i_2) | |
1183 | i_2 = i_1 +/- ... */ | |
1184 | ||
1185 | static bool | |
1186 | simple_iv_increment_p (tree stmt) | |
1187 | { | |
1188 | tree lhs, rhs, preinc, phi; | |
1189 | unsigned i; | |
1190 | ||
1191 | if (TREE_CODE (stmt) != GIMPLE_MODIFY_STMT) | |
1192 | return false; | |
1193 | ||
1194 | lhs = GIMPLE_STMT_OPERAND (stmt, 0); | |
1195 | if (TREE_CODE (lhs) != SSA_NAME) | |
1196 | return false; | |
1197 | ||
1198 | rhs = GIMPLE_STMT_OPERAND (stmt, 1); | |
1199 | ||
1200 | if (TREE_CODE (rhs) != PLUS_EXPR | |
1201 | && TREE_CODE (rhs) != MINUS_EXPR) | |
1202 | return false; | |
1203 | ||
1204 | preinc = TREE_OPERAND (rhs, 0); | |
1205 | if (TREE_CODE (preinc) != SSA_NAME) | |
1206 | return false; | |
1207 | ||
1208 | phi = SSA_NAME_DEF_STMT (preinc); | |
1209 | if (TREE_CODE (phi) != PHI_NODE) | |
1210 | return false; | |
1211 | ||
1212 | for (i = 0; i < (unsigned) PHI_NUM_ARGS (phi); i++) | |
1213 | if (PHI_ARG_DEF (phi, i) == lhs) | |
1214 | return true; | |
1215 | ||
1216 | return false; | |
1217 | } | |
1218 | ||
1219 | /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current | |
1220 | known value for that SSA_NAME (or NULL if no value is known). | |
1221 | ||
1222 | Propagate values from CONST_AND_COPIES into the PHI nodes of the | |
1223 | successors of BB. */ | |
1224 | ||
1225 | static void | |
1226 | cprop_into_successor_phis (basic_block bb) | |
1227 | { | |
1228 | edge e; | |
1229 | edge_iterator ei; | |
1230 | ||
1231 | FOR_EACH_EDGE (e, ei, bb->succs) | |
1232 | { | |
1233 | tree phi; | |
1234 | int indx; | |
1235 | ||
1236 | /* If this is an abnormal edge, then we do not want to copy propagate | |
1237 | into the PHI alternative associated with this edge. */ | |
1238 | if (e->flags & EDGE_ABNORMAL) | |
1239 | continue; | |
1240 | ||
1241 | phi = phi_nodes (e->dest); | |
1242 | if (! phi) | |
1243 | continue; | |
1244 | ||
1245 | indx = e->dest_idx; | |
1246 | for ( ; phi; phi = PHI_CHAIN (phi)) | |
1247 | { | |
1248 | tree new; | |
1249 | use_operand_p orig_p; | |
1250 | tree orig; | |
1251 | ||
1252 | /* The alternative may be associated with a constant, so verify | |
1253 | it is an SSA_NAME before doing anything with it. */ | |
1254 | orig_p = PHI_ARG_DEF_PTR (phi, indx); | |
1255 | orig = USE_FROM_PTR (orig_p); | |
1256 | if (TREE_CODE (orig) != SSA_NAME) | |
1257 | continue; | |
1258 | ||
1259 | /* If we have *ORIG_P in our constant/copy table, then replace | |
1260 | ORIG_P with its value in our constant/copy table. */ | |
1261 | new = SSA_NAME_VALUE (orig); | |
1262 | if (new | |
1263 | && new != orig | |
1264 | && (TREE_CODE (new) == SSA_NAME | |
1265 | || is_gimple_min_invariant (new)) | |
1266 | && may_propagate_copy (orig, new)) | |
1267 | propagate_value (orig_p, new); | |
1268 | } | |
1269 | } | |
1270 | } | |
1271 | ||
1272 | /* We have finished optimizing BB, record any information implied by | |
1273 | taking a specific outgoing edge from BB. */ | |
1274 | ||
1275 | static void | |
1276 | record_edge_info (basic_block bb) | |
1277 | { | |
1278 | block_stmt_iterator bsi = bsi_last (bb); | |
1279 | struct edge_info *edge_info; | |
1280 | ||
1281 | if (! bsi_end_p (bsi)) | |
1282 | { | |
1283 | tree stmt = bsi_stmt (bsi); | |
1284 | ||
1285 | if (stmt && TREE_CODE (stmt) == SWITCH_EXPR) | |
1286 | { | |
1287 | tree cond = SWITCH_COND (stmt); | |
1288 | ||
1289 | if (TREE_CODE (cond) == SSA_NAME) | |
1290 | { | |
1291 | tree labels = SWITCH_LABELS (stmt); | |
1292 | int i, n_labels = TREE_VEC_LENGTH (labels); | |
1293 | tree *info = XCNEWVEC (tree, last_basic_block); | |
1294 | edge e; | |
1295 | edge_iterator ei; | |
1296 | ||
1297 | for (i = 0; i < n_labels; i++) | |
1298 | { | |
1299 | tree label = TREE_VEC_ELT (labels, i); | |
1300 | basic_block target_bb = label_to_block (CASE_LABEL (label)); | |
1301 | ||
1302 | if (CASE_HIGH (label) | |
1303 | || !CASE_LOW (label) | |
1304 | || info[target_bb->index]) | |
1305 | info[target_bb->index] = error_mark_node; | |
1306 | else | |
1307 | info[target_bb->index] = label; | |
1308 | } | |
1309 | ||
1310 | FOR_EACH_EDGE (e, ei, bb->succs) | |
1311 | { | |
1312 | basic_block target_bb = e->dest; | |
1313 | tree node = info[target_bb->index]; | |
1314 | ||
1315 | if (node != NULL && node != error_mark_node) | |
1316 | { | |
1317 | tree x = fold_convert (TREE_TYPE (cond), CASE_LOW (node)); | |
1318 | edge_info = allocate_edge_info (e); | |
1319 | edge_info->lhs = cond; | |
1320 | edge_info->rhs = x; | |
1321 | } | |
1322 | } | |
1323 | free (info); | |
1324 | } | |
1325 | } | |
1326 | ||
1327 | /* A COND_EXPR may create equivalences too. */ | |
1328 | if (stmt && TREE_CODE (stmt) == COND_EXPR) | |
1329 | { | |
1330 | tree cond = COND_EXPR_COND (stmt); | |
1331 | edge true_edge; | |
1332 | edge false_edge; | |
1333 | ||
1334 | extract_true_false_edges_from_block (bb, &true_edge, &false_edge); | |
1335 | ||
1336 | /* If the conditional is a single variable 'X', record 'X = 1' | |
1337 | for the true edge and 'X = 0' on the false edge. */ | |
1338 | if (SSA_VAR_P (cond)) | |
1339 | { | |
1340 | struct edge_info *edge_info; | |
1341 | ||
1342 | edge_info = allocate_edge_info (true_edge); | |
1343 | edge_info->lhs = cond; | |
1344 | edge_info->rhs = constant_boolean_node (1, TREE_TYPE (cond)); | |
1345 | ||
1346 | edge_info = allocate_edge_info (false_edge); | |
1347 | edge_info->lhs = cond; | |
1348 | edge_info->rhs = constant_boolean_node (0, TREE_TYPE (cond)); | |
1349 | } | |
1350 | /* Equality tests may create one or two equivalences. */ | |
1351 | else if (COMPARISON_CLASS_P (cond)) | |
1352 | { | |
1353 | tree op0 = TREE_OPERAND (cond, 0); | |
1354 | tree op1 = TREE_OPERAND (cond, 1); | |
1355 | ||
1356 | /* Special case comparing booleans against a constant as we | |
1357 | know the value of OP0 on both arms of the branch. i.e., we | |
1358 | can record an equivalence for OP0 rather than COND. */ | |
1359 | if ((TREE_CODE (cond) == EQ_EXPR || TREE_CODE (cond) == NE_EXPR) | |
1360 | && TREE_CODE (op0) == SSA_NAME | |
1361 | && TREE_CODE (TREE_TYPE (op0)) == BOOLEAN_TYPE | |
1362 | && is_gimple_min_invariant (op1)) | |
1363 | { | |
1364 | if (TREE_CODE (cond) == EQ_EXPR) | |
1365 | { | |
1366 | edge_info = allocate_edge_info (true_edge); | |
1367 | edge_info->lhs = op0; | |
1368 | edge_info->rhs = (integer_zerop (op1) | |
1369 | ? boolean_false_node | |
1370 | : boolean_true_node); | |
1371 | ||
1372 | edge_info = allocate_edge_info (false_edge); | |
1373 | edge_info->lhs = op0; | |
1374 | edge_info->rhs = (integer_zerop (op1) | |
1375 | ? boolean_true_node | |
1376 | : boolean_false_node); | |
1377 | } | |
1378 | else | |
1379 | { | |
1380 | edge_info = allocate_edge_info (true_edge); | |
1381 | edge_info->lhs = op0; | |
1382 | edge_info->rhs = (integer_zerop (op1) | |
1383 | ? boolean_true_node | |
1384 | : boolean_false_node); | |
1385 | ||
1386 | edge_info = allocate_edge_info (false_edge); | |
1387 | edge_info->lhs = op0; | |
1388 | edge_info->rhs = (integer_zerop (op1) | |
1389 | ? boolean_false_node | |
1390 | : boolean_true_node); | |
1391 | } | |
1392 | } | |
1393 | ||
1394 | else if (is_gimple_min_invariant (op0) | |
1395 | && (TREE_CODE (op1) == SSA_NAME | |
1396 | || is_gimple_min_invariant (op1))) | |
1397 | { | |
1398 | tree inverted = invert_truthvalue (cond); | |
1399 | struct edge_info *edge_info; | |
1400 | ||
1401 | edge_info = allocate_edge_info (true_edge); | |
1402 | record_conditions (edge_info, cond, inverted); | |
1403 | ||
1404 | if (TREE_CODE (cond) == EQ_EXPR) | |
1405 | { | |
1406 | edge_info->lhs = op1; | |
1407 | edge_info->rhs = op0; | |
1408 | } | |
1409 | ||
1410 | edge_info = allocate_edge_info (false_edge); | |
1411 | record_conditions (edge_info, inverted, cond); | |
1412 | ||
1413 | if (TREE_CODE (cond) == NE_EXPR) | |
1414 | { | |
1415 | edge_info->lhs = op1; | |
1416 | edge_info->rhs = op0; | |
1417 | } | |
1418 | } | |
1419 | ||
1420 | else if (TREE_CODE (op0) == SSA_NAME | |
1421 | && (is_gimple_min_invariant (op1) | |
1422 | || TREE_CODE (op1) == SSA_NAME)) | |
1423 | { | |
1424 | tree inverted = invert_truthvalue (cond); | |
1425 | struct edge_info *edge_info; | |
1426 | ||
1427 | edge_info = allocate_edge_info (true_edge); | |
1428 | record_conditions (edge_info, cond, inverted); | |
1429 | ||
1430 | if (TREE_CODE (cond) == EQ_EXPR) | |
1431 | { | |
1432 | edge_info->lhs = op0; | |
1433 | edge_info->rhs = op1; | |
1434 | } | |
1435 | ||
1436 | edge_info = allocate_edge_info (false_edge); | |
1437 | record_conditions (edge_info, inverted, cond); | |
1438 | ||
1439 | if (TREE_CODE (cond) == NE_EXPR) | |
1440 | { | |
1441 | edge_info->lhs = op0; | |
1442 | edge_info->rhs = op1; | |
1443 | } | |
1444 | } | |
1445 | } | |
1446 | ||
1447 | /* ??? TRUTH_NOT_EXPR can create an equivalence too. */ | |
1448 | } | |
1449 | } | |
1450 | } | |
1451 | ||
1452 | /* Propagate information from BB to its outgoing edges. | |
1453 | ||
1454 | This can include equivalency information implied by control statements | |
1455 | at the end of BB and const/copy propagation into PHIs in BB's | |
1456 | successor blocks. */ | |
1457 | ||
1458 | static void | |
1459 | propagate_to_outgoing_edges (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED, | |
1460 | basic_block bb) | |
1461 | { | |
1462 | record_edge_info (bb); | |
1463 | cprop_into_successor_phis (bb); | |
1464 | } | |
1465 | ||
1466 | /* Search for redundant computations in STMT. If any are found, then | |
1467 | replace them with the variable holding the result of the computation. | |
1468 | ||
1469 | If safe, record this expression into the available expression hash | |
1470 | table. */ | |
1471 | ||
1472 | static bool | |
1473 | eliminate_redundant_computations (tree stmt) | |
1474 | { | |
1475 | tree *expr_p, def = NULL_TREE; | |
1476 | bool insert = true; | |
1477 | tree cached_lhs; | |
1478 | bool retval = false; | |
1479 | bool modify_expr_p = false; | |
1480 | ||
1481 | if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT) | |
1482 | def = GIMPLE_STMT_OPERAND (stmt, 0); | |
1483 | ||
1484 | /* Certain expressions on the RHS can be optimized away, but can not | |
1485 | themselves be entered into the hash tables. */ | |
1486 | if (! def | |
1487 | || TREE_CODE (def) != SSA_NAME | |
1488 | || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def) | |
1489 | || !ZERO_SSA_OPERANDS (stmt, SSA_OP_VDEF) | |
1490 | /* Do not record equivalences for increments of ivs. This would create | |
1491 | overlapping live ranges for a very questionable gain. */ | |
1492 | || simple_iv_increment_p (stmt)) | |
1493 | insert = false; | |
1494 | ||
1495 | /* Check if the expression has been computed before. */ | |
1496 | cached_lhs = lookup_avail_expr (stmt, insert); | |
1497 | ||
1498 | opt_stats.num_exprs_considered++; | |
1499 | ||
1500 | /* Get a pointer to the expression we are trying to optimize. */ | |
1501 | if (TREE_CODE (stmt) == COND_EXPR) | |
1502 | expr_p = &COND_EXPR_COND (stmt); | |
1503 | else if (TREE_CODE (stmt) == SWITCH_EXPR) | |
1504 | expr_p = &SWITCH_COND (stmt); | |
1505 | else if (TREE_CODE (stmt) == RETURN_EXPR && TREE_OPERAND (stmt, 0)) | |
1506 | { | |
1507 | expr_p = &GIMPLE_STMT_OPERAND (TREE_OPERAND (stmt, 0), 1); | |
1508 | modify_expr_p = true; | |
1509 | } | |
1510 | else | |
1511 | { | |
1512 | expr_p = &GENERIC_TREE_OPERAND (stmt, 1); | |
1513 | modify_expr_p = true; | |
1514 | } | |
1515 | ||
1516 | /* It is safe to ignore types here since we have already done | |
1517 | type checking in the hashing and equality routines. In fact | |
1518 | type checking here merely gets in the way of constant | |
1519 | propagation. Also, make sure that it is safe to propagate | |
1520 | CACHED_LHS into *EXPR_P. */ | |
1521 | if (cached_lhs | |
1522 | && ((TREE_CODE (cached_lhs) != SSA_NAME | |
1523 | && (modify_expr_p | |
1524 | || tree_ssa_useless_type_conversion_1 (TREE_TYPE (*expr_p), | |
1525 | TREE_TYPE (cached_lhs)))) | |
1526 | || may_propagate_copy (*expr_p, cached_lhs))) | |
1527 | { | |
1528 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
1529 | { | |
1530 | fprintf (dump_file, " Replaced redundant expr '"); | |
1531 | print_generic_expr (dump_file, *expr_p, dump_flags); | |
1532 | fprintf (dump_file, "' with '"); | |
1533 | print_generic_expr (dump_file, cached_lhs, dump_flags); | |
1534 | fprintf (dump_file, "'\n"); | |
1535 | } | |
1536 | ||
1537 | opt_stats.num_re++; | |
1538 | ||
1539 | #if defined ENABLE_CHECKING | |
1540 | gcc_assert (TREE_CODE (cached_lhs) == SSA_NAME | |
1541 | || is_gimple_min_invariant (cached_lhs)); | |
1542 | #endif | |
1543 | ||
1544 | if (TREE_CODE (cached_lhs) == ADDR_EXPR | |
1545 | || (POINTER_TYPE_P (TREE_TYPE (*expr_p)) | |
1546 | && is_gimple_min_invariant (cached_lhs))) | |
1547 | retval = true; | |
1548 | ||
1549 | if (modify_expr_p | |
1550 | && !tree_ssa_useless_type_conversion_1 (TREE_TYPE (*expr_p), | |
1551 | TREE_TYPE (cached_lhs))) | |
1552 | cached_lhs = fold_convert (TREE_TYPE (*expr_p), cached_lhs); | |
1553 | ||
1554 | propagate_tree_value (expr_p, cached_lhs); | |
1555 | mark_stmt_modified (stmt); | |
1556 | } | |
1557 | return retval; | |
1558 | } | |
1559 | ||
1560 | /* STMT, a GIMPLE_MODIFY_STMT, may create certain equivalences, in either | |
1561 | the available expressions table or the const_and_copies table. | |
1562 | Detect and record those equivalences. */ | |
1563 | ||
1564 | static void | |
1565 | record_equivalences_from_stmt (tree stmt, int may_optimize_p, stmt_ann_t ann) | |
1566 | { | |
1567 | tree lhs = GIMPLE_STMT_OPERAND (stmt, 0); | |
1568 | enum tree_code lhs_code = TREE_CODE (lhs); | |
1569 | ||
1570 | if (lhs_code == SSA_NAME) | |
1571 | { | |
1572 | tree rhs = GIMPLE_STMT_OPERAND (stmt, 1); | |
1573 | ||
1574 | /* Strip away any useless type conversions. */ | |
1575 | STRIP_USELESS_TYPE_CONVERSION (rhs); | |
1576 | ||
1577 | /* If the RHS of the assignment is a constant or another variable that | |
1578 | may be propagated, register it in the CONST_AND_COPIES table. We | |
1579 | do not need to record unwind data for this, since this is a true | |
1580 | assignment and not an equivalence inferred from a comparison. All | |
1581 | uses of this ssa name are dominated by this assignment, so unwinding | |
1582 | just costs time and space. */ | |
1583 | if (may_optimize_p | |
1584 | && (TREE_CODE (rhs) == SSA_NAME | |
1585 | || is_gimple_min_invariant (rhs))) | |
1586 | SSA_NAME_VALUE (lhs) = rhs; | |
1587 | } | |
1588 | ||
1589 | /* A memory store, even an aliased store, creates a useful | |
1590 | equivalence. By exchanging the LHS and RHS, creating suitable | |
1591 | vops and recording the result in the available expression table, | |
1592 | we may be able to expose more redundant loads. */ | |
1593 | if (!ann->has_volatile_ops | |
1594 | && stmt_references_memory_p (stmt) | |
1595 | && (TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1)) == SSA_NAME | |
1596 | || is_gimple_min_invariant (GIMPLE_STMT_OPERAND (stmt, 1))) | |
1597 | && !is_gimple_reg (lhs)) | |
1598 | { | |
1599 | tree rhs = GIMPLE_STMT_OPERAND (stmt, 1); | |
1600 | tree new; | |
1601 | ||
1602 | /* FIXME: If the LHS of the assignment is a bitfield and the RHS | |
1603 | is a constant, we need to adjust the constant to fit into the | |
1604 | type of the LHS. If the LHS is a bitfield and the RHS is not | |
1605 | a constant, then we can not record any equivalences for this | |
1606 | statement since we would need to represent the widening or | |
1607 | narrowing of RHS. This fixes gcc.c-torture/execute/921016-1.c | |
1608 | and should not be necessary if GCC represented bitfields | |
1609 | properly. */ | |
1610 | if (lhs_code == COMPONENT_REF | |
1611 | && DECL_BIT_FIELD (TREE_OPERAND (lhs, 1))) | |
1612 | { | |
1613 | if (TREE_CONSTANT (rhs)) | |
1614 | rhs = widen_bitfield (rhs, TREE_OPERAND (lhs, 1), lhs); | |
1615 | else | |
1616 | rhs = NULL; | |
1617 | ||
1618 | /* If the value overflowed, then we can not use this equivalence. */ | |
1619 | if (rhs && ! is_gimple_min_invariant (rhs)) | |
1620 | rhs = NULL; | |
1621 | } | |
1622 | ||
1623 | if (rhs) | |
1624 | { | |
1625 | /* Build a new statement with the RHS and LHS exchanged. */ | |
1626 | new = build_gimple_modify_stmt (rhs, lhs); | |
1627 | ||
1628 | create_ssa_artificial_load_stmt (new, stmt); | |
1629 | ||
1630 | /* Finally enter the statement into the available expression | |
1631 | table. */ | |
1632 | lookup_avail_expr (new, true); | |
1633 | } | |
1634 | } | |
1635 | } | |
1636 | ||
1637 | /* Replace *OP_P in STMT with any known equivalent value for *OP_P from | |
1638 | CONST_AND_COPIES. */ | |
1639 | ||
1640 | static bool | |
1641 | cprop_operand (tree stmt, use_operand_p op_p) | |
1642 | { | |
1643 | bool may_have_exposed_new_symbols = false; | |
1644 | tree val; | |
1645 | tree op = USE_FROM_PTR (op_p); | |
1646 | ||
1647 | /* If the operand has a known constant value or it is known to be a | |
1648 | copy of some other variable, use the value or copy stored in | |
1649 | CONST_AND_COPIES. */ | |
1650 | val = SSA_NAME_VALUE (op); | |
1651 | if (val && val != op && TREE_CODE (val) != VALUE_HANDLE) | |
1652 | { | |
1653 | tree op_type, val_type; | |
1654 | ||
1655 | /* Do not change the base variable in the virtual operand | |
1656 | tables. That would make it impossible to reconstruct | |
1657 | the renamed virtual operand if we later modify this | |
1658 | statement. Also only allow the new value to be an SSA_NAME | |
1659 | for propagation into virtual operands. */ | |
1660 | if (!is_gimple_reg (op) | |
1661 | && (TREE_CODE (val) != SSA_NAME | |
1662 | || is_gimple_reg (val) | |
1663 | || get_virtual_var (val) != get_virtual_var (op))) | |
1664 | return false; | |
1665 | ||
1666 | /* Do not replace hard register operands in asm statements. */ | |
1667 | if (TREE_CODE (stmt) == ASM_EXPR | |
1668 | && !may_propagate_copy_into_asm (op)) | |
1669 | return false; | |
1670 | ||
1671 | /* Get the toplevel type of each operand. */ | |
1672 | op_type = TREE_TYPE (op); | |
1673 | val_type = TREE_TYPE (val); | |
1674 | ||
1675 | /* While both types are pointers, get the type of the object | |
1676 | pointed to. */ | |
1677 | while (POINTER_TYPE_P (op_type) && POINTER_TYPE_P (val_type)) | |
1678 | { | |
1679 | op_type = TREE_TYPE (op_type); | |
1680 | val_type = TREE_TYPE (val_type); | |
1681 | } | |
1682 | ||
1683 | /* Make sure underlying types match before propagating a constant by | |
1684 | converting the constant to the proper type. Note that convert may | |
1685 | return a non-gimple expression, in which case we ignore this | |
1686 | propagation opportunity. */ | |
1687 | if (TREE_CODE (val) != SSA_NAME) | |
1688 | { | |
1689 | if (!lang_hooks.types_compatible_p (op_type, val_type)) | |
1690 | { | |
1691 | val = fold_convert (TREE_TYPE (op), val); | |
1692 | if (!is_gimple_min_invariant (val)) | |
1693 | return false; | |
1694 | } | |
1695 | } | |
1696 | ||
1697 | /* Certain operands are not allowed to be copy propagated due | |
1698 | to their interaction with exception handling and some GCC | |
1699 | extensions. */ | |
1700 | else if (!may_propagate_copy (op, val)) | |
1701 | return false; | |
1702 | ||
1703 | /* Do not propagate copies if the propagated value is at a deeper loop | |
1704 | depth than the propagatee. Otherwise, this may move loop variant | |
1705 | variables outside of their loops and prevent coalescing | |
1706 | opportunities. If the value was loop invariant, it will be hoisted | |
1707 | by LICM and exposed for copy propagation. */ | |
1708 | if (loop_depth_of_name (val) > loop_depth_of_name (op)) | |
1709 | return false; | |
1710 | ||
1711 | /* Dump details. */ | |
1712 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
1713 | { | |
1714 | fprintf (dump_file, " Replaced '"); | |
1715 | print_generic_expr (dump_file, op, dump_flags); | |
1716 | fprintf (dump_file, "' with %s '", | |
1717 | (TREE_CODE (val) != SSA_NAME ? "constant" : "variable")); | |
1718 | print_generic_expr (dump_file, val, dump_flags); | |
1719 | fprintf (dump_file, "'\n"); | |
1720 | } | |
1721 | ||
1722 | /* If VAL is an ADDR_EXPR or a constant of pointer type, note | |
1723 | that we may have exposed a new symbol for SSA renaming. */ | |
1724 | if (TREE_CODE (val) == ADDR_EXPR | |
1725 | || (POINTER_TYPE_P (TREE_TYPE (op)) | |
1726 | && is_gimple_min_invariant (val))) | |
1727 | may_have_exposed_new_symbols = true; | |
1728 | ||
1729 | if (TREE_CODE (val) != SSA_NAME) | |
1730 | opt_stats.num_const_prop++; | |
1731 | else | |
1732 | opt_stats.num_copy_prop++; | |
1733 | ||
1734 | propagate_value (op_p, val); | |
1735 | ||
1736 | /* And note that we modified this statement. This is now | |
1737 | safe, even if we changed virtual operands since we will | |
1738 | rescan the statement and rewrite its operands again. */ | |
1739 | mark_stmt_modified (stmt); | |
1740 | } | |
1741 | return may_have_exposed_new_symbols; | |
1742 | } | |
1743 | ||
1744 | /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current | |
1745 | known value for that SSA_NAME (or NULL if no value is known). | |
1746 | ||
1747 | Propagate values from CONST_AND_COPIES into the uses, vuses and | |
1748 | vdef_ops of STMT. */ | |
1749 | ||
1750 | static bool | |
1751 | cprop_into_stmt (tree stmt) | |
1752 | { | |
1753 | bool may_have_exposed_new_symbols = false; | |
1754 | use_operand_p op_p; | |
1755 | ssa_op_iter iter; | |
1756 | ||
1757 | FOR_EACH_SSA_USE_OPERAND (op_p, stmt, iter, SSA_OP_ALL_USES) | |
1758 | { | |
1759 | if (TREE_CODE (USE_FROM_PTR (op_p)) == SSA_NAME) | |
1760 | may_have_exposed_new_symbols |= cprop_operand (stmt, op_p); | |
1761 | } | |
1762 | ||
1763 | return may_have_exposed_new_symbols; | |
1764 | } | |
1765 | ||
1766 | ||
1767 | /* Optimize the statement pointed to by iterator SI. | |
1768 | ||
1769 | We try to perform some simplistic global redundancy elimination and | |
1770 | constant propagation: | |
1771 | ||
1772 | 1- To detect global redundancy, we keep track of expressions that have | |
1773 | been computed in this block and its dominators. If we find that the | |
1774 | same expression is computed more than once, we eliminate repeated | |
1775 | computations by using the target of the first one. | |
1776 | ||
1777 | 2- Constant values and copy assignments. This is used to do very | |
1778 | simplistic constant and copy propagation. When a constant or copy | |
1779 | assignment is found, we map the value on the RHS of the assignment to | |
1780 | the variable in the LHS in the CONST_AND_COPIES table. */ | |
1781 | ||
1782 | static void | |
1783 | optimize_stmt (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED, | |
1784 | basic_block bb, block_stmt_iterator si) | |
1785 | { | |
1786 | stmt_ann_t ann; | |
1787 | tree stmt, old_stmt; | |
1788 | bool may_optimize_p; | |
1789 | bool may_have_exposed_new_symbols = false; | |
1790 | ||
1791 | old_stmt = stmt = bsi_stmt (si); | |
1792 | ||
1793 | if (TREE_CODE (stmt) == COND_EXPR) | |
1794 | canonicalize_comparison (stmt); | |
1795 | ||
1796 | update_stmt_if_modified (stmt); | |
1797 | ann = stmt_ann (stmt); | |
1798 | opt_stats.num_stmts++; | |
1799 | may_have_exposed_new_symbols = false; | |
1800 | push_stmt_changes (bsi_stmt_ptr (si)); | |
1801 | ||
1802 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
1803 | { | |
1804 | fprintf (dump_file, "Optimizing statement "); | |
1805 | print_generic_stmt (dump_file, stmt, TDF_SLIM); | |
1806 | } | |
1807 | ||
1808 | /* Const/copy propagate into USES, VUSES and the RHS of VDEFs. */ | |
1809 | may_have_exposed_new_symbols = cprop_into_stmt (stmt); | |
1810 | ||
1811 | /* If the statement has been modified with constant replacements, | |
1812 | fold its RHS before checking for redundant computations. */ | |
1813 | if (ann->modified) | |
1814 | { | |
1815 | tree rhs; | |
1816 | ||
1817 | /* Try to fold the statement making sure that STMT is kept | |
1818 | up to date. */ | |
1819 | if (fold_stmt (bsi_stmt_ptr (si))) | |
1820 | { | |
1821 | stmt = bsi_stmt (si); | |
1822 | ann = stmt_ann (stmt); | |
1823 | ||
1824 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
1825 | { | |
1826 | fprintf (dump_file, " Folded to: "); | |
1827 | print_generic_stmt (dump_file, stmt, TDF_SLIM); | |
1828 | } | |
1829 | } | |
1830 | ||
1831 | rhs = get_rhs (stmt); | |
1832 | if (rhs && TREE_CODE (rhs) == ADDR_EXPR) | |
1833 | recompute_tree_invariant_for_addr_expr (rhs); | |
1834 | ||
1835 | /* Constant/copy propagation above may change the set of | |
1836 | virtual operands associated with this statement. Folding | |
1837 | may remove the need for some virtual operands. | |
1838 | ||
1839 | Indicate we will need to rescan and rewrite the statement. */ | |
1840 | may_have_exposed_new_symbols = true; | |
1841 | } | |
1842 | ||
1843 | /* Check for redundant computations. Do this optimization only | |
1844 | for assignments that have no volatile ops and conditionals. */ | |
1845 | may_optimize_p = (!ann->has_volatile_ops | |
1846 | && ((TREE_CODE (stmt) == RETURN_EXPR | |
1847 | && TREE_OPERAND (stmt, 0) | |
1848 | && TREE_CODE (TREE_OPERAND (stmt, 0)) | |
1849 | == GIMPLE_MODIFY_STMT | |
1850 | && ! (TREE_SIDE_EFFECTS | |
1851 | (GIMPLE_STMT_OPERAND | |
1852 | (TREE_OPERAND (stmt, 0), 1)))) | |
1853 | || (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT | |
1854 | && ! TREE_SIDE_EFFECTS (GIMPLE_STMT_OPERAND (stmt, | |
1855 | 1))) | |
1856 | || TREE_CODE (stmt) == COND_EXPR | |
1857 | || TREE_CODE (stmt) == SWITCH_EXPR)); | |
1858 | ||
1859 | if (may_optimize_p) | |
1860 | may_have_exposed_new_symbols |= eliminate_redundant_computations (stmt); | |
1861 | ||
1862 | /* Record any additional equivalences created by this statement. */ | |
1863 | if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT) | |
1864 | record_equivalences_from_stmt (stmt, may_optimize_p, ann); | |
1865 | ||
1866 | /* If STMT is a COND_EXPR and it was modified, then we may know | |
1867 | where it goes. If that is the case, then mark the CFG as altered. | |
1868 | ||
1869 | This will cause us to later call remove_unreachable_blocks and | |
1870 | cleanup_tree_cfg when it is safe to do so. It is not safe to | |
1871 | clean things up here since removal of edges and such can trigger | |
1872 | the removal of PHI nodes, which in turn can release SSA_NAMEs to | |
1873 | the manager. | |
1874 | ||
1875 | That's all fine and good, except that once SSA_NAMEs are released | |
1876 | to the manager, we must not call create_ssa_name until all references | |
1877 | to released SSA_NAMEs have been eliminated. | |
1878 | ||
1879 | All references to the deleted SSA_NAMEs can not be eliminated until | |
1880 | we remove unreachable blocks. | |
1881 | ||
1882 | We can not remove unreachable blocks until after we have completed | |
1883 | any queued jump threading. | |
1884 | ||
1885 | We can not complete any queued jump threads until we have taken | |
1886 | appropriate variables out of SSA form. Taking variables out of | |
1887 | SSA form can call create_ssa_name and thus we lose. | |
1888 | ||
1889 | Ultimately I suspect we're going to need to change the interface | |
1890 | into the SSA_NAME manager. */ | |
1891 | if (ann->modified) | |
1892 | { | |
1893 | tree val = NULL; | |
1894 | ||
1895 | if (TREE_CODE (stmt) == COND_EXPR) | |
1896 | val = COND_EXPR_COND (stmt); | |
1897 | else if (TREE_CODE (stmt) == SWITCH_EXPR) | |
1898 | val = SWITCH_COND (stmt); | |
1899 | ||
1900 | if (val && TREE_CODE (val) == INTEGER_CST && find_taken_edge (bb, val)) | |
1901 | cfg_altered = true; | |
1902 | ||
1903 | /* If we simplified a statement in such a way as to be shown that it | |
1904 | cannot trap, update the eh information and the cfg to match. */ | |
1905 | if (maybe_clean_or_replace_eh_stmt (old_stmt, stmt)) | |
1906 | { | |
1907 | bitmap_set_bit (need_eh_cleanup, bb->index); | |
1908 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
1909 | fprintf (dump_file, " Flagged to clear EH edges.\n"); | |
1910 | } | |
1911 | } | |
1912 | ||
1913 | if (may_have_exposed_new_symbols) | |
1914 | { | |
1915 | /* Queue the statement to be re-scanned after all the | |
1916 | AVAIL_EXPRS have been processed. The change buffer stack for | |
1917 | all the pushed statements will be processed when this queue | |
1918 | is emptied. */ | |
1919 | VEC_safe_push (tree_p, heap, stmts_to_rescan, bsi_stmt_ptr (si)); | |
1920 | } | |
1921 | else | |
1922 | { | |
1923 | /* Otherwise, just discard the recently pushed change buffer. If | |
1924 | not, the STMTS_TO_RESCAN queue will get out of synch with the | |
1925 | change buffer stack. */ | |
1926 | discard_stmt_changes (bsi_stmt_ptr (si)); | |
1927 | } | |
1928 | } | |
1929 | ||
1930 | /* Search for an existing instance of STMT in the AVAIL_EXPRS table. If | |
1931 | found, return its LHS. Otherwise insert STMT in the table and return | |
1932 | NULL_TREE. | |
1933 | ||
1934 | Also, when an expression is first inserted in the AVAIL_EXPRS table, it | |
1935 | is also added to the stack pointed to by BLOCK_AVAIL_EXPRS_P, so that they | |
1936 | can be removed when we finish processing this block and its children. | |
1937 | ||
1938 | NOTE: This function assumes that STMT is a GIMPLE_MODIFY_STMT node that | |
1939 | contains no CALL_EXPR on its RHS and makes no volatile nor | |
1940 | aliased references. */ | |
1941 | ||
1942 | static tree | |
1943 | lookup_avail_expr (tree stmt, bool insert) | |
1944 | { | |
1945 | void **slot; | |
1946 | tree lhs; | |
1947 | tree temp; | |
1948 | struct expr_hash_elt *element = XNEW (struct expr_hash_elt); | |
1949 | ||
1950 | lhs = TREE_CODE (stmt) == GIMPLE_MODIFY_STMT | |
1951 | ? GIMPLE_STMT_OPERAND (stmt, 0) : NULL; | |
1952 | ||
1953 | initialize_hash_element (stmt, lhs, element); | |
1954 | ||
1955 | /* Don't bother remembering constant assignments and copy operations. | |
1956 | Constants and copy operations are handled by the constant/copy propagator | |
1957 | in optimize_stmt. */ | |
1958 | if (TREE_CODE (element->rhs) == SSA_NAME | |
1959 | || is_gimple_min_invariant (element->rhs)) | |
1960 | { | |
1961 | free (element); | |
1962 | return NULL_TREE; | |
1963 | } | |
1964 | ||
1965 | /* Finally try to find the expression in the main expression hash table. */ | |
1966 | slot = htab_find_slot_with_hash (avail_exprs, element, element->hash, | |
1967 | (insert ? INSERT : NO_INSERT)); | |
1968 | if (slot == NULL) | |
1969 | { | |
1970 | free (element); | |
1971 | return NULL_TREE; | |
1972 | } | |
1973 | ||
1974 | if (*slot == NULL) | |
1975 | { | |
1976 | *slot = (void *) element; | |
1977 | VEC_safe_push (tree, heap, avail_exprs_stack, | |
1978 | stmt ? stmt : element->rhs); | |
1979 | return NULL_TREE; | |
1980 | } | |
1981 | ||
1982 | /* Extract the LHS of the assignment so that it can be used as the current | |
1983 | definition of another variable. */ | |
1984 | lhs = ((struct expr_hash_elt *)*slot)->lhs; | |
1985 | ||
1986 | /* See if the LHS appears in the CONST_AND_COPIES table. If it does, then | |
1987 | use the value from the const_and_copies table. */ | |
1988 | if (TREE_CODE (lhs) == SSA_NAME) | |
1989 | { | |
1990 | temp = SSA_NAME_VALUE (lhs); | |
1991 | if (temp && TREE_CODE (temp) != VALUE_HANDLE) | |
1992 | lhs = temp; | |
1993 | } | |
1994 | ||
1995 | free (element); | |
1996 | return lhs; | |
1997 | } | |
1998 | ||
1999 | /* Hashing and equality functions for AVAIL_EXPRS. The table stores | |
2000 | GIMPLE_MODIFY_STMT statements. We compute a value number for expressions | |
2001 | using the code of the expression and the SSA numbers of its operands. */ | |
2002 | ||
2003 | static hashval_t | |
2004 | avail_expr_hash (const void *p) | |
2005 | { | |
2006 | tree stmt = ((struct expr_hash_elt *)p)->stmt; | |
2007 | tree rhs = ((struct expr_hash_elt *)p)->rhs; | |
2008 | tree vuse; | |
2009 | ssa_op_iter iter; | |
2010 | hashval_t val = 0; | |
2011 | ||
2012 | /* iterative_hash_expr knows how to deal with any expression and | |
2013 | deals with commutative operators as well, so just use it instead | |
2014 | of duplicating such complexities here. */ | |
2015 | val = iterative_hash_expr (rhs, val); | |
2016 | ||
2017 | /* If the hash table entry is not associated with a statement, then we | |
2018 | can just hash the expression and not worry about virtual operands | |
2019 | and such. */ | |
2020 | if (!stmt || !stmt_ann (stmt)) | |
2021 | return val; | |
2022 | ||
2023 | /* Add the SSA version numbers of every vuse operand. This is important | |
2024 | because compound variables like arrays are not renamed in the | |
2025 | operands. Rather, the rename is done on the virtual variable | |
2026 | representing all the elements of the array. */ | |
2027 | FOR_EACH_SSA_TREE_OPERAND (vuse, stmt, iter, SSA_OP_VUSE) | |
2028 | val = iterative_hash_expr (vuse, val); | |
2029 | ||
2030 | return val; | |
2031 | } | |
2032 | ||
2033 | static hashval_t | |
2034 | real_avail_expr_hash (const void *p) | |
2035 | { | |
2036 | return ((const struct expr_hash_elt *)p)->hash; | |
2037 | } | |
2038 | ||
2039 | static int | |
2040 | avail_expr_eq (const void *p1, const void *p2) | |
2041 | { | |
2042 | tree stmt1 = ((struct expr_hash_elt *)p1)->stmt; | |
2043 | tree rhs1 = ((struct expr_hash_elt *)p1)->rhs; | |
2044 | tree stmt2 = ((struct expr_hash_elt *)p2)->stmt; | |
2045 | tree rhs2 = ((struct expr_hash_elt *)p2)->rhs; | |
2046 | ||
2047 | /* If they are the same physical expression, return true. */ | |
2048 | if (rhs1 == rhs2 && stmt1 == stmt2) | |
2049 | return true; | |
2050 | ||
2051 | /* If their codes are not equal, then quit now. */ | |
2052 | if (TREE_CODE (rhs1) != TREE_CODE (rhs2)) | |
2053 | return false; | |
2054 | ||
2055 | /* In case of a collision, both RHS have to be identical and have the | |
2056 | same VUSE operands. */ | |
2057 | if ((TREE_TYPE (rhs1) == TREE_TYPE (rhs2) | |
2058 | || lang_hooks.types_compatible_p (TREE_TYPE (rhs1), TREE_TYPE (rhs2))) | |
2059 | && operand_equal_p (rhs1, rhs2, OEP_PURE_SAME)) | |
2060 | { | |
2061 | bool ret = compare_ssa_operands_equal (stmt1, stmt2, SSA_OP_VUSE); | |
2062 | gcc_assert (!ret || ((struct expr_hash_elt *)p1)->hash | |
2063 | == ((struct expr_hash_elt *)p2)->hash); | |
2064 | return ret; | |
2065 | } | |
2066 | ||
2067 | return false; | |
2068 | } | |
2069 | ||
2070 | /* PHI-ONLY copy and constant propagation. This pass is meant to clean | |
2071 | up degenerate PHIs created by or exposed by jump threading. */ | |
2072 | ||
2073 | /* Given PHI, return its RHS if the PHI is a degenerate, otherwise return | |
2074 | NULL. */ | |
2075 | ||
2076 | static tree | |
2077 | degenerate_phi_result (tree phi) | |
2078 | { | |
2079 | tree lhs = PHI_RESULT (phi); | |
2080 | tree val = NULL; | |
2081 | int i; | |
2082 | ||
2083 | /* Ignoring arguments which are the same as LHS, if all the remaining | |
2084 | arguments are the same, then the PHI is a degenerate and has the | |
2085 | value of that common argument. */ | |
2086 | for (i = 0; i < PHI_NUM_ARGS (phi); i++) | |
2087 | { | |
2088 | tree arg = PHI_ARG_DEF (phi, i); | |
2089 | ||
2090 | if (arg == lhs) | |
2091 | continue; | |
2092 | else if (!val) | |
2093 | val = arg; | |
2094 | else if (!operand_equal_p (arg, val, 0)) | |
2095 | break; | |
2096 | } | |
2097 | return (i == PHI_NUM_ARGS (phi) ? val : NULL); | |
2098 | } | |
2099 | ||
2100 | /* Given a tree node T, which is either a PHI_NODE or GIMPLE_MODIFY_STMT, | |
2101 | remove it from the IL. */ | |
2102 | ||
2103 | static void | |
2104 | remove_stmt_or_phi (tree t) | |
2105 | { | |
2106 | if (TREE_CODE (t) == PHI_NODE) | |
2107 | remove_phi_node (t, NULL, true); | |
2108 | else | |
2109 | { | |
2110 | block_stmt_iterator bsi = bsi_for_stmt (t); | |
2111 | bsi_remove (&bsi, true); | |
2112 | release_defs (t); | |
2113 | } | |
2114 | } | |
2115 | ||
2116 | /* Given a tree node T, which is either a PHI_NODE or GIMPLE_MODIFY_STMT, | |
2117 | return the "rhs" of the node, in the case of a non-degenerate | |
2118 | PHI, NULL is returned. */ | |
2119 | ||
2120 | static tree | |
2121 | get_rhs_or_phi_arg (tree t) | |
2122 | { | |
2123 | if (TREE_CODE (t) == PHI_NODE) | |
2124 | return degenerate_phi_result (t); | |
2125 | else if (TREE_CODE (t) == GIMPLE_MODIFY_STMT) | |
2126 | return GIMPLE_STMT_OPERAND (t, 1); | |
2127 | gcc_unreachable (); | |
2128 | } | |
2129 | ||
2130 | ||
2131 | /* Given a tree node T, which is either a PHI_NODE or a GIMPLE_MODIFY_STMT, | |
2132 | return the "lhs" of the node. */ | |
2133 | ||
2134 | static tree | |
2135 | get_lhs_or_phi_result (tree t) | |
2136 | { | |
2137 | if (TREE_CODE (t) == PHI_NODE) | |
2138 | return PHI_RESULT (t); | |
2139 | else if (TREE_CODE (t) == GIMPLE_MODIFY_STMT) | |
2140 | return GIMPLE_STMT_OPERAND (t, 0); | |
2141 | gcc_unreachable (); | |
2142 | } | |
2143 | ||
2144 | /* Propagate RHS into all uses of LHS (when possible). | |
2145 | ||
2146 | RHS and LHS are derived from STMT, which is passed in solely so | |
2147 | that we can remove it if propagation is successful. | |
2148 | ||
2149 | When propagating into a PHI node or into a statement which turns | |
2150 | into a trivial copy or constant initialization, set the | |
2151 | appropriate bit in INTERESTING_NAMEs so that we will visit those | |
2152 | nodes as well in an effort to pick up secondary optimization | |
2153 | opportunities. */ | |
2154 | ||
2155 | static void | |
2156 | propagate_rhs_into_lhs (tree stmt, tree lhs, tree rhs, bitmap interesting_names) | |
2157 | { | |
2158 | /* First verify that propagation is valid and isn't going to move a | |
2159 | loop variant variable outside its loop. */ | |
2160 | if (! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs) | |
2161 | && (TREE_CODE (rhs) != SSA_NAME | |
2162 | || ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs)) | |
2163 | && may_propagate_copy (lhs, rhs) | |
2164 | && loop_depth_of_name (lhs) >= loop_depth_of_name (rhs)) | |
2165 | { | |
2166 | use_operand_p use_p; | |
2167 | imm_use_iterator iter; | |
2168 | tree use_stmt; | |
2169 | bool all = true; | |
2170 | ||
2171 | /* Dump details. */ | |
2172 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
2173 | { | |
2174 | fprintf (dump_file, " Replacing '"); | |
2175 | print_generic_expr (dump_file, lhs, dump_flags); | |
2176 | fprintf (dump_file, "' with %s '", | |
2177 | (TREE_CODE (rhs) != SSA_NAME ? "constant" : "variable")); | |
2178 | print_generic_expr (dump_file, rhs, dump_flags); | |
2179 | fprintf (dump_file, "'\n"); | |
2180 | } | |
2181 | ||
2182 | /* Walk over every use of LHS and try to replace the use with RHS. | |
2183 | At this point the only reason why such a propagation would not | |
2184 | be successful would be if the use occurs in an ASM_EXPR. */ | |
2185 | FOR_EACH_IMM_USE_STMT (use_stmt, iter, lhs) | |
2186 | { | |
2187 | ||
2188 | /* It's not always safe to propagate into an ASM_EXPR. */ | |
2189 | if (TREE_CODE (use_stmt) == ASM_EXPR | |
2190 | && ! may_propagate_copy_into_asm (lhs)) | |
2191 | { | |
2192 | all = false; | |
2193 | continue; | |
2194 | } | |
2195 | ||
2196 | /* Dump details. */ | |
2197 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
2198 | { | |
2199 | fprintf (dump_file, " Original statement:"); | |
2200 | print_generic_expr (dump_file, use_stmt, dump_flags); | |
2201 | fprintf (dump_file, "\n"); | |
2202 | } | |
2203 | ||
2204 | push_stmt_changes (&use_stmt); | |
2205 | ||
2206 | /* Propagate the RHS into this use of the LHS. */ | |
2207 | FOR_EACH_IMM_USE_ON_STMT (use_p, iter) | |
2208 | propagate_value (use_p, rhs); | |
2209 | ||
2210 | /* Special cases to avoid useless calls into the folding | |
2211 | routines, operand scanning, etc. | |
2212 | ||
2213 | First, propagation into a PHI may cause the PHI to become | |
2214 | a degenerate, so mark the PHI as interesting. No other | |
2215 | actions are necessary. | |
2216 | ||
2217 | Second, if we're propagating a virtual operand and the | |
2218 | propagation does not change the underlying _DECL node for | |
2219 | the virtual operand, then no further actions are necessary. */ | |
2220 | if (TREE_CODE (use_stmt) == PHI_NODE | |
2221 | || (! is_gimple_reg (lhs) | |
2222 | && TREE_CODE (rhs) == SSA_NAME | |
2223 | && SSA_NAME_VAR (lhs) == SSA_NAME_VAR (rhs))) | |
2224 | { | |
2225 | /* Dump details. */ | |
2226 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
2227 | { | |
2228 | fprintf (dump_file, " Updated statement:"); | |
2229 | print_generic_expr (dump_file, use_stmt, dump_flags); | |
2230 | fprintf (dump_file, "\n"); | |
2231 | } | |
2232 | ||
2233 | /* Propagation into a PHI may expose new degenerate PHIs, | |
2234 | so mark the result of the PHI as interesting. */ | |
2235 | if (TREE_CODE (use_stmt) == PHI_NODE) | |
2236 | { | |
2237 | tree result = get_lhs_or_phi_result (use_stmt); | |
2238 | bitmap_set_bit (interesting_names, SSA_NAME_VERSION (result)); | |
2239 | } | |
2240 | ||
2241 | discard_stmt_changes (&use_stmt); | |
2242 | continue; | |
2243 | } | |
2244 | ||
2245 | /* From this point onward we are propagating into a | |
2246 | real statement. Folding may (or may not) be possible, | |
2247 | we may expose new operands, expose dead EH edges, | |
2248 | etc. */ | |
2249 | fold_stmt_inplace (use_stmt); | |
2250 | ||
2251 | /* Sometimes propagation can expose new operands to the | |
2252 | renamer. Note this will call update_stmt at the | |
2253 | appropriate time. */ | |
2254 | pop_stmt_changes (&use_stmt); | |
2255 | ||
2256 | /* Dump details. */ | |
2257 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
2258 | { | |
2259 | fprintf (dump_file, " Updated statement:"); | |
2260 | print_generic_expr (dump_file, use_stmt, dump_flags); | |
2261 | fprintf (dump_file, "\n"); | |
2262 | } | |
2263 | ||
2264 | /* If we replaced a variable index with a constant, then | |
2265 | we would need to update the invariant flag for ADDR_EXPRs. */ | |
2266 | if (TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT | |
2267 | && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == ADDR_EXPR) | |
2268 | recompute_tree_invariant_for_addr_expr | |
2269 | (GIMPLE_STMT_OPERAND (use_stmt, 1)); | |
2270 | ||
2271 | /* If we cleaned up EH information from the statement, | |
2272 | mark its containing block as needing EH cleanups. */ | |
2273 | if (maybe_clean_or_replace_eh_stmt (use_stmt, use_stmt)) | |
2274 | { | |
2275 | bitmap_set_bit (need_eh_cleanup, bb_for_stmt (use_stmt)->index); | |
2276 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
2277 | fprintf (dump_file, " Flagged to clear EH edges.\n"); | |
2278 | } | |
2279 | ||
2280 | /* Propagation may expose new trivial copy/constant propagation | |
2281 | opportunities. */ | |
2282 | if (TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT | |
2283 | && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 0)) == SSA_NAME | |
2284 | && (TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == SSA_NAME | |
2285 | || is_gimple_min_invariant (GIMPLE_STMT_OPERAND (use_stmt, | |
2286 | 1)))) | |
2287 | { | |
2288 | tree result = get_lhs_or_phi_result (use_stmt); | |
2289 | bitmap_set_bit (interesting_names, SSA_NAME_VERSION (result)); | |
2290 | } | |
2291 | ||
2292 | /* Propagation into these nodes may make certain edges in | |
2293 | the CFG unexecutable. We want to identify them as PHI nodes | |
2294 | at the destination of those unexecutable edges may become | |
2295 | degenerates. */ | |
2296 | else if (TREE_CODE (use_stmt) == COND_EXPR | |
2297 | || TREE_CODE (use_stmt) == SWITCH_EXPR | |
2298 | || TREE_CODE (use_stmt) == GOTO_EXPR) | |
2299 | { | |
2300 | tree val; | |
2301 | ||
2302 | if (TREE_CODE (use_stmt) == COND_EXPR) | |
2303 | val = COND_EXPR_COND (use_stmt); | |
2304 | else if (TREE_CODE (use_stmt) == SWITCH_EXPR) | |
2305 | val = SWITCH_COND (use_stmt); | |
2306 | else | |
2307 | val = GOTO_DESTINATION (use_stmt); | |
2308 | ||
2309 | if (is_gimple_min_invariant (val)) | |
2310 | { | |
2311 | basic_block bb = bb_for_stmt (use_stmt); | |
2312 | edge te = find_taken_edge (bb, val); | |
2313 | edge_iterator ei; | |
2314 | edge e; | |
2315 | block_stmt_iterator bsi; | |
2316 | ||
2317 | /* Remove all outgoing edges except TE. */ | |
2318 | for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei));) | |
2319 | { | |
2320 | if (e != te) | |
2321 | { | |
2322 | tree phi; | |
2323 | ||
2324 | /* Mark all the PHI nodes at the destination of | |
2325 | the unexecutable edge as interesting. */ | |
2326 | for (phi = phi_nodes (e->dest); | |
2327 | phi; | |
2328 | phi = PHI_CHAIN (phi)) | |
2329 | { | |
2330 | tree result = PHI_RESULT (phi); | |
2331 | int version = SSA_NAME_VERSION (result); | |
2332 | ||
2333 | bitmap_set_bit (interesting_names, version); | |
2334 | } | |
2335 | ||
2336 | te->probability += e->probability; | |
2337 | ||
2338 | te->count += e->count; | |
2339 | remove_edge (e); | |
2340 | cfg_altered = true; | |
2341 | } | |
2342 | else | |
2343 | ei_next (&ei); | |
2344 | } | |
2345 | ||
2346 | bsi = bsi_last (bb_for_stmt (use_stmt)); | |
2347 | bsi_remove (&bsi, true); | |
2348 | ||
2349 | /* And fixup the flags on the single remaining edge. */ | |
2350 | te->flags &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE); | |
2351 | te->flags &= ~EDGE_ABNORMAL; | |
2352 | te->flags |= EDGE_FALLTHRU; | |
2353 | if (te->probability > REG_BR_PROB_BASE) | |
2354 | te->probability = REG_BR_PROB_BASE; | |
2355 | } | |
2356 | } | |
2357 | } | |
2358 | ||
2359 | /* Ensure there is nothing else to do. */ | |
2360 | gcc_assert (!all || has_zero_uses (lhs)); | |
2361 | ||
2362 | /* If we were able to propagate away all uses of LHS, then | |
2363 | we can remove STMT. */ | |
2364 | if (all) | |
2365 | remove_stmt_or_phi (stmt); | |
2366 | } | |
2367 | } | |
2368 | ||
2369 | /* T is either a PHI node (potentially a degenerate PHI node) or | |
2370 | a statement that is a trivial copy or constant initialization. | |
2371 | ||
2372 | Attempt to eliminate T by propagating its RHS into all uses of | |
2373 | its LHS. This may in turn set new bits in INTERESTING_NAMES | |
2374 | for nodes we want to revisit later. | |
2375 | ||
2376 | All exit paths should clear INTERESTING_NAMES for the result | |
2377 | of T. */ | |
2378 | ||
2379 | static void | |
2380 | eliminate_const_or_copy (tree t, bitmap interesting_names) | |
2381 | { | |
2382 | tree lhs = get_lhs_or_phi_result (t); | |
2383 | tree rhs; | |
2384 | int version = SSA_NAME_VERSION (lhs); | |
2385 | ||
2386 | /* If the LHS of this statement or PHI has no uses, then we can | |
2387 | just eliminate it. This can occur if, for example, the PHI | |
2388 | was created by block duplication due to threading and its only | |
2389 | use was in the conditional at the end of the block which was | |
2390 | deleted. */ | |
2391 | if (has_zero_uses (lhs)) | |
2392 | { | |
2393 | bitmap_clear_bit (interesting_names, version); | |
2394 | remove_stmt_or_phi (t); | |
2395 | return; | |
2396 | } | |
2397 | ||
2398 | /* Get the RHS of the assignment or PHI node if the PHI is a | |
2399 | degenerate. */ | |
2400 | rhs = get_rhs_or_phi_arg (t); | |
2401 | if (!rhs) | |
2402 | { | |
2403 | bitmap_clear_bit (interesting_names, version); | |
2404 | return; | |
2405 | } | |
2406 | ||
2407 | propagate_rhs_into_lhs (t, lhs, rhs, interesting_names); | |
2408 | ||
2409 | /* Note that T may well have been deleted by now, so do | |
2410 | not access it, instead use the saved version # to clear | |
2411 | T's entry in the worklist. */ | |
2412 | bitmap_clear_bit (interesting_names, version); | |
2413 | } | |
2414 | ||
2415 | /* The first phase in degenerate PHI elimination. | |
2416 | ||
2417 | Eliminate the degenerate PHIs in BB, then recurse on the | |
2418 | dominator children of BB. */ | |
2419 | ||
2420 | static void | |
2421 | eliminate_degenerate_phis_1 (basic_block bb, bitmap interesting_names) | |
2422 | { | |
2423 | tree phi, next; | |
2424 | basic_block son; | |
2425 | ||
2426 | for (phi = phi_nodes (bb); phi; phi = next) | |
2427 | { | |
2428 | next = PHI_CHAIN (phi); | |
2429 | eliminate_const_or_copy (phi, interesting_names); | |
2430 | } | |
2431 | ||
2432 | /* Recurse into the dominator children of BB. */ | |
2433 | for (son = first_dom_son (CDI_DOMINATORS, bb); | |
2434 | son; | |
2435 | son = next_dom_son (CDI_DOMINATORS, son)) | |
2436 | eliminate_degenerate_phis_1 (son, interesting_names); | |
2437 | } | |
2438 | ||
2439 | ||
2440 | /* A very simple pass to eliminate degenerate PHI nodes from the | |
2441 | IL. This is meant to be fast enough to be able to be run several | |
2442 | times in the optimization pipeline. | |
2443 | ||
2444 | Certain optimizations, particularly those which duplicate blocks | |
2445 | or remove edges from the CFG can create or expose PHIs which are | |
2446 | trivial copies or constant initializations. | |
2447 | ||
2448 | While we could pick up these optimizations in DOM or with the | |
2449 | combination of copy-prop and CCP, those solutions are far too | |
2450 | heavy-weight for our needs. | |
2451 | ||
2452 | This implementation has two phases so that we can efficiently | |
2453 | eliminate the first order degenerate PHIs and second order | |
2454 | degenerate PHIs. | |
2455 | ||
2456 | The first phase performs a dominator walk to identify and eliminate | |
2457 | the vast majority of the degenerate PHIs. When a degenerate PHI | |
2458 | is identified and eliminated any affected statements or PHIs | |
2459 | are put on a worklist. | |
2460 | ||
2461 | The second phase eliminates degenerate PHIs and trivial copies | |
2462 | or constant initializations using the worklist. This is how we | |
2463 | pick up the secondary optimization opportunities with minimal | |
2464 | cost. */ | |
2465 | ||
2466 | static unsigned int | |
2467 | eliminate_degenerate_phis (void) | |
2468 | { | |
2469 | bitmap interesting_names; | |
2470 | bitmap interesting_names1; | |
2471 | ||
2472 | /* Bitmap of blocks which need EH information updated. We can not | |
2473 | update it on-the-fly as doing so invalidates the dominator tree. */ | |
2474 | need_eh_cleanup = BITMAP_ALLOC (NULL); | |
2475 | ||
2476 | /* INTERESTING_NAMES is effectively our worklist, indexed by | |
2477 | SSA_NAME_VERSION. | |
2478 | ||
2479 | A set bit indicates that the statement or PHI node which | |
2480 | defines the SSA_NAME should be (re)examined to determine if | |
2481 | it has become a degenerate PHI or trivial const/copy propagation | |
2482 | opportunity. | |
2483 | ||
2484 | Experiments have show we generally get better compilation | |
2485 | time behavior with bitmaps rather than sbitmaps. */ | |
2486 | interesting_names = BITMAP_ALLOC (NULL); | |
2487 | interesting_names1 = BITMAP_ALLOC (NULL); | |
2488 | ||
2489 | calculate_dominance_info (CDI_DOMINATORS); | |
2490 | cfg_altered = false; | |
2491 | ||
2492 | /* First phase. Eliminate degenerate PHIs via a dominator | |
2493 | walk of the CFG. | |
2494 | ||
2495 | Experiments have indicated that we generally get better | |
2496 | compile-time behavior by visiting blocks in the first | |
2497 | phase in dominator order. Presumably this is because walking | |
2498 | in dominator order leaves fewer PHIs for later examination | |
2499 | by the worklist phase. */ | |
2500 | eliminate_degenerate_phis_1 (ENTRY_BLOCK_PTR, interesting_names); | |
2501 | ||
2502 | /* Second phase. Eliminate second order degenerate PHIs as well | |
2503 | as trivial copies or constant initializations identified by | |
2504 | the first phase or this phase. Basically we keep iterating | |
2505 | until our set of INTERESTING_NAMEs is empty. */ | |
2506 | while (!bitmap_empty_p (interesting_names)) | |
2507 | { | |
2508 | unsigned int i; | |
2509 | bitmap_iterator bi; | |
2510 | ||
2511 | /* EXECUTE_IF_SET_IN_BITMAP does not like its bitmap | |
2512 | changed during the loop. Copy it to another bitmap and | |
2513 | use that. */ | |
2514 | bitmap_copy (interesting_names1, interesting_names); | |
2515 | ||
2516 | EXECUTE_IF_SET_IN_BITMAP (interesting_names1, 0, i, bi) | |
2517 | { | |
2518 | tree name = ssa_name (i); | |
2519 | ||
2520 | /* Ignore SSA_NAMEs that have been released because | |
2521 | their defining statement was deleted (unreachable). */ | |
2522 | if (name) | |
2523 | eliminate_const_or_copy (SSA_NAME_DEF_STMT (ssa_name (i)), | |
2524 | interesting_names); | |
2525 | } | |
2526 | } | |
2527 | ||
2528 | if (cfg_altered) | |
2529 | free_dominance_info (CDI_DOMINATORS); | |
2530 | ||
2531 | /* Propagation of const and copies may make some EH edges dead. Purge | |
2532 | such edges from the CFG as needed. */ | |
2533 | if (!bitmap_empty_p (need_eh_cleanup)) | |
2534 | { | |
2535 | tree_purge_all_dead_eh_edges (need_eh_cleanup); | |
2536 | BITMAP_FREE (need_eh_cleanup); | |
2537 | } | |
2538 | ||
2539 | BITMAP_FREE (interesting_names); | |
2540 | BITMAP_FREE (interesting_names1); | |
2541 | return 0; | |
2542 | } | |
2543 | ||
2544 | struct tree_opt_pass pass_phi_only_cprop = | |
2545 | { | |
2546 | "phicprop", /* name */ | |
2547 | gate_dominator, /* gate */ | |
2548 | eliminate_degenerate_phis, /* execute */ | |
2549 | NULL, /* sub */ | |
2550 | NULL, /* next */ | |
2551 | 0, /* static_pass_number */ | |
2552 | TV_TREE_PHI_CPROP, /* tv_id */ | |
2553 | PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */ | |
2554 | 0, /* properties_provided */ | |
2555 | 0, /* properties_destroyed */ | |
2556 | 0, /* todo_flags_start */ | |
2557 | TODO_cleanup_cfg | |
2558 | | TODO_dump_func | |
2559 | | TODO_ggc_collect | |
2560 | | TODO_verify_ssa | |
2561 | | TODO_verify_stmts | |
2562 | | TODO_update_ssa, /* todo_flags_finish */ | |
2563 | 0 /* letter */ | |
2564 | }; |