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5f718c29 | 1 | /* Routines for discovering and unpropagating edge equivalences. |
711789cc | 2 | Copyright (C) 2005-2013 Free Software Foundation, Inc. |
5f718c29 | 3 | |
4 | This file is part of GCC. | |
5 | ||
6 | GCC is free software; you can redistribute it and/or modify | |
7 | it under the terms of the GNU General Public License as published by | |
8c4c00c1 | 8 | the Free Software Foundation; either version 3, or (at your option) |
5f718c29 | 9 | any later version. |
10 | ||
11 | GCC is distributed in the hope that it will be useful, | |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
14 | GNU General Public License for more details. | |
15 | ||
16 | You should have received a copy of the GNU General Public License | |
8c4c00c1 | 17 | along with GCC; see the file COPYING3. If not see |
18 | <http://www.gnu.org/licenses/>. */ | |
5f718c29 | 19 | |
20 | #include "config.h" | |
21 | #include "system.h" | |
22 | #include "coretypes.h" | |
23 | #include "tm.h" | |
24 | #include "tree.h" | |
9ed99284 | 25 | #include "stor-layout.h" |
5f718c29 | 26 | #include "flags.h" |
5f718c29 | 27 | #include "tm_p.h" |
5f718c29 | 28 | #include "basic-block.h" |
5f718c29 | 29 | #include "function.h" |
bc61cadb | 30 | #include "hash-table.h" |
31 | #include "tree-ssa-alias.h" | |
32 | #include "internal-fn.h" | |
33 | #include "gimple-expr.h" | |
34 | #include "is-a.h" | |
073c1fd5 | 35 | #include "gimple.h" |
dcf1a1ec | 36 | #include "gimple-iterator.h" |
073c1fd5 | 37 | #include "gimple-ssa.h" |
38 | #include "tree-cfg.h" | |
39 | #include "tree-phinodes.h" | |
40 | #include "ssa-iterators.h" | |
5f718c29 | 41 | #include "domwalk.h" |
5f718c29 | 42 | #include "tree-pass.h" |
43 | #include "tree-ssa-propagate.h" | |
5f718c29 | 44 | |
45 | /* The basic structure describing an equivalency created by traversing | |
46 | an edge. Traversing the edge effectively means that we can assume | |
47 | that we've seen an assignment LHS = RHS. */ | |
48 | struct edge_equivalency | |
49 | { | |
50 | tree rhs; | |
51 | tree lhs; | |
52 | }; | |
53 | ||
54 | /* This routine finds and records edge equivalences for every edge | |
55 | in the CFG. | |
56 | ||
57 | When complete, each edge that creates an equivalency will have an | |
48e1416a | 58 | EDGE_EQUIVALENCY structure hanging off the edge's AUX field. |
5f718c29 | 59 | The caller is responsible for freeing the AUX fields. */ |
60 | ||
61 | static void | |
62 | associate_equivalences_with_edges (void) | |
63 | { | |
64 | basic_block bb; | |
65 | ||
66 | /* Walk over each block. If the block ends with a control statement, | |
67 | then it might create a useful equivalence. */ | |
fc00614f | 68 | FOR_EACH_BB_FN (bb, cfun) |
5f718c29 | 69 | { |
75a70cf9 | 70 | gimple_stmt_iterator gsi = gsi_last_bb (bb); |
71 | gimple stmt; | |
5f718c29 | 72 | |
73 | /* If the block does not end with a COND_EXPR or SWITCH_EXPR | |
74 | then there is nothing to do. */ | |
75a70cf9 | 75 | if (gsi_end_p (gsi)) |
5f718c29 | 76 | continue; |
77 | ||
75a70cf9 | 78 | stmt = gsi_stmt (gsi); |
5f718c29 | 79 | |
80 | if (!stmt) | |
81 | continue; | |
82 | ||
83 | /* A COND_EXPR may create an equivalency in a variety of different | |
84 | ways. */ | |
75a70cf9 | 85 | if (gimple_code (stmt) == GIMPLE_COND) |
5f718c29 | 86 | { |
5f718c29 | 87 | edge true_edge; |
88 | edge false_edge; | |
89 | struct edge_equivalency *equivalency; | |
75a70cf9 | 90 | enum tree_code code = gimple_cond_code (stmt); |
5f718c29 | 91 | |
92 | extract_true_false_edges_from_block (bb, &true_edge, &false_edge); | |
93 | ||
5f718c29 | 94 | /* Equality tests may create one or two equivalences. */ |
75a70cf9 | 95 | if (code == EQ_EXPR || code == NE_EXPR) |
5f718c29 | 96 | { |
75a70cf9 | 97 | tree op0 = gimple_cond_lhs (stmt); |
98 | tree op1 = gimple_cond_rhs (stmt); | |
5f718c29 | 99 | |
100 | /* Special case comparing booleans against a constant as we | |
101 | know the value of OP0 on both arms of the branch. i.e., we | |
102 | can record an equivalence for OP0 rather than COND. */ | |
103 | if (TREE_CODE (op0) == SSA_NAME | |
932540b6 | 104 | && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (op0) |
5f718c29 | 105 | && TREE_CODE (TREE_TYPE (op0)) == BOOLEAN_TYPE |
106 | && is_gimple_min_invariant (op1)) | |
107 | { | |
75a70cf9 | 108 | if (code == EQ_EXPR) |
5f718c29 | 109 | { |
945865c5 | 110 | equivalency = XNEW (struct edge_equivalency); |
5f718c29 | 111 | equivalency->lhs = op0; |
112 | equivalency->rhs = (integer_zerop (op1) | |
113 | ? boolean_false_node | |
114 | : boolean_true_node); | |
115 | true_edge->aux = equivalency; | |
116 | ||
945865c5 | 117 | equivalency = XNEW (struct edge_equivalency); |
5f718c29 | 118 | equivalency->lhs = op0; |
119 | equivalency->rhs = (integer_zerop (op1) | |
120 | ? boolean_true_node | |
121 | : boolean_false_node); | |
122 | false_edge->aux = equivalency; | |
123 | } | |
124 | else | |
125 | { | |
945865c5 | 126 | equivalency = XNEW (struct edge_equivalency); |
5f718c29 | 127 | equivalency->lhs = op0; |
128 | equivalency->rhs = (integer_zerop (op1) | |
129 | ? boolean_true_node | |
130 | : boolean_false_node); | |
131 | true_edge->aux = equivalency; | |
132 | ||
945865c5 | 133 | equivalency = XNEW (struct edge_equivalency); |
5f718c29 | 134 | equivalency->lhs = op0; |
135 | equivalency->rhs = (integer_zerop (op1) | |
136 | ? boolean_false_node | |
137 | : boolean_true_node); | |
138 | false_edge->aux = equivalency; | |
139 | } | |
140 | } | |
141 | ||
024e445d | 142 | else if (TREE_CODE (op0) == SSA_NAME |
143 | && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (op0) | |
144 | && (is_gimple_min_invariant (op1) | |
145 | || (TREE_CODE (op1) == SSA_NAME | |
146 | && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (op1)))) | |
5f718c29 | 147 | { |
148 | /* For IEEE, -0.0 == 0.0, so we don't necessarily know | |
149 | the sign of a variable compared against zero. If | |
150 | we're honoring signed zeros, then we cannot record | |
151 | this value unless we know that the value is nonzero. */ | |
152 | if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (op0))) | |
153 | && (TREE_CODE (op1) != REAL_CST | |
154 | || REAL_VALUES_EQUAL (dconst0, TREE_REAL_CST (op1)))) | |
155 | continue; | |
156 | ||
945865c5 | 157 | equivalency = XNEW (struct edge_equivalency); |
5f718c29 | 158 | equivalency->lhs = op0; |
159 | equivalency->rhs = op1; | |
75a70cf9 | 160 | if (code == EQ_EXPR) |
5f718c29 | 161 | true_edge->aux = equivalency; |
48e1416a | 162 | else |
5f718c29 | 163 | false_edge->aux = equivalency; |
164 | ||
165 | } | |
166 | } | |
167 | ||
168 | /* ??? TRUTH_NOT_EXPR can create an equivalence too. */ | |
169 | } | |
170 | ||
171 | /* For a SWITCH_EXPR, a case label which represents a single | |
172 | value and which is the only case label which reaches the | |
173 | target block creates an equivalence. */ | |
75a70cf9 | 174 | else if (gimple_code (stmt) == GIMPLE_SWITCH) |
5f718c29 | 175 | { |
75a70cf9 | 176 | tree cond = gimple_switch_index (stmt); |
5f718c29 | 177 | |
932540b6 | 178 | if (TREE_CODE (cond) == SSA_NAME |
179 | && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (cond)) | |
5f718c29 | 180 | { |
75a70cf9 | 181 | int i, n_labels = gimple_switch_num_labels (stmt); |
fe672ac0 | 182 | tree *info = XCNEWVEC (tree, last_basic_block_for_fn (cfun)); |
5f718c29 | 183 | |
184 | /* Walk over the case label vector. Record blocks | |
185 | which are reached by a single case label which represents | |
186 | a single value. */ | |
187 | for (i = 0; i < n_labels; i++) | |
188 | { | |
75a70cf9 | 189 | tree label = gimple_switch_label (stmt, i); |
5f718c29 | 190 | basic_block bb = label_to_block (CASE_LABEL (label)); |
191 | ||
5f718c29 | 192 | if (CASE_HIGH (label) |
193 | || !CASE_LOW (label) | |
194 | || info[bb->index]) | |
195 | info[bb->index] = error_mark_node; | |
196 | else | |
197 | info[bb->index] = label; | |
198 | } | |
199 | ||
200 | /* Now walk over the blocks to determine which ones were | |
201 | marked as being reached by a useful case label. */ | |
a28770e1 | 202 | for (i = 0; i < n_basic_blocks_for_fn (cfun); i++) |
5f718c29 | 203 | { |
204 | tree node = info[i]; | |
205 | ||
206 | if (node != NULL | |
207 | && node != error_mark_node) | |
208 | { | |
209 | tree x = fold_convert (TREE_TYPE (cond), CASE_LOW (node)); | |
210 | struct edge_equivalency *equivalency; | |
211 | ||
212 | /* Record an equivalency on the edge from BB to basic | |
213 | block I. */ | |
945865c5 | 214 | equivalency = XNEW (struct edge_equivalency); |
5f718c29 | 215 | equivalency->rhs = x; |
216 | equivalency->lhs = cond; | |
f5a6b05f | 217 | find_edge (bb, BASIC_BLOCK_FOR_FN (cfun, i))->aux = |
218 | equivalency; | |
5f718c29 | 219 | } |
220 | } | |
221 | free (info); | |
222 | } | |
223 | } | |
224 | ||
225 | } | |
226 | } | |
227 | ||
228 | ||
229 | /* Translating out of SSA sometimes requires inserting copies and | |
230 | constant initializations on edges to eliminate PHI nodes. | |
231 | ||
232 | In some cases those copies and constant initializations are | |
233 | redundant because the target already has the value on the | |
234 | RHS of the assignment. | |
235 | ||
236 | We previously tried to catch these cases after translating | |
237 | out of SSA form. However, that code often missed cases. Worse | |
238 | yet, the cases it missed were also often missed by the RTL | |
239 | optimizers. Thus the resulting code had redundant instructions. | |
240 | ||
241 | This pass attempts to detect these situations before translating | |
242 | out of SSA form. | |
243 | ||
244 | The key concept that this pass is built upon is that these | |
245 | redundant copies and constant initializations often occur | |
246 | due to constant/copy propagating equivalences resulting from | |
247 | COND_EXPRs and SWITCH_EXPRs. | |
248 | ||
249 | We want to do those propagations as they can sometimes allow | |
25f6297d | 250 | the SSA optimizers to do a better job. However, in the cases |
5f718c29 | 251 | where such propagations do not result in further optimization, |
252 | we would like to "undo" the propagation to avoid the redundant | |
253 | copies and constant initializations. | |
254 | ||
255 | This pass works by first associating equivalences with edges in | |
256 | the CFG. For example, the edge leading from a SWITCH_EXPR to | |
257 | its associated CASE_LABEL will have an equivalency between | |
258 | SWITCH_COND and the value in the case label. | |
259 | ||
260 | Once we have found the edge equivalences, we proceed to walk | |
261 | the CFG in dominator order. As we traverse edges we record | |
262 | equivalences associated with those edges we traverse. | |
263 | ||
264 | When we encounter a PHI node, we walk its arguments to see if we | |
265 | have an equivalence for the PHI argument. If so, then we replace | |
266 | the argument. | |
267 | ||
268 | Equivalences are looked up based on their value (think of it as | |
269 | the RHS of an assignment). A value may be an SSA_NAME or an | |
270 | invariant. We may have several SSA_NAMEs with the same value, | |
271 | so with each value we have a list of SSA_NAMEs that have the | |
272 | same value. */ | |
273 | ||
5f718c29 | 274 | |
5f718c29 | 275 | /* Main structure for recording equivalences into our hash table. */ |
276 | struct equiv_hash_elt | |
277 | { | |
278 | /* The value/key of this entry. */ | |
279 | tree value; | |
280 | ||
281 | /* List of SSA_NAMEs which have the same value/key. */ | |
f1f41a6c | 282 | vec<tree> equivalences; |
5f718c29 | 283 | }; |
284 | ||
d9dd21a8 | 285 | /* Value to ssa name equivalence hashtable helpers. */ |
5f718c29 | 286 | |
d9dd21a8 | 287 | struct val_ssa_equiv_hasher |
288 | { | |
289 | typedef equiv_hash_elt value_type; | |
290 | typedef equiv_hash_elt compare_type; | |
291 | static inline hashval_t hash (const value_type *); | |
292 | static inline bool equal (const value_type *, const compare_type *); | |
293 | static inline void remove (value_type *); | |
294 | }; | |
5f718c29 | 295 | |
d9dd21a8 | 296 | inline hashval_t |
297 | val_ssa_equiv_hasher::hash (const value_type *p) | |
5f718c29 | 298 | { |
d9dd21a8 | 299 | tree const value = p->value; |
5f718c29 | 300 | return iterative_hash_expr (value, 0); |
301 | } | |
302 | ||
d9dd21a8 | 303 | inline bool |
304 | val_ssa_equiv_hasher::equal (const value_type *p1, const compare_type *p2) | |
5f718c29 | 305 | { |
d9dd21a8 | 306 | tree value1 = p1->value; |
307 | tree value2 = p2->value; | |
5f718c29 | 308 | |
309 | return operand_equal_p (value1, value2, 0); | |
310 | } | |
311 | ||
96a7ab57 | 312 | /* Free an instance of equiv_hash_elt. */ |
313 | ||
d9dd21a8 | 314 | inline void |
315 | val_ssa_equiv_hasher::remove (value_type *elt) | |
96a7ab57 | 316 | { |
f1f41a6c | 317 | elt->equivalences.release (); |
96a7ab57 | 318 | free (elt); |
319 | } | |
320 | ||
d9dd21a8 | 321 | /* Global hash table implementing a mapping from invariant values |
322 | to a list of SSA_NAMEs which have the same value. We might be | |
323 | able to reuse tree-vn for this code. */ | |
324 | static hash_table <val_ssa_equiv_hasher> val_ssa_equiv; | |
325 | ||
d9dd21a8 | 326 | static void uncprop_into_successor_phis (basic_block); |
327 | ||
5f718c29 | 328 | /* Remove the most recently recorded equivalency for VALUE. */ |
329 | ||
330 | static void | |
331 | remove_equivalence (tree value) | |
332 | { | |
d9dd21a8 | 333 | struct equiv_hash_elt an_equiv_elt, *an_equiv_elt_p; |
334 | equiv_hash_elt **slot; | |
5f718c29 | 335 | |
d9dd21a8 | 336 | an_equiv_elt.value = value; |
337 | an_equiv_elt.equivalences.create (0); | |
5f718c29 | 338 | |
d9dd21a8 | 339 | slot = val_ssa_equiv.find_slot (&an_equiv_elt, NO_INSERT); |
5f718c29 | 340 | |
d9dd21a8 | 341 | an_equiv_elt_p = *slot; |
342 | an_equiv_elt_p->equivalences.pop (); | |
5f718c29 | 343 | } |
344 | ||
345 | /* Record EQUIVALENCE = VALUE into our hash table. */ | |
346 | ||
347 | static void | |
348 | record_equiv (tree value, tree equivalence) | |
349 | { | |
d9dd21a8 | 350 | equiv_hash_elt *an_equiv_elt_p; |
351 | equiv_hash_elt **slot; | |
5f718c29 | 352 | |
d9dd21a8 | 353 | an_equiv_elt_p = XNEW (struct equiv_hash_elt); |
354 | an_equiv_elt_p->value = value; | |
355 | an_equiv_elt_p->equivalences.create (0); | |
5f718c29 | 356 | |
d9dd21a8 | 357 | slot = val_ssa_equiv.find_slot (an_equiv_elt_p, INSERT); |
5f718c29 | 358 | |
359 | if (*slot == NULL) | |
d9dd21a8 | 360 | *slot = an_equiv_elt_p; |
5f718c29 | 361 | else |
d9dd21a8 | 362 | free (an_equiv_elt_p); |
5f718c29 | 363 | |
d9dd21a8 | 364 | an_equiv_elt_p = *slot; |
48e1416a | 365 | |
d9dd21a8 | 366 | an_equiv_elt_p->equivalences.safe_push (equivalence); |
5f718c29 | 367 | } |
368 | ||
54c91640 | 369 | class uncprop_dom_walker : public dom_walker |
370 | { | |
371 | public: | |
e85cf4e5 | 372 | uncprop_dom_walker (cdi_direction direction) : dom_walker (direction) {} |
54c91640 | 373 | |
374 | virtual void before_dom_children (basic_block); | |
375 | virtual void after_dom_children (basic_block); | |
376 | ||
377 | private: | |
378 | ||
ae84f584 | 379 | /* As we enter each block we record the value for any edge equivalency |
380 | leading to this block. If no such edge equivalency exists, then we | |
381 | record NULL. These equivalences are live until we leave the dominator | |
382 | subtree rooted at the block where we record the equivalency. */ | |
4997014d | 383 | auto_vec<tree, 2> m_equiv_stack; |
54c91640 | 384 | }; |
385 | ||
5f718c29 | 386 | /* Main driver for un-cprop. */ |
387 | ||
2a1990e9 | 388 | static unsigned int |
5f718c29 | 389 | tree_ssa_uncprop (void) |
390 | { | |
5f718c29 | 391 | basic_block bb; |
392 | ||
393 | associate_equivalences_with_edges (); | |
394 | ||
395 | /* Create our global data structures. */ | |
d9dd21a8 | 396 | val_ssa_equiv.create (1024); |
5f718c29 | 397 | |
398 | /* We're going to do a dominator walk, so ensure that we have | |
399 | dominance information. */ | |
400 | calculate_dominance_info (CDI_DOMINATORS); | |
401 | ||
5f718c29 | 402 | /* Recursively walk the dominator tree undoing unprofitable |
403 | constant/copy propagations. */ | |
54c91640 | 404 | uncprop_dom_walker (CDI_DOMINATORS).walk (cfun->cfg->x_entry_block_ptr); |
5f718c29 | 405 | |
54c91640 | 406 | /* we just need to empty elements out of the hash table, and cleanup the |
407 | AUX field on the edges. */ | |
d9dd21a8 | 408 | val_ssa_equiv.dispose (); |
fc00614f | 409 | FOR_EACH_BB_FN (bb, cfun) |
5f718c29 | 410 | { |
411 | edge e; | |
412 | edge_iterator ei; | |
413 | ||
414 | FOR_EACH_EDGE (e, ei, bb->succs) | |
415 | { | |
416 | if (e->aux) | |
417 | { | |
418 | free (e->aux); | |
419 | e->aux = NULL; | |
420 | } | |
421 | } | |
422 | } | |
2a1990e9 | 423 | return 0; |
5f718c29 | 424 | } |
425 | ||
426 | ||
427 | /* We have finished processing the dominator children of BB, perform | |
428 | any finalization actions in preparation for leaving this node in | |
429 | the dominator tree. */ | |
430 | ||
54c91640 | 431 | void |
432 | uncprop_dom_walker::after_dom_children (basic_block bb ATTRIBUTE_UNUSED) | |
5f718c29 | 433 | { |
5f718c29 | 434 | /* Pop the topmost value off the equiv stack. */ |
ae84f584 | 435 | tree value = m_equiv_stack.pop (); |
5f718c29 | 436 | |
437 | /* If that value was non-null, then pop the topmost equivalency off | |
438 | its equivalency stack. */ | |
439 | if (value != NULL) | |
440 | remove_equivalence (value); | |
441 | } | |
442 | ||
443 | /* Unpropagate values from PHI nodes in successor blocks of BB. */ | |
444 | ||
445 | static void | |
6bf320fb | 446 | uncprop_into_successor_phis (basic_block bb) |
5f718c29 | 447 | { |
448 | edge e; | |
449 | edge_iterator ei; | |
450 | ||
451 | /* For each successor edge, first temporarily record any equivalence | |
452 | on that edge. Then unpropagate values in any PHI nodes at the | |
453 | destination of the edge. Then remove the temporary equivalence. */ | |
454 | FOR_EACH_EDGE (e, ei, bb->succs) | |
455 | { | |
75a70cf9 | 456 | gimple_seq phis = phi_nodes (e->dest); |
457 | gimple_stmt_iterator gsi; | |
5f718c29 | 458 | |
459 | /* If there are no PHI nodes in this destination, then there is | |
460 | no sense in recording any equivalences. */ | |
be2517f5 | 461 | if (gimple_seq_empty_p (phis)) |
5f718c29 | 462 | continue; |
463 | ||
464 | /* Record any equivalency associated with E. */ | |
465 | if (e->aux) | |
466 | { | |
945865c5 | 467 | struct edge_equivalency *equiv = (struct edge_equivalency *) e->aux; |
5f718c29 | 468 | record_equiv (equiv->rhs, equiv->lhs); |
469 | } | |
470 | ||
471 | /* Walk over the PHI nodes, unpropagating values. */ | |
75a70cf9 | 472 | for (gsi = gsi_start (phis) ; !gsi_end_p (gsi); gsi_next (&gsi)) |
5f718c29 | 473 | { |
75a70cf9 | 474 | gimple phi = gsi_stmt (gsi); |
5f718c29 | 475 | tree arg = PHI_ARG_DEF (phi, e->dest_idx); |
ec11736b | 476 | tree res = PHI_RESULT (phi); |
d9dd21a8 | 477 | equiv_hash_elt an_equiv_elt; |
478 | equiv_hash_elt **slot; | |
5f718c29 | 479 | |
f82f0ea5 | 480 | /* If the argument is not an invariant and can be potentially |
481 | coalesced with the result, then there's no point in | |
482 | un-propagating the argument. */ | |
5f718c29 | 483 | if (!is_gimple_min_invariant (arg) |
f82f0ea5 | 484 | && gimple_can_coalesce_p (arg, res)) |
5f718c29 | 485 | continue; |
486 | ||
487 | /* Lookup this argument's value in the hash table. */ | |
d9dd21a8 | 488 | an_equiv_elt.value = arg; |
489 | an_equiv_elt.equivalences.create (0); | |
490 | slot = val_ssa_equiv.find_slot (&an_equiv_elt, NO_INSERT); | |
5f718c29 | 491 | |
492 | if (slot) | |
493 | { | |
d9dd21a8 | 494 | struct equiv_hash_elt *elt = *slot; |
5f718c29 | 495 | int j; |
496 | ||
497 | /* Walk every equivalence with the same value. If we find | |
f82f0ea5 | 498 | one that can potentially coalesce with the PHI rsult, |
5f718c29 | 499 | then replace the value in the argument with its equivalent |
25f6297d | 500 | SSA_NAME. Use the most recent equivalence as hopefully |
5f718c29 | 501 | that results in shortest lifetimes. */ |
f1f41a6c | 502 | for (j = elt->equivalences.length () - 1; j >= 0; j--) |
5f718c29 | 503 | { |
f1f41a6c | 504 | tree equiv = elt->equivalences[j]; |
5f718c29 | 505 | |
f82f0ea5 | 506 | if (gimple_can_coalesce_p (equiv, res)) |
5f718c29 | 507 | { |
508 | SET_PHI_ARG_DEF (phi, e->dest_idx, equiv); | |
509 | break; | |
510 | } | |
511 | } | |
512 | } | |
513 | } | |
514 | ||
515 | /* If we had an equivalence associated with this edge, remove it. */ | |
516 | if (e->aux) | |
517 | { | |
945865c5 | 518 | struct edge_equivalency *equiv = (struct edge_equivalency *) e->aux; |
5f718c29 | 519 | remove_equivalence (equiv->rhs); |
520 | } | |
521 | } | |
522 | } | |
523 | ||
524 | /* Ignoring loop backedges, if BB has precisely one incoming edge then | |
525 | return that edge. Otherwise return NULL. */ | |
526 | static edge | |
527 | single_incoming_edge_ignoring_loop_edges (basic_block bb) | |
528 | { | |
529 | edge retval = NULL; | |
530 | edge e; | |
531 | edge_iterator ei; | |
532 | ||
533 | FOR_EACH_EDGE (e, ei, bb->preds) | |
534 | { | |
535 | /* A loop back edge can be identified by the destination of | |
536 | the edge dominating the source of the edge. */ | |
537 | if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest)) | |
538 | continue; | |
539 | ||
540 | /* If we have already seen a non-loop edge, then we must have | |
541 | multiple incoming non-loop edges and thus we return NULL. */ | |
542 | if (retval) | |
543 | return NULL; | |
544 | ||
545 | /* This is the first non-loop incoming edge we have found. Record | |
546 | it. */ | |
547 | retval = e; | |
548 | } | |
549 | ||
550 | return retval; | |
551 | } | |
552 | ||
54c91640 | 553 | void |
554 | uncprop_dom_walker::before_dom_children (basic_block bb) | |
5f718c29 | 555 | { |
556 | basic_block parent; | |
557 | edge e; | |
558 | bool recorded = false; | |
559 | ||
560 | /* If this block is dominated by a single incoming edge and that edge | |
561 | has an equivalency, then record the equivalency and push the | |
562 | VALUE onto EQUIV_STACK. Else push a NULL entry on EQUIV_STACK. */ | |
563 | parent = get_immediate_dominator (CDI_DOMINATORS, bb); | |
564 | if (parent) | |
565 | { | |
566 | e = single_incoming_edge_ignoring_loop_edges (bb); | |
567 | ||
568 | if (e && e->src == parent && e->aux) | |
569 | { | |
945865c5 | 570 | struct edge_equivalency *equiv = (struct edge_equivalency *) e->aux; |
5f718c29 | 571 | |
572 | record_equiv (equiv->rhs, equiv->lhs); | |
ae84f584 | 573 | m_equiv_stack.safe_push (equiv->rhs); |
5f718c29 | 574 | recorded = true; |
575 | } | |
576 | } | |
577 | ||
578 | if (!recorded) | |
ae84f584 | 579 | m_equiv_stack.safe_push (NULL_TREE); |
6bf320fb | 580 | |
581 | uncprop_into_successor_phis (bb); | |
5f718c29 | 582 | } |
583 | ||
584 | static bool | |
585 | gate_uncprop (void) | |
586 | { | |
587 | return flag_tree_dom != 0; | |
588 | } | |
589 | ||
cbe8bda8 | 590 | namespace { |
591 | ||
592 | const pass_data pass_data_uncprop = | |
5f718c29 | 593 | { |
cbe8bda8 | 594 | GIMPLE_PASS, /* type */ |
595 | "uncprop", /* name */ | |
596 | OPTGROUP_NONE, /* optinfo_flags */ | |
597 | true, /* has_gate */ | |
598 | true, /* has_execute */ | |
599 | TV_TREE_SSA_UNCPROP, /* tv_id */ | |
600 | ( PROP_cfg | PROP_ssa ), /* properties_required */ | |
601 | 0, /* properties_provided */ | |
602 | 0, /* properties_destroyed */ | |
603 | 0, /* todo_flags_start */ | |
604 | TODO_verify_ssa, /* todo_flags_finish */ | |
5f718c29 | 605 | }; |
cbe8bda8 | 606 | |
607 | class pass_uncprop : public gimple_opt_pass | |
608 | { | |
609 | public: | |
9af5ce0c | 610 | pass_uncprop (gcc::context *ctxt) |
611 | : gimple_opt_pass (pass_data_uncprop, ctxt) | |
cbe8bda8 | 612 | {} |
613 | ||
614 | /* opt_pass methods: */ | |
ae84f584 | 615 | opt_pass * clone () { return new pass_uncprop (m_ctxt); } |
cbe8bda8 | 616 | bool gate () { return gate_uncprop (); } |
617 | unsigned int execute () { return tree_ssa_uncprop (); } | |
618 | ||
619 | }; // class pass_uncprop | |
620 | ||
621 | } // anon namespace | |
622 | ||
623 | gimple_opt_pass * | |
624 | make_pass_uncprop (gcc::context *ctxt) | |
625 | { | |
626 | return new pass_uncprop (ctxt); | |
627 | } |