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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" | |
25 | #include "flags.h" | |
5f718c29 | 26 | #include "tm_p.h" |
5f718c29 | 27 | #include "basic-block.h" |
5f718c29 | 28 | #include "function.h" |
073c1fd5 | 29 | #include "gimple.h" |
dcf1a1ec | 30 | #include "gimple-iterator.h" |
073c1fd5 | 31 | #include "gimple-ssa.h" |
32 | #include "tree-cfg.h" | |
33 | #include "tree-phinodes.h" | |
34 | #include "ssa-iterators.h" | |
5f718c29 | 35 | #include "domwalk.h" |
5f718c29 | 36 | #include "tree-pass.h" |
37 | #include "tree-ssa-propagate.h" | |
5f718c29 | 38 | |
39 | /* The basic structure describing an equivalency created by traversing | |
40 | an edge. Traversing the edge effectively means that we can assume | |
41 | that we've seen an assignment LHS = RHS. */ | |
42 | struct edge_equivalency | |
43 | { | |
44 | tree rhs; | |
45 | tree lhs; | |
46 | }; | |
47 | ||
48 | /* This routine finds and records edge equivalences for every edge | |
49 | in the CFG. | |
50 | ||
51 | When complete, each edge that creates an equivalency will have an | |
48e1416a | 52 | EDGE_EQUIVALENCY structure hanging off the edge's AUX field. |
5f718c29 | 53 | The caller is responsible for freeing the AUX fields. */ |
54 | ||
55 | static void | |
56 | associate_equivalences_with_edges (void) | |
57 | { | |
58 | basic_block bb; | |
59 | ||
60 | /* Walk over each block. If the block ends with a control statement, | |
61 | then it might create a useful equivalence. */ | |
62 | FOR_EACH_BB (bb) | |
63 | { | |
75a70cf9 | 64 | gimple_stmt_iterator gsi = gsi_last_bb (bb); |
65 | gimple stmt; | |
5f718c29 | 66 | |
67 | /* If the block does not end with a COND_EXPR or SWITCH_EXPR | |
68 | then there is nothing to do. */ | |
75a70cf9 | 69 | if (gsi_end_p (gsi)) |
5f718c29 | 70 | continue; |
71 | ||
75a70cf9 | 72 | stmt = gsi_stmt (gsi); |
5f718c29 | 73 | |
74 | if (!stmt) | |
75 | continue; | |
76 | ||
77 | /* A COND_EXPR may create an equivalency in a variety of different | |
78 | ways. */ | |
75a70cf9 | 79 | if (gimple_code (stmt) == GIMPLE_COND) |
5f718c29 | 80 | { |
5f718c29 | 81 | edge true_edge; |
82 | edge false_edge; | |
83 | struct edge_equivalency *equivalency; | |
75a70cf9 | 84 | enum tree_code code = gimple_cond_code (stmt); |
5f718c29 | 85 | |
86 | extract_true_false_edges_from_block (bb, &true_edge, &false_edge); | |
87 | ||
5f718c29 | 88 | /* Equality tests may create one or two equivalences. */ |
75a70cf9 | 89 | if (code == EQ_EXPR || code == NE_EXPR) |
5f718c29 | 90 | { |
75a70cf9 | 91 | tree op0 = gimple_cond_lhs (stmt); |
92 | tree op1 = gimple_cond_rhs (stmt); | |
5f718c29 | 93 | |
94 | /* Special case comparing booleans against a constant as we | |
95 | know the value of OP0 on both arms of the branch. i.e., we | |
96 | can record an equivalence for OP0 rather than COND. */ | |
97 | if (TREE_CODE (op0) == SSA_NAME | |
932540b6 | 98 | && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (op0) |
5f718c29 | 99 | && TREE_CODE (TREE_TYPE (op0)) == BOOLEAN_TYPE |
100 | && is_gimple_min_invariant (op1)) | |
101 | { | |
75a70cf9 | 102 | if (code == EQ_EXPR) |
5f718c29 | 103 | { |
945865c5 | 104 | equivalency = XNEW (struct edge_equivalency); |
5f718c29 | 105 | equivalency->lhs = op0; |
106 | equivalency->rhs = (integer_zerop (op1) | |
107 | ? boolean_false_node | |
108 | : boolean_true_node); | |
109 | true_edge->aux = equivalency; | |
110 | ||
945865c5 | 111 | equivalency = XNEW (struct edge_equivalency); |
5f718c29 | 112 | equivalency->lhs = op0; |
113 | equivalency->rhs = (integer_zerop (op1) | |
114 | ? boolean_true_node | |
115 | : boolean_false_node); | |
116 | false_edge->aux = equivalency; | |
117 | } | |
118 | else | |
119 | { | |
945865c5 | 120 | equivalency = XNEW (struct edge_equivalency); |
5f718c29 | 121 | equivalency->lhs = op0; |
122 | equivalency->rhs = (integer_zerop (op1) | |
123 | ? boolean_true_node | |
124 | : boolean_false_node); | |
125 | true_edge->aux = equivalency; | |
126 | ||
945865c5 | 127 | equivalency = XNEW (struct edge_equivalency); |
5f718c29 | 128 | equivalency->lhs = op0; |
129 | equivalency->rhs = (integer_zerop (op1) | |
130 | ? boolean_false_node | |
131 | : boolean_true_node); | |
132 | false_edge->aux = equivalency; | |
133 | } | |
134 | } | |
135 | ||
024e445d | 136 | else if (TREE_CODE (op0) == SSA_NAME |
137 | && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (op0) | |
138 | && (is_gimple_min_invariant (op1) | |
139 | || (TREE_CODE (op1) == SSA_NAME | |
140 | && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (op1)))) | |
5f718c29 | 141 | { |
142 | /* For IEEE, -0.0 == 0.0, so we don't necessarily know | |
143 | the sign of a variable compared against zero. If | |
144 | we're honoring signed zeros, then we cannot record | |
145 | this value unless we know that the value is nonzero. */ | |
146 | if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (op0))) | |
147 | && (TREE_CODE (op1) != REAL_CST | |
148 | || REAL_VALUES_EQUAL (dconst0, TREE_REAL_CST (op1)))) | |
149 | continue; | |
150 | ||
945865c5 | 151 | equivalency = XNEW (struct edge_equivalency); |
5f718c29 | 152 | equivalency->lhs = op0; |
153 | equivalency->rhs = op1; | |
75a70cf9 | 154 | if (code == EQ_EXPR) |
5f718c29 | 155 | true_edge->aux = equivalency; |
48e1416a | 156 | else |
5f718c29 | 157 | false_edge->aux = equivalency; |
158 | ||
159 | } | |
160 | } | |
161 | ||
162 | /* ??? TRUTH_NOT_EXPR can create an equivalence too. */ | |
163 | } | |
164 | ||
165 | /* For a SWITCH_EXPR, a case label which represents a single | |
166 | value and which is the only case label which reaches the | |
167 | target block creates an equivalence. */ | |
75a70cf9 | 168 | else if (gimple_code (stmt) == GIMPLE_SWITCH) |
5f718c29 | 169 | { |
75a70cf9 | 170 | tree cond = gimple_switch_index (stmt); |
5f718c29 | 171 | |
932540b6 | 172 | if (TREE_CODE (cond) == SSA_NAME |
173 | && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (cond)) | |
5f718c29 | 174 | { |
75a70cf9 | 175 | int i, n_labels = gimple_switch_num_labels (stmt); |
87490e08 | 176 | tree *info = XCNEWVEC (tree, last_basic_block); |
5f718c29 | 177 | |
178 | /* Walk over the case label vector. Record blocks | |
179 | which are reached by a single case label which represents | |
180 | a single value. */ | |
181 | for (i = 0; i < n_labels; i++) | |
182 | { | |
75a70cf9 | 183 | tree label = gimple_switch_label (stmt, i); |
5f718c29 | 184 | basic_block bb = label_to_block (CASE_LABEL (label)); |
185 | ||
5f718c29 | 186 | if (CASE_HIGH (label) |
187 | || !CASE_LOW (label) | |
188 | || info[bb->index]) | |
189 | info[bb->index] = error_mark_node; | |
190 | else | |
191 | info[bb->index] = label; | |
192 | } | |
193 | ||
194 | /* Now walk over the blocks to determine which ones were | |
195 | marked as being reached by a useful case label. */ | |
a28770e1 | 196 | for (i = 0; i < n_basic_blocks_for_fn (cfun); i++) |
5f718c29 | 197 | { |
198 | tree node = info[i]; | |
199 | ||
200 | if (node != NULL | |
201 | && node != error_mark_node) | |
202 | { | |
203 | tree x = fold_convert (TREE_TYPE (cond), CASE_LOW (node)); | |
204 | struct edge_equivalency *equivalency; | |
205 | ||
206 | /* Record an equivalency on the edge from BB to basic | |
207 | block I. */ | |
945865c5 | 208 | equivalency = XNEW (struct edge_equivalency); |
5f718c29 | 209 | equivalency->rhs = x; |
210 | equivalency->lhs = cond; | |
211 | find_edge (bb, BASIC_BLOCK (i))->aux = equivalency; | |
212 | } | |
213 | } | |
214 | free (info); | |
215 | } | |
216 | } | |
217 | ||
218 | } | |
219 | } | |
220 | ||
221 | ||
222 | /* Translating out of SSA sometimes requires inserting copies and | |
223 | constant initializations on edges to eliminate PHI nodes. | |
224 | ||
225 | In some cases those copies and constant initializations are | |
226 | redundant because the target already has the value on the | |
227 | RHS of the assignment. | |
228 | ||
229 | We previously tried to catch these cases after translating | |
230 | out of SSA form. However, that code often missed cases. Worse | |
231 | yet, the cases it missed were also often missed by the RTL | |
232 | optimizers. Thus the resulting code had redundant instructions. | |
233 | ||
234 | This pass attempts to detect these situations before translating | |
235 | out of SSA form. | |
236 | ||
237 | The key concept that this pass is built upon is that these | |
238 | redundant copies and constant initializations often occur | |
239 | due to constant/copy propagating equivalences resulting from | |
240 | COND_EXPRs and SWITCH_EXPRs. | |
241 | ||
242 | We want to do those propagations as they can sometimes allow | |
25f6297d | 243 | the SSA optimizers to do a better job. However, in the cases |
5f718c29 | 244 | where such propagations do not result in further optimization, |
245 | we would like to "undo" the propagation to avoid the redundant | |
246 | copies and constant initializations. | |
247 | ||
248 | This pass works by first associating equivalences with edges in | |
249 | the CFG. For example, the edge leading from a SWITCH_EXPR to | |
250 | its associated CASE_LABEL will have an equivalency between | |
251 | SWITCH_COND and the value in the case label. | |
252 | ||
253 | Once we have found the edge equivalences, we proceed to walk | |
254 | the CFG in dominator order. As we traverse edges we record | |
255 | equivalences associated with those edges we traverse. | |
256 | ||
257 | When we encounter a PHI node, we walk its arguments to see if we | |
258 | have an equivalence for the PHI argument. If so, then we replace | |
259 | the argument. | |
260 | ||
261 | Equivalences are looked up based on their value (think of it as | |
262 | the RHS of an assignment). A value may be an SSA_NAME or an | |
263 | invariant. We may have several SSA_NAMEs with the same value, | |
264 | so with each value we have a list of SSA_NAMEs that have the | |
265 | same value. */ | |
266 | ||
5f718c29 | 267 | |
5f718c29 | 268 | /* Main structure for recording equivalences into our hash table. */ |
269 | struct equiv_hash_elt | |
270 | { | |
271 | /* The value/key of this entry. */ | |
272 | tree value; | |
273 | ||
274 | /* List of SSA_NAMEs which have the same value/key. */ | |
f1f41a6c | 275 | vec<tree> equivalences; |
5f718c29 | 276 | }; |
277 | ||
d9dd21a8 | 278 | /* Value to ssa name equivalence hashtable helpers. */ |
5f718c29 | 279 | |
d9dd21a8 | 280 | struct val_ssa_equiv_hasher |
281 | { | |
282 | typedef equiv_hash_elt value_type; | |
283 | typedef equiv_hash_elt compare_type; | |
284 | static inline hashval_t hash (const value_type *); | |
285 | static inline bool equal (const value_type *, const compare_type *); | |
286 | static inline void remove (value_type *); | |
287 | }; | |
5f718c29 | 288 | |
d9dd21a8 | 289 | inline hashval_t |
290 | val_ssa_equiv_hasher::hash (const value_type *p) | |
5f718c29 | 291 | { |
d9dd21a8 | 292 | tree const value = p->value; |
5f718c29 | 293 | return iterative_hash_expr (value, 0); |
294 | } | |
295 | ||
d9dd21a8 | 296 | inline bool |
297 | val_ssa_equiv_hasher::equal (const value_type *p1, const compare_type *p2) | |
5f718c29 | 298 | { |
d9dd21a8 | 299 | tree value1 = p1->value; |
300 | tree value2 = p2->value; | |
5f718c29 | 301 | |
302 | return operand_equal_p (value1, value2, 0); | |
303 | } | |
304 | ||
96a7ab57 | 305 | /* Free an instance of equiv_hash_elt. */ |
306 | ||
d9dd21a8 | 307 | inline void |
308 | val_ssa_equiv_hasher::remove (value_type *elt) | |
96a7ab57 | 309 | { |
f1f41a6c | 310 | elt->equivalences.release (); |
96a7ab57 | 311 | free (elt); |
312 | } | |
313 | ||
d9dd21a8 | 314 | /* Global hash table implementing a mapping from invariant values |
315 | to a list of SSA_NAMEs which have the same value. We might be | |
316 | able to reuse tree-vn for this code. */ | |
317 | static hash_table <val_ssa_equiv_hasher> val_ssa_equiv; | |
318 | ||
d9dd21a8 | 319 | static void uncprop_into_successor_phis (basic_block); |
320 | ||
5f718c29 | 321 | /* Remove the most recently recorded equivalency for VALUE. */ |
322 | ||
323 | static void | |
324 | remove_equivalence (tree value) | |
325 | { | |
d9dd21a8 | 326 | struct equiv_hash_elt an_equiv_elt, *an_equiv_elt_p; |
327 | equiv_hash_elt **slot; | |
5f718c29 | 328 | |
d9dd21a8 | 329 | an_equiv_elt.value = value; |
330 | an_equiv_elt.equivalences.create (0); | |
5f718c29 | 331 | |
d9dd21a8 | 332 | slot = val_ssa_equiv.find_slot (&an_equiv_elt, NO_INSERT); |
5f718c29 | 333 | |
d9dd21a8 | 334 | an_equiv_elt_p = *slot; |
335 | an_equiv_elt_p->equivalences.pop (); | |
5f718c29 | 336 | } |
337 | ||
338 | /* Record EQUIVALENCE = VALUE into our hash table. */ | |
339 | ||
340 | static void | |
341 | record_equiv (tree value, tree equivalence) | |
342 | { | |
d9dd21a8 | 343 | equiv_hash_elt *an_equiv_elt_p; |
344 | equiv_hash_elt **slot; | |
5f718c29 | 345 | |
d9dd21a8 | 346 | an_equiv_elt_p = XNEW (struct equiv_hash_elt); |
347 | an_equiv_elt_p->value = value; | |
348 | an_equiv_elt_p->equivalences.create (0); | |
5f718c29 | 349 | |
d9dd21a8 | 350 | slot = val_ssa_equiv.find_slot (an_equiv_elt_p, INSERT); |
5f718c29 | 351 | |
352 | if (*slot == NULL) | |
d9dd21a8 | 353 | *slot = an_equiv_elt_p; |
5f718c29 | 354 | else |
d9dd21a8 | 355 | free (an_equiv_elt_p); |
5f718c29 | 356 | |
d9dd21a8 | 357 | an_equiv_elt_p = *slot; |
48e1416a | 358 | |
d9dd21a8 | 359 | an_equiv_elt_p->equivalences.safe_push (equivalence); |
5f718c29 | 360 | } |
361 | ||
54c91640 | 362 | class uncprop_dom_walker : public dom_walker |
363 | { | |
364 | public: | |
e85cf4e5 | 365 | uncprop_dom_walker (cdi_direction direction) : dom_walker (direction) {} |
54c91640 | 366 | |
367 | virtual void before_dom_children (basic_block); | |
368 | virtual void after_dom_children (basic_block); | |
369 | ||
370 | private: | |
371 | ||
ae84f584 | 372 | /* As we enter each block we record the value for any edge equivalency |
373 | leading to this block. If no such edge equivalency exists, then we | |
374 | record NULL. These equivalences are live until we leave the dominator | |
375 | subtree rooted at the block where we record the equivalency. */ | |
e85cf4e5 | 376 | stack_vec<tree, 2> m_equiv_stack; |
54c91640 | 377 | }; |
378 | ||
5f718c29 | 379 | /* Main driver for un-cprop. */ |
380 | ||
2a1990e9 | 381 | static unsigned int |
5f718c29 | 382 | tree_ssa_uncprop (void) |
383 | { | |
5f718c29 | 384 | basic_block bb; |
385 | ||
386 | associate_equivalences_with_edges (); | |
387 | ||
388 | /* Create our global data structures. */ | |
d9dd21a8 | 389 | val_ssa_equiv.create (1024); |
5f718c29 | 390 | |
391 | /* We're going to do a dominator walk, so ensure that we have | |
392 | dominance information. */ | |
393 | calculate_dominance_info (CDI_DOMINATORS); | |
394 | ||
5f718c29 | 395 | /* Recursively walk the dominator tree undoing unprofitable |
396 | constant/copy propagations. */ | |
54c91640 | 397 | uncprop_dom_walker (CDI_DOMINATORS).walk (cfun->cfg->x_entry_block_ptr); |
5f718c29 | 398 | |
54c91640 | 399 | /* we just need to empty elements out of the hash table, and cleanup the |
400 | AUX field on the edges. */ | |
d9dd21a8 | 401 | val_ssa_equiv.dispose (); |
5f718c29 | 402 | FOR_EACH_BB (bb) |
403 | { | |
404 | edge e; | |
405 | edge_iterator ei; | |
406 | ||
407 | FOR_EACH_EDGE (e, ei, bb->succs) | |
408 | { | |
409 | if (e->aux) | |
410 | { | |
411 | free (e->aux); | |
412 | e->aux = NULL; | |
413 | } | |
414 | } | |
415 | } | |
2a1990e9 | 416 | return 0; |
5f718c29 | 417 | } |
418 | ||
419 | ||
420 | /* We have finished processing the dominator children of BB, perform | |
421 | any finalization actions in preparation for leaving this node in | |
422 | the dominator tree. */ | |
423 | ||
54c91640 | 424 | void |
425 | uncprop_dom_walker::after_dom_children (basic_block bb ATTRIBUTE_UNUSED) | |
5f718c29 | 426 | { |
5f718c29 | 427 | /* Pop the topmost value off the equiv stack. */ |
ae84f584 | 428 | tree value = m_equiv_stack.pop (); |
5f718c29 | 429 | |
430 | /* If that value was non-null, then pop the topmost equivalency off | |
431 | its equivalency stack. */ | |
432 | if (value != NULL) | |
433 | remove_equivalence (value); | |
434 | } | |
435 | ||
436 | /* Unpropagate values from PHI nodes in successor blocks of BB. */ | |
437 | ||
438 | static void | |
6bf320fb | 439 | uncprop_into_successor_phis (basic_block bb) |
5f718c29 | 440 | { |
441 | edge e; | |
442 | edge_iterator ei; | |
443 | ||
444 | /* For each successor edge, first temporarily record any equivalence | |
445 | on that edge. Then unpropagate values in any PHI nodes at the | |
446 | destination of the edge. Then remove the temporary equivalence. */ | |
447 | FOR_EACH_EDGE (e, ei, bb->succs) | |
448 | { | |
75a70cf9 | 449 | gimple_seq phis = phi_nodes (e->dest); |
450 | gimple_stmt_iterator gsi; | |
5f718c29 | 451 | |
452 | /* If there are no PHI nodes in this destination, then there is | |
453 | no sense in recording any equivalences. */ | |
be2517f5 | 454 | if (gimple_seq_empty_p (phis)) |
5f718c29 | 455 | continue; |
456 | ||
457 | /* Record any equivalency associated with E. */ | |
458 | if (e->aux) | |
459 | { | |
945865c5 | 460 | struct edge_equivalency *equiv = (struct edge_equivalency *) e->aux; |
5f718c29 | 461 | record_equiv (equiv->rhs, equiv->lhs); |
462 | } | |
463 | ||
464 | /* Walk over the PHI nodes, unpropagating values. */ | |
75a70cf9 | 465 | for (gsi = gsi_start (phis) ; !gsi_end_p (gsi); gsi_next (&gsi)) |
5f718c29 | 466 | { |
75a70cf9 | 467 | gimple phi = gsi_stmt (gsi); |
5f718c29 | 468 | tree arg = PHI_ARG_DEF (phi, e->dest_idx); |
ec11736b | 469 | tree res = PHI_RESULT (phi); |
d9dd21a8 | 470 | equiv_hash_elt an_equiv_elt; |
471 | equiv_hash_elt **slot; | |
5f718c29 | 472 | |
f82f0ea5 | 473 | /* If the argument is not an invariant and can be potentially |
474 | coalesced with the result, then there's no point in | |
475 | un-propagating the argument. */ | |
5f718c29 | 476 | if (!is_gimple_min_invariant (arg) |
f82f0ea5 | 477 | && gimple_can_coalesce_p (arg, res)) |
5f718c29 | 478 | continue; |
479 | ||
480 | /* Lookup this argument's value in the hash table. */ | |
d9dd21a8 | 481 | an_equiv_elt.value = arg; |
482 | an_equiv_elt.equivalences.create (0); | |
483 | slot = val_ssa_equiv.find_slot (&an_equiv_elt, NO_INSERT); | |
5f718c29 | 484 | |
485 | if (slot) | |
486 | { | |
d9dd21a8 | 487 | struct equiv_hash_elt *elt = *slot; |
5f718c29 | 488 | int j; |
489 | ||
490 | /* Walk every equivalence with the same value. If we find | |
f82f0ea5 | 491 | one that can potentially coalesce with the PHI rsult, |
5f718c29 | 492 | then replace the value in the argument with its equivalent |
25f6297d | 493 | SSA_NAME. Use the most recent equivalence as hopefully |
5f718c29 | 494 | that results in shortest lifetimes. */ |
f1f41a6c | 495 | for (j = elt->equivalences.length () - 1; j >= 0; j--) |
5f718c29 | 496 | { |
f1f41a6c | 497 | tree equiv = elt->equivalences[j]; |
5f718c29 | 498 | |
f82f0ea5 | 499 | if (gimple_can_coalesce_p (equiv, res)) |
5f718c29 | 500 | { |
501 | SET_PHI_ARG_DEF (phi, e->dest_idx, equiv); | |
502 | break; | |
503 | } | |
504 | } | |
505 | } | |
506 | } | |
507 | ||
508 | /* If we had an equivalence associated with this edge, remove it. */ | |
509 | if (e->aux) | |
510 | { | |
945865c5 | 511 | struct edge_equivalency *equiv = (struct edge_equivalency *) e->aux; |
5f718c29 | 512 | remove_equivalence (equiv->rhs); |
513 | } | |
514 | } | |
515 | } | |
516 | ||
517 | /* Ignoring loop backedges, if BB has precisely one incoming edge then | |
518 | return that edge. Otherwise return NULL. */ | |
519 | static edge | |
520 | single_incoming_edge_ignoring_loop_edges (basic_block bb) | |
521 | { | |
522 | edge retval = NULL; | |
523 | edge e; | |
524 | edge_iterator ei; | |
525 | ||
526 | FOR_EACH_EDGE (e, ei, bb->preds) | |
527 | { | |
528 | /* A loop back edge can be identified by the destination of | |
529 | the edge dominating the source of the edge. */ | |
530 | if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest)) | |
531 | continue; | |
532 | ||
533 | /* If we have already seen a non-loop edge, then we must have | |
534 | multiple incoming non-loop edges and thus we return NULL. */ | |
535 | if (retval) | |
536 | return NULL; | |
537 | ||
538 | /* This is the first non-loop incoming edge we have found. Record | |
539 | it. */ | |
540 | retval = e; | |
541 | } | |
542 | ||
543 | return retval; | |
544 | } | |
545 | ||
54c91640 | 546 | void |
547 | uncprop_dom_walker::before_dom_children (basic_block bb) | |
5f718c29 | 548 | { |
549 | basic_block parent; | |
550 | edge e; | |
551 | bool recorded = false; | |
552 | ||
553 | /* If this block is dominated by a single incoming edge and that edge | |
554 | has an equivalency, then record the equivalency and push the | |
555 | VALUE onto EQUIV_STACK. Else push a NULL entry on EQUIV_STACK. */ | |
556 | parent = get_immediate_dominator (CDI_DOMINATORS, bb); | |
557 | if (parent) | |
558 | { | |
559 | e = single_incoming_edge_ignoring_loop_edges (bb); | |
560 | ||
561 | if (e && e->src == parent && e->aux) | |
562 | { | |
945865c5 | 563 | struct edge_equivalency *equiv = (struct edge_equivalency *) e->aux; |
5f718c29 | 564 | |
565 | record_equiv (equiv->rhs, equiv->lhs); | |
ae84f584 | 566 | m_equiv_stack.safe_push (equiv->rhs); |
5f718c29 | 567 | recorded = true; |
568 | } | |
569 | } | |
570 | ||
571 | if (!recorded) | |
ae84f584 | 572 | m_equiv_stack.safe_push (NULL_TREE); |
6bf320fb | 573 | |
574 | uncprop_into_successor_phis (bb); | |
5f718c29 | 575 | } |
576 | ||
577 | static bool | |
578 | gate_uncprop (void) | |
579 | { | |
580 | return flag_tree_dom != 0; | |
581 | } | |
582 | ||
cbe8bda8 | 583 | namespace { |
584 | ||
585 | const pass_data pass_data_uncprop = | |
5f718c29 | 586 | { |
cbe8bda8 | 587 | GIMPLE_PASS, /* type */ |
588 | "uncprop", /* name */ | |
589 | OPTGROUP_NONE, /* optinfo_flags */ | |
590 | true, /* has_gate */ | |
591 | true, /* has_execute */ | |
592 | TV_TREE_SSA_UNCPROP, /* tv_id */ | |
593 | ( PROP_cfg | PROP_ssa ), /* properties_required */ | |
594 | 0, /* properties_provided */ | |
595 | 0, /* properties_destroyed */ | |
596 | 0, /* todo_flags_start */ | |
597 | TODO_verify_ssa, /* todo_flags_finish */ | |
5f718c29 | 598 | }; |
cbe8bda8 | 599 | |
600 | class pass_uncprop : public gimple_opt_pass | |
601 | { | |
602 | public: | |
9af5ce0c | 603 | pass_uncprop (gcc::context *ctxt) |
604 | : gimple_opt_pass (pass_data_uncprop, ctxt) | |
cbe8bda8 | 605 | {} |
606 | ||
607 | /* opt_pass methods: */ | |
ae84f584 | 608 | opt_pass * clone () { return new pass_uncprop (m_ctxt); } |
cbe8bda8 | 609 | bool gate () { return gate_uncprop (); } |
610 | unsigned int execute () { return tree_ssa_uncprop (); } | |
611 | ||
612 | }; // class pass_uncprop | |
613 | ||
614 | } // anon namespace | |
615 | ||
616 | gimple_opt_pass * | |
617 | make_pass_uncprop (gcc::context *ctxt) | |
618 | { | |
619 | return new pass_uncprop (ctxt); | |
620 | } |