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88dbf20f | 1 | /* Copy propagation and SSA_NAME replacement support routines. |
fbd26352 | 2 | Copyright (C) 2004-2019 Free Software Foundation, Inc. |
4ee9c684 | 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) |
4ee9c684 | 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/>. */ | |
4ee9c684 | 19 | |
20 | #include "config.h" | |
21 | #include "system.h" | |
22 | #include "coretypes.h" | |
9ef16211 | 23 | #include "backend.h" |
4ee9c684 | 24 | #include "tree.h" |
9ef16211 | 25 | #include "gimple.h" |
7c29e30e | 26 | #include "tree-pass.h" |
9ef16211 | 27 | #include "ssa.h" |
7c29e30e | 28 | #include "gimple-pretty-print.h" |
b20a8bb4 | 29 | #include "fold-const.h" |
dcf1a1ec | 30 | #include "gimple-iterator.h" |
073c1fd5 | 31 | #include "tree-cfg.h" |
88dbf20f | 32 | #include "tree-ssa-propagate.h" |
23a3430d | 33 | #include "cfgloop.h" |
f6568ea4 | 34 | #include "tree-scalar-evolution.h" |
c919e493 | 35 | #include "tree-ssa-loop-niter.h" |
36 | ||
4ee9c684 | 37 | |
88dbf20f | 38 | /* This file implements the copy propagation pass and provides a |
39 | handful of interfaces for performing const/copy propagation and | |
40 | simple expression replacement which keep variable annotations | |
41 | up-to-date. | |
4ee9c684 | 42 | |
43 | We require that for any copy operation where the RHS and LHS have | |
f7406879 | 44 | a non-null memory tag the memory tag be the same. It is OK |
4ee9c684 | 45 | for one or both of the memory tags to be NULL. |
46 | ||
47 | We also require tracking if a variable is dereferenced in a load or | |
48 | store operation. | |
49 | ||
50 | We enforce these requirements by having all copy propagation and | |
51 | replacements of one SSA_NAME with a different SSA_NAME to use the | |
52 | APIs defined in this file. */ | |
53 | ||
88dbf20f | 54 | /*--------------------------------------------------------------------------- |
55 | Copy propagation | |
56 | ---------------------------------------------------------------------------*/ | |
6ecedef2 | 57 | /* Lattice for copy-propagation. The lattice is initialized to |
58 | UNDEFINED (value == NULL) for SSA names that can become a copy | |
59 | of something or VARYING (value == self) if not (see get_copy_of_val | |
60 | and stmt_may_generate_copy). Other values make the name a COPY | |
61 | of that value. | |
88dbf20f | 62 | |
6ecedef2 | 63 | When visiting a statement or PHI node the lattice value for an |
64 | SSA name can transition from UNDEFINED to COPY to VARYING. */ | |
14f101cf | 65 | |
9908fe4d | 66 | struct prop_value_t { |
14f101cf | 67 | /* Copy-of value. */ |
68 | tree value; | |
69 | }; | |
14f101cf | 70 | |
6bd87d95 | 71 | class copy_prop : public ssa_propagation_engine |
72 | { | |
73 | public: | |
74 | enum ssa_prop_result visit_stmt (gimple *, edge *, tree *) FINAL OVERRIDE; | |
75 | enum ssa_prop_result visit_phi (gphi *) FINAL OVERRIDE; | |
76 | }; | |
77 | ||
88dbf20f | 78 | static prop_value_t *copy_of; |
285df01b | 79 | static unsigned n_copy_of; |
88dbf20f | 80 | |
88dbf20f | 81 | |
82 | /* Return true if this statement may generate a useful copy. */ | |
83 | ||
84 | static bool | |
42acab1c | 85 | stmt_may_generate_copy (gimple *stmt) |
88dbf20f | 86 | { |
75a70cf9 | 87 | if (gimple_code (stmt) == GIMPLE_PHI) |
88 | return !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (gimple_phi_result (stmt)); | |
88dbf20f | 89 | |
75a70cf9 | 90 | if (gimple_code (stmt) != GIMPLE_ASSIGN) |
88dbf20f | 91 | return false; |
92 | ||
88dbf20f | 93 | /* If the statement has volatile operands, it won't generate a |
94 | useful copy. */ | |
75a70cf9 | 95 | if (gimple_has_volatile_ops (stmt)) |
88dbf20f | 96 | return false; |
97 | ||
317d3b82 | 98 | /* Statements with loads and/or stores will never generate a useful copy. */ |
dd277d48 | 99 | if (gimple_vuse (stmt)) |
88dbf20f | 100 | return false; |
101 | ||
102 | /* Otherwise, the only statements that generate useful copies are | |
103 | assignments whose RHS is just an SSA name that doesn't flow | |
104 | through abnormal edges. */ | |
f82efd77 | 105 | return ((gimple_assign_rhs_code (stmt) == SSA_NAME |
106 | && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (gimple_assign_rhs1 (stmt))) | |
107 | || is_gimple_min_invariant (gimple_assign_rhs1 (stmt))); | |
88dbf20f | 108 | } |
109 | ||
110 | ||
111 | /* Return the copy-of value for VAR. */ | |
112 | ||
113 | static inline prop_value_t * | |
114 | get_copy_of_val (tree var) | |
115 | { | |
116 | prop_value_t *val = ©_of[SSA_NAME_VERSION (var)]; | |
117 | ||
118 | if (val->value == NULL_TREE | |
119 | && !stmt_may_generate_copy (SSA_NAME_DEF_STMT (var))) | |
120 | { | |
121 | /* If the variable will never generate a useful copy relation, | |
122 | make it its own copy. */ | |
123 | val->value = var; | |
88dbf20f | 124 | } |
125 | ||
126 | return val; | |
127 | } | |
128 | ||
6ecedef2 | 129 | /* Return the variable VAR is a copy of or VAR if VAR isn't the result |
130 | of a copy. */ | |
88dbf20f | 131 | |
6ecedef2 | 132 | static inline tree |
133 | valueize_val (tree var) | |
88dbf20f | 134 | { |
6ecedef2 | 135 | if (TREE_CODE (var) == SSA_NAME) |
88dbf20f | 136 | { |
6ecedef2 | 137 | tree val = get_copy_of_val (var)->value; |
138 | if (val) | |
139 | return val; | |
88dbf20f | 140 | } |
6ecedef2 | 141 | return var; |
88dbf20f | 142 | } |
143 | ||
6ecedef2 | 144 | /* Set VAL to be the copy of VAR. If that changed return true. */ |
88dbf20f | 145 | |
146 | static inline bool | |
6ecedef2 | 147 | set_copy_of_val (tree var, tree val) |
88dbf20f | 148 | { |
6ecedef2 | 149 | unsigned int ver = SSA_NAME_VERSION (var); |
150 | tree old; | |
48e1416a | 151 | |
88dbf20f | 152 | /* Set FIRST to be the first link in COPY_OF[DEST]. If that |
153 | changed, return true. */ | |
6ecedef2 | 154 | old = copy_of[ver].value; |
155 | copy_of[ver].value = val; | |
88dbf20f | 156 | |
82f6f8b4 | 157 | if (old != val |
dd3604c1 | 158 | && (!old || !operand_equal_p (old, val, 0))) |
88dbf20f | 159 | return true; |
160 | ||
6ecedef2 | 161 | return false; |
88dbf20f | 162 | } |
163 | ||
164 | ||
3f5be5f4 | 165 | /* Dump the copy-of value for variable VAR to FILE. */ |
88dbf20f | 166 | |
167 | static void | |
3f5be5f4 | 168 | dump_copy_of (FILE *file, tree var) |
88dbf20f | 169 | { |
170 | tree val; | |
171 | ||
3f5be5f4 | 172 | print_generic_expr (file, var, dump_flags); |
88dbf20f | 173 | if (TREE_CODE (var) != SSA_NAME) |
174 | return; | |
48e1416a | 175 | |
6ecedef2 | 176 | val = copy_of[SSA_NAME_VERSION (var)].value; |
3f5be5f4 | 177 | fprintf (file, " copy-of chain: "); |
1ffa4346 | 178 | print_generic_expr (file, var); |
3f5be5f4 | 179 | fprintf (file, " "); |
6ecedef2 | 180 | if (!val) |
181 | fprintf (file, "[UNDEFINED]"); | |
182 | else if (val == var) | |
183 | fprintf (file, "[NOT A COPY]"); | |
184 | else | |
88dbf20f | 185 | { |
3f5be5f4 | 186 | fprintf (file, "-> "); |
1ffa4346 | 187 | print_generic_expr (file, val); |
3f5be5f4 | 188 | fprintf (file, " "); |
6ecedef2 | 189 | fprintf (file, "[COPY]"); |
88dbf20f | 190 | } |
88dbf20f | 191 | } |
192 | ||
193 | ||
194 | /* Evaluate the RHS of STMT. If it produces a valid copy, set the LHS | |
6ecedef2 | 195 | value and store the LHS into *RESULT_P. */ |
88dbf20f | 196 | |
197 | static enum ssa_prop_result | |
42acab1c | 198 | copy_prop_visit_assignment (gimple *stmt, tree *result_p) |
88dbf20f | 199 | { |
200 | tree lhs, rhs; | |
88dbf20f | 201 | |
75a70cf9 | 202 | lhs = gimple_assign_lhs (stmt); |
82f6f8b4 | 203 | rhs = valueize_val (gimple_assign_rhs1 (stmt)); |
88dbf20f | 204 | |
205 | if (TREE_CODE (lhs) == SSA_NAME) | |
206 | { | |
207 | /* Straight copy between two SSA names. First, make sure that | |
208 | we can propagate the RHS into uses of LHS. */ | |
209 | if (!may_propagate_copy (lhs, rhs)) | |
210 | return SSA_PROP_VARYING; | |
211 | ||
88dbf20f | 212 | *result_p = lhs; |
82f6f8b4 | 213 | if (set_copy_of_val (*result_p, rhs)) |
88dbf20f | 214 | return SSA_PROP_INTERESTING; |
215 | else | |
216 | return SSA_PROP_NOT_INTERESTING; | |
217 | } | |
218 | ||
88dbf20f | 219 | return SSA_PROP_VARYING; |
220 | } | |
221 | ||
222 | ||
75a70cf9 | 223 | /* Visit the GIMPLE_COND STMT. Return SSA_PROP_INTERESTING |
88dbf20f | 224 | if it can determine which edge will be taken. Otherwise, return |
225 | SSA_PROP_VARYING. */ | |
226 | ||
227 | static enum ssa_prop_result | |
42acab1c | 228 | copy_prop_visit_cond_stmt (gimple *stmt, edge *taken_edge_p) |
88dbf20f | 229 | { |
75a70cf9 | 230 | enum ssa_prop_result retval = SSA_PROP_VARYING; |
389dd41b | 231 | location_t loc = gimple_location (stmt); |
88dbf20f | 232 | |
06a06ab5 | 233 | tree op0 = valueize_val (gimple_cond_lhs (stmt)); |
234 | tree op1 = valueize_val (gimple_cond_rhs (stmt)); | |
88dbf20f | 235 | |
06a06ab5 | 236 | /* See if we can determine the predicate's value. */ |
237 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
88dbf20f | 238 | { |
06a06ab5 | 239 | fprintf (dump_file, "Trying to determine truth value of "); |
240 | fprintf (dump_file, "predicate "); | |
1ffa4346 | 241 | print_gimple_stmt (dump_file, stmt, 0); |
06a06ab5 | 242 | } |
243 | ||
244 | /* Fold COND and see whether we get a useful result. */ | |
245 | tree folded_cond = fold_binary_loc (loc, gimple_cond_code (stmt), | |
246 | boolean_type_node, op0, op1); | |
247 | if (folded_cond) | |
248 | { | |
249 | basic_block bb = gimple_bb (stmt); | |
250 | *taken_edge_p = find_taken_edge (bb, folded_cond); | |
251 | if (*taken_edge_p) | |
252 | retval = SSA_PROP_INTERESTING; | |
88dbf20f | 253 | } |
254 | ||
255 | if (dump_file && (dump_flags & TDF_DETAILS) && *taken_edge_p) | |
256 | fprintf (dump_file, "\nConditional will always take edge %d->%d\n", | |
257 | (*taken_edge_p)->src->index, (*taken_edge_p)->dest->index); | |
258 | ||
259 | return retval; | |
260 | } | |
261 | ||
262 | ||
263 | /* Evaluate statement STMT. If the statement produces a new output | |
264 | value, return SSA_PROP_INTERESTING and store the SSA_NAME holding | |
265 | the new value in *RESULT_P. | |
266 | ||
267 | If STMT is a conditional branch and we can determine its truth | |
268 | value, set *TAKEN_EDGE_P accordingly. | |
269 | ||
270 | If the new value produced by STMT is varying, return | |
271 | SSA_PROP_VARYING. */ | |
272 | ||
6bd87d95 | 273 | enum ssa_prop_result |
274 | copy_prop::visit_stmt (gimple *stmt, edge *taken_edge_p, tree *result_p) | |
88dbf20f | 275 | { |
88dbf20f | 276 | enum ssa_prop_result retval; |
277 | ||
278 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
279 | { | |
280 | fprintf (dump_file, "\nVisiting statement:\n"); | |
75a70cf9 | 281 | print_gimple_stmt (dump_file, stmt, 0, dump_flags); |
88dbf20f | 282 | fprintf (dump_file, "\n"); |
283 | } | |
284 | ||
75a70cf9 | 285 | if (gimple_assign_single_p (stmt) |
286 | && TREE_CODE (gimple_assign_lhs (stmt)) == SSA_NAME | |
82f6f8b4 | 287 | && (TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME |
288 | || is_gimple_min_invariant (gimple_assign_rhs1 (stmt)))) | |
88dbf20f | 289 | { |
290 | /* If the statement is a copy assignment, evaluate its RHS to | |
291 | see if the lattice value of its output has changed. */ | |
292 | retval = copy_prop_visit_assignment (stmt, result_p); | |
293 | } | |
75a70cf9 | 294 | else if (gimple_code (stmt) == GIMPLE_COND) |
88dbf20f | 295 | { |
296 | /* See if we can determine which edge goes out of a conditional | |
297 | jump. */ | |
298 | retval = copy_prop_visit_cond_stmt (stmt, taken_edge_p); | |
299 | } | |
300 | else | |
301 | retval = SSA_PROP_VARYING; | |
302 | ||
303 | if (retval == SSA_PROP_VARYING) | |
304 | { | |
305 | tree def; | |
306 | ssa_op_iter i; | |
307 | ||
308 | /* Any other kind of statement is not interesting for constant | |
309 | propagation and, therefore, not worth simulating. */ | |
310 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
311 | fprintf (dump_file, "No interesting values produced.\n"); | |
312 | ||
313 | /* The assignment is not a copy operation. Don't visit this | |
314 | statement again and mark all the definitions in the statement | |
315 | to be copies of nothing. */ | |
316 | FOR_EACH_SSA_TREE_OPERAND (def, stmt, i, SSA_OP_ALL_DEFS) | |
317d3b82 | 317 | set_copy_of_val (def, def); |
88dbf20f | 318 | } |
319 | ||
320 | return retval; | |
321 | } | |
322 | ||
323 | ||
324 | /* Visit PHI node PHI. If all the arguments produce the same value, | |
325 | set it to be the value of the LHS of PHI. */ | |
326 | ||
6bd87d95 | 327 | enum ssa_prop_result |
328 | copy_prop::visit_phi (gphi *phi) | |
88dbf20f | 329 | { |
330 | enum ssa_prop_result retval; | |
75a70cf9 | 331 | unsigned i; |
14f101cf | 332 | prop_value_t phi_val = { NULL_TREE }; |
88dbf20f | 333 | |
75a70cf9 | 334 | tree lhs = gimple_phi_result (phi); |
88dbf20f | 335 | |
336 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
337 | { | |
338 | fprintf (dump_file, "\nVisiting PHI node: "); | |
75a70cf9 | 339 | print_gimple_stmt (dump_file, phi, 0, dump_flags); |
88dbf20f | 340 | } |
341 | ||
75a70cf9 | 342 | for (i = 0; i < gimple_phi_num_args (phi); i++) |
88dbf20f | 343 | { |
344 | prop_value_t *arg_val; | |
abb08aa8 | 345 | tree arg_value; |
75a70cf9 | 346 | tree arg = gimple_phi_arg_def (phi, i); |
347 | edge e = gimple_phi_arg_edge (phi, i); | |
88dbf20f | 348 | |
349 | /* We don't care about values flowing through non-executable | |
350 | edges. */ | |
351 | if (!(e->flags & EDGE_EXECUTABLE)) | |
352 | continue; | |
353 | ||
abb08aa8 | 354 | /* Names that flow through abnormal edges cannot be used to |
355 | derive copies. */ | |
356 | if (TREE_CODE (arg) == SSA_NAME && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (arg)) | |
88dbf20f | 357 | { |
358 | phi_val.value = lhs; | |
359 | break; | |
360 | } | |
361 | ||
88dbf20f | 362 | if (dump_file && (dump_flags & TDF_DETAILS)) |
363 | { | |
364 | fprintf (dump_file, "\tArgument #%d: ", i); | |
365 | dump_copy_of (dump_file, arg); | |
366 | fprintf (dump_file, "\n"); | |
367 | } | |
368 | ||
abb08aa8 | 369 | if (TREE_CODE (arg) == SSA_NAME) |
370 | { | |
371 | arg_val = get_copy_of_val (arg); | |
372 | ||
373 | /* If we didn't visit the definition of arg yet treat it as | |
374 | UNDEFINED. This also handles PHI arguments that are the | |
375 | same as lhs. We'll come here again. */ | |
376 | if (!arg_val->value) | |
377 | continue; | |
88dbf20f | 378 | |
abb08aa8 | 379 | arg_value = arg_val->value; |
380 | } | |
381 | else | |
382 | arg_value = valueize_val (arg); | |
383 | ||
3beff0e1 | 384 | /* In loop-closed SSA form do not copy-propagate SSA-names across |
385 | loop exit edges. */ | |
386 | if (loops_state_satisfies_p (LOOP_CLOSED_SSA) | |
387 | && TREE_CODE (arg_value) == SSA_NAME | |
388 | && loop_exit_edge_p (e->src->loop_father, e)) | |
abb08aa8 | 389 | { |
390 | phi_val.value = lhs; | |
391 | break; | |
392 | } | |
6ecedef2 | 393 | |
88dbf20f | 394 | /* If the LHS didn't have a value yet, make it a copy of the |
6ecedef2 | 395 | first argument we find. */ |
88dbf20f | 396 | if (phi_val.value == NULL_TREE) |
397 | { | |
abb08aa8 | 398 | phi_val.value = arg_value; |
88dbf20f | 399 | continue; |
400 | } | |
401 | ||
402 | /* If PHI_VAL and ARG don't have a common copy-of chain, then | |
6ecedef2 | 403 | this PHI node cannot be a copy operation. */ |
abb08aa8 | 404 | if (phi_val.value != arg_value |
405 | && !operand_equal_p (phi_val.value, arg_value, 0)) | |
88dbf20f | 406 | { |
407 | phi_val.value = lhs; | |
408 | break; | |
409 | } | |
410 | } | |
411 | ||
6ecedef2 | 412 | if (phi_val.value |
413 | && may_propagate_copy (lhs, phi_val.value) | |
b87f0847 | 414 | && set_copy_of_val (lhs, phi_val.value)) |
88dbf20f | 415 | retval = (phi_val.value != lhs) ? SSA_PROP_INTERESTING : SSA_PROP_VARYING; |
416 | else | |
417 | retval = SSA_PROP_NOT_INTERESTING; | |
418 | ||
419 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
420 | { | |
6ecedef2 | 421 | fprintf (dump_file, "PHI node "); |
88dbf20f | 422 | dump_copy_of (dump_file, lhs); |
423 | fprintf (dump_file, "\nTelling the propagator to "); | |
424 | if (retval == SSA_PROP_INTERESTING) | |
425 | fprintf (dump_file, "add SSA edges out of this PHI and continue."); | |
426 | else if (retval == SSA_PROP_VARYING) | |
427 | fprintf (dump_file, "add SSA edges out of this PHI and never visit again."); | |
428 | else | |
429 | fprintf (dump_file, "do nothing with SSA edges and keep iterating."); | |
430 | fprintf (dump_file, "\n\n"); | |
431 | } | |
432 | ||
433 | return retval; | |
434 | } | |
435 | ||
436 | ||
6ecedef2 | 437 | /* Initialize structures used for copy propagation. */ |
88dbf20f | 438 | |
439 | static void | |
d1d2af7d | 440 | init_copy_prop (void) |
88dbf20f | 441 | { |
442 | basic_block bb; | |
443 | ||
285df01b | 444 | n_copy_of = num_ssa_names; |
445 | copy_of = XCNEWVEC (prop_value_t, n_copy_of); | |
88dbf20f | 446 | |
fc00614f | 447 | FOR_EACH_BB_FN (bb, cfun) |
88dbf20f | 448 | { |
1a91d914 | 449 | for (gimple_stmt_iterator si = gsi_start_bb (bb); !gsi_end_p (si); |
450 | gsi_next (&si)) | |
88dbf20f | 451 | { |
42acab1c | 452 | gimple *stmt = gsi_stmt (si); |
2166ab0e | 453 | ssa_op_iter iter; |
75a70cf9 | 454 | tree def; |
88dbf20f | 455 | |
456 | /* The only statements that we care about are those that may | |
457 | generate useful copies. We also need to mark conditional | |
458 | jumps so that their outgoing edges are added to the work | |
3beff0e1 | 459 | lists of the propagator. */ |
88dbf20f | 460 | if (stmt_ends_bb_p (stmt)) |
75a70cf9 | 461 | prop_set_simulate_again (stmt, true); |
3beff0e1 | 462 | else if (stmt_may_generate_copy (stmt)) |
75a70cf9 | 463 | prop_set_simulate_again (stmt, true); |
88dbf20f | 464 | else |
75a70cf9 | 465 | prop_set_simulate_again (stmt, false); |
2166ab0e | 466 | |
467 | /* Mark all the outputs of this statement as not being | |
468 | the copy of anything. */ | |
469 | FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS) | |
75a70cf9 | 470 | if (!prop_simulate_again_p (stmt)) |
317d3b82 | 471 | set_copy_of_val (def, def); |
88dbf20f | 472 | } |
473 | ||
1a91d914 | 474 | for (gphi_iterator si = gsi_start_phis (bb); !gsi_end_p (si); |
475 | gsi_next (&si)) | |
2166ab0e | 476 | { |
1a91d914 | 477 | gphi *phi = si.phi (); |
75a70cf9 | 478 | tree def; |
479 | ||
480 | def = gimple_phi_result (phi); | |
7c782c9b | 481 | if (virtual_operand_p (def)) |
75a70cf9 | 482 | prop_set_simulate_again (phi, false); |
2166ab0e | 483 | else |
75a70cf9 | 484 | prop_set_simulate_again (phi, true); |
2166ab0e | 485 | |
75a70cf9 | 486 | if (!prop_simulate_again_p (phi)) |
317d3b82 | 487 | set_copy_of_val (def, def); |
2166ab0e | 488 | } |
88dbf20f | 489 | } |
490 | } | |
491 | ||
b08e7364 | 492 | class copy_folder : public substitute_and_fold_engine |
493 | { | |
494 | public: | |
495 | tree get_value (tree) FINAL OVERRIDE; | |
496 | }; | |
497 | ||
14f101cf | 498 | /* Callback for substitute_and_fold to get at the final copy-of values. */ |
499 | ||
b08e7364 | 500 | tree |
501 | copy_folder::get_value (tree name) | |
14f101cf | 502 | { |
285df01b | 503 | tree val; |
504 | if (SSA_NAME_VERSION (name) >= n_copy_of) | |
505 | return NULL_TREE; | |
506 | val = copy_of[SSA_NAME_VERSION (name)].value; | |
14f101cf | 507 | if (val && val != name) |
508 | return val; | |
509 | return NULL_TREE; | |
510 | } | |
88dbf20f | 511 | |
512 | /* Deallocate memory used in copy propagation and do final | |
513 | substitution. */ | |
514 | ||
c919e493 | 515 | static bool |
88dbf20f | 516 | fini_copy_prop (void) |
517 | { | |
14f101cf | 518 | unsigned i; |
f211616e | 519 | tree var; |
48e1416a | 520 | |
88dbf20f | 521 | /* Set the final copy-of value for each variable by traversing the |
522 | copy-of chains. */ | |
f211616e | 523 | FOR_EACH_SSA_NAME (i, var, cfun) |
88dbf20f | 524 | { |
f211616e | 525 | if (!copy_of[i].value |
ba3f9c71 | 526 | || copy_of[i].value == var) |
527 | continue; | |
528 | ||
ba3f9c71 | 529 | /* In theory the points-to solution of all members of the |
530 | copy chain is their intersection. For now we do not bother | |
531 | to compute this but only make sure we do not lose points-to | |
532 | information completely by setting the points-to solution | |
533 | of the representative to the first solution we find if | |
534 | it doesn't have one already. */ | |
14f101cf | 535 | if (copy_of[i].value != var |
0cf78115 | 536 | && TREE_CODE (copy_of[i].value) == SSA_NAME) |
537 | { | |
64243ab0 | 538 | basic_block copy_of_bb |
539 | = gimple_bb (SSA_NAME_DEF_STMT (copy_of[i].value)); | |
540 | basic_block var_bb = gimple_bb (SSA_NAME_DEF_STMT (var)); | |
0cf78115 | 541 | if (POINTER_TYPE_P (TREE_TYPE (var)) |
542 | && SSA_NAME_PTR_INFO (var) | |
543 | && !SSA_NAME_PTR_INFO (copy_of[i].value)) | |
64243ab0 | 544 | { |
545 | duplicate_ssa_name_ptr_info (copy_of[i].value, | |
546 | SSA_NAME_PTR_INFO (var)); | |
547 | /* Points-to information is cfg insensitive, | |
548 | but alignment info might be cfg sensitive, if it | |
549 | e.g. is derived from VRP derived non-zero bits. | |
550 | So, do not copy alignment info if the two SSA_NAMEs | |
551 | aren't defined in the same basic block. */ | |
552 | if (var_bb != copy_of_bb) | |
553 | mark_ptr_info_alignment_unknown | |
554 | (SSA_NAME_PTR_INFO (copy_of[i].value)); | |
555 | } | |
0cf78115 | 556 | else if (!POINTER_TYPE_P (TREE_TYPE (var)) |
557 | && SSA_NAME_RANGE_INFO (var) | |
64243ab0 | 558 | && !SSA_NAME_RANGE_INFO (copy_of[i].value) |
559 | && var_bb == copy_of_bb) | |
0cf78115 | 560 | duplicate_ssa_name_range_info (copy_of[i].value, |
c6a711c3 | 561 | SSA_NAME_RANGE_TYPE (var), |
0cf78115 | 562 | SSA_NAME_RANGE_INFO (var)); |
563 | } | |
88dbf20f | 564 | } |
565 | ||
b08e7364 | 566 | class copy_folder copy_folder; |
567 | bool changed = copy_folder.substitute_and_fold (); | |
c919e493 | 568 | if (changed) |
569 | { | |
d4f078b5 | 570 | free_numbers_of_iterations_estimates (cfun); |
c919e493 | 571 | if (scev_initialized_p ()) |
572 | scev_reset (); | |
573 | } | |
88dbf20f | 574 | |
575 | free (copy_of); | |
c919e493 | 576 | |
577 | return changed; | |
88dbf20f | 578 | } |
579 | ||
580 | ||
421828b0 | 581 | /* Main entry point to the copy propagator. |
582 | ||
583 | PHIS_ONLY is true if we should only consider PHI nodes as generating | |
48e1416a | 584 | copy propagation opportunities. |
421828b0 | 585 | |
586 | The algorithm propagates the value COPY-OF using ssa_propagate. For | |
587 | every variable X_i, COPY-OF(X_i) indicates which variable is X_i created | |
588 | from. The following example shows how the algorithm proceeds at a | |
589 | high level: | |
88dbf20f | 590 | |
591 | 1 a_24 = x_1 | |
592 | 2 a_2 = PHI <a_24, x_1> | |
593 | 3 a_5 = PHI <a_2> | |
594 | 4 x_1 = PHI <x_298, a_5, a_2> | |
595 | ||
596 | The end result should be that a_2, a_5, a_24 and x_1 are a copy of | |
597 | x_298. Propagation proceeds as follows. | |
598 | ||
599 | Visit #1: a_24 is copy-of x_1. Value changed. | |
600 | Visit #2: a_2 is copy-of x_1. Value changed. | |
601 | Visit #3: a_5 is copy-of x_1. Value changed. | |
602 | Visit #4: x_1 is copy-of x_298. Value changed. | |
603 | Visit #1: a_24 is copy-of x_298. Value changed. | |
604 | Visit #2: a_2 is copy-of x_298. Value changed. | |
605 | Visit #3: a_5 is copy-of x_298. Value changed. | |
606 | Visit #4: x_1 is copy-of x_298. Stable state reached. | |
48e1416a | 607 | |
88dbf20f | 608 | When visiting PHI nodes, we only consider arguments that flow |
609 | through edges marked executable by the propagation engine. So, | |
610 | when visiting statement #2 for the first time, we will only look at | |
611 | the first argument (a_24) and optimistically assume that its value | |
6ecedef2 | 612 | is the copy of a_24 (x_1). */ |
88dbf20f | 613 | |
317d3b82 | 614 | static unsigned int |
615 | execute_copy_prop (void) | |
88dbf20f | 616 | { |
d1d2af7d | 617 | init_copy_prop (); |
6bd87d95 | 618 | class copy_prop copy_prop; |
619 | copy_prop.ssa_propagate (); | |
c919e493 | 620 | if (fini_copy_prop ()) |
621 | return TODO_cleanup_cfg; | |
317d3b82 | 622 | return 0; |
88dbf20f | 623 | } |
624 | ||
cbe8bda8 | 625 | namespace { |
626 | ||
627 | const pass_data pass_data_copy_prop = | |
88dbf20f | 628 | { |
cbe8bda8 | 629 | GIMPLE_PASS, /* type */ |
630 | "copyprop", /* name */ | |
631 | OPTGROUP_NONE, /* optinfo_flags */ | |
cbe8bda8 | 632 | TV_TREE_COPY_PROP, /* tv_id */ |
633 | ( PROP_ssa | PROP_cfg ), /* properties_required */ | |
634 | 0, /* properties_provided */ | |
635 | 0, /* properties_destroyed */ | |
636 | 0, /* todo_flags_start */ | |
c919e493 | 637 | 0, /* todo_flags_finish */ |
88dbf20f | 638 | }; |
cbe8bda8 | 639 | |
640 | class pass_copy_prop : public gimple_opt_pass | |
641 | { | |
642 | public: | |
9af5ce0c | 643 | pass_copy_prop (gcc::context *ctxt) |
644 | : gimple_opt_pass (pass_data_copy_prop, ctxt) | |
cbe8bda8 | 645 | {} |
646 | ||
647 | /* opt_pass methods: */ | |
ae84f584 | 648 | opt_pass * clone () { return new pass_copy_prop (m_ctxt); } |
31315c24 | 649 | virtual bool gate (function *) { return flag_tree_copy_prop != 0; } |
65b0537f | 650 | virtual unsigned int execute (function *) { return execute_copy_prop (); } |
cbe8bda8 | 651 | |
652 | }; // class pass_copy_prop | |
653 | ||
654 | } // anon namespace | |
655 | ||
656 | gimple_opt_pass * | |
657 | make_pass_copy_prop (gcc::context *ctxt) | |
658 | { | |
659 | return new pass_copy_prop (ctxt); | |
660 | } |