]>
Commit | Line | Data |
---|---|---|
88dbf20f | 1 | /* Copy propagation and SSA_NAME replacement support routines. |
3aea1f79 | 2 | Copyright (C) 2004-2014 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" | |
23 | #include "tm.h" | |
24 | #include "tree.h" | |
25 | #include "flags.h" | |
4ee9c684 | 26 | #include "tm_p.h" |
4ee9c684 | 27 | #include "basic-block.h" |
4ee9c684 | 28 | #include "function.h" |
ce084dfc | 29 | #include "gimple-pretty-print.h" |
bc61cadb | 30 | #include "tree-ssa-alias.h" |
31 | #include "internal-fn.h" | |
32 | #include "gimple-expr.h" | |
33 | #include "is-a.h" | |
073c1fd5 | 34 | #include "gimple.h" |
dcf1a1ec | 35 | #include "gimple-iterator.h" |
073c1fd5 | 36 | #include "gimple-ssa.h" |
37 | #include "tree-cfg.h" | |
38 | #include "tree-phinodes.h" | |
39 | #include "ssa-iterators.h" | |
9ed99284 | 40 | #include "stringpool.h" |
073c1fd5 | 41 | #include "tree-ssanames.h" |
4ee9c684 | 42 | #include "tree-pass.h" |
88dbf20f | 43 | #include "tree-ssa-propagate.h" |
4ee9c684 | 44 | #include "langhooks.h" |
23a3430d | 45 | #include "cfgloop.h" |
f6568ea4 | 46 | #include "tree-scalar-evolution.h" |
424a4a92 | 47 | #include "tree-ssa-dom.h" |
c919e493 | 48 | #include "tree-ssa-loop-niter.h" |
49 | ||
4ee9c684 | 50 | |
88dbf20f | 51 | /* This file implements the copy propagation pass and provides a |
52 | handful of interfaces for performing const/copy propagation and | |
53 | simple expression replacement which keep variable annotations | |
54 | up-to-date. | |
4ee9c684 | 55 | |
56 | We require that for any copy operation where the RHS and LHS have | |
f7406879 | 57 | a non-null memory tag the memory tag be the same. It is OK |
4ee9c684 | 58 | for one or both of the memory tags to be NULL. |
59 | ||
60 | We also require tracking if a variable is dereferenced in a load or | |
61 | store operation. | |
62 | ||
63 | We enforce these requirements by having all copy propagation and | |
64 | replacements of one SSA_NAME with a different SSA_NAME to use the | |
65 | APIs defined in this file. */ | |
66 | ||
88dbf20f | 67 | /*--------------------------------------------------------------------------- |
68 | Copy propagation | |
69 | ---------------------------------------------------------------------------*/ | |
6ecedef2 | 70 | /* Lattice for copy-propagation. The lattice is initialized to |
71 | UNDEFINED (value == NULL) for SSA names that can become a copy | |
72 | of something or VARYING (value == self) if not (see get_copy_of_val | |
73 | and stmt_may_generate_copy). Other values make the name a COPY | |
74 | of that value. | |
88dbf20f | 75 | |
6ecedef2 | 76 | When visiting a statement or PHI node the lattice value for an |
77 | SSA name can transition from UNDEFINED to COPY to VARYING. */ | |
14f101cf | 78 | |
79 | struct prop_value_d { | |
80 | /* Copy-of value. */ | |
81 | tree value; | |
82 | }; | |
14f101cf | 83 | typedef struct prop_value_d prop_value_t; |
84 | ||
88dbf20f | 85 | static prop_value_t *copy_of; |
285df01b | 86 | static unsigned n_copy_of; |
88dbf20f | 87 | |
88dbf20f | 88 | |
89 | /* Return true if this statement may generate a useful copy. */ | |
90 | ||
91 | static bool | |
75a70cf9 | 92 | stmt_may_generate_copy (gimple stmt) |
88dbf20f | 93 | { |
75a70cf9 | 94 | if (gimple_code (stmt) == GIMPLE_PHI) |
95 | return !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (gimple_phi_result (stmt)); | |
88dbf20f | 96 | |
75a70cf9 | 97 | if (gimple_code (stmt) != GIMPLE_ASSIGN) |
88dbf20f | 98 | return false; |
99 | ||
88dbf20f | 100 | /* If the statement has volatile operands, it won't generate a |
101 | useful copy. */ | |
75a70cf9 | 102 | if (gimple_has_volatile_ops (stmt)) |
88dbf20f | 103 | return false; |
104 | ||
317d3b82 | 105 | /* Statements with loads and/or stores will never generate a useful copy. */ |
dd277d48 | 106 | if (gimple_vuse (stmt)) |
88dbf20f | 107 | return false; |
108 | ||
109 | /* Otherwise, the only statements that generate useful copies are | |
110 | assignments whose RHS is just an SSA name that doesn't flow | |
111 | through abnormal edges. */ | |
f82efd77 | 112 | return ((gimple_assign_rhs_code (stmt) == SSA_NAME |
113 | && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (gimple_assign_rhs1 (stmt))) | |
114 | || is_gimple_min_invariant (gimple_assign_rhs1 (stmt))); | |
88dbf20f | 115 | } |
116 | ||
117 | ||
118 | /* Return the copy-of value for VAR. */ | |
119 | ||
120 | static inline prop_value_t * | |
121 | get_copy_of_val (tree var) | |
122 | { | |
123 | prop_value_t *val = ©_of[SSA_NAME_VERSION (var)]; | |
124 | ||
125 | if (val->value == NULL_TREE | |
126 | && !stmt_may_generate_copy (SSA_NAME_DEF_STMT (var))) | |
127 | { | |
128 | /* If the variable will never generate a useful copy relation, | |
129 | make it its own copy. */ | |
130 | val->value = var; | |
88dbf20f | 131 | } |
132 | ||
133 | return val; | |
134 | } | |
135 | ||
6ecedef2 | 136 | /* Return the variable VAR is a copy of or VAR if VAR isn't the result |
137 | of a copy. */ | |
88dbf20f | 138 | |
6ecedef2 | 139 | static inline tree |
140 | valueize_val (tree var) | |
88dbf20f | 141 | { |
6ecedef2 | 142 | if (TREE_CODE (var) == SSA_NAME) |
88dbf20f | 143 | { |
6ecedef2 | 144 | tree val = get_copy_of_val (var)->value; |
145 | if (val) | |
146 | return val; | |
88dbf20f | 147 | } |
6ecedef2 | 148 | return var; |
88dbf20f | 149 | } |
150 | ||
6ecedef2 | 151 | /* Set VAL to be the copy of VAR. If that changed return true. */ |
88dbf20f | 152 | |
153 | static inline bool | |
6ecedef2 | 154 | set_copy_of_val (tree var, tree val) |
88dbf20f | 155 | { |
6ecedef2 | 156 | unsigned int ver = SSA_NAME_VERSION (var); |
157 | tree old; | |
48e1416a | 158 | |
88dbf20f | 159 | /* Set FIRST to be the first link in COPY_OF[DEST]. If that |
160 | changed, return true. */ | |
6ecedef2 | 161 | old = copy_of[ver].value; |
162 | copy_of[ver].value = val; | |
88dbf20f | 163 | |
82f6f8b4 | 164 | if (old != val |
165 | || (val && !operand_equal_p (old, val, 0))) | |
88dbf20f | 166 | return true; |
167 | ||
6ecedef2 | 168 | return false; |
88dbf20f | 169 | } |
170 | ||
171 | ||
3f5be5f4 | 172 | /* Dump the copy-of value for variable VAR to FILE. */ |
88dbf20f | 173 | |
174 | static void | |
3f5be5f4 | 175 | dump_copy_of (FILE *file, tree var) |
88dbf20f | 176 | { |
177 | tree val; | |
178 | ||
3f5be5f4 | 179 | print_generic_expr (file, var, dump_flags); |
88dbf20f | 180 | if (TREE_CODE (var) != SSA_NAME) |
181 | return; | |
48e1416a | 182 | |
6ecedef2 | 183 | val = copy_of[SSA_NAME_VERSION (var)].value; |
3f5be5f4 | 184 | fprintf (file, " copy-of chain: "); |
6ecedef2 | 185 | print_generic_expr (file, var, 0); |
3f5be5f4 | 186 | fprintf (file, " "); |
6ecedef2 | 187 | if (!val) |
188 | fprintf (file, "[UNDEFINED]"); | |
189 | else if (val == var) | |
190 | fprintf (file, "[NOT A COPY]"); | |
191 | else | |
88dbf20f | 192 | { |
3f5be5f4 | 193 | fprintf (file, "-> "); |
3f5be5f4 | 194 | print_generic_expr (file, val, 0); |
195 | fprintf (file, " "); | |
6ecedef2 | 196 | fprintf (file, "[COPY]"); |
88dbf20f | 197 | } |
88dbf20f | 198 | } |
199 | ||
200 | ||
201 | /* Evaluate the RHS of STMT. If it produces a valid copy, set the LHS | |
6ecedef2 | 202 | value and store the LHS into *RESULT_P. */ |
88dbf20f | 203 | |
204 | static enum ssa_prop_result | |
75a70cf9 | 205 | copy_prop_visit_assignment (gimple stmt, tree *result_p) |
88dbf20f | 206 | { |
207 | tree lhs, rhs; | |
88dbf20f | 208 | |
75a70cf9 | 209 | lhs = gimple_assign_lhs (stmt); |
82f6f8b4 | 210 | rhs = valueize_val (gimple_assign_rhs1 (stmt)); |
88dbf20f | 211 | |
212 | if (TREE_CODE (lhs) == SSA_NAME) | |
213 | { | |
214 | /* Straight copy between two SSA names. First, make sure that | |
215 | we can propagate the RHS into uses of LHS. */ | |
216 | if (!may_propagate_copy (lhs, rhs)) | |
217 | return SSA_PROP_VARYING; | |
218 | ||
88dbf20f | 219 | *result_p = lhs; |
82f6f8b4 | 220 | if (set_copy_of_val (*result_p, rhs)) |
88dbf20f | 221 | return SSA_PROP_INTERESTING; |
222 | else | |
223 | return SSA_PROP_NOT_INTERESTING; | |
224 | } | |
225 | ||
88dbf20f | 226 | return SSA_PROP_VARYING; |
227 | } | |
228 | ||
229 | ||
75a70cf9 | 230 | /* Visit the GIMPLE_COND STMT. Return SSA_PROP_INTERESTING |
88dbf20f | 231 | if it can determine which edge will be taken. Otherwise, return |
232 | SSA_PROP_VARYING. */ | |
233 | ||
234 | static enum ssa_prop_result | |
75a70cf9 | 235 | copy_prop_visit_cond_stmt (gimple stmt, edge *taken_edge_p) |
88dbf20f | 236 | { |
75a70cf9 | 237 | enum ssa_prop_result retval = SSA_PROP_VARYING; |
389dd41b | 238 | location_t loc = gimple_location (stmt); |
88dbf20f | 239 | |
75a70cf9 | 240 | tree op0 = gimple_cond_lhs (stmt); |
241 | tree op1 = gimple_cond_rhs (stmt); | |
88dbf20f | 242 | |
243 | /* The only conditionals that we may be able to compute statically | |
20bd2b8f | 244 | are predicates involving two SSA_NAMEs. */ |
75a70cf9 | 245 | if (TREE_CODE (op0) == SSA_NAME && TREE_CODE (op1) == SSA_NAME) |
88dbf20f | 246 | { |
6ecedef2 | 247 | op0 = valueize_val (op0); |
248 | op1 = valueize_val (op1); | |
88dbf20f | 249 | |
250 | /* See if we can determine the predicate's value. */ | |
251 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
252 | { | |
253 | fprintf (dump_file, "Trying to determine truth value of "); | |
254 | fprintf (dump_file, "predicate "); | |
75a70cf9 | 255 | print_gimple_stmt (dump_file, stmt, 0, 0); |
88dbf20f | 256 | } |
257 | ||
20bd2b8f | 258 | /* We can fold COND and get a useful result only when we have |
259 | the same SSA_NAME on both sides of a comparison operator. */ | |
260 | if (op0 == op1) | |
f21dcb28 | 261 | { |
389dd41b | 262 | tree folded_cond = fold_binary_loc (loc, gimple_cond_code (stmt), |
75a70cf9 | 263 | boolean_type_node, op0, op1); |
20bd2b8f | 264 | if (folded_cond) |
265 | { | |
75a70cf9 | 266 | basic_block bb = gimple_bb (stmt); |
20bd2b8f | 267 | *taken_edge_p = find_taken_edge (bb, folded_cond); |
268 | if (*taken_edge_p) | |
269 | retval = SSA_PROP_INTERESTING; | |
270 | } | |
f21dcb28 | 271 | } |
88dbf20f | 272 | } |
273 | ||
274 | if (dump_file && (dump_flags & TDF_DETAILS) && *taken_edge_p) | |
275 | fprintf (dump_file, "\nConditional will always take edge %d->%d\n", | |
276 | (*taken_edge_p)->src->index, (*taken_edge_p)->dest->index); | |
277 | ||
278 | return retval; | |
279 | } | |
280 | ||
281 | ||
282 | /* Evaluate statement STMT. If the statement produces a new output | |
283 | value, return SSA_PROP_INTERESTING and store the SSA_NAME holding | |
284 | the new value in *RESULT_P. | |
285 | ||
286 | If STMT is a conditional branch and we can determine its truth | |
287 | value, set *TAKEN_EDGE_P accordingly. | |
288 | ||
289 | If the new value produced by STMT is varying, return | |
290 | SSA_PROP_VARYING. */ | |
291 | ||
292 | static enum ssa_prop_result | |
75a70cf9 | 293 | copy_prop_visit_stmt (gimple stmt, edge *taken_edge_p, tree *result_p) |
88dbf20f | 294 | { |
88dbf20f | 295 | enum ssa_prop_result retval; |
296 | ||
297 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
298 | { | |
299 | fprintf (dump_file, "\nVisiting statement:\n"); | |
75a70cf9 | 300 | print_gimple_stmt (dump_file, stmt, 0, dump_flags); |
88dbf20f | 301 | fprintf (dump_file, "\n"); |
302 | } | |
303 | ||
75a70cf9 | 304 | if (gimple_assign_single_p (stmt) |
305 | && TREE_CODE (gimple_assign_lhs (stmt)) == SSA_NAME | |
82f6f8b4 | 306 | && (TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME |
307 | || is_gimple_min_invariant (gimple_assign_rhs1 (stmt)))) | |
88dbf20f | 308 | { |
309 | /* If the statement is a copy assignment, evaluate its RHS to | |
310 | see if the lattice value of its output has changed. */ | |
311 | retval = copy_prop_visit_assignment (stmt, result_p); | |
312 | } | |
75a70cf9 | 313 | else if (gimple_code (stmt) == GIMPLE_COND) |
88dbf20f | 314 | { |
315 | /* See if we can determine which edge goes out of a conditional | |
316 | jump. */ | |
317 | retval = copy_prop_visit_cond_stmt (stmt, taken_edge_p); | |
318 | } | |
319 | else | |
320 | retval = SSA_PROP_VARYING; | |
321 | ||
322 | if (retval == SSA_PROP_VARYING) | |
323 | { | |
324 | tree def; | |
325 | ssa_op_iter i; | |
326 | ||
327 | /* Any other kind of statement is not interesting for constant | |
328 | propagation and, therefore, not worth simulating. */ | |
329 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
330 | fprintf (dump_file, "No interesting values produced.\n"); | |
331 | ||
332 | /* The assignment is not a copy operation. Don't visit this | |
333 | statement again and mark all the definitions in the statement | |
334 | to be copies of nothing. */ | |
335 | FOR_EACH_SSA_TREE_OPERAND (def, stmt, i, SSA_OP_ALL_DEFS) | |
317d3b82 | 336 | set_copy_of_val (def, def); |
88dbf20f | 337 | } |
338 | ||
339 | return retval; | |
340 | } | |
341 | ||
342 | ||
343 | /* Visit PHI node PHI. If all the arguments produce the same value, | |
344 | set it to be the value of the LHS of PHI. */ | |
345 | ||
346 | static enum ssa_prop_result | |
75a70cf9 | 347 | copy_prop_visit_phi_node (gimple phi) |
88dbf20f | 348 | { |
349 | enum ssa_prop_result retval; | |
75a70cf9 | 350 | unsigned i; |
14f101cf | 351 | prop_value_t phi_val = { NULL_TREE }; |
88dbf20f | 352 | |
75a70cf9 | 353 | tree lhs = gimple_phi_result (phi); |
88dbf20f | 354 | |
355 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
356 | { | |
357 | fprintf (dump_file, "\nVisiting PHI node: "); | |
75a70cf9 | 358 | print_gimple_stmt (dump_file, phi, 0, dump_flags); |
88dbf20f | 359 | } |
360 | ||
75a70cf9 | 361 | for (i = 0; i < gimple_phi_num_args (phi); i++) |
88dbf20f | 362 | { |
363 | prop_value_t *arg_val; | |
abb08aa8 | 364 | tree arg_value; |
75a70cf9 | 365 | tree arg = gimple_phi_arg_def (phi, i); |
366 | edge e = gimple_phi_arg_edge (phi, i); | |
88dbf20f | 367 | |
368 | /* We don't care about values flowing through non-executable | |
369 | edges. */ | |
370 | if (!(e->flags & EDGE_EXECUTABLE)) | |
371 | continue; | |
372 | ||
abb08aa8 | 373 | /* Names that flow through abnormal edges cannot be used to |
374 | derive copies. */ | |
375 | if (TREE_CODE (arg) == SSA_NAME && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (arg)) | |
88dbf20f | 376 | { |
377 | phi_val.value = lhs; | |
378 | break; | |
379 | } | |
380 | ||
88dbf20f | 381 | if (dump_file && (dump_flags & TDF_DETAILS)) |
382 | { | |
383 | fprintf (dump_file, "\tArgument #%d: ", i); | |
384 | dump_copy_of (dump_file, arg); | |
385 | fprintf (dump_file, "\n"); | |
386 | } | |
387 | ||
abb08aa8 | 388 | if (TREE_CODE (arg) == SSA_NAME) |
389 | { | |
390 | arg_val = get_copy_of_val (arg); | |
391 | ||
392 | /* If we didn't visit the definition of arg yet treat it as | |
393 | UNDEFINED. This also handles PHI arguments that are the | |
394 | same as lhs. We'll come here again. */ | |
395 | if (!arg_val->value) | |
396 | continue; | |
88dbf20f | 397 | |
abb08aa8 | 398 | arg_value = arg_val->value; |
399 | } | |
400 | else | |
401 | arg_value = valueize_val (arg); | |
402 | ||
3beff0e1 | 403 | /* In loop-closed SSA form do not copy-propagate SSA-names across |
404 | loop exit edges. */ | |
405 | if (loops_state_satisfies_p (LOOP_CLOSED_SSA) | |
406 | && TREE_CODE (arg_value) == SSA_NAME | |
407 | && loop_exit_edge_p (e->src->loop_father, e)) | |
abb08aa8 | 408 | { |
409 | phi_val.value = lhs; | |
410 | break; | |
411 | } | |
6ecedef2 | 412 | |
88dbf20f | 413 | /* If the LHS didn't have a value yet, make it a copy of the |
6ecedef2 | 414 | first argument we find. */ |
88dbf20f | 415 | if (phi_val.value == NULL_TREE) |
416 | { | |
abb08aa8 | 417 | phi_val.value = arg_value; |
88dbf20f | 418 | continue; |
419 | } | |
420 | ||
421 | /* If PHI_VAL and ARG don't have a common copy-of chain, then | |
6ecedef2 | 422 | this PHI node cannot be a copy operation. */ |
abb08aa8 | 423 | if (phi_val.value != arg_value |
424 | && !operand_equal_p (phi_val.value, arg_value, 0)) | |
88dbf20f | 425 | { |
426 | phi_val.value = lhs; | |
427 | break; | |
428 | } | |
429 | } | |
430 | ||
6ecedef2 | 431 | if (phi_val.value |
432 | && may_propagate_copy (lhs, phi_val.value) | |
b87f0847 | 433 | && set_copy_of_val (lhs, phi_val.value)) |
88dbf20f | 434 | retval = (phi_val.value != lhs) ? SSA_PROP_INTERESTING : SSA_PROP_VARYING; |
435 | else | |
436 | retval = SSA_PROP_NOT_INTERESTING; | |
437 | ||
438 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
439 | { | |
6ecedef2 | 440 | fprintf (dump_file, "PHI node "); |
88dbf20f | 441 | dump_copy_of (dump_file, lhs); |
442 | fprintf (dump_file, "\nTelling the propagator to "); | |
443 | if (retval == SSA_PROP_INTERESTING) | |
444 | fprintf (dump_file, "add SSA edges out of this PHI and continue."); | |
445 | else if (retval == SSA_PROP_VARYING) | |
446 | fprintf (dump_file, "add SSA edges out of this PHI and never visit again."); | |
447 | else | |
448 | fprintf (dump_file, "do nothing with SSA edges and keep iterating."); | |
449 | fprintf (dump_file, "\n\n"); | |
450 | } | |
451 | ||
452 | return retval; | |
453 | } | |
454 | ||
455 | ||
6ecedef2 | 456 | /* Initialize structures used for copy propagation. */ |
88dbf20f | 457 | |
458 | static void | |
d1d2af7d | 459 | init_copy_prop (void) |
88dbf20f | 460 | { |
461 | basic_block bb; | |
462 | ||
285df01b | 463 | n_copy_of = num_ssa_names; |
464 | copy_of = XCNEWVEC (prop_value_t, n_copy_of); | |
88dbf20f | 465 | |
fc00614f | 466 | FOR_EACH_BB_FN (bb, cfun) |
88dbf20f | 467 | { |
75a70cf9 | 468 | gimple_stmt_iterator si; |
88dbf20f | 469 | |
75a70cf9 | 470 | for (si = gsi_start_bb (bb); !gsi_end_p (si); gsi_next (&si)) |
88dbf20f | 471 | { |
75a70cf9 | 472 | gimple stmt = gsi_stmt (si); |
2166ab0e | 473 | ssa_op_iter iter; |
75a70cf9 | 474 | tree def; |
88dbf20f | 475 | |
476 | /* The only statements that we care about are those that may | |
477 | generate useful copies. We also need to mark conditional | |
478 | jumps so that their outgoing edges are added to the work | |
3beff0e1 | 479 | lists of the propagator. */ |
88dbf20f | 480 | if (stmt_ends_bb_p (stmt)) |
75a70cf9 | 481 | prop_set_simulate_again (stmt, true); |
3beff0e1 | 482 | else if (stmt_may_generate_copy (stmt)) |
75a70cf9 | 483 | prop_set_simulate_again (stmt, true); |
88dbf20f | 484 | else |
75a70cf9 | 485 | prop_set_simulate_again (stmt, false); |
2166ab0e | 486 | |
487 | /* Mark all the outputs of this statement as not being | |
488 | the copy of anything. */ | |
489 | FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS) | |
75a70cf9 | 490 | if (!prop_simulate_again_p (stmt)) |
317d3b82 | 491 | set_copy_of_val (def, def); |
88dbf20f | 492 | } |
493 | ||
75a70cf9 | 494 | for (si = gsi_start_phis (bb); !gsi_end_p (si); gsi_next (&si)) |
2166ab0e | 495 | { |
75a70cf9 | 496 | gimple phi = gsi_stmt (si); |
497 | tree def; | |
498 | ||
499 | def = gimple_phi_result (phi); | |
7c782c9b | 500 | if (virtual_operand_p (def)) |
75a70cf9 | 501 | prop_set_simulate_again (phi, false); |
2166ab0e | 502 | else |
75a70cf9 | 503 | prop_set_simulate_again (phi, true); |
2166ab0e | 504 | |
75a70cf9 | 505 | if (!prop_simulate_again_p (phi)) |
317d3b82 | 506 | set_copy_of_val (def, def); |
2166ab0e | 507 | } |
88dbf20f | 508 | } |
509 | } | |
510 | ||
14f101cf | 511 | /* Callback for substitute_and_fold to get at the final copy-of values. */ |
512 | ||
513 | static tree | |
514 | get_value (tree name) | |
515 | { | |
285df01b | 516 | tree val; |
517 | if (SSA_NAME_VERSION (name) >= n_copy_of) | |
518 | return NULL_TREE; | |
519 | val = copy_of[SSA_NAME_VERSION (name)].value; | |
14f101cf | 520 | if (val && val != name) |
521 | return val; | |
522 | return NULL_TREE; | |
523 | } | |
88dbf20f | 524 | |
525 | /* Deallocate memory used in copy propagation and do final | |
526 | substitution. */ | |
527 | ||
c919e493 | 528 | static bool |
88dbf20f | 529 | fini_copy_prop (void) |
530 | { | |
14f101cf | 531 | unsigned i; |
48e1416a | 532 | |
88dbf20f | 533 | /* Set the final copy-of value for each variable by traversing the |
534 | copy-of chains. */ | |
535 | for (i = 1; i < num_ssa_names; i++) | |
536 | { | |
537 | tree var = ssa_name (i); | |
ba3f9c71 | 538 | if (!var |
539 | || !copy_of[i].value | |
540 | || copy_of[i].value == var) | |
541 | continue; | |
542 | ||
ba3f9c71 | 543 | /* In theory the points-to solution of all members of the |
544 | copy chain is their intersection. For now we do not bother | |
545 | to compute this but only make sure we do not lose points-to | |
546 | information completely by setting the points-to solution | |
547 | of the representative to the first solution we find if | |
548 | it doesn't have one already. */ | |
14f101cf | 549 | if (copy_of[i].value != var |
0cf78115 | 550 | && TREE_CODE (copy_of[i].value) == SSA_NAME) |
551 | { | |
64243ab0 | 552 | basic_block copy_of_bb |
553 | = gimple_bb (SSA_NAME_DEF_STMT (copy_of[i].value)); | |
554 | basic_block var_bb = gimple_bb (SSA_NAME_DEF_STMT (var)); | |
0cf78115 | 555 | if (POINTER_TYPE_P (TREE_TYPE (var)) |
556 | && SSA_NAME_PTR_INFO (var) | |
557 | && !SSA_NAME_PTR_INFO (copy_of[i].value)) | |
64243ab0 | 558 | { |
559 | duplicate_ssa_name_ptr_info (copy_of[i].value, | |
560 | SSA_NAME_PTR_INFO (var)); | |
561 | /* Points-to information is cfg insensitive, | |
562 | but alignment info might be cfg sensitive, if it | |
563 | e.g. is derived from VRP derived non-zero bits. | |
564 | So, do not copy alignment info if the two SSA_NAMEs | |
565 | aren't defined in the same basic block. */ | |
566 | if (var_bb != copy_of_bb) | |
567 | mark_ptr_info_alignment_unknown | |
568 | (SSA_NAME_PTR_INFO (copy_of[i].value)); | |
569 | } | |
0cf78115 | 570 | else if (!POINTER_TYPE_P (TREE_TYPE (var)) |
571 | && SSA_NAME_RANGE_INFO (var) | |
64243ab0 | 572 | && !SSA_NAME_RANGE_INFO (copy_of[i].value) |
573 | && var_bb == copy_of_bb) | |
0cf78115 | 574 | duplicate_ssa_name_range_info (copy_of[i].value, |
c6a711c3 | 575 | SSA_NAME_RANGE_TYPE (var), |
0cf78115 | 576 | SSA_NAME_RANGE_INFO (var)); |
577 | } | |
88dbf20f | 578 | } |
579 | ||
c919e493 | 580 | bool changed = substitute_and_fold (get_value, NULL, true); |
581 | if (changed) | |
582 | { | |
583 | free_numbers_of_iterations_estimates (); | |
584 | if (scev_initialized_p ()) | |
585 | scev_reset (); | |
586 | } | |
88dbf20f | 587 | |
588 | free (copy_of); | |
c919e493 | 589 | |
590 | return changed; | |
88dbf20f | 591 | } |
592 | ||
593 | ||
421828b0 | 594 | /* Main entry point to the copy propagator. |
595 | ||
596 | PHIS_ONLY is true if we should only consider PHI nodes as generating | |
48e1416a | 597 | copy propagation opportunities. |
421828b0 | 598 | |
599 | The algorithm propagates the value COPY-OF using ssa_propagate. For | |
600 | every variable X_i, COPY-OF(X_i) indicates which variable is X_i created | |
601 | from. The following example shows how the algorithm proceeds at a | |
602 | high level: | |
88dbf20f | 603 | |
604 | 1 a_24 = x_1 | |
605 | 2 a_2 = PHI <a_24, x_1> | |
606 | 3 a_5 = PHI <a_2> | |
607 | 4 x_1 = PHI <x_298, a_5, a_2> | |
608 | ||
609 | The end result should be that a_2, a_5, a_24 and x_1 are a copy of | |
610 | x_298. Propagation proceeds as follows. | |
611 | ||
612 | Visit #1: a_24 is copy-of x_1. Value changed. | |
613 | Visit #2: a_2 is copy-of x_1. Value changed. | |
614 | Visit #3: a_5 is copy-of x_1. Value changed. | |
615 | Visit #4: x_1 is copy-of x_298. Value changed. | |
616 | Visit #1: a_24 is copy-of x_298. Value changed. | |
617 | Visit #2: a_2 is copy-of x_298. Value changed. | |
618 | Visit #3: a_5 is copy-of x_298. Value changed. | |
619 | Visit #4: x_1 is copy-of x_298. Stable state reached. | |
48e1416a | 620 | |
88dbf20f | 621 | When visiting PHI nodes, we only consider arguments that flow |
622 | through edges marked executable by the propagation engine. So, | |
623 | when visiting statement #2 for the first time, we will only look at | |
624 | the first argument (a_24) and optimistically assume that its value | |
6ecedef2 | 625 | is the copy of a_24 (x_1). */ |
88dbf20f | 626 | |
317d3b82 | 627 | static unsigned int |
628 | execute_copy_prop (void) | |
88dbf20f | 629 | { |
d1d2af7d | 630 | init_copy_prop (); |
88dbf20f | 631 | ssa_propagate (copy_prop_visit_stmt, copy_prop_visit_phi_node); |
c919e493 | 632 | if (fini_copy_prop ()) |
633 | return TODO_cleanup_cfg; | |
317d3b82 | 634 | return 0; |
88dbf20f | 635 | } |
636 | ||
cbe8bda8 | 637 | namespace { |
638 | ||
639 | const pass_data pass_data_copy_prop = | |
88dbf20f | 640 | { |
cbe8bda8 | 641 | GIMPLE_PASS, /* type */ |
642 | "copyprop", /* name */ | |
643 | OPTGROUP_NONE, /* optinfo_flags */ | |
cbe8bda8 | 644 | TV_TREE_COPY_PROP, /* tv_id */ |
645 | ( PROP_ssa | PROP_cfg ), /* properties_required */ | |
646 | 0, /* properties_provided */ | |
647 | 0, /* properties_destroyed */ | |
648 | 0, /* todo_flags_start */ | |
c919e493 | 649 | 0, /* todo_flags_finish */ |
88dbf20f | 650 | }; |
cbe8bda8 | 651 | |
652 | class pass_copy_prop : public gimple_opt_pass | |
653 | { | |
654 | public: | |
9af5ce0c | 655 | pass_copy_prop (gcc::context *ctxt) |
656 | : gimple_opt_pass (pass_data_copy_prop, ctxt) | |
cbe8bda8 | 657 | {} |
658 | ||
659 | /* opt_pass methods: */ | |
ae84f584 | 660 | opt_pass * clone () { return new pass_copy_prop (m_ctxt); } |
31315c24 | 661 | virtual bool gate (function *) { return flag_tree_copy_prop != 0; } |
65b0537f | 662 | virtual unsigned int execute (function *) { return execute_copy_prop (); } |
cbe8bda8 | 663 | |
664 | }; // class pass_copy_prop | |
665 | ||
666 | } // anon namespace | |
667 | ||
668 | gimple_opt_pass * | |
669 | make_pass_copy_prop (gcc::context *ctxt) | |
670 | { | |
671 | return new pass_copy_prop (ctxt); | |
672 | } |