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88dbf20f | 1 | /* Copy propagation and SSA_NAME replacement support routines. |
7cf0dbf3 | 2 | Copyright (C) 2004, 2005, 2006, 2007, 2008, 2010 |
3 | Free Software Foundation, Inc. | |
4ee9c684 | 4 | |
5 | This file is part of GCC. | |
6 | ||
7 | GCC is free software; you can redistribute it and/or modify | |
8 | it under the terms of the GNU General Public License as published by | |
8c4c00c1 | 9 | the Free Software Foundation; either version 3, or (at your option) |
4ee9c684 | 10 | any later version. |
11 | ||
12 | GCC is distributed in the hope that it will be useful, | |
13 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
15 | GNU General Public License for more details. | |
16 | ||
17 | You should have received a copy of the GNU General Public License | |
8c4c00c1 | 18 | along with GCC; see the file COPYING3. If not see |
19 | <http://www.gnu.org/licenses/>. */ | |
4ee9c684 | 20 | |
21 | #include "config.h" | |
22 | #include "system.h" | |
23 | #include "coretypes.h" | |
24 | #include "tm.h" | |
25 | #include "tree.h" | |
26 | #include "flags.h" | |
4ee9c684 | 27 | #include "tm_p.h" |
4ee9c684 | 28 | #include "basic-block.h" |
4ee9c684 | 29 | #include "function.h" |
ce084dfc | 30 | #include "gimple-pretty-print.h" |
4ee9c684 | 31 | #include "tree-flow.h" |
32 | #include "tree-pass.h" | |
88dbf20f | 33 | #include "tree-ssa-propagate.h" |
4ee9c684 | 34 | #include "langhooks.h" |
23a3430d | 35 | #include "cfgloop.h" |
4ee9c684 | 36 | |
88dbf20f | 37 | /* This file implements the copy propagation pass and provides a |
38 | handful of interfaces for performing const/copy propagation and | |
39 | simple expression replacement which keep variable annotations | |
40 | up-to-date. | |
4ee9c684 | 41 | |
42 | We require that for any copy operation where the RHS and LHS have | |
f7406879 | 43 | a non-null memory tag the memory tag be the same. It is OK |
4ee9c684 | 44 | for one or both of the memory tags to be NULL. |
45 | ||
46 | We also require tracking if a variable is dereferenced in a load or | |
47 | store operation. | |
48 | ||
49 | We enforce these requirements by having all copy propagation and | |
50 | replacements of one SSA_NAME with a different SSA_NAME to use the | |
51 | APIs defined in this file. */ | |
52 | ||
4f7f73c8 | 53 | /* Return true if we may propagate ORIG into DEST, false otherwise. */ |
54 | ||
55 | bool | |
56 | may_propagate_copy (tree dest, tree orig) | |
57 | { | |
58 | tree type_d = TREE_TYPE (dest); | |
59 | tree type_o = TREE_TYPE (orig); | |
60 | ||
5c6e4974 | 61 | /* If ORIG flows in from an abnormal edge, it cannot be propagated. */ |
62 | if (TREE_CODE (orig) == SSA_NAME | |
63 | && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (orig)) | |
64 | return false; | |
65 | ||
66 | /* If DEST is an SSA_NAME that flows from an abnormal edge, then it | |
67 | cannot be replaced. */ | |
68 | if (TREE_CODE (dest) == SSA_NAME | |
69 | && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (dest)) | |
70 | return false; | |
48e1416a | 71 | |
4f7f73c8 | 72 | /* Do not copy between types for which we *do* need a conversion. */ |
548044d8 | 73 | if (!useless_type_conversion_p (type_d, type_o)) |
4f7f73c8 | 74 | return false; |
75 | ||
dd277d48 | 76 | /* Propagating virtual operands is always ok. */ |
7c782c9b | 77 | if (TREE_CODE (dest) == SSA_NAME && virtual_operand_p (dest)) |
4f7f73c8 | 78 | { |
dd277d48 | 79 | /* But only between virtual operands. */ |
7c782c9b | 80 | gcc_assert (TREE_CODE (orig) == SSA_NAME && virtual_operand_p (orig)); |
dd277d48 | 81 | |
82 | return true; | |
4f7f73c8 | 83 | } |
84 | ||
4f7f73c8 | 85 | /* Anything else is OK. */ |
86 | return true; | |
87 | } | |
88 | ||
75a70cf9 | 89 | /* Like may_propagate_copy, but use as the destination expression |
90 | the principal expression (typically, the RHS) contained in | |
91 | statement DEST. This is more efficient when working with the | |
92 | gimple tuples representation. */ | |
93 | ||
94 | bool | |
95 | may_propagate_copy_into_stmt (gimple dest, tree orig) | |
96 | { | |
97 | tree type_d; | |
98 | tree type_o; | |
99 | ||
100 | /* If the statement is a switch or a single-rhs assignment, | |
101 | then the expression to be replaced by the propagation may | |
102 | be an SSA_NAME. Fortunately, there is an explicit tree | |
103 | for the expression, so we delegate to may_propagate_copy. */ | |
104 | ||
105 | if (gimple_assign_single_p (dest)) | |
106 | return may_propagate_copy (gimple_assign_rhs1 (dest), orig); | |
107 | else if (gimple_code (dest) == GIMPLE_SWITCH) | |
108 | return may_propagate_copy (gimple_switch_index (dest), orig); | |
109 | ||
110 | /* In other cases, the expression is not materialized, so there | |
111 | is no destination to pass to may_propagate_copy. On the other | |
112 | hand, the expression cannot be an SSA_NAME, so the analysis | |
113 | is much simpler. */ | |
114 | ||
115 | if (TREE_CODE (orig) == SSA_NAME | |
dd277d48 | 116 | && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (orig)) |
75a70cf9 | 117 | return false; |
118 | ||
119 | if (is_gimple_assign (dest)) | |
120 | type_d = TREE_TYPE (gimple_assign_lhs (dest)); | |
121 | else if (gimple_code (dest) == GIMPLE_COND) | |
122 | type_d = boolean_type_node; | |
123 | else if (is_gimple_call (dest) | |
124 | && gimple_call_lhs (dest) != NULL_TREE) | |
125 | type_d = TREE_TYPE (gimple_call_lhs (dest)); | |
126 | else | |
127 | gcc_unreachable (); | |
128 | ||
129 | type_o = TREE_TYPE (orig); | |
130 | ||
131 | if (!useless_type_conversion_p (type_d, type_o)) | |
132 | return false; | |
133 | ||
134 | return true; | |
135 | } | |
136 | ||
93b4f514 | 137 | /* Similarly, but we know that we're propagating into an ASM_EXPR. */ |
138 | ||
139 | bool | |
1ba198c0 | 140 | may_propagate_copy_into_asm (tree dest ATTRIBUTE_UNUSED) |
93b4f514 | 141 | { |
1ba198c0 | 142 | return true; |
93b4f514 | 143 | } |
144 | ||
4ee9c684 | 145 | |
4ee9c684 | 146 | /* Common code for propagate_value and replace_exp. |
147 | ||
ac13e8d9 | 148 | Replace use operand OP_P with VAL. FOR_PROPAGATION indicates if the |
56004dc5 | 149 | replacement is done to propagate a value or not. */ |
4ee9c684 | 150 | |
151 | static void | |
cbbefea4 | 152 | replace_exp_1 (use_operand_p op_p, tree val, |
75a70cf9 | 153 | bool for_propagation ATTRIBUTE_UNUSED) |
4ee9c684 | 154 | { |
cbbefea4 | 155 | #if defined ENABLE_CHECKING |
f2e585c3 | 156 | tree op = USE_FROM_PTR (op_p); |
7496b609 | 157 | |
8c0963c4 | 158 | gcc_assert (!(for_propagation |
159 | && TREE_CODE (op) == SSA_NAME | |
160 | && TREE_CODE (val) == SSA_NAME | |
161 | && !may_propagate_copy (op, val))); | |
cbbefea4 | 162 | #endif |
163 | ||
4ee9c684 | 164 | if (TREE_CODE (val) == SSA_NAME) |
ba3f9c71 | 165 | SET_USE (op_p, val); |
4ee9c684 | 166 | else |
ac13e8d9 | 167 | SET_USE (op_p, unsave_expr_now (val)); |
4ee9c684 | 168 | } |
169 | ||
591c2a30 | 170 | |
4ee9c684 | 171 | /* Propagate the value VAL (assumed to be a constant or another SSA_NAME) |
5206b159 | 172 | into the operand pointed to by OP_P. |
4ee9c684 | 173 | |
174 | Use this version for const/copy propagation as it will perform additional | |
175 | checks to ensure validity of the const/copy propagation. */ | |
176 | ||
177 | void | |
56004dc5 | 178 | propagate_value (use_operand_p op_p, tree val) |
4ee9c684 | 179 | { |
180 | replace_exp_1 (op_p, val, true); | |
181 | } | |
182 | ||
75a70cf9 | 183 | /* Replace *OP_P with value VAL (assumed to be a constant or another SSA_NAME). |
184 | ||
185 | Use this version when not const/copy propagating values. For example, | |
186 | PRE uses this version when building expressions as they would appear | |
40463847 | 187 | in specific blocks taking into account actions of PHI nodes. |
188 | ||
189 | The statement in which an expression has been replaced should be | |
190 | folded using fold_stmt_inplace. */ | |
75a70cf9 | 191 | |
192 | void | |
193 | replace_exp (use_operand_p op_p, tree val) | |
194 | { | |
195 | replace_exp_1 (op_p, val, false); | |
196 | } | |
197 | ||
591c2a30 | 198 | |
56004dc5 | 199 | /* Propagate the value VAL (assumed to be a constant or another SSA_NAME) |
5206b159 | 200 | into the tree pointed to by OP_P. |
56004dc5 | 201 | |
ac13e8d9 | 202 | Use this version for const/copy propagation when SSA operands are not |
203 | available. It will perform the additional checks to ensure validity of | |
56004dc5 | 204 | the const/copy propagation, but will not update any operand information. |
205 | Be sure to mark the stmt as modified. */ | |
206 | ||
207 | void | |
208 | propagate_tree_value (tree *op_p, tree val) | |
209 | { | |
1b4345f7 | 210 | gcc_checking_assert (!(TREE_CODE (val) == SSA_NAME |
211 | && *op_p | |
212 | && TREE_CODE (*op_p) == SSA_NAME | |
213 | && !may_propagate_copy (*op_p, val))); | |
cbbefea4 | 214 | |
56004dc5 | 215 | if (TREE_CODE (val) == SSA_NAME) |
ba3f9c71 | 216 | *op_p = val; |
56004dc5 | 217 | else |
ac13e8d9 | 218 | *op_p = unsave_expr_now (val); |
56004dc5 | 219 | } |
220 | ||
591c2a30 | 221 | |
75a70cf9 | 222 | /* Like propagate_tree_value, but use as the operand to replace |
223 | the principal expression (typically, the RHS) contained in the | |
224 | statement referenced by iterator GSI. Note that it is not | |
225 | always possible to update the statement in-place, so a new | |
226 | statement may be created to replace the original. */ | |
4ee9c684 | 227 | |
228 | void | |
75a70cf9 | 229 | propagate_tree_value_into_stmt (gimple_stmt_iterator *gsi, tree val) |
4ee9c684 | 230 | { |
75a70cf9 | 231 | gimple stmt = gsi_stmt (*gsi); |
88dbf20f | 232 | |
75a70cf9 | 233 | if (is_gimple_assign (stmt)) |
234 | { | |
235 | tree expr = NULL_TREE; | |
236 | if (gimple_assign_single_p (stmt)) | |
237 | expr = gimple_assign_rhs1 (stmt); | |
238 | propagate_tree_value (&expr, val); | |
239 | gimple_assign_set_rhs_from_tree (gsi, expr); | |
75a70cf9 | 240 | } |
241 | else if (gimple_code (stmt) == GIMPLE_COND) | |
242 | { | |
243 | tree lhs = NULL_TREE; | |
385f3f36 | 244 | tree rhs = build_zero_cst (TREE_TYPE (val)); |
75a70cf9 | 245 | propagate_tree_value (&lhs, val); |
246 | gimple_cond_set_code (stmt, NE_EXPR); | |
247 | gimple_cond_set_lhs (stmt, lhs); | |
248 | gimple_cond_set_rhs (stmt, rhs); | |
249 | } | |
250 | else if (is_gimple_call (stmt) | |
251 | && gimple_call_lhs (stmt) != NULL_TREE) | |
252 | { | |
75a70cf9 | 253 | tree expr = NULL_TREE; |
ebc3ea23 | 254 | bool res; |
75a70cf9 | 255 | propagate_tree_value (&expr, val); |
ebc3ea23 | 256 | res = update_call_from_tree (gsi, expr); |
257 | gcc_assert (res); | |
75a70cf9 | 258 | } |
259 | else if (gimple_code (stmt) == GIMPLE_SWITCH) | |
260 | propagate_tree_value (gimple_switch_index_ptr (stmt), val); | |
261 | else | |
262 | gcc_unreachable (); | |
263 | } | |
88dbf20f | 264 | |
265 | /*--------------------------------------------------------------------------- | |
266 | Copy propagation | |
267 | ---------------------------------------------------------------------------*/ | |
6ecedef2 | 268 | /* Lattice for copy-propagation. The lattice is initialized to |
269 | UNDEFINED (value == NULL) for SSA names that can become a copy | |
270 | of something or VARYING (value == self) if not (see get_copy_of_val | |
271 | and stmt_may_generate_copy). Other values make the name a COPY | |
272 | of that value. | |
88dbf20f | 273 | |
6ecedef2 | 274 | When visiting a statement or PHI node the lattice value for an |
275 | SSA name can transition from UNDEFINED to COPY to VARYING. */ | |
14f101cf | 276 | |
277 | struct prop_value_d { | |
278 | /* Copy-of value. */ | |
279 | tree value; | |
280 | }; | |
14f101cf | 281 | typedef struct prop_value_d prop_value_t; |
282 | ||
88dbf20f | 283 | static prop_value_t *copy_of; |
284 | ||
88dbf20f | 285 | |
286 | /* Return true if this statement may generate a useful copy. */ | |
287 | ||
288 | static bool | |
75a70cf9 | 289 | stmt_may_generate_copy (gimple stmt) |
88dbf20f | 290 | { |
75a70cf9 | 291 | if (gimple_code (stmt) == GIMPLE_PHI) |
292 | return !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (gimple_phi_result (stmt)); | |
88dbf20f | 293 | |
75a70cf9 | 294 | if (gimple_code (stmt) != GIMPLE_ASSIGN) |
88dbf20f | 295 | return false; |
296 | ||
88dbf20f | 297 | /* If the statement has volatile operands, it won't generate a |
298 | useful copy. */ | |
75a70cf9 | 299 | if (gimple_has_volatile_ops (stmt)) |
88dbf20f | 300 | return false; |
301 | ||
317d3b82 | 302 | /* Statements with loads and/or stores will never generate a useful copy. */ |
dd277d48 | 303 | if (gimple_vuse (stmt)) |
88dbf20f | 304 | return false; |
305 | ||
306 | /* Otherwise, the only statements that generate useful copies are | |
307 | assignments whose RHS is just an SSA name that doesn't flow | |
308 | through abnormal edges. */ | |
f82efd77 | 309 | return ((gimple_assign_rhs_code (stmt) == SSA_NAME |
310 | && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (gimple_assign_rhs1 (stmt))) | |
311 | || is_gimple_min_invariant (gimple_assign_rhs1 (stmt))); | |
88dbf20f | 312 | } |
313 | ||
314 | ||
315 | /* Return the copy-of value for VAR. */ | |
316 | ||
317 | static inline prop_value_t * | |
318 | get_copy_of_val (tree var) | |
319 | { | |
320 | prop_value_t *val = ©_of[SSA_NAME_VERSION (var)]; | |
321 | ||
322 | if (val->value == NULL_TREE | |
323 | && !stmt_may_generate_copy (SSA_NAME_DEF_STMT (var))) | |
324 | { | |
325 | /* If the variable will never generate a useful copy relation, | |
326 | make it its own copy. */ | |
327 | val->value = var; | |
88dbf20f | 328 | } |
329 | ||
330 | return val; | |
331 | } | |
332 | ||
6ecedef2 | 333 | /* Return the variable VAR is a copy of or VAR if VAR isn't the result |
334 | of a copy. */ | |
88dbf20f | 335 | |
6ecedef2 | 336 | static inline tree |
337 | valueize_val (tree var) | |
88dbf20f | 338 | { |
6ecedef2 | 339 | if (TREE_CODE (var) == SSA_NAME) |
88dbf20f | 340 | { |
6ecedef2 | 341 | tree val = get_copy_of_val (var)->value; |
342 | if (val) | |
343 | return val; | |
88dbf20f | 344 | } |
6ecedef2 | 345 | return var; |
88dbf20f | 346 | } |
347 | ||
6ecedef2 | 348 | /* Set VAL to be the copy of VAR. If that changed return true. */ |
88dbf20f | 349 | |
350 | static inline bool | |
6ecedef2 | 351 | set_copy_of_val (tree var, tree val) |
88dbf20f | 352 | { |
6ecedef2 | 353 | unsigned int ver = SSA_NAME_VERSION (var); |
354 | tree old; | |
48e1416a | 355 | |
88dbf20f | 356 | /* Set FIRST to be the first link in COPY_OF[DEST]. If that |
357 | changed, return true. */ | |
6ecedef2 | 358 | old = copy_of[ver].value; |
359 | copy_of[ver].value = val; | |
88dbf20f | 360 | |
82f6f8b4 | 361 | if (old != val |
362 | || (val && !operand_equal_p (old, val, 0))) | |
88dbf20f | 363 | return true; |
364 | ||
6ecedef2 | 365 | return false; |
88dbf20f | 366 | } |
367 | ||
368 | ||
3f5be5f4 | 369 | /* Dump the copy-of value for variable VAR to FILE. */ |
88dbf20f | 370 | |
371 | static void | |
3f5be5f4 | 372 | dump_copy_of (FILE *file, tree var) |
88dbf20f | 373 | { |
374 | tree val; | |
375 | ||
3f5be5f4 | 376 | print_generic_expr (file, var, dump_flags); |
88dbf20f | 377 | if (TREE_CODE (var) != SSA_NAME) |
378 | return; | |
48e1416a | 379 | |
6ecedef2 | 380 | val = copy_of[SSA_NAME_VERSION (var)].value; |
3f5be5f4 | 381 | fprintf (file, " copy-of chain: "); |
6ecedef2 | 382 | print_generic_expr (file, var, 0); |
3f5be5f4 | 383 | fprintf (file, " "); |
6ecedef2 | 384 | if (!val) |
385 | fprintf (file, "[UNDEFINED]"); | |
386 | else if (val == var) | |
387 | fprintf (file, "[NOT A COPY]"); | |
388 | else | |
88dbf20f | 389 | { |
3f5be5f4 | 390 | fprintf (file, "-> "); |
3f5be5f4 | 391 | print_generic_expr (file, val, 0); |
392 | fprintf (file, " "); | |
6ecedef2 | 393 | fprintf (file, "[COPY]"); |
88dbf20f | 394 | } |
88dbf20f | 395 | } |
396 | ||
397 | ||
398 | /* Evaluate the RHS of STMT. If it produces a valid copy, set the LHS | |
6ecedef2 | 399 | value and store the LHS into *RESULT_P. */ |
88dbf20f | 400 | |
401 | static enum ssa_prop_result | |
75a70cf9 | 402 | copy_prop_visit_assignment (gimple stmt, tree *result_p) |
88dbf20f | 403 | { |
404 | tree lhs, rhs; | |
88dbf20f | 405 | |
75a70cf9 | 406 | lhs = gimple_assign_lhs (stmt); |
82f6f8b4 | 407 | rhs = valueize_val (gimple_assign_rhs1 (stmt)); |
88dbf20f | 408 | |
409 | if (TREE_CODE (lhs) == SSA_NAME) | |
410 | { | |
411 | /* Straight copy between two SSA names. First, make sure that | |
412 | we can propagate the RHS into uses of LHS. */ | |
413 | if (!may_propagate_copy (lhs, rhs)) | |
414 | return SSA_PROP_VARYING; | |
415 | ||
88dbf20f | 416 | *result_p = lhs; |
82f6f8b4 | 417 | if (set_copy_of_val (*result_p, rhs)) |
88dbf20f | 418 | return SSA_PROP_INTERESTING; |
419 | else | |
420 | return SSA_PROP_NOT_INTERESTING; | |
421 | } | |
422 | ||
88dbf20f | 423 | return SSA_PROP_VARYING; |
424 | } | |
425 | ||
426 | ||
75a70cf9 | 427 | /* Visit the GIMPLE_COND STMT. Return SSA_PROP_INTERESTING |
88dbf20f | 428 | if it can determine which edge will be taken. Otherwise, return |
429 | SSA_PROP_VARYING. */ | |
430 | ||
431 | static enum ssa_prop_result | |
75a70cf9 | 432 | copy_prop_visit_cond_stmt (gimple stmt, edge *taken_edge_p) |
88dbf20f | 433 | { |
75a70cf9 | 434 | enum ssa_prop_result retval = SSA_PROP_VARYING; |
389dd41b | 435 | location_t loc = gimple_location (stmt); |
88dbf20f | 436 | |
75a70cf9 | 437 | tree op0 = gimple_cond_lhs (stmt); |
438 | tree op1 = gimple_cond_rhs (stmt); | |
88dbf20f | 439 | |
440 | /* The only conditionals that we may be able to compute statically | |
20bd2b8f | 441 | are predicates involving two SSA_NAMEs. */ |
75a70cf9 | 442 | if (TREE_CODE (op0) == SSA_NAME && TREE_CODE (op1) == SSA_NAME) |
88dbf20f | 443 | { |
6ecedef2 | 444 | op0 = valueize_val (op0); |
445 | op1 = valueize_val (op1); | |
88dbf20f | 446 | |
447 | /* See if we can determine the predicate's value. */ | |
448 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
449 | { | |
450 | fprintf (dump_file, "Trying to determine truth value of "); | |
451 | fprintf (dump_file, "predicate "); | |
75a70cf9 | 452 | print_gimple_stmt (dump_file, stmt, 0, 0); |
88dbf20f | 453 | } |
454 | ||
20bd2b8f | 455 | /* We can fold COND and get a useful result only when we have |
456 | the same SSA_NAME on both sides of a comparison operator. */ | |
457 | if (op0 == op1) | |
f21dcb28 | 458 | { |
389dd41b | 459 | tree folded_cond = fold_binary_loc (loc, gimple_cond_code (stmt), |
75a70cf9 | 460 | boolean_type_node, op0, op1); |
20bd2b8f | 461 | if (folded_cond) |
462 | { | |
75a70cf9 | 463 | basic_block bb = gimple_bb (stmt); |
20bd2b8f | 464 | *taken_edge_p = find_taken_edge (bb, folded_cond); |
465 | if (*taken_edge_p) | |
466 | retval = SSA_PROP_INTERESTING; | |
467 | } | |
f21dcb28 | 468 | } |
88dbf20f | 469 | } |
470 | ||
471 | if (dump_file && (dump_flags & TDF_DETAILS) && *taken_edge_p) | |
472 | fprintf (dump_file, "\nConditional will always take edge %d->%d\n", | |
473 | (*taken_edge_p)->src->index, (*taken_edge_p)->dest->index); | |
474 | ||
475 | return retval; | |
476 | } | |
477 | ||
478 | ||
479 | /* Evaluate statement STMT. If the statement produces a new output | |
480 | value, return SSA_PROP_INTERESTING and store the SSA_NAME holding | |
481 | the new value in *RESULT_P. | |
482 | ||
483 | If STMT is a conditional branch and we can determine its truth | |
484 | value, set *TAKEN_EDGE_P accordingly. | |
485 | ||
486 | If the new value produced by STMT is varying, return | |
487 | SSA_PROP_VARYING. */ | |
488 | ||
489 | static enum ssa_prop_result | |
75a70cf9 | 490 | copy_prop_visit_stmt (gimple stmt, edge *taken_edge_p, tree *result_p) |
88dbf20f | 491 | { |
88dbf20f | 492 | enum ssa_prop_result retval; |
493 | ||
494 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
495 | { | |
496 | fprintf (dump_file, "\nVisiting statement:\n"); | |
75a70cf9 | 497 | print_gimple_stmt (dump_file, stmt, 0, dump_flags); |
88dbf20f | 498 | fprintf (dump_file, "\n"); |
499 | } | |
500 | ||
75a70cf9 | 501 | if (gimple_assign_single_p (stmt) |
502 | && TREE_CODE (gimple_assign_lhs (stmt)) == SSA_NAME | |
82f6f8b4 | 503 | && (TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME |
504 | || is_gimple_min_invariant (gimple_assign_rhs1 (stmt)))) | |
88dbf20f | 505 | { |
506 | /* If the statement is a copy assignment, evaluate its RHS to | |
507 | see if the lattice value of its output has changed. */ | |
508 | retval = copy_prop_visit_assignment (stmt, result_p); | |
509 | } | |
75a70cf9 | 510 | else if (gimple_code (stmt) == GIMPLE_COND) |
88dbf20f | 511 | { |
512 | /* See if we can determine which edge goes out of a conditional | |
513 | jump. */ | |
514 | retval = copy_prop_visit_cond_stmt (stmt, taken_edge_p); | |
515 | } | |
516 | else | |
517 | retval = SSA_PROP_VARYING; | |
518 | ||
519 | if (retval == SSA_PROP_VARYING) | |
520 | { | |
521 | tree def; | |
522 | ssa_op_iter i; | |
523 | ||
524 | /* Any other kind of statement is not interesting for constant | |
525 | propagation and, therefore, not worth simulating. */ | |
526 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
527 | fprintf (dump_file, "No interesting values produced.\n"); | |
528 | ||
529 | /* The assignment is not a copy operation. Don't visit this | |
530 | statement again and mark all the definitions in the statement | |
531 | to be copies of nothing. */ | |
532 | FOR_EACH_SSA_TREE_OPERAND (def, stmt, i, SSA_OP_ALL_DEFS) | |
317d3b82 | 533 | set_copy_of_val (def, def); |
88dbf20f | 534 | } |
535 | ||
536 | return retval; | |
537 | } | |
538 | ||
539 | ||
540 | /* Visit PHI node PHI. If all the arguments produce the same value, | |
541 | set it to be the value of the LHS of PHI. */ | |
542 | ||
543 | static enum ssa_prop_result | |
75a70cf9 | 544 | copy_prop_visit_phi_node (gimple phi) |
88dbf20f | 545 | { |
546 | enum ssa_prop_result retval; | |
75a70cf9 | 547 | unsigned i; |
14f101cf | 548 | prop_value_t phi_val = { NULL_TREE }; |
88dbf20f | 549 | |
75a70cf9 | 550 | tree lhs = gimple_phi_result (phi); |
88dbf20f | 551 | |
552 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
553 | { | |
554 | fprintf (dump_file, "\nVisiting PHI node: "); | |
75a70cf9 | 555 | print_gimple_stmt (dump_file, phi, 0, dump_flags); |
88dbf20f | 556 | } |
557 | ||
75a70cf9 | 558 | for (i = 0; i < gimple_phi_num_args (phi); i++) |
88dbf20f | 559 | { |
560 | prop_value_t *arg_val; | |
abb08aa8 | 561 | tree arg_value; |
75a70cf9 | 562 | tree arg = gimple_phi_arg_def (phi, i); |
563 | edge e = gimple_phi_arg_edge (phi, i); | |
88dbf20f | 564 | |
565 | /* We don't care about values flowing through non-executable | |
566 | edges. */ | |
567 | if (!(e->flags & EDGE_EXECUTABLE)) | |
568 | continue; | |
569 | ||
abb08aa8 | 570 | /* Names that flow through abnormal edges cannot be used to |
571 | derive copies. */ | |
572 | if (TREE_CODE (arg) == SSA_NAME && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (arg)) | |
88dbf20f | 573 | { |
574 | phi_val.value = lhs; | |
575 | break; | |
576 | } | |
577 | ||
88dbf20f | 578 | if (dump_file && (dump_flags & TDF_DETAILS)) |
579 | { | |
580 | fprintf (dump_file, "\tArgument #%d: ", i); | |
581 | dump_copy_of (dump_file, arg); | |
582 | fprintf (dump_file, "\n"); | |
583 | } | |
584 | ||
abb08aa8 | 585 | if (TREE_CODE (arg) == SSA_NAME) |
586 | { | |
587 | arg_val = get_copy_of_val (arg); | |
588 | ||
589 | /* If we didn't visit the definition of arg yet treat it as | |
590 | UNDEFINED. This also handles PHI arguments that are the | |
591 | same as lhs. We'll come here again. */ | |
592 | if (!arg_val->value) | |
593 | continue; | |
88dbf20f | 594 | |
abb08aa8 | 595 | arg_value = arg_val->value; |
596 | } | |
597 | else | |
598 | arg_value = valueize_val (arg); | |
599 | ||
600 | /* Avoid copy propagation from an inner into an outer loop. | |
601 | Otherwise, this may move loop variant variables outside of | |
602 | their loops and prevent coalescing opportunities. If the | |
603 | value was loop invariant, it will be hoisted by LICM and | |
604 | exposed for copy propagation. | |
605 | ??? The value will be always loop invariant. | |
606 | In loop-closed SSA form do not copy-propagate through | |
607 | PHI nodes in blocks with a loop exit edge predecessor. */ | |
608 | if (current_loops | |
609 | && TREE_CODE (arg_value) == SSA_NAME | |
610 | && (loop_depth_of_name (arg_value) > loop_depth_of_name (lhs) | |
611 | || (loops_state_satisfies_p (LOOP_CLOSED_SSA) | |
612 | && loop_exit_edge_p (e->src->loop_father, e)))) | |
613 | { | |
614 | phi_val.value = lhs; | |
615 | break; | |
616 | } | |
6ecedef2 | 617 | |
88dbf20f | 618 | /* If the LHS didn't have a value yet, make it a copy of the |
6ecedef2 | 619 | first argument we find. */ |
88dbf20f | 620 | if (phi_val.value == NULL_TREE) |
621 | { | |
abb08aa8 | 622 | phi_val.value = arg_value; |
88dbf20f | 623 | continue; |
624 | } | |
625 | ||
626 | /* If PHI_VAL and ARG don't have a common copy-of chain, then | |
6ecedef2 | 627 | this PHI node cannot be a copy operation. */ |
abb08aa8 | 628 | if (phi_val.value != arg_value |
629 | && !operand_equal_p (phi_val.value, arg_value, 0)) | |
88dbf20f | 630 | { |
631 | phi_val.value = lhs; | |
632 | break; | |
633 | } | |
634 | } | |
635 | ||
6ecedef2 | 636 | if (phi_val.value |
637 | && may_propagate_copy (lhs, phi_val.value) | |
b87f0847 | 638 | && set_copy_of_val (lhs, phi_val.value)) |
88dbf20f | 639 | retval = (phi_val.value != lhs) ? SSA_PROP_INTERESTING : SSA_PROP_VARYING; |
640 | else | |
641 | retval = SSA_PROP_NOT_INTERESTING; | |
642 | ||
643 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
644 | { | |
6ecedef2 | 645 | fprintf (dump_file, "PHI node "); |
88dbf20f | 646 | dump_copy_of (dump_file, lhs); |
647 | fprintf (dump_file, "\nTelling the propagator to "); | |
648 | if (retval == SSA_PROP_INTERESTING) | |
649 | fprintf (dump_file, "add SSA edges out of this PHI and continue."); | |
650 | else if (retval == SSA_PROP_VARYING) | |
651 | fprintf (dump_file, "add SSA edges out of this PHI and never visit again."); | |
652 | else | |
653 | fprintf (dump_file, "do nothing with SSA edges and keep iterating."); | |
654 | fprintf (dump_file, "\n\n"); | |
655 | } | |
656 | ||
657 | return retval; | |
658 | } | |
659 | ||
660 | ||
6ecedef2 | 661 | /* Initialize structures used for copy propagation. */ |
88dbf20f | 662 | |
663 | static void | |
d1d2af7d | 664 | init_copy_prop (void) |
88dbf20f | 665 | { |
666 | basic_block bb; | |
667 | ||
43959b95 | 668 | copy_of = XCNEWVEC (prop_value_t, num_ssa_names); |
88dbf20f | 669 | |
88dbf20f | 670 | FOR_EACH_BB (bb) |
671 | { | |
75a70cf9 | 672 | gimple_stmt_iterator si; |
6b42039a | 673 | int depth = bb_loop_depth (bb); |
88dbf20f | 674 | |
75a70cf9 | 675 | for (si = gsi_start_bb (bb); !gsi_end_p (si); gsi_next (&si)) |
88dbf20f | 676 | { |
75a70cf9 | 677 | gimple stmt = gsi_stmt (si); |
2166ab0e | 678 | ssa_op_iter iter; |
75a70cf9 | 679 | tree def; |
88dbf20f | 680 | |
681 | /* The only statements that we care about are those that may | |
682 | generate useful copies. We also need to mark conditional | |
683 | jumps so that their outgoing edges are added to the work | |
2166ab0e | 684 | lists of the propagator. |
685 | ||
686 | Avoid copy propagation from an inner into an outer loop. | |
687 | Otherwise, this may move loop variant variables outside of | |
688 | their loops and prevent coalescing opportunities. If the | |
689 | value was loop invariant, it will be hoisted by LICM and | |
6ecedef2 | 690 | exposed for copy propagation. |
691 | ??? This doesn't make sense. */ | |
88dbf20f | 692 | if (stmt_ends_bb_p (stmt)) |
75a70cf9 | 693 | prop_set_simulate_again (stmt, true); |
2166ab0e | 694 | else if (stmt_may_generate_copy (stmt) |
75a70cf9 | 695 | /* Since we are iterating over the statements in |
696 | BB, not the phi nodes, STMT will always be an | |
697 | assignment. */ | |
698 | && loop_depth_of_name (gimple_assign_rhs1 (stmt)) <= depth) | |
699 | prop_set_simulate_again (stmt, true); | |
88dbf20f | 700 | else |
75a70cf9 | 701 | prop_set_simulate_again (stmt, false); |
2166ab0e | 702 | |
703 | /* Mark all the outputs of this statement as not being | |
704 | the copy of anything. */ | |
705 | FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS) | |
75a70cf9 | 706 | if (!prop_simulate_again_p (stmt)) |
317d3b82 | 707 | set_copy_of_val (def, def); |
88dbf20f | 708 | } |
709 | ||
75a70cf9 | 710 | for (si = gsi_start_phis (bb); !gsi_end_p (si); gsi_next (&si)) |
2166ab0e | 711 | { |
75a70cf9 | 712 | gimple phi = gsi_stmt (si); |
713 | tree def; | |
714 | ||
715 | def = gimple_phi_result (phi); | |
7c782c9b | 716 | if (virtual_operand_p (def)) |
75a70cf9 | 717 | prop_set_simulate_again (phi, false); |
2166ab0e | 718 | else |
75a70cf9 | 719 | prop_set_simulate_again (phi, true); |
2166ab0e | 720 | |
75a70cf9 | 721 | if (!prop_simulate_again_p (phi)) |
317d3b82 | 722 | set_copy_of_val (def, def); |
2166ab0e | 723 | } |
88dbf20f | 724 | } |
725 | } | |
726 | ||
14f101cf | 727 | /* Callback for substitute_and_fold to get at the final copy-of values. */ |
728 | ||
729 | static tree | |
730 | get_value (tree name) | |
731 | { | |
732 | tree val = copy_of[SSA_NAME_VERSION (name)].value; | |
733 | if (val && val != name) | |
734 | return val; | |
735 | return NULL_TREE; | |
736 | } | |
88dbf20f | 737 | |
738 | /* Deallocate memory used in copy propagation and do final | |
739 | substitution. */ | |
740 | ||
741 | static void | |
742 | fini_copy_prop (void) | |
743 | { | |
14f101cf | 744 | unsigned i; |
48e1416a | 745 | |
88dbf20f | 746 | /* Set the final copy-of value for each variable by traversing the |
747 | copy-of chains. */ | |
748 | for (i = 1; i < num_ssa_names; i++) | |
749 | { | |
750 | tree var = ssa_name (i); | |
ba3f9c71 | 751 | if (!var |
752 | || !copy_of[i].value | |
753 | || copy_of[i].value == var) | |
754 | continue; | |
755 | ||
ba3f9c71 | 756 | /* In theory the points-to solution of all members of the |
757 | copy chain is their intersection. For now we do not bother | |
758 | to compute this but only make sure we do not lose points-to | |
759 | information completely by setting the points-to solution | |
760 | of the representative to the first solution we find if | |
761 | it doesn't have one already. */ | |
14f101cf | 762 | if (copy_of[i].value != var |
f82efd77 | 763 | && TREE_CODE (copy_of[i].value) == SSA_NAME |
ba3f9c71 | 764 | && POINTER_TYPE_P (TREE_TYPE (var)) |
765 | && SSA_NAME_PTR_INFO (var) | |
14f101cf | 766 | && !SSA_NAME_PTR_INFO (copy_of[i].value)) |
767 | duplicate_ssa_name_ptr_info (copy_of[i].value, SSA_NAME_PTR_INFO (var)); | |
88dbf20f | 768 | } |
769 | ||
0d63aa16 | 770 | /* Don't do DCE if we have loops. That's the simplest way to not |
771 | destroy the scev cache. */ | |
772 | substitute_and_fold (get_value, NULL, !current_loops); | |
88dbf20f | 773 | |
774 | free (copy_of); | |
775 | } | |
776 | ||
777 | ||
421828b0 | 778 | /* Main entry point to the copy propagator. |
779 | ||
780 | PHIS_ONLY is true if we should only consider PHI nodes as generating | |
48e1416a | 781 | copy propagation opportunities. |
421828b0 | 782 | |
783 | The algorithm propagates the value COPY-OF using ssa_propagate. For | |
784 | every variable X_i, COPY-OF(X_i) indicates which variable is X_i created | |
785 | from. The following example shows how the algorithm proceeds at a | |
786 | high level: | |
88dbf20f | 787 | |
788 | 1 a_24 = x_1 | |
789 | 2 a_2 = PHI <a_24, x_1> | |
790 | 3 a_5 = PHI <a_2> | |
791 | 4 x_1 = PHI <x_298, a_5, a_2> | |
792 | ||
793 | The end result should be that a_2, a_5, a_24 and x_1 are a copy of | |
794 | x_298. Propagation proceeds as follows. | |
795 | ||
796 | Visit #1: a_24 is copy-of x_1. Value changed. | |
797 | Visit #2: a_2 is copy-of x_1. Value changed. | |
798 | Visit #3: a_5 is copy-of x_1. Value changed. | |
799 | Visit #4: x_1 is copy-of x_298. Value changed. | |
800 | Visit #1: a_24 is copy-of x_298. Value changed. | |
801 | Visit #2: a_2 is copy-of x_298. Value changed. | |
802 | Visit #3: a_5 is copy-of x_298. Value changed. | |
803 | Visit #4: x_1 is copy-of x_298. Stable state reached. | |
48e1416a | 804 | |
88dbf20f | 805 | When visiting PHI nodes, we only consider arguments that flow |
806 | through edges marked executable by the propagation engine. So, | |
807 | when visiting statement #2 for the first time, we will only look at | |
808 | the first argument (a_24) and optimistically assume that its value | |
6ecedef2 | 809 | is the copy of a_24 (x_1). */ |
88dbf20f | 810 | |
317d3b82 | 811 | static unsigned int |
812 | execute_copy_prop (void) | |
88dbf20f | 813 | { |
d1d2af7d | 814 | init_copy_prop (); |
88dbf20f | 815 | ssa_propagate (copy_prop_visit_stmt, copy_prop_visit_phi_node); |
816 | fini_copy_prop (); | |
317d3b82 | 817 | return 0; |
88dbf20f | 818 | } |
819 | ||
88dbf20f | 820 | static bool |
821 | gate_copy_prop (void) | |
822 | { | |
823 | return flag_tree_copy_prop != 0; | |
824 | } | |
825 | ||
20099e35 | 826 | struct gimple_opt_pass pass_copy_prop = |
88dbf20f | 827 | { |
20099e35 | 828 | { |
829 | GIMPLE_PASS, | |
88dbf20f | 830 | "copyprop", /* name */ |
c7875731 | 831 | OPTGROUP_NONE, /* optinfo_flags */ |
88dbf20f | 832 | gate_copy_prop, /* gate */ |
317d3b82 | 833 | execute_copy_prop, /* execute */ |
88dbf20f | 834 | NULL, /* sub */ |
835 | NULL, /* next */ | |
836 | 0, /* static_pass_number */ | |
837 | TV_TREE_COPY_PROP, /* tv_id */ | |
49290934 | 838 | PROP_ssa | PROP_cfg, /* properties_required */ |
88dbf20f | 839 | 0, /* properties_provided */ |
840 | 0, /* properties_destroyed */ | |
841 | 0, /* todo_flags_start */ | |
842 | TODO_cleanup_cfg | |
88dbf20f | 843 | | TODO_ggc_collect |
844 | | TODO_verify_ssa | |
20099e35 | 845 | | TODO_update_ssa /* todo_flags_finish */ |
846 | } | |
88dbf20f | 847 | }; |