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annotate gcc/tree-ssa-propagate.c @ 158:494b0b89df80 default tip
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| author | Shinji KONO <kono@ie.u-ryukyu.ac.jp> |
|---|---|
| date | Mon, 25 May 2020 18:13:55 +0900 |
| parents | 1830386684a0 |
| children |
| rev | line source |
|---|---|
| 0 | 1 /* Generic SSA value propagation engine. |
| 145 | 2 Copyright (C) 2004-2020 Free Software Foundation, Inc. |
| 0 | 3 Contributed by Diego Novillo <dnovillo@redhat.com> |
| 4 | |
| 5 This file is part of GCC. | |
| 6 | |
| 7 GCC is free software; you can redistribute it and/or modify it | |
| 8 under the terms of the GNU General Public License as published by the | |
| 9 Free Software Foundation; either version 3, or (at your option) any | |
| 10 later version. | |
| 11 | |
| 12 GCC is distributed in the hope that it will be useful, but WITHOUT | |
| 13 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| 14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| 15 for more details. | |
| 16 | |
| 17 You should have received a copy of the GNU General Public License | |
| 18 along with GCC; see the file COPYING3. If not see | |
| 19 <http://www.gnu.org/licenses/>. */ | |
| 20 | |
| 21 #include "config.h" | |
| 22 #include "system.h" | |
| 23 #include "coretypes.h" | |
| 111 | 24 #include "backend.h" |
| 0 | 25 #include "tree.h" |
| 111 | 26 #include "gimple.h" |
| 27 #include "ssa.h" | |
|
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28 #include "gimple-pretty-print.h" |
| 111 | 29 #include "dumpfile.h" |
| 30 #include "gimple-fold.h" | |
| 31 #include "tree-eh.h" | |
| 32 #include "gimplify.h" | |
| 33 #include "gimple-iterator.h" | |
| 34 #include "tree-cfg.h" | |
| 35 #include "tree-ssa.h" | |
| 0 | 36 #include "tree-ssa-propagate.h" |
| 111 | 37 #include "domwalk.h" |
| 38 #include "cfgloop.h" | |
| 39 #include "tree-cfgcleanup.h" | |
| 40 #include "cfganal.h" | |
| 0 | 41 |
| 42 /* This file implements a generic value propagation engine based on | |
| 43 the same propagation used by the SSA-CCP algorithm [1]. | |
| 44 | |
| 45 Propagation is performed by simulating the execution of every | |
| 46 statement that produces the value being propagated. Simulation | |
| 47 proceeds as follows: | |
| 48 | |
| 49 1- Initially, all edges of the CFG are marked not executable and | |
| 50 the CFG worklist is seeded with all the statements in the entry | |
| 51 basic block (block 0). | |
| 52 | |
| 53 2- Every statement S is simulated with a call to the call-back | |
| 54 function SSA_PROP_VISIT_STMT. This evaluation may produce 3 | |
| 55 results: | |
| 56 | |
| 57 SSA_PROP_NOT_INTERESTING: Statement S produces nothing of | |
| 58 interest and does not affect any of the work lists. | |
| 111 | 59 The statement may be simulated again if any of its input |
| 60 operands change in future iterations of the simulator. | |
| 0 | 61 |
| 62 SSA_PROP_VARYING: The value produced by S cannot be determined | |
| 63 at compile time. Further simulation of S is not required. | |
| 64 If S is a conditional jump, all the outgoing edges for the | |
| 65 block are considered executable and added to the work | |
| 66 list. | |
| 67 | |
| 68 SSA_PROP_INTERESTING: S produces a value that can be computed | |
| 69 at compile time. Its result can be propagated into the | |
| 70 statements that feed from S. Furthermore, if S is a | |
| 71 conditional jump, only the edge known to be taken is added | |
| 72 to the work list. Edges that are known not to execute are | |
| 73 never simulated. | |
| 74 | |
| 75 3- PHI nodes are simulated with a call to SSA_PROP_VISIT_PHI. The | |
| 76 return value from SSA_PROP_VISIT_PHI has the same semantics as | |
| 77 described in #2. | |
| 78 | |
| 79 4- Three work lists are kept. Statements are only added to these | |
| 80 lists if they produce one of SSA_PROP_INTERESTING or | |
| 81 SSA_PROP_VARYING. | |
| 82 | |
| 83 CFG_BLOCKS contains the list of blocks to be simulated. | |
| 84 Blocks are added to this list if their incoming edges are | |
| 85 found executable. | |
| 86 | |
| 111 | 87 SSA_EDGE_WORKLIST contains the list of statements that we |
| 88 need to revisit. | |
| 0 | 89 |
| 90 5- Simulation terminates when all three work lists are drained. | |
| 91 | |
| 92 Before calling ssa_propagate, it is important to clear | |
| 93 prop_simulate_again_p for all the statements in the program that | |
| 94 should be simulated. This initialization allows an implementation | |
| 95 to specify which statements should never be simulated. | |
| 96 | |
| 97 It is also important to compute def-use information before calling | |
| 98 ssa_propagate. | |
| 99 | |
| 100 References: | |
| 101 | |
| 102 [1] Constant propagation with conditional branches, | |
| 103 Wegman and Zadeck, ACM TOPLAS 13(2):181-210. | |
| 104 | |
| 105 [2] Building an Optimizing Compiler, | |
| 106 Robert Morgan, Butterworth-Heinemann, 1998, Section 8.9. | |
| 107 | |
| 108 [3] Advanced Compiler Design and Implementation, | |
| 109 Steven Muchnick, Morgan Kaufmann, 1997, Section 12.6 */ | |
| 110 | |
| 131 | 111 /* Worklists of control flow edge destinations. This contains |
| 111 | 112 the CFG order number of the blocks so we can iterate in CFG |
| 131 | 113 order by visiting in bit-order. We use two worklists to |
| 114 first make forward progress before iterating. */ | |
| 111 | 115 static bitmap cfg_blocks; |
| 131 | 116 static bitmap cfg_blocks_back; |
| 111 | 117 static int *bb_to_cfg_order; |
| 118 static int *cfg_order_to_bb; | |
| 0 | 119 |
| 131 | 120 /* Worklists of SSA edges which will need reexamination as their |
| 0 | 121 definition has changed. SSA edges are def-use edges in the SSA |
| 122 web. For each D-U edge, we store the target statement or PHI node | |
| 131 | 123 UID in a bitmap. UIDs order stmts in execution order. We use |
| 124 two worklists to first make forward progress before iterating. */ | |
| 111 | 125 static bitmap ssa_edge_worklist; |
| 131 | 126 static bitmap ssa_edge_worklist_back; |
| 111 | 127 static vec<gimple *> uid_to_stmt; |
| 0 | 128 |
| 131 | 129 /* Current RPO index in the iteration. */ |
| 130 static int curr_order; | |
| 0 | 131 |
| 132 | |
| 133 /* We have just defined a new value for VAR. If IS_VARYING is true, | |
| 134 add all immediate uses of VAR to VARYING_SSA_EDGES, otherwise add | |
| 135 them to INTERESTING_SSA_EDGES. */ | |
| 136 | |
| 137 static void | |
| 111 | 138 add_ssa_edge (tree var) |
| 0 | 139 { |
| 140 imm_use_iterator iter; | |
| 141 use_operand_p use_p; | |
| 142 | |
| 143 FOR_EACH_IMM_USE_FAST (use_p, iter, var) | |
| 144 { | |
| 111 | 145 gimple *use_stmt = USE_STMT (use_p); |
| 131 | 146 if (!prop_simulate_again_p (use_stmt)) |
| 147 continue; | |
| 111 | 148 |
| 149 /* If we did not yet simulate the block wait for this to happen | |
| 150 and do not add the stmt to the SSA edge worklist. */ | |
| 131 | 151 basic_block use_bb = gimple_bb (use_stmt); |
| 152 if (! (use_bb->flags & BB_VISITED)) | |
| 111 | 153 continue; |
| 0 | 154 |
| 131 | 155 /* If this is a use on a not yet executable edge do not bother to |
| 156 queue it. */ | |
| 157 if (gimple_code (use_stmt) == GIMPLE_PHI | |
| 158 && !(EDGE_PRED (use_bb, PHI_ARG_INDEX_FROM_USE (use_p))->flags | |
| 159 & EDGE_EXECUTABLE)) | |
| 160 continue; | |
| 161 | |
| 162 bitmap worklist; | |
| 163 if (bb_to_cfg_order[gimple_bb (use_stmt)->index] < curr_order) | |
| 164 worklist = ssa_edge_worklist_back; | |
| 165 else | |
| 166 worklist = ssa_edge_worklist; | |
| 167 if (bitmap_set_bit (worklist, gimple_uid (use_stmt))) | |
| 0 | 168 { |
| 111 | 169 uid_to_stmt[gimple_uid (use_stmt)] = use_stmt; |
| 170 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 171 { | |
| 172 fprintf (dump_file, "ssa_edge_worklist: adding SSA use in "); | |
| 173 print_gimple_stmt (dump_file, use_stmt, 0, TDF_SLIM); | |
| 174 } | |
| 0 | 175 } |
| 176 } | |
| 177 } | |
| 178 | |
| 179 | |
| 180 /* Add edge E to the control flow worklist. */ | |
| 181 | |
| 182 static void | |
| 183 add_control_edge (edge e) | |
| 184 { | |
| 185 basic_block bb = e->dest; | |
| 111 | 186 if (bb == EXIT_BLOCK_PTR_FOR_FN (cfun)) |
| 0 | 187 return; |
| 188 | |
| 189 /* If the edge had already been executed, skip it. */ | |
| 190 if (e->flags & EDGE_EXECUTABLE) | |
| 191 return; | |
| 192 | |
| 193 e->flags |= EDGE_EXECUTABLE; | |
| 194 | |
| 131 | 195 int bb_order = bb_to_cfg_order[bb->index]; |
| 196 if (bb_order < curr_order) | |
| 197 bitmap_set_bit (cfg_blocks_back, bb_order); | |
| 198 else | |
| 199 bitmap_set_bit (cfg_blocks, bb_order); | |
| 0 | 200 |
| 201 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 111 | 202 fprintf (dump_file, "Adding destination of edge (%d -> %d) to worklist\n", |
| 0 | 203 e->src->index, e->dest->index); |
| 204 } | |
| 205 | |
| 206 | |
| 207 /* Simulate the execution of STMT and update the work lists accordingly. */ | |
| 208 | |
| 131 | 209 void |
| 210 ssa_propagation_engine::simulate_stmt (gimple *stmt) | |
| 0 | 211 { |
| 212 enum ssa_prop_result val = SSA_PROP_NOT_INTERESTING; | |
| 213 edge taken_edge = NULL; | |
| 214 tree output_name = NULL_TREE; | |
| 215 | |
| 111 | 216 /* Pull the stmt off the SSA edge worklist. */ |
| 217 bitmap_clear_bit (ssa_edge_worklist, gimple_uid (stmt)); | |
| 218 | |
| 0 | 219 /* Don't bother visiting statements that are already |
| 220 considered varying by the propagator. */ | |
| 221 if (!prop_simulate_again_p (stmt)) | |
| 222 return; | |
| 223 | |
| 224 if (gimple_code (stmt) == GIMPLE_PHI) | |
| 225 { | |
| 131 | 226 val = visit_phi (as_a <gphi *> (stmt)); |
| 0 | 227 output_name = gimple_phi_result (stmt); |
| 228 } | |
| 229 else | |
| 131 | 230 val = visit_stmt (stmt, &taken_edge, &output_name); |
| 0 | 231 |
| 232 if (val == SSA_PROP_VARYING) | |
| 233 { | |
| 234 prop_set_simulate_again (stmt, false); | |
| 235 | |
| 236 /* If the statement produced a new varying value, add the SSA | |
| 237 edges coming out of OUTPUT_NAME. */ | |
| 238 if (output_name) | |
| 111 | 239 add_ssa_edge (output_name); |
| 0 | 240 |
| 241 /* If STMT transfers control out of its basic block, add | |
| 242 all outgoing edges to the work list. */ | |
| 243 if (stmt_ends_bb_p (stmt)) | |
| 244 { | |
| 245 edge e; | |
| 246 edge_iterator ei; | |
| 247 basic_block bb = gimple_bb (stmt); | |
| 248 FOR_EACH_EDGE (e, ei, bb->succs) | |
| 249 add_control_edge (e); | |
| 250 } | |
| 111 | 251 return; |
| 0 | 252 } |
| 253 else if (val == SSA_PROP_INTERESTING) | |
| 254 { | |
| 255 /* If the statement produced new value, add the SSA edges coming | |
| 256 out of OUTPUT_NAME. */ | |
| 257 if (output_name) | |
| 111 | 258 add_ssa_edge (output_name); |
| 0 | 259 |
| 260 /* If we know which edge is going to be taken out of this block, | |
| 261 add it to the CFG work list. */ | |
| 262 if (taken_edge) | |
| 263 add_control_edge (taken_edge); | |
| 264 } | |
| 111 | 265 |
| 266 /* If there are no SSA uses on the stmt whose defs are simulated | |
| 267 again then this stmt will be never visited again. */ | |
| 268 bool has_simulate_again_uses = false; | |
| 269 use_operand_p use_p; | |
| 270 ssa_op_iter iter; | |
| 271 if (gimple_code (stmt) == GIMPLE_PHI) | |
| 272 { | |
| 273 edge_iterator ei; | |
| 274 edge e; | |
| 275 tree arg; | |
| 276 FOR_EACH_EDGE (e, ei, gimple_bb (stmt)->preds) | |
| 277 if (!(e->flags & EDGE_EXECUTABLE) | |
| 278 || ((arg = PHI_ARG_DEF_FROM_EDGE (stmt, e)) | |
| 279 && TREE_CODE (arg) == SSA_NAME | |
| 280 && !SSA_NAME_IS_DEFAULT_DEF (arg) | |
| 281 && prop_simulate_again_p (SSA_NAME_DEF_STMT (arg)))) | |
| 282 { | |
| 283 has_simulate_again_uses = true; | |
| 284 break; | |
| 285 } | |
| 286 } | |
| 287 else | |
| 288 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE) | |
| 289 { | |
| 290 gimple *def_stmt = SSA_NAME_DEF_STMT (USE_FROM_PTR (use_p)); | |
| 291 if (!gimple_nop_p (def_stmt) | |
| 292 && prop_simulate_again_p (def_stmt)) | |
| 293 { | |
| 294 has_simulate_again_uses = true; | |
| 295 break; | |
| 296 } | |
| 297 } | |
| 298 if (!has_simulate_again_uses) | |
| 299 { | |
| 300 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 301 fprintf (dump_file, "marking stmt to be not simulated again\n"); | |
| 302 prop_set_simulate_again (stmt, false); | |
| 303 } | |
| 0 | 304 } |
| 305 | |
| 306 | |
| 307 /* Simulate the execution of BLOCK. Evaluate the statement associated | |
| 308 with each variable reference inside the block. */ | |
| 309 | |
| 131 | 310 void |
| 311 ssa_propagation_engine::simulate_block (basic_block block) | |
| 0 | 312 { |
| 313 gimple_stmt_iterator gsi; | |
| 314 | |
| 315 /* There is nothing to do for the exit block. */ | |
| 111 | 316 if (block == EXIT_BLOCK_PTR_FOR_FN (cfun)) |
| 0 | 317 return; |
| 318 | |
| 319 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 320 fprintf (dump_file, "\nSimulating block %d\n", block->index); | |
| 321 | |
| 322 /* Always simulate PHI nodes, even if we have simulated this block | |
| 323 before. */ | |
| 324 for (gsi = gsi_start_phis (block); !gsi_end_p (gsi); gsi_next (&gsi)) | |
| 325 simulate_stmt (gsi_stmt (gsi)); | |
| 326 | |
| 327 /* If this is the first time we've simulated this block, then we | |
| 328 must simulate each of its statements. */ | |
| 111 | 329 if (! (block->flags & BB_VISITED)) |
| 0 | 330 { |
| 331 gimple_stmt_iterator j; | |
| 332 unsigned int normal_edge_count; | |
| 333 edge e, normal_edge; | |
| 334 edge_iterator ei; | |
| 335 | |
| 336 for (j = gsi_start_bb (block); !gsi_end_p (j); gsi_next (&j)) | |
| 111 | 337 simulate_stmt (gsi_stmt (j)); |
| 0 | 338 |
| 111 | 339 /* Note that we have simulated this block. */ |
| 340 block->flags |= BB_VISITED; | |
| 0 | 341 |
| 145 | 342 /* We cannot predict when abnormal and EH edges will be executed, so |
| 0 | 343 once a block is considered executable, we consider any |
| 344 outgoing abnormal edges as executable. | |
| 345 | |
|
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346 TODO: This is not exactly true. Simplifying statement might |
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347 prove it non-throwing and also computed goto can be handled |
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348 when destination is known. |
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349 |
| 0 | 350 At the same time, if this block has only one successor that is |
| 351 reached by non-abnormal edges, then add that successor to the | |
| 352 worklist. */ | |
| 353 normal_edge_count = 0; | |
| 354 normal_edge = NULL; | |
| 355 FOR_EACH_EDGE (e, ei, block->succs) | |
| 356 { | |
|
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357 if (e->flags & (EDGE_ABNORMAL | EDGE_EH)) |
| 0 | 358 add_control_edge (e); |
| 359 else | |
| 360 { | |
| 361 normal_edge_count++; | |
| 362 normal_edge = e; | |
| 363 } | |
| 364 } | |
| 365 | |
| 366 if (normal_edge_count == 1) | |
| 367 add_control_edge (normal_edge); | |
| 368 } | |
| 369 } | |
| 370 | |
| 371 | |
| 372 /* Initialize local data structures and work lists. */ | |
| 373 | |
| 374 static void | |
| 375 ssa_prop_init (void) | |
| 376 { | |
| 377 edge e; | |
| 378 edge_iterator ei; | |
| 379 basic_block bb; | |
| 380 | |
| 381 /* Worklists of SSA edges. */ | |
| 111 | 382 ssa_edge_worklist = BITMAP_ALLOC (NULL); |
| 131 | 383 ssa_edge_worklist_back = BITMAP_ALLOC (NULL); |
| 384 bitmap_tree_view (ssa_edge_worklist); | |
| 385 bitmap_tree_view (ssa_edge_worklist_back); | |
| 0 | 386 |
| 111 | 387 /* Worklist of basic-blocks. */ |
| 388 bb_to_cfg_order = XNEWVEC (int, last_basic_block_for_fn (cfun) + 1); | |
| 389 cfg_order_to_bb = XNEWVEC (int, n_basic_blocks_for_fn (cfun)); | |
| 390 int n = pre_and_rev_post_order_compute_fn (cfun, NULL, | |
| 391 cfg_order_to_bb, false); | |
| 392 for (int i = 0; i < n; ++i) | |
| 393 bb_to_cfg_order[cfg_order_to_bb[i]] = i; | |
| 394 cfg_blocks = BITMAP_ALLOC (NULL); | |
| 131 | 395 cfg_blocks_back = BITMAP_ALLOC (NULL); |
| 0 | 396 |
| 397 /* Initially assume that every edge in the CFG is not executable. | |
| 111 | 398 (including the edges coming out of the entry block). Mark blocks |
| 399 as not visited, blocks not yet visited will have all their statements | |
| 400 simulated once an incoming edge gets executable. */ | |
| 401 set_gimple_stmt_max_uid (cfun, 0); | |
| 402 for (int i = 0; i < n; ++i) | |
| 0 | 403 { |
| 404 gimple_stmt_iterator si; | |
| 111 | 405 bb = BASIC_BLOCK_FOR_FN (cfun, cfg_order_to_bb[i]); |
| 406 | |
| 407 for (si = gsi_start_phis (bb); !gsi_end_p (si); gsi_next (&si)) | |
| 408 { | |
| 409 gimple *stmt = gsi_stmt (si); | |
| 410 gimple_set_uid (stmt, inc_gimple_stmt_max_uid (cfun)); | |
| 411 } | |
| 0 | 412 |
| 413 for (si = gsi_start_bb (bb); !gsi_end_p (si); gsi_next (&si)) | |
| 111 | 414 { |
| 415 gimple *stmt = gsi_stmt (si); | |
| 416 gimple_set_uid (stmt, inc_gimple_stmt_max_uid (cfun)); | |
| 417 } | |
|
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418 |
| 111 | 419 bb->flags &= ~BB_VISITED; |
| 0 | 420 FOR_EACH_EDGE (e, ei, bb->succs) |
| 421 e->flags &= ~EDGE_EXECUTABLE; | |
| 422 } | |
| 111 | 423 uid_to_stmt.safe_grow (gimple_stmt_max_uid (cfun)); |
| 0 | 424 |
| 425 /* Seed the algorithm by adding the successors of the entry block to the | |
| 426 edge worklist. */ | |
| 111 | 427 FOR_EACH_EDGE (e, ei, ENTRY_BLOCK_PTR_FOR_FN (cfun)->succs) |
| 428 { | |
| 429 e->flags &= ~EDGE_EXECUTABLE; | |
| 430 add_control_edge (e); | |
| 431 } | |
| 0 | 432 } |
| 433 | |
| 434 | |
| 435 /* Free allocated storage. */ | |
| 436 | |
| 437 static void | |
| 438 ssa_prop_fini (void) | |
| 439 { | |
| 111 | 440 BITMAP_FREE (cfg_blocks); |
| 131 | 441 BITMAP_FREE (cfg_blocks_back); |
| 111 | 442 free (bb_to_cfg_order); |
| 443 free (cfg_order_to_bb); | |
| 444 BITMAP_FREE (ssa_edge_worklist); | |
| 131 | 445 BITMAP_FREE (ssa_edge_worklist_back); |
| 111 | 446 uid_to_stmt.release (); |
| 0 | 447 } |
| 448 | |
| 449 | |
| 450 /* Return true if EXPR is an acceptable right-hand-side for a | |
| 451 GIMPLE assignment. We validate the entire tree, not just | |
| 452 the root node, thus catching expressions that embed complex | |
| 453 operands that are not permitted in GIMPLE. This function | |
| 454 is needed because the folding routines in fold-const.c | |
| 455 may return such expressions in some cases, e.g., an array | |
| 456 access with an embedded index addition. It may make more | |
| 457 sense to have folding routines that are sensitive to the | |
| 458 constraints on GIMPLE operands, rather than abandoning any | |
| 459 any attempt to fold if the usual folding turns out to be too | |
| 460 aggressive. */ | |
| 461 | |
| 462 bool | |
| 463 valid_gimple_rhs_p (tree expr) | |
| 464 { | |
| 465 enum tree_code code = TREE_CODE (expr); | |
| 466 | |
| 467 switch (TREE_CODE_CLASS (code)) | |
| 468 { | |
| 469 case tcc_declaration: | |
| 470 if (!is_gimple_variable (expr)) | |
| 471 return false; | |
| 472 break; | |
| 473 | |
| 474 case tcc_constant: | |
| 475 /* All constants are ok. */ | |
| 476 break; | |
| 477 | |
| 111 | 478 case tcc_comparison: |
| 479 /* GENERIC allows comparisons with non-boolean types, reject | |
| 480 those for GIMPLE. Let vector-typed comparisons pass - rules | |
| 481 for GENERIC and GIMPLE are the same here. */ | |
| 482 if (!(INTEGRAL_TYPE_P (TREE_TYPE (expr)) | |
| 483 && (TREE_CODE (TREE_TYPE (expr)) == BOOLEAN_TYPE | |
| 484 || TYPE_PRECISION (TREE_TYPE (expr)) == 1)) | |
| 485 && ! VECTOR_TYPE_P (TREE_TYPE (expr))) | |
| 486 return false; | |
| 487 | |
| 488 /* Fallthru. */ | |
| 0 | 489 case tcc_binary: |
| 490 if (!is_gimple_val (TREE_OPERAND (expr, 0)) | |
| 491 || !is_gimple_val (TREE_OPERAND (expr, 1))) | |
| 492 return false; | |
| 493 break; | |
| 494 | |
| 495 case tcc_unary: | |
| 496 if (!is_gimple_val (TREE_OPERAND (expr, 0))) | |
| 497 return false; | |
| 498 break; | |
| 499 | |
| 500 case tcc_expression: | |
| 501 switch (code) | |
| 502 { | |
| 503 case ADDR_EXPR: | |
| 504 { | |
| 505 tree t; | |
| 506 if (is_gimple_min_invariant (expr)) | |
| 507 return true; | |
| 508 t = TREE_OPERAND (expr, 0); | |
| 509 while (handled_component_p (t)) | |
| 510 { | |
| 511 /* ??? More checks needed, see the GIMPLE verifier. */ | |
| 512 if ((TREE_CODE (t) == ARRAY_REF | |
| 513 || TREE_CODE (t) == ARRAY_RANGE_REF) | |
| 514 && !is_gimple_val (TREE_OPERAND (t, 1))) | |
| 515 return false; | |
| 516 t = TREE_OPERAND (t, 0); | |
| 517 } | |
| 518 if (!is_gimple_id (t)) | |
| 519 return false; | |
| 520 } | |
| 521 break; | |
| 522 | |
| 523 default: | |
| 111 | 524 if (get_gimple_rhs_class (code) == GIMPLE_TERNARY_RHS) |
| 525 { | |
| 526 if (((code == VEC_COND_EXPR || code == COND_EXPR) | |
| 527 ? !is_gimple_condexpr (TREE_OPERAND (expr, 0)) | |
| 528 : !is_gimple_val (TREE_OPERAND (expr, 0))) | |
| 529 || !is_gimple_val (TREE_OPERAND (expr, 1)) | |
| 530 || !is_gimple_val (TREE_OPERAND (expr, 2))) | |
| 531 return false; | |
| 532 break; | |
| 533 } | |
| 0 | 534 return false; |
| 535 } | |
| 536 break; | |
| 537 | |
| 538 case tcc_vl_exp: | |
| 539 return false; | |
| 540 | |
| 541 case tcc_exceptional: | |
| 111 | 542 if (code == CONSTRUCTOR) |
| 543 { | |
| 544 unsigned i; | |
| 545 tree elt; | |
| 546 FOR_EACH_CONSTRUCTOR_VALUE (CONSTRUCTOR_ELTS (expr), i, elt) | |
| 547 if (!is_gimple_val (elt)) | |
| 548 return false; | |
| 549 return true; | |
| 550 } | |
| 0 | 551 if (code != SSA_NAME) |
| 552 return false; | |
| 553 break; | |
| 554 | |
| 111 | 555 case tcc_reference: |
| 556 if (code == BIT_FIELD_REF) | |
| 557 return is_gimple_val (TREE_OPERAND (expr, 0)); | |
| 558 return false; | |
| 559 | |
| 0 | 560 default: |
| 561 return false; | |
| 562 } | |
| 563 | |
| 564 return true; | |
| 565 } | |
| 566 | |
| 567 | |
| 568 /* Return true if EXPR is a CALL_EXPR suitable for representation | |
| 569 as a single GIMPLE_CALL statement. If the arguments require | |
| 570 further gimplification, return false. */ | |
| 571 | |
|
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572 static bool |
| 0 | 573 valid_gimple_call_p (tree expr) |
| 574 { | |
| 575 unsigned i, nargs; | |
| 576 | |
| 577 if (TREE_CODE (expr) != CALL_EXPR) | |
| 578 return false; | |
| 579 | |
| 580 nargs = call_expr_nargs (expr); | |
| 581 for (i = 0; i < nargs; i++) | |
|
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582 { |
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583 tree arg = CALL_EXPR_ARG (expr, i); |
| 111 | 584 if (is_gimple_reg_type (TREE_TYPE (arg))) |
|
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585 { |
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586 if (!is_gimple_val (arg)) |
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587 return false; |
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588 } |
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589 else |
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590 if (!is_gimple_lvalue (arg)) |
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591 return false; |
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592 } |
| 0 | 593 |
| 594 return true; | |
| 595 } | |
| 596 | |
| 597 | |
| 598 /* Make SSA names defined by OLD_STMT point to NEW_STMT | |
| 599 as their defining statement. */ | |
| 600 | |
| 601 void | |
| 111 | 602 move_ssa_defining_stmt_for_defs (gimple *new_stmt, gimple *old_stmt) |
| 0 | 603 { |
| 604 tree var; | |
| 605 ssa_op_iter iter; | |
| 606 | |
| 607 if (gimple_in_ssa_p (cfun)) | |
| 608 { | |
| 609 /* Make defined SSA_NAMEs point to the new | |
| 610 statement as their definition. */ | |
| 611 FOR_EACH_SSA_TREE_OPERAND (var, old_stmt, iter, SSA_OP_ALL_DEFS) | |
| 612 { | |
| 613 if (TREE_CODE (var) == SSA_NAME) | |
| 614 SSA_NAME_DEF_STMT (var) = new_stmt; | |
| 615 } | |
| 616 } | |
| 617 } | |
| 618 | |
| 111 | 619 /* Helper function for update_gimple_call and update_call_from_tree. |
| 620 A GIMPLE_CALL STMT is being replaced with GIMPLE_CALL NEW_STMT. */ | |
| 621 | |
| 622 static void | |
| 623 finish_update_gimple_call (gimple_stmt_iterator *si_p, gimple *new_stmt, | |
| 624 gimple *stmt) | |
| 625 { | |
| 626 gimple_call_set_lhs (new_stmt, gimple_call_lhs (stmt)); | |
| 627 move_ssa_defining_stmt_for_defs (new_stmt, stmt); | |
| 145 | 628 gimple_move_vops (new_stmt, stmt); |
| 111 | 629 gimple_set_location (new_stmt, gimple_location (stmt)); |
| 630 if (gimple_block (new_stmt) == NULL_TREE) | |
| 631 gimple_set_block (new_stmt, gimple_block (stmt)); | |
| 632 gsi_replace (si_p, new_stmt, false); | |
| 633 } | |
| 634 | |
| 635 /* Update a GIMPLE_CALL statement at iterator *SI_P to call to FN | |
| 636 with number of arguments NARGS, where the arguments in GIMPLE form | |
| 637 follow NARGS argument. */ | |
| 638 | |
| 639 bool | |
| 640 update_gimple_call (gimple_stmt_iterator *si_p, tree fn, int nargs, ...) | |
| 641 { | |
| 642 va_list ap; | |
| 643 gcall *new_stmt, *stmt = as_a <gcall *> (gsi_stmt (*si_p)); | |
| 644 | |
| 645 gcc_assert (is_gimple_call (stmt)); | |
| 646 va_start (ap, nargs); | |
| 647 new_stmt = gimple_build_call_valist (fn, nargs, ap); | |
| 648 finish_update_gimple_call (si_p, new_stmt, stmt); | |
| 649 va_end (ap); | |
| 650 return true; | |
| 651 } | |
| 0 | 652 |
| 653 /* Update a GIMPLE_CALL statement at iterator *SI_P to reflect the | |
| 654 value of EXPR, which is expected to be the result of folding the | |
| 655 call. This can only be done if EXPR is a CALL_EXPR with valid | |
| 656 GIMPLE operands as arguments, or if it is a suitable RHS expression | |
| 657 for a GIMPLE_ASSIGN. More complex expressions will require | |
| 111 | 658 gimplification, which will introduce additional statements. In this |
| 0 | 659 event, no update is performed, and the function returns false. |
| 660 Note that we cannot mutate a GIMPLE_CALL in-place, so we always | |
| 661 replace the statement at *SI_P with an entirely new statement. | |
| 662 The new statement need not be a call, e.g., if the original call | |
| 663 folded to a constant. */ | |
| 664 | |
| 665 bool | |
| 666 update_call_from_tree (gimple_stmt_iterator *si_p, tree expr) | |
| 667 { | |
| 111 | 668 gimple *stmt = gsi_stmt (*si_p); |
| 0 | 669 |
| 670 if (valid_gimple_call_p (expr)) | |
| 671 { | |
| 672 /* The call has simplified to another call. */ | |
| 673 tree fn = CALL_EXPR_FN (expr); | |
| 674 unsigned i; | |
| 675 unsigned nargs = call_expr_nargs (expr); | |
| 111 | 676 vec<tree> args = vNULL; |
| 677 gcall *new_stmt; | |
| 0 | 678 |
| 679 if (nargs > 0) | |
| 680 { | |
| 111 | 681 args.create (nargs); |
| 682 args.safe_grow_cleared (nargs); | |
|
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683 |
| 0 | 684 for (i = 0; i < nargs; i++) |
| 111 | 685 args[i] = CALL_EXPR_ARG (expr, i); |
| 0 | 686 } |
| 687 | |
| 688 new_stmt = gimple_build_call_vec (fn, args); | |
| 111 | 689 finish_update_gimple_call (si_p, new_stmt, stmt); |
| 690 args.release (); | |
| 0 | 691 |
| 692 return true; | |
| 693 } | |
| 694 else if (valid_gimple_rhs_p (expr)) | |
| 695 { | |
| 111 | 696 tree lhs = gimple_call_lhs (stmt); |
| 697 gimple *new_stmt; | |
| 0 | 698 |
| 699 /* The call has simplified to an expression | |
| 700 that cannot be represented as a GIMPLE_CALL. */ | |
| 701 if (lhs) | |
| 702 { | |
| 703 /* A value is expected. | |
| 704 Introduce a new GIMPLE_ASSIGN statement. */ | |
| 705 STRIP_USELESS_TYPE_CONVERSION (expr); | |
| 706 new_stmt = gimple_build_assign (lhs, expr); | |
| 707 move_ssa_defining_stmt_for_defs (new_stmt, stmt); | |
| 145 | 708 gimple_move_vops (new_stmt, stmt); |
| 0 | 709 } |
| 710 else if (!TREE_SIDE_EFFECTS (expr)) | |
| 711 { | |
| 712 /* No value is expected, and EXPR has no effect. | |
| 713 Replace it with an empty statement. */ | |
| 714 new_stmt = gimple_build_nop (); | |
|
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715 if (gimple_in_ssa_p (cfun)) |
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716 { |
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717 unlink_stmt_vdef (stmt); |
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718 release_defs (stmt); |
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719 } |
| 0 | 720 } |
| 721 else | |
| 722 { | |
| 723 /* No value is expected, but EXPR has an effect, | |
| 724 e.g., it could be a reference to a volatile | |
| 725 variable. Create an assignment statement | |
| 726 with a dummy (unused) lhs variable. */ | |
| 727 STRIP_USELESS_TYPE_CONVERSION (expr); | |
| 111 | 728 if (gimple_in_ssa_p (cfun)) |
| 729 lhs = make_ssa_name (TREE_TYPE (expr)); | |
| 730 else | |
| 731 lhs = create_tmp_var (TREE_TYPE (expr)); | |
| 0 | 732 new_stmt = gimple_build_assign (lhs, expr); |
| 145 | 733 gimple_move_vops (new_stmt, stmt); |
| 0 | 734 move_ssa_defining_stmt_for_defs (new_stmt, stmt); |
| 735 } | |
| 736 gimple_set_location (new_stmt, gimple_location (stmt)); | |
| 737 gsi_replace (si_p, new_stmt, false); | |
| 738 return true; | |
| 739 } | |
| 740 else | |
| 741 /* The call simplified to an expression that is | |
| 742 not a valid GIMPLE RHS. */ | |
| 743 return false; | |
| 744 } | |
| 745 | |
| 746 /* Entry point to the propagation engine. | |
| 747 | |
| 131 | 748 The VISIT_STMT virtual function is called for every statement |
| 749 visited and the VISIT_PHI virtual function is called for every PHI | |
| 750 node visited. */ | |
| 0 | 751 |
| 752 void | |
| 131 | 753 ssa_propagation_engine::ssa_propagate (void) |
| 0 | 754 { |
| 755 ssa_prop_init (); | |
| 756 | |
| 131 | 757 curr_order = 0; |
| 758 | |
| 759 /* Iterate until the worklists are empty. We iterate both blocks | |
| 760 and stmts in RPO order, using sets of two worklists to first | |
| 761 complete the current iteration before iterating over backedges. */ | |
| 762 while (1) | |
| 0 | 763 { |
| 131 | 764 int next_block_order = (bitmap_empty_p (cfg_blocks) |
| 765 ? -1 : bitmap_first_set_bit (cfg_blocks)); | |
| 766 int next_stmt_uid = (bitmap_empty_p (ssa_edge_worklist) | |
| 767 ? -1 : bitmap_first_set_bit (ssa_edge_worklist)); | |
| 768 if (next_block_order == -1 && next_stmt_uid == -1) | |
| 0 | 769 { |
| 131 | 770 if (bitmap_empty_p (cfg_blocks_back) |
| 771 && bitmap_empty_p (ssa_edge_worklist_back)) | |
| 772 break; | |
| 773 | |
| 774 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 775 fprintf (dump_file, "Regular worklists empty, now processing " | |
| 776 "backedge destinations\n"); | |
| 777 std::swap (cfg_blocks, cfg_blocks_back); | |
| 778 std::swap (ssa_edge_worklist, ssa_edge_worklist_back); | |
| 111 | 779 continue; |
| 0 | 780 } |
| 781 | |
| 131 | 782 int next_stmt_bb_order = -1; |
| 783 gimple *next_stmt = NULL; | |
| 784 if (next_stmt_uid != -1) | |
| 785 { | |
| 786 next_stmt = uid_to_stmt[next_stmt_uid]; | |
| 787 next_stmt_bb_order = bb_to_cfg_order[gimple_bb (next_stmt)->index]; | |
| 788 } | |
| 789 | |
| 790 /* Pull the next block to simulate off the worklist if it comes first. */ | |
| 791 if (next_block_order != -1 | |
| 792 && (next_stmt_bb_order == -1 | |
| 793 || next_block_order <= next_stmt_bb_order)) | |
| 794 { | |
| 795 curr_order = next_block_order; | |
| 796 bitmap_clear_bit (cfg_blocks, next_block_order); | |
| 797 basic_block bb | |
| 798 = BASIC_BLOCK_FOR_FN (cfun, cfg_order_to_bb [next_block_order]); | |
| 799 simulate_block (bb); | |
| 800 } | |
| 801 /* Else simulate from the SSA edge worklist. */ | |
| 802 else | |
| 803 { | |
| 804 curr_order = next_stmt_bb_order; | |
| 805 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 806 { | |
| 807 fprintf (dump_file, "\nSimulating statement: "); | |
| 808 print_gimple_stmt (dump_file, next_stmt, 0, dump_flags); | |
| 809 } | |
| 810 simulate_stmt (next_stmt); | |
| 811 } | |
| 0 | 812 } |
| 813 | |
| 814 ssa_prop_fini (); | |
| 815 } | |
| 816 | |
| 817 /* Return true if STMT is of the form 'mem_ref = RHS', where 'mem_ref' | |
| 818 is a non-volatile pointer dereference, a structure reference or a | |
| 819 reference to a single _DECL. Ignore volatile memory references | |
| 820 because they are not interesting for the optimizers. */ | |
| 821 | |
| 822 bool | |
| 111 | 823 stmt_makes_single_store (gimple *stmt) |
| 0 | 824 { |
| 825 tree lhs; | |
| 826 | |
| 827 if (gimple_code (stmt) != GIMPLE_ASSIGN | |
| 828 && gimple_code (stmt) != GIMPLE_CALL) | |
| 829 return false; | |
| 830 | |
|
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831 if (!gimple_vdef (stmt)) |
| 0 | 832 return false; |
| 833 | |
| 834 lhs = gimple_get_lhs (stmt); | |
| 835 | |
| 836 /* A call statement may have a null LHS. */ | |
| 837 if (!lhs) | |
| 838 return false; | |
| 839 | |
| 840 return (!TREE_THIS_VOLATILE (lhs) | |
| 841 && (DECL_P (lhs) | |
| 842 || REFERENCE_CLASS_P (lhs))); | |
| 843 } | |
| 844 | |
| 845 | |
| 846 /* Propagation statistics. */ | |
| 847 struct prop_stats_d | |
| 848 { | |
| 849 long num_const_prop; | |
| 850 long num_copy_prop; | |
|
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851 long num_stmts_folded; |
| 0 | 852 long num_dce; |
| 853 }; | |
| 854 | |
| 855 static struct prop_stats_d prop_stats; | |
| 856 | |
| 857 /* Replace USE references in statement STMT with the values stored in | |
| 858 PROP_VALUE. Return true if at least one reference was replaced. */ | |
| 859 | |
| 111 | 860 bool |
| 131 | 861 substitute_and_fold_engine::replace_uses_in (gimple *stmt) |
| 0 | 862 { |
| 863 bool replaced = false; | |
| 864 use_operand_p use; | |
| 865 ssa_op_iter iter; | |
| 866 | |
| 867 FOR_EACH_SSA_USE_OPERAND (use, stmt, iter, SSA_OP_USE) | |
| 868 { | |
| 869 tree tuse = USE_FROM_PTR (use); | |
| 131 | 870 tree val = get_value (tuse); |
| 0 | 871 |
| 872 if (val == tuse || val == NULL_TREE) | |
| 873 continue; | |
| 874 | |
| 875 if (gimple_code (stmt) == GIMPLE_ASM | |
| 876 && !may_propagate_copy_into_asm (tuse)) | |
| 877 continue; | |
| 878 | |
| 879 if (!may_propagate_copy (tuse, val)) | |
| 880 continue; | |
| 881 | |
| 882 if (TREE_CODE (val) != SSA_NAME) | |
| 883 prop_stats.num_const_prop++; | |
| 884 else | |
| 885 prop_stats.num_copy_prop++; | |
| 886 | |
| 887 propagate_value (use, val); | |
| 888 | |
| 889 replaced = true; | |
| 890 } | |
| 891 | |
| 892 return replaced; | |
| 893 } | |
| 894 | |
| 895 | |
| 896 /* Replace propagated values into all the arguments for PHI using the | |
| 897 values from PROP_VALUE. */ | |
| 898 | |
| 131 | 899 bool |
| 900 substitute_and_fold_engine::replace_phi_args_in (gphi *phi) | |
| 0 | 901 { |
| 902 size_t i; | |
| 903 bool replaced = false; | |
| 904 | |
| 905 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 906 { | |
| 907 fprintf (dump_file, "Folding PHI node: "); | |
| 908 print_gimple_stmt (dump_file, phi, 0, TDF_SLIM); | |
| 909 } | |
| 910 | |
| 911 for (i = 0; i < gimple_phi_num_args (phi); i++) | |
| 912 { | |
| 913 tree arg = gimple_phi_arg_def (phi, i); | |
| 914 | |
| 915 if (TREE_CODE (arg) == SSA_NAME) | |
| 916 { | |
| 131 | 917 tree val = get_value (arg); |
| 0 | 918 |
| 919 if (val && val != arg && may_propagate_copy (arg, val)) | |
| 920 { | |
| 111 | 921 edge e = gimple_phi_arg_edge (phi, i); |
| 922 | |
| 0 | 923 if (TREE_CODE (val) != SSA_NAME) |
| 924 prop_stats.num_const_prop++; | |
| 925 else | |
| 926 prop_stats.num_copy_prop++; | |
| 927 | |
| 928 propagate_value (PHI_ARG_DEF_PTR (phi, i), val); | |
| 929 replaced = true; | |
| 930 | |
| 931 /* If we propagated a copy and this argument flows | |
| 932 through an abnormal edge, update the replacement | |
| 933 accordingly. */ | |
| 934 if (TREE_CODE (val) == SSA_NAME | |
| 111 | 935 && e->flags & EDGE_ABNORMAL |
| 936 && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (val)) | |
| 937 { | |
| 938 /* This can only occur for virtual operands, since | |
| 939 for the real ones SSA_NAME_OCCURS_IN_ABNORMAL_PHI (val)) | |
| 940 would prevent replacement. */ | |
| 941 gcc_checking_assert (virtual_operand_p (val)); | |
| 942 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (val) = 1; | |
| 943 } | |
| 0 | 944 } |
| 945 } | |
| 946 } | |
|
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947 |
| 0 | 948 if (dump_file && (dump_flags & TDF_DETAILS)) |
| 949 { | |
| 950 if (!replaced) | |
| 951 fprintf (dump_file, "No folding possible\n"); | |
| 952 else | |
| 953 { | |
| 954 fprintf (dump_file, "Folded into: "); | |
| 955 print_gimple_stmt (dump_file, phi, 0, TDF_SLIM); | |
| 956 fprintf (dump_file, "\n"); | |
| 957 } | |
| 958 } | |
| 111 | 959 |
| 960 return replaced; | |
| 0 | 961 } |
| 962 | |
| 963 | |
| 111 | 964 class substitute_and_fold_dom_walker : public dom_walker |
| 965 { | |
| 966 public: | |
| 967 substitute_and_fold_dom_walker (cdi_direction direction, | |
| 131 | 968 class substitute_and_fold_engine *engine) |
| 969 : dom_walker (direction), | |
| 970 something_changed (false), | |
| 971 substitute_and_fold_engine (engine) | |
| 111 | 972 { |
| 973 stmts_to_remove.create (0); | |
| 974 stmts_to_fixup.create (0); | |
| 975 need_eh_cleanup = BITMAP_ALLOC (NULL); | |
| 976 } | |
| 977 ~substitute_and_fold_dom_walker () | |
| 978 { | |
| 979 stmts_to_remove.release (); | |
| 980 stmts_to_fixup.release (); | |
| 981 BITMAP_FREE (need_eh_cleanup); | |
| 982 } | |
| 983 | |
| 984 virtual edge before_dom_children (basic_block); | |
| 985 virtual void after_dom_children (basic_block) {} | |
| 986 | |
| 987 bool something_changed; | |
| 988 vec<gimple *> stmts_to_remove; | |
| 989 vec<gimple *> stmts_to_fixup; | |
| 990 bitmap need_eh_cleanup; | |
| 131 | 991 |
| 992 class substitute_and_fold_engine *substitute_and_fold_engine; | |
| 111 | 993 }; |
| 994 | |
| 995 edge | |
| 996 substitute_and_fold_dom_walker::before_dom_children (basic_block bb) | |
| 997 { | |
| 998 /* Propagate known values into PHI nodes. */ | |
| 999 for (gphi_iterator i = gsi_start_phis (bb); | |
| 1000 !gsi_end_p (i); | |
| 1001 gsi_next (&i)) | |
| 1002 { | |
| 1003 gphi *phi = i.phi (); | |
| 1004 tree res = gimple_phi_result (phi); | |
| 1005 if (virtual_operand_p (res)) | |
| 1006 continue; | |
| 1007 if (res && TREE_CODE (res) == SSA_NAME) | |
| 1008 { | |
| 131 | 1009 tree sprime = substitute_and_fold_engine->get_value (res); |
| 111 | 1010 if (sprime |
| 1011 && sprime != res | |
| 1012 && may_propagate_copy (res, sprime)) | |
| 1013 { | |
| 1014 stmts_to_remove.safe_push (phi); | |
| 1015 continue; | |
| 1016 } | |
| 1017 } | |
| 131 | 1018 something_changed |= substitute_and_fold_engine->replace_phi_args_in (phi); |
| 111 | 1019 } |
| 1020 | |
| 1021 /* Propagate known values into stmts. In some case it exposes | |
| 1022 more trivially deletable stmts to walk backward. */ | |
| 1023 for (gimple_stmt_iterator i = gsi_start_bb (bb); | |
| 1024 !gsi_end_p (i); | |
| 1025 gsi_next (&i)) | |
| 1026 { | |
| 1027 bool did_replace; | |
| 1028 gimple *stmt = gsi_stmt (i); | |
| 1029 | |
| 1030 /* No point propagating into a stmt we have a value for we | |
| 1031 can propagate into all uses. Mark it for removal instead. */ | |
| 1032 tree lhs = gimple_get_lhs (stmt); | |
| 1033 if (lhs && TREE_CODE (lhs) == SSA_NAME) | |
| 1034 { | |
| 131 | 1035 tree sprime = substitute_and_fold_engine->get_value (lhs); |
| 111 | 1036 if (sprime |
| 1037 && sprime != lhs | |
| 1038 && may_propagate_copy (lhs, sprime) | |
| 131 | 1039 && !stmt_could_throw_p (cfun, stmt) |
| 111 | 1040 && !gimple_has_side_effects (stmt) |
| 1041 /* We have to leave ASSERT_EXPRs around for jump-threading. */ | |
| 1042 && (!is_gimple_assign (stmt) | |
| 1043 || gimple_assign_rhs_code (stmt) != ASSERT_EXPR)) | |
| 1044 { | |
| 1045 stmts_to_remove.safe_push (stmt); | |
| 1046 continue; | |
| 1047 } | |
| 1048 } | |
| 1049 | |
| 1050 /* Replace the statement with its folded version and mark it | |
| 1051 folded. */ | |
| 1052 did_replace = false; | |
| 1053 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 1054 { | |
| 1055 fprintf (dump_file, "Folding statement: "); | |
| 1056 print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM); | |
| 1057 } | |
| 1058 | |
| 1059 gimple *old_stmt = stmt; | |
| 1060 bool was_noreturn = (is_gimple_call (stmt) | |
| 1061 && gimple_call_noreturn_p (stmt)); | |
| 1062 | |
| 1063 /* Replace real uses in the statement. */ | |
| 131 | 1064 did_replace |= substitute_and_fold_engine->replace_uses_in (stmt); |
| 111 | 1065 |
| 1066 /* If we made a replacement, fold the statement. */ | |
| 1067 if (did_replace) | |
| 1068 { | |
| 1069 fold_stmt (&i, follow_single_use_edges); | |
| 1070 stmt = gsi_stmt (i); | |
| 1071 gimple_set_modified (stmt, true); | |
| 1072 } | |
| 145 | 1073 /* Also fold if we want to fold all statements. */ |
| 1074 else if (substitute_and_fold_engine->fold_all_stmts | |
| 1075 && fold_stmt (&i, follow_single_use_edges)) | |
| 1076 { | |
| 1077 did_replace = true; | |
| 1078 stmt = gsi_stmt (i); | |
| 1079 gimple_set_modified (stmt, true); | |
| 1080 } | |
| 111 | 1081 |
| 1082 /* Some statements may be simplified using propagator | |
| 1083 specific information. Do this before propagating | |
| 1084 into the stmt to not disturb pass specific information. */ | |
| 131 | 1085 update_stmt_if_modified (stmt); |
| 1086 if (substitute_and_fold_engine->fold_stmt(&i)) | |
| 111 | 1087 { |
| 131 | 1088 did_replace = true; |
| 1089 prop_stats.num_stmts_folded++; | |
| 1090 stmt = gsi_stmt (i); | |
| 1091 gimple_set_modified (stmt, true); | |
| 111 | 1092 } |
| 1093 | |
| 1094 /* If this is a control statement the propagator left edges | |
| 1095 unexecuted on force the condition in a way consistent with | |
| 1096 that. See PR66945 for cases where the propagator can end | |
| 1097 up with a different idea of a taken edge than folding | |
| 1098 (once undefined behavior is involved). */ | |
| 1099 if (gimple_code (stmt) == GIMPLE_COND) | |
| 1100 { | |
| 1101 if ((EDGE_SUCC (bb, 0)->flags & EDGE_EXECUTABLE) | |
| 1102 ^ (EDGE_SUCC (bb, 1)->flags & EDGE_EXECUTABLE)) | |
| 1103 { | |
| 1104 if (((EDGE_SUCC (bb, 0)->flags & EDGE_TRUE_VALUE) != 0) | |
| 1105 == ((EDGE_SUCC (bb, 0)->flags & EDGE_EXECUTABLE) != 0)) | |
| 1106 gimple_cond_make_true (as_a <gcond *> (stmt)); | |
| 1107 else | |
| 1108 gimple_cond_make_false (as_a <gcond *> (stmt)); | |
| 1109 gimple_set_modified (stmt, true); | |
| 1110 did_replace = true; | |
| 1111 } | |
| 1112 } | |
| 1113 | |
| 1114 /* Now cleanup. */ | |
| 1115 if (did_replace) | |
| 1116 { | |
| 1117 /* If we cleaned up EH information from the statement, | |
| 1118 remove EH edges. */ | |
| 1119 if (maybe_clean_or_replace_eh_stmt (old_stmt, stmt)) | |
| 1120 bitmap_set_bit (need_eh_cleanup, bb->index); | |
| 1121 | |
| 1122 /* If we turned a not noreturn call into a noreturn one | |
| 1123 schedule it for fixup. */ | |
| 1124 if (!was_noreturn | |
| 1125 && is_gimple_call (stmt) | |
| 1126 && gimple_call_noreturn_p (stmt)) | |
| 1127 stmts_to_fixup.safe_push (stmt); | |
| 1128 | |
| 1129 if (gimple_assign_single_p (stmt)) | |
| 1130 { | |
| 1131 tree rhs = gimple_assign_rhs1 (stmt); | |
| 1132 | |
| 1133 if (TREE_CODE (rhs) == ADDR_EXPR) | |
| 1134 recompute_tree_invariant_for_addr_expr (rhs); | |
| 1135 } | |
| 1136 | |
| 1137 /* Determine what needs to be done to update the SSA form. */ | |
| 1138 update_stmt_if_modified (stmt); | |
| 1139 if (!is_gimple_debug (stmt)) | |
| 1140 something_changed = true; | |
| 1141 } | |
| 1142 | |
| 1143 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 1144 { | |
| 1145 if (did_replace) | |
| 1146 { | |
| 1147 fprintf (dump_file, "Folded into: "); | |
| 1148 print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM); | |
| 1149 fprintf (dump_file, "\n"); | |
| 1150 } | |
| 1151 else | |
| 1152 fprintf (dump_file, "Not folded\n"); | |
| 1153 } | |
| 1154 } | |
| 1155 return NULL; | |
| 1156 } | |
| 1157 | |
| 1158 | |
| 1159 | |
| 0 | 1160 /* Perform final substitution and folding of propagated values. |
| 145 | 1161 Process the whole function if BLOCK is null, otherwise only |
| 1162 process the blocks that BLOCK dominates. In the latter case, | |
| 1163 it is the caller's responsibility to ensure that dominator | |
| 1164 information is available and up-to-date. | |
| 0 | 1165 |
| 1166 PROP_VALUE[I] contains the single value that should be substituted | |
| 1167 at every use of SSA name N_I. If PROP_VALUE is NULL, no values are | |
| 1168 substituted. | |
| 1169 | |
|
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1170 If FOLD_FN is non-NULL the function will be invoked on all statements |
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1171 before propagating values for pass specific simplification. |
| 0 | 1172 |
|
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1173 DO_DCE is true if trivially dead stmts can be removed. |
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1174 |
| 111 | 1175 If DO_DCE is true, the statements within a BB are walked from |
| 1176 last to first element. Otherwise we scan from first to last element. | |
| 1177 | |
| 0 | 1178 Return TRUE when something changed. */ |
| 1179 | |
| 1180 bool | |
| 145 | 1181 substitute_and_fold_engine::substitute_and_fold (basic_block block) |
| 0 | 1182 { |
| 1183 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 1184 fprintf (dump_file, "\nSubstituting values and folding statements\n\n"); | |
| 1185 | |
| 1186 memset (&prop_stats, 0, sizeof (prop_stats)); | |
| 1187 | |
| 145 | 1188 /* Don't call calculate_dominance_info when iterating over a subgraph. |
| 1189 Callers that are using the interface this way are likely to want to | |
| 1190 iterate over several disjoint subgraphs, and it would be expensive | |
| 1191 in enable-checking builds to revalidate the whole dominance tree | |
| 1192 each time. */ | |
| 1193 if (block) | |
| 1194 gcc_assert (dom_info_state (CDI_DOMINATORS)); | |
| 1195 else | |
| 1196 calculate_dominance_info (CDI_DOMINATORS); | |
| 131 | 1197 substitute_and_fold_dom_walker walker (CDI_DOMINATORS, this); |
| 145 | 1198 walker.walk (block ? block : ENTRY_BLOCK_PTR_FOR_FN (cfun)); |
| 0 | 1199 |
| 111 | 1200 /* We cannot remove stmts during the BB walk, especially not release |
| 1201 SSA names there as that destroys the lattice of our callers. | |
| 1202 Remove stmts in reverse order to make debug stmt creation possible. */ | |
| 1203 while (!walker.stmts_to_remove.is_empty ()) | |
| 1204 { | |
| 1205 gimple *stmt = walker.stmts_to_remove.pop (); | |
| 1206 if (dump_file && dump_flags & TDF_DETAILS) | |
| 1207 { | |
| 1208 fprintf (dump_file, "Removing dead stmt "); | |
| 1209 print_gimple_stmt (dump_file, stmt, 0); | |
| 1210 fprintf (dump_file, "\n"); | |
| 1211 } | |
| 1212 prop_stats.num_dce++; | |
| 1213 gimple_stmt_iterator gsi = gsi_for_stmt (stmt); | |
| 1214 if (gimple_code (stmt) == GIMPLE_PHI) | |
| 1215 remove_phi_node (&gsi, true); | |
| 1216 else | |
| 1217 { | |
| 1218 unlink_stmt_vdef (stmt); | |
| 1219 gsi_remove (&gsi, true); | |
| 1220 release_defs (stmt); | |
| 1221 } | |
| 1222 } | |
|
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1223 |
| 111 | 1224 if (!bitmap_empty_p (walker.need_eh_cleanup)) |
| 1225 gimple_purge_all_dead_eh_edges (walker.need_eh_cleanup); | |
| 0 | 1226 |
| 111 | 1227 /* Fixup stmts that became noreturn calls. This may require splitting |
| 1228 blocks and thus isn't possible during the dominator walk. Do this | |
| 1229 in reverse order so we don't inadvertedly remove a stmt we want to | |
| 1230 fixup by visiting a dominating now noreturn call first. */ | |
| 1231 while (!walker.stmts_to_fixup.is_empty ()) | |
| 1232 { | |
| 1233 gimple *stmt = walker.stmts_to_fixup.pop (); | |
| 1234 if (dump_file && dump_flags & TDF_DETAILS) | |
| 1235 { | |
| 1236 fprintf (dump_file, "Fixing up noreturn call "); | |
| 1237 print_gimple_stmt (dump_file, stmt, 0); | |
| 1238 fprintf (dump_file, "\n"); | |
| 0 | 1239 } |
| 111 | 1240 fixup_noreturn_call (stmt); |
| 0 | 1241 } |
| 1242 | |
| 1243 statistics_counter_event (cfun, "Constants propagated", | |
| 1244 prop_stats.num_const_prop); | |
| 1245 statistics_counter_event (cfun, "Copies propagated", | |
| 1246 prop_stats.num_copy_prop); | |
|
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1247 statistics_counter_event (cfun, "Statements folded", |
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1248 prop_stats.num_stmts_folded); |
| 0 | 1249 statistics_counter_event (cfun, "Statements deleted", |
| 1250 prop_stats.num_dce); | |
| 111 | 1251 |
| 1252 return walker.something_changed; | |
| 1253 } | |
| 1254 | |
| 1255 | |
| 1256 /* Return true if we may propagate ORIG into DEST, false otherwise. */ | |
| 1257 | |
| 1258 bool | |
| 1259 may_propagate_copy (tree dest, tree orig) | |
| 1260 { | |
| 1261 tree type_d = TREE_TYPE (dest); | |
| 1262 tree type_o = TREE_TYPE (orig); | |
| 1263 | |
| 1264 /* If ORIG is a default definition which flows in from an abnormal edge | |
| 1265 then the copy can be propagated. It is important that we do so to avoid | |
| 1266 uninitialized copies. */ | |
| 1267 if (TREE_CODE (orig) == SSA_NAME | |
| 1268 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (orig) | |
| 1269 && SSA_NAME_IS_DEFAULT_DEF (orig) | |
| 1270 && (SSA_NAME_VAR (orig) == NULL_TREE | |
| 1271 || TREE_CODE (SSA_NAME_VAR (orig)) == VAR_DECL)) | |
| 1272 ; | |
| 1273 /* Otherwise if ORIG just flows in from an abnormal edge then the copy cannot | |
| 1274 be propagated. */ | |
| 1275 else if (TREE_CODE (orig) == SSA_NAME | |
| 1276 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (orig)) | |
| 1277 return false; | |
| 1278 /* Similarly if DEST flows in from an abnormal edge then the copy cannot be | |
| 1279 propagated. */ | |
| 1280 else if (TREE_CODE (dest) == SSA_NAME | |
| 1281 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (dest)) | |
| 1282 return false; | |
| 1283 | |
| 1284 /* Do not copy between types for which we *do* need a conversion. */ | |
| 1285 if (!useless_type_conversion_p (type_d, type_o)) | |
| 1286 return false; | |
| 1287 | |
| 1288 /* Generally propagating virtual operands is not ok as that may | |
| 1289 create overlapping life-ranges. */ | |
| 1290 if (TREE_CODE (dest) == SSA_NAME && virtual_operand_p (dest)) | |
| 1291 return false; | |
| 1292 | |
| 1293 /* Anything else is OK. */ | |
| 1294 return true; | |
| 1295 } | |
| 1296 | |
| 1297 /* Like may_propagate_copy, but use as the destination expression | |
| 1298 the principal expression (typically, the RHS) contained in | |
| 1299 statement DEST. This is more efficient when working with the | |
| 1300 gimple tuples representation. */ | |
| 1301 | |
| 1302 bool | |
| 1303 may_propagate_copy_into_stmt (gimple *dest, tree orig) | |
| 1304 { | |
| 1305 tree type_d; | |
| 1306 tree type_o; | |
| 1307 | |
| 1308 /* If the statement is a switch or a single-rhs assignment, | |
| 1309 then the expression to be replaced by the propagation may | |
| 1310 be an SSA_NAME. Fortunately, there is an explicit tree | |
| 1311 for the expression, so we delegate to may_propagate_copy. */ | |
| 1312 | |
| 1313 if (gimple_assign_single_p (dest)) | |
| 1314 return may_propagate_copy (gimple_assign_rhs1 (dest), orig); | |
| 1315 else if (gswitch *dest_swtch = dyn_cast <gswitch *> (dest)) | |
| 1316 return may_propagate_copy (gimple_switch_index (dest_swtch), orig); | |
| 1317 | |
| 1318 /* In other cases, the expression is not materialized, so there | |
| 1319 is no destination to pass to may_propagate_copy. On the other | |
| 1320 hand, the expression cannot be an SSA_NAME, so the analysis | |
| 1321 is much simpler. */ | |
| 1322 | |
| 1323 if (TREE_CODE (orig) == SSA_NAME | |
| 1324 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (orig)) | |
| 1325 return false; | |
| 1326 | |
| 1327 if (is_gimple_assign (dest)) | |
| 1328 type_d = TREE_TYPE (gimple_assign_lhs (dest)); | |
| 1329 else if (gimple_code (dest) == GIMPLE_COND) | |
| 1330 type_d = boolean_type_node; | |
| 1331 else if (is_gimple_call (dest) | |
| 1332 && gimple_call_lhs (dest) != NULL_TREE) | |
| 1333 type_d = TREE_TYPE (gimple_call_lhs (dest)); | |
| 1334 else | |
| 1335 gcc_unreachable (); | |
| 1336 | |
| 1337 type_o = TREE_TYPE (orig); | |
| 1338 | |
| 1339 if (!useless_type_conversion_p (type_d, type_o)) | |
| 1340 return false; | |
| 1341 | |
| 1342 return true; | |
| 1343 } | |
| 1344 | |
| 1345 /* Similarly, but we know that we're propagating into an ASM_EXPR. */ | |
| 1346 | |
| 1347 bool | |
| 1348 may_propagate_copy_into_asm (tree dest ATTRIBUTE_UNUSED) | |
| 1349 { | |
| 1350 return true; | |
| 0 | 1351 } |
| 1352 | |
| 111 | 1353 |
| 1354 /* Common code for propagate_value and replace_exp. | |
| 1355 | |
| 1356 Replace use operand OP_P with VAL. FOR_PROPAGATION indicates if the | |
| 1357 replacement is done to propagate a value or not. */ | |
| 1358 | |
| 1359 static void | |
| 1360 replace_exp_1 (use_operand_p op_p, tree val, | |
| 1361 bool for_propagation ATTRIBUTE_UNUSED) | |
| 1362 { | |
| 1363 if (flag_checking) | |
| 1364 { | |
| 1365 tree op = USE_FROM_PTR (op_p); | |
| 1366 gcc_assert (!(for_propagation | |
| 1367 && TREE_CODE (op) == SSA_NAME | |
| 1368 && TREE_CODE (val) == SSA_NAME | |
| 1369 && !may_propagate_copy (op, val))); | |
| 1370 } | |
| 1371 | |
| 1372 if (TREE_CODE (val) == SSA_NAME) | |
| 1373 SET_USE (op_p, val); | |
| 1374 else | |
| 1375 SET_USE (op_p, unshare_expr (val)); | |
| 1376 } | |
| 1377 | |
| 1378 | |
| 1379 /* Propagate the value VAL (assumed to be a constant or another SSA_NAME) | |
| 1380 into the operand pointed to by OP_P. | |
| 1381 | |
| 1382 Use this version for const/copy propagation as it will perform additional | |
| 1383 checks to ensure validity of the const/copy propagation. */ | |
| 1384 | |
| 1385 void | |
| 1386 propagate_value (use_operand_p op_p, tree val) | |
| 1387 { | |
| 1388 replace_exp_1 (op_p, val, true); | |
| 1389 } | |
| 1390 | |
| 1391 /* Replace *OP_P with value VAL (assumed to be a constant or another SSA_NAME). | |
| 1392 | |
| 1393 Use this version when not const/copy propagating values. For example, | |
| 1394 PRE uses this version when building expressions as they would appear | |
| 1395 in specific blocks taking into account actions of PHI nodes. | |
| 1396 | |
| 1397 The statement in which an expression has been replaced should be | |
| 1398 folded using fold_stmt_inplace. */ | |
| 1399 | |
| 1400 void | |
| 1401 replace_exp (use_operand_p op_p, tree val) | |
| 1402 { | |
| 1403 replace_exp_1 (op_p, val, false); | |
| 1404 } | |
| 1405 | |
| 1406 | |
| 1407 /* Propagate the value VAL (assumed to be a constant or another SSA_NAME) | |
| 1408 into the tree pointed to by OP_P. | |
| 1409 | |
| 1410 Use this version for const/copy propagation when SSA operands are not | |
| 1411 available. It will perform the additional checks to ensure validity of | |
| 1412 the const/copy propagation, but will not update any operand information. | |
| 1413 Be sure to mark the stmt as modified. */ | |
| 1414 | |
| 1415 void | |
| 1416 propagate_tree_value (tree *op_p, tree val) | |
| 1417 { | |
| 1418 if (TREE_CODE (val) == SSA_NAME) | |
| 1419 *op_p = val; | |
| 1420 else | |
| 1421 *op_p = unshare_expr (val); | |
| 1422 } | |
| 1423 | |
| 1424 | |
| 1425 /* Like propagate_tree_value, but use as the operand to replace | |
| 1426 the principal expression (typically, the RHS) contained in the | |
| 1427 statement referenced by iterator GSI. Note that it is not | |
| 1428 always possible to update the statement in-place, so a new | |
| 1429 statement may be created to replace the original. */ | |
| 1430 | |
| 1431 void | |
| 1432 propagate_tree_value_into_stmt (gimple_stmt_iterator *gsi, tree val) | |
| 1433 { | |
| 1434 gimple *stmt = gsi_stmt (*gsi); | |
| 1435 | |
| 1436 if (is_gimple_assign (stmt)) | |
| 1437 { | |
| 1438 tree expr = NULL_TREE; | |
| 1439 if (gimple_assign_single_p (stmt)) | |
| 1440 expr = gimple_assign_rhs1 (stmt); | |
| 1441 propagate_tree_value (&expr, val); | |
| 1442 gimple_assign_set_rhs_from_tree (gsi, expr); | |
| 1443 } | |
| 1444 else if (gcond *cond_stmt = dyn_cast <gcond *> (stmt)) | |
| 1445 { | |
| 1446 tree lhs = NULL_TREE; | |
| 1447 tree rhs = build_zero_cst (TREE_TYPE (val)); | |
| 1448 propagate_tree_value (&lhs, val); | |
| 1449 gimple_cond_set_code (cond_stmt, NE_EXPR); | |
| 1450 gimple_cond_set_lhs (cond_stmt, lhs); | |
| 1451 gimple_cond_set_rhs (cond_stmt, rhs); | |
| 1452 } | |
| 1453 else if (is_gimple_call (stmt) | |
| 1454 && gimple_call_lhs (stmt) != NULL_TREE) | |
| 1455 { | |
| 1456 tree expr = NULL_TREE; | |
| 1457 bool res; | |
| 1458 propagate_tree_value (&expr, val); | |
| 1459 res = update_call_from_tree (gsi, expr); | |
| 1460 gcc_assert (res); | |
| 1461 } | |
| 1462 else if (gswitch *swtch_stmt = dyn_cast <gswitch *> (stmt)) | |
| 1463 propagate_tree_value (gimple_switch_index_ptr (swtch_stmt), val); | |
| 1464 else | |
| 1465 gcc_unreachable (); | |
| 1466 } |