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f3ec9a6c | 1 | /* Code sinking for trees |
71e45bc2 | 2 | Copyright (C) 2001, 2002, 2003, 2004, 2007, 2008, 2009, 2010, 2011, 2012 |
e15deb4b | 3 | Free Software Foundation, Inc. |
f3ec9a6c | 4 | Contributed by Daniel Berlin <dan@dberlin.org> |
5 | ||
6 | This file is part of GCC. | |
7 | ||
8 | GCC is free software; you can redistribute it and/or modify | |
9 | it under the terms of the GNU General Public License as published by | |
8c4c00c1 | 10 | the Free Software Foundation; either version 3, or (at your option) |
f3ec9a6c | 11 | any later version. |
12 | ||
13 | GCC is distributed in the hope that it will be useful, | |
14 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
16 | GNU General Public License for more details. | |
17 | ||
18 | You should have received a copy of the GNU General Public License | |
8c4c00c1 | 19 | along with GCC; see the file COPYING3. If not see |
20 | <http://www.gnu.org/licenses/>. */ | |
f3ec9a6c | 21 | |
22 | #include "config.h" | |
23 | #include "system.h" | |
24 | #include "coretypes.h" | |
25 | #include "tm.h" | |
f3ec9a6c | 26 | #include "tree.h" |
27 | #include "basic-block.h" | |
ce084dfc | 28 | #include "gimple-pretty-print.h" |
f3ec9a6c | 29 | #include "tree-inline.h" |
30 | #include "tree-flow.h" | |
75a70cf9 | 31 | #include "gimple.h" |
f3ec9a6c | 32 | #include "hashtab.h" |
33 | #include "tree-iterator.h" | |
f3ec9a6c | 34 | #include "alloc-pool.h" |
35 | #include "tree-pass.h" | |
36 | #include "flags.h" | |
37 | #include "bitmap.h" | |
f3ec9a6c | 38 | #include "cfgloop.h" |
77ecaaba | 39 | #include "params.h" |
f3ec9a6c | 40 | |
41 | /* TODO: | |
42 | 1. Sinking store only using scalar promotion (IE without moving the RHS): | |
43 | ||
44 | *q = p; | |
45 | p = p + 1; | |
46 | if (something) | |
47 | *q = <not p>; | |
48 | else | |
49 | y = *q; | |
50 | ||
48e1416a | 51 | |
f3ec9a6c | 52 | should become |
53 | sinktemp = p; | |
54 | p = p + 1; | |
55 | if (something) | |
56 | *q = <not p>; | |
57 | else | |
58 | { | |
59 | *q = sinktemp; | |
60 | y = *q | |
61 | } | |
62 | Store copy propagation will take care of the store elimination above. | |
48e1416a | 63 | |
f3ec9a6c | 64 | |
65 | 2. Sinking using Partial Dead Code Elimination. */ | |
66 | ||
67 | ||
68 | static struct | |
48e1416a | 69 | { |
f7f07c95 | 70 | /* The number of statements sunk down the flowgraph by code sinking. */ |
f3ec9a6c | 71 | int sunk; |
48e1416a | 72 | |
f3ec9a6c | 73 | } sink_stats; |
74 | ||
75 | ||
fe24f256 | 76 | /* Given a PHI, and one of its arguments (DEF), find the edge for |
f3ec9a6c | 77 | that argument and return it. If the argument occurs twice in the PHI node, |
78 | we return NULL. */ | |
79 | ||
80 | static basic_block | |
75a70cf9 | 81 | find_bb_for_arg (gimple phi, tree def) |
f3ec9a6c | 82 | { |
75a70cf9 | 83 | size_t i; |
f3ec9a6c | 84 | bool foundone = false; |
85 | basic_block result = NULL; | |
75a70cf9 | 86 | for (i = 0; i < gimple_phi_num_args (phi); i++) |
f3ec9a6c | 87 | if (PHI_ARG_DEF (phi, i) == def) |
88 | { | |
89 | if (foundone) | |
90 | return NULL; | |
91 | foundone = true; | |
75a70cf9 | 92 | result = gimple_phi_arg_edge (phi, i)->src; |
f3ec9a6c | 93 | } |
94 | return result; | |
95 | } | |
96 | ||
97 | /* When the first immediate use is in a statement, then return true if all | |
98 | immediate uses in IMM are in the same statement. | |
99 | We could also do the case where the first immediate use is in a phi node, | |
100 | and all the other uses are in phis in the same basic block, but this | |
101 | requires some expensive checking later (you have to make sure no def/vdef | |
102 | in the statement occurs for multiple edges in the various phi nodes it's | |
f7f07c95 | 103 | used in, so that you only have one place you can sink it to. */ |
f3ec9a6c | 104 | |
105 | static bool | |
75a70cf9 | 106 | all_immediate_uses_same_place (gimple stmt) |
f3ec9a6c | 107 | { |
75a70cf9 | 108 | gimple firstuse = NULL; |
22aa74c4 | 109 | ssa_op_iter op_iter; |
110 | imm_use_iterator imm_iter; | |
111 | use_operand_p use_p; | |
112 | tree var; | |
f3ec9a6c | 113 | |
22aa74c4 | 114 | FOR_EACH_SSA_TREE_OPERAND (var, stmt, op_iter, SSA_OP_ALL_DEFS) |
f3ec9a6c | 115 | { |
22aa74c4 | 116 | FOR_EACH_IMM_USE_FAST (use_p, imm_iter, var) |
117 | { | |
9845d120 | 118 | if (is_gimple_debug (USE_STMT (use_p))) |
119 | continue; | |
75a70cf9 | 120 | if (firstuse == NULL) |
22aa74c4 | 121 | firstuse = USE_STMT (use_p); |
122 | else | |
123 | if (firstuse != USE_STMT (use_p)) | |
124 | return false; | |
125 | } | |
f3ec9a6c | 126 | } |
22aa74c4 | 127 | |
f3ec9a6c | 128 | return true; |
129 | } | |
130 | ||
f3ec9a6c | 131 | /* Find the nearest common dominator of all of the immediate uses in IMM. */ |
132 | ||
133 | static basic_block | |
9845d120 | 134 | nearest_common_dominator_of_uses (gimple stmt, bool *debug_stmts) |
48e1416a | 135 | { |
f3ec9a6c | 136 | bitmap blocks = BITMAP_ALLOC (NULL); |
137 | basic_block commondom; | |
f3ec9a6c | 138 | unsigned int j; |
139 | bitmap_iterator bi; | |
22aa74c4 | 140 | ssa_op_iter op_iter; |
141 | imm_use_iterator imm_iter; | |
142 | use_operand_p use_p; | |
143 | tree var; | |
144 | ||
f3ec9a6c | 145 | bitmap_clear (blocks); |
22aa74c4 | 146 | FOR_EACH_SSA_TREE_OPERAND (var, stmt, op_iter, SSA_OP_ALL_DEFS) |
f3ec9a6c | 147 | { |
22aa74c4 | 148 | FOR_EACH_IMM_USE_FAST (use_p, imm_iter, var) |
149 | { | |
75a70cf9 | 150 | gimple usestmt = USE_STMT (use_p); |
22aa74c4 | 151 | basic_block useblock; |
c52a36cc | 152 | |
75a70cf9 | 153 | if (gimple_code (usestmt) == GIMPLE_PHI) |
22aa74c4 | 154 | { |
737b5433 | 155 | int idx = PHI_ARG_INDEX_FROM_USE (use_p); |
c48d3403 | 156 | |
75a70cf9 | 157 | useblock = gimple_phi_arg_edge (usestmt, idx)->src; |
22aa74c4 | 158 | } |
9845d120 | 159 | else if (is_gimple_debug (usestmt)) |
160 | { | |
161 | *debug_stmts = true; | |
162 | continue; | |
163 | } | |
22aa74c4 | 164 | else |
f3ec9a6c | 165 | { |
75a70cf9 | 166 | useblock = gimple_bb (usestmt); |
c52a36cc | 167 | } |
22aa74c4 | 168 | |
c52a36cc | 169 | /* Short circuit. Nothing dominates the entry block. */ |
170 | if (useblock == ENTRY_BLOCK_PTR) | |
171 | { | |
172 | BITMAP_FREE (blocks); | |
173 | return NULL; | |
f3ec9a6c | 174 | } |
c52a36cc | 175 | bitmap_set_bit (blocks, useblock->index); |
f3ec9a6c | 176 | } |
f3ec9a6c | 177 | } |
178 | commondom = BASIC_BLOCK (bitmap_first_set_bit (blocks)); | |
179 | EXECUTE_IF_SET_IN_BITMAP (blocks, 0, j, bi) | |
48e1416a | 180 | commondom = nearest_common_dominator (CDI_DOMINATORS, commondom, |
f3ec9a6c | 181 | BASIC_BLOCK (j)); |
182 | BITMAP_FREE (blocks); | |
183 | return commondom; | |
184 | } | |
185 | ||
77ecaaba | 186 | /* Given EARLY_BB and LATE_BB, two blocks in a path through the dominator |
187 | tree, return the best basic block between them (inclusive) to place | |
188 | statements. | |
189 | ||
190 | We want the most control dependent block in the shallowest loop nest. | |
191 | ||
192 | If the resulting block is in a shallower loop nest, then use it. Else | |
193 | only use the resulting block if it has significantly lower execution | |
194 | frequency than EARLY_BB to avoid gratutious statement movement. We | |
195 | consider statements with VOPS more desirable to move. | |
196 | ||
197 | This pass would obviously benefit from PDO as it utilizes block | |
198 | frequencies. It would also benefit from recomputing frequencies | |
199 | if profile data is not available since frequencies often get out | |
200 | of sync with reality. */ | |
201 | ||
202 | static basic_block | |
203 | select_best_block (basic_block early_bb, | |
204 | basic_block late_bb, | |
205 | gimple stmt) | |
206 | { | |
207 | basic_block best_bb = late_bb; | |
208 | basic_block temp_bb = late_bb; | |
209 | int threshold; | |
210 | ||
211 | while (temp_bb != early_bb) | |
212 | { | |
213 | /* If we've moved into a lower loop nest, then that becomes | |
214 | our best block. */ | |
6b42039a | 215 | if (bb_loop_depth (temp_bb) < bb_loop_depth (best_bb)) |
77ecaaba | 216 | best_bb = temp_bb; |
217 | ||
218 | /* Walk up the dominator tree, hopefully we'll find a shallower | |
219 | loop nest. */ | |
220 | temp_bb = get_immediate_dominator (CDI_DOMINATORS, temp_bb); | |
221 | } | |
222 | ||
223 | /* If we found a shallower loop nest, then we always consider that | |
224 | a win. This will always give us the most control dependent block | |
225 | within that loop nest. */ | |
6b42039a | 226 | if (bb_loop_depth (best_bb) < bb_loop_depth (early_bb)) |
77ecaaba | 227 | return best_bb; |
228 | ||
229 | /* Get the sinking threshold. If the statement to be moved has memory | |
230 | operands, then increase the threshold by 7% as those are even more | |
231 | profitable to avoid, clamping at 100%. */ | |
232 | threshold = PARAM_VALUE (PARAM_SINK_FREQUENCY_THRESHOLD); | |
233 | if (gimple_vuse (stmt) || gimple_vdef (stmt)) | |
234 | { | |
235 | threshold += 7; | |
236 | if (threshold > 100) | |
237 | threshold = 100; | |
238 | } | |
239 | ||
240 | /* If BEST_BB is at the same nesting level, then require it to have | |
241 | significantly lower execution frequency to avoid gratutious movement. */ | |
6b42039a | 242 | if (bb_loop_depth (best_bb) == bb_loop_depth (early_bb) |
77ecaaba | 243 | && best_bb->frequency < (early_bb->frequency * threshold / 100.0)) |
244 | return best_bb; | |
245 | ||
246 | /* No better block found, so return EARLY_BB, which happens to be the | |
247 | statement's original block. */ | |
248 | return early_bb; | |
249 | } | |
250 | ||
48e1416a | 251 | /* Given a statement (STMT) and the basic block it is currently in (FROMBB), |
f3ec9a6c | 252 | determine the location to sink the statement to, if any. |
75a70cf9 | 253 | Returns true if there is such location; in that case, TOGSI points to the |
254 | statement before that STMT should be moved. */ | |
f3ec9a6c | 255 | |
4122c2d4 | 256 | static bool |
75a70cf9 | 257 | statement_sink_location (gimple stmt, basic_block frombb, |
258 | gimple_stmt_iterator *togsi) | |
f3ec9a6c | 259 | { |
75a70cf9 | 260 | gimple use; |
22aa74c4 | 261 | use_operand_p one_use = NULL_USE_OPERAND_P; |
f3ec9a6c | 262 | basic_block sinkbb; |
263 | use_operand_p use_p; | |
264 | def_operand_p def_p; | |
265 | ssa_op_iter iter; | |
22aa74c4 | 266 | imm_use_iterator imm_iter; |
267 | ||
2109076a | 268 | /* We only can sink assignments. */ |
269 | if (!is_gimple_assign (stmt)) | |
270 | return false; | |
f3ec9a6c | 271 | |
2109076a | 272 | /* We only can sink stmts with a single definition. */ |
273 | def_p = single_ssa_def_operand (stmt, SSA_OP_ALL_DEFS); | |
274 | if (def_p == NULL_DEF_OPERAND_P) | |
4122c2d4 | 275 | return false; |
f3ec9a6c | 276 | |
2109076a | 277 | /* Return if there are no immediate uses of this stmt. */ |
278 | if (has_zero_uses (DEF_FROM_PTR (def_p))) | |
4122c2d4 | 279 | return false; |
f3ec9a6c | 280 | |
281 | /* There are a few classes of things we can't or don't move, some because we | |
282 | don't have code to handle it, some because it's not profitable and some | |
48e1416a | 283 | because it's not legal. |
284 | ||
f3ec9a6c | 285 | We can't sink things that may be global stores, at least not without |
286 | calculating a lot more information, because we may cause it to no longer | |
287 | be seen by an external routine that needs it depending on where it gets | |
48e1416a | 288 | moved to. |
289 | ||
f3ec9a6c | 290 | We don't want to sink loads from memory. |
291 | ||
292 | We can't sink statements that end basic blocks without splitting the | |
293 | incoming edge for the sink location to place it there. | |
294 | ||
48e1416a | 295 | We can't sink statements that have volatile operands. |
f3ec9a6c | 296 | |
297 | We don't want to sink dead code, so anything with 0 immediate uses is not | |
e15deb4b | 298 | sunk. |
299 | ||
300 | Don't sink BLKmode assignments if current function has any local explicit | |
301 | register variables, as BLKmode assignments may involve memcpy or memset | |
302 | calls or, on some targets, inline expansion thereof that sometimes need | |
303 | to use specific hard registers. | |
f3ec9a6c | 304 | |
305 | */ | |
b66731e8 | 306 | if (stmt_ends_bb_p (stmt) |
75a70cf9 | 307 | || gimple_has_side_effects (stmt) |
75a70cf9 | 308 | || gimple_has_volatile_ops (stmt) |
2109076a | 309 | || (gimple_vuse (stmt) && !gimple_vdef (stmt)) |
e15deb4b | 310 | || (cfun->has_local_explicit_reg_vars |
311 | && TYPE_MODE (TREE_TYPE (gimple_assign_lhs (stmt))) == BLKmode)) | |
4122c2d4 | 312 | return false; |
48e1416a | 313 | |
2109076a | 314 | if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (DEF_FROM_PTR (def_p))) |
315 | return false; | |
48e1416a | 316 | |
f3ec9a6c | 317 | FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES) |
318 | { | |
319 | tree use = USE_FROM_PTR (use_p); | |
320 | if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (use)) | |
4122c2d4 | 321 | return false; |
f3ec9a6c | 322 | } |
48e1416a | 323 | |
2109076a | 324 | use = NULL; |
325 | ||
326 | /* If stmt is a store the one and only use needs to be the VOP | |
327 | merging PHI node. */ | |
328 | if (gimple_vdef (stmt)) | |
329 | { | |
330 | FOR_EACH_IMM_USE_FAST (use_p, imm_iter, DEF_FROM_PTR (def_p)) | |
331 | { | |
332 | gimple use_stmt = USE_STMT (use_p); | |
333 | ||
334 | /* A killing definition is not a use. */ | |
335 | if (gimple_assign_single_p (use_stmt) | |
336 | && gimple_vdef (use_stmt) | |
337 | && operand_equal_p (gimple_assign_lhs (stmt), | |
338 | gimple_assign_lhs (use_stmt), 0)) | |
339 | continue; | |
340 | ||
341 | if (gimple_code (use_stmt) != GIMPLE_PHI) | |
342 | return false; | |
343 | ||
344 | if (use | |
345 | && use != use_stmt) | |
346 | return false; | |
347 | ||
348 | use = use_stmt; | |
349 | } | |
350 | if (!use) | |
351 | return false; | |
352 | } | |
f3ec9a6c | 353 | /* If all the immediate uses are not in the same place, find the nearest |
354 | common dominator of all the immediate uses. For PHI nodes, we have to | |
355 | find the nearest common dominator of all of the predecessor blocks, since | |
356 | that is where insertion would have to take place. */ | |
2109076a | 357 | else if (!all_immediate_uses_same_place (stmt)) |
f3ec9a6c | 358 | { |
9845d120 | 359 | bool debug_stmts = false; |
360 | basic_block commondom = nearest_common_dominator_of_uses (stmt, | |
361 | &debug_stmts); | |
48e1416a | 362 | |
f3ec9a6c | 363 | if (commondom == frombb) |
4122c2d4 | 364 | return false; |
f3ec9a6c | 365 | |
366 | /* Our common dominator has to be dominated by frombb in order to be a | |
367 | trivially safe place to put this statement, since it has multiple | |
48e1416a | 368 | uses. */ |
f3ec9a6c | 369 | if (!dominated_by_p (CDI_DOMINATORS, commondom, frombb)) |
4122c2d4 | 370 | return false; |
48e1416a | 371 | |
77ecaaba | 372 | commondom = select_best_block (frombb, commondom, stmt); |
f3ec9a6c | 373 | |
77ecaaba | 374 | if (commondom == frombb) |
375 | return false; | |
9845d120 | 376 | |
75a70cf9 | 377 | *togsi = gsi_after_labels (commondom); |
9845d120 | 378 | |
4122c2d4 | 379 | return true; |
f3ec9a6c | 380 | } |
2109076a | 381 | else |
f3ec9a6c | 382 | { |
2109076a | 383 | FOR_EACH_IMM_USE_FAST (one_use, imm_iter, DEF_FROM_PTR (def_p)) |
384 | { | |
385 | if (is_gimple_debug (USE_STMT (one_use))) | |
386 | continue; | |
387 | break; | |
388 | } | |
389 | use = USE_STMT (one_use); | |
75a70cf9 | 390 | |
2109076a | 391 | if (gimple_code (use) != GIMPLE_PHI) |
392 | { | |
393 | sinkbb = gimple_bb (use); | |
77ecaaba | 394 | sinkbb = select_best_block (frombb, gimple_bb (use), stmt); |
258b3d02 | 395 | |
77ecaaba | 396 | if (sinkbb == frombb) |
2109076a | 397 | return false; |
9845d120 | 398 | |
2109076a | 399 | *togsi = gsi_for_stmt (use); |
f3ec9a6c | 400 | |
2109076a | 401 | return true; |
402 | } | |
403 | } | |
b66731e8 | 404 | |
2109076a | 405 | sinkbb = find_bb_for_arg (use, DEF_FROM_PTR (def_p)); |
f3ec9a6c | 406 | |
77ecaaba | 407 | /* This can happen if there are multiple uses in a PHI. */ |
408 | if (!sinkbb) | |
4122c2d4 | 409 | return false; |
77ecaaba | 410 | |
411 | sinkbb = select_best_block (frombb, sinkbb, stmt); | |
412 | if (!sinkbb || sinkbb == frombb) | |
4122c2d4 | 413 | return false; |
414 | ||
87e53408 | 415 | /* If the latch block is empty, don't make it non-empty by sinking |
416 | something into it. */ | |
417 | if (sinkbb == frombb->loop_father->latch | |
418 | && empty_block_p (sinkbb)) | |
419 | return false; | |
420 | ||
75a70cf9 | 421 | *togsi = gsi_after_labels (sinkbb); |
f3ec9a6c | 422 | |
4122c2d4 | 423 | return true; |
f3ec9a6c | 424 | } |
425 | ||
426 | /* Perform code sinking on BB */ | |
427 | ||
428 | static void | |
429 | sink_code_in_bb (basic_block bb) | |
430 | { | |
431 | basic_block son; | |
75a70cf9 | 432 | gimple_stmt_iterator gsi; |
f3ec9a6c | 433 | edge_iterator ei; |
434 | edge e; | |
5add5f91 | 435 | bool last = true; |
48e1416a | 436 | |
f3ec9a6c | 437 | /* If this block doesn't dominate anything, there can't be any place to sink |
438 | the statements to. */ | |
439 | if (first_dom_son (CDI_DOMINATORS, bb) == NULL) | |
440 | goto earlyout; | |
441 | ||
442 | /* We can't move things across abnormal edges, so don't try. */ | |
443 | FOR_EACH_EDGE (e, ei, bb->succs) | |
444 | if (e->flags & EDGE_ABNORMAL) | |
445 | goto earlyout; | |
446 | ||
75a70cf9 | 447 | for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi);) |
f3ec9a6c | 448 | { |
48e1416a | 449 | gimple stmt = gsi_stmt (gsi); |
75a70cf9 | 450 | gimple_stmt_iterator togsi; |
4122c2d4 | 451 | |
75a70cf9 | 452 | if (!statement_sink_location (stmt, bb, &togsi)) |
f3ec9a6c | 453 | { |
75a70cf9 | 454 | if (!gsi_end_p (gsi)) |
455 | gsi_prev (&gsi); | |
5add5f91 | 456 | last = false; |
f3ec9a6c | 457 | continue; |
48e1416a | 458 | } |
f3ec9a6c | 459 | if (dump_file) |
460 | { | |
461 | fprintf (dump_file, "Sinking "); | |
75a70cf9 | 462 | print_gimple_stmt (dump_file, stmt, 0, TDF_VOPS); |
f3ec9a6c | 463 | fprintf (dump_file, " from bb %d to bb %d\n", |
75a70cf9 | 464 | bb->index, (gsi_bb (togsi))->index); |
f3ec9a6c | 465 | } |
48e1416a | 466 | |
63eb2430 | 467 | /* Update virtual operands of statements in the path we |
468 | do not sink to. */ | |
2109076a | 469 | if (gimple_vdef (stmt)) |
470 | { | |
63eb2430 | 471 | imm_use_iterator iter; |
472 | use_operand_p use_p; | |
473 | gimple vuse_stmt; | |
474 | ||
475 | FOR_EACH_IMM_USE_STMT (vuse_stmt, iter, gimple_vdef (stmt)) | |
476 | if (gimple_code (vuse_stmt) != GIMPLE_PHI) | |
477 | FOR_EACH_IMM_USE_ON_STMT (use_p, iter) | |
478 | SET_USE (use_p, gimple_vuse (stmt)); | |
2109076a | 479 | } |
480 | ||
f3ec9a6c | 481 | /* If this is the end of the basic block, we need to insert at the end |
482 | of the basic block. */ | |
75a70cf9 | 483 | if (gsi_end_p (togsi)) |
484 | gsi_move_to_bb_end (&gsi, gsi_bb (togsi)); | |
f3ec9a6c | 485 | else |
75a70cf9 | 486 | gsi_move_before (&gsi, &togsi); |
f3ec9a6c | 487 | |
488 | sink_stats.sunk++; | |
5add5f91 | 489 | |
490 | /* If we've just removed the last statement of the BB, the | |
75a70cf9 | 491 | gsi_end_p() test below would fail, but gsi_prev() would have |
5add5f91 | 492 | succeeded, and we want it to succeed. So we keep track of |
493 | whether we're at the last statement and pick up the new last | |
494 | statement. */ | |
495 | if (last) | |
496 | { | |
75a70cf9 | 497 | gsi = gsi_last_bb (bb); |
5add5f91 | 498 | continue; |
499 | } | |
500 | ||
501 | last = false; | |
75a70cf9 | 502 | if (!gsi_end_p (gsi)) |
503 | gsi_prev (&gsi); | |
48e1416a | 504 | |
f3ec9a6c | 505 | } |
506 | earlyout: | |
507 | for (son = first_dom_son (CDI_POST_DOMINATORS, bb); | |
508 | son; | |
509 | son = next_dom_son (CDI_POST_DOMINATORS, son)) | |
510 | { | |
511 | sink_code_in_bb (son); | |
512 | } | |
48e1416a | 513 | } |
f3ec9a6c | 514 | |
515 | /* Perform code sinking. | |
516 | This moves code down the flowgraph when we know it would be | |
517 | profitable to do so, or it wouldn't increase the number of | |
518 | executions of the statement. | |
519 | ||
520 | IE given | |
48e1416a | 521 | |
f3ec9a6c | 522 | a_1 = b + c; |
523 | if (<something>) | |
524 | { | |
525 | } | |
526 | else | |
527 | { | |
528 | foo (&b, &c); | |
529 | a_5 = b + c; | |
530 | } | |
531 | a_6 = PHI (a_5, a_1); | |
532 | USE a_6. | |
533 | ||
534 | we'll transform this into: | |
535 | ||
536 | if (<something>) | |
537 | { | |
538 | a_1 = b + c; | |
539 | } | |
540 | else | |
541 | { | |
542 | foo (&b, &c); | |
543 | a_5 = b + c; | |
544 | } | |
545 | a_6 = PHI (a_5, a_1); | |
546 | USE a_6. | |
547 | ||
548 | Note that this reduces the number of computations of a = b + c to 1 | |
549 | when we take the else edge, instead of 2. | |
550 | */ | |
551 | static void | |
552 | execute_sink_code (void) | |
553 | { | |
88e6f696 | 554 | loop_optimizer_init (LOOPS_NORMAL); |
3f5be5f4 | 555 | |
f3ec9a6c | 556 | connect_infinite_loops_to_exit (); |
557 | memset (&sink_stats, 0, sizeof (sink_stats)); | |
f1456a87 | 558 | calculate_dominance_info (CDI_DOMINATORS); |
559 | calculate_dominance_info (CDI_POST_DOMINATORS); | |
48e1416a | 560 | sink_code_in_bb (EXIT_BLOCK_PTR); |
581f8050 | 561 | statistics_counter_event (cfun, "Sunk statements", sink_stats.sunk); |
f3ec9a6c | 562 | free_dominance_info (CDI_POST_DOMINATORS); |
563 | remove_fake_exit_edges (); | |
88e6f696 | 564 | loop_optimizer_finalize (); |
f3ec9a6c | 565 | } |
566 | ||
567 | /* Gate and execute functions for PRE. */ | |
568 | ||
2a1990e9 | 569 | static unsigned int |
f3ec9a6c | 570 | do_sink (void) |
571 | { | |
572 | execute_sink_code (); | |
2a1990e9 | 573 | return 0; |
f3ec9a6c | 574 | } |
575 | ||
576 | static bool | |
577 | gate_sink (void) | |
578 | { | |
579 | return flag_tree_sink != 0; | |
580 | } | |
581 | ||
20099e35 | 582 | struct gimple_opt_pass pass_sink_code = |
f3ec9a6c | 583 | { |
20099e35 | 584 | { |
585 | GIMPLE_PASS, | |
f3ec9a6c | 586 | "sink", /* name */ |
c7875731 | 587 | OPTGROUP_NONE, /* optinfo_flags */ |
f3ec9a6c | 588 | gate_sink, /* gate */ |
589 | do_sink, /* execute */ | |
590 | NULL, /* sub */ | |
591 | NULL, /* next */ | |
592 | 0, /* static_pass_number */ | |
593 | TV_TREE_SINK, /* tv_id */ | |
594 | PROP_no_crit_edges | PROP_cfg | |
2f8eb909 | 595 | | PROP_ssa, /* properties_required */ |
f3ec9a6c | 596 | 0, /* properties_provided */ |
597 | 0, /* properties_destroyed */ | |
598 | 0, /* todo_flags_start */ | |
48e1416a | 599 | TODO_update_ssa |
a2676c4f | 600 | | TODO_verify_ssa |
601 | | TODO_verify_flow | |
a2676c4f | 602 | | TODO_ggc_collect /* todo_flags_finish */ |
20099e35 | 603 | } |
f3ec9a6c | 604 | }; |