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Commit | Line | Data |
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ec1e9f7c | 1 | /* Code sinking for trees |
66647d44 | 2 | Copyright (C) 2001, 2002, 2003, 2004, 2007, 2008, 2009 |
fc3103e7 | 3 | Free Software Foundation, Inc. |
ec1e9f7c DB |
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 | |
9dcd6f09 | 10 | the Free Software Foundation; either version 3, or (at your option) |
ec1e9f7c DB |
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 | |
9dcd6f09 NC |
19 | along with GCC; see the file COPYING3. If not see |
20 | <http://www.gnu.org/licenses/>. */ | |
ec1e9f7c DB |
21 | |
22 | #include "config.h" | |
23 | #include "system.h" | |
24 | #include "coretypes.h" | |
25 | #include "tm.h" | |
ec1e9f7c DB |
26 | #include "ggc.h" |
27 | #include "tree.h" | |
28 | #include "basic-block.h" | |
29 | #include "diagnostic.h" | |
30 | #include "tree-inline.h" | |
31 | #include "tree-flow.h" | |
726a989a | 32 | #include "gimple.h" |
ec1e9f7c DB |
33 | #include "tree-dump.h" |
34 | #include "timevar.h" | |
35 | #include "fibheap.h" | |
36 | #include "hashtab.h" | |
37 | #include "tree-iterator.h" | |
38 | #include "real.h" | |
39 | #include "alloc-pool.h" | |
40 | #include "tree-pass.h" | |
41 | #include "flags.h" | |
42 | #include "bitmap.h" | |
43 | #include "langhooks.h" | |
44 | #include "cfgloop.h" | |
45 | ||
46 | /* TODO: | |
47 | 1. Sinking store only using scalar promotion (IE without moving the RHS): | |
48 | ||
49 | *q = p; | |
50 | p = p + 1; | |
51 | if (something) | |
52 | *q = <not p>; | |
53 | else | |
54 | y = *q; | |
55 | ||
b8698a0f | 56 | |
ec1e9f7c DB |
57 | should become |
58 | sinktemp = p; | |
59 | p = p + 1; | |
60 | if (something) | |
61 | *q = <not p>; | |
62 | else | |
63 | { | |
64 | *q = sinktemp; | |
65 | y = *q | |
66 | } | |
67 | Store copy propagation will take care of the store elimination above. | |
b8698a0f | 68 | |
ec1e9f7c DB |
69 | |
70 | 2. Sinking using Partial Dead Code Elimination. */ | |
71 | ||
72 | ||
73 | static struct | |
b8698a0f | 74 | { |
6c6cfbfd | 75 | /* The number of statements sunk down the flowgraph by code sinking. */ |
ec1e9f7c | 76 | int sunk; |
b8698a0f | 77 | |
ec1e9f7c DB |
78 | } sink_stats; |
79 | ||
80 | ||
f652d14b | 81 | /* Given a PHI, and one of its arguments (DEF), find the edge for |
ec1e9f7c DB |
82 | that argument and return it. If the argument occurs twice in the PHI node, |
83 | we return NULL. */ | |
84 | ||
85 | static basic_block | |
726a989a | 86 | find_bb_for_arg (gimple phi, tree def) |
ec1e9f7c | 87 | { |
726a989a | 88 | size_t i; |
ec1e9f7c DB |
89 | bool foundone = false; |
90 | basic_block result = NULL; | |
726a989a | 91 | for (i = 0; i < gimple_phi_num_args (phi); i++) |
ec1e9f7c DB |
92 | if (PHI_ARG_DEF (phi, i) == def) |
93 | { | |
94 | if (foundone) | |
95 | return NULL; | |
96 | foundone = true; | |
726a989a | 97 | result = gimple_phi_arg_edge (phi, i)->src; |
ec1e9f7c DB |
98 | } |
99 | return result; | |
100 | } | |
101 | ||
102 | /* When the first immediate use is in a statement, then return true if all | |
103 | immediate uses in IMM are in the same statement. | |
104 | We could also do the case where the first immediate use is in a phi node, | |
105 | and all the other uses are in phis in the same basic block, but this | |
106 | requires some expensive checking later (you have to make sure no def/vdef | |
107 | in the statement occurs for multiple edges in the various phi nodes it's | |
6c6cfbfd | 108 | used in, so that you only have one place you can sink it to. */ |
ec1e9f7c DB |
109 | |
110 | static bool | |
726a989a | 111 | all_immediate_uses_same_place (gimple stmt) |
ec1e9f7c | 112 | { |
726a989a | 113 | gimple firstuse = NULL; |
f430bae8 AM |
114 | ssa_op_iter op_iter; |
115 | imm_use_iterator imm_iter; | |
116 | use_operand_p use_p; | |
117 | tree var; | |
ec1e9f7c | 118 | |
f430bae8 | 119 | FOR_EACH_SSA_TREE_OPERAND (var, stmt, op_iter, SSA_OP_ALL_DEFS) |
ec1e9f7c | 120 | { |
f430bae8 AM |
121 | FOR_EACH_IMM_USE_FAST (use_p, imm_iter, var) |
122 | { | |
b5b8b0ac AO |
123 | if (is_gimple_debug (USE_STMT (use_p))) |
124 | continue; | |
726a989a | 125 | if (firstuse == NULL) |
f430bae8 AM |
126 | firstuse = USE_STMT (use_p); |
127 | else | |
128 | if (firstuse != USE_STMT (use_p)) | |
129 | return false; | |
130 | } | |
ec1e9f7c | 131 | } |
f430bae8 | 132 | |
ec1e9f7c DB |
133 | return true; |
134 | } | |
135 | ||
38635499 | 136 | /* Some global stores don't necessarily have VDEF's of global variables, |
ec1e9f7c DB |
137 | but we still must avoid moving them around. */ |
138 | ||
139 | bool | |
726a989a | 140 | is_hidden_global_store (gimple stmt) |
ec1e9f7c | 141 | { |
ec1e9f7c | 142 | /* Check virtual definitions. If we get here, the only virtual |
726a989a | 143 | definitions we should see are those generated by assignment or call |
ec1e9f7c | 144 | statements. */ |
5006671f | 145 | if (gimple_vdef (stmt)) |
ec1e9f7c DB |
146 | { |
147 | tree lhs; | |
148 | ||
726a989a | 149 | gcc_assert (is_gimple_assign (stmt) || is_gimple_call (stmt)); |
ec1e9f7c DB |
150 | |
151 | /* Note that we must not check the individual virtual operands | |
152 | here. In particular, if this is an aliased store, we could | |
153 | end up with something like the following (SSA notation | |
154 | redacted for brevity): | |
155 | ||
156 | foo (int *p, int i) | |
157 | { | |
158 | int x; | |
159 | p_1 = (i_2 > 3) ? &x : p; | |
160 | ||
38635499 | 161 | # x_4 = VDEF <x_3> |
ec1e9f7c DB |
162 | *p_1 = 5; |
163 | ||
164 | return 2; | |
165 | } | |
166 | ||
167 | Notice that the store to '*p_1' should be preserved, if we | |
168 | were to check the virtual definitions in that store, we would | |
169 | not mark it needed. This is because 'x' is not a global | |
170 | variable. | |
171 | ||
172 | Therefore, we check the base address of the LHS. If the | |
18cd8a03 | 173 | address is a pointer, we check if its name tag or symbol tag is |
ec1e9f7c DB |
174 | a global variable. Otherwise, we check if the base variable |
175 | is a global. */ | |
726a989a RB |
176 | lhs = gimple_get_lhs (stmt); |
177 | ||
ec1e9f7c DB |
178 | if (REFERENCE_CLASS_P (lhs)) |
179 | lhs = get_base_address (lhs); | |
180 | ||
181 | if (lhs == NULL_TREE) | |
182 | { | |
183 | /* If LHS is NULL, it means that we couldn't get the base | |
184 | address of the reference. In which case, we should not | |
185 | move this store. */ | |
186 | return true; | |
187 | } | |
188 | else if (DECL_P (lhs)) | |
189 | { | |
190 | /* If the store is to a global symbol, we need to keep it. */ | |
191 | if (is_global_var (lhs)) | |
192 | return true; | |
193 | ||
194 | } | |
195 | else if (INDIRECT_REF_P (lhs)) | |
5006671f | 196 | return ptr_deref_may_alias_global_p (TREE_OPERAND (lhs, 0)); |
ec1e9f7c DB |
197 | else |
198 | gcc_unreachable (); | |
199 | } | |
38635499 | 200 | |
ec1e9f7c DB |
201 | return false; |
202 | } | |
203 | ||
204 | /* Find the nearest common dominator of all of the immediate uses in IMM. */ | |
205 | ||
206 | static basic_block | |
b5b8b0ac | 207 | nearest_common_dominator_of_uses (gimple stmt, bool *debug_stmts) |
b8698a0f | 208 | { |
ec1e9f7c DB |
209 | bitmap blocks = BITMAP_ALLOC (NULL); |
210 | basic_block commondom; | |
ec1e9f7c DB |
211 | unsigned int j; |
212 | bitmap_iterator bi; | |
f430bae8 AM |
213 | ssa_op_iter op_iter; |
214 | imm_use_iterator imm_iter; | |
215 | use_operand_p use_p; | |
216 | tree var; | |
217 | ||
ec1e9f7c | 218 | bitmap_clear (blocks); |
f430bae8 | 219 | FOR_EACH_SSA_TREE_OPERAND (var, stmt, op_iter, SSA_OP_ALL_DEFS) |
ec1e9f7c | 220 | { |
f430bae8 AM |
221 | FOR_EACH_IMM_USE_FAST (use_p, imm_iter, var) |
222 | { | |
726a989a | 223 | gimple usestmt = USE_STMT (use_p); |
f430bae8 | 224 | basic_block useblock; |
000b62dc | 225 | |
726a989a | 226 | if (gimple_code (usestmt) == GIMPLE_PHI) |
f430bae8 | 227 | { |
55b12f0d | 228 | int idx = PHI_ARG_INDEX_FROM_USE (use_p); |
ab798313 | 229 | |
726a989a | 230 | useblock = gimple_phi_arg_edge (usestmt, idx)->src; |
f430bae8 | 231 | } |
b5b8b0ac AO |
232 | else if (is_gimple_debug (usestmt)) |
233 | { | |
234 | *debug_stmts = true; | |
235 | continue; | |
236 | } | |
f430bae8 | 237 | else |
ec1e9f7c | 238 | { |
726a989a | 239 | useblock = gimple_bb (usestmt); |
000b62dc | 240 | } |
f430bae8 | 241 | |
000b62dc KH |
242 | /* Short circuit. Nothing dominates the entry block. */ |
243 | if (useblock == ENTRY_BLOCK_PTR) | |
244 | { | |
245 | BITMAP_FREE (blocks); | |
246 | return NULL; | |
ec1e9f7c | 247 | } |
000b62dc | 248 | bitmap_set_bit (blocks, useblock->index); |
ec1e9f7c | 249 | } |
ec1e9f7c DB |
250 | } |
251 | commondom = BASIC_BLOCK (bitmap_first_set_bit (blocks)); | |
252 | EXECUTE_IF_SET_IN_BITMAP (blocks, 0, j, bi) | |
b8698a0f | 253 | commondom = nearest_common_dominator (CDI_DOMINATORS, commondom, |
ec1e9f7c DB |
254 | BASIC_BLOCK (j)); |
255 | BITMAP_FREE (blocks); | |
256 | return commondom; | |
257 | } | |
258 | ||
b8698a0f | 259 | /* Given a statement (STMT) and the basic block it is currently in (FROMBB), |
ec1e9f7c | 260 | determine the location to sink the statement to, if any. |
726a989a RB |
261 | Returns true if there is such location; in that case, TOGSI points to the |
262 | statement before that STMT should be moved. */ | |
ec1e9f7c | 263 | |
18965703 | 264 | static bool |
726a989a RB |
265 | statement_sink_location (gimple stmt, basic_block frombb, |
266 | gimple_stmt_iterator *togsi) | |
ec1e9f7c | 267 | { |
726a989a RB |
268 | gimple use; |
269 | tree def; | |
f430bae8 | 270 | use_operand_p one_use = NULL_USE_OPERAND_P; |
ec1e9f7c DB |
271 | basic_block sinkbb; |
272 | use_operand_p use_p; | |
273 | def_operand_p def_p; | |
274 | ssa_op_iter iter; | |
f430bae8 AM |
275 | imm_use_iterator imm_iter; |
276 | ||
277 | FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS) | |
278 | { | |
279 | FOR_EACH_IMM_USE_FAST (one_use, imm_iter, def) | |
280 | { | |
b5b8b0ac AO |
281 | if (is_gimple_debug (USE_STMT (one_use))) |
282 | continue; | |
283 | ||
f430bae8 AM |
284 | break; |
285 | } | |
286 | if (one_use != NULL_USE_OPERAND_P) | |
287 | break; | |
288 | } | |
ec1e9f7c | 289 | |
f430bae8 AM |
290 | /* Return if there are no immediate uses of this stmt. */ |
291 | if (one_use == NULL_USE_OPERAND_P) | |
18965703 | 292 | return false; |
ec1e9f7c | 293 | |
726a989a | 294 | if (gimple_code (stmt) != GIMPLE_ASSIGN) |
18965703 | 295 | return false; |
ec1e9f7c DB |
296 | |
297 | /* There are a few classes of things we can't or don't move, some because we | |
298 | don't have code to handle it, some because it's not profitable and some | |
b8698a0f L |
299 | because it's not legal. |
300 | ||
ec1e9f7c DB |
301 | We can't sink things that may be global stores, at least not without |
302 | calculating a lot more information, because we may cause it to no longer | |
303 | be seen by an external routine that needs it depending on where it gets | |
b8698a0f L |
304 | moved to. |
305 | ||
ec1e9f7c DB |
306 | We don't want to sink loads from memory. |
307 | ||
308 | We can't sink statements that end basic blocks without splitting the | |
309 | incoming edge for the sink location to place it there. | |
310 | ||
b8698a0f | 311 | We can't sink statements that have volatile operands. |
ec1e9f7c DB |
312 | |
313 | We don't want to sink dead code, so anything with 0 immediate uses is not | |
fc3103e7 JJ |
314 | sunk. |
315 | ||
316 | Don't sink BLKmode assignments if current function has any local explicit | |
317 | register variables, as BLKmode assignments may involve memcpy or memset | |
318 | calls or, on some targets, inline expansion thereof that sometimes need | |
319 | to use specific hard registers. | |
ec1e9f7c DB |
320 | |
321 | */ | |
f47c96aa | 322 | if (stmt_ends_bb_p (stmt) |
726a989a | 323 | || gimple_has_side_effects (stmt) |
ec1e9f7c | 324 | || is_hidden_global_store (stmt) |
726a989a | 325 | || gimple_has_volatile_ops (stmt) |
5006671f | 326 | || gimple_vuse (stmt) |
fc3103e7 JJ |
327 | || (cfun->has_local_explicit_reg_vars |
328 | && TYPE_MODE (TREE_TYPE (gimple_assign_lhs (stmt))) == BLKmode)) | |
18965703 | 329 | return false; |
b8698a0f | 330 | |
ec1e9f7c DB |
331 | FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_ALL_DEFS) |
332 | { | |
333 | tree def = DEF_FROM_PTR (def_p); | |
334 | if (is_global_var (SSA_NAME_VAR (def)) | |
335 | || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def)) | |
18965703 | 336 | return false; |
ec1e9f7c | 337 | } |
b8698a0f | 338 | |
ec1e9f7c DB |
339 | FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES) |
340 | { | |
341 | tree use = USE_FROM_PTR (use_p); | |
342 | if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (use)) | |
18965703 | 343 | return false; |
ec1e9f7c | 344 | } |
b8698a0f | 345 | |
ec1e9f7c DB |
346 | /* If all the immediate uses are not in the same place, find the nearest |
347 | common dominator of all the immediate uses. For PHI nodes, we have to | |
348 | find the nearest common dominator of all of the predecessor blocks, since | |
349 | that is where insertion would have to take place. */ | |
f430bae8 | 350 | if (!all_immediate_uses_same_place (stmt)) |
ec1e9f7c | 351 | { |
b5b8b0ac AO |
352 | bool debug_stmts = false; |
353 | basic_block commondom = nearest_common_dominator_of_uses (stmt, | |
354 | &debug_stmts); | |
b8698a0f | 355 | |
ec1e9f7c | 356 | if (commondom == frombb) |
18965703 | 357 | return false; |
ec1e9f7c DB |
358 | |
359 | /* Our common dominator has to be dominated by frombb in order to be a | |
360 | trivially safe place to put this statement, since it has multiple | |
b8698a0f | 361 | uses. */ |
ec1e9f7c | 362 | if (!dominated_by_p (CDI_DOMINATORS, commondom, frombb)) |
18965703 | 363 | return false; |
b8698a0f | 364 | |
ec1e9f7c DB |
365 | /* It doesn't make sense to move to a dominator that post-dominates |
366 | frombb, because it means we've just moved it into a path that always | |
367 | executes if frombb executes, instead of reducing the number of | |
368 | executions . */ | |
369 | if (dominated_by_p (CDI_POST_DOMINATORS, frombb, commondom)) | |
370 | { | |
371 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
372 | fprintf (dump_file, "Not moving store, common dominator post-dominates from block.\n"); | |
18965703 | 373 | return false; |
ec1e9f7c DB |
374 | } |
375 | ||
376 | if (commondom == frombb || commondom->loop_depth > frombb->loop_depth) | |
18965703 | 377 | return false; |
ec1e9f7c DB |
378 | if (dump_file && (dump_flags & TDF_DETAILS)) |
379 | { | |
380 | fprintf (dump_file, "Common dominator of all uses is %d\n", | |
381 | commondom->index); | |
382 | } | |
b5b8b0ac | 383 | |
726a989a | 384 | *togsi = gsi_after_labels (commondom); |
b5b8b0ac | 385 | |
18965703 | 386 | return true; |
ec1e9f7c DB |
387 | } |
388 | ||
f430bae8 | 389 | use = USE_STMT (one_use); |
726a989a | 390 | if (gimple_code (use) != GIMPLE_PHI) |
ec1e9f7c | 391 | { |
726a989a | 392 | sinkbb = gimple_bb (use); |
ec1e9f7c DB |
393 | if (sinkbb == frombb || sinkbb->loop_depth > frombb->loop_depth |
394 | || sinkbb->loop_father != frombb->loop_father) | |
18965703 | 395 | return false; |
726a989a | 396 | |
791b59e3 WG |
397 | /* Move the expression to a post dominator can't reduce the number of |
398 | executions. */ | |
399 | if (dominated_by_p (CDI_POST_DOMINATORS, frombb, sinkbb)) | |
400 | return false; | |
401 | ||
726a989a | 402 | *togsi = gsi_for_stmt (use); |
b5b8b0ac | 403 | |
18965703 | 404 | return true; |
ec1e9f7c DB |
405 | } |
406 | ||
407 | /* Note that at this point, all uses must be in the same statement, so it | |
f47c96aa AM |
408 | doesn't matter which def op we choose, pick the first one. */ |
409 | FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS) | |
410 | break; | |
411 | ||
ec1e9f7c DB |
412 | sinkbb = find_bb_for_arg (use, def); |
413 | if (!sinkbb) | |
18965703 | 414 | return false; |
ec1e9f7c DB |
415 | |
416 | /* This will happen when you have | |
417 | a_3 = PHI <a_13, a_26> | |
ec1e9f7c | 418 | |
b8698a0f L |
419 | a_26 = VDEF <a_3> |
420 | ||
421 | If the use is a phi, and is in the same bb as the def, | |
ec1e9f7c DB |
422 | we can't sink it. */ |
423 | ||
726a989a | 424 | if (gimple_bb (use) == frombb) |
18965703 | 425 | return false; |
ec1e9f7c DB |
426 | if (sinkbb == frombb || sinkbb->loop_depth > frombb->loop_depth |
427 | || sinkbb->loop_father != frombb->loop_father) | |
18965703 ZD |
428 | return false; |
429 | ||
791b59e3 WG |
430 | /* Move the expression to a post dominator can't reduce the number of |
431 | executions. */ | |
432 | if (dominated_by_p (CDI_POST_DOMINATORS, frombb, sinkbb)) | |
433 | return false; | |
434 | ||
726a989a | 435 | *togsi = gsi_after_labels (sinkbb); |
ec1e9f7c | 436 | |
18965703 | 437 | return true; |
ec1e9f7c DB |
438 | } |
439 | ||
440 | /* Perform code sinking on BB */ | |
441 | ||
442 | static void | |
443 | sink_code_in_bb (basic_block bb) | |
444 | { | |
445 | basic_block son; | |
726a989a | 446 | gimple_stmt_iterator gsi; |
ec1e9f7c DB |
447 | edge_iterator ei; |
448 | edge e; | |
9a287593 | 449 | bool last = true; |
b8698a0f | 450 | |
ec1e9f7c DB |
451 | /* If this block doesn't dominate anything, there can't be any place to sink |
452 | the statements to. */ | |
453 | if (first_dom_son (CDI_DOMINATORS, bb) == NULL) | |
454 | goto earlyout; | |
455 | ||
456 | /* We can't move things across abnormal edges, so don't try. */ | |
457 | FOR_EACH_EDGE (e, ei, bb->succs) | |
458 | if (e->flags & EDGE_ABNORMAL) | |
459 | goto earlyout; | |
460 | ||
726a989a | 461 | for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi);) |
ec1e9f7c | 462 | { |
b8698a0f | 463 | gimple stmt = gsi_stmt (gsi); |
726a989a | 464 | gimple_stmt_iterator togsi; |
18965703 | 465 | |
726a989a | 466 | if (!statement_sink_location (stmt, bb, &togsi)) |
ec1e9f7c | 467 | { |
726a989a RB |
468 | if (!gsi_end_p (gsi)) |
469 | gsi_prev (&gsi); | |
9a287593 | 470 | last = false; |
ec1e9f7c | 471 | continue; |
b8698a0f | 472 | } |
ec1e9f7c DB |
473 | if (dump_file) |
474 | { | |
475 | fprintf (dump_file, "Sinking "); | |
726a989a | 476 | print_gimple_stmt (dump_file, stmt, 0, TDF_VOPS); |
ec1e9f7c | 477 | fprintf (dump_file, " from bb %d to bb %d\n", |
726a989a | 478 | bb->index, (gsi_bb (togsi))->index); |
ec1e9f7c | 479 | } |
b8698a0f | 480 | |
ec1e9f7c DB |
481 | /* If this is the end of the basic block, we need to insert at the end |
482 | of the basic block. */ | |
726a989a RB |
483 | if (gsi_end_p (togsi)) |
484 | gsi_move_to_bb_end (&gsi, gsi_bb (togsi)); | |
ec1e9f7c | 485 | else |
726a989a | 486 | gsi_move_before (&gsi, &togsi); |
ec1e9f7c DB |
487 | |
488 | sink_stats.sunk++; | |
9a287593 AO |
489 | |
490 | /* If we've just removed the last statement of the BB, the | |
726a989a | 491 | gsi_end_p() test below would fail, but gsi_prev() would have |
9a287593 AO |
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 | { | |
726a989a | 497 | gsi = gsi_last_bb (bb); |
9a287593 AO |
498 | continue; |
499 | } | |
500 | ||
501 | last = false; | |
726a989a RB |
502 | if (!gsi_end_p (gsi)) |
503 | gsi_prev (&gsi); | |
b8698a0f | 504 | |
ec1e9f7c DB |
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 | } | |
b8698a0f | 513 | } |
ec1e9f7c DB |
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 | |
b8698a0f | 521 | |
ec1e9f7c DB |
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 | { | |
598ec7bd | 554 | loop_optimizer_init (LOOPS_NORMAL); |
10d22567 | 555 | |
ec1e9f7c DB |
556 | connect_infinite_loops_to_exit (); |
557 | memset (&sink_stats, 0, sizeof (sink_stats)); | |
3b5ee6a4 RG |
558 | calculate_dominance_info (CDI_DOMINATORS); |
559 | calculate_dominance_info (CDI_POST_DOMINATORS); | |
b8698a0f | 560 | sink_code_in_bb (EXIT_BLOCK_PTR); |
01902653 | 561 | statistics_counter_event (cfun, "Sunk statements", sink_stats.sunk); |
ec1e9f7c DB |
562 | free_dominance_info (CDI_POST_DOMINATORS); |
563 | remove_fake_exit_edges (); | |
598ec7bd | 564 | loop_optimizer_finalize (); |
ec1e9f7c DB |
565 | } |
566 | ||
567 | /* Gate and execute functions for PRE. */ | |
568 | ||
c2924966 | 569 | static unsigned int |
ec1e9f7c DB |
570 | do_sink (void) |
571 | { | |
572 | execute_sink_code (); | |
c2924966 | 573 | return 0; |
ec1e9f7c DB |
574 | } |
575 | ||
576 | static bool | |
577 | gate_sink (void) | |
578 | { | |
579 | return flag_tree_sink != 0; | |
580 | } | |
581 | ||
8ddbbcae | 582 | struct gimple_opt_pass pass_sink_code = |
ec1e9f7c | 583 | { |
8ddbbcae JH |
584 | { |
585 | GIMPLE_PASS, | |
ec1e9f7c DB |
586 | "sink", /* name */ |
587 | gate_sink, /* gate */ | |
588 | do_sink, /* execute */ | |
589 | NULL, /* sub */ | |
590 | NULL, /* next */ | |
591 | 0, /* static_pass_number */ | |
592 | TV_TREE_SINK, /* tv_id */ | |
593 | PROP_no_crit_edges | PROP_cfg | |
4effdf02 | 594 | | PROP_ssa, /* properties_required */ |
ec1e9f7c DB |
595 | 0, /* properties_provided */ |
596 | 0, /* properties_destroyed */ | |
597 | 0, /* todo_flags_start */ | |
b8698a0f | 598 | TODO_update_ssa |
0bca51f0 DN |
599 | | TODO_dump_func |
600 | | TODO_ggc_collect | |
8ddbbcae JH |
601 | | TODO_verify_ssa /* todo_flags_finish */ |
602 | } | |
ec1e9f7c | 603 | }; |