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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 "tree.h" |
27 | #include "basic-block.h" | |
28 | #include "diagnostic.h" | |
29 | #include "tree-inline.h" | |
30 | #include "tree-flow.h" | |
726a989a | 31 | #include "gimple.h" |
ec1e9f7c DB |
32 | #include "tree-dump.h" |
33 | #include "timevar.h" | |
34 | #include "fibheap.h" | |
35 | #include "hashtab.h" | |
36 | #include "tree-iterator.h" | |
ec1e9f7c DB |
37 | #include "alloc-pool.h" |
38 | #include "tree-pass.h" | |
39 | #include "flags.h" | |
40 | #include "bitmap.h" | |
41 | #include "langhooks.h" | |
42 | #include "cfgloop.h" | |
43 | ||
44 | /* TODO: | |
45 | 1. Sinking store only using scalar promotion (IE without moving the RHS): | |
46 | ||
47 | *q = p; | |
48 | p = p + 1; | |
49 | if (something) | |
50 | *q = <not p>; | |
51 | else | |
52 | y = *q; | |
53 | ||
b8698a0f | 54 | |
ec1e9f7c DB |
55 | should become |
56 | sinktemp = p; | |
57 | p = p + 1; | |
58 | if (something) | |
59 | *q = <not p>; | |
60 | else | |
61 | { | |
62 | *q = sinktemp; | |
63 | y = *q | |
64 | } | |
65 | Store copy propagation will take care of the store elimination above. | |
b8698a0f | 66 | |
ec1e9f7c DB |
67 | |
68 | 2. Sinking using Partial Dead Code Elimination. */ | |
69 | ||
70 | ||
71 | static struct | |
b8698a0f | 72 | { |
6c6cfbfd | 73 | /* The number of statements sunk down the flowgraph by code sinking. */ |
ec1e9f7c | 74 | int sunk; |
b8698a0f | 75 | |
ec1e9f7c DB |
76 | } sink_stats; |
77 | ||
78 | ||
f652d14b | 79 | /* Given a PHI, and one of its arguments (DEF), find the edge for |
ec1e9f7c DB |
80 | that argument and return it. If the argument occurs twice in the PHI node, |
81 | we return NULL. */ | |
82 | ||
83 | static basic_block | |
726a989a | 84 | find_bb_for_arg (gimple phi, tree def) |
ec1e9f7c | 85 | { |
726a989a | 86 | size_t i; |
ec1e9f7c DB |
87 | bool foundone = false; |
88 | basic_block result = NULL; | |
726a989a | 89 | for (i = 0; i < gimple_phi_num_args (phi); i++) |
ec1e9f7c DB |
90 | if (PHI_ARG_DEF (phi, i) == def) |
91 | { | |
92 | if (foundone) | |
93 | return NULL; | |
94 | foundone = true; | |
726a989a | 95 | result = gimple_phi_arg_edge (phi, i)->src; |
ec1e9f7c DB |
96 | } |
97 | return result; | |
98 | } | |
99 | ||
100 | /* When the first immediate use is in a statement, then return true if all | |
101 | immediate uses in IMM are in the same statement. | |
102 | We could also do the case where the first immediate use is in a phi node, | |
103 | and all the other uses are in phis in the same basic block, but this | |
104 | requires some expensive checking later (you have to make sure no def/vdef | |
105 | in the statement occurs for multiple edges in the various phi nodes it's | |
6c6cfbfd | 106 | used in, so that you only have one place you can sink it to. */ |
ec1e9f7c DB |
107 | |
108 | static bool | |
726a989a | 109 | all_immediate_uses_same_place (gimple stmt) |
ec1e9f7c | 110 | { |
726a989a | 111 | gimple firstuse = NULL; |
f430bae8 AM |
112 | ssa_op_iter op_iter; |
113 | imm_use_iterator imm_iter; | |
114 | use_operand_p use_p; | |
115 | tree var; | |
ec1e9f7c | 116 | |
f430bae8 | 117 | FOR_EACH_SSA_TREE_OPERAND (var, stmt, op_iter, SSA_OP_ALL_DEFS) |
ec1e9f7c | 118 | { |
f430bae8 AM |
119 | FOR_EACH_IMM_USE_FAST (use_p, imm_iter, var) |
120 | { | |
b5b8b0ac AO |
121 | if (is_gimple_debug (USE_STMT (use_p))) |
122 | continue; | |
726a989a | 123 | if (firstuse == NULL) |
f430bae8 AM |
124 | firstuse = USE_STMT (use_p); |
125 | else | |
126 | if (firstuse != USE_STMT (use_p)) | |
127 | return false; | |
128 | } | |
ec1e9f7c | 129 | } |
f430bae8 | 130 | |
ec1e9f7c DB |
131 | return true; |
132 | } | |
133 | ||
38635499 | 134 | /* Some global stores don't necessarily have VDEF's of global variables, |
ec1e9f7c DB |
135 | but we still must avoid moving them around. */ |
136 | ||
137 | bool | |
726a989a | 138 | is_hidden_global_store (gimple stmt) |
ec1e9f7c | 139 | { |
ec1e9f7c | 140 | /* Check virtual definitions. If we get here, the only virtual |
726a989a | 141 | definitions we should see are those generated by assignment or call |
ec1e9f7c | 142 | statements. */ |
5006671f | 143 | if (gimple_vdef (stmt)) |
ec1e9f7c DB |
144 | { |
145 | tree lhs; | |
146 | ||
726a989a | 147 | gcc_assert (is_gimple_assign (stmt) || is_gimple_call (stmt)); |
ec1e9f7c DB |
148 | |
149 | /* Note that we must not check the individual virtual operands | |
150 | here. In particular, if this is an aliased store, we could | |
151 | end up with something like the following (SSA notation | |
152 | redacted for brevity): | |
153 | ||
154 | foo (int *p, int i) | |
155 | { | |
156 | int x; | |
157 | p_1 = (i_2 > 3) ? &x : p; | |
158 | ||
38635499 | 159 | # x_4 = VDEF <x_3> |
ec1e9f7c DB |
160 | *p_1 = 5; |
161 | ||
162 | return 2; | |
163 | } | |
164 | ||
165 | Notice that the store to '*p_1' should be preserved, if we | |
166 | were to check the virtual definitions in that store, we would | |
167 | not mark it needed. This is because 'x' is not a global | |
168 | variable. | |
169 | ||
170 | Therefore, we check the base address of the LHS. If the | |
18cd8a03 | 171 | address is a pointer, we check if its name tag or symbol tag is |
ec1e9f7c DB |
172 | a global variable. Otherwise, we check if the base variable |
173 | is a global. */ | |
726a989a RB |
174 | lhs = gimple_get_lhs (stmt); |
175 | ||
ec1e9f7c DB |
176 | if (REFERENCE_CLASS_P (lhs)) |
177 | lhs = get_base_address (lhs); | |
178 | ||
179 | if (lhs == NULL_TREE) | |
180 | { | |
181 | /* If LHS is NULL, it means that we couldn't get the base | |
182 | address of the reference. In which case, we should not | |
183 | move this store. */ | |
184 | return true; | |
185 | } | |
186 | else if (DECL_P (lhs)) | |
187 | { | |
188 | /* If the store is to a global symbol, we need to keep it. */ | |
189 | if (is_global_var (lhs)) | |
190 | return true; | |
191 | ||
192 | } | |
193 | else if (INDIRECT_REF_P (lhs)) | |
5006671f | 194 | return ptr_deref_may_alias_global_p (TREE_OPERAND (lhs, 0)); |
ec1e9f7c DB |
195 | else |
196 | gcc_unreachable (); | |
197 | } | |
38635499 | 198 | |
ec1e9f7c DB |
199 | return false; |
200 | } | |
201 | ||
202 | /* Find the nearest common dominator of all of the immediate uses in IMM. */ | |
203 | ||
204 | static basic_block | |
b5b8b0ac | 205 | nearest_common_dominator_of_uses (gimple stmt, bool *debug_stmts) |
b8698a0f | 206 | { |
ec1e9f7c DB |
207 | bitmap blocks = BITMAP_ALLOC (NULL); |
208 | basic_block commondom; | |
ec1e9f7c DB |
209 | unsigned int j; |
210 | bitmap_iterator bi; | |
f430bae8 AM |
211 | ssa_op_iter op_iter; |
212 | imm_use_iterator imm_iter; | |
213 | use_operand_p use_p; | |
214 | tree var; | |
215 | ||
ec1e9f7c | 216 | bitmap_clear (blocks); |
f430bae8 | 217 | FOR_EACH_SSA_TREE_OPERAND (var, stmt, op_iter, SSA_OP_ALL_DEFS) |
ec1e9f7c | 218 | { |
f430bae8 AM |
219 | FOR_EACH_IMM_USE_FAST (use_p, imm_iter, var) |
220 | { | |
726a989a | 221 | gimple usestmt = USE_STMT (use_p); |
f430bae8 | 222 | basic_block useblock; |
000b62dc | 223 | |
726a989a | 224 | if (gimple_code (usestmt) == GIMPLE_PHI) |
f430bae8 | 225 | { |
55b12f0d | 226 | int idx = PHI_ARG_INDEX_FROM_USE (use_p); |
ab798313 | 227 | |
726a989a | 228 | useblock = gimple_phi_arg_edge (usestmt, idx)->src; |
f430bae8 | 229 | } |
b5b8b0ac AO |
230 | else if (is_gimple_debug (usestmt)) |
231 | { | |
232 | *debug_stmts = true; | |
233 | continue; | |
234 | } | |
f430bae8 | 235 | else |
ec1e9f7c | 236 | { |
726a989a | 237 | useblock = gimple_bb (usestmt); |
000b62dc | 238 | } |
f430bae8 | 239 | |
000b62dc KH |
240 | /* Short circuit. Nothing dominates the entry block. */ |
241 | if (useblock == ENTRY_BLOCK_PTR) | |
242 | { | |
243 | BITMAP_FREE (blocks); | |
244 | return NULL; | |
ec1e9f7c | 245 | } |
000b62dc | 246 | bitmap_set_bit (blocks, useblock->index); |
ec1e9f7c | 247 | } |
ec1e9f7c DB |
248 | } |
249 | commondom = BASIC_BLOCK (bitmap_first_set_bit (blocks)); | |
250 | EXECUTE_IF_SET_IN_BITMAP (blocks, 0, j, bi) | |
b8698a0f | 251 | commondom = nearest_common_dominator (CDI_DOMINATORS, commondom, |
ec1e9f7c DB |
252 | BASIC_BLOCK (j)); |
253 | BITMAP_FREE (blocks); | |
254 | return commondom; | |
255 | } | |
256 | ||
b8698a0f | 257 | /* Given a statement (STMT) and the basic block it is currently in (FROMBB), |
ec1e9f7c | 258 | determine the location to sink the statement to, if any. |
726a989a RB |
259 | Returns true if there is such location; in that case, TOGSI points to the |
260 | statement before that STMT should be moved. */ | |
ec1e9f7c | 261 | |
18965703 | 262 | static bool |
726a989a RB |
263 | statement_sink_location (gimple stmt, basic_block frombb, |
264 | gimple_stmt_iterator *togsi) | |
ec1e9f7c | 265 | { |
726a989a RB |
266 | gimple use; |
267 | tree def; | |
f430bae8 | 268 | use_operand_p one_use = NULL_USE_OPERAND_P; |
ec1e9f7c DB |
269 | basic_block sinkbb; |
270 | use_operand_p use_p; | |
271 | def_operand_p def_p; | |
272 | ssa_op_iter iter; | |
f430bae8 AM |
273 | imm_use_iterator imm_iter; |
274 | ||
275 | FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS) | |
276 | { | |
277 | FOR_EACH_IMM_USE_FAST (one_use, imm_iter, def) | |
278 | { | |
b5b8b0ac AO |
279 | if (is_gimple_debug (USE_STMT (one_use))) |
280 | continue; | |
281 | ||
f430bae8 AM |
282 | break; |
283 | } | |
284 | if (one_use != NULL_USE_OPERAND_P) | |
285 | break; | |
286 | } | |
ec1e9f7c | 287 | |
f430bae8 AM |
288 | /* Return if there are no immediate uses of this stmt. */ |
289 | if (one_use == NULL_USE_OPERAND_P) | |
18965703 | 290 | return false; |
ec1e9f7c | 291 | |
726a989a | 292 | if (gimple_code (stmt) != GIMPLE_ASSIGN) |
18965703 | 293 | return false; |
ec1e9f7c DB |
294 | |
295 | /* There are a few classes of things we can't or don't move, some because we | |
296 | don't have code to handle it, some because it's not profitable and some | |
b8698a0f L |
297 | because it's not legal. |
298 | ||
ec1e9f7c DB |
299 | We can't sink things that may be global stores, at least not without |
300 | calculating a lot more information, because we may cause it to no longer | |
301 | be seen by an external routine that needs it depending on where it gets | |
b8698a0f L |
302 | moved to. |
303 | ||
ec1e9f7c DB |
304 | We don't want to sink loads from memory. |
305 | ||
306 | We can't sink statements that end basic blocks without splitting the | |
307 | incoming edge for the sink location to place it there. | |
308 | ||
b8698a0f | 309 | We can't sink statements that have volatile operands. |
ec1e9f7c DB |
310 | |
311 | We don't want to sink dead code, so anything with 0 immediate uses is not | |
fc3103e7 JJ |
312 | sunk. |
313 | ||
314 | Don't sink BLKmode assignments if current function has any local explicit | |
315 | register variables, as BLKmode assignments may involve memcpy or memset | |
316 | calls or, on some targets, inline expansion thereof that sometimes need | |
317 | to use specific hard registers. | |
ec1e9f7c DB |
318 | |
319 | */ | |
f47c96aa | 320 | if (stmt_ends_bb_p (stmt) |
726a989a | 321 | || gimple_has_side_effects (stmt) |
ec1e9f7c | 322 | || is_hidden_global_store (stmt) |
726a989a | 323 | || gimple_has_volatile_ops (stmt) |
5006671f | 324 | || gimple_vuse (stmt) |
fc3103e7 JJ |
325 | || (cfun->has_local_explicit_reg_vars |
326 | && TYPE_MODE (TREE_TYPE (gimple_assign_lhs (stmt))) == BLKmode)) | |
18965703 | 327 | return false; |
b8698a0f | 328 | |
ec1e9f7c DB |
329 | FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_ALL_DEFS) |
330 | { | |
331 | tree def = DEF_FROM_PTR (def_p); | |
332 | if (is_global_var (SSA_NAME_VAR (def)) | |
333 | || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def)) | |
18965703 | 334 | return false; |
ec1e9f7c | 335 | } |
b8698a0f | 336 | |
ec1e9f7c DB |
337 | FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES) |
338 | { | |
339 | tree use = USE_FROM_PTR (use_p); | |
340 | if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (use)) | |
18965703 | 341 | return false; |
ec1e9f7c | 342 | } |
b8698a0f | 343 | |
ec1e9f7c DB |
344 | /* If all the immediate uses are not in the same place, find the nearest |
345 | common dominator of all the immediate uses. For PHI nodes, we have to | |
346 | find the nearest common dominator of all of the predecessor blocks, since | |
347 | that is where insertion would have to take place. */ | |
f430bae8 | 348 | if (!all_immediate_uses_same_place (stmt)) |
ec1e9f7c | 349 | { |
b5b8b0ac AO |
350 | bool debug_stmts = false; |
351 | basic_block commondom = nearest_common_dominator_of_uses (stmt, | |
352 | &debug_stmts); | |
b8698a0f | 353 | |
ec1e9f7c | 354 | if (commondom == frombb) |
18965703 | 355 | return false; |
ec1e9f7c DB |
356 | |
357 | /* Our common dominator has to be dominated by frombb in order to be a | |
358 | trivially safe place to put this statement, since it has multiple | |
b8698a0f | 359 | uses. */ |
ec1e9f7c | 360 | if (!dominated_by_p (CDI_DOMINATORS, commondom, frombb)) |
18965703 | 361 | return false; |
b8698a0f | 362 | |
ec1e9f7c DB |
363 | /* It doesn't make sense to move to a dominator that post-dominates |
364 | frombb, because it means we've just moved it into a path that always | |
365 | executes if frombb executes, instead of reducing the number of | |
366 | executions . */ | |
367 | if (dominated_by_p (CDI_POST_DOMINATORS, frombb, commondom)) | |
368 | { | |
369 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
370 | fprintf (dump_file, "Not moving store, common dominator post-dominates from block.\n"); | |
18965703 | 371 | return false; |
ec1e9f7c DB |
372 | } |
373 | ||
374 | if (commondom == frombb || commondom->loop_depth > frombb->loop_depth) | |
18965703 | 375 | return false; |
ec1e9f7c DB |
376 | if (dump_file && (dump_flags & TDF_DETAILS)) |
377 | { | |
378 | fprintf (dump_file, "Common dominator of all uses is %d\n", | |
379 | commondom->index); | |
380 | } | |
b5b8b0ac | 381 | |
726a989a | 382 | *togsi = gsi_after_labels (commondom); |
b5b8b0ac | 383 | |
18965703 | 384 | return true; |
ec1e9f7c DB |
385 | } |
386 | ||
f430bae8 | 387 | use = USE_STMT (one_use); |
726a989a | 388 | if (gimple_code (use) != GIMPLE_PHI) |
ec1e9f7c | 389 | { |
726a989a | 390 | sinkbb = gimple_bb (use); |
ec1e9f7c DB |
391 | if (sinkbb == frombb || sinkbb->loop_depth > frombb->loop_depth |
392 | || sinkbb->loop_father != frombb->loop_father) | |
18965703 | 393 | return false; |
726a989a | 394 | |
791b59e3 WG |
395 | /* Move the expression to a post dominator can't reduce the number of |
396 | executions. */ | |
397 | if (dominated_by_p (CDI_POST_DOMINATORS, frombb, sinkbb)) | |
398 | return false; | |
399 | ||
726a989a | 400 | *togsi = gsi_for_stmt (use); |
b5b8b0ac | 401 | |
18965703 | 402 | return true; |
ec1e9f7c DB |
403 | } |
404 | ||
405 | /* Note that at this point, all uses must be in the same statement, so it | |
f47c96aa AM |
406 | doesn't matter which def op we choose, pick the first one. */ |
407 | FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS) | |
408 | break; | |
409 | ||
ec1e9f7c DB |
410 | sinkbb = find_bb_for_arg (use, def); |
411 | if (!sinkbb) | |
18965703 | 412 | return false; |
ec1e9f7c DB |
413 | |
414 | /* This will happen when you have | |
415 | a_3 = PHI <a_13, a_26> | |
ec1e9f7c | 416 | |
b8698a0f L |
417 | a_26 = VDEF <a_3> |
418 | ||
419 | If the use is a phi, and is in the same bb as the def, | |
ec1e9f7c DB |
420 | we can't sink it. */ |
421 | ||
726a989a | 422 | if (gimple_bb (use) == frombb) |
18965703 | 423 | return false; |
ec1e9f7c DB |
424 | if (sinkbb == frombb || sinkbb->loop_depth > frombb->loop_depth |
425 | || sinkbb->loop_father != frombb->loop_father) | |
18965703 ZD |
426 | return false; |
427 | ||
791b59e3 WG |
428 | /* Move the expression to a post dominator can't reduce the number of |
429 | executions. */ | |
430 | if (dominated_by_p (CDI_POST_DOMINATORS, frombb, sinkbb)) | |
431 | return false; | |
432 | ||
726a989a | 433 | *togsi = gsi_after_labels (sinkbb); |
ec1e9f7c | 434 | |
18965703 | 435 | return true; |
ec1e9f7c DB |
436 | } |
437 | ||
438 | /* Perform code sinking on BB */ | |
439 | ||
440 | static void | |
441 | sink_code_in_bb (basic_block bb) | |
442 | { | |
443 | basic_block son; | |
726a989a | 444 | gimple_stmt_iterator gsi; |
ec1e9f7c DB |
445 | edge_iterator ei; |
446 | edge e; | |
9a287593 | 447 | bool last = true; |
b8698a0f | 448 | |
ec1e9f7c DB |
449 | /* If this block doesn't dominate anything, there can't be any place to sink |
450 | the statements to. */ | |
451 | if (first_dom_son (CDI_DOMINATORS, bb) == NULL) | |
452 | goto earlyout; | |
453 | ||
454 | /* We can't move things across abnormal edges, so don't try. */ | |
455 | FOR_EACH_EDGE (e, ei, bb->succs) | |
456 | if (e->flags & EDGE_ABNORMAL) | |
457 | goto earlyout; | |
458 | ||
726a989a | 459 | for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi);) |
ec1e9f7c | 460 | { |
b8698a0f | 461 | gimple stmt = gsi_stmt (gsi); |
726a989a | 462 | gimple_stmt_iterator togsi; |
18965703 | 463 | |
726a989a | 464 | if (!statement_sink_location (stmt, bb, &togsi)) |
ec1e9f7c | 465 | { |
726a989a RB |
466 | if (!gsi_end_p (gsi)) |
467 | gsi_prev (&gsi); | |
9a287593 | 468 | last = false; |
ec1e9f7c | 469 | continue; |
b8698a0f | 470 | } |
ec1e9f7c DB |
471 | if (dump_file) |
472 | { | |
473 | fprintf (dump_file, "Sinking "); | |
726a989a | 474 | print_gimple_stmt (dump_file, stmt, 0, TDF_VOPS); |
ec1e9f7c | 475 | fprintf (dump_file, " from bb %d to bb %d\n", |
726a989a | 476 | bb->index, (gsi_bb (togsi))->index); |
ec1e9f7c | 477 | } |
b8698a0f | 478 | |
ec1e9f7c DB |
479 | /* If this is the end of the basic block, we need to insert at the end |
480 | of the basic block. */ | |
726a989a RB |
481 | if (gsi_end_p (togsi)) |
482 | gsi_move_to_bb_end (&gsi, gsi_bb (togsi)); | |
ec1e9f7c | 483 | else |
726a989a | 484 | gsi_move_before (&gsi, &togsi); |
ec1e9f7c DB |
485 | |
486 | sink_stats.sunk++; | |
9a287593 AO |
487 | |
488 | /* If we've just removed the last statement of the BB, the | |
726a989a | 489 | gsi_end_p() test below would fail, but gsi_prev() would have |
9a287593 AO |
490 | succeeded, and we want it to succeed. So we keep track of |
491 | whether we're at the last statement and pick up the new last | |
492 | statement. */ | |
493 | if (last) | |
494 | { | |
726a989a | 495 | gsi = gsi_last_bb (bb); |
9a287593 AO |
496 | continue; |
497 | } | |
498 | ||
499 | last = false; | |
726a989a RB |
500 | if (!gsi_end_p (gsi)) |
501 | gsi_prev (&gsi); | |
b8698a0f | 502 | |
ec1e9f7c DB |
503 | } |
504 | earlyout: | |
505 | for (son = first_dom_son (CDI_POST_DOMINATORS, bb); | |
506 | son; | |
507 | son = next_dom_son (CDI_POST_DOMINATORS, son)) | |
508 | { | |
509 | sink_code_in_bb (son); | |
510 | } | |
b8698a0f | 511 | } |
ec1e9f7c DB |
512 | |
513 | /* Perform code sinking. | |
514 | This moves code down the flowgraph when we know it would be | |
515 | profitable to do so, or it wouldn't increase the number of | |
516 | executions of the statement. | |
517 | ||
518 | IE given | |
b8698a0f | 519 | |
ec1e9f7c DB |
520 | a_1 = b + c; |
521 | if (<something>) | |
522 | { | |
523 | } | |
524 | else | |
525 | { | |
526 | foo (&b, &c); | |
527 | a_5 = b + c; | |
528 | } | |
529 | a_6 = PHI (a_5, a_1); | |
530 | USE a_6. | |
531 | ||
532 | we'll transform this into: | |
533 | ||
534 | if (<something>) | |
535 | { | |
536 | a_1 = b + c; | |
537 | } | |
538 | else | |
539 | { | |
540 | foo (&b, &c); | |
541 | a_5 = b + c; | |
542 | } | |
543 | a_6 = PHI (a_5, a_1); | |
544 | USE a_6. | |
545 | ||
546 | Note that this reduces the number of computations of a = b + c to 1 | |
547 | when we take the else edge, instead of 2. | |
548 | */ | |
549 | static void | |
550 | execute_sink_code (void) | |
551 | { | |
598ec7bd | 552 | loop_optimizer_init (LOOPS_NORMAL); |
10d22567 | 553 | |
ec1e9f7c DB |
554 | connect_infinite_loops_to_exit (); |
555 | memset (&sink_stats, 0, sizeof (sink_stats)); | |
3b5ee6a4 RG |
556 | calculate_dominance_info (CDI_DOMINATORS); |
557 | calculate_dominance_info (CDI_POST_DOMINATORS); | |
b8698a0f | 558 | sink_code_in_bb (EXIT_BLOCK_PTR); |
01902653 | 559 | statistics_counter_event (cfun, "Sunk statements", sink_stats.sunk); |
ec1e9f7c DB |
560 | free_dominance_info (CDI_POST_DOMINATORS); |
561 | remove_fake_exit_edges (); | |
598ec7bd | 562 | loop_optimizer_finalize (); |
ec1e9f7c DB |
563 | } |
564 | ||
565 | /* Gate and execute functions for PRE. */ | |
566 | ||
c2924966 | 567 | static unsigned int |
ec1e9f7c DB |
568 | do_sink (void) |
569 | { | |
570 | execute_sink_code (); | |
c2924966 | 571 | return 0; |
ec1e9f7c DB |
572 | } |
573 | ||
574 | static bool | |
575 | gate_sink (void) | |
576 | { | |
577 | return flag_tree_sink != 0; | |
578 | } | |
579 | ||
8ddbbcae | 580 | struct gimple_opt_pass pass_sink_code = |
ec1e9f7c | 581 | { |
8ddbbcae JH |
582 | { |
583 | GIMPLE_PASS, | |
ec1e9f7c DB |
584 | "sink", /* name */ |
585 | gate_sink, /* gate */ | |
586 | do_sink, /* execute */ | |
587 | NULL, /* sub */ | |
588 | NULL, /* next */ | |
589 | 0, /* static_pass_number */ | |
590 | TV_TREE_SINK, /* tv_id */ | |
591 | PROP_no_crit_edges | PROP_cfg | |
4effdf02 | 592 | | PROP_ssa, /* properties_required */ |
ec1e9f7c DB |
593 | 0, /* properties_provided */ |
594 | 0, /* properties_destroyed */ | |
595 | 0, /* todo_flags_start */ | |
b8698a0f | 596 | TODO_update_ssa |
0bca51f0 DN |
597 | | TODO_dump_func |
598 | | TODO_ggc_collect | |
8ddbbcae JH |
599 | | TODO_verify_ssa /* todo_flags_finish */ |
600 | } | |
ec1e9f7c | 601 | }; |