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92fc4a2f | 1 | /* Loop unswitching. |
cbe34bb5 | 2 | Copyright (C) 2004-2017 Free Software Foundation, Inc. |
b8698a0f | 3 | |
92fc4a2f | 4 | This file is part of GCC. |
b8698a0f | 5 | |
92fc4a2f ZD |
6 | GCC is free software; you can redistribute it and/or modify it |
7 | under the terms of the GNU General Public License as published by the | |
9dcd6f09 | 8 | Free Software Foundation; either version 3, or (at your option) any |
92fc4a2f | 9 | later version. |
b8698a0f | 10 | |
92fc4a2f ZD |
11 | GCC is distributed in the hope that it will be useful, but WITHOUT |
12 | ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
13 | FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
14 | for more details. | |
b8698a0f | 15 | |
92fc4a2f | 16 | You should have received a copy of the GNU General Public License |
9dcd6f09 NC |
17 | along with GCC; see the file COPYING3. If not see |
18 | <http://www.gnu.org/licenses/>. */ | |
92fc4a2f ZD |
19 | |
20 | #include "config.h" | |
21 | #include "system.h" | |
22 | #include "coretypes.h" | |
c7131fb2 | 23 | #include "backend.h" |
92fc4a2f | 24 | #include "tree.h" |
c7131fb2 | 25 | #include "gimple.h" |
957060b5 | 26 | #include "tree-pass.h" |
c7131fb2 | 27 | #include "ssa.h" |
40e23961 | 28 | #include "fold-const.h" |
45b0be94 | 29 | #include "gimplify.h" |
442b4905 | 30 | #include "tree-cfg.h" |
f813d16e | 31 | #include "tree-ssa.h" |
e28030cf | 32 | #include "tree-ssa-loop-niter.h" |
442b4905 AM |
33 | #include "tree-ssa-loop.h" |
34 | #include "tree-into-ssa.h" | |
92fc4a2f | 35 | #include "cfgloop.h" |
92fc4a2f | 36 | #include "params.h" |
7f9bc51b | 37 | #include "tree-inline.h" |
a01e93f1 YR |
38 | #include "gimple-iterator.h" |
39 | #include "cfghooks.h" | |
622d8b69 | 40 | #include "tree-ssa-loop-manip.h" |
92fc4a2f ZD |
41 | |
42 | /* This file implements the loop unswitching, i.e. transformation of loops like | |
43 | ||
44 | while (A) | |
45 | { | |
46 | if (inv) | |
47 | B; | |
48 | ||
49 | X; | |
50 | ||
51 | if (!inv) | |
52 | C; | |
53 | } | |
54 | ||
55 | where inv is the loop invariant, into | |
56 | ||
57 | if (inv) | |
58 | { | |
59 | while (A) | |
60 | { | |
61 | B; | |
62 | X; | |
63 | } | |
64 | } | |
65 | else | |
66 | { | |
67 | while (A) | |
68 | { | |
69 | X; | |
70 | C; | |
71 | } | |
72 | } | |
73 | ||
74 | Inv is considered invariant iff the values it compares are both invariant; | |
75 | tree-ssa-loop-im.c ensures that all the suitable conditions are in this | |
76 | shape. */ | |
77 | ||
d73be268 ZD |
78 | static struct loop *tree_unswitch_loop (struct loop *, basic_block, tree); |
79 | static bool tree_unswitch_single_loop (struct loop *, int); | |
92fc4a2f | 80 | static tree tree_may_unswitch_on (basic_block, struct loop *); |
a01e93f1 YR |
81 | static bool tree_unswitch_outer_loop (struct loop *); |
82 | static edge find_loop_guard (struct loop *); | |
83 | static bool empty_bb_without_guard_p (struct loop *, basic_block); | |
84 | static bool used_outside_loop_p (struct loop *, tree); | |
85 | static void hoist_guard (struct loop *, edge); | |
86 | static bool check_exit_phi (struct loop *); | |
87 | static tree get_vop_from_header (struct loop *); | |
92fc4a2f | 88 | |
d73be268 | 89 | /* Main entry point. Perform loop unswitching on all suitable loops. */ |
92fc4a2f | 90 | |
c7f965b6 | 91 | unsigned int |
d73be268 | 92 | tree_ssa_unswitch_loops (void) |
92fc4a2f | 93 | { |
92fc4a2f ZD |
94 | struct loop *loop; |
95 | bool changed = false; | |
96 | ||
a01e93f1 YR |
97 | /* Go through all loops starting from innermost. */ |
98 | FOR_EACH_LOOP (loop, LI_FROM_INNERMOST) | |
92fc4a2f | 99 | { |
a01e93f1 YR |
100 | if (!loop->inner) |
101 | /* Unswitch innermost loop. */ | |
102 | changed |= tree_unswitch_single_loop (loop, 0); | |
103 | else | |
104 | changed |= tree_unswitch_outer_loop (loop); | |
92fc4a2f ZD |
105 | } |
106 | ||
92fc4a2f | 107 | if (changed) |
c7f965b6 AP |
108 | return TODO_cleanup_cfg; |
109 | return 0; | |
92fc4a2f ZD |
110 | } |
111 | ||
8b670f93 AH |
112 | /* Return TRUE if an SSA_NAME maybe undefined and is therefore |
113 | unsuitable for unswitching. STMT is the statement we are | |
114 | considering for unswitching and LOOP is the loop it appears in. */ | |
115 | ||
116 | static bool | |
117 | is_maybe_undefined (const tree name, gimple *stmt, struct loop *loop) | |
118 | { | |
119 | /* The loop header is the only block we can trivially determine that | |
120 | will always be executed. If the comparison is in the loop | |
121 | header, we know it's OK to unswitch on it. */ | |
122 | if (gimple_bb (stmt) == loop->header) | |
123 | return false; | |
124 | ||
125 | auto_bitmap visited_ssa; | |
126 | auto_vec<tree> worklist; | |
127 | worklist.safe_push (name); | |
128 | bitmap_set_bit (visited_ssa, SSA_NAME_VERSION (name)); | |
129 | while (!worklist.is_empty ()) | |
130 | { | |
131 | tree t = worklist.pop (); | |
132 | ||
133 | /* If it's obviously undefined, avoid further computations. */ | |
134 | if (ssa_undefined_value_p (t, true)) | |
135 | return true; | |
136 | ||
c6b0d21d | 137 | if (ssa_defined_default_def_p (t)) |
8b670f93 AH |
138 | continue; |
139 | ||
140 | gimple *def = SSA_NAME_DEF_STMT (t); | |
141 | ||
142 | /* Check that all the PHI args are fully defined. */ | |
143 | if (gphi *phi = dyn_cast <gphi *> (def)) | |
144 | { | |
145 | for (unsigned i = 0; i < gimple_phi_num_args (phi); ++i) | |
146 | { | |
147 | tree t = gimple_phi_arg_def (phi, i); | |
148 | /* If an SSA has already been seen, it may be a loop, | |
149 | but we can continue and ignore this use. Otherwise, | |
150 | add the SSA_NAME to the queue and visit it later. */ | |
151 | if (TREE_CODE (t) == SSA_NAME | |
152 | && bitmap_set_bit (visited_ssa, SSA_NAME_VERSION (t))) | |
153 | worklist.safe_push (t); | |
154 | } | |
155 | continue; | |
156 | } | |
157 | ||
158 | /* Uses in stmts always executed when the region header executes | |
159 | are fine. */ | |
160 | if (dominated_by_p (CDI_DOMINATORS, loop->header, gimple_bb (def))) | |
161 | continue; | |
162 | ||
163 | /* Handle calls and memory loads conservatively. */ | |
164 | if (!is_gimple_assign (def) | |
165 | || (gimple_assign_single_p (def) | |
166 | && gimple_vuse (def))) | |
167 | return true; | |
168 | ||
169 | /* Check that any SSA names used to define NAME are also fully | |
170 | defined. */ | |
171 | use_operand_p use_p; | |
172 | ssa_op_iter iter; | |
173 | FOR_EACH_SSA_USE_OPERAND (use_p, def, iter, SSA_OP_USE) | |
174 | { | |
175 | tree t = USE_FROM_PTR (use_p); | |
176 | /* If an SSA has already been seen, it may be a loop, | |
177 | but we can continue and ignore this use. Otherwise, | |
178 | add the SSA_NAME to the queue and visit it later. */ | |
179 | if (bitmap_set_bit (visited_ssa, SSA_NAME_VERSION (t))) | |
180 | worklist.safe_push (t); | |
181 | } | |
182 | } | |
183 | return false; | |
184 | } | |
185 | ||
92fc4a2f ZD |
186 | /* Checks whether we can unswitch LOOP on condition at end of BB -- one of its |
187 | basic blocks (for what it means see comments below). */ | |
188 | ||
189 | static tree | |
190 | tree_may_unswitch_on (basic_block bb, struct loop *loop) | |
191 | { | |
355fe088 | 192 | gimple *last, *def; |
538dd0b7 | 193 | gcond *stmt; |
726a989a | 194 | tree cond, use; |
92fc4a2f | 195 | basic_block def_bb; |
f47c96aa | 196 | ssa_op_iter iter; |
92fc4a2f ZD |
197 | |
198 | /* BB must end in a simple conditional jump. */ | |
538dd0b7 DM |
199 | last = last_stmt (bb); |
200 | if (!last || gimple_code (last) != GIMPLE_COND) | |
92fc4a2f | 201 | return NULL_TREE; |
538dd0b7 | 202 | stmt = as_a <gcond *> (last); |
92fc4a2f | 203 | |
7a2eceff JJ |
204 | /* To keep the things simple, we do not directly remove the conditions, |
205 | but just replace tests with 0 != 0 resp. 1 != 0. Prevent the infinite | |
206 | loop where we would unswitch again on such a condition. */ | |
207 | if (gimple_cond_true_p (stmt) || gimple_cond_false_p (stmt)) | |
208 | return NULL_TREE; | |
209 | ||
92fc4a2f | 210 | /* Condition must be invariant. */ |
f47c96aa | 211 | FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE) |
92fc4a2f | 212 | { |
f47c96aa | 213 | def = SSA_NAME_DEF_STMT (use); |
726a989a | 214 | def_bb = gimple_bb (def); |
92fc4a2f ZD |
215 | if (def_bb |
216 | && flow_bb_inside_loop_p (loop, def_bb)) | |
217 | return NULL_TREE; | |
8b670f93 AH |
218 | /* Unswitching on undefined values would introduce undefined |
219 | behavior that the original program might never exercise. */ | |
220 | if (is_maybe_undefined (use, stmt, loop)) | |
221 | return NULL_TREE; | |
92fc4a2f ZD |
222 | } |
223 | ||
12aea97a RG |
224 | cond = build2 (gimple_cond_code (stmt), boolean_type_node, |
225 | gimple_cond_lhs (stmt), gimple_cond_rhs (stmt)); | |
726a989a | 226 | |
92fc4a2f ZD |
227 | return cond; |
228 | } | |
229 | ||
230 | /* Simplifies COND using checks in front of the entry of the LOOP. Just very | |
231 | simplish (sufficient to prevent us from duplicating loop in unswitching | |
e75220c8 | 232 | unnecessarily). */ |
92fc4a2f ZD |
233 | |
234 | static tree | |
235 | simplify_using_entry_checks (struct loop *loop, tree cond) | |
236 | { | |
237 | edge e = loop_preheader_edge (loop); | |
355fe088 | 238 | gimple *stmt; |
92fc4a2f ZD |
239 | |
240 | while (1) | |
241 | { | |
242 | stmt = last_stmt (e->src); | |
243 | if (stmt | |
726a989a RB |
244 | && gimple_code (stmt) == GIMPLE_COND |
245 | && gimple_cond_code (stmt) == TREE_CODE (cond) | |
246 | && operand_equal_p (gimple_cond_lhs (stmt), | |
247 | TREE_OPERAND (cond, 0), 0) | |
248 | && operand_equal_p (gimple_cond_rhs (stmt), | |
249 | TREE_OPERAND (cond, 1), 0)) | |
92fc4a2f ZD |
250 | return (e->flags & EDGE_TRUE_VALUE |
251 | ? boolean_true_node | |
252 | : boolean_false_node); | |
253 | ||
c5cbcccf | 254 | if (!single_pred_p (e->src)) |
92fc4a2f ZD |
255 | return cond; |
256 | ||
c5cbcccf | 257 | e = single_pred_edge (e->src); |
fefa31b5 | 258 | if (e->src == ENTRY_BLOCK_PTR_FOR_FN (cfun)) |
92fc4a2f ZD |
259 | return cond; |
260 | } | |
261 | } | |
262 | ||
263 | /* Unswitch single LOOP. NUM is number of unswitchings done; we do not allow | |
264 | it to grow too much, it is too easy to create example on that the code would | |
265 | grow exponentially. */ | |
266 | ||
267 | static bool | |
d73be268 | 268 | tree_unswitch_single_loop (struct loop *loop, int num) |
92fc4a2f ZD |
269 | { |
270 | basic_block *bbs; | |
271 | struct loop *nloop; | |
7a2eceff | 272 | unsigned i, found; |
726a989a | 273 | tree cond = NULL_TREE; |
355fe088 | 274 | gimple *stmt; |
92fc4a2f | 275 | bool changed = false; |
a01e93f1 YR |
276 | HOST_WIDE_INT iterations; |
277 | ||
278 | /* Perform initial tests if unswitch is eligible. */ | |
279 | if (num == 0) | |
280 | { | |
281 | /* Do not unswitch in cold regions. */ | |
282 | if (optimize_loop_for_size_p (loop)) | |
283 | { | |
284 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
285 | fprintf (dump_file, ";; Not unswitching cold loops\n"); | |
286 | return false; | |
287 | } | |
288 | ||
289 | /* The loop should not be too large, to limit code growth. */ | |
290 | if (tree_num_loop_insns (loop, &eni_size_weights) | |
291 | > (unsigned) PARAM_VALUE (PARAM_MAX_UNSWITCH_INSNS)) | |
292 | { | |
293 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
294 | fprintf (dump_file, ";; Not unswitching, loop too big\n"); | |
295 | return false; | |
296 | } | |
297 | ||
298 | /* If the loop is not expected to iterate, there is no need | |
299 | for unswitching. */ | |
300 | iterations = estimated_loop_iterations_int (loop); | |
f0305f3a | 301 | if (iterations < 0) |
ae7a7472 | 302 | iterations = likely_max_loop_iterations_int (loop); |
a01e93f1 YR |
303 | if (iterations >= 0 && iterations <= 1) |
304 | { | |
305 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
306 | fprintf (dump_file, ";; Not unswitching, loop is not expected" | |
307 | " to iterate\n"); | |
308 | return false; | |
309 | } | |
310 | } | |
92fc4a2f | 311 | |
92fc4a2f ZD |
312 | i = 0; |
313 | bbs = get_loop_body (loop); | |
7a2eceff | 314 | found = loop->num_nodes; |
b8698a0f | 315 | |
92fc4a2f ZD |
316 | while (1) |
317 | { | |
318 | /* Find a bb to unswitch on. */ | |
319 | for (; i < loop->num_nodes; i++) | |
320 | if ((cond = tree_may_unswitch_on (bbs[i], loop))) | |
321 | break; | |
322 | ||
323 | if (i == loop->num_nodes) | |
324 | { | |
7a2eceff JJ |
325 | if (dump_file |
326 | && num > PARAM_VALUE (PARAM_MAX_UNSWITCH_LEVEL) | |
327 | && (dump_flags & TDF_DETAILS)) | |
328 | fprintf (dump_file, ";; Not unswitching anymore, hit max level\n"); | |
329 | ||
330 | if (found == loop->num_nodes) | |
331 | { | |
332 | free (bbs); | |
333 | return changed; | |
334 | } | |
335 | break; | |
92fc4a2f ZD |
336 | } |
337 | ||
338 | cond = simplify_using_entry_checks (loop, cond); | |
339 | stmt = last_stmt (bbs[i]); | |
340 | if (integer_nonzerop (cond)) | |
341 | { | |
342 | /* Remove false path. */ | |
538dd0b7 DM |
343 | gimple_cond_set_condition_from_tree (as_a <gcond *> (stmt), |
344 | boolean_true_node); | |
92fc4a2f ZD |
345 | changed = true; |
346 | } | |
347 | else if (integer_zerop (cond)) | |
348 | { | |
349 | /* Remove true path. */ | |
538dd0b7 DM |
350 | gimple_cond_set_condition_from_tree (as_a <gcond *> (stmt), |
351 | boolean_false_node); | |
92fc4a2f ZD |
352 | changed = true; |
353 | } | |
7a2eceff JJ |
354 | /* Do not unswitch too much. */ |
355 | else if (num > PARAM_VALUE (PARAM_MAX_UNSWITCH_LEVEL)) | |
356 | { | |
357 | i++; | |
358 | continue; | |
359 | } | |
360 | /* In nested tree_unswitch_single_loop first optimize all conditions | |
361 | using entry checks, then discover still reachable blocks in the | |
362 | loop and find the condition only among those still reachable bbs. */ | |
363 | else if (num != 0) | |
364 | { | |
365 | if (found == loop->num_nodes) | |
366 | found = i; | |
367 | i++; | |
368 | continue; | |
369 | } | |
92fc4a2f | 370 | else |
7a2eceff JJ |
371 | { |
372 | found = i; | |
373 | break; | |
374 | } | |
92fc4a2f | 375 | |
f430bae8 | 376 | update_stmt (stmt); |
92fc4a2f ZD |
377 | i++; |
378 | } | |
379 | ||
7a2eceff JJ |
380 | if (num != 0) |
381 | { | |
382 | basic_block *tos, *worklist; | |
383 | ||
384 | /* When called recursively, first do a quick discovery | |
385 | of reachable bbs after the above changes and only | |
386 | consider conditions in still reachable bbs. */ | |
387 | tos = worklist = XNEWVEC (basic_block, loop->num_nodes); | |
388 | ||
389 | for (i = 0; i < loop->num_nodes; i++) | |
390 | bbs[i]->flags &= ~BB_REACHABLE; | |
391 | ||
392 | /* Start with marking header. */ | |
393 | *tos++ = bbs[0]; | |
394 | bbs[0]->flags |= BB_REACHABLE; | |
395 | ||
396 | /* Iterate: find everything reachable from what we've already seen | |
397 | within the same innermost loop. Don't look through false edges | |
398 | if condition is always true or true edges if condition is | |
399 | always false. */ | |
400 | while (tos != worklist) | |
401 | { | |
402 | basic_block b = *--tos; | |
403 | edge e; | |
404 | edge_iterator ei; | |
405 | int flags = 0; | |
406 | ||
407 | if (EDGE_COUNT (b->succs) == 2) | |
408 | { | |
355fe088 | 409 | gimple *stmt = last_stmt (b); |
7a2eceff JJ |
410 | if (stmt |
411 | && gimple_code (stmt) == GIMPLE_COND) | |
412 | { | |
538dd0b7 DM |
413 | gcond *cond_stmt = as_a <gcond *> (stmt); |
414 | if (gimple_cond_true_p (cond_stmt)) | |
7a2eceff | 415 | flags = EDGE_FALSE_VALUE; |
538dd0b7 | 416 | else if (gimple_cond_false_p (cond_stmt)) |
7a2eceff JJ |
417 | flags = EDGE_TRUE_VALUE; |
418 | } | |
419 | } | |
420 | ||
421 | FOR_EACH_EDGE (e, ei, b->succs) | |
422 | { | |
423 | basic_block dest = e->dest; | |
424 | ||
425 | if (dest->loop_father == loop | |
426 | && !(dest->flags & BB_REACHABLE) | |
427 | && !(e->flags & flags)) | |
428 | { | |
429 | *tos++ = dest; | |
430 | dest->flags |= BB_REACHABLE; | |
431 | } | |
432 | } | |
433 | } | |
434 | ||
435 | free (worklist); | |
436 | ||
437 | /* Find a bb to unswitch on. */ | |
438 | for (; found < loop->num_nodes; found++) | |
439 | if ((bbs[found]->flags & BB_REACHABLE) | |
440 | && (cond = tree_may_unswitch_on (bbs[found], loop))) | |
441 | break; | |
442 | ||
443 | if (found == loop->num_nodes) | |
444 | { | |
445 | free (bbs); | |
446 | return changed; | |
447 | } | |
448 | } | |
449 | ||
92fc4a2f ZD |
450 | if (dump_file && (dump_flags & TDF_DETAILS)) |
451 | fprintf (dump_file, ";; Unswitching loop\n"); | |
452 | ||
6580ee77 | 453 | initialize_original_copy_tables (); |
92fc4a2f | 454 | /* Unswitch the loop on this condition. */ |
7a2eceff | 455 | nloop = tree_unswitch_loop (loop, bbs[found], cond); |
92fc4a2f | 456 | if (!nloop) |
094bb856 JH |
457 | { |
458 | free_original_copy_tables (); | |
77f6ec05 | 459 | free (bbs); |
094bb856 JH |
460 | return changed; |
461 | } | |
92fc4a2f | 462 | |
84d65814 DN |
463 | /* Update the SSA form after unswitching. */ |
464 | update_ssa (TODO_update_ssa); | |
6580ee77 | 465 | free_original_copy_tables (); |
84d65814 | 466 | |
92fc4a2f | 467 | /* Invoke itself on modified loops. */ |
d73be268 ZD |
468 | tree_unswitch_single_loop (nloop, num + 1); |
469 | tree_unswitch_single_loop (loop, num + 1); | |
77f6ec05 | 470 | free (bbs); |
92fc4a2f ZD |
471 | return true; |
472 | } | |
473 | ||
474 | /* Unswitch a LOOP w.r. to given basic block UNSWITCH_ON. We only support | |
475 | unswitching of innermost loops. COND is the condition determining which | |
476 | loop is entered -- the new loop is entered if COND is true. Returns NULL | |
477 | if impossible, new loop otherwise. */ | |
478 | ||
479 | static struct loop * | |
d73be268 | 480 | tree_unswitch_loop (struct loop *loop, |
92fc4a2f ZD |
481 | basic_block unswitch_on, tree cond) |
482 | { | |
357067f2 | 483 | profile_probability prob_true; |
03cb2019 | 484 | edge edge_true, edge_false; |
92fc4a2f ZD |
485 | |
486 | /* Some sanity checking. */ | |
487 | gcc_assert (flow_bb_inside_loop_p (loop, unswitch_on)); | |
628f6a4e | 488 | gcc_assert (EDGE_COUNT (unswitch_on->succs) == 2); |
92fc4a2f ZD |
489 | gcc_assert (loop->inner == NULL); |
490 | ||
03cb2019 ZD |
491 | extract_true_false_edges_from_block (unswitch_on, &edge_true, &edge_false); |
492 | prob_true = edge_true->probability; | |
b8698a0f | 493 | return loop_version (loop, unshare_expr (cond), |
357067f2 JH |
494 | NULL, prob_true, |
495 | prob_true.invert (), | |
af2bbc51 | 496 | prob_true, prob_true.invert (), |
357067f2 | 497 | false); |
92fc4a2f | 498 | } |
71343877 | 499 | |
a01e93f1 YR |
500 | /* Unswitch outer loops by hoisting invariant guard on |
501 | inner loop without code duplication. */ | |
502 | static bool | |
503 | tree_unswitch_outer_loop (struct loop *loop) | |
504 | { | |
505 | edge exit, guard; | |
506 | HOST_WIDE_INT iterations; | |
507 | ||
508 | gcc_assert (loop->inner); | |
509 | if (loop->inner->next) | |
510 | return false; | |
5c846df7 | 511 | /* Accept loops with single exit only which is not from inner loop. */ |
a01e93f1 | 512 | exit = single_exit (loop); |
5c846df7 | 513 | if (!exit || exit->src->loop_father != loop) |
a01e93f1 YR |
514 | return false; |
515 | /* Check that phi argument of exit edge is not defined inside loop. */ | |
516 | if (!check_exit_phi (loop)) | |
517 | return false; | |
518 | /* If the loop is not expected to iterate, there is no need | |
519 | for unswitching. */ | |
520 | iterations = estimated_loop_iterations_int (loop); | |
f0305f3a | 521 | if (iterations < 0) |
ae7a7472 | 522 | iterations = likely_max_loop_iterations_int (loop); |
a01e93f1 YR |
523 | if (iterations >= 0 && iterations <= 1) |
524 | { | |
525 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
526 | fprintf (dump_file, ";; Not unswitching, loop is not expected" | |
527 | " to iterate\n"); | |
0581d86f | 528 | return false; |
a01e93f1 YR |
529 | } |
530 | ||
622d8b69 RB |
531 | bool changed = false; |
532 | while ((guard = find_loop_guard (loop))) | |
a01e93f1 | 533 | { |
622d8b69 RB |
534 | if (! changed) |
535 | rewrite_virtuals_into_loop_closed_ssa (loop); | |
a01e93f1 | 536 | hoist_guard (loop, guard); |
622d8b69 | 537 | changed = true; |
a01e93f1 | 538 | } |
622d8b69 | 539 | return changed; |
a01e93f1 YR |
540 | } |
541 | ||
542 | /* Checks if the body of the LOOP is within an invariant guard. If this | |
543 | is the case, returns the edge that jumps over the real body of the loop, | |
544 | otherwise returns NULL. */ | |
545 | ||
546 | static edge | |
547 | find_loop_guard (struct loop *loop) | |
548 | { | |
549 | basic_block header = loop->header; | |
550 | edge guard_edge, te, fe; | |
a01e93f1 YR |
551 | basic_block *body = NULL; |
552 | unsigned i; | |
553 | tree use; | |
554 | ssa_op_iter iter; | |
555 | ||
556 | /* We check for the following situation: | |
557 | ||
558 | while (1) | |
559 | { | |
560 | [header]] | |
561 | loop_phi_nodes; | |
562 | something1; | |
563 | if (cond1) | |
564 | body; | |
565 | nvar = phi(orig, bvar) ... for all variables changed in body; | |
566 | [guard_end] | |
567 | something2; | |
568 | if (cond2) | |
569 | break; | |
570 | something3; | |
571 | } | |
572 | ||
573 | where: | |
574 | ||
575 | 1) cond1 is loop invariant | |
576 | 2) If cond1 is false, then the loop is essentially empty; i.e., | |
577 | a) nothing in something1, something2 and something3 has side | |
578 | effects | |
579 | b) anything defined in something1, something2 and something3 | |
580 | is not used outside of the loop. */ | |
581 | ||
622d8b69 RB |
582 | gcond *cond; |
583 | do | |
584 | { | |
1aa54f90 | 585 | basic_block next = NULL; |
622d8b69 | 586 | if (single_succ_p (header)) |
1aa54f90 | 587 | next = single_succ (header); |
622d8b69 RB |
588 | else |
589 | { | |
590 | cond = dyn_cast <gcond *> (last_stmt (header)); | |
591 | if (! cond) | |
592 | return NULL; | |
593 | extract_true_false_edges_from_block (header, &te, &fe); | |
594 | /* Make sure to skip earlier hoisted guards that are left | |
595 | in place as if (true). */ | |
596 | if (gimple_cond_true_p (cond)) | |
1aa54f90 | 597 | next = te->dest; |
622d8b69 | 598 | else if (gimple_cond_false_p (cond)) |
1aa54f90 | 599 | next = fe->dest; |
622d8b69 RB |
600 | else |
601 | break; | |
602 | } | |
1aa54f90 RB |
603 | /* Never traverse a backedge. */ |
604 | if (header->loop_father->header == next) | |
605 | return NULL; | |
606 | header = next; | |
622d8b69 RB |
607 | } |
608 | while (1); | |
a01e93f1 YR |
609 | if (!flow_bb_inside_loop_p (loop, te->dest) |
610 | || !flow_bb_inside_loop_p (loop, fe->dest)) | |
611 | return NULL; | |
612 | ||
613 | if (just_once_each_iteration_p (loop, te->dest) | |
614 | || (single_succ_p (te->dest) | |
615 | && just_once_each_iteration_p (loop, single_succ (te->dest)))) | |
616 | { | |
617 | if (just_once_each_iteration_p (loop, fe->dest)) | |
618 | return NULL; | |
619 | guard_edge = te; | |
620 | } | |
621 | else if (just_once_each_iteration_p (loop, fe->dest) | |
622 | || (single_succ_p (fe->dest) | |
623 | && just_once_each_iteration_p (loop, single_succ (fe->dest)))) | |
624 | guard_edge = fe; | |
625 | else | |
626 | return NULL; | |
627 | ||
8a18fcf4 YR |
628 | /* Guard edge must skip inner loop. */ |
629 | if (!dominated_by_p (CDI_DOMINATORS, loop->inner->header, | |
630 | guard_edge == fe ? te->dest : fe->dest)) | |
631 | { | |
632 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
633 | fprintf (dump_file, "Guard edge %d --> %d is not around the loop!\n", | |
634 | guard_edge->src->index, guard_edge->dest->index); | |
635 | return NULL; | |
636 | } | |
19aa23d8 YR |
637 | if (guard_edge->dest == loop->latch) |
638 | { | |
639 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
640 | fprintf (dump_file, "Guard edge destination is loop latch.\n"); | |
641 | return NULL; | |
642 | } | |
8a18fcf4 | 643 | |
a01e93f1 YR |
644 | if (dump_file && (dump_flags & TDF_DETAILS)) |
645 | fprintf (dump_file, | |
646 | "Considering guard %d -> %d in loop %d\n", | |
647 | guard_edge->src->index, guard_edge->dest->index, loop->num); | |
648 | /* Check if condition operands do not have definitions inside loop since | |
649 | any bb copying is not performed. */ | |
622d8b69 | 650 | FOR_EACH_SSA_TREE_OPERAND (use, cond, iter, SSA_OP_USE) |
a01e93f1 YR |
651 | { |
652 | gimple *def = SSA_NAME_DEF_STMT (use); | |
653 | basic_block def_bb = gimple_bb (def); | |
654 | if (def_bb | |
655 | && flow_bb_inside_loop_p (loop, def_bb)) | |
656 | { | |
657 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
658 | fprintf (dump_file, " guard operands have definitions" | |
659 | " inside loop\n"); | |
660 | return NULL; | |
661 | } | |
662 | } | |
663 | ||
664 | body = get_loop_body (loop); | |
665 | for (i = 0; i < loop->num_nodes; i++) | |
666 | { | |
667 | basic_block bb = body[i]; | |
668 | if (bb->loop_father != loop) | |
669 | continue; | |
670 | if (bb->flags & BB_IRREDUCIBLE_LOOP) | |
671 | { | |
672 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
673 | fprintf (dump_file, "Block %d is marked as irreducible in loop\n", | |
674 | bb->index); | |
675 | guard_edge = NULL; | |
676 | goto end; | |
677 | } | |
678 | if (!empty_bb_without_guard_p (loop, bb)) | |
679 | { | |
680 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
681 | fprintf (dump_file, " block %d has side effects\n", bb->index); | |
682 | guard_edge = NULL; | |
683 | goto end; | |
684 | } | |
685 | } | |
686 | ||
687 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
688 | fprintf (dump_file, " suitable to hoist\n"); | |
689 | end: | |
690 | if (body) | |
691 | free (body); | |
692 | return guard_edge; | |
693 | } | |
694 | ||
695 | /* Returns true if | |
696 | 1) no statement in BB has side effects | |
697 | 2) assuming that edge GUARD is always taken, all definitions in BB | |
698 | are noy used outside of the loop. | |
699 | KNOWN_INVARIANTS is a set of ssa names we know to be invariant, and | |
700 | PROCESSED is a set of ssa names for that we already tested whether they | |
701 | are invariant or not. */ | |
702 | ||
703 | static bool | |
704 | empty_bb_without_guard_p (struct loop *loop, basic_block bb) | |
705 | { | |
706 | basic_block exit_bb = single_exit (loop)->src; | |
707 | bool may_be_used_outside = (bb == exit_bb | |
708 | || !dominated_by_p (CDI_DOMINATORS, bb, exit_bb)); | |
709 | tree name; | |
710 | ssa_op_iter op_iter; | |
711 | ||
712 | /* Phi nodes do not have side effects, but their results might be used | |
713 | outside of the loop. */ | |
714 | if (may_be_used_outside) | |
715 | { | |
716 | for (gphi_iterator gsi = gsi_start_phis (bb); | |
717 | !gsi_end_p (gsi); gsi_next (&gsi)) | |
718 | { | |
719 | gphi *phi = gsi.phi (); | |
720 | name = PHI_RESULT (phi); | |
721 | if (virtual_operand_p (name)) | |
722 | continue; | |
723 | ||
724 | if (used_outside_loop_p (loop, name)) | |
725 | return false; | |
726 | } | |
727 | } | |
728 | ||
729 | for (gimple_stmt_iterator gsi = gsi_start_bb (bb); | |
730 | !gsi_end_p (gsi); gsi_next (&gsi)) | |
731 | { | |
732 | gimple *stmt = gsi_stmt (gsi); | |
733 | if (gimple_has_side_effects (stmt)) | |
734 | return false; | |
735 | ||
736 | if (gimple_vdef(stmt)) | |
737 | return false; | |
738 | ||
739 | FOR_EACH_SSA_TREE_OPERAND (name, stmt, op_iter, SSA_OP_DEF) | |
740 | { | |
741 | if (may_be_used_outside | |
742 | && used_outside_loop_p (loop, name)) | |
743 | return false; | |
744 | } | |
745 | } | |
746 | return true; | |
747 | } | |
748 | ||
749 | /* Return true if NAME is used outside of LOOP. */ | |
750 | ||
751 | static bool | |
752 | used_outside_loop_p (struct loop *loop, tree name) | |
753 | { | |
754 | imm_use_iterator it; | |
755 | use_operand_p use; | |
756 | ||
757 | FOR_EACH_IMM_USE_FAST (use, it, name) | |
758 | { | |
759 | gimple *stmt = USE_STMT (use); | |
760 | if (!flow_bb_inside_loop_p (loop, gimple_bb (stmt))) | |
761 | return true; | |
762 | } | |
763 | ||
764 | return false; | |
765 | } | |
766 | ||
767 | /* Return argument for loop preheader edge in header virtual phi if any. */ | |
768 | ||
769 | static tree | |
770 | get_vop_from_header (struct loop *loop) | |
771 | { | |
772 | for (gphi_iterator gsi = gsi_start_phis (loop->header); | |
773 | !gsi_end_p (gsi); gsi_next (&gsi)) | |
774 | { | |
775 | gphi *phi = gsi.phi (); | |
776 | if (!virtual_operand_p (gimple_phi_result (phi))) | |
777 | continue; | |
778 | return PHI_ARG_DEF_FROM_EDGE (phi, loop_preheader_edge (loop)); | |
779 | } | |
780 | return NULL_TREE; | |
781 | } | |
782 | ||
783 | /* Move the check of GUARD outside of LOOP. */ | |
784 | ||
785 | static void | |
786 | hoist_guard (struct loop *loop, edge guard) | |
787 | { | |
788 | edge exit = single_exit (loop); | |
789 | edge preh = loop_preheader_edge (loop); | |
790 | basic_block pre_header = preh->src; | |
791 | basic_block bb; | |
792 | edge te, fe, e, new_edge; | |
793 | gimple *stmt; | |
794 | basic_block guard_bb = guard->src; | |
0b90c541 | 795 | edge not_guard; |
a01e93f1 YR |
796 | gimple_stmt_iterator gsi; |
797 | int flags = 0; | |
798 | bool fix_dom_of_exit; | |
799 | gcond *cond_stmt, *new_cond_stmt; | |
800 | ||
801 | bb = get_immediate_dominator (CDI_DOMINATORS, exit->dest); | |
802 | fix_dom_of_exit = flow_bb_inside_loop_p (loop, bb); | |
803 | gsi = gsi_last_bb (guard_bb); | |
804 | stmt = gsi_stmt (gsi); | |
805 | gcc_assert (gimple_code (stmt) == GIMPLE_COND); | |
806 | cond_stmt = as_a <gcond *> (stmt); | |
807 | extract_true_false_edges_from_block (guard_bb, &te, &fe); | |
808 | /* Insert guard to PRE_HEADER. */ | |
809 | if (!empty_block_p (pre_header)) | |
810 | gsi = gsi_last_bb (pre_header); | |
811 | else | |
812 | gsi = gsi_start_bb (pre_header); | |
813 | /* Create copy of COND_STMT. */ | |
814 | new_cond_stmt = gimple_build_cond (gimple_cond_code (cond_stmt), | |
815 | gimple_cond_lhs (cond_stmt), | |
816 | gimple_cond_rhs (cond_stmt), | |
817 | NULL_TREE, NULL_TREE); | |
818 | gsi_insert_after (&gsi, new_cond_stmt, GSI_NEW_STMT); | |
819 | /* Convert COND_STMT to true/false conditional. */ | |
820 | if (guard == te) | |
821 | gimple_cond_make_false (cond_stmt); | |
822 | else | |
823 | gimple_cond_make_true (cond_stmt); | |
824 | update_stmt (cond_stmt); | |
825 | /* Create new loop pre-header. */ | |
826 | e = split_block (pre_header, last_stmt (pre_header)); | |
0b90c541 | 827 | if (dump_file && (dump_flags & TDF_DETAILS)) |
357067f2 JH |
828 | { |
829 | fprintf (dump_file, " Moving guard %i->%i (prob ", | |
830 | guard->src->index, guard->dest->index); | |
831 | guard->probability.dump (dump_file); | |
832 | fprintf (dump_file, ") to bb %i, new preheader is %i\n", | |
833 | e->src->index, e->dest->index); | |
834 | } | |
0b90c541 | 835 | |
a01e93f1 | 836 | gcc_assert (loop_preheader_edge (loop)->src == e->dest); |
0b90c541 | 837 | |
a01e93f1 YR |
838 | if (guard == fe) |
839 | { | |
840 | e->flags = EDGE_TRUE_VALUE; | |
841 | flags |= EDGE_FALSE_VALUE; | |
0b90c541 | 842 | not_guard = te; |
a01e93f1 YR |
843 | } |
844 | else | |
845 | { | |
846 | e->flags = EDGE_FALSE_VALUE; | |
847 | flags |= EDGE_TRUE_VALUE; | |
0b90c541 | 848 | not_guard = fe; |
a01e93f1 YR |
849 | } |
850 | new_edge = make_edge (pre_header, exit->dest, flags); | |
0b90c541 JH |
851 | |
852 | /* Determine the probability that we skip the loop. Assume that loop has | |
853 | same average number of iterations regardless outcome of guard. */ | |
854 | new_edge->probability = guard->probability; | |
3995f3a2 | 855 | profile_count skip_count = guard->src->count > 0 |
ef30ab83 | 856 | ? guard->count ().apply_scale (pre_header->count, |
3995f3a2 | 857 | guard->src->count) |
ef30ab83 | 858 | : guard->count ().apply_probability (new_edge->probability); |
0b90c541 | 859 | |
ef30ab83 | 860 | if (skip_count > e->count ()) |
0b90c541 JH |
861 | { |
862 | fprintf (dump_file, " Capping count; expect profile inconsistency\n"); | |
ef30ab83 | 863 | skip_count = e->count (); |
0b90c541 | 864 | } |
0b90c541 | 865 | if (dump_file && (dump_flags & TDF_DETAILS)) |
357067f2 JH |
866 | { |
867 | fprintf (dump_file, " Estimated probability of skipping loop is "); | |
868 | new_edge->probability.dump (dump_file); | |
869 | fprintf (dump_file, "\n"); | |
870 | } | |
0b90c541 JH |
871 | |
872 | /* Update profile after the transform: | |
873 | ||
874 | First decrease count of path from newly hoisted loop guard | |
875 | to loop header... */ | |
357067f2 | 876 | e->probability = new_edge->probability.invert (); |
ef30ab83 | 877 | e->dest->count = e->count (); |
0b90c541 JH |
878 | e->dest->frequency = EDGE_FREQUENCY (e); |
879 | ||
880 | /* ... now update profile to represent that original guard will be optimized | |
881 | away ... */ | |
357067f2 | 882 | guard->probability = profile_probability::never (); |
357067f2 | 883 | not_guard->probability = profile_probability::always (); |
0b90c541 JH |
884 | |
885 | /* ... finally scale everything in the loop except for guarded basic blocks | |
886 | where profile does not change. */ | |
887 | basic_block *body = get_loop_body (loop); | |
da9cd044 | 888 | |
0b90c541 JH |
889 | if (dump_file && (dump_flags & TDF_DETAILS)) |
890 | fprintf (dump_file, " Scaling nonguarded BBs in loop:"); | |
891 | for (unsigned int i = 0; i < loop->num_nodes; i++) | |
892 | { | |
893 | basic_block bb = body[i]; | |
894 | if (!dominated_by_p (CDI_DOMINATORS, bb, not_guard->dest)) | |
895 | { | |
896 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
897 | fprintf (dump_file, " %i", bb->index); | |
357067f2 | 898 | if (e->probability.initialized_p ()) |
77ba27b4 | 899 | scale_bbs_frequencies (&bb, 1, e->probability); |
0b90c541 JH |
900 | } |
901 | } | |
902 | ||
a01e93f1 YR |
903 | if (fix_dom_of_exit) |
904 | set_immediate_dominator (CDI_DOMINATORS, exit->dest, pre_header); | |
905 | /* Add NEW_ADGE argument for all phi in post-header block. */ | |
906 | bb = exit->dest; | |
907 | for (gphi_iterator gsi = gsi_start_phis (bb); | |
908 | !gsi_end_p (gsi); gsi_next (&gsi)) | |
909 | { | |
910 | gphi *phi = gsi.phi (); | |
911 | tree arg; | |
912 | if (virtual_operand_p (gimple_phi_result (phi))) | |
913 | { | |
914 | arg = get_vop_from_header (loop); | |
915 | if (arg == NULL_TREE) | |
916 | /* Use exit edge argument. */ | |
917 | arg = PHI_ARG_DEF_FROM_EDGE (phi, exit); | |
918 | add_phi_arg (phi, arg, new_edge, UNKNOWN_LOCATION); | |
919 | } | |
920 | else | |
921 | { | |
922 | /* Use exit edge argument. */ | |
923 | arg = PHI_ARG_DEF_FROM_EDGE (phi, exit); | |
924 | add_phi_arg (phi, arg, new_edge, UNKNOWN_LOCATION); | |
925 | } | |
926 | } | |
927 | ||
a01e93f1 | 928 | if (dump_file && (dump_flags & TDF_DETAILS)) |
0b90c541 | 929 | fprintf (dump_file, "\n guard hoisted.\n"); |
da9cd044 ML |
930 | |
931 | free (body); | |
a01e93f1 YR |
932 | } |
933 | ||
934 | /* Return true if phi argument for exit edge can be used | |
935 | for edge around loop. */ | |
936 | ||
937 | static bool | |
938 | check_exit_phi (struct loop *loop) | |
939 | { | |
940 | edge exit = single_exit (loop); | |
941 | basic_block pre_header = loop_preheader_edge (loop)->src; | |
942 | ||
943 | for (gphi_iterator gsi = gsi_start_phis (exit->dest); | |
944 | !gsi_end_p (gsi); gsi_next (&gsi)) | |
945 | { | |
946 | gphi *phi = gsi.phi (); | |
947 | tree arg; | |
948 | gimple *def; | |
949 | basic_block def_bb; | |
950 | if (virtual_operand_p (gimple_phi_result (phi))) | |
951 | continue; | |
952 | arg = PHI_ARG_DEF_FROM_EDGE (phi, exit); | |
953 | if (TREE_CODE (arg) != SSA_NAME) | |
954 | continue; | |
955 | def = SSA_NAME_DEF_STMT (arg); | |
956 | if (!def) | |
957 | continue; | |
958 | def_bb = gimple_bb (def); | |
959 | if (!def_bb) | |
960 | continue; | |
961 | if (!dominated_by_p (CDI_DOMINATORS, pre_header, def_bb)) | |
962 | /* Definition inside loop! */ | |
963 | return false; | |
964 | /* Check loop closed phi invariant. */ | |
965 | if (!flow_bb_inside_loop_p (def_bb->loop_father, pre_header)) | |
966 | return false; | |
967 | } | |
968 | return true; | |
969 | } | |
970 | ||
71343877 AM |
971 | /* Loop unswitching pass. */ |
972 | ||
71343877 AM |
973 | namespace { |
974 | ||
975 | const pass_data pass_data_tree_unswitch = | |
976 | { | |
977 | GIMPLE_PASS, /* type */ | |
978 | "unswitch", /* name */ | |
979 | OPTGROUP_LOOP, /* optinfo_flags */ | |
71343877 AM |
980 | TV_TREE_LOOP_UNSWITCH, /* tv_id */ |
981 | PROP_cfg, /* properties_required */ | |
982 | 0, /* properties_provided */ | |
983 | 0, /* properties_destroyed */ | |
984 | 0, /* todo_flags_start */ | |
985 | 0, /* todo_flags_finish */ | |
986 | }; | |
987 | ||
988 | class pass_tree_unswitch : public gimple_opt_pass | |
989 | { | |
990 | public: | |
991 | pass_tree_unswitch (gcc::context *ctxt) | |
992 | : gimple_opt_pass (pass_data_tree_unswitch, ctxt) | |
993 | {} | |
994 | ||
995 | /* opt_pass methods: */ | |
1a3d085c | 996 | virtual bool gate (function *) { return flag_unswitch_loops != 0; } |
be55bfe6 | 997 | virtual unsigned int execute (function *); |
71343877 AM |
998 | |
999 | }; // class pass_tree_unswitch | |
1000 | ||
be55bfe6 TS |
1001 | unsigned int |
1002 | pass_tree_unswitch::execute (function *fun) | |
1003 | { | |
1004 | if (number_of_loops (fun) <= 1) | |
1005 | return 0; | |
1006 | ||
1007 | return tree_ssa_unswitch_loops (); | |
1008 | } | |
1009 | ||
71343877 AM |
1010 | } // anon namespace |
1011 | ||
1012 | gimple_opt_pass * | |
1013 | make_pass_tree_unswitch (gcc::context *ctxt) | |
1014 | { | |
1015 | return new pass_tree_unswitch (ctxt); | |
1016 | } | |
1017 | ||
1018 |