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92fc4a2f | 1 | /* Loop unswitching. |
8d9254fc | 2 | Copyright (C) 2004-2020 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" |
7f9bc51b | 36 | #include "tree-inline.h" |
a01e93f1 YR |
37 | #include "gimple-iterator.h" |
38 | #include "cfghooks.h" | |
622d8b69 | 39 | #include "tree-ssa-loop-manip.h" |
92fc4a2f ZD |
40 | |
41 | /* This file implements the loop unswitching, i.e. transformation of loops like | |
42 | ||
43 | while (A) | |
44 | { | |
45 | if (inv) | |
46 | B; | |
47 | ||
48 | X; | |
49 | ||
50 | if (!inv) | |
51 | C; | |
52 | } | |
53 | ||
54 | where inv is the loop invariant, into | |
55 | ||
56 | if (inv) | |
57 | { | |
58 | while (A) | |
59 | { | |
60 | B; | |
61 | X; | |
62 | } | |
63 | } | |
64 | else | |
65 | { | |
66 | while (A) | |
67 | { | |
68 | X; | |
69 | C; | |
70 | } | |
71 | } | |
72 | ||
73 | Inv is considered invariant iff the values it compares are both invariant; | |
74 | tree-ssa-loop-im.c ensures that all the suitable conditions are in this | |
75 | shape. */ | |
76 | ||
99b1c316 MS |
77 | static class loop *tree_unswitch_loop (class loop *, basic_block, tree); |
78 | static bool tree_unswitch_single_loop (class loop *, int); | |
79 | static tree tree_may_unswitch_on (basic_block, class loop *); | |
80 | static bool tree_unswitch_outer_loop (class loop *); | |
81 | static edge find_loop_guard (class loop *); | |
82 | static bool empty_bb_without_guard_p (class loop *, basic_block); | |
83 | static bool used_outside_loop_p (class loop *, tree); | |
84 | static void hoist_guard (class loop *, edge); | |
85 | static bool check_exit_phi (class loop *); | |
86 | static tree get_vop_from_header (class loop *); | |
92fc4a2f | 87 | |
d73be268 | 88 | /* Main entry point. Perform loop unswitching on all suitable loops. */ |
92fc4a2f | 89 | |
c7f965b6 | 90 | unsigned int |
d73be268 | 91 | tree_ssa_unswitch_loops (void) |
92fc4a2f | 92 | { |
99b1c316 | 93 | class loop *loop; |
92fc4a2f ZD |
94 | bool changed = false; |
95 | ||
a01e93f1 YR |
96 | /* Go through all loops starting from innermost. */ |
97 | FOR_EACH_LOOP (loop, LI_FROM_INNERMOST) | |
92fc4a2f | 98 | { |
a01e93f1 YR |
99 | if (!loop->inner) |
100 | /* Unswitch innermost loop. */ | |
101 | changed |= tree_unswitch_single_loop (loop, 0); | |
102 | else | |
103 | changed |= tree_unswitch_outer_loop (loop); | |
92fc4a2f ZD |
104 | } |
105 | ||
92fc4a2f | 106 | if (changed) |
c7f965b6 AP |
107 | return TODO_cleanup_cfg; |
108 | return 0; | |
92fc4a2f ZD |
109 | } |
110 | ||
8b670f93 AH |
111 | /* Return TRUE if an SSA_NAME maybe undefined and is therefore |
112 | unsuitable for unswitching. STMT is the statement we are | |
113 | considering for unswitching and LOOP is the loop it appears in. */ | |
114 | ||
115 | static bool | |
99b1c316 | 116 | is_maybe_undefined (const tree name, gimple *stmt, class loop *loop) |
8b670f93 AH |
117 | { |
118 | /* The loop header is the only block we can trivially determine that | |
119 | will always be executed. If the comparison is in the loop | |
120 | header, we know it's OK to unswitch on it. */ | |
121 | if (gimple_bb (stmt) == loop->header) | |
122 | return false; | |
123 | ||
124 | auto_bitmap visited_ssa; | |
125 | auto_vec<tree> worklist; | |
126 | worklist.safe_push (name); | |
127 | bitmap_set_bit (visited_ssa, SSA_NAME_VERSION (name)); | |
128 | while (!worklist.is_empty ()) | |
129 | { | |
130 | tree t = worklist.pop (); | |
131 | ||
132 | /* If it's obviously undefined, avoid further computations. */ | |
133 | if (ssa_undefined_value_p (t, true)) | |
134 | return true; | |
135 | ||
c6b0d21d | 136 | if (ssa_defined_default_def_p (t)) |
8b670f93 AH |
137 | continue; |
138 | ||
139 | gimple *def = SSA_NAME_DEF_STMT (t); | |
140 | ||
141 | /* Check that all the PHI args are fully defined. */ | |
142 | if (gphi *phi = dyn_cast <gphi *> (def)) | |
143 | { | |
144 | for (unsigned i = 0; i < gimple_phi_num_args (phi); ++i) | |
145 | { | |
146 | tree t = gimple_phi_arg_def (phi, i); | |
147 | /* If an SSA has already been seen, it may be a loop, | |
148 | but we can continue and ignore this use. Otherwise, | |
149 | add the SSA_NAME to the queue and visit it later. */ | |
150 | if (TREE_CODE (t) == SSA_NAME | |
151 | && bitmap_set_bit (visited_ssa, SSA_NAME_VERSION (t))) | |
152 | worklist.safe_push (t); | |
153 | } | |
154 | continue; | |
155 | } | |
156 | ||
157 | /* Uses in stmts always executed when the region header executes | |
158 | are fine. */ | |
159 | if (dominated_by_p (CDI_DOMINATORS, loop->header, gimple_bb (def))) | |
160 | continue; | |
161 | ||
162 | /* Handle calls and memory loads conservatively. */ | |
163 | if (!is_gimple_assign (def) | |
164 | || (gimple_assign_single_p (def) | |
165 | && gimple_vuse (def))) | |
166 | return true; | |
167 | ||
168 | /* Check that any SSA names used to define NAME are also fully | |
169 | defined. */ | |
170 | use_operand_p use_p; | |
171 | ssa_op_iter iter; | |
172 | FOR_EACH_SSA_USE_OPERAND (use_p, def, iter, SSA_OP_USE) | |
173 | { | |
174 | tree t = USE_FROM_PTR (use_p); | |
175 | /* If an SSA has already been seen, it may be a loop, | |
176 | but we can continue and ignore this use. Otherwise, | |
177 | add the SSA_NAME to the queue and visit it later. */ | |
178 | if (bitmap_set_bit (visited_ssa, SSA_NAME_VERSION (t))) | |
179 | worklist.safe_push (t); | |
180 | } | |
181 | } | |
182 | return false; | |
183 | } | |
184 | ||
92fc4a2f ZD |
185 | /* Checks whether we can unswitch LOOP on condition at end of BB -- one of its |
186 | basic blocks (for what it means see comments below). */ | |
187 | ||
188 | static tree | |
99b1c316 | 189 | tree_may_unswitch_on (basic_block bb, class loop *loop) |
92fc4a2f | 190 | { |
355fe088 | 191 | gimple *last, *def; |
538dd0b7 | 192 | gcond *stmt; |
726a989a | 193 | tree cond, use; |
92fc4a2f | 194 | basic_block def_bb; |
f47c96aa | 195 | ssa_op_iter iter; |
92fc4a2f ZD |
196 | |
197 | /* BB must end in a simple conditional jump. */ | |
538dd0b7 DM |
198 | last = last_stmt (bb); |
199 | if (!last || gimple_code (last) != GIMPLE_COND) | |
92fc4a2f | 200 | return NULL_TREE; |
538dd0b7 | 201 | stmt = as_a <gcond *> (last); |
92fc4a2f | 202 | |
7a2eceff JJ |
203 | /* To keep the things simple, we do not directly remove the conditions, |
204 | but just replace tests with 0 != 0 resp. 1 != 0. Prevent the infinite | |
205 | loop where we would unswitch again on such a condition. */ | |
206 | if (gimple_cond_true_p (stmt) || gimple_cond_false_p (stmt)) | |
207 | return NULL_TREE; | |
208 | ||
92fc4a2f | 209 | /* Condition must be invariant. */ |
f47c96aa | 210 | FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE) |
92fc4a2f | 211 | { |
f47c96aa | 212 | def = SSA_NAME_DEF_STMT (use); |
726a989a | 213 | def_bb = gimple_bb (def); |
92fc4a2f ZD |
214 | if (def_bb |
215 | && flow_bb_inside_loop_p (loop, def_bb)) | |
216 | return NULL_TREE; | |
8b670f93 AH |
217 | /* Unswitching on undefined values would introduce undefined |
218 | behavior that the original program might never exercise. */ | |
219 | if (is_maybe_undefined (use, stmt, loop)) | |
220 | return NULL_TREE; | |
92fc4a2f ZD |
221 | } |
222 | ||
12aea97a RG |
223 | cond = build2 (gimple_cond_code (stmt), boolean_type_node, |
224 | gimple_cond_lhs (stmt), gimple_cond_rhs (stmt)); | |
726a989a | 225 | |
92fc4a2f ZD |
226 | return cond; |
227 | } | |
228 | ||
229 | /* Simplifies COND using checks in front of the entry of the LOOP. Just very | |
230 | simplish (sufficient to prevent us from duplicating loop in unswitching | |
e75220c8 | 231 | unnecessarily). */ |
92fc4a2f ZD |
232 | |
233 | static tree | |
99b1c316 | 234 | simplify_using_entry_checks (class loop *loop, tree cond) |
92fc4a2f ZD |
235 | { |
236 | edge e = loop_preheader_edge (loop); | |
355fe088 | 237 | gimple *stmt; |
92fc4a2f ZD |
238 | |
239 | while (1) | |
240 | { | |
241 | stmt = last_stmt (e->src); | |
242 | if (stmt | |
726a989a RB |
243 | && gimple_code (stmt) == GIMPLE_COND |
244 | && gimple_cond_code (stmt) == TREE_CODE (cond) | |
245 | && operand_equal_p (gimple_cond_lhs (stmt), | |
246 | TREE_OPERAND (cond, 0), 0) | |
247 | && operand_equal_p (gimple_cond_rhs (stmt), | |
248 | TREE_OPERAND (cond, 1), 0)) | |
92fc4a2f ZD |
249 | return (e->flags & EDGE_TRUE_VALUE |
250 | ? boolean_true_node | |
251 | : boolean_false_node); | |
252 | ||
c5cbcccf | 253 | if (!single_pred_p (e->src)) |
92fc4a2f ZD |
254 | return cond; |
255 | ||
c5cbcccf | 256 | e = single_pred_edge (e->src); |
fefa31b5 | 257 | if (e->src == ENTRY_BLOCK_PTR_FOR_FN (cfun)) |
92fc4a2f ZD |
258 | return cond; |
259 | } | |
260 | } | |
261 | ||
262 | /* Unswitch single LOOP. NUM is number of unswitchings done; we do not allow | |
263 | it to grow too much, it is too easy to create example on that the code would | |
264 | grow exponentially. */ | |
265 | ||
266 | static bool | |
99b1c316 | 267 | tree_unswitch_single_loop (class loop *loop, int num) |
92fc4a2f ZD |
268 | { |
269 | basic_block *bbs; | |
99b1c316 | 270 | class loop *nloop; |
7a2eceff | 271 | unsigned i, found; |
726a989a | 272 | tree cond = NULL_TREE; |
355fe088 | 273 | gimple *stmt; |
92fc4a2f | 274 | bool changed = false; |
a01e93f1 YR |
275 | HOST_WIDE_INT iterations; |
276 | ||
277 | /* Perform initial tests if unswitch is eligible. */ | |
278 | if (num == 0) | |
279 | { | |
280 | /* Do not unswitch in cold regions. */ | |
281 | if (optimize_loop_for_size_p (loop)) | |
282 | { | |
283 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
284 | fprintf (dump_file, ";; Not unswitching cold loops\n"); | |
285 | return false; | |
286 | } | |
287 | ||
288 | /* The loop should not be too large, to limit code growth. */ | |
289 | if (tree_num_loop_insns (loop, &eni_size_weights) | |
028d4092 | 290 | > (unsigned) param_max_unswitch_insns) |
a01e93f1 YR |
291 | { |
292 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
293 | fprintf (dump_file, ";; Not unswitching, loop too big\n"); | |
294 | return false; | |
295 | } | |
296 | ||
297 | /* If the loop is not expected to iterate, there is no need | |
298 | for unswitching. */ | |
299 | iterations = estimated_loop_iterations_int (loop); | |
f0305f3a | 300 | if (iterations < 0) |
ae7a7472 | 301 | iterations = likely_max_loop_iterations_int (loop); |
a01e93f1 YR |
302 | if (iterations >= 0 && iterations <= 1) |
303 | { | |
304 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
305 | fprintf (dump_file, ";; Not unswitching, loop is not expected" | |
306 | " to iterate\n"); | |
307 | return false; | |
308 | } | |
309 | } | |
92fc4a2f | 310 | |
92fc4a2f ZD |
311 | i = 0; |
312 | bbs = get_loop_body (loop); | |
7a2eceff | 313 | found = loop->num_nodes; |
b8698a0f | 314 | |
92fc4a2f ZD |
315 | while (1) |
316 | { | |
317 | /* Find a bb to unswitch on. */ | |
318 | for (; i < loop->num_nodes; i++) | |
319 | if ((cond = tree_may_unswitch_on (bbs[i], loop))) | |
320 | break; | |
321 | ||
322 | if (i == loop->num_nodes) | |
323 | { | |
7a2eceff | 324 | if (dump_file |
028d4092 | 325 | && num > param_max_unswitch_level |
7a2eceff JJ |
326 | && (dump_flags & TDF_DETAILS)) |
327 | fprintf (dump_file, ";; Not unswitching anymore, hit max level\n"); | |
328 | ||
329 | if (found == loop->num_nodes) | |
330 | { | |
331 | free (bbs); | |
332 | return changed; | |
333 | } | |
334 | break; | |
92fc4a2f ZD |
335 | } |
336 | ||
337 | cond = simplify_using_entry_checks (loop, cond); | |
338 | stmt = last_stmt (bbs[i]); | |
339 | if (integer_nonzerop (cond)) | |
340 | { | |
341 | /* Remove false path. */ | |
538dd0b7 DM |
342 | gimple_cond_set_condition_from_tree (as_a <gcond *> (stmt), |
343 | boolean_true_node); | |
92fc4a2f ZD |
344 | changed = true; |
345 | } | |
346 | else if (integer_zerop (cond)) | |
347 | { | |
348 | /* Remove true path. */ | |
538dd0b7 DM |
349 | gimple_cond_set_condition_from_tree (as_a <gcond *> (stmt), |
350 | boolean_false_node); | |
92fc4a2f ZD |
351 | changed = true; |
352 | } | |
7a2eceff | 353 | /* Do not unswitch too much. */ |
028d4092 | 354 | else if (num > param_max_unswitch_level) |
7a2eceff JJ |
355 | { |
356 | i++; | |
357 | continue; | |
358 | } | |
359 | /* In nested tree_unswitch_single_loop first optimize all conditions | |
360 | using entry checks, then discover still reachable blocks in the | |
361 | loop and find the condition only among those still reachable bbs. */ | |
362 | else if (num != 0) | |
363 | { | |
364 | if (found == loop->num_nodes) | |
365 | found = i; | |
366 | i++; | |
367 | continue; | |
368 | } | |
92fc4a2f | 369 | else |
7a2eceff JJ |
370 | { |
371 | found = i; | |
372 | break; | |
373 | } | |
92fc4a2f | 374 | |
f430bae8 | 375 | update_stmt (stmt); |
92fc4a2f ZD |
376 | i++; |
377 | } | |
378 | ||
7a2eceff JJ |
379 | if (num != 0) |
380 | { | |
381 | basic_block *tos, *worklist; | |
382 | ||
383 | /* When called recursively, first do a quick discovery | |
384 | of reachable bbs after the above changes and only | |
385 | consider conditions in still reachable bbs. */ | |
386 | tos = worklist = XNEWVEC (basic_block, loop->num_nodes); | |
387 | ||
388 | for (i = 0; i < loop->num_nodes; i++) | |
389 | bbs[i]->flags &= ~BB_REACHABLE; | |
390 | ||
391 | /* Start with marking header. */ | |
392 | *tos++ = bbs[0]; | |
393 | bbs[0]->flags |= BB_REACHABLE; | |
394 | ||
395 | /* Iterate: find everything reachable from what we've already seen | |
396 | within the same innermost loop. Don't look through false edges | |
397 | if condition is always true or true edges if condition is | |
398 | always false. */ | |
399 | while (tos != worklist) | |
400 | { | |
401 | basic_block b = *--tos; | |
402 | edge e; | |
403 | edge_iterator ei; | |
404 | int flags = 0; | |
405 | ||
406 | if (EDGE_COUNT (b->succs) == 2) | |
407 | { | |
355fe088 | 408 | gimple *stmt = last_stmt (b); |
7a2eceff JJ |
409 | if (stmt |
410 | && gimple_code (stmt) == GIMPLE_COND) | |
411 | { | |
538dd0b7 DM |
412 | gcond *cond_stmt = as_a <gcond *> (stmt); |
413 | if (gimple_cond_true_p (cond_stmt)) | |
7a2eceff | 414 | flags = EDGE_FALSE_VALUE; |
538dd0b7 | 415 | else if (gimple_cond_false_p (cond_stmt)) |
7a2eceff JJ |
416 | flags = EDGE_TRUE_VALUE; |
417 | } | |
418 | } | |
419 | ||
420 | FOR_EACH_EDGE (e, ei, b->succs) | |
421 | { | |
422 | basic_block dest = e->dest; | |
423 | ||
424 | if (dest->loop_father == loop | |
425 | && !(dest->flags & BB_REACHABLE) | |
426 | && !(e->flags & flags)) | |
427 | { | |
428 | *tos++ = dest; | |
429 | dest->flags |= BB_REACHABLE; | |
430 | } | |
431 | } | |
432 | } | |
433 | ||
434 | free (worklist); | |
435 | ||
436 | /* Find a bb to unswitch on. */ | |
437 | for (; found < loop->num_nodes; found++) | |
438 | if ((bbs[found]->flags & BB_REACHABLE) | |
439 | && (cond = tree_may_unswitch_on (bbs[found], loop))) | |
440 | break; | |
441 | ||
442 | if (found == loop->num_nodes) | |
443 | { | |
444 | free (bbs); | |
445 | return changed; | |
446 | } | |
447 | } | |
448 | ||
92fc4a2f ZD |
449 | if (dump_file && (dump_flags & TDF_DETAILS)) |
450 | fprintf (dump_file, ";; Unswitching loop\n"); | |
451 | ||
6580ee77 | 452 | initialize_original_copy_tables (); |
92fc4a2f | 453 | /* Unswitch the loop on this condition. */ |
7a2eceff | 454 | nloop = tree_unswitch_loop (loop, bbs[found], cond); |
92fc4a2f | 455 | if (!nloop) |
094bb856 JH |
456 | { |
457 | free_original_copy_tables (); | |
77f6ec05 | 458 | free (bbs); |
094bb856 JH |
459 | return changed; |
460 | } | |
92fc4a2f | 461 | |
84d65814 DN |
462 | /* Update the SSA form after unswitching. */ |
463 | update_ssa (TODO_update_ssa); | |
6580ee77 | 464 | free_original_copy_tables (); |
84d65814 | 465 | |
92fc4a2f | 466 | /* Invoke itself on modified loops. */ |
d73be268 ZD |
467 | tree_unswitch_single_loop (nloop, num + 1); |
468 | tree_unswitch_single_loop (loop, num + 1); | |
77f6ec05 | 469 | free (bbs); |
92fc4a2f ZD |
470 | return true; |
471 | } | |
472 | ||
473 | /* Unswitch a LOOP w.r. to given basic block UNSWITCH_ON. We only support | |
474 | unswitching of innermost loops. COND is the condition determining which | |
475 | loop is entered -- the new loop is entered if COND is true. Returns NULL | |
476 | if impossible, new loop otherwise. */ | |
477 | ||
99b1c316 MS |
478 | static class loop * |
479 | tree_unswitch_loop (class loop *loop, | |
92fc4a2f ZD |
480 | basic_block unswitch_on, tree cond) |
481 | { | |
357067f2 | 482 | profile_probability prob_true; |
03cb2019 | 483 | edge edge_true, edge_false; |
92fc4a2f ZD |
484 | |
485 | /* Some sanity checking. */ | |
486 | gcc_assert (flow_bb_inside_loop_p (loop, unswitch_on)); | |
628f6a4e | 487 | gcc_assert (EDGE_COUNT (unswitch_on->succs) == 2); |
92fc4a2f ZD |
488 | gcc_assert (loop->inner == NULL); |
489 | ||
03cb2019 ZD |
490 | extract_true_false_edges_from_block (unswitch_on, &edge_true, &edge_false); |
491 | prob_true = edge_true->probability; | |
b8698a0f | 492 | return loop_version (loop, unshare_expr (cond), |
357067f2 JH |
493 | NULL, prob_true, |
494 | prob_true.invert (), | |
af2bbc51 | 495 | prob_true, prob_true.invert (), |
357067f2 | 496 | false); |
92fc4a2f | 497 | } |
71343877 | 498 | |
a01e93f1 YR |
499 | /* Unswitch outer loops by hoisting invariant guard on |
500 | inner loop without code duplication. */ | |
501 | static bool | |
99b1c316 | 502 | tree_unswitch_outer_loop (class loop *loop) |
a01e93f1 YR |
503 | { |
504 | edge exit, guard; | |
505 | HOST_WIDE_INT iterations; | |
506 | ||
507 | gcc_assert (loop->inner); | |
508 | if (loop->inner->next) | |
509 | return false; | |
5c846df7 | 510 | /* Accept loops with single exit only which is not from inner loop. */ |
a01e93f1 | 511 | exit = single_exit (loop); |
5c846df7 | 512 | if (!exit || exit->src->loop_father != loop) |
a01e93f1 YR |
513 | return false; |
514 | /* Check that phi argument of exit edge is not defined inside loop. */ | |
515 | if (!check_exit_phi (loop)) | |
516 | return false; | |
517 | /* If the loop is not expected to iterate, there is no need | |
518 | for unswitching. */ | |
519 | iterations = estimated_loop_iterations_int (loop); | |
f0305f3a | 520 | if (iterations < 0) |
ae7a7472 | 521 | iterations = likely_max_loop_iterations_int (loop); |
a01e93f1 YR |
522 | if (iterations >= 0 && iterations <= 1) |
523 | { | |
524 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
525 | fprintf (dump_file, ";; Not unswitching, loop is not expected" | |
526 | " to iterate\n"); | |
0581d86f | 527 | return false; |
a01e93f1 YR |
528 | } |
529 | ||
622d8b69 RB |
530 | bool changed = false; |
531 | while ((guard = find_loop_guard (loop))) | |
a01e93f1 | 532 | { |
622d8b69 RB |
533 | if (! changed) |
534 | rewrite_virtuals_into_loop_closed_ssa (loop); | |
a01e93f1 | 535 | hoist_guard (loop, guard); |
622d8b69 | 536 | changed = true; |
a01e93f1 | 537 | } |
622d8b69 | 538 | return changed; |
a01e93f1 YR |
539 | } |
540 | ||
541 | /* Checks if the body of the LOOP is within an invariant guard. If this | |
542 | is the case, returns the edge that jumps over the real body of the loop, | |
543 | otherwise returns NULL. */ | |
544 | ||
545 | static edge | |
99b1c316 | 546 | find_loop_guard (class loop *loop) |
a01e93f1 YR |
547 | { |
548 | basic_block header = loop->header; | |
549 | edge guard_edge, te, fe; | |
a01e93f1 YR |
550 | basic_block *body = NULL; |
551 | unsigned i; | |
552 | tree use; | |
553 | ssa_op_iter iter; | |
554 | ||
555 | /* We check for the following situation: | |
556 | ||
557 | while (1) | |
558 | { | |
559 | [header]] | |
560 | loop_phi_nodes; | |
561 | something1; | |
562 | if (cond1) | |
563 | body; | |
564 | nvar = phi(orig, bvar) ... for all variables changed in body; | |
565 | [guard_end] | |
566 | something2; | |
567 | if (cond2) | |
568 | break; | |
569 | something3; | |
570 | } | |
571 | ||
572 | where: | |
573 | ||
574 | 1) cond1 is loop invariant | |
575 | 2) If cond1 is false, then the loop is essentially empty; i.e., | |
576 | a) nothing in something1, something2 and something3 has side | |
577 | effects | |
578 | b) anything defined in something1, something2 and something3 | |
579 | is not used outside of the loop. */ | |
580 | ||
622d8b69 RB |
581 | gcond *cond; |
582 | do | |
583 | { | |
1aa54f90 | 584 | basic_block next = NULL; |
622d8b69 | 585 | if (single_succ_p (header)) |
1aa54f90 | 586 | next = single_succ (header); |
622d8b69 RB |
587 | else |
588 | { | |
b30e83f8 | 589 | cond = safe_dyn_cast <gcond *> (last_stmt (header)); |
622d8b69 RB |
590 | if (! cond) |
591 | return NULL; | |
592 | extract_true_false_edges_from_block (header, &te, &fe); | |
593 | /* Make sure to skip earlier hoisted guards that are left | |
594 | in place as if (true). */ | |
595 | if (gimple_cond_true_p (cond)) | |
1aa54f90 | 596 | next = te->dest; |
622d8b69 | 597 | else if (gimple_cond_false_p (cond)) |
1aa54f90 | 598 | next = fe->dest; |
622d8b69 RB |
599 | else |
600 | break; | |
601 | } | |
1aa54f90 RB |
602 | /* Never traverse a backedge. */ |
603 | if (header->loop_father->header == next) | |
604 | return NULL; | |
605 | header = next; | |
622d8b69 RB |
606 | } |
607 | while (1); | |
a01e93f1 YR |
608 | if (!flow_bb_inside_loop_p (loop, te->dest) |
609 | || !flow_bb_inside_loop_p (loop, fe->dest)) | |
610 | return NULL; | |
611 | ||
612 | if (just_once_each_iteration_p (loop, te->dest) | |
613 | || (single_succ_p (te->dest) | |
614 | && just_once_each_iteration_p (loop, single_succ (te->dest)))) | |
615 | { | |
616 | if (just_once_each_iteration_p (loop, fe->dest)) | |
617 | return NULL; | |
618 | guard_edge = te; | |
619 | } | |
620 | else if (just_once_each_iteration_p (loop, fe->dest) | |
621 | || (single_succ_p (fe->dest) | |
622 | && just_once_each_iteration_p (loop, single_succ (fe->dest)))) | |
623 | guard_edge = fe; | |
624 | else | |
625 | return NULL; | |
626 | ||
8a18fcf4 YR |
627 | /* Guard edge must skip inner loop. */ |
628 | if (!dominated_by_p (CDI_DOMINATORS, loop->inner->header, | |
629 | guard_edge == fe ? te->dest : fe->dest)) | |
630 | { | |
631 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
632 | fprintf (dump_file, "Guard edge %d --> %d is not around the loop!\n", | |
633 | guard_edge->src->index, guard_edge->dest->index); | |
634 | return NULL; | |
635 | } | |
19aa23d8 YR |
636 | if (guard_edge->dest == loop->latch) |
637 | { | |
638 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
639 | fprintf (dump_file, "Guard edge destination is loop latch.\n"); | |
640 | return NULL; | |
641 | } | |
8a18fcf4 | 642 | |
a01e93f1 YR |
643 | if (dump_file && (dump_flags & TDF_DETAILS)) |
644 | fprintf (dump_file, | |
645 | "Considering guard %d -> %d in loop %d\n", | |
646 | guard_edge->src->index, guard_edge->dest->index, loop->num); | |
647 | /* Check if condition operands do not have definitions inside loop since | |
648 | any bb copying is not performed. */ | |
622d8b69 | 649 | FOR_EACH_SSA_TREE_OPERAND (use, cond, iter, SSA_OP_USE) |
a01e93f1 YR |
650 | { |
651 | gimple *def = SSA_NAME_DEF_STMT (use); | |
652 | basic_block def_bb = gimple_bb (def); | |
653 | if (def_bb | |
654 | && flow_bb_inside_loop_p (loop, def_bb)) | |
655 | { | |
656 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
657 | fprintf (dump_file, " guard operands have definitions" | |
658 | " inside loop\n"); | |
659 | return NULL; | |
660 | } | |
661 | } | |
662 | ||
663 | body = get_loop_body (loop); | |
664 | for (i = 0; i < loop->num_nodes; i++) | |
665 | { | |
666 | basic_block bb = body[i]; | |
667 | if (bb->loop_father != loop) | |
668 | continue; | |
669 | if (bb->flags & BB_IRREDUCIBLE_LOOP) | |
670 | { | |
671 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
672 | fprintf (dump_file, "Block %d is marked as irreducible in loop\n", | |
673 | bb->index); | |
674 | guard_edge = NULL; | |
675 | goto end; | |
676 | } | |
677 | if (!empty_bb_without_guard_p (loop, bb)) | |
678 | { | |
679 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
680 | fprintf (dump_file, " block %d has side effects\n", bb->index); | |
681 | guard_edge = NULL; | |
682 | goto end; | |
683 | } | |
684 | } | |
685 | ||
686 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
687 | fprintf (dump_file, " suitable to hoist\n"); | |
688 | end: | |
689 | if (body) | |
690 | free (body); | |
691 | return guard_edge; | |
692 | } | |
693 | ||
694 | /* Returns true if | |
695 | 1) no statement in BB has side effects | |
696 | 2) assuming that edge GUARD is always taken, all definitions in BB | |
697 | are noy used outside of the loop. | |
698 | KNOWN_INVARIANTS is a set of ssa names we know to be invariant, and | |
699 | PROCESSED is a set of ssa names for that we already tested whether they | |
700 | are invariant or not. */ | |
701 | ||
702 | static bool | |
99b1c316 | 703 | empty_bb_without_guard_p (class loop *loop, basic_block bb) |
a01e93f1 YR |
704 | { |
705 | basic_block exit_bb = single_exit (loop)->src; | |
706 | bool may_be_used_outside = (bb == exit_bb | |
707 | || !dominated_by_p (CDI_DOMINATORS, bb, exit_bb)); | |
708 | tree name; | |
709 | ssa_op_iter op_iter; | |
710 | ||
711 | /* Phi nodes do not have side effects, but their results might be used | |
712 | outside of the loop. */ | |
713 | if (may_be_used_outside) | |
714 | { | |
715 | for (gphi_iterator gsi = gsi_start_phis (bb); | |
716 | !gsi_end_p (gsi); gsi_next (&gsi)) | |
717 | { | |
718 | gphi *phi = gsi.phi (); | |
719 | name = PHI_RESULT (phi); | |
720 | if (virtual_operand_p (name)) | |
721 | continue; | |
722 | ||
723 | if (used_outside_loop_p (loop, name)) | |
724 | return false; | |
725 | } | |
726 | } | |
727 | ||
728 | for (gimple_stmt_iterator gsi = gsi_start_bb (bb); | |
729 | !gsi_end_p (gsi); gsi_next (&gsi)) | |
730 | { | |
731 | gimple *stmt = gsi_stmt (gsi); | |
732 | if (gimple_has_side_effects (stmt)) | |
733 | return false; | |
734 | ||
735 | if (gimple_vdef(stmt)) | |
736 | return false; | |
737 | ||
738 | FOR_EACH_SSA_TREE_OPERAND (name, stmt, op_iter, SSA_OP_DEF) | |
739 | { | |
740 | if (may_be_used_outside | |
741 | && used_outside_loop_p (loop, name)) | |
742 | return false; | |
743 | } | |
744 | } | |
745 | return true; | |
746 | } | |
747 | ||
748 | /* Return true if NAME is used outside of LOOP. */ | |
749 | ||
750 | static bool | |
99b1c316 | 751 | used_outside_loop_p (class loop *loop, tree name) |
a01e93f1 YR |
752 | { |
753 | imm_use_iterator it; | |
754 | use_operand_p use; | |
755 | ||
756 | FOR_EACH_IMM_USE_FAST (use, it, name) | |
757 | { | |
758 | gimple *stmt = USE_STMT (use); | |
759 | if (!flow_bb_inside_loop_p (loop, gimple_bb (stmt))) | |
760 | return true; | |
761 | } | |
762 | ||
763 | return false; | |
764 | } | |
765 | ||
766 | /* Return argument for loop preheader edge in header virtual phi if any. */ | |
767 | ||
768 | static tree | |
99b1c316 | 769 | get_vop_from_header (class loop *loop) |
a01e93f1 YR |
770 | { |
771 | for (gphi_iterator gsi = gsi_start_phis (loop->header); | |
772 | !gsi_end_p (gsi); gsi_next (&gsi)) | |
773 | { | |
774 | gphi *phi = gsi.phi (); | |
775 | if (!virtual_operand_p (gimple_phi_result (phi))) | |
776 | continue; | |
777 | return PHI_ARG_DEF_FROM_EDGE (phi, loop_preheader_edge (loop)); | |
778 | } | |
779 | return NULL_TREE; | |
780 | } | |
781 | ||
782 | /* Move the check of GUARD outside of LOOP. */ | |
783 | ||
784 | static void | |
99b1c316 | 785 | hoist_guard (class loop *loop, edge guard) |
a01e93f1 YR |
786 | { |
787 | edge exit = single_exit (loop); | |
788 | edge preh = loop_preheader_edge (loop); | |
789 | basic_block pre_header = preh->src; | |
790 | basic_block bb; | |
791 | edge te, fe, e, new_edge; | |
792 | gimple *stmt; | |
793 | basic_block guard_bb = guard->src; | |
0b90c541 | 794 | edge not_guard; |
a01e93f1 YR |
795 | gimple_stmt_iterator gsi; |
796 | int flags = 0; | |
797 | bool fix_dom_of_exit; | |
798 | gcond *cond_stmt, *new_cond_stmt; | |
799 | ||
800 | bb = get_immediate_dominator (CDI_DOMINATORS, exit->dest); | |
801 | fix_dom_of_exit = flow_bb_inside_loop_p (loop, bb); | |
802 | gsi = gsi_last_bb (guard_bb); | |
803 | stmt = gsi_stmt (gsi); | |
804 | gcc_assert (gimple_code (stmt) == GIMPLE_COND); | |
805 | cond_stmt = as_a <gcond *> (stmt); | |
806 | extract_true_false_edges_from_block (guard_bb, &te, &fe); | |
807 | /* Insert guard to PRE_HEADER. */ | |
808 | if (!empty_block_p (pre_header)) | |
809 | gsi = gsi_last_bb (pre_header); | |
810 | else | |
811 | gsi = gsi_start_bb (pre_header); | |
812 | /* Create copy of COND_STMT. */ | |
813 | new_cond_stmt = gimple_build_cond (gimple_cond_code (cond_stmt), | |
814 | gimple_cond_lhs (cond_stmt), | |
815 | gimple_cond_rhs (cond_stmt), | |
816 | NULL_TREE, NULL_TREE); | |
817 | gsi_insert_after (&gsi, new_cond_stmt, GSI_NEW_STMT); | |
818 | /* Convert COND_STMT to true/false conditional. */ | |
819 | if (guard == te) | |
820 | gimple_cond_make_false (cond_stmt); | |
821 | else | |
822 | gimple_cond_make_true (cond_stmt); | |
823 | update_stmt (cond_stmt); | |
824 | /* Create new loop pre-header. */ | |
825 | e = split_block (pre_header, last_stmt (pre_header)); | |
0b90c541 | 826 | if (dump_file && (dump_flags & TDF_DETAILS)) |
357067f2 JH |
827 | { |
828 | fprintf (dump_file, " Moving guard %i->%i (prob ", | |
829 | guard->src->index, guard->dest->index); | |
830 | guard->probability.dump (dump_file); | |
831 | fprintf (dump_file, ") to bb %i, new preheader is %i\n", | |
832 | e->src->index, e->dest->index); | |
833 | } | |
0b90c541 | 834 | |
a01e93f1 | 835 | gcc_assert (loop_preheader_edge (loop)->src == e->dest); |
0b90c541 | 836 | |
a01e93f1 YR |
837 | if (guard == fe) |
838 | { | |
839 | e->flags = EDGE_TRUE_VALUE; | |
840 | flags |= EDGE_FALSE_VALUE; | |
0b90c541 | 841 | not_guard = te; |
a01e93f1 YR |
842 | } |
843 | else | |
844 | { | |
845 | e->flags = EDGE_FALSE_VALUE; | |
846 | flags |= EDGE_TRUE_VALUE; | |
0b90c541 | 847 | not_guard = fe; |
a01e93f1 YR |
848 | } |
849 | new_edge = make_edge (pre_header, exit->dest, flags); | |
0b90c541 JH |
850 | |
851 | /* Determine the probability that we skip the loop. Assume that loop has | |
852 | same average number of iterations regardless outcome of guard. */ | |
853 | new_edge->probability = guard->probability; | |
e7a74006 | 854 | profile_count skip_count = guard->src->count.nonzero_p () |
ef30ab83 | 855 | ? guard->count ().apply_scale (pre_header->count, |
3995f3a2 | 856 | guard->src->count) |
ef30ab83 | 857 | : guard->count ().apply_probability (new_edge->probability); |
0b90c541 | 858 | |
ef30ab83 | 859 | if (skip_count > e->count ()) |
0b90c541 JH |
860 | { |
861 | fprintf (dump_file, " Capping count; expect profile inconsistency\n"); | |
ef30ab83 | 862 | skip_count = e->count (); |
0b90c541 | 863 | } |
0b90c541 | 864 | if (dump_file && (dump_flags & TDF_DETAILS)) |
357067f2 JH |
865 | { |
866 | fprintf (dump_file, " Estimated probability of skipping loop is "); | |
867 | new_edge->probability.dump (dump_file); | |
868 | fprintf (dump_file, "\n"); | |
869 | } | |
0b90c541 JH |
870 | |
871 | /* Update profile after the transform: | |
872 | ||
873 | First decrease count of path from newly hoisted loop guard | |
874 | to loop header... */ | |
357067f2 | 875 | e->probability = new_edge->probability.invert (); |
ef30ab83 | 876 | e->dest->count = e->count (); |
0b90c541 JH |
877 | |
878 | /* ... now update profile to represent that original guard will be optimized | |
879 | away ... */ | |
357067f2 | 880 | guard->probability = profile_probability::never (); |
357067f2 | 881 | not_guard->probability = profile_probability::always (); |
0b90c541 JH |
882 | |
883 | /* ... finally scale everything in the loop except for guarded basic blocks | |
884 | where profile does not change. */ | |
885 | basic_block *body = get_loop_body (loop); | |
da9cd044 | 886 | |
0b90c541 JH |
887 | if (dump_file && (dump_flags & TDF_DETAILS)) |
888 | fprintf (dump_file, " Scaling nonguarded BBs in loop:"); | |
889 | for (unsigned int i = 0; i < loop->num_nodes; i++) | |
890 | { | |
891 | basic_block bb = body[i]; | |
892 | if (!dominated_by_p (CDI_DOMINATORS, bb, not_guard->dest)) | |
893 | { | |
894 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
895 | fprintf (dump_file, " %i", bb->index); | |
357067f2 | 896 | if (e->probability.initialized_p ()) |
77ba27b4 | 897 | scale_bbs_frequencies (&bb, 1, e->probability); |
0b90c541 JH |
898 | } |
899 | } | |
900 | ||
a01e93f1 YR |
901 | if (fix_dom_of_exit) |
902 | set_immediate_dominator (CDI_DOMINATORS, exit->dest, pre_header); | |
903 | /* Add NEW_ADGE argument for all phi in post-header block. */ | |
904 | bb = exit->dest; | |
905 | for (gphi_iterator gsi = gsi_start_phis (bb); | |
906 | !gsi_end_p (gsi); gsi_next (&gsi)) | |
907 | { | |
908 | gphi *phi = gsi.phi (); | |
909 | tree arg; | |
910 | if (virtual_operand_p (gimple_phi_result (phi))) | |
911 | { | |
912 | arg = get_vop_from_header (loop); | |
913 | if (arg == NULL_TREE) | |
914 | /* Use exit edge argument. */ | |
915 | arg = PHI_ARG_DEF_FROM_EDGE (phi, exit); | |
916 | add_phi_arg (phi, arg, new_edge, UNKNOWN_LOCATION); | |
917 | } | |
918 | else | |
919 | { | |
920 | /* Use exit edge argument. */ | |
921 | arg = PHI_ARG_DEF_FROM_EDGE (phi, exit); | |
922 | add_phi_arg (phi, arg, new_edge, UNKNOWN_LOCATION); | |
923 | } | |
924 | } | |
925 | ||
a01e93f1 | 926 | if (dump_file && (dump_flags & TDF_DETAILS)) |
0b90c541 | 927 | fprintf (dump_file, "\n guard hoisted.\n"); |
da9cd044 ML |
928 | |
929 | free (body); | |
a01e93f1 YR |
930 | } |
931 | ||
932 | /* Return true if phi argument for exit edge can be used | |
933 | for edge around loop. */ | |
934 | ||
935 | static bool | |
99b1c316 | 936 | check_exit_phi (class loop *loop) |
a01e93f1 YR |
937 | { |
938 | edge exit = single_exit (loop); | |
939 | basic_block pre_header = loop_preheader_edge (loop)->src; | |
940 | ||
941 | for (gphi_iterator gsi = gsi_start_phis (exit->dest); | |
942 | !gsi_end_p (gsi); gsi_next (&gsi)) | |
943 | { | |
944 | gphi *phi = gsi.phi (); | |
945 | tree arg; | |
946 | gimple *def; | |
947 | basic_block def_bb; | |
948 | if (virtual_operand_p (gimple_phi_result (phi))) | |
949 | continue; | |
950 | arg = PHI_ARG_DEF_FROM_EDGE (phi, exit); | |
951 | if (TREE_CODE (arg) != SSA_NAME) | |
952 | continue; | |
953 | def = SSA_NAME_DEF_STMT (arg); | |
954 | if (!def) | |
955 | continue; | |
956 | def_bb = gimple_bb (def); | |
957 | if (!def_bb) | |
958 | continue; | |
959 | if (!dominated_by_p (CDI_DOMINATORS, pre_header, def_bb)) | |
960 | /* Definition inside loop! */ | |
961 | return false; | |
962 | /* Check loop closed phi invariant. */ | |
963 | if (!flow_bb_inside_loop_p (def_bb->loop_father, pre_header)) | |
964 | return false; | |
965 | } | |
966 | return true; | |
967 | } | |
968 | ||
71343877 AM |
969 | /* Loop unswitching pass. */ |
970 | ||
71343877 AM |
971 | namespace { |
972 | ||
973 | const pass_data pass_data_tree_unswitch = | |
974 | { | |
975 | GIMPLE_PASS, /* type */ | |
976 | "unswitch", /* name */ | |
977 | OPTGROUP_LOOP, /* optinfo_flags */ | |
71343877 AM |
978 | TV_TREE_LOOP_UNSWITCH, /* tv_id */ |
979 | PROP_cfg, /* properties_required */ | |
980 | 0, /* properties_provided */ | |
981 | 0, /* properties_destroyed */ | |
982 | 0, /* todo_flags_start */ | |
983 | 0, /* todo_flags_finish */ | |
984 | }; | |
985 | ||
986 | class pass_tree_unswitch : public gimple_opt_pass | |
987 | { | |
988 | public: | |
989 | pass_tree_unswitch (gcc::context *ctxt) | |
990 | : gimple_opt_pass (pass_data_tree_unswitch, ctxt) | |
991 | {} | |
992 | ||
993 | /* opt_pass methods: */ | |
1a3d085c | 994 | virtual bool gate (function *) { return flag_unswitch_loops != 0; } |
be55bfe6 | 995 | virtual unsigned int execute (function *); |
71343877 AM |
996 | |
997 | }; // class pass_tree_unswitch | |
998 | ||
be55bfe6 TS |
999 | unsigned int |
1000 | pass_tree_unswitch::execute (function *fun) | |
1001 | { | |
1002 | if (number_of_loops (fun) <= 1) | |
1003 | return 0; | |
1004 | ||
1005 | return tree_ssa_unswitch_loops (); | |
1006 | } | |
1007 | ||
71343877 AM |
1008 | } // anon namespace |
1009 | ||
1010 | gimple_opt_pass * | |
1011 | make_pass_tree_unswitch (gcc::context *ctxt) | |
1012 | { | |
1013 | return new pass_tree_unswitch (ctxt); | |
1014 | } | |
1015 | ||
1016 |