PR sanitizer/65400
[official-gcc.git] / gcc / tree-ssa-loop-unswitch.c
blob7225acda3025717660e23b7550fbaa73bd6941f1
1 /* Loop unswitching.
2 Copyright (C) 2004-2015 Free Software Foundation, Inc.
4 This file is part of GCC.
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
8 Free Software Foundation; either version 3, or (at your option) any
9 later version.
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.
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING3. If not see
18 <http://www.gnu.org/licenses/>. */
20 #include "config.h"
21 #include "system.h"
22 #include "coretypes.h"
23 #include "tm.h"
24 #include "hash-set.h"
25 #include "machmode.h"
26 #include "vec.h"
27 #include "double-int.h"
28 #include "input.h"
29 #include "alias.h"
30 #include "symtab.h"
31 #include "wide-int.h"
32 #include "inchash.h"
33 #include "tree.h"
34 #include "fold-const.h"
35 #include "tm_p.h"
36 #include "predict.h"
37 #include "hard-reg-set.h"
38 #include "input.h"
39 #include "function.h"
40 #include "dominance.h"
41 #include "cfg.h"
42 #include "basic-block.h"
43 #include "tree-ssa-alias.h"
44 #include "internal-fn.h"
45 #include "gimple-expr.h"
46 #include "is-a.h"
47 #include "gimple.h"
48 #include "gimplify.h"
49 #include "gimple-ssa.h"
50 #include "tree-cfg.h"
51 #include "tree-phinodes.h"
52 #include "ssa-iterators.h"
53 #include "tree-ssa-loop-niter.h"
54 #include "tree-ssa-loop.h"
55 #include "tree-into-ssa.h"
56 #include "cfgloop.h"
57 #include "params.h"
58 #include "tree-pass.h"
59 #include "tree-inline.h"
61 /* This file implements the loop unswitching, i.e. transformation of loops like
63 while (A)
65 if (inv)
70 if (!inv)
74 where inv is the loop invariant, into
76 if (inv)
78 while (A)
84 else
86 while (A)
93 Inv is considered invariant iff the values it compares are both invariant;
94 tree-ssa-loop-im.c ensures that all the suitable conditions are in this
95 shape. */
97 static struct loop *tree_unswitch_loop (struct loop *, basic_block, tree);
98 static bool tree_unswitch_single_loop (struct loop *, int);
99 static tree tree_may_unswitch_on (basic_block, struct loop *);
101 /* Main entry point. Perform loop unswitching on all suitable loops. */
103 unsigned int
104 tree_ssa_unswitch_loops (void)
106 struct loop *loop;
107 bool changed = false;
108 HOST_WIDE_INT iterations;
110 /* Go through inner loops (only original ones). */
111 FOR_EACH_LOOP (loop, LI_ONLY_INNERMOST)
113 if (dump_file && (dump_flags & TDF_DETAILS))
114 fprintf (dump_file, ";; Considering loop %d\n", loop->num);
116 /* Do not unswitch in cold regions. */
117 if (optimize_loop_for_size_p (loop))
119 if (dump_file && (dump_flags & TDF_DETAILS))
120 fprintf (dump_file, ";; Not unswitching cold loops\n");
121 continue;
124 /* The loop should not be too large, to limit code growth. */
125 if (tree_num_loop_insns (loop, &eni_size_weights)
126 > (unsigned) PARAM_VALUE (PARAM_MAX_UNSWITCH_INSNS))
128 if (dump_file && (dump_flags & TDF_DETAILS))
129 fprintf (dump_file, ";; Not unswitching, loop too big\n");
130 continue;
133 /* If the loop is not expected to iterate, there is no need
134 for unswitching. */
135 iterations = estimated_loop_iterations_int (loop);
136 if (iterations >= 0 && iterations <= 1)
138 if (dump_file && (dump_flags & TDF_DETAILS))
139 fprintf (dump_file, ";; Not unswitching, loop is not expected to iterate\n");
140 continue;
143 changed |= tree_unswitch_single_loop (loop, 0);
146 if (changed)
147 return TODO_cleanup_cfg;
148 return 0;
151 /* Checks whether we can unswitch LOOP on condition at end of BB -- one of its
152 basic blocks (for what it means see comments below). */
154 static tree
155 tree_may_unswitch_on (basic_block bb, struct loop *loop)
157 gimple last, def;
158 gcond *stmt;
159 tree cond, use;
160 basic_block def_bb;
161 ssa_op_iter iter;
163 /* BB must end in a simple conditional jump. */
164 last = last_stmt (bb);
165 if (!last || gimple_code (last) != GIMPLE_COND)
166 return NULL_TREE;
167 stmt = as_a <gcond *> (last);
169 /* To keep the things simple, we do not directly remove the conditions,
170 but just replace tests with 0 != 0 resp. 1 != 0. Prevent the infinite
171 loop where we would unswitch again on such a condition. */
172 if (gimple_cond_true_p (stmt) || gimple_cond_false_p (stmt))
173 return NULL_TREE;
175 /* Condition must be invariant. */
176 FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE)
178 def = SSA_NAME_DEF_STMT (use);
179 def_bb = gimple_bb (def);
180 if (def_bb
181 && flow_bb_inside_loop_p (loop, def_bb))
182 return NULL_TREE;
185 cond = build2 (gimple_cond_code (stmt), boolean_type_node,
186 gimple_cond_lhs (stmt), gimple_cond_rhs (stmt));
188 return cond;
191 /* Simplifies COND using checks in front of the entry of the LOOP. Just very
192 simplish (sufficient to prevent us from duplicating loop in unswitching
193 unnecessarily). */
195 static tree
196 simplify_using_entry_checks (struct loop *loop, tree cond)
198 edge e = loop_preheader_edge (loop);
199 gimple stmt;
201 while (1)
203 stmt = last_stmt (e->src);
204 if (stmt
205 && gimple_code (stmt) == GIMPLE_COND
206 && gimple_cond_code (stmt) == TREE_CODE (cond)
207 && operand_equal_p (gimple_cond_lhs (stmt),
208 TREE_OPERAND (cond, 0), 0)
209 && operand_equal_p (gimple_cond_rhs (stmt),
210 TREE_OPERAND (cond, 1), 0))
211 return (e->flags & EDGE_TRUE_VALUE
212 ? boolean_true_node
213 : boolean_false_node);
215 if (!single_pred_p (e->src))
216 return cond;
218 e = single_pred_edge (e->src);
219 if (e->src == ENTRY_BLOCK_PTR_FOR_FN (cfun))
220 return cond;
224 /* Unswitch single LOOP. NUM is number of unswitchings done; we do not allow
225 it to grow too much, it is too easy to create example on that the code would
226 grow exponentially. */
228 static bool
229 tree_unswitch_single_loop (struct loop *loop, int num)
231 basic_block *bbs;
232 struct loop *nloop;
233 unsigned i, found;
234 tree cond = NULL_TREE;
235 gimple stmt;
236 bool changed = false;
238 i = 0;
239 bbs = get_loop_body (loop);
240 found = loop->num_nodes;
242 while (1)
244 /* Find a bb to unswitch on. */
245 for (; i < loop->num_nodes; i++)
246 if ((cond = tree_may_unswitch_on (bbs[i], loop)))
247 break;
249 if (i == loop->num_nodes)
251 if (dump_file
252 && num > PARAM_VALUE (PARAM_MAX_UNSWITCH_LEVEL)
253 && (dump_flags & TDF_DETAILS))
254 fprintf (dump_file, ";; Not unswitching anymore, hit max level\n");
256 if (found == loop->num_nodes)
258 free (bbs);
259 return changed;
261 break;
264 cond = simplify_using_entry_checks (loop, cond);
265 stmt = last_stmt (bbs[i]);
266 if (integer_nonzerop (cond))
268 /* Remove false path. */
269 gimple_cond_set_condition_from_tree (as_a <gcond *> (stmt),
270 boolean_true_node);
271 changed = true;
273 else if (integer_zerop (cond))
275 /* Remove true path. */
276 gimple_cond_set_condition_from_tree (as_a <gcond *> (stmt),
277 boolean_false_node);
278 changed = true;
280 /* Do not unswitch too much. */
281 else if (num > PARAM_VALUE (PARAM_MAX_UNSWITCH_LEVEL))
283 i++;
284 continue;
286 /* In nested tree_unswitch_single_loop first optimize all conditions
287 using entry checks, then discover still reachable blocks in the
288 loop and find the condition only among those still reachable bbs. */
289 else if (num != 0)
291 if (found == loop->num_nodes)
292 found = i;
293 i++;
294 continue;
296 else
298 found = i;
299 break;
302 update_stmt (stmt);
303 i++;
306 if (num != 0)
308 basic_block *tos, *worklist;
310 /* When called recursively, first do a quick discovery
311 of reachable bbs after the above changes and only
312 consider conditions in still reachable bbs. */
313 tos = worklist = XNEWVEC (basic_block, loop->num_nodes);
315 for (i = 0; i < loop->num_nodes; i++)
316 bbs[i]->flags &= ~BB_REACHABLE;
318 /* Start with marking header. */
319 *tos++ = bbs[0];
320 bbs[0]->flags |= BB_REACHABLE;
322 /* Iterate: find everything reachable from what we've already seen
323 within the same innermost loop. Don't look through false edges
324 if condition is always true or true edges if condition is
325 always false. */
326 while (tos != worklist)
328 basic_block b = *--tos;
329 edge e;
330 edge_iterator ei;
331 int flags = 0;
333 if (EDGE_COUNT (b->succs) == 2)
335 gimple stmt = last_stmt (b);
336 if (stmt
337 && gimple_code (stmt) == GIMPLE_COND)
339 gcond *cond_stmt = as_a <gcond *> (stmt);
340 if (gimple_cond_true_p (cond_stmt))
341 flags = EDGE_FALSE_VALUE;
342 else if (gimple_cond_false_p (cond_stmt))
343 flags = EDGE_TRUE_VALUE;
347 FOR_EACH_EDGE (e, ei, b->succs)
349 basic_block dest = e->dest;
351 if (dest->loop_father == loop
352 && !(dest->flags & BB_REACHABLE)
353 && !(e->flags & flags))
355 *tos++ = dest;
356 dest->flags |= BB_REACHABLE;
361 free (worklist);
363 /* Find a bb to unswitch on. */
364 for (; found < loop->num_nodes; found++)
365 if ((bbs[found]->flags & BB_REACHABLE)
366 && (cond = tree_may_unswitch_on (bbs[found], loop)))
367 break;
369 if (found == loop->num_nodes)
371 free (bbs);
372 return changed;
376 if (dump_file && (dump_flags & TDF_DETAILS))
377 fprintf (dump_file, ";; Unswitching loop\n");
379 initialize_original_copy_tables ();
380 /* Unswitch the loop on this condition. */
381 nloop = tree_unswitch_loop (loop, bbs[found], cond);
382 if (!nloop)
384 free_original_copy_tables ();
385 free (bbs);
386 return changed;
389 /* Update the SSA form after unswitching. */
390 update_ssa (TODO_update_ssa);
391 free_original_copy_tables ();
393 /* Invoke itself on modified loops. */
394 tree_unswitch_single_loop (nloop, num + 1);
395 tree_unswitch_single_loop (loop, num + 1);
396 free (bbs);
397 return true;
400 /* Unswitch a LOOP w.r. to given basic block UNSWITCH_ON. We only support
401 unswitching of innermost loops. COND is the condition determining which
402 loop is entered -- the new loop is entered if COND is true. Returns NULL
403 if impossible, new loop otherwise. */
405 static struct loop *
406 tree_unswitch_loop (struct loop *loop,
407 basic_block unswitch_on, tree cond)
409 unsigned prob_true;
410 edge edge_true, edge_false;
412 /* Some sanity checking. */
413 gcc_assert (flow_bb_inside_loop_p (loop, unswitch_on));
414 gcc_assert (EDGE_COUNT (unswitch_on->succs) == 2);
415 gcc_assert (loop->inner == NULL);
417 extract_true_false_edges_from_block (unswitch_on, &edge_true, &edge_false);
418 prob_true = edge_true->probability;
419 return loop_version (loop, unshare_expr (cond),
420 NULL, prob_true, prob_true,
421 REG_BR_PROB_BASE - prob_true, false);
424 /* Loop unswitching pass. */
426 namespace {
428 const pass_data pass_data_tree_unswitch =
430 GIMPLE_PASS, /* type */
431 "unswitch", /* name */
432 OPTGROUP_LOOP, /* optinfo_flags */
433 TV_TREE_LOOP_UNSWITCH, /* tv_id */
434 PROP_cfg, /* properties_required */
435 0, /* properties_provided */
436 0, /* properties_destroyed */
437 0, /* todo_flags_start */
438 0, /* todo_flags_finish */
441 class pass_tree_unswitch : public gimple_opt_pass
443 public:
444 pass_tree_unswitch (gcc::context *ctxt)
445 : gimple_opt_pass (pass_data_tree_unswitch, ctxt)
448 /* opt_pass methods: */
449 virtual bool gate (function *) { return flag_unswitch_loops != 0; }
450 virtual unsigned int execute (function *);
452 }; // class pass_tree_unswitch
454 unsigned int
455 pass_tree_unswitch::execute (function *fun)
457 if (number_of_loops (fun) <= 1)
458 return 0;
460 return tree_ssa_unswitch_loops ();
463 } // anon namespace
465 gimple_opt_pass *
466 make_pass_tree_unswitch (gcc::context *ctxt)
468 return new pass_tree_unswitch (ctxt);