* cgraph.c (cgraph_edge::maybe_hot_p): Do not check
[official-gcc.git] / gcc / tracer.c
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1 /* The tracer pass for the GNU compiler.
2 Contributed by Jan Hubicka, SuSE Labs.
3 Adapted to work on GIMPLE instead of RTL by Robert Kidd, UIUC.
4 Copyright (C) 2001-2017 Free Software Foundation, Inc.
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify it
9 under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 3, or (at your option)
11 any later version.
13 GCC is distributed in the hope that it will be useful, but WITHOUT
14 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
15 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
16 License for more details.
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING3. If not see
20 <http://www.gnu.org/licenses/>. */
22 /* This pass performs the tail duplication needed for superblock formation.
23 For more information see:
25 Design and Analysis of Profile-Based Optimization in Compaq's
26 Compilation Tools for Alpha; Journal of Instruction-Level
27 Parallelism 3 (2000) 1-25
29 Unlike Compaq's implementation we don't do the loop peeling as most
30 probably a better job can be done by a special pass and we don't
31 need to worry too much about the code size implications as the tail
32 duplicates are crossjumped again if optimizations are not
33 performed. */
36 #include "config.h"
37 #include "system.h"
38 #include "coretypes.h"
39 #include "backend.h"
40 #include "rtl.h"
41 #include "tree.h"
42 #include "gimple.h"
43 #include "cfghooks.h"
44 #include "tree-pass.h"
45 #include "profile.h"
46 #include "cfganal.h"
47 #include "params.h"
48 #include "gimple-iterator.h"
49 #include "tree-cfg.h"
50 #include "tree-ssa.h"
51 #include "tree-inline.h"
52 #include "cfgloop.h"
53 #include "fibonacci_heap.h"
54 #include "tracer.h"
56 static int count_insns (basic_block);
57 static bool better_p (const_edge, const_edge);
58 static edge find_best_successor (basic_block);
59 static edge find_best_predecessor (basic_block);
60 static int find_trace (basic_block, basic_block *);
62 /* Minimal outgoing edge probability considered for superblock formation. */
63 static int probability_cutoff;
64 static int branch_ratio_cutoff;
66 /* A bit BB->index is set if BB has already been seen, i.e. it is
67 connected to some trace already. */
68 static sbitmap bb_seen;
70 static inline void
71 mark_bb_seen (basic_block bb)
73 unsigned int size = SBITMAP_SIZE (bb_seen);
75 if ((unsigned int)bb->index >= size)
76 bb_seen = sbitmap_resize (bb_seen, size * 2, 0);
78 bitmap_set_bit (bb_seen, bb->index);
81 static inline bool
82 bb_seen_p (basic_block bb)
84 return bitmap_bit_p (bb_seen, bb->index);
87 /* Return true if we should ignore the basic block for purposes of tracing. */
88 bool
89 ignore_bb_p (const_basic_block bb)
91 if (bb->index < NUM_FIXED_BLOCKS)
92 return true;
93 if (optimize_bb_for_size_p (bb))
94 return true;
96 if (gimple *g = last_stmt (CONST_CAST_BB (bb)))
98 /* A transaction is a single entry multiple exit region. It
99 must be duplicated in its entirety or not at all. */
100 if (gimple_code (g) == GIMPLE_TRANSACTION)
101 return true;
103 /* An IFN_UNIQUE call must be duplicated as part of its group,
104 or not at all. */
105 if (is_gimple_call (g)
106 && gimple_call_internal_p (g)
107 && gimple_call_internal_unique_p (g))
108 return true;
111 return false;
114 /* Return number of instructions in the block. */
116 static int
117 count_insns (basic_block bb)
119 gimple_stmt_iterator gsi;
120 gimple *stmt;
121 int n = 0;
123 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
125 stmt = gsi_stmt (gsi);
126 n += estimate_num_insns (stmt, &eni_size_weights);
128 return n;
131 /* Return true if E1 is more frequent than E2. */
132 static bool
133 better_p (const_edge e1, const_edge e2)
135 if (e1->count.initialized_p () && e2->count.initialized_p ()
136 && !(e1->count == e2->count))
137 return e1->count > e2->count;
138 if (e1->src->frequency * e1->probability !=
139 e2->src->frequency * e2->probability)
140 return (e1->src->frequency * e1->probability
141 > e2->src->frequency * e2->probability);
142 /* This is needed to avoid changes in the decision after
143 CFG is modified. */
144 if (e1->src != e2->src)
145 return e1->src->index > e2->src->index;
146 return e1->dest->index > e2->dest->index;
149 /* Return most frequent successor of basic block BB. */
151 static edge
152 find_best_successor (basic_block bb)
154 edge e;
155 edge best = NULL;
156 edge_iterator ei;
158 FOR_EACH_EDGE (e, ei, bb->succs)
159 if (!best || better_p (e, best))
160 best = e;
161 if (!best || ignore_bb_p (best->dest))
162 return NULL;
163 if (best->probability <= probability_cutoff)
164 return NULL;
165 return best;
168 /* Return most frequent predecessor of basic block BB. */
170 static edge
171 find_best_predecessor (basic_block bb)
173 edge e;
174 edge best = NULL;
175 edge_iterator ei;
177 FOR_EACH_EDGE (e, ei, bb->preds)
178 if (!best || better_p (e, best))
179 best = e;
180 if (!best || ignore_bb_p (best->src))
181 return NULL;
182 if (EDGE_FREQUENCY (best) * REG_BR_PROB_BASE
183 < bb->frequency * branch_ratio_cutoff)
184 return NULL;
185 return best;
188 /* Find the trace using bb and record it in the TRACE array.
189 Return number of basic blocks recorded. */
191 static int
192 find_trace (basic_block bb, basic_block *trace)
194 int i = 0;
195 edge e;
197 if (dump_file)
198 fprintf (dump_file, "Trace seed %i [%i]", bb->index, bb->frequency);
200 while ((e = find_best_predecessor (bb)) != NULL)
202 basic_block bb2 = e->src;
203 if (bb_seen_p (bb2) || (e->flags & (EDGE_DFS_BACK | EDGE_COMPLEX))
204 || find_best_successor (bb2) != e)
205 break;
206 if (dump_file)
207 fprintf (dump_file, ",%i [%i]", bb->index, bb->frequency);
208 bb = bb2;
210 if (dump_file)
211 fprintf (dump_file, " forward %i [%i]", bb->index, bb->frequency);
212 trace[i++] = bb;
214 /* Follow the trace in forward direction. */
215 while ((e = find_best_successor (bb)) != NULL)
217 bb = e->dest;
218 if (bb_seen_p (bb) || (e->flags & (EDGE_DFS_BACK | EDGE_COMPLEX))
219 || find_best_predecessor (bb) != e)
220 break;
221 if (dump_file)
222 fprintf (dump_file, ",%i [%i]", bb->index, bb->frequency);
223 trace[i++] = bb;
225 if (dump_file)
226 fprintf (dump_file, "\n");
227 return i;
230 /* Duplicate block BB2, placing it after BB in the CFG. Return the
231 newly created block. */
232 basic_block
233 transform_duplicate (basic_block bb, basic_block bb2)
235 edge e;
236 basic_block copy;
238 e = find_edge (bb, bb2);
240 copy = duplicate_block (bb2, e, bb);
241 flush_pending_stmts (e);
243 add_phi_args_after_copy (&copy, 1, NULL);
245 return (copy);
248 /* Look for basic blocks in frequency order, construct traces and tail duplicate
249 if profitable. */
251 static bool
252 tail_duplicate (void)
254 auto_vec<fibonacci_node<long, basic_block_def>*> blocks;
255 blocks.safe_grow_cleared (last_basic_block_for_fn (cfun));
257 basic_block *trace = XNEWVEC (basic_block, n_basic_blocks_for_fn (cfun));
258 int *counts = XNEWVEC (int, last_basic_block_for_fn (cfun));
259 int ninsns = 0, nduplicated = 0;
260 gcov_type weighted_insns = 0, traced_insns = 0;
261 fibonacci_heap<long, basic_block_def> heap (LONG_MIN);
262 gcov_type cover_insns;
263 int max_dup_insns;
264 basic_block bb;
265 bool changed = false;
267 /* Create an oversized sbitmap to reduce the chance that we need to
268 resize it. */
269 bb_seen = sbitmap_alloc (last_basic_block_for_fn (cfun) * 2);
270 bitmap_clear (bb_seen);
271 initialize_original_copy_tables ();
273 if (profile_info && profile_status_for_fn (cfun) == PROFILE_READ)
274 probability_cutoff = PARAM_VALUE (TRACER_MIN_BRANCH_PROBABILITY_FEEDBACK);
275 else
276 probability_cutoff = PARAM_VALUE (TRACER_MIN_BRANCH_PROBABILITY);
277 probability_cutoff = REG_BR_PROB_BASE / 100 * probability_cutoff;
279 branch_ratio_cutoff =
280 (REG_BR_PROB_BASE / 100 * PARAM_VALUE (TRACER_MIN_BRANCH_RATIO));
282 FOR_EACH_BB_FN (bb, cfun)
284 int n = count_insns (bb);
285 if (!ignore_bb_p (bb))
286 blocks[bb->index] = heap.insert (-bb->frequency, bb);
288 counts [bb->index] = n;
289 ninsns += n;
290 weighted_insns += n * bb->frequency;
293 if (profile_info && profile_status_for_fn (cfun) == PROFILE_READ)
294 cover_insns = PARAM_VALUE (TRACER_DYNAMIC_COVERAGE_FEEDBACK);
295 else
296 cover_insns = PARAM_VALUE (TRACER_DYNAMIC_COVERAGE);
297 cover_insns = (weighted_insns * cover_insns + 50) / 100;
298 max_dup_insns = (ninsns * PARAM_VALUE (TRACER_MAX_CODE_GROWTH) + 50) / 100;
300 while (traced_insns < cover_insns && nduplicated < max_dup_insns
301 && !heap.empty ())
303 basic_block bb = heap.extract_min ();
304 int n, pos;
306 if (!bb)
307 break;
309 blocks[bb->index] = NULL;
311 if (ignore_bb_p (bb))
312 continue;
313 gcc_assert (!bb_seen_p (bb));
315 n = find_trace (bb, trace);
317 bb = trace[0];
318 traced_insns += bb->frequency * counts [bb->index];
319 if (blocks[bb->index])
321 heap.delete_node (blocks[bb->index]);
322 blocks[bb->index] = NULL;
325 for (pos = 1; pos < n; pos++)
327 basic_block bb2 = trace[pos];
329 if (blocks[bb2->index])
331 heap.delete_node (blocks[bb2->index]);
332 blocks[bb2->index] = NULL;
334 traced_insns += bb2->frequency * counts [bb2->index];
335 if (EDGE_COUNT (bb2->preds) > 1
336 && can_duplicate_block_p (bb2)
337 /* We have the tendency to duplicate the loop header
338 of all do { } while loops. Do not do that - it is
339 not profitable and it might create a loop with multiple
340 entries or at least rotate the loop. */
341 && bb2->loop_father->header != bb2)
343 nduplicated += counts [bb2->index];
344 basic_block copy = transform_duplicate (bb, bb2);
346 /* Reconsider the original copy of block we've duplicated.
347 Removing the most common predecessor may make it to be
348 head. */
349 blocks[bb2->index] = heap.insert (-bb2->frequency, bb2);
351 if (dump_file)
352 fprintf (dump_file, "Duplicated %i as %i [%i]\n",
353 bb2->index, copy->index, copy->frequency);
355 bb2 = copy;
356 changed = true;
358 mark_bb_seen (bb2);
359 bb = bb2;
360 /* In case the trace became infrequent, stop duplicating. */
361 if (ignore_bb_p (bb))
362 break;
364 if (dump_file)
365 fprintf (dump_file, " covered now %.1f\n\n",
366 traced_insns * 100.0 / weighted_insns);
368 if (dump_file)
369 fprintf (dump_file, "Duplicated %i insns (%i%%)\n", nduplicated,
370 nduplicated * 100 / ninsns);
372 free_original_copy_tables ();
373 sbitmap_free (bb_seen);
374 free (trace);
375 free (counts);
377 return changed;
380 namespace {
382 const pass_data pass_data_tracer =
384 GIMPLE_PASS, /* type */
385 "tracer", /* name */
386 OPTGROUP_NONE, /* optinfo_flags */
387 TV_TRACER, /* tv_id */
388 0, /* properties_required */
389 0, /* properties_provided */
390 0, /* properties_destroyed */
391 0, /* todo_flags_start */
392 TODO_update_ssa, /* todo_flags_finish */
395 class pass_tracer : public gimple_opt_pass
397 public:
398 pass_tracer (gcc::context *ctxt)
399 : gimple_opt_pass (pass_data_tracer, ctxt)
402 /* opt_pass methods: */
403 virtual bool gate (function *)
405 return (optimize > 0 && flag_tracer && flag_reorder_blocks);
408 virtual unsigned int execute (function *);
410 }; // class pass_tracer
412 unsigned int
413 pass_tracer::execute (function *fun)
415 bool changed;
417 if (n_basic_blocks_for_fn (fun) <= NUM_FIXED_BLOCKS + 1)
418 return 0;
420 mark_dfs_back_edges ();
421 if (dump_file)
422 brief_dump_cfg (dump_file, dump_flags);
424 /* Trace formation is done on the fly inside tail_duplicate */
425 changed = tail_duplicate ();
426 if (changed)
428 free_dominance_info (CDI_DOMINATORS);
429 /* If we changed the CFG schedule loops for fixup by cleanup_cfg. */
430 loops_state_set (LOOPS_NEED_FIXUP);
433 if (dump_file)
434 brief_dump_cfg (dump_file, dump_flags);
436 return changed ? TODO_cleanup_cfg : 0;
438 } // anon namespace
440 gimple_opt_pass *
441 make_pass_tracer (gcc::context *ctxt)
443 return new pass_tracer (ctxt);