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[/] [openrisc/] [trunk/] [gnu-src/] [gcc-4.5.1/] [gcc/] [tracer.c] - Blame information for rev 328

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1 280 jeremybenn
/* 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, 2002, 2003, 2004, 2005, 2006, 2007, 2008
5
   Free Software Foundation, Inc.
6
 
7
   This file is part of GCC.
8
 
9
   GCC is free software; you can redistribute it and/or modify it
10
   under the terms of the GNU General Public License as published by
11
   the Free Software Foundation; either version 3, or (at your option)
12
   any later version.
13
 
14
   GCC is distributed in the hope that it will be useful, but WITHOUT
15
   ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
16
   or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
17
   License for more details.
18
 
19
   You should have received a copy of the GNU General Public License
20
   along with GCC; see the file COPYING3.  If not see
21
   <http://www.gnu.org/licenses/>.  */
22
 
23
/* This pass performs the tail duplication needed for superblock formation.
24
   For more information see:
25
 
26
     Design and Analysis of Profile-Based Optimization in Compaq's
27
     Compilation Tools for Alpha; Journal of Instruction-Level
28
     Parallelism 3 (2000) 1-25
29
 
30
   Unlike Compaq's implementation we don't do the loop peeling as most
31
   probably a better job can be done by a special pass and we don't
32
   need to worry too much about the code size implications as the tail
33
   duplicates are crossjumped again if optimizations are not
34
   performed.  */
35
 
36
 
37
#include "config.h"
38
#include "system.h"
39
#include "coretypes.h"
40
#include "tm.h"
41
#include "tree.h"
42
#include "rtl.h"
43
#include "hard-reg-set.h"
44
#include "basic-block.h"
45
#include "output.h"
46
#include "cfglayout.h"
47
#include "fibheap.h"
48
#include "flags.h"
49
#include "timevar.h"
50
#include "params.h"
51
#include "coverage.h"
52
#include "tree-pass.h"
53
#include "tree-flow.h"
54
#include "tree-inline.h"
55
 
56
static int count_insns (basic_block);
57
static bool ignore_bb_p (const_basic_block);
58
static bool better_p (const_edge, const_edge);
59
static edge find_best_successor (basic_block);
60
static edge find_best_predecessor (basic_block);
61
static int find_trace (basic_block, basic_block *);
62
static void tail_duplicate (void);
63
 
64
/* Minimal outgoing edge probability considered for superblock formation.  */
65
static int probability_cutoff;
66
static int branch_ratio_cutoff;
67
 
68
/* A bit BB->index is set if BB has already been seen, i.e. it is
69
   connected to some trace already.  */
70
sbitmap bb_seen;
71
 
72
static inline void
73
mark_bb_seen (basic_block bb)
74
{
75
  unsigned int size = SBITMAP_SIZE_BYTES (bb_seen) * 8;
76
 
77
  if ((unsigned int)bb->index >= size)
78
    bb_seen = sbitmap_resize (bb_seen, size * 2, 0);
79
 
80
  SET_BIT (bb_seen, bb->index);
81
}
82
 
83
static inline bool
84
bb_seen_p (basic_block bb)
85
{
86
  return TEST_BIT (bb_seen, bb->index);
87
}
88
 
89
/* Return true if we should ignore the basic block for purposes of tracing.  */
90
static bool
91
ignore_bb_p (const_basic_block bb)
92
{
93
  if (bb->index < NUM_FIXED_BLOCKS)
94
    return true;
95
  if (optimize_bb_for_size_p (bb))
96
    return true;
97
  return false;
98
}
99
 
100
/* Return number of instructions in the block.  */
101
 
102
static int
103
count_insns (basic_block bb)
104
{
105
  gimple_stmt_iterator gsi;
106
  gimple stmt;
107
  int n = 0;
108
 
109
  for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
110
    {
111
      stmt = gsi_stmt (gsi);
112
      n += estimate_num_insns (stmt, &eni_size_weights);
113
    }
114
  return n;
115
}
116
 
117
/* Return true if E1 is more frequent than E2.  */
118
static bool
119
better_p (const_edge e1, const_edge e2)
120
{
121
  if (e1->count != e2->count)
122
    return e1->count > e2->count;
123
  if (e1->src->frequency * e1->probability !=
124
      e2->src->frequency * e2->probability)
125
    return (e1->src->frequency * e1->probability
126
            > e2->src->frequency * e2->probability);
127
  /* This is needed to avoid changes in the decision after
128
     CFG is modified.  */
129
  if (e1->src != e2->src)
130
    return e1->src->index > e2->src->index;
131
  return e1->dest->index > e2->dest->index;
132
}
133
 
134
/* Return most frequent successor of basic block BB.  */
135
 
136
static edge
137
find_best_successor (basic_block bb)
138
{
139
  edge e;
140
  edge best = NULL;
141
  edge_iterator ei;
142
 
143
  FOR_EACH_EDGE (e, ei, bb->succs)
144
    if (!best || better_p (e, best))
145
      best = e;
146
  if (!best || ignore_bb_p (best->dest))
147
    return NULL;
148
  if (best->probability <= probability_cutoff)
149
    return NULL;
150
  return best;
151
}
152
 
153
/* Return most frequent predecessor of basic block BB.  */
154
 
155
static edge
156
find_best_predecessor (basic_block bb)
157
{
158
  edge e;
159
  edge best = NULL;
160
  edge_iterator ei;
161
 
162
  FOR_EACH_EDGE (e, ei, bb->preds)
163
    if (!best || better_p (e, best))
164
      best = e;
165
  if (!best || ignore_bb_p (best->src))
166
    return NULL;
167
  if (EDGE_FREQUENCY (best) * REG_BR_PROB_BASE
168
      < bb->frequency * branch_ratio_cutoff)
169
    return NULL;
170
  return best;
171
}
172
 
173
/* Find the trace using bb and record it in the TRACE array.
174
   Return number of basic blocks recorded.  */
175
 
176
static int
177
find_trace (basic_block bb, basic_block *trace)
178
{
179
  int i = 0;
180
  edge e;
181
 
182
  if (dump_file)
183
    fprintf (dump_file, "Trace seed %i [%i]", bb->index, bb->frequency);
184
 
185
  while ((e = find_best_predecessor (bb)) != NULL)
186
    {
187
      basic_block bb2 = e->src;
188
      if (bb_seen_p (bb2) || (e->flags & (EDGE_DFS_BACK | EDGE_COMPLEX))
189
          || find_best_successor (bb2) != e)
190
        break;
191
      if (dump_file)
192
        fprintf (dump_file, ",%i [%i]", bb->index, bb->frequency);
193
      bb = bb2;
194
    }
195
  if (dump_file)
196
    fprintf (dump_file, " forward %i [%i]", bb->index, bb->frequency);
197
  trace[i++] = bb;
198
 
199
  /* Follow the trace in forward direction.  */
200
  while ((e = find_best_successor (bb)) != NULL)
201
    {
202
      bb = e->dest;
203
      if (bb_seen_p (bb) || (e->flags & (EDGE_DFS_BACK | EDGE_COMPLEX))
204
          || find_best_predecessor (bb) != e)
205
        break;
206
      if (dump_file)
207
        fprintf (dump_file, ",%i [%i]", bb->index, bb->frequency);
208
      trace[i++] = bb;
209
    }
210
  if (dump_file)
211
    fprintf (dump_file, "\n");
212
  return i;
213
}
214
 
215
/* Look for basic blocks in frequency order, construct traces and tail duplicate
216
   if profitable.  */
217
 
218
static void
219
tail_duplicate (void)
220
{
221
  fibnode_t *blocks = XCNEWVEC (fibnode_t, last_basic_block);
222
  basic_block *trace = XNEWVEC (basic_block, n_basic_blocks);
223
  int *counts = XNEWVEC (int, last_basic_block);
224
  int ninsns = 0, nduplicated = 0;
225
  gcov_type weighted_insns = 0, traced_insns = 0;
226
  fibheap_t heap = fibheap_new ();
227
  gcov_type cover_insns;
228
  int max_dup_insns;
229
  basic_block bb;
230
 
231
  /* Create an oversized sbitmap to reduce the chance that we need to
232
     resize it.  */
233
  bb_seen = sbitmap_alloc (last_basic_block * 2);
234
  sbitmap_zero (bb_seen);
235
  initialize_original_copy_tables ();
236
 
237
  if (profile_info && flag_branch_probabilities)
238
    probability_cutoff = PARAM_VALUE (TRACER_MIN_BRANCH_PROBABILITY_FEEDBACK);
239
  else
240
    probability_cutoff = PARAM_VALUE (TRACER_MIN_BRANCH_PROBABILITY);
241
  probability_cutoff = REG_BR_PROB_BASE / 100 * probability_cutoff;
242
 
243
  branch_ratio_cutoff =
244
    (REG_BR_PROB_BASE / 100 * PARAM_VALUE (TRACER_MIN_BRANCH_RATIO));
245
 
246
  FOR_EACH_BB (bb)
247
    {
248
      int n = count_insns (bb);
249
      if (!ignore_bb_p (bb))
250
        blocks[bb->index] = fibheap_insert (heap, -bb->frequency,
251
                                            bb);
252
 
253
      counts [bb->index] = n;
254
      ninsns += n;
255
      weighted_insns += n * bb->frequency;
256
    }
257
 
258
  if (profile_info && flag_branch_probabilities)
259
    cover_insns = PARAM_VALUE (TRACER_DYNAMIC_COVERAGE_FEEDBACK);
260
  else
261
    cover_insns = PARAM_VALUE (TRACER_DYNAMIC_COVERAGE);
262
  cover_insns = (weighted_insns * cover_insns + 50) / 100;
263
  max_dup_insns = (ninsns * PARAM_VALUE (TRACER_MAX_CODE_GROWTH) + 50) / 100;
264
 
265
  while (traced_insns < cover_insns && nduplicated < max_dup_insns
266
         && !fibheap_empty (heap))
267
    {
268
      basic_block bb = (basic_block) fibheap_extract_min (heap);
269
      int n, pos;
270
 
271
      if (!bb)
272
        break;
273
 
274
      blocks[bb->index] = NULL;
275
 
276
      if (ignore_bb_p (bb))
277
        continue;
278
      gcc_assert (!bb_seen_p (bb));
279
 
280
      n = find_trace (bb, trace);
281
 
282
      bb = trace[0];
283
      traced_insns += bb->frequency * counts [bb->index];
284
      if (blocks[bb->index])
285
        {
286
          fibheap_delete_node (heap, blocks[bb->index]);
287
          blocks[bb->index] = NULL;
288
        }
289
 
290
      for (pos = 1; pos < n; pos++)
291
        {
292
          basic_block bb2 = trace[pos];
293
 
294
          if (blocks[bb2->index])
295
            {
296
              fibheap_delete_node (heap, blocks[bb2->index]);
297
              blocks[bb2->index] = NULL;
298
            }
299
          traced_insns += bb2->frequency * counts [bb2->index];
300
          if (EDGE_COUNT (bb2->preds) > 1
301
              && can_duplicate_block_p (bb2))
302
            {
303
              edge e;
304
              basic_block copy;
305
 
306
              nduplicated += counts [bb2->index];
307
 
308
              e = find_edge (bb, bb2);
309
 
310
              copy = duplicate_block (bb2, e, bb);
311
              flush_pending_stmts (e);
312
 
313
              add_phi_args_after_copy (&copy, 1, NULL);
314
 
315
              /* Reconsider the original copy of block we've duplicated.
316
                 Removing the most common predecessor may make it to be
317
                 head.  */
318
              blocks[bb2->index] =
319
                fibheap_insert (heap, -bb2->frequency, bb2);
320
 
321
              if (dump_file)
322
                fprintf (dump_file, "Duplicated %i as %i [%i]\n",
323
                         bb2->index, copy->index, copy->frequency);
324
 
325
              bb2 = copy;
326
            }
327
          mark_bb_seen (bb2);
328
          bb = bb2;
329
          /* In case the trace became infrequent, stop duplicating.  */
330
          if (ignore_bb_p (bb))
331
            break;
332
        }
333
      if (dump_file)
334
        fprintf (dump_file, " covered now %.1f\n\n",
335
                 traced_insns * 100.0 / weighted_insns);
336
    }
337
  if (dump_file)
338
    fprintf (dump_file, "Duplicated %i insns (%i%%)\n", nduplicated,
339
             nduplicated * 100 / ninsns);
340
 
341
  free_original_copy_tables ();
342
  sbitmap_free (bb_seen);
343
  free (blocks);
344
  free (trace);
345
  free (counts);
346
  fibheap_delete (heap);
347
}
348
 
349
/* Main entry point to this file.  */
350
 
351
static unsigned int
352
tracer (void)
353
{
354
  gcc_assert (current_ir_type () == IR_GIMPLE);
355
 
356
  if (n_basic_blocks <= NUM_FIXED_BLOCKS + 1)
357
    return 0;
358
 
359
  mark_dfs_back_edges ();
360
  if (dump_file)
361
    dump_flow_info (dump_file, dump_flags);
362
 
363
  /* Trace formation is done on the fly inside tail_duplicate */
364
  tail_duplicate ();
365
 
366
  /* FIXME: We really only need to do this when we know tail duplication
367
            has altered the CFG. */
368
  free_dominance_info (CDI_DOMINATORS);
369
  if (dump_file)
370
    dump_flow_info (dump_file, dump_flags);
371
 
372
  return 0;
373
}
374
 
375
static bool
376
gate_tracer (void)
377
{
378
  return (optimize > 0 && flag_tracer && flag_reorder_blocks);
379
}
380
 
381
struct gimple_opt_pass pass_tracer =
382
{
383
 {
384
  GIMPLE_PASS,
385
  "tracer",                             /* name */
386
  gate_tracer,                          /* gate */
387
  tracer,                               /* execute */
388
  NULL,                                 /* sub */
389
  NULL,                                 /* next */
390
  0,                                    /* static_pass_number */
391
  TV_TRACER,                            /* tv_id */
392
  0,                                    /* properties_required */
393
  0,                                    /* properties_provided */
394
  0,                                    /* properties_destroyed */
395
  0,                                    /* todo_flags_start */
396
  TODO_dump_func
397
    | TODO_update_ssa
398
    | TODO_verify_ssa                   /* todo_flags_finish */
399
 }
400
};

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