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[/] [openrisc/] [trunk/] [gnu-stable/] [gcc-4.5.1/] [gcc/] [tree-ssa-phiopt.c] - Blame information for rev 847

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1 280 jeremybenn
/* Optimization of PHI nodes by converting them into straightline code.
2
   Copyright (C) 2004, 2005, 2006, 2007, 2008 Free Software Foundation,
3
   Inc.
4
 
5
This file is part of GCC.
6
 
7
GCC is free software; you can redistribute it and/or modify it
8
under the terms of the GNU General Public License as published by the
9
Free Software Foundation; either version 3, or (at your option) any
10
later version.
11
 
12
GCC is distributed in the hope that it will be useful, but WITHOUT
13
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
15
for more details.
16
 
17
You should have received a copy of the GNU General Public License
18
along with GCC; see the file COPYING3.  If not see
19
<http://www.gnu.org/licenses/>.  */
20
 
21
#include "config.h"
22
#include "system.h"
23
#include "coretypes.h"
24
#include "tm.h"
25
#include "ggc.h"
26
#include "tree.h"
27
#include "rtl.h"
28
#include "flags.h"
29
#include "tm_p.h"
30
#include "basic-block.h"
31
#include "timevar.h"
32
#include "diagnostic.h"
33
#include "tree-flow.h"
34
#include "tree-pass.h"
35
#include "tree-dump.h"
36
#include "langhooks.h"
37
#include "pointer-set.h"
38
#include "domwalk.h"
39
 
40
static unsigned int tree_ssa_phiopt (void);
41
static unsigned int tree_ssa_phiopt_worker (bool);
42
static bool conditional_replacement (basic_block, basic_block,
43
                                     edge, edge, gimple, tree, tree);
44
static bool value_replacement (basic_block, basic_block,
45
                               edge, edge, gimple, tree, tree);
46
static bool minmax_replacement (basic_block, basic_block,
47
                                edge, edge, gimple, tree, tree);
48
static bool abs_replacement (basic_block, basic_block,
49
                             edge, edge, gimple, tree, tree);
50
static bool cond_store_replacement (basic_block, basic_block, edge, edge,
51
                                    struct pointer_set_t *);
52
static struct pointer_set_t * get_non_trapping (void);
53
static void replace_phi_edge_with_variable (basic_block, edge, gimple, tree);
54
 
55
/* This pass tries to replaces an if-then-else block with an
56
   assignment.  We have four kinds of transformations.  Some of these
57
   transformations are also performed by the ifcvt RTL optimizer.
58
 
59
   Conditional Replacement
60
   -----------------------
61
 
62
   This transformation, implemented in conditional_replacement,
63
   replaces
64
 
65
     bb0:
66
      if (cond) goto bb2; else goto bb1;
67
     bb1:
68
     bb2:
69
      x = PHI <0 (bb1), 1 (bb0), ...>;
70
 
71
   with
72
 
73
     bb0:
74
      x' = cond;
75
      goto bb2;
76
     bb2:
77
      x = PHI <x' (bb0), ...>;
78
 
79
   We remove bb1 as it becomes unreachable.  This occurs often due to
80
   gimplification of conditionals.
81
 
82
   Value Replacement
83
   -----------------
84
 
85
   This transformation, implemented in value_replacement, replaces
86
 
87
     bb0:
88
       if (a != b) goto bb2; else goto bb1;
89
     bb1:
90
     bb2:
91
       x = PHI <a (bb1), b (bb0), ...>;
92
 
93
   with
94
 
95
     bb0:
96
     bb2:
97
       x = PHI <b (bb0), ...>;
98
 
99
   This opportunity can sometimes occur as a result of other
100
   optimizations.
101
 
102
   ABS Replacement
103
   ---------------
104
 
105
   This transformation, implemented in abs_replacement, replaces
106
 
107
     bb0:
108
       if (a >= 0) goto bb2; else goto bb1;
109
     bb1:
110
       x = -a;
111
     bb2:
112
       x = PHI <x (bb1), a (bb0), ...>;
113
 
114
   with
115
 
116
     bb0:
117
       x' = ABS_EXPR< a >;
118
     bb2:
119
       x = PHI <x' (bb0), ...>;
120
 
121
   MIN/MAX Replacement
122
   -------------------
123
 
124
   This transformation, minmax_replacement replaces
125
 
126
     bb0:
127
       if (a <= b) goto bb2; else goto bb1;
128
     bb1:
129
     bb2:
130
       x = PHI <b (bb1), a (bb0), ...>;
131
 
132
   with
133
 
134
     bb0:
135
       x' = MIN_EXPR (a, b)
136
     bb2:
137
       x = PHI <x' (bb0), ...>;
138
 
139
   A similar transformation is done for MAX_EXPR.  */
140
 
141
static unsigned int
142
tree_ssa_phiopt (void)
143
{
144
  return tree_ssa_phiopt_worker (false);
145
}
146
 
147
/* This pass tries to transform conditional stores into unconditional
148
   ones, enabling further simplifications with the simpler then and else
149
   blocks.  In particular it replaces this:
150
 
151
     bb0:
152
       if (cond) goto bb2; else goto bb1;
153
     bb1:
154
       *p = RHS
155
     bb2:
156
 
157
   with
158
 
159
     bb0:
160
       if (cond) goto bb1; else goto bb2;
161
     bb1:
162
       condtmp' = *p;
163
     bb2:
164
       condtmp = PHI <RHS, condtmp'>
165
       *p = condtmp
166
 
167
   This transformation can only be done under several constraints,
168
   documented below.  */
169
 
170
static unsigned int
171
tree_ssa_cs_elim (void)
172
{
173
  return tree_ssa_phiopt_worker (true);
174
}
175
 
176
/* For conditional store replacement we need a temporary to
177
   put the old contents of the memory in.  */
178
static tree condstoretemp;
179
 
180
/* The core routine of conditional store replacement and normal
181
   phi optimizations.  Both share much of the infrastructure in how
182
   to match applicable basic block patterns.  DO_STORE_ELIM is true
183
   when we want to do conditional store replacement, false otherwise.  */
184
static unsigned int
185
tree_ssa_phiopt_worker (bool do_store_elim)
186
{
187
  basic_block bb;
188
  basic_block *bb_order;
189
  unsigned n, i;
190
  bool cfgchanged = false;
191
  struct pointer_set_t *nontrap = 0;
192
 
193
  if (do_store_elim)
194
    {
195
      condstoretemp = NULL_TREE;
196
      /* Calculate the set of non-trapping memory accesses.  */
197
      nontrap = get_non_trapping ();
198
    }
199
 
200
  /* Search every basic block for COND_EXPR we may be able to optimize.
201
 
202
     We walk the blocks in order that guarantees that a block with
203
     a single predecessor is processed before the predecessor.
204
     This ensures that we collapse inner ifs before visiting the
205
     outer ones, and also that we do not try to visit a removed
206
     block.  */
207
  bb_order = blocks_in_phiopt_order ();
208
  n = n_basic_blocks - NUM_FIXED_BLOCKS;
209
 
210
  for (i = 0; i < n; i++)
211
    {
212
      gimple cond_stmt, phi;
213
      basic_block bb1, bb2;
214
      edge e1, e2;
215
      tree arg0, arg1;
216
 
217
      bb = bb_order[i];
218
 
219
      cond_stmt = last_stmt (bb);
220
      /* Check to see if the last statement is a GIMPLE_COND.  */
221
      if (!cond_stmt
222
          || gimple_code (cond_stmt) != GIMPLE_COND)
223
        continue;
224
 
225
      e1 = EDGE_SUCC (bb, 0);
226
      bb1 = e1->dest;
227
      e2 = EDGE_SUCC (bb, 1);
228
      bb2 = e2->dest;
229
 
230
      /* We cannot do the optimization on abnormal edges.  */
231
      if ((e1->flags & EDGE_ABNORMAL) != 0
232
          || (e2->flags & EDGE_ABNORMAL) != 0)
233
       continue;
234
 
235
      /* If either bb1's succ or bb2 or bb2's succ is non NULL.  */
236
      if (EDGE_COUNT (bb1->succs) == 0
237
          || bb2 == NULL
238
          || EDGE_COUNT (bb2->succs) == 0)
239
        continue;
240
 
241
      /* Find the bb which is the fall through to the other.  */
242
      if (EDGE_SUCC (bb1, 0)->dest == bb2)
243
        ;
244
      else if (EDGE_SUCC (bb2, 0)->dest == bb1)
245
        {
246
          basic_block bb_tmp = bb1;
247
          edge e_tmp = e1;
248
          bb1 = bb2;
249
          bb2 = bb_tmp;
250
          e1 = e2;
251
          e2 = e_tmp;
252
        }
253
      else
254
        continue;
255
 
256
      e1 = EDGE_SUCC (bb1, 0);
257
 
258
      /* Make sure that bb1 is just a fall through.  */
259
      if (!single_succ_p (bb1)
260
          || (e1->flags & EDGE_FALLTHRU) == 0)
261
        continue;
262
 
263
      /* Also make sure that bb1 only have one predecessor and that it
264
         is bb.  */
265
      if (!single_pred_p (bb1)
266
          || single_pred (bb1) != bb)
267
        continue;
268
 
269
      if (do_store_elim)
270
        {
271
          /* bb1 is the middle block, bb2 the join block, bb the split block,
272
             e1 the fallthrough edge from bb1 to bb2.  We can't do the
273
             optimization if the join block has more than two predecessors.  */
274
          if (EDGE_COUNT (bb2->preds) > 2)
275
            continue;
276
          if (cond_store_replacement (bb1, bb2, e1, e2, nontrap))
277
            cfgchanged = true;
278
        }
279
      else
280
        {
281
          gimple_seq phis = phi_nodes (bb2);
282
 
283
          /* Check to make sure that there is only one PHI node.
284
             TODO: we could do it with more than one iff the other PHI nodes
285
             have the same elements for these two edges.  */
286
          if (! gimple_seq_singleton_p (phis))
287
            continue;
288
 
289
          phi = gsi_stmt (gsi_start (phis));
290
          arg0 = gimple_phi_arg_def (phi, e1->dest_idx);
291
          arg1 = gimple_phi_arg_def (phi, e2->dest_idx);
292
 
293
          /* Something is wrong if we cannot find the arguments in the PHI
294
             node.  */
295
          gcc_assert (arg0 != NULL && arg1 != NULL);
296
 
297
          /* Do the replacement of conditional if it can be done.  */
298
          if (conditional_replacement (bb, bb1, e1, e2, phi, arg0, arg1))
299
            cfgchanged = true;
300
          else if (value_replacement (bb, bb1, e1, e2, phi, arg0, arg1))
301
            cfgchanged = true;
302
          else if (abs_replacement (bb, bb1, e1, e2, phi, arg0, arg1))
303
            cfgchanged = true;
304
          else if (minmax_replacement (bb, bb1, e1, e2, phi, arg0, arg1))
305
            cfgchanged = true;
306
        }
307
    }
308
 
309
  free (bb_order);
310
 
311
  if (do_store_elim)
312
    pointer_set_destroy (nontrap);
313
  /* If the CFG has changed, we should cleanup the CFG.  */
314
  if (cfgchanged && do_store_elim)
315
    {
316
      /* In cond-store replacement we have added some loads on edges
317
         and new VOPS (as we moved the store, and created a load).  */
318
      gsi_commit_edge_inserts ();
319
      return TODO_cleanup_cfg | TODO_update_ssa_only_virtuals;
320
    }
321
  else if (cfgchanged)
322
    return TODO_cleanup_cfg;
323
  return 0;
324
}
325
 
326
/* Returns the list of basic blocks in the function in an order that guarantees
327
   that if a block X has just a single predecessor Y, then Y is after X in the
328
   ordering.  */
329
 
330
basic_block *
331
blocks_in_phiopt_order (void)
332
{
333
  basic_block x, y;
334
  basic_block *order = XNEWVEC (basic_block, n_basic_blocks);
335
  unsigned n = n_basic_blocks - NUM_FIXED_BLOCKS;
336
  unsigned np, i;
337
  sbitmap visited = sbitmap_alloc (last_basic_block);
338
 
339
#define MARK_VISITED(BB) (SET_BIT (visited, (BB)->index))
340
#define VISITED_P(BB) (TEST_BIT (visited, (BB)->index))
341
 
342
  sbitmap_zero (visited);
343
 
344
  MARK_VISITED (ENTRY_BLOCK_PTR);
345
  FOR_EACH_BB (x)
346
    {
347
      if (VISITED_P (x))
348
        continue;
349
 
350
      /* Walk the predecessors of x as long as they have precisely one
351
         predecessor and add them to the list, so that they get stored
352
         after x.  */
353
      for (y = x, np = 1;
354
           single_pred_p (y) && !VISITED_P (single_pred (y));
355
           y = single_pred (y))
356
        np++;
357
      for (y = x, i = n - np;
358
           single_pred_p (y) && !VISITED_P (single_pred (y));
359
           y = single_pred (y), i++)
360
        {
361
          order[i] = y;
362
          MARK_VISITED (y);
363
        }
364
      order[i] = y;
365
      MARK_VISITED (y);
366
 
367
      gcc_assert (i == n - 1);
368
      n -= np;
369
    }
370
 
371
  sbitmap_free (visited);
372
  gcc_assert (n == 0);
373
  return order;
374
 
375
#undef MARK_VISITED
376
#undef VISITED_P
377
}
378
 
379
 
380
/* Return TRUE if block BB has no executable statements, otherwise return
381
   FALSE.  */
382
 
383
bool
384
empty_block_p (basic_block bb)
385
{
386
  /* BB must have no executable statements.  */
387
  gimple_stmt_iterator gsi = gsi_after_labels (bb);
388
  if (gsi_end_p (gsi))
389
    return true;
390
  if (is_gimple_debug (gsi_stmt (gsi)))
391
    gsi_next_nondebug (&gsi);
392
  return gsi_end_p (gsi);
393
}
394
 
395
/* Replace PHI node element whose edge is E in block BB with variable NEW.
396
   Remove the edge from COND_BLOCK which does not lead to BB (COND_BLOCK
397
   is known to have two edges, one of which must reach BB).  */
398
 
399
static void
400
replace_phi_edge_with_variable (basic_block cond_block,
401
                                edge e, gimple phi, tree new_tree)
402
{
403
  basic_block bb = gimple_bb (phi);
404
  basic_block block_to_remove;
405
  gimple_stmt_iterator gsi;
406
 
407
  /* Change the PHI argument to new.  */
408
  SET_USE (PHI_ARG_DEF_PTR (phi, e->dest_idx), new_tree);
409
 
410
  /* Remove the empty basic block.  */
411
  if (EDGE_SUCC (cond_block, 0)->dest == bb)
412
    {
413
      EDGE_SUCC (cond_block, 0)->flags |= EDGE_FALLTHRU;
414
      EDGE_SUCC (cond_block, 0)->flags &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE);
415
      EDGE_SUCC (cond_block, 0)->probability = REG_BR_PROB_BASE;
416
      EDGE_SUCC (cond_block, 0)->count += EDGE_SUCC (cond_block, 1)->count;
417
 
418
      block_to_remove = EDGE_SUCC (cond_block, 1)->dest;
419
    }
420
  else
421
    {
422
      EDGE_SUCC (cond_block, 1)->flags |= EDGE_FALLTHRU;
423
      EDGE_SUCC (cond_block, 1)->flags
424
        &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE);
425
      EDGE_SUCC (cond_block, 1)->probability = REG_BR_PROB_BASE;
426
      EDGE_SUCC (cond_block, 1)->count += EDGE_SUCC (cond_block, 0)->count;
427
 
428
      block_to_remove = EDGE_SUCC (cond_block, 0)->dest;
429
    }
430
  delete_basic_block (block_to_remove);
431
 
432
  /* Eliminate the COND_EXPR at the end of COND_BLOCK.  */
433
  gsi = gsi_last_bb (cond_block);
434
  gsi_remove (&gsi, true);
435
 
436
  if (dump_file && (dump_flags & TDF_DETAILS))
437
    fprintf (dump_file,
438
              "COND_EXPR in block %d and PHI in block %d converted to straightline code.\n",
439
              cond_block->index,
440
              bb->index);
441
}
442
 
443
/*  The function conditional_replacement does the main work of doing the
444
    conditional replacement.  Return true if the replacement is done.
445
    Otherwise return false.
446
    BB is the basic block where the replacement is going to be done on.  ARG0
447
    is argument 0 from PHI.  Likewise for ARG1.  */
448
 
449
static bool
450
conditional_replacement (basic_block cond_bb, basic_block middle_bb,
451
                         edge e0, edge e1, gimple phi,
452
                         tree arg0, tree arg1)
453
{
454
  tree result;
455
  gimple stmt, new_stmt;
456
  tree cond;
457
  gimple_stmt_iterator gsi;
458
  edge true_edge, false_edge;
459
  tree new_var, new_var2;
460
 
461
  /* FIXME: Gimplification of complex type is too hard for now.  */
462
  if (TREE_CODE (TREE_TYPE (arg0)) == COMPLEX_TYPE
463
      || TREE_CODE (TREE_TYPE (arg1)) == COMPLEX_TYPE)
464
    return false;
465
 
466
  /* The PHI arguments have the constants 0 and 1, then convert
467
     it to the conditional.  */
468
  if ((integer_zerop (arg0) && integer_onep (arg1))
469
      || (integer_zerop (arg1) && integer_onep (arg0)))
470
    ;
471
  else
472
    return false;
473
 
474
  if (!empty_block_p (middle_bb))
475
    return false;
476
 
477
  /* At this point we know we have a GIMPLE_COND with two successors.
478
     One successor is BB, the other successor is an empty block which
479
     falls through into BB.
480
 
481
     There is a single PHI node at the join point (BB) and its arguments
482
     are constants (0, 1).
483
 
484
     So, given the condition COND, and the two PHI arguments, we can
485
     rewrite this PHI into non-branching code:
486
 
487
       dest = (COND) or dest = COND'
488
 
489
     We use the condition as-is if the argument associated with the
490
     true edge has the value one or the argument associated with the
491
     false edge as the value zero.  Note that those conditions are not
492
     the same since only one of the outgoing edges from the GIMPLE_COND
493
     will directly reach BB and thus be associated with an argument.  */
494
 
495
  stmt = last_stmt (cond_bb);
496
  result = PHI_RESULT (phi);
497
 
498
  /* To handle special cases like floating point comparison, it is easier and
499
     less error-prone to build a tree and gimplify it on the fly though it is
500
     less efficient.  */
501
  cond = fold_build2 (gimple_cond_code (stmt), boolean_type_node,
502
                      gimple_cond_lhs (stmt), gimple_cond_rhs (stmt));
503
 
504
  /* We need to know which is the true edge and which is the false
505
     edge so that we know when to invert the condition below.  */
506
  extract_true_false_edges_from_block (cond_bb, &true_edge, &false_edge);
507
  if ((e0 == true_edge && integer_zerop (arg0))
508
      || (e0 == false_edge && integer_onep (arg0))
509
      || (e1 == true_edge && integer_zerop (arg1))
510
      || (e1 == false_edge && integer_onep (arg1)))
511
    cond = fold_build1 (TRUTH_NOT_EXPR, TREE_TYPE (cond), cond);
512
 
513
  /* Insert our new statements at the end of conditional block before the
514
     COND_STMT.  */
515
  gsi = gsi_for_stmt (stmt);
516
  new_var = force_gimple_operand_gsi (&gsi, cond, true, NULL, true,
517
                                      GSI_SAME_STMT);
518
 
519
  if (!useless_type_conversion_p (TREE_TYPE (result), TREE_TYPE (new_var)))
520
    {
521
      source_location locus_0, locus_1;
522
 
523
      new_var2 = create_tmp_var (TREE_TYPE (result), NULL);
524
      add_referenced_var (new_var2);
525
      new_stmt = gimple_build_assign_with_ops (CONVERT_EXPR, new_var2,
526
                                               new_var, NULL);
527
      new_var2 = make_ssa_name (new_var2, new_stmt);
528
      gimple_assign_set_lhs (new_stmt, new_var2);
529
      gsi_insert_before (&gsi, new_stmt, GSI_SAME_STMT);
530
      new_var = new_var2;
531
 
532
      /* Set the locus to the first argument, unless is doesn't have one.  */
533
      locus_0 = gimple_phi_arg_location (phi, 0);
534
      locus_1 = gimple_phi_arg_location (phi, 1);
535
      if (locus_0 == UNKNOWN_LOCATION)
536
        locus_0 = locus_1;
537
      gimple_set_location (new_stmt, locus_0);
538
    }
539
 
540
  replace_phi_edge_with_variable (cond_bb, e1, phi, new_var);
541
 
542
  /* Note that we optimized this PHI.  */
543
  return true;
544
}
545
 
546
/*  The function value_replacement does the main work of doing the value
547
    replacement.  Return true if the replacement is done.  Otherwise return
548
    false.
549
    BB is the basic block where the replacement is going to be done on.  ARG0
550
    is argument 0 from the PHI.  Likewise for ARG1.  */
551
 
552
static bool
553
value_replacement (basic_block cond_bb, basic_block middle_bb,
554
                   edge e0, edge e1, gimple phi,
555
                   tree arg0, tree arg1)
556
{
557
  gimple cond;
558
  edge true_edge, false_edge;
559
  enum tree_code code;
560
 
561
  /* If the type says honor signed zeros we cannot do this
562
     optimization.  */
563
  if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (arg1))))
564
    return false;
565
 
566
  if (!empty_block_p (middle_bb))
567
    return false;
568
 
569
  cond = last_stmt (cond_bb);
570
  code = gimple_cond_code (cond);
571
 
572
  /* This transformation is only valid for equality comparisons.  */
573
  if (code != NE_EXPR && code != EQ_EXPR)
574
    return false;
575
 
576
  /* We need to know which is the true edge and which is the false
577
      edge so that we know if have abs or negative abs.  */
578
  extract_true_false_edges_from_block (cond_bb, &true_edge, &false_edge);
579
 
580
  /* At this point we know we have a COND_EXPR with two successors.
581
     One successor is BB, the other successor is an empty block which
582
     falls through into BB.
583
 
584
     The condition for the COND_EXPR is known to be NE_EXPR or EQ_EXPR.
585
 
586
     There is a single PHI node at the join point (BB) with two arguments.
587
 
588
     We now need to verify that the two arguments in the PHI node match
589
     the two arguments to the equality comparison.  */
590
 
591
  if ((operand_equal_for_phi_arg_p (arg0, gimple_cond_lhs (cond))
592
       && operand_equal_for_phi_arg_p (arg1, gimple_cond_rhs (cond)))
593
      || (operand_equal_for_phi_arg_p (arg1, gimple_cond_lhs (cond))
594
          && operand_equal_for_phi_arg_p (arg0, gimple_cond_rhs (cond))))
595
    {
596
      edge e;
597
      tree arg;
598
 
599
      /* For NE_EXPR, we want to build an assignment result = arg where
600
         arg is the PHI argument associated with the true edge.  For
601
         EQ_EXPR we want the PHI argument associated with the false edge.  */
602
      e = (code == NE_EXPR ? true_edge : false_edge);
603
 
604
      /* Unfortunately, E may not reach BB (it may instead have gone to
605
         OTHER_BLOCK).  If that is the case, then we want the single outgoing
606
         edge from OTHER_BLOCK which reaches BB and represents the desired
607
         path from COND_BLOCK.  */
608
      if (e->dest == middle_bb)
609
        e = single_succ_edge (e->dest);
610
 
611
      /* Now we know the incoming edge to BB that has the argument for the
612
         RHS of our new assignment statement.  */
613
      if (e0 == e)
614
        arg = arg0;
615
      else
616
        arg = arg1;
617
 
618
      replace_phi_edge_with_variable (cond_bb, e1, phi, arg);
619
 
620
      /* Note that we optimized this PHI.  */
621
      return true;
622
    }
623
  return false;
624
}
625
 
626
/*  The function minmax_replacement does the main work of doing the minmax
627
    replacement.  Return true if the replacement is done.  Otherwise return
628
    false.
629
    BB is the basic block where the replacement is going to be done on.  ARG0
630
    is argument 0 from the PHI.  Likewise for ARG1.  */
631
 
632
static bool
633
minmax_replacement (basic_block cond_bb, basic_block middle_bb,
634
                    edge e0, edge e1, gimple phi,
635
                    tree arg0, tree arg1)
636
{
637
  tree result, type;
638
  gimple cond, new_stmt;
639
  edge true_edge, false_edge;
640
  enum tree_code cmp, minmax, ass_code;
641
  tree smaller, larger, arg_true, arg_false;
642
  gimple_stmt_iterator gsi, gsi_from;
643
 
644
  type = TREE_TYPE (PHI_RESULT (phi));
645
 
646
  /* The optimization may be unsafe due to NaNs.  */
647
  if (HONOR_NANS (TYPE_MODE (type)))
648
    return false;
649
 
650
  cond = last_stmt (cond_bb);
651
  cmp = gimple_cond_code (cond);
652
  result = PHI_RESULT (phi);
653
 
654
  /* This transformation is only valid for order comparisons.  Record which
655
     operand is smaller/larger if the result of the comparison is true.  */
656
  if (cmp == LT_EXPR || cmp == LE_EXPR)
657
    {
658
      smaller = gimple_cond_lhs (cond);
659
      larger = gimple_cond_rhs (cond);
660
    }
661
  else if (cmp == GT_EXPR || cmp == GE_EXPR)
662
    {
663
      smaller = gimple_cond_rhs (cond);
664
      larger = gimple_cond_lhs (cond);
665
    }
666
  else
667
    return false;
668
 
669
  /* We need to know which is the true edge and which is the false
670
      edge so that we know if have abs or negative abs.  */
671
  extract_true_false_edges_from_block (cond_bb, &true_edge, &false_edge);
672
 
673
  /* Forward the edges over the middle basic block.  */
674
  if (true_edge->dest == middle_bb)
675
    true_edge = EDGE_SUCC (true_edge->dest, 0);
676
  if (false_edge->dest == middle_bb)
677
    false_edge = EDGE_SUCC (false_edge->dest, 0);
678
 
679
  if (true_edge == e0)
680
    {
681
      gcc_assert (false_edge == e1);
682
      arg_true = arg0;
683
      arg_false = arg1;
684
    }
685
  else
686
    {
687
      gcc_assert (false_edge == e0);
688
      gcc_assert (true_edge == e1);
689
      arg_true = arg1;
690
      arg_false = arg0;
691
    }
692
 
693
  if (empty_block_p (middle_bb))
694
    {
695
      if (operand_equal_for_phi_arg_p (arg_true, smaller)
696
          && operand_equal_for_phi_arg_p (arg_false, larger))
697
        {
698
          /* Case
699
 
700
             if (smaller < larger)
701
             rslt = smaller;
702
             else
703
             rslt = larger;  */
704
          minmax = MIN_EXPR;
705
        }
706
      else if (operand_equal_for_phi_arg_p (arg_false, smaller)
707
               && operand_equal_for_phi_arg_p (arg_true, larger))
708
        minmax = MAX_EXPR;
709
      else
710
        return false;
711
    }
712
  else
713
    {
714
      /* Recognize the following case, assuming d <= u:
715
 
716
         if (a <= u)
717
           b = MAX (a, d);
718
         x = PHI <b, u>
719
 
720
         This is equivalent to
721
 
722
         b = MAX (a, d);
723
         x = MIN (b, u);  */
724
 
725
      gimple assign = last_and_only_stmt (middle_bb);
726
      tree lhs, op0, op1, bound;
727
 
728
      if (!assign
729
          || gimple_code (assign) != GIMPLE_ASSIGN)
730
        return false;
731
 
732
      lhs = gimple_assign_lhs (assign);
733
      ass_code = gimple_assign_rhs_code (assign);
734
      if (ass_code != MAX_EXPR && ass_code != MIN_EXPR)
735
        return false;
736
      op0 = gimple_assign_rhs1 (assign);
737
      op1 = gimple_assign_rhs2 (assign);
738
 
739
      if (true_edge->src == middle_bb)
740
        {
741
          /* We got here if the condition is true, i.e., SMALLER < LARGER.  */
742
          if (!operand_equal_for_phi_arg_p (lhs, arg_true))
743
            return false;
744
 
745
          if (operand_equal_for_phi_arg_p (arg_false, larger))
746
            {
747
              /* Case
748
 
749
                 if (smaller < larger)
750
                   {
751
                     r' = MAX_EXPR (smaller, bound)
752
                   }
753
                 r = PHI <r', larger>  --> to be turned to MIN_EXPR.  */
754
              if (ass_code != MAX_EXPR)
755
                return false;
756
 
757
              minmax = MIN_EXPR;
758
              if (operand_equal_for_phi_arg_p (op0, smaller))
759
                bound = op1;
760
              else if (operand_equal_for_phi_arg_p (op1, smaller))
761
                bound = op0;
762
              else
763
                return false;
764
 
765
              /* We need BOUND <= LARGER.  */
766
              if (!integer_nonzerop (fold_build2 (LE_EXPR, boolean_type_node,
767
                                                  bound, larger)))
768
                return false;
769
            }
770
          else if (operand_equal_for_phi_arg_p (arg_false, smaller))
771
            {
772
              /* Case
773
 
774
                 if (smaller < larger)
775
                   {
776
                     r' = MIN_EXPR (larger, bound)
777
                   }
778
                 r = PHI <r', smaller>  --> to be turned to MAX_EXPR.  */
779
              if (ass_code != MIN_EXPR)
780
                return false;
781
 
782
              minmax = MAX_EXPR;
783
              if (operand_equal_for_phi_arg_p (op0, larger))
784
                bound = op1;
785
              else if (operand_equal_for_phi_arg_p (op1, larger))
786
                bound = op0;
787
              else
788
                return false;
789
 
790
              /* We need BOUND >= SMALLER.  */
791
              if (!integer_nonzerop (fold_build2 (GE_EXPR, boolean_type_node,
792
                                                  bound, smaller)))
793
                return false;
794
            }
795
          else
796
            return false;
797
        }
798
      else
799
        {
800
          /* We got here if the condition is false, i.e., SMALLER > LARGER.  */
801
          if (!operand_equal_for_phi_arg_p (lhs, arg_false))
802
            return false;
803
 
804
          if (operand_equal_for_phi_arg_p (arg_true, larger))
805
            {
806
              /* Case
807
 
808
                 if (smaller > larger)
809
                   {
810
                     r' = MIN_EXPR (smaller, bound)
811
                   }
812
                 r = PHI <r', larger>  --> to be turned to MAX_EXPR.  */
813
              if (ass_code != MIN_EXPR)
814
                return false;
815
 
816
              minmax = MAX_EXPR;
817
              if (operand_equal_for_phi_arg_p (op0, smaller))
818
                bound = op1;
819
              else if (operand_equal_for_phi_arg_p (op1, smaller))
820
                bound = op0;
821
              else
822
                return false;
823
 
824
              /* We need BOUND >= LARGER.  */
825
              if (!integer_nonzerop (fold_build2 (GE_EXPR, boolean_type_node,
826
                                                  bound, larger)))
827
                return false;
828
            }
829
          else if (operand_equal_for_phi_arg_p (arg_true, smaller))
830
            {
831
              /* Case
832
 
833
                 if (smaller > larger)
834
                   {
835
                     r' = MAX_EXPR (larger, bound)
836
                   }
837
                 r = PHI <r', smaller>  --> to be turned to MIN_EXPR.  */
838
              if (ass_code != MAX_EXPR)
839
                return false;
840
 
841
              minmax = MIN_EXPR;
842
              if (operand_equal_for_phi_arg_p (op0, larger))
843
                bound = op1;
844
              else if (operand_equal_for_phi_arg_p (op1, larger))
845
                bound = op0;
846
              else
847
                return false;
848
 
849
              /* We need BOUND <= SMALLER.  */
850
              if (!integer_nonzerop (fold_build2 (LE_EXPR, boolean_type_node,
851
                                                  bound, smaller)))
852
                return false;
853
            }
854
          else
855
            return false;
856
        }
857
 
858
      /* Move the statement from the middle block.  */
859
      gsi = gsi_last_bb (cond_bb);
860
      gsi_from = gsi_last_nondebug_bb (middle_bb);
861
      gsi_move_before (&gsi_from, &gsi);
862
    }
863
 
864
  /* Emit the statement to compute min/max.  */
865
  result = duplicate_ssa_name (PHI_RESULT (phi), NULL);
866
  new_stmt = gimple_build_assign_with_ops (minmax, result, arg0, arg1);
867
  gsi = gsi_last_bb (cond_bb);
868
  gsi_insert_before (&gsi, new_stmt, GSI_NEW_STMT);
869
 
870
  replace_phi_edge_with_variable (cond_bb, e1, phi, result);
871
  return true;
872
}
873
 
874
/*  The function absolute_replacement does the main work of doing the absolute
875
    replacement.  Return true if the replacement is done.  Otherwise return
876
    false.
877
    bb is the basic block where the replacement is going to be done on.  arg0
878
    is argument 0 from the phi.  Likewise for arg1.  */
879
 
880
static bool
881
abs_replacement (basic_block cond_bb, basic_block middle_bb,
882
                 edge e0 ATTRIBUTE_UNUSED, edge e1,
883
                 gimple phi, tree arg0, tree arg1)
884
{
885
  tree result;
886
  gimple new_stmt, cond;
887
  gimple_stmt_iterator gsi;
888
  edge true_edge, false_edge;
889
  gimple assign;
890
  edge e;
891
  tree rhs, lhs;
892
  bool negate;
893
  enum tree_code cond_code;
894
 
895
  /* If the type says honor signed zeros we cannot do this
896
     optimization.  */
897
  if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (arg1))))
898
    return false;
899
 
900
  /* OTHER_BLOCK must have only one executable statement which must have the
901
     form arg0 = -arg1 or arg1 = -arg0.  */
902
 
903
  assign = last_and_only_stmt (middle_bb);
904
  /* If we did not find the proper negation assignment, then we can not
905
     optimize.  */
906
  if (assign == NULL)
907
    return false;
908
 
909
  /* If we got here, then we have found the only executable statement
910
     in OTHER_BLOCK.  If it is anything other than arg = -arg1 or
911
     arg1 = -arg0, then we can not optimize.  */
912
  if (gimple_code (assign) != GIMPLE_ASSIGN)
913
    return false;
914
 
915
  lhs = gimple_assign_lhs (assign);
916
 
917
  if (gimple_assign_rhs_code (assign) != NEGATE_EXPR)
918
    return false;
919
 
920
  rhs = gimple_assign_rhs1 (assign);
921
 
922
  /* The assignment has to be arg0 = -arg1 or arg1 = -arg0.  */
923
  if (!(lhs == arg0 && rhs == arg1)
924
      && !(lhs == arg1 && rhs == arg0))
925
    return false;
926
 
927
  cond = last_stmt (cond_bb);
928
  result = PHI_RESULT (phi);
929
 
930
  /* Only relationals comparing arg[01] against zero are interesting.  */
931
  cond_code = gimple_cond_code (cond);
932
  if (cond_code != GT_EXPR && cond_code != GE_EXPR
933
      && cond_code != LT_EXPR && cond_code != LE_EXPR)
934
    return false;
935
 
936
  /* Make sure the conditional is arg[01] OP y.  */
937
  if (gimple_cond_lhs (cond) != rhs)
938
    return false;
939
 
940
  if (FLOAT_TYPE_P (TREE_TYPE (gimple_cond_rhs (cond)))
941
               ? real_zerop (gimple_cond_rhs (cond))
942
               : integer_zerop (gimple_cond_rhs (cond)))
943
    ;
944
  else
945
    return false;
946
 
947
  /* We need to know which is the true edge and which is the false
948
     edge so that we know if have abs or negative abs.  */
949
  extract_true_false_edges_from_block (cond_bb, &true_edge, &false_edge);
950
 
951
  /* For GT_EXPR/GE_EXPR, if the true edge goes to OTHER_BLOCK, then we
952
     will need to negate the result.  Similarly for LT_EXPR/LE_EXPR if
953
     the false edge goes to OTHER_BLOCK.  */
954
  if (cond_code == GT_EXPR || cond_code == GE_EXPR)
955
    e = true_edge;
956
  else
957
    e = false_edge;
958
 
959
  if (e->dest == middle_bb)
960
    negate = true;
961
  else
962
    negate = false;
963
 
964
  result = duplicate_ssa_name (result, NULL);
965
 
966
  if (negate)
967
    {
968
      tree tmp = create_tmp_var (TREE_TYPE (result), NULL);
969
      add_referenced_var (tmp);
970
      lhs = make_ssa_name (tmp, NULL);
971
    }
972
  else
973
    lhs = result;
974
 
975
  /* Build the modify expression with abs expression.  */
976
  new_stmt = gimple_build_assign_with_ops (ABS_EXPR, lhs, rhs, NULL);
977
 
978
  gsi = gsi_last_bb (cond_bb);
979
  gsi_insert_before (&gsi, new_stmt, GSI_NEW_STMT);
980
 
981
  if (negate)
982
    {
983
      /* Get the right GSI.  We want to insert after the recently
984
         added ABS_EXPR statement (which we know is the first statement
985
         in the block.  */
986
      new_stmt = gimple_build_assign_with_ops (NEGATE_EXPR, result, lhs, NULL);
987
 
988
      gsi_insert_after (&gsi, new_stmt, GSI_NEW_STMT);
989
    }
990
 
991
  replace_phi_edge_with_variable (cond_bb, e1, phi, result);
992
 
993
  /* Note that we optimized this PHI.  */
994
  return true;
995
}
996
 
997
/* Auxiliary functions to determine the set of memory accesses which
998
   can't trap because they are preceded by accesses to the same memory
999
   portion.  We do that for INDIRECT_REFs, so we only need to track
1000
   the SSA_NAME of the pointer indirectly referenced.  The algorithm
1001
   simply is a walk over all instructions in dominator order.  When
1002
   we see an INDIRECT_REF we determine if we've already seen a same
1003
   ref anywhere up to the root of the dominator tree.  If we do the
1004
   current access can't trap.  If we don't see any dominating access
1005
   the current access might trap, but might also make later accesses
1006
   non-trapping, so we remember it.  We need to be careful with loads
1007
   or stores, for instance a load might not trap, while a store would,
1008
   so if we see a dominating read access this doesn't mean that a later
1009
   write access would not trap.  Hence we also need to differentiate the
1010
   type of access(es) seen.
1011
 
1012
   ??? We currently are very conservative and assume that a load might
1013
   trap even if a store doesn't (write-only memory).  This probably is
1014
   overly conservative.  */
1015
 
1016
/* A hash-table of SSA_NAMEs, and in which basic block an INDIRECT_REF
1017
   through it was seen, which would constitute a no-trap region for
1018
   same accesses.  */
1019
struct name_to_bb
1020
{
1021
  tree ssa_name;
1022
  basic_block bb;
1023
  unsigned store : 1;
1024
};
1025
 
1026
/* The hash table for remembering what we've seen.  */
1027
static htab_t seen_ssa_names;
1028
 
1029
/* The set of INDIRECT_REFs which can't trap.  */
1030
static struct pointer_set_t *nontrap_set;
1031
 
1032
/* The hash function, based on the pointer to the pointer SSA_NAME.  */
1033
static hashval_t
1034
name_to_bb_hash (const void *p)
1035
{
1036
  const_tree n = ((const struct name_to_bb *)p)->ssa_name;
1037
  return htab_hash_pointer (n) ^ ((const struct name_to_bb *)p)->store;
1038
}
1039
 
1040
/* The equality function of *P1 and *P2.  SSA_NAMEs are shared, so
1041
   it's enough to simply compare them for equality.  */
1042
static int
1043
name_to_bb_eq (const void *p1, const void *p2)
1044
{
1045
  const struct name_to_bb *n1 = (const struct name_to_bb *)p1;
1046
  const struct name_to_bb *n2 = (const struct name_to_bb *)p2;
1047
 
1048
  return n1->ssa_name == n2->ssa_name && n1->store == n2->store;
1049
}
1050
 
1051
/* We see the expression EXP in basic block BB.  If it's an interesting
1052
   expression (an INDIRECT_REF through an SSA_NAME) possibly insert the
1053
   expression into the set NONTRAP or the hash table of seen expressions.
1054
   STORE is true if this expression is on the LHS, otherwise it's on
1055
   the RHS.  */
1056
static void
1057
add_or_mark_expr (basic_block bb, tree exp,
1058
                  struct pointer_set_t *nontrap, bool store)
1059
{
1060
  if (INDIRECT_REF_P (exp)
1061
      && TREE_CODE (TREE_OPERAND (exp, 0)) == SSA_NAME)
1062
    {
1063
      tree name = TREE_OPERAND (exp, 0);
1064
      struct name_to_bb map;
1065
      void **slot;
1066
      struct name_to_bb *n2bb;
1067
      basic_block found_bb = 0;
1068
 
1069
      /* Try to find the last seen INDIRECT_REF through the same
1070
         SSA_NAME, which can trap.  */
1071
      map.ssa_name = name;
1072
      map.bb = 0;
1073
      map.store = store;
1074
      slot = htab_find_slot (seen_ssa_names, &map, INSERT);
1075
      n2bb = (struct name_to_bb *) *slot;
1076
      if (n2bb)
1077
        found_bb = n2bb->bb;
1078
 
1079
      /* If we've found a trapping INDIRECT_REF, _and_ it dominates EXP
1080
         (it's in a basic block on the path from us to the dominator root)
1081
         then we can't trap.  */
1082
      if (found_bb && found_bb->aux == (void *)1)
1083
        {
1084
          pointer_set_insert (nontrap, exp);
1085
        }
1086
      else
1087
        {
1088
          /* EXP might trap, so insert it into the hash table.  */
1089
          if (n2bb)
1090
            {
1091
              n2bb->bb = bb;
1092
            }
1093
          else
1094
            {
1095
              n2bb = XNEW (struct name_to_bb);
1096
              n2bb->ssa_name = name;
1097
              n2bb->bb = bb;
1098
              n2bb->store = store;
1099
              *slot = n2bb;
1100
            }
1101
        }
1102
    }
1103
}
1104
 
1105
/* Called by walk_dominator_tree, when entering the block BB.  */
1106
static void
1107
nt_init_block (struct dom_walk_data *data ATTRIBUTE_UNUSED, basic_block bb)
1108
{
1109
  gimple_stmt_iterator gsi;
1110
  /* Mark this BB as being on the path to dominator root.  */
1111
  bb->aux = (void*)1;
1112
 
1113
  /* And walk the statements in order.  */
1114
  for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
1115
    {
1116
      gimple stmt = gsi_stmt (gsi);
1117
 
1118
      if (is_gimple_assign (stmt))
1119
        {
1120
          add_or_mark_expr (bb, gimple_assign_lhs (stmt), nontrap_set, true);
1121
          add_or_mark_expr (bb, gimple_assign_rhs1 (stmt), nontrap_set, false);
1122
          if (get_gimple_rhs_num_ops (gimple_assign_rhs_code (stmt)) > 1)
1123
            add_or_mark_expr (bb, gimple_assign_rhs2 (stmt), nontrap_set,
1124
                              false);
1125
        }
1126
    }
1127
}
1128
 
1129
/* Called by walk_dominator_tree, when basic block BB is exited.  */
1130
static void
1131
nt_fini_block (struct dom_walk_data *data ATTRIBUTE_UNUSED, basic_block bb)
1132
{
1133
  /* This BB isn't on the path to dominator root anymore.  */
1134
  bb->aux = NULL;
1135
}
1136
 
1137
/* This is the entry point of gathering non trapping memory accesses.
1138
   It will do a dominator walk over the whole function, and it will
1139
   make use of the bb->aux pointers.  It returns a set of trees
1140
   (the INDIRECT_REFs itself) which can't trap.  */
1141
static struct pointer_set_t *
1142
get_non_trapping (void)
1143
{
1144
  struct pointer_set_t *nontrap;
1145
  struct dom_walk_data walk_data;
1146
 
1147
  nontrap = pointer_set_create ();
1148
  seen_ssa_names = htab_create (128, name_to_bb_hash, name_to_bb_eq,
1149
                                free);
1150
  /* We're going to do a dominator walk, so ensure that we have
1151
     dominance information.  */
1152
  calculate_dominance_info (CDI_DOMINATORS);
1153
 
1154
  /* Setup callbacks for the generic dominator tree walker.  */
1155
  nontrap_set = nontrap;
1156
  walk_data.dom_direction = CDI_DOMINATORS;
1157
  walk_data.initialize_block_local_data = NULL;
1158
  walk_data.before_dom_children = nt_init_block;
1159
  walk_data.after_dom_children = nt_fini_block;
1160
  walk_data.global_data = NULL;
1161
  walk_data.block_local_data_size = 0;
1162
 
1163
  init_walk_dominator_tree (&walk_data);
1164
  walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR);
1165
  fini_walk_dominator_tree (&walk_data);
1166
  htab_delete (seen_ssa_names);
1167
 
1168
  return nontrap;
1169
}
1170
 
1171
/* Do the main work of conditional store replacement.  We already know
1172
   that the recognized pattern looks like so:
1173
 
1174
   split:
1175
     if (cond) goto MIDDLE_BB; else goto JOIN_BB (edge E1)
1176
   MIDDLE_BB:
1177
     something
1178
     fallthrough (edge E0)
1179
   JOIN_BB:
1180
     some more
1181
 
1182
   We check that MIDDLE_BB contains only one store, that that store
1183
   doesn't trap (not via NOTRAP, but via checking if an access to the same
1184
   memory location dominates us) and that the store has a "simple" RHS.  */
1185
 
1186
static bool
1187
cond_store_replacement (basic_block middle_bb, basic_block join_bb,
1188
                        edge e0, edge e1, struct pointer_set_t *nontrap)
1189
{
1190
  gimple assign = last_and_only_stmt (middle_bb);
1191
  tree lhs, rhs, name;
1192
  gimple newphi, new_stmt;
1193
  gimple_stmt_iterator gsi;
1194
  source_location locus;
1195
  enum tree_code code;
1196
 
1197
  /* Check if middle_bb contains of only one store.  */
1198
  if (!assign
1199
      || gimple_code (assign) != GIMPLE_ASSIGN)
1200
    return false;
1201
 
1202
  locus = gimple_location (assign);
1203
  lhs = gimple_assign_lhs (assign);
1204
  rhs = gimple_assign_rhs1 (assign);
1205
  if (!INDIRECT_REF_P (lhs))
1206
    return false;
1207
 
1208
  /* RHS is either a single SSA_NAME or a constant. */
1209
  code = gimple_assign_rhs_code (assign);
1210
  if (get_gimple_rhs_class (code) != GIMPLE_SINGLE_RHS
1211
      || (code != SSA_NAME && !is_gimple_min_invariant (rhs)))
1212
    return false;
1213
  /* Prove that we can move the store down.  We could also check
1214
     TREE_THIS_NOTRAP here, but in that case we also could move stores,
1215
     whose value is not available readily, which we want to avoid.  */
1216
  if (!pointer_set_contains (nontrap, lhs))
1217
    return false;
1218
 
1219
  /* Now we've checked the constraints, so do the transformation:
1220
     1) Remove the single store.  */
1221
  mark_symbols_for_renaming (assign);
1222
  gsi = gsi_for_stmt (assign);
1223
  gsi_remove (&gsi, true);
1224
 
1225
  /* 2) Create a temporary where we can store the old content
1226
        of the memory touched by the store, if we need to.  */
1227
  if (!condstoretemp || TREE_TYPE (lhs) != TREE_TYPE (condstoretemp))
1228
    {
1229
      condstoretemp = create_tmp_var (TREE_TYPE (lhs), "cstore");
1230
      get_var_ann (condstoretemp);
1231
      if (TREE_CODE (TREE_TYPE (lhs)) == COMPLEX_TYPE
1232
          || TREE_CODE (TREE_TYPE (lhs)) == VECTOR_TYPE)
1233
        DECL_GIMPLE_REG_P (condstoretemp) = 1;
1234
    }
1235
  add_referenced_var (condstoretemp);
1236
 
1237
  /* 3) Insert a load from the memory of the store to the temporary
1238
        on the edge which did not contain the store.  */
1239
  lhs = unshare_expr (lhs);
1240
  new_stmt = gimple_build_assign (condstoretemp, lhs);
1241
  name = make_ssa_name (condstoretemp, new_stmt);
1242
  gimple_assign_set_lhs (new_stmt, name);
1243
  gimple_set_location (new_stmt, locus);
1244
  mark_symbols_for_renaming (new_stmt);
1245
  gsi_insert_on_edge (e1, new_stmt);
1246
 
1247
  /* 4) Create a PHI node at the join block, with one argument
1248
        holding the old RHS, and the other holding the temporary
1249
        where we stored the old memory contents.  */
1250
  newphi = create_phi_node (condstoretemp, join_bb);
1251
  add_phi_arg (newphi, rhs, e0, locus);
1252
  add_phi_arg (newphi, name, e1, locus);
1253
 
1254
  lhs = unshare_expr (lhs);
1255
  new_stmt = gimple_build_assign (lhs, PHI_RESULT (newphi));
1256
  mark_symbols_for_renaming (new_stmt);
1257
 
1258
  /* 5) Insert that PHI node.  */
1259
  gsi = gsi_after_labels (join_bb);
1260
  if (gsi_end_p (gsi))
1261
    {
1262
      gsi = gsi_last_bb (join_bb);
1263
      gsi_insert_after (&gsi, new_stmt, GSI_NEW_STMT);
1264
    }
1265
  else
1266
    gsi_insert_before (&gsi, new_stmt, GSI_NEW_STMT);
1267
 
1268
  return true;
1269
}
1270
 
1271
/* Always do these optimizations if we have SSA
1272
   trees to work on.  */
1273
static bool
1274
gate_phiopt (void)
1275
{
1276
  return 1;
1277
}
1278
 
1279
struct gimple_opt_pass pass_phiopt =
1280
{
1281
 {
1282
  GIMPLE_PASS,
1283
  "phiopt",                             /* name */
1284
  gate_phiopt,                          /* gate */
1285
  tree_ssa_phiopt,                      /* execute */
1286
  NULL,                                 /* sub */
1287
  NULL,                                 /* next */
1288
  0,                                     /* static_pass_number */
1289
  TV_TREE_PHIOPT,                       /* tv_id */
1290
  PROP_cfg | PROP_ssa,                  /* properties_required */
1291
  0,                                     /* properties_provided */
1292
  0,                                     /* properties_destroyed */
1293
  0,                                     /* todo_flags_start */
1294
  TODO_dump_func
1295
    | TODO_ggc_collect
1296
    | TODO_verify_ssa
1297
    | TODO_verify_flow
1298
    | TODO_verify_stmts                 /* todo_flags_finish */
1299
 }
1300
};
1301
 
1302
static bool
1303
gate_cselim (void)
1304
{
1305
  return flag_tree_cselim;
1306
}
1307
 
1308
struct gimple_opt_pass pass_cselim =
1309
{
1310
 {
1311
  GIMPLE_PASS,
1312
  "cselim",                             /* name */
1313
  gate_cselim,                          /* gate */
1314
  tree_ssa_cs_elim,                     /* execute */
1315
  NULL,                                 /* sub */
1316
  NULL,                                 /* next */
1317
  0,                                     /* static_pass_number */
1318
  TV_TREE_PHIOPT,                       /* tv_id */
1319
  PROP_cfg | PROP_ssa,                  /* properties_required */
1320
  0,                                     /* properties_provided */
1321
  0,                                     /* properties_destroyed */
1322
  0,                                     /* todo_flags_start */
1323
  TODO_dump_func
1324
    | TODO_ggc_collect
1325
    | TODO_verify_ssa
1326
    | TODO_verify_flow
1327
    | TODO_verify_stmts                 /* todo_flags_finish */
1328
 }
1329
};

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