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1 205 julius
// icf.cc -- Identical Code Folding.
2
//
3
// Copyright 2009 Free Software Foundation, Inc.
4
// Written by Sriraman Tallam <tmsriram@google.com>.
5
 
6
// This file is part of gold.
7
 
8
// This program is free software; you can redistribute it and/or modify
9
// it under the terms of the GNU General Public License as published by
10
// the Free Software Foundation; either version 3 of the License, or
11
// (at your option) any later version.
12
 
13
// This program is distributed in the hope that it will be useful,
14
// but WITHOUT ANY WARRANTY; without even the implied warranty of
15
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16
// GNU General Public License for more details.
17
 
18
// You should have received a copy of the GNU General Public License
19
// along with this program; if not, write to the Free Software
20
// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
21
// MA 02110-1301, USA.
22
 
23
// Identical Code Folding Algorithm
24
// ----------------------------------
25
// Detecting identical functions is done here and the basic algorithm
26
// is as follows.  A checksum is computed on each .text section using
27
// its contents and relocations.  If the symbol name corresponding to
28
// a relocation is known it is used to compute the checksum.  If the
29
// symbol name is not known the stringified name of the object and the
30
// section number pointed to by the relocation is used.  The checksums
31
// are stored as keys in a hash map and a section is identical to some
32
// other section if its checksum is already present in the hash map.
33
// Checksum collisions are handled by using a multimap and explicitly
34
// checking the contents when two sections have the same checksum.
35
//
36
// However, two functions A and B with identical text but with
37
// relocations pointing to different .text sections can be identical if
38
// the corresponding .text sections to which their relocations point to
39
// turn out to be identical.  Hence, this checksumming process must be
40
// done repeatedly until convergence is obtained.  Here is an example for
41
// the following case :
42
//
43
// int funcA ()               int funcB ()
44
// {                          {
45
//   return foo();              return goo();
46
// }                          }
47
//
48
// The functions funcA and funcB are identical if functions foo() and
49
// goo() are identical.
50
//
51
// Hence, as described above, we repeatedly do the checksumming,
52
// assigning identical functions to the same group, until convergence is
53
// obtained.  Now, we have two different ways to do this depending on how
54
// we initialize.
55
//
56
// Algorithm I :
57
// -----------
58
// We can start with marking all functions as different and repeatedly do
59
// the checksumming.  This has the advantage that we do not need to wait
60
// for convergence. We can stop at any point and correctness will be
61
// guaranteed although not all cases would have been found.  However, this
62
// has a problem that some cases can never be found even if it is run until
63
// convergence.  Here is an example with mutually recursive functions :
64
//
65
// int funcA (int a)            int funcB (int a)
66
// {                            {
67
//   if (a == 1)                  if (a == 1)
68
//     return 1;                    return 1;
69
//   return 1 + funcB(a - 1);     return 1 + funcA(a - 1);
70
// }                            }
71
//
72
// In this example funcA and funcB are identical and one of them could be
73
// folded into the other.  However, if we start with assuming that funcA
74
// and funcB are not identical, the algorithm, even after it is run to
75
// convergence, cannot detect that they are identical.  It should be noted
76
// that even if the functions were self-recursive, Algorithm I cannot catch
77
// that they are identical, at least as is.
78
//
79
// Algorithm II :
80
// ------------
81
// Here we start with marking all functions as identical and then repeat
82
// the checksumming until convergence.  This can detect the above case
83
// mentioned above.  It can detect all cases that Algorithm I can and more.
84
// However, the caveat is that it has to be run to convergence.  It cannot
85
// be stopped arbitrarily like Algorithm I as correctness cannot be
86
// guaranteed.  Algorithm II is not implemented.
87
//
88
// Algorithm I is used because experiments show that about three
89
// iterations are more than enough to achieve convergence. Algorithm I can
90
// handle recursive calls if it is changed to use a special common symbol
91
// for recursive relocs.  This seems to be the most common case that
92
// Algorithm I could not catch as is.  Mutually recursive calls are not
93
// frequent and Algorithm I wins because of its ability to be stopped
94
// arbitrarily.
95
//
96
// Caveat with using function pointers :
97
// ------------------------------------
98
//
99
// Programs using function pointer comparisons/checks should use function
100
// folding with caution as the result of such comparisons could be different
101
// when folding takes place.  This could lead to unexpected run-time
102
// behaviour.
103
//
104
//
105
// How to run  : --icf
106
// Optional parameters : --icf-iterations <num> --print-icf-sections
107
//
108
// Performance : Less than 20 % link-time overhead on industry strength
109
// applications.  Up to 6 %  text size reductions.
110
 
111
#include "gold.h"
112
#include "object.h"
113
#include "gc.h"
114
#include "icf.h"
115
#include "symtab.h"
116
#include "libiberty.h"
117
#include "demangle.h"
118
 
119
namespace gold
120
{
121
 
122
// This function determines if a section or a group of identical
123
// sections has unique contents.  Such unique sections or groups can be
124
// declared final and need not be processed any further.
125
// Parameters :
126
// ID_SECTION : Vector mapping a section index to a Section_id pair.
127
// IS_SECN_OR_GROUP_UNIQUE : To check if a section or a group of identical
128
//                            sections is already known to be unique.
129
// SECTION_CONTENTS : Contains the section's text and relocs to sections
130
//                    that cannot be folded.   SECTION_CONTENTS are NULL
131
//                    implies that this function is being called for the
132
//                    first time before the first iteration of icf.
133
 
134
static void
135
preprocess_for_unique_sections(const std::vector<Section_id>& id_section,
136
                               std::vector<bool>* is_secn_or_group_unique,
137
                               std::vector<std::string>* section_contents)
138
{
139
  Unordered_map<uint32_t, unsigned int> uniq_map;
140
  std::pair<Unordered_map<uint32_t, unsigned int>::iterator, bool>
141
    uniq_map_insert;
142
 
143
  for (unsigned int i = 0; i < id_section.size(); i++)
144
    {
145
      if ((*is_secn_or_group_unique)[i])
146
        continue;
147
 
148
      uint32_t cksum;
149
      Section_id secn = id_section[i];
150
      section_size_type plen;
151
      if (section_contents == NULL)
152
        {
153
          const unsigned char* contents;
154
          contents = secn.first->section_contents(secn.second,
155
                                                  &plen,
156
                                                  false);
157
          cksum = xcrc32(contents, plen, 0xffffffff);
158
        }
159
      else
160
        {
161
          const unsigned char* contents_array = reinterpret_cast
162
            <const unsigned char*>((*section_contents)[i].c_str());
163
          cksum = xcrc32(contents_array, (*section_contents)[i].length(),
164
                         0xffffffff);
165
        }
166
      uniq_map_insert = uniq_map.insert(std::make_pair(cksum, i));
167
      if (uniq_map_insert.second)
168
        {
169
          (*is_secn_or_group_unique)[i] = true;
170
        }
171
      else
172
        {
173
          (*is_secn_or_group_unique)[i] = false;
174
          (*is_secn_or_group_unique)[uniq_map_insert.first->second] = false;
175
        }
176
    }
177
}
178
 
179
// This returns the buffer containing the section's contents, both
180
// text and relocs.  Relocs are differentiated as those pointing to
181
// sections that could be folded and those that cannot.  Only relocs
182
// pointing to sections that could be folded are recomputed on
183
// subsequent invocations of this function.
184
// Parameters  :
185
// FIRST_ITERATION    : true if it is the first invocation.
186
// SECN               : Section for which contents are desired.
187
// SECTION_NUM        : Unique section number of this section.
188
// NUM_TRACKED_RELOCS : Vector reference to store the number of relocs
189
//                      to ICF sections.
190
// KEPT_SECTION_ID    : Vector which maps folded sections to kept sections.
191
// SECTION_CONTENTS   : Store the section's text and relocs to non-ICF
192
//                      sections.
193
 
194
static std::string
195
get_section_contents(bool first_iteration,
196
                     const Section_id& secn,
197
                     unsigned int section_num,
198
                     unsigned int* num_tracked_relocs,
199
                     Symbol_table* symtab,
200
                     const std::vector<unsigned int>& kept_section_id,
201
                     std::vector<std::string>* section_contents)
202
{
203
  section_size_type plen;
204
  const unsigned char* contents = NULL;
205
 
206
  if (first_iteration)
207
    {
208
      contents = secn.first->section_contents(secn.second,
209
                                              &plen,
210
                                              false);
211
    }
212
 
213
  // The buffer to hold all the contents including relocs.  A checksum
214
  // is then computed on this buffer.
215
  std::string buffer;
216
  std::string icf_reloc_buffer;
217
 
218
  if (num_tracked_relocs)
219
    *num_tracked_relocs = 0;
220
 
221
  Icf::Section_list& seclist = symtab->icf()->section_reloc_list();
222
  Icf::Symbol_list& symlist = symtab->icf()->symbol_reloc_list();
223
  Icf::Addend_list& addendlist = symtab->icf()->addend_reloc_list();
224
 
225
  Icf::Section_list::iterator it_seclist = seclist.find(secn);
226
  Icf::Symbol_list::iterator it_symlist = symlist.find(secn);
227
  Icf::Addend_list::iterator it_addendlist = addendlist.find(secn);
228
 
229
  buffer.clear();
230
  icf_reloc_buffer.clear();
231
 
232
  // Process relocs and put them into the buffer.
233
 
234
  if (it_seclist != seclist.end())
235
    {
236
      gold_assert(it_symlist != symlist.end());
237
      gold_assert(it_addendlist != addendlist.end());
238
      Icf::Sections_reachable_list v = it_seclist->second;
239
      Icf::Symbol_info s = it_symlist->second;
240
      Icf::Addend_info a = it_addendlist->second;
241
      Icf::Sections_reachable_list::iterator it_v = v.begin();
242
      Icf::Symbol_info::iterator it_s = s.begin();
243
      Icf::Addend_info::iterator it_a = a.begin();
244
 
245
      for (; it_v != v.end(); ++it_v, ++it_s, ++it_a)
246
        {
247
          // ADDEND_STR stores the symbol value and addend, each
248
          // atmost 16 hex digits long.  it_v points to a pair
249
          // where first is the symbol value and second is the
250
          // addend.
251
          char addend_str[34];
252
          snprintf(addend_str, sizeof(addend_str), "%llx %llx",
253
                   (*it_a).first, (*it_a).second);
254
          Section_id reloc_secn(it_v->first, it_v->second);
255
 
256
          // If this reloc turns back and points to the same section,
257
          // like a recursive call, use a special symbol to mark this.
258
          if (reloc_secn.first == secn.first
259
              && reloc_secn.second == secn.second)
260
            {
261
              if (first_iteration)
262
                {
263
                  buffer.append("R");
264
                  buffer.append(addend_str);
265
                  buffer.append("@");
266
                }
267
              continue;
268
            }
269
          Icf::Uniq_secn_id_map& section_id_map =
270
            symtab->icf()->section_to_int_map();
271
          Icf::Uniq_secn_id_map::iterator section_id_map_it =
272
            section_id_map.find(reloc_secn);
273
          if (section_id_map_it != section_id_map.end())
274
            {
275
              // This is a reloc to a section that might be folded.
276
              if (num_tracked_relocs)
277
                (*num_tracked_relocs)++;
278
 
279
              char kept_section_str[10];
280
              unsigned int secn_id = section_id_map_it->second;
281
              snprintf(kept_section_str, sizeof(kept_section_str), "%u",
282
                       kept_section_id[secn_id]);
283
              if (first_iteration)
284
                {
285
                  buffer.append("ICF_R");
286
                  buffer.append(addend_str);
287
                }
288
              icf_reloc_buffer.append(kept_section_str);
289
              // Append the addend.
290
              icf_reloc_buffer.append(addend_str);
291
              icf_reloc_buffer.append("@");
292
            }
293
          else
294
            {
295
              // This is a reloc to a section that cannot be folded.
296
              // Process it only in the first iteration.
297
              if (!first_iteration)
298
                continue;
299
 
300
              uint64_t secn_flags = (it_v->first)->section_flags(it_v->second);
301
              // This reloc points to a merge section.  Hash the
302
              // contents of this section.
303
              if ((secn_flags & elfcpp::SHF_MERGE) != 0)
304
                {
305
                  uint64_t entsize =
306
                    (it_v->first)->section_entsize(it_v->second);
307
                  long long offset = it_a->first + it_a->second;
308
                  section_size_type secn_len;
309
                  const unsigned char* str_contents =
310
                  (it_v->first)->section_contents(it_v->second,
311
                                                  &secn_len,
312
                                                  false) + offset;
313
                  if ((secn_flags & elfcpp::SHF_STRINGS) != 0)
314
                    {
315
                      // String merge section.
316
                      const char* str_char =
317
                        reinterpret_cast<const char*>(str_contents);
318
                      switch(entsize)
319
                        {
320
                        case 1:
321
                          {
322
                            buffer.append(str_char);
323
                            break;
324
                          }
325
                        case 2:
326
                          {
327
                            const uint16_t* ptr_16 =
328
                              reinterpret_cast<const uint16_t*>(str_char);
329
                            unsigned int strlen_16 = 0;
330
                            // Find the NULL character.
331
                            while(*(ptr_16 + strlen_16) != 0)
332
                                strlen_16++;
333
                            buffer.append(str_char, strlen_16 * 2);
334
                          }
335
                          break;
336
                        case 4:
337
                          {
338
                            const uint32_t* ptr_32 =
339
                              reinterpret_cast<const uint32_t*>(str_char);
340
                            unsigned int strlen_32 = 0;
341
                            // Find the NULL character.
342
                            while(*(ptr_32 + strlen_32) != 0)
343
                                strlen_32++;
344
                            buffer.append(str_char, strlen_32 * 4);
345
                          }
346
                          break;
347
                        default:
348
                          gold_unreachable();
349
                        }
350
                    }
351
                  else
352
                    {
353
                      // Use the entsize to determine the length.
354
                      buffer.append(reinterpret_cast<const
355
                                                     char*>(str_contents),
356
                                    entsize);
357
                    }
358
                }
359
              else if ((*it_s) != NULL)
360
                {
361
                  // If symbol name is available use that.
362
                  const char *sym_name = (*it_s)->name();
363
                  buffer.append(sym_name);
364
                  // Append the addend.
365
                  buffer.append(addend_str);
366
                  buffer.append("@");
367
                }
368
              else
369
                {
370
                  // Symbol name is not available, like for a local symbol,
371
                  // use object and section id.
372
                  buffer.append(it_v->first->name());
373
                  char secn_id[10];
374
                  snprintf(secn_id, sizeof(secn_id), "%u",it_v->second);
375
                  buffer.append(secn_id);
376
                  // Append the addend.
377
                  buffer.append(addend_str);
378
                  buffer.append("@");
379
                }
380
            }
381
        }
382
    }
383
 
384
  if (first_iteration)
385
    {
386
      buffer.append("Contents = ");
387
      buffer.append(reinterpret_cast<const char*>(contents), plen);
388
      // Store the section contents that dont change to avoid recomputing
389
      // during the next call to this function.
390
      (*section_contents)[section_num] = buffer;
391
    }
392
  else
393
    {
394
      gold_assert(buffer.empty());
395
      // Reuse the contents computed in the previous iteration.
396
      buffer.append((*section_contents)[section_num]);
397
    }
398
 
399
  buffer.append(icf_reloc_buffer);
400
  return buffer;
401
}
402
 
403
// This function computes a checksum on each section to detect and form
404
// groups of identical sections.  The first iteration does this for all 
405
// sections.
406
// Further iterations do this only for the kept sections from each group to
407
// determine if larger groups of identical sections could be formed.  The
408
// first section in each group is the kept section for that group.
409
//
410
// CRC32 is the checksumming algorithm and can have collisions.  That is,
411
// two sections with different contents can have the same checksum. Hence,
412
// a multimap is used to maintain more than one group of checksum
413
// identical sections.  A section is added to a group only after its
414
// contents are explicitly compared with the kept section of the group.
415
//
416
// Parameters  :
417
// ITERATION_NUM           : Invocation instance of this function.
418
// NUM_TRACKED_RELOCS : Vector reference to store the number of relocs
419
//                      to ICF sections.
420
// KEPT_SECTION_ID    : Vector which maps folded sections to kept sections.
421
// ID_SECTION         : Vector mapping a section to an unique integer.
422
// IS_SECN_OR_GROUP_UNIQUE : To check if a section or a group of identical
423
//                            sectionsis already known to be unique.
424
// SECTION_CONTENTS   : Store the section's text and relocs to non-ICF
425
//                      sections.
426
 
427
static bool
428
match_sections(unsigned int iteration_num,
429
               Symbol_table* symtab,
430
               std::vector<unsigned int>* num_tracked_relocs,
431
               std::vector<unsigned int>* kept_section_id,
432
               const std::vector<Section_id>& id_section,
433
               std::vector<bool>* is_secn_or_group_unique,
434
               std::vector<std::string>* section_contents)
435
{
436
  Unordered_multimap<uint32_t, unsigned int> section_cksum;
437
  std::pair<Unordered_multimap<uint32_t, unsigned int>::iterator,
438
            Unordered_multimap<uint32_t, unsigned int>::iterator> key_range;
439
  bool converged = true;
440
 
441
  if (iteration_num == 1)
442
    preprocess_for_unique_sections(id_section,
443
                                   is_secn_or_group_unique,
444
                                   NULL);
445
  else
446
    preprocess_for_unique_sections(id_section,
447
                                   is_secn_or_group_unique,
448
                                   section_contents);
449
 
450
  std::vector<std::string> full_section_contents;
451
 
452
  for (unsigned int i = 0; i < id_section.size(); i++)
453
    {
454
      full_section_contents.push_back("");
455
      if ((*is_secn_or_group_unique)[i])
456
        continue;
457
 
458
      Section_id secn = id_section[i];
459
      std::string this_secn_contents;
460
      uint32_t cksum;
461
      if (iteration_num == 1)
462
        {
463
          unsigned int num_relocs = 0;
464
          this_secn_contents = get_section_contents(true, secn, i, &num_relocs,
465
                                                    symtab, (*kept_section_id),
466
                                                    section_contents);
467
          (*num_tracked_relocs)[i] = num_relocs;
468
        }
469
      else
470
        {
471
          if ((*kept_section_id)[i] != i)
472
            {
473
              // This section is already folded into something.  See
474
              // if it should point to a different kept section.
475
              unsigned int kept_section = (*kept_section_id)[i];
476
              if (kept_section != (*kept_section_id)[kept_section])
477
                {
478
                  (*kept_section_id)[i] = (*kept_section_id)[kept_section];
479
                }
480
              continue;
481
            }
482
          this_secn_contents = get_section_contents(false, secn, i, NULL,
483
                                                    symtab, (*kept_section_id),
484
                                                    section_contents);
485
        }
486
 
487
      const unsigned char* this_secn_contents_array =
488
            reinterpret_cast<const unsigned char*>(this_secn_contents.c_str());
489
      cksum = xcrc32(this_secn_contents_array, this_secn_contents.length(),
490
                     0xffffffff);
491
      size_t count = section_cksum.count(cksum);
492
 
493
      if (count == 0)
494
        {
495
          // Start a group with this cksum.
496
          section_cksum.insert(std::make_pair(cksum, i));
497
          full_section_contents[i] = this_secn_contents;
498
        }
499
      else
500
        {
501
          key_range = section_cksum.equal_range(cksum);
502
          Unordered_multimap<uint32_t, unsigned int>::iterator it;
503
          // Search all the groups with this cksum for a match.
504
          for (it = key_range.first; it != key_range.second; ++it)
505
            {
506
              unsigned int kept_section = it->second;
507
              if (full_section_contents[kept_section].length()
508
                  != this_secn_contents.length())
509
                  continue;
510
              if (memcmp(full_section_contents[kept_section].c_str(),
511
                         this_secn_contents.c_str(),
512
                         this_secn_contents.length()) != 0)
513
                  continue;
514
              (*kept_section_id)[i] = kept_section;
515
              converged = false;
516
              break;
517
            }
518
          if (it == key_range.second)
519
            {
520
              // Create a new group for this cksum.
521
              section_cksum.insert(std::make_pair(cksum, i));
522
              full_section_contents[i] = this_secn_contents;
523
            }
524
        }
525
      // If there are no relocs to foldable sections do not process
526
      // this section any further.
527
      if (iteration_num == 1 && (*num_tracked_relocs)[i] == 0)
528
        (*is_secn_or_group_unique)[i] = true;
529
    }
530
 
531
  return converged;
532
}
533
 
534
// During safe icf (--icf=safe), only fold functions that are ctors or dtors.
535
// This function returns true if the mangled function name is a ctor or a
536
// dtor.
537
 
538
static bool
539
is_function_ctor_or_dtor(const char* mangled_func_name)
540
{
541
  if ((is_prefix_of("_ZN", mangled_func_name)
542
       || is_prefix_of("_ZZ", mangled_func_name))
543
      && (is_gnu_v3_mangled_ctor(mangled_func_name)
544
          || is_gnu_v3_mangled_dtor(mangled_func_name)))
545
    {
546
      return true;
547
    }
548
  return false;
549
}
550
 
551
// This is the main ICF function called in gold.cc.  This does the
552
// initialization and calls match_sections repeatedly (twice by default)
553
// which computes the crc checksums and detects identical functions.
554
 
555
void
556
Icf::find_identical_sections(const Input_objects* input_objects,
557
                             Symbol_table* symtab)
558
{
559
  unsigned int section_num = 0;
560
  std::vector<unsigned int> num_tracked_relocs;
561
  std::vector<bool> is_secn_or_group_unique;
562
  std::vector<std::string> section_contents;
563
 
564
  // Decide which sections are possible candidates first.
565
 
566
  for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
567
       p != input_objects->relobj_end();
568
       ++p)
569
    {
570
      for (unsigned int i = 0;i < (*p)->shnum(); ++i)
571
        {
572
          const char* section_name = (*p)->section_name(i).c_str();
573
          // Only looking to fold functions, so just look at .text sections.
574
          if (!is_prefix_of(".text.", section_name))
575
            continue;
576
          if (!(*p)->is_section_included(i))
577
            continue;
578
          if (parameters->options().gc_sections()
579
              && symtab->gc()->is_section_garbage(*p, i))
580
              continue;
581
          // With --icf=safe, check if mangled name is a ctor or a dtor.
582
          if (parameters->options().icf_safe_folding()
583
              && !is_function_ctor_or_dtor(section_name + 6))
584
            continue;
585
          this->id_section_.push_back(Section_id(*p, i));
586
          this->section_id_[Section_id(*p, i)] = section_num;
587
          this->kept_section_id_.push_back(section_num);
588
          num_tracked_relocs.push_back(0);
589
          is_secn_or_group_unique.push_back(false);
590
          section_contents.push_back("");
591
          section_num++;
592
        }
593
    }
594
 
595
  unsigned int num_iterations = 0;
596
 
597
  // Default number of iterations to run ICF is 2.
598
  unsigned int max_iterations = (parameters->options().icf_iterations() > 0)
599
                            ? parameters->options().icf_iterations()
600
                            : 2;
601
 
602
  bool converged = false;
603
 
604
  while (!converged && (num_iterations < max_iterations))
605
    {
606
      num_iterations++;
607
      converged = match_sections(num_iterations, symtab,
608
                                 &num_tracked_relocs, &this->kept_section_id_,
609
                                 this->id_section_, &is_secn_or_group_unique,
610
                                 &section_contents);
611
    }
612
 
613
  if (parameters->options().print_icf_sections())
614
    {
615
      if (converged)
616
        gold_info(_("%s: ICF Converged after %u iteration(s)"),
617
                  program_name, num_iterations);
618
      else
619
        gold_info(_("%s: ICF stopped after %u iteration(s)"),
620
                  program_name, num_iterations);
621
    }
622
 
623
  // Unfold --keep-unique symbols.
624
  for (options::String_set::const_iterator p =
625
         parameters->options().keep_unique_begin();
626
       p != parameters->options().keep_unique_end();
627
       ++p)
628
    {
629
      const char* name = p->c_str();
630
      Symbol* sym = symtab->lookup(name);
631
      if (sym == NULL)
632
        {
633
          gold_warning(_("Could not find symbol %s to unfold\n"), name);
634
        }
635
      else if (sym->source() == Symbol::FROM_OBJECT
636
               && !sym->object()->is_dynamic())
637
        {
638
          Object* obj = sym->object();
639
          bool is_ordinary;
640
          unsigned int shndx = sym->shndx(&is_ordinary);
641
          if (is_ordinary)
642
            {
643
              this->unfold_section(obj, shndx);
644
            }
645
        }
646
 
647
    }
648
 
649
  this->icf_ready();
650
}
651
 
652
// Unfolds the section denoted by OBJ and SHNDX if folded.
653
 
654
void
655
Icf::unfold_section(Object* obj, unsigned int shndx)
656
{
657
  Section_id secn(obj, shndx);
658
  Uniq_secn_id_map::iterator it = this->section_id_.find(secn);
659
  if (it == this->section_id_.end())
660
    return;
661
  unsigned int section_num = it->second;
662
  unsigned int kept_section_id = this->kept_section_id_[section_num];
663
  if (kept_section_id != section_num)
664
    this->kept_section_id_[section_num] = section_num;
665
}
666
 
667
// This function determines if the section corresponding to the
668
// given object and index is folded based on if the kept section
669
// is different from this section.
670
 
671
bool
672
Icf::is_section_folded(Object* obj, unsigned int shndx)
673
{
674
  Section_id secn(obj, shndx);
675
  Uniq_secn_id_map::iterator it = this->section_id_.find(secn);
676
  if (it == this->section_id_.end())
677
    return false;
678
  unsigned int section_num = it->second;
679
  unsigned int kept_section_id = this->kept_section_id_[section_num];
680
  return kept_section_id != section_num;
681
}
682
 
683
// This function returns the folded section for the given section.
684
 
685
Section_id
686
Icf::get_folded_section(Object* dup_obj, unsigned int dup_shndx)
687
{
688
  Section_id dup_secn(dup_obj, dup_shndx);
689
  Uniq_secn_id_map::iterator it = this->section_id_.find(dup_secn);
690
  gold_assert(it != this->section_id_.end());
691
  unsigned int section_num = it->second;
692
  unsigned int kept_section_id = this->kept_section_id_[section_num];
693
  Section_id folded_section = this->id_section_[kept_section_id];
694
  return folded_section;
695
}
696
 
697
} // End of namespace gold.

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