1 // icf.cc -- Identical Code Folding.
3 // Copyright (C) 2009-2016 Free Software Foundation, Inc.
4 // Written by Sriraman Tallam <tmsriram@google.com>.
6 // This file is part of gold.
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.
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.
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.
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 foldable 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.
36 // However, two functions A and B with identical text but with
37 // relocations pointing to different foldable sections can be identical if
38 // the corresponding foldable 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 :
43 // int funcA () int funcB ()
45 // return foo(); return goo();
48 // The functions funcA and funcB are identical if functions foo() and
49 // goo() are identical.
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
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 :
65 // int funcA (int a) int funcB (int a)
67 // if (a == 1) if (a == 1)
68 // return 1; return 1;
69 // return 1 + funcB(a - 1); return 1 + funcA(a - 1);
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.
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.
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
96 // Caveat with using function pointers :
97 // ------------------------------------
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
107 // ICF in safe mode folds only ctors and dtors if their function pointers can
108 // never be taken. Also, for X86-64, safe folding uses the relocation
109 // type to determine if a function's pointer is taken or not and only folds
110 // functions whose pointers are definitely not taken.
112 // Caveat with safe folding :
113 // ------------------------
115 // This applies only to x86_64.
117 // Position independent executables are created from PIC objects (compiled
118 // with -fPIC) and/or PIE objects (compiled with -fPIE). For PIE objects, the
119 // relocation types for function pointer taken and a call are the same.
120 // Now, it is not always possible to tell if an object used in the link of
121 // a pie executable is a PIC object or a PIE object. Hence, for pie
122 // executables, using relocation types to disambiguate function pointers is
123 // currently disabled.
125 // Further, it is not correct to use safe folding to build non-pie
126 // executables using PIC/PIE objects. PIC/PIE objects have different
127 // relocation types for function pointers than non-PIC objects, and the
128 // current implementation of safe folding does not handle those relocation
129 // types. Hence, if used, functions whose pointers are taken could still be
130 // folded causing unpredictable run-time behaviour if the pointers were used
135 // How to run : --icf=[safe|all|none]
136 // Optional parameters : --icf-iterations <num> --print-icf-sections
138 // Performance : Less than 20 % link-time overhead on industry strength
139 // applications. Up to 6 % text size reductions.
146 #include "libiberty.h"
147 #include "demangle.h"
149 #include "int_encoding.h"
154 // This function determines if a section or a group of identical
155 // sections has unique contents. Such unique sections or groups can be
156 // declared final and need not be processed any further.
158 // ID_SECTION : Vector mapping a section index to a Section_id pair.
159 // IS_SECN_OR_GROUP_UNIQUE : To check if a section or a group of identical
160 // sections is already known to be unique.
161 // SECTION_CONTENTS : Contains the section's text and relocs to sections
162 // that cannot be folded. SECTION_CONTENTS are NULL
163 // implies that this function is being called for the
164 // first time before the first iteration of icf.
167 preprocess_for_unique_sections(const std::vector<Section_id>& id_section,
168 std::vector<bool>* is_secn_or_group_unique,
169 std::vector<std::string>* section_contents)
171 Unordered_map<uint32_t, unsigned int> uniq_map;
172 std::pair<Unordered_map<uint32_t, unsigned int>::iterator, bool>
175 for (unsigned int i = 0; i < id_section.size(); i++)
177 if ((*is_secn_or_group_unique)[i])
181 Section_id secn = id_section[i];
182 section_size_type plen;
183 if (section_contents == NULL)
185 // Lock the object so we can read from it. This is only called
186 // single-threaded from queue_middle_tasks, so it is OK to lock.
187 // Unfortunately we have no way to pass in a Task token.
188 const Task* dummy_task = reinterpret_cast<const Task*>(-1);
189 Task_lock_obj<Object> tl(dummy_task, secn.first);
190 const unsigned char* contents;
191 contents = secn.first->section_contents(secn.second,
194 cksum = xcrc32(contents, plen, 0xffffffff);
198 const unsigned char* contents_array = reinterpret_cast
199 <const unsigned char*>((*section_contents)[i].c_str());
200 cksum = xcrc32(contents_array, (*section_contents)[i].length(),
203 uniq_map_insert = uniq_map.insert(std::make_pair(cksum, i));
204 if (uniq_map_insert.second)
206 (*is_secn_or_group_unique)[i] = true;
210 (*is_secn_or_group_unique)[i] = false;
211 (*is_secn_or_group_unique)[uniq_map_insert.first->second] = false;
216 // This returns the buffer containing the section's contents, both
217 // text and relocs. Relocs are differentiated as those pointing to
218 // sections that could be folded and those that cannot. Only relocs
219 // pointing to sections that could be folded are recomputed on
220 // subsequent invocations of this function.
222 // FIRST_ITERATION : true if it is the first invocation.
223 // SECN : Section for which contents are desired.
224 // SECTION_NUM : Unique section number of this section.
225 // NUM_TRACKED_RELOCS : Vector reference to store the number of relocs
227 // KEPT_SECTION_ID : Vector which maps folded sections to kept sections.
228 // SECTION_CONTENTS : Store the section's text and relocs to non-ICF
232 get_section_contents(bool first_iteration,
233 const Section_id& secn,
234 unsigned int section_num,
235 unsigned int* num_tracked_relocs,
236 Symbol_table* symtab,
237 const std::vector<unsigned int>& kept_section_id,
238 std::vector<std::string>* section_contents)
240 // Lock the object so we can read from it. This is only called
241 // single-threaded from queue_middle_tasks, so it is OK to lock.
242 // Unfortunately we have no way to pass in a Task token.
243 const Task* dummy_task = reinterpret_cast<const Task*>(-1);
244 Task_lock_obj<Object> tl(dummy_task, secn.first);
246 section_size_type plen;
247 const unsigned char* contents = NULL;
249 contents = secn.first->section_contents(secn.second, &plen, false);
251 // The buffer to hold all the contents including relocs. A checksum
252 // is then computed on this buffer.
254 std::string icf_reloc_buffer;
256 if (num_tracked_relocs)
257 *num_tracked_relocs = 0;
259 Icf::Reloc_info_list& reloc_info_list =
260 symtab->icf()->reloc_info_list();
262 Icf::Reloc_info_list::iterator it_reloc_info_list =
263 reloc_info_list.find(secn);
266 icf_reloc_buffer.clear();
268 // Process relocs and put them into the buffer.
270 if (it_reloc_info_list != reloc_info_list.end())
272 Icf::Sections_reachable_info &v =
273 (it_reloc_info_list->second).section_info;
274 // Stores the information of the symbol pointed to by the reloc.
275 const Icf::Symbol_info &s = (it_reloc_info_list->second).symbol_info;
276 // Stores the addend and the symbol value.
277 Icf::Addend_info &a = (it_reloc_info_list->second).addend_info;
278 // Stores the offset of the reloc.
279 const Icf::Offset_info &o = (it_reloc_info_list->second).offset_info;
280 const Icf::Reloc_addend_size_info &reloc_addend_size_info =
281 (it_reloc_info_list->second).reloc_addend_size_info;
282 Icf::Sections_reachable_info::iterator it_v = v.begin();
283 Icf::Symbol_info::const_iterator it_s = s.begin();
284 Icf::Addend_info::iterator it_a = a.begin();
285 Icf::Offset_info::const_iterator it_o = o.begin();
286 Icf::Reloc_addend_size_info::const_iterator it_addend_size =
287 reloc_addend_size_info.begin();
289 for (; it_v != v.end(); ++it_v, ++it_s, ++it_a, ++it_o, ++it_addend_size)
292 && it_v->first != NULL)
295 loc.object = it_v->first;
296 loc.shndx = it_v->second;
297 loc.offset = convert_types<off_t, long long>(it_a->first
299 // Look through function descriptors
300 parameters->target().function_location(&loc);
301 if (loc.shndx != it_v->second)
303 it_v->second = loc.shndx;
304 // Modify symvalue/addend to the code entry.
305 it_a->first = loc.offset;
310 // ADDEND_STR stores the symbol value and addend and offset,
311 // each at most 16 hex digits long. it_a points to a pair
312 // where first is the symbol value and second is the
316 // It would be nice if we could use format macros in inttypes.h
317 // here but there are not in ISO/IEC C++ 1998.
318 snprintf(addend_str, sizeof(addend_str), "%llx %llx %llux",
319 static_cast<long long>((*it_a).first),
320 static_cast<long long>((*it_a).second),
321 static_cast<unsigned long long>(*it_o));
323 // If the symbol pointed to by the reloc is not in an ordinary
324 // section or if the symbol type is not FROM_OBJECT, then the
326 if (it_v->first == NULL)
330 // If the symbol name is available, use it.
332 buffer.append((*it_s)->name());
333 // Append the addend.
334 buffer.append(addend_str);
340 Section_id reloc_secn(it_v->first, it_v->second);
342 // If this reloc turns back and points to the same section,
343 // like a recursive call, use a special symbol to mark this.
344 if (reloc_secn.first == secn.first
345 && reloc_secn.second == secn.second)
350 buffer.append(addend_str);
355 Icf::Uniq_secn_id_map& section_id_map =
356 symtab->icf()->section_to_int_map();
357 Icf::Uniq_secn_id_map::iterator section_id_map_it =
358 section_id_map.find(reloc_secn);
359 bool is_sym_preemptible = (*it_s != NULL
360 && !(*it_s)->is_from_dynobj()
361 && !(*it_s)->is_undefined()
362 && (*it_s)->is_preemptible());
363 if (!is_sym_preemptible
364 && section_id_map_it != section_id_map.end())
366 // This is a reloc to a section that might be folded.
367 if (num_tracked_relocs)
368 (*num_tracked_relocs)++;
370 char kept_section_str[10];
371 unsigned int secn_id = section_id_map_it->second;
372 snprintf(kept_section_str, sizeof(kept_section_str), "%u",
373 kept_section_id[secn_id]);
376 buffer.append("ICF_R");
377 buffer.append(addend_str);
379 icf_reloc_buffer.append(kept_section_str);
380 // Append the addend.
381 icf_reloc_buffer.append(addend_str);
382 icf_reloc_buffer.append("@");
386 // This is a reloc to a section that cannot be folded.
387 // Process it only in the first iteration.
388 if (!first_iteration)
391 uint64_t secn_flags = (it_v->first)->section_flags(it_v->second);
392 // This reloc points to a merge section. Hash the
393 // contents of this section.
394 if ((secn_flags & elfcpp::SHF_MERGE) != 0
395 && parameters->target().can_icf_inline_merge_sections())
398 (it_v->first)->section_entsize(it_v->second);
399 long long offset = it_a->first;
401 unsigned long long addend = it_a->second;
402 // Ignoring the addend when it is a negative value. See the
403 // comments in Merged_symbol_value::Value in object.h.
404 if (addend < 0xffffff00)
405 offset = offset + addend;
407 // For SHT_REL relocation sections, the addend is stored in the
408 // text section at the relocation offset.
409 uint64_t reloc_addend_value = 0;
410 const unsigned char* reloc_addend_ptr =
411 contents + static_cast<unsigned long long>(*it_o);
412 switch(*it_addend_size)
421 read_from_pointer<8>(reloc_addend_ptr);
427 read_from_pointer<16>(reloc_addend_ptr);
433 read_from_pointer<32>(reloc_addend_ptr);
439 read_from_pointer<64>(reloc_addend_ptr);
445 offset = offset + reloc_addend_value;
447 section_size_type secn_len;
448 const unsigned char* str_contents =
449 (it_v->first)->section_contents(it_v->second,
452 if ((secn_flags & elfcpp::SHF_STRINGS) != 0)
454 // String merge section.
455 const char* str_char =
456 reinterpret_cast<const char*>(str_contents);
461 buffer.append(str_char);
466 const uint16_t* ptr_16 =
467 reinterpret_cast<const uint16_t*>(str_char);
468 unsigned int strlen_16 = 0;
469 // Find the NULL character.
470 while(*(ptr_16 + strlen_16) != 0)
472 buffer.append(str_char, strlen_16 * 2);
477 const uint32_t* ptr_32 =
478 reinterpret_cast<const uint32_t*>(str_char);
479 unsigned int strlen_32 = 0;
480 // Find the NULL character.
481 while(*(ptr_32 + strlen_32) != 0)
483 buffer.append(str_char, strlen_32 * 4);
492 // Use the entsize to determine the length.
493 buffer.append(reinterpret_cast<const
494 char*>(str_contents),
499 else if ((*it_s) != NULL)
501 // If symbol name is available use that.
502 buffer.append((*it_s)->name());
503 // Append the addend.
504 buffer.append(addend_str);
509 // Symbol name is not available, like for a local symbol,
510 // use object and section id.
511 buffer.append(it_v->first->name());
513 snprintf(secn_id, sizeof(secn_id), "%u",it_v->second);
514 buffer.append(secn_id);
515 // Append the addend.
516 buffer.append(addend_str);
525 buffer.append("Contents = ");
526 buffer.append(reinterpret_cast<const char*>(contents), plen);
527 // Store the section contents that dont change to avoid recomputing
528 // during the next call to this function.
529 (*section_contents)[section_num] = buffer;
533 gold_assert(buffer.empty());
534 // Reuse the contents computed in the previous iteration.
535 buffer.append((*section_contents)[section_num]);
538 buffer.append(icf_reloc_buffer);
542 // This function computes a checksum on each section to detect and form
543 // groups of identical sections. The first iteration does this for all
545 // Further iterations do this only for the kept sections from each group to
546 // determine if larger groups of identical sections could be formed. The
547 // first section in each group is the kept section for that group.
549 // CRC32 is the checksumming algorithm and can have collisions. That is,
550 // two sections with different contents can have the same checksum. Hence,
551 // a multimap is used to maintain more than one group of checksum
552 // identical sections. A section is added to a group only after its
553 // contents are explicitly compared with the kept section of the group.
556 // ITERATION_NUM : Invocation instance of this function.
557 // NUM_TRACKED_RELOCS : Vector reference to store the number of relocs
559 // KEPT_SECTION_ID : Vector which maps folded sections to kept sections.
560 // ID_SECTION : Vector mapping a section to an unique integer.
561 // IS_SECN_OR_GROUP_UNIQUE : To check if a section or a group of identical
562 // sections is already known to be unique.
563 // SECTION_CONTENTS : Store the section's text and relocs to non-ICF
567 match_sections(unsigned int iteration_num,
568 Symbol_table* symtab,
569 std::vector<unsigned int>* num_tracked_relocs,
570 std::vector<unsigned int>* kept_section_id,
571 const std::vector<Section_id>& id_section,
572 std::vector<bool>* is_secn_or_group_unique,
573 std::vector<std::string>* section_contents)
575 Unordered_multimap<uint32_t, unsigned int> section_cksum;
576 std::pair<Unordered_multimap<uint32_t, unsigned int>::iterator,
577 Unordered_multimap<uint32_t, unsigned int>::iterator> key_range;
578 bool converged = true;
580 if (iteration_num == 1)
581 preprocess_for_unique_sections(id_section,
582 is_secn_or_group_unique,
585 preprocess_for_unique_sections(id_section,
586 is_secn_or_group_unique,
589 std::vector<std::string> full_section_contents;
591 for (unsigned int i = 0; i < id_section.size(); i++)
593 full_section_contents.push_back("");
594 if ((*is_secn_or_group_unique)[i])
597 Section_id secn = id_section[i];
598 std::string this_secn_contents;
600 if (iteration_num == 1)
602 unsigned int num_relocs = 0;
603 this_secn_contents = get_section_contents(true, secn, i, &num_relocs,
604 symtab, (*kept_section_id),
606 (*num_tracked_relocs)[i] = num_relocs;
610 if ((*kept_section_id)[i] != i)
612 // This section is already folded into something. See
613 // if it should point to a different kept section.
614 unsigned int kept_section = (*kept_section_id)[i];
615 if (kept_section != (*kept_section_id)[kept_section])
617 (*kept_section_id)[i] = (*kept_section_id)[kept_section];
621 this_secn_contents = get_section_contents(false, secn, i, NULL,
622 symtab, (*kept_section_id),
626 const unsigned char* this_secn_contents_array =
627 reinterpret_cast<const unsigned char*>(this_secn_contents.c_str());
628 cksum = xcrc32(this_secn_contents_array, this_secn_contents.length(),
630 size_t count = section_cksum.count(cksum);
634 // Start a group with this cksum.
635 section_cksum.insert(std::make_pair(cksum, i));
636 full_section_contents[i] = this_secn_contents;
640 key_range = section_cksum.equal_range(cksum);
641 Unordered_multimap<uint32_t, unsigned int>::iterator it;
642 // Search all the groups with this cksum for a match.
643 for (it = key_range.first; it != key_range.second; ++it)
645 unsigned int kept_section = it->second;
646 if (full_section_contents[kept_section].length()
647 != this_secn_contents.length())
649 if (memcmp(full_section_contents[kept_section].c_str(),
650 this_secn_contents.c_str(),
651 this_secn_contents.length()) != 0)
653 (*kept_section_id)[i] = kept_section;
657 if (it == key_range.second)
659 // Create a new group for this cksum.
660 section_cksum.insert(std::make_pair(cksum, i));
661 full_section_contents[i] = this_secn_contents;
664 // If there are no relocs to foldable sections do not process
665 // this section any further.
666 if (iteration_num == 1 && (*num_tracked_relocs)[i] == 0)
667 (*is_secn_or_group_unique)[i] = true;
673 // During safe icf (--icf=safe), only fold functions that are ctors or dtors.
674 // This function returns true if the section name is that of a ctor or a dtor.
677 is_function_ctor_or_dtor(const std::string& section_name)
679 const char* mangled_func_name = strrchr(section_name.c_str(), '.');
680 gold_assert(mangled_func_name != NULL);
681 if ((is_prefix_of("._ZN", mangled_func_name)
682 || is_prefix_of("._ZZ", mangled_func_name))
683 && (is_gnu_v3_mangled_ctor(mangled_func_name + 1)
684 || is_gnu_v3_mangled_dtor(mangled_func_name + 1)))
691 // This is the main ICF function called in gold.cc. This does the
692 // initialization and calls match_sections repeatedly (twice by default)
693 // which computes the crc checksums and detects identical functions.
696 Icf::find_identical_sections(const Input_objects* input_objects,
697 Symbol_table* symtab)
699 unsigned int section_num = 0;
700 std::vector<unsigned int> num_tracked_relocs;
701 std::vector<bool> is_secn_or_group_unique;
702 std::vector<std::string> section_contents;
703 const Target& target = parameters->target();
705 // Decide which sections are possible candidates first.
707 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
708 p != input_objects->relobj_end();
711 // Lock the object so we can read from it. This is only called
712 // single-threaded from queue_middle_tasks, so it is OK to lock.
713 // Unfortunately we have no way to pass in a Task token.
714 const Task* dummy_task = reinterpret_cast<const Task*>(-1);
715 Task_lock_obj<Object> tl(dummy_task, *p);
717 for (unsigned int i = 0;i < (*p)->shnum(); ++i)
719 const std::string section_name = (*p)->section_name(i);
720 if (!is_section_foldable_candidate(section_name))
722 if (!(*p)->is_section_included(i))
724 if (parameters->options().gc_sections()
725 && symtab->gc()->is_section_garbage(*p, i))
727 // With --icf=safe, check if the mangled function name is a ctor
728 // or a dtor. The mangled function name can be obtained from the
729 // section name by stripping the section prefix.
730 if (parameters->options().icf_safe_folding()
731 && !is_function_ctor_or_dtor(section_name)
732 && (!target.can_check_for_function_pointers()
733 || section_has_function_pointers(*p, i)))
737 this->id_section_.push_back(Section_id(*p, i));
738 this->section_id_[Section_id(*p, i)] = section_num;
739 this->kept_section_id_.push_back(section_num);
740 num_tracked_relocs.push_back(0);
741 is_secn_or_group_unique.push_back(false);
742 section_contents.push_back("");
747 unsigned int num_iterations = 0;
749 // Default number of iterations to run ICF is 2.
750 unsigned int max_iterations = (parameters->options().icf_iterations() > 0)
751 ? parameters->options().icf_iterations()
754 bool converged = false;
756 while (!converged && (num_iterations < max_iterations))
759 converged = match_sections(num_iterations, symtab,
760 &num_tracked_relocs, &this->kept_section_id_,
761 this->id_section_, &is_secn_or_group_unique,
765 if (parameters->options().print_icf_sections())
768 gold_info(_("%s: ICF Converged after %u iteration(s)"),
769 program_name, num_iterations);
771 gold_info(_("%s: ICF stopped after %u iteration(s)"),
772 program_name, num_iterations);
775 // Unfold --keep-unique symbols.
776 for (options::String_set::const_iterator p =
777 parameters->options().keep_unique_begin();
778 p != parameters->options().keep_unique_end();
781 const char* name = p->c_str();
782 Symbol* sym = symtab->lookup(name);
785 gold_warning(_("Could not find symbol %s to unfold\n"), name);
787 else if (sym->source() == Symbol::FROM_OBJECT
788 && !sym->object()->is_dynamic())
790 Relobj* obj = static_cast<Relobj*>(sym->object());
792 unsigned int shndx = sym->shndx(&is_ordinary);
795 this->unfold_section(obj, shndx);
804 // Unfolds the section denoted by OBJ and SHNDX if folded.
807 Icf::unfold_section(Relobj* obj, unsigned int shndx)
809 Section_id secn(obj, shndx);
810 Uniq_secn_id_map::iterator it = this->section_id_.find(secn);
811 if (it == this->section_id_.end())
813 unsigned int section_num = it->second;
814 unsigned int kept_section_id = this->kept_section_id_[section_num];
815 if (kept_section_id != section_num)
816 this->kept_section_id_[section_num] = section_num;
819 // This function determines if the section corresponding to the
820 // given object and index is folded based on if the kept section
821 // is different from this section.
824 Icf::is_section_folded(Relobj* obj, unsigned int shndx)
826 Section_id secn(obj, shndx);
827 Uniq_secn_id_map::iterator it = this->section_id_.find(secn);
828 if (it == this->section_id_.end())
830 unsigned int section_num = it->second;
831 unsigned int kept_section_id = this->kept_section_id_[section_num];
832 return kept_section_id != section_num;
835 // This function returns the folded section for the given section.
838 Icf::get_folded_section(Relobj* dup_obj, unsigned int dup_shndx)
840 Section_id dup_secn(dup_obj, dup_shndx);
841 Uniq_secn_id_map::iterator it = this->section_id_.find(dup_secn);
842 gold_assert(it != this->section_id_.end());
843 unsigned int section_num = it->second;
844 unsigned int kept_section_id = this->kept_section_id_[section_num];
845 Section_id folded_section = this->id_section_[kept_section_id];
846 return folded_section;
849 } // End of namespace gold.