* elf32-spu.c (build_stub): Fix malloc under-allocation.
[binutils.git] / gold / icf.cc
blob5935c5be2fe30fb41bfaa58c6857ea49e67312f6
1 // icf.cc -- Identical Code Folding.
2 //
3 // Copyright 2009, 2010, 2011 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 ()
44 // { {
45 // return foo(); return goo();
46 // } }
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
54 // we initialize.
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 :
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 // } }
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.
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.
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.
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
102 // behaviour.
104 // Safe Folding :
105 // ------------
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
131 // in comparisons.
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.
141 #include "gold.h"
142 #include "object.h"
143 #include "gc.h"
144 #include "icf.h"
145 #include "symtab.h"
146 #include "libiberty.h"
147 #include "demangle.h"
148 #include "elfcpp.h"
149 #include "int_encoding.h"
151 namespace gold
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.
157 // Parameters :
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.
166 static void
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>
173 uniq_map_insert;
175 for (unsigned int i = 0; i < id_section.size(); i++)
177 if ((*is_secn_or_group_unique)[i])
178 continue;
180 uint32_t cksum;
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,
192 &plen,
193 false);
194 cksum = xcrc32(contents, plen, 0xffffffff);
196 else
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(),
201 0xffffffff);
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;
208 else
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.
221 // Parameters :
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
226 // to ICF sections.
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
229 // sections.
231 static std::string
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;
248 if (first_iteration)
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.
253 std::string 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);
265 buffer.clear();
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 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 Icf::Offset_info o = (it_reloc_info_list->second).offset_info;
280 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::iterator it_s = s.begin();
284 Icf::Addend_info::iterator it_a = a.begin();
285 Icf::Offset_info::iterator it_o = o.begin();
286 Icf::Reloc_addend_size_info::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)
291 // ADDEND_STR stores the symbol value and addend and offset,
292 // each at most 16 hex digits long. it_a points to a pair
293 // where first is the symbol value and second is the
294 // addend.
295 char addend_str[50];
297 // It would be nice if we could use format macros in inttypes.h
298 // here but there are not in ISO/IEC C++ 1998.
299 snprintf(addend_str, sizeof(addend_str), "%llx %llx %llux",
300 static_cast<long long>((*it_a).first),
301 static_cast<long long>((*it_a).second),
302 static_cast<unsigned long long>(*it_o));
304 // If the symbol pointed to by the reloc is not in an ordinary
305 // section or if the symbol type is not FROM_OBJECT, then the
306 // object is NULL.
307 if (it_v->first == NULL)
309 if (first_iteration)
311 // If the symbol name is available, use it.
312 if ((*it_s) != NULL)
313 buffer.append((*it_s)->name());
314 // Append the addend.
315 buffer.append(addend_str);
316 buffer.append("@");
318 continue;
321 Section_id reloc_secn(it_v->first, it_v->second);
323 // If this reloc turns back and points to the same section,
324 // like a recursive call, use a special symbol to mark this.
325 if (reloc_secn.first == secn.first
326 && reloc_secn.second == secn.second)
328 if (first_iteration)
330 buffer.append("R");
331 buffer.append(addend_str);
332 buffer.append("@");
334 continue;
336 Icf::Uniq_secn_id_map& section_id_map =
337 symtab->icf()->section_to_int_map();
338 Icf::Uniq_secn_id_map::iterator section_id_map_it =
339 section_id_map.find(reloc_secn);
340 bool is_sym_preemptible = (*it_s != NULL
341 && !(*it_s)->is_from_dynobj()
342 && !(*it_s)->is_undefined()
343 && (*it_s)->is_preemptible());
344 if (!is_sym_preemptible
345 && section_id_map_it != section_id_map.end())
347 // This is a reloc to a section that might be folded.
348 if (num_tracked_relocs)
349 (*num_tracked_relocs)++;
351 char kept_section_str[10];
352 unsigned int secn_id = section_id_map_it->second;
353 snprintf(kept_section_str, sizeof(kept_section_str), "%u",
354 kept_section_id[secn_id]);
355 if (first_iteration)
357 buffer.append("ICF_R");
358 buffer.append(addend_str);
360 icf_reloc_buffer.append(kept_section_str);
361 // Append the addend.
362 icf_reloc_buffer.append(addend_str);
363 icf_reloc_buffer.append("@");
365 else
367 // This is a reloc to a section that cannot be folded.
368 // Process it only in the first iteration.
369 if (!first_iteration)
370 continue;
372 uint64_t secn_flags = (it_v->first)->section_flags(it_v->second);
373 // This reloc points to a merge section. Hash the
374 // contents of this section.
375 if ((secn_flags & elfcpp::SHF_MERGE) != 0
376 && parameters->target().can_icf_inline_merge_sections())
378 uint64_t entsize =
379 (it_v->first)->section_entsize(it_v->second);
380 long long offset = it_a->first;
382 unsigned long long addend = it_a->second;
383 // Ignoring the addend when it is a negative value. See the
384 // comments in Merged_symbol_value::Value in object.h.
385 if (addend < 0xffffff00)
386 offset = offset + addend;
388 // For SHT_REL relocation sections, the addend is stored in the
389 // text section at the relocation offset.
390 uint64_t reloc_addend_value = 0;
391 const unsigned char* reloc_addend_ptr =
392 contents + static_cast<unsigned long long>(*it_o);
393 switch(*it_addend_size)
395 case 0:
397 break;
399 case 1:
401 reloc_addend_value =
402 read_from_pointer<8>(reloc_addend_ptr);
403 break;
405 case 2:
407 reloc_addend_value =
408 read_from_pointer<16>(reloc_addend_ptr);
409 break;
411 case 4:
413 reloc_addend_value =
414 read_from_pointer<32>(reloc_addend_ptr);
415 break;
417 case 8:
419 reloc_addend_value =
420 read_from_pointer<64>(reloc_addend_ptr);
421 break;
423 default:
424 gold_unreachable();
426 offset = offset + reloc_addend_value;
428 section_size_type secn_len;
429 const unsigned char* str_contents =
430 (it_v->first)->section_contents(it_v->second,
431 &secn_len,
432 false) + offset;
433 if ((secn_flags & elfcpp::SHF_STRINGS) != 0)
435 // String merge section.
436 const char* str_char =
437 reinterpret_cast<const char*>(str_contents);
438 switch(entsize)
440 case 1:
442 buffer.append(str_char);
443 break;
445 case 2:
447 const uint16_t* ptr_16 =
448 reinterpret_cast<const uint16_t*>(str_char);
449 unsigned int strlen_16 = 0;
450 // Find the NULL character.
451 while(*(ptr_16 + strlen_16) != 0)
452 strlen_16++;
453 buffer.append(str_char, strlen_16 * 2);
455 break;
456 case 4:
458 const uint32_t* ptr_32 =
459 reinterpret_cast<const uint32_t*>(str_char);
460 unsigned int strlen_32 = 0;
461 // Find the NULL character.
462 while(*(ptr_32 + strlen_32) != 0)
463 strlen_32++;
464 buffer.append(str_char, strlen_32 * 4);
466 break;
467 default:
468 gold_unreachable();
471 else
473 // Use the entsize to determine the length.
474 buffer.append(reinterpret_cast<const
475 char*>(str_contents),
476 entsize);
478 buffer.append("@");
480 else if ((*it_s) != NULL)
482 // If symbol name is available use that.
483 buffer.append((*it_s)->name());
484 // Append the addend.
485 buffer.append(addend_str);
486 buffer.append("@");
488 else
490 // Symbol name is not available, like for a local symbol,
491 // use object and section id.
492 buffer.append(it_v->first->name());
493 char secn_id[10];
494 snprintf(secn_id, sizeof(secn_id), "%u",it_v->second);
495 buffer.append(secn_id);
496 // Append the addend.
497 buffer.append(addend_str);
498 buffer.append("@");
504 if (first_iteration)
506 buffer.append("Contents = ");
507 buffer.append(reinterpret_cast<const char*>(contents), plen);
508 // Store the section contents that dont change to avoid recomputing
509 // during the next call to this function.
510 (*section_contents)[section_num] = buffer;
512 else
514 gold_assert(buffer.empty());
515 // Reuse the contents computed in the previous iteration.
516 buffer.append((*section_contents)[section_num]);
519 buffer.append(icf_reloc_buffer);
520 return buffer;
523 // This function computes a checksum on each section to detect and form
524 // groups of identical sections. The first iteration does this for all
525 // sections.
526 // Further iterations do this only for the kept sections from each group to
527 // determine if larger groups of identical sections could be formed. The
528 // first section in each group is the kept section for that group.
530 // CRC32 is the checksumming algorithm and can have collisions. That is,
531 // two sections with different contents can have the same checksum. Hence,
532 // a multimap is used to maintain more than one group of checksum
533 // identical sections. A section is added to a group only after its
534 // contents are explicitly compared with the kept section of the group.
536 // Parameters :
537 // ITERATION_NUM : Invocation instance of this function.
538 // NUM_TRACKED_RELOCS : Vector reference to store the number of relocs
539 // to ICF sections.
540 // KEPT_SECTION_ID : Vector which maps folded sections to kept sections.
541 // ID_SECTION : Vector mapping a section to an unique integer.
542 // IS_SECN_OR_GROUP_UNIQUE : To check if a section or a group of identical
543 // sections is already known to be unique.
544 // SECTION_CONTENTS : Store the section's text and relocs to non-ICF
545 // sections.
547 static bool
548 match_sections(unsigned int iteration_num,
549 Symbol_table* symtab,
550 std::vector<unsigned int>* num_tracked_relocs,
551 std::vector<unsigned int>* kept_section_id,
552 const std::vector<Section_id>& id_section,
553 std::vector<bool>* is_secn_or_group_unique,
554 std::vector<std::string>* section_contents)
556 Unordered_multimap<uint32_t, unsigned int> section_cksum;
557 std::pair<Unordered_multimap<uint32_t, unsigned int>::iterator,
558 Unordered_multimap<uint32_t, unsigned int>::iterator> key_range;
559 bool converged = true;
561 if (iteration_num == 1)
562 preprocess_for_unique_sections(id_section,
563 is_secn_or_group_unique,
564 NULL);
565 else
566 preprocess_for_unique_sections(id_section,
567 is_secn_or_group_unique,
568 section_contents);
570 std::vector<std::string> full_section_contents;
572 for (unsigned int i = 0; i < id_section.size(); i++)
574 full_section_contents.push_back("");
575 if ((*is_secn_or_group_unique)[i])
576 continue;
578 Section_id secn = id_section[i];
579 std::string this_secn_contents;
580 uint32_t cksum;
581 if (iteration_num == 1)
583 unsigned int num_relocs = 0;
584 this_secn_contents = get_section_contents(true, secn, i, &num_relocs,
585 symtab, (*kept_section_id),
586 section_contents);
587 (*num_tracked_relocs)[i] = num_relocs;
589 else
591 if ((*kept_section_id)[i] != i)
593 // This section is already folded into something. See
594 // if it should point to a different kept section.
595 unsigned int kept_section = (*kept_section_id)[i];
596 if (kept_section != (*kept_section_id)[kept_section])
598 (*kept_section_id)[i] = (*kept_section_id)[kept_section];
600 continue;
602 this_secn_contents = get_section_contents(false, secn, i, NULL,
603 symtab, (*kept_section_id),
604 section_contents);
607 const unsigned char* this_secn_contents_array =
608 reinterpret_cast<const unsigned char*>(this_secn_contents.c_str());
609 cksum = xcrc32(this_secn_contents_array, this_secn_contents.length(),
610 0xffffffff);
611 size_t count = section_cksum.count(cksum);
613 if (count == 0)
615 // Start a group with this cksum.
616 section_cksum.insert(std::make_pair(cksum, i));
617 full_section_contents[i] = this_secn_contents;
619 else
621 key_range = section_cksum.equal_range(cksum);
622 Unordered_multimap<uint32_t, unsigned int>::iterator it;
623 // Search all the groups with this cksum for a match.
624 for (it = key_range.first; it != key_range.second; ++it)
626 unsigned int kept_section = it->second;
627 if (full_section_contents[kept_section].length()
628 != this_secn_contents.length())
629 continue;
630 if (memcmp(full_section_contents[kept_section].c_str(),
631 this_secn_contents.c_str(),
632 this_secn_contents.length()) != 0)
633 continue;
634 (*kept_section_id)[i] = kept_section;
635 converged = false;
636 break;
638 if (it == key_range.second)
640 // Create a new group for this cksum.
641 section_cksum.insert(std::make_pair(cksum, i));
642 full_section_contents[i] = this_secn_contents;
645 // If there are no relocs to foldable sections do not process
646 // this section any further.
647 if (iteration_num == 1 && (*num_tracked_relocs)[i] == 0)
648 (*is_secn_or_group_unique)[i] = true;
651 return converged;
654 // During safe icf (--icf=safe), only fold functions that are ctors or dtors.
655 // This function returns true if the section name is that of a ctor or a dtor.
657 static bool
658 is_function_ctor_or_dtor(const std::string& section_name)
660 const char* mangled_func_name = strrchr(section_name.c_str(), '.');
661 gold_assert(mangled_func_name != NULL);
662 if ((is_prefix_of("._ZN", mangled_func_name)
663 || is_prefix_of("._ZZ", mangled_func_name))
664 && (is_gnu_v3_mangled_ctor(mangled_func_name + 1)
665 || is_gnu_v3_mangled_dtor(mangled_func_name + 1)))
667 return true;
669 return false;
672 // This is the main ICF function called in gold.cc. This does the
673 // initialization and calls match_sections repeatedly (twice by default)
674 // which computes the crc checksums and detects identical functions.
676 void
677 Icf::find_identical_sections(const Input_objects* input_objects,
678 Symbol_table* symtab)
680 unsigned int section_num = 0;
681 std::vector<unsigned int> num_tracked_relocs;
682 std::vector<bool> is_secn_or_group_unique;
683 std::vector<std::string> section_contents;
684 const Target& target = parameters->target();
686 // Decide which sections are possible candidates first.
688 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
689 p != input_objects->relobj_end();
690 ++p)
692 // Lock the object so we can read from it. This is only called
693 // single-threaded from queue_middle_tasks, so it is OK to lock.
694 // Unfortunately we have no way to pass in a Task token.
695 const Task* dummy_task = reinterpret_cast<const Task*>(-1);
696 Task_lock_obj<Object> tl(dummy_task, *p);
698 for (unsigned int i = 0;i < (*p)->shnum(); ++i)
700 const std::string section_name = (*p)->section_name(i);
701 if (!is_section_foldable_candidate(section_name))
702 continue;
703 if (!(*p)->is_section_included(i))
704 continue;
705 if (parameters->options().gc_sections()
706 && symtab->gc()->is_section_garbage(*p, i))
707 continue;
708 // With --icf=safe, check if the mangled function name is a ctor
709 // or a dtor. The mangled function name can be obtained from the
710 // section name by stripping the section prefix.
711 if (parameters->options().icf_safe_folding()
712 && !is_function_ctor_or_dtor(section_name)
713 && (!target.can_check_for_function_pointers()
714 || section_has_function_pointers(*p, i)))
716 continue;
718 this->id_section_.push_back(Section_id(*p, i));
719 this->section_id_[Section_id(*p, i)] = section_num;
720 this->kept_section_id_.push_back(section_num);
721 num_tracked_relocs.push_back(0);
722 is_secn_or_group_unique.push_back(false);
723 section_contents.push_back("");
724 section_num++;
728 unsigned int num_iterations = 0;
730 // Default number of iterations to run ICF is 2.
731 unsigned int max_iterations = (parameters->options().icf_iterations() > 0)
732 ? parameters->options().icf_iterations()
733 : 2;
735 bool converged = false;
737 while (!converged && (num_iterations < max_iterations))
739 num_iterations++;
740 converged = match_sections(num_iterations, symtab,
741 &num_tracked_relocs, &this->kept_section_id_,
742 this->id_section_, &is_secn_or_group_unique,
743 &section_contents);
746 if (parameters->options().print_icf_sections())
748 if (converged)
749 gold_info(_("%s: ICF Converged after %u iteration(s)"),
750 program_name, num_iterations);
751 else
752 gold_info(_("%s: ICF stopped after %u iteration(s)"),
753 program_name, num_iterations);
756 // Unfold --keep-unique symbols.
757 for (options::String_set::const_iterator p =
758 parameters->options().keep_unique_begin();
759 p != parameters->options().keep_unique_end();
760 ++p)
762 const char* name = p->c_str();
763 Symbol* sym = symtab->lookup(name);
764 if (sym == NULL)
766 gold_warning(_("Could not find symbol %s to unfold\n"), name);
768 else if (sym->source() == Symbol::FROM_OBJECT
769 && !sym->object()->is_dynamic())
771 Object* obj = sym->object();
772 bool is_ordinary;
773 unsigned int shndx = sym->shndx(&is_ordinary);
774 if (is_ordinary)
776 this->unfold_section(obj, shndx);
782 this->icf_ready();
785 // Unfolds the section denoted by OBJ and SHNDX if folded.
787 void
788 Icf::unfold_section(Object* obj, unsigned int shndx)
790 Section_id secn(obj, shndx);
791 Uniq_secn_id_map::iterator it = this->section_id_.find(secn);
792 if (it == this->section_id_.end())
793 return;
794 unsigned int section_num = it->second;
795 unsigned int kept_section_id = this->kept_section_id_[section_num];
796 if (kept_section_id != section_num)
797 this->kept_section_id_[section_num] = section_num;
800 // This function determines if the section corresponding to the
801 // given object and index is folded based on if the kept section
802 // is different from this section.
804 bool
805 Icf::is_section_folded(Object* obj, unsigned int shndx)
807 Section_id secn(obj, shndx);
808 Uniq_secn_id_map::iterator it = this->section_id_.find(secn);
809 if (it == this->section_id_.end())
810 return false;
811 unsigned int section_num = it->second;
812 unsigned int kept_section_id = this->kept_section_id_[section_num];
813 return kept_section_id != section_num;
816 // This function returns the folded section for the given section.
818 Section_id
819 Icf::get_folded_section(Object* dup_obj, unsigned int dup_shndx)
821 Section_id dup_secn(dup_obj, dup_shndx);
822 Uniq_secn_id_map::iterator it = this->section_id_.find(dup_secn);
823 gold_assert(it != this->section_id_.end());
824 unsigned int section_num = it->second;
825 unsigned int kept_section_id = this->kept_section_id_[section_num];
826 Section_id folded_section = this->id_section_[kept_section_id];
827 return folded_section;
830 } // End of namespace gold.