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julius |
// gc.h -- garbage collection of unused sections
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// Copyright 2009 Free Software Foundation, Inc.
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// Written by Sriraman Tallam <tmsriram@google.com>.
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// This file is part of gold.
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 3 of the License, or
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// (at your option) any later version.
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
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// MA 02110-1301, USA.
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#ifndef GOLD_GC_H
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#define GOLD_GC_H
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#include <queue>
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#include <vector>
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#include "elfcpp.h"
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#include "symtab.h"
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#include "icf.h"
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namespace gold
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{
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class Object;
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template<int size, bool big_endian>
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class Sized_relobj;
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template<int sh_type, int size, bool big_endian>
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class Reloc_types;
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class Output_section;
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class General_options;
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class Layout;
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typedef std::pair<Object *, unsigned int> Section_id;
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class Garbage_collection
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{
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struct Section_id_hash
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{
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size_t operator()(const Section_id& loc) const
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{ return reinterpret_cast<uintptr_t>(loc.first) ^ loc.second; }
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};
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public:
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typedef Unordered_set<Section_id, Section_id_hash> Sections_reachable;
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typedef std::map<Section_id, Sections_reachable> Section_ref;
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typedef std::queue<Section_id> Worklist_type;
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Garbage_collection()
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: is_worklist_ready_(false)
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{ }
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// Accessor methods for the private members.
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Sections_reachable&
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referenced_list()
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{ return referenced_list_; }
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Section_ref&
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section_reloc_map()
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{ return this->section_reloc_map_; }
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Worklist_type&
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worklist()
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{ return this->work_list_; }
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bool
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is_worklist_ready()
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{ return this->is_worklist_ready_; }
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void
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worklist_ready()
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{ this->is_worklist_ready_ = true; }
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void
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do_transitive_closure();
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bool
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is_section_garbage(Object* obj, unsigned int shndx)
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{ return (this->referenced_list().find(Section_id(obj, shndx))
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== this->referenced_list().end()); }
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private:
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Worklist_type work_list_;
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bool is_worklist_ready_;
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Section_ref section_reloc_map_;
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Sections_reachable referenced_list_;
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};
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// Data to pass between successive invocations of do_layout
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// in object.cc while garbage collecting. This data structure
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// is filled by using the data from Read_symbols_data.
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struct Symbols_data
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{
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// Section headers.
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unsigned char* section_headers_data;
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// Section names.
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unsigned char* section_names_data;
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// Size of section name data in bytes.
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section_size_type section_names_size;
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// Symbol data.
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unsigned char* symbols_data;
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// Size of symbol data in bytes.
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section_size_type symbols_size;
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// Offset of external symbols within symbol data. This structure
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// sometimes contains only external symbols, in which case this will
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// be zero. Sometimes it contains all symbols.
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section_offset_type external_symbols_offset;
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// Symbol names.
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unsigned char* symbol_names_data;
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// Size of symbol name data in bytes.
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section_size_type symbol_names_size;
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};
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// This function implements the generic part of reloc
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// processing to map a section to all the sections it
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// references through relocs. It is called only during
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// garbage collection (--gc-sections) and identical code
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// folding (--icf).
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template<int size, bool big_endian, typename Target_type, int sh_type,
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typename Scan>
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inline void
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gc_process_relocs(
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const General_options& ,
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Symbol_table* symtab,
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Layout*,
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Target_type* ,
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Sized_relobj<size, big_endian>* src_obj,
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unsigned int src_indx,
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const unsigned char* prelocs,
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size_t reloc_count,
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Output_section*,
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bool ,
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size_t local_count,
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const unsigned char* plocal_syms)
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{
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Object *dst_obj;
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unsigned int dst_indx;
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typedef typename Reloc_types<sh_type, size, big_endian>::Reloc Reltype;
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const int reloc_size = Reloc_types<sh_type, size, big_endian>::reloc_size;
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const int sym_size = elfcpp::Elf_sizes<size>::sym_size;
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std::vector<Section_id>* secvec = NULL;
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std::vector<Symbol*>* symvec = NULL;
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std::vector<std::pair<long long, long long> >* addendvec = NULL;
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bool is_icf_tracked = false;
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if (parameters->options().icf_enabled()
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&& is_prefix_of(".text.", (src_obj)->section_name(src_indx).c_str()))
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{
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is_icf_tracked = true;
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Section_id src_id(src_obj, src_indx);
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secvec = &symtab->icf()->section_reloc_list()[src_id];
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symvec = &symtab->icf()->symbol_reloc_list()[src_id];
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addendvec = &symtab->icf()->addend_reloc_list()[src_id];
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}
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for (size_t i = 0; i < reloc_count; ++i, prelocs += reloc_size)
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{
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Reltype reloc(prelocs);
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typename elfcpp::Elf_types<size>::Elf_WXword r_info = reloc.get_r_info();
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unsigned int r_sym = elfcpp::elf_r_sym<size>(r_info);
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typename elfcpp::Elf_types<size>::Elf_Swxword addend =
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Reloc_types<sh_type, size, big_endian>::get_reloc_addend_noerror(&reloc);
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if (r_sym < local_count)
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{
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gold_assert(plocal_syms != NULL);
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typename elfcpp::Sym<size, big_endian> lsym(plocal_syms
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+ r_sym * sym_size);
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unsigned int shndx = lsym.get_st_shndx();
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bool is_ordinary;
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shndx = src_obj->adjust_sym_shndx(r_sym, shndx, &is_ordinary);
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if (!is_ordinary)
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continue;
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dst_obj = src_obj;
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dst_indx = shndx;
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Section_id dst_id(dst_obj, dst_indx);
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if (is_icf_tracked)
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{
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(*secvec).push_back(dst_id);
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(*symvec).push_back(NULL);
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long long symvalue = static_cast<long long>(lsym.get_st_value());
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(*addendvec).push_back(std::make_pair(symvalue,
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static_cast<long long>(addend)));
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}
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if (shndx == src_indx)
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continue;
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}
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else
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{
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Symbol* gsym = src_obj->global_symbol(r_sym);
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gold_assert(gsym != NULL);
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if (gsym->is_forwarder())
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gsym = symtab->resolve_forwards(gsym);
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if (gsym->source() != Symbol::FROM_OBJECT)
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continue;
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bool is_ordinary;
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dst_obj = gsym->object();
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dst_indx = gsym->shndx(&is_ordinary);
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if (!is_ordinary)
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continue;
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Section_id dst_id(dst_obj, dst_indx);
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if (is_icf_tracked)
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{
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(*secvec).push_back(dst_id);
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(*symvec).push_back(gsym);
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Sized_symbol<size>* sized_gsym =
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static_cast<Sized_symbol<size>* >(gsym);
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long long symvalue =
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static_cast<long long>(sized_gsym->value());
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(*addendvec).push_back(std::make_pair(symvalue,
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static_cast<long long>(addend)));
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}
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}
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if (parameters->options().gc_sections())
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{
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Section_id src_id(src_obj, src_indx);
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Section_id dst_id(dst_obj, dst_indx);
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Garbage_collection::Section_ref::iterator map_it;
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map_it = symtab->gc()->section_reloc_map().find(src_id);
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if (map_it == symtab->gc()->section_reloc_map().end())
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{
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symtab->gc()->section_reloc_map()[src_id].insert(dst_id);
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}
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else
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{
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Garbage_collection::Sections_reachable& v(map_it->second);
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v.insert(dst_id);
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}
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}
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}
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return;
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}
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} // End of namespace gold.
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#endif
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