gold/gc.cc

   1 // gc.cc -- garbage collection of unused sections
   2
   3 // Copyright (C) 2009-2020 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
  24 #include "gold.h"
  25 #include "object.h"
  26 #include "gc.h"
  27 #include "symtab.h"
  28
  29 namespace gold
  30 {
  31
  32 // Garbage collection uses a worklist style algorithm to determine the
  33 // transitive closure of all referenced sections.
  34 void
  35 Garbage_collection::do_transitive_closure()
  36 {
  37   while (!this->worklist().empty())
  38     {
  39       // Add elements from the work list to the referenced list
  40       // one by one.
  41       Section_id entry = this->worklist().back();
  42       this->worklist().pop_back();
  43       if (!this->referenced_list().insert(entry).second)
  44         continue;
  45       Garbage_collection::Section_ref::iterator find_it =
  46                 this->section_reloc_map().find(entry);
  47       if (find_it == this->section_reloc_map().end())
  48           continue;
  49       const Garbage_collection::Sections_reachable &v = find_it->second;
  50       // Scan the vector of references for each work_list entry.
  51       for (Garbage_collection::Sections_reachable::const_iterator it_v =
  52                v.begin();
  53            it_v != v.end();
  54            ++it_v)
  55         {
  56           // Do not add already processed sections to the work_list.
  57           if (this->referenced_list().find(*it_v)
  58               == this->referenced_list().end())
  59             {
  60               this->worklist().push_back(*it_v);
  61             }
  62         }
  63     }
  64   this->worklist_ready();
  65 }
  66
  67 } // End namespace gold.
  68